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905857 | Cross River State | https://en.wikipedia.org/w/index.php?title=Cross%20River%20State | Cross River State
of volcanic-stone monoliths of unknown age), the Mary Slessor Tomb, Calabar Drill Monkey Sanctuary, Cross River National Park, Afi Mountain walkway canopy, Kwa falls, Agbokim waterfalls, Tinapa Business Resort, Mono rail way and the annual Calabar Carnival that takes place during the Christmas period.
Cross River State can be accessed by air through the Margaret Ekpo International Airport at Calabar. There are daily flights to Calabar from Lagos and Abuja serviced by airlines such as Arik Airlines and Aero Contractors. Aero Contractors also have flights to the Bebi airstrip at Obanliku for trips to the Obanliku Mountain Resort.
# Education.
Tertiary educational institutions in the State includes | 18,600 |
905857 | Cross River State | https://en.wikipedia.org/w/index.php?title=Cross%20River%20State | Cross River State
trips to the Obanliku Mountain Resort.
# Education.
Tertiary educational institutions in the State includes University of Calabar and Cross River State University of Technology located in the state capital Calabar, Ibrahim Babangida College of Agriculture located in Obubra Local Government Area, Cross River State College of Education located in Akamkpa Local Government Area, College of Health Technology, Iboko Okpoma, Federal College of Education located in Obudu and Technical College Ugep located in Yakurr Local Government Area.
# See also.
- Tinapa Resort
- Akwa Akpa
- Obudu Ranch Resort
# External links.
- Cross River State Government website
- http://crossriverwatch.com/?p=25473 | 18,601 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
Ford LTD (Americas)
The Ford LTD (pronounced "el-tee-dee") is a range of automobiles manufactured by Ford Motor Company for the 1965 to 1986 model years. Introduced as the highest trim of the full-size Ford model range, the LTD introduced options and features normally reserved for more luxurious Lincoln and Mercury models. The largest vehicle produced by Ford in North America for most of its production, the LTD was joined by the intermediate Ford LTD II from 1977 to 1979; the LTD II served as the replacement for the Torino/Gran Torino range. At various times throughout its production, the LTD range included two- and four-door pillared and hardtop sedans, a two-door convertible, and the Country | 18,602 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
Squire five-door woodgrain station wagon.
For the 1979 model year, the LTD was downsized, becoming externally smaller than the LTD II, and for 1983, it became a mid-size car. The Ford Granada was discontinued, with the LTD nameplate moving to a restyled version of that car; the full-size LTD then became LTD Crown Victoria. The mid-size LTD was replaced by the 1986 Ford Taurus, as Ford continued its shift towards front-wheel drive vehicles.
Outside of North America, the 1966 Ford Galaxie 500 was manufactured in South America into the 1980s and marketed as the Ford LTD.
# Etymology.
The LTD designation has been speculated by some to be an abbreviation of "Luxury Trim Decor" and by others as | 18,603 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
a "Limited" trim designation for the Galaxie. There is evidence in early 1970s Australian LTD sales brochures, that "Lincoln Type Design" was adapted by Ford's Australian marketing, as the meaning of the LTD nameplate to play up Lincoln-like exclusitivity and design influence of its Falcon-based LTD luxury car, since actual Lincoln models were not sold in that country. However, there is no evidence of "Lincoln Type Design" nor any other meaning ever being used in brochures or advertising copy of North American sales literature. The original "Car Life" review at the time the first Galaxie 500 LTD was released suggests that "LTD" stood for nothing and was ambiguous in meaning.
# First generation | 18,604 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
(1965–1968).
The Ford Galaxie 500 LTD was introduced in August 1964 at the start of the 1965 model year and prompted the Chevrolet Caprice at midyear 1965, the AMC Ambassador "DPL" in 1966, the Plymouth Fury "VIP," and the similar Dodge Monaco. These upscale models had features found primarily on luxury models from these same manufacturers, namely Cadillac, Lincoln and Imperial, but were sold at much lower retail prices. These cars commonly came equipped with options like power windows, a power driver's seat, power brakes, power steering, air conditioning, and a full or half-vinyl top (called a landau or brougham interchangeably across different models by the same manufacturers). Other upgrades | 18,605 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
were interiors made of better materials and more powerful engines. Most of these upper trim models were usually hardtops as opposed to pillared bodies.
In 1966, the LTD series became completely separate from the Galaxie 500, which continued as the mid-line offering (the performance-oriented Galaxie 500 XL shared top billing with the LTD). The Twin Comfort Lounge Seat (a split bench seat) was a new option.
The 1967 LTD two-door hardtop got a new formal roofline, keeping up with the competition. All models received the 1967 federally-mandated safety features, including a large, soft "crash pad" in the center of the steering wheel, non-protruding instrument panel knobs, a dual-circuit brake master | 18,606 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
cylinder, four-way hazard flashers, and front outboard shoulder belt mounting points.
The 1968 model year would be transitional for the LTD and all full-size Fords. Though the body and frame of the 1965–1967 models were carryovers, the 1968 model featured horizontal hidden headlights and a more formal roofline. It was the last model with the 119" wheelbase. The standard LTD interior was downgraded a bit in luxury compared to past versions, but a new "Brougham" option package effectively brought the interior trim up to previous standards of luxury. In a major change for the 1968 model year, Ford added sedan model names to the separate model series for some of its full-size station wagons; the | 18,607 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
wood-grained Country Squire became the "LTD Country Squire."
This generation was introduced with covered headlights on the top level LTD coupe, sedan and station wagon, which were deployed using a vacuum canister system that kept the doors down when a vacuum condition existed in the lines, provided by the engine when it was running. If a loss of vacuum occurred, the doors would retract up so that the headlights were visible if the system should fail. 1968s also included side marker lights and reflectors, and the parking lights now illuminated with the headlights. Front outboard shoulder belts were fitted to cars built effective January 1, 1968. The large soft hub in the steering wheel hub gave | 18,608 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
way to a more conventional design, and an energy-absorbing steering column was introduced as part of the 1968 safety package.
## Limousine.
A limousine version of the car was also considered, with the extra length at the C-pillar and the rear doors. At least one example was built, by Lehmann-Peterson. This car does not appear to have a B-pillar or a division window. Andy Hotton Associates also built about 10 examples of an LTD limo, in which the extra length was added at the B-pillar and C-pillar.
# Second generation (1969–1978).
For the 1969 model year, the LTD was given a major redesign. Based on a largely carryover chassis, the wheelbase of all full-size Ford sedans now stretched to 121 | 18,609 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
inches.
## Timeline.
1969:Ford LTD is given a redesign on a longer (121-inch) wheelbase chassis; the hidden headlights and formal roofline introduced in 1967 are retained. An all-new body features a split grille with a horizontal center divider (shared with XLs and Country Squires).
- 1970: The split grille was discontinued; while its Mercury Marquis counterpart continues its Lincoln-style fascia, Ford redesigned the front end of the LTD with a three-segment grille with a prominent center section (a toned down version of the Ford Thunderbird (fifth generation)). All LTDs got a new Federally-mandated locking steering column and wheel, with the ignition switch located on the right side of the | 18,610 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
column.
- 1971: The LTD was given a styling update. In the rear, the long-running Ford styling tradition ended as the twin round or square "jet exhaust" taillights were replaced by horizontal taillights on all full-size Fords. In between the two tail lamps was a center "third" brakelight; on the Galaxie 500, this space was an alloy trim panel while Custom 500s had body-color trim. In front, the LTD lost its hidden headlamps to Lincoln-Mercury, but got a new front end treatment with a tall center grille section and "LTD" spelled out in block letters on the hood.
With the discontinuation of the XL series, the convertible was moved to the LTD line. These were produced with bucket seats and center | 18,611 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
consoles; the console was similar to the console in the XLs and Mercury Marauders of 1969–1970, with a "stirrup" style shift handle.
A customized 1971 LTD is featured prominently in the 1973 American film White Lightning. It is the car driven by the film’s lead character, portrayed by Burt Reynolds.
- 1972: 1972 models were virtually the same as the 1971s, although the bumper now stretched across the lower section of the grille. A new rear bumper integrated the taillights; also in the rear, the design of the trunklid was squared off. Due to decreased demand in the segment, 1972 was the final model year for the LTD convertible.
- 1973: In 1972, in order to comply with federal regulations, | 18,612 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
the LTD was given a major redesign for 1973. The requirements for 5-mph front bumpers had taken effect, with larger rear bumpers to be added in 1973. While the redesign slightly decreased the weight of the LTD, it still was far in excess of two tons, making agility and fuel economy both key weak points. The new styling was bulkier, making the car look significantly larger and heavier than previous models. Four-door models (sharing rooflines with Mercury) were given thin B-pillars for roof reinforcement and branded as "pillared hardtops" (frameless door glass remained on all Ford LTD models). The 460 engine became an option for the first time.
- 1974: Five-mph bumpers added to the rear. Mostly | 18,613 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
carryover from the 1973 model year. Mid-year, a non-woodgrain LTD wagon became available. A new Federal law required seat belts to be buckled before the starter would operate; public protests prompted the government to relax this requirement. Subsequent models got a simple "Fasten Seat Belt" warning light and buzzer for 1975, and owners were now permitted to disable the starter interlock on their 1974s.
- 1975: Following the discontinuation of the Galaxie series after 1974, Ford sought to fill its place by expanding the LTD trim lineup. Above the Custom 500 was the standard LTD, the LTD Brougham, and newly introduced for 1975, the LTD Landau. In an effort to comply with pending rollover standards | 18,614 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
(as well as to differentiate it from the Mercury Marquis), the two-door was converted from a hardtop to a coupe with wide B-pillars and a tall, narrow "opera window" (Chevrolet did the same thing in 1973 with the Caprice Coupe). More or less the Ford counterpart to the Mercury Grand Marquis, the LTD Landau featured rear fender skirts and various decor packages for additional luxury; it was distinguished by the return of hidden headlamps (exclusive to its trim level). Hidden headlamps were also shared with the LTD Country Squire wagon. The 429 engine was replaced by the 460 V8 sourced from Lincoln-Mercury for 1975. A catalytic converter now required the use of unleaded fuel, and the gas gauge | 18,615 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
and fuel filler sported warnings to this effect.
- 1976: Four-wheel disc brakes and 8-track were optional. Last year for LTD Brougham trim level.
- 1977: Since the LTD Brougham had been discontinued, the LTD Landau received the former Brougham interior as the base offering. Optional interiors, including the LTD Landau Luxury Group, were still available.
- 1978: Final year for 121-inch wheelbase LTD, as it is replaced by the downsized Panther-platform generation LTD for 1979.
Approximately 7,850,000 full-size Fords and Mercurys were sold over the 1969–1978 period. This makes it the second best selling Ford automobile platform after the Ford Model T.
## Mechanical Details.
For the first | 18,616 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
time since the 1940s, the full-size Ford line was powered exclusively by V8 engines. The base engine was the 302 cid V8. The next largest engine was Ford's 351 CID V8, the most common choice. Still larger was Ford's 400 CID V8. Topping the range was the 429 cid V8, in 1974 this was replaced by the 460 CID V8. The full-sized Fords remained strong sellers each year during this period, due to their high comfort, powerful engines, good build quality and reasonable cost.
## LTD II.
When Ford updated its mid-size product line for 1977, they took on the LTD name as well. To differentiate them from the full-size product lineup, the mid-size cars were called the LTD II in an attempt to appeal to buyers | 18,617 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
as a downsized alternative to the full-sized LTD which had competition from GM's newly downsized full-sized cars. The LTD II was based on the Ford Torino and served as a restyled replacement for it. The LTD II styling was also adapted to update the final generation of the Ford Ranchero. The LTD II was discontinued after 1979 without being replaced, as the new Panther-platform LTD was nearly a foot shorter than an LTD II and the Granada became Ford's mid-size product line with its 1981 redesign.
# Third generation (1979–1982).
For the 1977 model year, General Motors downsized its full-size car lines closely within the exterior size of many intermediates. At the time, Ford marketers took a cynical | 18,618 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
view that such a radically smaller "full-size car" would turn off buyers; advertisements for LTD and Mercury Marquis touted the "road-hugging weight" of the larger cars and compared their larger dimensions side by side with GM flagship sedan Cadillac Fleetwood Brougham. For owners who would still prefer a downsized big car, Ford offered the "Trim Size LTD II," which was simply a refreshed Torino with stacked quad rectangular headlights and LTD-like styling at the rear.
Ford was taken by surprise when the downsized GM cars proved to be an enormous sales success and along with the advent of CAFE regulations, they were forced to follow suit. Production of the 1979 models began July 31, 1978 at | 18,619 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
Louisville Assembly, with Atlanta Assembly, Los Angeles Assembly, and Oakville Assembly following suit in August. Unlike the Chrysler R platform, the Ford Panther platform was completely new from the ground up. The LTD and Marquis lost nearly 15 inches in length and some 400 pounds of curb weight without a significant loss of interior space over the old 1969-vintage platform. Like GM's "downsized" 1977 big cars, the new 1979 LTD featured a trimmer body profile, more nimble handling due to its smaller size, and better fuel economy. Big-block engines were gone and the small-block 302 V8 became standard, with the 351 Windsor V8 optional. However, due to CAFE requirements, the 351 became a police-only | 18,620 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
option in 1982. For 1981, to further improve fuel economy (while avoiding diesel or 6-cylinder engines), Ford introduced a variant of the Windsor V8. The 255 proved an unpopular choice; at 115 hp, its output was ill-suited for the LTD's size and the engine was dropped after 1982. Most LTDs of this era were fitted with a Motorcraft 7200VV two-barrel variable venturi carburetor; a conventional carburetor was available with the police option high-output 351.
In Canada, the Custom 500 continued as the base model through 1981. Low-end cars were identifiable by single rectangular headlamps, while the higher models received duals. For 1980, the LTD S was added as a lower-priced model and the Crown | 18,621 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
Victoria replaced the Landau on a permanent basis; it had a landau roof with a brushed aluminum band, a stylistic element shared with the 1977–1979 Thunderbird and ultimately traced back to the 1955 Ford from whence the Crown Victoria name originated. Mercury's contemporary Grand Marquis was equivalently optioned.
In 1982, the LTD got a new grille with the revived Ford blue oval emblem and throttle body fuel injection became available. For 1983, as part of a major product shift, the LTD and LTD Crown Victoria were split into separate product lines. The LTD was downsized to the Fox platform (along with the Mercury Marquis) to replace the Granada, while the full-size LTD Crown Victoria became | 18,622 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
a stand-alone model (as did the Mercury Grand Marquis).
# Fourth generation (1983–1986).
For model year 1983, Ford introduced the LTD and Mercury Marquis as rebadged variants of the second generation Ford Granada and Mercury Cougar (sedan and wagon), all using the Fox platform. The full-size cars retained only the LTD Crown Victoria and Grand Marquis nameplates; Lincoln followed suit, with the Town Car becoming its sole full-size vehicle in 1983.
As with the Granada, the LTD was available in a four-door sedan and five-door station wagon body styles; no two-door version was produced. At its launch, the LTD/Marquis shared a common engine with the Fairmont and Granada; a 2.3 L "Lima" 4-cylinder, | 18,623 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
a 3.3 L "Thriftpower Six" inline-6, and a "5.0L Windsor" V8 (upgraded to fuel injection). Inherited from the Granada was a 3.8 L "Essex" V6; after 1984, the V6 replaced the inline-6 entirely. For 1984, the V6 gained fuel injection in United States versions (Canadian-market versions remained carbureted until 1986). A rare option, seen only in 1982–1984, was an LPG (propane)-powered version of the four-cylinder engine; it was largely discontinued due to poor sales and lack of propane fueling infrastructure.
The LTD became the third-best-selling car in the U.S. in 1983–1984. Following the success of the Chrysler K-Cars and the General Motors X-body cars which popularized the use of front-wheel | 18,624 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
drive in the mid-size segment; the LTD/Marquis was ultimately superseded by the Ford Taurus/Mercury Sable model year 1986, with Ford marketing both the LTD/Marquis and the Ford Taurus for the 1986 model year. The last LTD rolled off the Atlanta, Georgia assembly line on December 13, 1985 and off the Chicago, Illinois assembly line on January 3, 1986.
## LTD LX.
From the mid-1984 model year and throughout the 1985 model year, Ford had a performance version of the LTD marketed as the "LTD LX". It came standard with the high output 5.0L CFI V8 engine, four-speed automatic transmission with overdrive, 600 lb-in front and 270 lb-in rear coil springs, front and rear sway bars, 10 inch front disc | 18,625 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
and 10 inch rear drum brakes, and a 3.27:1 rear gear ratio with a Traction-Lok differential. The LX model was the only LTD to have a tachometer in the instrument cluster. The center console and floor-mounted shifter re-appeared, having last been available in the full-size 1972 model year. Police Package editions were also produced alongside the LX. Notable for its bigger sway bars and brakes, it also included bench seats with an automatic trunk opener located underneath the steering wheel. They were a factory option and most were equipped with light bars and police accessories, although some came without. Mercury's sister car to the LX, the Marquis LTS, was available only in Canada and only | 18,626 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
in the 1985 model year, with only 134 produced that year.
# Brazil.
The LTD was built locally in Brazil between 1967 and 1983, based on the 1966 Galaxie platform. A stretch limousine version was assembled locally as well.
# Venezuela.
The LTD was introduced to the Venezuelan market in 1966, aiming to compete with Chrysler's New Yorker, with the LTD performing much better than its rivals. Over 85,000 LTDs were assembled in the Ford plant of Valencia, Venezuela, some for export to Colombia, Bolivia, Ecuador and Peru.
Versions of the Fox-body 1983–1986 North American LTD manufactured in Venezuela continued the use of the Granada name complete with uplevel Elite badged versions. There was also | 18,627 |
905858 | Ford LTD (Americas) | https://en.wikipedia.org/w/index.php?title=Ford%20LTD%20(Americas) | Ford LTD (Americas)
LTDs were assembled in the Ford plant of Valencia, Venezuela, some for export to Colombia, Bolivia, Ecuador and Peru.
Versions of the Fox-body 1983–1986 North American LTD manufactured in Venezuela continued the use of the Granada name complete with uplevel Elite badged versions. There was also a Ford Cougar equivalent to the North American Mercury Marquis.
# External links.
- LTDworld.com - Ford LTD World
- Four Eyed Pride —- A resource for all early Foxes, including 1983-1986 LTD
- LTD LX Registry and Owners Association —- For the preservation and restoration of 1984 & 1985 Ford LTD LX
- 1979 Ford LTD Landau
- Decode LTD and other classic Ford VINs
- Ford LTD in television and film | 18,628 |
905896 | Buenaventura Báez | https://en.wikipedia.org/w/index.php?title=Buenaventura%20Báez | Buenaventura Báez
Buenaventura Báez
Ramón Buenaventura Báez Méndez, better known as Buenaventura Báez (July 14, 1812March 14, 1884) was the President of the Dominican Republic for five nonconsecutive terms. He is known for attempting to annex the Dominican Republic to other countries on several occasions. His son Ramón Báez was briefly president in 1914.
# Early years and family.
Báez was born in Rincón (now Cabral) in the Captaincy General of Santo Domingo, he was raised in his father's hometown Azua.
Báez was the son of Pablo Altagracia Báez and Teresa de Jesús Méndez. His father Pablo, a wealthy merchant from Azua, was a left in an orphanage when he was born, as he was the result of an extramarital affair | 18,629 |
905896 | Buenaventura Báez | https://en.wikipedia.org/w/index.php?title=Buenaventura%20Báez | Buenaventura Báez
between a married Spanish woman and the priest Antonio Sánchez-Valverde. Pablo was raised by a French silversmith (a factor that generated a deep francophilia in both Pablo and Buenaventura) known as "Monsieur Capellier", and became a wealthy businessman, slaveholder and politician. Teresa de Jesús Méndez was a beautiful, busty, mixed-race former slave from Rincón. She was born to a slave and a master, and was sold to Pablo Altagracia Báez, who freed her to take her as his mistress when his wife María Quezada told him to do so when realized that she was infertile herself; Pablo and Teresa had 7 children.
Báez was light-haired and blue-eyed like his father but had curly hair and was somewhat | 18,630 |
905896 | Buenaventura Báez | https://en.wikipedia.org/w/index.php?title=Buenaventura%20Báez | Buenaventura Báez
swarthy, earning the nickname of "Jabao". Cultured and good-looking, Báez was very popular among women, especially because of his gallantry.
Due to his family's fortune he was able to study in Europe, particularly France. There, he learned various languages including English and French. When his father died in 1841, Báez, aged 29, inherited a large fortune that he used assiduously in politics, becoming elected in 1843 deputy to the Haitian Constituent Assembly.
# Political career.
From 1843 Báez served as deputy of Azua to the ruling Haitian government. This post was gained in part because of his role in the revolution that overthrew President Jean-Pierre Boyer from power. As a deputy, Báez | 18,631 |
905896 | Buenaventura Báez | https://en.wikipedia.org/w/index.php?title=Buenaventura%20Báez | Buenaventura Báez
led a faction of Dominicans that tried to remove the anti-white bias in the Haitian Constitution, but failed.
Báez was, at first, completely and totally against any move to leave the union with Haiti. Then, on 15 December 1843 Báez, as leader of the Dominican legislative faction, proposed to French consul Auguste Levasseur to establish a French protectorate in the Spanish-speaking side of the island with a governor appointed by Paris, in exchange for guns and warships to compel or fight Port-au-Prince for a retreat. Consul Levasseur was very well disposed and constantly exchanged correspondence between Paris and the conspirators.
When the independence revolution started, he opposed the Trinitarians | 18,632 |
905896 | Buenaventura Báez | https://en.wikipedia.org/w/index.php?title=Buenaventura%20Báez | Buenaventura Báez
and imprisoned some of them, tried futilely to prevent the publication of a copy of the Act of Independence in January 1844 in Azua, and in February did not allow the flag of the newly Dominican state to be raised in the city plaza; in part, he was very pessimistic due to the numerical superiority of Haitians and thought that a rebellion against Port-au-Prince with no foreign support was futile. He changed his mind once he saw the popular fervor and decided that the time had come to part ways with Port-au-Prince.
In 1844, Báez helped to lead a successful rebellion against Haiti, which established the independence of the Dominican Republic. He went to Europe in 1846 to convince France to establish | 18,633 |
905896 | Buenaventura Báez | https://en.wikipedia.org/w/index.php?title=Buenaventura%20Báez | Buenaventura Báez
a protectorate over the Dominican Republic, but the French refused. As president for the first time, from 1849 until 1853, he attempted to convince the United States to take over the country. He was president again from 1856 until 1857, when he was deposed in a coup.
Báez next supported the idea of having the Dominican Republic be taken over by Spain. He went into exile in Spain and led a luxurious life there. The Spanish agreed to occupy the Dominican Republic in 1861, but by 1865 they had abandoned it (see Dominican Restoration War). Báez then returned to the Dominican Republic and became president again until he was deposed in another coup in May 1866. He then served his longest term as | 18,634 |
905896 | Buenaventura Báez | https://en.wikipedia.org/w/index.php?title=Buenaventura%20Báez | Buenaventura Báez
president, from 1868 until 1874, during which time he again attempted to have the United States annex the Dominican Republic. This time he was almost successful, as he convinced American President Ulysses S. Grant to send warships to the Dominican Republic, and drew up an annexation treaty which reached the United States Senate floor. The treaty, however, was not ratified in the US Senate, and it became an embarrassment for Grant.
# Exile and death.
Báez became President again from 1876 until 1878, when he was deposed in a final coup and sent into exile to Puerto Rico, at the time a Spanish colony, where he lived his final days.
He is buried in the Basilica Cathedral of Santa María la Menor.
# | 18,635 |
905896 | Buenaventura Báez | https://en.wikipedia.org/w/index.php?title=Buenaventura%20Báez | Buenaventura Báez
Offspring.
Genealogical studies have identified President Báez, and President Espaillat as well, as the most recent common ancestors for most of the Dominican oligarchy, since their offspring managed to establish bonds with the most rich and powerful families from Santiago, and thus, from the country.
- Ramón Buenaventura Báez Méndez (1812–1884)
- Manuel Báez Batista (1839–?)
- Altagracia Amelia Báez Andújar (†1879)
- José María Cabral y Báez (1864–1937)
- Amelia María Cabral Bermúdez (1899–1996)
- Juan Bautista Vicini Cabral (1924–2015)
- Felipe Augusto Antonio Vicini Lluberes (b. 1960)
- Amelia Stella María Vicini Lluberes (b. 1974)
- Juan Bautista Vicini Lluberes (b. 1975)
- Laura | 18,636 |
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Amelia Vicini Cabral de Barletta (1925–2006)
- José María Vicini Cabral (1926–2007)
- José Leopoldo Vicini Pérez
- Marco Vicini Pérez
- Felipe Vicini Cabral (1936–1997)
- Auristela Cabral Bermúdez (1901–1988)
- Donald Joseph Reid Cabral (1923–2006)
- William John Reid Cabral (1925–2010)
- Patricia Reid Baquero (b. 1953)
- Isabela Egan Reid de Pittaluga
- Meghan Egan Reid
- Robert Reid Cabral (1929–1961)
- José María Cabral Bermúdez (1902–1984)
- María Josefina Cabral Vega
- Manuel Díez Cabral (b. 1964)
- José María Cabral Vega
- Amalia Josefina Gabriela Cabral Lluberes (b. 1963)
- Claudia Cabral Lluberes (b. 1964)
- Ana Amelia Batlle Cabral
- Laura Emilia Batlle Cabral
- | 18,637 |
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José María Cabral Lluberes (b. 1967)
- Petrica Cabral Vega (b. 1938)
- María Amalia León Cabral (b. 1960)
- Sarah Amalia Jorge León
- Lidia Josefina León Cabral (b. 1962)
- José Eduardo León Cabral (1963–1975)
- Marco Buenaventura Cabral Vega
- Marco Antonio Cabral Bermúdez (1906–1973)
- Josefina Eugenia Cabral Bermúdez (1910–1994)
- Pedro Ramón Espaillat Cabral
- Alejandro Augusto Espaillat Cabral
- Alejandro José Espaillat Imbert
- Pedro José Espaillat Vélez
- Carlos José Espaillat Vélez
- Fineta Rosario Espaillat Cabral
- Pedro Pablo Cabral Bermúdez (1916–1988)
- Lucía Amelia Cabral Arzeno de Herrera
- José María Cabral Arzeno (b. 1959)
- José María Cabral González (b. 1988)
- | 18,638 |
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Luis José Cabral Arzeno
- Lucía Amelia Cabral Arzeno
- Virginia Cabral Arzeno
- Ramona Antonio Cabral y Báez
- Eduardo Sánchez Cabral
- Buenaventura Cabral y Báez
- Carmen Amelia Mercedes Cabral Machado
- Carlos Alberto Cabral Machado
- Pablo Buenaventura Cabral Machado
- Mario Fermín Cabral y Báez (1877–1961)
- Manuel Antonio Cabral Tavares (1907–1999)
- Alba María Antonia "Peggy" Cabral Cornero (b. 1947)
- Teodoro Osvaldo Buenaventura Báez Machado (1857–?)
- José Ramón Báez López-Penha (1909–1995)
- Buenaventura Báez López-Penha
- Marcos Antonio Báez Cocco
- Ramón Báez Machado (1858–1929)
- Buenaventura Báez Soler
- Ramón Báez Romano
- Ramón Buenaventura Báez Figueroa (b. | 18,639 |
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o
- Mario Fermín Cabral y Báez (1877–1961)
- Manuel Antonio Cabral Tavares (1907–1999)
- Alba María Antonia "Peggy" Cabral Cornero (b. 1947)
- Teodoro Osvaldo Buenaventura Báez Machado (1857–?)
- José Ramón Báez López-Penha (1909–1995)
- Buenaventura Báez López-Penha
- Marcos Antonio Báez Cocco
- Ramón Báez Machado (1858–1929)
- Buenaventura Báez Soler
- Ramón Báez Romano
- Ramón Buenaventura Báez Figueroa (b. 1956)
- Ramón Buenaventura Báez Zeller (b. 1982)
- José Ramón Báez Alvarez (b.1999)
- José Miguel Báez Figueroa
- Mercedes Báez Soler
- Julio Ernesto de la Rocha Báez
- Ramón de la Rocha Pimentel (b. 1951)
- Clarissa Altagracia de la Rocha Pimentel de Torres (b. 1959) | 18,640 |
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Transparent ceramics
Many ceramic materials, both glassy and crystalline, have found use as optically transparent materials in various forms from bulk solid-state components to high surface area forms such as thin films, coatings, and fibers. Such devices have found widespread use for various applications in the electro-optical field including: optical fibers for guided lightwave transmission, optical switches, laser amplifiers and lenses, hosts for solid-state lasers and optical window materials for gas lasers, and infrared (IR) heat seeking devices for missile guidance systems and IR night vision.
While single-crystalline ceramics may be largely defect-free (particularly within the spatial | 18,641 |
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scale of the incident light wave), optical transparency in polycrystalline materials is limited by the amount of light that is scattered by their microstructural features. The amount of light scattering therefore depends on the wavelength of the incident radiation, or light.
For example, since visible light has a wavelength scale on the order of hundreds of nanometers, scattering centers will have dimensions on a similar spatial scale. Most ceramic materials, such as alumina and its compounds, are formed from fine powders, yielding a fine grained polycrystalline microstructure that is filled with scattering centers comparable to the wavelength of visible light. Thus, they are generally opaque | 18,642 |
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as opposed to transparent materials. Recent nanoscale technology, however, has made possible the production of (poly)crystalline transparent ceramics such as alumina AlO, yttria alumina garnet (YAG), and neodymium-doped .
# Introduction.
Transparent ceramics have recently acquired a high degree of interest and notoriety. Basic applications include lasers and cutting tools, transparent armor windows, night vision devices (NVD), and nose cones for heat seeking missiles. Currently available infrared (IR) transparent materials typically exhibit a trade-off between optical performance and mechanical strength. For example, sapphire (crystalline alumina) is very strong, but lacks full transparency | 18,643 |
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throughout the 3–5 micrometer mid-IR range. Yttria is fully transparent from 3–5 micrometers, but lacks sufficient strength, hardness, and thermal shock resistance for high-performance aerospace applications. Not surprisingly, a combination of these two materials in the form of the yttria-alumina garnet (YAG) has proven to be one of the top performers in the field.
In 1961, General Electric began selling transparent alumina Lucalox bulbs. In 1966, GE announced a ceramic "transparent as glass," called Yttralox. In 2004, Anatoly Rosenflanz and colleagues at 3M used a "flame-spray" technique to alloy aluminium oxide (or alumina) with rare-earth metal oxides in order to produce high strength glass-ceramics | 18,644 |
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with good optical properties. The method avoids many of the problems encountered in conventional glass forming and may be extensible to other oxides. This goal has been readily accomplished and amply demonstrated in laboratories and research facilities worldwide using the emerging chemical processing methods encompassed by the methods of sol-gel chemistry and nanotechnology.
Many ceramic materials, both glassy and crystalline, have found use as hosts for solid-state lasers and as optical window materials for gas lasers. The first working laser was made by Theodore H. Maiman in 1960 at Hughes Research Laboratories in Malibu, who had the edge on other research teams led by Charles H. Townes at | 18,645 |
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Columbia University, Arthur Schawlow at Bell Labs, and Gould at TRG (Technical Research Group). Maiman used a solid-state light-pumped synthetic ruby to produce red laser light at a wavelength of 694 nanometers (nm). Synthethic ruby lasers are still in use. Both sapphires and rubies are corundum, a crystalline form of aluminium oxide (Al2O3).
## Crystals.
Ruby lasers consist of single-crystal sapphire alumina (AlO) rods doped with a small concentration of chromium Cr, typically in the range of 0.05%. The end faces are highly polished with a planar and parallel configuration. Neodymium-doped YAG (Nd:YAG) has proven to be one of the best solid-state laser materials. Its indisputable dominance | 18,646 |
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in a broad variety of laser applications is determined by a combination of high emission cross section with long spontaneous emission lifetime, high damage threshold, mechanical strength, thermal conductivity, and low thermal beam distortion. The fact that the Czochralski crystal growth of Nd:YAG is a matured, highly reproducible and relatively simple technological procedure adds significantly to the value of the material.
Nd:YAG lasers are used in manufacturing for engraving, etching, or marking a variety of metals and plastics. They are extensively used in manufacturing for cutting and welding steel and various alloys. For automotive applications (cutting and welding steel) the power levels | 18,647 |
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are typically 1–5 kW.
In addition, Nd:YAG lasers are used in ophthalmology to correct posterior capsular opacification, a condition that may occur after cataract surgery, and for peripheral iridotomy in patients with acute angle-closure glaucoma, where it has superseded surgical iridectomy. Frequency-doubled Nd:YAG lasers (wavelength 532 nm) are used for pan-retinal photocoagulation in patients with diabetic retinopathy. In oncology, Nd:YAG lasers can be used to remove skin cancers.
These lasers are also used extensively in the field of cosmetic medicine for laser hair removal and the treatment of minor vascular defects such as spider veins on the face and legs. Recently used for dissecting | 18,648 |
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cellulitis, a rare skin disease usually occurring on the scalp. Using hysteroscopy in the field of gynecology, the Nd:YAG laser has been used for removal of uterine septa within the inside of the uterus.
In dentistry, Nd:YAG lasers are used for soft tissue surgeries in the oral cavity.
## Glasses.
Glasses (non-crystalline ceramics) also are used widely as host materials for lasers. Relative to crystalline lasers, they offer improved flexibility in size and shape and may be readily manufactured as large, homogeneous, isotropic solids with excellent optical properties. The indices of refraction of glass laser hosts may be varied between approximately 1.5 and 2.0, and both the temperature coefficient | 18,649 |
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of n and the strain-optical coefficient may be tailored by altering the chemical composition. Glasses have lower thermal conductivities than the alumina or YAG, however, which imposes limitations on their use in continuous and high repetition-rate applications.
The principal differences between the behavior of glass and crystalline ceramic laser host materials are associated with the greater variation in the local environment of lasing ions in amorphous solids. This leads to a broadening of the fluorescent levels in glasses. For example, the width of the Nd emission in YAG is ~ 10 angstroms as compared to ~ 300 angstroms in typical oxide glasses. The broadened fluorescent lines in glasses make | 18,650 |
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it more difficult to obtain continuous wave laser operation (CW), relative to the same lasing ions in crystalline solid laser hosts.
Several glasses are used in transparent armor, such as normal plate glass (soda-lime-silica), borosilicate glass, and fused silica. Plate glass has been the most common glass used due to its low cost. But greater requirements for the optical properties and ballistic performance have necessitated the development of new materials. Chemical or thermal treatments can increase the strength of glasses, and the controlled crystallization of certain glass compositions can produce optical quality glass-ceramics. Alstom Grid Ltd. currently produces a lithium di-silicate | 18,651 |
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based glass-ceramic known as TransArm, for use in transparent armor systems. It has all the workability of an amorphous glass, but upon recrystallization it demonstrates properties similar to a crystalline ceramic. Vycor is 96% fused silica glass, which is crystal clear, lightweight and high strength. One advantage of these type of materials is that they can be produced in large sheets and other curved shapes.
## Nanomaterials.
It has been shown fairly recently that laser elements (amplifiers, switches, ion hosts, etc.) made from fine-grained ceramic nanomaterials—produced by the low temperature sintering of high purity nanoparticles and powders—can be produced at a relatively low cost. These | 18,652 |
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components are free of internal stress or intrinsic birefringence, and allow relatively large doping levels or optimized custom-designed doping profiles. This highlights the use of ceramic nanomaterials as being particularly important for high-energy laser elements and applications.
Primary scattering centers in polycrystalline nanomaterials—made from the sintering of high purity nanoparticles and powders—include microstructural defects such as residual porosity and grain boundaries (see Transparent materials). Thus, opacity partly results from the incoherent scattering of light at internal surfaces and interfaces. In addition to porosity, most of the interfaces or internal surfaces in ceramic | 18,653 |
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nanomaterials are in the form of grain boundaries which separate nanoscale regions of crystalline order. Moreover, when the size of the scattering center (or grain boundary) is reduced well below the size of the wavelength of the light being scattered, the light scattering no longer occurs to any significant extent.
In the processing of high performance ceramic nanomaterials with superior opto-mechanical properties under adverse conditions, the size of the crystalline grains is determined largely by the size of the crystalline particles present in the raw material during the synthesis or formation of the object. Thus a reduction of the original particle size well below the wavelength of visible | 18,654 |
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light (~ 0.5 µm or 500 nm) eliminates much of the light scattering, resulting in a translucent or even transparent material.
Furthermore, results indicate that microscopic pores in sintered ceramic nanomaterials, mainly trapped at the junctions of microcrystalline grains, cause light to scatter and prevented true transparency. It has been observed that the total volume fraction of these nanoscale pores (both intergranular and intragranular porosity) must be less than 1% for high-quality optical transmission, i.e. the density has to be 99.99% of the theoretical crystalline density.
# Lasers.
### YAG.
For example, a 1.46 kW Nd:YAG laser has been demonstrated by Konoshima Chemical Co. in Japan. | 18,655 |
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In addition, Livermore researchers realized that these fine-grained ceramic nanomaterials might greatly benefit high-powered lasers used in the National Ignition Facility (NIF) Programs Directorate. In particular, a Livermore research team began to acquire advanced transparent nanomaterials from Konoshima to determine if they could meet the optical requirements needed for Livermore's Solid-State Heat Capacity Laser (SSHCL). Livermore researchers have also been testing applications of these materials for applications such as advanced drivers for laser-driven fusion power plants.
Assisted by several workers from the NIF, the Livermore team has produced 15 mm diameter samples of transparent Nd:YAG | 18,656 |
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from nanoscale particles and powders, and determined the most important parameters affecting their quality. In these objects, the team largely followed the Japanese production and processing methodologies, and used an in house furnace to vacuum sinter the nanopowders. All specimens were then sent out for hot isostatic pressing (HIP). Finally, the components were returned to Livermore for coating and testing, with results indicating exceptional optical quality and properties.
One Japanese/East Indian consortium has focused specifically on the spectroscopic and stimulated emission characteristics of Nd in transparent YAG nanomaterials for laser applications. Their materials were synthesized using | 18,657 |
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vacuum sintering techniques. The spectroscopic studies suggest overall improvement in absorption and emission and reduction in scattering loss. Scanning electron microscope and transmission electron microscope observations revealed an excellent optical quality with low pore volume and narrow grain boundary width. Fluorescence and Raman measurements reveal that the Nd doped YAG nanomaterial is comparable in quality to its single-crystal counterpart in both its radiative and non-radiative properties. Individual Stark levels are obtained from the absorption and fluorescence spectra and are analyzed in order to identify the stimulated emission channels possible in the material. Laser performance | 18,658 |
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studies favor the use of high dopant concentration in the design of an efficient microchip laser. With 4 at% dopant, the group obtained a slope efficiency of 40%. High-power laser experiments yield an optical-to-optical conversion efficiency of 30% for Nd (0.6 at%) YAG nanomaterial as compared to 34% for an Nd (0.6 at%) YAG single crystal. Optical gain measurements conducted in these materials also show values comparable to single crystal, supporting the contention that these materials could be suitable substitutes to single crystals in solid-state laser applications.
## Yttria, YO.
The initial work in developing transparent yttrium oxide nanomaterials was carried out by General Electric in | 18,659 |
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the 1960s.
In 1966, a transparent ceramic, Yttralox, was invented by Dr. Richard C. Anderson at the General Electric Research Laboratory, with further work at GE's Metallurgy and Ceramics Laboratory by Drs. Paul J. Jorgensen, Joseph H. Rosolowski, and Douglas St. Pierre. Yttralox is "transparent as glass," has a melting point twice as high, and transmits frequencies in the near infrared band as well as visible light.
Further development of yttrium ceramic nanomaterials was carried out by General Electric in the 1970s in Schenectady and Cleveland, motivated by lighting and ceramic laser applications. Yttralox, transparent yttrium oxide YO containing ~ 10% thorium oxide (ThO) was fabricated | 18,660 |
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by Greskovich and Woods. The additive served to control grain growth during densification, so that porosity remained on grain boundaries and not trapped inside grains where it would be quite difficult to eliminate during the initial stages of sintering. Typically, as polycrystalline ceramics densify during heat treatment, grains grow in size while the remaining porosity decreases both in volume fraction and in size. Optically transparent ceramics must be virtually pore-free.
GE's transparent Yttralox was followed by GTE's lanthana-doped yttria with similar level of additive. Both of these materials required extended firing times at temperatures above 2000 °C. LaO – doped YO is of interest for | 18,661 |
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infrared (IR) applications because it is one of the longest wavelength transmitting oxides. It is refractory with a melting point of 2430 °C and has a moderate coefficient of thermal expansion coefficient. The thermal shock and erosion resistance is considered to be intermediate among the oxides, but outstanding compared to non-oxide IR transmitting materials. A major consideration is the low emissivity of yttria, which limits background radiation upon heating. It is also known that the phonon edge gradually moves to shorter wavelengths as a material is heated.
In addition, ytrria itself, YO has been clearly identified as a prospective solid-state laser material. In particular, lasers with | 18,662 |
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ytterbium as dopant allow the efficient operation both in cw operation
and in pulsed regimes.
At high concentration of excitations (of order of 1%) and poor cooling, the quenching of emission at laser frequency and avalanche broadband emission takes place.
## Future.
The Livermore team is also exploring new ways to chemically synthesize the initial nanopowders. Borrowing on expertise developed in CMS over the past 5 years, the team is synthesizing nanopowders based on sol-gel processing, and then sintering them accordingly in order to obtain the solid-state laser components. Another technique being tested utilizes a combustion process in order to generate the powders by burning an organic | 18,663 |
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solid containing yttrium, aluminum, and neodymium. The smoke is then collected, which consists of spherical nanoparticles.
The Livermore team is also exploring new forming techniques (e.g. extrusion molding) which have the capacity to create more diverse, and possibly more complicated, shapes. These include shells and tubes for improved coupling to the pump light and for more efficient heat transfer. In addition, different materials can be co-extruded and then sintered into a monolithic transparent solid. An amplifier slab can formed so that part of the structure acts in guided lightwave transmission in order to focus pump light from laser diodes into regions with a high concentration of dopant | 18,664 |
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ions near the slab center.
In general, nanomaterials promise to greatly expand the availability of low-cost, high-end laser components in much larger sizes than would be possible with traditional single crystalline ceramics. Many classes of laser designs could benefit from nanomaterial-based laser structures such as amplifies with built-in edge claddings. Nanomaterials could also provide more robust and compact designs for high-peak power, fusion-class lasers for stockpile stewardship, as well as high-average-power lasers for global theater ICBM missile defense systems (e.g. Strategic Defense Initiative SDI, or more recently the Missile Defense Agency.
# Night vision.
A night vision device | 18,665 |
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(NVD) is an optical instrument that allows images to be produced in levels of light approaching total darkness. They are most often used by the military and law enforcement agencies, but are available to civilian users. Night vision devices were first used in World War II,
and came into wide use during the Vietnam War. The technology has evolved greatly since their introduction, leading to several "generations" of night vision equipment with performance increasing and price decreasing. The United States Air Force is experimenting with Panoramic Night Vision Goggles (PNVGs) which double the user's field of view to approximately 95 degrees by using four 16 mm image intensifiers tubes, rather | 18,666 |
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than the more standard two 18 mm tubes.
Thermal images are visual displays of the amount of infrared (IR) energy emitted, transmitted, and reflected by an object. Because there are multiple sources of the infrared energy, it is difficult to get an accurate temperature of an object using this method. A thermal imaging camera is capable of performing algorithms to interpret that data and build an image. Although the image shows the viewer an approximation of the temperature at which the object is operating, the camera is using multiple sources of data based on the areas surrounding the object to determine that value rather than detecting the temperature.
Night vision infrared devices image in | 18,667 |
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the near-infrared, just beyond the visual spectrum, and can see emitted or reflected near-infrared in complete visual darkness. All objects above the absolute zero temperature (0 K) emit infrared radiation. Hence, an excellent way to measure thermal variations is to use an infrared vision device, usually a focal plane array (FPA) infrared camera capable of detecting radiation in the mid (3 to 5 µm) and long (7 to 14 µm) wave infrared bands, denoted as MWIR and LWIR, corresponding to two of the high transmittance infrared windows. Abnormal temperature profiles at the surface of an object are an indication of a potential problem.
Infrared thermography, thermal imaging, and thermal video, are | 18,668 |
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examples of infrared imaging science. Thermal imaging cameras detect radiation in the infrared range of the electromagnetic spectrum (roughly 900–14,000 nanometers or 0.9–14 µm) and produce images of that radiation, called "thermograms".
Since infrared radiation is emitted by all objects near room temperature, according to the black body radiation law, thermography makes it possible to see one's environment with or without visible illumination. The amount of radiation emitted by an object increases with temperature. Therefore, thermography allows one to see variations in temperature. When viewed through a thermal imaging camera, warm objects stand out well against cooler backgrounds; humans | 18,669 |
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and other warm-blooded animals become easily visible against the environment, day or night. As a result, thermography is particularly useful to the military and to security services.
## Thermography.
In thermographic imaging, infrared radiation with wavelengths between 8–13 micrometers strikes the detector material, heating it, and thus changing its electrical resistance. This resistance change is measured and processed into temperatures which can be used to create an image. Unlike other types of infrared detecting equipment, microbolometers utilizing a transparent ceramic detector do not require cooling. Thus, a microbolometer is essentially an uncooled thermal sensor.
The material used | 18,670 |
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in the detector must demonstrate large changes in resistance as a result of minute changes in temperature. As the material is heated, due to the incoming infrared radiation, the resistance of the material decreases. This is related to the material's temperature coefficient of resistance (TCR) specifically its negative temperature coefficient. Industry currently manufactures microbolometers that contain materials with TCRs near −2%.
## VO and VO.
The most commonly used ceramic material in IR radiation microbolometers is vanadium oxide. The various crystalline forms of vanadium oxide include both VO and VO. Deposition at high temperatures and performing post-annealing allows for the production | 18,671 |
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of thin films of these crystlalline compounds with superior properties, which may be easily integrated into the fabrication process. VO has low resistance but undergoes a metal-insulator phase change near 67 °C and also has a lower TCR value. On the other hand, VO exhibits high resistance and also high TCR.
Other IR transparent ceramic materials that have been investigated include doped forms of CuO, MnO and SiO.
# Missiles.
Many ceramic nanomaterials of interest for transparent armor solutions are also used for electromagnetic (EM) windows. These applications include radomes, IR domes, sensor protection, and multi-spectral windows. Optical properties of the materials used for these applications | 18,672 |
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are critical, as the transmission window and related cut-offs (UV – IR) control the spectral bandwidth over which the window is operational. Not only must these materials possess abrasion resistance and strength properties common of most armor applications, but due to the extreme temperatures associated with the environment of military aircraft and missiles, they must also possess excellent thermal stability.
Thermal radiation is electromagnetic radiation emitted from the surface of an object which is due to the object's temperature. Infrared homing refers to a passive missile guidance system which uses the emission from a target of electromagnetic radiation in the infrared part of the spectrum | 18,673 |
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to track it. Missiles that use infrared seeking are often referred to as "heat-seekers", since infrared is just below the visible spectrum of light in frequency and is radiated strongly by hot bodies. Many objects such as people, vehicle engines and aircraft generate and retain heat, and as such, are especially visible in the infrared wavelengths of light compared to objects in the background.
## Sapphire.
The current material of choice for high-speed infrared-guided missile domes is single-crystal sapphire. The optical transmission of sapphire does not extend to cover the entire mid-infrared range (3–5 µm), but starts to drop off at wavelengths greater than approximately 4.5 µm at room temperature. | 18,674 |
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While the strength of sapphire is better than that of other available mid-range infrared dome materials at room temperature, it weakens above ~600 °C.
Limitations to larger area sapphires are often business related, in that larger induction furnaces and costly tooling dies are necessary in order to exceed current fabrication limits. However, as an industry, sapphire producers have remained competitive in the face of coating-hardened glass and new ceramic nanomaterials, and still managed to offer high performance and an expanded market.
## Yttria, YO.
Alternative materials, such as yttrium oxide, offer better optical performance, but inferior mechanical durability. Future high-speed infrared-guided | 18,675 |
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missiles will require new domes that are substantially more durable than those in use today, while still retaining maximum transparency across a wide wavelength range. A long-standing trade-off exists between optical bandpass and mechanical durability within the current collection of single-phase infrared transmitting materials, forcing missile designers to compromise on system performance. Optical nanocomposites may present the opportunity to engineer new materials that overcome this traditional compromise.
The first full scale missile domes of transparent yttria manufactured from nanoscale ceramic powders were developed in the 1980s under Navy funding. Raytheon perfected and characterized | 18,676 |
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its undoped polycrystalline yttria, while lanthana-doped yttria was similarly developed by GTE Labs. The two versions had comparable IR transmittance, fracture toughness, and thermal expansion, while the undoped version exhibited twice the value of thermal conductivity.
Renewed interest in yttria windows and domes has prompted efforts to enhance mechanical properties by using nanoscale materials with submicrometer or nanosized grains. In one study, three vendors were selected to provide nanoscale powders for testing and evaluation, and they were compared to a conventional (5 μm) yttria powder previously used to prepare transparent yttria. While all of the nanopowders evaluated had impurity | 18,677 |
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levels that were too high to allow processing to full transparency, 2 of them were processed to theoretical density and moderate transparency. Samples were sintered to a closed pore state at temperatures as low as 1400 C.
After the relatively short sintering period, the component is placed in a hot isostatic press (HIP) and processed for 3 – 10 hours at ~ 30 kpsi(~200 MPa) at a temperature similar to that of the initial sintering. The applied isostatic pressure provides additional driving force for densification by substantially increasing the atomic diffusion coefficients, which promotes additional viscous flow at or near grain boundaries and intergranular pores. Using this method, transparent | 18,678 |
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yttria nanomaterials were produced at lower temperatures, shorter total firing times, and without extra additives which tend to reduce the thermal conductivity.
Recently, a newer method has been developed by Mouzon, which relies on the methods of glass-encapsulation, combined with vacuum sintering at 1600 °C followed by hot isostatic pressing (HIP) at 1500 °C of a highly agglomerated commercial powder. The use of evacuated glass capsules to perform HIP treatment allowed samples that showed open porosity after vacuum sintering to be sintered to transparency. The sintering response of the investigated powder was studied by careful microstructural observations using scanning electron microscopy | 18,679 |
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and optical microscopy both in reflection and transmission. The key to this method is to keep porosity intergranular during pre-sintering, so that it can be removed subsequently by HIP treatment. It was found that agglomerates of closely packed particles are helpful to reach that purpose, since they densify fully and leave only intergranular porosity.
## Composites.
Prior to the work done at Raytheon, optical properties in nanocomposite ceramic materials had received little attention. Their studies clearly demonstrated near theoretical transmission in nanocomposite optical ceramics for the first time. The yttria/magnesia binary system is an ideal model system for nanocomposite formation. There | 18,680 |
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is limited solid solubility in either one of the constituent phases, permitting a wide range of compositions to be investigated and compared to each other. According to the phase diagram, bi-phase mixtures are stable for all temperatures below ~ 2100 °C. In addition, neither yttria nor magnesia shows any absorption in the 3 – 5 μm mid-range IR portion of the EM spectrum.
In optical nanocomposites, two or more interpenetrating phases are mixed in a sub-micrometer grain sized, fully dense body. Infrared light scattering can be minimized (or even eliminated) in the material as long as the grain size of the individual phases is significantly smaller than infrared wavelengths. Experimental data | 18,681 |
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suggests that limiting the grain size of the nanocomposite to approximately 1/15th of the wavelength of light is sufficient to limit scattering.
Nanocomposites of yttria and magnesia have been produced with a grain size of approximately 200 nm. These materials have yielded good transmission in the 3–5 µm range and strengths higher than that for single-phase individual constituents. Enhancement of mechanical properties in nanocomposite ceramic materials has been extensively studied. Significant increases in strength (2–5 times), toughness (1–4 times), and creep resistance have been observed in systems including SiC/AlO, SiC/SiN, SiC/MgO, and AlO/ZrO.
The strengthening mechanisms observed vary | 18,682 |
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depending on the material system, and there does not appear to be any general consensus regarding strengthening mechanisms, even within a given system. In the SiC/AlO system, for example, it is widely known and accepted that the addition of SiC particles to the AlO matrix results in a change of failure mechanism from intergranular (between grains) to intragranular (within grains) fracture. The explanations for improved strength include:
- A simple reduction of processing flaw concentration during nanocomposite fabrication.
- Reduction of the critical flaw size in the material—resulting in increased strength as predicted by the Hall-Petch relation)
- Crack deflection at nanophase particels | 18,683 |
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due to residual thermal stresses introduced upon cooling form processing temperatures.
- Microcracking along stress-induced dislocations in the matrix material.
# Armor.
There is an increasing need in the military sector for high-strength, robust materials which have the capability to transmit light around the visible (0.4–0.7 micrometers) and mid-infrared (1–5 micrometers) regions of the spectrum. These materials are needed for applications requiring transparent armor. Transparent armor is a material or system of materials designed to be optically transparent, yet protect from fragmentation or ballistic impacts. The primary requirement for a transparent armor system is to not only defeat | 18,684 |
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the designated threat but also provide a multi-hit capability with minimized distortion of surrounding areas. Transparent armor windows must also be compatible with night vision equipment. New materials that are thinner, lightweight, and offer better ballistic performance are being sought.
Existing transparent armor systems typically have many layers, separated by polymer (e.g. polycarbonate) interlayers. The polymer interlayer is used to mitigate the stresses from thermal expansion mismatches, as well as to stop crack propagation from ceramic to polymer. The polycarbonate is also currently used in applications such as visors, face shields and laser protection goggles. The search for lighter | 18,685 |
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materials has also led to investigations into other polymeric materials such as transparent nylons, polyurethane, and acrylics. The optical properties and durability of transparent plastics limit their use in armor applications. Investigations carried out in the 1970s had shown promise for the use of polyurethane as armor material, but the optical properties were not adequate for transparent armor applications.
Several glasses are utilized in transparent armor, such as normal plate glass (soda-lime-silica), borosilicate glasses, and fused silica. Plate glass has been the most common glass used due to its low cost, but greater requirements for the optical properties and ballistic performance | 18,686 |
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have generated the need for new materials. Chemical or thermal treatments can increase the strength of glasses, and the controlled crystallization of certain glass systems can produce transparent glass-ceramics. Alstom Grid Research & Technology (Stafford, UK), produced a lithium disilicate based glass-ceramic known as TransArm, for use in transparent armor systems with continuous production yielding vehicle windscreen sized pieces (and larger). The inherent advantages of glasses and glass-ceramics include having lower cost than most other ceramic materials, the ability to be produced in curved shapes, and the ability to be formed into large sheets.
Transparent crystalline ceramics are used | 18,687 |
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to defeat advanced threats. Three major transparent candidates currently exist: aluminum oxynitride (AlON), magnesium aluminate spinel (spinel), and single crystal aluminum oxide (sapphire).
## Aluminium oxynitride spinel.
Aluminium oxynitride spinel (AlON), abbreviated as AlON, is one of the leading candidates for transparent armor. It is produced by the Surmet Corporation under the trademark ALON. The incorporation of nitrogen into aluminium oxide stabilizes a crystalline spinel phase, which due to its cubic crystal structure and unit cell, is an isotropic material which can be produced as transparent ceramic nanomaterial. Thus, fine-grained polycrystalline nanomaterials can be produced | 18,688 |
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and formed into complex geometries using conventional ceramic forming techniques such as hot isostatic pressing, and slip casting.
The Surmet Corporation has acquired Raytheon's ALON business and is currently building a market for this technology in the area of Transparent Armor, Sensor windows, Reconnaissance windows and IR Optics such as Lenses and Domes and as an alternative to quartz and sapphire in the semiconductor market. The AlON based transparent armor has been tested to stop multi-hit threats including of 30calAPM2 rounds and 50calAPM2 rounds successfully. The high hardness of AlON provides a scratch resistance which exceeds even the most durable coatings for glass scanner windows, | 18,689 |
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such as those used in supermarkets. Surmet has successfully produced a 15"x18" curved AlON window and is currently attempting to scale up the technology and reduce the cost. In addition, the U.S. Army and U.S. Air Force are both seeking development into next generation applications.
## Spinel.
Magnesium aluminate spinel (MgAlO) is a transparent ceramic with a cubic crystal structure with an excellent optical transmission from 0.2 to 5.5 micrometers in its polycrystalline form. Optical quality transparent spinel has been produced by sinter/HIP, hot pressing, and hot press/HIP operations, and it has been shown that the use of a hot isostatic press can improve its optical and physical properties.
Spinel | 18,690 |
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offers some processing advantages over AlON, such as the fact that spinel powder is available from commercial manufacturers while AlON powders are proprietary to Raytheon. It is also capable of being processed at much lower temperatures than AlON and has been shown to possess superior optical properties within the infrared (IR) region. The improved optical characteristics make spinel attractive in sensor applications where effective communication is impacted by the protective missile dome's absorption characteristics.
Spinel shows promise for many applications, but is currently not available in bulk form from any manufacturer, although efforts to commercialize spinel are underway. The spinel | 18,691 |
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products business is being pursued by two key U.S. manufacturers: "Technology Assessment and Transfer" and the "Surmet Corporation".
An extensive NRL review of the literature has indicated clearly that attempts to make high-quality spinel have failed to date because the densification dynamics of spinel are poorly understood. They have conducted extensive research into the dynamics involved during the densification of spinel. Their research has shown that LiF, although necessary, also has extremely adverse effects during the final stages of densification. Additionally, its distribution in the precursor spinel powders is of critical importance.
Traditional bulk mixing processes used to mix LiF | 18,692 |
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sintering aid into a powder leave fairly inhomogeneous distribution of Lif that must be homogenized by extended heat treatment times at elevated temperatures. The homogenizing temperature for Lif/Spinel occurs at the temperature of fast reaction between the LiF and the AlO. In order to avoid this detrimental reaction, they have developed a new process that uniformly coats the spinel particles with the sintering aid. This allows them to reduce the amount of Lif necessary for densification and to rapidly heat through the temperature of maximum reactivity. These developments have allowed NRL to fabricate MgAlO spinel to high transparency with extremely high reproducibility that should enable military | 18,693 |
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as well as commercial use of spinel.
## Sapphire.
Single-crystal aluminum oxide (sapphire – AlO) is a transparent ceramic. Sapphire's crystal structure is rhombohedral and thus its properties are anisotropic, varying with crystallographic orientation. Transparent alumina is currently one of the most mature transparent ceramics from a production and application perspective, and is available from several manufacturers. But the cost is high due to the processing temperature involved, as well as machining costs to cut parts out of single crystal boules. It also has a very high mechanical strength – but that is dependent on the surface finish.
The high level of maturity of sapphire from a production | 18,694 |
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and application standpoint can be attributed to two areas of business: electromagnetic spectrum windows for missiles and domes, and electronic/semiconductor industries and applications.
There are current programs to scale-up sapphire grown by the heat exchanger method or edge defined film-fed growth (EFG) processes. Its maturity stems from its use as windows and in semiconductor industry. Crystal Systems Inc. which uses single crystal growth techniques, is currently scaling their sapphire boules to diameter and larger. Another producer, the Saint-Gobain Group produces transparent sapphire using an edge-defined growth technique. Sapphire grown by this technique produces an optically inferior | 18,695 |
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material to that which is grown via single crystal techniques, but is much less expensive, and retains much of the hardness, transmission, and scratch-resistant characteristics. Saint-Gobain is currently capable of producing 0.43" thick (as grown) sapphire, in 12" × 18.5" sheets, as well as thick, single-curved sheets. The U.S. Army Research Laboratory is currently investigating use of this material in a laminate design for transparent armor systems. The Saint Gobain Group have commercialized the capability to meet flight requirements on the F-35 Joint Strike Fighter and F-22 Raptor next generation fighter aircraft.
## Composites.
Future high-speed infrared-guided missiles will require new | 18,696 |
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dome materials that are substantially more durable than those in use today, while retaining maximum transparency across the entire operational spectrum or bandwidth. A long-standing compromise exists between optical bandpass and mechanical durability within the current group of single-phase (crystalline or glassy) IR transmitting ceramic materials, forcing missile designers to accept substandard overall system performance. Optical nanocomposites may provide the opportunity to engineer new materials that may overcome these traditional limitations.
For example, transparent ceramic armor consisting of a lightweight composite has been formed by utilizing a face plate of transparent alumina AlO | 18,697 |
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(or magnesia MgO) with a back-up plate of transparent plastic. The two plates (bonded together with a transparent adhesive) afford complete ballistic protection against 0.30 AP M2 projectiles at 0° obliquity with a muzzle velocity of per second.
Another transparent composite armor provided complete protection for small arms projectiles up to and including caliber .50 AP M2 projectiles consisting of two or more layers of transparent ceramic material.
Nanocomposites of yttria and magnesia have been produced with an average grain size of ~200 nm. These materials have exhibited near theoretical transmission in the 3 – 5 μm IR band. Additionally, such composites have yielded higher strengths than | 18,698 |
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those observed for single phase solid-state components. Despite a lack of agreement regarding mechanism of failure, it is widely accepted that nanocomposite ceramic materials can and do offer improved mechanical properties over those of single phase materials or nanomaterials of uniform chemical composition.
It should also be noted here that nanocomposite ceramic materials also offer interesting mechanical properties not achievable in other materials, such as superplastic flow and metal-like machinability. It is anticipated that further development will result in high strength, high transparency nanomaterials which are suitable for application as next generation armor.
# See also.
- Ceramic | 18,699 |
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