omniomni/omni-engineering huggingface dataset:
Rhodium(III) oxide. Rhodium(III) oxide (or Rhodium sesquioxide) is the inorganic compound with the formula Rh2O3. It is a gray solid that is insoluble in ordinary solvents.

Structure
Rh2O3 has been found in two major forms. The hexagonal form adopts the corundum structure. It transforms into an orthorhombic structure when heated above 750 °C.

Production
Rhodium oxide can be produced via several routes:
 Treating RhCl3 with oxygen at high temperatures.
 Rh metal powder is fused with potassium hydrogen sulfate. Adding sodium hydroxide results in hydrated rhodium oxide, which upon heating converts to Rh2O3.
 Rhodium oxide thin films can be produced by exposing Rh layer to oxygen plasma.
 Nanoparticles can be produced by the hydrothermal synthesis.

Physical properties
Rhodium oxide films behave as a fast two-color electrochromic system: Reversible yellow ↔ dark green or yellow ↔ brown-purple color changes are obtained in KOH solutions by applying voltage ~1 V.

Rhodium oxide films are transparent and conductive, like indium tin oxide (ITO) - the common transparent electrode, but Rh2O3 has 0.2 eV lower work function than ITO. Consequently, deposition of rhodium oxide on ITO improves the carrier injection from ITO thereby improving the electrical properties of organic light-emitting diodes.

Catalytic properties
Rhodium oxides are catalysts for hydroformylation of alkenes, N2O production from NO, and the hydrogenation of CO.

See also
Rhodium
Rhodium(IV) oxide
Rhodium-platinum oxide

References

Transition metal oxides
Rhodium(III) compounds
Sesquioxides
Chromism
Ruthenium(IV) oxide. Ruthenium(IV) oxide is the inorganic compound with the formula RuO2.  This black solid is the most common oxide of ruthenium.  It is widely used as an electrocatalyst for producing chlorine, chlorine oxides, and O2. Like many dioxides, RuO2 adopts the rutile structure.

Preparation
It is usually prepared by oxidation of ruthenium trichloride.  Nearly stoichiometric single crystals of RuO2 can be obtained by chemical vapor transport, using O2 as the transport agent:

RuO2  +  O2   RuO4

Films of RuO2 can be prepared by chemical vapor deposition (CVD) from volatile ruthenium compounds.  RuO2 can also be prepared through electroplating from a solution of ruthenium trichloride.

Electrostatically stabilized hydrosols of pristine ruthenium dioxide hydrate have been prepared by exploiting the autocatalytic reduction of ruthenium tetroxide in aqueous solution. The resulting particle populations may be controlled to comprise substantially monodisperse, uniform spheres with diameters in the range 40nm - 160nm.

Uses
Ruthenium(IV) oxide is being used as the main component in the catalyst of the Sumitomo-Deacon process which produces chlorine by the oxidation of hydrogen chloride.

RuO2 can be used as catalyst in many other situations.  Noteworthy reactions are the Fischer–Tropsch process, Haber–Bosch process, and various manifestations of fuel cells.

Aspirational and niche applications
RuO2 is extensively used for the coating of titanium anodes for the electrolytic production of chlorine and for the preparation of resistors or integrated circuits. Ruthenium oxide resistors can be used as sensitive thermometers in the temperature range .02 < T < 4 K. It can be also used as active material in supercapacitor because it has very high charge transfer capability.  Ruthenium oxide has great capacity to store charge when used in aqueous solutions. Average capacities of ruthenium(IV) oxide have reached 650 F/g when in sulfuric acid and annealed at temperatures lower than 200 °C. In attempts to optimise its capacitive properties, prior work has looked at the hydration, crystallinity and particle size of ruthenium oxide.

References

External links

 Los Alamos National Laboratory – Ruthenium 

Ruthenium(IV) compounds
Transition metal oxides
Selenium tetrafluoride. Selenium tetrafluoride (SeF4) is an inorganic compound. It is a colourless liquid that reacts readily with water. It can be used as a fluorinating reagent in organic syntheses (fluorination of alcohols, carboxylic acids or carbonyl compounds) and has advantages over sulfur tetrafluoride in that milder conditions can be employed and it is a liquid rather than a gas.

Synthesis
The first reported synthesis of selenium tetrafluoride was by Paul Lebeau in 1907, who treated selenium with fluorine:
Se  +  2 F2   →   SeF4
A synthesis involving more easily handled reagents entails the fluorination of selenium dioxide with sulfur tetrafluoride:
SF4 + SeO2 → SeF4 + SO2
An intermediate in this reaction is seleninyl fluoride (SeOF2).

Other methods of preparation include fluorinating elemental selenium with chlorine trifluoride:
3 Se + 4 ClF3 → 3 SeF4 + 2 Cl2

Structure and bonding
Selenium in SeF4 has an oxidation state of +4. Its shape in the gaseous phase is similar to that of SF4, having a see-saw shape. VSEPR theory predicts a pseudo-trigonal pyramidal disposition of the five electron pairs around the selenium atom. The axial Se-F bonds are 177 pm with an F-Se-F bond angle of 169.2°. The two other fluorine atoms are attached by shorter bonds (168 pm), with an F-Se-F bond angle of 100.6°. In solution at low concentrations this monomeric structure predominates, but at higher concentrations evidence suggests weak association between SeF4 molecules leading to a distorted octahedral coordination around the selenium atom. In the solid the selenium center also has a distorted octahedral environment.

Reactions
In HF, SeF4 behaves as a weak base, weaker than sulfur tetrafluoride, SF4 (Kb= 2 X 10−2):
SeF4 + HF → SeF3+ + HF2−; (Kb = 4 X 10−4)

Ionic adducts containing the SeF3+ cation are formed with SbF5, AsF5, NbF5, TaF5, and BF3.
With caesium fluoride, CsF, the SeF5− anion is formed, which has a square pyramidal structure similar to the isoelectronic chlorine pentafluoride, ClF5 and bromine pentafluoride, BrF5.
With 1,1,3,3,5,5-hexamethylpiperidinium fluoride or 1,2-dimethylpropyltrimethylammonium fluoride, the SeF62− anion is formed. This has a distorted octahedral shape which contrasts to the regular octahedral shape of the analogous SeCl62−.

References

 Selenium: Inorganic Chemistry Krebs. B., Bonmann S., Eidenschink I.; Encyclopedia of Inorganic Chemistry (1994) John Wiley and Sons

See also
Selenium hexafluoride
Sulfur tetrafluoride
Tellurium tetrafluoride

External links
 WebBook page for SeF4

Fluorides
Selenium(IV) compounds
Fluorinating agents
Chalcohalides
Selenium halides
Substances discovered in the 1900s
Silicon tetraiodide. Silicon tetraiodide is the chemical compound with the formula SiI4.  It is a tetrahedral molecule with Si-I bond lengths of 2.432(5) Å.

SiI4 is a precursor to silicon amides of the formula Si(NR2)4 (R = alkyl). It has also been of interest in the manufacture and etching of silicon in microelectronics.

Synthesis and reactions
This compound is produced by treating silicon-copper mixture with iodine:

It reacts quickly with water and moisture in the air.

It can also be made on a large scale by reaction of silicon or silicon carbide with iodine on heating to about 200 °C. Of more academic interest is the reaction of silane with iodine vapour at 130 - 150 °C, as this produces a series of compounds ranging from iodosilane SiH3I to diiodosilane SiH2I2 and triiodosilane SiHI3 as well. These compounds are colourless liquids at room temperature. The last one can be readily distinguished from the similar carbon compound, iodoform which is a yellow solid at room temperature.

Comparison with other SiX4 compounds

References

External links
 webelements page

Iodides
Inorganic silicon compounds
Nonmetal halides
Silicon disulfide. Silicon disulfide is the inorganic compound with the formula SiS2.  Like silicon dioxide, this material is polymeric, but it adopts a 1-dimensional structure quite different from the usual forms of SiO2.

Synthesis, structure, and properties
The material is formed by heating silicon and sulfur or by the exchange reaction between SiO2 and Al2S3.  The material consists of chains of edge-shared tetrahedra, -Si(μ-S)2Si(μ-S)2-.

Like other silicon sulfur-compounds (e.g., bis(trimethylsilyl)sulfide) SiS2 hydrolyzes readily to release H2S.
In liquid ammonia it is reported to form the imide Si(NH)2 and NH4SH, but a recent report has identified crystalline (NH4)2[SiS3(NH3)]·2NH3 as a product which contains the tetrahedral thiosilicate anion, SiS3(NH3)2-.

Reaction with ethanol gives the alkoxide tetraethyl orthosilicate and H2S. With bulky tert-butanol, alcoholysis gives tris(tert-butoxy)silanethiol:
3 (CH3)3COH  +  SiS2    →    [(CH3)3CO]3SiSH  +  H2S

Reaction with sodium sulfide, magnesium sulfide and aluminum sulfide give thiosilicates.

SiS2 is claimed to occur in certain interstellar objects.

References

Inorganic silicon compounds
Sulfides
Inorganic polymers
Dichalcogenides
Sodium hexafluoroaluminate. Sodium hexafluoroaluminate is an inorganic compound with formula Na3AlF6. This white solid, discovered in 1799 by Peder Christian Abildgaard (1740–1801), occurs naturally as the mineral cryolite and is used extensively in the industrial production of aluminium. The compound is the sodium (Na+) salt of the hexafluoroaluminate (AlF63−) ion.

Production
Most cryolite is manufactured by a variety of related pathways. One route entails combining sodium aluminate and hydrofluoric acid:
Na3Al(OH)6  +  6 HF   →   Na3AlF6  +  6 H2O

Other routes include:

Often the hexafluoroaluminic acid, which is recovered from phosphate mining, is the precursor in a two-step process beginning with neutralization with ammonia to give ammonium hexafluoroaluminate:
H3AlF6  +  3NH3   →   (NH4)3AlF6
(NH4)3AlF6  +  3NaOH   →   Na3AlF6  +  3NH3 +  3H2O

The mineral form of sodium hexafluoroaluminate, which is called cryolite, was mined at Ivigtût on the west coast of Greenland until the deposit was depleted in 1987.

Use
The dominant application of synthetic cryolite is as a solvent (or flux) for electrolysis of aluminium oxides such as bauxite. The conversion of aluminium oxides into metallic aluminium requires that the metal ions be dissolved so that they can accept the electrons provided in the electrolysis cell.  A mixture of cryolite and some aluminium trifluoride is used as that solvent.  Unlike typical solutions, this one requires temperatures approaching 1000 °C to melt. Other uses include a whitener for enamels and an opacifier for glass.

Structure
It adopts a perovskite-like structure.  The  centers are nearly idealized octahedra.  Na+ occupy both six- and distorted 8-coordinate sites.

Safety
The  is 600 mg/kg for the comparable compound aluminium trifluoride. Cryolite is poorly soluble in water.

Related compounds
Chiolite ( ), another sodium fluoroaluminate.

References

External links
Chemical Land 21
ESPI Metals
CDC - NIOSH Pocket Guide to Chemical Hazards

Aluminium complexes
Fluoro complexes
Sodium compounds
Fluorometallates
Sodium telluride. Sodium telluride is the chemical compound with the formula Na2Te.  This salt is the conjugate base of the thermally unstable acid hydrogen telluride, but it is usually prepared by reduction of tellurium with sodium.  Na2Te is a challenging material to handle because it is very sensitive to air.  Air oxidizes it initially to polytellurides, which have the formula Na2Tex (x > 1), and ultimately Te metal.  Samples of Na2Te, which are colourless when absolutely pure, generally appear purple or dark gray due to the effects of air oxidation.

Synthesis, structure, and solution properties
The synthesis is typically conducted using ammonia as the solvent.

Na2Te, like many related compounds with the formula M2X, adopts the antifluorite structure.  Thus, in solid Na2Te each Te2− ion is surrounded by eight Na+ ions and each Na+ ion is surrounded by four Te2− ions.

Simple salts of the type M2X, where X is a monatomic anion, are not typically soluble in any solvent because they have a high lattice energy.  Upon addition of water - even moist air - or treatment with alcohols, Te2− protonates:
Na2Te  +  H2O  →  NaHTe  +  NaOH
Because of this reaction, many processes attributed to Na2Te may involve NaHTe (CAS # 65312-92-7), which is more soluble and formed readily.

Applications in organic chemistry
Na2Te finds use in organic synthesis, both as a reagent for reductions and as a source of Te in the synthesis of organotellurium compounds.  Aryl halides are substituted to diaryl tellurides, as illustrated by the synthesis of dinaphthyltelluride:
Na2Te  +  2 C10H7I  →  (C10H7)2Te  +  2  NaI

Na2Te reacts with 1,3-diynes to give the corresponding tellurophene, which are structurally analogous to thiophenes:
Na2Te  +  RC≡C-C≡CR  +  2 H2O  →  TeC4R2H2  +  2  NaOH

As a reducing agent, Na2Te converts nitro groups to amines and will cleave certain C-X bonds.

References

Tellurides
Sodium compounds
Fluorite crystal structure
Strontium hexaboride. Strontium boride (SrB6) is an inorganic compound. At room temperature, it appears as a crystalline black powder. Closer examination reveals slightly translucent dark red crystals capable of scratching quartz. It is very stable and has a high melting point and density. Although not thought to be toxic, it is an irritant to the skin, eyes, and respiratory tract.

Magnetism
Strontium boride, along with other alkali-earth metal borides, has been shown to exhibit weak ferromagnetism at low temperatures. This is thought by some to be caused by slight impurities or aberrations in the crystal lattice, while others suggest different explanations are needed. Strontium boride has also been examined for semiconducting properties at lower temperatures.

Preparation
In his book The Electric Furnace, Henri Moissan describes an early synthesis of strontium boride by mixing strontium borate, aluminum, and carbon in an electric furnace. Alternatively, a solid-phase synthesis of strontium boride can be carried out by reacting two moles of strontium carbonate with three moles of boron carbide and one mole of carbon inside a vacuum furnace.

Uses
Strontium boride is used in insulation and nuclear control rods. A recent patent filed for aircraft windows uses SrB6 nanoparticles in a transparent acrylic sheet. The IR-absorbing properties of these nanoparticles prevents the transmittance of infrared wavelengths while still allowing the transmittance of visible light.

References

Borides
Strontium compounds
Halpin–Tsai model. Halpin–Tsai model is a mathematical model for the prediction of elasticity of composite material based on the geometry and orientation of the filler and the elastic properties of the filler and matrix. The model is based on the self-consistent field method although often consider to be empirical.

See also 
 Cadec-online.com implements the Halpin–Tsai model among others.

References
 J. C. Halpin Effect of Environmental Factors on Composite Materials, US Air Force Material Laboratory, Technical Report AFML-TR-67-423, June 1969
 J.C. Halpin and J. L. Kardos Halpin-Tsai equations:A review, Polymer Engineering and Science, 1976, v16, N5, pp 344-352
 Halpin-Tsai model on about.com 

Composite materials
Continuum mechanics
Materials science
Digital circuit multiplication equipment. Digital circuit multiplication equipment (DCME) was a type of voice compression equipment that is installed at both ends of a long-distance telecommunication link, typically a link via communications satellite or submarine communications cable.  The main characteristics of DCME are defined in ITU-T recommendation G.763.  DCME consists of a time-assignment speech interpolation (TASI) voice interpolation stage, which is a form of statistical multiplexor applied to voiceband signals, and a low rate encoding stage which exploits correlation between successive voiceband samples on an individual input channel to reduce the transmitted bitrate from that required by PCM of equivalent quality.

Under heavy loading conditions, for example when a large number of channels show continuous activity due to voiceband data or Group III facsimile signals, the voice interpolation may not be able to operate within a satisfactory quality range – discontinuous signals such as speech being affected by competitive clipping of the initial part of the activity.  To combat this DCME may incorporate Dynamic Load Control on a range of input channels. Dynamic load control is a form of back busying to the telephone switch.

The DCME's functionality, from the point of view of the telephone switch attached to its local interface, is standardised by ITU-T Recommendation Q.50.

See also 
 Time-assignment speech interpolation

References

Multiplexing
International Federation of Automatic Control. The International Federation of Automatic Control (IFAC), founded in September 1957 in France, is a multinational federation of 49 national member organizations (NMO), each one representing the engineering and scientific societies concerned with automatic control in its own country.

The aim of the Federation is to promote the science and technology of control in the broadest sense in all systems, whether, for example, engineering, physical, biological, social or economic, in both theory and application. IFAC is also concerned with the impact of control technology on society.

IFAC pursues its purpose by organizing technical meetings, by publications, and by any other means consistent with its constitution and which will enhance the interchange and circulation of information on automatic control activities.
 
International World Congresses are held every three years. Between congresses, IFAC sponsors many symposia, conferences and workshops covering particular aspects of automatic control.

The official journals of IFAC are Automatica, Control Engineering Practice, Annual Reviews in Control, Journal of Process Control, Engineering Applications of Artificial Intelligence, the Journal of Mechatronics, Nonlinear Analysis: Hybrid Systems, and the IFAC Journal of Systems and Control.

Awards
IFAC Fellows

Major Medals
 Giorgio Quazza Medal
 Nathaniel B. Nichols Medal
 Industrial Achievement Award
 Manfred Thoma Medal
High Impact Paper Award
 Automatica Prize Paper Award
 Control Engineering Practice Prize Paper Award
 Journal of Process Control Prize Paper Award
 Engineering Applications of Artificial Intelligence Prize Paper Award
 Mechatronics Journal Prize Paper Award
 Congress Applications Paper Prize
 IFAC Congress Young Author Prize
 Control Engineering Textbook Prize
 Congress Poster Paper Prize
Outstanding Service Award

See also 
 American Automatic Control Council
 Harold Chestnut
 Karl Reinisch
 Li Huatian
 John C. Lozier

References

External links
Elsevier publishers

Engineering organizations
Control engineering
Supraorganizations
I. S. O. Playfair. Major General Ian Stanley Ord Playfair,  (10 April 1894 – 21 March 1972) was a British Army officer.

Military career
Born the son of Colonel F.H.G. Playfair of the Hampshire Regiment and educated at Cheltenham College, Playfair joined the Royal Engineers in 1913. He served in France and Belgium during the First World War and was mentioned in despatches, awarded the Military Cross and Bar and the Distinguished Service Order.

Playfair became officer commanding the Gentlemen Cadets of the Royal Marine Artillery in 1920, attended the Staff College, Camberley, from 1929 to 1930, was chief instructor in field works and bridging at the Royal School of Military Engineering in 1930 and an instructor at the Indian Army Staff College in Quetta in 1934. After attending the Imperial Defence College in 1938, he became commandant of the Army Gas School in Wiltshire in 1939.

In 1940, following the outbreak of the Second World War, Playfair was appointed director of plans at the War Office. In early 1942, he was appointed deputy commander (and chief of staff) of land forces in the American-British-Dutch-Australian Command (ABDACOM), a short-lived, supreme command for Allied forces in Southeast Asia and the southwest Pacific. In 1943, Playfair was appointed to the general staff of the 11th Army Group, in the South East Asia Command.

Playfair retired in 1947. He later wrote several books, and was co-author of a Second World War official campaign history: The Mediterranean and Middle East.

Family
In 1930, Playfair married Jocelyn Malan; they had two sons, including Guy Lyon Playfair.

Works
 The Mediterranean and Middle East
 Volume 1: The Early Successes Against Italy, to May 1941, 1954, 
 Volume 2: The Germans Come to the Help of Their Ally, 1941, 1956, 
 Volume 3: British Fortunes Reach Their Lowest Ebb, 1960, 
 Volume 4: The Destruction of the Axis Forces in Africa, 1966,

References

Bibliography

External links
National Portrait Gallery
Generals of World War II

1894 births
1972 deaths
British Army major generals
People educated at Cheltenham College
Companions of the Order of the Bath
Companions of the Distinguished Service Order
Royal Engineers officers
British Army personnel of World War I
British Army generals of World War II
Recipients of the Military Cross
Graduates of the Staff College, Camberley
Graduates of the Royal College of Defence Studies
Academics of the Staff College, Quetta
Chugaev elimination. The Chugaev elimination is a chemical reaction that involves the elimination of water from alcohols to produce alkenes. The intermediate is a xanthate. It is named for its discoverer, the Russian chemist Lev Aleksandrovich Chugaev (1873–1922), who first reported the reaction sequence in 1899.

In the first step, a xanthate salt is formed out of the alkoxide and carbon disulfide (CS2). With the addition of iodomethane, the alkoxide is transformed into a methyl xanthate.

At about 200 °C, the alkene is formed by an intramolecular elimination. In a 6-membered cyclic transition state the hydrogen atom is removed from the carbon atom β to the xanthate oxygen in a syn-elimination. The side product decomposes to carbonyl sulfide (OCS) and methanethiol.

The Chugaev elimination is similar in mechanism to other thermal elimination reactions such as the Cope elimination and ester pyrolysis. Xanthates typically undergo elimination from 120 to 200 °C, while esters typically require 400 to 500 °C and amine oxides routinely react between 80 and 160 °C.

In the development of Cram's rule, structural assignment of the reaction products were made by applying Chugaev elimination, wherein the threo isomer reacts to the cis isomer of -α-methyl-stilbene and the erythro isomer to the trans version.

See also
 Barton–McCombie deoxygenation

References

External links 
 Animation of the mechanism of the Chugaev elimination

1899 introductions
1899 in science
Elimination reactions
Olefination reactions
Name reactions
C-22 process. Introduced by Kodak in the 1956, C-22 is an obsolete process for developing color film, superseded by the C-41 process in 1972 for the launch of 110 film and in 1974 for all other formats.

The development of the film material is carried out at temperatures of around 75°F (24°C), making the process incompatible with the more modern C-41 process, which uses a temperature of 100°F (38°C).  C-22 uses Color Developing Agent 3, unlike C-41, which uses Color Developing Agent 4.

The most common film requiring this process is Kodacolor-X.

C-22 film can still (as of 2020) be developed in black and white.

References

Photographic film processes
Means of transport. Means of transport are transport facilities used to carry people or cargo.


Examples of means of transport

Space

Spacecraft

Air

Aircraft
Drone

Water

Ships

Land

Automobiles
Bicycles
Carriages
Pack animals
Riding animals
Rickshaws
Trains
Trucks
Vehicles
Wagons

Pipeline

Pipes
Pneumatic tubes

See also 

Mode of transport

References

Broad-concept articles
Transport by function