Pressure-crystallized powder

Table XI gives the room-temperature, atmospheric pressure crystal structures, densities, and atomic volumes, along with the melting points and standard enthalpies of vaporization (cohesive energies), for the actinide metals. These particular physical properties have been chosen as those of concern to the preparative chemist who wishes to prepare an actinide metal and then characterize it via X-ray powder diffraction. The numerical values have been selected from the literature by the authors.

White crystal, powder or flake highly hygroscopic the compound and its solutions absorb moisture from the air at various rates depending on calcium chloride concentrations, relative humidity and vapor pressure of water in the air, temperature, surface area of exposed material, and the rate of air circulation at 40% and 95% relative humidity and 25°C, one gram anhydrous calcium chloride may absorb about 1.4 g and 17 g water, respectively. (Shearer, W. L. 1978. In Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed., vol. 4, pp. 432-6. New York Wiley Interscience) density 2.15, 2.24, 1.85, 1.83 and 1.71 g/cm for the anhydrous salt and its mono-, di-, tetra- and hexahy-drates, respectively anhydrous salts melts at 772°C, while the mono-, di-, tetra- and hexahydrates decompose at 260°, 175°, 45.5° and 30°C, respectively the anhydrous salt vaporizes at 1,935°C highly soluble in water, moderate to high solubility in alcohol. 

There are four principal methods of determining crystal structures at high pressures employing powders or single-crystals, using X-rays or neutrons. Here 1 will give a brief review of the relevant diffraction techniques and analysis methods used with each technique, focusing on recent developments. 

Some sophisticated cells now make possible diffraction experiments at pressures higher than 400 GPa, thus approaching those at the earth s center, but this has a cost in terms of reduced sample size, nonhydrostaticity, and so on [92]. At such high pressures only powder diffraction patterns can be obtained, while the unrestricted three-dimensional collection of single-crystal diffraction data is possible only up to a few gigapascal. Fortunately,... 

From mixtures of arc-melted binary alloys (CaMg, YbMg) and Co rods, by adding LiH as a flux, at up to 800 K and 155 bar hydrogen pressure black powders, Ca compound containing brownish translucent single crystals partially... 

Oxidative purification of ND powders was conducted under isothermal conditions using the heating stage and a tube furnace. Isothermal experiments included two steps (1) rapid heating at 50°C/min to the selected temperature and (2) isothermal oxidation for 5 h in ambient air at atmospheric pressure. ND powders used for crystal size characterization were oxidized for 2, 6, 17, 26, and 42 h at 430°C, in a closed tube furnace in static air at atmospheric pressure. 

Cylindrically converging shock waves on powders were used to make mixtures of diamonds and hBN. BN fiber reinforced Zr02 was described . A nanostructured composite of magnetic particles of FOj N in a nonmagnetic matrix of BN is made via an inorganic geP. Fabrication of BN-B4 composites was reported . Consolidation of novel sintered composites formed from high pressure crystallization of amorphous ceramics was also described. The literature discusses other ceramics reinforced with BN fibers, as welF . ... 

Known as special K, jet, green, and other names on the street, ketamine is sometimes injected, but can be evaporated to solid crystals, powdered, and smoked, snorted, or swallowed. Marijuana cigarettes are sometimes soaked in the ketamine solution, allowed to dry, and then smoked. Ketamine has become popular as a rave club drug. Side effects include signiflcant transient increases in blood pressure and heart rate, respiratory depression, airway obstruction, apnea, muscular hypertonia, psychomotor and psychotomimetic effects, and acute dystonic reactions. Following overdose, seizures, polyneuropathy, increased intracranial pressure, respiratory arrest, and cardiac arrest may occur. 

As follows from the consideration of the third-law method (Chapter4), its use for determining the reaction enthalpy requires estimation of the equivalent pressure Peqp of the gaseous product under the conditions of free-surface vaporization of the reactant. This, in turn, involves determination of the absolute rate of decomposition J (kg m and, hence, of the effective surface area of the decomposing sample. This problem, as applied to crystals, powders, and melts, is discussed below. 

Mossbauer spectroscopy is a nondestructive technique which probes a specific element which may occupy one or more crystallographic sites, may have one or more electronic configurations, and may or may not carry a magnetic moment. The absorbers may be in the form of single crystals, powders, foils, surfaces, or frozen solutions solutions or liquids can not be studied. The influence of temperature, pressure, applied magnetic field, and electromagnetic irradiation is easily studied by Mossbauer spectroscopy. 

By subjecting boron nitride (a white powder) to high pressure and temperature small crystals of a substance harder than diamond, known as borazon, are obtained. This pressure-temperature treatment changes the structure from the original graphite-like layer structure (p. 163) to a diamond-like structure this hard form can withstand temperatures up to 2000 K. 

Microcapsules are used in several film coatings other than carbonless paper. Encapsulated Hquid crystal formulations coated on polyester film are used to produce a variety of display products including thermometers. Polyester film coated with capsules loaded with leuco dyes analogous to those used in carbonless copy paper is used as a means of measuring line and force pressures (79). Encapsulated deodorants that release their core contents as a function of moisture developed because of sweating represent another commercial appHcation. Microcapsules are incorporated in several cosmetic creams, powders, and cleansing products (80). 

Beryllium Sulfate. BeiyUium sulfate tetiahydiate [7787-56-6], BeSO TH O, is produced commeicially in a highly purified state by fiactional crystallization from a berylhum sulfate solution obtained by the reaction of berylhum hydroxide and sulfuric acid. The salt is used primarily for the production of berylhum oxide powder for ceramics. Berylhum sulfate chhydrate [14215-00-0], is obtained by heating the tetrahydrate at 92°C. Anhydrous berylhum sulfate [13510-49-1] results on heating the chbydrate in air to 400°C. Decomposition to BeO starts at about 650°C, the rate is accelerated by heating up to 1450°C. At 750°C the vapor pressure of SO over BeSO is 48.7 kPa (365 mm Hg). 

---