Powder chamber pressure measurements

Particles consist of both internal and external surface area. The external surface area represents that caused by exterior topography, whereas the internal surface area measures that caused by microcracks, capillaries, and closed voids inside the particles. Since the chosen surface area technique should relate to the ultimate use of the data, not all techniques are useful for fine powders. The commonly used approaches are permeametry and gas adsorption according to the Brunauer, Emmet, and Teller (BET) equation [9]. Because of simplicity of operation and speed of operation, permeametry methods have received much attention. The permeametry apparatus consists of a chamber for placing the material to be measured and a device to force fluid to flow through the powder bed. The pressure drop and rate of flow across the powder bed are measured and related to an average particle size and surface area. Especially for porous powders, permeametry data include some internal surface area, thus decreasing their value. 

Thermal decomposition of samples has been made by the method of prolong exposure at constant temperature on installation of high gas pressure. Specific surface of the samples has been measured by the BET method with accuracy 10% on devise Autosorb-1 (Quantchrome, USA). X-ray powder diffraction data have been obtained with Cu Ka radiation. Samples treatment under high quasihydrostatic pressures (3 GPa, 800°C, 1 h) has been done in the chamber of a high pressure. 

The pressure generated in the chamber of a weapon its value depends to a large extent on the nature of the weapon and of the powder selected. Standard determinations of gas pressure are carried out with the aid of a crusher ( measuring egg ) - a copper cylinder or a copper... 

Put 400ml of sample into a 500ml dewer vessel. Put on the lid of the heat insulator. Put the vessel in a constant temperature chamber. Measure the temperature to indicate the start of self-heating and the self-accelerating decomposition. The method is very useful but it cannot apply to a substance which has a high vapor pressure, such as 5—CT. Chemical and pharmaceutical companies in Europe use a method to measure heat stability of solid deposit 3 >. The method applies to the drying process of powder products to avoid accidents. It is not yet used in Japan. 

May and Marienko [120] used a 1 cm micropyknometer, with ethylene glycol as the fill liquid, for measuring the density of small amounts of material. Stein et. al. [121] found this method time consuming and difficult and developed a method in that air was used as the fill liquid. Their micropyknometer had a 2 mm bore stem, accurately calibrated with mercury, at 0.30 cm and 0.50 cm. A known weight of powder was placed in the pyknometer and the neck sealed with a mercury plug. This was forced down to the 0.50 cm level in a pressure chamber at pressure Pj and then to the 0.30 cm level at pressure P2. The volume of powder (F) is given by ... 

Explosion parameters have been measured for ferromanganese, ferrosilicon and fenotitanimn powders in a 1 m chamber. Maximum pressures of 2.8-3.9 bar, at maximmn rates of rise of 8.9-21.8 bar/s were determined. Individual entries are Fenomanganese, 4389... 

Fig. 14. Transmission spectra of polymeric nitrogen as a fimction of temperature. Spectra are shifted vertically for clarity. The characteristic peak of the T) phase is marked by a vertical arrow. Inset (a) shows the pressure dependence of the absorption spectra of nitrogen at very high pressures and room temperature. Gray lines represent the Tauc fits to the speetra in an appropriate spectral range. The determination of the energy gap from these measurements is obscured by additional losses caused by the presence of a fine ruby powder in the chamber. The high-energy absorption edge is most probably due to stress-induced absorption of diamond anvils (Ref. 62). (b) Urbach plots at 200 GPa and different temperatures (shifted vertically). Gray lines are guides to the eye.

Rubrene was purchased from Aldrich (elemental purity > 98%) and additionally purified by gradient sublimation Freshly cleaved mica (001) was used as substrate. Rubrene thin films were deposited by hot wall epitaxy in a vacuum chamber with a base pressure below 10 Pa at different deposition rates and substrate temperatures (Ts). Pole figures were measured with a Philips X pert x-ray diffractometer using CrKa radiation and a secondary side graphite monochromator. Specular scans were performed on a Bruker D8-Discover diffractometer using CuKa radiation. POWDER CELL and STEREOPOLE were used for the evaluation of the specular scans and simulation of pole figures. 

The method most commonly used to study photodecomposition of azides measures the rate of gas evolved from a sample under irradiation in a vacuum chamber. Typically, a powder in a 10" -10" -torr vacuum is exposed to UV radiation with intensities of lO -lO photons/cm sec. This energy input is sufficient to produce photochemical decomposition of azide molecules in the near-surface regions of the sample. The experimental rates of gas evolution are either calculated from pressure vs. time curves in a closed system or measured directly in a pumped system by relating the rate to the pressure rise. 

The XPS experiments on polymer films were performed on a SCIENTA 300 spectrometer (energy resolution of 0.4 eV on Ag 3d lines) equipped with the A1 Ka (1486.7 eV) monochromatized source. The X-ray source is run at 2.5 kW, a take-off angle of 80° is used and the pressure in the analysis chamber is maintained at lO lO Torr in all the measurements. The powder analysis are made with the XPS HP 5950A spectrometer (energy resolution 0.9 eV and take-off angle 45°) equipped with the same source running at 0.8 kW. 

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