Sintered powders

Kapton resin (5) (113) and Upilex (6) resin (114) are sold as films, partially polymerized resin coating solutions, and sinterable powders. Allied Signal also offers Apical polyimide film. 

In different forms (bar, casting such as sand, centrifugal, die, pernianenl mould, etc., extrusion, forging, impact extrusion, pressing, sintered, powder pressing)... 

Magnesium oxide is always blended with the zinc oxide prior to ignition. Magnesium oxide promotes densification of the zinc oxide, preserves its whiteness and renders the sintered powder easier to pulverize (Crowell, 1929). The sintered mixed oxide has been shown to contain zinc oxide and a solid solution of zinc oxide in magnesium oxide (Zhuravlev, Volfson Sheveleva, 1950). Specific surface area is reduced compared with that of pure zinc oxide and cements prepared from the mixed oxides are stronger (Crowell, 1929 Zhuravlev, Volfson Sheveleva, 1950). 

The expense in preparation derives from the need for high purity products. The cost in fabricating three-dimensional shapes of SiC, SijN or BN arises from the need to sinter powders of these materials at high temperatures (>1500°C) and often under high pressure. Coatings of these materials are at present produced by chemical or... 

Fig. 4.3. Thermal resistance Rk multiplied by surface area A between 3He and Ag sintered powder. Experimental data from [70]. The dashed line represents the prediction of the acoustic mismatch theory for bulk Ag. The full line is the prediction for the coupling of (zero) sound modes of liquid 3He with modes with a characteristic... 

PTFE sintering, pressing, ram or paste extrusion, compression moulding or isostatic moulding, machining, hot stamping, extrusion of pre-sintered powders on special machines. 

Synthesis of niobates and tantalates of alkaline metals at high temperatures may result in the products with unintended stoichiometry because of high volatility of alkaline metal (especially lithium) oxides. Therefore, their synthesis in the form of efficiently sintering powders presents a serious problem. Films of alkaline niobates and tantalates can find wide range of applications in acousto- and optoelectronics and are usually prepared by rf-sputtering techniques, also giving rise to stoichiometry problems. 

Hall effect measurements enable the number of electrons in the conduction band of ZnO to be established during the chemisorption of oxygen. Though this investigation has been carried out in the dark only, the results are very important in this context 26>. Hall effect measurements may be carried out with polycrystalline sintered powders. They are not disturbed by grain boundaries, narrow connecting necks, pores and cavities, as are conductivity measurements. 

The preparation of well-defined single-crystal surfaces of copper oxides in UHV or of well-sintered powders, starting from polycrystalline materials, is difficult. Consequently, structure-catalytic property correlations remain to be established. 

The agreement between fee bulk modulus deduced from Brillouin scattering measurements and fee ADX results is very good. The determination of fee elastic moduli by ultrasonics was made by fee measurement of surface acoustic wave velocities on thin films [22], The second ultrasonics experiment was made on sintered powder, by measuring fee longitudinal and transverse sound velocity at ambient and under uniaxial compression. From feat, fee bulk modulus and its pressure derivative were deduced, but this result seems to be quite imprecise. The ultrasonics experiment on thin films gives rise to a very small difference in fee bulk modulus (5%), but fee ADX or Brillouin determination should be utilised for preference. 

Homogeneous distribution can be attained by controlled coprecipitation of hydroxides which are then decomposed by calcination yielding powders of fine particle sizes. Active sinterable powders are produced commercially, usually by hydrolysis of a mixture of ZrOQ 2 and YQ3 to precipitate the mixed... 

From binary alloy Mg2Ni by hydrogenation at temperatures above 623 K, or by sintering powder mixtures of the elements at 723 -773 K under 90 bar hydrogen pressure fine powder... 

By sintering powder mixtures of BaMg2 ahoy, BaH2, and Ru with LiH flux at temperatures of up to 803 K and H2 pressures of up to 150bar greenish powder ... 

By sintering powder mixtures of NaH and Os (Ru) at temperatures of up to 870 K and H2 pressures of up to 1500 (Os) and 6000 (Ru)bar. ordered stmcture (Figure 43) by npd on deuteride of Os compounds at room temperature PAilmnm, Z = 4 contains isolated distorted pentagonal bipyramid [OsHy] 18-electron units having Os site symmetry m.2m surrounded by eight Na+ (from two Na sites) forming a distorted cube four D sites transforms into a HT modification at 459 K lif 3Na+ [TH7] , T, d (supported by experimentally measured weak temperature independent paramagnetism on Os compound). Diffraction evidence for the existence of cubic phases M3 THy- (M = K, Rb, Cs T = Ru, Os 5 0.12 for the K-Ru compound). 

By sintering powder mixtures of alkali hydrides and Os under conditions similar to NayOsHy (XLIII). Partially disordered stmcture (Figure 44) by npd on deuteride of Cs compound at room temperature Pm3m, Z = 1 contains... 

From either hydrogenated binary Mg3lr alloy or by sintering powder mixtures of the elements at up to 773 K under a H2 pressure of up to 150 bar. Red colored hydride partially disordered structure (Figure 45) from npd on deuteride, P2 /c, Z = 8 contains four symmetry independent Ir hydride complexes a spy [IrHs]" " and three sad [lrFl4] complexes of which two are disordered, and five hydride anions are exclusively bonded to Mg all complexes are surrounded by Mg in distorted cubic... 

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