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Porosity, of powders

By results of our experiments mean coefficient of effective thermal conductivity of powder LaNi5 is Xe l.25 0.05 W/(m-K). The porosity of powder layer was 0.5-0.55. Effective thermal conductivity of ZrCrFei.2 powder was 0.5 W/(m-K). [Pg.845]

Nitrogen Adsorption, for determination of pigment surface areas and porosity of powders. [Pg.334]

Although the symbol PSA stands for Particle Size Analysis, there has always been included in each PSA Conference a scientific session on surface area estimation. At PSA 91, two main thrusts were to be found one being on the measurement on porosity of powders in terms of meso- and micro-porosity [Sing Buczek Cowan and Wenman] and the other, because of the global need to have traceability and mandatory powder product specifications, on the characterisation and conparability of reference materials [Stanley-Wbod, Osborne and Till] and the need for Standards [Lines]. The particle size distributions reported by several types of measuring instruments for the same materials were presented [Jimbo, Tsubaki and Yamamoto],... [Pg.551]

Diffusion is based mainly on the diffusion of vacancies grain boundaries may act as sinks for these vacancies. This vacancy movement and annihilation cause the porosity of the powder compact to decrease during sintering. [Pg.185]

Copper and silver combined with refractory metals, such as tungsten, tungsten carbide, and molybdenum, are the principal materials for electrical contacts. A mixture of the powders is pressed and sintered, or a previously pressed and sintered refractory matrix is infiltrated with molten copper or silver in a separate heating operation. The composition is controlled by the porosity of the refractory matrix. Copper—tungsten contacts are used primarily in power-circuit breakers and transformer-tap charges. They are confined to an oil bath because of the rapid oxidation of copper in air. Copper—tungsten carbide compositions are used where greater mechanical wear resistance is necessary. [Pg.190]

Space Applications. The growth of powder metahurgy in space technology has arisen from the difficulty of handling many materials in conventional fusion-metahurgy techniques, the need for controhed porosity, and the requirement of many special and unique properties (60,61). Powder metahurgy is applied in low density components with emphasis on porous tungsten for W—Ag stmctures, beryhium compounds, titanium and... [Pg.191]

Two more recent appHcations for amorphous siHcas are expected to grow to large volumes. Precipitated siHcas are used ia the manufacture of separator sheets placed between cells ia automotive batteries. Their function is to provide a controlled path for the migration of conductive ions as a result of the porosity of the siHca particles. Additionally, both precipitated siHcas and aerogels are being developed for use ia low temperature iasulation, where the low thermal conductivity of the dry siHca powders makes them useful ia consumer products such as refrigerators (83). [Pg.481]

To further characterize the event it is first necessary to identify critical features of the initial configuration that will strongly influence the process. For powder compacts, the most obvious features are the morphological characteristics of the powders, their microstructures, and the porosity of the compact. For solid density samples, the grain structure, grain boundaries, defect level, impurities, and inclusions are critical features. [Pg.145]

A mixture of powdered poly(vinyl chloride), cyclohexanone as solvent, silica, and water is extruded and rolled in a calender into a profiled separator material. The solvent is extracted by hot water, which is evaporated in an oven, and a semiflexible, microporous sheet of very high porosity ( 70 percent) is formed [19]. Further developments up to the 75 percent porosity have been reported [85,86], but these materials suffer increasingly from brittleness. The high porosity results in excellent values for acid displacement and electrical resistance. For profiles, the usual vertical or diagonal ribs on the positive side, and as an option low ribs on the negative side, are available [86],... [Pg.275]

This technique has also been used in combination with nitrogen absorption to study the pore structure of some excipients, particularly MCC in both the powdered and compacted state. The intraparticulate porosity of MCC has been shown to be unaffected by tableting the interparticular pores, however, are gradually reduced in size [38]. Recently this method has been used to evaluate the internal structure of tablets prepared from microcapsules [150]. [Pg.333]

Button cells consist of cathode and anode cans (used as the terminals), powdered zinc anode, containing gelled electrolyte and the corrosion inhibitor, separator with electrolyte, thin (0.5 mm) carbon cathode with catalyst and PTFE, waterproof gas-permeable (teflon) layer and air distribution layer for the even air assess over the cathode surface. Parameters of battery depend on the air transfer rate, which is determined by quantity and diameters of air access holes or porosity of the gas-diffusion membrane. Air-zinc batteries at low rate (J=0,002-0,01C at the idle drain and J= 0,02-0,04C at the peak continuous current) have flat discharge curves (typical curve is shown by Figure 1). [Pg.164]

Powder X-ray diffraction (XRD) data were collected via a Siemens D5005 diffractometer with CuKa radiation (A. = 1.5418 A). Routine transmission electron microscopy (TEM) and Z-contrast microscopy were carried out using an HITACH HD-2000 scanning transmission electron microscope (STEM) operated at 200 kV. Nitrogen gas adsorption measurements (Micromeritics Gemini) were used to determine the surface area and porosity of the catalyst supports. Inductively coupled plasma (ICP) analysis was performed via an IRIS Intrepid II XSP spectrometer (Thermo Electron Corporation). [Pg.58]

Most practical electrodes are a complex composite of powders composed of particles of the active material, a conductive diluent (usually carbon or metal powder), and a polymer binder to hold the mix together and bond the mix to a conductive current collector. Typically, a composite battery electrode has 30% porosity with a complex surface extending throughout the volume of the porous electrode. This yields a much greater surface area for reaction than the geometric area and lowers polarization. The pores of the electrode structures are filled with electrolyte. [Pg.12]

Shimizu et al. has developed a low-cost MgO porous particle separator, which possessed both the high porosity ( 85%) of the BN felt and the high mechanical resistance of powder separators. The separator was prepared by loosely sintering fine MgO powder with Mg(NOs)2 as the binder. The particles thus formed showed excellent performance as separators in Li—Al/FeS r cells. [Pg.206]

This reaction involves ion diffusion in apatites and the reaction rate depends on the temperature, the size of the crystals and the porosity of the ceramics. At 900°C, the reaction is relatively fast and crystals of a few hundred microns can be totally exchanged in a few hours. The advantage of these processes is that they can be easily performed from existing HA powders or ceramics and... [Pg.306]


See other pages where Porosity, of powders is mentioned: [Pg.3]    [Pg.1077]    [Pg.362]    [Pg.174]    [Pg.251]    [Pg.3]    [Pg.1077]    [Pg.362]    [Pg.174]    [Pg.251]    [Pg.322]    [Pg.136]    [Pg.185]    [Pg.109]    [Pg.241]    [Pg.392]    [Pg.554]    [Pg.1821]    [Pg.1895]    [Pg.527]    [Pg.839]    [Pg.82]    [Pg.1547]    [Pg.305]    [Pg.725]    [Pg.83]    [Pg.221]    [Pg.255]    [Pg.272]    [Pg.87]    [Pg.98]    [Pg.618]    [Pg.10]    [Pg.73]    [Pg.107]    [Pg.108]    [Pg.307]    [Pg.165]    [Pg.167]   
See also in sourсe #XX -- [ Pg.143 , Pg.165 ]




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