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Dry and water-saturated sintered fiber metal wick thermal conductivity, obtaining semiempirical correlations for solid and fluid phases and void fraction
Sintered diamond compacts using cobalt as binder
High temperature friction and wear characteristics of self lubricating composite disks of sintered tungsten, molybdenum, and cobalt molybdenum, impregnated with fluoride eutectic
Monolayer submicron self supporting particle film samples preparation for sintering by transmission electron microscopy
Method is developed for sintering diamond powder which uses metallic cobalt as binder. Present samples show maximum microhardness of over 3000 kg/sq mm on Knoop scale. Material may be used as hard surface coating or may compete with cubic boron nitride as abrasive grain.
Experiments seem to indicate that at the low pressures characteristic of an ejecta blanket, sintering or sintering/devitrification could have lithified boulder 1 matrix materials and produced the textural types observed in 72255 and 72275. This very preliminary conclusion is consistent with other observations that granitic clasts have undergone a slight degree of partial melting (and have therefore experienced temperatures on the order of 1000 C). It is concluded that maskelynite in the boulder is completely devitrified.
Essentially pore-free Sialon bodies were obtained by pressure sintering for three blends (mol ratios of 4:1, 2:3, and 3:2) of Si3N4 and Al2O3 powders under the conditions of 27.6 MN/sq m and a temperature of 1700 C for 2 h. These dense bodies consist mainly of a Sialon solid solution with a minor amount of a particular second phase. The higher the Al2O3 content (20 to 60 mol% range) in Sialon, the higher the densification rate. Fully dense bodies can be obtained at temperatures as low as 1500 C at 27.6 MN/sq m for 2 h with no second phase detectable by X-ray diffraction. A 100% dense body can be obtained by heating at 1700 C at 27.6 MN/sq m without a holding time.
Argon adsorption measurements are presented over a wide range of temperature and coverage on a series of three progressively sintered SnO2 surfaces. These data are analyzed by mercury porosimetry, the BET method, the CAEDMON distribution analysis, and the Singleton-Halsey equation. Isosteric heats are computed, and the high-temperature virial expansion of the data presented. The advantages and disadvantages of each method are discussed with particular attention to the ability of physical adsorption to discriminate among surfaces beyond the measurement of surface area.
Furnace design and filler material allow uniform sintered nickel plaque to be manufactured reliably.
Grain boundaries in silicon with a predetermined orientation were prepared by the sintering of two single crystals. A combination of standard transmission electron microscopy and lattice imaging was used to investigate the structure of the boundaries produced. Low angle grain boundaries on (100) and (111) planes, and twin boundaries on (111) planes are discussed in detail.
The preliminary design and a demonstration of the feasibility of fabricating submodules of an automotive Stirling engine recuperator for waste heat recovery at 370 C are described. Sinterable silicon nitride (Sialon) tubing and plates were fabricated by extrusion and hydrostatic pressing, respectively, suitable for demonstrating a potential method of constructing ceramic recuperator-type heat exchangers. These components were fired in nitrogen atmosphere to 1800 C without significant scale formation so that they can be used in the as-fired condition. A refractory glass composition (Al2O3 x 4.5 CaO.MgO x 11SiO2) was used to join and seal component parts by a brazing technique which formed strong recuperator submodules capable of withstanding repeated thermal cycling to 1370 C. The corrosion resistance of these materials to Na2SO4 + NaCl carbon mixtures was also assessed in atmospheres of air, hydrogen and CO2-N2-H2O mixtures at both 870 C and 1370 C for times to 1000 hours. No significant reaction was observed under any of these test conditions.
The microstructure of reaction sintered silicon nitride (RSSN) was changed over a wide range by varying the grain density, grain size of the silicon starting powder, nitriding conditions, and by introducing artificial pores. The influence of single microstructural parameters on mechanical properties like room temperature strength, creep behavior, and resistance to thermal shock was investigated. The essential factors influencing these properties were found to be total porosity, pore size distribution, and the fractions of alpha and beta Si3N4. In view of high temperature engineering applications of RSSN, potentials for optimizing the material's properties by controlled processing are discussed.
Si3N4-base ceramics were made from milled Si3N4 containing 11.1 wt% SiO2 and oxide additives by pressureless sintering at 1760 C. The four-point-average moduli of rupture were 460, 515, and 515 MPa at room temperature and 270, 256, and 227 MPa at 1400 C for compositions with 3.67, 7.22, and 14.0 wt% Y2O3, respectively. The oxidation resistance of these compositions decreased with increasing Y2O3 in the 600 to 1400 C range, and no surface oxide cracking or spalling was noted. Partial substitution of Al2O3 for Y2O3 reduced both strength and oxidation resistance.
The sinterability of alpha Si3N4 with 0-5.07 equivalent per cent of CeO2, MgO, or Y2O3 has been studied in the temperature range 1650-1820 C by density measurements and X-ray diffraction analysis. Maximum densities were obtained in the range 1765-1820 C and were 99.6% of theoretical with 2.5% CeO2; 98.5% of theoretical with 1.24 to 1.87% MgO, and 99.2% of theoretical with 2.5% Y2O3. Densities 94% or more of theoretical value were obtained with as little as 0.62 equivalent per cent additive.
Fabrication of a sintered alpha silicon carbide turbine blade by injection molding is described. An extensive process variation matrix was carried out to define the optimum fabrication conditions. Variation of molding parameters had a significant impact on yield. Turbine blades were produced in a reasonable yield which met a rigid quality and dimensional specification. Application of injection molding technology to more complex components such as integral rotors is also described.
In order to study strength characteristics at room temperature and the strength evaluating method of ceramic materials, the following tests were conducted on pressureless sintered silicon nitride specimens: bending tests, the three tensile tests of rectangular plates, holed plates, and notched plates, and spin tests of centrally holed disks. The relationship between the mean strength of specimens and the effective volume of specimens are examined using Weibull's theory. The effect of surface grinding on the strength of specimens is discussed.
A description is given of treating silicon carbide sinters by heating in nitrogen. A detailed explanation of the invention is presented. Two procedures to be followed in the invention are described.
The most suitable SiC mass for injection molding of SiC articles (for subsequent pressureless sintering) consisted of beta SiC 84, a wax mixture 8, and polyethylene or polystyrene 8 parts. The most effective method for adding the binders was by dissolving them in a solvent and subsequent evaporation. The sequence of component addition was significant, and all parameters were optimized together rather than individually.