Silicon nitride powders

The high temperature tx-fi transformation of shock-activated silicon nitride powder has been investigated at temperatures of 1600 and 1700°C [84B01]. 

Schwier, G., On the Preparation of Fine Silicon Nitride Powders, inProgress in Nitrogen Ceramics, (F. Riley, ed.), pp. 156-157, MartinusNijhoff, Boston, MA (1983)... 

Bauer,R., Smulders,R, Geus,E., vanderPut, J., and Schoomman, J., Laser Vapor Phase Synthesis of Submicron Silicon and Silicon Nitride Powders from Halogenated Silanes, Ceram. Eng. Sci. Proc., 9(7-8) 949-956(1988)... 

In the area of preceramic polysilazanes, sufficient progress has been made to produce precursors for silicon nitride fibers, coatings and as binders for silicon nitride powder. However, particular problems still remain to be solved particularly with regard to reducing impurity levels and improving densification during pyrolysis. 

Using silicon nitride powder in a polypropylene/microcrystalline wax/stearic acid binder formulation, the effect of filler volume fraction (V) (over the range 50 to 70%) on relative viscosity (rjj.) was predicted from Eq. 5 ... 

Silicon nitride powder can be made by the reaction of silicon tetrachloride vapor with gaseous ammonia. The by-product is gaseous hydrogen chloride. Write a balanced equation for the reaction. 

Herrmann M, Schulz I, Hintermayer J (1995) Materials From Low Cost Silicon Nitride Powders In Galassi C (ed) Proc 4th EcerS Conf, Riccione, Gruppo Editoriale Faenza Editrice, p 211... 

Cochran GA, Conner CL, Eismann GA, Weimer AW, Carroll DF, Dunmead SD, Hwang CJ (1994) The Synthesis of a High Quality, Low Cost Silicon Nitride Powder by the Carbothermal Reduction of Silica. In Hoffmann MJ, Becher PF, Petzow G (eds) Silicon Nitride 93. Key Eng Mater 89-91. Trans Tech Publications Ltd, Switzerland, p 3... 

Arakawa T (1987) State of the art of silicon nitride powders obtained by thermal decomposition of Si(NH)2 and the injection molding thereof. In Somiya S, Mitomo M, Yoshimura M (eds) Silicon Nitride I. Elsevier, New York, p 81... 

Deeley, G., Herbert, J. (1961), Dense Silicon Nitride , Powder Metall., 8, 145. 

Exposure limits for silicon carbide and powders of zirconium compounds (including zirconium dioxide) have been established by ACGIH. TLV —TWA s are 10 mg/m3 and 5 mg/m3, respectively. OSHA guidelines for zirconium compounds call for a PEL of 5 liig/m3. There are no exposure limits for silicon nitride powder, but prudent practice suggests a TLV—TWA of 0.1 mg/m3. The solid ceramics present no apparent health hazard. In machining such ceramics, however, care should be taken to prevent inhalation of respirable particles in amounts in excess of established limits. Disposal should be in approved landfills the materials are inert and should pose no danger to the environment. 

FIGURE 1.22 Micrograph of silicon nitride powder, SN-EIO, from UBE Industries, ltd. [16] with sedigraph size distributions for various grades of this powder with 3 mV gm (EOS), 5 mVgm (E ), and 10 mVgm (ElO). 

The industrial ceramics produced by conventional sintering of 8-phase Si3N4 powders synthesized by SHS (Petrovskii et al, 1981) can be used as high-temperature articles with attractive dielectric properties (tan6=4.4 10 at/= 10 Hz, and dielectric strength, Ea=9.2 kV/mm). Also, silicon nitride powders with a relatively high a-phase content ( 80%) have been used for the production of advanced structural ceramics with good mechanical properties ([Pg.109]

NIST produce two standard powders for gravity sedimentation. SRM 659 is a silicon nitride powder that has equiaxed particles in the size range 0.2 to 10 pm. SRM 1978 is a zirconium oxide powder of granular irregulary shaped particles in the size range 0.33 pm to 2.19 pm. 

Within the past decade, research on the development of new Si3N4 compositions has greatly intensified. These efforts have resulted in a proliferation of new synthetic procedures. Preparative routes have been developed with increasing emphasis on the control of purity and physical properties. Silicon nitride powders, fibers, coatings, and composites each have their own characteristic requirements, which can dictate the choice of a particular route (i). 

To produce silicon nitride powder, silicon can be nitridated at elevated temperatures in an atmosphere of nitrogen or ammonia ... 

This route is useful for only silicon nitride powder and can not be used for silicon nitride fibers or coatings (2-3). 

Silicon nitride powders have also been prepared from more readily available starting materials. The preparations involve the reduction of silica by carbon in the presence of nitrogen (2) or of silicic acid reacting with ammonia (4-7) ... 

Figure 11.9 shows a stability diagram for silicon nitride powder in water. 

Metallurgical grade silicon is marketed in a coarsely crushed form or as a finely ground powder in different particle sizes. Powders with increased purity due to acid washing, particularly for the removal of metallic impurities, are specialty products. They are utilized, for example, in the manufacture of silicon nitride powder or reaction-bonded silicon nitride ceramic components and are therefore the starting materials for engineering ceramic specialties. 

The Effect of Silicon Nitride Powders on Grain Morphology... 

Bergstrom, L. and Bostedt, E.. Surface chemistry of silicon nitride powders Electrokinetic behaviour and ESCA studies. Colloids Surf.. 49, 183, 1990. 

Zhmud, B.V., Sonnefeld, J., and Bergstrom, L., Influence of chemical pretreatment on the surface properties of silicon nitride powder, Colloids Surf. A, 158, 327, 1999. Ludwig, Ch. and Schindler, P.W., Surface complexation on TiOj. I. Adsorption of H+ and t lP ions onto TiO, (anatase), 7. Colloid Interf. Sci., 169, 284,1995. 

Bergstrom, L. et al.. The effect of wet and dry milling on the surface properties of silicon nitride powders, in Ceramics Today—Tomorrow s Ceramics, Vincenzini, P., ed., Elsevier, New York, 1991, p. 1005. 

Hackley, V.A., Wang, P.S., and Malghan, S.G., Effects of Soxhlet extraction on the surface oxide layer of silicon nitride powders. Mater. Chem. Phys., 36, 112, 1993. 

Huang, Y. et al., Water-based gelcasting of surface-coated silicon nitride powder, J. Am. Ceram. Soc., 84, 701,2001. 

Milonjic, S.K., Cerovic, L., and Uskokovic, D.P., Sol-gel synthesis of silicon carbide and silicon nitride powders and their surface properties, in Materials Science of Carbides, Gogotsi, Y.G. and Andrievski, R.A., eds., Kluwer, Dordrecht, 1999, p. 343. 

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