Nitride powders

Exposure limits for siHcon carbide and powders of zirconium compounds (including zirconium dioxide) have been estabHshed by ACGIH. TLV—TWA s are 10 mg/m and 5 mg/m, respectively. OSHA guidelines for zirconium compounds call for a PEL of 5 mg/m. There are no exposure limits for siHcon nitride powder, but pmdent practice suggests a TLV—TWA of 0.1 mg/m. The soHd 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 estabHshed limits. Disposal should be in approved landfills the materials are inert and should pose no danger to the environment. 

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. 

M. Sheiif El-Eskandarany, K. Aoki, K. Suzuki, Formation of amorphous aluminum tantalum nitride powders by mechanical alloying, Appl. Phys. Lett. 60 (1992) 1562-1563. 

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 ... 

Cemented carbides and nitrides are manufactured by a powder metallurgy process using liquid phase sintering (Figure 2.1). The cobalt or nickel binder metal, in the form of fine powder, is blended with the carbide or nitride powders in ball mills or attritor mills lined with carbide sleeves. 

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. 

According to both the NFPA Guide and Bretherick (Refs 5 13), sulfuric acid causes explosions and/or fires when in intimate contact with a large number (over 70) of materials including acetic anhydride, acet and nitric acid, acrolein, alcohols, alcohols and hydrogen peroxide, anun hydroxide, aniline, bromine and metals, carbides, chlorates, cyclopentadiene, ethylene glycol, various hydrocarbons, hydrochloric acid, iron, mercuric nitride, powdered metals, perchlorates, picrates, pyridine, Na carbonate, steel, sucrose, vinyl acetate, and w. Illustrative... 

The gas phase processes and the diimide process offer a very fine, high purity powder with high sinterability. The main disadvantage of these powders are the poorer shaping behaviour and the higher price in comparison to direct nitrided powders. 

Reaction at phase boundaries liquid/liquid or liquid/gas or in the gas phase High purity powder, high [21, 197, 206] a content fine particle size, special treatment fine /i powders processing/ shaping more sensitive than for direct nitrided powders... 

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. 

M. Seth, S. G. Hatzikiriakos, and T. Clere, Gross Melt Fracture Elimination The Role of Surface Energy of Boron Nitride Powders, Polym. Eng. Sci., 42, 743-752 (2002). 

Baraton, M. I., Chen, X., and Gonsalves, K. E., FTIR study of nanostructured aluminum nitride powder surface determination of the acidic/basic sites by CO, CO2 and acetic acid adsorptions. Nanostructured Materials 8 (4), 435-445 (1997). 

Finally, remanence enhancement has been achieved by producing a coherent nanocrystalline structure in mechanically alloyed isotropic Sm7Fe93-nitride powders consisting of a-Fe and Sm2Fei7N3 [100],... 

Other Metal Nitrides Many other metal nitrides are used in ceramic formulations. These include AIN, TiN, VN, and BN. These metal nitride powders are produced by carbothermal reduction of the relevant metal oxide in a nitrogen-containing atmosphere or reaction of the relevant metal with a nitrogen-containing reducing atmosphere. These metal nitrides are used as abrasives and in hi -temperature wear applications. 

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). 

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