Sintering of powders

Conta.ctMa.teria.ls, Electrical contact materials are produced by either slicing rod made from metal powder, infiltrating a porous refractory skeleton, or compaction and sintering of powders (see Electrical CONNECTORS) (51—53). 

Bulk ceramics are produced conventionally by the sintering of powders. The strength, toughness, thermal stability, and dielectric properties of the fired ceramic depend strongly on the size and uniformity of the precursor powder and on the chemical properties of the powder smface. 

Sintering of powdered metals such as aluminum, beryllium, tungsten, and zinc as well as ceramics under pressure is widely practiced as a shaping process, but that is different from the sintering process described here. 

Ultimately, a knowledge of kinetics is valuable because it leads to prediction of the rates of materials processes of practical importance. Analyses of the kinetics of such processes are included here as an alternative to a purely theoretical approach. Some examples of these processes with well-developed kinetic models are the rates of diffusion of a chemical species through a material, conduction of heat during casting, grain growth, vapor deposition, sintering of powders, solidification, and diffusional creep. 

Similar reactions are known to take place in sintering of powder mixtures consisting of an intermetallic compound and an elementary substance.393 394 For example, I.F. Martynova et al394 found the Fe2Ti and TiNi3 layers to grow at the interface between FeTi and nickel (Fig. 5.25). 

Descriptions of shock compression and very high pressure sintering detonation methods and shock wave sintering of powders of sphaleritic BN are available. 

Fig. 9.15 Typical temperature profile of a continuous furnace for the sintering of powder metallurgical parts [B.25].

Experiments were started with the metal powder in order to reveal principal possibilities of laser sintering of powder layers deposited onto a substrate [2], In these experiments, the layer of Ni powder (with particle size about 0.5 pm) was deposited onto the surface of Ni substrate manufactured by traditional powder metallurgy (with particle size about 5 pm) and subjected to sintering by CW-Nd YAG laser (X = 1.06 pm). Layer thickness was about 2 pm. The joining of powder layer with the substrate was provided during sintering. The graded porous structure was formed on the surface as it is shown in Fig. 1 (the size of pores is about 2 pm for the sintered layer and 6 pm for the substrate). 

Sol-gel process is proven to be an attractive fabrication method of multi-component oxide ceramics. In addition to the achieved homogeneity and purity of the products, the sol-gel method also enables a lower phase-formation and sintering temperature in comparison to the conventional sintering of powder With good size scaling possibility, colloidal sol-gel materials are suitable for depositing layers on macroporous substrates to serve as support of polymeric sol-gel derived layers preventing infiltration of the sol. 

Nd2Fei4B permanent magnets can be prepared by induction melting, followed by liquid-phase sintering of powder, in a similar way to SmCoj materials. On cooling the melt, the first solid formed is y-Fe. To prevent... 

Ono, Kawamura, and Fujimura in 1964 described the sequence of reactions that occur during sintering of powders of calcite, clay, siliceous rock, and copper slag (an iron bearing glass) through chemistry, XRD, and transmitted light microscopy. 

Bouvard D, Carry C, Chaix JM, Martin CM, Missiaen JM, Perier-Camby L et al (2001) Compression and sintering of powder mixtures experiments and modelling. Adv Eng Mater... 

Modification of the thermal cycle provides opportunities to improve the sinterability of powder compacts. Typical examples are fast firing and heating-rate-controlled sintering. 

In contrast to DTA and thermogravimetry, diffusion structural analysis makes it possible to investigate processes that are not accompanied by thermal effects or mass changes. DSA permits, to examine consolidation, annealing of defects and sintering of powdered or geleous samples, which would be difficult to examine by means of dilatometry. 

With the exception of UHMWPE, PE can be melt processed. UHMWPE has a high melting point and, like PTFE, is formed by pressing and sintering of powders. 

R. Roy D. Agrawal J. Cheng S. Gedevanishvili. Full Sintering of Powdered-Metal Bodies in a Microwave Field. Nature. 399, 668-670, 1999. 

HHG Jellinek, Ibrahim SH. Sintering of powdered iee. Journal of Colloid and Interfaee Seienee 25 245-254, 1967. 

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