Rise Of Sintering Temperature Research Articles

The sintering process of a porcelain body has been studied from a view point of rate-process by following the change of α difined as under:α=ρa-ρ0/ρt-ρ0where ρa: apparent density of sintered bodyρ0: apparent density before sinteringρt: true density after sinteringIt has been found that the following velocity equation is generally valid.dα/dt=K(1-α)nor by putting p=100α, dp/dt=K(T)(100-p/100)n(T)By determining graphically the following two values ψ and φ, the order of the reaction (n) and the reaction constant (K) of the sintering process can be expressed as follows:n=2/ψ-φK=exp{n(2-φ)}=exp{2(2-φ)/ψ-φ}whereφ=log(100-p) when logdp/dt=0 or dp/dt=1andψ=log(100-p) when logdp/dt=2 or dp/dt=100To the contrary of the conclusion given by many other researchers that n is a constant, we found by sintering samples at several constant temperatures that n as well as φ are dependent on temperature as follows:n(T)=A/T-B=6.35/T⋅104-36φ(T)=C/T-D=0.921/T⋅104-4.62thereforelogK(T)=(A/T-B)(2+D-C/T)=-5.85/T2⋅108+75.2/T⋅104-238We found further that the sintering proceeded in forming a zonal structure. The growth of vitrified outer layer with the rise of sintering temperature or the increase of sintering time was traced by the change in its thickness or the area of inner part which remained porous and therefore easily stained with graphite or polishing powder such as chrome oxide, but such an observation satisfied not for the explanation of the process.The development of hardness within the samples was successfully measured on its section by means of the Rockwell Tester “Superficial” 15 N and 15 T. The relation between the hardness in inner part (Hs) and the mean apparent density (ρa) is given by:ρa=8.6×10-3Hs+1.58

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