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S.M. Kwa,S. Ramesh,L.T. Bang,Y.H. Wong,W.J. Kelvin Chew,C.Y. Tan,J. Purbolaksono,H. Misran,W.D. Teng 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.2
The sintering of yttria-tetragonal zirconia polycrystals (Y-TZP) is commonly carried at a predefined temperature using a long holding time of 2 hours. This often has resulted in grain coarsening which affects the mechanical properties of the sintered body and low temperature degradation (LTD) behaviour of the ceramic when exposed to moist environment. In this research, the effect of using a short holding time of 1 min. during sintering coupled with small amounts (0.5 and 1 wt%) of manganese oxide, MnO2 as dopant on the mechanical properties and LTD behaviour of 3 mol% Y-TZP were investigated. The results showed that the mechanical properties improved significantly with the addition of 0.5 wt% MnO2 for the 1-min. and 12-min. holding time samples when compared to 2 hours holding time sintered at the same temperature of 1350 ℃. Nevertheless, regardless of the holding time employed, the 1 wt% MnO2 addition was not effective in improving the mechanical properties and ageing resistance of Y-TZP ceramic.
C.H. Ting,S. Ramesh,C.Y. Tan,N.I. Zainal Abidin,W.D. Teng,I. Urriés,L.T. Bang 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.8
In the present work, the effect of low temperature sintering, focusing on varying the sintering holding times on the mechanicalproperties, microstructure and low temperature degradation behavior of undoped and MnO2-doped Y-TZP ceramics wereinvestigated. Green samples were sintered at temperatures ranging from 1100 to 1250 oC at varying holding times rangingfrom 12 min. to 480 min. The sintered bodies were characterized in terms of bulk density, Vickers hardness, fracturetoughness, phase stability and grain size. The results indicated that the relative density of above 95%, Vickers hardness of 14GPa and fracture toughness of 5 MPam1/2 were obtained when sintered at lower sintering temperature (below 1250 oC) andlonger sintering times for MnO2-doped Y-TZP samples. Grain growth was marginal and the average grain size of all samplesranged between 0.14 and 0.28 µm. The results indicated that the grain growth kinetics was influenced mainly by the sinteringtemperature and not by the sintering holding time. The addition of MnO2 was found to be beneficial in enhancing densificationand mechanical properties of Y-TZP particularly at low sintering temperature of 1100 oC and low holding time of 12 min. Thelow-temperature degradation experiment conducted in superheated steam indicated that all the samples did not transformedto the monoclinic symmetry, attributed mainly to the lower grain size sintered at relatively low sintering temperatures
The Expression of Genes Related to Egg Production in the Liver of Taiwan Country Chickens
Ding, S.T.,Ko, Y.H.,Ou, B.R.,Wang, P.H.,Chen, C.L.,Huang, M.C.,Lee, Y.P.,Lin, E.C.,Chen, C.F.,Lin, H.W.,Cheng, Winston Teng Kuei Asian Australasian Association of Animal Productio 2008 Animal Bioscience Vol.21 No.1
The purpose of this study was to detect expression of genes related to egg production in Taiwan Country chickens by suppression subtractive hybridization. Liver samples of mRNA extraction from two Taiwan Country chicken strains (L2 and B), originated from the same population but with very distinct egg production rates after long-term selection for egg and meat production respectively. Two-way subtraction was performed. The hepatic cDNA from the low egg production chickens (B) was subtracted from the hepatic cDNA from the high egg production strain (L2). The reversed subtraction (L2 from B) was also performed. The resulting differentially expressed gene fragments were cloned and sequenced. We sequenced 288 clones from the forward subtraction and 96 clones from the reverse subtraction. These genes were subjected to further screening to confirm the differential expression between the two genetic breeds of chickens. The apolipoprotein B (apoB) was expressed to a greater extent in the liver of the L2 than in the B line chickens. The 5-aminoimidazole- 4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (PURH) was expressed to a greater extent in the liver of the B than in the L2 strain chickens. We demonstrated that both apoB and PURH were more highly expressed in the liver than that in other tissues (muscle, ovary, and oviduct) in laying Taiwan Country chickens. Taken together, these data suggest that after the selection for egg production, expression of apoB and PURH genes were also changed. Whether the changed expression of these genes is directly related to egg production is not known, but these two genes may be useful markers for egg laying performance in Taiwan Country chickens.