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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 124-126 (June 2007), p. 807-810 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Highly sinterable lithium titanate (Li2TiO3) powder was fabricated by an organic-inorganicsolution route. Liquid-type ethylene glycol (EG) was used as an organic carrier for the metal cations.Titanium isopropoxide and lithium nitrate were dissolved in the liquid-type ethylene glycol withoutany precipitation. The dried precursor gel showed crystalline form at 300 °C and carbon-free Li2TiO3was observed above 400 °C. The primary particle size of the carbon-free Li2TiO3 was about 100 nm,and the structure of the crystallized powder was porous and agglomerated. The porous powder wasball-milled and easily ground to fine particles. The powder compact was densified to 93% theoreticaldensity (TD) at relatively low sintering temperature of 1100 °C for 2 h. The densifed Li2TiO3 showeda small grain size of 1.2 μm. As well, the grain size was notably increased at 1200 °C and above. Afterthe over grain growth, further densification was no more observed
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 124-126 (June 2007), p. 1293-1296 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: A hydrothermal method has been used to produce nanoparticles of 3 mol% yttria-stabilizedtetragonal zirconia (3Y-TZP) with high fracture toughness. The effects of reaction temperature andpH on crystallite size and sintered density, and the influence of Nb2O5 addition into 3Y-TZP ontoughness have been investigated. The particle size increased with increasing the processingparameters and the influence of temperature was more significant than pH. The density of nanosized3Y-TZP increased with increasing pH up to 9 and then decreased abruptly with further increase. Thedensity increased slightly with the reaction temperature up to 140°C and then changed little withincreasing temperature. The toughness increased in proportional to the Nb2O5 content. After sinteringfor 1 h at 1270°C, the highest relative density of 98% was obtained from nanoparticles of about 17nm, prepared at 200°C and pH 9, and the toughness of 3Y-TZP was increased from 2.5 to 8.3MPam1/2 by addition of 1.2 mol% Nb2O5
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 330-332 (Feb. 2007), p. 1377-1380 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This study was designed to evaluate mechanical properties and the marginal fitness ofglass infiltrated alumina core fabricated from aqueous alumina tape. Utilizing the automatic Dr.Blade model (DP-150 of Japan JinChungjungGi manufacturer) fabricated the slurry into 0.5 ㎜thickness aqueous-based alumina tape. The coefficient of thermal expansion and biaxial flexuralstrength of alumina composite produced from alumina tape were investigated. Three upper centralresin incisors were prepared with 90o, 110o, 135o shoulder margin for all-ceramic crown. Individualtooth model’s impressions were taken 15times each to make epoxy resin die. Cores were made ofalumina tape to each and every dies. Crown setting was done on the epoxy resin dies. Thespecimens were evaluated for measuring for marginal gaps of glass infiltrated alumina corefabricated from aqueous alumina tapes under 180 magnifications with Kan Scope(SometechVision, Korea) was done. The retained measurements were analyzed with Turkey’s StudentizedRange Test for marginal fitness of each specimen. Coefficient of thermal expansion of alumina tapewas 7.5x10-6/℃, and biaxial flexural strength was observed to be 498±32MPa. The marginal fits ofalumina cores made of alumina tapes showed the least marginal gap of 41.5 ㎛ in the 110o shouldermargin, and increasingly with 135o, 90o shoulder margin. Marginal fitness should be better in angleslarger than 90o
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 342-343 (July 2007), p. 877-880 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Nanosized hydroxyapatite(HAp) was synthesized hydrothermally and influence ofprocessing parameters, such as reaction temperature and time, pH, and Ca/P ratio, on the phasestability of HAp was evaluated after pressureless sintering at 1250°C in air. The highest stabilitywas achieved from the powder obtained at a processing condition for the lowest solubility of Ca2+,which corresponds to temperature close to 200°C, time 〈4h, pH〉9.0, and Ca/P = 1.67. The stabilityof nanosized HAp in HAp/3Y-TZP composites was slightly inferior to commercial one, but theinvolvement of hydrothermally synthesized HAp improved sintered density of the composites andstability of t-ZrO2 phase in the composites
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 342-343 (July 2007), p. 557-560 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The sliding wear of four different compositions of novel low temperaturedegradation-free zirconia/alumina (LTD-free Z/A) composites were characterized in a ceramicceramicpoint contact pair. The wear tests were performed by a pin-on-disk type wear tester in alinear reciprocal sliding motion with a point contact in both dry and bovine serum lubricatedconditions at room temperature. For the dry sliding wear tests, AZ-2 (20 vol% (Y,Nb,Ce)-TZP/80 vol% Al2O3) showed the best wear resistance among four kinds of LTD-free Z/A composites.For the bovine serum lubricated sliding wear tests, wear was too little to be measured for all kindsof Z/A composites. These novel LTD-free Z/A composites having excellent wear resistancedemonstrated a potential as the alternative materials for the ceramic- ceramic contact pairs offemoral head and acetabular liner in total hip replacement
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 330-332 (Feb. 2007), p. 23-26 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The aim of this paper was the HA and β-TCP powers were synthesized by a new wetchemicalmethod using eggshell and phosphoric acid. The biocompatibility of synthesized naturalHA, HA/β-TCP(50:50) and β-TCP derived from eggshell was compared with those of ascommercial chemical powder with mesenchymal stem cells derived from human bone marrow.Development of crystalline phases of the mixtures was studied as functions of mixing ratio andtemperature using X-ray diffractometer. The morphological characteristics of the calcinedeggshell and synthesized powders were examined by scaning electron microscopy. The in-vitrocytotoxicity and cell attachment of sintered disks were examined using human bone marrowderivedmultipotent stem cells(hBMSCs). Cell response was characterized by MTT assay ,Alkaline phosphatase stain and RT-PCR analysis. Pure HA was synthesized in the mixing ratio of1:1.1 wt% at 900℃ for 1h. the crystallization of HA was started at 800℃ in the 1:1.1 mixingratio, ant the HA phase was continued up to the high temperatures. In the ratio of 1:1.3 and1:1.5 wt%, β-TCP was effectively synthesized at 900℃. In the 1:1.5 ratio, β-TCP phase wasdetected at 700℃, and complete crystallized β-TCP was observed above 900℃. At the highertemperature than 1000℃, the β-TCP was gradually decreased and α-TCP was observed. The HAand β-TCP disk does not exert cytotoxic effect on the hBMSCs undergoing osteoblasticdifferentiation. In addition, the hBMSCs are adhered on the surface of synthesized natural HAand β-TCP disk as successfully as on the culture plate or as commercial chemical HA and β-TCPdisk. The hBMSCs adhered on either synthesized natural HA, β-TCP or as commercial chemicalHA, β-TCP disk displays undistinguishable actin arrangement and cellular phenotypes, indicatingthat synthesized natural HA, β-TCP does not disrupt normal cellular responses. Analysis ofdifferentiation of the hBMSCs cultured on culture plate, synthesized natural HA, β-TCP and ascommercial chemichal HA, β-TCP disk shows that three matrices are able to support osteoblasticdifferentiation of the hBMSCs as accessed by alkaline phosphatase staining
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 330-332 (Feb. 2007), p. 147-150 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The effect of hydrothermal reaction temperature and pH on crystallite size, phase stability,and sintered density of hydroxyapatite (HAp) has been investigated. The crystallite size increasedwith the increase in temperature but was not significantly affected by pH. The decomposition ofHAp into tricalcium phosphate was observed at 1250°C and the extent of decomposition decreasedwith increase in pH. The influence of temperature and pH on the crystallite size and thedecomposition was related to the decrease in solubility of Ca2+. The phase stability of HAp,prepared hydrothermally, in HAp/zirconia composites was higher than that of commercial HAp dueto its high sintered density
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 330-332 (Feb. 2007), p. 1421-1424 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Yttria and iron co-doped tetragonal zirconia polycrystals ((Y, Fe)-TZPs) were investigatedto evaluate the feasibility for the ceramic bracket application. Presintered the (Y,Fe)-TZPs bracketswere machined, abraded and coated with granule spray containing 10~50 wt% of flux. Finally, thebase-coated brackets were sintered. Roughness of the coated surface was decreased to 13 um and 10um when the flux content was 30 wt% and 50 wt%, respectively. It may be due to the fusion and thecollapse of the granules as a result of the high amount of flux. Better adhesion to the base surface ofthe brackets and irregular shape were observed by raising the amount of flux in the slurries. Wettingangle of ethylene glycol droplet on the (Y,Fe)-TZP bare surface was determined to be 41.85°,however, the angle became 0° after the granule spraying treatments. The (Y,Fe)-TZP bracketsexhibited uniform embossed base and good wetting. The newly developed base-coated bracket couldbe highly applicable to enhance retention and to reduce adhesive resin remnant during the bracketdebonding
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 47-50 (June 2008), p. 999-1002 
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Bond coatings, CoNiCrAlY, are prepared on Inconel 738 substrate by vacuum plasmaspray (VPS). Mechanical properties of VPSed CoNiCrAlY coatings are investigated via Taguchimethod and L18(21×37)[removed info]orthogonal arrays to determine the optimal setting and the relationship ofexperimental variables. Seven parameters were considered as follows: (A) arc current; (B) primarygas flow rate; (C) secondary gas flow rate; (D) stand-off distance; (E) working pressure; (F) carriergas flow rate (Ar); and (G) powder feeding rate.[removed info]The effect of carrier gas flow rate on the porosity isdetermined to be the highest among the parameters investigated. Higher microhardness values areobserved for the VPSed coatings as compared to the coatings prepared by conventional highvelocity oxygen fuel probably due to low amount of the porosity
    Type of Medium: Electronic Resource
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