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Key engineering materials
Trans Tech Publications Ltd.
Key engineering materials

Trans Tech Publications Ltd.

半月刊

1013-9826

Key engineering materials/Journal Key engineering materials
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    Structure and Morphology of Sol-Gel Nanocrystalline TiO_2 Films Coated on Glass Substrates

    G.J. JiZ.M. ShiG. Zhao
    565-567页
    查看更多>>摘要：The Ce~(3+)-doped and undoped nanocrystalline TiO_2 films were prepared on glass substrates surface by sol-gel dip coating technique. The crystal structure and surface morphology of TiO_2 films were characterized by means of X-ray diffractometer (XRD), transmission electron microscopy (TEM) and atomic force microscope (AFM). The results indicated that the Ce~(3+)-doped TiO_2 films were solely composed of the anatase phase whereas in the undoped films small amount of the rutile phase of TiO_2 were present. The average crystallite size of the undoped TiO_2 films was about 30nm and was decreased with Ce~(3+)-doping in the TiO_2 films. Moreover, the grains distributed more uniform and the surface roughness was smaller in the Ce~(3+)-doped TiO_2 films than in the undoped one. The action mechanism of Ce~(3+)-doping inhibits the crystallization of the rutile phase and decreases the anatase granularity of TiO_2 films is associated with its physicochemical properties, as well as ionic diffusion and valance change of Ce~(3+) to Ce~(4+) in the sintering process.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Influence of Liquid Evaporation on the Components of SiC High Emissivity Coating

    J. YiX.D. HeC.L. Guan
    568-571页
    查看更多>>摘要：The process of Electron Beam-Physical Vapor Deposition (EB-PVD) preparing SiC coating with liquid evaporation was firstly discussed from a thermodynamic viewpoint. The results showed that the ratio of SiC in the as-deposited coating gradually increases and tends to reach a stable maximum of 0.73 with the evaporation temperature increase from 2500 K to 3400 K. To verify the thermodynamic analysis, amorphous SiC coating was deposited on Si substrate by EB-PVD at 3100 K. SiC concentration across the cross section of coating was calculated from the area of elements spectrum in X-ray photoelectron spectroscopy (XPS) depth profile analysis. The results showed that the average SiC concentration was about 0.7.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Phase Evolution and Microstructure Characteristics of Calcium Phosphate Based Glass Ceramics Prepared by Sol-gel Technique

    Xudong LiShu CaiWenjuan ZhangZhe Zhang...
    572-575页
    查看更多>>摘要：Calcium phosphate based glasses and glass-ceramics in the system of 54CaO-36P_2O_5-(10-x)Na_2O-xSrO were fabricated by sol-gel method. The structures of the glasses were investigated by Fourier transform infrared spectroscopy and X-ray diffraction has been used to determine the crystallize phase from glass matrix. The synthesized glass matrix shows a metaphosphate-like structure which consists of a chain and /or ring structure. After sintered at 1150℃, the crystalline phase β-Ca_2P_2O_7 and a small quantity of amorphous glass were observed clearly. With 1.0 mol% addition of SrO, the average grain size of β-Ca_2P_2O_7 was obviously decreased and some of them were covered with amorphous glass. When the content of strontium reached to 5.0 mol%, only a little crystalline phase β-Ca_2P_2O_7 can be found in the glass matrix, while the grain size has no significant change, compared with that of the sample containing 1.0 mol% SrO. The results showed that SrO addition to 54CaO-36P_2O_5-10Na_2O system can inhibit the crystallization of β-Ca_2P_2O_7 and decrease the grain size, and then adjust the degradation rate in body fluid by controlling the ratio of β-Ca_2P_2O_7 to amorphous glass.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Deposition of Bioactive Titania Layers on Non-Metallic Substrates Under Ambient Conditions Due to Hydrolysis of Titanium Oxysulfate Solution

    Fan XiaoRenguo Song
    576-578页
    查看更多>>摘要：Titania layer is deposited on polyethylene substrates when they are soaked in TiOSO_4/H_2O_2 solution and aged in hot water. The aging in hot water promoted the precipitation of anatase and rutile in the surface layer, indicating that cleavage and recombination of the Ti-O-Ti bond took place. The Ti-OH functional groups were rearranged and emerged accompanying the structure relaxation in the layer. Moreover, the aging in hot water enhanced crystalline of titania and then obtained well apatite-forming ability on the polyethylene substrates in SBF. This was accounted for by the removal of residual impurities due to TiOSO_4/H_2O_2 treatment. They had an anatase/rutile dual layer microstructure: the dense bottom layer predominantly consisted of rutile, while the upper layer consisted of loosely packed aggregation of anatase particles. The titania deposition was the results of compromise among two conflicting processes: 1) hydrolysis of titanium oxysulfate to yield either soluble titanol-complexes or titania, 2) dissolution of the titania under the presence of hydrogen peroxide to yield similar complexes or compounds. Various soaking periods were carried out to investigate the dissolution-deposition equilibrium in the solution. Anatase/rutile dual layers were thus deposited on titanium and polyethylene substrates when they were soaked in TiOSO_4/H_2O_2 solution and aged in hot water. The proper soaking time in the treating solution is the other key factors to control the formation of dense titania layers. The resulted titania layers have apatite-forming ability.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    UV-Enhanced Bioactivity of PS/TiO_2 Coating Prepared by Layer-by-Layer Self-Assembly Method

    Zhang ZhixianXiao FanGao Fei
    579-581页
    查看更多>>摘要：The TiO_2 nanopowder was prepared with TiOSO_4 as raw material at low temperature by hydrolysis method, and microspheres coated polyethylene and TiO_2 were then fabricated on titanium by layer-by-layer self-assembly technology. Using ultraviolet irradiation of titanium coating in distilled water for some time, titanium with enhanced bioactivity was achieved when immersed in simulated body fluid (SBF). The morphology, size and crystal shape before and after ultraviolet irradiation were characterized by scanning electron microcopy (SEM) and X-ray diffraction (XRD). UV irradiation of titanium results in the conversion of Ti~(4+) to Ti~(3+) and the generation of oxygen vacancies, which could react with the absorbed water to form basic Ti-OH groups. Compared with the coating non-UV irradiation, the UV-irradiated coatings do not present any obvious differences in morphology, surface roughness, grain size and phase component; however, they have more abundant basic Ti-OH groups thus the water contact angle decreases greatly so the surface become much more hydrophilic.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    The Color of Fe_2O_3 and Bi_2O_3 Pigmented Dental Zirconia Ceramic

    Ning WenYuanfu YiWeiwei ZhangBin Deng...
    582-585页
    查看更多>>摘要：The aim of this study was to explored the effects of Fe_2O_3 and Bi_2O_3 on the color properties of a 3Y-TZP zirconia ceramics for dental application. Pigmented dental ZrO_2 powders were prepared by mixing different concentration of Fe_2O_3 and Bi_2O_3, also in their combinations with 3Y-TZP powders. The mixture was compacted by isostastic pressure, then densely sintered. Color parameters were measured by Minolta cm~2600d spectrophotometer. XRD was used to exam the structure of colored 3Y-TZP. Experimental results showed that the hue of the materials shift from yellow-green to yellow-red with the increasing concentration of the Fe_2O_3 and Bi_2O_3 Combined use of Fe_2O_3 and Bi_2O_3 could further decrease the L~* value, which color scope was suitable for dental color matching. The XRD spectra showed only tetragonal phase was detected.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Effect of Ceria Additive on Microstructure and Properties of Laser-Cladded Bioceramic Coating

    Min ZhengDing FanJian-Bin ZhangXiu-Kun Li...
    586-589页
    查看更多>>摘要：The calcium phosphate bioceramic coating was fabricated on titanium alloy (Ti-6A1-4V) substrate by a 5kW continuous transverse flow CO_2 laser. Due to the peculiar role of rare earth oxide in laser cladding, the effect of ceria additive on the microstructure and properties of laser-cladded bioceramic coating was investigated by means of scanning electron microscope (SEM), X-ray diffraction (XRD), microhardness and corrosion resistance testing. The results indicate that the appearance of rare earth oxide ceria in the precursor powders has an impact on the microstructure and properties of the laser-cladded bioceramic coating. Calcium phosphate bioceramic such as hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) are synthesized on the top surface of laser-cladded specimens. And the addition of rare earth oxide ceria in pre-placed powders has an influence on the formation of calcium phosphate bioceramic phases. Furthermore, it reveals that the laser-cladded bioceramic coating of ceria additive in pre-placed powders has more favorable microhardness and corrosion resistance compared with the coating without rare earth oxide.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Preparation and Properties of Injectable Hydroxyapatite for Bone Repair Materials

    Hua LiuXiaofeng ChenChangren Zhou
    590-593页
    查看更多>>摘要：The aim of this study was to develop a novel injectable hydroxyapatite for bone repair materials. This study was based on the in situ setting properties of calcium phosphate cement (CPC), which properties were improved. The solid phase consisted of tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA). The liquid phase was the weak acidic solution of chitosan. The CPC powder was mixed with the chitosan solution to form a paste that could conform to the bone cavity even for irregularly shaped cavities. All the by-production disappeared by neutralization reaction. The CPC paste could then set in situ to form hydroxyapatite (HA) as the final product. The chemical process of CPC hydration was studied. The process was controlled by dissolution and precipitation chemical reaction. The kinetic model of hydration reaction was established. The effects of preparing conditions, such as powder to liquid ratio and particle size, on setting time and compressive strength were investigated systematically. The optimal condition was that the liquid phase contained 3% chitosan, 5% citric acid and 15% glucose (wt%), powder to liquid ratio was 0.8 g/ml, and powders were respectively ground for 40 hours.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Microstructure and Mechanical Property of Zirconia Nanocomposites

    Wenxu LiDezhen YuFuping Wang
    594-596页
    查看更多>>摘要：ZrO_2 nanocomposites were prepared and studied by microstructure observation and mechanical property detection. First, yttria stabilized zirconia (3Y-TZP) nanopowders were synthesized by sol-gel method. TEM photograph showed that the addition of yttria restrained the growth of the grain, but caused the agglomeration of the nanopowder. XRD analysis showed that the amount of yttria influenced the phase character of the materials, and the monoclinic zirconia changed gradually into tetragonal and cubic phase with increasing yttria content. Second, the micro-size 3Y-TZP materials was mixed with the former prepared nano-size particles and pressed by cold isostatic pressing, and then sintered at 1300℃ to prepare ZrO_2 ceramic nanocomposites. The results of microstructure analysis showed that the amount of nano-size powder affected the fracture mode of nanocomposites, thus changed the fracture toughness. The mechanical testing results indicated that both the flexural strength and the hardness decreased with increasing nano-size powder, whereas fracture toughness increased and decreased subsequently. ZrO_2 ceramic nanocomposites with 20% nano-size powder would be a promising kind of dental restoration material due to its low hardness, high fracture toughness and moderate flexural strength.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Controlled Growth and Self-Assembly of CaCO_3 Superstructures Between the Organic-Water Interfaces

    Liang XiaohongXiang JunhuiZhang FushiXing Li...
    597-600页
    查看更多>>摘要：In this paper, the crystallization behavior of calcium carbonate between the organic-water interfaces using a slow gas-diffusion procedure is studied. The organic-water interfaces can control the crystallization of calcium carbonate to form a flower-shaped superstructure. The precipitates of calcium carbonate were identified by X-ray diffraction (XRD) and scanning electron microscopy (SEM). A possible mechanism about the self-assembly process of CaCO_3 crystals has been analyzed. It is found that the morphology of CaCO_3 superstructure depends on the properties of organic solvent. This paper also presents the influence of surfactant monolayer, between the biphase interfaces, on the CaCO_3 superstructure. This study suggests that it is possible to control morphogenesis of calcium carbonate by a combination of a surfactant monolayer with the organic-water interfaces.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd