Chlorapatite Glass-Ceramics

Apatite glass-ceramics are attractive for medical and dental applications, and fluorapatite glass-ceramics based on aluminosilicate glasses have been extensively studied. This study is the first study of chlorapatite glass-ceramics based on calcium chloride-containing Q² bioactive phosphosilicate glasses. The crystallization behavior of oxychloride glasses is examined and compared with mixed oxychloride/fluoride and oxyfluoride glasses. The glass transition temperature decreased for all three series with increasing halogen content. On increasing the halogen content, there was an increasing tendency of the glasses to crystallize. The halogen-free glass surface crystallized to pseudowollastonite and an apatite. On incorporating a halide, the glasses exhibited largely bulk crystallization to a haloapatite. In the case of chloride, the glasses crystallized to chlorapatite. This is the first time to our knowledge that chlorapatite has been shown to crystallize from a glass. Chlorapatite is very attractive for medical applications because it converts to hydroxyapatite the mineral phase of tooth and bone on immersion in water.     

High-Strength Mica-Containing Glass-Ceramics

Glass-ceramics containing barium–mica in the system Ba_0.5 Mg₃ (Si₃AIO₁₀)F₂–2MgO · 2Al₂O₃· 5SiO₂–Ca₃ (PO₄)₂ are two to three times stronger than conventional mica-containing glass-ceramics. Moreover, the barium-mica glass-ceramics are easier to machine, as confirmed by a drilling test using conventional steel tools. Such mechanical properties are attributable to the microstructure of the barium–mica glass-ceramics. Very fine, interlocking mica crystals are precipitated in the glass, and a crack-deflection mechanism is observed by scanning electron microscopy.     

Monopyroxenic Basalt-Based Glass-Ceramics

Uniform, ultrafine, microcrystalline, hard, pyroxenic glass-ceramic materials have been obtained successfully from basalt rock; instead of adding nucleation catalysts, the FeO:Fe₂O₃, CaO:Na₂O, and CaO:MgO ratios have been rectified. This process has been accomplished by deliberately adding the smallest permissible amounts of oxidizers, limestone, dolomite, and soda ash (as additives) that are necessary to fulfill the monominerality requirements; these requirements affect the melting, workability, crystallization, and microstructure of the glass-ceramics. The melting temperature decreases as the ratios decrease (beyond certain limits); in addition, the workability, crystallization, and microstructure also improve as the ratios decrease. An almost-stable solid solution of augite or aegirine-augite composition is the only crystalline phase that is formed. The minimal FeO:Fe₂O₃ ratio and the likelihood of a greater affinity of the Na⁺ cation for the Fe³⁺ cation, rather than the Al³⁺ cation, may be responsible for increasing the stability and widening of the crystallization field of the complex aluminum-bearing pyroxene solid solution.     

Transparent Magnetic Glass-Ceramics

Transparent magnetic glass-ceramics were produced by infiltrating nano-porous glass with nitrate salts and firing. The resultant glass-ceramics contained spinel ferrite nanocrystals that exhibited ferromagnetic and superparamagnetic behavior depending on composition and firing temperature. Transparency in the near infrared was obtained when oxidizing conditions were used to prevent Fe²⁺ formation, while the porous matrix ensured nano-sized crystallites to limit scattering losses. MnFe₂O₄ glass-ceramics treated at 1000°C offered the best combination of magnetic and optical properties with a saturation magnetization of 5.6 emu/g, a Verdet constant of 16.5°/cm, and losses below 3 dB/mm at 1550 nm.     

Microwave-Hydrothermal Synthesis of Nanophase Ferrites

This paper reports the synthesis of technologically important ferrites such as ZnFe₂O₄, NiFe₂O₄, MnFe₂O₄, and CoFe₂O₄ by using novel microwave-hydrothermal processing. Nanophase ferrites with high surface areas, in the range of 72-247m²/g, have been synthesized in a matter of a few minutes at temperatures as low as 164°C. The rapid synthesis of nanophase ferrites via an acceleration of reaction rates under microwave-hydrothermal conditions is expected to lead to energy savings.     

纳米材料在火炸药中的应用研究现状

纳米材料因其具有许多优异的性能而成为国内外诸多领域研究的热点.从固体推进剂、发射药及烟火剂、炸药3个方面综述了纳米材料在火炸药领域中的应用,并提出了以后有待深入研究的几个问题.     

上转换微晶玻璃的发展近况

上转换微晶玻璃结合了玻璃的易加工性和晶体的高发光效率的优点,改善了传统上转换玻璃的机械强度和稳定性,将上转换发光材料的发展推向了新的高度.综述了近年来上转换微晶玻璃的发展近况,总结了上转换微晶玻璃的制备方法和主要分析方法,对当前研究的上转换微晶玻璃进行系统分类,并对上转换微晶玻璃的发展提出了展望.     

Glass-Ceramics by Photosensitive Processes

Glass-ceramics constitute a unique set of materials as they hold the promise of producing interesting crystal-like properties utilizing glass-making capability. One property that would make them more interesting and useful would be whether they could be produced by a photosensitive process similar to that in special glasses. One such material already exists, namely Corning's photomachinable Fotoform^™. In this study, we will describe two new photosensitive glass-ceramic materials: (1) Fotoform as a tunable CTE material and (2) a new photosensitively produced nepheline phase glass-ceramic.     

Glass-Ceramics and Solid-State Lighting

Yttrium aluminum garnet (YAG) doped with Ce³⁺ ion is known as an excellent phosphor for light-emitting diode (LED), usually used as a powder form dispersed in organic resins. We have developed translucent glass-ceramics (GC) of YAG: Ce³⁺ microcrystals in 2004. The GC sheet with half millimeter thick can work efficiently to make identical emission spectra with conventional white LED when combined with a blue LED. This report reviews the development history of the GC materials and impact for all inorganic solution for solid-state lighting.     

Infrared Transparent Germanate Glass-Ceramics

A new germanate glass-ceramic material in the BaO-Ga₂O₃-GeO₂ system is developed for infrared (IR) dome and window applications. This glass-ceramic material has a grain size of ∼0.2–0.5 μm and is transparent in the 3–5 μm IR region. Glass ceramization results in 40% improvement in hardness, 65% increase in elastic modulus, 116% increase in strength, and 134% increase in fracture toughness over the base glass.     

Strong Sintered Miserite Glass-Ceramics

Strong and tough glass-ceramic materials based on the complex chain silicate miserite (KCa₅open square(Si₂O₇)(Si₆O₁₅)F) have been prepared using standard frit sintering and internal nucleation processes. The miserite may be accompanied by crystals of fluorite, cristobalite, xonotlite, a canasite-like phase, and fluorapatite. The highly crystalline glass-ceramics have a microstructure composed primarily of interlocked, lath- or log-shaped miserite crystals with pronounced cleavage planes. This microstructure provides abraded flexural strength values as high as 235 MPa (34 000 psi) and fracture toughness values >3.0 MPa·m^1/2. These strength and toughness values are quite high for a glass-derived material. Miserite glass-ceramics may be useful for many applications in which such strength and toughness are desired.     

Bioactivity of Zirconia-Toughened Glass-Ceramics

Bioactivity of zirconia-toughened glass-ceramic composites was evaluated by their surface reaction in simulated body fluid and the bonding strength to living bone. The composite containing 30 vol% zirconia showed high bioactivity, whereas that containing 50 vol% zirconia, extremely low. TEM observation indicated that Ca in the glass-ceramic particles reacted with the zirconia during sintering. It was found that the decrease in Ca in the particles degraded the bioactivity of the composite. In this study, the optimum composition was determined for high-strength and bioactive ceramic.     

Tribological Properties of Glass-Ceramics

Tribological properties of five glass-ceramics are reported. The materials were tested unlubricated against themselves. Testing was performed using a simulated inertial sample dynamometer. Sliding speeds were between 0.5 and 1.8 m /S with an applied load of 225 N. Average friction coefficients were in the range 0.07 to 0.5. The wear rate of a lithium aluminosilicate was 43 ×10–14 m3/N.m, in good agreemen2 with previous pin-on-disk results. Wear surfaces exhibited cracking, ploughing, delamination, and viscous flow or plastic deformation.     

Crystallization Mechanisms in Glass-Ceramics

Transmission electron microscopy, electron diffraction, and microprobe X-ray analysis were used to study crystallization of glasses in the systems Li₂O-SiO₂, BaO-SiO₂, and Li₂O-A1₂O₃-SO₂. The ternary system, with 4 mol% TiO₂ added to an Li₂O-Al₂O₃-4SiO₂ composition, crystallizes with a simple morphology of equiaxed grains of the β-quartz metastable phase which transforms at higher temperatures to the stable β-spodumene structure. The binary systems exhibit a more complex crystallization morphology dictated by crystal anisotropy, temperature, impurity content, and susceptibility either to intermediate-phase formation (BaO-SiO₂) or to liquid immiscibility (Li₂O-SiO₂). The initial crystal growth units formed in these systems are frequently two-phase branched morphologies many micrometers in diameter. They may be recrystallized to form polycrystalline glass-ceramics with submicrometer grain sizes.     

纳米LaF3的介电性能

采用水溶液沉淀法制备了平均粒径17纳米的LaF3粉体,通过真空压结成形法制备了纳米LaF3块体,通过测量复阻抗谱研究了纳米LaF3块体材料的介电性能。     

纳米氧化铟的制备研究

以金属硝酸盐作为氧化剂，有机物尿素为燃料的混合物经点火燃烧，制得疏松状的纳米粉末产品，并对产品进行形貌及粒度分析。