渗透烧烤工艺对GI—Ⅱ型渗透陶瓷颜色的影响

目的：旨在研究不同的玻璃渗透烧烤工艺条件下,渗透陶瓷样本颜色参数的变化规律,以考察材料颜色的稳定性和可重复性。方法：制作直径为12.5mm,厚度为0.5mm的盘片状GI－Ⅱ及Vita InCeram Alumina氧化铝试件,分别选用IG2和A2色玻璃料进行渗透。按渗透时间不同分为0.5,1.0,2.0,4.0和6.0hrs组,渗透温度为1100℃;按渗透温度不同分为1080℃,1100℃,1120℃组,渗透时间2.0hrs。用TC－PⅡG全自动测色色差仪（D65光源,0^0/d,10^0视场,波长范围380－780nm)测量样本的颜色参数（CIE1976L*a*b*颜色系统）,计算样品的色相值（hab)、色饱和度值（C*ab)和色差值（△E）。结果：随渗透时间的增加,样本的明度值降低,饱和度值增加,色相变化不明显。在本实验所选定的渗透时间范围内,渗透时间所引起的颜色变化超出了临床可接受的范围（△E＞3）;随渗透温度的提高,两种样品的明度值降低,色相变化虽不明显,但有红色方向偏移的趋势,Vita材料的彩度值增加,GI样本则无明显变化。所选温度范围所引起的颜色变化程度处于临床可接受的范围（△E＜3）。结论：GI-Ⅱ型渗透陶瓷及Vita In-Ceram Alumina底层材料的颜色受不同渗透工艺的影响,应采用固定的渗透工艺以保证渗透完全并稳定地获得所需的颜色。     

Molecular Dynamics Study on Structure,Vibrational Properties,and Transport Coefficients of Liquid Alumina

The structure, vibrational density of states, and transport coefficients of liquid alumina were studied using molecular dynamics simulations. At the temperature of 2500 K, 3000 K, 3500 K, and 4000 K, systems with three different densities were constructed, respectively, including the configurations with densities of 2.81 g/cm³ and 3.17 g/cm³, and the relaxed ones with nearly zero pressure at each temperature. With the changes in temperature or density, the transformations on the structural, vibrational and transport properties were discussed. The Born–Mayer–Huggins type of atomic interactions was used, with newly optimized parameters. The analysis of the interatomic correlations indicated that the short-range order of liquid alumina was mainly constructed by AlO₄ tetrahedra, also a certain number of AlO₃ and AlO₅ was present. Meanwhile, the structural transitions on the elemental units occurred as either the temperature or density increased. Two primary frequency bands were observed in each vibrational density of states spectrum, with the higher frequency bands produced by the O atom vibrations, and the lower frequency ones generated by the Al atom vibrations. Self-diffusion coefficients were estimated using the linear behavior of the mean-squared displacement at long time, while by using the Green–Kubo relation during equilibrium molecular dynamics simulations, thermal conductivities and viscosities were calculated. Significantly, the viscosity at 2500 K with a density of 2.81 g/cm³ was equal to 25.23 mPa s, which was very close to the experimental finding.     

Study on Adsorption Properties of Calcined Mg–Al Hydrotalcite for Sulfate Ion and Chloride Ion in Cement Paste

In the marine environment, sulfate ions and chloride ions are abundant. Therefore, sulfate attack and chloride ion attack are common failure forms of marine concrete. Mg–Al hydrotalcite is a layered bimetallic hydroxide, which can be used as guest molecular adsorbent. In this experiment, we synthesized Mg–Al hydrotalcite, and the crystal state, surface morphology, and composition of this adsorbent were investigated by modern micro-analysis technology. Mg–Al hydrotalcite was added into the prepared target ion solution, to explore the influence of various factors on the adsorption performance of Mg–Al hydrotalcite, and then calcined Mg–Al hydrotalcite was added into cement paste, to study the mechanical properties and durability of the paste samples. The experimental results show that the optimum conditions for adsorption of chloride ions by calcined Mg–Al hydrotalcite are an adsorption time of 4 h, temperature of 35 °C, LDO (calcined Mg-Al hydrotalcite) dosage of 3.5 g/L, and a pH of 8. The adsorption effect of sulfate ion is best when the adsorption time is 6 h, the temperature is 35 °C, the dosage of LDO is 4 g/L, and the pH = 8. The optimal adsorption conditions of calcined Mg–Al hydrotalcite for chloride ion and sulfate ion are not completely the same, and the adsorption of these two ions in mixed solution shows competitive adsorption. Compared with the common paste specimens without Mg–Al hydrotalcite, the mechanical properties and deformation properties of cement specimens can be significantly improved by adding Mg–Al hydrotalcite.     

Selective Laser Melting of Al-Based Matrix Composites with Al2O3 Reinforcement: Features and Advantages

Aluminum matrix composites (AMC) are of great interest and importance as high-performance materials with enhanced mechanical properties. Al₂O₃ is a commonly used reinforcement in AMCs fabricated by means of various technological methods, including casting and sintering. Selective laser melting (SLM) is a suitable modern method of the fabrication of net-shape fully dense parts from AMC with alumina. The main results, achievements, and difficulties of SLM applied to AMCs with alumina are discussed in this review and compared with conventional methods. It was shown that the initial powder preparation, namely the particle size distribution, sphericity, and thorough mixing, affected the final microstructure and properties of SLMed materials drastically. The distribution of reinforcing particles tends to consolidate the near-melting pool-edges process because of pushing by the liquid–solid interface during the solidification process that is a common problem of various fabrication methods. The achievement of an homogeneous distribution was shown to be possible through both the thorough mixing of the initial powders and the precise optimization of SLM parameters. The strength of the AMCs fabricated by the SLM method was relatively low compared with materials produced by conventional methods, while for superior relative densities of more than 99%, hardness and tribological properties were obtained, making SLM a promising method for the Al-based matrix composites with Al₂O₃.     

The shear strength between bone and porous ceramic root implants in the guinea pig incisor socket

Porous alumina and apatite implants have been placed in 67 guinea pig incisor tooth sockets after tooth extraction under anaesthetic. Bone readily grew into the spaces of the implant, and reduced the fibrous connective tissue between implant and bone. 'Pushout' tests have monitored the shear strength of the interlock between bone and implant. Despite considerable variation in the interlock strength, apatite produced the strongest bone interlock. The interlock with alumina tended to be more fibrous. The relative merits of fibrous and bone interlocks in immediate root implants are considered for the augmentation of the alveolar ridge and prosthetic treatment.     

纳米氧化铝玻璃复合体强度及断裂韧性的研究

为了研制出一种能被牙科计算机辅助制作技术加工并能被镧硼硅玻璃渗透的多孔氧化铝块，采用α型高纯度、超细氧化铝粉末，经等静压处理，在１３５０℃下烧结成多孔氧化铝坯体，经镧硼硅玻璃渗透，制作氧化铝玻璃复合体，并对其密度、强度、断裂韧性进行测试。结果显示：多孔氧化铝坯体密度为２．１２ｇ／ｃｍ３，三点弯曲强度为１０２ＭＰａ，断裂韧性为１．６１ＭＰａｍ１／２，氧化铝玻璃复合体体积密度为３．８５ｇ／ｃｍ３，三点弯曲强度为３８５ＭＰａ，断裂韧性为４．０５ＭＰａｍ１／２。扫描电镜及Ｘ线能谱分析表明，镧硼硅玻璃在经１１５０℃保持６小时热处理后，能够完全渗透厚３ｍｍ的多孔氧化铝坯体。提示用这种方法制作的氧化铝块可以满足临床的需要。     

Determination of some metal ions by flame-AAS after their preconcentration using sodium dodecyl sulfate coated alumina modified with 2-hydroxy-(3-((1-H-indol 3-yle)phenyl) methyl) 1-H-indol (2-HIYPMI)

Selective, sensitive and efficient methods for preconcentration of trace amounts of metal ions including Cr³⁺, Cu²⁺, Zn²⁺ and Ni²⁺ ions by incorporation of 2-hydroxy-(3-((1-H-indol 3-yle)phenyl) methyl) 1-H-indol (2-HIYPMI) on SDS-A has been reported. The proposed methods are based on the uptake of chelate of under study metal ions with these new ligands loaded on SDS-A. The influences of the analytical parameters including pH, ligand and SDS amount, eluting solution (type and concentrations) and sample volume on metal ions recoveries were investigated. The extraction efficiency was >95% with relative standard deviation lower than 5%. The method has been successfully applied for the extraction and determination of these ions content in some real samples.     

单晶陶瓷心脏瓣膜的寿命估算

单晶氧化铝陶瓷复合材料已被考虑用于制造人工心脏瓣膜，因此首先要对陶瓷碟瓣的疲劳性能进行研究，本文对单晶氧化铝陶瓷制成的斜碟式心脏地瓣膜进行静态和动态疲劳裂纹扩展分析以及寿命估算，其中包含24度潮湿空气和37度 Ringer液体（模拟的生理环境）二种环境条件下穿透裂纹，表面裂纹和角裂纹等多种损伤情况。结果表明：在500mgHg静态和脉冲压力作用下，当碾瓣上的表面裂纹或角裂纹大小一旦达到了疲劳裂纹扩展的阀值，它们会很快向厚度方向扩展变成穿透裂纹，然后停止扩展，而对于穿爱裂纹情况，人工心脏碟瓣不会采生疲劳破坏。     

Immobilization of Methyltrioxorhenium on Mesoporous Aluminosilicate Materials

The presented report focuses on an in-depth detailed characterization of immobilized methyltrioxorhenium (MTO), giving catalysts with a wide spectra of utilization. The range of mesoporous materials with different SiO₂/Al₂O₃ ratios, namely mesoporous alumina (MA), aluminosilicates type Siral (with Al content 60%–90%) and MCM-41, were used as supports for immobilization of MTO. The tested support materials (aluminous/siliceous) exhibited high surface area, well-defined regular structure and narrow pore size distribution of mesopores, and therefore represent excellent supports for the active components. Some of the supports were modified by zinc chloride in order to obtain catalysts with higher activities for instance in metathesis reactions. The immobilization of MTO was optimized using these supports and it was successful using all supports. The success of the immobilization of MTO and the properties of the prepared heterogeneous catalysts were characterized using X-ray Fluorescence (XRF), atomic absorption spectroscopy (AAS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), physical adsorption of N₂, ultraviolet-visible spectroscopy (UV-Vis), infrared spectroscopy (FTIR), Fourier Transform Infrared Spectroscopy (FTIR) using pyridine as a probe molecule and X-ray photoelectron spectroscopy (XPS). Furthermore, the catalytic activity of the immobilized MTO on the tested supports was demonstrated on metathesis reactions of various substrates.