Effects of MO (M = Mg, Ca, Ba) on crystallization and flexural strength of semi-transparent lithium disilicate glass-ceramics

In this study, semitransparent lithium disilicate glass-ceramics in the Li₂O-K₂O-Al₂O₃-Y₂O₃-La₂O₃-SiO₂ system was investigated by incorporation of P₂O₅ as nucleation agent and alkaline earth oxides as additive. The influence of alkaline earth oxides on the structure of glasses network, crystalline phases, microstructure and mechanical properties were investigated by means of Raman spectra, differential scanning calorimetry (DSC), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The mechanical strength was measured corresponding to norm ISO 6872. The Raman spectra predominantly showed that small additions of alkaline earth oxides not only form asymmetrical vibrations of the M-Si-O bonds, but also enhance the intensities of symmetrical vibrations of the P-O bonds, making the glass network more stable. And the small additions of CaO or BaO has more influence on the crystallization behaviour, crystalline phase, microstructure and mechanical properties of the glass-ceramics than the addition of MgO. The additions of alkaline earth oxides enhanced the first exothermic peak temperature but decreased the flexural strength of lithium disilicate glass-ceramics.     

Crystallization and microstructures of Y-Si-Al-O-N glass-ceramics containing main crystal phase Y<Subscript>3</Subscript>Al<Subscript>5</Subscript>O<Subscript>12</Subscript>

A glass with the nominal composition of 28Y48Si24Al83O17N (in equal percentage) was chosen as parent glass in this paper to prepare Y₃Al₅O₁₂-based glass-ceramics. Differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to assess the crystallization process of the parent glass. YAG as the only crystalline phase appears in all glass-ceramics produced under 1250°C. A small amount of O’-Sialon secondary phase starts to precipitate from parent glass samples as heat treatment temperature increases to 1250°C. Grain size of the dendrite crystal which corresponds to YAG phase increases and the dendrite branches get thickened as heat treatment temperature increases. Moreover, grain size of YAG phase resulting from two-stage heat treatment is much smaller than that of YAG phase obtained by one-stage heat treatment. The results are relevant to developing improved crystallization treatments for glasses with potential for crystallization to YAG-based glass-ceramics and for heat treatments of YAG/β-SiAlON materials.     

云峰水电站大坝右F15断层处理工程抗滑墩地基工程地质评价

云峰水电站已运行五十余年,电站建设期间未能解决的问题逐渐显现。51#、52#坝段坝基存在右F15断层,由于中朝双方在对断层性质认识上的分歧及断层对坝基的稳定影响程度各持己见,意见不统一,难以对右F15断层进行工程处理。云峰水电站大坝交中方管理后,进一步查清了51#、52#坝段的地质情况和右F15断层的性状特征,提出了抗滑墩支护处理方案及相关的地质参数,并对右F15断层及抗滑墩地基进行相应的工程处理。     

PCD刀具刃磨用细粒度陶瓷结合剂金刚石砂轮的研制及应用

探讨了刃磨PCD刀具用细粒度陶瓷结合剂金刚石砂轮的制造工艺与应用,选用Li2O-ZnO-SiO2微晶玻璃作结合剂,研究了砂轮中金刚石浓度、结合剂含量及造孔剂种类、含量变化对砂轮磨削性能的影响。     

Comparison between vitrified bond and resin bond diamond grinding wheel in grinding PDC

In this research, the advantages and disadvantages of the cylindrical grinding process of Polycrystalline Diamond Compacts (short for PDC) with vitrified and resin bond diamond grinding wheel are compared. The research results show that the vitrified bond diamond grinding wheels, which use Ti-coated diamond grains as abrasive and glass ceramic as bond, have many advantages in grinding PDC . Compared with resin diamond grinding wheel,vitrified bond wheels lead to 35% grinding cost reduced, 40% grinding time of each PDC saved, and the size precision of PDC improved (from ±0.03mm to ±0.01mm). When grinding feed is ＜0.10 mm, the grinding ratio increases with increased grinding feed. However, when the grinding feed exceeds 0.10 mm, the grinding radio decreases rapidly with the increasing of grinding feed. The disadvantage of this kind of grinding wheel is that the brightness of the ground PDC cylinder is not as shining as that processed by resin bond diamond grinding wheel.     

等离子体显示器封装用透明介质浆料的研究现状

介绍了等离子体显示器(PDP)封装用介质浆料的发展概况,综述了PDP对透明介质浆料的性能要求、介质浆料的组成及制备工艺。着重分析讨论了近年来PDP透明介质浆料所采用的几种基础玻璃系统的优缺点。     

晶核剂对Li2 O-Al2 O3-SiO2系统微晶玻璃结构和性能的影响

通过传统熔体冷却法制得了以P2O5和TiO2为晶核剂的Li2O-Al2O3-SiO2系统基础玻璃,并经过热处理制得了微晶玻璃.利用红外光谱分析、X射线衍射分析和扫描电子显微镜等对晶化试样的物相和显微结构进行了研究,着重探索了不同晶核剂对玻璃析晶、微晶玻璃结构、微晶玻璃力学和热学性能的影响.结果表明:TiO2更有利于玻璃析晶,但以P2O5为晶核剂的微晶玻璃具有更好的力学和热学性能.     

Li2 O-ZnO-SiO2系微晶玻璃的结晶行为与热膨胀变化规律

以Li2O-ZnO-SiO2系统为基础玻璃组成,通过DTA、XRD、SEM及热膨胀系数等测试手段分别对不含Al2O3和含5wt%Al2O3的微晶玻璃的结晶行为、结构和热膨胀变化规律进行了研究探讨.结果表明,高热膨胀相方石英微晶体较快生长的温度为750℃左右,Al2O3部分取代SiO2后对方石英的析出有阻碍作用,同时导致低热膨胀锂辉石微晶体的生成.     

In situ synthesis and properties of self-reinforced $$\hbox {Si}_{3} \hbox {N}_{4}\textendash \hbox {SiO}_{2}\textendash \hbox {Al}_{2} \hbox {O}_{3}\textendash \hbox {Y}_{2}\hbox {O}_{3} \ (\hbox {La}_{2}\hbox {O}_{3}$$) glass–ceramic composites

In-situ-grown \(\upbeta \!\hbox {-Si}_{3}\hbox {N}_{4}\)-reinforced \(\hbox {SiO}_{2}\textendash \hbox {Al}_{2}\hbox {O}_{3}\textendash \hbox {Y}_{2}\hbox {O}_{3}\) \((\hbox {La}_{2}\hbox {O}_{3})\) self-reinforced glass–ceramic composites were obtained without any \(\upbeta \!\hbox {-Si}_{3}\hbox {N}_{4}\) seed crystal. These composites with different compositions were prepared in a nitrogen atmosphere for comparison of phase transformation and mechanical properties. The results showed that \(\hbox {SiO}_{2}\textendash \hbox {Al}_{2}\hbox {O}_{3}\textendash \hbox {Y}_{2}\hbox {O}_{3}\) \((\hbox {La}_{2}\hbox {O}_{3})\) glass can effectively promote \(\upalpha \)- to \(\upbeta \!\hbox {-Si}_{3}\hbox {N}_{4}\) phase transformation. The crystallized \(\hbox {Y}_{2}\hbox {Si}_{2}\hbox {O}_{7}\textendash \hbox {La}_{4.67}\hbox {Si}_{3}\hbox {O}_{13}\) phases with a high melting point significantly benefited the high-temperature mechanical properties of the composites. The \(\hbox {Si}_{3}\hbox {N}_{4}\textendash \hbox {SiO}_{2}\textendash \hbox {Al}_{2} \hbox {O}_{3}\textendash \hbox {Y}_{2}\hbox {O}_{3}\) \((\hbox {La}_{2}\hbox {O}_{3})\) glass–ceramic composites exhibit excellent mechanical properties compared with unreinforced glass–ceramic matrix, which is undoubtedly attributed to the elongated \(\upbeta \!\hbox {-Si}_{3}\hbox {N}_{4}\) grains. These glass–ceramic \(\hbox {Si}_{3}\hbox {N}_{4}\) composites with excellent comprehensive properties might be a promising material for high-temperature applications.     

高温下微晶玻璃结合剂对金刚石磨料浸润性研究

本文研究用 Li2O-ZnO-SiO2 系微晶玻璃代替普通玻璃用作金刚石砂轮结合剂以克服普通玻璃结合剂对金刚石浸润性差、热膨胀系数与金刚石相差大的缺点.研究了温度、结合剂组成及金刚石表面镀钛对Li2O-ZnO-SiO2微晶玻璃结合剂对金刚石浸润角的影响,研究发现:当温度从963 K升至993 K 时,微晶玻璃结合剂对金刚石的浸润角从129.6°降至34.5°;结合剂中的[BO3]团的存在能降低玻璃结合剂对金刚石的浸润角,Na2O对改善玻璃结合剂对金刚石浸润性无明显作用;并且金刚石表面镀钛也能明显降低微晶玻璃结合剂对金刚石的浸润角.