Li2O-ZnO-SiO2微晶玻璃析晶动力学研究

利用经典Johnson-Mehl-Avrami(JMA)方程分析了含成核剂氧化钛的Li2O-ZnO-SiO2微晶玻璃的析晶动力学,并用XRD与SEM研究了热处理制度对玻璃析晶行为的影响.结果表明玻璃的晶化过程为多阶段晶化,在析晶初始阶段析出的晶体为γⅡ-LZS,当温度大于760℃时由在γⅡ-LZS的晶界开始生成方石英新相.采用Kissinger法计算得到γⅡ-LZS与方石英晶体的析晶活化能分别为315.2KJ/mol与343.7KJ/mol.     

金刚石配比对微晶玻璃结合剂砂轮磨削寿命影响分析

以某微晶玻璃结合剂为实验结合剂,制备了不同金刚石含量与粒度的金刚石试样。通过对试样的抗弯强度测试以及断口扫描电镜(SEM)观察,研究了不同金刚石含量对金刚石试样在力学方面的影响。通过金刚石试样与YG8立方块的磨削实验,研究了在不同金刚石含量与粒度的条件下试样对硬质合金在加工性能上的影响。实验结果表明,在设计范围内,金刚石浓度对试样的抗弯强度影响不明显。金刚石粒度相同时,5 s/0.01 mm的进刀速度下,磨耗比随着金刚石浓度提升先升高、后少量波动降低;2 s/0.01 mm的进刀速度下,磨耗比随着金刚石含量提升先增大、后减小。在不同金刚石粒度的情况下,5 s/0.01 mm的进刀速度时,磨耗比随着粒度变大而缓慢降低;2 s/0.01 mm的进刀速度时,磨耗比随着粒度变大而先缓慢增大、后急速降低。     

Li2O-ZnO-SiO2系高膨胀微晶玻璃的制备和研究

利用传统熔体冷却方法制得了以P2O5为晶核剂的Li2O-ZnO-SiO2系统玻璃,并探索了该系统微晶玻璃的制备工艺。同时借助X射线衍射仪和和膨胀系数测定仪确定了试样的晶相种类、基玻璃的转化和软化温度以及玻璃的热膨胀系数,探讨了热处理时间对微晶玻璃膨胀系数的影响,从而对该系统玻璃焊料与金属封接的应用前景作了分析。     

Li2O-ZnO-SiO2-PbO系高膨胀封接微晶玻璃的研究

以Ｌｉ２Ｏ－ＺｎＯ－ＳｉＯ２－ＰｂＯ系为基础成分,以Ｐ２Ｏ５为成核剂,制备了膨胀系数在１２７．５＊１０＾－７－１９６．７＾－７℃＾－范围内的高膨胀微晶玻璃。对影响膨胀系数的因素进行了分析。     

Fe2O3对CaO-SiO2玻璃和微晶玻璃性能的影响

利用溶胶-凝胶法制得Fe2O3-CaO-SiO2系基础玻璃,研究不同含量的Fe2O3对CaO-SiO2玻璃和微晶玻璃性能的影响.经分析,不同组分的玻璃凝结时间不同,处于低共熔点的样品凝结时间最短,而离低共熔点最远的样品凝结时间最长.样品的密度并不随成分而变化.溶胶凝胶转变过程中,不同组分所得的凝胶玻璃有一定的耐酸碱性.而微晶玻璃的耐酸碱性比玻璃都略有增强.微晶玻璃的饱和磁化强度和磁铁矿在玻璃中所占的体积分数有关.随着玻璃中Fe2O3含量的增加,饱和磁化强度增大.     

Li2O对近零膨胀Li2O-Al2O3-SiO2透明微晶玻璃性能的影响

以Li2O-Al2O3-SiO2(LAS)系微晶玻璃为研究对象,采用示差扫描量热(DSC),X射线衍射分析(XRD),扫描电镜(SEM)等测试方法研究不同Li2O含量锂铝硅透明微晶玻璃的相转变及其各项性能.结果表明,随着Li2O含量的增加,玻璃的熔化温度降低,熔化质量提高,析晶峰温度降低.热处理后的玻璃试样,随着Li2O含量的增加,主晶相由LixAlxSi3-xO6逐渐转变为LiAlSi2O6,颗粒尺寸变大,热膨胀系数变大,化学稳定性提高,透明性变差.     

Na2O和K2O对CaO—Al2O3—SiO2—R2O—ZnO红色微晶玻璃若干性能的影响

研究了碱金属Ｎａ２Ｏ和Ｋ２Ｏ对ＣａＯ－Ａｌ２Ｏ３－ＳｉＯ２－Ｒ２Ｏ－ＺｎＯ红色微晶玻璃着色及烧结和折晶的影响及作用,以及微晶玻璃烧结和析晶随热处理温度变化的规律。     

Li2O-ZnO-SiO2系微晶玻璃的结晶及其封接特性

采用X射线衍射定性分析、差热分析、扫描电镜等手段研究了Li2O-ZnO-SiO2(组成为9.0%Li2O,27.1%ZnO,55.6%SiO2,2%K2O,3.2%P2O5,3.1?O,质量分数)玻璃粉末处理后的微晶玻璃的的结晶特性.结果表明:当热处理温度低于800℃时,主晶相为半蜷曲状二硅酸锂和硅酸锌,次晶相为圆柱状α-方石英;当热处理温度超过800℃后,a-方石英逐步转变成β-方石英并成为主晶相,次晶相为二硅酸锂和硅酸锌且部分晶体重熔转变成玻璃.重熔过程有利于与金属材料封接.当热处理温度为950℃,封接后的封接件(不锈钢壳体,铜针引线)中微晶玻璃的外观良好,呈乳白色.密封气密性良好.500℃热冲击实验[(-55±2)～(500±5)℃]后,微晶玻璃无损伤.微晶玻璃在500℃时绝缘强度为3 3×1012Ω·cm,膨胀系数为129×10-7/℃.     

石英玻璃对Li2O-Al2O3-SiO2系统微晶玻璃性能的影响

向水淬后的Li2O-Al2O3-SiO2系统玻璃粉中加入石英玻璃粉，参照玻璃粉末的DTA曲线确定晶化温度，采用烧结法制备出了低膨胀微晶玻璃材料。运用XRD分析了材料的晶相种类，测定了材料的热膨胀系数、密度、抗折强度等性能，分析讨论了石英玻璃粉对材料性能的影响结果表明，石英玻璃粉含量增大，材料的热膨胀系数值减小。密度值增大，抗折强度值降低，析出主晶相为β-锂辉石固溶体。     

Li2O-ZnO-SiO2系微晶玻璃结构和性能的研究

介绍了利用传统熔体冷却方法制得以P2O5为晶核剂的Li2O-ZnO-SiO2系玻璃,并探索了该系统微晶玻璃的制备工艺,用XRD、SEM和FT-IR以及膨胀系数测定仪对微晶玻璃的结构和性能进行了研究,表明了该微晶玻璃可望作为镍、镍合金及1010钢等金属的封接材料.     

陶瓷结合剂金刚石砂轮的制备研究

陶瓷结合剂金刚石砂轮广泛运用于磨削加工,文章研究了金刚石粒度、烧结温度及结合剂含量对陶瓷结合剂金刚石砂轮性能的影响.研究结果发现金刚石表面微观结构呈多孔状,粒度越细,烧结过程中与结合剂的反应活性越低,砂轮硬度越高.同时在一定范围内烧结温度越高,结合剂含量越低,砂轮硬度越高.     

Fabrication of porous structure vitrified bond diamond grinding wheel via direct ink writing

Porous vitrified bond grinding wheels with complex structure, high porosity, controllable pore size have fundamental application in high efficiency and precision grinding of hard and brittle materials. In this paper, direct ink writing (DIW) is proposed to fabricate three kinds of grinding wheels, including solid structure, triangle structure, and lattice structure. Moreover, the rheological property of ceramic ink with different doses of xanthan gum (XG) solution was investigated to ensure printability, demonstrating 3% XG solution can meet requirements. Additionally, the effect of sintering temperature and pore former (PMMA) contents on size shrinkage rate, morphology, mechanical strength, and porosity et al. were studied. The results indicate that the diamond grinding wheel with 30 vol% PMMA and sintered at 670 °C possess the best comprehensive performance. Besides, grinding performance was evaluated by surface morphology, surface roughness, and material removal rate. Among the DIW-fabricated wheels, triangle structure grinding wheel and lattice structure grinding wheel possess a higher material removal rate than solid structure grinding wheel. Therefore, the porous structure grinding wheels fabricated by DIW present the advantage of controllable porosity, excellent self-sharpening ability, and higher bond strength, which may pave the way for designing a new generation vitrified bond diamond grinding wheel.     

Preparation of a novel vitrified bond CBN grinding wheel and study on the grinding performance

The vitrified bond CBN grinding wheels are characterized by high efficiency, high precision, and low environmental pollution. In recent years, the vitrified bond CBN grinding wheel has been widely used in manufacturing industries such as aerospace, automotive, and machine tools. In this study, a novel vitrified bond formulation containing nano SiO₂ and nano CeO₂ is selected to prepare the grinding wheel. The grinding experiments on 45# steel and YG20 alloy indicate that the grinding performance of the nano vitrified bond grinding wheel is significantly better than that of the conventional vitrified bond grinding wheel. The introduction of nano SiO₂ and nano CeO₂ greatly improves the machining performance of the vitrified bond CBN grinding wheel.     

Li2O-Na2O-K2O-CaO-MgO-Al2O3-SiO2系统乳浊釉的研究

对Li2O-Na2O-K2O-CaO-MgO-Al2O3-SiO2系统釉进行了较全面的正交试验研究,找到了影响该系统釉乳浊及釉面质量的主次因素,获得了性能良好的乳浊釉及其较优乳浊釉配方.     

母液中Na2O和Na2SO4对无模板剂合成ZSM-5分子筛的影响

以水玻璃为硅源在无模板剂条件下合成ZSM-5分子筛,体系中Na2O含量通过加入硫酸进行调变.实验详细考察了不同水硅比条件下母液中Na2O和Na2SO4对ZSM-5分子筛合成的影响,并采用XRD、SEM等手段对合成样品进行表征.结果表明,母液中Na2O的比例不仅起到调节碱度的作用,同时对ZSM-5的形成具有结构导向性.当Na2O含量过高时,产物易出现MOR杂晶相,而Na2O含量过低则产生无定形物质.另外,随着母液中水硅比的减小,合成ZSM-5体系所需Na2O/SiO2的范围也相应变窄.合成体系中的Na2SO4对ZSM-5分子筛的晶相影响不大,然而对ZSM-5分子筛的结晶速度有着显著的影响.     

Li2O-Na2O-K2O-CaO-MgO-Al2O3-SiO2系统乳浊釉的乳浊机理研究

本文对Li2O-Na2O-K2O-CaO-MgO-Al2O3-SiO2系统乳浊釉的乳浊机理进行了研究.借助于XRD分析,发现该系统乳浊釉为熔析乳浊釉,主要乳浊相是α-CaSiO3,晶相和CaSiO3晶相.     

The effect of Nb2O5 and ZrO2 additions on the behaviour of Li/MgO and Li/Na/MgO catalysts for the oxidative coupling of methane

Incorporation of Nb₂O₅ or ZrO₂ into both Li/MgO and Li/Na/MgO systems produced ternary and quaternary catalysts, respectively, capable of attaining optimal C₂ yields and selectivities at lower temperatures relative to the unpromoted materials. The degree of enhancement effected by these metal oxide additives was compared to that produced by Li/MgO and Li/Na/MgO catalysts promoted with SnO₂ or Co₃O₄. At reaction temperatures < 700°C, the Li/Co/MgO ternary system showed marked differences in behaviour compared to the other ternary catalysts tested. This was particularly evident in the variation in C₂ selectivity with time on stream during ageing studies of (i) untreated materials, (ii) materials pretreated in CO₂, and (iii) materials dosed periodically with CHCI₃.     

锂铝硅透明微晶玻璃着色研究

引入Cr2O3、CoO、NiO、MnO2等过渡金属氧化物对低膨胀锂铝硅透明微晶玻璃进行着色研究,结果表明,微晶玻璃与其母体玻璃相比,颜色有明显的不同,主波长向长波方向移动。研究还发现,在从核化阶段到晶化阶段的过程中颜色变化最为明显,而在核化阶段和晶化阶段颜色没有发生明显的变化。同时运用配位场理论和光散射原理来解释这种颜色变化的原因。     

Effect of porosity on the grinding performance of vitrified bond diamond wheels for grinding PCD blades

In this paper, the preparation of nano-AlN modified Na₂O–B₂O₃–SiO₂ vitrified bond diamond tools with various porosities is reported. The effects of porosity on the impact strength and grinding properties of the wheels for grinding PCD blades are also discussed. The results show that the porosity not only affects the impact strength of the wheels but also the grinding properties, such as the grinding efficiency, the self-dressing, the service life and the surface roughness of the work pieces. The optimum porosity for nano-AlN modified Na₂O–B₂O₃–SiO₂ vitrified bond diamond wheels for grinding PCD tools is approximately 40.5 vol%.