Na2O-CaO-Al2O3-SiO2系统微晶玻璃的析晶动力学研究

Na2O-CaO-Al2O3-SiO2系统微晶玻璃是一种新型建筑材料,该材料不仅具有一定的力学性能,还具有良好的装饰效果.本文采用差热分析 (DTA)方法对 Na2O-CaO-Al2O3-SiO2系统微晶玻璃的析晶动力学参数进行了测定,研究了该系统微晶玻璃析晶动力学.其结果表明:随着CaO含量的增加,该系统微晶玻璃的析晶活化能E和动力学析晶参数k(Tp)总体上是上升的.晶化指数n均小于3,表明该系统微晶玻璃以表面析晶的方式析晶.     

CaO-Al2O3-SiO2系统微晶玻璃表面析晶研究

采用差热分析(DTA),X衍射分析(XRD),扫描电镜分析(SEM)等测试手段,研究了CaO-Al2O3-SiO2系统微晶玻璃的析晶热力学,计算出了该组分微晶玻璃表面析晶的析晶活化能E,并确定了最佳热处理制度.其主晶相为β-硅灰石晶体,晶体呈针状,晶体从颗粒表面向内部生长.随着玻璃颗粒粒径的减小,玻璃中的晶体的数目增大,晶体的体积变小.     

Al2O3对CaO-Al2O3-SiO2系微晶玻璃晶化和性能的影响

以CaO-Al2O3-SiO2三元系微晶玻璃为研究对象,从玻璃析晶动力学方面进行研究,通过DTA和SEM等分析方法,对微晶玻璃析晶行为进行研究,利用析晶活化能E和析晶参数n值来分析析晶机理;实验结果表明:析晶参数n=2,体系属于整体析晶。随着Al2O3含量的增加,析晶温度有升高的趋势,析晶活化能增大,有利于玻璃的烧结;试样密度增大,显微硬度增加。     

TiO2对凝胶法制备Li2O-Al2O3-SiO2系微晶玻璃析晶性能的影响

采用高分子网络凝胶法制得Li2O-Al2O3-SiO2系微晶玻璃粉体,加入TiO2以调节其析晶性能,采用TG-DTA、IR、XRD等手段来表征和分析烧结产物,研究掺杂TiO2对微晶玻璃晶化行为的影响。结果表明:TiO2的掺杂使析晶温度提前,降低了析晶活化能,引起了玻璃的整体析晶,促使β-石英固溶体向β-锂霞石固溶体的转变,掺杂还使晶粒细化。     

ZrO2对CaO-Al2O3-SiO2系统微晶玻璃烧结过程的影响研究

CaO-Al2O3-SiO2系统微晶玻璃作为微晶玻璃中的一个新品种,具有非常鲜明的特点.本文讨论了在CaO-Al2O3-SiO2系统微晶玻璃中加入ZrO2,研究了ZrO2对CaO-Al2O3-SiO2系统微晶玻璃烧结的影响.随着ZrO2加入量的增加,玻璃颗粒的烧结收缩率下降,说明ZrO2的加入对玻璃颗粒的烧结收缩有一定的阻碍作用.ZrO2的加入对CaO-Al2O3-SiO2系统微晶玻璃中的主晶相(β-硅灰石晶体)的析出没有大的影响.     

CaO对CaO-Al2O3-SiO2系微晶玻璃析晶和性能的影响

以CaO-Al2O3-SiO2三元系微晶玻璃为研究对象,通过DTA,XRD,SEM等手段对微晶玻璃析晶的动力学进行研究,利用析晶活化能E和析晶参数n值来分析析晶机理;实验结果表明：析晶参数n=2,体系属于整体析晶。随着氧化钙含量的增加,析晶温度降低,析晶活化能降低,有利于微晶玻璃的晶化,使其密度增大,显微硬度增加。但氧化钙加入量不能过大,否则会因烧结温度区范围变窄而产生坑点、突起、断裂等缺陷。     

Y2O3掺杂对Al2O3-SiO2-P2O5系统玻璃结构和析晶性能的影响

采用高温熔融冷淬法制备了Al2O3-SiO2-P2O5（ASP）系统玻璃,用原位晶化法获得了磷酸盐微晶玻璃;用IR、DSC、XRD、SEM等测试方法表征了玻璃结构及析晶性能,讨论了稀土Y2O3掺杂对ASP玻璃结构和析晶性能的影响。结果表明：Y2O3处于ASP的玻璃结构空隙中,起网络修饰体的作用,并未改变玻璃的基本结构,但Y^3＋离子会加强玻璃中P-O^-键的伸缩振动。当Y2O3的掺杂量少于1．5wt％时,随着Y2O3含量的增加,玻璃的稳定性增强,析晶活化能升高;引入量为1．5wt％时,玻璃的稳定性最好,析晶活化能最大,玻璃不易析晶;掺杂量多于1．5wt％时,稳定性开始下降,析晶活化能降低。少量Y2O3掺杂并未改变玻璃析出的晶相种类,析出的主晶相仍为AlPO4,次晶相为Mg3（CO4）2,但玻璃中加入适量的Y2O3会减少次晶相Mg3（PO4）2的析出量。     

CaO-Al2O3-SiO2系统玻璃颗粒的烧结过程研究

通过大量实验得到了CaO-Al2O3-SiO2系统玻璃颗粒的起始烧结温度(Ts),起始析晶温度(Tc)以及烧结收缩曲线,通过对他们的分析,讨论了组分、烧结温度、烧结时间对玻璃颗粒烧结的影响.确定了有利于烧结的较佳CaO,Al2O3,B2O3含量范围,从而为烧结法生产微晶玻璃提供了有利的理论依据.     

整体法制备CaO—Al2O3-SiO2系统微晶玻璃晶核剂的选择

措助X射线衍射仪、扫描电镜等现代分析测试手段．分析研究在基础玻璃中加入不同的晶核剂,对整体析晶法制备CaO-Al2O3-SiO2。系统微晶玻璃晶化行为的影响。研究表明．CaF2能有效促进CaO-Al2O3-SiO2系统玻璃的整体析晶．形成以β-硅灰石为主晶相的微晶玻璃．晶核剂质量浓度不同对玻璃析晶的影响不同。     

BaO-Al2O3-B2O3-SiO2系微晶玻璃低温共烧陶瓷研究

采用烧结法制备了BaO-Al2O3-B2O3-SiO2系微晶玻璃低温共烧陶瓷。通过差热分析仪、影像式烧结点试验仪、x射线衍射仪等方法研究了玻璃组成以及烧结制度对微晶玻璃结构和性能的影响。结果表明：随着B2O3替代Al2O3量的增加,玻璃转变温度和烧结温度逐渐降低,析晶能力增强,有利于重硅酸钡晶体的析出,但不利于钡长石晶...     

生物玻璃的烧结与析晶

利用玻璃的烧结收缩,结合差热分析和X射线衍射分析,研究了CaO-SjO_2-P_2O_5系统生物玻璃的烧结和析晶动力学。确定它的烧结机制主要是粘性流动烧结。A玻璃和Ⅰ-2玻璃的烧结活化能分别为540kJ/mol和476kJ/mol。析晶相是磷灰石和硅灰石。A玻璃和Ⅰ-2玻璃的析晶表观活化能分别约为480kJ/mol和390kJ/mol。通过分析烧结温度、Na_2O含量对烧结和析晶的影响,选择了合适的烧结条件,控制烧结和析晶程度,获得了既有足够的自身强度,又有一定的结合强度的多孔玻璃陶瓷。     

Final-stage densification kinetics of direct current–sintered ZrB2

Final-stage sintering was analyzed for nominally phase pure zirconium diboride synthesized by borothermal reduction of high-purity ZrO₂. Analysis was conducted on ZrB₂ ceramics with relative densities greater than 90% using the Nabarro–Herring stress–directed vacancy diffusion model. Temperatures of 1900°C or above and an applied uniaxial pressure of 50 MPa were required to fully densify ZrB₂ ceramics by direct current sintering. Ram travel data were collected and used to determine the relative density of the specimens during sintering. Specimens sintered between 1900 and 2100°C achieved relative densities greater than 97%, whereas specimens sintered below 1900°C failed to reach the final stage of sintering. The average grain size ranged from 1.0 to 14.7 μm. The activation energy was calculated from the slope of an Arrhenius plot that used the Kalish equation. The activation energy was 162 ± 34 kJ/mol, which is consistent with the activation energy for dislocation movement in ZrB₂. The diffusion coefficients for dislocation motion that controls densification were 5.1 × 10⁻⁶ cm²/s at 1900°C and 5.1 × 10⁻⁵ cm²/s at 2100°C, as calculated from activation energy and average grain sizes. This study provides evidence that the dominant mechanism for final-stage sintering of ZrB₂ ceramics is dislocation motion.     

CaO-MgO-Al2O3-SiO2系统玻璃表面析晶的研究

以浮选法黄金生产过程中排放的尾砂为主要原料，综合运用差热分析、X射线衍射、光学显微镜等测试手段，对CaO-MgO-Al2O3-SiO2系统玻璃的表面析晶行为及其动力学等内容进行了研究，其结果对进一步探索该系统玻璃粉末的烧结过程有一定的指导作用，对于合理利用固体废弃物，开发环保型烧结微晶玻璃材料具有实际意义 。     

TiO2加入量对高炉渣微晶玻璃析晶的影响

以高炉渣微晶玻璃为研究对象,改变配料中晶核剂TiO2的含量,制得微晶玻璃样品. 以不同的升温速率对样品进行差热分析,根据升温速率和差热分析曲线上的晶化峰温度,采用3种不同的方法计算微晶玻璃样品的析晶活化能. 结果表明,随着TiO2含量的增加,析晶活化能呈现出先减小后增大的趋势,在TiO2的加入量为3.1%时,微晶玻璃的析晶活化能最低,此时拟合出的3种析晶活化能最小值分别为135.7, 143.9, 151.7 kJ/mol. 样品的红外谱图表明,TiO2的含量为3%~4%时析出晶体较多. TiO2含量为3%和4%的样品的X射线衍射图谱表明,样品中析出了以透辉石为主晶相、金红石为次晶相的晶体.     

Nonisothermal sintering of Cr2AlC powder

This work studies the sintering behavior of ultrafine powder of Cr₂AlC compound during nonisothermal heating using a dilatometer. Sample exhibits relatively slower densification under pressureless condition where relative density increased from about 61% (green compact) to about 73% during heating up to 1350°C. Axial shrinkage data were analyzed through the volume diffusion and grain boundary diffusion‐based sintering models. Estimated activation energy of sintering (352 kJ/mol) for volume diffusion mechanism, was found to be closely matching with the reported activation energy of chromium diffusivity, indicating volume diffusion as a controlling mechanism and chromium as a major diffuser in Cr₂AlC.     

ZrO2对钼渣微晶陶瓷性能的影响

制备了以钼渣为主要原料，以ZrO2作品核剂的微晶陶瓷材料。研究了ZrO2含量变化对钼渣玻璃晶化行为和力学性能的影响。采用XRD、SEM、DTA等测试技术，对该体系的晶化机理进行了探讨。结果发现，当ZrO2的含量为1％时可发生整体析晶，析晶活化能为212．834kJ／mol，抗弯强度为66.9918MPa，显微硬度为6.95GPa。     

氧化铁包覆云母对聚对苯二甲酸乙二醇酯非等温结晶动力学的影响

以氧化铁包覆云母为成核剂,对聚对苯二甲酸乙二醇酯（PET）进行成核改性,采用差示扫描量热法分别研究了不同降温速率下PET和PET/氧化铁包覆云母复合材料的非等温结晶行为,用Jeziorny法和莫志深法对非等温结晶过程进行了分析,并用Flynn-Wall-Ozawa法计算其活化能。结果表明：氧化铁包覆云母对PET具有异相成核的作用,可明显提高PET的结晶速率;与Jeziorny法相比,莫志深法可较好描述PET和PET／氧化铁包覆云母复合材料的非等温结晶过程。进一步分析表明,氧化铁包覆云母的加入并没有明显改变PET基体的成核机理和生长方式,但降低了PET的结晶活化能,从而提高了PET的结晶性能。     

Y2O3掺杂CaO-Al2O3-SiO2系微晶玻璃的研究

在CaO-Al2O3-SiO2(CAS)系统微晶玻璃中引入稀土氧化物Y2O3,结合XRD、SEM等测试手段,研究了Y2O3的引入对微晶玻璃烧结过程、微观结构以及性能的影响。实验结果表明:随着Y2O3的引入,微晶玻璃烧结温度降低,烧结时间变短。当Y2O3质量分数为3.25%时,CAS微晶玻璃具有最佳的制备工艺和最好的力学性能。     

Variation of non‐isothermal crystallization behavior of isotactic polypropylene with varying β‐nucleating agent content

The non‐isothermal crystallization behavior, the crystallization kinetics, the crystallization activation energy and the morphology of isotactic polypropylene (iPP) with varying content of β‐nucleating agent were investigated using differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The DSC results showed that the Avrami equation modified by Jeziorny and a method developed by Mo and co‐workers could be successfully used to describe the non‐isothermal crystallization process of the nucleated iPPs. The values of n showed that the non‐isothermal crystallization of α‐ and β‐nucleated iPPs corresponded to a tridimensional growth with homogeneous and heterogeneous nucleation, respectively. The values of crystallization rate constant showed that the rate of crystallization decreased for iPPs with the addition of β‐nucleating agent. The crystallization activation energy increased with a small amount (less than 0.1 wt%) of β‐nucleating agent and decreased with higher concentration (more than 0.1 wt%). The changes of crystallization rate, crystallization time and crystallization activation energy of iPPs with varying contents of β‐nucleating agent were mainly determined by the ratio of the content of α‐ and β‐phase in iPP (α‐PP and β‐PP) from the DSC investigation, and the large size and many intercrossing lamellae between boundaries of β‐spherulites for iPPs with small amounts of β‐nucleating agent and the small size and few intercrossing bands among the boundaries of β‐spherulites for iPPs with large amounts of β‐nucleating agent from the SEM examination. Copyright © 2010 Society of Chemical Industry