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.     

La2O3的添加对P2O5-Al2O3-SiO2系微晶玻璃性能的影响

以ZrO2为晶核剂,根据DSC图谱制定合理的热处理制度,制备了磷扩散源P2O5-Al2O3-SiO2系微晶玻璃。采用XRD分析观察了P2O5-Al2O3-SiO2系微晶玻璃的析晶状况,热膨胀仪测试了该微晶玻璃的膨胀系数,分析La2O3的含量对P2O5-Al2O3-SiO2系微晶玻璃在高温下释放P2O5速率的影响。结果表明:随着La2O3含量增加,P2O5-Al2O3-SiO2系微晶玻璃中晶体含量增加,主晶相未发生改变,都为磷酸锆晶体;同时,该微晶玻璃的热膨胀系数相对降低,P2O5的释放速率也随之增加。     

烧结法制备Li2O-Al2O3-SiO2微晶玻璃的烧结制度及性能研究

采用烧结法制备了Li2O-Al2O3-SiO2(LAS)微晶玻璃。通过DSC分析，并结合对LAS微晶玻璃烧结过程的研究，提出了其较合适的烧结制度。用XRD对该微晶玻璃的物相组成进行了研究，讨论了烧结温度对LAS微晶玻璃热膨胀系数及抗弯强度的影响。为获得具有结构均匀致密、晶相含量高的LAS微晶玻璃，应使烧结温度尽量接近主晶相析晶温度。本文研究的LAS微晶玻璃的适宜烧结温度为1130℃。     

MgO-Al2O3-SiO2系统微晶玻璃晶化行为及性能研究

本文制备了MgO-Al2O3-SiO2系微晶玻璃，用XRD、DTA、SEM等方法对该系统微晶玻璃材料的析晶过程进行了研究。在此基础上，讨论了晶化行为对微晶玻璃的热学及力学性能的影响。结果表明：材料的热学性能及力学性能取决于热处理工艺。晶化温度950-980℃段，微晶玻璃试样的致密性好，力学强度优良。     

溶胶-凝胶制备Li2O-Al2O3-SiO2微晶玻璃的研究进展

Li2OAl2O3SiO2系统微晶玻璃由于其膨胀系数低,耐高温及抗热冲击性等优异性能而受到广泛重视。本文主要介绍了溶胶凝胶工艺原理、制备过程,及在Li2OAl2O3SiO2系微晶玻璃上的应用,最后简述了Li2OAl2O3SiO2系微晶玻璃的应用现状。     

复合晶核剂TiO2/ZrO2对MgO-Al2O3-SiO2系统微晶玻璃的影响研究

本文制备了Mg0-Al2O3-SiO2系微晶玻璃,用XRD、DTA等方法对该系统微晶玻璃材料进行了研究;讨论了复合晶核剂对材料热膨胀性能及热处理温度的影响.结果表明TiO2/ZrO2复合晶核剂中,少量ZrO2(＜0.5wt%)能够降低微晶玻璃材料的热处理温度和热膨胀系数.     

CaO-Al2O3-SiO2系统微晶玻璃的冲蚀磨损研究

CaO-Al2O3-SiO2系统微晶玻璃装饰板材是一种新型建筑装饰材料。本文利用冲蚀磨损实验研究了影响CaO-Al2O3-SiO2系统烧结法微晶玻璃装饰板材磨蚀行为。讨论了微晶玻璃组成、结构、磨粒粒径、冲蚀角、冲蚀时间对CaO-Al2O3-SiO2系统微晶玻璃的冲蚀性的影响。结果表明:随着微晶玻璃中晶相含量的增加,磨料对其表面的冲蚀磨损量明显下降。微晶玻璃的冲蚀量随冲蚀角的增大、冲蚀时间的增长、磨粒粒度的增大而增加。     

K2O含量对B2O3-Al2O3-Na2O玻璃结构及物理性能的影响

选取B_2O_3-Al_2O_3-Na_2O三元玻璃系统,研究改变玻璃系统中K_2O的含量对硼酸盐低熔点封接玻璃性能的影响。通过XRD、DTA等手段对玻璃样品的膨胀系数、转变温度、软化温度、电阻率、介电常数等性能进行了测试。结果表明:在B_2O_3-Al_2O_3-Na_2O三元玻璃系统中,随着K_2O含量的增加,硼酸盐玻璃的膨胀系数呈先下降后上升的趋势,在K_2O含量位于5 mol%左右时,硼酸盐玻璃的膨胀系数小幅下降,这是硼反常现象的体现。K_2O含量在7～8 mol%左右时,膨胀系数出现最低值。玻璃的体积电阻率和介电常数的变化也存在着硼反常现象,随着K_2O含量的增加,均呈现先下降再上升后又下降的趋势。玻璃的转变温度T_g和软化温度T_f的变化趋势基本一致,均呈现先下降后上升再下降的趋势。     

Li2O-Al2O3-SiO2系低膨胀微晶玻璃的研究

本文以Li2O-Al2O3-SiO2(LAS)系统为基础玻璃成分，锂辉石、高岭土、石英砂、滑石等矿物和部分化学试剂为主要原料，采用熔融法制备了LAS系低膨胀微晶玻璃。运用XED和SEM等现代测试分析手段对材料的晶相和显微结构进行了观察和分析，并讨论了不同的Li2O、Al2O3、SiO2之比和不同的晶核剂对析出主晶相的影响。实验表明，所制微晶玻璃的主晶相为β-锂辉石固溶体，晶粒尺寸为0.5～2μm，材料不透明，其抗折强度为80～108MPa。     

Na2O-Al2O3-B2O3系统低熔点玻璃的热学性质研究

介绍了Na2O-Al2O3-B2O3系统玻璃的制备，确定了Na2O-Al2O3-B2O3系统玻璃的成玻范围，研究了玻璃的转变温度（Tg）、软化温度（Tf）和热膨胀系数（α），以及玻璃的Tg、Tf、α与玻璃组成的关系。     

Na2O-Al2O3-B2O3玻璃的热学性质和红外光谱

制备了Na2OAl2O3B2O3系统低熔点玻璃,确定了Na2OAl2O3B2O3系统玻璃成玻范围,研究了玻璃的转变温度(Tg)、热膨胀系数(α)和玻璃的红外光谱,表明这种玻璃的熔化温度低、转变温度也较低、玻璃的热膨胀系数较大,在近红外区有一水分的吸收带,在中红外区有BO、AlO的特征吸收带,以及玻璃的Tg、α与玻璃组成的关系。     

热塑性聚酰亚胺的热膨胀系数研究

利用静态热机械分析仪（TMA）测定了热塑性聚酰亚胺（TPI）注塑件的热膨胀系数α，考察了TPI的各向异性、尺寸稳定性以及添加不同填料对α的影响。结果表明：TPI存在着各向异性，且流向面的α最低。在正常的使用范围内，试样经历一个升降温循环后尺寸基本没发生变化。经消除热历史后，材料的α降低；类似地，热处理也能使。减小。在主链相同的TPI树脂中，加入玻纤、碳纤维等高强度、高热稳定性的填料有助于降低TPI的α。     

Effect of CuO addition on crystallization and thermal expansion properties of Li2O–ZnO–SiO2 glass-ceramics

A Li₂O-ZnO-SiO₂ (LZS) glass system was modified with CuO, and its phase development, microstructure evolution, crystallization kinetics and thermal expansion properties were investigated as a function of heat treatment temperature. As a result of the X-ray diffraction study and microstructure observation, lithium zinc silicate formed as the first crystalline phase with increasing heat treatment temperature. Silica polymorph developed as minor crystalline phase at higher temperatures. From the X-ray diffraction patterns, CuO addition led to a decrease in both the crystallization temperature of lithium zinc silicate phase and the volume fraction of quartz phase. According to the crystallization kinetics, the crystallization activation energy for lithium zinc silicates is almost equal to the diffusion activation energy of Zn²⁺ in glass, it suggests that the diffusion of network modifier Zn²⁺ dominates the crystallization of lithium zinc silicates. Additionally, CuO addition caused the transition of Zn²⁺ from network modifiers to network formers. From the thermal expansion coefficient measurements, two abrupt changes in slope of the thermal expansion curves were observed and attributed to the phase transitions of cristobalite and lithium zinc silicate, respectively. Comparison of the thermal expansion coefficient of two types of glass-ceramics revealed that CuO addition in the LZS system can partly inhibit the formation of cristobalite at high temperatures.     

微波固化环氧树脂/苯酚封端的聚氨酯预聚体系的热膨胀行为研究

以二苯甲烷二胺(DDM)为交联剂，研究了环氧树脂／苯酚封端的聚氨酯(EP／PU)预聚体系在微波固化条件下的热膨胀行为；并通过热膨胀行为考察了体系热膨胀系数、玻璃化转变及其与微波功率、体系组成之间的关系。结果表明：当体系组成一定时，随着微波功率的增加，体系中富EP相和富PU相的玻璃化转变移向高温，过渡相的转变加宽，膨胀系数变小。在一定组成范围内，体系具有两个玻璃化转变，随着PU和EP含量的接近，富EP相和富PU相的玻璃化转变温度差值缩小。组成相同的体系，微波固化产品的热膨胀系数低于热固化。     

含ZnO/SnO_2的SiO_2-B_2O_3-Bi_3O_2封接玻璃性能的研究

用传统熔融冷却法制得SiO_2-B2O3-Bi3O_2系统玻璃,采用差热分析法研究了玻璃的结构和玻璃的特征温度Tg和Tf,测试了玻璃的密度、热膨胀系数、介电常数等性能。结果表明,在SiO_2-B_2O_3-Bi_3O_2系统玻璃中,当ZnO含量增加,ZnO/SnO_2质量比上升时,玻璃的热膨胀系数、密度和摩尔体积均呈下降趋势,玻璃的转化温度Tg和软化温度Tf变化不大,析晶温度Ts则有明显的上升。     

Crystallization and thermal expansion behavior of lithium zinc silicate sealing glass

Effect of heat treatment schedule on the crystallization and thermal expansion behavior of a lithium zinc silicate glass system was investigated by differential scanning calorimeter (DSC), X-ray diffraction, and linear thermal expansion test. Two well-defined crystallization exothermic peaks were observed from the DSC trace. According to the apparent activation energies and avrami parameter values calculated from the two crystallization exothermal peaks, the first crystallization exothermal peak was attributed to a combining surface and internal crystallization behavior, while the second one was found to be internal crystallization. Additionally, the phase evolution and the thermal expansion behavior with increasing heat treatment temperature were found to be closely related. Interestingly, it was found in comparison with previous reports that addition of CaO varies the phase composition of the resulting glass–ceramic in an opposite way to K₂O and the deep rooted reason has been discussed which may cast light on the modulation of properties of glass–ceramic involved crystalline phase of quartz or cristobalite. At last, average thermal expansion coefficient of 7.99–15.38×10⁻⁶ K⁻¹ in the temperature range of 25–400 °C has been obtained with different heat treatment schedules.     

Evidence of anomalous thermal expansion of water in cement paste

A comparative study of permeability measurement by thermopermeametry (TPA) and beam bending was performed on cement paste. To bring the two measurements into agreement, it is necessary to recognize that the pore solution has a thermal expansion coefficient about one and a half times that of bulk liquid and to account for viscoelastic stress relaxation during TPA experiments. The anomalous thermal expansion is not accounted for by the presence of ions in the cement paste pore solution.     

Role of CaF2 on mechanochemically synthesized leucite as dental veneering glass ceramics

Leucite based glass ceramic is widely used in dental ceramics as porcelain fused to metals for veneering applications. Main properties considered here are high coefficient of thermal expansion and good mechanical properties. Owing to these requirements, high expansion phase such as leucite is incorporated in these glass ceramics. The present work was aimed to synthesise leucite using its stoichiometric batch compositions and subsequent high energy ball milling. CaF₂ was also added in another mix to study its role on leucite formation. Further prepared, leucite phase was added in separately prepared low temperature glass frit powders to control amount of glass and leucite content. X-ray diffraction results displayed that high energy ball milling and additive promoted the formation of leucite as a major crystalline phase. Furthermore, CaF₂ also suppressed the subsidiary crystallisation of kalsilite phase. Evaluated average coefficient of thermal expansion in the temperature range of 20–500°C was very close to the theoretical value of pure leucite.