含碱金属离子的CaO-B2O3-SiO2系玻璃陶瓷性能研究

研究了碱金属氧化物对CaO-B2O3-SiO2(CBS)系玻璃陶瓷的软化析晶温度以及材料的烧结、介电等方面性能的影响。结果表明:对于添加双碱的CBS玻璃,随双碱金属离子半径增大软化温度呈升高趋势,而析晶峰值温度呈降低趋势。Na2O和K2O添加对于改善CBS系玻璃陶瓷烧结性能效果更好,试样内部晶粒分布均匀、结构致密。烧成试样主晶相均为CaSiO3,CaB2O4和石英。试样的介电常数和介电损耗随频率的增加而减小。随着测试温度的升高,试样的介电常数略有增加,而介电损耗呈降低趋势。     

低温烧结Ca[(Li0.33Nb0.67)0.7Ti0.3]O3-δ陶瓷及其微波介电性能

采用锌硼硅玻璃作为烧结助剂实现了Ca[(Li0.33Nb.0.67)0.7Ti0.3]O.3-δ陶瓷的低温烧结,研究了锌硼硅玻璃添加量对Ca[(Li0.33Nb0.67)0.7Ti.0.3]O.3-δ陶瓷的烧结特性、微观结构和微波介电性能的影响.研究表明:随着锌硼硅玻璃添加量的增加,陶瓷体密度和介电常数迅速增加,而Q@f值下降.在910℃的温度下,通过掺入8wt%的锌硼硅玻璃,获得了介电性能较好的低温共烧陶瓷,其εr=36.94,Q@f=4380GHz(3.35GHz).     

不同形态SiO2改性钙硅硼系微晶玻璃结构与性能

分别研究了高硅氧玻璃(96wt%SiO2,非晶态)与二氧化硅(99wt%,石英相)的添加对CaO-SiO2-B2O3(CSB)微晶玻璃微观结构、烧结性能以及介电性能的影响.结果表明:不同形态SiO2的添加均可以有效地降低介电常数,同时高硅氧玻璃的引入增加了试样的介电损耗.添加15wt%SiO2、850℃低温烧结试样,在10MHz下,介电常数为6.01,介电损耗1.2 × 10-3,且在5～40MHz频率范围内,介电常数随频率的变化不大.烧结试样的主要晶相为Quartz、CaSiO3和CaB2O4.     

硼硅玻璃—SiO2系统的介电性能研究

对硼硅玻璃－ＳｉＯ２系统的介电性能进行了研究，通过调整配比，得出４０ｗｔ％硼硅玻璃－６０ｗｔ％ＳｉＯ２的玻璃陶瓷在８５０℃烧结样品的介电常数εｒ为４．８０。并研究了不同频率下硼硅玻璃－ＳｉＯ２玻璃陶瓷的介电性能。     

添加铅硅玻璃对烧结堇青石基微晶玻璃性能的影响

研究了铅硅玻璃在堇青石基微晶玻璃烧结中的作用及其添加量对微晶玻璃性能的影响．结果表明：铅硅玻璃的加入可以促进微晶玻璃的烧结致密化;随着铅硅玻璃加入量的增加,烧结样品的介电常数亦增加,且与密度变化曲线相似;微晶玻璃烧结样品的热膨胀系数符合加和性规律．     

CBS玻璃/堇青石陶瓷复合材料制备与性能

采用电子陶瓷工艺制备了一系列钙硼硅玻璃／堇青石陶瓷复合材料，堇青石含量分别为50％，60％，70％和80％（质量分数）。对复合材料进行了X射线衍射分析、扫描电镜（SEM）观察和性能测试。结果表明：复合材料的介电常数和热膨胀系数随陶瓷含量的增加而减小，显微硬度随陶瓷含量的增加而增加。堇青石的加入抑制了钙硼硅玻璃中石英的析出，并生成了新相钙长石，其数量随堇青石和烧结温度的增加而增加，但它没有恶化复合材料的物理性能。所制得的复合材料具有高的相对密度（≥96％）、低的介电常数（～6）、低的介电损耗（0.3％～0．5％）、低的热膨胀系数（4．2×10^-6℃^-1～5．2×10^-6℃^-1）和低的烧结温度（≤950℃），有望用作介电材料和基板材料。     

掺CaO-B2O3-SiO2玻璃烧结制备MnZn铁氧体及其磁性能

采用传统陶瓷工艺制备了CaO-B2O3-SiO2(CBS)玻璃掺杂的MnZn铁氧体.研究了CBS玻璃掺入量及烧结温度对MnZn铁氧体的烧结特性及磁性能的影响.结果表明:样品的密度随着CBS掺入量的增加而不断减小,磁性能随着温度的升高而不断增强;掺入适量CBS可在烧结时形成液相,使固体颗粒间产生液相烧结并促进晶粒的长大....     

低温烧结玻璃陶瓷复合材料的性能

采用电子陶瓷工艺制备了一系列玻璃陶瓷复合材料，对复合材料进行了X射线衍射分析、扫描电镜（SEM）观察和性能测试。结果表明：复合材料的介电常数和热膨胀系数随硅灰石含量的增加而减小，显微硬度随硅灰石含量的增加而增加。随着硅灰石量的增加，复合材料烧结致密化温度移向高温。硅灰石的加入抑制了玻璃中方石英和钙硼石的析出，有利于硅灰石相的形成。当硅灰石含量为40％时所制得复合材料的性能最佳，即有高的相对密度（96％）、低的介电常数（5）、低的介电损耗（约0．2％）、低的热膨胀系数（约7．1×10^-6/℃）和低的烧结温度（950℃），有望用于基板材料。     

氧化锆/锌硼硅微晶玻璃的制备与研究

在锌硼硅玻璃中添加0％～20％（wt）的超细部分稳定氧化锆粉体，分别采用熔融法和烧结法制备氧化锆／锌硼硅微晶玻璃。通过对实验现象的观测与分析，发现采用烧结法可以较好地制备氧化锆／锌硼硅微晶玻璃。采用X射线衍射仪观测玻璃样品中的晶相组成，用烧结点试验仪测试微晶玻璃的半球温度，通过维氏硬度计在玻璃表面的压痕尺寸计算微晶玻璃的韧性。结果表明，在ZnO-B2O3-SiO2玻璃中添加部分稳定超细ZrO2后，微晶玻璃的烧结温度升高，韧性得到很大的改善。     

不同Ca/Si比对钙硼硅三元微晶玻璃的性能影响

采用XRD、SEM、DSC等测试分析手段研究了Ca/Si比变化对CBS微晶玻璃晶相、微观结构和电性能的影响。结果表明在固定B2O3的含量为17%（摩尔分数）时,发现当m（Ca/Si比）〈1.08时,CBS微晶玻璃的烧结温度〉900℃,当m〉1.08时,CBS微晶玻璃的烧结温度900℃。当m达到1.767时,CBS微晶玻璃无法烧结;随着CaO含量的增加,Ca2SiO4晶体逐渐增加,硅灰石相逐渐减少,石英相逐渐增加;在1MHz下,C2、C5和C7试样烧结后电损耗均〈2×10-3。     

Preparation of ZrO2-CeO2 and HfO2-CeO2 nanopowders

We prepared weakly agglomerated powders of ZrO₂-CeO₂ and HfO₂-CeO₂ solid solutions 5–8 nm in particle size, consisting of monoclinic and tetragonal phases. After heat treatment at 1200°C, the crystallite size was 30 and 14 nm, respectively. We also examined the effect of precipitate freeze drying on the crystallization of hafnia-based solid solutions containing up to 20 mol % CeO₂.     

Comparison of the Electronic Structures of La2CuO4, Sr2CuO2Cl2, and Sr2CuO2F2

First-principles cluster calculations are reported of the local electronic structure of the three compounds: La₂CuO₄, Sr₂CuO₂Cl₂, and Sr₂CuO₂F₂. The copper ${\text{3d}}_{x^2 - y^2 } $ and the planar oxygen 2p _σ atomic orbitals exhibit a similar degree of covalency. The out-of-plane orbitals, however, are quite different with the ${\text{3}}d_{3z^2 - r^2 } $ atomic orbital lowered significantly in energy for chlorine and fluorine apical positions.     

Thermoelectric power of single-phase samples of Tl2CaBa2Cu2O y and Ba2CaSr2Cu2O y

Single-phase 2122 samples of thallium and bismuth superconductors were made by the precursor matrix method. The thermopower of these samples was measured in the temperature range 250 K-T _c . The thermopower was positive and decreased linearly with increasing temperature aboveT _c (onset). The exponential enhancement of thermopower seen in the undoped and doped YBCO was not observed in these samples. The linear variation of thermopower can be explained on the basis of either a two-band model or a narrow band model.     

VLE data for CO2-CF2Cl2, N2-CO2, N2-CF2Cl2 and N2-CO2-CF2Cl

Knowledge about vapour-liquid (VLE) is required as a basis of reliable calculations for separation processes. Correlations available for the prediction of T, p, x, y data are less accurate for mixtures at high pressures and mixtures containing supercritical components. The results of VLE experiments are reported and compared with data calculated with equations of state.     

Structure of Na2O·2TiO2 glass

X-ray radial distribution analysis and Raman spectroscopic measurement were carried out on Na₂O-2TiO₂ glass prepared by twin-roller quenching method. It is found that four-coordinated Ti⁴⁺ ions may be predominant over six-coordinated ones in the present glass. It is also found that the fraction of six-coordinated Ti⁴⁺ ions is larger in the present glass than in K₂O·2TiO₂ and Cs₂O·2TiO₂ glasses. Poorer glass-forming ability of the Na₂O-TiO₂ system compared with the K₂O-TiO₂ and Cs₂O-TiO₂ systems is ascribed to a larger fraction of TiO₆ octahedron for the former system.     

SiO2—TiO2—ZrO2系涂层的制备及其特性

用溶胶－凝胶法（sol-gel method）在不锈钢表面制备了SiO2-TiO2-ZrO2系无机氧化膜（STZ）。用DTA／TG、IR、XRD和SEM等手段研究了涂层制备时由凝胶向玻璃态的转变以及涂层薄膜的显微结构特点，考察了涂层对基体的保护效果。试验结果表明，在溶胶至凝胶最终转变为无机氧化物的过程中形成了无机网络，Si^4 和Zr^4 充当了网络骨架的形成离子。涂层为无定型玻璃态，其间混有石英、锐钛矿或金红石等微晶。     

Elastic and Electronic Properties of Superconducting CaPd 2 As 2 and SrPd 2 As 2 vs. Non-superconducting BaPd 2 As 2

The first-principles calculations were performed to predict the elastic and electronic properties of the superconducting ThCr₂Si₂-type phases CaPd₂As₂ and SrPd₂As₂ in comparison with the non-superconducting CeMg₂Si₂-type phase BaPd₂As₂. Besides, the same properties were compared for CeMg₂Si₂- and ThCr₂Si₂-type polymorphs of BaPd₂As₂. We found that all these phases are mechanically stable and belong to soft materials with low hardness. The near-Fermi region is formed by the valence states of the blocks [Pd₂As₂] with decisive contributions of Pd 4d states. The values of N(E _F) increase in the sequence: CaPd₂As₂ < SrPd₂As₂ < BaPd₂As₂, i.e. in the reverse sequence relative to the transition temperatures T _C. Thus, the change in T _C cannot be explained by the electronic factor, i.e. by the simple correlation T _C～N(E _F). Most likely the decrease in T _C in the sequence CaPd₂As₂ → SrPd₂As₂ and the absence of a superconducting transition in BaPd₂As₂ are related to the structural factors and the peculiarities of the electron–phonon coupling mechanism.     

Investigation of Instability of Lattice of Bi_2Sr_2CaCu_2O_x

Bi2Sr2CaCu2Ox superconductor was studied by differential scanning calorimetry (DSC) and thermogravimetry (TG) in different atmospheres. It is discovered that there is a thermal anomaly in the DSC curve, associated with a weight loss in the TG curve before the melting of the sample. Careful thermal analysis and high temperature X-ray diffraction reveal that the thermal anomaly and the weight loss show an instability of the crystalline Iattice. By annealing the sample in oxygen and argon, respectively and then by TC measurement and thermal analysis, the coincidence of transition temperature with the instability is found. The coincidence is further confirmed by Y-doped 2212 phase.     

Thermal conductivity of the system N2O4 ⇄ 2NO2 ⇄ 2NO + O2

Experimental data on the thermal conductivity of dissociating nitrogen tetroxide have been obtained by the hot-wire method in the temperature range from 290 to 870° K at pressures up to 10⁵ N/m².