低熔可切削生物活性微晶玻璃的研究

选择一种出SiO₂-MgO-Al₂O₃-K₂O-CaO-P₂O₅-F基础玻璃体系,并添加不同量的ZnO,制备出性能良好的可切削生物微晶玻璃.结果表明,由于ZnO的添加,可使母玻璃的熔化温度由1450℃降至1300℃,可切削生物活性微晶玻璃的母玻璃能够在较低的温度熔化制备.母玻璃晶化后析出相主要为云母相和氟磷灰石相;各种晶相的组合形貌为花瓣形态,其断口呈现穿晶断裂的特征,并有晶体拔出,使材料具备了较高的强度;由于析出了较多的云母相,该微晶玻璃兼具良好的可切削性能.     

赤泥-粉煤灰微晶玻璃晶化行为研究

综合利用赤泥和粉煤灰两种废渣制备高附加值的微晶玻璃材料,两种废渣总吃渣量能够达到90wt%以上,降低了生产成本.对不同核化温度、晶化温度对微晶玻璃显微组织的影响进行了研究.结果表明:最佳核化温度由基础玻璃的DTA曲线的吸热峰确定,大约697℃;最佳的晶化温度略高于DTA析晶峰的温度,大约为950℃.     

ZrO2对低温烧结 BaO-Al2O3-SiO2系微晶玻璃析晶和晶型转变的影响

用烧结法制备了化学计量比和高Ba含量的两组BaO-Al2O3-SiO2(BAS)系微晶玻璃,采用差示扫描量热法(DSC)和X射线衍射分析(XRD)等手段研究了ZrO2对BAS系微晶玻璃中六方钡长石析晶和六方钡长石向单斜钡长石晶型转变的影响.研究表明,两组BAS系玻璃的烧结温度低于850℃,晶化温度低于900℃.六方钡长石的析出为整体析晶.不加形核剂晶型转变为整体析晶;添加ZrO2晶型转变为表面析晶.提高Ba含量或添加ZrO2促进六方钡长石的析出和晶粒细化.化学计量比的BAS系微晶玻璃中添加ZrO2明显促进晶型转变.高Ba含量的BAS系微晶玻璃中添加ZrO2表现为抑制晶型转变,850℃保温100h不发生转变.     

Cr2O3对尾矿氟金云母微晶玻璃电学性能和切削性能的影响

以金尾矿为主要原料,采用传统熔融法制备尾矿氟金云母微晶玻璃。利用DSC、XRD、SEM等检测手段,对尾矿氟金云母微晶玻璃的组织结构、电学性能、加工性能进行研究。实验结果表明:以Cr_2O_3为晶核剂,650℃核化2 h,860℃晶化3 h,可制备主晶相为KMg_3(Si_3AlO_(10))F_2的氟金云母微晶玻璃。随着Cr_2O_3含量增加,其晶体交错程度增大,径厚比达73。常温下,尾矿微晶玻璃体积电阻率达10~(12)Ω·m,而温度达到600℃时,尾矿微晶玻璃体积电阻率为10~6Ω·m;常温100 kHz时,尾矿微晶玻璃的介电常数为8.79～9.64,介电损耗为10~(-3)。随着Cr_2O_3含量增加,材料硬度逐渐下降后达到稳定,材料切削性能先增强,之后趋于稳定,基于材料硬度计算所得的切削性大于0.032。     

烧结法制备煤矸石微晶玻璃及其烧结性能研究

以淮南矿区煤矸石为主要原料,采用烧结法制备了微晶玻璃,并研究了Na_2O含量对基础玻璃熔制温度、微晶玻璃晶化温度、物相组成和微观结构的影响及其对微晶玻璃体积密度、耐酸碱等物化性能的影响。结果表明,以淮南矿区煤矸石为主要原料可以制备出性能优良的微晶玻璃;并且随Na_2O含量从10%增至25%,玻璃熔制和晶化温度分别从1450℃降低到1300℃,950℃降低到700℃;微晶玻璃的主晶相由含铁镁橄榄石相转变为霞石相,最终转变为硅铝酸钠相,且微晶玻璃的结构均匀性不断提高;微晶玻璃的致密性先增加后降低,耐酸碱性良好,但Na_2O含量过多对微晶玻璃耐酸性不利。     

含F-锂镁铝硅微晶玻璃的制备及晶化行为的研究

采用熔融烧结法,引入一定量的MgF2,制备出LMASF系微晶玻璃,采用DTA、XRD对该微晶玻璃的析晶温度和物相组成进行了分析,并采用SEM观察了微晶玻璃的断面形貌.讨论了热处理对微晶玻璃析晶的影响,并对其晶化行为和微观形貌进行了研究.实验结果表明,该微晶玻璃首先析出LixAlx Si1-xO2晶体,后随着温度的升高析出β-锂辉石晶体;最佳晶化温度为786℃,在该温度下保温2h,析出棒状β-锂辉石晶体,晶体长度为2～5μm,长径比较大.     

核化温度对CaO—Al2O3-SiO2-Fe2O3系微晶玻璃微观结构及性能的影响

本文以钢渣和赤泥为主料,采用熔融法制备了CaO对微晶玻璃物相、微观结构及性能的影响。分析测试结果表明,化温度的升高,主晶相衍射峰先增高后降低,晶相析出量增加,晶玻璃的抗弯强度和耐腐蚀性最好。CaO-Al2O3-SiO2-Fe2O3系微晶玻璃,探讨了不同核化温度微晶玻璃的结晶物相不随核化温度的变化而改变。随着核且析出的晶粒尺寸逐渐增大。当核化温度为770℃时,微     

FeO-Fe2O3-CaO-SiO2体系铁磁微晶玻璃的磁性及生物活性

具有生物活性和磁性的微晶玻璃材料被认为是温热疗法治疗癌症的有效热种子材料.本文制备了添加少量B2O3和P2O5后的FeO-Fe2O3-CaO-SiO2体系铁磁微晶玻璃,并进行了微观结构分析、XRD分析、磁性检测以及生理模拟液的浸泡实验.实验结果表明,制备的微晶玻璃材料同时具备磁性和生物活性这两种重要性能.不经过核化处理在1000℃晶化2h能够获得较理想的磁铁矿主晶相和硅灰石次晶相均匀致密分布的微观组织,所得微晶玻璃具有最佳的磁性能.铁含量提高能够增加微晶玻璃的磁性,然而会抑制微晶玻璃表面羟基磷灰石的形成,从而降低其生物活性.     

β-锂霞石负膨胀微晶玻璃的制备技术及结构特征

研究了β锂霞石微晶玻璃的制备技术、结构特征及其负膨胀特征。首先采用玻璃结晶法制备β锂霞石负膨胀微晶玻璃材料,然后通过XRD、SEM等测试手段,表征了β锂霞石微晶玻璃材料的结构特征。并讨论β锂霞石负膨胀微晶玻璃的膨胀系数及其与晶相组成和晶化温度及时间的依从关系,使其负膨胀系数在一定范围内连续可调。研究并制备出热膨胀系数可达到为-1.037×10-5/℃的β锂霞石微晶玻璃。     

MgO-Al2O3-SiO2系堇青石微晶玻璃的制备及性能研究

采用高温熔融法制备了MgO-Al2O3-SiO2系堇青石微晶玻璃,采用DTA、XRD等对试样的热处理工艺和力学性能进行了分析,详细讨论了晶化温度、晶化时间、核化温度及核化时间对该系微晶玻璃力学性能及显微结构的影响。结果表明,对于实验研究的MgO-Al2O3-SiO2系玻璃,于600℃核化处理4h,于1100℃晶化处理2h,可以得到具有较好性能的堇青石基微晶玻璃,其抗弯强度可达182MPa。     

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.     

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.     

Thermal diffusion in binary mixtures H2-CCl2F2 and H2-CHClF2

Thermal diffusion coefficients were measured in two gaseous mixtures, in which one component was close to the critical temperature, in the pressure range (19.6–127.4)·10⁴ N/m² and at a freon concentration of 0.25–0.8.     

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.     

Radial GRIN glasses in Li2O-Na2O-Al2O3-TiO2-SiO2 systems

A series of GRIN glass rods have been developed in Li2O-Na2O-Al2O3-TiO2-SiO2 systems. Negative radial refractive index profiles were generated by exchanging Na+ for Li+ ions in these glass rods. It has been observed that TiO2 plays a vital role in increase in the profile depth and maximum change in the refractive index because of its ambivalent nature. Change in the refractive index can be further increased by increasing the concentration of exchanging cation in the base glass.     

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.     

Si_2N_2O-Al_2O_3-La_2O_3和Si_2N_2O-Al_2O_3-CaO系统的亚固相关系

本文给出了 Si_2N_2O-Al_2O_3-La_2O_3和 Si_2N_2O-Al_2O_3-CaO 系统的亚固相图。实验结果表明:在 Si_2N_2O-Al_2O_3-CaO 系统中有一个未知结构的新化合物 CaO·Si_2N_2O,在3CaO·Si_2N_2O 和3CaO·Al_2O_3两化合物之间形成连续立方固溶体。而 Si_2N_2O-Al_2O_3-La_2O_3系统中则没有发现新化合物。在两个系统的富 Si_2N_2O区,过量的 Si_2N_2O 与 La_2O_3和 CaO 分别反应形成 Si_3N_4与 La_(10)[SiO_4]_(?)N_2(H-相)(和 CaSiO_3。所研究的这两个三元系统中,分别形成了如下几个四元相容性区。在 Si_2N_2O-Al_2O_3-La_2O_3系统内有:H-Si_3N_4-La_2O_3·Si_2N_2O-La_2O_3·Al_2O_3;H-Si_3N_4-La_2O_3·Al_2O_3-La_2O_3·11 Al_2O_3;H-Si_3N_4-La_2O_3·11 Al_2O_3-Al_2O_3;H-Si_3N_4-Al_2O_3-O′s.s;H-Si_3N_4-O′s.s-Si_2N_2O在 Si_2N_2O-Al_2O_3-CaO 系统内有:Si_3N_4-CaSiO_3-CaO·Si_2N_2O-3CaO·Al_2O_3;Si_3N_3-CaSiO_3-3CaO·Al_2O_3-2CaO·Al_2O_3·SiO_(?);Si_(?)N_(?)-CaSiO_3-2CaO·Al_2O_3·SiO_2-Al_2O_3;Si_3N_4-CaSiO_3-Al_2O_(?)-O′s.s;Si_3N_4-CaSiO_3-O′s.s-Si_(?)N_(?)O     

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.