TBA/H2O溶液冷冻干燥制备多孔Al2O3支架及其生物性能

以叔丁醇/蒸馏水(TBA/H2O)结晶体为模板,用冷冻干燥法制备出片层孔及圆形孔的两种孔型氧化铝支架材料,利用SEM观察支架形貌,测试了其生物性能,系统研究浆料溶剂组分含量、冷冻温度对支架材料形貌影响,探讨支架孔结构对成骨细胞附着的影响.结果表明:纯水浆料的多孔陶瓷支架形貌为片层状;加入叔丁醇后,片层间距减少;浆料中叔丁醇含量为90wt;时,孔道呈片层孔及圆形孔的双孔状;纯叔丁醇浆料的陶瓷支架形貌为圆形孔.双孔形貌支架的开孔孔隙率及总孔隙率最高,分别为78.5;和81.8;.孔径随冷冻温度的降低而减小.体外模拟实验表明:片层孔及圆形孔的双孔支架材料有利于细胞在其表面生长,材料表面细胞结构清晰,铺展形态良好.多孔支架材料对细胞的吸附率随孔径的增大而增大.冷冻温度为-10℃时,支架的压缩强度为90.6 MPa,符合骨组织工程中支架材料的强度值要求.     

多孔双相磷酸钙骨组织工程生物支架的制备及性能研究

以碳酸钙(CaCO3)和磷酸(H3PO4)为原料,用湿法合成了双相磷酸钙陶瓷粉体,再采用激光成型技术处理聚氨酯泡沫载体,通过有机泡沫浸渍法合成多孔双相磷酸钙生物支架.采用X射线衍射仪(XRD),红外光谱分析(FT-IR)和扫描电镜(SEM)对样品的组成和形貌进行了表征.结果表明:制得的粉体为双相磷酸钙粉体,包含β-TCP和HAP两相,其中β-TCP为主相,其质量比占86.7;;制得的多孔支架为双相磷酸钙生物支架,孔隙率为90;以上,抗压强度为0.12 MPa,多孔支架具有规则直通孔与不规则三维通孔相结合的孔洞结构,直通孔孔径范围为1.0～1.3 mm,三维通孔孔径范围为200 ～ 700 μm,满足骨组织工程支架对多孔材料的孔径要求;双相磷酸钙粉体和双相磷酸钙生物支架均表现为无细胞毒性.     

粉体粒度对硅藻土基微孔陶瓷结构和性能的影响

以硅藻土为主要原料,采用固相烧结法,制备了硅藻土基微孔陶瓷,探讨了粉体粒度对其比表面积、烧结样品的孔径及其分布、孔隙率等性能的影响.结合SEM、BET、压汞仪等手段对样品进行了表征.结果表明:在d50=3.57～1.17 μm间,随粉体粒度的减小,粉体比表面积上升,烧结样品的平均孔径及孔隙率下降,其后孔径分布变宽并出现团聚;d50=1.17 μm时,粉体比表面积48.59 m2/g,烧结样品平均孔径157.8 nm,孔隙率39.3;;对孔雀石绿溶液的脱色研究表明,粉体粒度减小,多孔陶瓷的脱色能力增强,反应420 min,d50=1.17 μm粉体烧结样品的脱色率达90.8;.     

聚乳酸/羟基磷灰石晶须复合多孔支架的制备与性能研究

采用溶剂浇铸/真空挥发/粒子沥滤方法,采用氯化钠为造孔剂、氯仿为溶剂,最终制备出聚乳酸(PLA)/羟基磷灰石晶须(HAw)复合多孔支架.通过SEM表征了聚乳酸支架的表面形貌,用XRD、SEM、FT-IR等分析了加入不同量HAw的聚乳酸的成分、形貌以及结构特征,并研究羟基磷灰石晶须的添加量对支架的孔洞结构参数、力学性能及生物性能的影响,结果表明:可以通过控制氯化钠的粒度及用量来调节支架的孔径及孔隙率;聚乳酸(PLA)/羟基磷灰石晶须(HAw)复合多孔支架结构均匀,具有较高的孔隙率和良好的孔隙连通性;支架孔隙率在83.94;～91.08;范围内,可以满足骨组织工程对支架材料的要求;复合多孔支架的抗压强度达到5.72～ 12.73 MPa,在羟基磷灰石晶须质量比为10;时达到最大值,为12.73 MPa.     

冷冻干燥法结合淀粉固化制备莫来石多孔陶瓷

以高岭土、氢氧化铝为原料,淀粉为造孔剂和粘结剂,Y2O3为烧结助剂,采用冷冻干燥法结合淀粉固化工艺制备了具有连通开孔结构的莫来石多孔陶瓷.研究了淀粉添加量对浆料前驱体的流变性能、多孔陶瓷的气孔率、孔径分布、显微结构以及力学性能的影响.结果表明:当淀粉含量由15.84vol;增至20.59vol;,浆料前驱体的粘度增加明显;随着剪切速率的增加,浆料前驱体的粘度先显著降低然后趋于稳定,表现为剪切稀化行为.随着淀粉含量的增加,所得多孔陶瓷的孔径尺寸减小,孔径分布趋于均匀,从双峰分布向单峰变化,孔隙率缓慢增加,维持在61.5;～66.2;范围内,当淀粉含量增加到15.84vol;时,抗压强度达到最高值9.5 MPa,孔隙率也达到65.7;.但当淀粉含量进一步增加后,抗压强度有下降的趋势.     

烧成温度对La0.7Ca0.3CrO3/Al2O3导电陶瓷微滤膜支撑体结构与性能的影响

采用高温固相反应烧结法制备La0.7Ca0.3CrO3(LCC)/Al2O3导电陶瓷微滤膜支撑体.研究了烧成温度对制备的LCC/Al2O3支撑体样品的物相组成、微观结构、烧成收缩、孔隙率和孔径分布、电导率、抗弯强度、渗透通量及耐腐蚀性能等的影响.结果表明,高温烧成过程中LCC与Al2O3发生复杂的固相反应,样品主晶相为菱形结构La07Ca0.3Cr1-xAlxO3,并生成了少量LaAl11O18和CaCr2O4等.烧成温度从1350℃提高到1600℃时,样品的烧结程度、电导率、抗弯强度和耐酸腐蚀性能明显提高,而孔隙率明显减小.样品的平均孔径和纯水渗透通量随烧成温度提高,表现出先增大后减小的变化趋势.在1550℃时保温2h烧成制备的LCC/Al2O3支撑体,具有高的孔隙率(43.4;)和抗弯强度(36.9 MPa),其平均孔径(d50)为1.02 μm、纯水通量为2.24 m3/m2·h·bar、电导率为0.11 S/m,且具有良好的耐腐蚀性能.     

SiC泡沫陶瓷的凝胶注模制备与表征

以高分子多糖明胶为胶凝剂,采用凝胶注模工艺制备SiC泡沫陶瓷.测量了分散剂加入前后浆料的ζ电位的变化.研究了分散剂四甲基氢氧化铵(TMAH)、明胶加入量、固含量等对SiC浆料流变性能的影响.结果表明:分散剂的加入对SiC颗粒的动力学行为有显著影响.在碱性范围内,ζ电位绝对值随TMAH加入量的增加而增大;明胶的加入明显提高了浆料的粘度;固含量为65;~74;时,为使浆料具有好的稳定性和流动性,同时保证明胶的成胶性能,TMAH和明胶的加入量应分别控制在2.5;左右及5;~7;为宜.制备的泡沫陶瓷由相互贯通的球形孔室构成,孔隙率最高可达到92;,其孔径分布取决于泡沫体孔隙率,对于孔隙率为76;和90;的样品,其孔径分别达到120 μm 和200 μm.泡沫陶瓷的抗弯强度随相对密度增大而提高,相对密度达到25;时,其抗弯强度可达到25.2 MPa.     

电气石对硅藻土基多孔陶瓷孔结构与孔雀石绿脱色效果的影响

以硅藻土为主要原料,采用固相烧结法和低温煅烧工艺,制备了硅藻土基多孔陶瓷.着重考察了电气石对材料的微观结构、孔径分布等材料孔结构及孔雀石绿溶液脱色能力的影响,通过扫描电镜、压汞仪等手段对不同电气石含量的硅藻土基多孔陶瓷进行了表征.结果表明:当电气石含量为12;时,材料内孔径细小,平均孔径最小177.5 nm,比表面积最大6.83 m2/g;电气石含量由0提高到16;,材料的孔隙率由49.3;降至36.5;,对孔雀石绿溶液的脱色能力逐渐增强.当电气石含量为16;时,反应6 h后,412 nm与618 nm处吸收峰消失.     

纳米ZnO改性对A12O3微滤膜孔径分布及渗透通量的影响

以Zn(NO3)2和尿素为主要原料,采用均相沉淀法对Al2O3微滤膜进行了纳米ZnO修饰改性,研究了改性溶液中Zn(NO3)2浓度和改性次数对Al2O3微滤膜孔径分布、孔隙率和纯水渗透通量的影响.结果表明:Zn(NO3)2浓度增大和改性次数增加时,膜孔径和孔隙率明显减小,孔径分布变窄.当Zn(NO3)2浓度为0.3 mol/L并经2次改性后,可在Al2O3微滤膜孔表面形成致密的纳米ZnO改性涂层,改性膜平均孔径约为0.80 pn且孔径分布最窄,在膜平均孔径减小25.2;的情况下,水通量可提高49.3;.     

双模板法制备分级孔结构SiC陶瓷

以冰晶和聚苯乙烯(PS)微球为模板,微米级SiC粉体为原料,通过双模板法制备了具有三级孔径分布的多孔SiC陶瓷.研究了SiC的固含量和PS微球的大小对多孔SiC陶瓷的微观形貌、孔隙率和压缩强度的影响.研究结果表明:分级孔结构的多孔SiC陶瓷具有冰模板升华后遗留下的对齐排列的大孔、分布于孔壁中的由PS微球热解留下的中孔和颗粒之间堆积形成的小孔.随着SiC固相含量的增加,大孔孔径和孔容降低,但压缩强度增加.当PS微球粒径约为0.90 μm时,中孔孔径分布在0.7～1.5 μm之间;当PS微球粒径约为2.51 μm时,孔径分布较宽,约为1～3 μm.     

Modelling of mechanism of agglomeration of KCl crystallization

The article presents an analysis into agglomeration during KCl vacuum crystallization. The theoretical and experimental investigations into the mechanism of agglomeration during mass crystallization result in an extension of the growth phenomena within the known model equations. The basis for this is essentially constituted by the collision model concepts of the theory of floculation in disperse systems. The parameters derived from the microprocess analysis (energy dissipation, content of solids, growth rate of individual grains) lead to model equations which are confirmed by laboratory and test trials.     

Relationship of Morphological Types of Dynamic Forms of Crystals

Crystallography Reports - The relationship of morphological spectra (sets of data on the morphological types of real polyhedral crystals and their probabilities under current physicochemical...     

Development of Pauling's concepts of geometric characteristics of atoms

The evolution of the geometric characteristics introduced by Pauling and their dependence on the specific features of the structure and chemical bonds have been considered. The values of the covalent and van der Waals radii are given as well as their relationships and mutual transitions.     

A review of measurement of thermophysical properties of silicon melt

Measurements of thermophysical properties of Si melt and supplementary study of X-ray scattering/diffraction by the authors' group were reviewed. The values obtained differed variously from those of literature. Density was 2–3% larger, surface tension 20–30% smaller, viscosity up to 40% larger, electrical conductivity 8% smaller, spectral emissivity more or less in good agreement with literature values, and thermal diffusivity a few percent larger. An anomalous density jump was found near the melting point. Surface tension and viscosity also showed anomaly. A strange time-dependent change of density was observed over 3 h after melting. X-ray analyses suggested a slight change in local atom ordering, but showed no sign of cluster formation. An addition of 0.1 at% gallium caused the density jump to disappear, while that of boron caused no change. An EXAFS study of the former melt indicated a strong interaction between Ga and Si atoms as if molecules of GaSi₃ existed. The implications of the measured properties are a possibility of soft-turbulence in an Si melt in a relatively large crucible, a more complicated manner of intake of oxygen depleted molten Si from the free surface region to underneath the growing crystal, and a relaxation of the melt after melting arising from trapped gas species.     

Generation of crystal structures of heteromolecular compounds by the method of discrete modeling of packings

Within the method of discrete modeling of packings, an algorithm of generation of possible crystal structures of heteromolecular compounds containing two or three molecules in the primitive unit cell, one of which has an arbitrary shape and the other (two others) has a shape close to spherical, is proposed. On the basis of this algorithm, a software package for personal computers is developed. This package has been approved for a number of compounds, investigated previously by X-ray diffraction analysis. The results of generation of structures of five compounds—four organic salts (with one or two spherical anions) and one solvate—are represented.     

Velocities of Disappearance and Lifetime of Faces of Growing Crystals

The formulae for absolute R_disap and relative R velocities of disappearance and lifetime τ of faces of growing crystals have been derived for stationary growth. It was shown that the quantities are determined by the relative growth velocity R_A/R_critA of the vanishing face A with respect to the critical growth velocity R_critA and by the geometry of a crystal expressed by the trigonometric functions of interfacial angles β and γ formed between face A and the adjacent faces. R increases and τ decreases with the increase in R_A/R_critA to certain limiting values. The calculations have been verified and illustrated by the experimental results for triclinic potassium bichromate (KBC) crystals. Results enable ones to predict values of velocities of disappearance and lifetimes of undesirable, supplementary faces of any real crystal.     

Dependence of the parameters of equations of viscous flow on chemical composition of silicate melts

The temperature dependence of viscosity of silicate melts is discussed in the framework of the Avramov–Milchev (AM) equation. The composition is described by means of two parameters: the molar fraction, x, and the “lubricant fraction”, l. The molar fraction is the sum of the molar parts x_i of all oxides dissolved in SiO₂, the molar fraction of the latter being 1 ? x. It is shown that, with sufficient precision, two of the parameters of the AM equation can be presented as unique functions of the molar fraction. On the other hand, x is not sufficient to determine properly the reference temperature T_r , at which viscosity is η_r = 10¹³ [dPa.s]. Therefore, additional parameter, “lubricant fraction” l, is introduced. For each of the components, l_i is a product of molar part x_i and a specific dimensionless coefficient 0 ≤ k_i ≤ 1 accounting for the specific contribution of this component to the increased mobility of the system. It is demonstrated that, for l > 0, the reference temperature is related to the “lubricant fraction” l through the reference temperature T_r,SiO2 of pure SiO₂.     

Comparative analysis of two methods of calculation of the orientation of domain walls in ferroelastics

Two types of domain-wall equations are analyzed: the equations derived by the Sapriel method and the equations obtained by interface matching of the thermal-expansion tensor. It is shown that, for W-type domain walls, these methods yield the same equations. For W′-type domain walls, the equations obtained by different methods coincide for proper ferroelastics and differ for improper ferroelastics.     

Mechanism of thermal expansion of structural modifications of zinc pyrovanadate

Crystal chemical characteristics of the α and β modifications of Zn₂V₂O₇ are calculated based on in situ high-temperature X-ray measurements. The expansion of the structure is found to be strongly anisotropic up to the negative volumetric thermal expansion of the α-Zn₂V₂O₇ unit cell in the temperature range of 300–600°С, α _V =–17.94 × 10^–6 1/K. The transformations of the “hard” and “soft” sublattices with an increase temperature and at the phase transition are considered in detail. It is shown that the negative volumetric thermal expansion of α-Zn₂V₂O₇ is due to the degeneracy of the zigzag-like shape of zinc–oxygen columns at constant distances between their vertices.