氨基酸/氧化石墨烯/羟基磷灰石复合材料在酸蚀人牙釉质体外再矿化中的应用

本文研究了甘氨酸(Gly)和氧化石墨烯(GO)复合改性羟基磷灰石(Gly/GO/HA),以及天冬氨酸(Asp)和GO复合改性羟基磷灰石(Asp/GO/HA)对酸蚀人牙釉质(HE)体外再矿化的影响。通过CCK-8法测定不同复合材料的细胞毒性,通过场发射扫描电镜、EDX能谱分析、X射线衍射和显微硬度测试,对再矿化前/后HE表面及剖面形貌、表面元素组成、表面成分结构和表面力学性能进行表征。结果表明:Gly/GO/HA和Asp/GO/HA均有良好的安全性和生物相容性,且均能使酸蚀HE得到一定的修复,其中Gly/GO/HA对酸蚀HE表面和深层脱矿的修复效果优于Asp/GO/HA。     

EDTA辅助Ti3Al/HAP复合材料表面沉积HAP涂层及表征

本研究利用Ca(NO3)2·4H2O,EDTA-2Na,NaH2PO4配制钙磷溶液,将热压烧结法制备的Ti3Al/HAP复合材料进行抛光并酸蚀后,放入钙磷溶液中浸泡矿化.经过一定矿化阶段,可以在复合材料样品条表面形成一层由六方棱柱状HAP晶体组成的致密涂层,SEM测试结果显示,六方棱柱状HAP晶体平行排列,垂直于复合材料表面,XRD图谱显示晶体沿c轴排列,(001)晶面平行于复合材料表面.将上述涂层放入模拟体液中浸泡,可以在其上面再形成一层由细小晶粒组成的涂层,新涂层新晶粒发育不完整,晶体取向不明显.     

Ti3Al/HAP复合材料的制备与性能研究

采用化学沉淀法在模拟体液中制备了纳米羟基磷灰石(HAPs)粉体,用金属钛粉和铝粉经过机械合金法,制备了金属间化合物Ti3 Al;将制备的HAP粉体作为基体材料加入第二相Ti3Al粉体,经过球磨分散得到Ti3Al/HAP复合粉体,经过热压烧结,得到羟基磷灰石与金属间化合物Ti3Al的复合材料.通过XRD、SEM及TEM等测试方法,分析了用普通化学沉淀法制备的羟基磷灰石(HAPc)和在模拟体液中生成的羟基磷灰石(HAPs)的区别及Ti3Al对羟基磷灰石结构和性能的影响.测试结果显示:在模拟体液中生成的羟基磷灰石颗粒均匀细小,纯度较高,结晶度较低;羟基磷灰石掺入一定量的Ti3Al后,弯曲强度和断裂韧性有所降低,X射线衍射显示复合材料中只有Ti3 Al和HAP两种物质,没有新物质生成.     

基于正交实验优化沉淀法制备针状羟基磷灰石

羟基磷灰石(HAP)已在临床得到运用,但其强度低、韧性差、不易成型等缺点依旧制约着其的广泛应用.为制备出理想且能满足临床应用的纳米针状羟基磷灰石,本文在不添加任何分散剂和表面活性剂的条件下以磷酸钠与硝酸钙为原料,氢氧化钠调节pH,使用正交实验设计对沉淀法中针状HAP的制备工艺进行优化.结果表明,反应条件对HAP晶体形貌的影响程度为:温度>滴加速度>pH;当反应pH=9、反应温度为90 ℃和滴加速度为2 mL/min时为其优方案,可制备出性状规则、粒度均匀、结晶度高、趋向于针状的纳米羟基磷灰石粉体.反应温度升高可提高HAP的结晶速度,可增大HAP晶体的大小,使晶形更趋于针状,但温度过高时对长轴的促进作用开始逐渐降低,长径比的增加趋势有所减缓;降低滴加速度,可提高产物结晶程度,有利于针状羟基磷灰石的形成;此外,反应pH值升高虽可加速晶核形成,提高产物的结晶率和产物纯度,但是不利于晶粒长大,且pH过高会减缓形成针状的趋势.     

有机模板诱导/均相沉淀法对羟基磷灰石(HAP)晶体形貌的控制生长

通过添加不同有机模板剂,采用均相沉淀法,制备了粒状、柱状、晶须状、片状、多孔状羟基磷灰石(HAP).利用TEM及SEM对其晶体形貌进行了表征,结果表明:不同有机模板剂的氢键作用能力对HAP六方柱面m{1010}、平行双面c{0001}、六方锥面o{1011}表面能的影响决定了这些晶面的相对发育程度,从而实现了HAP晶体形貌的控制生长.     

水热体系中表面活性剂对合成羟基磷灰石晶体的影响

以CaCO3和CaHPO4·2H2O为前驱物,利用XRD、SEM及FT-IR系统研究了水热体系中不同表面活性剂对合成羟基磷灰石(HAP)晶体微结构及晶体生长的影响,同时利用配位体理论对其生长机理进行了探讨.结果表明:不同类型表面活性剂对合成HAP晶体的分散性、微结构及结晶度有一定的影响,添加菲离子型表面活性剂制备的HAP晶体规整性、完整性、分散性、均一性、结晶度较好,长径比较大,呈一维纳米结构.非离子型表面活性剂种类的不同对HAP晶体的微结构及分散性也有一定的影响.阳离子型表面活性剂的加入对HAP晶体a、b轴方向的OH-Ca6,生长基元起到一定的促进作用,合成的HAP晶体长径比较小,长约1.1～1.5 μm,径向直径约为100～140 nm,阴离子型的促进作用明显大于阳离子型表面活性剂.EDS及FT-IR分析证实,水热环境下表面活性剂仅起到形貌调控和分散作用,对HAP产物的纯度没有任何影响.     

Fe3Al/HAP生物陶瓷的制备及力学性能

本文采用化学沉淀法制备了羟基磷灰石(HAP)纳米粉体,利用铁粉和铝粉经过高能机械球磨和热处理工艺制备了金属间化合物Fe3Al粉体;将制备的HAP粉体为基体按质量百分含量加入4;的Fe3Al粉体,经过球磨分散得到复合粉体,然后经过冷压成型和160MPa冷等静压成型及1200℃真空无压烧结,得到羟基磷灰石与金属间化合物Fe3Al的生物复合材料.通过XRD、SEM等测试方法揭示了材料的相组成及微观结构,研究结果表明:采用化学沉淀法制备的羟基磷灰石粉体粒径在100纳米以内,结晶度高、粒度均匀,纯度高;Fe3Al质量含量为4;的Fe3Al/HAP生物复合材料HAP的基本晶体结构没有因为Fe3Al的加入而发生变化,其抗弯强度为89.6MPa,较纯羟基磷灰石陶瓷有了较大的提高,证明Fe3Al增强HAP是有效的.     

氟羟基磷灰石在明胶凝胶中的制备与表征

以明胶形成的凝胶为媒介物,通过为含有PO43-、F-的明胶凝胶提供钙源,调节氟羟基磷灰石生成的环境pH值,生成条带状氟羟基磷灰石晶体,并利用XRD、EDX、SEM及FT-IR对生成的粉体进行分析测试.研究表明,在pH值为7.0～5.0环境下生成的氟羟基磷灰石具有相同的微观形貌,均为条带状晶体.能谱分析结果表明生成的为Ca/P比小于其化学计量比的缺钙羟基磷灰石,其XRD图谱与FAP一致性较好,在pH值较低时有杂质导致的弱峰产生.     

CuO/氧化石墨烯复合材料合成、表征及光催化研究

以醋酸铜Cu(Ac)2和氧化石墨烯(GO)为原料,去离子水作溶剂,十六烷基三甲基溴化铵(CTMAB)为表面活性剂,通过水热反应制备了CuO/GO纳米复合材料.傅里叶红外光谱(FT-IR)、X-射线粉末衍射(XRD)以及光电子能谱仪(XPS)和透射电镜(TEM)对合成的复合材料结构表征以及形貌分析,结果发现CuO纳米粒子均匀地分散在GO上.并将制备的复合材料对罗丹明B溶液进行光催化降解研究,结果发现在光反应80 min后,罗丹明B的浓度降低率达到85;,因此CuO/GO复合材料对罗丹明B表现出了良好的光催化性能.     

六方短棒状ZnO/氧化石墨烯复合材料的制备及其光催化性能

以乙酸锌为锌源,NaOH溶液作为沉淀剂,采用水热法结晶得到六方短棒状ZnO颗粒.再以化学氧化法制备的氧化石墨烯为改性剂,在ZnO颗粒合成过程中加入不同量的氧化石墨烯(GO)分散液.在水热条件下ZnO颗粒与氧化石墨烯片发生自组装形成ZnO/GO复合材料.通过X-射线衍射仪(XRD)、扫描电子显微镜(SEM)、傅里叶变换红外光谱(FT-IR)与紫外-可见漫反射光谱(DRS)对样品的物相组成、显微形貌、官能团特征及光学性质进行表征.在紫外光和可见光照条件下,分别研究了ZnO及不同GO含量的ZnO/GO复合材料对亚甲基蓝(MB)的光催化降解活性.结果表明:合成的ZnO为六方短棒状形貌,且GO的加入量对样品的形貌产生较大影响,同时GO可以有效促进光生电子和空穴的分离,所得ZnO/GO复合材料在紫外光光照条件下对MB具有良好的光催化降解性能,而在可见光光照下光催化活性很低,从而推测ZnO极性面与非极性面的暴露比例对复合样品的光响应范围及其光催化性能产生重要影响.     

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...     

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.     

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.     

Investigation of the Mechanism of Influence of Stress Corrosion on the Development of Macroplastic Instabilities of Aluminum–Magnesium Alloy

Crystallography Reports - Macroscopic jumps of plastic deformation (few percent in amplitude) on creep curves of aluminum–magnesium alloy, caused by a local effect of concentrated solution of...     

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.     

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.     

A SAXS study of kinetics of aggregation of silica sols

SAXS in situ experiments on the evolution of TMOS solutions during hydrolysis and polycondensation lead to power laws with scaling exponents ≈ 2. It is suggested that this could be the result of the polydispersity of the samples and that only an apparent fractal dimension can be obtained in this way. Kinetic studies tend to indicate that agglomeration in the sol is the result of a diffusion-controlled process.     

Study of the possibility of interactive control of the surface profile of X-ray optical elements

We investigate the possibility of controlling the curvature parameters of parabolic mirrors that are modular elements of two types consisting of a base and thin inserts placed at the opposite side of the work surface. In the first type of modular elements, bending is controlled by the difference in the coefficients of the thermal expansion of the base and inserts. In the second type of elements, the profile is changed by the piezoelectric straining of the inserts under an electric field. A correlation is established between the parameters of modular elements and their surface curvature profile.