大颗粒磷钼酸铵:制备与结晶动力学

通过缓慢滴加焦磷酸钾的硝酸溶液到钼酸铵溶液中制得了大颗粒磷钼酸铵(AMP)。研究了AMP的成核速率(G)与晶体生长速率。与晶体生长速率相比成核速率的反应级数更高。最初, 大颗粒磷钼酸铵的结晶过程处于相变反应控制的动力学区域, 此时溶液的过饱和生成速率比过饱和消除速率高。晶体线生长速率与溶液的过饱和度先增加后降低。在滴加中期, 过饱和消除速率增长到与其生成速率相当。在滴加后期, 晶体成核速率快速增高, 而晶体的线生长速率下降。晶体的成核速率成为过饱和消除的唯一控制步骤。因此, AMP成核大部分是在首先接触到滴加液的局部溶液中完成的。     

气相扩散速率对溶菌酶晶体生长的影响

为研究气相扩散速率对溶菌酶晶体生长的影响,特设计了一种可方便调节气相扩散速率的晶体生长样品池,并用动态光散射法对不同气相扩散速率下晶体生长过程进行了研究.实验结果表明,随着气相扩散速率的增加,晶体生长过程中的成核阶段缩短.气相扩散速率通过影响溶菌酶溶液形成过饱和的速率来影响生长出的晶体的数量和大小.     

蚕丝纤维增强聚乳酸体系中柱晶的形成及结构分析

采用溶液法制备聚乳酸(PLA)薄膜,并利用偏光显微镜在线研究了不同温度及不同牵引速率下,单根蚕丝纤维(SF)诱导PLA柱晶的形成,并利用显微红外光谱表征柱晶结构.结果表明,当牵引速率大于或等于临界速率时,纤维表面有连续的柱晶生成,反之柱晶不连续;当牵引速率大于临界饱和速率时,柱晶的结晶度和取向度分别趋于稳定值;在等温条件下,随着牵引速率的增大,柱晶的成核诱导期缩短,晶体的成核密度增大,取向度增加;当牵引速率一定时,与130℃相比,温度为120℃时形成柱晶的成核诱导期较短,成核密度更大,结晶度更高,柱晶层的生长更快.     

配液结晶法制备溶菌酶蛋白质晶体的生长机理研究

采用配液结晶法制取了溶菌酶蛋白质晶体, 使用动态光散射测量了溶液中聚集体的颗粒度几率分布; 使用Zeiss显微镜测定了溶菌酶(110)晶面的生长速度. 实验表明: 随着蛋白质和NaCl浓度的增加, 溶液中聚集体的颗粒尺寸也相应增加. 随着反应时间的增加, 溶菌酶分子在溶液中的聚集反应, 逐渐达到平衡; 在蛋白质和NaCl浓度较高时, 溶菌酶晶体的(110)面生长较快, 而在蛋白质和NaCl浓度较低时, 该晶面生长较慢. 基于二维成核生长机理, 从晶体生长动力学理论方程出发, 计算了二维成核的形成能α＝4.01×10^－8 J•cm^－2.     

蒸汽相中含硼多孔玻璃自转变合成沸石——Ⅱ．自转变动力学

以XRD为表征手段详细研究了408—453K温度范围、多孔玻璃粉在乙胺和水的蒸 汽相中自转变为B-Al-MFI型沸石的自转变动力学。由动力学曲线计算得到的成核活 化能和晶体生长活化能分别是102．0kJ／mol和34．7kJ／mol。沸石的结晶速率显 著受温度影响，低温有利于晶体成核和形成小晶体，高温有利于晶体生长和形成大 晶体。不同反应温度下的结晶速率几乎在相同时间内(cα．132h)达到最大值(νm) 。     

Na_5P_3O_(10)-Ca(OH)_2-CO_2-H_2O体系纳米CaCO_3的成核与生长

通过化学分析、SEM显微分析技术结合RosinRamiler概率统计理论从介观层次研究Na5P3O10CaOH2CO2H2O体系纳米CaCO3的合成反应及其成核和生长过程。结果表明Na5P3O10对CaOH2的碳化反应具有抑制作用。随着Na5P3O10的增加体系中CaCO3的成核速率B0逐渐增大。在Na5P3O10=0ppm时CaCO3结晶的生长由长程扩散和凝聚生长控制Na5P3O10=380.4760.9ppm时前期受短程扩散和界面反应控制、后期受长程扩散控制。Na5P3O10的存在抑制了纳米CaCO3的晶体生长。     

Na5P3O10-Ca(OH)2-CO2-H2O体系纳米CaCO3的成核与生长

通过化学分析、SEM显微分析技术,结合Rosin-Ramiler概率统计理论,从介观层次研究Na5P3O10-Ca(OH)2-CO2-H2O体系纳米CaCO3的合成反应及其成核和生长过程。结果表明,Na5P3O10对Ca(OH)2的碳化反应具有抑制作用。随着[Na5P3O10]的增加,体系中CaCO3的成核速率B^0逐渐增大。在[Na5P3O10]＝0ppm时,CaCO3结晶的生长由长程扩散和凝聚生长控制;[Na5P3O10]=380.4,760.9ppm时,前期受短程扩散和界面反应控制、后期受长程扩散控制。Na5P3O10的存在,抑制了纳米CaCO3的晶体生长。     

CaMoO4微晶生长过程的原位微量热法研究

在碱性条件下采用原位微量热法对CaMoO4微晶的构建进行了研究. 首次呈现了CaMoO4微晶生长过程能量变化的特征热谱曲线; 该特征热谱曲线由一个反映最初反应成核的典型吸热曲线和随后晶体生长的两个相对较弱的不连续放热曲线组成. 在导向机制的基础上, 结合CaMoO4微晶生长过程的形貌演变, 简要地讨论了CaMoO4微晶生长过程的热动力学信息. 反应成核过程、晶化过程及微晶的二次生长过程的速率常数分别为1.54×10-4、1.09×10-4和0.71×10-4 s-1. 由于晶体的聚集和扩散二者之间强烈的相互作用, 使得反应速率下降, 从而呈现出一个相对较平坦的第二次放热曲线.     

医用CVIC/C复合材料表面仿生沉积生物活性钙磷涂层

为了在医用化学气相渗透工艺(CVI)C/C复合材料表面制备生物活性钙磷涂层,用阴极声电化学工艺处理CVIC/C复合材料,再将试样浸泡于过饱和钙磷溶液中,使其诱导钙磷晶体生长.XPS研究表明,经声电工艺处理后,CVIC/C复合材料表面发生了改性;SEM,XRD和FTIR研究表明,在过饱和钙磷溶液中,未经声电化学处理的CVIC/C复合材料不具有诱导钙磷晶体生长的功能,而改性的CVIC/C表面能够诱导钙磷晶体生长,形成片状五水磷酸八钙(OCP)涂层.同时讨论了OCP沉积的形成机理.     

Pt在多晶Au微盘电极上电沉积成核与晶体生长

于不同H2PtCl6浓度和超电势下,应用Fleischmann的电结晶成核及晶体生长模型和Barradas Bosco的电化学成相吸附成核模型,拟合多晶Au微盘电极( =30μm)上电沉积Pt的恒电势阶跃电流暂态曲线.得出:在稀H2PtCl6溶液中,上述沉积过程初期,发生H2PtCl6吸附并遵循二维瞬时成核与圆柱形生长模型.二维生长速率常数随超电势线性增加.跟随其后的是核的层状生长,其速率常数随超电势呈非线性变化.而在高浓H2PtCl溶液中,沉积机理转变为H2PtCl6的吸附、瞬时成核及三维正圆锥形的生长模式.其晶核的垂直生长速率常数kPERP比水平生长速率常数kPARA大两个数量级以上.况且,logkPERP随超电势线性增加,而logkPARA则随超电势呈反S形变化的关系.相同超电势下,无论kPERP还是kPARA,均比稀H2PtCl6溶液中的二维层状生长速率常数大几个数量级.     

Metal-Organic Framework (MOF) Morphology Control by Design

Exerting morphological control over metal-organic frameworks (MOFs) is critical for determining their catalytic performance and to optimize their packing behavior in areas from separations to fuel gas storage. A mechanism-based approach to tailor the morphology of MOFs is introduced and experimentally demonstrated for five cubic Zn₄O-based MOFs. This methodology provides three key features: 1) computational screening for selection of appropriate additives to change crystal morphology based on knowledge of the crystal structure alone; 2) use of additive to metal cluster geometric relationships to achieve morphologies expressing desired crystallographic facets; 3) potential for suppression of interpenetration for certain phases.     

Morphological and solidification studies of the naphthalene-thymol eutectic

The mechanism of eutectic solidification of the naphthalene-thymol system has been investigated by spontaneous crystallization, linear velocity of crystallization and microscopic studies. The kinetic data for all the compositions of the system suggests that the growth is governed by a screw dislocation mechanism. The diffusion process has been found to be a dominant factor in explaining the decrease in the velocity of crystallization when one component is added to the other and also explains the higher growth rate for the eutectic mixture. Both the kinetic and microscopic studies confirm the interdependent nature of the growth of the two phases of the eutectic. The two phases grow simultaneously side by side and are controlled by the cross-diffusion ahead of the solid-liquid interface.     

Study of Growth Mechanism of Lysozyme Crystal by Batch Crystallization Method

Space environment is regarded as the perfect environment for the production of higher quality protein crystals since the sedimentation movement and convective flow due to the gravity is negligible under the microgravity condition of space environment. A n…     

Crystalline Behavior and Structure of a Liquid Crystal Compound, 5‐{[4′‐(((Pentyl)oxy)‐4‐biphenylyl)carbonyl]oxy}‐1‐pentyne

Single crystals of two liquid crystal compounds, 5‐{[4′‐(((pentyl)oxy)‐4‐biphenylyl)carbonyl]oxy}‐1‐pentyne (A3EO5) and 5‐{[(4′‐nonyloxy‐4‐biphenylyl)carbonyl]oxy}‐1‐pentyne (A3EO9), have been prepared by solution growth technique. The morphologies and structures of A3EO5 and A3EO9 crystals were investigated by wide angle X‐ray diffraction (WXRD), atom force microscope (AFM) and transmission electron microscope (TEM). In contrast to the same series of compounds which have a longer alkyl tail, 5‐{[(4′‐heptoxy‐4‐biphenylyl)carbonyl]oxy}‐1‐pentyne (A3EO7), 5‐{[(4′‐heptoxy‐4‐biphenylyl)oxy]carbonyl}‐1‐pentyne (A3E′O7) and A3EO9, A3EO5 shows strikingly different crystalline behavior. The former three compounds have only one crystal form, whereas A3EO5 exhibits polymorphism. Specifically, A3EO5 crystals grown from toluene solution show two crystal forms. The first one is crystal I which adopts a monoclinic P112/m space group with unit cell parameters of a?5.79 Å, b?8.34 Å, c?43.92 Å, γ?96°, and the other one is crystal II which adopts a monoclinic P112 space group with unit cell parameters of a?5.55 Å, b?7.38 Å, c?31.75 Å, γ?94°. When using dioxane as the solvent to grow A3EO5 crystal, we can selectively obtain crystal I. A3EO5 melt‐grown crystals also have two crystal forms which derive from crystal I and crystal II, respectively. The different crystalline behavior of the compounds should correlate with their different electron dipole moment resulting from the different length of alkyl tail.     

单分子膜诱导下的矿物晶体生长

介绍了近几年单分子膜诱导下矿物晶体生长的最新进展。讨论了单分子膜诱导下的矿物晶体生长与溶溶中的异同,成膜材料,单分子膜性质和聚集态,矿物晶体的选择性及晶体的表征方法。     

Nucleation: What Happens at the Initial Stage?

Crystallizing growth : The initial structure of crystal nuclei is supersaturation‐dependent. At low degrees of supersaturation, liquid‐like nuclei are formed initially, which undergo a continuous structure transition from liquid‐like to crystal‐like as the size N increases. This gradual structure evolution substantially lowers the nucleation barrier ΔG* and facilitates the nucleation relative to the formation of crystal‐like clusters from the beginning.

     

Kristallstruktur von Hexamincyclotriphosphazen,P3N3(NH2)6

Crystal Structure of Hexamine Cyclotriphosphazene, P₃N₃(NH₂)₆ In the presence of KNH₂ hexamine cyclotriphosphazene semi ammoniate (molar ratio 12:1) in NH₃ gives crystals of solvent free P₃N₃(NH₂)₆ within 5 d at 130°C and p(NH₃) = 110 bar. The structure was solved by X-rax methods: P₃N₃(NH₂)₆: P2₁/c, Z = 4, a = 10.889(6) Å, b = 5.9531(6) Å, c = 13.744(8) Å, β = 97.83(3)°, Z(F_o) = 1 721 with (F_o)² ≥ 3σ(F_o)², Z(var.) = 157, R/R_w = 0,036/0,041 The structure contains columns of molecules P₃N₃(NH₂)₆ all in the same orientation. The six-membered rings within one molecule have boat conformation. The columns are stacked together in a way that one is surrounded by four others shifted by half a lattice constant in direction [010]. Strong hydrogen bridge-bonds N? H…?N connect molecules within the columns and between them.     

Kristallstrukturanalyse von (NH4)2NaInF6

Single Crystal Structure of (NH₄)₂NaInF₆ (NH₄)₂NaInF₆ has been synthesized via a novel route from In₂O₃, NaF and NH₄F and its crystal structure has been determined using single crystal techniques (Fm3 m, a = 8.6675(3) Å, Z = 4, 4 106 reflections, R = 0.007). The crystal structure derives from the elpasolite type of structure, the ammonium ions are not disordered.