硫酸钾枝状晶的生长与EBSD测定

采用单玻片溶液蒸发法、双玻片溶液蒸发法以及凝胶法,在不同条件下分别获得了硫酸钾枝晶和枝蔓晶,并利用EBSD技术对硫酸钾枝晶和枝蔓晶的结晶学取向进行了测试和分析.研究表明:硫酸钾(K2SO4)枝晶的主干主要沿着＜ 111＞方向生长;而硫酸钾(K2SO4)枝蔓晶中,组成枝蔓晶的相邻枝晶(晶粒)之间存在典型的双晶关系,其双晶轴为＜011＞,双晶面为(053).     

Di-Ab-An、Q-Lc体系非平衡结晶及枝晶结晶学方向测试研究

本文对两个典型的硅酸盐体系:Di(透辉石)-Ab(钠长石)-An(钙长石)体系和Q(石英)-Lc(白榴石)体中结晶物相系进行了枝状形貌、枝体结晶学方向测试及结晶能力方面的研究.通过偏光显微镜(PL)、扫描电镜(SEM)观察发现:透辉石、低鳞石英、α-方石英都发育为枝晶,而斜长石发育成放射状球粒晶和针状晶体.通过电子背散射衍射(EBSD)测试确定出透辉石是沿<001>方向发育成枝晶的主干、低鳞石英是沿<100>和<010>方向发育成枝晶主干、α-方石英是沿两个<100>方向发育成枝晶的主干.并发现两个体系在相同降温速度下的结晶能力不同.     

K2SO4晶体枝状形貌及结晶学模型

生长了具有枝状形貌的K2SO4晶体.基于单偏光显微镜下的形貌观察和背散射电子衍射分析,测定了枝晶的生长方向,建立了K2SO4晶体枝状形貌的结晶学模型.研究表明,K2SO4晶体的生长方向为[111]方向和[(1)-(1)1]方向,且两者夹角为114.4°;发育的晶面为(1(1)0)面,是由[111]晶向和[(1)-(1)-1]晶向组成的晶面.K2SO4枝晶具有两种生长模型,当其作为单枝生长时,一个< 111>方向的枝体连续发育做主枝,另一个<111>方向的枝体不连续发育作为侧枝;当其多枝同时生长时,<111>方向既可作为一个主枝,又可以作为其它主枝的一个侧枝.两种模型均指示出了K2SO4枝晶生长的不对称性.该研究揭示了结晶学方向在枝晶形成过程中的控制作用.     

KAl(SO4)2·12H2O晶体聚集体形貌及结晶学规律

采用双玻片凝胶法得到了等轴晶系水溶性晶体KAl(So4)2·12H2O(钾明矾)的晶体聚集体形貌.通过光学显微镜和扫描电镜下的形貌观察和分析,根据结晶学和晶体形貌学的基本原理,探讨了该晶体聚集体形貌中蕴含的结晶学规律.钾明矾晶体发育单形{111},以{100}贴在载玻片上生长,形成聚集体形貌时,晶粒{111}以平行连生的方式形成“十字形”枝晶或柱状枝晶,以(320)或(230)为共格晶界形成“Z”形枝状形貌.     

枝晶研究的发展现状

本文主要介绍了枝晶研究的发展现状,主要包括枝晶形貌研究和生长理论研究两个方面.枝晶形貌方面:对生长形态选择问题,比较符合实际的解是"最大质量沉积速率"选择规律;枝晶分枝程度与过冷度和晶体对称性有关,分枝反映晶体的对称性.生长理论方面主要介绍三种生长模型:Zener近似因子模型,扩散限制聚集(DLA)模型和成核限制聚集(NLA)模型.并探讨了需进一步研究的两个方面:具对称结构的枝晶的生长机理和枝晶形貌的统一规范化描述.     

电化学沉积法制备镍枝晶

采用电化学沉积法制备了镍枝晶沉积物,考察了不同的试验参数对枝晶生长过程以及微观形貌的影响.结果表明,枝晶具有典型的自相似性,枝晶容易在高的电流密度下生长,电流密度高,提高了阴极过电位,有利于枝晶形成;电解液里Ni2浓度的增加,沉积层分型更加明显,制备的镍枝晶逐渐稀疏,分叉也相应减小.随着电解液温度的提高,沉积层由开放型向致密型转化.这是因为在很高电流密度下,很容易发生析氢反应,释放大量气泡;金属离子在气泡之间的空隙被还原形成多孔的沉积层.     

NaCl枝状形貌的制备及生长机理探讨

采用溶剂蒸发法,在不同的条件下分别获得了具有四次对称和二次对称的Na Cl枝晶、"Z"字形枝蔓晶以及主要由枝晶呈放射状分布的球粒晶。借助于X射线衍射仪、光学显微镜、扫描电镜以及电子背散射衍射仪(EBSD),对Na Cl枝状形貌进行了测试分析。结果表明,Na Cl球粒晶主要由主干沿着<111>方向生长的一系列枝晶组成。Na Cl晶体(111)面网由同号离子组成,且钠离子层与氯离子层相间分布,层与层之间的联结力强,且(111)的面网间距最小,是导致Na Cl枝晶优先沿<111>方向生长的主要原因。溶剂的蒸发速度等环境因素的变化对Na Cl枝状形貌的形成具有很大的影响。     

Di-An-Ab体系快速冷却结晶的枝晶研究

对透辉石-钙长石-拉长石(Di-An-Ab)三元体系在不同降温速度条件下形成的枝晶进行了研究.其中,透辉石枝晶为规则树枝状,主枝和分枝明显;斜长石枝晶呈放射纤维状集合.枝晶形貌随降温速度变快没有明显变化,枝晶晶体结构随降温速度不同而有改变,降温速度减小,透辉石枝晶晶胞参数a值呈增加趋势,b、c呈减小趋势,斜长石枝晶b值呈减少趋势,c值呈增加趋势,两者β值呈增加趋势,但改变不大.随着降温速度增大,透辉石枝晶、斜长石枝晶硅氧骨干中,铝硅比值增大,铝更大程度地替代硅.另外还发现,降温越快,枝晶结晶数量越少.     

不同形态Cu2O枝晶的可控制备及形成机理

以酒石酸、铜盐以及碱为主要原料,在水热条件下通过控制相关的实验参数,制备了一系列不同形态的Cu2O晶体和枝晶.采用XRD、SEM等手段对不同形态的Cu2O晶体进行了表征,初步探讨了不同形态的Cu2O晶体和枝晶的成因.结果表明,晶体生长条件的改变主要是通过影响晶体的生长过程而影响晶体颗粒的大小及具体形貌.在低温(110 ℃)、高过饱和的碱性溶液中,所得Cu2O为形态稍有差异的粒状晶体;在高温(150℃)、较弱的碱性溶液中,只需较短的时间就可以获得三维十字枝状Cu2O晶体.     

N-(4-吡啶甲基)-L-丝氨酸铜配合物的合成、晶体结构和磁性

氨基酸还原希夫碱HL (N-(4-吡啶甲基)-L-丝氨酸)与CuCl2·2H2O在室温条件通过扩散法合成了配位聚合物{[Cu2(L)2(Cl)2]·H2O}n(I).采用元素分析、红外光谱、X-射线单晶衍射、粉末衍射和热重分析进行了表征.两个结晶学独立Cu(II) 包含于其晶体结构中,Cu1为变形八面体CuO2N2Cl2几何构型;Cu2则呈现略有变形的四方锥结构.Cu1和Cu2通过配体L-的吡啶氮原子以及氯离子的桥连作用连接为2D网状结构.变温磁化率实验表明在温度为2~300 K,配合物I表现为铁磁性耦合.     

枝晶生长理论中的热-动力学协同

随加工工艺趋于复杂化和极端化,基于热力学驱动力和动力学能垒相对独立的枝晶生长理论已无法精确描述多种机制共同作用的非平衡凝固过程,大大限制了该理论与工业应用的结合。首先,本文综述基于热-动力学相对独立的枝晶生长理论的发展,分析其内涵的本征热-动力学相关性,并集成于以双辊薄带连铸技术为背景的基于热-动力学相关性的枝晶生长模型。其次,定量证明了热力学驱动力和动力学能垒的相关性,通过选择不同的驱动力-能垒组合,试图在双辊薄带连铸技术中实现合金设计和工艺优化。最后,通过分析现有模型的不足,对进一步枝晶生长模型的发展以及与工艺的结合进行展望。     

Dendrite spacing in unidirectionally solidified Al-Cu alloy

Directional solidification experiments have been carried out to study the variation in primary and secondary arm spacings with solidification parameters in the Al-Cu system. It is found that the primary arm spacing Z₁ obeys the common correlation Z₁ = KG^-aV^-b in the high velocity regime or low temperature gradient regime, where a and b are constants, the value of K included the composition dependence, G is the temperature gradient in the liquid and V the growth rate; however, it does not obey this correlation for the low velocity regime or high temperature gradient regime but goes through a maximum or a catastrophe as a function of V or G at V = V_cs/k or G = kG_cs, where k is the equilibrium distribution coefficient, and V_cs and G_cs are the critical velocity and temperature gradient at the limit of constitutional undercooling respectively. The initial secondary arm spacings Z₂₀ are nearly independent of G and mainly depended on V, Z₂₀ = 0.016 V^-0.54 (mm). The secondary arm spacing Z₂ tends to c oarsen with time and thus is a function of coarsening time t_f, Z₂ = 0.016t^0.34_f (mm). Theoretical analyses of the primary arm spac ing and the initial secondary arm spacing have been proposed, and the derived relationships agree reasonably well with the above experimental results.     

水热条件下氧化物枝蔓晶的形成

本文在采用水热盐溶液卸压技术制备氧化物粉体时发现制得的氧化物颗粒之间按一定的规律连生在一起,形成类似于枝蔓晶的生长形态.通过对其连生方式的分析发现,在过饱和度较低的条件下连生也存在各向异性.即晶粒生长速度快的晶面易连生在一起.     

钛源对CaTiO3枝晶结构的光催化性能影响

通过改变不同钛源,在无模板或表面活性剂条件下采用溶剂热法制备了CaTiO3枝晶结构.样品用X射线衍射、扫描电子显微镜和比表面积分析仪进行了表征,并用紫外-可见吸收光度计测试样品的光吸收.研究不同钛源种类对CaTiO3样品的微观结构和光降解率的影响.结果表明:钛源为钛酸丁酯所制备的CaTiO3样品呈现发育良好的枝晶结构,其降解罗丹明B溶液的降解率最高.这主要是由于样品的结晶度高、枝晶结构使其具有低的反射率,因此样品呈现出较高的光降解率.     

负离子配位多面体生长基元与枝蔓晶的形成

本文运用负离子配位多面体生长基元理论模型讨论了KNbO3,β-SiO2和雪花枝蔓晶的形成机理,提出了枝蔓晶的结晶形态和对称性与晶体中的负离子配位多面体相互联结时的稳定方面密切相关.枝蔓晶是在远离晶体生长平衡态的条件下,以负离子配位多面体为生长基元,相互按照最稳定的联结方位延伸的.     

水热-均匀沉淀法制备Zr(OH)x/NH4Cl复合结构枝蔓晶

本文以ZrOC l2.8H2O和CO(NH2)2为原料,采用水热-均匀沉淀法,制备出了一种新型Zr(OH)x/NH4C l复合结构对枝蔓晶,并用XRD、SEM、TEM、EDS对产品进行表征。对枝蔓晶的结构和形成进行了分析认为NH4C l通过氢键作用对Zr(OH)x形成不完全包覆,并通过晶体生长方式形成枝蔓晶。     

Syntheses and structures of N-phenylmaleimidetriazoles and by-products

The syntheses, properties, and structures of N-phenylmaleimidetriazole derivatives are described. Intermediates and by-products are also discussed. 1b. a = 43.997(7) Å, 5.7610(9) Å, 8.245(1) Å, = 99.339(4), C₂/c; 2a. a = 13.646(4) Å, b = 7.744(2) Å, c = 10.612(3) Å, = 91.979(6), P2₁/c. 3a. a = 22.245(1) Å, b = 22.245(1) Å, 10.010(1) Å, P42/n. 3a. a = 11.727(2) Å, b = 14.075(3) Å, c = 16.080(3) Å, = 105.859(3), = 105.331(3), = 98.187(3), P-1. 3b. a = 8.561(3) Å, b = 14.755(5) Å, c = 22.771(7) Å, = 97.006(5), P2₁/c. 3c. a = 10.500(2) Å, b = 12.189(2) Å, c = 13.040(2) Å, = 109.091(3), = 106.089(3), = 101.022(3), P-1. 8a. a = 16.389(8) Å, b = 5.749(3) Å, c = 19.316(3) Å, = 97.467(9), P2₁/n. 8b. a = 5.822(2) Å, b = 10.114(3) Å, c = 16.705(4) Å, = 84.681(5), = 82.840(5), = 75.769(4), P-1. 9b. a = 11.251(1) Å, 13.335(3) Å, 13.376(3) Å, = 102.456(4), P2₁/n. 9c. a = 15.836(3) Å, b = 8.236(2) Å, c = 5.447(3) Å, = 92.551(3), P2₁/c. 10a. a = 13.177(2) Å, b = 14.597(2) Å, c = 5.5505(8) Å, = 110.979(2), Cc. 11a. a = 14.720(2) Å, b = 13.995(2) Å, c = 38.245(6) Å, = 94.430(3), P2₁/n. 12b. a = 15.067(5) Å, b = 20.378(6) Å, c = 8.669(5) Å, = 99.16(4), = 99.32(3), = 105.23(3), P-1. 13b. a = 8.2824(6) Å, b = 10.5245(7) Å, c = 15.518(1) Å, = 92.305(1), = 100.473(1), = 100.124(1), P-1. 15a. a = 15.357(3) Å, b = 7.778(2) Å, c = 22.957(2) Å, Pbca. 16b. a = 18.0384(4) Å, b = 12.474(3) Å, c = 20.078(5) Å, Pbca.     

Sol-gel synthesis and characterization of adsorbent and photoluminescent nanocomposites of starch and silica

Using sol-gel method, mesoporous and photoluminescent silica nanocomposites of soluble starch have been synthesized and characterized. Different ratios of H₂O, TEOS and EtOH were used at fixed template (soluble starch) and catalyst (NH₄OH) concentrations to obtain materials of different performances in terms of heavy metal binding from a solution which has been monitored using Cd(II) as representative divalent heavy metal ion. Optimum material was obtained when H₂O, TEOS and EtOH were used in 14:1:2 ratio. This sample was not only an efficient metal ion adsorbent but also had an intense luminescence in ultra-violet region and potentially may be used in silicon-based UV-emitting devices. Metal binding by the material was further enhanced after calcination (at 800 °C in air) while its luminescence had a multipeak profile in UV-visible region. In a batch adsorption study, calcined hybrid composite (0.25 g/L) could remove 98.5% Cd(II) from 100 mg/L Cd(II) solution in 2 h. The chemical, structural and textural characteristics of the synthesized materials have been investigated using Fourier Transform Infrared Spectroscopy (FTIR), X-rays Diffraction (XRD), Thermal Analysis (TGA/DTA), Photoluminescence (PL), Brunauer-Emmett-Teller Analysis (BET) and Scanning Electron Microscopy (SEM).     

Chemistry and Electrocrystallization of Organic Metals and Superconductors

Abstract

Considerable variation in the conditions of electrochemical crystal growth of TMTSF₂X (i.e., constant current versus constant potential, ambient versus inert atmosphere, etc.) and in the purity of the constituents (donor, electrolyte, solvent) does not significantly affect the unusual low-temperature properties of this class of materials. Our results suggest that the electrocrystallization procedure may be self-purifying by selecting for conducting crystal phases with constituents having specific oxidation potentials and solubility properties. However, doping solutions with structurally and chemically similar constituents (i.e., TMTTF, and IO^? ₄ in CIO^? ₄) leads to their incorporation in the crystal structure where they have a profound effect. Several mole percent of these dopants suppress superconductivity in the PF^? ₆ and CIO^? ₄ salts, and increase and broaden the metal-insulator phase transition.