KTP晶体在磷酸盐助熔剂中的生长机制和结晶习性

本文描述在K_5,K_6和K_8磷酸盐助熔剂中对KTP晶体进行的一系列生长动力学实验并讨论了晶体生长速度随过饱和度的变化规律,导出了两者间的函数关系。结果倾向于小核二维成核的生长机制。这与晶体表面形貌观察结果一致。实验还表明,在固定过饱和度情况下,KTP晶体生长速度将随溶液中正磷酸盐相对含量增加而减少。KTP晶体结晶习性的变化主要受KTP在磷酸盐溶液中的中间产物状态变化的影响。     

磷酸盐助熔剂中KTP晶体生长的物理化学过程

本文通过纸上色层法对KTP磷酸盐溶液成分进行了定量分析,得到了K_5、K_6和K_8三种磷酸盐助熔剂体系随KTP溶解度增加而引起的磷酸盐成分变化情况。结果表明,溶解于磷酸盐助熔剂中的KTP“分子”以链状中间产物形式存在。根据这一结果,本文提出了KTP在磷酸盐助熔剂中的溶解和生长反应机制,并很好地解释了包裹体的形式与磷酸盐成分之间的关系等问题。 本文还报道了用光学法测得的KTP在这些助熔剂中从1100℃到600℃之间的溶解度曲线,以及相应的溶解度曲线方程。综合溶解度及成分分析结果发现,正磷酸盐在溶液中对KTP的溶解度起重要作用。     

KTNNP晶体生长研究

本文采用高温溶液降温法生长出了掺Nb5+和Nd3+不同浓度的KTP(简称KTNNP)晶体,研究了晶体的生长习性与掺质种类的关系.测定了晶体的晶胞参数,并与KTP晶体作了对比,以掺质后结构的变化探讨了KTNNP晶体生长习性的成因.确定了掺质在生长体系中的分配系数,发现掺铌1%时使Nd3+的分配系数增大12.6倍,并提出了进一步提高晶体中Nd3+含量的设想.     

不同溶剂中TSB晶体的生长与形貌分析

根据晶体生长溶剂选取原则、溶剂特性和结晶实验结果,筛选出有机溶剂环戊酮、环己酮和苯甲酸乙酯,继而采用溶液降温法分别在这几种溶剂中进行了反式二苯乙烯(TSB)晶体生长,获得了透明度好的厘米级TSB晶体。研究了不同溶剂对TSB晶体生长形貌、生长习性和完整性的影响。结果表明:与国外所用溶剂苯甲醚和甲苯相比,这3种溶剂毒害性小,且有利于TSB晶体块体生长,是更合适的溶剂;在两种环酮溶剂中得到的晶体横截面为六边形,而在苯甲酸乙酯中晶体截面为平行四边形;另外由于溶剂种类不同,晶体的最佳生长温度区间和宏观缺陷的形式也有所不同。     

抗灰迹Rb∶KTP晶体的生长及性能研究

本文采用K6P4O13(K6)作助熔剂来生长Rb∶KTP晶体,所生长的晶体具有电导率低,吸收系数稳定和好的抗灰迹性能等优点.本文按照生长比例KTP∶K6=1.345∶1(物质的量比),Rb离子浓度为取代溶液中K离子浓度的1.4 mol％左右来进行配料.测量了Rb∶KTP晶体中掺杂的Rb离子浓度为0.87 mol％,经过测试,晶体的电导率达到10-10 S/cm.测试了晶体随时间延长的光能吸收,发现Rb∶KTP晶体的吸收系数比较稳定,并进行了晶体抗灰迹性能激光测试,发现Rb∶KTP晶体较普通KTP晶体具有很好的抗灰迹性能.     

TSB溶液的回流热处理与晶体生长

首先对反式二苯乙烯(TSB)的环己酮溶液进行回流热处理,考察不同回流加热时间对TSB溶液饱和点的影响,以高效液相色谱(HPLC)及气质联用技术(GC-MS)检测与分析回流加热过程中溶液的成分,随后采用降温法在该溶液中进行晶体生长,并观测了所生长TSB晶体的完整性。结果表明:环己酮是适合生长TSB晶体的溶剂,对溶液进行适当的回流热处理虽然会产生少量杂质,但在一定程度上能够加快溶剂合反应平衡并提高溶液稳定性,同时,晶体的完整性和闪烁性能也有所改善。     

负离子配位多面体生长基元与晶体的结晶习性

研究了晶体中负离子配位多面体的结晶方位与晶体形貌之间的关系。根据对溶液（水热、溶剂）中结构的测定，发现有与晶体中负离子配位体相同的结构基元存在，提出晶体生长基元为负离子配位多面体的生长模型。生长基元往界面上叠合是生长基元与晶体界面上负离子配位多面体的结合反应。文中列举了ＢａＴｉＯ３，ＬＢＯ和ＫＴＰ晶体的结晶习性与形成机理。     

稀土五磷酸盐晶体的生长及其性质

本文系统地研究了稀土五磷酸盐晶体的生长及其性质。对比了不同炉管对 LnP_5O_(14)晶体生长的影响,在选择合适的工艺条件下已生长出一些尺寸大、光学质量好的 LnP_5O_(14)晶体。测定了 15个LnP_5O_(14)晶体的磁化率、分解温度、红外光谱、密度和部分晶体的结构,归纳出一些规律性的结果。认为稀土化合物的性质变化规律不仅与稀土离子的特性有关,而且与周围环境的改变有关。     

K4体系KTP晶体的制备及其性能研究

本文选用K4P2O7助溶剂体系生长KTP晶体,所生长的晶体具有低吸收率和蓝、绿光波段抗灰迹性能,确定其最佳生长配比为KTP/K4 =0.8 mol/mol,测定其饱和点为850℃左右,从饱和点缓慢降温到820℃所生长晶体质量最佳,并对其进行了PCI抗灰迹吸收测试、倍频效率测试、电导率测试.结果表明:在同样原料纯度的情况下,吸收系数只有普通K6体系KTP晶体的十几分之一;1064 nm调Q到绿光的转化效率为61.8％(普通KTP转化效率为50％);在1 kV直流长时间加压条件下,Z向电导率达到10-10S/cm量级,较普通K6体系生长的KTP晶体低2～3个数量级.     

Nb:KTP晶体的水热法生长研究

文章研究了水热法Nb:KTP晶体的生长习性以及矿化剂体系、籽晶片的取向、矿化剂溶液的填充度对水热法生长Nb:KTP晶体的影响。在上述研究的基础上,采用水热法生长出了尺寸达28.2×24.2×9.8mm3无色透明的Nb:KTP晶体。     

水溶液晶体的空间生长及其地基模拟实验

空间水溶液晶体生长是通过搭载人造卫星、宇宙飞船和空间站等飞行器,在微重力条件下从水溶液中进行晶体生长实验.许多透明单晶体,诸如:KDP(磷酸二氢钾,potassium dihydrogen phosphate)、ADP(磷酸二氢铵,ammonium dihydrogen phosphate)、TGS(硫酸三甘氨酸,triglycine sulfae)、沸石和α-碘酸锂(α-LiIO3)等无机非线性光学晶体,尿素等有机非线性光学晶体以及蛋白质等生物晶体,均可采用水溶液法生长.美国、前苏联、西欧和日本等国在从事空间材料科学研究的高科技发展计划中,均把水溶液晶体生长作为一项重要项目.由于水溶液晶体生长方法的研究在地面上已有丰富的基础,而且具有温度低,能耗小,可实现原位实时观察等优点,所以,它是探索空间晶体生长原理和方法、研究晶体生长微重力效应的重要材料制备技术.由于空间晶体生长受搭载条件限制,空间实验的次数与地面相比是十分稀少的,为了获得空间实验的高成功率,在地面上必须建立相应的实验基地,开展深入的地基研究工作.本文将分别从空间实验和地基研究两个方面作系列介绍,包括蛋白质晶体,沸石晶体,α-LiIO3晶体的空间生长以及TGS,NaClO3(sodium chlorate,氯酸钠),Sr(NO3)2(strontium nitrate,硝酸鍶)和Ba(NO3)2(barium nitrate,硝酸钡)等晶体生长过程的原位实时观察,并展望了空间晶体生长的发展前景.     

铁离子对磷酸氢二铵结晶过程的影响

首先,采用动态激光法测定了不同铁离子含量的磷酸氢二铵溶液结晶介稳区的宽度;其次,借助倒置显微镜,通过单晶生长法来研究铁离子对磷酸氢二铵晶体生长速率的影响;此外,还通过对产品粒度分布的分析,考察了掺杂铁离子对磷酸氢二铵颗粒大小的影响.实验结果发现:随着铁离子质量浓度百分数由0增加至0.007,结晶介稳区宽度由3.32 ℃增大到7.68 ℃.随着Fe3+质量浓度百分数的增大,单晶各个方向的生长速率都逐渐减小.当Fe3+质量浓度百分数X(Fe3+)=0.005时,在过饱和度(△)C=6 g·(100 g)-1的溶液中,磷酸氢二铵晶体x方向的生长速率Gx由未添加Fe3+时的 60.29 nm·s-1减小为28.35 nm·s-1;平均粒径D50由不加Fe3+时267.1 μm减小到137.6 μm;40～80目的晶体粒子体积分率,由未掺杂时的88.85％减小到48.75％.产品粒度分布的重复性下降.     

Electrocrystallization of Calcium Phosphates

The interest in electrocrystallization of calcium phosphates (CaP) in general, and of hydroxyapatite (HAp) specifically, results from the promising industrial benefits, unique microstructures, and properties of the deposits produced by this process, and the possible similarity to bone mineralization in vivo. In this paper, our work on electrocrystallization of HAp and octacalcium phosphate (OCP) on CP-Ti and Ti-6A1-4V alloy, in solution containing calcium nitrate and ammonium dihydrogen phosphate, is briefly reviewed. The early stages of nucleation and growth are characterized in real time by means such as electrochemical quartz crystal microbalance (EQCM) and electrochemical atomic force microscope (EC-AFM). The change in growth mode and the role of precursors to HAp are explained. The role of charge transfer and local increase in pH is discussed.     

Growth kinetics of ammonium- and potassium-dihydrogen phosphate crystals

Growth rates of ammonium- and potassium-dihydrogen phosphate crystal faces have been measured in a simple laboratory apparatus under carefully controlled conditions of temperature, supersaturation and solution velocity. The growth process, which was found to be second-order with respect to the supersaturation, is considered to be controlled by surface reaction. Growth rates of the ammonium salt (ADP) are much higher than those of the potassium-salt (KDP) under equivalent conditions. It is suggested that this is due to the occurrence of hydrogen bonding between ADP molecules, which give larger integrating units (thicker growth layers) than occur with KDP.     

铁离子对磷酸二氢钾结晶过程的影响

采用激光散射法测定了含有不同铁离子含量的磷酸二氢钾水溶液介稳区宽度,在介稳区宽度内测得不同铁离子含量对磷酸二氢钾结晶生长速率的影响。并采用间歇冷却结晶法在未加晶种条件下测定了铁离子对磷酸二氢钾结晶形态、晶体堆积密度及晶体铁含量的影响。结果表明：随着掺入铁离子含量的增大,结晶介稳区宽度变宽,生长速率下降; 晶体由规则棱柱状变为针状,晶体出现开裂,光泽不均匀;晶体堆积密度逐渐减小,包裹铁含量逐渐增大。     

二水硫酸钙结晶过程及活化疏松剂对其影响的研究

以碳酸钙、磷酸和硫酸为原料。在MSMPR结晶器中研究二水硫酸钙的结晶过程。分别讨论了结晶温度、平均停留时间、硫酸质量分数等因素对结晶成核速率、晶体成长速率以及晶体形状、大小的影响。另外还研究了添加不同类型的活化疏松剂对二水硫酸钙结晶过程的影响。     

Mechanism of magnesium phosphate cement retardation by citric acid

Citric acid modulates the release of heat and the rates of reaction in magnesium phosphate cements, chemically-bonded ceramics employed in biomaterials, for the encapsulation of nuclear wastes and in civil engineering. To gain knowledge on the mechanism of action of citric acid and, therefore, help in the effective material design, the reaction was studied in-situ to address molecular issues. The results indicated that citric acid enhances dissolution of MgO by promoting surface ligand-exchange reaction which leads to a net acceleration of the first reaction step. The Mg²⁺ ions released in solution are complexed by citrates. The degree of supersaturation is therefore reduced, delaying the nucleation of phosphates. The growth of stable nuclei, the crystal growth, and the amorphous-to-crystalline transformation are hindered due to citrate adsorption. The formed surface complexes are prevalently inner-sphere complexes exhibiting the combined coordination of hydroxyl and carboxylate groups. The mutating chemical environment dictates the coordination modes of citrate, the competition with phosphates, and the stable forms of phosphate products.     

氟硅酸钾(钠)在湿法磷酸中的结晶动力学研究

在MSMPR结晶器中系统地研究了氟硅酸钾（钠）在湿法磷酸中的结晶动力学及主要杂质F^-、Mg^2 、Fe^3 、Al^3 的影响。结果表明,在纯硫磷混酸中,Na2SiF6为八面体晶体、K2SiF6为由立方体晶体聚在一起的聚晶;SO4^2-、Mg^2 结氟硅酸钾（钠）晶体生长有促进作用,F^-的影响不明显,Fe^3 、AI^3 能抑制其生长;四种杂质共存的模拟湿法磷酸及磷矿萃取磷本台氟硅酸钾（钠）晶体生长速率、平均粒径均明显减小,形态发生很大变化。     

The hindering function of phosphate on the grain growth behavior of nanosized zirconia powders calcined at high temperatures

Nanosized zirconia was prepared by a hydrothermal method using ZrOCl₂·8H₂O and NaOH as raw materials. The obtained ZrO₂ powders were soaked in the phosphate solution with different concentrations. The as-prepared ZrO₂ powders and the powders treated with phosphate solution were calcined at different temperatures from 600 to 1000 °C. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray photoelectronic spectroscopy (XPS). The experimental results show that the untreated nanosized ZrO₂ grow and agglomerate to bulk when the ZrO₂ powders were calcined at high temperatures, while the ZrO₂ powders treated with phosphate solution grow slowly and remain nanosized crystal at the same calcination temperature. This phenomenon implied that phosphate treatment played an important role in inhibiting the crystal grain growth of ZrO₂. The possible inhibition mechanism could be explained to that P species on the surface of ZrO₂ can reduce the grain boundary mobility and prevent direct contact of ZrO₂ particles.     

Driving Force of Crystallization Based on Diffusion in the Boundary and the Integration Layers

Crystal growth rates are notoriously difficult to predict and even experimental data are often inconsistent. By allowing for mass and energy diffusion through the molecular and thermal layers surrounding a growing crystal and for the heat effect of crystallization, a new model of crystal growth from solution is proposed and applied to crystallization of potassium chloride from aqueous solution. The driving force for crystal growth was calculated using the solubility at the interface temperature in contrast to the conventional one based on bulk temperature. A positive heat effect at the crystal interface as well as the resistances to the mass and energy transfer processes to and from the crystal surface can reduce the conventional driving force for crystal growth by more than 20 %.