均匀沉淀法制备羟基磷灰石的研究

对以硝酸钙和磷酸作为反应物,采用均匀沉淀法制备的羟基磷灰石粉体进行了研究。研究发现,硝酸钙溶液的初始浓度和粉末的煅烧温度对所制备的羟基磷灰石(HAP)的粒径、比表面积有较大的影响。采用XRD射线衍射谱、BET比表面积测试、粒径测试等分析手段,探索出较好的工艺条件,进而探讨了在形成生物陶瓷过程中,煅烧温度对HAP密度及收缩率的影响。     

正交法优化均匀沉淀法制备超细氧化锆粉体工艺

研究以氧氯化锆、尿素为原料,采用均匀沉淀法制备超细氧化锆粉体,考察反应温度、尿素溶液浓度、反应物投料比、干燥方式、煅烧温度等对氧化锫粉体粒径的影响.确定最佳工艺条件:反应温度为100℃,尿素溶液浓度为13％,反应物投料摩尔比为2.1∶1,抽滤后的湿凝胶采用喷雾干燥,煅烧温度为550℃.在此条件下,可获得平均粒径为113.5 nm的单斜晶超细氧化锫粉体.     

快速均匀沉淀法制备纳米级HAP粉末

尝试采用快速均匀沉淀法制备了纳米级HAP粉末.70℃干燥的粉末,进行XRD分析,主晶相为HAP,但结晶性不好;经750℃焙烧后,得到了结晶性比较好的HAP粉末,晶粒大小约为80nm.该法与湿法相比,大大缩短了制备的周期.     

Gas- and Liquid-Phase Reactions on Sulphated Zirconia Prepared by Precipitation

Sulphated zirconia (SZ) was synthesized under different precipitation and ageing conditions. Catalysts were characterized by nitrogen adsorption–desorption, thermal analysis, FTIR and Raman spectroscopy. The catalytic performance of these SZ systems in both gas and liquid-phase reactions has been investigated. The effect of precipitation and ageing conditions has been studied and a correlation with catalytic activity has been tried.     

Crystal Structure of Zirconia Prepared with Alumina by Coprecipitation

Zirconia was prepared by firing the coprecipitate from ZrOCl₂and AlCl₃mixed aqueous solution with ammonia. When fired above 600°C, the products were fine crystalline tetragonal zirconia of crystallite size <10 nm. In previous studies, the tetragonal phase had been assumed to be a (Zr_{1− x} ⁴⁺Al _x ³⁺)O_{2− x /2}solid solution, where x ≤ 0.25. However, X-ray diffraction pattern simulation and Al K -edge XANES spectroscopy confirmed the present product to be a mixture of t -ZrO₂fine powder with a small amount of δ-Al₂O₃of very low crystallinity, even below the expected compositional range of x ≤ 0.25 in the (Zr_{1− x} ⁴⁺Al _x ³⁺)O_{2− x /2}solid solution.     

微波均相沉淀法制备纳米ZnO及其光催化性能

以硫酸锌和尿素为原料,采用微波均相沉淀法制备出了纳米ZnO. 探讨了反应物配比、反应物浓度、反应时间、反应温度等条件对产物的影响. 并用TEM, IR, TGA, XRD, UV-Vis等测试手段对其进行了表征. 利用紫外-可见分光光度计测试了光吸收特性,发现纳米ZnO对200~380 nm波长范围的光有很强的吸收性,在可见光范围内也有较强的吸收. 研究了纳米ZnO光催化降解甲基橙的动力学行为,在紫外光直接照射下,光催化降解甲基橙,以分光光度法测量甲基橙的即时浓度,从而得出了不同条件下甲基橙降解的脱色速率,以比较不同的降解效果.     

沉淀法制备纳米白炭黑的结构及性质的研究

研究了用硫酸沉淀法制备纳米白炭黑的方法和工艺路线,利用现代分析测试手段对制备的白炭黑的结构、粒径、表观物理化学性质进行了表征.研究表明:本实验制备的白炭黑为纳米非晶态,平均粒径35nm,其原子平均距离0.726 nm,有序畴尺寸为几个原子距离,表观活化能35.566 kJ/mol.     

均相沉淀法制备掺钕钇铝石榴石纳米粉末的研究

掺钕钇铝石榴石（Nd：YAG）多晶透明陶瓷具有容易制造、成本低、光学性能好、热导率高等优点,是一种很有前途的激光工作物质。以AI（N03）·9H2O,Y2O3,Nd2O3,（NH4）2SO4和尿素为原料,正硅酸乙酯为添加剂,采用均相沉淀法制备出分散均匀、纯YAG立方晶相的Nd：YAG纳米前驱体粉末。采用XRD、FT-IR、TEM等测试手段对前驱体粉末进行表征。研究结果表明：Nd：YAG前驱体粉末在800℃时为无定型态,当温度达到890℃时析出大量的中间相YAlO3（Y=AP）和少量的Y3Al5O5（YAG）,当温度达到1000℃时就全部转化为YAG立方晶相。     

Nanocrystallization and Phase Transformation in Monodispersed Ultrafine Zirconia Particles from Various Homogeneous Precipitation Methods

Monodispersed ultrafine (nano- to micrometer) zirconia precursor powders were synthesized by three different physicochemical methods: (I) forced hydrolysis, (II) homogeneous precipitation in inorganic salt solutions, and (III) hydrolysis/condensation of alkoxide. The forced hydrolysis method produced monoclinic nanocrystalline particles (cube shaped) of nanometer scale, which depended largely on the initial salt concentration. Methods II and III, both involving the use of alcohol as a solvent, exhibited a faster particle formation rate and generated amorphous ultrafine (submicrometer) monodispersed microspheres, indicating that the presence of alcohol may have stimulated particle nucleation due to its low dielectric property (and, thus, the low solubility of nucleus species in mixed water-alcohol solutions). Nucleation and growth of the particles in solutions are discussed based on the measurements obtained by small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS). High-temperature X-ray diffraction (HTXRD) and TGA/DTA studies elucidated the differences in phase transformation for different types of powders. The most interesting finding was the nonconventional monoclinic nanocrystal nucleation and growth that occurred prior to transformation to the tetragonal phase (at 1200°C) during the heat treatment of the nanocrystalline powders produced by the forced hydrolysis.     

二氧化锆对低品位菱镁矿制备镁铝尖晶石材料组成结构的影响

以低品位菱镁矿与工业氧化铝为原料制备镁铝尖晶石材料,分析研究二氧化锆对以低品位菱镁矿为原料制备的镁铝尖晶石的组成、结晶度、晶胞参数和微观结构的影响,用XRD和SEM对烧后试样的相组成和显微结构进行研究.利用X'pert plus软件对试样中结晶相的相对结晶度进行计算,并对镁铝尖晶石相的晶胞参数进行分析.结果表明:适量引入二氧化锆有利于以低品位菱镁矿与工业氧化铝为原料制备镁铝尖晶石材料;材料中结晶相的结晶度随二氧化锆加入量的增加呈现出先增加后降低的现象;镁铝尖晶石材料中主晶相镁铝尖晶石的晶胞参数及晶胞体积受到锆离子的置换固溶作用的影响;当二氧化锆加入量为1.2％时,镁铝尖晶石的晶胞参数和晶胞体积最大,结构中镁铝尖晶石形成量最大,而玻璃相形成量最小.因此对于以低品位菱镁矿与工业氧化铝为原料制备的镁铝尖晶石材料,二氧化锆的最佳引入量为1.2％.     

均匀沉淀法制备纳米ZnO

硝酸锌和尿素的浓度、反应温度以及表面活性剂的种类都是影响均匀沉淀法制备纳米ZnO的重要因素。实验结果表明:均匀沉淀法制备纳米ZnO时,控制硝酸锌的浓度0.6~0.9mol/L,尿素的浓度2.6~2.8mol/L,反应温度95℃,加入表面活性剂能制备出粒径在40~70nmZnO。     

不同工艺制备的水合氧化锆凝胶之特性

用水解沉淀法和中和沉淀法两种工艺制备了水合氧化锆凝胶，并与经乙醇脱水处理后的水合氧化锆凝胶的形貌、热性能、相态以及红外吸收光谱作了比较。     

Sintering Behavior of Nanocrystalline Zirconia Prepared by Chemical Vapor Synthesis

Powder synthesis and ceramic processing methods have to be improved to take full advantages of new, improved properties of nanocrystalline ceramics. Sintered nanocrystalline ceramics of pure, undoped zirconia are formed from nanocrystalline powder of optimized quality obtained by the chemical vapor synthesis (CVS) method. The as-synthesized CVS ZrO₂ powder is nonagglomerated with a crystallite size of about 5 nm, narrow size distribution, and high crystallinity. On uniaxial compaction a transparent green body of ultrafine, uniform microstructure and narrow pore size distribution corresponding to the grain size distribution is formed, which is sintered under vacuum at 950°C into a transparent, fully dense ZrO₂ ceramic with a grain size of 60 nm.     

Precipitation in Partially Stabilized Zirconia

Transmission electron microscopy was used to study the sub-structure of partially stabilized ZrO₂ (PSZ) samples, i.e. 2-phase "alloys" containing both cubic and monoclinic modifications of zirconia, after various heat treatments. Monoclinic ZrO₂ exists as (1) isolated grains within the polycrystalline aggregate (a grain-boundary phase) and (2) small plate-like particles within cubic grains. These intragranular precipitates are believed to contribute to the useful properties of PSZ via a form of precipitation hardening. These precipitates initially form as tetragonal ZrO₂, with a habit plane parallel to the {100} matrix planes. The orientation relations between the tetragonal precipitates and the cubic matrix are
and      

Synthesis and Characterization of ZnCr2O4 Nanospinel Prepared via Homogeneous Precipitation Using Urea Hydrolysis

In situ and homogeneous hydrolysis of urea was utilized to design a homogeneous precipitation method to synthesize the ZnCr₂O₄ functional material. The as‐prepared nanospinel was systematically studied in terms of crystal structure, morphology, texture, and light absorption. A well‐crystalline single phase of ZnCr₂O₄ nanospinel with a spongy network structure was obtained. Transmission electron microscopy and X‐ray diffraction observations confirmed the formation of monocrystalline nanoparticles of ZnCr₂O₄ with the nanosize of 13 nm. The synthesized nanospinel showed a low direct band gap value of 1.8 eV with appropriate absorption in the visible light region, which was a remarkable result for this route.     

Preparation of Lead Zirconate by Homogeneous Precipitation and Calcination

Antiferroelectric PbZrO₃ has been synthesized by homogeneous precipitation from aqueous solutions in the presence of urea (NH₂CONH₂) and calcination for 6 h at 700°C. SEM studies displayed the presence of submicrometer powder, with a significant degree of agglomeration.     

均匀沉淀法制备不同粒径的纳米氧化锌

由于纳米氧化锌的功能和用途不同,因而需要制备出不同平均粒径的纳米氧化锌。论文以六水硝酸锌为原料,尿素为沉淀剂,研究了均匀沉淀法制备不同平均粒径纳米氧化锌的工艺条件,讨论了工艺条件对其粒径和产率的影响规律。结果表明:通过均匀沉淀法制备的纳米氧化锌的前驱体为Zn5(OH)6(CO3)2;制备的纳米氧化锌为六方晶系的球形颗粒,平均粒径为20～50nm;纳米氧化锌的产率随反应物浓度的增大、反应温度的升高、反应配比(n尿素/nZn2+)的增大而增大;纳米氧化锌颗粒的平均粒径随反应物浓度的减小、反应温度和煅烧温度的降低而减小。     

Stabilized Zirconia Nanoceramics Prepared by Magnetic Pulsed Compaction of Nanosized Powders

Ceramic materials with a fine structure are synthesized from zirconia-based nanopowders through magnetic pulsed compaction and subsequent sintering under different temperature-time conditions. The kinetics of crystallite growth and polymorphic phase transformations are analyzed. Unstabilized zirconia ceramic materials with a density of 96% and a crystallite size of 50 nm are prepared. It is found that, in the case when the ceramic materials with a cubic or tetragonal yttrium-stabilized zirconia (YSZ) matrix are synthesized with small additives of alumina nanopowders, the temperatures of active shrinkage and the polymorphic transformation γ-Al₂O₃ → α-Al₂O₃ are shifted to the high-temperature range, the density and microhardness of the final ceramics slightly decrease, and the size of α -Al₂O₃ crystallites does not exceed 100 nm. It is also established that the alumina additives have no noticeable effect on the growth of crystallites of the YSZ matrixOriginal Russian Text Copyright © 2005 by Fizika i Khimiya Stekla, Ivanov, Khrustov, Paranin, Medvedev, Shtol’ts, Ivanova, Nozdrin.     

对采用三种烧结技术制备的氧化锆的致密化和性能的研究

由氨基乙酸／硝酸盐闷烧方法制备了含8％Y2O3的纳米晶钇稳定氧化锆粉末,用火花等离子体烧结（SPS）、热压（HP）和传统烧结法（CS）研究了其致密性。SPS技术比其余烧结方法优异,能在较低温度和较短烧结时间获取具有均匀形态的致密化材料（≥96％）。经SiX5、热压和传统烧结方法制备的材料,其晶粒尺寸分别是0．21、0．37和12μm。材料的总电导率与晶粒尺寸并无明确关系,但SPS烧结材料的活化能比其余两种致密化方法的稍高。由Vickers压痕法测得的硬度与晶粒尺寸无关,而断裂韧性（由压痕法测得）随晶粒尺寸增大而轻微下降。     

Precipitation During Controlled Cooling of Magnesia-Partially-Stabilized Zirconia

A study has been made of the precipitation and growth processes which occur during cooling from solution treatment and under isothermal hold conditions in a magnesia-partially-stabilized zirconia alloy. Three types of precipitate have been identified which develop during cooling or during isothermal hold treatments just above and below the eutectoid temperature. These precipitate forms are termed (i) primary, (ii) large random, and (iii) secondary. Further precipitation, slow growth of existing precipitates, and subeutectoid decomposition result when an additional 1100°C aging treatment is given to the previously cooled material. It is shown that type (iii) secondary precipitates form rapidly within the temperature range of 1300° to 1375°C. The secondary precipitates are largely responsible for the improved room-temperature strength properties of the heat-treated samples. The formation and effects on mechanical properties of each type of precipitate are discussed.