W-Cu纳米晶粉体的制备及表征

采用机械舍金化技术制备了W-20％Cu和W-50％Cu纳米晶粉体，通过XRD、SEM、TEM等手段对机械舍佥化过程中W-Cu纳米晶复合粉的组成、晶格常数、晶粒尺寸和形貌结构进行了表征与分析。结果表明，W-20％Cu混合粉经过高能球磨，Cu元素完全固溶进w晶格中，形成W（Cu）固溶体；W-50％Cu复合粉经过高能球磨，形成W（Cu）和Cu（W）两种固溶体。W、Cu的合金化主要是依靠高能球磨过程中产生的大量纳米晶界和高密度的缺陷（位错、层错等）促使W、Cu之间的固溶。W-Cu复合粉的晶格常数和晶粒尺寸随着球磨时间的延长而减小，球磨一定时间后，都趋于稳定。球磨20h后，W-20％Cu和W-50％Cu复合粉中W（Cu）的晶粒尺寸分别为6．6和8．0nm。     

纳米Fe-Cu粉末的制备及其对铁基压坯烧结行为的影响

以化学共沉淀法制备出纳米Fe-Cu复合粉末并对其性能进行了表征,分别以此纳米Fe-Cu粉末和电解Cu粉与铁粉进行混合获得铁基粉末混合料,成形压坯在H2气氛中不同温度下进行烧结,测定基加入不同形态Cu(合金）粉末铁基烧结坯的烧结性能,结果表明,在相同的Cu添加量及烧结条件下,添加纳米Fe-Cu粉末较加入电解Cu粉于铁基压坯中可以明显地提高压坯烧结后的密度,硬度及强度等性能,而添加纳米Fe-Cu粉末压坯在较低温度下烧结可达到添加电解Cu粉压坯在较高温度下烧结后的性能水平,说明采用纳米Fe-Cu粉末形式向铁基压坯中引入Cu有利于制备高密度,高性能的铁基烧结材料。     

纳米羟基磷灰石/壳聚糖复合骨修复材料的共沉淀法制备及其性能表征

通过共沉淀法制备了纳米羟基磷灰石/壳聚糖复合骨修复材料,并采用 TEM、IR、XRD、TGA 及万能材料试验机等手段对材料进行分析表征,还通过对材料的燃烧试验研究了复合材料中两相间的分散均匀性。结果表明:复合材料中的羟基磷灰石为类似于自然骨矿物相的弱结晶含碳酸纳米晶体,并均匀分散于有机相壳聚糖中;复合后壳聚糖在 1655cm-1的酰胺Ⅰ谱带和 1599cm-1 的—NH2 吸收峰均向低波数方向移动,暗示复合材料中两相间发生了相互作用。复合材料的力学性能较之两种单组分材料有明显的改善,当纳米羟基磷灰石/壳聚糖重量比为 70/30 时,复合材料的抗压强度最高,达120MPa左右,可满足骨组织修复与替代材料的要求。     

均相共沉淀法合成钇铝石榴石(YAG)纳米粉末的研究

透明YAG多晶陶瓷具有容易制造、成本低、尺寸大、掺杂浓度高、热导率高、耐热冲击性好、可大批量生产、易实现多层和多功能的陶瓷结构等优点,使得它作为激光介质而成为单晶的强有力的替代者.本实验以Y2O3、Al(NO3)3*9H2O、(NH4)2SO4为原料,尿素为沉淀剂,正硅酸乙酯作为添加剂,采用均相共沉淀法制备出YAG前驱体粉末,在沉淀过程中采用静电稳定、聚合物空间位阻以及共沸方法相结合有效地防止了纳米颗粒硬团聚的形成,YAG前驱体颗粒尺寸小于50nm,并对反应过程中pH值的变化进行研究.采用DTA/TG、IR、 XRD和TEM测试手段对粉末材料进行了表征,根据Scherrer公式计算出晶粒大小,研究了晶粒尺寸分布及其变化情况.研究结果表明:前驱体粉末经过1 200℃温度烧结后,全部转化YAG相,其晶粒尺寸小于50nm,随着烧结温度升高,晶粒平均尺寸增大.     

均相共沉淀法制备钇铝石榴石(YAG)纳米粉末

以Y2O3、Al(NO3)3·9H2O、(NH4)2SO4为原料,尿素为沉淀剂,正硅酸乙酯作为添加剂,采用均相共沉淀法制备出YAG前驱体粉末,在沉淀过程中采用静电稳定、聚合物位阻以及共沸方法相结合有效地防止了纳米颗粒硬团聚的形成,前驱体颗粒尺寸小于100nm.采用DTA/TG、IR、XRD和TEM测试手段对粉末材料进行了表征,根据Scherrer公式计算出晶粒大小,研究了晶粒尺寸分布及其变化情况.研究结果表明前驱体粉末经过1200℃温度烧结后,全部转化YAG相,其晶粒尺寸小于50nm,随着烧结温度提高,晶粒平均尺寸增大.     

Fe-Ni纳米复合粉末的制备及其表征

通过差热分析(DSC)、透射电镜(TEM)和X射线衍射分析(XRD)等方法,研究以硝酸铁和硝酸镍为主要原料、采用溶胶凝胶法(Sol-Gel)和化学共还原法制取的Ni含量分别为10%和20%的Fe-Ni纳米复合粉末,同时比较聚乙二醇和柠檬酸在制备凝胶时的分散效果结果表明:以柠檬酸为分散剂,用化学溶胶凝胶法制备的Fe-Ni纳米复合粉末的粒径在30nm左右,成分为(Fe,Ni),无其它杂质.     

SnO2／Fe2O3纳米复合粉的制备与表征

用共沉淀法制备了ＳｎＯ２／ＦｅＯ３纳米复合粉体,用Ｘ射线衍射（ＸＲＤ）、Ｍｏｅｓｓｂａｕｅｒ谱研究了它的物相,晶粒度及变化过程。结果表明,煅烧温度在７００℃以下时,它可能是以四方ＳｎＯ２纳米晶为主体（其平均粒径为３．０ｎｍ）,α－Ｆｅ２Ｏ３纳米晶包裹在ＳｎＯ２晶界的复合相,其中α－Ｆｅ２Ｏ３结晶很不充分,５４．７％聚集于晶界。这种复合相的结构阻碍了ＳｎＯ２晶粒的长大,有利于煅烧后保持纳米晶结构。     

NiO-YSZ纳米复合粉体的制备及其表征

以氯氧化锆、硝酸钇、硫酸镍为原料,采用超声波-共沉淀法制备NiO-YSZ纳米复合粉体.通过TEM,TPR与XRD等测试手段,分析产物形貌、晶相及还原过程,对不同Ni含量的Ni-YSZ材料的电导率通过四端电极法进行了测定.结果表明:产物粒径分布窄,颗粒小,分散性好;Ni的质量分数为50%时较为合适.对机械混合法和超声波-...     

ITO纳米棒的制备及其表征

利用化学共沉淀法,在InCl3和SnCl4混和溶液中添加PEG-1000,并滴加浓度为25%氨水,制备了ITO前驱体,在温度700℃煅烧3h后得到ITO纳米棒.利用SEM、XRD、TEM-EDS和傅立叶-红外光谱仪分别对ITO纳米棒的形貌和尺寸、结构和物相、EDS能谱和FT-IR光谱分析,并对ITO纳米棒形貌形成机理进行了探讨分析.研究结果表明,ITO纳米棒具有立方铁锰矿结构,且具有纯度高和分散性好等特点,平均直径约为φ300nm,长度可迭3000nm,长径比约达10.随着煅烧时间的延长,ITO纳米棒形貌不变,对尺寸影响不大.     

均相共沉淀法制备纳米氧化锆复合粉体

以氨水、氧氯化锆为原料,在旋转填充床中进行均相共沉淀制备了纳米级ZrO2.采用XRD、TEM、BET测试手段对前驱体及纳米级ZrO2粉体进行表征.研究了转速、醇洗脱水工艺、煅烧温度对粉体粒径、分散性、晶型的影响.研究结果表明,在转速为1800r/min时,采用无水乙醇乳化脱水工艺,550℃下热处理能得到粒度分布窄、硬团...     

Preparation and characterization of ATO nanoparticles by various coprecipitation

A series of Sb doped SnO₂ (ATO) nanoparticles, with Sb doping levels 0–20 at.% has been prepared by two different coprecipitation routes. Effect of preparation process, Sb doping concentration and calcination temperature on the crystallinity and morphology of ATO nanoparticles were investigated and analyzed. The prepared nanoparticles were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, selective area electron diffraction, X-ray diffraction and energy dispersive X-ray spectroscopy. Results indicated that the prepared ATO nanoparticles were tetragonal, and isostructural with rutile lattice structure as known from bulk SnO₂. The ATO nanoparticles prepared via process I (homogeneous coprecipitation) presented obviously weaker crystallinity, smaller average crystallite size and harder agglomeration than that prepared via process II (heterogeneous coprecipitation). The crystallinity and average crystallite size of ATO nanoparticles prepared via process II increased with increasing calcination temperatures and reducing Sb doping concentrations, respectively. The increased crystallinity, dispersibility and average crystallite size for ATO nanoparticles prepared via process II may be due to the formation of ATO crystal nuclei, leading to an improved formation dynamics of ATO nanoparticles.     

Preparation and characterization of submicron-cerium oxide by hypergravity coprecipitation method

Submicron-cerium oxide particles were synthesized by applying hypergravity using ammonium bicarbonate (precipitant) and cerium nitrate hexahydrate (precursor). The influence of the concentration, pH, dispersant loading, flow rate, rotation speed of the hypergravity rotating bed, calcination temperature, and time on the cerium oxide particle size were examined by zeta potential, solid–liquid contact angle, thermo-gravimetry–differential scanning calorimetry, scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The cerium oxide particles were highly dispersed, with an average particle size of 200 nm. Calcining at 650 °C for 1.5 h afforded the smallest particles. The crystallite size and fraction crystallinity increased with prolonged calcination. Crystalline cerium dioxide grew along three crystal planes, forming a complete face-centered cube, affording high hardness and activity of the polishing powder. The optimal conditions were: cerium nitrate concentration: 0.7 mol/L, cerium nitrate/ammonium bicarbonate molar ratio: 1:3, dispersant mass fraction: 3%, cerium nitrate initial pH: 4–5; the precursor solution was adjusted to pH 9 with ammonia water. Hypergravity coprecipitation with 1.5 h calcination afforded submicron-sized cerium oxide with a uniform size distribution using ammonium bicarbonate in an industrially viable process. The simple and low-cost manufacturing process may enable the development of hypergravity-assisted chemical synthesis technology.     

Preparation,characterization and photocatalytic properties of terbium orthoferrite nanopowder

Perovskite-type terbium orthoferrite (TbFeO₃) nanopowder was synthesized through a polyacrylamide gel route. The as-synthesized particles were characterized by XRD, TEM, BET surface area, UV–visible absorption spectroscopy, and XPS. It is shown that the particles are uniformly and regularly shaped like spheres with an average size of ～50 nm, and have a BET specific surface area of 15.4 m² g^?1. The optical energy bandgap of the nanosized TbFeO₃ is obtained to be 1.98 eV. The photocatalytic activity of the TbFeO₃ particles was evaluated by the photodegradation of various organic dyes including methyl orange (MO), rhodamine B (RhB), methylene blue (MB), acid fuchsine (AF), and congo red (CR). It is demonstrated that the product exhibits a pronounced photocatalytic degradation of the dyes under visible-light irradiation. The photocatalytic efficiency is observed to depend on the dye type, and under the present experimental conditions it follows the sequence: CR > AF > MB > RhB > MO.     

Preparation of lead magnesium niobate by a coprecipitation method

The ferroelectric complex perovskite lead magnesium niobate, Pb(Mg_1/3Nb_2/3)O₃ (PMN), was prepared by a coprecipitation method. As the niobium component, niobium oxalate was used. Among the various precipitants, tetramethylammonium hydroxide was effective for the formation of single-phase PMN without pyrochlore phase. The dielectric constant and the dissipation factor of PMN changed either the sintering temperature or the grain size. The maximum dielectric constant at the Curie point was obtained by sintering at 1220 °C in air for 2 h.     

钨铜化合物氢还原制备钨铜复合粉研究

通过对钨铜化合物氢还原过程进行热力学分析,找到了制备均匀细颗粒钨铜复合粉的热力学途径--彻底快速除去还原系统中的水分.设计了封闭还原系统,用此系统进行氢气热还原,不仅使氢气得到充分利用,而且容易判断反应终点.通过系统内的特殊装置除水,降低了还原温度,在600℃下还原得到了混合均匀的钨铜复合粉.系统能彻底快速除去反应生成的水分,使反应物的湿度大大降低,确保得到细颗粒的钨铜复合粉,其平均粒径小于80nm.     

Synthesis of barium titanate nanopowder by a soft chemical process

A simple soft chemical method of synthesizing barium titanate nanopowders and nanorods is described here, where titanium dioxide/titanium isopropoxide was taken as a source of titanium, tartaric acid was taken as a template material, nitric acid as an oxidizing agent. The synthesized powders and rods were characterized by XRD, TG and DTA, SEM and IR spectroscopy. In this process phase pure barium titanate nanopowders and nanorods can be prepared at a temperature of 900 °C and the process is simple and cost-effective.     

Co(Pd)CuZnLa/硅藻土催化剂改性共沉淀法制备与表征

添加阳离子表面活性剂CTAB,利用共沉淀法制备了硅藻土负载Co-Cu-Zn-La和Pd-Cu-Zn-La的复合金属催化剂,利用SEM、TEM、XRD、FT-IR、TPR等技术对催化剂的表面形貌、结构及还原性能进行了表征。结果表明,制备的催化剂有丰富孔结构,4～15nm的活性氧化物组分呈200～400nm花状分布,分散良好;制备催化剂经H2程序升温还原后,除有金属单质存在外,可能还有合金生成。     

Preparation and characterization of a novel willemite bioceramic

Willemite (Zn₂SiO₄) ceramics were prepared by sintering the willemite green compacts. The effects of sintering temperature on the linear shrinkage, porosity and mechanical strength of the ceramics were examined. With the sintering temperature increased, the linear shrinkage of the ceramics increased and the porosity decreased. When sintered at 1,300°C, willemite ceramics showed mechanical properties of the same order of magnitude as values for human cortical bone, as measured by bending strength (91.2 ± 4.2 MPa) and Young’s modulus (37.5 ± 1.5 GPa). In addition, the adhesion and proliferation of rabbit bone marrow stromal cells (BMSCs) on willemite ceramics was investigated. The results showed that the ceramics supported cell adhesion and stimulated the proliferation. All these findings suggest that willemite ceramics possess suitable mechanical properties and favorable biocompatibility and might be a promising biomaterial for bone implant applications.