Preparation and Characterization of Nanocrystalline CeO2 by Precipitation Method

CeO2 nanocrystalline particulates with different sizes were prepared by precipitation method using ethanol as dispersive and protective reagent. XRD spectra show that the synthesized CeO2 has cubic crystalline structure of space group OH^H-FM3M, when calcination temperature is in the range of 250 - 800 ℃. TEM images reveal that CeO2 particles are spherical in shape. The average size of the particles increases with the increase of calcination temperature. Thermogravimetric analysis indicates that the weight loss of precursor mainly depends on the calcination temperature, and little depends on the calcination time. Measurements of CeO2 relative density show that the relative density of CeO2 nanocrystalline powders increases with increasing CeO2 particle size.     

Preparation of large particle rare earth oxides by precipitation with oxalic acid

The large particle CeO2 and Y2O3 were prepared using oxalic acid as precipitator. The effects of operational parameters such as stirring velocity, precipitation temperature, feeding speed, aging time, precipitation method, and calcination temperature on particle size and loose density of CeO2 were studied. Under the particular conditions, particle median size of D50≥30μm, loose density of ≥2.0 g/mlof CeO2, and particle median size of D50≥20 μm of Y2O3 were prepared. This technology had advantages of simple process, less equipment investment, ease of use, and suitability for industrialization products.     

不同沉淀剂制备氧化铈抛光粉

氧化铈(CeO₂)抛光粉在光学玻璃、手机盖板、集成电路等领域内有着广泛的应用。合成高端CeO₂抛光粉主要采用液相沉淀得到前驱体,再经过煅烧转型制得CeO₂。前驱体是决定CeO₂抛光粉性质和性能的关键因素之一。通过模拟工业上常用的制备方法,以氯化铈(CeCl₃)为铈源,使用碳酸钠(Na₂CO₃)、碳酸铵[(NH₄)₂CO₃]、碳酸氢铵(NH₄HCO₃)、二水合草酸(H₂C2O₄·2H₂O)和氢氧化钠(NaOH)为沉淀剂,合成了一系列CeO₂抛光粉的前驱体。利用X-射线衍射仪(XRD)、扫描电子显微镜(SEM)、激光粒度仪等手段表征了前驱体的晶相、形貌、粒度等性质,并研究了前驱体煅烧转型后的CeO₂性质及其对K9光学玻璃的...     

Synthesis of Ce:YAG Phosphor via Homogeneous Precipitation under Microwave Irradiation

Ultra-fine Ce:YAG phosphors were prepared by homogeneous precipitation under microwave irradiation method. The formation of Ce:YAG was investigated by means of XRD and DTA/TG. The purified YAG crystallized phase was obtained at a lower temperature (1100 ℃). Basically spherical Ce:YAG powders were indicated from TEM images, and the size of the particles is about 80 nm. Two peaks of 436 and 473 nm can be seen from the excitation spectrum in the range of 402～510 nm. A broad emission band located at 480～630 nm shows the phosphors prepared by this method have good emission properties.     

Synthesis and Luminescence Properties of Gd_2O_3∶Eu~(3+) Phosphors

Gd2 O3∶Eu3+ isanefficientredemittinglumines centmaterial ,whichcanbeappliedindisplays[1,2 ] .TheconventionalcommercialGd2 O3∶Eu3+ ismainlysynthesizedbyhightemperaturesolid statereactionandchemicalco precipitationmethods .Anadvancedperformanceofdisplaysrequireshighqualityphospho rssuchashighbrightnessandefficiency ,monodisper sityandfinegrainsize .Muchresearchhasanticipatedthatsubmicrometer sizedandnanometerluminescentmaterialswillhavethesepotentialadvantages[3～ 8] ,sosubmicrometer sizedan…     

碳酸氢铵沉淀法制备氧化铈抛光粉

利用碳酸氢铵做沉淀剂制备氧化铈抛光粉,通过L16(44)正交试验,研究了温度、硝酸铈浓度、滴加速度和搅拌速度对氧化铈粒度和比表面积的影响。得到的最佳粒度制备工艺条件为:温度60℃、硝酸铈浓度50g/L、搅拌速率500r/min、滴加速度50mL/min。并对最佳制备工艺条件下制取的抛光粉进行粒度、形貌和抛蚀量进行研究。     

Synthesis and Characterization of Y-Doped Mesoporous CeO2 Using A Chemical Precipitation Method

Using cetyltrimethylammonium bromide （CTAB） as the template agent, cerium nitrate as the cerium resource, yttrium nitrate as the yttrium resource, and ammonium carbonate as the precipitating agent, mesoporous CeO2 powders doped with different yttrium contents were successfully synthesized using a chemical precipitation method, under an alkalescent condition. Properties of the obtained samples were characterized and analyzed with X-ray diffraction （XRD）, energy dispersive analysis of X-rays （EDAX）, transmission electron microscopy （TEM）, infrared （IR） absorbance, and the BET method. For the prepared samples with 20% （molar ratio） Y-doped content, a BET specific surface area of 106. 6 m^2 · g^- 1, with an average pore size of3~27 nm were obtained. XRD patterns showed that the doped samples were with a cubic fluorite structure. TEM micrographs revealed that the doped samples showed a spherical morphology with a diameter ranging from 20 to 30 nm and a round pore shape. IR results indicated that the Ce-O-Ce vibration intensity decreased as the Y-doped content increased. N2 adsorption-desorption isotherms showed that the samples possessed typical mesopore characteristics. The average pore size of the samples decreased alter mesoporous CeO2 was doped with yttrium, and the average pore size decreased largely as the Y-doped content increased.     

Synthesis of Ti-Ce-Si Binary and Ternary Nanocomposite Photocatalyst by Supercritical Fluid Drying Technology

Recently,photodegratation of various organiccontaminants with powdered semiconductors as cata-lysts has received much attention for their potential inthe utilization of light energy.TiO2is one of the mostwidely used photocatalysts due toits relatively nontox-ic,high activity,strong oxidizing property,and excel-lent stability.However,some weaknesses such as poormechanic strength,compressive strength and thermalstability have li mited its industrial applications.Therefore,it is necessary to i mp…     

Preparation of High-Surface Area Nano-CeO2 by Template-Assisted Precipitation Method

The high-surface area nano-CeO2 was prepared by Ce（NO3）3 by precipitation method, with surfactant cetyhrimethyl ammonium bromide （CTAB） as templating agent. The effects of the precipitating agents, reaction temperature, ageing time, and calcination temperature on the surface area, as well as the pore structure and the mean crystallite size of nano-CeO2 were studied. It was found that the reaction of Ce（NO3）3 with NaOH in the presence of CTAB at 90℃ for 12 h yieldsed a cerium oxide/surfaetant mixture, which after calcination at 400℃ resulted in high-surface area nano-CeO2. The mean crystallite size of CeO2 was approximately 6 nm, surface area was in excess of 200 m^2· g ^- 1, pore size was approximately 9 nm, and the pore distribution was concentrative. Moreover, the surface area can still reach 147 m^2·g^- 1 after calcination at 700 ℃, which showed the good thermal stability of the CeO2. The number of oxygen vacancies in the structure of CeO2 corresponded with the surface area of CeO2, and the high surface area was propitious to the formalion of oxygen vacancies.     

Preparation and Characterization of CeO2 Superfine Powder

The CeO2 superfine powder was prepared by the co-precipitation method, using the industrial grade Ce2(CO3)3 and NH4HCO3 as starting material and precipitating reagent, respectively. The precipitated precursons and the calcinated products were characterized by the thermogravimetric analysis/thermoanalysis (TGA/DTA), X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The results show that using NH4HCO3 as a precipitating reagent,the precipitate decomposed full as it was heated to 360℃. The CeO2 superfine powder formed by calcinating the precipitate belongs to a cubic CaF2-type structure and has the first mean particle diameter 140nm and second mean particle diameter 630nm. The CeO2 powder particles aggregate and grow with raising the calcination temperature.     

Characteristic of macroporous CeO2-ZrO2 oxygen carrier for chemical-looping steam methane reforming

Chemical-looping steam methane reforming （CL-SMR） is a novel process towards the production of pure hydrogen and syngas, consisting ofa syngas production reaction and a hydrogen production reaction. Macroporous CeQ-ZrO2 oxygen carders with different pore sizes prepared by colloidal crystal templating method and characterized by techniques of scalming electron microscopy （SEM）, transmission electron microscopy （TEM）, Brunauer-Emmett-Teller （BET）, X-ray diffraction （XRD） and temperature pro- grammed reduction （H2-TPR） were tested in CL-SMR process. For comparison, nonporous CeO2-ZrO2 oxygen carrier prepared by precipitation method was also investigated. It was found that macroporous CeO2-ZrO2 oxygen carriers owned higher reducibility and reactivity in CL-SMR process than nonporous samples. For the macroporous CeO2-ZrO2 sample, the decline of pore size could im- prove the reducibility and reactivity. The macroporous sample with a pore size of 100 nm （labeled as Ce-Zr-100） showed the highest performance for the co-production of syngas and hydrogen during the successive CL-SMR redox cycles. After 10 redox cycles, it still retained good porous structure and reducibility. It was found that the porous structure could accelerate the oxygen release from bulk to surface, leading to a good mobility of oxygen and higher reducibility. In addition, it was also favorable for diffusion and penetration of methane and water steam into the sample particles to accelerate the reaction rate.     

电化学法和沉淀法制备的纳米结构CeO_2的微观结构比较

利用X射线衍射、X射线小角散射、扫描电子显微镜、透射电子显微镜等分析手段对电化学法、沉淀法制备的纳米结构的CeO2 的微观结构进行了比较 ,发现电化学法制备CeO2 是由分散的纳米颗粒组成 ,而沉淀法制备的CeO2 则是由粗大片状颗粒组成 ,而该片状颗粒具有纳米的结构。电化学法的CeO2 比沉淀法CeO2 具有更细的纳米结构     

溶胶-凝胶法制备稀土CeO2掺杂纳米钨粉的研究

以偏钨酸铵(AMT)、柠檬酸和硝酸铈为原料,用溶胶-凝胶法(sol-gel)制备稀土CeO2掺杂纳米钨粉。通过热重-差热(TG-DSC)、X射线衍射(XRD)、扫描电子显微镜(SEM)、比表面积法(BET)等测试手段对复合粉体的合成工艺、物相、颗粒形貌和粒径进行了分析。结果表明:当pH值为1时,还原后的粉体颗粒呈准球形,无团聚,稀土元素以CeO2形式存在且均匀地分布在钨粉中,平均颗粒粒径为80nm左右,满足制备高性能掺杂稀土氧化物亚微米结构浸渍阴极的要求。     

约束弧等离子体制备铝纳米粉体的研究

利用自行研制的约束弧等离子体制备金属纳米粉试验装置,成功制备了平均粒度为44nm的铝纳米粉体。利用X射线衍射(XRD)、BET吸附法、透射电子显微镜(TEM)和相应选区电子衍射(SAED)等测试手段对所制备样品的晶体结构、形貌、粒度及其分布、比表面积进行性能表征。试验结果表明:约束弧等离子体法制备的铝纳米粉晶体结构为fcc结构的晶态,与体材料相比晶格常数发生膨胀。比表面积为41m2.g-1,粒径范围分布在20~70nm之间,平均粒径为44nm,粒度均匀,分散性好,呈规则球形链状分布。     

Synthesis of Y2O3 Nano-Powder from Yttrium Oxalate under Ambient Temperature

ThereareseveralprecipitationmethodsinthesynthesisofY2 O3 nano powdersuchascarbonatemethod ,ammoniumsaltmethodandoxyhydratemeth odetc .[1～ 5] ,buttheoxalateprecipitationmethodisconsideredtobethebestmethodinindustryandtheadvantagesofoxalicacidastheagentofp…     

热镀锌渣的利用

以硫酸浸出热镀锌渣获得硫酸锌溶液和饱和碳酸氢铵溶液为原料,用直接沉淀法制备出了平均粒径20 nm左右的纳米氧化锌。制备过程中对影响前驱体和纳米氧化锌的粒度的一些因素进行了实验研究。结果表明:在反应温度55℃,饱和碳酸氢铵的加入速度4 mL/min,沉淀终点pH=7.0的条件下,从锌浓度为100 g/L的ZnSO4溶液中可以获得平均粒径1.6μm的碱式碳酸锌前驱体。在600℃,焙解60min的条件下可获得粒径20 nm左右的纳米氧化锌。     

Preparation and performance of CeO_2 hollow spheres and nanoparticles

CeO_2 hollow spheres were synthesized by polystryrene sphere(PS) templates and CeO_2 nanoparticles were prepared by a facile method. The as-obtained products were characterized by scanning electron microscopy(SEM), N_2 adsorption-desorption, X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR) and UV-vis diffuse reflectance spectra. The results showed that the structure of the obtained CeO_2 hollow spheres was hollow microsphere with a diameter of 380 nm and the average particle size of CeO_2 nanoparticles was about 1700 nm. The two samples' Brunauer-Emmett-Teller(BET) surface area was 67.1 and 37.2 m~2/g. The CeO_2 hollow spheres had a better performance than nanoparticles at UV-shielding because of higher surface area and the structure of hollow sphere.     

Preparation and characterization of nano-rare earth composite materials:application in selectivity catalytic oxidation of ammonia and its cytotoxicity study

The manufacture,physical characterization,environmental applications and cytotoxicity properties of nanocomposites consisting of CuO/CeO2 nano-rare earth composite materials prepared using the coprecipitation method at molar ratio of 6:4 with aqueous solutions of copper nitrate and cerium nitrate were reported.The performance of the selective catalytic oxidation of ammonia to N2(NH3-SCO) over a CuO/CeO2 nano-rare earth composite materials in a tubular fixed-bed reactor(TFBR) at temperatures from 423 to 673 K in the presence of oxygen was elucidated.The catalytic redox behavior was determined by cyclic voltammetry(CV).The nanocomposite particles were characterized by TEM,with a tiny particle size around 10 nm with high dispersion phenomena.Further,cell cytotoxicity and the percentage cell survival were determined by using 3-(4,5-dimethylthiazol-2-yl)-5(3-carboxymethoxyphenol)-2-(4-sulfophenyl)-2H-tetra-zolium(MTS) assay on human lung MRC-5 cell line.Experimental results showed that no apparent cytotoxicity was observed when the MRC-5 was exposed to the CuO/CeO2 nanocomposite materials.     

加料方式对葡萄糖还原法制备的氧化亚铜形貌和粒度的影响

研究不同温度下,并流和分步加料方式对葡萄糖还原法制备的氧化亚铜形貌及粒度的影响.结果表明:采用并流加料制备氧化亚铜,其粒度随温度升高而减小,而分步加料方式与之相反.采用NaOH和C6H12O6溶液并流加料方式下,所得氧化亚铜为晶粒直径10～30 nm的规则球形颗粒,反应温度对形貌影响不大,且粒度随温度升高而减小;而分步加料方式下,50℃所得氧化亚铜颗粒形貌为类球形;随温度升高逐渐转变为立方堆积体,但颗粒粒度却随温度升高而增大.     

Effects of Technical Conditions on Structure, Morphology and Crystalline Size of Nanocrystalline Nd-Doped Ceria Powders

Nanocrystalline solid solution CeO2-Nd2O3 powders were prepared by low temperature combustion process.Special attention was paid to the influence of the glycine/metal ratio and calcination temperature on the powders phase structure, morphology and particle size.TG-DSC curves and XRD peaks of different glycine/metal ratio show that smaller particle size can be obtained with a slightly fuel-deficient ratio.XRD results indicate that the as-prepared powders are crystallized in a single fluorite structure.The crystalline size ranges from 9 to 24 nm, which increases with the increase of calcination temperature.The lower SEM images were characterized by the spongy and form-like microstructure of the powders.Organic agent may be gradually eliminated by high temperature calcination process.