用碳酸氢铵沉淀制备晶状碳酸钇的机理研究

在一定的条件下，从硫酸钇溶液中用碳酸氢铵沉淀时，可制得水合晶状的正碳酸钇或水合的晶状碳酸钇铵复盐。通过化学组成分析，X射线粉末衍射，红外光谱，热分析和扫描电镜等检测手段，研究了在沉淀和陈化过程中由无定形沉淀转为晶状沉淀的过程和机理。     

NH4HCO3沉淀法制备纳米CeO2棒状晶的研究

以Ce(NO3)3·6H2O和NH4HCO3为原料,采用化学沉淀法制得了平均长度84nm,直径15nm的CeO2棒状晶.利用XRD、TEM对CeO2粉体及其前驱体进行分析表征,发现CeO2晶粒继承了前驱体的棒状形貌.借助FTIR确定了前驱体的化学组成为Ce2O(CO3)2·H2O,从化学反应过程出发研究了CeO2棒状晶的具体形成过程.     

碳铵沉淀法制备纳米氧化铈的研究

采用碳铵沉淀工艺进行了纳米氧化铈制备的研究,探讨了表面活性剂的加入量对氧化铈颗粒大小的影响,随着表面活性剂量的增加氧化铈颗粒粒径减小;煅烧温度对氧化铈粉末性能影响较大,随着煅烧温度的升高氧化铈粉末的晶粒尺寸增大,比表面积减小,煅烧温度为450℃时就已经形成了立方相的氧化铈。优化工艺条件制备出了单一粒径小于50nm、团聚体粒度重量累积中值粒径D50<150nm,粉末比表面积大于15m2/g,粉末的团聚常数(D50/DBET)小于6,形状为球形的纳米氧化铈粉末。     

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.     

用碳酸氢铵转型剂制备活性氧化锌的生产实践

本文叙述用碳酸氢铵为转型剂制备活性氧化锌的生产实践及沉淀中和的工艺条件.     

酸沉淀法制备超微细球形钨粉

以钨酸铵为原料,在超声和机械搅拌下与强酸发生反应得到钨酸沉淀,再经干燥、研磨、过筛后在常规氢气炉中进行还原得到钨粉。研究了酸的种类及用量和分散剂对钨粉粒度、颗粒形貌及分散程度的影响。结果表明,强酸种类及用量都对钨粉形貌产生影响,当硫酸与钨酸铵的体积比为17∶100时所得钨粉粒度均匀且近乎球形。此外,采用硫酸为沉淀剂的反应体系中(H2SO4∶(NH4)2WO4=17∶100),分散剂十二烷基硫酸钠的加入可使钨粉粒度更均匀,颗粒更分散,形状为球形,平均粒径1.5μm左右。     

球形MnCO3粉的制备及其粒径控制

以MnSO4为锰源,NH4 HCO3为沉淀剂,六偏磷酸钠(SHMP)为分散剂,采用液相沉淀法制备出了粒径均一的球形MnCO3粉.考察了反应温度、反应物浓度比、SHMP用量比等因素对MnCO3粉粒径的影响,并利用激光粒度分析仪、扫描电镜和X射线衍射对实验结果进行了表征.研究结果表明,在10～50℃范围内,MnCO3粉的粒...     

RECl3与NH4HCO3的沉淀反应及伴生杂质的共沉淀行为

本文通过对沉淀过程的ｐＨ值变化特征研究和沉淀物的组成分析，确定了ＮＨ４ＨＣＯ３与ＲＥＣｌ３的沉淀反应。研究了伴生金属离子Ａｌ３＋、Ｆｅ２＋、Ｍｎ２＋、Ｃａ２＋、Ｍｇ２＋随稀土的共沉淀行为，讨论了杂质离子对产品纯度的影响。     

以碳酸铈为前驱体制备超细氧化铈及其抛光性能

研究了以水合碳酸铈为前驱体,采用直接球磨和煅烧的方法制备了中位粒径小于3μm的超细氧化铈。结果表明:所得产物均具有立方萤石型结构,随着煅烧温度的升高,产物粒径呈下降趋势,粒度分布也越来越窄,结晶度提高。但对三种不同玻璃的抛光能力均在900℃~1000℃之间呈现出极大值。因此认为抛光过程中玻璃表面物质的去除速率受抛光粉粒度、结晶度和表面活性的影响较大。     

沉淀法和沉淀二氧化硅微粒

介绍了制备二氧化硅的各种沉淀方法,对硅酸钠溶液中二氧化硅的沉淀过程进行了详细的描述,从描述中指出沉淀形成的三次沉淀粒子,最后指明沉淀法制备二氧化硅未来研究的方向.     

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.     

碳酸氢铵沉淀法制备超细CeO2 粉体工艺条件研究

用碳酸氢铵从硝酸铈溶液中沉淀制备了超细CeO2粉体,研究了沉淀工艺条件对制备CeO2的一次粒径、团聚粒径以及粉体团聚性的影响.研究表明形成的碳酸铈胶状沉淀物需要在高温下陈化足够长的时间才能制备出一次粒径小,分散性好的CeO2产品,否则将形成大的团聚体.当碳酸氢铵与硝酸铈的摩尔比为31左右、沉淀温度为50℃左右时制备的CeO2具有小的一次粒径,而且产品的分散性好.适当地增大加料速度和初始料液的pH值有利于减小CeO2的一次粒径和团聚性.     

Nano Lanthanum Oxide Preparation by Alkalescent Ammonium Citrate System and Its Primary Biological Effect

Nanomaterialshavebacteriostaticandbacterici dalactivityonplant[1,2 ] .Rareearthmaterialsnoton lypossessbacteriostaticandbactericidalactivity ,butalsohavetheactionofnutrientbearerandactasnu trientregulator[3] .Becausetheparticlesizeandho mogeneityofmaterialshavenotbeenrequiredexactly ,nanorareearthmaterialwhichisfrom 1nmto 10 0nmforbiologyapplicationisalsopreparedbyamethodhomogeneousprecipitant[4 ,5] .Currently ,generalpre cipitatorsaremostlyammonia ,urea ,oxalicacidandammoniumbicarbonateaswell…     

Effect of Ceria on Structure and Thermostability of Copper-Iron-Oxide Catalyst

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稀土氟化物的沉淀方法及组成研究

本文研究了湿法制备稀土氟化物的工艺过程,考察了HF用量、稀土浓度、反应温度和添加大分子助沉剂对稀土收率和沉淀速率的影响。报道了一种快速沉淀稀土氟化物的新方法,并用透射电镜、X射线衍射、X射线荧光光谱和差热-热重等分析方法测定了氟化物的形貌、粒径和组成。     

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.     

稀土草酸盐沉淀过程中颗粒大小的控制

稀土草酸盐沉淀法是制备稀土氧化物的主要方法。本文对硝酸体系中的稀土沉淀过程进行了研究,推导出草酸盐、草酸铵盐、草酸钾盐和草酸钠盐的平均粒径与过饱和度之间的关系。     

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.     

氧化钴生产过程的非草酸盐沉钴工艺研究之一碳铵(反加)法自氯化钴溶液中沉钴

通过系统的沉淀剂筛选试验,确定了碳酸氢铵是适宜的非草酸盐沉钴剂,采用沉钴剂反加法再辅以添加适量的分散剂和絮凝剂,可自氯化钴溶液中以高于97%的沉钴率沉出含钴沉淀产物,沉淀产物氯根含量低,煅烧产物疏松、理化性能优异,符合用户的质量要求。沉淀工序的加工成本可降低50%。     

Synthesis and Characterization of Large Surface Area Yttrium Oxide by Precipitation Method

Rareearthoxides(REO)withlargesurfaceareahavehighchemicalreactionactivity ,soitisusedwidelyinthefieldofcatalysis ,SOFC ,advancedce ramicandsoon[1] .Inordertosatisfythedemandofthenewfunctionmaterials ,thepreparationmethodofspecialphysicalpropertyREcompoundneedstobedeveloped .Yttriumoxide ,especiallywithlargesur faceareaisaREOandwidelyusedintheabovefield .Industrially ,yttriumoxideusuallywaspreparedbythermaldecompositionofyttriumoxalateat 80 0～10 0 0℃for 2h .Itssurfaceareaisonly 2～ 4m2 ·…