分步沉淀法制备YAG:Ce~(3+)荧光粉及其发光性能

采用分步沉淀法,首先用草酸沉淀剂使钇和铈沉淀完全,再以草酸盐沉淀作为晶核,用氨水使铝盐沉积在钇和铈盐沉淀物的外层.对沉淀反应的发生顺序、氨水沉淀反应结束时体系的pH值条件、YAG晶相生成过程及机理进行了研究,利用荧光分光光度计分析了粉体的发光性能.结果表明,粉末粒径约为2μm,激发光谱为双峰结构,最大波长470 nm,发射波长为534 nm,适用于白光LED.     

共沉淀法制备BaHfO3：Ce纳米粉体及发光性能

研究以草酸和氨水作为沉淀剂制备BaHfO3:Ce纳米粉体的工艺.用XRD、TEM等测试技术,分析不同沉淀剂对粉体合成中的物相变化、形貌及Ce3 '掺杂量对粉体激发光谱和发射光谱的影响.结果表明:以氨水做沉淀剂在900℃煅烧2 h合成的BaHfO3:Ce粉体形貌近似球形,平均粒径约15 nm.用草酸做沉淀剂、合成温度为1 000℃时其粉体形貌呈多边形,粒径约60 mn.微量Ce3 的掺杂不改变BaHfO3的晶体结构.Ce3 掺杂量(摩尔分数)为0.3%的JBaHfO3发射光谱相对峰强度最高,当Ce3 掺杂量大于0.3%时出现浓度淬灭现象.粉体的激发和发射光谱均存在较宽的谱带,主要由激活Ce3 的5d→2F5/2和5d→2F7/2宽带能级跃迁产生.     

铁包覆T-ZnOw复合粉体的制备及其性能研究

采用化学包覆法,以氨水为沉淀剂,在碱性体系中制备了Fe(OH)3包覆T-ZnOw复合粉体,在600℃下通氢气还原获得了Fe/T-ZnOw包覆复合粉体.用XRD,SEM和EDX对粉体进行表征,结果表明:复合粉体存在金属铁相和T-ZnOw相,T-ZnOw四针保持完整,表面包覆完整,铁颗粒为球形,颗粒细小均匀,并T-ZnOw表层外有部分散落铁颗粒,颗粒粒径约为3 μm.用VSM分析测定粉体的磁饱和强度和矫顽力,分别为32.10 emu/g和140.5 Oe.     

氧化银微纳米粉体的制备研究

为制得形貌和粒径均匀的氧化银(Ag2O)微纳米粉体,对比研究了氧化银的3种化学合成法。结果表明,采用常规方法可制备出类球形氧化银,添加剂PVP不改变氧化银粉体形貌,但可减小其粒径,氧化银产率为100%;采用铵盐络合法可制备出正八面体和削角八面体的氧化银粉体,且粒径均匀(平均粒径为1~2μm),氧化银产率为100%;采用氨水络合法可制备出八面体、削角八面体、类球形、六足体、正方体的氧化银粉体,随AgNO3:NH3·H2O摩尔比增大,氧化银粉体粒径增大,氧化银产率降低,为提高氧化银产率,可增大NaOH摩尔占比,所得氧化银粉体其物相为立方晶系氧化银且无其他杂质相。     

球形氧化锆及氧化锆/镍复合粉体的制备

采用化学沉淀法分别制备球形氧化锆及镍/氧化锆复合微球粉体。考察加料速度、加料方式和反应器结构等因素对粒径分布、结晶状态及形貌的影响,初步得到优化工艺条件,并在优化条件下制得粒径分布均匀的球形氧化锆粉体和镍包裹氧化锆复合粉体。利用扫描电镜、能谱及X射线衍射仪分别对前驱体及热处理产物的形貌和物相进行分析,利用激光粒度分析仪检测球形氧化锆前驱体的粒径分布。研究表明,采用化学沉淀法,通过优化制备工艺条件,可以制备粒径分布较均匀的球形氧化锆粉体;利用非均相化学沉淀包裹技术制备的金属镍包裹氧化锆微球粉体,球形氧化锆颗粒表面作为异相成核的场所,通过控制颗粒浓度、加料速度以及添加表面活性剂等工艺条件,可以调控包裹层厚度、表面均匀度以及表面裂纹等。     

纳米CeO2及其复合催化剂的制备及对CO氧化的催化性能

以硝酸铈和氢氧化钠为原料,使用超声雾化工艺实现微区反应制备纳米CeO2粉体和掺铜CeO2复合粉体;再以硝酸铈为铈源,氨水为沉淀剂,用凹凸棒石为载体合成凹凸棒石负载CeO2纳米复合材料.利用XRD、TEM、HRTEM和BET-N2等手段对所得产物的成分、物相结构和形貌进行表征,研究所制备的纳米CeO2及其复合催化剂对CO氧化的催化性能.结果表明:所制备的纳米CeO2粉体和掺铜CeO2复合粉体呈球形,粒径均为4～5 nm,且单分散性好;所合成的CeO2/凹凸棒石纳米复合材料中,CeO2颗粒均匀包覆在凹凸棒石表面.催化实验结果表明:CeO2颗粒越小、比表面积越大,对CO氧化的催化活性就越高;凹凸棒石负载CeO2纳米复合催化剂具有很强的协同催化效应,可提高其催化活性;Cu(5%)-Ce-O催化剂对CO氧化具有最好的催化活性,表明铜的掺入有利于提高CeO2在CO催化氧化反应中的低温活性,降低起燃温度.     

La_2Sn_2O_7粉体制备及其表面载银改性

以氨水为沉淀剂,EDTA+草酸为组合胶凝剂,采用化学共沉淀法成功合成了高纯度锡酸镧(La_2Sn_2O_7)粉体。采用氧化还原法﹑光催化还原反应对锡酸镧粉体进行表面载银工艺研究。并通过附带能谱仪的扫描电子显微镜(SEM/EDS)与X射线电子衍射(XRD)仪对其形貌及物相进行表征。结果表明:以甲醛为还原剂,当反应溶液在pH=8.5以上时,所合成的La_2Sn_2O_7载银粉体烧结后呈近球形或球形结构,但物相的纯度不高,存在杂质相SnO_2;以CTAB为分散剂,当CAg+=0.088mol/L时,合成La2Sn2O7载银复合粉体呈近球形结构,物相纯度高。     

RF-PCVD法纳米TiO2的制备及光催化研究

采用RF-PCVD法，以TiCl4 O2为反应体系，制备出纳米级的TiO2粉体。经TEM，XRD及粒度分布仪测试表明：粉体呈近球形，为锐钛矿型和金红石型的混晶体，粒径范围为15nm～45nm，团聚后，粒径≤116nm的粉体占90％，并对纳米粉体的形成、分布和晶型进行了初步探讨。苯酚降解实验表明，TiO2粉体具有明显的光催化活性。     

热化学共还原法制备W包覆Cu纳米复合粉体(英文)

采用两种粒径的氧化铜粉末和粒径为1.5μm的三氧化钨粉末来制备高纯度的CuWO4粉末,分别通过控制CuWO4粉末在360和750℃两个阶段的氢气还原作用,制备出钨包覆铜纳米复合粉体。复合粉体的微观形貌,组织结构与颗粒尺寸采用扫描电子显微镜(SEM),X线衍射分析仪(XRD)和透射电子显微镜(TEM)进行测试,激光粒度测试仪(LPSA)用来测试CuWO4粉末的粒度。由小粒度CuWO4粉末制备出的钨包覆铜纳米复合粉体的钨包覆层厚度小,氢气还原制备的钨包覆铜复合粉体的平均粒径约50nm。     

配位剂在制备纳米铜粉中的作用

本文报道了用KBH_4作还原剂制备纳米铜粉的方法,实验表明,当采用氨水做配位剂添加至溶液中时生成的产物为铜粉,通过比表面积分析和透射电镜观察,确认铜粉为纳米级,粒径约为40nm。     

Preparation of silver tin oxide powders by hydrothermal reduction and crystallization

Silver tin oxide composite powders were synthesized by the hydrothermal method with a silver ammine solution and a Na2SnO3 solution as raw materials. H2C2O4 was used as the co-precipitator of silver ions and tin ions. The co-precipitation conditions were investigated. The results show that the co-precipitate of Ag2C2O4 and Sn（OH）4 is available when the pH value of the solution is 4.27-8.36. Using the obtained precipitate as precursor,the reduction of Ag＋ and the crystallization of tin oxide were carried out simultaneously by the hydrothermal method and silver tin oxide composite powders were obtained. The composite powders were characterized by X-ray diffraction （XRD） analysis,scanning electron microscope （SEM）,and energy spectrum analysis. The results show that the silver tin oxide composite powders are small with a diameter of about 2 μm and with homogeneous distribution of tin.     

Preparation of flake AgSnO2 composite powders by hydrothermal method

Silver-tin oxide composite powders and silver powders were synthesized by hydrothermal method using NHs to complex Ag^＋, SO3^2- to reduce Ag（NH3）2^＋ and Na2SnO3 as the source of tin. The powders were characterized by XRD, SEM and EDX. The results show that there are macroscopic and microscopic differences between two kinds of powders. Spherical silver powders are 3μm in diameter, and silver-tin oxide composite powders are mainly flake of about 0.3μm in thickness. Silver crystal in silver-tin oxide composite powders is preferentially oriented in the （111） crystallographic direction and its oriented index is 2.581. Crystal lattice parameter of silver crystal of silver tin-oxide composite powders is 0.409 34 nm, larger than 0.408 68 nm of silver powders. The XPS analysis shows that silver in silver-tin oxide composite powders is metallic silver and tin oxide in silver tin-oxide composite powders has the red shift for Sn^4＋（3d（5/2）） and O^2-（1s）.     

WCu复合粉体的溶胶-凝胶制备及其还原行为研究

以偏钨酸铵和硝酸铜为原料,柠檬酸为络合剂的溶胶-凝胶法制备WCu复合粉体。利用XRD和TEM对还原前后粉末的物相组成﹑形貌﹑粒度进行分析。TEM显示还原后WCu粉末粒度在100 nm左右,Cu相均匀包覆在W颗粒表面。对氧化物粉体的还原性能和机理进行了系统的分析。程序升温还原(TPR)确定了氧化物粉体最佳的两步还原温度分别为500和700 ℃。红外光谱(FT-IR)分析表明,铜通过氧与钨键合,削弱W-O-W键,使得钨铜复合氧化物还原性增强。     

Preparation of antimony-doped nanoparticles by hydrothermal method

Antimony-doped tin oxide (ATO) nanoparticles were prepared by the mild hydrothermal method at 200℃ using sodium stannate, antimony oxide, sodium hydroxide and sulfuric acid as the starting materials. The doped powders were examined by differential thermal analysis(DTA), X-ray diffractometry(XRD) and transmission electron microscopy(TEM). The doping levels of antimony were determined by volumetric method and iodimetry.The results show that antimony is incorporated into the crystal lattice of tin oxide and the doping levels of antimony in the resulting powders are 2.4%, 4.3%and 5.1%(molar fraction). The mean particle size of ATO nanoparticles is in the range of 25 - 30 nm. The effects of antimony doping level on the crystalline size and crystallinity were also discussed.     

纳米银粉的水热LSS法制备与表征

以乙醇和油酸为液相(L),油酸钠为固相(S),硝酸银水溶液为溶液相(S),用水热LSS相转移法制备了纳米银粉并对其进行表征。正交实验表明,影响纳米银粉产率的因素依次为水热处理时间乙醇用量油酸用量油酸钠用量,优化条件下所得纳米银粉产率达75.4%;用XRD、TEM和SAXS对制备的银粉进行表征,结果显示所得纳米银粉为形状规则的近球形纯银颗粒,粒度均匀且无明显团聚,平均粒径约23.7 nm。     

Preparation of CeO_2 Nanoparticles and Its Application to Ion-selective Electrodes Based on Acetyl Cellulose

Recently, an increasing interest has beenfound in synthesizing nanoscale particles andclusters[l]' The physical and cheAncal proper-ties vary drastically with size and the use of ul-tTafine particles represents a potentially feftilefield fOr materials research[2]. In particular,the preparation and characterization of ceriumoxide nanopowders have attracted much atten-tion over the past few years due to their greatpotential in many fields. It is commonly used inglass, ceramics, fluorescent powd…     

高浓度硝酸银还原制备超细银粉的试验

采用高浓度硝酸银溶液为银源,以抗坏血酸为还原剂,聚乙烯吡咯烷酮为分散剂,制备超细银粉,用扫描电子显微镜和振实密度测试仪对银粉进行表征。结果表明,提高硝酸银溶液浓度的同时,调整抗坏血酸和分散剂PVP的加入量,能够获得类球形、粒径分布窄的银粉颗粒,分散剂的种类和用量仍需进一步优化。     

Indium tin oxide nanosized composite powder prepared using waste ITO target

Indium tin oxide （ITO） nano-particles were prepared directly using waste ITO target, which had been coated by magnetron controlled sputtering. The waste ITO target was cleaned with de-ionized water, and then dissolved in acid, filtrated, neutralized, manipulated through azeotropic distillation and finally dried, and in this way the precursor of indium tin hydroxide was obtained. The nanosized rio composite powder was prepared after the precursor heat-treated at 500℃ for 2 h. TEM images show a narrow distribution of particle size is 5-20 nm and the particle size can be controlled. Its granule has a spherical shape and the dispersion of the particle is well. X-ray diffraction （XRD） patterns indicate the only cubic In2O3 phase in the ITO powder hot-treated at 500℃. The purity of ITO composite powder is 99.9907%. The content of radium within filtrate was detected by using the EDTA titration of determination of indium in the ITO powder and ITO target. Appropriate amount of SnCl4.5H2O was dissolved in the filtrate, and then ITO powder containing 10 wt.% SnO2 was successfully prepared by heat-treating.     

Novel method for preparation of silver-tin oxide electrical contacts

A novel method of coating tin oxide particles with silver by an electroless plating process has been developed to produce silver-tin oxide electrical contact materials. A powder metallurgy process has been developed to consolidate the electroless plated silver- tin oxide composite powders. The effect of the various plating conditions on the morphology of the composite powder was studied using the transmission electron microscope (TEM) and the scanning electron microscope (SEM). An optical microscope and electron microprobe analysis (EMPA) were used to characterize the structure of the sintered silver-tin oxide compact. Ductility and hardness were measured to ensure that the mechanical properties are adequate, and electrical conductivity was also measured.     

纳米银溶胶的固液分离研究

以次磷酸钠液相还原法制备纳米银溶胶,通过添加试剂破坏银溶胶的稳定性,使银粒子产生聚沉或絮凝,分析了纳米银溶胶的稳定条件.考查了加入氨水的工艺条件对从银溶胶中过滤分离纳米银粉的影响,控制溶胶的pH范围可以得到不同粒度的纳米银.用有机碱性混合试剂可使溶胶中的银粒子絮凝,易于固液分离,干燥后的银粉经快速渗透剂T分散后,银粉的粒度小（10 nm～20 nm）、稳定性好.提供了从银溶胶中过滤纳米银粉的新方法,该方法工艺简单、对设备要求低、能耗小、银粉的收率高,易于实现工业化.试样经TEM分析发现,该法制备的纳米银粉粒度小（10nm～40 nm）,分散性好.XRD物相分析证实其为纯的金属银.