机械搅拌制备半固态浆料固相颗粒形貌的研究

采用自行研制开发的新型转简式流变成形设备，通过改变不同的制浆工艺参数，研究半固态组织中固相颗粒的形貌特点，并对形成半固态固相颗粒的机理和固相颗粒的三维形貌进行了探讨？研究结果表明，在相同剪切速率条件下，连续冷却条件制备的半固态颗粒的形貌要比恒温条件的好，颗粒的圆整度高、尺寸小且均匀。机械搅拌作用下标准半固态固相颗粒的三维形状初步断定主要是近似椭球形。     

机械固相化学反应制备纳米β-Co粉及其反应热力学研究

以H2C2O4·2H2O及Co(NO3)2·6H2O为原料,在高速球磨中进行固相化学反应,经洗涤并喷雾干燥获得分布均匀的球形纳米晶前驱物,再经高温分解,制备出目标物。对分解产物进行了XRD/SEM分析。结果表明,产物形貌为球形、平均粒径在100 nm左右的纳米粉体,其晶型为面心立方结构β-Co,同时对制备反应进行了热力学的研究。     

O2浓度对纳米氧化锌形貌、产量和发光性质的影响

目的研究不同O_2体积浓度下,双管管式炉内不同沉积位置处纳米ZnO形貌、产量和发光性质的变化规律。方法采用化学气相沉积法,在双管管式炉的三个不同沉积位置制备了具有不同形貌、产量和性质的纳米ZnO产物。采用扫描电子显微镜(SEM)、X-射线衍射仪(XRD)和荧光分光光度计(PL)等对产物的形貌、结构和光致发光性能进行表征和测试。结果 SEM表明O_2体积浓度较小时,有利于形成针状的多脚结构。O_2体积浓度较大时,有利于生成棒状的多脚状结构。通过对比沉积产物产量发现,当O_2体积浓度较低时,沉积反应主要发生在内管外。随着O_2体积浓度的增大,沉积产物逐渐向内管内部转移,内管口附近的沉积产物增多。XRD结果表明所有产物均为六方纤锌矿结构,当O_2体积浓度为0.0625%时,产物沿c轴择优生长。随着O_2体积浓度的增加,无明显择优取向。PL结果表明,紫外发射峰与绿光发射峰强度的比值随着O_2体积浓度的增加而增大,说明绿光发射峰主要由氧空位引起,随着O_2体积浓度的增加,氧空位逐渐减少。结论通过调节O_2体积浓度可以制备出不同形貌和发光性质的纳米ZnO,从而应用于不同领域,并且在适当的沉积位置可以获得最大产量。     

室温球磨固相法制备镧掺杂纳米二氧化锡及其性能研究

以SnCl2.2H2O、C2H2O4.2H2O和La(NO3)3.6H2O为主要原料,采用室温球磨固相法制备La3+掺杂纳米SnO2。利用X射线衍射仪、扫描电镜、紫外分光光度计等分析方法,研究了掺杂量、焙烧温度对粉体粒径、吸收率的影响。结果表明,La3+的掺杂抑制SnO2晶粒的长大,并且随其含量的增加,抑制SnO2长大的效果更明显;La3+的掺杂明显降低了粉体对紫外光的反射能力,增加了粉体对紫外光的吸收能力;在焙烧温度为700℃、La3+掺杂量为2wt%时,得到了对紫外光吸收率最好的粉体。     

气相氧化法制备氧化锌的结晶形貌

研究了锌蒸气高温气相氧化条件对氧化锌结晶形貌的影响结果.结果表明:气相氧化法制备的氧化锌有无定形、颗粒状、单针状、四针状、多针状等5种典型的结晶形貌;这些结晶形貌与原料锌粉的粒度及表面状态没有直接联系,但都强烈地依赖于锌蒸气氧化时的物理化学环境;在不同的氧分压下,锌蒸气具有不同的氧化行为,由此导致了不同形貌的氧化锌结晶;通过改变制备条件可以有效地调控氧化锌的结晶形貌.     

机械搅拌制备半固态浆料固相颗粒形貌的研究

采用自行研制开发的新型转筒式流变成形设备,通过改变不同的制浆工艺参数,研究半固态组织中固相颗粒的形貌特点,并对形成半固态固相颗粒的机理和固相颗粒的三维形貌进行了探讨.研究结果表明,在相同剪切速率条件下,连续冷却条件制备的半固态颗粒的形貌要比恒温条件的好,颗粒的圆整度高、尺寸小且大小均匀.机械搅拌作用下标准半固态固相颗粒的三维形状初步断定主要是近似椭球形.     

电纺丝法制备氧化锌纳米纤维

以聚乙烯醇(PVA)与乙酸锌的混合溶液为前驱体,采用静电纺丝法制得乙酸锌/PVA复合纤维,经煅烧后得到直径分布均匀的ZnO纳米纤维.对所制得的复合纤维及ZnO纳米纤维分别采用了热失重、X射线衍射、红外光谱(IR)、扫描电镜(SEM)等分析测试手段进行了表征.研究了纤维平均直径受电纺丝溶液配比的影响.     

制备条件对固相反应法制取YAG多晶体透光性的影响

在制备YAG(钇铝石榴石)多晶体的不同条件下，对其固相反应过程中的物相变化、YAG烧结体透明程度、密度和显微组织进行了观测和分析。结果表明：Y^3 的扩散速率是决定固相反应进程的主要因素，将高活性的Y2O3纳米微粒与A12O3粉均匀混合，可促进固相反应的完成，使获得YAG透明体的烧结温度降低100—200℃，保温时间也显著缩短；气孔和晶界对光的反射和散射是YAG多晶体透光性降低的主要原因，采用真空烧结可提高YAG烧结体的密度，改善晶体结构的均匀度，有利于提高YAG多晶体的透光性。     

烧结温度对固相法制备ZrW2O8的影响

以ZrO2和WO3为原料,采用固相法制备了负热膨胀材料ZrW2O8,研究了不同烧结温度时烧结样品中ZrW2O8的含量,从而发现ZrW2O8纯度随烧结温度变化的规律。     

改良固相法制备透明YAG陶瓷的研究

以高纯氧化铝(Al2O3)、氧化钇(Y2O3)为原料,使用卧式搅拌磨,系统研究了一种制备YAG粉体的改良固相法工艺。该工艺利用高达2000r/min的转速以及直径0.5mm的高纯氧化铝球球磨介质实现了Al2O3、Y2O3粉体亚微米级的均匀混合,可在1350℃实现两种粉体的固相反应,并完全转化为纯YAG粉体,大幅度地降低了YAG的转相温度。作者还初步研究了该粉体的烧结性能,成功制得了透明的YAG陶瓷。     

Effect of Annealing Temperature on the Morphology and Sensitivity of the Zinc Oxide Nanorods-Based Methane Senor

ZnO nanorods in the form of thin films were synthesized by a facile chemical route and the effect of annealing temperature on the structure and sensitivity of such ZnO-based sensors was studied in detail towards methane sensing.Morphological analyses of such films were carried out by scanning electron microscopy,whereas,the crystalline structure and phase purity of the films were analysed by X-ray diffraction technique.The films were observed to display a gradual change in their morphology from granular to dense nanorods and each of them was used to fabricate methane sensor prototype.They were also tested for temperature-dependent methane-sensing capability with varying methane concentrations.The optimized sensor exhibited highest gas response of *80% at 250 °C with significantly low response and recovery time.     

Synthesis and Characterization of the Antibacterial Activity of Zinc Oxide Nanoparticles against Salmonella typhi

Metal oxides can be used as a series of new and effective anti-bacterial agents.In this study,four concentrations of ZnO nanoparticles(0.2,0.5,0.7 and 1.0 mol/L) were synthesized using a low-temperature sol-gel method annealed at400 and 550 °C.The products were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM)and Fourier transform infrared spectroscopy(FTER).XRD results show the hexagonal wurtzite structure of the nanoparticles with the grain size in the range of 38-43 nm.TEM micrographs exhibit a polyhedral form of the synthesized nanoparticles.The antimicrobial activity of different concentrations of nanoparticles against Salmonella typhi PTCC 1609 was determined by disk diffusion and agar dilution method at five concentrations of 10,5,2.5,1.25 and 0.625 mg/mL.Analysis shows that the prepared ZnO nanoparticles have a very effective antimicrobial activity against Salmonella typhi.This activity increases by reducing the size of nanoparticles and increasing their content in the bacterial growth medium.     

Influence of Yttrium Addition on the Reduction Property of Tungsten Oxide Prepared via Wet Chemical Method

W-Y_2O_3 composite nanopowders prepared via wet chemical method exhibit unique morphologies and micro structures.The yttrium addition during chemical reaction process affects not only the composition of tungsten acid hydrate precursors,but also the reduction property of tungsten oxide transformed from precursors.In this study,the morphology evolution of the samples with and without yttrium during reduction process has been studied,and it is found that the addition of yttrium can exert a strong influence on the reduction route of tungsten oxide and the final morphology of tungsten particles.The cause of the difference of reduction route and tungsten particle morphology is also analyzed.It is suggested that the composition of the samples with yttrium at the beginning of reduction is pure cubic system WO_3(c-WO_3),and the c-WO_3 particles have c-WO_3 whiskers attached to the surface.This kind of whiskers is essential for c-WO_3 to be reduced directly to tungsten and also helpful to obtain W-Y_2O_3 powders with small size and good uniformity.     

溶剂对溶剂热合成CdS纳米晶体的形貌控制

以溶剂热法在不同溶剂里的160℃下反应12 h制备不同形貌的CdS纳米晶粒,分别选用水(H2O)、二甲基甲酰胺(DMF)、乙醇胺(an)和乙二胺(en)为溶剂来控制纳米CdS的形貌和尺寸.对样品的结构和性能进行表征,重点分析了溶剂的物理性质和结构特征对CdS纳米粒子晶体结构、形貌和尺寸的影响,不同溶剂的作用机制不同,可通过选择合适的反应溶剂来控制纳米粒子的形貌和尺寸,以制备满足不同应用需要的纳米结构,尤其是性能独特的一维纳米结构.     

溶胶凝胶法制备纳米贵金属稀土复合氧化物研究

通过溶胶凝胶法以无机盐为原料制备纳米贵金属稀土复合氧化物,并采用透射电镜(TEM)、低温氮吸附、X射线衍射(XRD)和程序升温H2还原(TPR-H2)对其形貌特征和物化性能进行了研究.复合氧化物为无定形或不规则多晶物质,以不规则球形粒子聚集成团存在,平均粒径约为70 nm.其比表面积和总孔容适中,孔容呈现双峰分布特征.其储氧值和还原起点温度分别为2767 μmol/g和200℃,具有作为汽车尾气净化三元催化剂涂层料的潜在优异起燃和储氧特性.     

Effects of temperature and pressure on morphologies of quasi-one-dimensional ZnO nanostructures fabricated via thermal evaporation

Quasi one-dimensional zinc oxide nanomaterials were synthesized by thermal evaporation. The structure, morphologies and composition of ZnO nanomaterials prepared under different conditions were studied by XRD, TEM, SEM and EDX. The morphologies are strongly sensitive to the temperature and the pressure during growth, including nanowires, nanobelts, nanocombs and pyramidal-like nanomaterials.     

燃料量和温度对固相燃烧合成LiMn_2O_4的影响

以碳酸锰和碳酸锂为原料、淀粉为燃料,研究了温度(500, 600, 700 ℃)和燃料量(0～30%,质量分数)对固相燃烧合成尖晶石型LiMn_2O_4的影响.实验结果表明,通过固相燃烧合成方法在1 h可快速制备高纯度或单相的尖晶石型LiMn_2O_4产物.在500, 600, 700 ℃添加10%～30%淀粉时,可得到主晶相为LiMn_2O_4的产物,但600 ℃时最好.在600 ℃添加20%淀粉时,固相燃烧合成可得到单相尖晶石型LiMn_2O_4产物;在500和700 ℃淀粉量≤10%时,产物中杂相为Mn_2O_3,而淀粉量≥20%为Mn_3O_4.在600 ℃时,淀粉量达到30%产物中才有极少Mn_3O_4出现.温度较低时易生成Mn_2O_3,高温时易生成Mn_3O_4;加热温度相同时淀粉量对产物晶粒的结晶度影响不大,而淀粉量相同时,产物晶粒的结晶度随加热温度而增加.从化学热力学原理的角度探讨了不同温度和燃料量对固相燃烧合成产物组成的影响.     

Effect of pH on Crystal Size and Photoluminescence Property of ZnO Nanoparticles Prepared by Chemical Precipitation Method

The effects of pH value on crystal size and optical property of zinc oxide nanoparticles prepared by chemical precipitation method were investigated.Prepared samples have been characterized by means of X-ray diffraction,scanning electron microscopy,ultraviolet-visible spectrometer and photoluminescence spectrometer.From X-ray diffraction profile,it is found that the particle size of sample increases from 13.8 to 33 nm when the pH value of the solution was increased from 6 to 13.Microstructural study also shows that the particle size increases with pH value.Hexagonal shape of the zinc oxide nanoparticle has been confirmed by the scanning electron microscopy image.The recorded ultraviolet-visible spectrum shows excitonic absorption peaks around 381 nm.The energy gap of the prepared samples has been determined from the ultraviolet-visible absorption spectrum,effective mass model equation and Tauc's relation.It was found that the energy gap of the prepared samples decreases with increase in pH value.The recorded blue shift confirmed the quantum confinement effect in the prepared zinc oxide samples.Photoluminescence spectrum infers that the increase in pH value shifts the ultraviolet-visible emission but not the violet and green emissions.     

沉淀条件对钌粉粒度和形貌的影响

采用化学法制备高纯钌粉,研究了沉淀条件对制备的钌粉粒度和形貌的影响,对钌粉的纯度进行了分析。结果表明,氯气氧化作用对钌粉的粒度和形貌影响较大,在沉淀过程进行搅拌能有效细化氯钌酸铵晶粒。采用氯化铵饱和溶液沉淀,沉淀过程进行搅拌,并通入氯气进行氧化,得到(NH4)2Ru Cl6晶体,烘干后在800℃煅烧6 h,得到的钌氧化物在750℃条件下通氢还原30 min,得到的钌粉粒度约5~20μm,呈近球形的多边形,辉光放电质谱法(GDMS)分析表明钌粉纯度达到99.95%以上。