配位均匀共沉淀法制备Ag/ZnO纳米复合材料的研究

采用配位均匀共沉淀法成功制备出了粒径20～50nm的Ag/ZnO纳米复合材料,用TG-DTA、XRD、IR及TEM等技术对前驱物及不同温度下焙烧前驱物所得的产品进行了表征分析.结果表明,当前驱物的焙烧温度为300℃时,粒子呈球形,粒径小,且其粒径随前驱物焙烧温度的升高而增大.对Ag/ZnO晶粒生长动力学的研究发现,在较低温度范围内,晶粒生长速度较快,其晶粒生长动力学指数为1.32.     

熔盐法合成ZnO纳米微粉

采用熔盐法制备得到了单一六方纤锌矿结构的ZnO纳米微粉,并对其反应条件进行了研究。通过XRD、TEM和BET等分析手段对纳米粉的形貌结构进行表征,通过TG分析对反应过程进行研究。通过调控焙烧温度、熔盐含量、焙烧时间等反应条件,可以将其平均粒径尺寸有效控制在50～150nm范围。结果表明,通常所得ZnO纳米微粉晶化程度高,团聚较少,粒径分布较均匀;但熔盐含量较低时,微粉产物中将生成一定量的ZnO纳米棒。     

水热与真空冷冻干燥技术结合制备纳米CeO_2

采用水热法,结合真空冷冻干燥技术并在一定的焙烧温度条件下,成功地制得了单分散类球形CeO_2纳米粒子。用SEM、TEM及ICP等分析手段对样品进行了表征,研究了水热和焙烧温度对产物粒径、形貌的影响。结果表明:反应温度为200℃、焙烧温度为700℃下制备的纳米CeO_2粉末颗粒的粒径为55～65nm,分散性好,粒径分布均匀且呈类球形,纯度达到99.9%。     

氧化锌纳米晶体的生长及生长机理分析

采用沉淀法生长了不同粒径且性能良好的氧化锌纳米晶体,探讨了晶粒尺寸与煅烧温度的变化关系,研究了ZnO纳米晶体的生长机理.通过实验验证了在中间产物Zn(OH)2中加入NH4HCO3后,ZnO纳米晶体实现了局域生长,很好地阻碍了晶核的过度生长,从而使生成的ZnO纳米晶体保持很小的粒径.煅烧温度较低时,ZnO纳米晶体的生长模式为正常扩散生长,煅烧温度在800℃时,发生了竞争生长现象.     

纳米ZnO低温脱除H2S工艺条件的研究

采用均匀沉淀法制备纳米ZnO,以其作为低温脱除H2S的活性组分,考察了纳米ZnO粒径、空速、反应温度、氧分压等因素对纳米ZnO脱硫性能的影响,并对脱硫剂的结构进行了表征.结果表明:在常压、低温、氧分压较低的条件下,粒径越小脱硫性能越强,260℃焙烧制得的纳米ZnO脱硫剂具有高的脱硫活性,H2S可选择性地被氧化为单质S,转化率高达100%,脱硫活性时间是分析纯ZnO的40倍.尾气中未见SO2产生.     

溶胶-凝胶法制备纳米氧化锡及其性能表征

以SnCl4·5H2O为原料,采用溶胶-凝胶法制备了纳米SnO2粒子,研究了焙烧温度、碱的种类及反应物浓度对纳米SnO2粒子大小和分散状态的影响。采用XRD、TEM、ED等技术对SnO2纳米粒子的性能进行了表征。实验结果表明:用氨水和尿素作为沉淀剂,控制反应结束时pH值为7,在600℃焙烧,制备得到粒子尺寸约为15nm、分散性良好的纳米SnO2粒子。     

超临界流体干燥法制备纳米ZnO的研究

氧化锌是少数可以实现量子效应的半导体,与普通氧化锌相比,纳米氧化锌具有许多特殊的性质,如无毒和非迁移性、压电性、吸收和散射紫外线能力.以廉价无机锌盐为原料,采用液相化学法结合超临界流体干燥法制备了纳米级ZnO,并采用TEM、XRD等手段对其物性进行了表征,考察了制备条件对产物粒径、形貌、收率的影响.研究结果表明:随着锌盐浓度的提高,产物粒径逐渐增大;pH值<8～9时,随着pH值增加粒径逐渐变小;pH=8～9时,粒径达到最小,继续增加体系pH值,ZnO粒子迅速长大;相同的陈化时间,陈化温度越高,ZnO的粒径越大,在相同温度下,陈化时间越长,粒径越大;SCFD可实现干燥、晶化一步完成,与普通干燥相比,SCFD法制备的纳米粒子具有粒径分布均匀,大小可控等优点.     

高分子网络法合成纳米ZnO粉体的XRD分析

以丙烯酰胺为单体，N，N’-亚甲基双丙烯酰胺为网络剂，采用高分子网络凝胶法制备了纳米ZnO粉体。通过XRD、TEM分析结果表明，本研究所制备的ZnO粒子均为六方晶系结构，平均晶粒尺寸在45-60nm范围内；单体和网络剂比例为5：1，热处理温度为650℃，制备的纳米ZnO的平均晶粒尺寸最小为48．62nm；随热处理温度的升高，纳米ZnO的平均晶粒尺寸呈现出先减小后增大的趋势，而平均结晶度却呈现出相反的趋势；随着晶粒粒径的减小，纳米ZnO晶粒在总体上呈现出先收缩后膨胀的非单调、各向异性的晶格畸变现象。     

焙烧温度对滑动弧等离子体制备纳米TiO_2光催化剂的影响

采用滑动弧等离子体制备出不同颗粒形貌和锐钛矿相初始含量(fA)的纳米Ti O2粉体。采用X射线衍射(XRD)、透射电镜(TEM)和物理吸附仪对焙烧前后的样品进行表征,考察了焙烧温度对纳米Ti O2的晶相组成、晶体粒径、比表面积(SBET)和颗粒形貌的影响。通过光催化氧化亚甲基蓝反应评价样品焙烧后的光催化活性。结果表明,滑动弧等离子体制备的纳米Ti O2的锐钛矿相向金红石相转变温度约为650℃,锐钛矿相向金红石相的转变速率取决于焙烧温度、颗粒形貌和锐钛矿相初始含量。随焙烧温度升高,球形颗粒的锐钛矿晶体粒径略微增大,SBET缓慢减小;非球形颗粒的锐钛矿晶体粒径快速增大,SBET迅速减小。随着fA的增加,纳米Ti O2粉体的光催化表观反应速率常数(k)呈现三种不同的变化趋势:当fA70%时,k随之缓慢增加;当70%fA85%时,k随之快速增加;当fA85%时,k转为快速降低。     

用于自组装巨磁阻材料的铁磁性纳米Co粒子的研制

采用化学液相法合成可控制尺寸的六方晶形Co纳米粒子 ,对其形状和大小进行了透射电镜及激光散射分析 ,确认Co纳米粒子为球形 ,平均粒径为 4 0 0nm。在正己烷中基本无团聚。本文着重探索了制备纳米级钴粒子的工艺流程 ,通过改变反应物浓度、反应温度、反应时间、分散剂的添加量和反应过程搅拌情况等 ,寻找到制备Co纳米粒子的最佳反应条件。并初步进行了自组装实验。     

Efficient doping and energy transfer from ZnO to Eu3+ ions in Eu(3+)-doped ZnO nanocrystals

Successful doping of Eu3+ ions into ZnO nanocrystals has been realized by using a low temperature wet chemical doping technique. The substitution of Eu3+ for Zn2+ is shown to be dominant in the Eu-doped ZnO nanocrystals by analyzing the X-ray diffraction patterns, transmission electron microscopy images, Raman and selectively excited photoluminescence spectra. Measurement of the luminescence from the samples shows that the excited ZnO transfers the excited energy efficiently to the doped Eu3+ ions, giving rise to efficient emission at red spectral region. The red emission quantum yield is measured to be 31% at room temperature. The temperature dependence of photoluminescence and the photoluminescence excitation spectra have also been investigated, showing strong energy coupling between the ZnO host and Eu3+ ions through free and bound excitons. The result indicates that Eu3+ ion-doped ZnO nanocrystals are promising light-conversion materials and have potential application in highly distinguishable emissive flat panel display and LED backlights.     

Effect of Zn2+ source concentration on hydrothermally grown ZnO nanorods

We studied the effect of Zn2+ source concentration on the structural and optical properties of hydrothermally grown ZnO nanorods. The nanorods were grown on ZnO/p-Si(111) substrate using by a hydrothermal process in various concentrations of reagent at a low temperature (approximately 95 degrees C) and the structural and optical characteristics of ZnO nanorods were subsequently investigated by X-ray diffraction, field-emission scanning electron microscopy, and room temperature photoluminescence. The results demonstrate that the morphology and crystallinity of ZnO nanorods are influenced by the overall concentration of the precursor. The density and diameter of ZnO nanorods with a hexagonal structure are especially sensitivite to concentration of reactants. Furthermore, the structural transition is shown by increasing concentration. At the lowest concentration of Zn2+, the ZnO nanorods grow as single crystals with a low density and variable orientations. On the contrary, at the highest concentration, the nanorods grow as polycrystas due to the supersaturated Zn2+ source.     

尖晶石结构Ni掺杂ZnFe2O4纳米颗粒的性能表征

利用水热法成功合成了纯ZnFe2O4和不同含量Ni掺杂Zn1-xNixFe2O4纳米颗粒。采用X射线衍射(XRD)、高分辨透射电子显微镜(HRTEM)、选区电子衍射(SAED)、X射线能量色散分析(XEDS)、紫外可见吸收光谱(UV-Vis)、傅里叶变换红外光谱(FT-IR)和振动样品磁强计(VSM)等测试技术研究掺杂浓度对Zn1-xNixFe2O4(x=0,0.1,0.3,0.5)样品的晶体结构、形貌、光学性能和磁学性能的影响。结果表明:所制备的Zn1-xNixFe2O4纳米颗粒结晶良好,Ni2+以替代Zn2+的形式掺杂到ZnFe2O4晶格中,生成立方尖晶石结构ZnFe2O4。随着Ni含量的增加,晶粒尺寸增大,晶格常数发生收缩。样品的形貌呈不规则的椭球形,且颗粒大小比较均匀。红外光谱的吸收峰位置并没有随Ni掺杂浓度的增加而变化。Zn1-xNixFe2O4纳米晶的光学带隙随Ni掺杂浓度增加而增大,与相应块体相比发生蓝移。在室温下,纯ZnFe2O4纳米晶呈现超顺磁性,掺杂样品具有明显的铁磁性。     

Hydrothermal synthesis of hexagonal ZnO clusters

Hydrothermal process was applied to synthesize zinc oxide nanocrystals. X-ray powder diffraction and scanning electron microscopy were used to analyze the crystal structure and surface morphology. XRD pattern analysis showed that the ZnO clusters are single hexagonal phase of wurtzite structure (space group P63 mc) with no impurity of Zn and Zn(OH)₂. Also, SEM images revealed that the size of a single ZnO crystal is between 200-500 nm in diameter and 2-5 μm in length. The influence of potassium iodide (KI) as a surfactant on the crystallinity of ZnO has been investigated.     

Influence of Mn impurity on formation of secondary phases and optical properties of ZnO NPs

ZnO:Mn nanoparticles with various Mn concentrations (1–7%) were synthesized by a simple chemical method at low temperature. Structural and optical properties of as synthesized samples were investigated by X-ray diffraction (XRD), UV–vis absorbance, and photoluminescence (PL) spectrophotometers, respectively. XRD patterns of the ZnO:Mn nanocrystals indicate that in low Mn concentrations (1 and 3%), the ZnMn₂O₄ nanoparticles are formed, whereas in high Mn concentrations (5 and 7%), more Mn atoms replace Zn atoms in crystalline lattice, so that Mn₃O₄ is formed. It is also found that the size of the ZnO:Mn nanocrystals increases from 7.82 to 76.07?nm with increasing Mn concentration from 1 to 7%. Band gap energy of the samples, calculated by extrapolation of (αhν)² versus hν curves, shows a decrease in band gap with increasing the Mn concentration from 1 to 7%. The size of nanoparticles calculated by effective mass approximation model is nearly in accordance with the one calculated by Scherrer formula. The PL spectra of low Mn concentration ZnO:Mn nanoparticles indicate a weak green emission which vanishes in highly Mn concentrated ZnO:Mn samples.     

ZnO micro and nanocrystals with enhanced visible light absorption

In this paper, we investigate the effect of the particle size and morphology on the optical properties of ZnO. A series of ZnO micro and nanocrystals were synthesized by the hydrothermal processing of zinc acetate dihydrate and sodium hydroxide as the starting materials, and polyvinylpyrrolidone (PVP) as the polymer surfactant. The particle size and morphology were tailored by adjusting the reactant molar ratios [Zn²⁺]/[OH⁻], while the reaction temperature and the time remained unchanged. X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and high-resolution TEM (HRTEM) have shown that the micro and nanocrystals have a high crystalline pure wurtzite-type hexagonal structure with nanosized crystallites. The size and morphology of the ZnO micro and nanocrystals were investigated by field emission scanning electron microscopy (FE-SEM), which showed a modification from micro-rods via hexagonal-faceted prismatic morphology to nanospheres, caused by simple adjustment of the reactant molar ratio [Zn²⁺]/[OH⁻] from 1:1 to 1:5. The optical properties of the ZnO micro and nanocrystals, as well as their dependence on the particle size and morphology were investigated by Raman and ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy (DRS). The UV–vis spectra showed that the modification of the particle size and morphology from nanospheres to micro-rods resulted in increased absorption, and a slight red-shift of the absorption edge (0.06 eV). Besides, the band gap energy of the synthesized ZnO micro and nanocrystals showed the red shift (∼0.20 eV) compared to bulk ZnO. According to the results of a Raman spectroscopy, the enhanced visible light absorption of the ZnO micro and nanocrystals is related to two phenomena: (1) the existence of lattice defects (oxygen vacancies and zinc interstitials), and (2) the particle surface sensitization by PVP.     

离子注入氧化锌纳米晶体光致发光特性(英文)

为进一步了解离子注入过程对纳米晶体发光响应的损伤效果,研究了注入氢离子和氦离子对氧化锌纳米晶体光致发光(PL)特性的影响.首先在二氧化硅衬底上制备了直径为4 nm和9 nm的氧化锌纳米晶体薄膜,接着在室温下向生成的薄膜中注入氢离子和氦离子,并研究其PL响应变化.结果表明,与未注入离子的纳米晶体相比,注入氦离子导致缺陷PL发光增加,而当注入氢离子之后,缺陷发光大幅降低,表明氢原子对注入损伤有钝化作用.比较近谱带边沿(NBE)与缺陷发光之比发现,较大颗粒的纳米晶体其近谱带边沿与缺陷发光比在注入氢离子后增大,而在注入氦离子后降低.该规律同样适用于较小颗粒的纳米晶体,但其近谱带边沿与缺陷发光比在注入氢离子之后的增幅比大颗粒晶体的小得多.     

Optical and magnetic properties of Cu-doped ZnO nanoparticles

Cu-doped ZnO nanoparticles were synthesized by a simple chemical method at low temperature with Cu:Zn atomic ratio from 0 to 5 %. The synthesis process was based on the hydrolysis of zinc acetate dehydrate and copper acetate tetrahydrate heated under reflux to 65 °C using methanol as a solvent. X-ray diffraction (XRD) analysis reveals that the Cu-doped ZnO crystallize in a wurtzite structure with a change of crystal size from 12 nm for undoped ZnO to 5 nm for Cu-doped ZnO. These nano size crystallites of Cu doped ZnO self-organized into microspheres. The XRD patterns, Scanning electron microscopy and transmission electron microscopy micrographs of doping of Cu in ZnO confirmed the formation of microspheres and indicated that the Cu²⁺ is successfully substituted into the ZnO host structure of the Zn²⁺ site. Cu doping shifts the absorption onset to blue from 373 to 350 nm, indicating an increase in the band gap from 3.33 to 3.55 eV. A relative increase in the intensity of the deep trap emission of Cu-doped ZnO is observed when increasing the concentration of Cu. Magnetic measurements indicate that Cu-doped ZnO samples are ferromagnetic at room temperature except pure ZnO.     

液氨沉淀法制备ZnO超微粉

以Zn(NO3 ) 2 为原料 ,NH3 ·H2 O为沉淀剂 ,采用直接沉淀法制备Zn(OH) 2 白色沉淀 ,经洗涤、干燥、煅烧后生成ZnO超微粉末。通过TEM观察到ZnO为球形晶体 ,平均粒径 15 0nm。探讨了溶液pH值、沉淀剂浓度、反应时间、反应温度对前躯体Zn(OH) 2 粒度的影响以及煅烧过程中煅烧温度与煅烧时间对ZnO粒度的影响 ,得出了最佳工艺条件。