共查询到18条相似文献，搜索用时 322 毫秒
1.
利用FLUENT软件模拟了CVD法制备ZnO时双管管式炉内流场的分布。研究了在无化学反应发生时,重力对Zn蒸汽分布的影响,以及在有化学反应发生时,保持进气总量不变的情况下,O_2含量对ZnO质量分布和反应速率分布的影响。模拟结果表明:重力有利于Zn蒸汽由内管向外管的扩散及Zn蒸汽与O_2的充分接触;当有化学反应时,保持进气总量不变,最大反应速率及对应的ZnO质量分数随着O_2含量减小而增大;反应生成的ZnO主要均匀分布在管式炉外管的下游区域。 相似文献
2.
以Zn（NO3）2.6H2O和NaOH为原料,采用改进的水热法通过控制反应溶液的浓度、反应温度和反应时间等沉积参数,合成了包括氧化锌纳米棒阵列、蜂窝状氧化锌纳米棒、花状氧化锌纳米棒等纳米结构.用XRD、SEM和HR-TEM对样品进行了表征,结果表明所制样品为六方纤维锌矿结构的ZnO晶体;SEM测试结果显示ZnO晶体的形貌呈花状和蜂窝棒状等形貌,HR-TEM结果表明单晶纳米棒沿[0001]方向生长.研究了玻璃衬底上装配的花状氧化锌纳米棒的场发射特性,测试结果表明花状氧化锌纳米棒具有优良的场发射;开启场强为4.3V/μm,当场强为8V/μm时,发射电流密度达到2.2mA/cm2. 相似文献
3.
本论文选择目前研究较少的ZnO立方闪锌矿结构,基于密度泛涵理论的超软赝势法(USPP),结合局域密度近似(LDA),应用Material Studio5.5软件采用LDA+U方法进行计算。计算本征态下ZnO(1*1*1,2*1*1,2*2*1不同超晶胞)的电子态密度,能带结构,分析得出本征态ZnO的总态密度价带主要由Zn的3d和O的2p轨道电子组成,验证了靠近费米能级附近处的价带。计算Co替代立方结构ZnO的Zn的态密度和能带结构,并与本征态下ZnO的态密度和能带结构做比较,发现掺杂后电子态密度无较大变化,导带在Co掺杂浓度为25%时最宽即导电性最强,禁带宽度在掺杂后变窄。由实验得出的Zn1-xCoxO的磁化强度随温度和磁场强度的变化,绘制不同掺杂浓度样品的M-T和M-H曲线,讨论材料的磁化性质,并结合电子结构计算结果。 相似文献
4.
在无催化剂的条件下,采用溶胶凝胶与化学气相沉积相结合的方法,制备出了高产率的片状ZnO纳米结构。并利用扫描电子显微镜、X射线衍射仪、拉曼光谱仪和荧光测试仪对其结构和性质进行了分析。结果表明,所合成的产物为结晶良好的片状纤锌矿ZnO纳米结构,室温光致发光谱显示,该ZnO纳米结构表现为弱的紫外发射峰和强而宽的绿光发射峰。 相似文献
5.
《实验室研究与探索》2017,(5):36-39
以ZnO、S粉和六水氯化铬为原料(CrCl_3·6H_2O),乙二胺、乙醇胺为有机溶剂,在190℃下,用溶剂热法成功地合成室温铁磁性铬掺杂ZnS纳米颗粒半导体。X-射线衍仪测试表明,Cr掺杂ZnS为纤锌矿结构。透射电镜表征不同Cr掺杂浓度ZnS的形貌为纳米颗粒,Cr掺杂浓度为5.27%的ZnS纳米颗粒平均尺寸在30~40 nm。电子能量散射谱表明产物由Zn、S、Cr元素组成。光致发光测试表明,Cr掺杂ZnS相对未掺杂ZnS吸收带边向短波方向微小移动。振动样品磁强计测试表明未掺杂的ZnS为抗磁性,而Cr掺ZnS为室温强铁磁性,Zn_(1-x)Cr_xS(x=0.0527)纳米颗粒的饱和磁化强度为4.275 A/m。Cr掺ZnS纳米颗粒具有室温铁磁性的实验结果与通过第一性原理预言Cr掺ZnS纳米片具有室温铁磁性相一致。Cr掺杂ZnS纳米颗粒的铁磁性是稀磁半导体的固有属性。 相似文献
6.
《实验室研究与探索》2018,(10)
在氧化铟锡(Indium Tin Oxide,ITO)玻璃上制备ZnO纳米棒,并采用一种简单的自组装方法在含有ZnO纳米棒的ITO玻璃上制备Co(2. 6-NDC)(4,4'-Bipy)0. 5配合物。实验表明,含Co配合物并没有和ZnO纳米棒发生反应,而是比较均匀地沉积在ZnO纳米棒上。在光电化学实验中,做了仅有ZnO和含Co配合物的ZnO纳米棒的线性伏安法测试对比实验,证明含Co配合物起到了良好的催化能力。说明这种简单的自组装方法制备的金属氧化物半导体和MOFs组成的复合材料在光电化学中具有潜在的应用价值。 相似文献
7.
闫晔 《化工职业技术教育》2009,(Z1)
以纳米TiO_2为催化剂的光催化氧化技术是一种新型的废水处理技术,具有高效、价廉、无二次污染、成本低等优点,受到广泛关注。本文利用纳米TiO_2催化剂对模拟苯酚废水进行光催化处理,研究了光源种类、pH值、苯酚初始浓度、催化剂的用量、添加H_2O_2对降解过程的影响。通过实验确定:改变催化剂的投加量,调节适当的pH值,减小溶液的初始浓度,适当加入H_2O_2氧化剂等方法,可以提高含酚废水的处理效率。当苯酚溶液初始溶度为100mg/L,催化剂的用量为1.5g/L,溶液pH=4,氧化剂H_2O_2用量为2.5ml/L时,紫外光照反应4hr,苯酚降解率可达56%。苯酚浓度不高时,光催化降解反应符合一级动力学方程。 相似文献
8.
以透明导电玻璃(TCO)为衬底,用硝酸锌水溶液作为电解液,采用阴极电沉积法合成了ZnO薄膜.通过改变电解液浓度、温度和沉积电压等实验条件,系统研究了锌氧化物薄膜材料的电化学沉积过程.用扫描电镜、X射线衍射、紫外-可见光谱法等技术对沉积物的形貌、结构及光学性质进行了表征.结果表明,通过控制电解液的浓度和温度及沉积电压等反应条件可以制备出不同形貌的ZnO薄膜.XRD结果表明,所得的ZnO纯度高且呈六方纤锌矿结构;光谱法研究表明,该薄膜在344 nm和552 nm处有两个吸收峰,禁带宽度为3.25 eV. 相似文献
9.
文中详细地综述了由相对简单的热蒸发法合成ZnO微纳米空心球结构的制备情况和研究进展,主要包括用热蒸发法制备ZnO微纳米空心球的生产设备与过程、实验条件、产品形貌和生长机理几个方面。同时展望了ZnO微纳米空心球结构材料的应用前景。 相似文献
10.
《淮北师范大学学报》2010,(2)
采用第一性原理的平面波赝势方法和广义梯度近似,研究纤锌矿ZnO的能带结构、电子态密度和吸收光谱.计算结果表明,纤锌矿ZnO为直接带隙半导体,计算带隙宽度为0.81 eV.由配位场理论分析知,Zn3 d电子劈裂后形成的t2带对应Zn—O成键态,t2*带对应Zn—O反键态,e带为非键态.计算得ZnO的光学吸收边为3.47 eV,计算结果与实验值相一致. 相似文献
11.
A novel metallo-organic chemical vapor deposition (MOCVD) technique has been applied to the preparation of the photocatalytic
titanium dioxide supported on activated carbon. The effects of various condition parameters such as carrier gas flow rate,
source temperature and deposition temperature on the deposition rate were investigated. The maximum deposition rate of 8.2
mg/(g·h) was obtained under conditions of carrier gas flow rate of 400 ml/min, source temperature of 423 K and deposition
temperature of 913 K. The deposition rate followed Arrhenius behavior at temperature of 753 K to 913 K, corresponding to activation
energy E
a of 51.09 kJ/mol. TiO2 existed only in anatase phase when the deposition temperature was 773 K to 973 K. With increase of deposition temperature
from 1073 K to 1273 K, the rutile content sharply increased from 7% to 70%. It was found that a deposition temperature of
773 K and a higher source temperature of 448 K resulted in finely dispersed TiO2 particles, which were mainly in the range of 10–20 nm.
Project (No. 90206007) supported by the National Natural Science Foundation of China 相似文献
12.
The synthesis of methanol and dimethyl ether (DME) from CO hydrogenation has been investigated on Cu-based catalysts. A series
of Cu/ZnO/Al2O3 catalysts were prepared using a solvent-free routine which involved a direct blend of copper/zinc/aluminum salts and citric
acid, followed by calcination at 450 °C. The calcination processes were monitored using thermogravimetry differential scanning
calorimetry (TG-DSC). Catalysts were further characterized using N2 adsorption, scanning electronic microscopy (SEM), X-ray diffraction (XRD), N2O oxidation followed by H2 titration, and temperature-programmed reduction with H2 (H2-TPR). The reduction processes were also monitored with in-situ XRD. The physicochemical properties of catalysts depended
strongly on the types of precursor salts, and catalysts prepared using Al acetate and Cu nitrate as starting materials had
a larger surface area, larger exposed metallic copper surface area, and lower reduction temperature. The CO hydrogenation
performances of these catalysts were compared and discussed in terms of their structures. Catalysts prepared with copper nitrate,
zinc and aluminum acetates exhibited the highest catalytic activity. 相似文献
13.
以纳米氧化锌为载体,采用正交试验法研究了Ag／ZnO纳米复合抗菌剂的最优合成工艺。实验结果表明,Ag／ZnO质量比、反应时间、反应温度、溶液的pH值都对纳米氧化锌对Ag^＋的吸附率有影响;采用纳米Ag／ZnO矿质量比为20：1,pH值为8,在60℃的水浴中机械搅拌60min为最佳制备工艺。 相似文献
14.
A novel metallo-organic chemical vapor deposition (MOCVD) technique has been applied to the preparation of the photocatalytic titanium dioxide supported on activated carbon. The effects of various condition parameters such as carrier gas flow rate, source temperature and deposition temperature on the deposition rate were investigated. The maximum deposition rate of 8.2 mg/(g.h) was obtained under conditions of carrier gas flow rate of 400 ml/min, source temperature of 423 K and deposition temperature of 913 K. The deposition rate followed Arrhenius behavior at temperature of 753 K to 913 K, corresponding to activation energy Ea of 51.09 kJ/mol. TiO2 existed only in anatase phase when the deposition temperature was 773 K to 973 K. With increase of deposition temperature from 1073 K to 1273 K, the rutile content sharply increased from 7% to 70%. It was found that a deposition temperature of 773 K and a higher source temperature of 448 K resulted in finely dispersed TiO2 particles, which were mainly in the range of 10-20 nm. 相似文献
15.
16.
HNCO hydrolysis performance in urea-water solution thermohydrolysis process with and without catalysts 总被引：1，自引：0，他引：1
Zhen-chao Chen Wei-juan Yang Jun-hu Zhou Hong-kun Lv Jian-zhong Liu Ke-fa Cen 《浙江大学学报(A卷英文版)》2010,11(11):849-856
The thermolysis of urea-water solution and its product, HNCO hydrolysis is investigated in a dual-reactor system. For the thermal decomposition below about 1073 K, the main products are ammonia (NH3) and isocyanic acid (HNCO) whereas at higher temperatures the oxidation processes take effect and the products include a low concentration of nitric oxide (NO) and nitrous oxide (N2O). The gas HNCO is quite stable and a high yield of HNCO is observed. The ratio of NH3 to HNCO increases from approximately 1.2 to 1.7 with the temperature. The chemical analysis shows that H radical is in favor of HNCO hydrolysis by instigating the reaction HNCO+H·→·NH2+CO and high temperature has positive effect on H radical. The hydrolysis of HNCO over an alumina catalyst made using a sol-gel process (designated as γ-Al2O3) is investigated. The conversion of HNCO is high even at the high space velocities (6×105 h-1) and low temperatures (393–673 K) in the tests with catalysts, which enhances HNCO hydrolysis and raises the ratio of NH3 to HNCO to approximately 100. The pure γ-Al2O3 shows a better catalytic performance than CuO/γ-Al2O3. The addition of CuO not only reduces the surface area but also decreases the Lewis acid sites which are recognized to have a positive effect on the catalytic activity. The apparent activation energy of the hydrolysis reaction amounts to about 25 kJ/mol in 393–473 K while 13 kJ/mol over 473 K. The overall hydrolysis reaction rate on catalysts is mainly determined by external and internal mass-transfer limitations. 相似文献
17.
This new type nanocomposite powder was prepared with electroless plating enhanced by ultrasonic wave. High-resolution transmission
electron microscopy (HRTEM) showed that As-plated particles have nanometer scale average size. X-ray diffraction (XRD) analysis
showed the presence of a noncrystalline structure in the plating layer on the nano-Al2O3 matrix. The content of the plating layer was analyzed by energy dispersive X-ray spectroscopy (EDX) technology. The plating
layer content was adjustable by changing the solution concentration. 相似文献
18.
TiO2 fibers were prepared via alternatively introducing water vapor and Ti precursor carried by N2 to an APCVD （chemical vapor deposition under atmospheric pressure） reactor at ≤200 ℃. Activated carbon fibers （ACFs） were used as templates for deposition and later removed by calcinations. The obtained catalysts were characterized by scanning electron micros- copy （SEM）, transmission electron microscopy （TEM）, Brunauer, Emmett and Teller （BET） and X-ray diffraction （XRD） analysis The pores within TiO2 fibers included micro-range and meso-range, e.g., 7 nm, and the specific surface areas for TiO2 fibers were 141 m^2/g and 148 m^2/g for samples deposited at 100 ℃ and 200℃ （using ACFI700 as template）, respectively. The deposition temperature significantly influenced TiO2 morphology. The special advantages of this technique for preparing porous nano-material include no consumption of organic solvent in the process and easy control of deposition conditions and speeds. 相似文献