纳米GaP粉体在水溶液中的分散性能及其PVP复合薄膜的制备

采用三种不同类型的分散剂对纳米磷化镓(GaP)粉体进行分散,并用测量滤液吸光度的方法来比较分散效果;测定了纳米GaP粉体的等电点,以及采用十二烷基苯磺酸钠分散时的Zeta电位,并初步制备了纳米GaP /聚乙烯吡咯烷酮(PVP)复合薄膜.结果表明,分散剂的选择、分散剂的浓度、pH值都对分散效果有着重要的影响;制备的纳米GaP / PVP复合薄膜具有良好的可见光透光性和一定的紫外线吸收性能.     

CB@SiO2-BaTiO3-Epoxy复合材料制备及性能研究

对炭黑和钛酸钡颗粒进行表面改性,然后作为无机填料填充到环氧树脂中,制备得到CB@SiO2-BaTiO3-Epoxy复合介质材料.研究该复合材料的微观结构,探讨其介电性能、绝缘性能与填料含量和外加场频率等的关系.结果表明:改性后的炭黑、钛酸钡均与环氧树脂有良好的相容性,均匀分散在聚合物基体中;随着CB@SiO2和钛酸钡体积含量的增加,复合材料的介电常数逐渐增大,介电损耗也随之增加,同时漏导电流增加;炭黑和钛酸钡两种无机填料含量具有最优化结构,BaTiO3含量为20vol;、炭黑含量在5vol;的复合介质在低频下出现损耗极小值,这种最优化结构效果在复合材料的电导率上也有体现.当CB@SiO2含量为10vol;,BaTiO3含量为30vol;时,在1 kHz下复合介质材料的介电常数达62.7,介电损耗为0.0632,体积电导率为4.13 × 10-5S/m.     

三维石墨烯/In2O3/聚吡咯复合材料制备及室温气敏性能

采用两步法制备三维石墨烯/In2O3/聚吡咯(3D-rGO/In2O3/PPy)三元复合材料,首先合成二元复合材料三维石墨烯/In2O3(3D-rGO/In2O3),然后以此为载体,通过吡咯单体的原位聚合得到最终产物.通过XRD、FTIR、FESEM、TEM和氮气吸附-脱附对合成材料进行表征,研究了其室温气敏性能,分析了三元复合材料的气敏机理.结果 表明,复合3D-rGO与PPy后,三元复合材料的工作温度降低至室温,室温时对200ppm NH3的灵敏度达到18.8,对NH3有较高的灵敏度,响应和恢复时间较短.     

C_(sf)(α-Al_2O_(3p))强韧无机聚合物基复合材料的机械性能及断裂行为

本文通过超声波将短碳纤维(Csf)与偏高岭土、α-Al2O3颗粒(α-Al2O3p)预分散混合,然后加入到碱金属溶液中的方式制备了及Csf单独以及Csf与α-Al2O3p复合强韧的无机聚合物基复合材料,研究了及Csf、α-Al2O3p含量对复合材料的组织结构,机械性能以及断裂行为的影响规律。结果表明:及Csf在基体中分散均匀。采用及Csf单独强韧复合材料的抗弯强度、断裂韧性随着纤维含量的增加都呈先减小后增加的规律,其中纤维含量为2 vol%时分别达到28.4 MPa和0.6 MPa.m1/2,相比基体分别增加了0.85倍和1倍。采用及Csf与α-Al2O3p复合强韧的无机聚合物基复合材料,虽然其抗弯强度较及Csf单独强韧的复合材料低并与α-Al2O3p的含量成反比,但是其断裂韧性较及Csf单独强韧复合材料的高,并在α-Al2O3p加入量为8 wt%时达到最大值为0.75 MPa.m1/2。复合材料在断裂过程中呈现非脆性断裂方式,并且及Csf与α-Al2O3p复合强韧的无机聚合物基复合材料在断裂过程中载荷位移曲线呈现锯齿形增长。复合材料断裂行为和断口分析表明,碳纤维的桥联,拔出是复合材料主要的强韧化机制。     

聚乙烯醇改性磷酸银的光催化活性研究

在制备的磷酸银表面吸附少量的聚乙烯醇(PVA),并通过热处理制备了DPVA/Ag3 PO4复合材料.使用傅立叶红外光谱法(FT-IR)和荧光光谱法(PL)对DPVA/Ag3 PO4复合材料进行表征.分析得知,经聚乙烯醇复合改性的DPVA/Ag3 PO4复合微粒中存在共轭结构,光生电子-空穴对复合率降低,光催化活性得到显著提高.研究了不同条件(复合比例、热处理温度、热处理时间)下制备的复合光催化剂在可见光下催化降解甲基橙的光催化性能.当PVA与Ag3 PO4质量比为1:4000,热处理温度为190℃,热处理1 h时光催化效果最好.     

常温改性半水硫酸钙晶须及其稳定化机理研究

性能优良的半水硫酸钙晶须常用于增强增韧有机复合材料和无机复合材料.为防止半水硫酸钙晶须与水接触或在潮湿的环境中发生水化反应而导致晶体结构与性能的破坏,因此需要对半水硫酸钙晶须进行表面改性.本文基于溶度积原理,探寻常温下复合改性介质中改性半水硫酸钙晶须的新途径.采用单掺月桂酸钠、海藻酸钠、硅酸钠、草酸钠和氟化钠作为改性剂,并设计正交试验探索影响改性效果的显著性因素和最佳改性工艺.利用XRD、FTIR和SEM对晶须改性前后进行化学组成和微观结构的分析.研究结果表明,复合改性介质体积比和改性剂种类是影响改性工艺的显著性因素,改性剂在复合介质中的溶解度直接影响着最终表面改性产物层的性能.单掺15;氟化钠或海藻酸钠、复合介质体积比29:1、改性时间5 min时,改性半水硫酸钙晶须在水中溶解度降低并且能够保持晶体结构和性能的稳定.     

CVT法生长GaP多晶

阐述了CVT(化学气相输运)法生长GaP的基本反应和输运速度,采用CVT法生长出了GaP多晶.设计了石英管的结构以制造出一个局部的低温区域,防止了GaP在管壁的生长.生长出的GaP多晶相对密度为98;,红外透过率达到30;,努普硬度为611kg/mm2.散射颗粒测试表明主要的光散射颗粒为多晶中存在的孔隙.     

合成GaP纳米晶过程的关键影响因素

本文系统研究了在有机溶剂中常压合成GaP纳米晶过程中反应温度、反应时间、反应体系的均匀性和原料的比例等关键影响因素.GaP纳米晶的产率、形貌以及平均粒度随着这些关键因素的改变有很大的不同.制备的GaP纳米晶用X射线衍射仪和透射电镜进行了表征.发现了最优化的合成工艺条件,实现了GaP纳米晶的高产率(达85;)制备,而且形貌和粒度可以根据需要进行调控.     

煅烧时间与温度对超导/铁磁复合材料性能的影响

采用传统的固相反应法在较低的烧结温度与较短的煅烧时间下制备了(La1.85Sr0.15CuO4)1-x(La2/3 Sr1/3MnO3)x(简写为LSCO/LSMO)超导/铁磁复合材料.结果显示:复合后LSMO中的结构没有发生明显改变,随着温度的降低,所有的复合材料在38 K左右均会出现电阻急剧下降,最终呈现超导现象.甚至当LSMO铁磁性材料掺入达到O.20mol时,复合材料仍旧呈现超导态.同时所有复合样品的超导转变温度TC随着x的增加呈现线性下降的趋势.因此,通过低温与短时的烧结方法可以避免处于晶界处的LSCO的CuO面被破坏,进而提高超导/铁磁复合材料中在晶界处的铁磁的共存含量.     

ZnO/g-C3N4复合光催化剂制备及其光催化性能研究

以硝酸锌、三聚氰胺为原料,采用热解法合成ZnO掺杂g-C3N4复合光催化剂.利用XRD、SEM、UV-Vis等对合成产物的组成、形貌及光吸收性能进行了表征.研究了热解温度及ZnO的掺杂量对合成产物性能的影响,并以亚甲蓝溶液为模拟污染物,对合成ZnO/g-C3N4进行光催化性能评价.结果表明:ZnO掺杂有利于提高ZnO/g-C3N4复合材料的光催化性能,当热解温度为650℃、保温时间为60 min、ZnO的掺杂量为2.5wt;时,合成的ZnO/g-C3N4光催化性能最佳,在高压汞灯照射240 min时,对亚甲蓝溶液的降解率为84.1;,比同条件下单一g-C3N4光催化性能提高26.2;.     

On the early deposition of GaP onto GaAs

It has been examined whether the presence of liquid Ga produced by the thermal decomposition of the GaAs substrate could influence the deposition of GaP. It was found that the surface tension of liquid Ga changed quickly and sensitively with small initial changes of the atmosphere in the reactor. Model experiments explained why and when the presence of free HCl is disadvantageous for the process.     

Heteroepitaxial growth of ZnS on GaP by the close-spaced technique

Heteroepitaxial growth of ZnS on GaP substrates was achieved with high growth rate by the close-spaced technique. Source temperatures were between 900 and 1150° C. The apparent enthalpy change of 36.6 kcal/mol obtained from the temperature dependence of the evaporation rate of source ZnS powder suggests that the material transport is carried out via the reaction between the source and hydrogen by diffusion and convection. The dependence of the growth rate on the substrate orientation is (100) > (111)Ga > (111)P, and the growth rates on these faces at a source temperature of 1000° C are about 1.6, 0.85, and 0.4 μm/min, respectively. The growth kinetics on the (111)Ga face are close to the mass transport limited case. The growth kinetics on the (111)P face are close to the surface reaction limited case, and that on the (100) face are almost the mass transport limited case. The surface morphology and X-ray analysis show that the crystal structure depends on the orientation of the substrate. The (0001) oriented α (hexagonal) modification of ZnS is obtained on the (111)Ga face, the (111) oriented β (cubic) modification on the (111)P face, and the (100) oriented β modification on the (100) face in the studied range of temperature.     

On the kinetics of nitrogen incorporation in GaP LPE layers using NH3 vapour doping

The partial substitution of N for P in GaP has a considerable effect on the luminescence quantum efficiency of GaP epitactic layers. The incorporation of N in GaP liquid phase epitactic layers using NH₃ vapour doping has been studied at different H₂ partial pressures in argon gas. It is shown that the incorporation of N in different ambients is conveniently described by just one parameter. The reaction of NH₃ with Ga is found to be an equilibrium process. The N concentration in the layer is directly proportional to the GaN concentration in the melt. From the correlation of the dissociation of NH₃ with the formation of GaN it is concluded that the NH₃ pressure, as measured in the exit gas, is not representative of the NH₃ pressure at the melt. The dissociation of NH₃ is found to be strongly retarded by H₂ owing to adsorption of H₂ on the surface of reactor materials which catalyse the dissociation.     

三维铜(咪唑)配位化合物的合成、晶体结构及性质

本文用CuCl2·2H2O和等摩尔咪唑反应合成了[Cu(im)6]Cl2·2H2O(1),[im=咪唑],单晶结构解析表明:该化合物属于单斜晶系,P21/n空间群,晶胞参数为:a=0.8073(2)nm,b=1.3239(2)nm,c=1.50810(10)nm,β=97.940(10)°.在化合物中,[Cu(im)6]2+阳离子和Cl-阴离子、没有参加配位的水在水平面形成复杂的氢键网格.本文报道了该化合物的热稳定性、红外及荧光性质.     

The Characteristics of GaP Window Layer Grown by Indium‐added Liquid Phase Epitaxy

The effects of added Indium on the growth characteristics of GaP were systematically studied using conventional liquid phase epitaxy technique with Ga‐rich GaP source melt. The GaP growth rate uniformly increase with the source melt of increasing Indium addition against Gallium solvent. These epilayers have mirror‐like surface morphology examined by optical microscope except several grown films with large amount of Indium addition meet a terrible interface. The surface morphologies examined by AFM showed the ripples in samples of R_0.05 and R_0.4 and distinct islands with elliptical base shape in the sample of R_0.7 (R‐In ratio). The epitaxial layer with incorporation of Indium addition during growth had good performance on the carrier concentrations and resistivity. The composition of compound semiconductor become to InGaP at higher amount of In addition to Ga was examined by double‐crystal X‐ray diffraction and the distribution of Indium examined by SIMS also provided the evidences in sample of R_0.7.     

Growth of low defect density GaP layers on Si substrates within the critical thickness by optimized shutter sequence and post-growth annealing

We have developed a growth procedure for realizing a low defect density GaP layer on an Si substrate. The growth procedure consists of two parts. One is the post-growth annealing for the annihilation of stacking faults (SFs). We have investigated an annihilation mechanism with molecular beam epitaxy grown GaP layers. 1-monolayer-thick SFs typically generate from the GaP/Si interface in a non-annealed GaP layer. In a 700 °C annealed GaP layer, generation points of these SFs tend to shift toward the GaP surface. In a 730 °C annealed GaP layer, SFs density is effectively decreased. These results suggest that SFs are annihilated through the climb motion of two partial dislocations during the post-growth annealing. Another one is the optimized shutter sequence for migration enhanced epitaxy. We have revealed that it is effective for the suppression of both three-dimensional growth and melt-back etching to increase in a stepwise manner the number of supplied Ga atoms per cycle. As a result, the generation of threading dislocations and pits is remarkably suppressed. A root mean square surface roughness of 0.13 nm is obtained within the critical thickness. We have estimated etch pit density (EPD) to be ∼7×10⁵ cm⁻² with a GaPN/GaP/Si structure. To the best of our knowledge, this value is same as that of commercially available GaP substrates and is the lowest one in the EPD of GaP/Si heteroepitaxy.     

Vacancy defects in as-grown and nº-irradiated GaP and GaAs1−xPx Studied by Positrons

Measurements of positron lifetime τ and of the shape parameter S of the Doppler-broadened annihilation line are used to study bulk and defect properties in GaP and GaAs_1−xP_x. τ and S decrease linearly with the composition x of GaAs_1−xP_x layers. A second lifetime component (τ₂ = 290 ps) observed in as-grown GaP is attributed to stoichiometric P vacancies. After neutron irradiation of GaP and GaAs_0.13P_0.87 positrons are trapped by Ga vacancies (τ₂ = 250 ps). These vacancies anneal out in two stages at 200–550 °C and 550–800 °C.     

Characterization of L‐ascorbic acid single crystals grown from solution with different solvents

Single crystals of L‐ascorbic acid, popularly known as vitamin‐C, were grown from solutions with different solvents and solvent combinations by low temperature solution growth methods. The suitability of different solvents and solvent combinations such as acetone, ethanol, methanol, isopropyl alcohol, water, water + acetone (1:1), water + ethanol (3:1), water + isopropyl alcohol (3:1) and isopropyl alcohol + methanol (1:1) for crystal growth of L‐ascorbic acid was found out by assessing the solubility and crystallization behaviours. Solubility of L‐ascorbic acid in selected solvents and solvent combinations in a range of temperatures was determined by gravimetric method. Solution prepared with water, water + acetone (1:1), water + ethanol (3:1) and water + isopropyl alcohol (3:1) were yielded crystals with tabular, columnar and prismatic habits and their morphologies were evaluated by goniometry. Grown single crystals were characterized with various instrumental techniques such as powder X‐ray diffraction, Fourier infrared spectroscopy, optical transmittance study, differential scanning calorimetry and second harmonic generation studies. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Relaxation mechanism of GaP/InGaAlP/GaAs heterostructure

Transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM) were carried out to investigate the structural properties of the GaP/In_0.48(Al_0.7Ga_0.3)_0.52P heterostructures grown on GaAs (0 0 1) substrates. The lattice-matched In_0.48(Al_0.7Ga_0.3)_0.52P/GaAs material system could be used as a defect-free substrate because no lattice misfit exists between the In(AlGa)P layer and the GaAs substrate. Both TEM and HREM measurements indicated that there were not only misfit dislocations, but also microtwins at the GaP/In(AlGa)P heterointerface. The mechanism of the microtwins formation is elucidated.     

蒙脱石基生物纳米复合功能材料及应用研究

生物纳米复合功能材料的理论与应用研究已成为关注焦点,是生命科学与材料科学前沿交叉方向.粘土矿物是一类天然纳米结构的硅酸盐矿物,其特殊的层状纳米结构,使其具有吸附能力强,稳定性好,应用广泛等特点.本文主要介绍了蒙脱石基生物纳米复合功能材料在酶催化、抗菌、医药和环保等领域中的研究、开发及应用情况,并探讨了粘土矿物基纳米复合材料的发展前景.