碲化镉粉的液相还原与氢处理法制备研究

以氯化镉和二氧化碲为原料,水合肼为还原剂和络合剂,原位制备出了纳米级混合均匀的前驱体粉末,在110~400℃氢气还原制备了碲化镉粉末,并结合X射线衍射(XRD)、热重分析(TG)、扫描电子显微镜(SEM)等分析手段研究了上述过程中物相和微观结构演变。结果表明,制备前驱体过程中四价碲被水合肼还原成纳米级的碲单质,同时镉离子以2~5μm Cd(N2H4)x Cl2配合物的形式沉淀析出,且单质碲和Cd(N2H4)x Cl2均匀分散;当氯化镉和二氧化碲按摩尔比1∶1进行混合时得到的前驱体经400℃氢处理后,可获得单一相组成的碲化镉粉末。     

NiO/Ba_2CaWO_6的合成及其光催化分解水性能

以半湿法合成了双钙钛矿类物质Ba2CaWO6,对前驱体进行了热失重-差热分析,对焙烧样品进行了X射线衍射及扫描电镜分析。通过等体积浸渍法制备了NiO/Ba2CaWO6负载型催化剂,并对其光催化分解水的活性进行了测试。实验着重考察了前驱体pH值对Ba2CaWO6性能的影响,结果显示:合成前驱体的pH值增大,样品的杂质含量增大,光催化活性降低。选择较适宜的制备条件,即前驱体pH值为7,1000℃焙烧处理6h可以制得结晶完整性较好,CaO6,WO6八面体排列有序性较高的Ba2CaWO6晶体,上述晶体负载0.1%的NiO后具有分解水制氢的光催化活性。     

三元共电沉积法制备Cu_2ZnSnS_4薄膜

利用三元共电沉积制备金属前驱体,经预加热和硫化热处理后,成功合成了Cu_2ZnSnS_4薄膜。借助循环伏安法确定三元共沉积电位为E=-1.25V,考察pH值和电解液离子浓度对金属前驱体元素成分和物相的影响,筛选出电沉积的最佳工艺参数(8mmol/L SnSO_4,22mmol/L CuSO_4·5H_2O,22mmol/L ZnSO_4·7H_2O,200mmol/LNa_3C_6H_5O_7·2H_2O和pH值=5.7),沉积到成分比例接近最佳元素比的金属前驱体(n(Cu)/n(Zn+Sn)≈0.8,n(Zn)/n(Sn)≈1.2)。经300℃预加热后,金属前驱体转变成以Cu_5Zn_8和Cu_6Sn_5二元合金为主的金属固溶体,为后续硫化热处理形成纯相的CZTS奠定了基础。硫化过程中,硫化时间和硫化温度对薄膜结构形貌的影响显著。随着硫化时间的增大,CZTS的特征峰的强度增大,杂相衍射峰(Cu_(2-x)S、SnS和Cu_2SnS_3)的强度减弱,CZTS逐渐纯化。硫化时间为60min时,薄膜具有良好结构和形貌,而进一步硫化,易促使薄膜分解。过低的硫化温度会导致薄膜产生较多的二元和三元杂相,而硫化温度过高则会产生Sn和Zn的挥发流失。580℃时,CZTS薄膜的晶粒轮廓分明、晶界清晰、分布致密均匀,薄膜厚度约为2μm,与Mo层的接触紧密,无间隙,附着性增强。     

2种方法制备的Y2O3:Yb,Er前驱体对Y2O2S:Yb,Er性能的影响

利用溶胶-凝胶燃烧合成法和共沉淀法成功地制备出单一均相的Y2O3:Yb,Er前驱体,采用传统的硫熔法制备了单一均相的Y2O2S:Yb,Er粉体,同时对传统硫熔法的后处理过程进行了改进.分别采用XRD、FTIR、SEM和EDS对合成的粉体进行了物相分析、化学键分析、形貌表征和元素组成分析,并对粉体进行了发光性能测试,在980nm激发下,共沉淀法制备的前驱体硫化后得到的Y2O2S;Yb,Er发光强度比溶胶-凝胶燃烧合成法制备的前驱体硫化后得到的Y2O2S:Yb,Er发光强度高得多.     

自燃/球磨法制备NiZn系铁氧体

以金属硝酸盐和柠檬酸为原料,用溶胶凝胶自燃烧法制备NiZn系铁氧体前驱体粉末(Ni0.4Zn0.6Fe2O4,Ni0.2Zn0.6Cu0.2Fe2O4,Ni0.33Zn0.59Cu0.11Fe1.97O4(Bi2O3)0.002和Ni0.33Zn0.59Cu0.11 Fe1.97O4(Bi2O3)0.002(MnO2)0.02),然后经30小时高能球磨,从X-ray衍射谱中发现前驱体粉末虽然基本上是尖晶石结构,但是还有一些杂相,经过球磨,杂相明显减少,结构更加完整,颗粒减小.前驱体粉末Ni0.33Zn0.59Cu0.11Fe1.97O4(Bi2O3)0.002经30小时球磨后,在空气中退火,退火温度分别为400℃,600℃,800℃,900℃,1000℃.用X-ray衍射谱分析其物相,发现在800℃退火得到单相的尖晶石结构,无杂相.该样品的最佳退火温度低于1000℃.用振动样品磁强计分别测量制备态和退火态样品粉末的磁性,可以看出,随退火温度的升高,比饱和磁化强度σs逐渐增大,矫顽力Hc逐渐减小,当900℃退火后,比饱和磁化强度已接近块状NiZn系铁氧体.1000℃退火后,上述四种样品中Ni0.4Zn0.6Fe2O4具有最高的比饱和磁化强度σs=65.09emu/g.本文为NiZn铁氧体的低温烧结提供了有用的实验数据.     

Cu2 ZnSn(SSe)4薄膜的制备及其性能研究

通过不同液相前驱体合成了Cu_2ZnSn(SSe)_4(CZTSSe)薄膜,采用XRD、SEM等手段进行表征,结果表明,前驱体中Zn源的活性直接影响到最终生成CZTSSe晶体材料的性能;通过肼、S粉和Zn粉提供的Zn源不容易形成晶核,发生反应所需反应温度较高,但是容易形成大的晶型,制备的CZTSSe晶体能量转化率为6.21%;而通过干冰、N_2H_4和Zn粉提供的Zn源容易形成晶核,但其后续晶体长大的反应进行比较困难,不容易形成大的晶型,制备的CZTSSe晶体能量转化率只有5.50%。揭示了不同Zn前驱体对CZTSSe薄膜结构、晶体尺寸以及转化率的影响,并对机理进行了初步探讨。     

共蒸发法制备Cu_2ZnSnS_4薄膜的研究

利用真空蒸镀技术共蒸发Cu,Zn,Sn金属丝在玻璃衬底上制备前驱体Cu-Zn-Sn(CZT),并采用高温硫化金属前驱体的方法制备Cu2Zn Sn S4(CZTS)薄膜。本文采用X射线衍射和扫描电子显微镜对薄膜进行表征,探究前驱体的蒸镀条件以及硫化温度对薄膜生长情况的影响,结果表明:溅射Mo作为缓冲层有利于Zn原子的沉积;硫化温度为500℃时,薄膜的结晶度较好,能够生成单一的CZTS薄膜;气压越低越有利于形成优质薄膜;衬底温度升高为220℃时,薄膜的结晶度有所提高,有利于抑制杂质的生成;等离子体的辅助可以提高薄膜的结晶质量。     

烘干温度对氮掺杂二氧化钛光催化剂性能的影响

以Ti(SO4)2为原料,通过氨水水解法制备氮掺杂二氧化钛前驱体,煅烧前驱体制备氮掺杂纳米二氧化钛。用X射线衍射、紫外-可见吸收光谱、透射电镜、热重-差热分析和比表面等方法对制备的样品进行表征。以蓝色发光二极管为光源,用甲醛降解反应考察了光催化剂的活性。结果表明,制备的样品均为锐钛矿,氮掺杂使二氧化钛在可见光区的光吸收明显增强;低温烘干制备的催化剂相对高温烘干的具有较小的粒子尺寸和较大的比表面。烘干温度显著影响光催化性能,低温烘干的催化剂活性较高。     

MgNH改性Li-Mg-N-H体系的储氢性能及其机理

研究了MgNH改性的Mg(NH2)2-2LiH体系的吸放氢性能及其机理。结果显示,MgNH的出现明显改变了样品的热分解行为,大部分氢能够在180℃以下放出,但总的放氢量从5.0wt%降低到了4.2wt%。MgNH部分替代Mg(NH2)2提高了样品的吸放氢平台压力,改善了滞后性能。结构研究表明,不同的化学成分导致了不同结构的吸放氢产物。原始Mg(NH2)2-2LiH样品的放氢产物主要为正交结构的亚氨基化物,而包含MgNH的样品的放氢产物为立方结构的亚氨基化物。吸氢后,Mg(NH2)2-2LiH样品能够回到起始反应物质,但包含MgNH的样品中可以明显观察到新的三元亚氨基化物Li2Mg2N3H3。     

石墨烯-CuO/TiO_2复合催化剂的合成及光催化制氢活性

采用溶剂热法合成了石墨烯-CuO/TiO_2复合催化剂,通过扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、紫外-可见漫反射(DRS)表征复合催化剂的微观形貌、结构和光学特性。以H_2PtCl_6为无机前驱体对其进行Pt负载,研究了不同石墨烯负载量对制氢活性的影响及太阳光下的制氢活性。结果表明,石墨烯负载量为0.5%(质量分数)时,复合催化剂制氢活性最高,石墨烯和CuO协同作用提高了TiO_2对可见光的利用及光催化分解C_2H_5OH/H_2O制氢活性。在可见光下照射5h后,样品的产氢量达到1 083.54μmol,太阳光光照5h后产氢量(4 374.51μmol)为P25(1598.25μmol)的2.74倍。     

Shape and size control of ZnO nanostructures via a simple solution route

ZnO nanostructures with different morphologies were synthesized by condensing the Zn(OH)4(2-) precursors under hydrothermal conditions in the presence of a surfactant, cetyltrimethylammonium bromide (CTAB). Shape and size control of ZnO nanostructures was achieved by relatively simple variations of molar ratio of CTAB to Zn(OH)4(2-). With a higher molar ratio, ZnO nanotubes were obtained, whereas with a lower molar ratio, ZnO nanorods were formed; furthermore, with a moderate w value, the coexistence of ZnO nanorods and nanotubes was also observed. The photoluminescence of ZnO nanorods and nanotubes was also investigated.     

Synthesis of Zn(1-x)Cd(x)S:Mn/ZnS quantum dots and their application to light-emitting diodes

3.6?nm sized Mn-doped Zn(1-x)Cd(x)S quantum dots (QDs) with the composition (x) of 1, 0.5, 0.2 and 0 were synthesized by a reverse micelle approach. The bandgap energy of Zn(1-x)Cd(x)S:Mn QDs was tuned to a higher energy by increasing the Zn content, and the actual composition of alloyed Zn(1-x)Cd(x)S:Mn QDs was found to be different from the solution composition. Consecutive overcoating of the Zn(1-x)Cd(x)S:Mn QD surface by a ZnS shell was done, and the core/shell structured QDs exhibited quantum yields of 14-30%, depending on the composition of the core QDs. Using CdS:Mn/ZnS QDs, orange and white light-emitting diodes (LEDs) pumped by a near-UV and blue LED chips, respectively, were fabricated and their optical properties are described.     

Synthesis spectrum properties of high-quality CdS quantum dots

High-quality CdS quantum dots with zinc-blende structure were prepared in noncoordinating solvent 1-octadence (ODE), using N-oleoyl-morpholine as an alternative solvent for sulfur powder, oleic acid (OA) as capping ligand. Sulfur powder could be dissolved in N-oleoyl-morpholine at room temperature. The kinetics of nucleation/growth was monitored via the temporal evolution of optical properties of the as-prepared CdS quantum dots. Various synthetic parameters were systematically investigated, such as growth temperature of 190 degrees C-260 degrees C, OA concentrations of 1.5 mL-2 mL, and the feed molar ratios of (0.5-3) Cd/1S. With increasing feed molar ratio of Cd/S, little trap emission could be observed. The feed molar ratio of 3Cd/1S was suggested to be the optimal synthetic window, together with the amount of OA 1.5 mL and the growth temperature of 210 degrees C. The quantum dots with growth periods ranging from 0 to 900 s at 210 degrees C exhibited their first excitonic absorption peak changing from 359 nm to 429 nm and the corresponding average size moved from 2.26 nm to 4.41 nm. The narrowest PL FWHM we obtained was 16 nm. Typical HRTEM images revealed that the as-prepared CdS quantum dots had narrow size distribution and high crystallinity.     

Synthesis of N-acetyl-L-cysteine-capped ZnCdSe quantum dots via hydrothermal method and their characterization

Compared with the most studied green-red emitting (530–650 nm) quantum dots (QDs), the preparation of short-wavelength-emitting QDs remains difficult. Besides, one of the representative short-wavelength QDs materials, ZnCdSe, has a shortcoming of high content of toxic cadmium metal. In this paper, we report the synthesis of high-quality water-soluble ZnCdSe QDs via optimized one-step hydrothermal method with a new thiol as ligand, within a short time of 65 min. The emission wavelength of prepared QDs is tunable in the range of 425–540 nm by merely controlling the molar ratio of Cd:Zn or Se:Zn, and the quantum yield reaches 35%. More importantly, the maximum Cd:Zn molar ratio has been reduced to 0.04:1.0, much lower than that reported in the literature (0.5:1.0), resulting in excellent biological compatibility of prepared QDs and thus their promising applications in biological fields. Moreover, the transmission electron microscopy was employed to examine the effect of Cd:Zn ratio on the size of prepared ZnCdSe QDs, which were also characterized by x-ray photoelectron spectroscopy and electron diffraction spectroscopy.     

Phosphine-free synthesis of high-quality reverse type-I ZnSe/CdSe core with CdS/Cd(x)Zn(1 - x)S/ZnS multishell nanocrystals and their application for detection of human hepatitis B surface antigen

Highly photoluminescent (PL) reverse type-I ZnSe/CdSe nanocrystals (NCs) and ZnSe/CdSe/CdS/Cd(x)Zn(1 - x)S/ZnS core/multishell NCs were successfully synthesized by a phosphine-free method. By this low-cost, 'green' synthesis route, more than 10 g of high-quality ZnSe/CdSe/CdS/Cd(x)Zn(1 - x)S/ZnS NCs were synthesized in a large scale synthesis. After the overgrowth of a CdS/Cd(x)Zn(1 - x)S/ZnS multishell on ZnSe/CdSe cores, the PL quantum yields (QYs) increased from 28% to 75% along with the stability improvement. An amphiphilic oligomer was used as a surface coating agent to conduct a phase transfer experiment, core/multishell NCs were dissolved in water by such surface modification and the QYs were still kept above 70%. The as-prepared water dispersible ZnSe/CdSe/CdS/Cd(x)Zn(1 - x)S/ZnS core/multishell NCs not only have high fluorescence QYs but also are extremely stable in various physiological conditions. Furthermore, a biosensor system (lateral flow immunoassay system, LFIA) for the detection of human hepatitis B surface antigen (HBsAg) was developed by using this water-soluble core/multishell NCs as a fluorescent label and a nitrocellulose filter membrane for lateral flow. The result showed that such ZnSe/CdSe/CdS/Cd(x)Zn(1 - x)S/ZnS core/multishell NCs were excellent fluorescent labels to detect HBsAg. The sensitivity of HBsAg detection could reach as high as 0.05 ng ml( - 1).     

Biosorption of Hg2+, Cd2+, and Zn2+ by Ca-alginate and immobilized wood-rotting fungus Funalia trogii

Funalia trogii biomass was immobilized in Ca-alginate gel beads. The live and heat inactivated immobilized forms were used for the biosorption of Hg2+, Cd2+ and Zn2+ ions by using plain Ca-alginate gel beads as a control system. The effect of pH was investigated and the maximum adsorption of metal ions on the Ca-alginate and both live and inactivated immobilized fungal preparations were observed at pH 6.0. The temperature change between 15 and 45 degrees C did not affect the biosorption capacity. The biosorption of Hg2+, Cd2+ and Zn2+ ions on the Ca-alginate beads and on both immobilized forms was studied in aqueous solutions in the concentration range of 30-600 mg/L. The metal biosorption capacities of the heat inactivated immobilized F. trogii for Hg2+, Cd2+ and Zn2+ were 403.2, 191.6, and 54.0 mg/g, respectively, while Hg2+, Cd2+ and Zn2+ biosorption capacities of the immobilized live form were 333.0, 164.8 and 42.1 mg/g, respectively. The same affinity order on a molar basis was observed for single or multi-metal ions (Hg2+ > Cd2+ > Zn2+). The Langmuir and the Freundlich type models were found to exhibit good fit to the experimental data. The experimental data were analyzed using the first-order (Langergren equations) and the second order (Ritchie equations). The experimental biosorption capacity with time is found to be best fit the second-order equations. The alginate-fungus system could be regenerated by washing with a solution of hydrochloride acid (10 mM). The percent desorption achieved was as high as 97. The biosorbents were reused in five biosorption-desorption cycles without significant loss of their initial biosorption capacity.     

One-step and rapid synthesis of composition-tunable and water-soluble ZnCdS quantum dots

ZnCdS quantum dots have been successfully prepared at room temperature in aqueous solution with sodium hexametaphosphate as stabilizer and thioacetamide as the source of S. The photoluminescence (PL) spectra and UV-Vis absorption spectra of the ZnCdS quantum dots were determined on the basis of the initial Cd/Zn mole ratio (Cd/Zn = 8/0, 7/1, 6/2, 5/3, 4/4, 3/5, 2/6, 1/7 and 0/8) and the concentration of thioacetamide. The emission peaks first showed a red shift and then a blue shift with the increasing initial Zn concentration, which provided the evidence of formation of CdS/ZnCdS core/shell and ZnCdS alloyed quantum dots. The ZnCdS quantum dots were compared with CdS (ZnS) quantum dots doped with Zn2+ (Cd2+). The samples have also been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectra (XPS).     

The effect of grain size of rock phosphate amendment on metal immobilization in contaminated soils

When rock phosphates (RP) are used to remediate Pb-contaminated soils, their effectiveness is likely affected by their grain size. In this study, the effect of grain size of rock phosphate on the effectiveness of heavy metal immobilization in two contaminated soils was measured in pot experiment. Rock phosphate was used with four different grain sizes: <35, 35-72, 72-133 and 133-266microm. The application rate of rock phosphate in two soils was determined based on P/metals (Pb, Zn, Cu and Cd) molar ratio of 5.0 in the soils. The results showed that rock phosphate of the smallest grain size (<35microm) was superior to all of other grain sizes more than 35microm for reducing uptake in plant (Brassica oleracea L.) shoots for Cd (19.6-50.0%), Pb (21.9-51.4%) and Zn (22.4-34.6%), respectively, as compared with the soil without application of rock phosphate. Sequential extraction analysis indicated that rock phosphate was most effective for soil Pb to induced transformation from non-residual fractions to a residual fraction than that for Zn and Cd. Such transformation was probably through dissolution of Pb associated with exchangeable (EX), organic fraction (OC), acidic fraction (AC) and amorphous Fe and Al oxides-bound (OX) fraction and precipitation of pyromorphite-like minerals. Results suggested that the rock phosphate with small grain size was superior to that with large grain size for in situ remediation technology.     

Industrial symbiosis: high purity recovery of metals from Waelz sintering waste by aqueous SO2 solution

Sintering operation in the production of Zn, Cd, and Pb by Waelz process produces a powdery waste containing mainly (about 70%) ZnO, CdO, and PbO. The waste may be referred to as Waelz sintering waste (WSW). The aim of this study is to develop a process for the separation and recovery of the metals from WSW with high purities. The process is based on the dissolution of the WSW in aqueous SO2 solution. The research reported here concentrated on the effect of some important operational parameters on dissolution process. The parameters investigated and their ranges were as follows: SO(2) gas flow rate (V); 38-590 ml/min, stirring speed (W); 100-1000 rpm, reaction temperature (T); 13-60 degrees C, reaction time (t); 1-16 min, and solid-liquid ratio (S/L); 0.1-0.5 g/ml. The results showed that the dissolution rate increased with increasing W, V, and S/L and decreasing T. The best dissolution conditions were found to be V=325 ml/min, W=600 rpm, t=6 min, T=21 degrees C, and S/L=0.1g/ml. Separation of Zn from Cd involved precipitation of ZnSO3 from a mixture solution. The best pH level for the precipitation was observed to be 6.     

Sulfidation of zinc plating sludge with Na2S for zinc resource recovery

A high amount of zinc disposed in the landfill sites as a mixed-metal plating sludge represents a valuable zinc source. To recover zinc from the plating sludge, a sulfidation treatment is proposed in this study, while it is assumed that ZnS formed could be separated by flotation. The sulfidation treatment was conducted by contacting simulated zinc plating sludge with Na(2)S solution at S(2-) to Zn(2+) molar ratio of 1.5 for a period of 1-48 h, while changing the solid to liquid (S:L) ratio from 0.25:50 to 1.00:50. The conversion of zinc compounds to ZnS was determined based on the consumption of sulfide ions. The reaction products formed by the sulfidation of zinc were identified by X-ray diffraction (XRD). As a result, it was found that the conversion of zinc compounds to ZnS increased with an increase in S:L ratio. A maximum conversion of 0.809 was obtained at an S:L ratio of 1.00:50 after 48 h. However, when the zinc sludge treated at S:L ratio of 1.00:50 for 48 h was subjected to XRD analyses, only ZnS was identified in the treated zinc sludge. The result suggested that the rest of zinc sludge remained unreacted inside the agglomerates of ZnS. The formation behavior of ZnS was predicted by Elovich equation, which was found to describe the system satisfactorily indicating the heterogeneous nature of the sludge.