Hydrothermal synthesis of monoclinic zirconia sol

In this study, we demonstrate a synthetic method of zirconia sol using ZrO(NO₃)₂·xH₂O as Zr⁴⁺ precursor, tetramethylammonium hydroxide as mineralizer, and oxalic acid as a complexing agent. X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and UV–vis adsorption spectroscopy were used to characterize the nanocrystals. The effect of oxalic acid content on the growth of zirconia nanocrystals was investigated. Zirconia sol cannot be synthesized without oxalic acid. The oxalic acid content has no obvious effect on the phase formation of monoclinic zirconia. The transparent and monoclinic zirconia sol with particle size <10 nm was synthesized. This provides a new hydrothermal system for the synthesis of zirconia sol.     

Single step electrosynthesis of Cu2ZnSnS4 (CZTS) thin films for solar cell application

The Cu₂ZnSnS₄ (CZTS) thin films have been electrodeposited onto the Mo coated and ITO glass substrates, in potentiostatic mode at room temperature. The deposition mechanism of the CZTS thin film has been studied using electrochemical techniques like cyclic voltammetery. For the synthesis of these CZTS films, tri-sodium citrate and tartaric acid were used as complexing agents in precursor solution. The structural, morphological, compositional, and optical properties of the CZTS thin films have been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), EDAX and optical absorption techniques respectively. These properties are found to be strongly dependent on the post-annealing treatment. The polycrystalline CZTS thin films with kieserite crystal structure have been obtained after annealing as-deposited thin films at 550 in Ar atmosphere for 1 h. The electrosynthesized CZTS film exhibits a quite smooth, uniform and dense topography. EDAX study reveals that the deposited thin films are nearly stoichiometric. The direct band gap energy for the CZTS thin films is found to be about 1.50 eV. The photoelectrochemical (PEC) characterization showed that the annealed CZTS thin films are photoactive.     

The influence of citrate and tartrate on the electrodeposition and surface morphology of Cu–Ni layers

This study examined the influence of citrate and tartrate as complexing agents on the electrodeposition and surface morphology of Cu–Ni layers. The alloys obtained in the tartaric acid and sulphate baths were nobler than those obtained in the citric acid/citrate and citric acid/citrate/tartaric acid media. The results indicated that the complexing medium influences the nobility and the type of mass transport of the alloy formed. The morphology of the electrodeposited Cu–Ni layers changed from a rather porous appearance in the absence of the complexing agents to nodular, cracked mud and cauliflower appearances for the citric acid/sodium citrate/sodium sulphate medium, tartaric acid/sodium sulphate medium and citric acid/sodium citrate/tartaric acid/sodium sulphate medium, respectively. The chemical composition of the Cu–Ni layers revealed the preferential deposition of copper. The ultraviolet–visible spectrophotometry measurements indicated the occurrence of the d–d type transition, regardless of the complexing medium employed.     

Formation of nanometric hard materials by cold milling

The fabrication of nanosized, single crystal TiC or TiN powders from ilmenite or TiO₂ within a single low temperature stage is reported in this paper. The titaniferous powders were ball milled for 100 h in a laboratory scale mill with magnesium powder and either graphite or nitrogen. The resultant powders were then subjected to an annealing step at 1200°C. Differential thermal analysis and X-ray diffraction showed that the phases formed within the milling step and underwent grain growth on annealing. Acid leaching of the powders selectively removed the unwanted product phases leaving only the hard material. The final particle size and Scherrer XRD crystallite size were similar after annealing, implying that the particles produced were single crystal.     

Effect of complexing agents on liquid‐phase adsorption and desorption of copper(II) using chitosan

The effect of complexing agents on adsorption and desorption of Cu(II) from aqueous solutions using chitosan was investigated. Three complexing agents were used including EDTA (ethylenediaminetetraacetic acid), citric acid, and tartaric acid. It was shown that the isotherm data could be fitted by the Langmuir equation under a limited concentration range. Furthermore, the adsorption processes were analyzed by an intraparticle diffusion model and the rate parameters of intraparticle diffusion for Cu(II) adsorption could be correlated with the initial Cu(II) concentrations. Finally, the desorption of Cu(II) and its complexes from the loaded chitosan was tested using complexing agent solutions. Under comparable conditions, tartaric acid solution gave the best desorption efficiency. © 1999 Society of Chemical Industry     

锅炉炉水中磷酸盐掩蔽剂的掩蔽效果分析

介绍了硅钼蓝分光光度法测定锅炉炉水中SiO2含量时,不同掩蔽剂对磷酸盐的掩蔽效果。通过实验对比,确认草酸对磷酸盐的掩蔽效果优于酒石酸对磷酸盐的掩蔽效果。     

The use of organic acids as precipitants for metal recovery from galvanic solutions

The abundance of metal ions in galvanic waste solutions enables these solutions to be used for recovery of metals as well as complexing agents such as citrate and tartrate. The addition of oxalic acid to solutions containing complexing agents precipitates pure metal oxalate or mixtures of metal oxalate and tartrate or citrate, the product depending on pH and concentration of components. The addition of oxalic acid to the rinsing bath after electroplating precipitates the most of the metals such as Cu(II), Zn(II) and Pb(II). ©1997 SCI     

Formation of zircon-type DyCrO4 and its magnetic properties

The formation mechanism of hydrolytic sol-gel synthesized DyCrO₄ with a complexing agent in acidic and basic mediums is thoroughly studied. The role of complexing agents and pH on phase formation temperature is also intensively investigated. The formation temperature for DyCrO₄ is ～500 °C in the absence and presence of complexing agents such as oxalic acid and ethylenediaminetetraacetic acid (EDTA) at pH 10. When critic acid is used, the DyCrO₄ forms with Cr₂O₃ impurity. The crystallite size in the presence of a complexing agent in the basic medium is ～55 nm which is small as compared to only ammonia solution. The various reaction modes lead to tetragonal zircon-type DyCrO₄ at ～500 °C, transforming into orthorhombic perovskite DyCrO₃ at 800 °C. The magnetization curve shows the ferromagnetic behavior of DyCrO₄ below transition temperature T_c ～21 K. This low T_c makes nanocrystalline DyCrO₄ a potential material for cryogenic applications.     

Improving on electrokinetic remediation in spiked Mn kaolinite by addition of complexing agents

During the electrokinetic treatment of kaolinite polluted with Mn, metal ions migrated to the cathode side, but the alkaline front generated by the reduction of water at the cathode provoked their precipitation as Mn hydroxide. It prevented their collection in the cathode chamber. Most Mn precipitated in a thin soil layer close to the cathode (68%), and only 26% of the initial Mn was found in the cathodic solution. Solubility of manganese can be enhanced with the addition of organic compounds (EDTA, oxalic acid and citric acid) that form complexes or chelates with Mn²⁺ ions. Besides, the complexing agents tested in this work are environmentally benign and do not provoked negative effects in soil. The addition of EDTA and oxalic acid to the spiked Mn kaolinite improved metal removal from kaolinite. Thus, 38% of Mn was colleted at the cathode chamber when oxalic acid was used as complexing agent. EDTA was more effective since 42% of Mn reached the cathode. The rest of the Mn remained into the kaolinite, mainly in the last section, close to the cathode. When citric acid was added to kaolinite, the behaviour of the electrokinetic treatment was totally different. Mn was completely removed and no accumulation was detected into the kaolinite. All contaminated metal was recovered in the cathodic solution. This good result was attributed to the complexing activity of citric acid and to the high electro-osmotic flow induced by the presence of citric acid into the kaolinite sample.     

Glycine–nitrate synthesis of Sr doped La2Zr2O7 pyrochlore powder

Abstract

Abstract

Materials with A₂B₂O₇ (pyrochlore) structure have received significant attention for their applications as new protonic conductors and materials used in electronic devices. One of the unique synthesis routes for La₂Zr₂O₇ (pyrochlore) powders is the glycine–nitrate combustion method, which shows superior properties of the synthesised powder using glycine as a complexing agent. The Sr doped La₂Zr₂O₇ powders in pure pyrochlore structure were produced using this approach. Selected characteristics of the synthesised powders, such as crystal structure, lattice parameters, crystallite size, the vibrational properties, the morphology of the particles, along with the specific surface area and particle size, have been investigated. The dependence of some properties on annealing temperatures of the powders has been studied.     

络合剂对AA/AM共聚物阻垢的增效作用

为提高聚丙烯酸盐类高分子水处理剂的功能,特别是加强阻垢效果,在对丙烯酸(AA)/丙烯酰胺(AM)共聚物中加入络合剂,采用模拟蒸发试验对其阻垢效果进行研究,结果表明:加入添加有EDTA-2Na、酒石酸(TA)或柠檬酸(CA)络合剂的AA/AM共聚物0.02 mL/L,阻垢率可达97%～98%,与不加络合剂的AA/AM共聚物比较,阻垢率提高了约10%。     

Cadmium (zinc) manganese sulfide nanocrystalline (Cd1-xMnxS and Zn1-xMnxS) dilute magnetic semiconductors. synthesis,annealing, and effects of surface oxidation on magnetic properties

Cd_1-xMn_xS and Zn_1-xMn_xS dilute magnetic semiconductor nanocrystals were prepared in aqueous and non-aqueous solutions by simple precipitation methods with x values ranging from 0.1 to 0.5. X-ray powder diffraction showed the asprepared sample crystal sizes were about 2–3 nm with zinc blende cubic structure. After thermal annealing, the crystals converted to the hexagonal wurzite structure as the crystallite size reached 100–120 nm. The manganese ions on the surface were very easily oxidized in the air and were the cause of an antiferromagnetic transition at near 37 K.     

Annealing effects for calcination of tin oxide powder prepared via homogeneous precipitation

Tin oxide powders were prepared from a homogeneous precipitation using the aqueous solution of SnCl₄ with urea as a precipitator at 90 °C and followed by a calcination process. The calcination was performed using two different methods; conventional furnace annealing (CFA) and rapid thermal annealing (RTA). The crystallization of the tin oxide finished at 600 °C regardless of the calcination method used. The crystallite size increased with as the calcination temperature increased due to the crystal growth and agglomeration. The tin oxide calcined using RTA has a relative smaller crystallite size than CFA at the same temperature. The tin oxide powders calcined with RTA showed higher specific surface areas than those that used CFA over a wide range of temperatures.     

碳化法制备硅钢氧化镁过程中杂质脱除研究

以轻烧氧化镁粉为原料,经消化、碳化制得重镁水,在热解反应前采用络合剂对重镁水中的杂质钙、铁进行络合掩蔽,再经热解得到碱式碳酸镁,碱式碳酸镁经煅烧可制得钙、铁杂质含量较低的氧化镁。在重镁水络合除杂过程中,考察了络合剂三乙醇胺、柠檬酸、草酸单独和复合使用的除铁、除钙效果。以三乙醇胺为络合剂时,在 200 mL重镁水中加10 mL三乙醇胺（1∶1）,氧化镁产品中w（氧化镁）=99.3%、w（氧化钙）=0.31%、w（氧化铁）= 0.042%;使用草酸和柠檬酸作为复合络合剂时,在200 mL重镁水中加入1.0 g柠檬酸和2.0 g草酸,氧化镁产品中 w（氧化镁）=98.2%、w（氧化钙）=0.24%、w（氧化铁）=0.030%。     

Removal of nitrogen compounds from lubricating base stocks with complexing of oxalic acid

A new method to remove the nitrogen compounds from lubricating base stocks was revealed by using the complexing and crystallization of oxalic acid and nitrogen compounds in this paper. The data indicated that the reaction and filtration temperatures obviously influence the nitrogen removal efficiency. The suitable reaction temperature was 100–130 °C and the reaction time is more than 20 min. The crystal water in oxalic acid can lower the removal efficiency, which can be improved when inert gas is introduced to take out the crystal water in oxalic acid. When clay was used in the reaction system, the nitrogen removal efficiency was improved and the filtration temperature was also elevated. Oxalic acid can remove more than 98% of basic nitrogen compounds and more than 70% of nonbasic nitrogen compounds from the lubricating base stocks. The removal of basic nitrogen showed a linear relationship with the removal of nonbasic nitrogen.     

Annealing temperature and environment effects on ZnO nanocrystals embedded in SiO2: a photoluminescence and TEM study

We report on efficient ZnO nanocrystal (ZnO-NC) emission in the near-UV region. We show that luminescence from ZnO nanocrystals embedded in a SiO₂ matrix can vary significantly as a function of the annealing temperature from 450°C to 700°C. We manage to correlate the emission of the ZnO nanocrystals embedded in SiO₂ thin films with transmission electron microscopy images in order to optimize the fabrication process. Emission can be explained using two main contributions, near-band-edge emission (UV range) and defect-related emissions (visible). Both contributions over 500°C are found to be size dependent in intensity due to a decrease of the absorption cross section. For the smallest-size nanocrystals, UV emission can only be accounted for using a blueshifted UV contribution as compared to the ZnO band gap. In order to further optimize the emission properties, we have studied different annealing atmospheres under oxygen and under argon gas. We conclude that a softer annealing temperature at 450°C but with longer annealing time under oxygen is the most preferable scenario in order to improve near-UV emission of the ZnO nanocrystals embedded in an SiO₂ matrix.     

添加剂对钒液流电池正极液的影响

研究了添加剂酒石酸、乙二酸、柠檬酸、葡萄糖对钒电池正极液电化学性能和稳定性的影响,并对其规律和机理进行了探讨。CV研究结果表明:含有多个-OH的有机物葡萄糖能明显提高正极液的阳极峰电流,含有多个-COOH的乙二酸能明显提高正极液的阴极峰电流,而含有多个-OH和多个-COOH的酒石酸对正极液的阴、阳极峰电流均有明显提高。同时,酒石酸(含氧官能团-OH和-COOH)能与5价钒作用,阻碍钒离子聚合,从而提高了5价钒的稳定性。交流阻抗测试表明,正极液中添加酒石酸能大大降低电荷传递电阻和溶液电阻,电解液的性能得到了显著提高。     

The effect of stresses during crystallization on the crystallite size distributions

In some glasses during thermal annealing, nano crystals are formed, which scarcely grow with time and exhibit a very narrow crystal size distribution. In this paper, considerations on the crystallite size distributions are given. A variant of the nucleation theory including the role of an induction period is included in the model. Since non-isochemical systems are considered, the oversaturation is decreasing with time and therefore a model is chosen according to which the nucleation rate decreases. For the crystal growth velocity, a model recently derived was used which takes into account the stresses formed during the course of the crystallization process. It is found, that a model taking into account decreasing oversaturation, an induction period as well as the occurrence of stresses fully explains the crystallite size distributions experimentally observed which might even be narrower than those according to the theory of Lifshitz, Slyozov and Wagner.     

Pulsed-Laser-Induced Simple Synthetic Route for Tb3Al5O12:Ce3+ Colloidal Nanocrystals and Their Luminescent Properties

Cerium-doped Tb₃Al₅O₁₂ (TAG:Ce³⁺) colloidal nanocrystals were synthesized by pulsed laser ablation (PLA) in de-ionized water and lauryl dimethylaminoacetic acid betain (LDA) aqueous solution for luminescent bio-labeling application. The influence of LDA molecules on the crystallinity, crystal morphology, crystallite size, and luminescent properties of the prepared TAG:Ce³⁺ colloidal nanocrystals was investigated in detail. When the LDA solution was used, smaller average crystallite size, narrower size distribution, and enhanced luminescence were observed. These characteristics were explained by the effective role of occupying the oxygen defects on the surface of TAG:Ce³⁺ colloidal nanocrystal because the amphoteric LDA molecules were attached by positively charged TAG:Ce³⁺ colloidal nanocrystals. The blue-shifted phenomena found in luminescent spectra of the TAG:Ce³⁺ colloidal nanocrystals could not be explained by previous crystal field theory. We discuss the 5d energy level of Ce³⁺ with decreased crystal size with a phenomenological model that explains the relationship between bond distance with 5d energy level of Ce³⁺ based on the concept of crystal field theory modified by covalency contribution.     

Colloidal chemical synthesis and formation kinetics of uniformly sized nanocrystals of metals, oxides, and chalcogenides

Nanocrystals exhibit interesting electrical, optical, magnetic, and chemical properties not achieved by their bulk counterparts. Consequently, to fully exploit the potential of nanocrystals, the synthesis of nanocrystals must focus on producing materials with uniform size and shape. Top-down physical processes can produce large quantities of nanocrystals, but controlling the size is difficult with these methods. On the other hand, colloidal chemical synthetic methods can produce uniform nanocrystals with a controlled particle size. In this Account, we present our synthesis of uniform nanocrystals of various shapes and materials, and we discuss the kinetics of nanocrystal formation. We employed four different synthetic approaches including thermal decomposition, nonhydrolytic sol-gel reactions, thermal reduction, and use of reactive chalcogen reagents. We synthesized uniform oxide nanocrystals via heat-up methods. This method involved slowly heat-up reaction mixtures composed of metal precursors, surfactants, and solvents from room temperature to high temperature. We then held reaction mixtures at an aging temperature for a few minutes to a few hours. Kinetics studies revealed a three-step mechanism for the synthesis of nanocrystals through the heat-up method with size distribution control. First, as metal precursors thermally decompose, monomers accumulate. At the aging temperature, burst nucleation occurs rapidly; at the end of this second phase, nucleation stops, but continued diffusion-controlled growth leads to size focusing to produce uniform nanocrystals. We used nonhydrolytic sol-gel reactions to synthesize various transition metal oxide nanocrystals. We employed ester elimination reactions for the synthesis of ZnO and TiO(2) nanocrystals. Uniform Pd nanoparticles were synthesized via a thermal reduction reaction induced by heating up a mixture of Pd(acac)(2), tri-n-octylphosphine, and oleylamine to the aging temperature. Similarly, we synthesized nanoparticles of copper and nickel using metal(II) acetylacetonates. Ni/Pd core/shell nanoparticles were synthesized by simply heating the reaction mixture composed of acetylacetonates of nickel and palladium. Using alternative chalcogen reagents, we synthesized uniform nanocrystals of various metal chalcogenides. Uniform nanocrystals of PbS, ZnS, CdS, and MnS were obtained by heating reaction mixtures composed of metal chlorides and sulfur dissolved in oleylamine. In the future, a detailed understanding of nanocrystal formation kinetics and synthetic chemistry will lead to the synthesis of uniform nanocrystals with controlled size, shape, and composition. In particular, the synthesis of uniform nanocrystals of doped materials, core/shell materials, and multicomponent materials is still a challenge. We expect that these uniformly sized nanocrystals will find important applications in areas including information technology, biomedicine, and energy/environmental technology.