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1.
The method parameters of an almost one century old method for analyzing nickel as dimethylglyoximate were critically examined for the analysis of nickel raw materials and many of the method parameters were observed to have a significant effect on the Ni recovery. Thus, because the Ni precipitation method parameters vary a lot in analytical literature and also in practice, the obtained Ni results by different methods are not comparable. During this study it was found that the double precipitation worked out perfectly in eliminating the effects of impurity elements. The residual Ni content in the filtrates should also be measured to obtain accurate and precise Ni results. In complexing the impurity elements, tartaric acid, stabilized by acetic acid, turned out to be effective, and when added to the sample solution before ammonium addition, the best pH conditions for homogenous Ni precipitation with dimethylglyoxime were obtained. The optimized Ni determination method described was found to be accurate and highly reproducible when tested with Ni concentrates and standard reference materials containing high Ni concentrations.  相似文献   

2.
Deposition precipitation of nickel hydroxide onto modified carbon nanofibers has been studied and compared to deposition onto silica. The carbon nanofiber support materials consisted of graphite-like material of the fishbone-type with a diameter of 20-50 nm and a specific surface area of 150 m2/g. Modification involved surface oxidation (CNF-O) optionally followed by partial reduction (CNF-OR) or thermal treatment (CNF-OT). Titration of the support materials showed the presence of 0.17 and 0.03 mmol/g carboxylic acid groups for CNF-O and CNF-OR, respectively. For the CNF-OT only basic groups were present. The deposition precipitation of 20 wt % nickel onto these supports has been studied by time dependent pH and nickel loading studies. With silica, nickel ion adsorption did not occur prior to nucleation of the nickel hydroxide phase at pH = 5.6. With CNF-O, nickel ion adsorption took place right from the start of the deposition process at pH = 3.5, and at pH = 5.6 already 4 wt % nickel was adsorbed. Nucleation of nickel hydroxide onto adsorbed nickel ion clusters proceeded subsequently. Characterization of the dried Ni/CNF-O samples with TEM and XRD showed well dispersed and thin (5 nm) platelets of nickel hydroxide adhering to the carbon nanofibers. After reduction at 773 K in hydrogen the Ni/CNF-O contained metallic nickel particles of 8 nm homogeneously distributed over the fibers. With CNF-OR and CNF-OT, precipitation of large platelets (> 500 nm) separate from the support took place. Clearly, the presence of carboxylic acid groups is essential to successfully deposit nickel hydroxide onto modified carbon nanofibers.  相似文献   

3.
Nickel nanoparticles were prepared from their coordination compounds, such as [Ni(NH3)6]Cl2, [Ni(N2H4)2Cl2], [Ni(HNEt2)6]Cl2, and [Ni(H2NBu)6]Cl2 in aqueous solution by chemical reduction. The reaction of nickel ammine and alkylamine complexes with hydrazine monohydrate as a reducing agent was carried out at 90 °C and pH = 10–12. Depending on the influencing parameters such as oxidizing agent, pH, and temperature, the hydrazine reaction can be carried out in different pathways. The chemical reduction method is a simple procedure and also is the best one in the controlling of composition, size, and shape of Ni powder. The reduction of nickel complexes into the metallic Ni powder occurs via the dissociation of complexes and reduction by hydrazine in alkaline solution. Therefore, complexing agents have the most effect on the reduction reaction. The results show that, when the ligands in complexes were changed from ammine to diethylamine and butylamine, respectively, the crystalline size and morphology of nickel metal nanoparticles are changed. The chemical reduction of nickel complexes into metallic nickel can be accompanied with a change in the crystalline system. The pure nickel crystalline has a face-centered cubic structure. The nickel nanoparticles were characterized using IR spectroscopy, X-ray powder diffraction, scanning electron microscopy and vibrating sample magnetometer analyses.  相似文献   

4.
镍湿法冶炼中间品是以含镍矿料经酸浸、碱沉等湿法冶炼工艺处理后得到的粗级产品,尤其以氢氧化镍为典型产品,该类产品粒度细,含水率高,在取制样过程中水分偏析严重。水分和镍品位是品质鉴定的关键要素,直接影响货值判定。通过对水分和镍含量的测定进行试验对比,水分测定采用两步法和一步法测定,结果上没有较大差异。对于主品位镍的分析取样,品质波动小,可以进一步扩大取样基数,减少份样数量表征货物品质,对验货同行人员具有一定的借鉴意义。  相似文献   

5.
An assessment of the voltammetric method based on chelate adsorption at the hanging mercury drop electrode is described for the simultaneous determination of nickel and cobalt in biological materials. The interfacial accumulation of the elements as metal dimethylglyoximates during the adsorption step, and the use of differential-pulse voltammetry during the reduction step, provide substantial gains in the sensitivity of their voltammetric responses. The decomposition of the sample material by direct dry ashing provides a blank-free approach for the accurate determination of the elements. Application of the method to the available certified biological reference materials for cobalt and nickel was successful. The limits of detection obtained under the conditions of this study were 0.01 μg g?1 and 0.02 μg g?1 for cobalt and nickel, respectively, in bovine liver.  相似文献   

6.
准确测定并控制材料中杂质元素含量是发挥高纯材料性能不可或缺的环节。辉光放电质谱法(GDMS)是准确、快速、高灵敏分析高纯材料中痕量及超痕量硫的理想方法。对GDMS分析高纯铜和镍基高温合金中痕量硫的质谱干扰进行了讨论,优化了放电电流和放电电压,采用多种标准物质对硫的相对灵敏度因子(RSF)进行了校准和验证,并与二次离子质谱法(SIMS)进行分析结果比对,验证了GDMS定量分析结果的准确性和可靠性。  相似文献   

7.
Nanocrystalline Ni(OH)2 powder synthesized by a chemical precipitation method was processed using the planetary ball milling (PBM), and the physical properties of both the ball-milled and unmilled Ni(OH)2 were characterized by scanning electron microscopy (SEM), specific surface area, particle size distribution, and X-ray diffraction. It was found that the PBM processing could significantly break up the agglomeration, uniformize the particle size distribution, increase the surface area, decrease the crystallite size, and reduce the crystallinity of nanocrystalline β-Ni(OH)2, which were advantageous to the improvement of the electrochemical activity of Ni(OH)2. The ball-milled nanocrystalline (BMN) Ni(OH)2 was then used to alter the microstructure of pasted nickel electrodes and improve the distribution of the active material in the porous electrode substrate. Electrochemical performances of pasted nickel electrodes with a mixture of BMN and spherical Ni(OH)2 as the active material were investigated, and were compared with those of pure spherical Ni(OH)2 electrodes. Charge/discharge tests showed that BMN Ni(OH)2 addition could enhance the charging efficiency, specific discharge capacity, discharge voltage, and high-rate capability of pasted nickel electrodes. This performance improvement could be attributed to a more compact electrode microstructure, better reaction reversibility, and lower electrochemical impedance, as indicated by SEM, cyclic voltammetry, and electrochemical impedance spectroscopy. Thus, it was an effective method to modify the microstructure and improve the electrochemical properties of pasted nickel electrodes by adding an appropriate amount of BMN Ni(OH)2 to spherical Ni(OH)2 as the active material.  相似文献   

8.
Microwave-assisted EPA method 3051 for nitric acid leaching of environmentally key elements from sediments, soils, and sludges was tested, and the influence of leaching temperature and time on element recovery for an estuarine sediment (CRM 277) was investigated. The extraction efficiencies for four certified reference materials applying EPA method 3051, an optimized nitric acid procedure, and an aqua regia (HCl/HNO3 3:1) procedure were compared. Digestions were carried out in a high-pressure microwave system offering simultaneous temperature and pressure control for all digestion vessels employed. Eight elements (Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn) were determined by ICP-AES and ICP-MS. Extraction efficiency strongly depended on the applied leaching parameters and varied for certain elements among different materials when a nitric acid procedure was applied. In general, element recoveries obtained from the aqua regia procedure were superior to those obtained from nitric acid procedures and showed good agreement with the 95% confidence interval of the certified value for most of the elements investigated. Received: 27 March 1998 / Revised: 29 June 1998 / Accepted: 3 July 1998  相似文献   

9.
Electroless cobalt plating on spherical nickel hydroxide is tested in order to improve the conductivity of Ni(OH)2 and the capacity of the electrode. The factors affecting the process of electroless cobalt plating are cobalt solution, temperature and pH, etc. The effects have been examined and the optimum process parameters have been obtained. The nickel hydroxide electrode which is made by nickel hydroxide deposited cobalt has excellent performance, the results showing that electroless cobalt plating on the surface of spherical nickel hydroxide particles is an effective method for modifying electrodes.  相似文献   

10.
The build-up of biofilms on metals surfaces may lead to severe corrosion, especially in the presence of sulphate-reducing bacteria (SRB). To prevent the deterioration of material caused by biofilms it is necessary to understand the processes governing biofilm development including mechanisms of cell adhesion. Additionally, corrosion of metallic surfaces due to bacteria may lead to the dissolution of metallic elements that may further affect adhesion and biofilm development. A study was carried out to evaluate how the presence of nickel in the substrata affects the adhesion ability of Desulfovibrio desulfuricans. The substrata tested were stainless steel 304 (SS), metallic nickel (Ni) and polymethylmetacrylate (PMMA), a non-metallic material used as control. The influence of nickel on SRB growth and its relation to adhesion was also checked. A statistically significant difference in the number of adhered cells to the materials tested was detected, with higher bacterial number on nickel, followed by SS and finally by PMMA. The higher number of SRB adhered to steel compared with PMMA may be explained by differences in hydrophobicity, in roughness and in the electron-acceptor character of the substrata. Additionally, bacterial growth was found to be positively affected by the presence of nickel as revealed by a significant increase in the specific growth rate of SRB in the presence of increased nickel concentrations.  相似文献   

11.
采用HNO3-HF-HCl酸体系消解样品,火焰原子吸收光谱法连续测定非金属材质仿真饰品中的铅、镉和镍。优化了仪器工作参数和消解条件,进行了共存离子的干扰试验。方法检出限分别为铅5.7 mg/kg、镉0.3 mg/kg、镍3.5 mg/kg。实际样品测定的相对标准偏差(n=6)为1.6%~5.2%,回收率为86.0%~105.8%。  相似文献   

12.
Platinized nickel and cobalt coatings, Pt(Ni) and Pt(Co), have been prepared on glassy carbon, GC, rotating disc electrode substrates by a two-step room temperature procedure that involved the electrodeposition of nickel and cobalt layers and their spontaneous partial replacement by platinum (“transmetalation”) when immersed into a chloroplatinic acid solution. By tuning the quantity of initially deposited nickel and cobalt, Pt(Ni) and Pt(Co) bimetallic coatings having a 26% atom Ni and 30% atom Co composition have been prepared. For both materials typical Pt surface electrochemistry was recorded during fast voltammetry in deaerated acid, pointing to the existence of a continuous Pt skin over a Pt–Ni and Pt–Co core. Oxygen reduction at the Pt(Ni)/GC and Pt(Co)/GC electrodes was studied by means of steady-state voltammetry at a rotating disc electrode and the construction of Tafel plots from corresponding voltammetric data. It was found that, when the initial potential of the voltammetric sweep allowed the formation of a complete Pt oxide monolayer, then oxygen reduction was hindered for low overpotentials at Pt(Ni) and Pt(Co), compared to pure bulk Pt. On the other hand, when the initial potential was less positive (thus leading to the formation of a fraction of surface oxide monolayer) the presence of Ni and Co enhanced the kinetics of oxygen reduction. The former behaviour is attributed to a decrease in oxide reduction ability of Pt in the presence of Ni and Co, while the latter to an increase in dissociative oxygen chemisorption due to Ni and Co.  相似文献   

13.
研究了ICP-AES法测定电镀铬溶液中杂质元素铜、铁、铝、镍含量的方法,对仪器的工作条件、分析线选择、基体影响、共存元素干扰、酸量的影响等进行了试验论证,通过与化学分析方法比较,结果表明方法快速、简便、准确、可靠,完全满足分析要求。  相似文献   

14.
The concentrations of 13 elements (As, Ca, Co, Cd, Cr, Fe, Ga, Ni, Pb, Pt, Ti, V and Zn) were determined in air particulate matter using total reflection X-ray fluorescence spectrometry (TXRF). For silicon analysis synthetic sapphire was chosen as a new sample carrier material – it is silicon-free, resistant to oxygen-plasma, microwaves and concentrated acids. The dust samples were collected on cellulose acetate filters. The decomposition of the filters was carried out by oxidation in a microwave-generated low-pressure oxygen-plasma directly on the TXRF sample carriers. The recovery of the investigated elements was verified with the standard reference material SRM 1648 (urban particulate matter) and ranged from 90 to 97%. The oxygen-plasma method was compared with conventional sample preparation by acid digestion. Received: 9 April 1999 / Revised: 18 May 1999 / Accepted: 3 June 1999  相似文献   

15.
The concentrations of 13 elements (As, Ca, Co, Cd, Cr, Fe, Ga, Ni, Pb, Pt, Ti, V and Zn) were determined in air particulate matter using total reflection X-ray fluorescence spectrometry (TXRF). For silicon analysis synthetic sapphire was chosen as a new sample carrier material – it is silicon-free, resistant to oxygen-plasma, microwaves and concentrated acids. The dust samples were collected on cellulose acetate filters. The decomposition of the filters was carried out by oxidation in a microwave-generated low-pressure oxygen-plasma directly on the TXRF sample carriers. The recovery of the investigated elements was verified with the standard reference material SRM 1648 (urban particulate matter) and ranged from 90 to 97%. The oxygen-plasma method was compared with conventional sample preparation by acid digestion. Received: 9 April 1999 / Revised: 18 May 1999 / Accepted: 3 June 1999  相似文献   

16.
镍盐前驱体对Ni/C催化剂乙醇气相羰化活性的影响   总被引:1,自引:0,他引:1  
采用等体积浸渍法制备了分别以乙酰丙酮镍、氯化镍、硝酸镍和醋酸镍为前驱体负载在活性炭上的四种催化剂。用BET、金属分散度、H2-TPR、CO-TPD和XRD等方法研究了四种催化剂的结构特点和乙醇气相羰化活性。结果表明,以醋酸镍制备的Ni/C催化剂的羰化活性最高,乙醇转化率和丙酸选择性分别为96.1%和95.7%,而以乙酰丙酮镍制备的Ni/C催化剂的羰化活性最低,乙醇转化率和丙酸选择性分别为68.9%和27.1%。这种活性的差异与镍盐前驱体和活性炭之间的相互作用强弱有着密切关系。醋酸镍组分与活性炭之间的相互作用较强,浸渍组分易在活性炭表面充分吸附,活性中心Ni0在240-340 ℃温度范围内对CO吸附量最大,还原后金属镍的分散度较好且晶粒较小。  相似文献   

17.
Summary Gradient reversed-phase liquid chromatography was examined with a view to using it as a separation technique for the speciation of vanadyl and nickel porphyrins in oil extracts. Poor separations were obtained when precipitation of the sample constituents occurred in the starting mobile phase. The reasons for the precipitation phenomena were found to be highly complex. Mixed crystal formation, slow dissolution kinetics and saturation may influence the elution behaviour of species present in the oil extracts. When precipitation was avoided the separation of the vanadyl porphyrins was significantly improved. Thus far, no satisfactory separations have been obtained for the nickel porphyrinic species.Although the occurrence of precipitation of the extracts hinders the distinct speciation of metalloporphyrins with reversed phase chromatography, the precipitation/dissolution phenomena showed some interesting features as a clean-up step for diluted crude oil samples and oil fractions.  相似文献   

18.
Cellulose and chromaton-N-super as solid supports for direct determination of the immobilized nickel complexes with dimethylglyoxime and benzyldioxime by diffuse reflection spectroscopy were compared. The advantage of chromaton-N-super with use of benzyldioxime is shown. Detection limit is 0.02 μg/mL. The proposed method was applied for the analysis of soil. Received: 12 April 1999 / Revised: 10 December 1999 / /Accepted: 15 December 1999  相似文献   

19.
A chromotropic acid-functionalized polyurethane foam has been developed for use in an on-line preconcentration system for cobalt and nickel determination. The packing material was prepared by covalent coupling of chromotropic acid with the polyurethane foam through an azo group. Co and Ni ions were sorbed in the mini-column, from which they could be eluted directly to the nebulizer-burner system of a flame atomic absorption spectrometer. Elution of cobalt and nickel from the mini-column can be accomplished with 0.50 and 0.75 M HCl solutions, respectively. The enrichment factors obtained were 22 (Co) and 27 (Ni), for 60 s preconcentration time, and 57 (Co) and 59 (Ni), if a preconcentration time of 180 s was used. Under the optimum conditions, the proposed procedure allowed the determination of metals with detection limits of 0.43 (cobalt) and 0.52 microg/L (nickel), respectively, on using preconcentration periods of 180 s. The accuracy of the developed procedure was evaluated by analysis of the certified reference materials NIST 1515 Apple Leaves and NIST 1570a Spinach Leaves. The method was applied to the analysis of lettuce samples. The contents of cobalt in the samples analyzed varied from 0.75 to 0.98 microg/g. Nickel was not detected in the lettuce samples.  相似文献   

20.
A series of nickel selenides (NiSe2 microcrystals, Ni(1-x)Se and Ni3Se2 microspheres) has been successfully synthesized through a convenient, low-temperature hydrothermal method. A good nucleation and growth environment has been created by forming a uniform and transparent solution reaction system. The compositions (including the x value of Ni(1-x)Se), phase structures, as well as the morphologies of nickel selenides, can be controlled by adjusting the Ni/Se ratio of the raw materials, the pH, the reaction temperatures and times, and so forth. The newly produced Se microspheres in the system have been used as both reactant and in situ template to the Ni(1-x)Se microspheres. It is found that Ni(1-x)Se microspheres act as the intermediate precursor during the formation of Ni3Se2 microspheres. Under certain conditions, hexagonal NiSe microspheres can be converted into rhombohedral NiSe nanowires in solution. The formation mechanisms of a series of nickel selenides has been investigated in detail by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. This work has provided a general, simple, and effective method to control the composition, phase structure, and morphology of metal selenides in aqueous solution, which will be important for inorganic synthesis methodology and further applications of selenides.  相似文献   

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