微波消解-光度法测定硼铸铁中的硼

采用微波消解样品处理技术,结合光度法测定硼铸铁中的硼元素,该方法与传统的酸溶法 熔法样品处理相比,不但分析结果相吻合,而且更具有快速、高效、清洁和污染少等优点,完全能满足铸铁分析的要求,不但分析结果相吻合,而且更具有快速、高效、清洁和污染少等优点,完全能满足铸铁分析的要求。     

火焰原子吸收光谱法测定鸭肾中六种元素

选择采用ＨＮＯ３＋Ｈ２Ｏ２（２＋１消化法对鸭肾进行消化处理,用火焰原子吸收光谱法测定鸭肾中铜、锌、铅、铁、钙、镉等六种元素,实验表明该法有耗样少,精确度高,快速等优点,结果令人满意,该法具有一定的实用意义。     

中草药有效成分山姜素的固体表现室温磷光法研究

本文选择滤纸作基质,以ＬｉＡｃ作重原子微扰剂,建立了测定中草药中痕量有效成分山姜素的滤纸表面室温磷光法。该法取样量少,线性范围宽,灵敏度高操作简便、快速。     

毛细管电泳法在酶抑制剂筛选中的应用

毛细管电泳法以其分离效率高、耗时短、样品用量少、灵敏度高以及易于实现自动化等诸多特点,在筛选酶抑制剂研究中有着不可替代的优势.本文综述了毛细管电泳法在酶抑制剂筛选中的应用.主要介绍了应用最广泛的离线分析(Off-line assay)和在线分析(In-line assay),即柱前酶反应(Pre-capillary enzyme reaction)和在柱酶分析(In-capillary enzyme reaction).并对该领域的未来发展进行了展望.     

四甲基氢氧化铵溶解石墨炉原子吸收测定人发中的铅和锰

我们用Groos的四甲基氢氧化铵(TMAH)-乙醇水溶液溶解法处理发样,用塞曼原子吸收测定其中的铅和锰,结果证明该法具有简单,快速、准确,取样量少的优点,适合分析多种元素、大量样品。     

稀土硅镁合金中硅的快速测定

该合金中硅的测定通常采用重量法,手续繁杂、费时,又需用铂器皿进行残渣处理。近年来,不少单位介绍用硅钼蓝比色法,手续虽简便、快速,但因显色时分取试样少引起误差较大,不易满足需要。本文采用氟硅酸钾容量法进行了试验,结果表明:该法以硝酸-氢氟酸分解试样反应剧烈,勿需加热,1—2分钟即能完全分     

石墨炉原子吸收法测定香根草中痕量Pb、Cd、Cu

采用石墨炉原子吸收法直接测定了香根草中重金属的含量,通过一系列实验,确定了石墨炉法测定Pb、Cd、Cu的最佳灰化温度和原子化温度,考察了精密度和回收率。结果表明,该法操作简单快捷,样品用量少,灵敏度高,稳定性好。     

神经网络扩展滤波算法及其多元光谱分辨应用

前馈神经网络(NN)误差反向传播算法(BP)应用较广, 但收敛较慢且易陷入局部极优, 针对这一不足, 本文提出了一种基于扩展滤波的快速学习新颖算法(EF)。与BP相比较, 该法不仅具有学习效率高, 收敛速度快, 所需学习次数少,数值稳定性好等优点, 而且所需调节参数少。由非线性系统建模与辨识的模拟结果表明, EF是一种有效的神经学习新算法。该法用于多元光谱校正与分辨,获得良好结果。     

溶剂萃取动力学研究方法——生长液滴法

在溶剂萃取动力学文献中,对恒界面池(Lews Cell)法、单液滴法(Single DropMethod)及高速搅拌法(Highly Stirredtanks)等动力学实验方法有较多的应用和描述,而生长液滴法(Growing DropMethod)则报道不多。该法具有操作简便,试剂用量少,测试准确等优点,本文介绍这种实验技术。     

乙醇脱水制乙烯新法

目前实验室制乙烯大多数采用浓硫酸做脱水剂,该法存在许多缺陷,本实验用P2O5做脱水剂制取乙烯具有反应速度快,反应温度低,副产物少,无污染等优点。     

简捷水热前驱物技术制备钛酸钡纳米棒与纳米球

A facile synthesis route has been developed to prepare barium titanate nanoparitcles via a low temperature (120 ℃) hydrothermal decomposition of single-source metal-organic precursor. A mixture of tetramethylammonium hydroxide (TMAH) and distilled water was used as reaction media, and Barium titanium ethyl-hexano- isoproxide [BaTi(O₂CC₇H₁₅)(OC₃H₇)₅] was used as precursor. The architecture of products can be selectively controlled from nanorods to nanospheres by adjusting the precursor′s concentration in the reaction system. Powder X-ray diffraction (XRD) analysis indicated that the products were in cubic phase. Transmission electronic microscopy (TEM) observation showed that the nanospheres were 30～50 nm in diameter, and the nanorods were 5～10 nm in diameter and 100～600 nm in length, respectively. Phase transformation behavior of the as-prepared products was also investigated.     

机械球磨固相化学反应制备AlH3及其放氢性能

以LiAlH4和AlCl3为原料, 采用机械球磨固相化学反应方法制备了铝氢化合物, 通过X射线衍射(XRD)、热分析(TG-DSC)和质谱(MS)分析等方法对反应产物进行分析和表征, 研究了不同球磨时间(4、8、15和20 h)对LiAlH4+AlCl体系的固相反应转变规律﹑合成产物和放氢性能的影响. 研究结果表明, 随球磨时间的增加, 球磨固相反应按3LiAlH4+AlCl3→4AlH3+3LiCl方向进行, 形成了非晶态铝氢化合物AlH3, 球磨20 h时反应基本完全. 球磨产物的放氢动力学特性随球磨时间增加而改善, 其放氢起始温度均低于100 ℃, 最大放氢量达到2.6%-3.6%(H2)(w), 接近反应体系的理论储氢量4.85%(H2)(w). 球磨过程中反应产物形成LiCl·H2O以及少量AlH3发生分解是影响球磨产物最大放氢量的主要因素.     

The non-isothermal decomposition of cobalt acetate tetrahydrate

The non-isothermal decomposition of cobalt acetate tetrahydrate was studied up to 500°C by means of TG, DTG, DTA and DSC techniques in different atmospheres of N₂, H₂ and in air. The complete course of the decomposition is described on the basis of six thermal events. Two intermediate compounds (i.e. acetyl cobalt acetate and cobalt acetate hydroxide) were found to participate in the decomposition reaction. IR spectroscopy, mass spectrometry and X-ray diffraction analysis were used to identify the solid products of calcination at different temperatures and in different atmospheres. CoO was identified as the final solid product in N₂, and Co₃O₄ was produced in air. A hydrogen atmosphere, on the other hand, produces cobalt metal. Scanning electron microscopy was used to investigate the solid decomposition products at different stages of the reaction. Identification of the volatile gaseous products (in nitrogen and in oxygen) was performed using gas chromatography. The main products were: acetone, acetic acid, CO₂ and acetaldehyde. The proportions of these products varied with the decomposition temperature and the prevailing atmosphere. Kinetic parameters (e.g.E and lnA) together with thermodynamic functions (e.g. °H, C _p and °S) were calculated for the different decomposition steps. In celebration of the 60^th birthday of Dr. Andrew K. Galwey     

固-固化学法制备Ce0.75Zr0．25O2氧化物固溶体及其表征

以碳酸铈、氯氧锆和草酸为原料,采用机械力活化固-固化学法制得前驱物,前驱物经热分解获得了相应的目标产物Ce0.75Zr0.25O2氧化物固溶体.对前驱体进行了热重-差热(TG-DTA)测试,分析了在球磨及煅烧过程中可能发生的化学反应.采用X-射线衍射(XRD),透射电镜(TEM)和光电子能谱(XPS)等对产物进行了表征,实验结果表明:产物为单一的立方晶系固溶体,没有单独的氧化锆或氧化铈存在,粉体分散性好,呈圆球状,分布均匀,平均粒径为15.8 nm,比表面积达85.4 m2/g.对机械力活化固相化学反应的机制进行了研究.     

Thermal decomposition route for synthesis of Mn3O4 nanoparticles in presence of a novel precursor

The synthesis of manganese oxide (Mn₃O₄) nanoparticles by using thermal decomposition and its physicochemical characterization are being reported in present investigation. As a new precursor, [bis(2-hydroxy-1-naphthaldehydato)manganese(II)] complex was used in the presence of oleylamine (C₁₈H₃₇N) as both surfactant and solvent to control the size of resulting nanoparticle. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and Raman spectrum. Synthesized manganese oxide nanoparticles have a tetragonal structure with average size of 9–24 nm. The phase pure samples were characterized by using X-ray photoelectron spectroscopy (XPS) for Mn 2p level. The values of binding energies are consistent with the relative values are reported in the literature. As a comparison between two methods, the novel precursor thermally was treated in solid state reaction in different temperature, 400, 500, and 600 °C and the products were characterized by SEM images. Magnetic property of the as-prepared Mn₃O₄ nanoparticle shows a ferromagnetic behavior with high saturation magnetization and coercivity.     

Single-Phase Precursors for the Preparation of Spinel Ferrites via Oxalate Route: the Study of Cobalt Ferrite Synthesis

This work explores the benefits of single-phase oxalate precursors for the preparation of spinel ferrites by thermal decomposition. A direct comparison between the genuine oxalate solid solution and the physical mixture of simple oxalates is presented using the case study of cobalt ferrite preparation. The mixing of metal cations within a single oxalate structure could be verified prior to its thermal decomposition by several non-destructive experimental techniques, namely Mössbauer spectroscopy, X-ray powder diffraction (XRD) and energy-dispersive X-ray spectroscopy. In situ XRD experiments were conducted to compare the decomposition processes of the solid solution and the physical mixture. Additionally, the decomposition products of the FeCo oxalate solid solution were studied ex situ by means of N₂ adsorption, Mössbauer spectroscopy and XRD. The results obtained for different reaction temperatures demonstrate the possibilities to easily control the physical properties of the prepared oxides.     

Photoionization Mass Spectrometry: A Useful Method to Evaluate the Pyrolysis Process of Glycoside Flavor Precursor

The thermal decomposition behavior and the pyrolysis products of benzyl‐2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranoside (BGLU) were studied with synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry at temperatures of 300, 500 and 700 °C at 0.062 Pa. Several pyrolysis products and intermediates were identified by the measurement of photoionization mass spectra at different photon energies. The results indicated that the primary decomposition reaction was the cleavage of O‐glycosidic bond of the glycoside at low temperature, proven by the discoveries of benzyloxy radical (m/z = 107) and glycon radical (m/z = 331) in mass spectra. As pyrolysis temperature increased from 300 to 700 °C, two possible pyrolytic modes were observed. This work reported an application of synchrotron VUV photoionization mass spectrometry in the study of the thermal decomposition of glycoside flavor precursor, which was expected to help understand the thermal decomposition mechanism of this type of compound. The possibility of this glycoside to be used as a flavor precursor in high temperature process was evaluated.     

The study of thermal decomposition kinetics of zinc oxide formation from zinc oxalate dihydrate

This study is devoted to the thermal decomposition of ZnC₂O₄·2H₂O, which was synthesized by solid-state reaction using C₂H₂O₄·2H₂O and Zn(CH₃COO)₂·2H₂O as raw materials. The initial samples and the final solid thermal decomposition products were characterized by Fourier transform infrared and X-ray diffraction. The particle size of the products was observed by transmission electron microscopy. The thermal decomposition behavior was investigated by thermogravimetry, derivative thermogravimetric and differential thermal analysis. Experimental results show that the thermal decomposition reaction includes two stages: dehydration and decomposition, with nanostructured ZnO as the final solid product. The Ozawa integral method along with Coats–Redfern integral method was used to determine the kinetic model and kinetic parameters of the second thermal decomposition stage of ZnC₂O₄·2H₂O. After calculation and comparison, the decomposition conforms to the nucleation and growth model and the physical interpretation is summarized. The activation energy and the kinetic mechanism function are determined to be 119.7 kJ mol^?1 and G(α) = ?ln(1 – α)^1/2, respectively.     

Kinetic Modeling of Plasma Methane Conversion Using Gliding Arc

Plasma methane (CH4) conversion in gliding arc discharge was examined. The result data of experiments regarding the performance of gliding arc discharge were presented in this paper. A simulation which is consisted some chemical kinetic mechanisms has been provided to analyze and describe the plasma process. The effect of total gas flow rate and input frequency refers to power consumption have been studied to evaluate the performance of gliding arc plasma system and the reaction mechanism of decomposition.Experiment results indicated that the maximum conversion of CH4 reached 50% at the total gas flow rate of 1 L/min. The plasma reaction was occurred at the atmospheric pressure and the main products were C (solid), hydrogen, and acetylene (C2H2). The plasma reaction of methane conversion was exothermic reaction which increased the product stream temperature around 30～50℃.     

Single-Source Molecular Precursor for Synthesis of Copper Sulfide Nanostructures

As a new precursor, [bis(thiosemicarbazide)copper(II)]chloride; ([Cu(TSC)₂]Cl₂), complex was used in thermal decomposition process for the synthesis of Cu₂S nanocrystals. The steric hindrance of the precursor raises the need of using co-surfactant, therefore oleylamine (C₁₈H₃₇N) and triphenylphosphine (C₁₈H₁₅P) were applied as solvent and surfactant of the reaction. CuS nanocrystals were synthesized via hydrothermal decomposition of [bis(thiosemicarbazide) copper(II)] without any surfactant. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and photoluminescence spectroscopy. Synthesized copper sulfide nanostructures have average size of 20–50?nm. Finally, optical properties of the products were examined and investigated by PL spectra.