提高Nb2O5中Ta2O5光谱分析的灵敏度

由于Ｎｂ２Ｏ５与Ｔａ２Ｏ５物理、化学性质相似，主体Ｎｂ２Ｏ５对Ｔａ分析线强度干扰很大。因此，Ｎｂ２Ｏ５中光谱测定Ｔａ２Ｏ５的灵敏度很差，为了提高Ｔａ分析线强度，通常的光谱条件选择是无效的。实验表明在旋流气室中，采用高含量Ａｒ的（Ａｒ、Ｏ２）控制气氛电弧激发，提高了Ｎｂ２Ｏ５中Ｔａ２Ｏ５的光谱分析灵敏度。然而，由于Ｎｂ２Ｏ５在高温下易于被碳还原，虽然用Ｓｔａｌｌｗｏｏｄ喷咀可以改善蒸发，减慢样品还原     

含第1长周期过渡金属的Nb/Ta三组元层状结构碲化物研究

总结了所研究的Ｎｂ／Ｔａ层状碲化物结构．对经Ｘ射线衍射结构表征的１４种化合物按其结构类型分别加以介绍．化合物Ｎｂ_２ＣｒＴｅ_４和Ｎｂ_２Ｃｕ_１．４８Ｔｅ_４的特点是第３组元原子插入与Ｎｂ／Ｔａ不同的层中．在其他化合物中,两种金属原子均插入同一层．分子式为Ｍ_２Ｍ_２Ｔｅ_４（Ｍ＝Ｎｂ／Ｔａ, Ｍ′＝ Ｎｉ, Ｃｏ, Ｆｅ）的 ６个化合物的结构可描述为由簇单元 “Ｍ_２Ｍ′_２ Ｔｅ_(１０)构成．在两个富金属簇合物 ＴａＣｏ_２Ｔｅ_２和 ＴａＮｉ_２Ｔｅ_２中, Ｔａ原子具有畸变单帽三角柱结构．而ＴａＦｅＴｅ_３,ＴａＮｉ_２Ｔｅ_３和ＮｂＮｉ_２Ｔｅ_３的结构可描述为以Ｎｂ／Ｔａ和Ｔｅ原子组成的双八面体链为基础构成．与此相联系,Ｔａ_２Ｎｉ_２Ｓｅ_５的结构,由于也可描述成另一种型式的双八面体排布而放在文中讨论．     

Ag4Fe（CN）6溶胶表面对PABA分子增强机制及吸附态的探讨

通过向对氨基苯甲酸（ＰＡＢＡ）－Ａｇ_４Ｆｅ（ＣＮ）_６溶胶体系分别滴加少量Ｋ_４Ｆｅ（ＣＮ）_６、Ｋ_３Ｆｅ（ＣＮ）_６、Ｎａ_２Ｓ_２Ｏ_３、Ｈ_２Ｏ_２、ＮａＣｌ和ＮａＮＯ_３水溶液，以及改变体系ｐＨ值对ＰＡＢＡＳＥＲＳ谱带影响的观测，探讨Ａｇ_４Ｆｅ（ＣＮ）_６溶胶体系对ＰＡＢＡ分子的增强机制及在胶体表面受到极大增强的分子吸附态。     

角分辨飞行时间法研究紫外激光烧蚀Ta2O5的反应

利用角分辨飞行时间法研究了３５５ｎｍ脉冲激光烧蚀Ｔａ２Ｏ５的反应，由四极质谱测得的煤蚀产物除了Ｏ，Ｔａ，ＴａＯ和ＴａＯ２中性碎片外，在较高激光能量密度时还有Ｏ，Ｔａ，ＴａＯ，ＴａＯ２离子碎片，它们的飞行时间（ＴＯＦ）谱可以用于级分带质心速度的Ｍａｘｗｅｌｌ－Ｂｏｌｚｔｍａｎｎ分布函数较好地拟合，原生离子碎片的平均动能与激光能量密度无关，烧蚀产物原生离子和中性粒子的角分布可以分别用ａｃｏｓ＾ｎθ（ｎ     

辣根过氧化物酶的电化学固定化及其对H2O2的生物电催化…

利用电化学固定化方法制备了聚吡咯／辣根过氧化物酶（ＰＰ／ＨＲＰ）膜电极，并研究了其电化学行为，在除氧的磷酸盐缓冲液介质中，ＰＰ／ＨＲＰ电极加速Ｈ２Ｏ２的还原，归因子酶加成物的直接电子传递，探索ＨＲＰ与电子传递体Ｋ４Ｆｅ（ＣＮ）６在聚吡咯（ＰＰ）膜中的同时固定化条件及其膜电极的电化学行为，实验证实，Ｋ４Ｆｅ（ＣＮ）６在酶膜中的存在使得Ｈ２Ｏ２的还原电位强烈正移，在－０．０５Ｖ的工作电位下能对Ｈ２Ｏ２     

卡宾与醚C——H键插入反应的理论研究（Ⅱ）：——二氯卡宾？…

用量子化学从头算方法在ＭＰ２／６－３１Ｇ（ｄ）水平上研究了单重态的ＣＸ２（Ｘ＝Ｆ,Ｃｌ）与二甲醚中Ｃ－－Ｈ键的插入反应。两个体系的插入反应都是自发的,插入过程是ＣＸ２的亲电－新核过程。ＣＸ２与二甲醇的插入势垒分别为１２５．９ＫＪ／ｍｏｌ（经零点能校正后为１３２．２ＫＪ／ｍｏｌ,Ｘ＝Ｃｌ）和２５５．３ＫＪ／ｍｏｌ（经零点能校正后为２５７．６ＫＪ／ｍｏｌ,Ｘ＝Ｆ）。ＣＦ２的插入反应实际上难以发生。     

COS对FT合成催化性能的影响

在５２４Ｋ、２．３１ＭＰａ和１８４５ｈ＾－１条件下，考察了合成气（Ｈ２／ＣＯ＝２．１）中ＣＯＳ浓度分别为５１．４、１２８．８、１６２．７和２４５．６ｐｐｍ对Ｆｅ－Ｃｕ－Ｋ工业催化剂ＦＴ合成催化性能的影响。实验表明，催化剂预先中毒比在线中毒速度快。大颗粒催化剂的抗硫能力比小颗粒催化剂强。催化剂ＦＴ合成失活速率与ＣＯＳ浓度有关，即高浓度条件下，催化剂的失活速率快。当温度为５２４Ｋ时，催化剂的失活速率最     

硼掺杂多晶金刚石薄膜电极的电化学特性

用循环伏安法和恒电位法研究了硼掺杂多晶金刚石薄膜电极（ＤＦＥ）的若干电化学特性。电极面积４×４ｍｍ＾２。在０．１ｍｏｌ／Ｌ ＫＣｌ，ＮａＮＯ３，ＮａＯＨ和ＫＨ２ＰＯ４＋Ｎａ２ＨＰＯ４（ｐＨ＝６．８６）电解质溶液中电势窗口均为－５００￣＋８００ｍＶ；而在０．１ｍｏｌ／Ｌ ＨＣｌ和Ｈ２ＳＯ４溶液中电势窗口为－２００￣＋１１００ｍＶ．Ｋ３Ｆｅ（ＣＮ）６的氧化峰电位为＋５００ｍＶ，与Ｐｔ电极测量相同；校正     

助剂钾对二氧化碳加氢反应活性及产物分布的影响

报导助剂Ｋ对Ａｌ２Ｏ３，ＴｉＯ２，ＺｒＯ２担载Ｆｅ催化剂，用于ＣＯ２加氢合成Ｃ２＋烃的催化活性及产物分布的影响。与不含Ｋ的催化剂相比，Ｋ的存在导致Ｆｅ／Ｋ－Ａｌ２Ｏ３的催化活性及Ｃ＾２＋烃选择性明显提高，但使Ｆｅ／Ｋ－ＴｉＯ２的催化活性及Ｃ２＋烃选择性显著下降，而对Ｆｅ／Ｋ－ＺｒＯ２，这种影响并不显著。Ｋ的明显有利于低碳烯烃的生存。     

掠射椭偏术对K4[Fe（CN）6]／K3[Fe（CN）6]电极反应的研究

提出掠射椭圆偏振测试技术的实验方案，应用该掠射式技术循环 安法研究了在镀有Ｉｎ２Ｏ３玻璃片上进行的Ｋ４「Ｆｅ（ＣＮ）６」／Ｋ３「Ｆｅ（ＣＮ）６」电极反应，结果证明：掠射椭圆偏嗥中在电化学反应过程中现场测定椭圆偏振参数及其变化规律，这些规律与所发生的表面电化学反应规律相对应，由此可以对电极体系进行研究，现场掠射椭圆偏振术还能用于分析表面扩散层的性质，弥补其它界面研究方法的缺陷。     

Determination of trace organic carbon and nitrogen in the presence of carbonates in anorganic bovine bone graft materials

The widespread concern of bovine spongiform encephalopathy (mad cow disease) has raised questions about the possibility of residual organic material in bovine-derived bone graft materials. Conflicting reports have shown both the presence and the absence of organic materials in bone derived products. This study compared residual organic levels in two commercial bone graft products: a bovine bone product treated chemically and at low temperature, and a bovine bone product treated at high temperature. In this study, organic carbon, the primary constituent of organic materials, is defined as carbon that is not liberated as CO₂ upon acidification (i.e. non-carbonate carbon). Three approaches to the determination were used: (1) organic carbon was calculated as the difference between total carbon determined by high temperature combustion and carbonate carbon determined by acid evolution of CO₂. (2) Organic carbon was determined by measuring total carbon by high temperature combustion of a sample that had been pretreated with acid to remove all carbonate. (3) The total organic carbon remaining in solution after acid dissolution was determined. In addition, organic nitrogen was determined as the difference between total Kjeldahl and ammonia nitrogen. Total nitrogen values were confirmed using an instrumental nitrogen analyzer. No detectable organic carbon or organic nitrogen was observed in the high temperature bone product. In the low temperature treated bovine product, however, approximately 2000 μg/g organic carbon was measured by all three methods, as well as 15 μg/g organic nitrogen.     

Pr_(0.15)Tb_(0.85)Fe_(1.9)B_x内禀磁致伸缩的测量与分析

利用电弧熔炼法制备了Pr_(0.15)Tb_(0.85)Fe_(1.9)B_x系列样品,通过X射线衍射法对粉末样品的(440)衍射峰进行精细步进扫描并拟合数据,分析获得样品的内禀磁致伸缩λ_(111),通过电阻应变片法测得块状样品在外加磁场下的磁致伸缩值变化趋势,外推得到宏观饱和磁致伸缩值λ_s,并从Laves相晶体结构特性出发对两者进行详细比较对照和进一步深化分析.结果表明,常温下Pr在Laves相化合物中对磁致伸缩具有较大的贡献,适量B的掺入可以增加Pr在Laves相化合物中的含量且不降低材料的磁致伸缩性能.     

Fractionated combustion analysis of carbon in forest soils — new possibilities for the analysis and characterization of different soils

The fractionated combustion analysis of carbon allows the sequential analysis of the total organic carbon (TOC), total inorganic carbon (TIC) and total carbon (TC) fractions in forest soils. Magnesium carbonate and calcium carbonate of the inorganic carbon fraction can also be detected separately. Soils from various forest stands cause different combustion characteristics of the organic carbon fraction, also depending on the soil profile depth. This automatic combustion technique is suitable to characterize the organic carbon fraction of different soil types.     

Determination of stable carbon isotopes of organic acids and carbonaceous aerosols in the atmosphere

A wet oxidation method for the compound-specific determination of stable carbon isotopes (delta(13)C) of organic acids in the gas and aerosol phase, as well as of water-soluble organic carbon (WSOC), is presented. Sampling of the organic acids was done using a wet effluent diffusion denuder/aerosol collector (WEDD/AC) coupled to an ion chromatography (IC) system. The method allows for compound-specific stable carbon isotope analysis by collecting different fractions of organic acids at the end of the IC system using a fraction collector. delta(13)C analyses of organic acids were conducted by oxidizing the organic acids with sodium persulfate at a temperature of 100 degrees C and determining the delta(13)C value of the resulting carbon dioxide (CO(2)) with an isotope ratio mass spectrometer. In addition, analysis of delta(13)C of the WSOC was performed for particulate carbon collected on aerosol filters. The WSOC was extracted from the filters using ultrapure water (MQ water), and the dissolved organic carbon was oxidized to CO(2) using the oxidation method. The wet oxidation method has an accuracy of 0.5 per thousand with a precision of +/-0.4 per thousand and provides a quantitative result for organic carbon with a detection limit of 150 ng of carbon.     

Photocatalytic oxidation for total organic carbon analysis

A new method and apparatus for the determination of organic carbon in water are described. Photocatalytic oxidation of organic matter by near-UV illuminated titanium dioxide is used to convert organic carbon to carbon dioxide. Atmospheric oxygen is the oxidant. The light source is a 20-W black-light fluorescent tube. The carbon dioxide equilibrates between the reaction loop and a conductivity detection loop and the recirculated air forms the interface between the two loops. The method is suitable for analysis of water containing 0.1–30 μg ml^?1 organic carbon and sample volumes of 1–40 ml. Higher concentrations can be determined after appropriate dilution. Times for 99% oxidation of organic solutes to carbon dioxide are of the order of 10 min or less. The main advantages of the apparatus are low cost and ease of operation.     

Thermal characterization of biomass smoke particles

In this paper we present results on characterization of filter-collected redwood (Sequoia sempevirens)-needle and eucalyptus smoke particles by thermal, optical, and solvent extraction methods. Our results show that black carbon and a significant fraction of organic carbon in biomass smoke particles have similar volatility and combustion temperatures. Combustion temperatures of both black carbon and this organic fraction critically depend on the concentrations of common constituents of biomass smoke such as Na and K. These species are also known to catalyze the combustion and therefore lower the combustion temperatures by more than 100 °C. Consequently, thermal methods that rely on a specific temperature to separate organic from black carbon may either underestimate or overestimate the black and organic carbon concentrations, depending on the amounts of Na and K and on the composition and concentration of organic material present in a sample. These results suggest that more than one method must be used to accurately determine the organic and black carbon concentrations in biomass smoke particles.     

Versatile Use of Carbon Dioxide in the Synthesis of Carbamates

Summary. Organic carbamates classically have been synthesized using harmful and toxic reagents like phosgene, its derivatives, and carbon monoxide. Recently, carbon dioxide was used as a cheap and harmless reagent for the synthesis of organic carbamates in the gaseous or supercritical state, or in an electrochemical process, or organic carbonates as sources of carbon dioxide as an alternative to the harmful reagents. The present review will deal with the extensive use of carbon dioxide in the synthesis of organic carbamates.     

Size-exclusion chromatography with organic carbon detection using a mass spectrometer

A novel organic carbon detector for size-exclusion chromatography (SEC) is described. The instrument uses the conventional UV-persulfate oxidation method to convert organic carbon to CO(2), which is then detected using a mass spectrometer. This system, using the mass spectrometer, had lower limits of detection (LOD) and limits of quantification (LOQ) than a previously described system using a Fourier transform infrared (FTIR) spectroscopy 'lightpipe' detector (i.e. when quantification was based on calibration using phthalate standards). When used to analyse natural organic matter (NOM) in water, it also had a superior signal-to-noise ratio to the previously described system. The use of a mass spectrometer to detect organic carbon (as CO(2)) enables the possibility of further characterisation of NOM by measuring the stable carbon isotope ratios of the various molecular size fractions of organic carbon, as obtained by SEC.