X射线荧光光谱法测定合金中钨的含量

采用X射线荧光光谱法测定了多种含钨合金钢以及含钨较高的镍基和钴基合金中钨的含量。方法中选择钨的Lβ1线为分析线,并选择2θ角在39.50°处作为背景位置。在合金中钽的Lβ2线对钨分析线有重叠干扰,选两套标准样品用基本参数法(FP)测出了干扰系数k,将k值列入仪器的FP工作软件中来消除钽对钨测定的重叠干扰。用所提出的方法分析了钨质量分数在0.054%～11.71%内的5个标准样品,测定值与认定值相符,测定值的相对标准偏差(n=7)在0.55%～9.5%之间。     

X射线荧光光谱法测定3类合金中的钽量

应用X射线荧光光谱法测定了镍基、钴基和铁基合金中质量分数在0.1%~8.50%范围内钽的含量。综合考虑,选择钽元素的Lβ1线作为分析谱线,并选择背景位置2θ为39.50°。在上述3类合金中常含有的铌(其Kβ1线)、铪(其Lβ2线)和钨(其Lβ4线)与钽的Lβ1线有重叠干扰,影响钽的测定。用合适的标准样品分别计算出上述3种元素对钽的重叠干扰系数K,并借助仪器的FP-工作软件用基本参数法消除这3种元素对钽测定的干扰。用所提出的方法分析了钽质量分数在0.015%~4.81%之间的11个标准样品或已知样品,测定结果与认定值或已知值相符。其中2个样品测定值的相对标准偏差(n=7)分别为0.46%(wTa=4.278%)和9.9%(wTa=0.020%)。     

X射线荧光光谱分析中谱线重叠校正系数的测量

应用整套标准样品法和基本参数(FP)法计算谱线重叠校正系数(K)效果较好。应用整套标准样品法需选用与被测样品具有相同基体和近似组成的标准样品;由于共存组分的谱线重叠的干扰常导致校正曲线产生较大的负截距,需通过多次迭代计算消除截距而使曲线通过原点,因为只有这样得到的K和M才是真值。实践中常有一些例子不能用整套标准样品法计算K值,例如钢中测定低含量铬时受到钒的重叠干扰问题。在此实例中除了钒对铬的谱线重叠干扰之外,还有仪器通道材料的干扰,此时,必须先用瑞利散射校正法消除此干扰后,选用铁基的标准样品,用FP法计算K值,可消除钒对铬的谱线重叠干扰。     

X射线荧光光谱法同时测定铁矿石中的主次量组分

采用熔融玻璃片制样,选用标准样品,以经验α系数和散射线内标法校正元素谱线重叠干扰和基体效应,使用ZSX Primus ⅡX射线荧光光谱仪对铁矿样品中的TFe、CaO、MsO、A12O3、SiO2、P205、TiO2、MnO、V2O5等组分进行测定,分析结果与标准值和化学值相吻合,12次测定的相对标准偏差小于10％．     

X射线荧光光谱法同时测定煤焦灰分中主次组分

采用玻璃熔融法制样,选用标准样品及其与其他标准样品的混合物制作工作曲线,并以经验α系数校正元素重叠干扰和基体效应,用X射线荧光光谱法对煤焦灰分中的二氧化硅、氧化钙、氧化镁、氧化铝、氧化锰、二氧化钛和氧化亚铁等7种主次组分进行测定。该法分析结果与化学法测定值相符;对同一样品测定6次,各组分测定值的相对标准偏差在0.11%～5.8%之间。     

X射线荧光光谱法同时测定矿石中钨钼锡

提出了X射线荧光光谱法同时测定钨钼锡矿石中钨、钼、锡元素含量的分析方法。方法选择四硼酸锂作熔剂,熔融制成样片,通过PW2403型X射线荧光光谱仪自带Super Q系统软件,以经验α系数法和Rh康普顿散射线内标法校正基体效应。以标准样品建立工作曲线,同时测量样品中钨、钼、锡元素含量。方法准确度和精密度能满足规范要求,钨、钼、锡的分析方法检出限分别为0.0042%、0.0026%、0.0072%。采用本法同时测定矿石中钨、钼、锡元素含量结果与传统分析方法测定结果相吻合,样品检测结果能满足矿区地质勘查的工作要求。     

电感耦合等离子体原子发射光谱法测定铝锰铁中硅和磷

采用电感耦合等离子体原子发射光谱法测定铝锰铁中硅、磷的含量。选择178.242nm和251.611nm作为磷、硅的分析谱线,可消除谱线的重叠干扰。使用与分析样品基体相接近的标准样品和相同的测定条件,可克服物理干扰,并比较了酸、碱熔样方式对待测元素的影响。本法已应用于铝锰铁样品中硅、磷的测定,对照试验测定结果的相对标准偏差(n=6)不大于7.0%。     

熔融制样–X射线荧光光谱法同时测定铀钼矿中主次成分

采用混合熔剂熔融制样,建立了同时测定铀钼矿中U,Mo,SiO_2,Fe_2O_3,Al_2O_3等的X射线荧光光谱法。以Li_2B_4O_7–LiBO_2作为熔融试剂,NH_4NO_3作为样品的氧化剂,样品与熔剂的质量比为1∶10。除使用铀矿石国家标准物质外,主要选取人工混合校准样品及历年实验室比对的铀钼矿校准样品绘制成工作曲线。采用理论系数法校正样品的基体效应,用Br Kα,Zr Kα,U Lα,Ba Lα,Zn Kα谱线扣除相应元素的谱线重叠干扰。该方法各组分测定结果的相对标准偏差均小于2.0%(n=10);用标准物质验证方法的准确度,测定值相对误差在0.00~8.00%之间,与标准值基本吻合。该法应用于生产实验中,可以满足对铀钼矿准确、快速的测量要求。     

X-射线荧光光谱法(XRF)测定钼精矿中多种元素

详细论述了压片法及熔融片法测定钼精矿的分析条件。其中压片法通过大量采用同一矿区的生产样品经化学定值后作为校准样品建立校准曲线,因此粒度效应和矿物效应基本上可忽略。详细地讨论了元素之间谱线干扰、背景和脉冲高度选择。使用经验系数法校正基体效应,可准确测定钼精矿中的钼、硫、铁、铜、铅、锌等11种元素。在熔融片法中主要讨论了元素谱线的选择及其相互之间的干扰,经理论α系数校正后,可准确测定不同钼矿中的多种元素,其适用范围更广。     

X射线荧光光谱法测定黏土中的主次组分

采用熔融玻璃片制样,选用标准样品,以经验α系数和散射线内标法校正元素谱线重叠干扰和基体效应,使用ZSX Primus Ⅱ X射线荧光光谱仪对黏土样品中的Al₂O₃、SiO₂、Fe₂O₃、CaO、MgO、K₂O、Na₂O、MnO、P₂O₅、TiO₂、Cu、Cr等组分进行测定,分析结果与标准值和化学值相吻合,12次测定的相对标准偏差小于10%.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.