涂层石墨管的制备和应用——铝合金中锡的测定

本文研究了各种涂层石墨管的制备方法和应用效果,提出了用超声浸渍法处理石墨管,大大地缩短了处理时间,效果良好。用涂层管测定锡,灵敏度和精密度都得到提高,应用于铝合金中锡的测定,结果较满意。     

平台石墨炉原子吸收法测定环境样品中锡

石墨炉原子吸收测定锡的方法具有灵敏度高取样量少的优点,目前已被广泛地应用,但锡易与石墨管表面反应及锡的硫化物和氧化物的易挥发性质,使测定方法存在着原子化效率低,基体干扰严重和测量再现性差等问题。许多作者研究将石墨管表面涂层改性处理,期望提高锡原子化效率及再现性,用基体改进剂硝酸铵,抗坏血酸和磷酸二氢铵消除或降低基体干扰。近几年发展的L＇vov平台技术的应用,对某些元素在提高灵敏度和改善基体干扰方面已获得良好效果。     

衬钽石墨炉原子吸收分光光度法测定水中痕量钡

石墨炉原子吸收分光光度法广泛地应用于痕量分析,但常局限于测定低温和中温元素。相当多的元素与石墨管形成稳定的碳化物,测定灵敏度低,常伴有记忆效应,石墨管也易损坏。钡属于形成碳化物的元素之列,而且特征波长在可见区,石墨管在高温下的背景发射影响测定。为了克服碳化物的影响,通常采用以下解决办法。常用的碳化物涂层法,虽然文献报导较多,但处理过程比较麻烦,而且结果重现性差,对钡的效果并不明显。也有使用热解石墨管测钡的,灵敏度有不同程度的提高。用金属原子化器。测定钡,灵敏度有所提高,但在通常的石墨炉上直接采用有一定的困难。还有在标准石墨管中衬入高熔点的金属     

涂层平台技术用于石墨炉原子吸收光谱法测定矿石中痕量金

关于改善石墨炉原子吸收光谱分析特性已有不少报导,其中以平台原子化技术和以难熔碳化物形式涂覆于石墨管表面的涂层技术具有成本低、简便易行的特点。本文则以氯氧酰锆涂覆处理平台(即涂层平台技术),不但解决了石墨管性能差异所引起的灵敏度差别,同时提高了灵敏度、稳定性,延长了石墨管使用寿命。本法用于矿石中痕量金的测定,灵敏度(特征浓度)为0.0004微克/毫升(1%吸收),变异系数小于10%。适用于地质样品中0.001～     

基体改进效应石墨炉原子吸收测定环境和生物样品中镓、铟和铊

本文研究了环境、地质及生物样品中镓、铟、铊的测定条件,试验了各种金属盐类、有机化合物及各种金属碳化物涂层石墨管对测定镓、铟、铊的基体改进作用,确定了每一个待测元素的最佳基体改进剂体系。实验表明:镍的存在可使镓的允许灰化温度由900℃增至1200℃,灵敏度提高6倍。     

热解石墨涂层石墨管在石墨炉原子吸收中的应用

热解石墨涂层石墨管在WFD-Y_3型原子吸收分光光度计上试用,经试验证明:采用2000℃或2109℃沉积温度,涂层厚度0.18—0.21毫米之间的热解石墨涂层石墨管使用寿命很长、重现性好、稳定性好。对高温元素如希土等使用热解石墨涂层石墨管的灵敏度比未涂层石墨管提高十倍左右。石墨炉原子吸收法是无火焰原子吸收分光光度法中最有前途的方法。环化所研制的Y_3型石墨炉能在4秒内升温到3000℃以上,为高温元素的分析打下了良好的基础。当时我们使用的石墨管是用哈尔滨电碳厂生产的高强,高密、高纯石墨制成。我们使用竖向表皮层来车制石墨管,其余部位不能使用,但这和石墨管分析高温元素时寿命不长。L＇vov等人指出,热解石墨就下述特性优于普通石墨:高的升华点;较强的抗氧化性能     

钨钽石墨管原子吸收光谱法直接测定土壤中痕量钕和钪

本文采用一种新型石墨管原子化器—钨钽石墨管,测定钕和钪。与普通热解涂层石墨管相比,灵敏度提高五倍多,1％吸收灵敏度钕为3.2×10~(-10)克,钪1.0×10~(-11)克;消除了记忆效应,提高了工作效率;原子化温度降低100多度,管的使用寿命延长1～3倍,达200次以上,测定精密度在5％以内;抗基体元素的干扰能力较好。土壤中20ppm以上的钕和200ppb以上的钪无需预分离富集,可以直接测定,结果与中子活化法一致。该方法简便、准确。     

缝管原子捕集法中的原子化机理

本文用Ｘ射线衍射分析法研究了１１个元素在开缝石英管中原子捕集与释放机理。Ａｇ和Ｂｉ以金属形式被捕集，而Ｃｄ、Ｃｕ、Ｉｎ、Ｎｉ、Ｓｂ、Ｚｎ、Ｐｂ、Ｃｏ、Ｇａ则以氧化物或硅酸盐形式捕集。这些元素在放时直接从熔融物蒸发原子化。５％乙醇或丙酮能提高大多数元素的灵敏度。大多数元素在Ａｌ２３涂层管上的灵敏度较高，在Ｌａ２Ｏ３涂层管上的检出限较低，精密度较高。     

恒温炉中加热管材料对灵敏度的影响

恒温炉中加热管石墨表面结构和物理性质,直接影响分析试样的原子化行为。目前,利用热解涂层石墨管改善原子吸收分析灵敏度,已被人们重视并广泛应用^[1-2]。本文采用Woodriff炉做原子化器,对Al、K、Ag、Cd在普通石墨管和玻璃碳管中的原子化行为进行了研究,结果四种元素在玻璃碳管中的灵敏度均获得提高。     

镧涂层表面效应初探

本实验通过对涂镧石墨管和非涂镧石墨管的电子显微分析，证实了镧涂层并未能对石墨管壁的孔洞起到有效的填充作用，这与测定金时吸收信号未明显变化的实验现象相吻合。通过对锡原子化前后石墨表面的Ｘ光电子谱分析，尝试提出了镧在管中的催化作用及影响某些元素原子化机理、从而改变其灵敏度的观点。     

Electrothermal atomization of arsenic,antimony and thallium using a graphite atomizer with refractory metal platforms

The electrothermal atomization of the volatile elements arsenic, antimony and thallium from a refractory metal platform consisting of a tungsten coil and/or a refractory metal foil with the dimensions of a conventional graphite platform was studied. Several combinations of refractory metal platforms were investigated, as follows: W platform; Ta platform; W coil; W coil on a W platform and W coil on a Ta platform. The best combination for these elements as regards both thermal stabilization and sensitivity is the W coil on a Ta platform. Thermal stabilization is also achieved with a W coil on a W platform. The presence of Pd-containing chemical modifier favors the thermal stabilization of the analytes. The sufficient amount is 2 micrograms of Pd. The maximal temperatures of pyrolysis are higher (arsenic, antimony) or equal (thallium) to those when using different chemical modifiers, added as solutions. It may be concluded, that the refractory metal platforms act as "built-in modifiers". They are suitable for the determination of arsenic, antimony and thallium in samples of complex matrix composition where high thermal stability of the analytes during the pyrolysis step is required.     

不同表面石墨管测定比较及采用WPGT直接测定水系沉积物及煤飞灰中的钇

本文采用自制的钨金属表面石墨管(WPGT)测钇,并与其它石墨管进行了比较。WPGT测钇灵敏度高,为PGT的340倍,重现性好,抗干扰能力强,可用于水系沉积物等样品中钇的直接测定。     

Application of gamma radiolysis of water for H2 production

The present work is devoted to the investigation of the effective use of radioactive waste for H₂ production by g-radiolysis of water, through both experiments and simulation. We have suceeded in improving the efficiency of hydrogen production by g-radiolysis of water via the conversion of g-rays to lower energy electrons and photons by introducing high Z metals, such as Ta, Pd, W and Pb, into water. We have also used exothermic hydrogen occluders like Ta and Pd to absorb the produced hydrogen, suppressing recombination of hydrogen to water. Surface oxidation which must be avoided, was also prevented using Pd.     

Ti and Ni tubes combined in thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) for the determination of copper in biological samples

This study presents an evaluation of Cu determination in thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) using Ni and Ti metal tube atomizers. The TS-FF-AAS system was equipped with Ti tubes inserted inside Ni tubes (called Ni/Ti), and also different configurations of Ti tube atomizers placed on an oxidizing air/acetylene flame. This new arrangement combining both tubes permitted an increased sensitivity (approximately 4 times) when it was compared with single Ni or Ti tubes. This high sensitivity is due to the formation of TiO₂ inside the Ti tubes (shown by X-ray diffractometry and microanalyses), improving the Cu atomization through the corresponding oxide. The estimated gaseous phase temperatures for the tubes (Ni, Ti and Ni/Ti) were of the same magnitude (varied from 1400 to 1800 °C). Tests with concomitants (Na, K, Ca and Mg) showed similar behavior of Ni and Ni/Ti tubes. The differences between Ni and Ni/Ti tube atomizers for Cu sensitivity were not related to differences between the tube atomizers' internal volumes. The method accuracy was verified using certified reference materials (CRM's) of biological samples prepared with a closed-vessel microwave system using diluted HNO₃. A 2 µg L^− 1 Cu detection limit was obtained using a Ni/Ti tube atomizer. The recoveries for Cu from the CRM's were about 100%. Finally, the use of a Ti tube inside a Ni tube increased the Ti tube lifetime.     

Relative sensitivity coefficients for the analysis of steel by spark-source mass-spectrometry

Quantitative analysis by spark-source mass-spectrometry requires the knowledge of socalled sensitivity coefficients for the elements being determined. Five series of analyses have been carried out on five different steel standard reference materials (NBS-SRM 661-665), using photoplate detection. The relative sensitivity coefficients (S(R)) of Ti, V, Cr, Mn, Co, Ni, Cu, As, Zr, Nb, Mo, Sn, Sb, La, Ta and W were determined vs. iron as an internal standard. The S(R) values were independent of the elemental concentration. A relative standard deviation of about 15% was obtained. The accuracy as confirmed by comparing the results for a pure iron sample with those obtained by neutron-activation analysis was within the same limits.     

Emission of secondary ions from 3d, 4d, and 5d transition metals under chloro-trifluoro-methane CClF3 as reactant gas

Surface interactions of CClF₃ with polycrystalline samples of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, Rh, Pd, Ag, Ta, W, Re, Ir, and Pt were investigated by means of moderate dynamic SIMS. As observed with other reactant gases these transition metals in most cases appear to be discernible into “dissociative” and (partial) “molecular” adsorbents. Small signals of oxidic secondary ions which are detectable for residual gas conditions vanished under the action of CClF₃. However, due to strong polarization by either of the halogens, the emission of Me²⁺ ions is enhanced for Ti, V, and Nb.     

Accuracy of analysis of steels by use of a spark-source mass spectrometer with electrical detection

The precision and accuracy of spark-source mass spectrometry with electrical detection has been studied, with five steel standard reference materials (NBS-SRM 661-665). Two different modes of analysis have been evaluated, magnetic scanning with electrical detection of the individual ions in sequence, using the total ion-current as reference, and magnetic switching between masses, with current integration. Measurements of isotope abundances have been used to evaluate the precision. The relative sensitivity coefficients of Ti, V, Cr, Mn, Co, Ni, Cu, As, Zr, Nb, Mo, Sb, La, Ta and W have been determined vs. iron as an internal standard. The accuracy of analyses based on these experimentally measured relative sensitivity coefficients was confirmed by comparing the results for a pure iron sample with those obtained by neutron-activation analysis.     

Ti/Pd bimetallic systems for the efficient allylation of carbonyl compounds and homocoupling reactions

The allylation, crotylation and prenylation of aldehydes and ketones with stable and easily handled allylic carbonates is promoted by a Ti/Pd catalytic system. This Ti/Pd bimetallic system is especially convenient for the allylation of ketones, which are infrequent substrates in other related protocols, and can be carried out intramolecularly to yield five- and six-membered cyclic products with good stereoselectivities. In addition, Ti/Pd-mediated reductions and Würtz-type dimerisation reactions can be readily carried out from allyl carbonates and carboxylates.     

ICP-OES 法测定高温合金中的多种化学成分

采用电感耦合等离子体光谱法（ICP－OES）测定了镍基高温合金中的Zr、Mo、W、Ta、Nb、Ti等多种化学成分。选择仪器最佳工作条件,研究了镍基体对被测元素的影响。方法的回收率为95．3％－102％,RSD为0．40％－1．7％。     

Electronic Structure of TiAl-2M(M=V,Nb,Ta,Cr,Mo,W,Mn) Alloy

1INTRODUCTIONTitaniumaluminidesbasedonY-TiAlarereceivingconsiderableattentionaspo-tentialcandidatesformaterialsinhightemperatureaerospaceapplication.Theirlowdensity,hightemperaturescreepresistance,highoxidationresistanceandstrengthmakesthemexcellentpotentialenginematerials.Howevertheirlowductilityandlowfracturetoughnessatroom'temperaturesaremajorhindrancestotheirpracticaluti-lization.TheTiAlalloymayhaveanelongationabout2%t'},furtherimprovementisnecessarybeforethesematerialscouldbeusedin…