225 resultados para 12-119_Site


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In this paper, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) were used to study the structure and compatibilization of poly(propylene) (PP)/nylon-12 (PA 12) blends. The compatibilizatio

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1:12 phosphomolybdic anion doped polypyrrole film electrode was characterized by in-situ UV-vis spectroelectrochemistry, X-ray photoelectron spectroscopy(XPS), scan electronic microscopy(SEM) and electron spin resonance(ESR) spectroscopy.

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在乙腈介质中合成了苯并-12-冠-4(简称B-12-C-4)和单环己基-12-冠-4(简称Cy-12-C-4)的六种希土配合物:RE(NO3)3·B-12-C-4(RE=Pr,Gd,Yb,Lu),RE(NO3)3·Cy-12-C-4(RE=La,Lu).研究了它们的IR及1HNMR性质,并测定了四种单晶的结构.用INDO法计算了Lu(NO3)3·B-12-C-4,Lu(NO3)3·Cy-12-C-4的电子结构.结果表明.B-12-C-4与希土的配合物稳定性按Pr,Gd,Yb,Lu顺序减弱,并且Cy-12-C-4与希土的配位能力大于B-12-C-4.发现冠醚分子通过自身不同程度的扭曲,改变冠醚环空穴的大小,实现与不同大小的希土离子的配位作用.

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研究了H_4SiW_(12)O_(40)·24H_2O(SiW_(12))在水、乙醇、乙酸、乙酸丁酯中在活性炭上的吸附得出,活性炭微孔结构对SiW_(12)在其表面的吸附起着分子筛作用。水溶剂化的SiW_(12)分子可顺利进入活性炭1.7nm左右的微孔,而其它溶剂化的SiW_(12)分子,则需较大的孔径。提出了SiW_(12)在活性炭表面吸附的微孔中孔扩散模型。

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本文用半经验量子化学方法MNDO研究了由联苯衍生物产生的[C12H8]2+双电荷离子的结构,讨论了其中的电荷定位和影响离子稳定性的因素,双电荷离子的两个电荷分别定位于两个苯环上,表明该离子是由联苯衍生物经两步反应产生。

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The title complex was prepared by reacting Yb(NO3)3 (12-crown-4) with 1, 10-phenanthiroline (hereafter phen) in acetone. It crystallized in the triclinic space group P1BAR with a = 10.095(5), b = 17.415(4), c = 8.710(2) angstrom; alpha = 92.45(2), beta = 115.83(3), gamma = 74.08(3)degrees and D(c), = 1.85 g cm-3; Z = 2. The metal ion in this complex is nine-coordinated to three bidentate nitrate ions, two nitrogen atoms of a phen and a water molecule. The crown ligand is hydrogen bonded to the coordination water molecule. The symmetry change of the crown ether is also discussed.

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A phosphomolybdic anion doped polypyrrole (PMo12O403- + PPy) film electrode has been prepared by electrochemical polymerization of pyrrole in an aqueous solution of 0.5 mol l-1 H2SO4 or 0.5 mol l-1 KNO3 containing PMo12O403- anions, and characterized by scanning electron microscopy and in-situ UV-visible spectroelectrochemical methods. The film electrode obtained is very stable upon potential cycling in acidic solution, but not in neutral solution. The catalytic effect of the film electrode on the reduction of ClO3- and BrO3- was studied.

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使用溶胶-凝胶法制备了平均粒径为20~150nm的Y_3Al_5O_(12)超微粉末。从凝胶至超微粉末的过程中,发生了较大的失重现象。纯相晶态的Y_3Al_5O_(12)超微粉末的最低生成温度为900℃。粉末平均粒径随着灼烧时间的增加而逐渐增大,随着灼烧温度的增加而显著增大。

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用蒸发溶液法从磷酸溶液中培养出两种形态的 KHoP_4O_(12)单晶,晶体结构测定表明是两种不同结构,即α型和β型。用 X 光衍射、显微镜、红外光谱和热分析方法研究了晶体的结构特性,并对结果进行了讨论。

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A vitamin B-12 chemically modified electrode (CME) was constructed by adsorption of vitamin B-12 onto a glassy carbon surface. The electrode catalyzes the electrooxidation of hydrazine compounds over a wide pH range. The electrocatalytic behavior of hydrazines is elucidated with respect to the CME preparation conditions, solution pH, operating potential, mobile phase flow rate, and other variables. When applied to liquid chromatographic detection of the analytes, the vitamin B-12 CME yielded a linear response range over 2 orders of magnitude, and detection limits at the picomole level. The vitamin B-12 CME offers acceptable catalytic stability in both batch and flow systems.

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来用连续加料法,以二元醇-KOH为引发剂合成一组不同组成的环氧乙烷-环氧丙烷无规共聚醚,并用核磁共振、红外光谱、示差扫描量热计和热失重等方法对其本体聚合物,用浊点和表面张力测定的方法对其水溶液,进行系统的表征。

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用差示扫描量热(DSC)和拉曼光谱方法考察了n-C_(12)H_(25)NH_3Br(DoAB)的固相性质,确定了DoAB固-固结构相变的温度及其焓变,通过6种状态下所对应的拉曼光谱讨论了相变过程中分子构象的变化。

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杂多化合物既有配合物和金属氧化物的结构特征,又有强酸性和氧化还原性。它是具有氧化还原和酸催化功能的双功能催化剂。另外,它还具有结构确定、再生速度快、活性高、不腐蚀设备和污染少等优点,被认为是继分子筛之后,最有研究价值和开发前景的催化剂之一。

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在所有众多结构的杂多化合物中,至今为止,具有Keggin结构的杂多酸(盐)是研究得最充分、也是唯一商品化了的杂多化合物。近年来,有许多关于Keggin结构杂多化合物作为催化剂的研究结果和应用报道。这些催化反应许多是在液相中进行的。由于杂多化合物易受酸碱影响而使结构改变或破坏,因此,反应体系中的酸碱度对杂多化合物结构的稳定性和催化活性都有明显作用。所以,研究酸碱对杂多化合物结构和催化性能的影响具有重要意义。本文考察了12-钨磷酸(盐)在苄醇氧化反应中的催化活性以及酸碱对催化活性的影响。