自组织人工神经网络在氟化物非晶态形成的判别条件中的应用

本文运用Ｔ．Ｋｏｈｏｎｅｎ自组织人工神经网络，利用化学健参数法，研究了三元系氟化物非晶态形成的判别条件，建立了相应的计算法判别智能软件．识别成功率较高．结果表明，该方法性能良好，可望成为研究化合物非晶态形成条件的有效的辅助手段．     

自组织学习联想神经树在氟化物非晶态形态的判别条件中的…

运用自组织学习联想神经树，利用化学键参数法，研究了三元系氟化物晶态形成的判别条件，建立了相应的计算机判别智能专家系统，对３个未知样本进行判别，分类结果正确。该方法可望成为研究化合物非晶态形成条件的有效辅助手段。     

遗传程度设计在氟化物非晶态形成的判别条件中的应用

遗传程度设计在氟化物非晶态形成的判别条件中的应用蔡煜东，许伟杰，陈念贻（中国科学院上海冶金研究所上海２０００５０）关键词氟化物，非晶态形成条件，遗传程序设计近几年来，随着遗传程序设计［１］的理论及应用的不断进步，该方法被逐渐应用于模式识别、优化控制、...     

电沉积非晶态铁—铬合金镀层的研究

本实验通过控制镀液组成和操作条件获得了非晶态铁－铬合金镀层，实验分析了ＰＨ值，电流密度以及镀层中铬含量对所形成镀层的非晶态结构的影响，阳极极化曲线测量结果表明，与晶态层相比，非晶态度层具有较高的耐蚀性。     

以次磷酸镍为原料制备NiP和NiPB非晶态合金的新方法

以次磷酸镍为原料用化学还原法制备出了NiP和NiPB非晶态合金.用ICP、XRD和TEM等方法对催化剂物性进行了表征.研究了制备条件，如原料浓度、温度、pH值及引发剂的加入对制备NiP非晶态合金的影响.在300 K下所制备的NiP非晶态合金平均粒径约为30 nm.研究了原料浓度与原料配比对NiPB非晶态合金物性的影响，可通过改变原料浓度和配比得到所需组成的NiPB非晶态合金. NiPB非晶合金平均粒径约为15 nm.     

制备方法对NiP非晶态合金性质及催化活性的影响

分别使用三种方法制备了NiP非晶态合金：次磷酸钠还原镍盐（方法1）、次磷酸镍自分解（方法2）和使用有机胺调节溶液pH值的次磷酸还原镍盐（方法3）。研究了产品的物性，并以环丁烯砜加氢反应为探针检测了NiP非晶态合金的催化活性。研究结果表明，次磷酸钠体系制备的产品性质比较稳定，条件的改变对产物性质的影响不显著，催化活性一般在50%～60%之间；次磷酸镍体系中制备的样品显示出较高的催化活性，环丁烯砜转化率在90%以上；次磷酸体系制备样品的性质对条件变化较为敏感，催化剂的活性在70%～98%之间波动。发现方法2得到的NiP非晶态合金呈现为分散的完美的球形颗粒，且颗粒之间不存在聚集现象；使用方法3可以得到高比表面积的NiP非晶态合金。两种新方法所制备的NiP非晶态合金具有较小的粒径、较高的比表面积、较高的热稳定性和较高的催化反应活性。     

机械合金化Al—Ce非晶态合金

采用高能球磨使晶态的Al-Ce合金转化成了非晶态的Al_(96)Ce_4合金,并结合X射线衍射、热分析和透射电子显微分析研究了机械研磨时从晶态到非晶态的固相反应过程。同时,探讨了机械合金化形成非晶态合金的机制。     

电刷镀含钛合金非晶态镀层的晶化动力学(Ⅰ)

电刷镀技术在我国推广应用已有十余年的历史．作者在研究中发现，用电刷镀方法制备的含铁合金镀层具有非晶态固体结构，并且肯定添加剂的存在对非晶态的形成有举足轻重的影响＊．非晶态镀层属亚稳态材料，温度较低时结构和性能都相对稳定．而且稳定性衡量指标最简单的方法可采用玻璃转变温度L或开始晶化温度C来表示非晶态材料的稳定性·见或℃越高，其稳定性就越高风．也可用凸c一又Tg或晶化活化能E作为稳定性的参数”‘」．凸℃或B值越大稳定性就越高．而所有这些指标都可以用热分析方法直接测得．本文研究了一组采用相同化学组成，但其…     

非晶态金属合金作催化材料的研究I:N-P非晶态合金对苯乙烯加氢活性的研究

本文用X射线光电子能谱(XPS), X射线衍射(XRD)和连续微型反应器等方法研究了以骤冷法制备的Ni-P非晶态催化剂的表面结构和加氢活性。结果表明, 非晶态Ni-P对于苯乙烯催化加氢具有很高的反应活性, 优于晶态Ni-P, 更优于Ni片, 催化剂表面不同的预处理条件, 对反应活性影响很大。XPS结果表明, 在适当的预处理条件下, 非晶态Ni-P被部分氧化;随着氧化态被还原, 反应活性逐渐下降。     

非晶态金属合金作催化材料的研究I:N-P非晶态合金对苯乙烯加氢活性的研究

本文用X射线光电子能谱(XPS), X射线衍射(XRD)和连续微型反应器等方法研究了以骤冷法制备的Ni-P非晶态催化剂的表面结构和加氢活性。结果表明, 非晶态Ni-P对于苯乙烯催化加氢具有很高的反应活性, 优于晶态Ni-P, 更优于Ni片, 催化剂表面不同的预处理条件, 对反应活性影响很大。XPS结果表明, 在适当的预处理条件下, 非晶态Ni-P被部分氧化;随着氧化态被还原, 反应活性逐渐下降。     

Recent developments in the preparation of high surface area metal fluorides

An overview of the main procedures for the preparation of fluorides with very high surface areas is given. Three processes are outlined: (i) plasma fluorination, (ii) sol–gel route and (iii) oxidative decomposition of inorganic precursors. From all three processes nanostructured metal fluorides with 100–400 m² g⁻¹ can be obtained. Prevention of the local overheating during fluorination seems to be the key factor to obtain the high surface area fluorides. TEM investigations of AlF₃ and CrF₃ obtained by oxidative decomposition revealed considerable differences in their morphologies and crystallinity. CrF₃ is completely amorphous and unstable under beam. AlF₃ contains an amorphous phase and nanocrystalline phases of α-AlF₃ and β-AlF₃. Nanocrystals are uniformly distributed within the amorphous phase. Also present are the rod-like nanostructures that consist of β-AlF₃ and are 5–10 nm wide.     

Fast Ion Conducting Nanocrystalline Alkaline Earth Fluorides Simply Prepared by Mixing or Manual Shaking

Simple mixing or shaking of alkaline earth hydroxides with ammonium fluoride results in nanocrystalline phase pure metal fluorides MF₂ (M: Ca, Sr, Ba). The formation of the alkaline earth fluorides was investigated by varying the reaction conditions. Evidence was found that just the contact between the starting materials is sufficient for the reaction to take place. X‐ray diffraction, elemental analysis, ¹⁹F MAS NMR spectroscopy, and measurements of DC conductivities were used to characterize the fluorides regarding properties like crystal structure, crystallite sizes, local fluorine coordination, and fluorine ion conductivity. The ¹⁹F MAS NMR spectra of the phase pure fluorides prepared showed several signals, which were assigned to defects, impurities, or geometric distortions. The fluorides prepared by mixing or shaking revealed fluorine ion conductivities several orders of magnitude higher than observed for the respective microcrystalline alkaline earth fluorides. Therefore, the synthesis routine presented in this study may open a path to a very quick and simple synthesis of nanocrystalline fast fluorine ion conductors.     

Paradoxes and paradigms: observations on pyrohydrolysis,oxygen bomb combustion,and alkaline carbonate fusion,most frequently used decomposition methods for subsequent determination of fluorine and accompanying thermochemistry

Pyrohydrolysis, oxygen bomb combustion, and alkaline carbonate fusion are the most frequently used methods for decomposition of fluorine containing materials. The efficiency of these methods was proven by the determination of fluorine content in certified reference materials of clay and vegetation. Possible reactions proceeding during decomposition were suggested and accompanying thermochemistry discussed. The Gibbs energies were estimated to establish if suggested reactions are thermodynamically favorable or not. In addition, linear relationships between the enthalpies of formation of metal fluorides and the balanced values of the enthalpies of formation of the plausible reaction products (metal tungstates, metal oxides, or metal carbonates), electronegativity of metals, and number of fluorine atoms in metal fluorides were established. These equations were suggested for the estimation of the enthalpies of formation of metal tungstates, metal oxides, or metal carbonates, for which experimental data are not available.     

Systems of fluorides and bromides of lithium, sodium, and cesium with mono- and invariant monotectic equilibria

Phase diagram with mono- and invariant equilibrium were studied by differential thermal analysis by the example of a system of fluorides and bromides of group 1 s-block elements (lithium, sodium, and cesium). Bordering elements were studied, the quaternary reciprocal system Li,Na,Cs∥F,Br was partitioned into simplexes, and a tree of phases was constructed. The liquidi of the systems LiF-NaBr-CsBr and LiF-NaF-CsBr were constructed, the T-x diagrams of polythermal sections passing through phase separation regions were built, and phases being in equilibrium under specific thermodynamic conditions were described.     

Nucleation and growth of CaCO3 mediated by the egg-white protein ovalbumin: a time-resolved in situ study using small-angle neutron scattering

Mineralization of calcium carbonate in aqueous solutions starting from its initiation was studied by time-resolved small-angle neutron scattering (SANS). SANS revealed that homogeneous crystallization of CaCO 3 involves an initial formation of thin plate-shaped nuclei which subsequently reassemble to 3-dimensional particles, first of fractal and finally of compact structure. The presence of the egg-white protein ovalbumin leads to a different progression of mineralization through several stages; the first step represents amorphous CaCO 3, whereas the other phases are crystalline. The formation and dissolution of the amorphous phase is accompanied by Ca (2+)-mediated unfolding and cross-linking of about 50 protein monomers showing the characteristic scattering of linear chains with a large statistical segment length. The protein complexes act as nucleation centers for the amorphous phase because of their enrichment by Ca (2+) ions. SANS revealed the sequential formation of CaCO 3 starting from the amorphous phase and the subsequent formation of the crystalline polymorphs vaterite and aragonite. This formation from less dense to more dense polymorphs follows the Ostwald-Volmer rule.     

Synthesis of acylphosphine sulfides by rhodium-catalyzed reaction of acid fluorides and diphosphine disulfides

A rhodium complex catalyzed the reaction of acid fluorides and tetraethyldiphosphine disulfide giving acylphosphine sulfides. Aromatic acid fluorides with electron donating p-groups reacted smoothly giving the products in high yields. Aliphatic acid fluorides with secondary and tertiary α-carbons were also converted to alkanoylphosphine sulfides, whereas the reaction of a substrate with an α-methylene carbon was accompanied by enol ester formation.     

Phase equilibria in the cutting elements LiF–KCl–Li<Subscript>2</Subscript>WO<Subscript>4</Subscript> and LiF–KCl–LiKWO<Subscript>4</Subscript> of the quaternary reciprocal system Li,K‖F,Cl, WO<Subscript>4</Subscript>

The quaternary reciprocal system comprising fluorides, chlorides, and tungstates of lithium and potassium was partitioned into simplexes using graph theory, and a phase tree of the system was constructed. In the cutting triangles LiF–KCl–Li₂WO₄ and LiF–KCl–LiKWO₄ by differential thermal analysis, the melting points and compositions of ternary eutectics were determined, and the crystallization fields of phases are delineated. For each element of the state diagram, phase reactions were described. The compositions of crystallizing phases in the cutting triangles LiF–KCl–Li₂WO₄ and LiF–KCl–LiKWO₄ were confirmed by X-ray powder diffraction analysis.     

Nanocomposite ta-C films prepared by the filtered vacuum arc process using nanosized Ni dots on a Si substrate

Recently, structural manipulation of tetrahedral amorphous carbon (ta-C) film at the nanometer scale has attracted much attention. We demonstrate a novel method to obtain a nanocomposite film where nanoscale columns of graphitic phase are embedded in a tetrahedral amorphous carbon matrix. When using a Si substrate with nanosized Ni dots on the surface, graphitic columns grew selectively on the Ni dots, while a dense ta-C film was deposited on the bare Si surface. The growth of the graphitic columns is closely related to the nanosized Ni dots that catalyze the graphitic-carbon formation in a filtered vacuum arc deposition condition.     

Thermochemistry of some mono-substituted iodine fluorides and a comparison of gas and solid phase structures

The heat of formation of iodine trifluoride, obtained from an ab initio calculation of its heat of dismutation to mono- and penta-fluorides, was close to their average value. The mean bond dissociation energies of these iodine fluorides is almost invariant. The reduction couples between penta and trifluoro, or tri and mono-fluoro compounds, were employed to calculate formation heats of phenyl and trifluoromethyl iodine fluorides via similar isodesmic reactions. The substituted derivatives were stronger oxidants than the unsubstituted iodine fluorides as quantified by their redox couples. Similarly the corresponding chloro-fluorides were stronger oxidants than the iodo-fluorides. Heats of formation of other iodine fluoride derivatives can be obtained by additivity methods. Recent X-ray structures, when compared with calculated gas-phase structures, showed a lesser tilt of axial I-F bonds to the vertical in the solids probably due to intermolecular association. Rotational barriers around C-I bonds were small enough to permit almost free rotation at ambient temperatures.