碱性基团在介孔分子筛上的表面功能化反应

采用3种硅偶联剂——γ-氨丙基三乙氧基硅烷(AM)、γ-乙二胺丙基三甲氧基硅烷(ED)和γ-哌嗪丙基三乙氧基硅烷(PZ)分别与分子筛表面的硅羟基反应,对六方和类六方纯硅介孔分子筛SBA-3和HMS进行了表面功能化。系统地考察了功能化条件,如偶联剂用量、样品含水量、功能化反应温度、功能基团的大小等对功能分子的负载量及其表面联接程度的影响。结果表明,硅偶联剂用量的增加、反应温度的升高以及母体样品含水量的加大都有利于功能分子的表面锚接。反应条件相同时,SBA-3和DDA-HMS上不同功能分子负载量的顺序为:ED>AM>PZ;而ODA-HMS上AM的负载量却与ED的负载量相近。     

ArF准分子激光立方氮化硼薄膜的制备

采用ＡｒＦ准分子脉冲激光沉积方法（ＰＬＤ），以六方氮化硼（ｈ－ＢＮ）作靶在Ｓｉ（１００）衬底上制备氮化硼薄膜。ＸＲＤ及ＦＴＩＲ透射谱测量表明生成的氮化硼薄膜是含有少量六方氮化硼结构的立方氮化硼（Ｃ－ＢＮ）．ＡＥＳ测量表明不同条件下生成的薄膜中Ｎ与Ｂ的相对含量是不同的，最大比例近乎为１：１，薄膜的维氏显微硬度ＨＶ最大值为１５８０ｋｇ／ｍｍ２。     

双散射信道条件下六边形多载波 调制系统的定时同步算法

 在双散射信道条件下,以时频平面上任一点处期望信号能量与脉冲间干扰能量以及加性噪声能量的信干噪比为目标函数,将目标函数取最大值的时刻作为六边形多载波调制系统的最优定时时刻,推导出最优定时时刻的迭代算法,得出信道平均时延可以作为近似最优定时时刻的结论,并提出一种频域近似最优定时同步算法.理论分析与计算机仿真结果表明,在双散射信道条件下与传统的定时时刻相比,最优定时时刻在信噪比为30dB时能够获得2~3dB的信干噪比增益,提出频域近似最优定时同步算法在存在载波频偏时估计的均方误差小于10^-4.     

准八面体CBN单晶的合成研究

通过对原料、触媒及合成工艺的研究,采用国产DS-029B型六面顶压机在4．2—5．3GPa,1350。1470℃的范围内,从hBN-单质触媒体系中合成出近乎完美的黑色八面体和截角八面体立方氮化硼单晶体。确定了该种形态的CBN晶体的生长区域。CBN晶体的尺寸在100—400μm,峰值粒度为125—150μm。对所得的晶体进行考察,发现这种CBN晶体结晶形貌发育比较完整、棱角尖锐、晶粒饱满,并且有较高的抗压强度。上述结果表明所用的单质触媒具有使CBN晶体均匀生长的能力,是一种合成CBN晶体的有效触媒,该种CBN晶体具有较好的破碎强度。     

Phenyl modification of Mn‐containing mesoporous silica and catalytic oxidation of toluene

BACKGROUND: Catalytic oxidation of toluene with dioxygen is a fundamental industrial technology because the oxidized products are important intermediates for many fine chemicals. In this study, phenyl modification was utilized to alter catalyst surface characteristics in order to enhance activity. RESULTS: Phenyl groups were successfully immobilized on the surface of Mn‐containing hexagonal mesoporous silica (HMS) through a one‐step synthesis route, as demonstrated by detailed characterization. As a result, the surface of the catalyst Ph? Mn? HMS was more hydrophobic with a water droplet contact angle of 96°. In the oxidation of toluene to benzoic acid with dioxygen under solvent‐free conditions, this new catalyst showed higher activity and selectivity than non‐organomodified Mn? HMS, and the conversion and selectivity increased by a factor of 40% and 9%, respectively. CONCLUSION: Modification of the catalyst surface with phenyl groups was an effective strategy to increase activity in the oxidation of toluene. Both conversion and selectivity were improved and this is linked to the hydrophobic character of the surface. This organic modification strategy may also be extended for oxidation of other hydrocarbons. Copyright © 2009 Society of Chemical Industry     

A NEW MINERAL——FLUORBRITHOLITE-(CE)

The new mineral fluorbritholite-(Ce)occurs innepheline syenite,marble xenoliths,sodalite syenite xenoliths andpegmatite dikes at Mont St.Hilaire,Quebec.It is associatedmainly with analcine,microcline,aegirine,zircon,biotite,Pyro-phanite,astrophylite,ancylite,natrolite,monazite etc.The mineral is hexagonal,P6_3/m,with a 9.517 (5) (?),c 6.983(4)(?),c/a 0.7337,v 547.7(8)(?),Z=2.The strongest Xray powder diffraction lines and their relative intensities(visual)are:2.851(100),2.821(30),2.753(30),1.970(20),1.969(30)(for MSH-3).Fluorbritholite-(Ce) crystal is shown prismatic.Its colouris pale yellow,tan,reddish-brown.Streak colourless to palebrown;Lustre adamantine;OPaque to translucent;Hardness 5;Brittle;Cleavage{0001}distinct;Fracture even to conchoidal;Density 4.66(1)(meas) or 4.66g/cm~3(calc.);Non-fluorscent.Optically umaxial(-),ω 1.792 (5),ε1.786(5) in Na light;Nonpleochroic.Electron microprobe analyses correspond to ((Ce_(1.69) La_(1.02)Na_(0.82) Nd_(0.44) Sr_(0.30) Ca_(0.17) Mn_(0.17) Y_(0.09) Pr_(0.06)     

GaN缓冲层对生长InN薄膜的影响

采用金属有机物化学气相沉积(MOCVD)方法生长六方相InN薄膜，利用氮化镓(GaN)缓冲层技术制备了高质量薄膜，得到了其能带带隙0.7eV附近对应的光致发光光谱(PL). 通过比较未采用缓冲层，同时采用低温和高温GaN缓冲层，以及低温GaN缓冲层结合高温退火三种生长过程，发现低温GaN缓冲层结合高温退火过程能够得到更优表面形貌和晶体质量的InN薄膜，同时表征了材料的电学性质和光学性质. 通过对InN薄膜生长模式的讨论，解释了薄膜表面形貌和晶体结构的差异.     

Iron Fibers Arrays Prepared by Electrodepositing in Reverse Liquid Crystalline

Ordered iron fiber arrays were electrodeposited on the surface of zinc foils using ＂FeSO4 solution-sodium caprylate-Decanol＂ 3-component reverse hexagonal liquid crystal as soft templates. The structure of the soft templates and the synthesized iron ,fibers were characterized by polarizing microscopy, X-ray diffraction （XRD）, scanning electron microscopy （SEM） and energy dispersive X-ray microanalysis etc. The experimental results shou that the synthesized iron fibers with a crystal phase grew up in the form of fiber clusters of about 200 nm along the direction perpendicular to the cathode surface. Each cluster was composed of several tens of fibers. The fibers had almost the same length of more than 10μm with a diameter of about 50 nm.     

乱层石墨结构的硼碳氮化合物在高温高压下的晶化与分相

以硼酸和三聚氰胺为原料,采用化学法制备了乱层石墨结构的B-C-N化合物.在5.5GPa、800～1500℃条件下对该化合物进行了高温高压处理.采用X射线衍射(XRD)、透射电子显微镜(TEM)以及电子能量损失谱(EELS)对所制备的样品进行了结构、形貌和成分分析.研究结果表明:在5.5GPa压力下,随着温度的升高,B-C-N化合物逐渐由乱层石墨结构转变为六方结构,在1200℃时,得到了结晶较好的六方B-C-N化合物,同时样品中含有少量的六方BN和非晶C.当温度高于1400℃,B-C-N化合物完全分解成六方BN和石墨.     

Controllable synthesis of elongated hexagonal bipyramid shaped La(OH)<Subscript>3</Subscript> nanorods and the distribution of electric property by off-axis electron holography

Rare earth oxides/hydroxides are important emerging materials owing to their unique properties. Shape-controlled synthesis of elongated hexagonal bipyramid shaped La(OH)₃ nanorods with different aspect ratios and trigram-shaped LaCO₃OH nanosheets was systematically carried out by controlling the reaction conditions. Hydrazine and polyvinylpyrrolidone (PVP) surfactants used in synthesis are assumed to play a key “dual-template” role in determining the aspect ratio and shape of the resulting nanostructures. Elongated hexagonal bipyramid shaped La(OH)₃ nanorods were found to grow along the preferred orientation [0001]. Six equivalent crystallographic facets, \((20\bar 20)\), \((02\bar 20)\), \((2\bar 200)\), \((0\bar 220)\), \((\bar 2200)\), and \((\bar 2020)\) lattice planes, were found to be exposed on the side surfaces on each nanorod as confirmed by combined transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) analyses. A double-polarization phenomenon was found to occur at the nanorod surfaces by employing off-axis electron holography, implying that the material could be used as an effective dielectric microwave absorber. La(OH)₃ nanorods with larger aspect ratios exhibit better absorption properties with respect to the maximum reflection loss and effective absorbing bandwidth. Thus, a novel method towards the reasonable design of bipyramid shaped La(OH)₃ nanorods exhibiting tunable microwave absorption properties is proposed based on our synthesis strategy.

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