蒙脱土的价电子结构与其同晶置换

为研究蒙脱土结构与其性能的关系,根据蒙脱土的晶体结构,设定其结构单元,运用"固体与分子经验电子理论(EET)"对蒙脱土的价电子结构进行计算.研究表明:与理想蒙脱土相比,八面体中0.66个铝被镁同晶置换后蒙脱土结构单元的结合能基本不变,且与氧桥相连的四面体和八面体中主要键的共价电子分布差距变小;蒙脱土3个亚层之间的作用力比片层之间的分子间作用力大两个数量级,证明了蒙脱土的3个亚层结构稳定;在极性介质中可以改变蒙脱土片层间距,但其3个亚层不易分离.     

煤矸石质硅铝基材料胶凝机理的研究

系统地开展了利用低温煅烧煤矸石为主要原料制备早期强度高、水化热低且具有良好固土特性的硅铝基胶凝材料的基础研究.采用结构分析的方法,运用高分辨固体核磁共振、液体核磁共振和红外光谱等分析手段研究了煤矸石和高岭石在煅烧、碱介质中溶出和胶凝过程中硅、铝配位的变化,结合其胶凝产物的物相、形貌和水化热,从结构、配位和物相转变的角度来研究煤矸石质硅铝基胶凝材料胶凝机理.揭示了煤矸石的煅烧过程就是铝氧八面体中铝的四配位转化以及铝氧四面体和硅氧四面体解聚过程的重要规律,其中铝氧八面体中铝的四配位转化是煤矸石产生胶凝活性的本源.证明了煤矸石和高岭石在煅烧过程中铝配位的变化与地质界Thompson定律相吻合.比较研究了煤矸石和高岭石的活性与其结构之间的关系,发现低于900℃煅烧煤矸石的红外光谱中,560cm-1附近吸收峰的强度与Si、Al离子的溶出量具有正相关性;五配位铝是偏高岭石具有高活性的主要原因.证明了由于一价和二价阳离子的存在,以高岭石为主要矿物的煤矸石在煅烧过程中没有出现五配位铝.通过对硅铝质物料Si2p、Al2p和Ols结合能与其胶凝材料力学性能之间关系的研究,提出用硅、铝电子结合能评价硅铝物料胶凝活性的新方法.深入研究了不同介质条件下煅烧煤矸石的溶出特性及其胶凝机理.研究表明:煅烧煤矸石在碱性溶液中是以单聚体硅酸根离子和单聚体铝酸根离子的形式溶出;(HO)3SiO-和Al(OH)4-的溶出证明硅铝基胶凝材料反应初期是硅氧四面体和铝氧四面体的再解聚过程,体现在反应后,27Al和29Si NMR谱的共振峰向低场偏移;以硅酸钾为溶出介质,煅烧煤矸石溶出渣29Si MAS NMR谱中-97.36×10-6共振峰的出现揭示了硅铝基胶凝材料胶凝过程中原位键合的作用;随着反应的进行,27Al和29Si NMR共振峰都向高场偏移,表明胶凝过程中与中心铝原子在次级配位圈上直接连接[SiO4]四面体数量增多以及反应产物中硅氧四面体聚合度的增加.根据胶凝过程中硅、铝配位的变化,提出了硅铝基胶凝材料原位键合的反应机理,并将胶凝过程概括为解聚过程、胶结过程、原位键合过程和缩聚过程.     

Fe2BP3O12的合成及晶体结构

采用固态反应方法合成了有序的铁基硼磷酸盐Fe2BP3O12,用X射线粉末衍射方法精修了其晶体结构,属三方晶系,空间群为P3,a=8.02703(6)A,c=7.40168(9)A,V=413.02(1)A3,Dx=3.2758(1)(g/cm3),Z=2,对于55个参数,用188条衍射线及18001个衍射强度全谱数据点精修到R(I)=6.35%,R(p)=15.36%,所对应的R(dbw)=10.12%.B原子具有三角形氧配位,P和Fe的氧配位分别是四面体和八面体.Fe的两配位八面体共面形成新结构单元,BO3三角形联接磷氧和铁氧多面体形成三维结构.对比同构的铬硼磷酸盐,此化合物期望具有类似的非线性光学及其它非线性物理性质.     

含Nd镁铝合金电子结构计算与强化机制分析

基于EET理论,计算了Nd元素加入Mg-Al合金后形成的Mg-Al-Nd固溶体,第二相Al2Nd,Al3Nd价电子结构,研究了价电子结构与合金固溶强化、第二相强化、高温稳定性和晶粒细化的关系.Mg-Al-Nd最强键共价电子对数nA值和共价电子密度ρCV值均大于α-Mg的nA值和ρCV值,表明Nd的固溶有利于基体强度的提高;第二相Al2Nd最强键(nA=0.44396)与Al3Nd最强键(nA=0.38949)的键合强度均远大于基体α-Mg(nA=0.11199)的键合强度,因此,Al2Nd和Al3Nd极大地阻碍了位错的运动,提高了合金的强度;Al2Nd和Al3Nd的单位体积成键能力FV值分别为145.91和242.35,与γ-Mg17Al12(Fγ-Mg17Al12V＝44.22)相比较,它们的高温稳定性更好,其存在有利于改善Mg-Al合金的高温性能;Nd提高了液态合金中邻近原子间键合强度,增加了基体的形核率,减缓了晶粒长大速度,进而细化了晶粒,提高了合金的力学性能.     

溶剂热合成YAG反应机理研究

以铝和钇的水合物为反应前驱体,用乙二胺永溶液作为溶剂,在温和条件下合成了钇铝石榴石微粉.研究结果表明,其反应机理是随着温度升高,钇和铝的水合物逐渐溶解,200℃时发生脱水反应,并开始形成Al-O,Y-O键和四面体;220℃时开始形成Al-O八面体、Y-O多面体及Y-O-Al键,并梅成YAG兰维骨架成核;至280℃,YAG晶核不断长大,最终形成稳定的YAG晶相.     

热处理温度对溶胶凝胶Bi2O3-SiO2-B2O3系玻璃粉体结构的影响

采用溶胶-凝胶法制备了一种Bi2O3-SiO2-B2O3系玻璃粉体,在200~800℃温度范围内对凝胶玻璃进行热处理,通过多种表征手段研究了热处理温度对玻璃粉体网络结构的影响。结果显示,在试验温度范围内,粉体始终呈现玻璃态结构;随热处理温度升高,Bi3+逐渐进入玻璃网络中,[BiO6]八面体和[BiO3]三角体、[BO4]四面体和[BO3]三角体分别与[SiO4]四面体以顶角相连的方式构建玻璃网络结构;O1s可分为桥氧和非桥氧,O1s和Bi4f的电子结合能逐渐增大,B1s的电子结合能减小,玻璃网络结构稳定性增强。     

硼硅玻璃与硅阳极键合界面形成机理分析

对硼硅玻璃与硅进行了阳极键合实验,通过扫描电镜对键合界面的微观结构进行分析表明:玻璃/硅的键合界面有明显的中间过渡层生成;分析认为电场力作用下玻璃耗尽层中的氧负离子向界面迁移扩散并与硅发生氧化反应是形成中间过渡层的主要原因,而界面过渡层的形成是硅/玻璃界面键合实现永久连接的直接原因.     

一种用电晕放电仪实现PDMS改性与键合方法

聚二甲基硅氧烷(PDMS)的表面改性与键合是微流控芯片制作中的关键技术之一。本文比较分析了PDMS常用表面改性方法的优缺点,利用电晕放电仪在常温环境下产生的氧等离子体实现了对PDMS表面改性及不可逆键合,优化了电晕放电仪的表面处理参数,重点测试了PDMS分别与PDMS和PMMA之间的键合强度。并与紫外照射、表面活化剂等表面改性方法得到的键合进行了强度比较。键合强度测试结果表明:常温下氧等离子体表面改性效果略逊于真空环境中的氧等离子体表面处理,但是其键合强度达到700KPa,高于其它表面改性方法的键合强度。     

焙烧温度对CuO在γ-Al2O3载体上的分散和催化CO完全氧化性能的影响

采用浸渍法制备了经不同温度焙烧的CuO/γ-Al2O3催化剂,并通过BET、XRD、UV-DRS、H2-TPR以及CO完全氧化反应,研究了不同焙烧温度对CuO/γ-Al2O3催化剂中CuO组分的分散、还原和催化性质的影响.结果表明:当焙烧温度为450℃时,CuO在γ-Al2O3上的分散容量约为0.56mmol/100m2;当焙烧温度达到750℃时,Cu2 同时占据γ-Al2O3载体(110)面上的八面体和四面体空位.对于450℃焙烧的低CuO含量的样品,在H2-TPR结果中只观察到处于八面体空位的CuO物种的还原,而经750℃焙烧的样品则同时观察到处于八面体和四面体空位的CuO物种的还原,且处于八面体空位的CuO的还原会促进处于四面体空位的CuO的还原.处于八面体空位的CuO在CO完全氧化反应中的活性要高于处于四面体空位的CuO.     

铝镍改性膨润土的制备及在处理染料废水中的应用

膨润土是一种重要的非金属矿,主要由蒙脱石构成,体结构由两层硅氧四面体晶片中夹有一层铝氧八面体晶片组成。文章主要论述铝镍改性膨润土的制备以及在染料废水处理中的应用。     

Calculation of crystal cohesive energy of ZrB<Subscript>2</Subscript> compound

The valence electron structure (VES) of ZrB₂ was set up with the bond length difference (BLD) method based on empirical electron theory (EET) of solids and molecules, and there were 43 potential hybridization combinations. Based on the calculation result of the melting point, the 16th hybridization step of Zr atom and fifth hybridization step of B atom are ascertained as the final hybridization combination. Therefore, the covalent electron number and the bonding energy of the strongest bond (the B-B bonds), the theoretical melting point, and the crystal cohesive energy of the ZrB₂ compound can be figured out.     

Calculation of crystal cohesive energy of ZrB2 compound

The valence electron structure (VES) of ZrB₂ was set up with the bond length difference (BLD) method based on empirical electron theory (EET) of solids and molecules, and there were 43 potential hybridization combinations. Based on the calculation result of the melting point, the 16th hybridization step of Zr atom and fifth hybridization step of B atom are ascertained as the final hybridization combination. Therefore, the covalent electron number and the bonding energy of the strongest bond (the B-B bonds), the theoretical melting point, and the crystal cohesive energy of the ZrB₂ compound can be figured out.     

应用量子化学研究Ca_2Fe_（2-x）Al_xO_5的水化活性

用量子化学ＳＣＣ—ＤＶ—Ｘａ方法分析了Ｃａ_２Ｆｅ_（２-ｘ）ＡｌｘＯ_５体系中的Ｃａ_２Ｆｅ_２Ｏ_５（即Ｃ_２Ｆ），Ｃａ_２Ｆｅ_（１．４３）Ａｌ_（０．５７）Ｏ_５和Ｃａ_２Ｆｅ_（１．２８）Ａｌ_（０．７２）Ｏ５．认为它们的水化活性随Ａｌ的增加而提高的原因是：（１）Ａｌ的净电荷比Ｆｅ高，易吸收水分子的孤对电子；（２）Ａｌ-Ｏ键比Ｆｅ-Ｏ键弱，易断裂而容易与水反应．     

FeB和Fe2B价电子结构与钢表面渗硼层硬化本质

依据EET理论,计算了FeB和Fe_2B价电子结构并分析了它们与钢渗硼层硬化的关系。研究发现:渗硼表面改性后,钢表面硬度和耐磨性提高的根本原因在于FeB和Fe_2B最强键的键合力远大于基体α-Fe最强键的键合力;FeB的硬度比Fe_2B大的微观本质在于FeB相最强键的键合力、主键络连接键的键合力和共价电子密度分别比Fe_2B的大27.12%、4.8%和3.66%;FeB相比Fe_2B脆性大的微观本质在于FeB共价键空间分布更不均匀,FeB相主键络具有较强的共价性,而Fe_2B相主键络具有较强的金属性;由于FeB相成键能力仅比Fe_2B的成键能力大0.85%,因此优先形成的Fe_2B相极易转变为FeB相,使得钢表面渗硼层的脆性增强。     

Influence of bond defects on coiling of graphite

Abstract

The effect of annealing at 1400 ?C in argon on the bond structure of graphite ball milled for 100 h at 400 rpm in polar (water) and in non-polar (n-dodecane) liquids was investigated primarily by near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and transmission electron microscopy (TEM). Carbon K-edge NEXAFS allows the distortion of bonds in the hexagonal lattice to be investigated. It is shown that in-plane sp² bonds are strained and distorted after ball milling because sp³ bonds are introduced. Not surprisingly, annealing of the milled product restores sp² bonds but at the same time, coiling and formation of tube-like structures takes place. It is well established that graphite is not formed on annealing, and hence the results shown here demonstrate that the loss of sp³ carbons on annealing must proceed via a different mechanism by which they are formed by milling.     

Study Segregation of Alloying Elements in Continuous Casting Slab with Valence Electron Structure

By calculating the electron structures of the phases that phosphor, sulfur and alloying elements dissolving inγ-Fe, the reason why alloying elements can bring centerline segregation in continuous casting slab (CCS) with nA, the number of electrons on the strongest covalent bonds, and the structure formation factor S were investigated, and an electron structural criterion to control and to eliminate the centerline segregation was advanced. Basing on this, the electron structures of a part of rare earth phosphides and sulfides are calculated, the physical mechanism that rare earth elements can control the segregation of phosphor and sulfur is analyzed, and the criterion is well verified.     

Influence of bond defects on coiling of graphite

The effect of annealing at 1400 °C in argon on the bond structure of graphite ball milled for 100 h at 400 rpm in polar (water) and in non-polar (n-dodecane) liquids was investigated primarily by near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and transmission electron microscopy (TEM). Carbon K-edge NEXAFS allows the distortion of bonds in the hexagonal lattice to be investigated. It is shown that in-plane sp² bonds are strained and distorted after ball milling because sp³ bonds are introduced. Not surprisingly, annealing of the milled product restores sp² bonds but at the same time, coiling and formation of tube-like structures takes place. It is well established that graphite is not formed on annealing, and hence the results shown here demonstrate that the loss of sp³ carbons on annealing must proceed via a different mechanism by which they are formed by milling.     

八面体形状的重钼酸钠纳米晶的制备及生长机制

采用热蒸发方法,以红外烧结炉为制备仪器,在玻璃衬底上制备了空心的八面体纳米晶。利用扫描电子显微镜、X射线衍射谱、透射电子显微镜及选区电子衍射分析产物的形貌、尺寸、成分及结构,并对纳米晶的形成机理进行了探讨分析。     

TiC-Mo-Fe体系价电子结构的模拟计算

以EET理论为基础,通过建立TiC-Mo-Fe体系金属陶瓷结构模型,分别计算了陶瓷相TiC、环形相(Ti1-xMox)C和金属相Fe的价电子结构,并在此基础上计算了各相间界面原子状态的变化和界面结合情况,以及环形相理论晶格常数值.结果表明:环形相的存在能使金属/陶瓷两相原子状态的突变差异形成渐变过渡;计算获得的环形相的晶格常数对Mo的掺入量不敏感,在x取不同值时仅有很小的变化,相对误差不超过1.2%,环形相与TiC间的原子状态差异非常小,二者界面结合良好;环形相与Fe界面结合明显强于TiC与Fe的界面结合,并且当x=0.5时,这种界面结合最强.     

Correlation between graphite crystallite distribution morphology and the mechanical properties of carbon fiber during heat treatment

The growth mechanism for the graphite crystallites in polyacrylonitrile (PAN)-based carbon fibers, heat-treated at various temperatures, has been proposed. The evolution of distribution morphologies for graphite crystallites is investigated, in relation to variations in the tensile properties of the fiber samples. At high temperatures, dangling bonds are created via the cleavage of weak bonds, such as CN, CH and CC at the edges of the graphite crystallites. The graphite crystallites grow through the bonding reactions between different dangling or dangling bonds and agraphitic carbon atoms. This results in graphite crystallites that increase in size with elevated temperatures that lead to changes in graphite crystallite distribution morphology. Between 1400 and 2400 °C, the distribution morphologies of the graphite crystallites go though three states: (I) a dispersed state, (II) a network state, and (III) a transfixion state. The tensile strength decreased rapidly with increasing heat treatment temperature for fibers with a dispersed state structure, but lowers with fibers bearing a network state structure. The decrease was more rapid for fibers with a transfixion state structure. The tensile modulus increased slowly in states I and II, and rapidly in state III.