Structure and Property of AgLaY Alloy

The structure of RE-Ag alloy was observed and analyzed using electron probe. The property changes of the alloy containing two rare earth elements AgLaY during cold forming and the high temperature softening-resistance during annealing were studied using Vickers hardness tester. The distribution and action of the rare earth elements in Ag-alloy were also analyzed. Experimental results show that AgLaY alloy has more remarkable work-hardening effect than AgLa and pure silver, and it also has better thermal-resistance. The effects of RE elements, La and Y, on the properties of Ag-alloy are attributable to their symbiotic distribution and complementary function. Because of the common properties of La and Y as RE elements, they have the completely similar distribution in Ag-alloy. At the same time, La and Y make full use of complementary role in the alloy since they belong to different periods in periodic table and have differences in atomic structure and properties.

STUDY ON STRUCTURE AND PROPERTY OF Nb-DOPED TiC CERAMIC WITH QUANTUM CHEMISTRY CALCULATIONS

Nb-doped TiC ceramic,or (NbyTi1-y) Cx,in which amount of Nb element added is increased from zero to 40Wt. %, synthisized -with self-propagating high temperature synthesis,is studied with SCF-Xa-DV,a quantum chemistry cal-culating method. The chemical bonding is studied to discuss the relation between structrues and properties. Several classes of models in which there is no vacancy,one vacancy or two vacan-cies have been calculated. From the calculated results of bond or-der, a measure of covalent bond strength,and molecule orbital contour map, it is concluded that when Nb element added in-creases, the vacancies increase correspondingly,the covalent com-ponent of chemical bonds of the samples decreases -while the met-al-bonding component increases, so the hardness and resistance of the samples decrease.

Modificatin of ITZ Structure and Properties of Regenerated Concrete

By means of reducing the ratio of water to cement （ w/c ）, incorporating a proper amount of fly ash and superplasticizer , and processing the surface of recycled aggregate （ RA ）, this paper aims at improving the interfacial transition zone （ITZ） submicro- structure of the regenerated concrete （ RC ）. The experimental resuits of mercury intrusion pressure （MIP） show that RA pretreated by PVA polymer solution and lyophobic active agent can jam its surface pore and hole, thus the porosity of RA is decreased. When reducing w/c ratio, incorporating 20% of fly ash （ FA ） and 2.5% of superplasticizer （ to cement ） in the RC , the width of ITZ is effectively narrowed, the structure of ITZ is combined much more compact and the compressive strength of RC is enhanced. Under the same conditions, using RA pretreated by 1% PVA polymer solution, the fluidity of fresh RC can be enhanced and the compressive strength of hardened RC can also be enhanced lightly. Whereas using RA pretreated by lyophobic active agent, the fluidity of fresh RC can be enhanced , but it impairs the adhesion of fresh cement paste and the surface of old concrete, and hinders the strength development of RC. In the ITZ structure of ordinary concrete （prepared with natural coarse and fine aggregate ）, there are much Ca （ OH）2, in plank-and sheet-like, distributing with priority tropism, whereas in the RC structure, Ca（ OH）2 with a coarse size is not found in ITZ ; the main reason is that the surface of coarse aggregate does not have a layer of water film.

Structure and Chemical Bond of Thermoelectric Ce-Co-Sb Skutterudites

The correlations among composition, structure, chemical bond andthermoelectric property of skutterudites CoSb_3 and CeCo_5Fe_3Sb_12have been studied by using density function and discrete variation(DFT- DVM) method. Three models for this study were proposed andcalculated by which the 'rattling' pattern was Described. Model 1 iswith Ce in the center, model 2 is with Ce away the center and near toSb, and model 3 is Also with Ce away the center but near to Fe. Thecalculated results show that in model 3, the ionic bond is theStrongest, but the covalent bond is the weakest.

STRUCTURES,PROPERTIES AND QUANTUM CHEMISTRY STUDIES OF As-S-X(X=Cl,Br,I)AND As-Y-Br(Y=S,Se,Te)GLASSES

As-S-X (X = Cl, Br, I) and As-Y-Br (Y = Sd Se, Te) glasses are studied with Self-Consistent-Field Discrete Variational X(a)(SCF-DV-X(a)) tone of the molecule orbital calculating methods in quantum chemistry. The chemical bonding is studied to discuss the relations between structures and properties with the variations of compositions of the glasses. The calculated results show that the strength of covalent and ionic bonds are both in the order of As-S-Cl > As-S-Br > As-S-I as well as As-S-Br > As-Se-Br > As-Te-Br, it is consistent with the experimental result of the glass-transition temperature (Tg) of the corresponding glasses. The differences of chemical bond strength and Tg among As-S-X (X = Cl ,Br ?I) glasses a-re larger are larger than those among As-Y-Br(Y = S, Se, Te) glasses and the largest difference of chemical bond strength is that of ionic bond of As-X among As-S-X (X = Cl, Br, I) glasses,so the variations of X (X = Cl, Br, I), the end atoms on the chains in the glasses, play the more important role to affect the structure and property of the glasses.

THE EFFECT OF SILICON ADDITIVE ON THESTRUCTURE AND PROPERTIES OFC－B_4C－SiC COMPOSITE

A Preliminary study of the effect of silicon additive on the structure and properites of C-B_4C-SiC composite was conducted. A liquid Phase has formed and the liquid Si reacts with C to form SiC at the grain boundary when sintering, which accelerates the sintering process and retards the grain growth. Consequently, the density and strength of the composite increase markedly. And the increase in the density increases the oxidation resistance and decreases the specific resistance of the composite. Furthermore,the C-B_4 C-SiC composite has good heat-shock resistance. The phenomena may be dueto the strengthening and toughening of microcracks.

The Quantum Chemistry Calculation and Thermoelectricsof Bi-Sb-Te Series

The density junction theory and discrete variation method ( DFT - DVM) was used to study correlation between composition, structure, chemical bond, and property of thermoelectrics of Bi-Sb-Te series. 8 models of Bi20-xSbxTe32(x = 0,2,6,8,12,14,18 and 20) were calculated. The results show that there is less difference in the ionic bonds between Te( I)-Bi(Sb) and Te(Ⅱ)-Bi(Sb) , but the covalent bond of Te(Ⅰ)-Bi( Sb ) is stronger than that of Te(Ⅱ)-Bi( Sb ) . The interaction between Te(Ⅰ) and Te(Ⅰ) in different layers is the weakest and the interaction should be Van Der Wools power. The charge of Sb is lower than that of Bi, and the ionic bond of Te-Sb is weaker than that of Te-Bi. The covalent bond of Te-Sb is also weaker than that of Te-Bi. Therefore, the thermoelectric property may be imfiroved by adjusting the electrical conductivity and thermal conductivity through changing the composition in the compounds of Bi-Sb-Te. The calculated results are consistent with the experiments.

STRUCTURE,HYDRATION ACTIVITY & CHEMICAL BOND OF FERRO-ALUMINATE OF CENMENT

Structures and hydration activities of ferro-aluminates (Ca2Fe2-xAlxO5 ,x = 0.0. 57 and 0. 72) of cement minerals are studied by SCF-DV-Xa method. one of the molecular orbital calculating method in quantum chemistry. The calculated results of net charges, energy levels of molecular orbitals and covalent bond orders are all consistent with the increase of Al element, there is superior hydration activity of Ca2Fe2-xAlxO5.

STUDY ON HYDRAULIC REACTIVITIES AND CHEMICAL BONDS OF MINERALS OF SULPHOALUMINATE CEMENTS

Structures and hydraulic reactivities of minerals of sulphoaluminate cements, Ca4Al6SO16 and SrCa3Al6SO16, are studied by SCF-DV-X alpha method. The calculated results of net charges, energy level's of moleclar orbitals and bond orders all give support to the experimental result that the hydraulic reaction of strontium sulphoaluminate takes place more moderately, so its hydrate has better mechanical properties.

GRADIENT VARIATION OF COMPOSITION AND QUANTUM CHEMISTRY CALCULATION OF(Ti-Nb)C-Ni COMPOSITE

(Ti, Nb)C-Ni composite is prepared. The analyses of SEM, EPMA and TEM/EDAX show that (Ti, Nb)C-Ni consists of three phases,which are called interior, transitional and Ni phases respectively. Several models are calculated by self-consistent-field variational X alpha(SCF-DV-X alpha) method, one of the quantum chemistry calculating methods. The calculated results show that when Ni element increases, the bond orders (measures of strength of covalent bonding) of Ti-C and Ni-C in the models decrease correspondingly, which is to say that there is a gradient variation of the covalent bond in the transitional phase which is compatible with both the interior and Ni phases. It is beneficial for improving the mechanical properties of the materials.

Prediction of the Physical Properties for the Ionic Liquid Based on Topological Index

Based on the distance matrix and adjacent matrix of molecular structure, a novel topological index is proposed. A set of topological parameters is built to reflect the magnitude, shape and other structure information of the substance. The interdependency between new topological index and conductivity for alkylimidazolium cations was analyzed and a quantitative relationship to describe this interdependency was obtained using the linear analyzing method. The analysis results show that the proposed topological index is quite satisfied with higher precision of the prediction. From the molecular structure of ionic liquid, the value of conductivity can be predicted correctly. This method can be also used to predict other physical properties of the ionic liquid.

Irradiation Effect of γ Rays on Diamond-Like Carbon Films

Diamond like carbon films, prepared by RF glow discharge on glass substrates, were irradiated by γ rays. The as deposited and irradiated films were characterized by Raman spectroscopy, electrical resistivity, and infrared transmittance. It is shown that the irradiation of the γ rays can lead to the breaking of SP 3 C H and SP 2 C H bonds, slight increasing of SP 3 C C bonds, and induced hydrogen recombination with H 2 molecules, subsequently diffusing to the surface of the films. When the γ rays irradiation dose reached 10×10 4 Gy, the numbers of SP 3 C H bonds was decreased by about 50%, the resistivity of irradiated DLC films was increased, and the diamond like character of the films became more obvious. The structure of DLC films was modified when irradiated by γ rays. The irradiation mechanisms are briefly discussed.

Progress and prospects in chitosan derivatives:Modification strategies and medical applications

Chitosan(CS)is the only natural alkaline polysaccharide originated from deacetylation of chitin that is the main component of shell from marine organisms.It has great potential medical application due to its broad-spectrum antimicrobial activity and good water solubility originated from its protonated amino groups under acidic condition and abundant hydroxyl groups.However,unprotonated NH_(2)group of CS leads to its poor solubility under physiological condition and limits its diverse applications.Therefore,it is highly necessary to summarize the modification strategies of CS derivatives systematically to help researchers select the most appropriate strategies for their specific applications.Herein,we have summarized the modification strategies of CS derivatives for improving their antimicrobial activity,water solubility,biocompatibility,and mechanical property by chemical reaction and physical integration.And then we have reviewed the CS derivatives in hydrogels,nanoparticles,or coatings for medical application in wound dressing,drug delivery,medical implant.Last but not the least,we have put forward the future perspectives of deep studies about structure-activity relationship and clinical applications of CS derivatives.

Modulation of Supramolecular Interactions of Urea-based Supramolecular Polymers via Molecular Structures

Linear bis-urea D230 series and branched tris-urea T403 series of supramolecular monomers were syn- thesized using low molecular weight polyetheramine D230, T403 and isocyanates with diverse functional groups. Rheological tests reveal that the materials possess special thermal and mechanical properties due to the strong hydrogen bonding interactions between terminal urea groups and the high flexibility of the polyetheramine middle segments. By enhancing the hydrogen bonding interactions through electronic effects of the substituted urea groups, the mechanical properties of the bulk material can be increased. Moreover, the branched T403 series with higher hy- drogen bonding density also shows better performance against D230 series with the same substituted urea groups. The presence of π-π stacking between the phenyl groups in samples with phenylurea residues, which complements the hydrogen bonding, was also confirmed by fluorescence spectroscopy, therefore resulting in a stronger supramolecular polymer network.

化合物PbGa_(4)Se_(7)中[PbSe_(3)]和[GaSe_(4)]功能基元的强极化实现高的相位匹配二次谐波效应

二次谐波效应和相位匹配能力对于二阶非线性光学晶体的实际应用至关重要.在本工作中,我们通过将具有立体化学活性电子对的Pb^(2+)引入非相位匹配的Ga_(2)Se_(3),增强其各向异性和二阶超极化率.基于以上策略,我们制备了一种硒化物PbGa_(4)Se_(7),其晶体结构由类金刚石阴离子骨架和插入到间隙中的Pb^(2+)组成.在1910 nm的激光照射下,PbGa_(4)Se_(7)具有大的二次谐波系数(3.3×AgGaS_(2));同时,其具有低的热膨胀系数各向异性(0.5)和合适的光学带隙(2.1 eV),在2090 nm激光照射下,表现出高的激光诱导损伤阈值(7.0×AgGaS_(2)).PbGa_(4)Se_(7)的相位匹配能力和强二次谐波效应可归因于非线性光学功能基元(四面体GaSe_(4)和金字塔PbSe_(3)结构单元)的协同作用产生了额外的各向异性和极化率.

Stress Transfer in Polymer Nanocomposites:A Coarse-grained Molecular Dynamics Study

In this work,we used coarse-grained molecular dynamics simulation methods to investigate the dispersion and percolation behavior of nanoparticles in polymer nanocomposite.Our aim was to investigate the correlation between particle arrangement in nearby layers and the stretching performance in composite systems by exploring the stress transfer processes during different stages of the stretching process.The machine learning technique of linear regression was used to quantitatively measure the efficiency of stress transfer between particles nearby.According to our research,increasing the strength of attraction can significantly enhance the particle dispersion and affect the percolation threshold.We also noticed a non-monotonic relationship between the interaction strength and the tensile stress.Additionally,we quantified the efficiency of nanoparticles and polymers at transferring stress to nearby nanoparticles.As a result,the stress value provided by each particle in the aggregation body is significantly increased by the aggregation behavior of nanoparticles.The non-monotonic behavior is caused by two variables:the rapid disintegration of aggregates and the improved stress transfer efficiency from polymers to nanoparticles.Significantly,it was discovered that the structural rearrangement of nanoparticles during stretching is the main reason that causes the yield-like behavior seen in poorly dispersed systems.

A Study on the Cloud Design Resource System Based on Ecology Theory

The cloud design resource system is an organic entity from the ecological system perspective, whose elements have the similar behavioral property of creature individuals, populations, and community. Hence, study on cloud design resource management can refer to the ecology theory. Based on analyzing the structure of cloud design resource system and the features of cloud design resources, the similarity between those are further dis cussed through the ecological system elements and features. An ecological based application framework of cloud design resource management is then presented.