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

The correlations among composition, structure, chemical bond and thermoelectric property of skutterudites CoSb3 and CeCo5Fe3Sb12 have been studied by using density function and discrete variation (DFT-DVM) method. Three models for this study were proposed and calculated by which the "rattling" pattern was described. Model 1 is with Ce in the center, model 2 is with Ce away the center and near to Sb, and model 3 is also with Ce away the center but near to Fe. The calculated results show that in model 3, the ionic bond is the strongest, but the covalent bond is the weakest. Due to the different changes between ionic and covalent bond, there is less difference in the stability among the models 1, 2 and 3. Therefore, these different models can exist at the same time, or can translate from one to another more easily. In other words, the "rattling" pattern has taken place. Unfilled model of CoSb3, without Ce and Fe, is called model 4. The covalent bond of Co-Sb or Fe-Sb in models 1, 2 and 3 is weaker than that of     

Electronic Structures and Bonding Properties of Ti_2AlC and Ti_3AlC_2

The relation among electronic structure, chemical bond and property of Ti2AlC, Ti3AlC2 and doping Si into Ti2AlC was studied by density function and the discrete variation (DFT-DVM) method. After adding Si into Ti2AlC, the interaction between Si and Ti is weaker than that between Al and Ti, and the strengths of ionic and covalent bonds decrease both. The ionic and covalent bonds in Ti3AlC2, especially in Ti-Al, are stronger than those in Ti2AlC. Therefore, in synthesis of Ti2AlC, the addition of Si enhances the Ti3AlC2 content instead of Ti2AlC. The density of state (DOS) shows that there is mixed conductor characteristic in Ti2AlC and Ti3AlC2. The DOS of Ti3AlC2 is much like that of Ti2AlC. Ti2SixAl1-xC has more obvious tendency to form a semiconductor than Ti2AlC, which is seen from the obvious difference of partial DOS between Si and Al 3p.     

Eleetronie Structures and Bonding Properties of Ti2AlC and Ti3AlC2

The relation among electronic structure, chemical bond and property of Ti2AlC, Ti3AlC2 and doping Si into Ti2AlC was studied by density function and the discrete variation （DFT-DVM） method. After adding Si into Ti2AlC, the interaction between Si and Ti is weaker than that between Al and Ti, and the strengths of ionic and covalent bonds decrease both. The ionic and covalent bonds in Ti3AlC2, especially in Ti-Al, are stronger than those in Ti2AlC. Therefore, in synthesis of Ti2AlC, the addition of Si enhances the Ti3AlC2 content instead of Ti2AlC. The density of state （DOS） shows that there is mixed conductor characteristic in Ti2AlC and Ti3AlC2. The DOS of Ti3AlC2 is much like that of Ti2AlC. Ti2SiAl1-xC has more obvious tendency to form a semiconductor than Ti2AlC, which is seen from the obvious difference of partial DOS between Si and Al 3/7.     

ON STRUCTURES,PROPERTIES AND CHEMICAL BOND OF Te-Se-I GLASS AND OF ADDING As,Ge ELEMENTS ONE

Te-Se glass and adding As,Ge elements to itare studied with Selt-Consistent-Field Discrete Variatioal X_α(SEF-DV-X_α),one of the molecule orbital calculating meth-ods in quantum chemistry.The chemical bonding is used todiscuss the relations between structures and properties with thevarations of compositions of the glasses.The calculated re-sults show that the strength of covalent and ionic bonds areboth in the order of Ge-Se>As>Se>Te-Se,which is consis-tent with the experimental result of the glass-transition tem-perature(T_g) of the corresponding glasses.The Te-I bond inwhich Ⅰ atom is one-coordinate is sstronger than that in whichⅠ atom is two-coordinate,As-Ⅰ and As-As bonds are bothstronger than the two types of Te-Ⅰ bonds.The waek Te-Ⅰbonds have been replaced by the stronger As-Ⅰ and As-Asbonds,which is just the reason why As addition in TeX glass-es can obviously improve the thermal and chemical properties.     

Electronic Structure and Thermoelectric Properties of Ca3 Co4O9

The relation among electronic structure, chemical bond and thermoelectric property of Ca3 Co4 O9 was studied using density function and discrete variation method （DFT-DVM）. The gap between the highest valence band （HVB） and the lowest conduction band （LCB） shows a semiconducting property. Ca3 Co4 O9 consists of CoO2 and Ca2 CoO3 two layers. The HVB and LCB near Fermi level are only mainly from O（ 2 ） 2p and Co （2） 3d in Ca2 CoO3 layer. Therefore, the semiconducting or thermoelectric property of Ca3 Co4 O9 should be mainly from Ca2 CoO3 layer, but it seems to have no direct relation to the CoO2 layer, which is consistent with that binary oxides hardly have a thermoelectric property, but trinary oxide compounds have quite a good thermoelectric property. The covalent and ionic bonds of Ca2 CoO3 layer are both weaker than those of CoO2 layer. Ca plays the role of connections between CoO2 and Ca2 CoO3 layers in Ca3 Co4 O9, decrease the ionic and covalent bond strength, and improve the thermoelectric property.     

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=S,Se,Te)glasses are studied with Self-Consistent-Field Dis-crete Variational X_α(SCF-DV-X_α),one of the molecule orbital.calculating methods in quantum chemistry.The chemicalbonding is studied to discuss the relations between structuresand properties with the variations of compositions of theglasses.The calculated results show that the strength of cova-lent 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 isconsistent with the experimental result of the glass-transitiontemperature (Tg) of the corresponding glasses.The differ-ences of chemical bond strength and Tg among As-S-X(X=Cl,Br,I)glasses are larger are larger than those among As-Y-Br(Y=S,Se,Te)glasses and the largest difference ofchemical bond strength is that of ionic bond of As-X amongAs-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 themore important role to affect the struture and property of theglasse     

Electronic Structure and Chemical Bond of Ti3SiC2 and Adding Al Element

The relation among electronic structure, chemical bond and property of Ti3SiC2 and Al-doped was studied by density function and discrete variation （ DFT- DVM） method. When Al element is added into Ti3 SiC2 , there is a less difference of ionic bond, which does not play a leading role to influent the properties. After adding Al, the covalent bond of Al and the near Ti becomes somewhat weaker, but the covalent bond of Al and the Si in the same layer is obviously stronger than that of Si and Si before adding. Therefore, in preparation of Ti3 SiC2 , adding a proper quantity of Al can promote the formation of Ti3 SiC2 . The density of stnte shows that there is a mixed conductor character in both of Ti3 SiC2 and adding Al element. Ti3 SiC2 is with more tendencies to form a semiconductor. The total density of state near Fermi lever after adding Al is larger than that before adding, so the electric conductivity may increase after adding Al.     

Electronic Structures and Chemical Bonds of Cobaltite and Ni-Doped

The relation among electronic structure, chemical bond and thermoelectric property of Ca3 Co2 O6 and Ni-doped was studied by density function theory and discrete variation method（DFT-DVM）. The results indicate that the highest valence band（ HVB ）attd the lowest conduction band（ LCB ） are mainly attribuled to Co3d, Ni3d and O2p atomic orbitals. The property of a semiconductor is shown from the gap between HVB and LCB. The gap of Ni-doped one is less than that of Ca3 Co2 O6. The non-metal bond or ceramic characteristic of Ni-doped one is weaker than that of Ca3 Co2 O6, but the metal characteristics of Ni-doped one are stronger than those of Ca3 Co2 O6. The thermoelectric property should be improved by adding Ni element into the system of Ca3 Co2 O6 .     

Thermoelectric properties of p-type (Bi_(0.15)Sb_(0.85))_2Te_3-PbTe graded thermoelectric materials with different barriers

The p-type (Bi0.15Sb0.85)2Te3 and PbTe are typical thermoelectric materials used for low and middle temperature range and functional graded materials (FGM) is an inevitable way to widen the working temperature range. Here two segments graded thermoelectric materials (GTM) consisting of (Bi0.15Sb0.85)2Te3, PbTe and different barriers were fabricated by the common hot pressure method. Metals Fe, Mg and Ni were used as barriers between the two segments. The diffusion of different barriers between the barriers and bases were analyzed by electron microprobe analysis (EMA). The phase and crystal structures were determined by X-ray diffraction analysis (XRD). The thermoelectric properties were measured at 303 K along the direction parallel to the pressing direction. The results show that the compositional diffusion occurs when there is no barrier at the interface of the two segments, and the diffusion of Pb is most obvious; as the barrier material, the diffusion of metals Fe, Mg and Ni between different bases is not very obvious, and the thermoelectric properties of GTM is much better than that of the original segment.     

Chemial Bond and Stability of Adsorption of [Au（ AsS3 ）]^2- on the Surface of Kaolinite

Density function theory and discrete variation method (DFT-DVM) were used to study the adsorption of [Au( AsS3 )]^2- on the surface of kaolinite. The correlation among structure, chemical bond and stability was discussed. Several models were selected with [ Au( AsS3)]^2- in different directions and sites. The results show that the models with gold on the edge of kaolinite basal layer contain pincerlike bond among gold and several oxygen atoms and form strong Au - 0 covalent bond, so these models are more stable than those with gold above or under the layer. The models with gold near to [ AlO2(OH)4] octahedra are more stable than those with gold near to the vacancy withont aluminium. These two stable tendencies in kaolinite- [ Au( AsS3)]^2- are stronger than that in kaolinite-Au systems. The interaction between [ Au( AsS3 )]^2- and kaolinite is stronger than that between gold and kaolinite, and this interaction is strong enough to form the surface complexes.     

Microstructural Probing of （1-x） GeS2- x Ga2S3 System Glasses By Raman Scattering

Roman scattering measurement of （ 1 - x ） GeS2-x Ga2S3 system glasses was conducted in order to understand the microstructural change caused by the addition of Ga2S3 . According to the change of Raman spectra with the addition of Ga2S3, two main structural transformations were deduced ： the gradual enhancement of ethane- like structural units S3 Ge- GeS3 （ 250 cm ^- 1） and S3 Ga- GaS3 （270 cm ^- 1 ） and the appearance of charge imbalanced units [ Ga2 S2 （ S1/2 ）4 ]^2- and [Ga（ S1/2 ）4 ]^- . And this change of structural aspect seems to give as a clue to understanding the cause of the increased rare-earth solubility.     

First-principle investigation on stability of Co-doped spinel λ-Mn4-xCoxO8

The mechanism of stability of Co-doped spinel λ-MnO2 that is referred to as spinel LixMn2O4 （x=0） was studied by using the first-principle calculation method. The total energy and formation enthalpy can be decreased remarkably due to the Co substation, resulting in a more stable structure ofλ-MnxCr2-xO4. The bond order and DOS analysis were given in detail to explain the nature of stability improvement. The calculated results show that as the content of Co dopant increases, the bond order of Mn-O becomes larger and the peak of density of states around Fermi level shifts toward lower energy. The charge density distribution illustrates that the Mn-O bonding is ionic and partially covalent, and the covalent Mn-O bonding becomes stronger with the increase of Co dopant content. The results confirm that the Co-doping will enhance the stability of λ-MnO2 and hence improve the electrochemistry performance of LixMn2O4.     

Solid State Reaction Synthesis and Thermoelectric Properties of Mg2Si doped with Sb and Te

Doped with Sb and Te, Mg₂ Si based compounds were prepared respectively by solid state reaction at 823K for 8h. Effects of dopants of Sb and Te on the structure and thermoelectric properties of the compounds were investigated. By calculating the values of the electrical conductivity for Sb-doped sample, the mechanism of electric conduction at 625 K is different. The figure of merit for sample doped with 0.4wt% Te at 500K is 2.4×10⁻³W/mK², and it reaches 3.3×10⁻³ W/mK² at 650K for the sample doped with 0.5wt% Sb. The values are more than 1.4 times and 2.3 times of the pure Mg₂Si sample. JIANG Hong-yi : Born in 1961     

The Antibacterial Effect of Silver-carrying B2O3-SiO2-Na2O Glass Material

The antibacterial effect of carrying silver B2O3-SiO2-Na2 O gloss material was studied by means of antibacterial ring, nephelometery , MIC value, thin film attachment and microcalorimetry , respectively.The experimental results of five kinds of antibacterial test methods are almost identical and can verify that carrying silver B2 O3-SiO2-Na2 O glass material exerts an excellent antibacterial performance. Antibacterial ring and nephelometety are simple, quick, but the precision is restrictive. MIC value, thin film attachment method and meicrocalorimetry can quantitatively compare the antibacterial effects of the antibacterial glass material. Compared with the traditional microbe test methods, the microcalorimetry can analyze the inhibiting effect of the cell‘ s growth and metabolism on the antibacterial gloss material by monitoring the thermal effect continuously and automatically .     

Properties and Microstructure of GeS2-Ga2S3-CdS Glasses

The samples of the GeS2-Ga2 S3-CdS pseudo-ternary glassy sysem were prepared by comventional melt-quenching techniques.The microstructure of the GeS2-Ca2 S3-CdS glasses was analyzed thoroughly using Raman spectra and the relationships among the composition,microstructure and properties（such as thermal properties,densities,optical properties）were probed.The experimental results indicate that the GeS2 acts as the network former,the Ga2S3 as the net intermediate,and the CdS as the net modifier,The GeS2 and Ga2S3 exist in the form of [GeS4/2],[GaS4/2]tetrahedra or S3G3（Ga）-（Ga）GeS3 ethane-like units within the glassy network,and the addition of CdS mainly breaks the Ge（Ga）-（Ga）Ge bonds among the ethane -like units,leading to the formation of [GeS4/2].[GaS4/2]tetrahedra.The Tg and Tx have tight relations on the congregated degree of glassy network,however,λvis,n and d are hardly involved into the connectional dependence of the space arrangement.     

Preparation and Properties of Ag—TiO2 Thin Films on Glass SUbstrates

Ag-TiO2 thin films were prepared on glasses.The morphology and structure of Ag-TiO2 films were investigated by XRD.SEM and FT-IR.The photocatalytic and hydrophilic properties of Ag-TiO2 thin films were also evaluated by examining photocatalytic degradation dichlorophos under sunlight illumination and the change of contact angle respectively.The research results show that the Ag-TiO2 thin film is mainly composed of 20-100nm Ag and TiO2 particles,The Ag-TiO2 thin films possess a super-hydrophilic ability and higher photocatalytic activity than that of pure TiO2 thin film.     

Magnetoresistance plateau in La2/3Ca1/3Bi x Mn1 − x O3 granular system

The effect of doping additional Bi on the magnetoresistance (MR) of La_2/3Ca_1/3B _x Mn_1−x O₃ was investigated. It is found that traditional colossal magnetoresistance (CMR) peak can only be observed in the x<0.05 samples and the peak value decreases with the increase of x, but the x≥0.05 samples show a magnetoresistance plateau above 200 K because of the presence of additional (La,Ca,Bi)-O layers. Moreover, this MR plateau is enhanced for the segregation of the La, Ca, and Bi elements. Funded by the Foundation for the Author of National Excellent Doctoral Dissertation of China (FANEDD) (No. 200233)