FORMABILITY AND CRYSTAL TYPES OF RARE EARTH-SILICON CONTAINING TERNARY COMPOUNDS

By pattern recognition chemical bond parameter method, the formability of NaZn13 type and BaCd11 type ternary compounds in RE-M Si （RE=La-Lu, M is any metallic element） systems has been investigated. And the existence of unknown ternary compounds is predicted by the pattern recognition method.

Relationship between atomic structure and crystal type studied by artificial neural network

We have used chemical bond parameters and pattern recognition method to investigatethe regularities of the crystal type of alloy phase,and achieved good results.Theparameters used,however,are semi-empirical paramters,which are not very strict fromtheoretical viewpoint.In this letter,we use the numbers describing atomic structure(thenumbers of valence electrons Z1,Z2,the principal quantum numbers of valence electrons n1,

Relationship between positron bulk lifetime and lattice constants-research on NaCl-type crystals

The positron lifetimes of some compounds with NaCl-type crystal structure are calculated with the method of atomic superposition approximation （ATSUP） based on the theories of local-density-approximation （LDA） and general- gradient-approximation （GGA）. The systematical results are fitted to a curve as a function of lattice constants. The positron bulk lifetimes of some other compounds with NaCl-type crystal structure, which are deduced from the systematical results, are in agreement with the experimental results given in other literature.

Crystal Structure of a Cadmium(Ⅱ) Complex Containing an Amide Type Ligand

The compound [Cd（L）2（NO3）]NO3·0.5H2O （L = N-benzyl-2-（quinolin-8-yloxy）aceta- mide） 1 has been synthesized and structurally determined by single-crystal X-ray diffraction, elemental analysis, IR and UV spectroscopy. The crystal belongs to the triclinic system, space group P1 with a = 11.7175（13）, b = 11.8873（13）, c = 14.0958（16） A, α = 74.889（2）, β= 78.228（2）, γ = 78.831（2）°, V= 1835.0（4） A3, Z= 1, Dc= 1.502 Mg/m3, Mr = 1660.17,μ = 0.662 mm-1, F（000） = 846, 2（MoKa） = 0.71073 A, the final R = 0.0585 and wR = 0.0577 for all observed reflections. The results show that the Cd（II） ion with a square antiprismatic geometry is coordinated by a N206 donor set, two NO2 sets from two ligands and two O atoms from a bidendate nitrate group. In the crystal, the O-H...O and N-H...O hydrogen bonds are helpful to consolidate the three- dimensional network.

Folding beam-type piezoelectric phononic crystal with low-frequency and broad band gap

A folding beam-type piezoelectric phononic crystal model is proposed to isolate vibration. Two piezoelectric bimorphs are joined by two masses as a folding structure to comprise each unit cell of the piezoelectric phononic crystal. Each bimorph is connected independently by a resistive-inductive resonant shunting circuit. The folding structure extends the propagation path of elastic waves, while its structure size remains quite small. Propagation of coupled extension-flexural elastic waves is studied by the classical laminated beam theory and transfer matrix method. The theoretical model is further verified with the finite element method(FEM). The effects of geometrical and circuit parameters on the band gaps are analyzed. With only 4 unit cells, the folding beam-type piezoelectric phononic crystal generates two Bragg band gaps of 369 Hz to1 687 Hz and 2 127 Hz to 4 000 Hz. In addition, between these two Bragg band gaps, a locally resonant band gap is induced by resonant shunting circuits. Appropriate circuit parameters are used to join these two Bragg band gaps by the locally resonant band gap.Thus, a low-frequency and broad band gap of 369 Hz to 4 000 Hz is obtained.

SYNTHESIS AND CHARACTERIZATION OF NOVEL CHIRAL SMECTIC C(Sc~*) PHASE SHISH-KEBAB TYPE LIQUID CRYSTALLINE BLOCK COPOLYMERS

A new series of chiral shish-kebab type liquid crystal block copolymers that form the smectic C(Sc*) phase was synthesized by solution polycondensation. The copolymers were characterized by GPC, DSC, TG, POM, X-ray diffraction and polarimeter. The copolymers 7 entered into liquid crystal phase whin they were heated to their melting temperatures (T-m) and the copolymers 8 were in liquid crystal phase at room temperature with low viscosities. The smectic sanded texture or focal-conic texture were observed on POM. All the chiral block copolymers showed high optical activity. No racemization has happened. Temperature-variable X-ray diffraction study together with POM and polarimetric analysis realized that they are chiral smectic C(Sc*) phase. Thus we offer in this report the first example of shish-kebab type liquid crystal block copolymers that form a chiral smectic C(Sc*) phase. The variation of melting and isotropization temperatures with molecular structure was also discussed.

Continuous Reaction Crystallization of Struvite in a DTM Type Crystallizer With Jet Pump of Ascending Suspension Flow in a Mixing Chamber–Kinetic Approach of the Process

Reaction crystallization of struvite in water solutions containing 0.20 mass % of phosphate(V) ions by magnesium and ammonium ions addition was investigated experimentally. Process was carried out in DTM type crystallizer with liquid jet pump device in 298 K assuming stoichiometric conditions. Struvite crystals of mean size Lm 5.2-23.0 μm were produced depending on pH (9-11) and mean residence time of suspension in a crystallizer τ (900-3600 s). Under these conditions linear growth rate of struvite crystals (SIG MSMPR kinetic model) decreased 2-time with the increase in pH and 3-time with the elongation of mean residence time of crystal suspension from 7.11×10-9 m/s (pH 9, τ900 s) to 1.65×10-9 m/s (pH 11, τ3600 s). Nucleation rate varied within the 7.9×108-1.8×1010 1/(sm3) limits. Struvite product of maximal linear size exceeded 100 μm with 10 vol. % of < 3 μm fraction corresponded to pH 9 and τ3600 s.

Crystallization Process of Calcium Sulfate Dihydrate in Gypsum Type Brine System

1 Introduction Calcium sulfate deposition is one of the most important and serious problems faced by heat transfer equipment during operation(Pavlos et al.,1999;Liu et al.,1996).The crystallization of calcium sulfate is known as a major

The Effect of Additives on Calcium Sulfate Dihydrate Crystallization Kinetics in Gypsum Type Brine System

1 Introduction There exist calcium and sulfate ions outside sodium chloride in solution mining for calcium sulfate brine.The calcium and sulfate ions not only affect the purity of the vacuum salt products,but also increase the scaling of vacuum evaporation tanks and brine reusing pipes.Additives have certain impacts on the crystallization dynamics(Randolph et al.,1971).The crystallization

Hydrothermal Synthesis,Crystal Structure and Characterization of a New Keggin Polyoxometalate {[Ag^I(4,4’-bipy)]_3[PW_(12)O_(40)]}·(4,4’-bipy)

A novel polyoxometalate {[Ag^I（4,4＇-bipy）]3[PW12O40]}·（4,4＇-bipy）·4H2O 1 has been synthesized hydrothermally and characterized by elemental analysis, IR and single-crystal X-ray diffraction. The crystal of 1 belongs to the triclinic system, space group P1 with a = 11.3710（17）, b = 12.0701（16）, c = 13.1061（12） A, α = 112.838（3）, β = 94.545（6）, γ = 99.526（4）°, V = 1614.4（4） A^3, Mr = 3825.40, Z = 1, Dc = 3.935, μ = 22.289mm^-1, F（000） = 1692, the final R = 0.0507 and wR = 0.1054. X-ray diffraction analysis reveals that the molecular structure of 1 consists of three coordinated cations [AgI（4,4＇-bipy）]＋, a polyanion unit [PW12O40]3-, and a discrete 4,4′-bipy molecule. Significantly, there exist two crystallographically independent silver（I） centers in 1 and all [AgI（4,4＇-bipy）]^＋ cations are linked with each other to form a one-dimensional Ag-4,4＇-bipy polymer chain. The neighboring polymer chains are further interconnected to form a 3D framework by the covalent effect of silver atoms and terminal oxygen atoms of the polyanion. The electrochemical behaviors of 1 have also been studied in detail by cyclic voltammograms.

Hydrothermal Synthesis, Crystal Structure and Fluorescent Property of a Keggin Polyoxometalate [Cu^I(2,2'-bipy)_2]_3[PW^(Ⅵ)_(12)O_(40)]

A Keggin-type tungstohosphate compound [Cu^l（2,2＇-bipy）2]3[PW^Ⅵ12O40] 1 （bipy = bipyddine） was prepared by the hydrothermal method for the first time. Single-crystal X-ray diffraction revealed that 1 （C60H48Cu3N12O40PW12） crystallizes in the monoclinic system, space group P21/c with a = 16.9837（10）, b = 17.9732（13） c = 27.8701（13）A°, β = 96.1039（10）°, V = 8459.2（9） A°^3, Mr = 4004.89, Z = 4, Dc = 3.145 g/cm^3, μ = 17.089 mm^-1, F（000） = 7208, S = 1.005, the final R = 0.0469 and wR = 0.0827 for 10807 observed reflections （I 〉 2σ（I））. Compound 1 consists of one discrete normal Keggin polyanion [PW^Ⅵ 12O40]^3- and three isolated coordinated cations [Cu^1（2,2＇-bipy）2]^＋. Significantly, there exist three crystallographically independent asymmetric reduced copper （I） centers in 1. Furthermore, the compound shows strong photoluminescence property in solid state at room temperature.

Influence of Pre-Compressive Creep on Internal Friction Stress and Creep Parameters of Nickel-Base Single Crystal Superalloys

By means of pre-compressive creep treatment, the cubic γ′ phase in a nickel base single crystal superalloy is transformed into the P-type rafted structure. And the influence of the pre-compressive creep on the internal friction stress and creep lifetimes of the superalloy are investigated by means of the measurement of the creep curves and microstructure observation. Results show that, compared to the P-type structure alloy, the full heat treated state alloy displays a bigger internal friction stress value of dislocation motion during steady state creep and a longer creep lifetimes. The creep activation energies of the full heat treated and P-type structures alloys are measured to be 462 kJ/mol and 412 kJ/mol, respectively. Thereinto, the P-type rafted γ′ phase in the alloy is transformed into the N-type structure during tensile creep. And the N-type γ′ phase transformed from the P-type structure displays a shorter size in length, this is a main reason of the P-type structure alloy possessing a shorter creep lifetimes due to creep dislocation moving easily over the rafted γ′ phase.

Evolution of nitrogen structure in N-doped diamond crystal after high pressure and high temperature annealing treatment

In this paper, we have reported an investigation on the evolution of nitrogen structures in diamond crystals which contain nitrogen donor atoms in the range of 1500 ppm-1600 ppm following an annealing treatment at a high pressure of about 6.5 GPa and high temperatures of 1920 K-2120 K. The annealing treatment was found to completely transform nitrogen atoms originally arranged in a single substitutional form （C-center）, into a pair form （A-center）, indicated from infrared （IR） spectra. The photoluminescence （PL） spectra revealed that a small fraction of nitrogen atoms remained in C-center form, while some nitrogen atoms in A-center form were further transformed into N3 and H3 center structures. In addition, PL spectra have revealed the existence of two newly observed nitrogen-related structures with zero phonon lines at 611 nm and 711 nm. All these findings above are very helpful in understanding the formation mechanism of natural diamond stones of the Ia-type, which contains nitrogen atoms in an aggregated form.

MULTIPLE CENTER d-β ORBITALS AND CHARGE TRANSFER OF HETERONUCLEAR COUSTERS WITH CUBANE TYPE (Mo_3S_4)_xM^n+ (x=1, 2, M = Cu, W, Ni, Sb. Mo, Sn, Cu_2; n = 4,8)

In this work, with the analysis on MO and electronic structure for a series of heteronuclear cluster with cubane type (Mo4S1 )xMn1(x=1.2. M = Cu, W, Ni, Sb, Mo, Sn, Cu2) we found that it is with the multiple center d-pir orbitals that the ligand Mo3S44+ bonds to the M atom to form these class clusters. It is revealed that the charges transfer from the M atom to Mo atom of the ligand Mo3S44+ and its relationship with the MC (multiple center) d-pπ orbitals. Based on the charge transfer the electronic spectrum and the magnetic property of some cubane clusters have been discussed.

A Novel Ni-capped Silverton-type Complex: H_4{[Ni(H_2O)_3]_2[CeMo_(12)O_(42)]}·13.5H_2O

A novel Ni-capped complex H4{[Ni（H2O）3]2[CeMo12O42] }· 13.5H2O has been synthesized, which is the first Silverton-type anion capped with two Ni units via three terminal oxygen atoms. Crystallographic data for the title compound： Trigonal, space group R-3, a = 13.0950（19）, b = 13.0950（19）, c = 33.029（7） A, α = β= γ = 58.727（17）A °, V = 4905.1（14） A °^3, Z = 3, Mr= 2437.17, Dc = 2.475 g/cm^3, F（000） = 3462, T = 293（2） K, μ（MoKa） = 3.564 mm^-1, Rt = 0.0369, wR2 = 0.0905 and GOF= 1.079 for 151 parameters and 1963 reflections with I 〉 2σ（I） in the range of 1.85≤θ≤25.50°.

Hydrothermal Synthesis and Crystal Structure of [Cu(en)_2(H_2O)]_2{PW_(11.5)Cu_(0.5)O_(40)[Cu(en)_2]}·2H_2O

A transition metal substituted polyoxotungstate, [Cu（en）2（H2O）]2{PW11.5Cu0.5O40[Cu（en）2] }·2H2O1 based on Keggin frameworks, has bccn hydrothcrmally synthesized and characterized by IR, TGA and single-crystal X-ray structural analysis. It is interesting to find that the structure unit contains two different valence cations, narncly, one [Cu（1）（en）2（H2O）]^＋ and one [Cu（2）（en）2（H2O）]^2＋. Data for the crystal： orthorhombic system, space group Pbca, a = 21.585（2）, b = 20.695（2）, c = 26.137（3）A, V = 11675（2）A^3, Z = 8, Mr = 3428.23, Dc = 3.901 g/cm^3, F（000） = 12156,μ（MoKα） = 23.932 mm^-1, the final R = 0.0468 and wR = 0.0969 for 6927 observed reflections （I 〉 2σ（I））.

Numerical Simulation and Prediction for Sticking Type Breakout Behavior in Slab Contiuous Casting

A two-dimensional heat transfer model was developed to calculate the mould wall temperature field under normal operations condition and to determine its changing behavior when breakout occured. On the numerical simulation of sticking type breakout process and the breakout related wall temperature evolution, parameters of prediction were suggested.

STRUCTURE OF MOLECULAR COMPOUND CRYSTAL A_2B(A =1, 6, 7, 8,-TETRA-PHENYL (3, 4-BENZO)BICYCLO[4, 2, 0]OCTA-7-ENE, B=CIS, CIS-1,2,3,4,-TETRAPHENYLBUTADIENE)

C100H78, (A: C36H28, B: C28H22) Mr = 1279. 74, monoclinic, P21/a, a=17. 282(3), b=10. 669(4), c= 19, 927(3) A , β =102. 99(1)°,V = 3580. 1(2) A3, Z=2, μ(MoKα) = 0. 623cm-1, F(000) = 1356, Dc=1. 187g/cm3, room temperature. The final R=0. 084, Rw = 0. 086 for 1255 independent observed reflections (I≥3σ(I)). Owing to the existence of 1,6,7, 8-Tetraphenyl (3,4-benzo)-bicyclo[4, 2, 0]octa-7-ene(A) , cis, cts-1, 2, 3, 4-Tetraphenylbutadiene (B) in A2B can take the different conformation from the one in the pure B crystal. The reason of the formation of this molecular compound crystal is put forward.

Effect of Rare Earth Elements on Structure and Electrochemical Properties of PuNi_3-type Hydrogen Storage Alloys

Structure and electrochemical properties of (La, Ce, Pr, Nd)_2MgNi_9 hydrogen storage alloys were investigated through orthogonal design experiments, and the alloys were obtained through induction melting followed by annealing treatment. The structure of main phase in alloys belongs to PuNi_3-type with a space group R3m. Rare earth elements, as a substitute of lanthanum, have a significant effect on phase structure of alloys, elements of cerium and neodymium are beneficial to the formation of Gd_2Co_7-type phase with a space group P 6_3/mmc. Rare earth elements can decrease the unit cell volume of main phase of alloys dramatically, and increase the axis ratio. The results of electrochemical experiment showed that the discharge capacity of alloy electrodes ranged from 342.97 to 380.68 mAh·g -1, and elements of cerium and neodymium can reduce the discharge capacity of alloy electrodes significantly. Compared to the electrode of La_2MgNi_9 alloy, the substitution of lanthanum by rare earth elements did not improve the cyclic stability of alloy electrodes due to the anisotropic structure change of unit cell. While rare-earth elements can improve the high rate dischargeability of alloy electrodes, the high rate dischargeability of alloy electrodes could reach the maximum when the unit cell volume of PuNi_3-type structure was about 0532 nm.

THE EFFECT OF SUBSTITUENT ON THE THERMAL PROPERTIES OF POLYESTERS CONSISTING OF AROMATIC TYPE SCHIFF BASE MESOGENIC UNITS AND POLYMETHYLENE SPACERS

Polyesters consisting of substituted aromatic type Schiff base mesogenic unit andpolymethylene spacers were synthesized and their thermal transitions and liquid crystallineproperties were studied. The liquid crystalline behaviour has been characterized by differentialscanning calorimetry (DSC) and optical polarizing microscopy. Structural broadening bysubstitution of methoxy group in 2, 2' positions of the mesogenic core produce polymers withlower transition temperatures. Polymers synthesized from ortho and meta substituted phenylenediamine did not form a liquid crystal phase.