Xieite, a new mineral of high-pressure FeCr2O4 polymorph

Xieite, a new mineral, occurs in the shock vein of the Suizhou meteorite. The mineral has an orthorhombic structure and its space group is Bbmm. The cell parameters are a = 9.462（6） A, b = 9.562（9） A, c = 2.916（1）A. The crystal-chemical formula is （Fe0.87Mg0.13Mn0.01）1.01（Cr1.62AI0.25Ti0.08V0.02）1.97O4, or simply formula FeCr2O4. Stronger X-ray diffraction lines are [d （A）, I/Io]： （2.675, 100）, （2.389, 20）, （2.089, 10）, （1.953, 90）, （1.566, 60）, （1.439, 15）, （1.425, 15）, （1.337, 40）. Xieite is a high pressure polymorph of FeCr2O4 and formed by solid-state transformation of chromite under shock-induced high pressure and temperature, in association with other high-pressure minerals including ringwoodite, majorite, lingunite and tuite. The P-Tcondition for the formation of xieite is estimated to be 18--23 GPa and 1800--1950℃, respectively. Xieite has recently been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association （IMA 2007-056）. The mineral name, xieite, is named after Xiande Xie.     

Synthesis and characterization of a three-ring bent-core compound

To investigate the vacuum-deposited films of the banana-shaped mesogens, we prepared a three-ring bent-core （that is, banana-shaped） compound m-bis（4-p-octoxysryrenyl）benzene （m-OSB） and used it as a prototype for studying the related film physics. Herein the synthesis and the structural characterization of m-OSB are reported.^13C and ^1H NMR spectra and ^1R spectrum confirm that m-OSB has a symmetric and all-trans conformation. The results of differential scanning calorimetry, polarizing optical microscopy and X-ray diffractometry indicate that no liquid crystalline phase but two crystalline phases are present in this material： phase Ⅰ （T〈66℃） and phase Ⅱ （66~C〈T〈157℃）; an isotropic state is observed at above 157℃. Combining the X-ray diffraction and the electronic diffraction, we assign the room-temperature crystalline phase I to orthorhombie system and P212121 space group with cell parameters of a = 7.43A°. b=6.34A°, c=72.07A°, and α=β=γ=90°. Molecular modeling reveals that the molecules in the unit cell adopt a layered structure with an antiferro-eleetrie alignment. The structure of phase Ⅱ is very similar to that of phase Ⅰ. Nonlinear optical measurement shows that m-OSB is active for the second harmonic generation （SHG）. Such characterization of the bulk material is necessary for the understanding of the growth and microstructures in the films.     

Crystal structure determining of 7-ADCA based on X-ray powder diffraction

Traditionally, crystal structure data can be collected and determined from single-crystal X-ray diffraction. However, in the fields of organic and macromolecular crystallography, it is often difficult or impractical to grow single crystals with suitable sizes and purity. Therefore, it will be benefited from the newly growing analytical tool that combining X-ray powder diffraction based on polycrystalline samples and ab initio calcula- tion[1]. 7-ADCA is one of the most important intermediate…     

Facile synthesis of nanosized sodium magnesium hydride, NaMgH3

The ternary magnesium hydride NaMgH 3 has been synthesised via reactive milling techniques.The method employed neither a reactive H2 atmosphere nor high pressure sintering or other post-treatment processes.The formation of the ternary hydride was studied as a function of milling time and ball:powder ratio.High purity NaMgH 3 powder(orthorhombic space group Pnma,a 5.437(2),b 7.705(5),c 5.477(2) ;Z 4) was prepared in 5 h at high ball:powder ratios and characterised by powder X-ray diffraction(PXD),Raman spectroscopy and scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDX).The products formed sub-micron scale(typically 200-400 nm in size) crystallites that were approximately isotropic in shape.The dehydrogenation behaviour of the ternary hydride was investigated by temperature programmed desorption(TPD).The nanostructured hydride releases hydrogen in two steps with an onset temperature for the first step of 513 K.     

Novel multiferroicity in orthorhombic SmCrO3

This paper reports the ferroelectricity in antiferromagnetic SmCrO_3 with a reasonably large value of spontaneous electric polarization(70μC/cm~2mC cm~(-2)at 50 K)based on the measurement of pyroelectric current.The experimental results showed that the temperature of the onset of polar order was evidently higher(about220 K)than the Neel temperature(T_N=197 K)in the magnetodielectric studies.The calculated magnetodielectric effect(MDE)value was explicitly negative with maximum|MDE|values of about 3.6%around 230 K.The absence of a convincing signature in MDE at antiferromagnetic ordering temperature T_Nindicated the absence of magnetoelectric coupling around this temperature regime.The results further confirmed that the onset of polar order can be attributed to the structural distortion,rather than the canted noncollinear magnetic structure.     

High-pressure polymorph of TiO2-II from the Xiuyan crater of China

Abundant TiO2-II, a high-pressure polymorph of titanium dioxide, was found in the gneiss fragments of impact-produced breccias from the Xiuyan crater. Rutile in the gneiss was severely fragmented and fine-grained clasts less than 2 ~tm in size had been transformed to TiO2-II. Irregular thin layered TiO2-II is also observed in coarse-grained ruffle fragments, where the TiO2-II layers distributes along fractures and cracks in rutile, About 30 percent of rutile in the gneiss had been transformed to TiO2-II. Fine grains of TiO2-II display light bluish grey to light yellow brown in plane-polarized reflected light. Crystallographic investigation shows that TiO2-II has an orthorhombic structure with space group Pbcn. The cell parameters are a=4.543（1）/~, b=5.491（9）/~ and c=4.895（2） ,~. Its empirical formula calculated on the basis of two oxygen atoms can be written as （Tio.985Feo.oosNbo.oor- Si0.003Zr0.0Ol）l.0O302, or simply formula TiO2. According to the shock effects of quartz and feldspars, the peak shock pressure and post-shock temperature in the TiO2-II-bearing gneiss are estimated to be between 35 and 43 GPa and 300-900~C, respectively. The finding of TiO2-II in the shock-metamorphosed gneiss provides another mineral physics evidence for shock origin of the Xiuyan crater.     

Chenguodaite （Ag9FeTe2S4）： a new tellurosulfide mineral from the gold district of East Shandong Peninsula,China

Chenguodaite, approved by IMA-CNMMN （2004-042a）, was discovered in the Bunan quartz vein-type gold deposit in the gold district of East Shandong Peninsula. The mineral occurs in high grade Au-Ag-Cu ores, coexisting with galena, chalcopyrite, hessite, electrum, unnamed Ag6TeS2 and AglsFeBiTe3Se, enclosed and replaced by native silver and acanthite. In the reflected light microscope, the mineral has light gray color, indistinguishable anistropism and hardness around 2-3. The color indices of chenguodaite relative to ICE C illuminator are： x=0.3027, y=0.3076, Y=25.78%,λd=474 nm, Pe=3.68%, similar to those of canfieldite. The average chemical composition from 16 microprobe analyses is Ag8.97Fe1.00Te1.99S4.04, idealized to AggFeTe2S4. The polycrystalline X-ray diffraction of chenguodaite by Gandolfi camera and synchrotron oscillation photography results in 67 reflections with the 12 strongest being （relative intensity in bracket）： 6.742（69）, 6.416（39）, 5.951（33）, 3.265（100）, 2.981（24）, 2.649（22）, 2.25（24）, 2.188（71）, 2.142（22）, 2.123（31）, 2.044（23）, 1.949（33）, which are indexed to a primitive orthorhombic cell with a=12.769 （2） A, b= 14.814（2） A, c= 16.233 （1） A, V= 3070.6 A^3, Z= 9, Dcal.=6.85 g/cm^3. The name is for the late Prof. Chen Guoda, a famous Chinese geologist and the founder of Diwa-Geodepression theory of tectonics.     

Mn-ion-enhanced red spectral emission from yttrium aluminum garnet doped cerium phosphor

Mnions were co-doped in yttrium aluminum garnet doped cerium(YAG:Ce) phosphors as a co-activator and host lattice element using the co-precipitation method.These ions broadened the emission spectra of the pure YAG:Ce phosphor,which is caused by the 2E-4A2,5E-5T2 or 1T2-5T2 transition.From our X-ray diffraction results,we observed that Ce3+(1.032 ) was substituted at the Y3+(0.900 ) site,and Mn4+(0.538 ) and Mn3+(0.67 ) were substituted at the Al3+(0.535 ) site.The chromaticity color co-ordinates of YAG:Ce0.06 is(0.203,0.167),and the indices of YAG:Ce0.06,Mn0.04 and YAG:Ce0.06,Mn0.08 are(0.249,0.181) and(0.233,0.194),respectively.The manganese co-doped yttrium aluminum garnet doped cerium blended with the YAG:Ce phosphor showed improved white light emission.     

Crystallization characteristics of iron-rich glass ceramics prepared from nickel slag and blast furnace slag

The crystallization process of iron-rich glass-ceramics prepared from the mixture of nickel slag (NS) and blast furnace slag (BFS) with a small amount of quartz sand was investigated. A modified melting method which was more energy-saving than the traditional methods was used to control the crystallization process. The results show that the iron-rich system has much lower melting temperature, glass transition temperature (T_g), and glass crystallization temperature (T_c), which can result in a further energy-saving process. The results also show that the system has a quick but controllable crystallization process with its peak crystallization temperature at 918℃. The crystallization of augite crystals begins from the edge of the sample and invades into the whole sample. The crystallization process can be completed in a few minutes. A distinct boundary between the crystallized part and the non-crystallized part exists during the process. In the non-crystallized part showing a black colour, some sphere-shaped augite crystals already exist in the glass matrix before samples are heated to T_c. In the crystallized part showing a khaki colour, a compact structure is formed by augite crystals.     

Synthesis of antiferroelectric (Bi0.534Na0.5)0.94Ba0.06TiO3 ceramics with high phase transition temperature and broad temperature range by a solid-state reaction method

Antiferroelectric 0.94(Bi 0.534 Na 0.5 )TiO 3 -0.06BaTiO 3 ceramics were prepared using a solid-state reaction method, involving the addition of excessive amounts of Bi2O3 . The resulting ceramics featured a very high phase transition temperature (Tm～330°C), from the antiferroelectric to the paraelectric phase, and a low depolarization temperature (Td<25°C). The broad temperature range, within which antiferroelectric properties are retained, of the prepared materials indicates their higher potential over lead-based antiferroelectric ceramics such as PZT-based materials that exhibit a lower T m ≤170°C. The lower Td and higher T m obtained val- ues, relative to those reported in the literature, are believed to be due to the formation of A-site vacancies originating from the incorporation of excess Bi into the perovskite structure of the studied sample. In addition, the synthesized sample shows a high dielectric constant of ～1460, in a temperature range of 50-150°C at 1 kHz, and a high energy storage density of 0.71 J/cm 3 , which is an asset in energy storage capacitor applications.     

Crystallographic studies on the binding of coenzyme analogs to D-glyceraldehyde-3-phosphate dehydrogenase fromPalinurus versicolor

In contrast with the coezyme, two coenzyme analogs, ADP-ribose and SNAD, bind non-cooperatively to D-glyceraldehyde-3-phosphate dehydrogenase (GAPDH).Palinurus versicolor (PV) GAPDH complexed with ADP-ribose and SNAD has been crystallized by the method of sitting-drop vapor diffusion. X-ray diffraction data analysis reveals that both crystals belong to the same space group (C2), and have similar cell dimensions: a =152.80 Å,b =100.35 Å, c =128.31 Å,β =110.28° and a =153.41 Å,b =100.51 Å,c =128.44 Å,β =110.48°, respectively. It is estimated that the asymmetric unit in each crystal contains 4 subunits. This is a novel crystal form which is quite different from that previously reported for holoand apo-GAPDH from the same source. The result suggests that the binding of the two coenzyme analogs to GAPDH may lead to some significant conformational changes, which are different from those induced by the coenzyme binding. The self-rotation function indicates that the tetramer of these two GAPDH complexes also has good 222 symmetry. The structural analysis and the comparison with holoand apo-GAPDH may give a clue to the cooperative mechanism of the enzyme.     

Hydrogen Adsorption on Metal-Organic Framework MOF-177

This review summarizes the recent literature on the synthesis, characterization, and adsorption properties of meal-organic framework MOF-177. MOF-177 is a porous crystalline material that consists of Zn4O tetrahedrons connected with benzene tribenzoate (BTB) ligands. It is an ideal adsorbent with an exceptionally high specific surface area (BET4500 m2/g), a uniform micropore size distribution with a median pore diameter of 12.7 ?, a large pore volume (2.65 cm3/g), and very promising adsorption properties for hydrogen storage and other gas separation and purification applications. A hydrogen adsorption amount of 19.6 wt.% on MOF-177 at 77 K and 100 bar was observed, and a CO2 uptake of 35 mmol/g on MOF-177 was measured at 45 bar and an ambient temperature. Other hydrogen properties (kinetics and heat of adsorption) along with adsorption of other gases including CO2, CO, CH4, and N2O on MOF-177 were also be discussed. It was observed in experiments that MOF-177 adsorbent tends to degrade or decompose when it is exposed to moisture. Thermogravimetric analysis showed that the structure of MOF-177 remains intact at temperatures below 330℃ under a flow of oxygen, but decomposes to zinc oxide at 420℃.     

Growth, structural, optical, thermal and dielectric properties of a novel semi-organic nonline ar optical crystal: Dichloro-diglycine zinc II

Dichloro-diglycine zinc II(DCDGZ II),a semi-organic nonlinear optical material has been synthesized and single crystals were grown from the aqueous solution up to dimensions 20×10×3 mm3.The title compound,DCDGZ II(C4H10Cl2N2O4Zn H2O) crystallizes into monoclinic structure with the space group of C2/c.The unit-cell parameters were found to be a=14.4191(7),b=6.9180(2),c=12.9452(6) and Z=4.In the crystal structure,DCDGZ II layer is building up alternatingly with layers of water in which the zinc ions lie on a twofold axis.Theoretical calculations for polarizability,which are useful for device fabrication were made using Clausius–Mosotti equation and Penn analysis and the results were compared.Fourier transform infrared(FTIR) spectroscopic studies were performed for the identification of the different functional groups presented in the compound.The UV–vis–NIR absorption spectrum reveals that the lower UV cut-off wavelength is 240 nm.The optical band gap of the crystal was estimated as 2.2 eV.The surface morphology,thermal behaviour,dielectric properties have been studied using SEM,TG/DTA and LCR HITESTER analyzer.The nonlinear optical property of the crystal was also confirmed using Kurtz powder technique.     

Phase transformation and reduction kinetics during the hydrogen reduction of ilmenite concentrate

The reduction of ilmenite concentrate by hydrogen gas was investigated in the temperature range of 500 to 1200℃. The microstructure and phase transition of the reduction products were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical microscopy (OM). It was found that the weight loss and iron metallization rate increased with the increase of reduction temperature and reaction time. The iron metallization rate could reach 87.5% when the sample was reduced at 1150℃ for 80 min. The final phase constituents mainly consist of Fe, M₃O₅ solid solution phase (M=Mg, Ti, and Fe), and few titanium oxide. Microstructure analysis shows that the surfaces of the reduction products have many holes and cracks and the reactions take place from the exterior of the grain to its interior. The kinetics of reduction indicates that the rate-controlling step is diffusion process control with the activation energy of 89 kJ·mol-1.     

Assignment of the μ4-O5 atom in catalytic center for water oxidation in photosystem II

The detailed structure of catalytic center of water oxidation, Mn4Ca-cluster, in photosystem ⅡI (PSII) has been reported recently. However, due to the radiation damage induced by X-ray and the complexity of the Mn4Ca-cluster, the assignment of the μ4-O5 atom coordinated by three Mn and one Ca2+ ions is still lack of essential evidences. In this article, we synthesized one Mn complex containing two μ4-O atoms. It is found that the lengths of all μ4-O-Mn bonds in this Mn complex are in the range of 1.89-2.10 , which are significantly shorter than 2.40-2.61 distance of μ4-O5-Mn bonds in Mn4Ca-cluster observed in the crystal structure of PSII. In addition, DFT calculations have been carried out on the Mn4Ca-cluster. It is found that the O atom of μ4-O or μ4-OH always trends to deviate from the center position of four metal ions, resulting in unequal bond lengths of four μ4-4-M (M=Mn or Ca), which is obviously different with larger and nearly equal distances between μ4-O and four metal ions observed in the crystal structure. Based on these results, we suggest that the μ4-atom in Mn4Ca-cluster of PSII is unlikely to be a μ4-O, μ4-OH or μ4-OH2 , and its assignment is still an open question.     

Preparation and magnetic properties of CoFe2O4/TiO2 composite films

Using （Ti（OC4H9）4） and metal chlorates as starting materials, CoFe2O4/TiO2 composite films were prepared by sol-gel method. The effects of heat treatment temperature and pH of the precursor on microstructure and magnetic properties were studied. The phase structure of the samples was examined by X-ray diffraction. The microstructure was examined by scanning electron microscope, atomic force microscope and polarized microscope. The magnetic property was measured by vibrating sample magnetometer. The results show that the crystals of different phases grow up independently. CoFe2O4 is uniformly embedded into the TiO2 matrix in the prepared composite films, and the growth of composite films is dependent on the heat treatment temperatures and PH of the precursor. The average size of CoFe2O4 crystal is 19 nm in Nanocomposite film prepared when the heat treatment temperature is 800℃ and the pH of the precursor is between 2 and 3. The magnetism of the composite films is enhanced as the heat treatment temperature increases.     

Structure and effect of diamagnetism on manganese lithium phosphate glass to cathode materials application

1-x(Li₂O–2P₂O₅)-xMnO₂ glasses where x ?= ?0.2, 0.3 and 0.4 ?mol%, respectively, were synthesized by melted-quenching method. The Mn and P oxidation states and local structures around Mn and P-ions including Mn–O and P–O bonding distances and coordination numbers have been studied via X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), respectively. XANES results exhibit a coexistence of oxidation state of Mn²⁺ and Mn³⁺ with a mean value of 2.82. Moreover, Mn and P K-edge EXAFS show the Mn–O and P–O bonding distances of approximately 2.083–2.094 ?Å and 1.766–1.774 ?Å, respectively. A paramagnetism was found for all Mn–P glasses. Additionally, the coercive field (H_c) and remnant magnetization (M_r) increased with increasing Mn contents. However, the low specific capacitances are seriously obtained (<40 ?F ?g^?1) suggesting the effect of natural diamagnetism of lithium phosphate based-glass unlike the borate based-glasses which originally exhibit paramagnetism.     

广西伊岭岩岩石(CaCO3)晶体结构、德拜温度以及硬度研究

本文从微观角度研究碳酸钙矿石的晶体结构与物理性能,为碳酸钙矿石的应用提供理论依据。利用X射线衍射(XRD)技术分析广西伊岭岩岩石2个样品(A_1、A_2)的相组成及其晶体结构,并利用带能谱仪的电子显微镜(SEM/EDS)测试这2个样品的各相成分。结果表明:广西伊岭岩岩石的主要成分为CaCO_3,其中A_1样品含有少量的K~+,A_2样品含有少量Na~+。通过Rietveld全谱图拟合晶体结构精修可知,K~+替代样品A_1主要物相CaCO_3中的Ca~(2+),使其点阵参数变大,单胞体积变大。同样A_2样品中的Na~+替代了样品中CaCO_3的Ca~(2+)位置,造成A_2中的CaCO_3点阵参数变小,单胞体积变小。德拜温度近似模型计算出2个样品的德拜温度分别为318.86K、324.82K。维氏硬度测试法测试出2个样品的硬度大小分别为132.6HV、148.9HV。     

SmCoO3钙钛矿氧化物的高压高温合成及其物性

采用高压高温方法合成钙钛矿型SmCoO₃氧化物, 利用XRD,Raman,电导率和热膨胀测试对样品的结构及性能进行表征. 实验结果表明, 在2.75~4.20 GPa, 1 061 ℃附近, Co₂O₃和 Sm₂O₃发生固相反应形成SmCoO₃, 但反应不完全. 单相SmCoO₃较好的合成条件为3.90 GPa和1 061 ℃左右. 室温Raman谱观察到单相样品中只有SmCoO₃正交相的特征峰. SmCoO₃样品在327 ℃以下为绝缘体, 在327 ℃以上电导率随温度升高而增加. 热膨胀系数在100~800 ℃呈线性变化.      

Determination of crystal structure of omphacite

The chemical formula of omphacite was expressed with (MⅡ MⅠ ) (Si, AI)2O6. Cations that occupied the MⅡ site were large cations such as Ca or Na, and (Na/(Na+Ca)) ratio ranged from 0.2 to 0.8; the 6-coordinated MⅠ site accommodated cations such as Mg, Fe2+, Al, Fe3+ ,and(AI/(AI+Fe3+)) ratio was more than 0.5. Omphacite space groups reported were C2/ c, P2, P2/n, P2/c, cell parameters are α0 = 0.9600-0.9630 nm,b0 = 0.8750-0.8830 nm,c0 = 0.5230-0.5290 nm,β = 106°40′-107°10'. The sample was picked up from the eclogites in Zhucheng County, Shangdong Province. The intensity data were collected with the RIGAKU RASA Ⅱ -S four-circle single crystal diffractometer.The correct structure model was obtained by using the Patterson method and Fourier synthesis, SHELX-76 program, structure refinement with 905 independent diffraction points (| F0 |> 3σ |F0 |). After the structure parameter refinement, the R-factor reduced to 0.0515. The crystal structure analysis indicates that omphacite has a new space group-Pn space group.