Coupled isomorphic substitution and exsolution of pyroxene,rutile, apatite and quartz in supersilicic garnet

Dissolution of pyroxene in garnet at ultrahigh pressures produces supersilicie garnet with the coupled substitutions of Si^Ⅵ M^Ⅵ= A^Ⅵ A^Ⅵ and Si^Ⅵ Na^Ⅷ=A^Ⅵ M^Ⅷ,which are enhanced by rising pressure. The supersilicic garnet and exsolution of pyroxene, rutile, apatite and quartz in garnet during decompression were found in natural rocks,pointing to the importance in studying mantle-derived rocks and ultrahigh pressure metamorphism related to plate deep subduction. Ti, P, K and H2O enters garnet via the substitutions of Ti = Si, P^Ⅵ Na^Ⅷ = Si^Ⅵ CaⅧ, Si^Ⅵ K^Ⅷ = AI^Ⅵ M^Ⅷ, and [(OH)4]^4- = [SiO4]^4- or [4H]^4 = Si^4 respectively. The possible entering of Eskola pyroxene component M0.5AlSi2O6 in clinopyroxene, together with the common pyroxene component M2Si2O6, into garnet can lead to the presence of the substitution of Si^Ⅵ 0.5□^Ⅷ= A^Ⅵ 0.5M^Ⅷ in garnet structure, which plays a key role in the exsolution of rntile, apatite and quartz in garnet. Two new breakdown reactions are thus proposed on the basis of the new coupled substitution, which can be regarded as a theoretical model for the exsolntion of the 3 minerals in garnet. The real exsolution may be a combination of several breakdown reactions.     

Surface chemical structure of titania-silica nanocomposite powder

Titania-silica （TS） nanocomposite powder with three different composite structures, containing 10-30 mol% SiO2 in each structure, have been prepared by sol-gel processes. The surface characteristics of these titania-silica samples have been investigated by X-ray photo-emission spectroscopy （XPS） and high resolution transmission electron microscopy （HRTEM）. The study for all TS oxides annealed at 773 and 1173 K showed： an abnormal surface enrichment in Si increased with increasing annealing temperature; the Ti^3＋, Ti^2＋, Si^3＋ and Si^2＋ oxides coexisted with Ti^4＋ and Si^4＋ oxides, and the contents of these Ti/Si suboxides increased with increasing SiO2 content and annealing temperature; there was a layer rich in O on the topmost surface and the excess O could be attributed to the chem-adsorption of H2O; different composite structures could lead to different contents of Ti/Si suboxides. These results indicated that the surface of TS oxide powder derived by sol-gel process was a double layer with enriched O first and then SiOx/TiOy（x, y〈2）. Ti/Si suboxides could result from the thermal diffusion of Ti^4＋ and Si^4＋, which might be induced by the strong interaction between Ti^4＋ and Si^4＋.     

Y2O2S:Eu3+,Zn2+,Ti4+荧光体的缺陷及红色长余辉发光性质

采用高温固相法合成了红色长余辉材料Y2O2S:Eu3+,Zn2+,Ti4+,实现了余辉发光中心和缺陷中心之间的能量传递。通过XRD、荧光发射和激发光谱、余辉发射光谱与衰减曲线、色坐标和热释光谱测试手段对Y2O2S:Eu3+,Zn2+、Y2O2S:Eu3+,Ti4+、Y2O2S:Eu3+,Zn2+,Ti4+和Y2O2S:Eu3+,Mg2+,Ti4+进行了结构与性能的表征,发现其荧光发射与余辉发射基本一致,红色余辉发光主峰位于625 nm附近,来源于Eu3+的5D0→7F2跃迁发射。相比而言,Y2O2S:Eu3+,Zn2+,Ti4+余辉发光性能最好,可持续1.5 h左右。     

Synthesis characterization and improved electrochemical performance of Li_2FeSiO_4/C as cathode for lithium-ion battery by metal doping

In this paper, Li_2FeSi_(0.98)M_(0.02)O_4/C(M = Mg, Zn, Co, Mn, Ni) was synthesized as cathode material for lithium ion battery by solid-state method. The results show that the materials doped with Mg and Zn at the Si-sites have good initial discharge capacity. Then Li_2FeSi_(1-x)M_xO_4/C(M = Mg, Zn; x = 0.01, 0.02, 0.03, 0.05) were also synthesized via solid-state method. It is concluded that Li_2FeSi_(0.99)Mg_(0.01)O_4/C and Li_2FeSi_(0.98)Zn_(0.02)O_4/C have better initial discharge capacity which is 125 mAh/g and 166.2 mAh/g, respectively. The capacity of Li_2Fe_(0.98)Zn_(0.02)SiO_4/C is 157.3 m Ah/g after 10 cycles at 0.1 C, and the capacity retention rate is 94.6%. The Li~+ diffusion coefficient of Li_2FeSi_(0.98)Zn_(0.02)O_4/C is higher than that of pure phase materials by one order of magnitude. The Li_2FeSi_(0.99)Mg_(0.01)O_4/C and Li_2FeSi_(0.98)Zn_(0.02)O_4/C were tested by XRD and SEM. XRD patterns indicate that the crystal structure of Li_2FeSiO_4 is not changed after being doped with metal ion at the Si-site. The SEM image indicates that no obvious agglomeration is detected in these materials. Li_2FeSi_(0.98)Zn_(0.02)O_4/C processes better electrochemical performance analyzed by EDS、XPS and FT-IR spectra. The data prove that Si~(4+) is successfully replaced by Zn~(2+) in the crystal structure of Li_2FeSiO_4.     

Synthesis and luminescence properties of Eu3+, Sm3+ doped (YxGd1-x)2O3:Si4+, Mg2+ long-lasting phosphor

A novel red long-lasting phosphor, (Y_1−x Gd _x )₂O₃:Eu³⁺, Sm³⁺, Si⁴⁺, Mg²⁺, was synthesized by the co-precipitation method using oxalate precipitation as the precursor. X-ray diffraction (XRD), scanning electronic microscopy (SEM), integrated thermal analyzer (TG), and photoluminescence spectra (PL) as well as the ST-900PM weak light photometer were used to study the synthesis conditions, morphology, luminescence properties, and the decay time of the phosphor. The XRD results show that the products synthesized at 1400°C for 4 h have good crystallization without any detectable impurity phases. Based on the PL spectra, the optimal conditions are as the following. The molar ratios of Y³⁺ to Gd³⁺ and Eu³⁺ to Sm³⁺ are 2:8 and 3:1, respectively, and the contents of Mg²⁺ and SiO₂ are 5mol% and 3mol%, respectively. The decay time monitored by the ST-900PM weak light photometer is 7200 s, increasing 44% and 100%, respectively, compared with the Eu³⁺ and Sm³⁺ single-doped phosphors. The results indicate that the energy transfer is from Sm³⁺ to Eu³⁺ ion, and Sm³⁺ is a good sensitizer to Eu³⁺.     

Thermal degradation of BaAl2Si2O8：Eu2＋ phosphor excited by near ultraviolet light

Eu2+ doped BaAl2Si2O8 phosphor was synthesized by one-step calcination of precursors that were prepared by chemical co-precipitation.The thermal degradation properties of BaAl2Si2O8:Eu2+ were investigated by photoluminescence,lifetime and chromaticity coordinate measurements.BaAl2Si2O8:Eu2+ is efficiently excited by incident light of 250-400 nm,which matches the emission of near ultraviolet LED chips well.BaAl2Si2O8:Eu2+ exhibits broad blue emission at 470 nm because of the 4f65d1-4f7(8S7/2) transition of Eu2+ ions,and the emission band shows an unusual blue shift with bandwidth broadening and emission intensity decreasing as the annealing temperature is increased.The luminescence decay and CIE chromaticity coordinates of BaAl2Si2O8:Eu2+ were determined to investigate its application in white LEDs.     

Experimental studies on silicate structures of basaltic glasses quenched at 1 65093 and 1–3.5 GPa

A series of melting experiments was carried cut at 1 650°C and 1.00–3.00 GPa using alkaline basalt as starting material. The cornpitions of quenched basaltic glasses in the products were detected by electron micro probe. Their CIPW norms were calculated and their refractive indices were determined by the oil-infused method. The Raman spectrum of the quenched basaltic glasses indicates that their main structural species are monomer [Si₂O₄]1⁴⁻, chain [Si₂O₆]1^4- and sheet [Si₂O₅]1^2-. The relationship at the same temperature between the proportions of integrated areas of structural species, and compositions and pressures was discussed.     

Investigation of the electronic structure and photoluminescence properties of Eu3＋ in Sr2Mgl_xZnxSi207 （0 〈x 〈 1）

Undoped and Eu 3+-doped Sr 2 Mg 1-x Zn x Si 2 O 7 (0≤x≤1) powder crystals were obtained by conventional solid-state reaction.X-ray diffraction,inductively coupled plasma analysis,and Fourier transform infrared spectroscopy results implied that a complete solid-solution formed between Sr 2 MgSi 2 O 7 and Sr 2 ZnSi 2 O 7 as well as local structural adjustment.Excitation spectra exhibited O 2-Eu 3+ charge transfer (CT) bands centered at 250 nm for Sr 2 MgSi 2 O 7:Eu 3+ and 258 nm for Sr 2 ZnSi 2 O 7:Eu 3+.Emission spectra exhibited a major band around 616 nm,which showed the environment around Eu 3+ was non-centrosymmetric in both Sr 2 MgSi 2 O 7:Eu 3+ and Sr 2 ZnSi 2 O 7:Eu 3+.In addition,first principles calculations within the local density approximation (LDA) of density functional theory (DFT) were used to calculate the electronic structure of Sr 2 MgSi 2 O 7 and Sr 2 ZnSi 2 O 7.Calculated results were correlated with experimental UV-vis reflection spectra and the observed shift of the O 2-Eu 3+ CT band.     

Summer monsoon and dust signals recorded in the Dasuopu firn core, central Himalayas

In September 1997, a 15-m firn core was recovered from an elevation of 7 000 m a. s.l. from the Dasuopu Glacier in the central Himalayas. The analysis of δ18O values and major ion (Ca2+ , Mg2+ , NH4+ , SO42- and NO3-) concentrations shows that average annual accumulation is 0.75 m (water equivalent) in the Dasuopu firn core. The seasonal variations of δ18O values and major ion concentrations in the core indicate that present summer monsoon and dust signals are recorded with high-resolution in the Dasuopu Glacier. δ18O in precipitation are controlled by amount effect in summer monsoon season, more negative δ18O is representative of summer monsoon signal in snow layers. Higher concentrations of Ca2+ , Mg2+ , SO42- and NO3-are dominated by spring dust storm imput derived from the arid and semi-arid desert regions in central Asia. Also EOF analysis verifies that high spring concentrations of major ions are consistent. Due to the possibly different sources, the secondary variations of NH4+ and NO3- are negatively relevant with that of Ca2+ and Mg2+ .     

Petrochemical characteristics of leucogranite and a case study of Bengbu leucogranites

Leucogranites have a relatively narrow variation in SiO2 content （70.5%-75.5%）. Giving similar SiO2 content, leucogranites have relatively higher Al2O3 （〉13.5%） and lower TFeO ＋ MgO （〈2.5%） contents than those of normal granites. These petrochemical characteristics suggest that leucogranites are de- rived from partial melting at relatively low temperature and are not significantly affected by fractional crystallization. In the present study, we propose that the Al2O3 vs SiO2 and TFeO ＋ MgO vs SiO2 dia- grams can be used to distinguish leucogranites from normal granites. In addition, we report the major element compositions of the Jurassic granitic intrusions from Jingshan-Tushan-Mayishan in the Bengbu area, east-central China. Using the Al2O3 vs SiO2 and TFeO ＋ MgO vs SiO2 diagrams and the comparison with the High Himalayan leucogranites in mineralogical and petrochemical characteristics, we suggest that the Jingshan-Tushan-Mayishan intrusions belong to a leucogranite belt. Similar to those of the High Himalayan leucogranites, the Bengbu leucogranites have low Mg# values, indicating that they resulted from low temperature dehydration partial melting of the subducted continental crust of the South China Block at the crustal depth.     

Phase analysis and thermal conductivity of in situ O′-sialon/β-Si3N4 composites

Typical O??-sialon-based ceramics, with a formula of Si_2?x Al _x O_1+x N_2?x , where x was set as 0.25, were fabricated by in-situ synthesis. Si₃N₄, Al₂O₃, and SiO₂ powders were used as raw materials, and MgO and Y₂O₃ were added as sintering additives. All the samples were sintered at different temperatures under a nitrogen pressure of 0.25?C0.30 MPa, and their microstructure, phase content, and thermal conductivity were evaluated. The effects of O??-sialon and ??-Si₃N₄ on the thermal conductivity were analyzed by numerical calculation in detail. In the case of the similar porosity, the thermal conductivity of O??-sialon-based ceramics decreased with the ratio of O??-sialon/??-Si₃N₄ increasing. When the ratio was 12, the thermal conductivity of O??-sialon ceramics sintered at 1360°C was 1.197 W·m^?1·K^?1.     

泡沫镍上原位生长CoMn2O4多级空心纳米球作为超级电容器电极材料的电化学性能研究

采用水热法结合空气气氛中的热处理过程,在泡沫镍（NF）表面生长了锰酸钴（CoMn₂O₄）多级空心纳米球,通过X射线衍射仪（XRD）、场发射扫描电镜（FE-SEM）和X射线光电子能谱（XPS）等测试手段对纳米球进行了表征.在三电极电化学测量系统中,0.1Co²⁺-250电极材料在5 mA·cm^-2时的面积比电容高达6 184 mF·cm^-2.以0.1Co²⁺-250为正极,商用活性炭（AC）为负极组装而成的混合超级电容器,在1.6 mW·cm^-2时的最大能量密度为0.112 mWh·cm^-2.即使在功率密度为16 mW·cm^-2时,能量密度仍达到0.064 mWh·cm^-2.在2 mA·cm^-2的电流密度下,经过10 000次充放电循环后,电容保持了初始值的93%.因其优越的电化学性能和低成本的便捷合成方法,CoMn₂O₄多级空心纳米球作为电极材料具有重要的应用前景.     

Near-infrared to visible up-conversion emissions of Er^3＋ doped Al2O3 powders derived from the sol-gel method

The Er3 doped Al2O3 powders were prepared by the sol-gel method using the aluminium isopropoxide [Al(OC3H7)3]-derived Al2O3 sols with addition of the erbium nitrate [Er(NO3)3.5H2O]. The different phase structure, including three crystalline types of (Al,Er)2O3 phases, γ, θ, α, and two Er-Al-O phases, ErAlO3 and Al10Er6O24, was obtained with the 1 mol% Er3 doped Al2O3 powders at the different sintering temperatures of 600―1200℃. The green and red up-conversion emissions centered at about 523, 545 and 660 nm, corresponding respectively to the 2H11/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3 , were detected by a 978 nm semiconductor laser diodes excitation. The phase structure and OH content had evident influence on the up-conversion emissions intensity. The maximum intensities of both the green and red emissions were obtained respectively for the Er3 doped Al2O3 powders sintered at 1200 ℃, which was composed mainly of α-(Al,Er)2O3, less of ErAlO3 and Al10Er6O24 phases, and with the least OH content. The two-photon absorption up-conversion process was involved in the green and red up-conversion emissions of the Er3 doped Al2O3 powders.     

Soft chemical synthesis and luminescence properties of red long-lasting phosphors Y2O2S:Sm3+

Sm³⁺-activated Y₂O₂S red phosphors were prepared by the combustion method and microemulsion method at the first time. X-ray characterization and electron diffraction show that, Y₂O₂S:Sm³⁺, Ti⁴⁺, Mg²⁺ samples prepared by these two methods are pure hexagonal crystals in structure with a trivial change due to dopants. Scanning electron microscopy (SEM) results show that the product presents an almond-like sheet in uniform size. Under the excitation of 269 nm ultraviolet light, Y₂O₂S:Sm³⁺ samples fabricated by these two methods exhibit three main groups of red emission lines located at 564, 604, and 656 nm, respectively, which are attributed to the transitions of 4G_5/2 →6H_5/2, 4G_5/2 →6H_7/2, 4G_5/2 →6H_9/2, respectively. The samples prepared by microemulsion are seven times higher in fluorescent emission intensity and half time longer in afterglow time than that prepared by combustion.     

基于植酸锆/普鲁士蓝复合膜的电催化行为研究

通过层层自组装技术,构建植酸锆/普鲁士蓝(Zr-IP_6/PB)多层结构膜.基于普鲁士蓝(PB)对双氧水(H_2O_2)有很高的电催化性能,加之5层植酸锆/普鲁士蓝膜多孔结构有利于传质过程,该H_2O_2传感器具有高灵敏度和高选择性.实验结果显示:修饰电极对H_2O_2响应的物质的量浓度范围为2.00×10~(-5)～1.76×10~(-3) mol·L~(-1),线性相关系数R=0.998 9.     

Crystallization and preliminary crystallographic studies of insulin T3R3 states created in different conditions

In the presence of a series of small organic molecules including 1, 4 dioxane, DMF, isopropanol, rDNA human insulin, mutants A21 Asn→Ser and (A21 Asn→Ser, B27 Thr→Arg) human insulin have been crystallized in both Zn 2+ containing and Zn 2+ free system. Preliminary crystallographic analyses show that they all belong to T 3R 3 structural type. The results indicate that, except phenolic derivatives and lyotropic anions reported before, some other appropriate organic molecules can also induce the T 3R 3 conformation transition of insulin.     

Mineralogical and sink-float studies of Jajarm low-grade bauxite

Jajarm’s bauxite deposits are mainly diasporic, and they have a low mass ratio of Al₂O₃/SiO₂. It is necessary to increase the run-of-mine mass ratio before feeding the material to the Bayer process. Chemical analysis indicated that the low-grade bauxite sample from Jajarm contained 43.9wt% Al₂O₃ and 13.35wt% SiO₂, resulting in a mass ratio of 3.29. According to mineralogical studies, the presence of aluminosilicate minerals such as kaolinite, illite, and quartz was the main reason for the decrease of the mass ratio. Microscopic observations revealed that, with the size reduction from -1000+710 to -38 μm, the liberation degree of diaspore increased from 10% to 60%, and that of aluminosilicates increased from 20% to 85%. Heavy liquids with the densities of 2.8, 3.0, 3.2, and 3.4 g/cm3 were used to evaluate the heavy media separation in three sizes, i.e., -3350+710, -710+212, and -212+125 μm. Laboratory studies confirm that the density of 3.2 g/cm3 can produce the concentrates (in sunk fractions) with recoveries of 89.09%, 91.24%, and 84.68% with the Al₂O₃/SiO₂ mass ratios of 5.03, 5.16, and 5.15 for the -3350+710, -710+212, and -212+125 μm sizes, respectively.     

High-pressure sound velocity of perovskite-enstatite and the possible composition of the Earth’s lower mantle

The compressional sound velocity V_p for enstatite of polycrystalline specimens were measured at pressures from 40 to 140 GPa using the optical analytical techniques under shock loading. The dependence of V_P, (in km/s) on Hugoniot pressure (P, in GPa) can be described by InV_p= 3.079-0.691 In(P) + 0.094(lnP)². V_p satisfies Birch’s law:V _p = 4.068 + 1.677_ρ, where ρ is corresponding density, which indicated that enstatite is stable throughout the conditions of the lower mantle. The wave velocityP is 0.5% lower and the wave velocity S is 2% higher than that of PREM respectively. We concluded that the lower mantle is mainly composed of perovskite-(Mg_1-x, Fe_x) SiO₃ and only a small amount of (Mg_1-x, Fe_x) O is allowed in it.     

Preparation and luminescence characteristics of Sr3SiO5：Eu^2＋ phosphor for white LED

The Sr3SiO5：Eu^2＋ phosphor was synthesized by high temperature solid-state reaction. The emission spectrum of Sr3SiO5：Eu^2＋ shows two bands centered at 487 and 575 nm, which well agree with the theoretic values of emission spectrum. The excitation spectrum for 575 nm emission center has several excitation bands at 365, 418, 458 and 473 nm. And the results show that the emission spectrum of Sr3SiO5：Eu^2＋ is influenced by the Eu^2＋ concentration. The relative emission spectra of the white-emitting InGaN-based YAG：Ce^3＋ LED and Sr3SiO5：Eu^2＋ LED were investigated. The results show that the color development of InGaN-based Sr3SiO5：Eu^2＋ is better than that of InGaN-based YAG：Ce^3＋, and the CIE chromaticity of InGaN-based Sr3SiO5：Eu^2＋ is （x=0.348, y=0.326）.     

Degradation of 2, 4-D acid using Mn2+ as catalyst under UV irradiation

In this paper, the oxidative degradation of 2, 4-dichlorophenoxyacetic acid (2, 4-D) using Mn²⁺/H₂O₂ reagent under UV irradiation was studied. The results show that 2, 4-D was degraded more completely in Mn²⁺/H₂O₂ solution than traditional Fenton solutions. The effects of the concentration of Mn²⁺, H₂O₂ and pH were also investigated. And under the optimal condition of 1.48×10⁻⁴ mol/L, 8.99×10⁻⁵ mol/L and pH 3.38, the formation of ·OH was the most, both the decomposition rate of H₂O₂ and the degradation rate of 2, 4-D were the fastest. In addition, the photoreaction process was monitored using spin-trapping electron paramagnetic resonance (EPR), and the results indicated that the oxidative process was predominated mainly by the hydroxyl radical (·OH) gennerated in the system. Biography: HUANG Yingping (1964–), Professor, Ph. D., research direction: pollution ecology and water pollution control.