Preparation and Characterization of Al8.31Si1.91Mg3.78O20/Al4.8Si1.2O9.6/Mg2.0Al4.02Si4.98O18 Multiphase Material

A two-step sintering method was used to prepare Al8.31Si1.91Mg3.78O20 (corundum solid solution)/Al4.8Si1.2O9.6 (mullite solid solution)/Mg2.0Al4.02Si4.98O18 (cordierite solid solution) multiphase material, for the purposes of making these three crystal structures have point defects which could help the particles diffuse and transfer at high temperature, accelerate the sintering efficiently and enhance the material strength as well as the bulk density. The impacts of different formulas on the structure and properties of the multiphase material were investigated. With XRD and SEM analyses, for each sample, the crystal structure and microstructure were characterized, the crystalline phase content and cell parameters were determined with Rietveld Quantification software, and the properties were tested. The comparative optimal formula determined was calcinated chamotte of 80wt% and calcinated sludge of 20wt%; and its corresponding bending strength and retention rate of bending strength after a thermal shock were 29.74 MPa and 80.15%, respectively.     

Synthesis and crystal structure of dehydrated, deaminated, and dealuminated zeolite Y (FAU): single-crystal structure of |Na33H26(Al5O4)|[Si126Al66O384]-FAU

Host–guest complexes of Docetaxel 1, an anti-cancer drug have been isolated and crystal structures are described. Docetaxel crystallized in the 1:1 molar ratio with n-butanol, dimethylformamide (DMF) and acetonitrile (ACN) during crystallization from the respective solvents. In all the three complexes (1 · n-butanol, 1 · DMF and 1 · ACN), docetaxel formed a host framework through hydrogen bonds and the guest solvent molecules occupied the channels. The host is hydrogen bonded to the guest molecules through hydroxyl moieties. Interestingly, 1 · n-butanol, 1 · DMF and a literature 1 · CH₃OH · H₂O (1:1:1) host–guest complexes are isomorphs. Further, 1 · ACN complex unit cell parameters are similar (same space group) to the marketed docetaxel trihydrate polymorph (form A).     

Fluoride-assisted synthesis of mullite (Al5.65Si0.35O9.175) nanowires

Novel silicon-deficient mullite (Al5.65Si0.35O9.175) single crystal nanowires were synthesized in large quantities on mica substrates assisted by the intermediate fluoride species. The nanowires have diameters in the range 50-100 nm and typical lengths of several microm. Aligned nanowires were observed at the substrate edge. The nanowires have strong photoluminescence (PL) emission bands at 310, 397, 452 and 468 nm.     

ChemInform Abstract: Single-Crystal Structure of Partially Dehydrated Partially Mg2+-Exchanged Zeolite Y (FAU), [Mg30.5Na14(H2O)2.5] [Si117Al75O384]-FAU.

The crystal structure and the distribution and coordination geometry of Mg²⁺ ions in the title zeolite are determined by single crystal XRD.     

Microstructures of Alkoxide-Derived Barium Osumilite (BaMg2Al6Si9O30) Glass Ceramics

The crystallisation sequence of stoichiometric barium osumilite prepared by partial-alkoxide (PAR) and all-alkoxide routes (AAR) and the microstructure of the fully crystallised glass ceramic were examined. Comparing the crystallisation behaviours of the gel-glasses obtained revealed that the first phase to crystallise was mullite in PAR but hexacelsian in AAR. Barium osumilite crystals grew randomly and more homogeneously in PAR while in AAR larger barium osumilite crystals grew in clusters. Cordierite formed as a secondary phase in both routes and it crystallised on and between the osumilite lamellae. Mullite and hexacelsian also persisted up to the stage when full crystallisation and taken place.     

Determination of Al,Si and O in isolated steel inclusions by 14 MeV neutron activation analysis

The method of non-destructive analysis for Al, Si and O in non-metallic inclusions isolated from steel is presented. The small powdered samples varying in mass from 2 mg to 40 mg were analysed, thus making the development of a proper technique of sample preparation necessary. The specific activation geometry and rotation of samples during irradiation were chosen to improve the accuracy and precision. Lower limits of determination for Al, Si, and O were: 1.4 mg, 0.3 mg, and 0.8 mg, respectively.     

Crystal structure of a methylamine sorption complex of fully dehydrated fully Ca2+ -exchanged zeolite X, |Ca46(CH3NH2)16|[Si100Al92O384]-FAU

The structure of a methylamine sorption complex of fully dehydrated fully Ca2+-exchanged zeolite X, |Ca46(CH3NH2)16|[Si100Al92O384]-FAU, has been determined in the cubic space group Fd3 at 21(1) degrees C (a = 24.994(4) angstroms) by single-crystal X-ray diffraction techniques. The crystal was prepared by ion exchange in a flowing stream of 0.05 M aqueous Ca(NO3)2 for 3 days, followed by dehydration at 480 degrees C and 2 x 10(-6) Torr for 2 days, and exposure to 160 Torr of zeolitically dry methylamine gas at 21(1) degrees C. The structure was determined in this atmosphere and was refined, using the 739 reflections for which I > 0, to the final error indices R1 = 0.152 and R2 = 0.061. In this structure, Ca2+ ions occupy three crystallographic sites. Sixteen Ca2+ ions fill the octahedral site at the centers of hexagonal prisms (Ca-O = 2.429(7) angstroms). The remaining 30 Ca2+ ions are found at two nonequivalent sites II (in the supercages) with occupancies of 14 and 16 ions. Each of these Ca2+ ions coordinates to three framework oxygens, either at 2.296(7) or 2.334(7) angstroms, respectively. Sixteen methylamine molecules have been sorbed per unit cell, two per supercage. Each coordinates to one of the latter 16 site-II Ca2+ ions: N-Ca = 2.30(9) angstroms. The imprecisely determined N-C bond length, 1.48(23) angstroms, differs insignificantly from that in methylamine(g), 1.474(5) angstroms. The positions of the hydrogen atoms were calculated. One of the amino hydrogen atoms hydrogen bonds to a 6-ring oxygen, and the other forms a bifurcated hydrogen bond to two other 6-ring oxygens. The methyl group does not hydrogen bond to anything.     

A quantum chemical study of silsesquioxanes: H8Si8O12, Me8Si8O12, H@Me8Si8O12, He@Me8Si8O 12 + , and He@Me8Si8O12

Quantum chemical PBE0 and B3LYP/cc-pVTZ, PBE0, B3LYP, RHF and MP2/6-31G(d,p) methods are employed to calculate the structural parameters of octa(silsesquioxane) H₈Si₈O₁₂ and octa(methylsilsesquioxane) Me₈Si₈O₁₂. These molecules and complexes H@Me₈Si₈O₁₂, He@Me₈Si₈O ₁₂ ⁺ , and He@Me₈Si₈O₁₂ have highly symmetric (O _h ) equilibrium configurations. With the use of the PBE0 method and a cc-pVTZ multicenter basis set common for the complex and its components coincidence is achieved between the calculated polarizability of a free He atom and the experimental value of 0.21 ų and the polarizability depression of 0.17 ų was found for He@Me₈Si₈O₁₂. In order to avoid the false conclusion about molecular symmetry the calculations of the structure of silsesquioxanes must be performed with sufficiently high accuracy (Int = ultrafine and Opt = tight in the use of the GAUSSIAN program).     

锂离子电池用非晶态Si/Al/Si薄膜负极材料

采用磁控溅射法在铜箔集流体上沉积了具有“三明治”结构的Si/Al/Si三层薄膜. 高分辨率透射电镜(HRTEM)和选区电子衍射(SAED)分析结果表明, 该薄膜为非晶态. 扫描电镜(SEM)和能量散射X射线能谱(EDS)结果表明, 该薄膜总厚度约为4.0 μm, 循环100周后体积膨胀率为225％. 在1.5~0.005 V(vs. Li+/Li)和0.1 mA/cm2条件下, 该薄膜电极前5周衰减较快, 而后趋于平缓. 首次放锂量为0.88 mA·h/cm2, 循环5周后, 放锂量为0.71 mA·h/cm2, 100周后的放锂量仍能保持在0.61 mA·h/cm2. 研究结果表明, Al的加入有效地抑制了Si膜的体积膨胀, 使之具有良好的循环寿命. 交流阻抗结果表明, 随着循环次数的增加, 极化电阻首先从46.9 Ω·cm2(第1周)降低到36.2 Ω·cm2(第50周), 而后又升高到47.3 Ω·cm2(第100周). Al的加入提高了Si膜的导电性, 有效地降低了其极化电阻, 改善了Si膜的电压滞后现象.     

The Ionic Conductivity of Ultrafine Solid Electrolytes for Li4.4Al0.4Si0.6O4‐xY2O3 Systems

The Li_4.4Al_0.4Si_0.6O₄‐xY₂O₃ (x = 0 to 0.5) ion conductors were prepared by the Sol‐Gel method and examined in detail. The powder and sintered samples were characterized by DTA‐TG, XRD, SEM, and AC impedance techniques. The experimental results show that the conductivity and sinterability increased with the amount of excess Y₂O₃ in the silicate. The particle size of the powder samples is about 0.12 μm. The maximum conductivity at 16 °C is 2.925 × 10^?5s·cm^?1 for Li_4.4Al_0.4Si_0.6O₄‐0.3 Y₂O₃.