用仪器中子活化分析研究岩庄陨石元素宇宙化学特征

用中子活化分析测定了新陨岩庄陨石的主量和微量元素含量。陨石浅灰色相的微量元素化学特征与Ｈ６型相似。金属粒子中稀土元素相对富集，有非常明显的Ｅｕ正异常，与Ｈ６型比较以低的Ｂｒ，Ｚｎ含量和高的Ｆｅ、Ｎｉ、Ｉｒ、Ａｕ丰度为其特征。讨论了岩庄陨石在微重力影响下，微量元素宇宙化学特征与太空八面体Ｆｅ－Ｎｉ金属四同心环微晶体结构生长可能的内在联系。

Formation kinetics and transition mechanism of CaO·SiO2 in low-calcium system during high-temperature sintering

The crystal structure,formation kinetics and micro-morphology of CaO·SiO2 during high-temperature sintering process were studied in low-calcium system by XRD,FT-IR,Raman and SEM-EDS methods.When the molar ratio of CaCO3 to SiO2 is 1.0,β-2CaO·SiO2 forms firstly during the heating process,and then CaO·SiO2 is generated by the transformation reaction of pre-formed 2CaO·SiO2 with SiO2.3CaO·SiO2 and 3CaO·2SiO2 do not form either in the heating or sintering process.Rising the sintering temperature and prolonging the holding time promote the phase transition of 2CaO·SiO2 to CaO·SiO2,resulting in the sintered products a small blue shift and broadening in Raman spectra.The content of CS can reach 97.4%when sintered at 1400℃ for 1 h.The formation kinetics of CaO·SiO2 follows the second-order chemical reaction model,and the corresponding apparent activation energy and pre-exponential factor are 505.82 kJ/mol and 2.16×10^14 s^−1 respectively.

Design of a ZnO/Poly(vinylidene fluoride)inverse opal film for photon localization-assisted full solar spectrum photocatalysis

Owing to its photonic band gap(PBG)and slow light effects,aniline black(AB)-poly(vinylidene fluoride)(PVDF)inverse opal(IO)photonic crystal(PC)was constructed to promote the utility of light and realize photothermal synergetic catalysis.As a highly efficient reaction platform with the capability of restricting heat,a microreactor was introduced to further amplify the photothermal effects of near infrared(NIR)radiation.The photocatalytic efficiency of ZnO/0.5AB-PVDF IO(Z0.5A)increases 1.63-fold compared to that of pure ZnO film under a full solar spectrum,indicating the effectiveness of synergetic promotion by slow light and photothermal effects.Moreover,a 5.85-fold increase is achieved by combining Z0.5A with a microreactor compared to the film in a beaker.The photon localization effect of PVDF IO was further exemplified by finite-difference time-domain(FDTD)calculations.In conclusion,photonic crystal-microreactor enhanced photothermal catalysis has immense potential for alleviating the deteriorating water environment.

Fabrication of 3D structure by combining AFM and chemical etching on crystalline silicon surface

AFM is used for forming silicon dioxide as a layer (mask) on the silicon wafer surface (100) during the cutting process in ambient atmosphere. The silicon dioxide is made through reaction of silicon and oxygen in the atmosphere. As a result of the anisotropic behavior of single crystalline silicon, the etching rates in alkaline solution depend greatly on the various crystal orientations. The anisotropic etching behaviors in KOH solution and reasons of crystalline silicon are described. Effect of etching conditions such as etching temperature and KOH concentration of the alkaline solution on height of the micro-protuberances has been described.

Synthesis and Crystal Structure of N-cyclopropyl-9 -(3,4-dicholophenyl)-1,2,3,4,5,6,7,8,9,10-decahydroacridine -1,8-dione under Microwave Irradiation

The N-cyclopropyl-9-（3,4-dicholophenyl）- 1,2,3,4,5,6,7,8,9,10-decahydroacri- dine-1,8-dione was synthesized by the reaction of 1,3-cyclohexanedione, N-cyclopropylamine and 3,4-dicholoaldehyde in water and glycol under microwave irradiation. Its crystal structure was determined by single-crystal X-ray diffraction analysis. It possesses P212121 space group, with a = 9.9103（5）, b = 13.3597（8）, c = 14.5633（8）A, V= 1928.16（18）A3 ,Mr = 402.30, Z = 4, Dc= 1.386 g/cm^3, 2 = 0.7107A,μ（MoKα）=0.354mm^-1 and F （000） = 840. The structure was refined to R = 0.0280 and wR = 0.0757. In the structure, the pyridine ring adopts a boat conformation.

Characterization of calcium deposition induced by Synechocystis sp. PCC6803 in BG11 culture medium

Calcium carbonate （CaCO3） crystals in their preferred orientation were obtained in BG11 culture media inoculated with Synechocystis sp. PCC6803 （inoculated BG11）. In this study, the features of calcium carbonate deposition were investigated. Inoculated BGll in different calcium ion concentrations was used for the experimental group, while the BGll culture medium was used for the control group. The surface morphologies of the calcium carbonate deposits in the experimental and control groups were determined by scanning and transmission electron microscopy. The deposits were analyzed by electronic probe micro-analysis, Fourier transform infrared spectrum, X-ray diffraction, thermal gravimetric analysis and differential scanning calorimetry. The results show that the surfaces of the crystals in the experimental group were hexahedral in a scaly pattern. The particle sizes were micrometer-sized and larger than those in the control group. The deposits of the control group contained calcium （Ca）, carbon （C）, oxygen （O）, phosphorus （P）, iron （Fe）, copper （Cu）, zinc （Zn）, and other elements. The deposits in the experimental group contained Ca, C, and O only. The deposits of both groups contained calcite. The thermal decomposition temperature of the deposits in the control group was lower than those in the experimental group. It showed that the CaCO3 deposits of the experimental group had higher thermal stability than those of the control group. This may be due to the secondary metabolites produced by the algae cells, which affect the carbonate crystal structure and result in a close-packed structure. The algae cells that remained after thermal weight loss were heavier in higher calcium concentrations in BGll culture media. There may be more calcium- containing crystals inside and outside of these cells. These results shall be beneficial for understanding the formation mechanism of carbonate minerals.

Self-assembled flower-like microstructure in Zn_(1-x)Cd_xO nanoparticles

The structural and optical characterization of cadmium-doped zinc oxide nanoparticles synthesized by precipitation method was studied.X-ray diffraction study confirmed the substitution of cadmium dopant without disturbing the basic wurtzite structure of zinc oxide.The average crystalline size,lattice constants and unit cell volume also increased up to4%of cadmium doping.Energy gaps of the samples were determined from the ultraviolet?visible absorption spectrum as well as Tauc’s plot which infers that the energy gap decreases with the increase of cadmium content.Fourier transformation infrared spectrum confirms the cadmium dopant through peak shifting from485to563cm?1.Photoluminescence spectrum also defines the cadmium dopant by intensity increase.The broad Raman peak at437cm?1indicates that the wurtzite structure of zinc oxide is weakened by5%cadmium doping.Field emission scanning electron microscope study also confirms the existence of particles in nanometer size and it indentifies the microstructure transformation from nanoparticles to jasmine flower-like structure on5%cadmium doping.

Effects of thermoelectric-magneto convection on the solidified microstructures of Al-4.5%Cu alloy

A magnetic field was used to directional solidification of dendritic Al-Cu alloys. The primary arm spacing of the dendrites is increased with increasing the external magnetic field strength. This microstructural coarsening is related to the thermoelectric current on the l/s interface, which is induced by difference of temperature on the inter- face. Within a magnetic field Lorentz force may be generated in front of the interface, causing a thermoelectric-magneto convection that makes the microstructure coarsened. This induced convection also leads to structural instability so that the secondary arms are well developed when grown in the external field.

SEM/EBSD analysis of quartz cementation and compaction microstructures during diagenesis of sandstone

Compaction and silicon cementation are the dominant processes reducing porosity and permeability in quartzose sandstones during diagenesis. Despite the wealth of information about quartz cementation, there are still unanswered questions related to mechanisms of growth of quartz cement and the diagenesis processes. In this study we present an electron backscatter diffraction （EBSD） analysis, combined with optics and cathodoluminescence （CL） information, for the quartz sandstones from the Upper Triassic Xujiahe Formation of Sichuan Basin, in order to reveal the microstructural and crystallographic features of the silica cementation and detrital grain during the compaction. The EBSD is a crucial technique to provide essential crystallographic data on the quartz grain and its cement. Quartz cement is shown to be syntaxial to its host quartz grain. EBSD data-based orientation maps show dauphin6 twinning and low angle boundary to be common in the host grains and quartz cement of the samples. The dauphin6 twins occurred in grain-grain contacts and in cement-crystal boundaries, and commonly crossed grain cement boundaries. These features indicate that there may be two types of dauphin6 twins, one inherited twins from the source area and the other developed by compaction-induced grain boundary deformation. These investigations suggest that strong mechanical compaction may occur after and/or during quartz cement growth in the later diagenesis of the Xujiahe sandstones. EBSD has a capability of revealing microstructural information and regarding mechanisms of diagenesis crystal growth in quartzose sandstones.

High-entropy alumino-silicides: a novel class of high-entropy ceramics

High-entropy ceramics(HECs) are gaining significant interest due to their huge composition space, unique microstructure, and adjustable properties. Previously reported studies focus mainly on HECs with the multi-cationic structure, while HECs with more than one anion are rarely studied. Herein we reported a new class of HECs, namely highentropy alumino-silicides(Mo0.25Nb0.25Ta0.25V0.25)(Al0.5Si0.5)2(HEAS-1) with multi-cationic and-anionic structure. The formation possibility of HEAS-1 was first theoretically analyzed from the aspects of thermodynamics and lattice size difference based on the first-principles calculations and then the HEAS-1 were successfully synthesized by the solid-state reaction at 1573K. The as-synthesized HEAS-1 exhibited good single-crystal hexagonal structure of metal alumino-silicides and simultaneously possessed high compositional uniformity.This study not only enriches the categories of HECs but also will open up a new research field on HECs with multi-cationic and-anionic structure.

Te-seeded growth of few-quintuple layer Bi2Te3 nanoplates

We report on a Te-seeded epitaxial growth of ultrathin Bi2Te3 nanoplates （down to three quintuple layers （QL）） with large planar sizes （up to tens of micrometers） through vapor transport. Optical contrast has been systematically investigated for the as-grown Bi2Te3 nanoplates on the SiO2/Si substrates, experimentally and computationally. The high and distinct optical contrast provides a fast and convenient method for the thickness determination of few-QL Bi2Te3 nanoplates. By aberration-corrected scanning transmission electron microscopy, a hexagonal crystalline structure has been identified for the Te seeds, which form naturally during the growth process and initiate an epitaxial growth of the rhombohedral- structured Bi2Te3 nanoplates. The epitaxial relationship between Te and Bi2T% is identified to be perfect along both in-plane and out-of-plane directions of the layered nanoplate. Similar growth mechanism might be expected for other bismuth chalcogenide layered materials.

Structure-property relationships in ILs: A study of the alkyl chain length dependence in vaporisation enthalpies of pyridinium based ionic liquids

The enthalpies of vaporization for the series of pyridinium-based ionic liquids with bis（trifluoromethylsulfonyl）imide anion [CnPy][NTfz] （n = 2, 3, 4, 5, and 6） have been determined with the quartz crystal microbalance technique combined with the Langmuir evaporation. The linear dependence of vaporization enthalpies on the chain length has been revealed. New approach based on volumetric, surface tension, and speed of sound measurements has been developed for estimation of heat capacity differences between gas and liquid phase, which were required for adjustment of measured vaporization enthalpies to the ref- erence temperature 298 K.

Crystal structure of histidine-containing phosphocarrier protein from Thermoanaerobacter tengcongensis MB4 and the implications for thermostability

Protein thermostability is an inherent characteristic of proteins from thermophilic microorganisms,and therefore enables these organisms to survive at extreme temperatures.Although it is well-known that thermostable proteins are critical for the growth of thermophilic organisms,the structural basis of protein thermostability is not yet fully understood.The histidine-containing phosphocarrier (HPr) protein,a phosphate shuttle protein in the phosphoenolpyruvate-dependent sugar transport system (PTS) of bacterial species,is an ideal model for investigating protein thermostability with respect to its small size and deficiency in disulphide bonds or cofactors.In this study,the HPr protein from Thermoanaerobacter tengcongensis (TtHPr) is cloned and purified.Crystal structure with good quality has been determined at 2.3 resolution,which provides a firm foundation for exploring the thermostable mechanism.However,it shows that the crystal structure is conserved and no clue can be obtained from this single structure.Furthermore,detailed comparison of sequence and structure with the homologs from mesoor thermophilic bacteria shows no obvious rule for thermostability,but the extra salt-bridge existing only in thermophilic bacteria might be a better explanation for thermostability of HPr.Thus,mutations are performed to interrupt the salt-bridge in HPrs in thermophilic bacteria.Using site-directed mutations and the circular dichroism method,thermostability is evaluated,and the mutational variations are shown to have a faster denaturing rate than for wild-type viruses,indicating that mutations cause instability in the HPrs.Understanding the higher-temperature resistance of thermophilic and hyperthermophilic proteins is essential to studies on protein folding and stability,and is critical in engineering efficient enzymes that can work at a high temperature.

Advances in organic micro/nanocrystals with tunable physicochemical properties

Organic micro/nanocrystals based on small organic molecules have drawn extensive attention due to their potential application in organic field-effect transistors,electrochemical sensors,solar cells,etc.Herein,the recent advances for organic micro/nanocrystals from the perspective of molecule aggregation mode,morphology modulation,and optical property modulation are reviewed.The stacking mode and the intermolecular interaction depend on the molecular structure,which eventually determines the morphology of organic micro/nanocrystals.The morphologies of the organic micro/nanocrystals make the aggregates exhibit photon confinement or light-guiding properties as organic miniaturized optoelectronic devices.In this review,we conclude with a summary and put forward our perspective on the current challenges and the future development of morphology and optical tunable direction for the organic micro/nanocrystals.

Effect of anions from calcium sources on the synthesis of nano-sized xonotlite fibers

The xonotlite fibers were synthesized via the hydrothermal synthesis method with CaO and SiO_2 as the raw materials and the molar ratio of Si/Ca of 1.0. Effect of anions from various calcium sources on the microstructure of the xonotlite fibers is studied in this paper. These obtained products were characterized by X-ray diffraction(XRD), transmission electron microscope(TEM) and scanning electron microscope(SEM) techniques to investigate their crystalline phase, crystal structure and morphology. The results indicate that anion from various calcium sources has little influence on the crystalline phases of xonotlite fibers but poses a great impact on their morphologies. Xonotlite fibers with single crystal characteristics and large aspect ratio of 50—100 were successfully fabricated from CaCl_2 as calcium material at 225 °C for 15 h. The existence of Cl-anion in the CaO-SiO_2-H_2O system significantly contributes to the formation of xonotlite crystal.

Integrated ionic sieving channels from engineering ordered monolayer two-dimensional crystallite structures

Atomically thin solid-state channels enabling selective molecular transport could potentially be used in a variety of separation and energy conversion applications.The density of channels,their height,distance and edge structure are the key factors that dramatically impact the selective transport performance.However,such channels with small constrictions and atomic precision have been limited to proof-ofconcept demonstrations based on microscale two-dimensional(2D)crystal stripes.Here,we report the engineering of highly ordered,scalable monolayer graphene crystallite arrays by chemical vapor deposition(CVD)method with a modified anisotropic etching approach.The size,shape,distance and edge structure of the graphene crystallite arrays in a large area could be delicately controlled through tailoring the synthetic parameters.This array structure can act as pillars to prop up a smooth single-crystal graphene film,and the fabricated integrated angstrom-size(3.4A)channels allow water transport but exclude hydrated ions,demonstrating potential in selective ionic sieving and nanofiltration practice.