Mineral dissemination and pore space distribution in ore particles are important features that influence heap leaching performance.To quantify the mineral dissemination and pore space distribution of an ore particle,a...Mineral dissemination and pore space distribution in ore particles are important features that influence heap leaching performance.To quantify the mineral dissemination and pore space distribution of an ore particle,a cylindrical copper oxide ore sample(I center dot 4.6 mm x 5.6 mm)was scanned using high-resolution X-ray computed tomography(HRXCT),a nondestructive imaging technology,at a spatial resolution of 4.85 mu m.Combined with three-dimensional(3D)image analysis techniques,the main mineral phases and pore space were segmented and the volume fraction of each phase was calculated.In addition,the mass fraction of each mineral phase was estimated and the result was validated with that obtained using traditional techniques.Furthermore,the pore phase features,including the pore size distribution,pore surface area,pore fractal dimension,pore centerline,and the pore connectivity,were investigated quantitatively.The pore space analysis results indicate that the pore size distribution closely fits a log-normal distribution and that the pore space morphology is complicated,with a large surface area and low connectivity.This study demonstrates that the combination of HRXCT and 3D image analysis is an effective tool for acquiring 3D mineralogical and pore structural data.展开更多
Developing scintillators with high light yield(LY),superior irradiation stability,and weak afterglow is of significance for the realization of low-dose high-resolution X-ray excited optical luminescence(XEOL)imaging.L...Developing scintillators with high light yield(LY),superior irradiation stability,and weak afterglow is of significance for the realization of low-dose high-resolution X-ray excited optical luminescence(XEOL)imaging.Lanthanide doped fluoride nanoparticles possess low toxicity,superior environmental stability,facial fabrication process,and tunable emissions,which are appropriate candidates for the next generation nanoscintillators(NSs).However,the low LY and strong positive hysteresis greatly restrict their practical application.Here,we propose an effective strategy that engineers energy gap to significantly enhance the LY.Our results verify that the tetragonal LiLuF4 host benefits the crystal level splitting of Tb^(3+)ions,which greatly promotes the electrons population on the Tb^(3+):5D4 level followed by the enhanced LY.The LY of LiLuF4:Tb@LiLuF4 NSs is calculated to be~31,169 photons/MeV,which is much higher than the lead halide perovskite colloidal CsPbBr3(~21,000 photons/MeV)and LuAG:Ce(~22,000 photons/MeV)scintillators.Moreover,the positive hysteresis is remarkably restricted after coating a thin shell.The X-ray detection limit and spatial resolution are measured to be~21.27 nGy/s and~7.2 lp/mm,respectively.We further verify that this core/shell NS can be employed as scintillating screen to realize XEOL imaging under the low dose rate of 13.86μGy/s.Our results provide an effective route to develop high performance NSs,which will promote great opportunities for the development of low-dose high-resolution XEOL imaging devices.展开更多
A petroleum pitch was heated at 420℃for 7 h in nitrogen to prepare a carbon fiber precursor with a softening point of 295℃.The precursor was successfully melt-spun into fibers through a circular nozzle of a monofila...A petroleum pitch was heated at 420℃for 7 h in nitrogen to prepare a carbon fiber precursor with a softening point of 295℃.The precursor was successfully melt-spun into fibers through a circular nozzle of a monofilament spinning apparatus,and these were then stabilized at 320℃in air and finally carbonized at 1000℃in nitrogen to produce carbon fibers.SEM,TGA,FT-IR,and XRD were performed to characterize the petroleum pitch,the precursor,the asspun fibers,the stabilized fibers,and the carbon fibers.It is found that the precursor contains 70.5%mass fraction of mesophase that is aligned upon spinning,and aliphatic side chains that are beneficial to spinning.The carbon fibers have a radial core structure with a linear and bent type anisotropic texture.The maximum tensile strength of the carbon fiber is 650 MPa.展开更多
Background：Trampolining is a form of gymnastics that has increased in popularity over the last decade and due to its concurrence with the formative years of bone development,it may have an important impact on bone he...Background：Trampolining is a form of gymnastics that has increased in popularity over the last decade and due to its concurrence with the formative years of bone development,it may have an important impact on bone health.However,bone density,microarchitecture,and bone strength of competitive trampolinists have not been explored.Therefore,the purpose of this cross-sectional study was to investigate the relationship between trampolining participation and（1） bone density,area,and microarchitecture;and（2） estimated bone strength and the role of muscle and impact loading in young female adults.Methods：We recruited 29 female participants aged 16–29 years for this study（n=14 trampolinists;n=15 controls）.Skeletal parameters were assessed using dual X-ray absorptiometry,high-resolution peripheral quantitative computed tomography（HR-pQCT）,and finit element analysis（FEA）.Muscle strength was measured using dynamometers.Results：Trampolinists had higher bone density at the hip and spine,greater trabecular density and thicker trabeculae at the tibia,as well as larger bones at both the tibia and radius than controls（p〈0.05）.Trampolinists also had higher muscle strength than controls at the lower body with no difference between groups in the upper body.Estimates of bone strength using FEA were greater for trampolinists than controls at both the radius and tibia.Conclusion：This is the firs study to investigate bone density,area,and microarchitecture in female trampolinists using HR-p QCT.Trampolinists had greater bone density,area,microarchitecture,and estimated bone strength than controls.展开更多
Soils contain various kinds of crystalline to amorphous solid particles with at least one dimension in the nanoscale （〈 100 nm）. These nanoparticles contribute greatly to dynamic soil processes such as soil genesis...Soils contain various kinds of crystalline to amorphous solid particles with at least one dimension in the nanoscale （〈 100 nm）. These nanoparticles contribute greatly to dynamic soil processes such as soil genesis, trace element cycling, contaminant transport, and chemical reaction. The nano-sized fraction of an Anthrosol was obtained to determine the occurrence, chemical composition, structure, and mineral phases of nanoparticles using high-resolution transmission electron microscopy （HRTEM） equipped with an energy-dispersive X-ray spectroscopy. Selected area electron diffraction or the fast Fourier transform of high-resolution images was used in structural characterization of the nanoparticles with HRTEM. Two nanoscale mineral types, i.e., mineral nanoparticles and nanomi- nerals, were observed in the Anthrosol. Mineral nanoparticles in soil included well crystalline aluminumsilicate nanosheets, nanorods, and nanoparticles. Nanosheets with a length of 120-150 nm and a width of about 10-20 nm were identified as chlorite/vermiculite series. The presence of clear lattice fringe spacing in HRTEM image of nanoparticles indicated that mineral nanoparticles had a relatively good crystallinity. The nanomineral ferrihydrite also existed in the Anthrosol. The HRTEM images and the particle size distribution histogram suggested that these ferrihydrite nanoparticles were quite homogeneous, and had a narrow size distribution range （1-7 nm） with a mean diameter of 3.6 4- 1.6 nm. Our HRTEM observation indicated that mineral nanoparticles and nanominerals were common and widely distributed in Anthrosols. HRTEM and selected area diffraction or lattice fringe spacing characterization provided further proofs to the structure of nanoparticles formed in soil.展开更多
Atomic-layer MoS_2 ultrathin films are synthesized using a hot filament chemical vapor deposition method. A combination of atomic force microscopy（AFM）, x-ray diffraction（XRD）, high-resolution transition electron ...Atomic-layer MoS_2 ultrathin films are synthesized using a hot filament chemical vapor deposition method. A combination of atomic force microscopy（AFM）, x-ray diffraction（XRD）, high-resolution transition electron microscopy（HRTEM）, photoluminescence（PL）, and x-ray photoelectron spectroscopy（XPS） characterization methods is applied to investigate the crystal structures, valence states, and compositions of the ultrathin film areas. The nucleation particles show irregular morphology, while for a larger size somewhere, the films are granular and the grains have a triangle shape. The films grow in a preferred orientation（002）. The HRTEM images present the graphene-like structure of stacked layers with low density of stacking fault, and the interlayer distance of plane is measured to be about 0.63 nm. It shows a clear quasihoneycomb-like structure and 6-fold coordination symmetry. Room-temperature PL spectra for the atomic layer MoS_2 under the condition of right and left circular light show that for both cases, the A1 and B1 direct excitonic transitions can be observed. In the meantime, valley polarization resolved PL spectra are obtained. XPS measurements provide high-purity samples aside from some contaminations from the air, and confirm the presence of pure MoS_2. The stoichiometric mole ratio of S/Mo is about 2.0–2.1, suggesting that sulfur is abundant rather than deficient in the atomic layer MoS_2 under our experimental conditions.展开更多
Exfoliated graphite was prepared by chemical route and then further subjected to thermal oxidation and sonication for size reduction and increased interlayer spacing in natural flake graphite. Exfoliated graphite/ABS ...Exfoliated graphite was prepared by chemical route and then further subjected to thermal oxidation and sonication for size reduction and increased interlayer spacing in natural flake graphite. Exfoliated graphite/ABS composites were pre-pared with varying filler concentration by solution casting method. Exfoliated graphite and composites were character-ised by scanning electron microscopy and energy dispersive X-ray analysis, Fourier transform infrared spectroscopy and X-ray diffractometry techniques. After thermal exfoliation significant peak of graphite at 2? = 26.4? disappeared completely, confirming successful exfoliation of graphite. SEM images revealed homogeneous dispersion of exfoliated graphite in the matrix and EDAX confirmed successful reduction of graphite oxide.展开更多
Organic geochemistry methods such as high temperature combustion, Rock-Eval pyrolysis and gas analysis were used to analyze oil shale from Babouri-Figuil Basin. Results show that the average content of organic matter ...Organic geochemistry methods such as high temperature combustion, Rock-Eval pyrolysis and gas analysis were used to analyze oil shale from Babouri-Figuil Basin. Results show that the average content of organic matter is 36.25 %wt, while that of mineral matter is 63.75 %wt. The total organic carbon (TOC) is between 15.93 %wt and 26.82 %wt. The HI vs. Tmax diagram indicates an immature Type I kerogen. The average value of the oil potential (S2b) is 149.95 mg HC/g rock. The gases obtained by retort process are H2, CO2, CO and CnH2n, CnH2n+2. Finally, it emerges that, the organic matter of Babouri-Figuil shales was immature or has just reached the beginning of the oil window. The mineralogical study of Babouri-Figuil oil shale has been carried out by means of XRD (X-Ray Diffractometry) and XRF (X-Ray Fluorescence spectrometry). The results show that mineral matrix contains silica, carbonates, sulphates, oxides and clay minerals. Besides, compounds contain metals and metalloids like Fe, In, Ca. The main oxides are SiO2 (majority), CaO, Fe2O3, Al2O3, SO3, and K2O.展开更多
One of the most important problems facing the gold industry is that the placer and free milling gold ores are almost terminating. Hence, the use of refractory ores has been increased during the recent years. In genera...One of the most important problems facing the gold industry is that the placer and free milling gold ores are almost terminating. Hence, the use of refractory ores has been increased during the recent years. In general, gold refractory ores occurs in various types of deposits associated with a range of minerals. Among the refractory ores, the sulfide type is the most common. The methodology employed in the mining process depends on the mode of occurrence of the ore and on the particle size, shape and degree of purity of the auriferous species. We have undertaken a mineralogical investigation of a representative sample of a complex gold mining ore collected in the municipality of Princesa Isabel, Paraiba, Brazil, using X-ray fluorescence spectrometry, X-ray diffractometry, infrared spectroscopy, inductively coupled plasma-atomic emission spectrometry and the Fire Assay. The results showed that the arsenic content of the ore was closely related to the gold content, and that the occurrence of “invisible gold” was associated primarily with pyrite and secondarily with arsenopyrite. The sulfur content of the ore was directly related to its refractoriness. It is concluded that gold mineralization in the study area is mainly of the gold-quartz-sulfide veins (lode gold), while the gold found in the mini-fractures of the deposits is probably associated with the hydrothermal processes that occurred in the region.展开更多
Tibolone, a synthetic steroid, is used in the treatment of natural or surgical menopause disturbs resultant of estrogenic deficiency. Isotibolone (Δ4-tibolone) is one of the three active metabolic degradation product...Tibolone, a synthetic steroid, is used in the treatment of natural or surgical menopause disturbs resultant of estrogenic deficiency. Isotibolone (Δ4-tibolone) is one of the three active metabolic degradation products of tibolone that displays progestagenic effects on carcinoma cell growth and gene regulation. Isotibolone can be present in raw material of tibolone due to some inadequate synthesis or storage. Its presence is necessary to be identified and quantified in active pharmaceutical ingredients (API), before its use in the manufacturing of medicines. After a recent study on the crystal structure determination of isotibolone, quantitative phase analyses of both tibolone and isotibolone in raw materials and tablets became possible to be conducted. X-ray powder diffraction is one recommended tool for this purpose, but it can be highly frustrating due to the extreme peak overlap when conventional laboratory equipments are used. In this work we show that the use of Brazilian Synchrotron Light Source X-ray powder diffraction data and the Rietveld method can be successfully applied to identify and quantify the isotibolone in two samples of tibolone raw materials.展开更多
The existing phases in BaxGd1-xMnO3 solid solution system （0≤x≤ 1） were studied by analyzing the detailed crystal structure of each composition from the results of the Rietveld method using powder X-ray diffractio...The existing phases in BaxGd1-xMnO3 solid solution system （0≤x≤ 1） were studied by analyzing the detailed crystal structure of each composition from the results of the Rietveld method using powder X-ray diffraction data. For a small substitution of Ba for Gd （0≤x〈0. 1）, the orthorhombic phase with a perovskite type structure （Pnma space group） was stably formed and this fact was supported by the electron diffraction data. There existed an intermediate phase of Ba0.33Gd0.67MnO3, which was characterized as the tetragonal phase with perovskite structure. The composition range of this phase was narrow and almost line compound. Between the regions of these phases, there existed two-phase region. There was also a two-phase region between the intermediate tetragonal phase and BaMnO3. Measurement of electrical conductivities of these orthorhombic solid solutions and tetragonal phases showed semiconducting behaviors for both phases and the existence of the phase transition at high temperature for the orthorhombic phase, The transition temperature decreased as the Ba content increased.展开更多
Single crystal of BaNdMnO4 with I4/mmm was synthesized by a floating zone method. A new phase of BaNdMnO4 was obtained by annealing the single crystal in a reducing atmosphere at 573 K for 10 d. The structural change ...Single crystal of BaNdMnO4 with I4/mmm was synthesized by a floating zone method. A new phase of BaNdMnO4 was obtained by annealing the single crystal in a reducing atmosphere at 573 K for 10 d. The structural change was analyzed by four-circle X-ray diffractometry and transmission electron microscopy. The new phase has an orthorhombic unit cell (Fmmm) of a=0.5486(2) nm, b=0.5484(2) nm, and c=1.3059(2) nm.展开更多
Spatial resolution is an important criterion to evaluate the performance of a scintillation screen for X-ray imaging.Perovskite-based X-ray screen,usually made of powders or polycrystalline films,suffers from low spat...Spatial resolution is an important criterion to evaluate the performance of a scintillation screen for X-ray imaging.Perovskite-based X-ray screen,usually made of powders or polycrystalline films,suffers from low spatial resolution(~200μm)due to the large thickness of scintillation layer despite of their compelling sensitivity to X-ray dose.In this work,a concentrated colloid of CsPbBr_(3)nanosheets was synthesized via a co-precipitation method at ambient condition.By drop casting,smooth scintillation screens of varied thickness were formed through self-assembly,which exhibited both high internal and external photoluminescence quantum yield(PL QY)(84.5%and 75.1%,respectively).The screen-based X-ray detector showed a high sensitivity down to 27 nGy/s,two orders of magnitude lower than the regular dose for medical diagnostics.Importantly,the screen of optimal thickness of 15μm showcased an unprecedented spatial resolution(26μm)when used for X-ray radiography,representing one order of magnitude improvement in perovskite community.展开更多
Strain engineering as one of the most powerful techniques for tuning optical and electronic properties of III-nitrides requires reliable methods for strain investigation.In this work,we reveal,that the linear model ba...Strain engineering as one of the most powerful techniques for tuning optical and electronic properties of III-nitrides requires reliable methods for strain investigation.In this work,we reveal,that the linear model based on the experimental data limited to within a small range of biaxial strains(<0.2%),which is widely used for the non-destructive Raman study of strain with nanometer-scale spatial resolution is not valid for the binary wurtzite-structure group-III nitrides GaN and AlN.Importantly,we found that the discrepancy between the experimental values of strain and those calculated via Raman spectroscopy increases as the strain in both GaN and AlN increases.Herein,a new model has been developed to describe the strain-induced Raman frequency shift in GaN and AlN for a wide range of biaxial strains(up to 2.5%).Finally,we proposed a new approach to correlate the Raman frequency shift and strain,which is based on the lattice coherency in the epitaxial layers of superlattice structures and can be used for a wide range of materials.展开更多
The CaO-P_(2)O_(5)-SiO_(2)-MgO system presents several compounds used as biomaterials such as hydroxyapatite(HA),tricalcium phosphate(TCP)and TCP with magnesium substituting partial calcium(TCMP).Theβ-TCMP phase with...The CaO-P_(2)O_(5)-SiO_(2)-MgO system presents several compounds used as biomaterials such as hydroxyapatite(HA),tricalcium phosphate(TCP)and TCP with magnesium substituting partial calcium(TCMP).Theβ-TCMP phase with whitlockite structure has interesting biological features and mechanical properties,meeting the requirements of a bioactive material for bone restoration.In this work,the production of Mg-doped TCP,β-TCMP,has been investigated by crystallization from a glass composed of 52.75 wt%3CaO·P_(2)O_(5),30 wt%SiO_(2)and 17.25 wt%MgO(i.e.,31.7 mol%CaO,10.6 mol%P_(2)O_(5),26.6 mol%MgO and 31.1 mol%SiO_(2))using heat treatments between 775℃and 1100℃for up to 8 h.The devitrification process of the glass has been accompanied by differential scanning calorimetry(DSC),high-resolution X-ray diffraction(HRXRD),relative density and bending strength measurements.The characterization by HRXRD and DSC revealed the occurrence of whitlockite soon after the bulk glass preparation,a transient non-cataloged silicate between 800℃and 1100℃,and the formation of diopside in samples treated at 1100℃as crystalline phases.The overall crystalline fraction varied from 26%to 70%depending on the heat treatments.Furthermore,contraction of the a-axis lattice parameter and expansion of the c-axis lattice parameter of the whitlockite structure have been observed during the heat treatments,which were attributed to theβ-TCMP formation with the partial substitution of Ca^(2+)by Mg^(2+).Relative densities near 99%and 97%for the glass and glass-ceramics respectively indicated a discrete reduction as a function of the devitrification treatment.Bending strengths of 70 MPa and 120 MPa were determined for the glass and glass-ceramic material crystallized at 975℃for 4 h,respectively.展开更多
Developing novel lead-free ferroelectric materials is crucial for next-generationmicroelectronic technologies that are energy efficient and environmentfriendly.However,materials discovery and property optimization are...Developing novel lead-free ferroelectric materials is crucial for next-generationmicroelectronic technologies that are energy efficient and environmentfriendly.However,materials discovery and property optimization are typicallytime-consuming due to the limited throughput of traditional synthesismethods.In this work,we use a high-throughput combinatorial synthesisapproach to fabricate lead-free ferroelectric superlattices and solid solutions of(Ba_(0.7)Ca_(0.3))TiO_(3)(BCT)and Ba(Zr_(0.2)Ti_(0.8))O_(3)(BZT)phases with continuous variationof composition and layer thickness.High-resolution x-ray diffraction(XRD)and analytical scanning transmission electron microscopy(STEM)demonstratehigh film quality and well-controlled compositional gradients.Ferroelectricand dielectric property measurements identify the“optimal propertypoint”achieved at the composition of 48BZT–52BCT.Displacement vectormaps reveal that ferroelectric domain sizes are tunable by varying{BCT–BZT}Nsuperlattice geometry.This high-throughput synthesis approach can be appliedto many other material systems to expedite new materials discovery and properties optimization,allowing for the exploration of a large area of phasespace within a single growth.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51304076)the Natural Science Foundation of Hunan Province,China(No.14JJ4064)
文摘Mineral dissemination and pore space distribution in ore particles are important features that influence heap leaching performance.To quantify the mineral dissemination and pore space distribution of an ore particle,a cylindrical copper oxide ore sample(I center dot 4.6 mm x 5.6 mm)was scanned using high-resolution X-ray computed tomography(HRXCT),a nondestructive imaging technology,at a spatial resolution of 4.85 mu m.Combined with three-dimensional(3D)image analysis techniques,the main mineral phases and pore space were segmented and the volume fraction of each phase was calculated.In addition,the mass fraction of each mineral phase was estimated and the result was validated with that obtained using traditional techniques.Furthermore,the pore phase features,including the pore size distribution,pore surface area,pore fractal dimension,pore centerline,and the pore connectivity,were investigated quantitatively.The pore space analysis results indicate that the pore size distribution closely fits a log-normal distribution and that the pore space morphology is complicated,with a large surface area and low connectivity.This study demonstrates that the combination of HRXCT and 3D image analysis is an effective tool for acquiring 3D mineralogical and pore structural data.
基金supported by Zhejiang Provincial Natural Science Foundation of China(No.LZ21A040002)the National Natural Science Foundation of China(Nos.52172164 and 51872270)+1 种基金the National Natural Science Foundation of China Joint Fund Project(No.U190920054)the Project funded by China Postdoctoral Science Foundation(No.2022T150582).
文摘Developing scintillators with high light yield(LY),superior irradiation stability,and weak afterglow is of significance for the realization of low-dose high-resolution X-ray excited optical luminescence(XEOL)imaging.Lanthanide doped fluoride nanoparticles possess low toxicity,superior environmental stability,facial fabrication process,and tunable emissions,which are appropriate candidates for the next generation nanoscintillators(NSs).However,the low LY and strong positive hysteresis greatly restrict their practical application.Here,we propose an effective strategy that engineers energy gap to significantly enhance the LY.Our results verify that the tetragonal LiLuF4 host benefits the crystal level splitting of Tb^(3+)ions,which greatly promotes the electrons population on the Tb^(3+):5D4 level followed by the enhanced LY.The LY of LiLuF4:Tb@LiLuF4 NSs is calculated to be~31,169 photons/MeV,which is much higher than the lead halide perovskite colloidal CsPbBr3(~21,000 photons/MeV)and LuAG:Ce(~22,000 photons/MeV)scintillators.Moreover,the positive hysteresis is remarkably restricted after coating a thin shell.The X-ray detection limit and spatial resolution are measured to be~21.27 nGy/s and~7.2 lp/mm,respectively.We further verify that this core/shell NS can be employed as scintillating screen to realize XEOL imaging under the low dose rate of 13.86μGy/s.Our results provide an effective route to develop high performance NSs,which will promote great opportunities for the development of low-dose high-resolution XEOL imaging devices.
文摘A petroleum pitch was heated at 420℃for 7 h in nitrogen to prepare a carbon fiber precursor with a softening point of 295℃.The precursor was successfully melt-spun into fibers through a circular nozzle of a monofilament spinning apparatus,and these were then stabilized at 320℃in air and finally carbonized at 1000℃in nitrogen to produce carbon fibers.SEM,TGA,FT-IR,and XRD were performed to characterize the petroleum pitch,the precursor,the asspun fibers,the stabilized fibers,and the carbon fibers.It is found that the precursor contains 70.5%mass fraction of mesophase that is aligned upon spinning,and aliphatic side chains that are beneficial to spinning.The carbon fibers have a radial core structure with a linear and bent type anisotropic texture.The maximum tensile strength of the carbon fiber is 650 MPa.
文摘Background：Trampolining is a form of gymnastics that has increased in popularity over the last decade and due to its concurrence with the formative years of bone development,it may have an important impact on bone health.However,bone density,microarchitecture,and bone strength of competitive trampolinists have not been explored.Therefore,the purpose of this cross-sectional study was to investigate the relationship between trampolining participation and（1） bone density,area,and microarchitecture;and（2） estimated bone strength and the role of muscle and impact loading in young female adults.Methods：We recruited 29 female participants aged 16–29 years for this study（n=14 trampolinists;n=15 controls）.Skeletal parameters were assessed using dual X-ray absorptiometry,high-resolution peripheral quantitative computed tomography（HR-pQCT）,and finit element analysis（FEA）.Muscle strength was measured using dynamometers.Results：Trampolinists had higher bone density at the hip and spine,greater trabecular density and thicker trabeculae at the tibia,as well as larger bones at both the tibia and radius than controls（p〈0.05）.Trampolinists also had higher muscle strength than controls at the lower body with no difference between groups in the upper body.Estimates of bone strength using FEA were greater for trampolinists than controls at both the radius and tibia.Conclusion：This is the firs study to investigate bone density,area,and microarchitecture in female trampolinists using HR-p QCT.Trampolinists had greater bone density,area,microarchitecture,and estimated bone strength than controls.
基金Supported by the National Natural Science Foundation of China (No. 40971131)the Ph.D. Program Foundation of Ministry of Education of China (No. 20090101110088)
文摘Soils contain various kinds of crystalline to amorphous solid particles with at least one dimension in the nanoscale （〈 100 nm）. These nanoparticles contribute greatly to dynamic soil processes such as soil genesis, trace element cycling, contaminant transport, and chemical reaction. The nano-sized fraction of an Anthrosol was obtained to determine the occurrence, chemical composition, structure, and mineral phases of nanoparticles using high-resolution transmission electron microscopy （HRTEM） equipped with an energy-dispersive X-ray spectroscopy. Selected area electron diffraction or the fast Fourier transform of high-resolution images was used in structural characterization of the nanoparticles with HRTEM. Two nanoscale mineral types, i.e., mineral nanoparticles and nanomi- nerals, were observed in the Anthrosol. Mineral nanoparticles in soil included well crystalline aluminumsilicate nanosheets, nanorods, and nanoparticles. Nanosheets with a length of 120-150 nm and a width of about 10-20 nm were identified as chlorite/vermiculite series. The presence of clear lattice fringe spacing in HRTEM image of nanoparticles indicated that mineral nanoparticles had a relatively good crystallinity. The nanomineral ferrihydrite also existed in the Anthrosol. The HRTEM images and the particle size distribution histogram suggested that these ferrihydrite nanoparticles were quite homogeneous, and had a narrow size distribution range （1-7 nm） with a mean diameter of 3.6 4- 1.6 nm. Our HRTEM observation indicated that mineral nanoparticles and nanominerals were common and widely distributed in Anthrosols. HRTEM and selected area diffraction or lattice fringe spacing characterization provided further proofs to the structure of nanoparticles formed in soil.
基金Project supported by the Natural Science Foundation of Zhejiang Province,China(Grant Nos.LY16F040003 and LY16A040007)the National Natural Science Foundation of China(Grant Nos.51401069 and 11574067)
文摘Atomic-layer MoS_2 ultrathin films are synthesized using a hot filament chemical vapor deposition method. A combination of atomic force microscopy（AFM）, x-ray diffraction（XRD）, high-resolution transition electron microscopy（HRTEM）, photoluminescence（PL）, and x-ray photoelectron spectroscopy（XPS） characterization methods is applied to investigate the crystal structures, valence states, and compositions of the ultrathin film areas. The nucleation particles show irregular morphology, while for a larger size somewhere, the films are granular and the grains have a triangle shape. The films grow in a preferred orientation（002）. The HRTEM images present the graphene-like structure of stacked layers with low density of stacking fault, and the interlayer distance of plane is measured to be about 0.63 nm. It shows a clear quasihoneycomb-like structure and 6-fold coordination symmetry. Room-temperature PL spectra for the atomic layer MoS_2 under the condition of right and left circular light show that for both cases, the A1 and B1 direct excitonic transitions can be observed. In the meantime, valley polarization resolved PL spectra are obtained. XPS measurements provide high-purity samples aside from some contaminations from the air, and confirm the presence of pure MoS_2. The stoichiometric mole ratio of S/Mo is about 2.0–2.1, suggesting that sulfur is abundant rather than deficient in the atomic layer MoS_2 under our experimental conditions.
文摘Exfoliated graphite was prepared by chemical route and then further subjected to thermal oxidation and sonication for size reduction and increased interlayer spacing in natural flake graphite. Exfoliated graphite/ABS composites were pre-pared with varying filler concentration by solution casting method. Exfoliated graphite and composites were character-ised by scanning electron microscopy and energy dispersive X-ray analysis, Fourier transform infrared spectroscopy and X-ray diffractometry techniques. After thermal exfoliation significant peak of graphite at 2? = 26.4? disappeared completely, confirming successful exfoliation of graphite. SEM images revealed homogeneous dispersion of exfoliated graphite in the matrix and EDAX confirmed successful reduction of graphite oxide.
基金financial and material supports from the“University Commission for Development”(UCD)and University of Liege-Belgium(ULg).
文摘Organic geochemistry methods such as high temperature combustion, Rock-Eval pyrolysis and gas analysis were used to analyze oil shale from Babouri-Figuil Basin. Results show that the average content of organic matter is 36.25 %wt, while that of mineral matter is 63.75 %wt. The total organic carbon (TOC) is between 15.93 %wt and 26.82 %wt. The HI vs. Tmax diagram indicates an immature Type I kerogen. The average value of the oil potential (S2b) is 149.95 mg HC/g rock. The gases obtained by retort process are H2, CO2, CO and CnH2n, CnH2n+2. Finally, it emerges that, the organic matter of Babouri-Figuil shales was immature or has just reached the beginning of the oil window. The mineralogical study of Babouri-Figuil oil shale has been carried out by means of XRD (X-Ray Diffractometry) and XRF (X-Ray Fluorescence spectrometry). The results show that mineral matrix contains silica, carbonates, sulphates, oxides and clay minerals. Besides, compounds contain metals and metalloids like Fe, In, Ca. The main oxides are SiO2 (majority), CaO, Fe2O3, Al2O3, SO3, and K2O.
基金the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico(CNPq,grant no.550261/2010-9)for financial support
文摘One of the most important problems facing the gold industry is that the placer and free milling gold ores are almost terminating. Hence, the use of refractory ores has been increased during the recent years. In general, gold refractory ores occurs in various types of deposits associated with a range of minerals. Among the refractory ores, the sulfide type is the most common. The methodology employed in the mining process depends on the mode of occurrence of the ore and on the particle size, shape and degree of purity of the auriferous species. We have undertaken a mineralogical investigation of a representative sample of a complex gold mining ore collected in the municipality of Princesa Isabel, Paraiba, Brazil, using X-ray fluorescence spectrometry, X-ray diffractometry, infrared spectroscopy, inductively coupled plasma-atomic emission spectrometry and the Fire Assay. The results showed that the arsenic content of the ore was closely related to the gold content, and that the occurrence of “invisible gold” was associated primarily with pyrite and secondarily with arsenopyrite. The sulfur content of the ore was directly related to its refractoriness. It is concluded that gold mineralization in the study area is mainly of the gold-quartz-sulfide veins (lode gold), while the gold found in the mini-fractures of the deposits is probably associated with the hydrothermal processes that occurred in the region.
基金the financial support of FAPESP(proc.nos.2008/10537-3,2010/06849-0)CAPES and CNPq(proc.nos.476335/2008-6,309811/2009-0,306293/2009-9 and 477296/2011-4)and the LNLS(Brazilian Synchrotron Light Laboratory)for beam time.
文摘Tibolone, a synthetic steroid, is used in the treatment of natural or surgical menopause disturbs resultant of estrogenic deficiency. Isotibolone (Δ4-tibolone) is one of the three active metabolic degradation products of tibolone that displays progestagenic effects on carcinoma cell growth and gene regulation. Isotibolone can be present in raw material of tibolone due to some inadequate synthesis or storage. Its presence is necessary to be identified and quantified in active pharmaceutical ingredients (API), before its use in the manufacturing of medicines. After a recent study on the crystal structure determination of isotibolone, quantitative phase analyses of both tibolone and isotibolone in raw materials and tablets became possible to be conducted. X-ray powder diffraction is one recommended tool for this purpose, but it can be highly frustrating due to the extreme peak overlap when conventional laboratory equipments are used. In this work we show that the use of Brazilian Synchrotron Light Source X-ray powder diffraction data and the Rietveld method can be successfully applied to identify and quantify the isotibolone in two samples of tibolone raw materials.
基金the Grant-in-Aid for Scientific Research (C) (18560662) by the Japan Society for the Promotion of Science
文摘The existing phases in BaxGd1-xMnO3 solid solution system （0≤x≤ 1） were studied by analyzing the detailed crystal structure of each composition from the results of the Rietveld method using powder X-ray diffraction data. For a small substitution of Ba for Gd （0≤x〈0. 1）, the orthorhombic phase with a perovskite type structure （Pnma space group） was stably formed and this fact was supported by the electron diffraction data. There existed an intermediate phase of Ba0.33Gd0.67MnO3, which was characterized as the tetragonal phase with perovskite structure. The composition range of this phase was narrow and almost line compound. Between the regions of these phases, there existed two-phase region. There was also a two-phase region between the intermediate tetragonal phase and BaMnO3. Measurement of electrical conductivities of these orthorhombic solid solutions and tetragonal phases showed semiconducting behaviors for both phases and the existence of the phase transition at high temperature for the orthorhombic phase, The transition temperature decreased as the Ba content increased.
基金a Grant-in Aidfor Scientific Research (c) (18560662) from the Japan Society for the Promotion of Science
文摘Single crystal of BaNdMnO4 with I4/mmm was synthesized by a floating zone method. A new phase of BaNdMnO4 was obtained by annealing the single crystal in a reducing atmosphere at 573 K for 10 d. The structural change was analyzed by four-circle X-ray diffractometry and transmission electron microscopy. The new phase has an orthorhombic unit cell (Fmmm) of a=0.5486(2) nm, b=0.5484(2) nm, and c=1.3059(2) nm.
基金the National Natural Science Foundation of China(No.21805111)Natural Science Foundation of Shandong Province(No.ZR2020YQ12)Taishan Scholar Project of Shandong Province(No.tsqn201812082).
文摘Spatial resolution is an important criterion to evaluate the performance of a scintillation screen for X-ray imaging.Perovskite-based X-ray screen,usually made of powders or polycrystalline films,suffers from low spatial resolution(~200μm)due to the large thickness of scintillation layer despite of their compelling sensitivity to X-ray dose.In this work,a concentrated colloid of CsPbBr_(3)nanosheets was synthesized via a co-precipitation method at ambient condition.By drop casting,smooth scintillation screens of varied thickness were formed through self-assembly,which exhibited both high internal and external photoluminescence quantum yield(PL QY)(84.5%and 75.1%,respectively).The screen-based X-ray detector showed a high sensitivity down to 27 nGy/s,two orders of magnitude lower than the regular dose for medical diagnostics.Importantly,the screen of optimal thickness of 15μm showcased an unprecedented spatial resolution(26μm)when used for X-ray radiography,representing one order of magnitude improvement in perovskite community.
基金the U.S.National Science Foundation Engineering Research Center for Power Optimization of Electro Thermal Systems(POETS)with cooperative agreement EEC-1449548F.M.O.and M.D.T.acknowledge the financial support of Coordenação de Aperfeiçoamento de Pessoal de Nível Superior-Brasil(CAPES)-Finance Code 001.
文摘Strain engineering as one of the most powerful techniques for tuning optical and electronic properties of III-nitrides requires reliable methods for strain investigation.In this work,we reveal,that the linear model based on the experimental data limited to within a small range of biaxial strains(<0.2%),which is widely used for the non-destructive Raman study of strain with nanometer-scale spatial resolution is not valid for the binary wurtzite-structure group-III nitrides GaN and AlN.Importantly,we found that the discrepancy between the experimental values of strain and those calculated via Raman spectroscopy increases as the strain in both GaN and AlN increases.Herein,a new model has been developed to describe the strain-induced Raman frequency shift in GaN and AlN for a wide range of biaxial strains(up to 2.5%).Finally,we proposed a new approach to correlate the Raman frequency shift and strain,which is based on the lattice coherency in the epitaxial layers of superlattice structures and can be used for a wide range of materials.
基金The authors would like to thank LNLS-Laboratório Nacional de Luz Síncrotron for technical support,and FAPESP for financial support,under grant No.07/50510-4.
文摘The CaO-P_(2)O_(5)-SiO_(2)-MgO system presents several compounds used as biomaterials such as hydroxyapatite(HA),tricalcium phosphate(TCP)and TCP with magnesium substituting partial calcium(TCMP).Theβ-TCMP phase with whitlockite structure has interesting biological features and mechanical properties,meeting the requirements of a bioactive material for bone restoration.In this work,the production of Mg-doped TCP,β-TCMP,has been investigated by crystallization from a glass composed of 52.75 wt%3CaO·P_(2)O_(5),30 wt%SiO_(2)and 17.25 wt%MgO(i.e.,31.7 mol%CaO,10.6 mol%P_(2)O_(5),26.6 mol%MgO and 31.1 mol%SiO_(2))using heat treatments between 775℃and 1100℃for up to 8 h.The devitrification process of the glass has been accompanied by differential scanning calorimetry(DSC),high-resolution X-ray diffraction(HRXRD),relative density and bending strength measurements.The characterization by HRXRD and DSC revealed the occurrence of whitlockite soon after the bulk glass preparation,a transient non-cataloged silicate between 800℃and 1100℃,and the formation of diopside in samples treated at 1100℃as crystalline phases.The overall crystalline fraction varied from 26%to 70%depending on the heat treatments.Furthermore,contraction of the a-axis lattice parameter and expansion of the c-axis lattice parameter of the whitlockite structure have been observed during the heat treatments,which were attributed to theβ-TCMP formation with the partial substitution of Ca^(2+)by Mg^(2+).Relative densities near 99%and 97%for the glass and glass-ceramics respectively indicated a discrete reduction as a function of the devitrification treatment.Bending strengths of 70 MPa and 120 MPa were determined for the glass and glass-ceramic material crystallized at 975℃for 4 h,respectively.
基金NNSA's Laboratory Directed Research andDevelopment ProgramCenter forIntegrated Nanotechnologies,an Office ofScience User Facility operated for theU.S.Department of Energy(DOE)Officeof Science by Los Alamos NationalLaboratory,Grant/Award Number:89233218CNA000001+5 种基金Sandia NationalLaboratories,Grant/Award Number:DENA0003525U.S.Department of Energy,Office of Science,Basic Energy Sciences,Materials Science and EngineeringDivisionArgonne National LaboratoryU.S.DOE Office of Science-Basic Energy Sciences,Grant/Award Number:DEAC02-06CH11357Center for NanophaseMaterials SciencesACS PetroleumResearch Fund under Doctoral NewInvestigator Grant,Grant/Award Number:62603-DNI10。
文摘Developing novel lead-free ferroelectric materials is crucial for next-generationmicroelectronic technologies that are energy efficient and environmentfriendly.However,materials discovery and property optimization are typicallytime-consuming due to the limited throughput of traditional synthesismethods.In this work,we use a high-throughput combinatorial synthesisapproach to fabricate lead-free ferroelectric superlattices and solid solutions of(Ba_(0.7)Ca_(0.3))TiO_(3)(BCT)and Ba(Zr_(0.2)Ti_(0.8))O_(3)(BZT)phases with continuous variationof composition and layer thickness.High-resolution x-ray diffraction(XRD)and analytical scanning transmission electron microscopy(STEM)demonstratehigh film quality and well-controlled compositional gradients.Ferroelectricand dielectric property measurements identify the“optimal propertypoint”achieved at the composition of 48BZT–52BCT.Displacement vectormaps reveal that ferroelectric domain sizes are tunable by varying{BCT–BZT}Nsuperlattice geometry.This high-throughput synthesis approach can be appliedto many other material systems to expedite new materials discovery and properties optimization,allowing for the exploration of a large area of phasespace within a single growth.
