To elucidate the effect of the internal fixation plates on the local bone blood sapply, we used microangiography and scanning electron microscopy to observe the morphological changes of microcirculation in the cortica...To elucidate the effect of the internal fixation plates on the local bone blood sapply, we used microangiography and scanning electron microscopy to observe the morphological changes of microcirculation in the cortical bones obtained from intact rabbit tibiae on which plates of two different stiffness had been fixed for comparison. The results indicated that both rigid stainless steel plate and less rigid methyl methacrylate plate could induce the bone microcirculation under the plate to undergo a process from early depression to late reactive recruitment. The features of the microcircuiation recruitment such as vascular number, arrangement and dilatation varied with plates of different stiffness and were more obvious in the cortex fixed by rigid stainless steel plate.展开更多
The functionalities and diverse metastable phases of multiferroic BiFeO_(3)(BFO)thin films depend on the misfit strain.Although mixed phase-induced strain relaxation in multiphase BFO thin films is well known,it is un...The functionalities and diverse metastable phases of multiferroic BiFeO_(3)(BFO)thin films depend on the misfit strain.Although mixed phase-induced strain relaxation in multiphase BFO thin films is well known,it is unclear whether a singlecrystalline BFO thin film can accommodate misfit strain without the involvement of its polymorphs.Thus,understanding the strain relaxation behavior is key to elucidating the lattice strain–property relationship.In this study,a correlative strain analysis based on dark-field inline electron holography(DIH)and quantitative scanning transmission electron microscopy(STEM)was performed to reveal the structural mechanism for strain accommodation of a single-crystalline BFO thin film.The nanoscale DIH strain analysis results indicated a random combination of multiple strain states that acted as a primary strain relief,forming irregularly strained nanodomains.The STEM-based bond length measurement of the corresponding strained nanodomains revealed a unique strain accommodation behavior achieved by a statistical combination of multiple modes of distorted structures on the unit-cell scale.The globally integrated strain for each nanodomain was estimated to be close to1.5%,irrespective of the nanoscale strain states,which was consistent with the fully strained BFO film on the SrTiO_(3) substrate.Density functional theory calculations suggested that strain accommodation by the combination of metastable phases was energetically favored compared to single-phase-mediated relaxation.This discovery allows a comprehensive understanding of strain accommodation behavior in ferroelectric oxide films,such as BFO,with various low-symmetry polymorphs.展开更多
Solid phase reactions of Cr（Ⅵ） with Fe（0） were investigated with spherical-aberration-corrected scanning transmission electron microscopy（Cs-STEM） integrated with X-ray energy-dispersive spectroscopy（XEDS）. N...Solid phase reactions of Cr（Ⅵ） with Fe（0） were investigated with spherical-aberration-corrected scanning transmission electron microscopy（Cs-STEM） integrated with X-ray energy-dispersive spectroscopy（XEDS）. Near-atomic resolution elemental mappings of Cr（Ⅵ）–Fe（0） reactions were acquired. Experimental results show that rate and extent of Cr（Ⅵ） encapsulation are strongly dependent on the initial concentration of Cr（Ⅵ） in solution. Low Cr loading in nZⅥ（〈1.0 wt%） promotes the electrochemical oxidation and continuous corrosion of n ZⅥ while high Cr loading（〉1.0 wt%） can quickly shut down the Cr uptake. With the progress of iron oxidation and dissolution, elements of Cr and O counter-diffuse into the nanoparticles and accumulate in the core region at low levels of Cr（Ⅵ）（e.g., 〈 10 mg/L）. Whereas the reacted n ZⅥ is quickly coated with a newly-formed layer of 2–4 nm in the presence of concentrated Cr（Ⅵ）（e.g., 〉 100 mg/L）. The passivation structure is stable over a wide range of pH unless pH is low enough to dissolve the passivation layer. X-ray photoelectron spectroscopy（XPS） depth profiling reconfirms that the composition of the newly-formed surface layer consists of Fe（Ⅲ）–Cr（Ⅲ）（oxy）hydroxides with Cr（Ⅵ） adsorbed on the outside surface. The insoluble and insulating Fe（Ⅲ）–Cr（Ⅲ）（oxy）hydroxide layer can completely cover the n ZⅥ surface above the critical Cr loading and shield the electron transfer. Thus, the fast passivation of nZⅥ in high Cr（Ⅵ） solution is detrimental to the performance of nZⅥ for Cr（Ⅵ） treatment and remediation.展开更多
In this study, an ecofriendly and economically viable waste management approach have been attempted towards the biosynthesis of agriculturally important nanoparticles from jarosite waste. Aspergillus terreus strain J4...In this study, an ecofriendly and economically viable waste management approach have been attempted towards the biosynthesis of agriculturally important nanoparticles from jarosite waste. Aspergillus terreus strain J4 isolated from jarosite（waste from Debari Zinc Smelter,Udaipur, India）, showed good leaching efficiency along with nanoparticles（NPs） formation under ambient conditions. Fourier-transform infrared spectroscopy（FT-IR） and transmission electron microscopy（TEM） confirmed the formation of NPs. Energy dispersive X-ray spectroscopy（EDX analysis） showed strong signals for zinc, iron, calcium and magnesium,with these materials being leached out. TEM analysis and high resolution transmission electron microscopy（HRTEM） showed semi-quasi spherical particles having average size of 10‐50 nm. Thus, a novel biomethodology was developed using fungal cell-free extract for bioleaching and subsequently nanoconversion of the waste materials into nanostructured form. These biosynthesized nanoparticles were tested for their efficacy on seed emergence activity of wheat（Triticum aestivum） seeds and showed enhanced growth at concentration of 20 ppm. These nanomaterials are expected to enhance plant growth properties and being targeted as additives in soil fertility and crop productivity enhancement.展开更多
Alloys containing chromium （Cr） and molybdenum （Mo）, as the major alloying elements, are widely used in various industries where the material experiences corrosive environments. Chromium （Cr）, when added in an o...Alloys containing chromium （Cr） and molybdenum （Mo）, as the major alloying elements, are widely used in various industries where the material experiences corrosive environments. Chromium （Cr）, when added in an optimum amount, forms a Cr203 passive film which protects the underlying metal in aggressive solutions. Molybdenum （Mo） forms its oxides in the low pH solutions, thus, enhances the uniform corrosion resistance of an alloy in reducing acids and assists in inhibition to localized corrosion. Minor alloying elements, like tungsten （W） and copper （Cu）, also improve the overall corrosion resistance of an alloy in specific solutions. In the present study, corrosion resistance behavior of commercial iron- based alloys （316L SS, 254 SMO and 20Cb3） and nickel-based alloys （Mone1400, Alloy 625 and C-276） was studied in the acidic solutions. While the corrosion behavior of wrought alloys has been widely studied, there is little to no information on the corrosion performance of their welds, typically being the weak regions for corrosion initiation and propagation. Therefore, an attempt was undertaken to investigate the uniform and localized corrosion performance of base metal, simulated heat-affected zone and all-weld-metal samples of a Ni-Cr-Mo-W alloy, C-276. The study was conducted in aggressive acidic solutions. Various corrosion and surface analytical techniques were utilized to analyze the results.展开更多
The crystallographic features of pearlite were investigated by experiments and edge-to-edge matching principle. Two new orientation relationships between ferrite and cementite were determinated by selected area electr...The crystallographic features of pearlite were investigated by experiments and edge-to-edge matching principle. Two new orientation relationships between ferrite and cementite were determinated by selected area electron diffraction and then explained by our modified edge-to-edge matching method. The consistence of the experimental results with theoretical prediction confirms the practicability of the modified edge-to-edge matching model.展开更多
Nanocrystalline CdS thin films have been deposited using precursors with different thiourea concentrationonto glass substrates by sol-gel spin coating method.The crystalline nature of the films has been observedto be ...Nanocrystalline CdS thin films have been deposited using precursors with different thiourea concentrationonto glass substrates by sol-gel spin coating method.The crystalline nature of the films has been observedto be strongly dependent on thiourea concentration and annealing temperature.The CdS films are found tobe nanocrystalline in nature with hexagonal structure.The grain size is found to be in the range of 7.6 to11.5 nm depending on the thiourea concentration and annealing temperature.The high resolution transmissionelectron microscopy （HRTEM） results of the CdS films prepared using cadmium to thiourea molar ratio of0.3：0.3 indicate the formation of nanocrystalline CdS with grain size of 5 nm.Fourier transform infrared （FTIR）analysis shows the absorption bands corresponding to Cd and S.The optical study carried out to determinethe band gap of the nanostructured CdS thin films shows a strong blue shift.The band gap energy has beenobserved to lie in the range of 3.97 to 3.62 eV following closely the quantum confinement dependence ofenergy on crystallite radius.The dependence of band gap of the CdS films on the annealing temperature andthiourea concentration has also been studied.The photoluminescence （PL） spectra display two main emissionpeaks corresponding to the blue and green emissions of CdS.展开更多
The microstructures of copper liners of shaped charges prepared byelectroforming technique were investigated by transmission electron microscopy (TEM). Meanwhile, theorientations distributing of the grains in the elec...The microstructures of copper liners of shaped charges prepared byelectroforming technique were investigated by transmission electron microscopy (TEM). Meanwhile, theorientations distributing of the grains in the electroformed copper liners of shaped charges wasexamined by the electron backscattering Kikuchi pattern (EBSP) technique. TEM observations haverevealed that these electroformed copper liners of shaped charges have the grain size of about 1-3mu m and the grains have a preferential orientation distribution along the growth direction. EBSPanalysis has demonstrated that the as-formed copper liners of shaped charges exhibit amicro-texture, i.e. one type of fiber texture, and the preferred growth direction is normal to thesurface of the liners.展开更多
AIM: To investigate whether the major kavalactone kavain imposes adverse effects on the liver ultrastructure and function by affecting vascular and microvascular architecture and altering hepatocellular morphology. ME...AIM: To investigate whether the major kavalactone kavain imposes adverse effects on the liver ultrastructure and function by affecting vascular and microvascular architecture and altering hepatocellular morphology. METHODS: Kavain solution (10 μg/mL or 43.5 μmol/L) was perfused for 2 h in isolated rat livers. After standard fi xation and tissue preparation,the samples were examined by scanning electron microscopy (SEM),transmission electron microscopy (TEM),and light microscopy (LM). RESULTS: LM,SEM,and TEM examinations indicated kavain-treated rat livers (n = 4) displayed severe vascular and endothelial damage compared to control livers (n = 4). CONCLUSION: The data so far support the hypothesis that kavain induces adverse effects on liver; additional investigations with other kavalactones and their effects on liver are urgently needed.展开更多
The results presented in this study were concerned with microstructures and mechanical properties of poly- crystalline Cu subjected to plastic deformation by a compression with oscillatory torsion process. Different d...The results presented in this study were concerned with microstructures and mechanical properties of poly- crystalline Cu subjected to plastic deformation by a compression with oscillatory torsion process. Different deformation parameters of the compression with oscillatory torsion process were adopted to study their effects on the microstructure and mechanical properties. The deformed microstructure was characterized quantitatively by electron backscattered diffraction （EBSD） and scanning transmission electron microscopy （STEM）. Mechanical properties were determined on an MTS QTest/10 machine equipped with digital image correlation. From the experimental results, processes performed at high compression speed and high torsion frequency are recommended for refining the grain size. The size of structure elements, such as average grain size （D） and subgrain size （d）, reached 0.42 μm and 0.30 μm, respectively, and the fraction of high angle boundaries was 35% when the sample was deformed at a torsion frequency f = 1.6 Hz and compression rate v= 0.04 mm/s. These deformation parameters led to an improvement in the strength properties. The material exhibited an ultimate tensile strength （UTS） of 434 MPa and a yield strength （YS） of 418 MPa. These values were about two times greater than those of the initial state.展开更多
Microstructure of SiC fiber manufactured by chemical vapor deposition （CVD） onto tungsten （W） wire core was investigated by analytical electron microscopy （AEM）. The results reveal that the fiber consists of W c...Microstructure of SiC fiber manufactured by chemical vapor deposition （CVD） onto tungsten （W） wire core was investigated by analytical electron microscopy （AEM）. The results reveal that the fiber consists of W core, SiC sheath and C-coating. SiC sheath could be subdivided into two parts according to whether containing C rich stripe, or not. An emphasis was put on W/SiC interfacial reaction products and the transition zone between sub-layers in SiC sheath. The W/SiC interface consists of three layers of reaction production, namely, W2C, W5Si3 and WC. And there are amounts of facet faults existing in （100） face of WC crystalline and two classes of stack faults in WC have been revealed. The formation essence of different sublayers in SiC sheath was also discussed.展开更多
Tensile properties of epoxy casts together with shape memory alloy（SMA）, glass（GF） and carbon（CF） woven fabric reinforced epoxy matrix super hybrid composites were investigated, respectively. In order to enhance...Tensile properties of epoxy casts together with shape memory alloy（SMA）, glass（GF） and carbon（CF） woven fabric reinforced epoxy matrix super hybrid composites were investigated, respectively. In order to enhance the mechanical strength of this advanced material, two categories of modifications including matrix blending and fiber surface coating by nano-silica were studied. Scanning electron microscopy（SEM） and fiber pull-out tests were adopted to complement the experimental results, respectively. Experimental results reveal that the toughness of epoxy matrix is enhanced significantly by adding 2 wt% nano-silica. The failure mechanism of SMA reinforced hybrid composites is different from that of GF/CF/epoxy composites. Compared with the matrix modification, the fibers modified by coating nano-silica on the surface have better tensile performances. Moreover, the fiber pull-out test results also indicate that composites with fiber surface modification have better interfacial performances. The modification method used in this paper can help to enhance the tensile performance of the mentioned composite materials in real engineering fields.展开更多
Microstructures of a CuZnAlMnNi shape memory alloy in the as-quenched andlong-term aged conditions were investigated by transmission electron microscopy. Aged for one yearin martensite phase, an equilibrium α-phase w...Microstructures of a CuZnAlMnNi shape memory alloy in the as-quenched andlong-term aged conditions were investigated by transmission electron microscopy. Aged for one yearin martensite phase, an equilibrium α-phase with fcc structure was observed in the M18R martensitematrix, accompanied by the appearance of a novel diffraction pattern. By analysis, it was suggestedthat the novel pattern results from the α-phase and the martensite matrix remaining in seven fineplates which produce intense secondary diffraction effect when the diffraction beams enter from onephase into another.展开更多
The local thermal conductivity of polycrystalline aluminum nitride （A1N） ceramics is measured and imaged by using a scanning thermal microscope （SThM） and complementary scanning electron microscope （SEM） based t...The local thermal conductivity of polycrystalline aluminum nitride （A1N） ceramics is measured and imaged by using a scanning thermal microscope （SThM） and complementary scanning electron microscope （SEM） based techniques at room temperature. The quantitative thermal conductivity for the A1N sample is gained by using a SThM with a spatial resolution of sub-micrometer scale through using the 3w method. A thermal conductivity of 308 W/m-K within grains corresponding to that of high-purity single crystal A1N is obtained. The slight differences in thermal conduction between the adjacent grains are found to result from crystallographic misorientations, as demonstrated in the electron backscattered diffraction. A much lower thermal conductivity at the grain boundary is due to impurities and defects enriched in these sites, as indicated by energy dispersive X-ray spectroscopy.展开更多
Low-energy electron microscopy （LEEM） has been used to study the structure, initial growth orientation, growth progression, and the number of layers of atomically thin hexagonal boron nitride （h-BN） films. The h-B...Low-energy electron microscopy （LEEM） has been used to study the structure, initial growth orientation, growth progression, and the number of layers of atomically thin hexagonal boron nitride （h-BN） films. The h-BN films are grown on heteroepitaxial Co using chemical vapor deposition （CVD） at low pressure. Our findings from LEEM studies include the growth of monolayer film having two, oppositely oriented, triangular BN domains commensurate with the Co lattice. The growth of h-BN appears to be self-limiting at a monolayer, with thicker domains only appearing in patches, presumably initiated between domain boundaries. Reflectivity measurements of the thicker h-BN films show oscillations resulting from the resonant electron transmission through quantized electronic states of the h-BN films, with the number of minima scaling up with the number of h-BN layers. First principles density functional theory （DFT） calculations show that the positions of oscillations are related to the electronic band structure of h-BN.展开更多
Protein coronas provide the biological identity of nanomaterials in vivo. Here we have used dynamic light scattering （DLS） and transmission electron microscopy （TEM） to investigate the adsorption of serum proteins...Protein coronas provide the biological identity of nanomaterials in vivo. Here we have used dynamic light scattering （DLS） and transmission electron microscopy （TEM） to investigate the adsorption of serum proteins, including bovine serum albumin （BSA）, transferrin （TRF） and fibrinogen （FIB）, on gold nanoparticles （AuNPs） with different surface modifications （citrate, thioglycolic acid, cysteine, polyethylene glycol （PEG, Mw = 2 k and 5 k））. AuNPs with PEG（5 k） surface modification showed no protein adsorption. AuNPs with non-PEG surface modifications showed aggregation with FIB. AuNPs with citrate and thioglycolic acid surface modifications showed 6-8 nm thick BSA and TRF coronas （corres- ponding to monolayer or bilayer proteins）, in which the microscopic dissociation constants of BSA and TRF protein coronas are in the range of 104 to 104 M.展开更多
Gases that are widely used in research and industry have a significant effect on both the configuration of solid materials and the evolution of reactive systems. Traditional studies on gas-solid interactions have most...Gases that are widely used in research and industry have a significant effect on both the configuration of solid materials and the evolution of reactive systems. Traditional studies on gas-solid interactions have mostly been static and post-mortem and unsatisfactory for elucidating the real active states during the reactions. Recent developments of controlled-atmosphere transmission electron microscopy （TEM） have led to impressive progress towards the simulation of real-world reaction environments, allowing the atomic-scale recording of dynamic events. In this review, on the basis of the in situ research of our group, we outline the principles and features of the controlled-atmosphere TEM techniques and summarize the significant recent progress in the research activities on gas-solid interactions, including nanowire growth, catalysis, and metal failure. Additionally, the challenges and opportunities in the real-time observations on such platform are discussed.展开更多
Direct observation of the dissolution behavior of nanomaterials could provide fundamental insight to understanding their anisotropic properties and stability. The dissolution mechanism in solution and vacuum has been ...Direct observation of the dissolution behavior of nanomaterials could provide fundamental insight to understanding their anisotropic properties and stability. The dissolution mechanism in solution and vacuum has been well documented. However, the gas-involved dissolution and regrowth have seldom been explored and the mechanisms remain elusive. We report herein, an in situ TEM study of the dissolution and regrowth dynamics of MoO2 nanowires under oxygen using environmental transmission electron microscopy （ETEM）. For the first time, oscillatory dissolution on the nanowire tip is revealed, and, intriguingly, simultaneous layer-by-layer regrowth on the sidewall facets is observed, leading to a shorter and wider nanowire. Combined with first-principles calculations, we found that electron beam irradiation caused oxygen loss in the tip facets, which resulted in changing the preferential growth facets and drove the morphology reshaping.展开更多
The pathogenic Wolbachia strain wMelPop rapidly over-replicates in the brain, muscles, and retina of Drosophila melanogaster, causing severe tissue degeneration and premature death of the host. The unique features of ...The pathogenic Wolbachia strain wMelPop rapidly over-replicates in the brain, muscles, and retina of Drosophila melanogaster, causing severe tissue degeneration and premature death of the host. The unique features of this endosymbiont make it an excellent tool to be used for biological control of insects, pests, and vectors of human diseases. To follow the dynamics of bacterial morphology and titer in the nerve cells we used transmission electron microscopy of 3-d-old female brains. The neurons and glial cells from central brain of the fly had different Wolbachia titers ranging from single bacteria to large accumulations, tearing cell apart and invading extracellular space. The neuropile regions of the brain were free of wMelPop. Wolbaehia tightly interacted with host cell organelles and underwent several morphological changes in nerve cells. Based on different morphological types of bacteria described we propose for the first time a scheme of wMelPop dynamics within the somatic tissue of the host.展开更多
Lipids exhibit an extraordinary polymorphism in self-assembled mesophases, with lamellar phases as the most relevant biological representative. To mimic lipid lamellar phases with amphiphilic designer peptides, seven ...Lipids exhibit an extraordinary polymorphism in self-assembled mesophases, with lamellar phases as the most relevant biological representative. To mimic lipid lamellar phases with amphiphilic designer peptides, seven systematically varied short peptides were engineered. Indeed, four peptide candidates （V4D, V4WD, V4WD2, I4WD2） readily self-assembled into lamellae in aqueous solution. Small-angle X-ray scattering （SAXS） patterns revealed ordered lamellar structures with a repeat distance of 4-5 nm. Transmission electron microscopy （TEM） images confirmed the presence of stacked sheets. Two derivatives （V3D and V4D2） remained as loose aggregates dispersed in solution; one peptide （L4WD2） formed twisted tapes with internal lameUae and an antiparaUel -type monomer aligrtment. To understand the interaction of peptides with lipids, they were mixed with phosphatidylcholines. Low peptide concentrations （1.1 mM） induced the formation of a heterogeneous mixture of vesicular structures. Large multilamellar vesicles （MLV, d-spacing - 6.3 nm） coexisted with oligo- or unilamellar vesicles （- 50 nm in diameter） and bicelle-like structures （- 45 nm length, - 18 nm width）. High peptide concentrations （11 mM） led to unilamellar vesicles （ULV, diameter - 260-280 nm） with a homogeneous mixing of lipids and peptides. SAXS revealed the temperature-dependent fine structure of these ULVs. At 25 ℃ the bilayer is in a fully Interdigitated state （headgroup-to-headgroup distance dH, -2.9 nm）, whereas at 50 ℃this interdigitation opens up （dtm- 3.6 nm）. Our results highlight the versatility of self-assembled peptide superstructures. Subtle changes in the amino acid composition are key design elements in creating peptide- or lipid- peptide nanostructures with richness in morphology similar to that of naturally occurrin~ lioids.展开更多
文摘To elucidate the effect of the internal fixation plates on the local bone blood sapply, we used microangiography and scanning electron microscopy to observe the morphological changes of microcirculation in the cortical bones obtained from intact rabbit tibiae on which plates of two different stiffness had been fixed for comparison. The results indicated that both rigid stainless steel plate and less rigid methyl methacrylate plate could induce the bone microcirculation under the plate to undergo a process from early depression to late reactive recruitment. The features of the microcircuiation recruitment such as vascular number, arrangement and dilatation varied with plates of different stiffness and were more obvious in the cortex fixed by rigid stainless steel plate.
基金Samsung Research Fundings&Incubation Center of Samsung Electronics(Grant No.SRFCMA1702-01)Y.-M.K acknowledges partial support from the National Research Foundation of Korea(NRF)(Grant No.2023R1A2C2002403)funded by the Korean government in KoreaA.Borisevich acknowledges support from FaCT,an Energy Frontier Research Center funded by the U.S.Department of Energy,Office of Science,Office of Basic Energy Science,Collaboratives Research Division.
文摘The functionalities and diverse metastable phases of multiferroic BiFeO_(3)(BFO)thin films depend on the misfit strain.Although mixed phase-induced strain relaxation in multiphase BFO thin films is well known,it is unclear whether a singlecrystalline BFO thin film can accommodate misfit strain without the involvement of its polymorphs.Thus,understanding the strain relaxation behavior is key to elucidating the lattice strain–property relationship.In this study,a correlative strain analysis based on dark-field inline electron holography(DIH)and quantitative scanning transmission electron microscopy(STEM)was performed to reveal the structural mechanism for strain accommodation of a single-crystalline BFO thin film.The nanoscale DIH strain analysis results indicated a random combination of multiple strain states that acted as a primary strain relief,forming irregularly strained nanodomains.The STEM-based bond length measurement of the corresponding strained nanodomains revealed a unique strain accommodation behavior achieved by a statistical combination of multiple modes of distorted structures on the unit-cell scale.The globally integrated strain for each nanodomain was estimated to be close to1.5%,irrespective of the nanoscale strain states,which was consistent with the fully strained BFO film on the SrTiO_(3) substrate.Density functional theory calculations suggested that strain accommodation by the combination of metastable phases was energetically favored compared to single-phase-mediated relaxation.This discovery allows a comprehensive understanding of strain accommodation behavior in ferroelectric oxide films,such as BFO,with various low-symmetry polymorphs.
基金supported by the National Natural Science Foundation of China(Nos.21677107,51578398)the Fundamental Research Funds for the Central Universities(No.0400219363)
文摘Solid phase reactions of Cr（Ⅵ） with Fe（0） were investigated with spherical-aberration-corrected scanning transmission electron microscopy（Cs-STEM） integrated with X-ray energy-dispersive spectroscopy（XEDS）. Near-atomic resolution elemental mappings of Cr（Ⅵ）–Fe（0） reactions were acquired. Experimental results show that rate and extent of Cr（Ⅵ） encapsulation are strongly dependent on the initial concentration of Cr（Ⅵ） in solution. Low Cr loading in nZⅥ（〈1.0 wt%） promotes the electrochemical oxidation and continuous corrosion of n ZⅥ while high Cr loading（〉1.0 wt%） can quickly shut down the Cr uptake. With the progress of iron oxidation and dissolution, elements of Cr and O counter-diffuse into the nanoparticles and accumulate in the core region at low levels of Cr（Ⅵ）（e.g., 〈 10 mg/L）. Whereas the reacted n ZⅥ is quickly coated with a newly-formed layer of 2–4 nm in the presence of concentrated Cr（Ⅵ）（e.g., 〉 100 mg/L）. The passivation structure is stable over a wide range of pH unless pH is low enough to dissolve the passivation layer. X-ray photoelectron spectroscopy（XPS） depth profiling reconfirms that the composition of the newly-formed surface layer consists of Fe（Ⅲ）–Cr（Ⅲ）（oxy）hydroxides with Cr（Ⅵ） adsorbed on the outside surface. The insoluble and insulating Fe（Ⅲ）–Cr（Ⅲ）（oxy）hydroxide layer can completely cover the n ZⅥ surface above the critical Cr loading and shield the electron transfer. Thus, the fast passivation of nZⅥ in high Cr（Ⅵ） solution is detrimental to the performance of nZⅥ for Cr（Ⅵ） treatment and remediation.
文摘In this study, an ecofriendly and economically viable waste management approach have been attempted towards the biosynthesis of agriculturally important nanoparticles from jarosite waste. Aspergillus terreus strain J4 isolated from jarosite（waste from Debari Zinc Smelter,Udaipur, India）, showed good leaching efficiency along with nanoparticles（NPs） formation under ambient conditions. Fourier-transform infrared spectroscopy（FT-IR） and transmission electron microscopy（TEM） confirmed the formation of NPs. Energy dispersive X-ray spectroscopy（EDX analysis） showed strong signals for zinc, iron, calcium and magnesium,with these materials being leached out. TEM analysis and high resolution transmission electron microscopy（HRTEM） showed semi-quasi spherical particles having average size of 10‐50 nm. Thus, a novel biomethodology was developed using fungal cell-free extract for bioleaching and subsequently nanoconversion of the waste materials into nanostructured form. These biosynthesized nanoparticles were tested for their efficacy on seed emergence activity of wheat（Triticum aestivum） seeds and showed enhanced growth at concentration of 20 ppm. These nanomaterials are expected to enhance plant growth properties and being targeted as additives in soil fertility and crop productivity enhancement.
文摘Alloys containing chromium （Cr） and molybdenum （Mo）, as the major alloying elements, are widely used in various industries where the material experiences corrosive environments. Chromium （Cr）, when added in an optimum amount, forms a Cr203 passive film which protects the underlying metal in aggressive solutions. Molybdenum （Mo） forms its oxides in the low pH solutions, thus, enhances the uniform corrosion resistance of an alloy in reducing acids and assists in inhibition to localized corrosion. Minor alloying elements, like tungsten （W） and copper （Cu）, also improve the overall corrosion resistance of an alloy in specific solutions. In the present study, corrosion resistance behavior of commercial iron- based alloys （316L SS, 254 SMO and 20Cb3） and nickel-based alloys （Mone1400, Alloy 625 and C-276） was studied in the acidic solutions. While the corrosion behavior of wrought alloys has been widely studied, there is little to no information on the corrosion performance of their welds, typically being the weak regions for corrosion initiation and propagation. Therefore, an attempt was undertaken to investigate the uniform and localized corrosion performance of base metal, simulated heat-affected zone and all-weld-metal samples of a Ni-Cr-Mo-W alloy, C-276. The study was conducted in aggressive acidic solutions. Various corrosion and surface analytical techniques were utilized to analyze the results.
基金supported by the National Natural Science Foundation of China (Grant Nos.51001069 and 51031001)
文摘The crystallographic features of pearlite were investigated by experiments and edge-to-edge matching principle. Two new orientation relationships between ferrite and cementite were determinated by selected area electron diffraction and then explained by our modified edge-to-edge matching method. The consistence of the experimental results with theoretical prediction confirms the practicability of the modified edge-to-edge matching model.
文摘Nanocrystalline CdS thin films have been deposited using precursors with different thiourea concentrationonto glass substrates by sol-gel spin coating method.The crystalline nature of the films has been observedto be strongly dependent on thiourea concentration and annealing temperature.The CdS films are found tobe nanocrystalline in nature with hexagonal structure.The grain size is found to be in the range of 7.6 to11.5 nm depending on the thiourea concentration and annealing temperature.The high resolution transmissionelectron microscopy （HRTEM） results of the CdS films prepared using cadmium to thiourea molar ratio of0.3：0.3 indicate the formation of nanocrystalline CdS with grain size of 5 nm.Fourier transform infrared （FTIR）analysis shows the absorption bands corresponding to Cd and S.The optical study carried out to determinethe band gap of the nanostructured CdS thin films shows a strong blue shift.The band gap energy has beenobserved to lie in the range of 3.97 to 3.62 eV following closely the quantum confinement dependence ofenergy on crystallite radius.The dependence of band gap of the CdS films on the annealing temperature andthiourea concentration has also been studied.The photoluminescence （PL） spectra display two main emissionpeaks corresponding to the blue and green emissions of CdS.
基金the National Natural Science Foundation of China (No. 59971008)
文摘The microstructures of copper liners of shaped charges prepared byelectroforming technique were investigated by transmission electron microscopy (TEM). Meanwhile, theorientations distributing of the grains in the electroformed copper liners of shaped charges wasexamined by the electron backscattering Kikuchi pattern (EBSP) technique. TEM observations haverevealed that these electroformed copper liners of shaped charges have the grain size of about 1-3mu m and the grains have a preferential orientation distribution along the growth direction. EBSPanalysis has demonstrated that the as-formed copper liners of shaped charges exhibit amicro-texture, i.e. one type of fiber texture, and the preferred growth direction is normal to thesurface of the liners.
文摘AIM: To investigate whether the major kavalactone kavain imposes adverse effects on the liver ultrastructure and function by affecting vascular and microvascular architecture and altering hepatocellular morphology. METHODS: Kavain solution (10 μg/mL or 43.5 μmol/L) was perfused for 2 h in isolated rat livers. After standard fi xation and tissue preparation,the samples were examined by scanning electron microscopy (SEM),transmission electron microscopy (TEM),and light microscopy (LM). RESULTS: LM,SEM,and TEM examinations indicated kavain-treated rat livers (n = 4) displayed severe vascular and endothelial damage compared to control livers (n = 4). CONCLUSION: The data so far support the hypothesis that kavain induces adverse effects on liver; additional investigations with other kavalactones and their effects on liver are urgently needed.
基金supported by the Polish Ministry of Science and Higher Education under research project No. N N507 373435
文摘The results presented in this study were concerned with microstructures and mechanical properties of poly- crystalline Cu subjected to plastic deformation by a compression with oscillatory torsion process. Different deformation parameters of the compression with oscillatory torsion process were adopted to study their effects on the microstructure and mechanical properties. The deformed microstructure was characterized quantitatively by electron backscattered diffraction （EBSD） and scanning transmission electron microscopy （STEM）. Mechanical properties were determined on an MTS QTest/10 machine equipped with digital image correlation. From the experimental results, processes performed at high compression speed and high torsion frequency are recommended for refining the grain size. The size of structure elements, such as average grain size （D） and subgrain size （d）, reached 0.42 μm and 0.30 μm, respectively, and the fraction of high angle boundaries was 35% when the sample was deformed at a torsion frequency f = 1.6 Hz and compression rate v= 0.04 mm/s. These deformation parameters led to an improvement in the strength properties. The material exhibited an ultimate tensile strength （UTS） of 434 MPa and a yield strength （YS） of 418 MPa. These values were about two times greater than those of the initial state.
文摘Microstructure of SiC fiber manufactured by chemical vapor deposition （CVD） onto tungsten （W） wire core was investigated by analytical electron microscopy （AEM）. The results reveal that the fiber consists of W core, SiC sheath and C-coating. SiC sheath could be subdivided into two parts according to whether containing C rich stripe, or not. An emphasis was put on W/SiC interfacial reaction products and the transition zone between sub-layers in SiC sheath. The W/SiC interface consists of three layers of reaction production, namely, W2C, W5Si3 and WC. And there are amounts of facet faults existing in （100） face of WC crystalline and two classes of stack faults in WC have been revealed. The formation essence of different sublayers in SiC sheath was also discussed.
基金Funded by the National Natural Science Foundation of China(Nos.11302054 and 11472086)the Hong Kong,Macao and Taiwan Science and Technology Cooperation Projects of Ministry of Science and Technology of China(No.2014DFH50060)+1 种基金the Natural Science Foundation of Heilongjiang Province of China(No.A2015012)the Fundamental Research Funds for the Central Universities(GK2010260256)
文摘Tensile properties of epoxy casts together with shape memory alloy（SMA）, glass（GF） and carbon（CF） woven fabric reinforced epoxy matrix super hybrid composites were investigated, respectively. In order to enhance the mechanical strength of this advanced material, two categories of modifications including matrix blending and fiber surface coating by nano-silica were studied. Scanning electron microscopy（SEM） and fiber pull-out tests were adopted to complement the experimental results, respectively. Experimental results reveal that the toughness of epoxy matrix is enhanced significantly by adding 2 wt% nano-silica. The failure mechanism of SMA reinforced hybrid composites is different from that of GF/CF/epoxy composites. Compared with the matrix modification, the fibers modified by coating nano-silica on the surface have better tensile performances. Moreover, the fiber pull-out test results also indicate that composites with fiber surface modification have better interfacial performances. The modification method used in this paper can help to enhance the tensile performance of the mentioned composite materials in real engineering fields.
基金This project is financially supported by the Natural Science Foundation of Shandong Province ( Y2001F06) and the Fund for Outstanding Young Researcher of Shandong Province
文摘Microstructures of a CuZnAlMnNi shape memory alloy in the as-quenched andlong-term aged conditions were investigated by transmission electron microscopy. Aged for one yearin martensite phase, an equilibrium α-phase with fcc structure was observed in the M18R martensitematrix, accompanied by the appearance of a novel diffraction pattern. By analysis, it was suggestedthat the novel pattern results from the α-phase and the martensite matrix remaining in seven fineplates which produce intense secondary diffraction effect when the diffraction beams enter from onephase into another.
基金Project supported by the National Basic Research Program of China(Grant No.2009CB623702)the National Natural Science Foundation of China(Grant No.10904001)the Key Project Funding Scheme of Beijing Municipal Education Committee,China(Grant No.KZ201010005002)
文摘The local thermal conductivity of polycrystalline aluminum nitride （A1N） ceramics is measured and imaged by using a scanning thermal microscope （SThM） and complementary scanning electron microscope （SEM） based techniques at room temperature. The quantitative thermal conductivity for the A1N sample is gained by using a SThM with a spatial resolution of sub-micrometer scale through using the 3w method. A thermal conductivity of 308 W/m-K within grains corresponding to that of high-purity single crystal A1N is obtained. The slight differences in thermal conduction between the adjacent grains are found to result from crystallographic misorientations, as demonstrated in the electron backscattered diffraction. A much lower thermal conductivity at the grain boundary is due to impurities and defects enriched in these sites, as indicated by energy dispersive X-ray spectroscopy.
文摘Low-energy electron microscopy （LEEM） has been used to study the structure, initial growth orientation, growth progression, and the number of layers of atomically thin hexagonal boron nitride （h-BN） films. The h-BN films are grown on heteroepitaxial Co using chemical vapor deposition （CVD） at low pressure. Our findings from LEEM studies include the growth of monolayer film having two, oppositely oriented, triangular BN domains commensurate with the Co lattice. The growth of h-BN appears to be self-limiting at a monolayer, with thicker domains only appearing in patches, presumably initiated between domain boundaries. Reflectivity measurements of the thicker h-BN films show oscillations resulting from the resonant electron transmission through quantized electronic states of the h-BN films, with the number of minima scaling up with the number of h-BN layers. First principles density functional theory （DFT） calculations show that the positions of oscillations are related to the electronic band structure of h-BN.
文摘Protein coronas provide the biological identity of nanomaterials in vivo. Here we have used dynamic light scattering （DLS） and transmission electron microscopy （TEM） to investigate the adsorption of serum proteins, including bovine serum albumin （BSA）, transferrin （TRF） and fibrinogen （FIB）, on gold nanoparticles （AuNPs） with different surface modifications （citrate, thioglycolic acid, cysteine, polyethylene glycol （PEG, Mw = 2 k and 5 k））. AuNPs with PEG（5 k） surface modification showed no protein adsorption. AuNPs with non-PEG surface modifications showed aggregation with FIB. AuNPs with citrate and thioglycolic acid surface modifications showed 6-8 nm thick BSA and TRF coronas （corres- ponding to monolayer or bilayer proteins）, in which the microscopic dissociation constants of BSA and TRF protein coronas are in the range of 104 to 104 M.
文摘Gases that are widely used in research and industry have a significant effect on both the configuration of solid materials and the evolution of reactive systems. Traditional studies on gas-solid interactions have mostly been static and post-mortem and unsatisfactory for elucidating the real active states during the reactions. Recent developments of controlled-atmosphere transmission electron microscopy （TEM） have led to impressive progress towards the simulation of real-world reaction environments, allowing the atomic-scale recording of dynamic events. In this review, on the basis of the in situ research of our group, we outline the principles and features of the controlled-atmosphere TEM techniques and summarize the significant recent progress in the research activities on gas-solid interactions, including nanowire growth, catalysis, and metal failure. Additionally, the challenges and opportunities in the real-time observations on such platform are discussed.
文摘Direct observation of the dissolution behavior of nanomaterials could provide fundamental insight to understanding their anisotropic properties and stability. The dissolution mechanism in solution and vacuum has been well documented. However, the gas-involved dissolution and regrowth have seldom been explored and the mechanisms remain elusive. We report herein, an in situ TEM study of the dissolution and regrowth dynamics of MoO2 nanowires under oxygen using environmental transmission electron microscopy （ETEM）. For the first time, oscillatory dissolution on the nanowire tip is revealed, and, intriguingly, simultaneous layer-by-layer regrowth on the sidewall facets is observed, leading to a shorter and wider nanowire. Combined with first-principles calculations, we found that electron beam irradiation caused oxygen loss in the tip facets, which resulted in changing the preferential growth facets and drove the morphology reshaping.
文摘The pathogenic Wolbachia strain wMelPop rapidly over-replicates in the brain, muscles, and retina of Drosophila melanogaster, causing severe tissue degeneration and premature death of the host. The unique features of this endosymbiont make it an excellent tool to be used for biological control of insects, pests, and vectors of human diseases. To follow the dynamics of bacterial morphology and titer in the nerve cells we used transmission electron microscopy of 3-d-old female brains. The neurons and glial cells from central brain of the fly had different Wolbachia titers ranging from single bacteria to large accumulations, tearing cell apart and invading extracellular space. The neuropile regions of the brain were free of wMelPop. Wolbaehia tightly interacted with host cell organelles and underwent several morphological changes in nerve cells. Based on different morphological types of bacteria described we propose for the first time a scheme of wMelPop dynamics within the somatic tissue of the host.
文摘Lipids exhibit an extraordinary polymorphism in self-assembled mesophases, with lamellar phases as the most relevant biological representative. To mimic lipid lamellar phases with amphiphilic designer peptides, seven systematically varied short peptides were engineered. Indeed, four peptide candidates （V4D, V4WD, V4WD2, I4WD2） readily self-assembled into lamellae in aqueous solution. Small-angle X-ray scattering （SAXS） patterns revealed ordered lamellar structures with a repeat distance of 4-5 nm. Transmission electron microscopy （TEM） images confirmed the presence of stacked sheets. Two derivatives （V3D and V4D2） remained as loose aggregates dispersed in solution; one peptide （L4WD2） formed twisted tapes with internal lameUae and an antiparaUel -type monomer aligrtment. To understand the interaction of peptides with lipids, they were mixed with phosphatidylcholines. Low peptide concentrations （1.1 mM） induced the formation of a heterogeneous mixture of vesicular structures. Large multilamellar vesicles （MLV, d-spacing - 6.3 nm） coexisted with oligo- or unilamellar vesicles （- 50 nm in diameter） and bicelle-like structures （- 45 nm length, - 18 nm width）. High peptide concentrations （11 mM） led to unilamellar vesicles （ULV, diameter - 260-280 nm） with a homogeneous mixing of lipids and peptides. SAXS revealed the temperature-dependent fine structure of these ULVs. At 25 ℃ the bilayer is in a fully Interdigitated state （headgroup-to-headgroup distance dH, -2.9 nm）, whereas at 50 ℃this interdigitation opens up （dtm- 3.6 nm）. Our results highlight the versatility of self-assembled peptide superstructures. Subtle changes in the amino acid composition are key design elements in creating peptide- or lipid- peptide nanostructures with richness in morphology similar to that of naturally occurrin~ lioids.
