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Fabrication and Performances of Graphene/TiO2 Composites Derived from Graphenes and Titanium(IV) Alkoxide Precursors
摘要： Graphene/TiO2 composites were synthesized by sol-gel technique using titanium(IV) n-butoxide (TNB), titanium(IV) isopropoxide (TIP) and titanium(IV) propoxide (TPP) as different titanium alkoxide precursors. The as-prepared composites were characterized by BET surface area, SEM, XRD, EDX and UV-visible absorption spectroscopy. The samples were evaluated for their photocatalytic activity towards the degradation of methylene blue (MB) under UV irradiation. The results indicated that the sample GTNB had best excellent photocatalytic activity among the three kinds of samples. According to the photocatalytic results, methylene blue removal by a treatment with graphene/TiO2 composites seems to have an excellent removal effect as order of GTIP, GTNB and GTPP composites due to a photolysis of the supported TiO2, the radical reaction and the adsorptivity and absorptivity of the graphene.
关键词： TiO2,Visible light,Graphene,Photocatalytic,TEM
更新于2025-09-09 09:28:46
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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Carbon-titanium multilayer films: Synthesis and characterization
摘要： To synthesize Carbon-Titanium (C-Ti) multilayer thin films deposited on silicon substrates was used Thermionic Vacuum Arc (TVA) method. The coated layers consisted of a base layer of about 100 nm of Carbon deposited at low evaporation rates. Subsequently, seven Carbon and Titanium layers were deposited alternatively on top of Carbon base layer, each of them has a final thickness up to 40 nm. In this study we obtained different batches of samples by variation of the substrate temperature between 0oC and 300oC, and the ion acceleration voltage applying a negative substrate bias voltage between 0V and -700V. To characterize the microstructure properties of as prepared C-Ti multilayer structures were used Electron Microscopy techniques (TEM, SEM, STEM) and Raman Spectroscopy. Results of tribological measurements are associated with the occurrence of atomic diffusion processes at Ti/C interface. To characterize the electrical conductive properties, the electrical resistance versus temperature have been measured.
关键词： Ti/C multilayer,TVA,STEM,tribological properties,SEM,EDX,Raman,electrical properties,TEM
更新于2025-09-09 09:28:46
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Recognizing and Preventing Artifacts in Microscopy: A Roundtable Discussion
摘要： In 1991 the Technologists’ Forum presented a symposium on artifacts in biological electron microscopy [1]. Since that time the topic has not been re-visited in our symposia, special topics or roundtable discussions. Artifacts are damage caused in specimen preparation and can be confused with specimen ultrastructure. Many artifacts are a result of mechanical or chemical action during sample preparation and some artifacts are due to irradiation by the electron beam during examination of the specimen in the microscope. Recognizing specimen damage is the initial step in preventing the same problem in future preparations and not reporting erroneous data.
关键词： electron microscopy,TEM,specimen preparation,microscopy,artifacts,SEM
更新于2025-09-09 09:28:46
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Depth sensitive imaging of graphene with an atomic resolution microscope
摘要： The three-dimensional information of atomic positions is required to determine the atomic structure of materials. However, images obtained using high-resolution transmission electron microscopes are generally two-dimensional projections of three-dimensional structures. The depth resolution of general microscopes is still on the order of nanometers, and a smaller depth of field is required to realize atomic depth-resolution imaging. Here, we propose highly depth-sensitive imaging using a low-voltage atomic-resolution transmission electron microscope equipped with a higher order geometrical aberration corrector and a monochromator. A long wavelength of low energy electrons and a large acceptance angle of the microscope allow for a shallow depth of field and atomic-level depth sensitivity. We demonstrate that the depth resolution and depth precision can allow for a?ngstr€om and sub-a?ngstr€om levels, respectively. Applying this highly depth-sensitive microscope, the depth deviation of monolayer graphene with dislocations is detected as the difference of defocus. The buckling structures of dislocation dipole and tripole are directly observed using a single image. Combining the proposed depth-sensitive microscope with through-focal imaging will allow for the analysis of various low-dimensional materials in three dimensions with atomic depth resolution.
关键词： atomic resolution microscope,low-voltage TEM,monochromator,three-dimensional atomic structural analysis,aberration corrector,depth-sensitive imaging,graphene
更新于2025-09-09 09:28:46
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Fabrication and analysis of the structural phase transition of ZrO <sub/>2</sub> nanoparticles using modified facile sol–gel route
摘要： The synthesis of zirconia nanoparticles is achieved through a modified facile sol–gel route. The as-prepared gel is analyzed thermally using TGA and DTA techniques to spot the crystallization process of zirconia nanoparticles. The prepared gel is then annealed at different temperatures and the structure was found to change between tetragonal and monoclinic crystal systems. The first stable tetragonal phase is achieved after annealing for 2 h at 400°C. The annealed powders between 600°C and 800°C demonstrate mixed tetragonal/monoclinic phases. Annealing at 1000°C and higher temperatures up to 1200°C resulted in pure monoclinic phase. Cubic phase was not detected within the annealing temperature range in this study. The elemental analysis of the annealed powder confirmed the formation of zirconia nanoparticles with the chemical formula ZrO2. The FTIR spectra of the annealed samples introduced a variation in the vibrational bands especially around the phase transition temperature. HR-TEM images reported the formation of nano-zirconia crystals with apparently large particle sizes. The optical energy gap of zirconia nanoparticles is investigated and determined.
关键词： ZrO2 nanoparticles,HR-TEM,sol–gel synthesis,EDAX,optical energy gap
更新于2025-09-09 09:28:46
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Synthesis and Characterization of Erbium Oxide Nanocrystallites
摘要： The present article describes a method of the preparation of erbium oxide nanocrystallites (nano Er2O3) via thermal decomposition of a transient complex formed in situ from Er(NO3)3 · 5H2O and glycine. Decomposition of the complex occurred at about of (250 ± 10) °C. Ultra-fine light pink powder of erbium oxide nanocrystallites was obtained via this method. The resulting nanocrystallites were characterized using X-ray powder diffraction analysis, which showed the nanocrystallites having the crystallite size equal to 10 nm. Morphology of the nanocrystallites was examined by scanning and transmission electron microscopy. Electron diffraction observed in transmission electron microscopy corresponds to the results obtained from X-ray diffraction analysis. The elemental composition of the product was confirmed by EDS analysis.
关键词： Erbium Oxide,SEM,XRD,TEM,Nanocrystallites,Thermal Decomposition
更新于2025-09-04 15:30:14
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Dumbbell to Core–Shell Structure Transformation of Ni–Au Nanoparticle Driven by External Stimuli
摘要： Conversion of CO2 gas to CO fuels is one of the most promising solutions for the increasing threat of global warming and energy crisis. The efficient catalyst Ni–Au dumbbell converting CO2 into CO at elevated temperatures has high CO product selectivity; however, the accompanied atomic diffusion and subsequent surface reconstruction affect the catalytic efficiency of chemical reaction. Atomic scale characterization of structural evolution of the catalyst, which is essential to correlate the functional mechanism to active catalyst surfaces, is yet to be studied. Here, in situ transmission electron microscopy experiments and atomistic simulations are performed to characterize the structural evolution of Ni–Au dumbbell nanoparticles under two different external stimuli. In the condition of high temperature and vacuum, the Ni–Au nanostructure reveals a clear shape reconstruction from the initial dumbbell to core–shell-like, which is induced by capillary force to minimize free surface energy of the system. The shape transformation involves two stages of processes, initial fast Au diffusion followed by slow source-controlled diffusion. At ambient temperature, the combination of CO2 and electron flux surprisingly induces analogous structural transformation of Ni–Au nanostructure, where the associated chemical reaction and CO absorption stimulate the Au migration on Ni surface. Such surface reconstruction can be widely present in catalytic reactions in different environmental conditions, and the results herein demonstrate the detailed processes of Ni–Au structure evolution, which provide important insights for understanding the catalyst performance.
关键词： core–shell,in situ TEM,catalyst,Ni–Au,gas cell
更新于2025-09-04 15:30:14
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Accurate semiempirical analytical formulas for spontaneous polarization by crystallographic parameters of SrTiO3-BaTiO3 system by ab initio calculations
摘要： Spontaneous polarizations (PS’s) of BaTiO3 and SrTiO3 under various conditions are calculated ab initio using different exchange-correlation functionals. The extensive theoretical sets of PS vs. ion positions are found to lie on a single curve, despite the chemical differences and the wide variations of PS and lattice parameters. This uncovers accurate simple analytical formulas of PS of SrTiO3-BaTiO3 system expressed by ion positions; a single formula predicts both macroscopic and atomic-scale PS of SrTiO3, BaTiO3 and SrTiO3-BaTiO alloys. The accuracy of the formula is demonstrated by the application to experiments, BaTiO3-SrTiO3 (-CaTiO3) alloys, Sr4Ti4O12 with PS // a-axis, a parallel domain, and a headon domain. In addition, the present results verify empirically that oxygen displacement is the primary identifier and the origin of PS of SrTiO3 and BaTiO3 and indicate that BaTiO3 and SrTiO3 may transforms into new state by an extremely large strain, e.g., ?3%. Furthermore, the earlier prediction of headon domain without aid of defects was confirmed. The present procedures for finding formulas can be applied to other materials.
关键词： Crystallographic estimation,Polarization,Strain,Atom position,Domain,TEM
更新于2025-09-04 15:30:14
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Formation mechanism of twin structures in p-type (Bi0.25Sb0.75)2Te3 thermoelectric compound
摘要： The formation mechanism of twin structures in p-type (Bi0.25Sb0.75)2Te3 compound was examined using high-resolution transmission electron microscopy (HR-TEM) and computer simulations. The results shown that the formation of twins is analogous to the twinning mechanism via synchronized activation of Shockley partial dislocations commonly observed terminating {111} growth and annealing twins in face centered cubic (FCC) metals. The f1010g boundary, as an incoherent twin boundary (ITB), is mobile due to its lower shear stress compared to that of the coherent {0001} twin boundary; thickness of the twin region can be reduced or increased according to the direction of the movement.
关键词： Twin structure,Interfacial step,Transmission electron microscopy (TEM),(Bi, Sb)2Te3 thermoelectric compound
更新于2025-09-04 15:30:14
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Evolution of microstructure and mechanical properties of a graded TiAlON thin film investigated by cross-sectional characterization techniques
摘要： In the last years, quaternary oxynitrides have emerged as a new class of materials due to their tunable properties. Within the present work, a graded TiAl(O)N film was grown by magnetron sputter deposition, using TiAl targets with a Ti/Al atomic ratio of 40/60, constant nitrogen and stepwise increasing oxygen partial pressure over the film thickness. The microstructural evolution of the film was investigated by transmission electron microscopy and synchrotron X-ray nanodiffraction. Complementary, cross-sectional μ-Raman spectroscopy was performed to further validate the phase evolution. The first layer, grown without the addition of oxygen, showed a prevalent wurtzite (w) structure and a subordinate face centered cubic (fcc) phase fraction. The addition of small amounts of oxygen resulted in the stabilization of the fcc-phase and the w-phase vanished. With increasing film thickness and thus, increasing oxygen content, increasing amounts of an additional amorphous phase fraction were observed. In the first layers, tensile in-plain strain was determined, which turns to compressive towards the film surface. Cross-sectional nanonindentation revealed increasing hardness and elastic modulus with increasing oxygen content in the first layers as a result of the w to fcc transition; however, towards the film surface the hardness decreases, which can be related to the increasing amorphous phase fraction.
关键词： sputtering,TiAlON,graded film,cross-sectional nanoindentation,synchrotron X-ray nanodiffraction,TEM
更新于2025-09-04 15:30:14