This paper describes the effects of temperature on the complex intermediate processes from the precursor to the fully-crystallized anatase TiO2 nanoparticles in hydrothermal synthesis. The anatase TiO2 nanoparticles were synthesized in a wide temperature range below 230°C. The composition, morphology, and methylene blue (MB) decoloration characteristics of the obtained products were investigated by X-ray diffraction, Fourier transform infrared spectroscope, X-ray photoelectron spectroscope, and scanning and transmission electron microscope. The dehydrating polycondensation of Ti(IV)-hydrates and the decomposition of (NH4)2Ti3O7 intermediates with the temperature increase lead to the direct formation of anatase TiO2 nanoparticles under the hydrothermal environments. The strong MB decoloration of the hydrothermal products obtained at the low (≤130°C) and high (≥180°C) temperatures are attributed to the adsorption of Ti(IV)-hydrates and the photocatalysis of anatase TiO2 nanoparticles, respectively.
LU HongBinZHOU YouZhenVONGEHR SaschaTANG ShaoChunMENG XiangKang
This article reviews recent advances in the utilization of various water based synthesis routes towards the shape-controlled synthesis of silver nanoparticles and microstructures in a diverse range of shapes and sizes from several nanometers to micrometers.A variety of very simple one-pot methods,at times employing commercial microwave ovens,inexpensive low power ultrasound cleaners,or two-electrode electro-chemistry,can be surprisingly effective in the controlled synthesis of a wide range of nanostructured products,if only parameters are carefully chosen.Many approaches which are adopted include synthesis of Ag nanostructures with various shapes in solution,doping of Ag nanoparticles on unmodified silica and on/inside carbon spheres,kinetically controlled growth of Ag micro-particles with novel nanostructures on flat substrates,and galvanic replacement towards bimetallic Ag-Au dendrites and carbon composites.Characterizations of shape,composition and microstructure are carried out via scanning and transmission electron microscopy,various spectroscopy methods,N2 absorption measurements and suchlike.The involved growth mechanisms are investigated in order to discover new means towards better control.Size,location and shape control,including micro-and nanostructure features,allows tuning the products properties towards desired applications.We focus on the optical properties and catalytic activities,but also the stability of compounds can be an issue of interest.
The fatigue fracture was characterized and the fracture behavior was analyzed,using scanning electron microscope(SEM)and electron back-scattered diffraction(EBSD),the fatigue tests of two strain amplitude at room temperature were 0.5%and 1.0%respectively,and the results showed that the fatigue deformation of different strain amplitude produced two typical fatigue fracture morphology,and when the strain amplitude was 1.0%,fatigue fracture mechanism of AZ31 magnesium alloy induced by{1012}twins,when the strain amplitude is 0.5%,it was induced by{1012}-{1012}double twins.In the present study,the average thickness of primary twin is^20μm at amplitude of 0.5%and^80μm at amplitude of 1.%.The thickness of{1012}primary twins was large enough to activate{1012}-{1012}secondary twins at a high strain amplitude,while the thickness of{1012}primary twins was too narrow to activate{1012}-{1012}secondary twins at a low strain amplitude.
We report the mechanical spectroscopy study of the cold-rolling induced dynamical behavior of crystalline defects in nanocrystalline (NC) nickel The results show that internal friction (IF) peaks in NC nickel can be induced by cold-rolling.An IF peak,originating from dislocation activity,occurs when the strain is in the range of 9.7- 32.8%.Two Bordoni peaks occur when the strain is 39.0% and an IF peak associated with deformation twinning appears when the strain is 42.6%.These results mean that deformation of NC nickel is mediated by different kinds of defects as the strain increases.
Thermal stability and strain rate sensitivity of ultrafine-grained(UFG)Fe produced by severe plastic deformation(SPD)were investigated.The UFG Fe was processed by equal-channel angular pressing(ECAP)via route Bc.After 6 passes,the grain size of UFG Fe reaches 600 nm, as confirmed by means of electron back scatter diffraction(EBSD).Examination of micro-hardness and grain size of UFG Fe as a function of post-ECAP annealing temperature shows a transition from recovery to recrystallization.The critical trans...
Fuping Yuan,~(a) Ping Jiang,~(b) and Xiaolei Wu~(c) State Key Laboratory of Nonlinear Mechanics,Institute of Mechanics Chinese Academy of Science, Beijing 100190,China
