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61.
A solid-state metathesis approach for the synthesis of hydrated MnV2O6·xH2O (x=2, 4) materials driven by mechanochemical activation energy has been demonstrated. The metathesis pathway of forming the desired product is confirmed by the presence of high lattice energy by-product such as NaCl. The structural, optical, and chemical properties of the synthesized materials are examined by powder X-ray diffraction, X-ray photoelectron spectroscopy, thermo gravimetric analysis, scanning electron microscopy, transmission electron microscopy, and diffused reflectance measurements in the UV–vis range. The valence state of Mn and V was determined to be +2 and +5, respectively, for the title compounds and the bandgap values determined showed these materials are likely to be semiconductors. 相似文献
62.
The effect of different nucleation agents such as ZrO2 and TiO2 was investigated for a first time with respect to their crystallisation behaviour in the glass system BaO-SrO-ZnO-SiO2. In all studied glasses, a Ba1-xSrxZn2Si2O7 (0.1 ≤ x ≤ 0.9) solid solution crystallized. This phase was first described in 2015 to possess a similar structure as the high temperature phase of BaZn2Si2O7 and a thermal expansion close to zero or even negative. It may find applications e.g. as cook panels, telescope mirrors, and furnace windows. Kinetic parameters of the crystallisation process were determined by supplying different heating rates in a differential scanning calorimeter (DSC). The results were evaluated using the equations of Ozawa and Kissinger with respect to the activation energies. Furthermore, the Ozawa method was used for the determination of Avrami parameters, which provides further information on the nucleation and crystallisation processes. Scanning electron microscopy including electron backscatter diffraction (EBSD) was used to characterise the microstructure, to determine the crystallite size and the crystal orientation. For the characterisation of the occurring crystalline phases, X-ray diffraction was used. 相似文献
63.
On the basis of a mathematical model proposed previously [S. Kobayashi, J. Crystal Growth 174 (1997) 163], oxygen precipitation in growing Czochralski (CZ) crystals is analyzed, and the calculated results are compared with experimental data of grown-in defects observed with laser scattering tomography (LST). The behavior of oxygen precipitates is qualitatively very similar to that of grown-in defects, but there are quantitative discrepancies between the calculation and the observation. The formation process of grown-in defects is discussed. 相似文献
64.
Shigeyasu Tanaka Yoshio Honda Norifumi Kameshiro Ryuta Iwasaki Nobuhiko Sawaki Takayoshi Tanji Mikio Ichihashi 《Journal of Crystal Growth》2004,260(3-4):360-365
We have investigated the morphology of the high-temperature-grown AlN nucleation layer and its role in the early stage of GaN growth, by means of transmission electron microscopy. The nitride was selectively grown on a 7-degree off-oriented (0 0 1) patterned Si substrate by metalorganic vapor phase epitaxy. AlN was deposited on the inclined unmasked (1 1 1) facet in the form of islands. The size of the islands varied along the slope, which is attributable to the diffusion of the growth species in the vapor phase. The GaN nucleation occurred at the region where rounded AlN islands formed densely. The threading dislocations were observed to generate in the GaN nucleated region. 相似文献
65.
Jakub Koza Margitta Uhlemann Annett Gebert Ludwig Schultz 《Journal of Solid State Electrochemistry》2008,12(2):181-192
The effect of a uniform magnetic field with flux density up to 1 T on the electrodeposition of Fe from sulphate electrolyte
has been investigated under different field configurations relative to the electrode surface. Voltammetric and chronoamperometric
experiments have been carried out coupled with an electrochemical quartz crystal microbalance for in situ mass change measurements.
The structure and morphology of the deposited films were determined by scanning electron microscopy, atomic force microscopy
and X-ray diffraction measurements. Results show that, when the magnetic field is applied parallel to the electrode surface,
the limiting current density and the deposition rate are increased due to the magnetohydrodynamic effect. The nucleation process
is also affected in parallel configuration; the current density of the maximum on the chronoamperograms is decreased, and
an additional nucleation step might be observed. This effect is attributed to the hydrodynamic response of the electrochemical
system. No significant influence on the electrochemical reaction was observed when a magnetic field was applied perpendicular
to the electrode. But in this configuration, the morphology of deposited layers is changed by the magnetic field. The morphology
changes are discussed. No effect of the magnetic field on the crystallographic structure was observed. 相似文献
66.
Dr. Xianzhong Yang Weiping Li Ziyan Chen Dr. Meng Tian Jun Peng Jinrong Luo Yiwen Su Yuhan Zou Gao Weng Prof. Yuanlong Shao Prof. Shixue Dou Prof. Jingyu Sun 《Angewandte Chemie (International ed. in English)》2023,62(10):e202218454
Despite conspicuous merits of Zn metal anodes, the commercialization is still handicapped by rampant dendrite formation and notorious side reaction. Manipulating the nucleation mode and deposition orientation of Zn is a key to rendering stabilized Zn anodes. Here, a dual electrolyte additive strategy is put forward via the direct cooperation of xylitol (XY) and graphene oxide (GO) species into typical zinc sulfate electrolyte. As verified by molecular dynamics simulations, the incorporated XY molecules could regulate the solvation structure of Zn2+, thus inhibiting hydrogen evolution and side reactions. The self-assembled GO layer is in favor of facilitating the desolvation process to accelerate reaction kinetics. Progressive nucleation and orientational deposition can be realized under the synergistic modulation, enabling a dense and uniform Zn deposition. Consequently, symmetric cell based on dual additives harvests a highly reversible cycling of 5600 h at 1.0 mA cm−2/1.0 mAh cm−2. 相似文献
67.
Yunchuan Pu Mingang Zhao Xu Liang Shaoyu Wang Dr. Hongjian Wang Ziting Zhu Dr. Yanxiong Ren Zhiming Zhang Prof. Guangwei He Prof. Dan Zhao Prof. Zhongyi Jiang 《Angewandte Chemie (International ed. in English)》2023,62(22):e202302355
We report a covalent organic framework (COF) induced seeding strategy to fabricate metal–organic framework (MOF) membranes. Contrary to graphene oxide nuclei-depositing substrate, COF substrate has uniform pore size, high microporosity and abundant functional groups. We designed a series of charged COF nanosheets to induce the formation of ZIF-8@COF nanosheet seeds with high aspect ratio over 150, which were readily processed into a compact and uniform seed layer. The resulting ZIF-8 membranes with thickness down to 100 nm exhibit an ultrahigh C3H6/C3H8 separation performance and superior long-term stability. Our strategy is also validated by fabricating ultrathin ZIF-67 and UiO-66 membranes. 相似文献
68.
碳纤维的微晶结构是影响其性能的决定性因素,本论文采用广角X-射线衍射法研究了聚丙烯腈预氧纤维在碳化阶段中微晶结构的形成、生长与转变过程。研究结果表明:在1000℃以下,经预氧化反应形成的不连续多环芳香平面结构沿平行于纤维轴的方向堆积并逐渐靠近,形成类似于晶核的微晶结构生长中心,表现为类石墨片层间距的减小而晶粒增长缓慢;当温度高于1000℃时,晶粒的生长速度明显加快,形成三维有序的微晶结构;在温度高于1500℃的石墨化阶段,类石墨微晶结构进行重排,晶粒尺寸迅速增加。根据这一规律,可以通过控制晶核生成和晶粒生长速度的匹配,进行碳纤维的结构设计和调控。 相似文献
69.
《Particuology》2023
Disodium 5′-ribonucleotide, which is composed of disodium 5′-inosine (IMP) and disodium 5′-guanosine (GMP), is an important food additive. The lack of kinetic studies of it causes a lack of clarity in understanding the complicated multi-solute crystallization of IMP + GMP in ethanol-water. In this work, process analytical technology tools were used to obtain the thermodynamics and kinetic data from the experiments, the kinetic parameters of anti-solvent and cooling crystallization were investigated. The crystal form of IMP + GMP mixed crystal was determined, which was consistent with the IMP whether crystallized from pure water or ethanol-water. The effects of different anti-solvent addition rates and cooling rates on the metastable zone widths were studied, and the opposite effect on metastable zone width was found. The modified exponential empirical function was developed to correlate nucleation and growth kinetic equations under different conditions. The kinetic data were well fitted with adjusted correlation coefficient (adj-R2 > 0.7), which is sufficient to provide a valid reference for process design and control. 相似文献
70.
Zirconium aluminium oxynitride multiphase composite film is deposited on zirconium substrate using energetic nitrogen ions delivered from dense plasma Focus device. X-ray diffractometer (XRD) results show that five Focus shots are sufficient to initiate the nucleation of ZrN and Al2O3 whereas 10 Focus shots are sufficient to initiate the nucleation of AlN. XRD results reveal that crystal growth of nitrides/oxides increases by increasing Focus shots (up to 30 Focus shots) and resputtering of the previously deposited film is taken place by further increase in Focus shots (40 Focus shots). Scanning electron microscopic (SEM) results indicate the uniform distribution of spherical grains (∼35 nm). A smoother surface is observed for 20 Focus shots at 0° angular position. SEM results also show a net-type microstructure (thread like features) of the sample treated for 30 Focus shots whereas rough surface morphology is observed for 40 Focus shots. Energy dispersive spectroscopic profiles show the distribution of different elements present in the deposited composite films. A typical microhardness value of the deposited composite films is 5255 ± 10 MPa for 10 grams imposed load which is 3.3 times than the microhardness values of unexposed sample. The microhardness values of the exposed samples increases with increasing Focus shots (up to 30 Focus shots) and decreases for 40 Focus shots treatment due to resputtering of the previously deposited composite film. The microhardness values of the composite films decreases by increasing the sample's angular position. 相似文献