Diameter Of Grains Research Articles

Preparation of La<sub>2</sub>(WO<sub>4</sub>)<sub>3</sub> by Two Step Method and Characterization

Lanthanum tungsten was prepared by two step method with lanthanum oxide, hydrochloric acid and sodium tungstate. The products were characterized by several analytical methods. Fourier transform infrared spectroscopy was used to determine whether the product was Lanthanum Tungsten. X-ray technique was used to study the phase composition. Scanning electron microscopy and scanning probe microscope were used to study micro-structure and surface morphology of powders. X-ray fluorescence spectrometer was used to study its content and impurity. DSC-TG was used to study its thermal stability. The results show that the prepared product is made of lanthanum tungsten mainly, its content of impurity is 3.91%, and there are traces of water in the powder. The prepared lanthanum tungsten has amorphous structure, the thermal stability is good, the powder grains present oval shape, and the diameter of grain is less than 1μm, the powder grains reunit partially.

Effectiveness of in-needle extraction device for liquid samples

In this work in-needle technique as the method for liquid samples preparation which faces with the problem of high flow resistance produced by a sorbent layer is considered. The influence of parameters (needle size, sorbent particle size and length of sorbent layer) of in-needle device on the flow rate was examined. Acceptable sampling conditions were selected on the basis of experiments and their chemometric evaluation. Darcy law was used to describe flow velocity through sorbent in the needle. Kozeny–Carman model and Brinkman model led to results significantly different from those obtained experimentally. Baaren model gave the most realistic results. Diameter of grain, porosity and a constant termed C were taken into account in this model. Incorporation of an additional parameter – “constant C” provides the completion of the model and allows predicting effectively the permeability of the extraction system. The so-called “constant C” is not constant but characteristic for a given system.The range for geometrical characteristics of the sorbent has been determined, where the extraction system works properly. To estimate suitability of a given extraction system, a new parameter PIN expressing the geometry of the system was proposed. The usefulness of the range of PIN parameter was confirmed experimentally. This tool might be used in designing and preparation of a number of in-needle devices having similar ability of liquid transportation.

Influence of the initial concentration of hydrogen and modes of vacuum annealing on the structure, phase composition, and mechanical properties of sheet billet of the VT6 alloy: Part 1. Influence of the initial hydrogen concentration and modes of vacuum annealing on the phase composition and the average diameter of grain of the VT6 alloy

The possibilities of using reversible hydrogen doping in combination with warm rolling for milling the structural components and the formation of a heterophase structure are shown by the example of the VT6 alloy. Alloy doping with 0.3–0.7 wt % hydrogen and the formation of a α + β + α2 structure is accompanied by the enhancement of the local nonuniformity of deformation and an increase in the number of recrystallization nuclei during warm sheet rolling. The relation between the initial hydrogen concentration and the temperature of vacuum annealing (VA) with the phase composition and the size of structural components is established.

Simulation Analysis of Static Recrystallization by Molecular Automaton

In this paper, people mainly take three two-dimensional arrays State, Energy and Ori (Ori is the positive integer of 1 ≤Ori≤Orimax ) to perform the molecular states and build models. According to the simulation results of molecular automaton, people have a research on the change and distribution of the grain diameter and the number of side during the process of static recrystallization, and conclude as follows, the relationship between the disappearing rate of individual deformation grain and the growth rate of individual recrystallization grain is characterized by randomness during the whole recrystallization process; the more the deformation, the smaller the mean diameter of grain is, at the finished moment of recrystallization; the grain diameters are not homogeneous during the static recrystallization process and at the finished moment of static recrystallization.

Grain Refinement in Al-Mg-Si Alloy TIG Welds Using Transverse Mechanical Arc Oscillation

Reduction in grain size in weld fusion zones (FZs) presents the advantages of increased resistance to solidification cracking and improvement in mechanical properties. Transverse mechanical arc oscillation was employed to obtain grain refinement in the weldment during tungsten inert gas welding of Al-Mg-Si alloy. Electron backscattered diffraction analysis was carried out on AA6061-AA4043 filler metal tungsten inert gas welds. Grain size, texture evolution, misorientation distribution, and aspect ratio of weld metal, PMZ, and BM have been observed at fixed arc oscillation amplitude and at three different frequencies levels. Arc oscillation showed grain size reduction and texture formation. Fine-grained arc oscillated welds exhibited better yield and ultimate tensile strengths and significant improvement in percent elongation. The obtained results were attributed to reduction in equivalent circular diameter of grains and increase in number of subgrain network structure of low angle grain boundaries.

Recrystallization in Ultra-Fine Grain Structures of AA3104 Alloy Processed by ECAP and HPT

The objective of this study was to determine the effect of deformation mode on recrystallization behavior of severely deformed material. Commercial purity AA3104 aluminum alloy was deformed via high pressure torsion and equal channel angular pressing to different strains and then annealed to obtain the state of partial recrystallization. The microstructure and the crystallographic texture were analysed using scanning and transmission electron microscopes equipped with orientation measurement facilities. The nucleation of new grains was observed in bulk recrystallized samples and during in-situ recrystallization in the transmission microscope. Irrespective of the applied deformation mode, a large non-deformable second phase particles strongly influenced strengthening of the matrix through deformation zones around them. It is known that relatively high stored energy stimulates the nucleation of new grains during the recrystalization. In most of the observed cases, the growth of recrystallized grains occurred by the coalescence of neighboring subcells. This process usually led to nearly homogeneous equiaxed grains of similar size. The diameter of grains in the vicinity of large second phase particles was only occasionally significantly larger than the average grain size. Large grains were most often observed in places far from the particles. TEM orientation mapping from highly deformed zones around particles showed that orientations of new grains were not random and only strictly defined groups of orientations were observed.

The Approaches for Estimation of Grain Size in Digital Steel Microscopic Image

The estimation of grain size is the important basis of metallographical analysis. The definitions of grain size, area, average area, chord, major axis, minor axis, diameter and average diameter are given in this article. A filling-and-elimination counting method is also introduced to count the number of grains in the digital steel microscopic image. The equations for calculating average area and diameter of grains are presented too. Finally, an algorithm for calculating grain’s average diameter is given. The experimental results show that the proposed approaches are efficient and practical.

Effects of rheo-squeeze casting parameters on microstructure and mechanical properties of AlCuMnTi alloy

Abstract The semisolid slurry of AlCu5MnTi alloy was prepared by indirect ultrasonic vibration (IUV), in which the horn was vibrated under the outside of the metallic cup containing alloy melt, then the slurry was formed by direct squeeze casting (SC). The effects of applied pressure, mould temperature and heat treatment on microstructure and mechanical properties of rheo-squeeze casting (RSC) AlCu5MnTi alloy were studied. The results show that with the increase of pressure, the average diameter of grain decreased continuously, while the average shape factor increased. With the increase of mould temperature, mechanical properties of RSC samples increased firstly and decreased afterward. When the pressure was 100 MPa and the mould temperature was 270 °C samples achieved the best mechanical properties after T5 heat treatment. The tensile strength and elongation were 326.5 MPa and 11% respectively, which were improved by 6.5% and 47% respectively compared with conventional squeeze casting samples.

Modeling and simulation of electrification of wind-blown-sand two-phase flow

The electrification of wind-blown sand, such as dust storms and dust devils, is known as the tribo-electric effect of sand particles and the stratification of different size particles. Combined with the grain electrification model, a new numerical method of gas-solid two-phase flow is developed for the simulation of wind-blown-sand two-phase flow, which is a hybrid method of computational fluid dynamics and discrete element method (CFD-DEM). In the developed wind-blown-sand two-phase flow of horizontal wind tunnel, the simulation results indicate that large size grains become positively charged while small size grains become negatively charged, and the critical diameter of grain with electric neutrality is about 300μm. The simulated charge-to-mass ratio and electric field intensity of the wind-blown sands in the field wind tunnel approach to the measured data, showing the rationality of this numerical method. The simulation also demonstrates that there occurs the maximum of electric field intensity over the sand bed of the field wind tunnel, which is the reason why the electric grounding of the field wind tunnel is used in experiment. The coupling of grain electrification model and gas-solid two-phase flow method provides an important tool for interpreting laboratory and field observations of wind-blown sands and insights into the physical dynamics of dust storms and dust devils as well.

Enhancement of luminescence properties of Eu3+:YVO4 in polymeric nanocomposites upon UV excitation

Abstract Highly emissive Eu 3+ :YVO 4 nanocrystals were successfully prepared by the hydrothermal method. The average diameter of grains was determined to be 15 nm. Transparent polymer nanocomposites composed of PMMA and well dispersed Eu 3+ :YVO 4 nanocrystals were fabricated by in situ polymerization. The nanocrystalline powders and nanocomposites were characterized by scanning and transmission electron microscopy (TEM) and X-ray diffraction (XRD). The luminescence properties of the obtained nanocomposites were investigated and compared with the starting powders and Eu 3+ :YVO 4 single crystal. The effect of the polymeric host on the luminescence properties of Eu 3+ :YVO 4 is presented and discussed.

Preparation and Characterization of Ce-Doped Ba<sub>0.2</sub>Sr<sub>0.8</sub>TiO<sub>3</sub> Ferroelectric Ceramics

The structure and property of Ce-doped Ba0.2Sr0.8TiO3 (BST) were investigated as a function of Ce content. The density experiment results confirmed that increasing the Ce doping ratio caused the decrease in shrinkage factor of BST in the sintering procedure. Additionally, both Scanning Electron Microscope (SEM) and X-ray diffraction (XRD) analysis showed that the grain size of Ce-doped BST was dependent on the Ce content. Further more, the dielectric constant and dielectric loss had a curve relationship with increasing Ce content. The improvement of the electrical properties of Ce doping BST may be related to the decrease in the concentration of oxygen vacancies. According to the research, the diameter of grain, the dielectric constant and loss factor of the 1mol% Ce-doped Ba0.2Sr0.8TiO3 were 500nm, 365.8 and 0.0063, respectively.

Microstructural Evolution of 7A04 Alloy Prepared by FE-ECAE in Semi-Solid State

In the paper, forward extrusion-equal channel angular extrusion (FE-ECAE), which is new strain-induced melt activation (SIMA) method, is introduced in making semi-solid billet of 7A04 alloy. The principle of the method is that by using FE-ECAE as strain induced step and semi-solid isothermal treatment as melt activation step. The results show that semi-solid billet with highly spheroidal and homogeneous refined grains can be prepared by FE-ECAE method. The equivalent strain in FE-ECAE before reheating has a great influence on its microstructural evolution. Grain size decreases and its shape also approaches to sphericity with increasing equivalent strain. The main mechanism of the initial semi-solid grains coarsening was coalescence. With the prolongation of isothermal holding time, the grains grew up and spheroidized, in which the mean diameter of grain and liquid volume fraction increased. In the meantime, the higher the reheating temperature, the faster the grain grew and spheroidized. Subsequently, the main mechanism of grains coarsening was Ostwald ripening. The suitable reheating temperature of 7A04 alloy was 610°C.

Silicon wafer surface patterning using femtosecond laser irradiation below ablation threshold

Abstract Surface patterning using femtosecond laser can be utilized for the fabrication of MEMS/NEMS, CMOS, 3D-microstructures, microtrenches, microchannels, microholes, periodical submicron gratings and nanophotonics. A unique high repetition rate femtosecond fiber laser system was used to study the effect of pulse width, repetition rate and pulse energy on the spacing of ripples as well as diameter of grains created during the surface patterning operations. Also, this report strides to identify the mechanisms that lead to ripple and grain formation at different pulse durations. In our experiments, the ripples formed at a lower laser fluence range 1.56–4.66 J/cm 2 , whereas the grains were created at a higher laser fluence range 3.34–6.77 J/cm 2 . The primary theory we used to explain the creation of ripples in the femtosecond regime was the Boson Condensation Hypothesis since mechanical and thermal forces are deemed to be negligible. For the picosecond pulse width range, the ripple formation can be based on any or a combination of the acoustic wave, surface tension gradient and interference between the incident light/surface wave mechanisms. The grain formation both in the femtosecond, as well as the picosecond span used in our experiments is due to the bond weakening and breaking in the silicon substrate and the short duration of the crystal lattice rearrangement following illumination by the laser. The small movements lead to the creation of new bonds between the atoms and eventual formation of grains. It was seen that for our pulse width, repetition rate and pulse energy range, the ripple spacing increased with laser pulse duration, while other parameters did not play an important role. In terms of grain diameter a similar trend was seen.

Investigations of Solidification Structures of High Carbon Alloy Cast Steel Containing RE-V-Ti

The solidification microstructural characteristics of rare earth (RE) and vanadium and titanium-treated high carbon alloy cast steel, whose chemical compositions are 0.90 wt.% C, 3.0 wt.% Si, and 1.0 wt.% Mn, were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), electron probe microanalyzer (EPMA), and energy dispersive X-ray spectrometry (EDS). The alloys were prepared in an induction furnace. The results showed that compound additions of RE-V-Ti could obviously refine the solidification structures and decrease the diameter of grains. The average grain diameter of untreated high carbon alloy cast steel was 80 μm. The average grain diameter of high carbon alloy cast steel containing RE-V-Ti decreased to 40 μm. Finally, the reasons that RE-V-Ti refined the solidification structure were analyzed in detail.

Evolução microestrutural da cerâmica KSr2Nb5O15 dopada com CuO:B2O3

A evolução microestrutural da cerâmica KSr2Nb5O15 dopada com CuO:B2O3 foi investigada. Os materiais cerâmicos foram sinterizados em duas etapas: aquecimento até 550 °C por 3 h e, em seguida, aquecimento até 1200 °C por 5 h. A microestrutura das cerâmicas foi investigada por microscopia eletrônica de varredura (MEV). As micrografias da cerâmica, na ausência de dopantes, revelaram uma microestrutura porosa constituída de grãos pequenos com diâmetro médio 1,09 μm e grãos maiores com diâmetro médio 2,33 μm, enquanto os sistemas cerâmicos dopados com CuO:B2O3 apresentaram uma microestrutura com grãos maiores, que estão circundados por grãos menores de formas irregulares. O sistema cerâmico dopado com 0,5% CuO + 0,5% B2O3 apresenta evidências de formação de fase secundária segregada nos contornos de grão. Contudo, em função do aumento do teor de óxido de boro, não é mais perceptível fase secundária nas micrografias. Defeitos de contorno do tipo maclas são também evidenciados nas micrografias dos sistemas dopados com CuO:B2O3. A distribuição de tamanho de grãos também foi avaliada, apresentando uma distribuição do tipo bimodal. Os valores médios de diâmetros de grão foram obtidos a partir das micrografias e, com esses dados foram construídos os histogramas da distribuição de tamanho de grãos em função da freqüência. A análise de distribuição de tamanho de grão mostrou um aumento no tamanho médio dos grãos em função dos dopantes e uma distribuição mais uniforme em relação às demais composições para a cerâmica KSr2N b5O15 dopada com 0,5% CuO + 2,0% B2O3.

Grain size correlation with the geometry of fracture surface profiles in polycrystalline iron by a continuous wavelet transformation method

A quantitative relationship is examined in this paper between the mean diameter of grains in iron of technical purity and the distance between the local maxima on the profiles Z( x) of the fracture surfaces obtained as results of Charpy impact tests at liquid nitrogen temperature. To this end, the profiles were digitized and analyzed with a Continuous Wavelet Transformation (CWT). Such a transformation assigns to each profile the scale and shift parameters C ( a, b), which are further used to measure the distance between the local maxima. The distance between local maxima has been determined for each profile and its average value calculated. The grain size of the iron was controlled by cold deformation and recrystallization for different times and temperatures. The cryo-impact tests were performed on samples with two types of notch: (a) typical of a Charpy Test and (b) obtained as fatigue pre-crack tips. The results of the investigation reveal a strongly non-linear relationship between the average size of grains and the distance between the local maxima on the fracture surface profiles. This finding is discussed in terms of crack interactions with the grain boundaries.

A Hybrid Optimization Approach for SRM FINOCYL Grain Design

This article presents a method to design and optimize 3D FINOCYL grain (FCG) configuration for solid rocket motors (SRMs). The design process of FCG configuration involves mathematical modeling of the geometry and parametric evaluation of various independent geometric variables that define the complex configuration. Virtually infinite combinations of these variables will satisfy the requirements of mass of propellant, thrust, and burning time in addition to satisfying basic needs for volumetric loading fraction and web fraction. In order to ensure the acquisition of the best possible design to be acquired, a sound approach of design and optimization is essentially demanded. To meet this need, a method is introduced to acquire the finest possible performance. A series of computations are carried out to formulate the grain geometry in terms of various combinations of key shapes inclusive of ellipsoid, cone, cylinder, sphere, torus, and inclined plane. A hybrid optimization (HO) technique is established by associating genetic algorithm (GA) for global solution convergence with sequential quadratic programming (SQP) for further local convergence of the solution, thus achieving the final optimal design. A comparison of the optimal design results derived from SQP, GA, and HO algorithms is presented. By using HO technique, the parameter of propellant mass is optimized to the minimum value with the required level of thrust staying within the constrained burning time, nozzle and propellant parameters, and a fixed length and outer diameter of grain.

Properties of sol–gel prepared BaCeO3 solid electrolyte using acetate precursors

A sol–gel route was used to prepare Yb-doped BaCeO3 at the relatively low temperature of 1,100 °C. At this calcination temperature, the carbonate residues were completely decomposed and the high crystallinity of Yb-doped BaCeO3 powders with orthorhombic structure was obtained. The loose particles in nanosized range was observed from scanning electron micrographs but agglomerates with size ranging from 200 to 500 nm seem to dominate the bulk powder. Density of the pellet sintered at 1,400 °C for 24 h was about 95% of the theoretical density. Morphology of the fractured pellet revealed that the diameter of grains was between 1 and 3 μm. AC electrical conductivity of the sample in wet air was carried out using impedance spectroscopy in the range of 1 Hz to 10 MHz. At 300 °C, it was found that at high frequencies the imaginary values of the impedance were positive. The effect was attributed to the presence of an inductive element in the experimental setup.

Effect of Tungsten Addition on Properties of Ni-Based Alloy Sheet Prepared by EB-PVD

Large scale Ni-based alloy sheets are prepared by electron beam physical vapor deposition with and without tungsten added into melting pools respectively. Addition W increased vapor rate and decreased compositional transformation during deposition. Chemical constitution of the sheet prepared through tungsten is more similar to that of the ingot. Microstructure of two alloy sheets is observed by scanning electron microscope (SEM) and atom force microscope (AFM). The results show that both of the sheets consist of columnar grains, whose major axes are almost parallel to the normal direction of the sheet. However, the average diameter of grains of the sheet through tungsten is larger than that of the sheet not through tungsten in minor axis direction. Mechanical properties and failure mechanisms of both sheets are studied. Tensile tests are conducted on a number of specimens. Strength, strain-to-failure are estimated under loading condition. The results show that the sheet prepared by EB-PVD through tungsten has a superior strength and an elongation percentage than that of the one prepared without tungsten.

Metastable effects on martensitic transformation in SMA

The efficiency of shape memory alloy (SMA) as damper and/or standard actuator is truly enhanced when the material can be cycled without any relevant accumulation of the permanent deformation (i.e. under 0.5% for several hundreds of cycles). The particular properties of the CuAlBe alloy permit relevant grain growth with reasonable reduction of mechanical properties (from 300-350 to 250-300 MPa at fracture). Samples prepared with an appropriate heat thermal treatment (HIT) and relevant mean diameter of grain avoids accumulative deformation for series of cycles (near 500) up to 3.5% of deformation. The analysis of different wires of CuAlBe alloy shows, in the first part of HIT, a proportionality between the grain surface and the time at 1123 K. In the last part of the HTT the grain growth shows an increased complexity related with interactions between the grain boundaries and the external surface of the samples.