Search results

When evaluating the effect of a grain size, a very good agreement of the MTT results was noted for all evaluated parameters for tensile samples with a grain size up to 100 µm.
This is remarkable with respect to the generally presented results which clarify minimum number of grains within the cross-sectional area of the MTT specimen.
Furthermore, the results suggest that the MTT technique might be applicable on materials with considerably coarser grains than predicted, about 10 grains within the cross-sectional area [1, 2].
Fig. 5 shows a comparison of the tensile test results for different grain sizes.
Fig. 5 The comparison of the tensile test results for different grain sizes.

C denotes the concentration (number density) of diffusing particles, x their position.
(3) C denotes the number density (concentration) of diffusing particles and x the position.
Usually in diffusion processes the number of diffusing particles is conserved.
It consists of an equal number of vacancies and lattice atoms or ions in interstitial sites of the host crystal.
These meetings focussed mainly on thermodynamics of grain-boundary properties, grain-boundary diffusion of solutes, and segregation of solutes into grain-boundaries.

A low-cost process for removing boron from metallurgical grade silicon was developed by Si-Al alloying, and the separation procedure of silicon grains from Si-Al melt by solidification was investigated in this paper.
In general, the metals used in alloying should meet the followings: (1)Easy access and safe operation; (2) To dissolve a sufficient number of solutes and yield useful measurements of the crystal; (3) At the growth temperature, in order to prevent unnecessary losses solvent, the vapor pressure should be low and exclude the danger of high-pressure; (4) The container materials should be chemical stability; (5) Easy to separate crystals and alloys .Purification of metallurgical grade silicon using Al as the solvent, it is not only to meet the above conditions, but also carry out the process at low temperatures with less energy consumption.
Figure 3 showed a dense and smooth surface of silicon with a small amount of aluminum impurity; Figure 4 indicated the lower Si-Al alloys’ surface has a structure of roughness, bumps and holes, containing a large number of Ti , K, Fe impurities and other substances[7].
The specific areas increased as the grain sizes decreased.
Table.1 Samples purified by different kinds of acid Sample Solution HCl and H2SO4 mixed solution HF solution 441#MG-Si 2 3 Alloying 4 5 Fig.5 The content of B in different samples Conclusions 1) Experiments showed that as the separation of Si grains from Si-Al melt during the solidification refining, the gravity force was found to be effective to obtain the Si with high purity. 2) Compared with leaching, the content of boron in silicon purified by alloying decreased from 128.00 ppmw to 27.62 ppmw, which indicated that this method was more effective than HF leaching to the removal of boron. 3) The content of B in silicon powder firstly treated by the purification of Si-Al alloying and then leached by low concentration of HF decreased to 13.81 ppmw ,with a removal ratio of 89.21%, which revealed the combination of the two processes was practical to remove impurities B from metallurgical grade silicon. 4) Acknowledge This work is supported by National

The average grain size of the casting strips was about 46 micron meters.
The average grain size was obtained by a Jeffries method.
The measurement region is circular and the number of grains in the region is set to 50 or more.
Table 2 shows the average grain size of the TRC strips.
The average grain size of the TRC strips is about 46 μm, and the grains are refined to about one-fifth as compared with that of normal cast material which is 200 μm.

For ferroelectric ceramics the dependence of dielectric response on the grain size was first observed already in 1954 [1].
The increase of the dielectric constant in fine-grained ferroelectric ceramics below the Curie temperature has been attributed to an increase in residual internal stress in submicron grains [2] or to the enhanced domain wall contribution [3].
The apparent dependence of the Curie temperature on the grain size was explained by various models e.g.
We assume, that our lattice is 3D and have an equal number of dipoles in all directions, say the lattice is cubic.
Each dipole interact with all nearest neighbors i.e. dipoles at the boundaries of lattice interact with reduced number of neighbors.

Two sets of sputtering parameters were employed in our experiments[10]: (1) Using table 1 (A) group of the experimental parameters, four pieces samples were prepared, the number of samples was a (0min), b (30min), c (60min) and d (90min), respectively
(2) On the basis of step one, using table 1 (B) group of the experimental parameters, four pieces of ZnO/AlN thin films were prepared, the number of samples was still a, b, c and d, respectively.
Thus, we can further found from the AFM images, the grains and the crystallites sizes of ZnO thin films are vary in the same trend when the AlN buffer layers sputtering time is 60 min and 90 min, respectively.
(1) (In the formula, D is the grain size, λ is the wavelength of X-rays, Δθ is the FWHM, θ is the diffraction peak corresponding to the diffraction angle) it is clearly seen that the smaller FWHM means the larger grain size and the better crystal quality of the whole films.This suggests that the ZnO thin films deposited on AlN buffer layer possess better overall crystallinity resulting from reduction of strain and defects and improvement in crystallite size with increasing of sputtering time.
It is shown that, with a buffer layer, due to AlN and ZnO possess the smaller lattice mismatch degree and similar thermal expansion coefficient, so the ZnO thin films possess larger grain size, and increases the crystallinity as well as due to the increase of crystallite size, and the electrical resistivity were reduced.

With the same amount of machine and the milling depth,three factors caninfluence the speed of consumption of heads consumption: grinding grain (mesh), feeding speed (m/min) and spindle speed (r/min), which in turn written for A, B and C[3].
Table 2:Three levels table Column number Level Experiment A 1 B 2 C 3 1 1 1 1 2 1 2 2 3 1 3 3 4 2 1 2 5 2 2 3 6 2 3 1 7 3 1 3 8 3 2 1 9 3 3 2 The method of Sure grinding head consumption level . there are two ways to inspect the grinding head consumption level of methods .The first one is through the observation in the processing of the grinding head ball head surface and listen to grinding head grinding abnormal sound, through the experience to judge wear.The second way is to suspend processing and take down grinding head; then we can clearly check up the surface of the grinding head by optical image measuring instrument.
Through the orthogonal experimental data analysis we can get the optimal scheme is A2B2C1, namely the grinding grain is 650 mesh, the feeding speed at 0.6 m to/min and spindle speed at 30000 r/min.
So the eventual optimal scheme; the grinding grain is 650 mesh, the feeding speed is 0.1 m /min and spindle speed is 30000 r/min.the fig.4 is showed an under processing of parts.
Convex platform processing choose grinding grain of 650 mesh, the feeding speed of 0.1 m in/min and the numerical control lathe spindle speed for 30000 r/min.By using this parameter combination completed the grinding, the surface quality meet the requirements and processing efficiency is high.

The chains of small grains of 0.35-0.55 μm size were recorded on the surface.
Microsection study of the surface near the cutting edge showed the following (Fig. 2): – near the boundary of the section (at a depth of 1.5-2.0 μm), carbide grain sizes are less than 0.5 μm (Fig. 2, a); – at a depth of more than 9.0 μm carbide grain sizes vary slightly in comparison with the size of carbide grains in the core and have dimensions of the order of 1.0-1.5 μm (Fig. 2, a); – tool core has a grain structure with inclusions in the nodes and on the carbide phase grain boundary with carbide sizes, on average, of 1.0-2.5 μm (Fig. 2, a).
At the same time, the number of nanoparticlesis markedly reduced outside the layer.
The surface fragment with clearly visible nanosized and larger particles separated from the carbide grain serves the evidence of carbides dissolving under the influence of the low-temperature plasma.
Moreover, only the partition of carbide grains into smaller ones can explain the appearance on the tool surface of the 0.35-0.55 μm grain size chains.

Besides, doping of a trace of rare-earth ion can help promoting the growth rate of ferrite material crystal grain.
According to the content of Nd3+ ion, the samples are numbered as B0, B1, B2, B3, B4.
Under the pressure of 130Mpa, press the grains into annuluses with 7mm outside diameters and 3mm inside diameters.
As doping of Nd3+ ion, grains largened gradually in the width direction, the length-width ratio decreased, the grains grew, the porosity decreased, the grains became more dense.
Since magnetic moment of Nd3+ ion (3.4μB) is also smaller than that of Fe3+ ion (5.0μB), it should have lead to decline of initial permeability, while as Nd3+ ion promoting the growth of grains in the progress of sintering, average dimension of the grains increased, the porosity decreased, the grains became more dense.

They are identified as Y2Ti2O7 and TiO2 precipitates but have a very small number density.
Thus, we could estimate a total number density of 2. 1023 m-3 and a volume fraction of 0.7 % NCs.
Grains have an average anisotropy factor or grain aspect ratio of 3 but the geometrical elongation during hot extrusion in our conditions is of about 14.
The observed features are in fact sub-grains inside of more elongated grains.
During hot extrusion, dislocations rearranged into sub-grains boundaries and tend to create sub-grains more equiaxed.