Search results

In the case of Ti addition the Ti (grain size 1–3 µm, MaTecK, 99% purity) was added in the amount of 10 wt. %.
The density of the MgBx inclusions is higher around big Ti grains than in the MgB2 matrix (Figs. 2e and 2f).
The layer of Mg-B-O with somewhat smaller amount of oxygen (Nos 1, 2) then in inclusions (Nos. 5, 6) are well observed near to the grain boundary between the grain contained Ti.
Because of this Mg and O diffuse deeper to the Ti grain then B (Fig. 2 e-g).
Nanostructural inhomogeneities acting as pinning centers in bulk MgB2 with low and enhanced grain connectivity, Supercond.

It was shown that better density, vickers micro hardness and corrosion resistance were achieved due to refinement of grain size.
Fig. 1(b) and (c) exhibits that equilibrium η (MgZn2) precipitates along the grain and grain boundaries are very fine as compared to Fig. 1 (a).
These micrographs clearly shows that the pits are individual are shown in Fig.3 (b) and (c), due to refinement of grain size.
(a) micrograph shows that the number of pits is more and pits size large.
The hardness of matrix and composites increased with increasing milling time due to refinement of grain size.

This is mainly because grain boundary structure plays a role in increasing PFZ and expanding corrosion channels.
This is due to the dual effects of grain boundary structure and grain morphology.
The 525℃ solid-soluble treatment of the specimen, the coarse residue phase is reduced, and the crystal grain is further grown.
On the one hand, with the solution treatment temperature, the precipitated crystal and the grain boundary phase increases, increasing consumption of solute atoms at grain boundaries, so that the width of PFZ slightly increased, and thus the corrosion expansion channel, Al-Cu-Mg-Ag alloy corrosion resistance decrease.
On the other hand, the alloy grain morphology also affect the corrosion resistance, with the solution temperature, recrystallized grains is increased, reducing the grain boundaries, while such micro cell corrosion at the grain boundaries is reduced, corrosion products per unit area need to join the smaller force is formed, thereby improving the corrosion resistance of the alloy.

There are very limited numbers of multiferroic materials in this world.
Single phase of BFO compounds have been fabricated by using a number of techniques such as co-precipitation method, sol-gel method, hydrothermal method and combustion method [4-7].
The average grain sizes of pure BFO samples are significantly higher than Sm-doped samples.
The average grain sizes of BFO and BSFO are 2.61 µm and 1.18 µm respectively.
Sm-doping of BFO inhibits the grain growth and leads to the smaller grain size.

Applications Fine Grain Materials.
Under the intense shearing, the initial grains are subdivided.
This increases the number of solutions which fit to the pattern of detected lines and decreases the reliability of the indexing and - ultimately - of the determined orientation [13].
Moreover, large number of diffracting planes leads to intricate patters.
With foil thickness similar to or larger than the grain/cell size, there are multiple grains/cells on the beam path through the specimen.

Thermal and XPS analyses on the exchanged powders proved that a part of cadmium was quickly adsorbed at the grains surface in the form of hydrated complexes [Cd(OH2)n] 2+ .
Adsorption reaction was mainly limited by the number of specific sites available on the grains surface.
Amount of cadmium (a, b) adsorbed at the grains surface and (c, d) incorporated into the solid solution, versus the surface area (SBET) or the bath temperature (Tbath).
This reaction is mainly limited by the number of these specific sites [2].
A diffusion of Cd would form grains of homogeneous composition, or with a gradient of composition from the surface to the heart.

It is shown that the as-prepared ADM samples are disperse monocrystals with well grain distribution and geometric shape, which can well meet the quality requirements for the subsequent production of molybdenum powders.
In order to control the number of ADM homogeneous nucleation during the nucleating and growing course, proper volume of aqueous ammonia (15 wt.%) should be continually added so as to ensure suitable crystal growing environment.
The collected filter cake was dried at 130˚C for 2 hours, and the clear crystals with even-distributed grains were achieved.
In fingerprint region from 470cm-1 to 1000cm-1 several characteristic peaks related to isopolymolybdate Mo2O72 -, such as 884 cm-1, 682 cm-1 and 476 cm-1 low wave number peaks, simultaneously arise, although they are not strong.
Through scientifically regulating and controling the number of secondary nucleation of ADM and keeping suitable pH value for the growth of fine grain, the ultrafine crystals can be dissolved and the overgrowing of normal crystal grains can be restrained so as to ensure the uniform distribution and non-reunion of as-prepared ADM crystals

Lange [3,4] demonstrated the aspect ratio of β-Si3N4 grains increased with the content of α-Si3N4 in the raw material powder and that the fracture toughness of polycrystalline Si3N4 ceramics increased with the size of elongated grains.
The resultant rod-like β-Si3N4 grains morphology is affected by the property of additives.
These samples exhibited different configuration of rod-like grains.
The β-Si3N4 particles existed in the initial powder can serve as nuclei for β-Si3N4 grain growth, so that the resultant size of the β-Si3N4 seeds was governed by the number of β-Si3N4 nuclei.
The heterogeneous nucleation was preferred for the uniform grain growth, while, α- to β- phase transformation was a main factor for formation of the rod-like β-Si3N4 grain.

α-SiAlONs are well established compounds with the general formula MxSi12-(m+n)Alm+nOnN16-n, where M is one of the cations Li, Mg, Ca, Y and most rare earths (excluding La, Ce, Pr and Eu), m is the number of Si-N bonds in α-Si3N4 replaced by Al-N; n is the number of Si-N bonds in α-Si3N4 replaced by Al-O; and x is equal to m divided by the valency of the M cation [2].
Elongated α-SiAlON grain morphology was observed in samples containing Sm cation (Fig. 1).
Representative BE images of (a) YE, (b) SmY and (c) 100Sm samples after sintering at 1800°C With the addition of Sm2O3 in the composition, anisotropic grain growth took place and grains became elongated (Figs. 1 b-c).
The α-SiAlON grains in SmY sample have elongated grains with low aspect ratio, but equiaxed α-SiAlON grains are also present.
In this sample, although pre-sintering treatment reduced the amounts of large grains compared sample in Fig. 1a, presence of elongated αSiAlON grains was not significant after the subsequent sintering step due to the low amount of transient liquid phase.

The picture of normalization sample shows coarse equiaxed grains, and the grain shape is irregular.
The average grain size is 470µm.
The laser surface remelting sample shows small dendrites grains, its grain size is 330µm, smaller than that of normalization sample.
The average grain size of the melt spinning sample is 7 µm, and the microstructure is well-proportioned equiaxed grain.
On the other hand, according to Hall-Petch relationship, the plasticity and toughness will be improved with the increase of grain number[11].