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The hydrogen atmosphere has a role of forming a high number density of C+ ions.
The grain sizes of NCD and UNCD have been quoted as less than 100 nm and 2-15 nm, respectively [1].
This implies that the number of the species decreases at the front-area of the plume and the collisions do not actively occur.
The situation with high number densities might be important rather than the kinetic energies.
The hydrogen atmosphere has a role of forming a high number density of C+ ions.

From Fig.1, the microstructure is composed of white α-Al phase and black eutectic silicon phase located grain boundary.
When solution temperature iss 515℃ as shown Fig.1(a), α grain is coarse, silicon particles segregate to grain boundaries and keep irregular shape.
Meanwhile, eutectic silicon particles change to spheroidal morphology and distributes uniformly grain boundary.
From Fig.1(c), when the solution temperature is up to 555℃, eutectic re-melting ball and triangle grain boundaries appears.
The size, number and speed of growth of the precipitation phase are also different, which exhibit different strengthening effect [11].

The increase of disposition rate would lead to the improvement of crystallinity and the increase of grain size, as shown in Figure 1(a) and 1(b).
The larger crystallite size results in lower grain boundaries for carrier transport.
As the substrate-to-target distance decreases to 7 cm, the deposition rate becomes faster, because the number of atoms is sputtered from the target and gets a higher energy that contributes to film growth.
However, when the deposition rate is too fast, there is no enough time to form good crystallinity and compact AZO films causing to the decrease of grain size, as shown in Figure 1(c).
(b) No. 5, Grain size 23.25 nm (c) No. 6, Grain size 21.47 nm (a) No. 4, Grain size 18.72 nm Fig. 1.

The unique compacting mechanism of the HCP leads a number of characteristics such as a higher compacting speed, wide applicability for net shape formation, flawless microstructure of the green compacts [4], etc.
Mean grain size was measured by linear intercept method.
The measured grain size on cross sectional plane was multiplied by 1.5 to estimate 3-dimensional grain size.
For mian grain size, Vickers hardness was measured from Vickers indentation with a load of 98 N.
Higher green density improves not only densification performance but also reduces concurrent grain growth during sintering.

A number of stress strain relationships can be found for steel, aluminum and magnesium alloy, but there is a lack of understanding of the underlying constitutive equation for AZ80 magnesium, especially at high temperatures and high strain rates.
At intermediate temperature of 350℃ and strain rate of 10s-1, a mix of fine and coarse grain structure forms a “necklace” of recrystallized grains along the original boundaries at the initial stage of deformation (see Fig. 2(a)).
As shown in Fig. 2(b), more and more coarse primary grains are replaced by the new fine grains with the progress of deformation.
The average grain size is less than 5μm.
Other compressed samples at temperature of 400℃ and 450℃ have similar grain structure features with Fig.2.

It could be seen that the grain size was about 2~6 µm and there were few pores in the samples.
For undoped samples sintered at 1190°C, there were many columnar grains and the length-width ratio was about 3:1, and, a little of glass phase was found in the triple area of grains [Fig.5 (a)].
Compared with undoped ZnNb2O6 samples, the numbers of pores were fewer, and the grains were more homogeneous and finer for ZnNb2O6 samples doped with MnCO3 of 0.25 wt% [Fig.5 (b)] and 0.5 wt% [Fig.5 (c)] and sintered at 1150 ℃.
Though the size of grains was almost the same for the samples with MnCO3 of 0.75 wt% [Fig.5 (d)] and 1 wt% [Fig.5 (e)], the distribution of grains became even more homogeneous.
This may be due to that the growth of grains was inhibited by MnCO3.

Cementite dissolution is accompanied by nanoscale ferrite grain refinement [3-6].
The true deformation γ can be estimated by means of the equation: γ = 2πRN/d (1) where R is the distance from the sample centre, N is the number of the anvil rotations, and d is the thickness of the sample.
The mean size of the grains is 10 nm.
Within this range the microstructure of ferrite corresponds to grains with size in the range 20 - 150 nm, separated by disordered grain boundaries or dislocation walls.
Fecht: in Ultrafine Grained Materials II.

The high-angle grain boundaries (HAGBs) were characterized as boundaries with misorientation angle θ≥15° and low-angle grain boundaries as boundaries with θ<15°.
Microstructure situated in the intrados of bend contained finer grains in comparison with extrados and straight part of pipe (Tab. 1).
Measurement of microtexture showed that extrados and straight parts of pipe contain higher number of grains having directions <110> oriented nearly parallel with pipe axis than intrados of bend (Tab. 2).
Sklenička, Effect of grain refinement by ECAP on creep of pure Cu, Mater.
Zhu, Microstructures and mechanical properties of ultrafine grained 7075Al alloy processed by ECAP and their evolutions during annealing, Acta Mater. 52 (2004) 4589-4599 [13] J.K.Kim, H.G.Jeong, S.I.

Fig. 4a shows the microstructure of fusion zone (FZ) is basket-weave structure which consists of coarse β grains and a large number of acicular α.
The smaller the distance to the centerline is, the lower subcooled temperature is, the bigger the β grains are.
Cooling to a certain temperature under the transformation point, acicular α nucleates at the β grain boundary and develops into the grain.
However, it can be seen in Fig. 5a and Fig.5b that the β grains boundary in FZ and HAZ is not obvious.
This is because plastic deformation taking place in part of the grains cause the release of the residual stress in the process of heat preservation.

Such material is usually obtained through spraying aluminum melt which is followed by grain-size screening.
At the same time the grains are shredded into smaller flocculent plates.
Hiding power of pigment shows more than the simple grain-size measurement, the shape image analysis, and also the specific surface area measurement.
Probably it is a case of relation between grinding energy and volume of the processed grains known as Kick’s "volume" theory.
We read this phenomenon as a result of inhomogeneity of ground stocks in taking the samples and, on the other hand, due to the mentioned small number of experiments.