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(i) The film thickness and deposition temperature are the main factors, controlling grain size of metal oxide films [10].
Influence of film thickness on grain size of SnO2 films deposited by spray pyrolysis: (a) grain size determined by x-ray diffraction (XRD); (b) grain size determined by SEM: 1, Tpyr = 350–375°C; 2, Tpyr = 450–475°C; 3, Tpyr = 510–535°C; (c, d) SEM cross-section images of spay pyrolyzed SnO2 films: (c) Tpyr = 330–350°C, d ≈ 70–80 nm; (d) Tpyr = 510°C, d ≈ 75–100 nm. [8].
Films deposited at low temperatures (Tpyr< 400 oC) are grained ones (Fig. 3c).
In both ceramics and thick film sensors the grain size does not depend on the thickness.
(a) Typical SEM images of agglomerated SnO2 films deposited at low temperatures, and (b) schematic illustration of agglomerated films: Ra, Rb and Rc are resistances of inter-agglomerate contacts, bulk of grains and inter-grain contacts, correspondingly.

Although the content of Nb and Ti is very low, they play an important role in inhibiting the growth of austenite grains, forming carbon-nitrogen compounds and refining the grains, the toughness is improved by precipitation strengthening and fine grain strengthening.
Titanium is a strong n-fixing element, fine TiN particles can effectively prevent the growth of austenite grain in the heating process.
The first rolling stage is completed in austentite recrystallization zone, and original austenite grains are completely broken and recrystallized to refine the grain and reduce the defects plate.
After quenching and tempering, the lath martensite with high dislocation density is decomposed, equiaxed grains with low dislocation density and good strength and toughness are transformed to form tempered sorbite structure composed of fine grained cementite and equiaxed ferrite.
Off-line quenching and tempering can reduce the size and dislocation density of M-A island, decrease the size and number of M-A component, and decrease the dislocation density [7,8].

All samples showed random grain size and orientation, with partial melting and high porosity.
The Tl-based high-temperature superconductor is an interesting family because it can form many phases with different number of CuO or TlO layers.
The SEM micrograph of the samples showed randomly oriented grains, evidence of partial melting and high porosity.
Acknowledgements We thank Universiti Kebangsaan Malaysia for supporting this work under grant number GP-K005338 and MOHE, Malaysia for the grant number FRGS/2/2013/SG02/UKM/01/1.
Phys. 105(7) (2009) Article Number 07E311

However, phase purity is influenced by the amount and type of the transition metals doped and with the addition of transition metals both bulk and grain boundary conductivities are increased.
Introduction Oxygen ion conducting materials are getting its popularity because of its number of applications in various field like, solid oxide fuel cells (SOFC), oxygen sensors, oxygen separation membranes, membrane reactors, etc [1, 2].
SEM micrographs as given in Fig.3, show the dense structure of the sample with grain sizes from 1-5mm.
Since grain and grain boundary behavior are differed with the applied frequency, their responses are also separated from the fitted equivalent circuit.
With the doping of transition metals both bulk and grain boundary conductivities are increased and the overall conductivity of LSGMC is found to be higher than the LSGM.

In the strengthened layer by LSP, because of laser fast strengthening, the original morphologies of temper troostite had been disappeared, a little carbide are distributed in fine grain martensite, the amount of carbide decrease obviously, it shown that most of carbide are dissolved into austenite to form martensite by fast cooling.
Seen from Fig.3, a severe plastic deformation was produced by laser shock processing, a large number of dislocation, the proliferation of dislocation and the interaction between dislocations is very obvious, and very difficult to dislocation movement, which improves the performances for the hardness.
Fig.5 Eeffects of residual stress on cracks (a) Tensile stress; (b) Compressive stress The micro-structures of 304 stainless steel by LSP are fine equiaxed grains; its dimension is small and uniform.
During crack initiation, driving force of hydrogen-induced crack is bore by fine grains, the difference of intragranular strain and grain boundary strain is smaller, and cracks are not produced (a) (b) easily.
During crack expansion, because volume score of grain boundary is high, adjacent grains have different tropisms, when tiny micro-cracks across its grain boundaries into other grain, tiny cracks is held in grain boundary, at the same time, once tiny cracks across grain boundary, expansion direction occurs change, more energies are depleted inevitably, tiny cracks can't grow up easily, therefore stress corrosion of 304 stainless steel by LSP have been improved greatly.

., breakage of the body of grains first into somewhat off-oriented cells and then into fragments.
It is seen that with an increase in strain degree there is grain extension and new grain formation, both-high-angle and low-angle, which points to formation of a developed substructure.
It is seen that the majority of grain boundaries have large-angle misorientation.
Fine recrystallized grains have equiaxed morphology.
Presence of a large number of twins within recrystallized grains (Fig. 4e ) is observed.

Although numerous alloys have been processed with L-PBF, only a limited number are commercially available and able to tolerate the special requirements of the L-PBF process [4]. 
After etching with Dix-Keller (10 s) and then W-Al (10 s) and using high magnification was found that the dark zones contain a very fine grains (FG) and light areas are coarse grains (CG) of the α-Al phase, Fig. 2b.
In the fine grains regions, Figs. 3d and 3e, the size of fine grains is approximately two microns.
The distribution of La and Ti fine particles is similar as for coarse grains.
The microstructure after T6 heat treatment is characterized by a mixture of fine equiaxed grains regions and coarse grains regions

Grain boundary strengthening also contributes to enhancing creep resistance.
Typically, carbon is added to form discrete grain boundary carbides that thwart grain boundary creep.
Fig. 4: Predicted Rayleigh number (at fs=0.5) for different size ESR ingots.
Using the temperature distribution, the Rayleigh number, which is the ratio of driving force to resistance to interdendritic flow can be calculated.
While refining grain size in cast/wrought products is challenging, the grain size in some powder products may be too fine and may need to be coarsened to achieve the creep resistance needed.

The free water is responsible for the movement of the grains, thus being the main generator of fluidity.
The improvement in fluidity favors the arrangement of the grains and their packaging in the mortar, reducing voids and contributing to the increase in mortar density. [15] observed a decrease in mass density in composites with a dry consistency, due to poor densification and the large number of voids.
It can be seen with a 100x magnification (Figure 4a) and a 200x magnification (Figure 4b), that there is a failure in the coverage of the grains by the cement paste, in addition to a large number of voids in the mortar A0.
In figure 5b, it is observed that the grains of natural aggregate show failure to be covered by the cement paste, while in figures 5c and 5d, the denser appearance, but with voids, of the paste covering the grains of natural aggregate and waste.
(b) A10 mortar with grain packaging failure (50x magnification).

Thereby, it is necessary to outline the advantages and disadvantages of them. 1) Close-Spaced Sublimation (CSS) The CSS method is one of the most favorite techniques in CdTe thin film solar cells fabrication due to its well-faceted grains, large grain size, the size of order of film thickness, high material utilization, and short deposition time.
However, the as-deposited films show n-type, high resistivity and small grain size about 0.2-0.5μm.
Research showed that the average grain size, preferred orientation, and stress all change with post-annealing time while the stoichiometry was decided by the deposition potential [4].
To allow the current to flow across the rectifying junction, one has to reduce the Schottky barrier height and thus increasing the probability of majority carrier tunneling or increasing the number of majority carriers at the metal-semiconductor surfaces by using heavily doping.
The advantage of each method includes large grain size (CSS), easy of doping and material-effective (ED), low processing temperature (MS), perfect orientation (EG) and cost-effective potential for nanostructure solar cell (VLS).