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In this case, the nano silica can be prepared with the grain size of 100 nm and the narrow particle size distribution.
Therefore, little silica grain with tiny size produced in early time.
When more water added into the system, the amount of silica grains increased on account of reactive probability.
In synthesis system, the nano SiO2 showed gelatinous masses and not single grain.
The surface characteristic before and after modification was obviously different, which showed in terms of more new wave numbers and the migration of wave number. 3.

According to the following formula (1) and (2), grain size and content of the different were calculated
After treated by NaOH solution (1 mol/L), a large number of hydroxyl was exposeded on the surface[14].
Increasing calcination temperature will cause the phase change and the growth of the TiO2 crystal grain.
Calculated the grain size and phase content of TiO2 according to the Scherrer formula, the results were listed in Table 1.
XRD pattens indicated that when calcinated at 500 ° C, the proportion of anatase phase of TiO2 in material is about 90%, while the grain size is 15nm.

Up to now, most of work focused on the grain boundary segregation and the cold shortness caused by non-metallic element of nitrogen had been done.
However, it is not clear that the reasons why the nitrogen element can generate the grain boundary segregation and the cold shortness at electron structural level.
It was found that the phase structure unit of α-Fe-N with bigger nA firstly segregates on grain boundary，then the Fe4N with smaller nA on grain boundary was precipitated from supersaturated solid solution α-Fe-N, resulting in the formation of Fe4N+α-Fe hybrid followed by the cold short in steel.
Table2 The valence electron structure of Fe4N phase N=1 R(1)=0.07000nm nc=3.0000 Fec=b10 R(1)=0.11458nm nc=3.5709 Fef=b14 R(1)=0.11153nm nc=4.7144 Bond name 12 0.19025 0.19018 0.75536 7.06×10-5 24 0.26905 0.26898 0.24894 7.06×10-5 24 0.26905 0.26898 0.22550 7.06×10-5 16 0.32952 0.32945 0.00911 7.06×10-5 6 0.38050 0.38043 0.00740 7.06×10-5 12 0.38050 0.38043 0.00607 7.06×10-5 =27.4225 =0.0710nm Valence electron structures of AlN phase Fig.2 Atom arrangement in AlN cell The crystal structure of AlN belongs to B4-type of hexagonal system, space group is (NO.186), the lattice constants of cell are =3.111Å, c=4.978Å, and c/ =1.600, the number of chemical formula in cell Z equals to 2[8].
(2) Comparing the phase structure factor nA of Fe4N with that of α-Fe-N, it was found that Fe4N with smaller nA on grain boundary was easily precipitated from supersaturated solid solution α-Fe-N, resulting in the formation of Fe4N+α-Fe hybrid followed by the cold shortness in steel

A large number of crystal nucleuses are produced, which results in the forming of fine dynamically-recrystallized grains via the grain boundary movements in WNZ [7].
Very fine grains are found between the layers.
A3 is a friction-stirred zone with finer and very uniform equiaxed dynamic recrystallization grains.
It is a very thin layer located in the bottom zone with fine but nonuniform grains.
Fig.6 Comparison of grain size in different parts along the welding direction Mechanical properties.

The hardening mechanism for gradient coating are second phase strengthening, grain refining strengthening and solid solution strengthening.
What can be seen from figure 2.5a was that the grain of second cladding layer was refined, compared with that of the first cladding layer.
The primary TiC has small grain, uniform microstructure and no interface pollution.
Grain refining strengthening and solid solution strengthening.
The main strengthening ways for gradient coating are particle strengthening, grain refinement strengthening and solid solution strengthening.

It is found that the α-HgI2 seed layers play an important role in reducing the grain sizes, increasing the density improving the crystallographic orientation and electrical properties of the polycrystalline α-HgI2 films.
Introduction Mercuric iodide (HgI2) is one of the most suitable semiconductor materials for γ- and X-ray detectors operating at room temperature because of its favorable characteristics such as high atomic number of its constituent elements and large band gap (2.13 eV), resulting in a high photopeak efficiency [1-3].
The detector applications require a lot of characteristics of polycrystalline films, some basic limitations still restrain their spectrometric use to X-ray and to low energy γ-ray [6], such as the grain sizes, the film growth orientation and the texture of the film.
However, large grain size of the poly-HgI2 always results in nonuniform X-ray response of the detectors, which plays a crucial role in restraining its application in large area imaging systems [7].
The grain sizes of the poly-HgI2 obtained with or without seed layers are about 30 and 50 μm, respectively.

SEM images indicated the small grain size of the final product.
The FTIR spectra in the wave number range from 400 cm-1 to 4000 cm-1, were obtained by the KBr pellet technique.
The sample at 1300 °C (Fig. 4b) indicates the further sintering of the grains forming larger particles.
The Nyquist plots show two depressed semicircles, well positioned at higher and lower frequency regions which are adequately attributed to grain and grain boundary oxygen ionic conductivities respectively.
The sample calcined at temperature as low as 1300 °C for 6h consists of small grains and shows no presence of secondary phases.

JCPDS CAS (Number 1314-13-2, CuKα1) was used as an internal X-ray standard.
(1) The raising of the intensity is influenced by the number of reflected areas in the composition of atoms inside the films.
Increasing substrate temperature leads to reducing scattering process on the grain boundaries.
Yang et al. reported that when the substrate temperature increases, the grain size of crystal will increase to cause less scattering on the grain boundaries [8].
The conductivity of ZnO film is conversely proportional to the film resistivity and directly related to the number of electrons.

Introduction Isothermal transformation (IT) diagrams of austenite are the main criterion for selecting the regimes of heat treatment for a great number of carbon steels and alloys [1, 2].
The RA stability at overcooling and resistance to the isothermal transformation in the above steels depend on the homogeneity of the solid solution of the g-phase, the content of austenite-forming elements in the phase, phase stresses, the size of a grain, dispersity and the number of secondary phases [1, 14].
The large value of ttransform is explained by the chemical nonhomogeneity in alloying elements, structural nonhomogeneity of the initial RA solid solution (grain size nonhomogeneity, coarse grain) and high level of the phase stresses in the structure of austenite quenched from 1000 °C.
At the same time, recrystallization takes place leading to the formation of the smallest grain (7-8 according to the grain-size scale) [21] in the steel structure, which provides the maximal (68 min) duration of the incubation period at quenching from 950 °C (Fig. 1, curve 1begin – 1end; Fig. 2, curve - tincub).
The decrease of the austenite stability after quenching from 1000 °C is due to the coarsening of the grain size as the result of collective recrystallization.

As result, formation of intermetallic grains of Al4Ce type was observed.
SEM/EDS observations lead to the conclusion that at least three microstructural components can be distinguished: (i) large bright grains (*1), (ii) gray areas with a large number of fine, uniformly distributed particles (*2) and (iii) dark areas without any noticeable particles (*3).
It was found that large grains (bright components, *1) are Al4Ce intermetallic compounds.
Formation of Al4Ce grains as an equilibrium phase in AlMg-CeO2 system was also confirmed by XRD analysis as shown in Fig. 4.
Decomposition of CeO2 particles at liquid state conditions results in Al4Ce grains and aluminum-magnesium oxides development.