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Even though a large number of papers are already published on the microwave dielectric properties of BaTi4O9 ceramics, effect of different particle size on the sintering behavior and microwave dielectric properties of BaTi4O9 ceramics have not been reported.
The grain sizes of powders were observed by scanning electron microscopy (SEM, HITACHI S-4800).
From Fig.6 (a), it is obvious that the grain size of BaTi4O9 ceramic prepared from 8-10 nm size powders is about 1 μm, and a lot of pores are observed in the grain boundary, which suggest the 8-10 nm size powders damage the sintering process.
When the powders increase to 70-170 nm, Fig.6 (b)-(d) show that the grains of BaTi4O9 ceramic grow to 3-5 μm and the pores disappear.

The crystal grains in the micro-composite coating are ridge shape and their sizes are uniform.
The small white spherical grains dispersed in the nickel coating are ultrafine Al2O3 powders.
The grains in the ultrafine composite coating are mainly four-pyramid shape (Fig.1c).
The ultrafine Al2O3 powders can strongly impede the slippage between crystal grains and have firm adhesion with nickel matrix, so the coating can strongly resist abrasion.
Fig.3 is equivalent circuit diagram for impedance spectra, Rs - electrolyte resistance, Cc(Qc)- coating capacitance, Rpo - diffusion resistance in the pores, Cdl (Q dl)-capacitance of double electrical layers, Rt -charge transfer resistance, n -dispersion exponential of constant phase angle component Q.There are two time constants in the impedance spectra as shown in Fig.2, and the corresponding equivalent circuit is shown in Fig.3 where the circuit of RpoQc represents penetrative diffusion process via pores of coating in corrosive medium corresponding to the high frequency zone, and the circuit RtQdl represents electrochemical process of iron substrate Coating Al2O3 Hardness Wear Loss NSS periods NSS periods Porosity mass % HV0.5 mg (showing yellow rust) (showing green rust) number/cm 2 Ni/ultrafine Al2O3 3.42% 258 14.6 7 10 3-5 Watts Ni 241 34.6

This paper presents a theoretical fundamental for understanding the phenomenon of increasing film hardness after Si atoms spread into the VN crystal to form a Si-N grain boundary.
In order to increase the number of plane waves, the k-point grid is taken as 11×11×11 while calculating the DOS.
In this paper the ideal vacancy model for forming Si grain boundary is studied as shown in Fig. 1 (b).
Therefore, in this paper the Si atoms are added into the vacancy of VN crystal, then a Si-N interface forms and the grain refines.
Acknowledgement This research work is supported by the National Natural Sciences Foundation project (50845065) on “The study on the superhard property of Ti-Si-N nanocomposite surface and the formation mechanism of such structures with the method of first-principles” and the Inner Mongolia Natural Sciences Foundation project (2010MS0803) on “Research for the influence of the size of nano-grains in Ti-Si-N composite surface on its hardness by multi-scale simulation”.

Introduction Usually unconsolidated formations present the drilling operation with few numbers of challenges and difficulties in maintaining mechanically stable wellbore, transporting drill cuttings with non-erosive flow, and preventing formation damage.
Conclusion Based on the studies, the result shows that the coarser grain size of bridging agent gives higher mud weight compare to the finer grain size.
Based on that, the finer grain size of bridging agent can be selected as the good size to be used for water-based drilling fluid in order to reduce fluid loss during the operation compare to the medium and coarse size.
The finer grain of bridging agent can form the best filter cake compare to the mud sample without bridging agent (mud A), mud with medium size bridging agent (mud C) and mud with coarse size bridging agent (mud D).

With the increase of PEG content, silver particle size becomes smaller, because when the PEG concentration is too low, the layer of PEG grains can not be fully cover the surface of silver, which can not fully suppress the grain growth and obtain relatively large silver particles, and some gather into agglomeration.
With the increase of the quality of PEG, this may mainly due to formation of silver nuclei after, PEG was adsorbed on the grain surface, forming a layer of film which inhibits the growth of silver nuclei effectively and formation rate of silver nuclei is greater than its growth rate, so silver particle size is relatively small [7].
When high concentrations of the PEG, may be wrapped part of the silver grains forming colloidal.
It can be seen in Figure 4 without the addition of ethanol, the silver particle size is 4.33μm, because solution produce a large number of air bubbles in high-speed rotation, which greatly affect the particle nucleation rate to prevent the silver crystal growth.

However, the name of alloys would be called as the alloys number.
Microstructure of the alloy 1 containing of 0.6 wt% silicon showed the huge equiaxed grains of the alpha + beta (α+β) phases (Fig. 1(a)).
Microstructure of the alloy 2 revealed equiaxed grains of the beta phase (Fig. 1(b)).
Moreover, the 0.6 wt% tin addition in the alloys containing 1.1 wt% silicon (alloy 6), the microstructure exhibited equiaxed grains of the beta phase as same as the structure of alloy 2.
With more silicon addition 2.0 wt% (alloy 7) together with 0.6 wt% tin addition, the structures changed to the dual phases of the beta matrix and the gamma phases dispersed in the matrix including the gamma formation along the grain boundary, namely gamma network, as shown in Fig. 2(c).

It is well known that the glass additives to ceramics can improve their breakdown strength (BDS), because the glass additives can modify the microstructures of the ceramics, such as the reduction of grain size and the decrease of porosity.
From Fig.2 (a), for the pure SBN ceramic, a large amount of columnar grains and a small degree of porosity are clearly seen.
On the other hand, from Fig.2 (a)-(c), when a small amount of glass added SBN ceramics, it is to be noted that glass additions have resulted in the decrease of the average grain size.
The inhibition of grain growth which occurred in the SBN ceramics with glass additions might be attributable to the occurrence of liquid phase occurred during sintering.
The reasonable values of BDS can be described by Xi=ln(Ei) (1) Yi=ln(-ln(1-i/(n+1))) (2) where Xi and Yi are the two parameters in Weibull distribution function, Ei is the specific breakdown voltage of each specimen in the experiments, n is the sum of specimens of each specimens, and the samples are arranged in ascending order of BDS values, i is serial number of samples.

A number of studies on the crystal structure and evolution sequence of Cu precipitation have been carried out[9, 10].
Copper dissolved in austenite retards the transformation from austenite to ferrite and inhibit the grain growth, which can be ascribed to the grain refinement for 1.5Cu steel observed in Fig.2(e).
It may be attributed to the reduction of grain size by Cu addition as shown in Fig.2(e).
The low temperature toughness was enhanced with the addition of Cu element, which may attribute to grain refinement and the interaction of Cu precipitates with dislocation.

The diameter of upper-side of columnar YSZ grains of coatings obtained using plasma gasses without H2 addition did not exceed 25 mm.
The diameter of columnar grains formed after introducing 2 NLPM hydrogen into the plasma plume was larger and exceeded even 40 mm.
Increasing the hydrogen flow in the plasma plume to 4 and 6 NLPM resulted in the formation of grains with a diameter of about 30 mm.
Between grains nano-size particles were visible.
The microstructure of YSZ ceramic layer deposited by PS-PVD method with addition of hydrogen to plasma gasses: a – 0 NLPM; b – 2 NLPM; c – 4 NLPM; d – 6 NLPM The addition of hydrogen reduces the number of small spheroidal particles between columns as results of plasma enthalpy increasing.

In generalized form, the constitutive relation that links the stress-strain rate, grain-size and temperature relation can be written as [2]: εm = ADGb (b/d)p (σ/G)n /kT , (1) where εm is the minimum and/or steady-state creep rate, A is a numerical constant, D is the appropriate diffusivity, G is shear modulus, b is the length of Burgers vector, k is the Boltzmann constant, T is the test temperature, d is the grain size, p is the grain size exponent, σ is the applied stress, and n is the apparent stress exponent of the minimum creep rate giving the strain rate sensitivity of the flow stress.
This can be explained by different operating creep deformation mechanism(s) based mainly on grain boundary mediated creep deformation processes.
Oakey (Ed.), Woodhead Publishing Series in Energy: Number 23, chapter 5, Woodhead Publishing Ltd. (2011)