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Oversize solids in the fluid are retained, but the separation is not complete; solids will be contaminated with some fluid and filtrate will contain fine particles (depending on the pore number)[3].The hollow fiber membrane filtration modules were selected as they offered substantially high packing density around 9000 m2m-3 as compared to packing density of around 30-500 m2m-3 offered by the plate and frame or tubular membrane format[4].
They are fine-grained and plastic in nature.
The microstructure indicates that the powders in green body distribute compactly and also the grains are connected by polymeric networks [11], which contribute to distribution of porosity in the samples.

So a number of studies were reported on attempts to develop coatings and coating techniques for protecting γ-TiAl [5].
In the lower portion of the coating's outer layer is dense and continuous, but some holes which were formed of vacancy aggregation were observed at the upper portion, as shown by the arrows in Fig.1 (point A), with the formation of coating, active Si diffused toward the substrate while vacancy aggregation diffused in the reverse direction, that the holes were caused by the diffusion of gas atoms gathered together in the vacancy aggregations, which passing through the defect, phase boundary and grain boundary of the upper portion of the coating's layer [9].
Fig.5 Friction coefficients of samples Fig.6 Mass losses of samples in friction （a） Sliding direction （b） Fig.7 Wear surface morphologies of γ-TiAl alloy: (a) In lower magnification; (b) In higher magnification （a） Sliding direction （b） Fatigue crack Fig.8 Wear surface morphologies of coating: (a) In lower magnification; (b) In higher magnification Fig.7 shows the worn surface morphology of the γ-TiAl alloy at different scales, grooves and grain-abrasion characteristics as shown Fig.7(b), which can be observed in the wear track, because of its poor load-carrying properties of γ-TiAl alloy in dry sliding[11], at the same time, TiO2 oxide film formed during the wear process which is brittle, and the film easy to scale off under contact stress, then TiO2 oxide film reformed on exposed surface, and scale off again, so the wear mechanisms are abrasion wear and oxidation wear [12].

It is clearly noted from image that cubic grains of different sizes from sub-micron to a few micron(marked as 1 and 2 in Fig. 3) are belong to Bi25FeO40 as an impurity phase.
Microstructural studies proved that the variation of grain morphologies may be an evidence of the formation of impurity phases.
Acknowledgment The financial supports of this work by the University of Tehran (Contract number: 8107004/1/01) and Iran Nanotechnology Initiative Council are gratefully acknowledged.

In all experiments, the repetition rates f = 30 kHz and the number of pulses ni = 1 item was left unchanged.
The scratches with sufficiently clear relief formed by the movement of individual diamond grains are highlighted.
The chaotic state of these defects on the surface of ceramics is determined by the random nature of form and arrangement of grains in the diamond wheel.

In the micro milling experiments, the super-fine-grained tungsten carbide precision micro milling cutter with a diameter of 500 micron were used in the machining experiments, of which the geographic parameters is shown as Table 2.
Table 2 Geographic parameters of micro milling cutter Cutter Diameter Core Diameter Number of Flutes Radial Rake Angle Helix Angle Radial Relief Angle Axial Relief Angle Edge Radius Tool Length 0.5mm 0.4mm 2 7° 30° 10° 10° 2μm 1 mm Experimental Results and Discussions.
Fig.6 Micro milling force （D=500 μm，n=30000rpm，ap=5μm，vf=5mm/s） Fig.7 Effect of feed speed on milling force Conclusion The finite element simulation model of micro cutting Elgiloy alloy was set up for research the effect of feed rate on the micro cutting force, meanwhile the experimental study on the milling force of the precision micro milling Elgiloy alloy was carried out using an ultra-precision micro milling machine tool with a 500 micro diameter super-fine-grained tungsten carbide precision micro milling cutter.

Metallic iron in reduced ilmenite is dissolved in the solution and diffused to a grain surface.
The chloride ion in solution assisted break down any passive oxide layer formed on the grain surface.
The effects of temperature on the rusting reaction were complicated because a number of temperature-dependent parameters are involved.

As high EO coefficients will allow for smaller size devices and lower operating voltages, a growing number of investigations have been focusing on PLZT thin films to achieve high optical responses.
Fig. 2(a) reveals that the films are crack-free, consist of round grains with a crystalline size of approximately 125 nm.
These characteristics, i.e. fine grain size and fibrous columnar structure are very advantageous in increasing the resistance to cracking [[] C.

In this study, the equivalent diameter ( eqD ) and shape factor ( F ) of primary particles are calculated using the following equations [3]: N A D N N N eq ∑== 1 /4 π (1) N AP F N N N N∑== 1 2 4/ π (2) Where NA and NP are the area and perimeter of a particle respectively, and N is the number of particles. 4.
The equivalent particle diameter and the corresponding intercept particle size were very close to each other as shown in Fig.3, which indicates that the primary solid particles obtained by the RBRM process is close to spherical. 0 20 40 60 80 0 5 10 15 20 25 30 Equivalent diameter Mean intercept length Frequency Grain size (μ m) Fig.3 The Equivalent diameter and corresponding intercept size of the primary α-Al particles in the RBRM process, a shear rate of 740s-1 at 873K for 8s The microstructure-processing relationship of different shear rate and average particle size at the identical solid fraction and shear time is shown in Fig.4.
Fig.4 The relationship of the shear rate and average particle size of A357 alloy at the identical solid fraction and shear time ( 52.0=sf , shear time is 8s) 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0 7 0 0 8 0 0 9 0 0 3 5 4 0 4 5 5 0 5 5 6 0 6 5 Average particle size /μ m S h e a r ra te /s-1 Table 2 Processing conditions and the microstructural properties of the rheocasting A357 alloy Shear time /s Solid fraction / sf Shear rate /s-1 Average grain size /µm 8 0.52 772 42 8 0.52 630 45 8 0.52 472 48 8 0.52 315 60 4.2 The fluid flow characteristics of the slurry in the RBRM The fluid flow characteristics of the SSM slurry inside the RBRM are complex.

Based on a large number of experimental results, the mechanisms of reactive-element effects have been reviewed by several authors [1-5].
The as-deposited coatings were nanocrystalline with grain size less than 100 nm [11].
The two effects are related to the segregation of RE ions to the scale grain boundaries and the metal-scale interface.

Therefore, rapid heating is available and the bulk compacts with fine grain microstructure can be obtained [17-19].
When the TiB content was increased to 70%, both the number and the size of the micro-pores in the TiB-Ti/TC4 composites increased significantly.
Whereas the tensile strength decreased rapidly when the TiB content increased from 50% to 70%.In addition to the effect of the relative density, the grain size also plays significant role in the tensile strength.