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Tests of oxidation resistance at temperature as low as 500 ℃ show that: the number of cracks of the composite coating (MoSi2-SiC or MoSi2-Si3N4) is smaller than that of the monolithic coating of MoSi2; its oxidation resistance at low temperature is enhanced obviously, which is achieved mainly by reducing the mismatch of thermal expansion coefficient between the composite coating and the Mo substrate, and the formation of highly volatile MoO3 [21, 22].
The addition of Al is beneficial in that when the composite was oxidated, Al2O3 will be produced at first place, whose volume expansion rate is much smaller than that of SiO2, which in turn reduce the negative effects brought about by the grain boundary glass phase of SiO2, and improve the high temperature strength of materials[24]
The addition of W and B elements has the function of refining grain and enhancing the room-temperature bending strength of materials[27].
Table2 Properties of samples Material Porosity Bending strength Micro-hardness Fracture toughness % MPa HV MPa·m1/2 MoSi2 2.9 160 1 341 2.52 10 %ZrO2-MoSi2 4.5 380 1 499 5.81 20 %SiC-MoSi2 2.7 215 1 912 3.84 (20 %ZrO2 + 10 %SiC)-MoSi2 4.1 470 1 975 7.65 In abroad, by comparing the high temperature performance of MoSi2 composites with different mole fraction of Mo5Si3 or WSi2, Schwarz[28] states that the addition of Mo5Si3 and WSi2 can increase the high-temperature bending strength of MoSi2 Matrix at temperature of 1200～1400℃ by 25 times, and the effect of solution treatment of WSi2 is more obvious than that of fine grain strengthening treatment of Mo5Si3.

The frictional force Pf between powder and dies of traditional single powder compaction process is reverse with the pressing direction, results the loss of pressing force P, the actual force P1 applying on powder green is less than the pressing force P, namely PP fP −=1 (1) When the powder compaction is made without friction, namely the ideal condition Pf=0, the actual force P2 applying on powder green is equal to the pressing force P, namely PP =2 (2) When the direction of frictional force Pf is same with the direction of pressing, the actual force pressing P3 on the powder green is more than the pressing force P, namely PP fP +=3 (3) This means that frictional force can be made of the part of pressing force to make displacement or deformation of powder grain, and can change the distribution
The total number of elements is 960, and the simulation model is shown in Fig.2.
The reason is that when pressing force is applying on the powder body during the compaction process, the plastic deform of powder grain is made, the internal stress - elastic stress- congregate in internal parts of powder grain, the direction of stress is reverse with outside force and resist deform of green.

In the simulations, the distribution of solid propellant grain is represented by the volume fraction of solid phase αp, which is determined from the distribution of representative particles.
These particles have the information of the burnup fraction, the volume and temperature of solid grains, and solid phase velocity.
The rate of mass decomposition and the linear burning rate on each grain surfaces are respectively given by () r V S m p p pρα−= 1& , r = a ⋅ pn (7) The resistant force due to the friction between the projectile and the launch tube wall acts on the projectile.
In the calculation, the number of the computational grid points is 341x31, and that of the representative particles is 20x20.

On the other hand up to date enormous numbers of experimental studies for the creep behaviour of MMCs have been performed, in which constitutive relations of steady state creep for the composites are mainly empirically derived [1].
This value is lower than that of grain-boundary diffusion of Ni, which is reported with 115kJmol -1[6].
The effective sectional area of a diffusion path, S, which usually seems a unknown parameter, was decided through the comparison of tangent modulus between experimental and simulated stress-strain curves of 10vol. % ZrO2/ Ni composites at 900 C o , and the pre-exponential term and activation energy for the interface diffusion were used with those of grain-boundary diffusion of Ni polycrystalline.
Young's modulus /GPa 207 200 Poisson's ratio 0.31 0.3 σ0 /MPa 25 Grain-boundary diffusion parameters for Ni [6] D0 (Pre-exp. term) / m 3s-1 : 3.5×10-7 , Activation energy / kJmol-1 : 115 Atomic volume / 1.09×10 -29m 3 : , Effective area of diffusion path S: 6.0 ×10 -11 m 2 .

The intrinsic thermal conductivity can be expressed as follows[8]: (2) where χ is the adjustable parameter, μ is the shear modulus, Vm is the unit cell volume per molecular, γ is the Grüneisen anharmoncity parameter, N is the number of atoms per molecular unit, ρ is the density, T is the temperature, A is the parameter independent of the temperature.
As we know, the mean path of the phonon which predominate the thermal conductivity of the dielectric solid is composed of three parts: (15) here li, lp and lb represent the phonon mean free path corresponding to Umklapp scattering, point defect scattering, and grain-boundary scattering processes, respectively.
Since the mean free path of the phonon is usually in the nanometer scale and the grain size of the ceramic is in the microm scale, the grain boundary scattering can be omitted.

Final characteristics of the diamond layer, such as grain size, thickness, hardness, are depending on the pre-treatment parameters.
In this paper investigations have been done in order to find an optimal configuration of pre-treatment function of carbide grade with a minimum number of tests.
Experiments have been performed on H10F carbide rods from Sandvick, which is a tungsten carbide with fine grain size (between 1 and 1.3 µm) bound by 10wt% of cobalt.
Pure abrasive wear is obtained instead of breakage of the grains and no blasting particles are embedded in the treated surface.

Samples and Experiments The five black-glazed shreds, numbered as QL1-QL5, are shown in Fig.1.
The image of low magnification of small oil spots is shown in Fig. 2(a), Fig. 2(b) is a close-up of one crystal grain, the length and width of the crystal grain were about 175nm and 75nm.Fig.2(c) is the electron diffraction pattern of Fig. 2(b), according the results of XRD and the electron diffraction pattern, it can be concluded that the crystal grain is mainly ε-Fe2O3 in the orientation of the zone axis [001], and the indexing of the electron diffraction pattern is shown in Fig. 2(c).

Vickers hardness number (HV) is the ratio of the applied load to the surface area of the indent.
For Trial 4 and from Sample 1, Sample 2, Sample 3 and Sample 4 we observe a refinement in the grain structure coupled with the formation and presence of “onion rings”.
The technique has the advantage of producing welds with (a) low heat input, (b) a low degree of distortion, (c) a smaller grain size in the weld, (d) a narrow thermally-affected zone, and (e) properties closer to that of the parent metal.
The formation of fine equiaxed grains coupled with uniformly distributed fine strengthening precipitates in the region of the weld are reasons for superior tensile properties of friction stir welded joints. 6.

However, the degree of compaction is affected by various factors such as mechanical properties of soil, water content, compaction thickness, number of compactions, compacting machinery, test equipment, test operators and so on [1].
The compaction characteristics of fine-grained soil and coarse-grained soil are different, and the compaction effect of sandy soil is better than that of cohesive soil [5].
As the sediments are mainly silts, loess belongs to fine-grained soil.

Introduction The CdSe thin films may be prepared by a number of deposition techniques like thermal evaporation, sputtering, chemical bath deposition, pulsed laser deposition, spray pyrolysis, molecular beam epitaxy and successive ionic layer adsorption and reaction method.
The grain size shows decreasing trend with increasing Indium content in Fig. 1a.
This can be ascribed to the increased lattice dislocation leading to an increase of donor sides developed at the nano grain boundaries.
The measured RMS value is about 8.1 which is less and shows rather smaller grain size as well as the more uniform morphology.