Search results

homogeneous microstructure in which laminar grains can be seen.
A comparison between Fig.2 and Fig.3 reveals no apparent grain growth after SPS, probably because the holding time was very short.
Additionally, we did not observe apparent preferential orientation of the grains, as also by the XRD results.
The absolute value of Seebeck coefficients increases in the extrinsic region and then decreases with increasing temperature due to the increasing number of thermally excited carriers.

However, these porous SiC ceramics were obtained at very high firing temperatures or with low melting point compositions in the SiC grain boundaries which commonly impair the mechanical and physical properties of the material.
The FTIR spectrum of the original PCS shows a number of sharp peaks at 2950, 2900 cm-1 (C-H stretching), 2100 cm-1 (Si-H stretching), 1410 cm-1 (CH3 deformation), 1250 cm-1 (Si-CH3 deformation), 1020 cm-1 (CH2 deformation in Si-CH2-Si), 829 cm-1 (Si-CH3 rocking).
It is shown that the SiC particles are bonded by PCS pyrolysis products and pores between SiC grains are evident.
Generally, the mechanical strength of porous ceramics depends on the volume fraction and geometry of pores, as well as the microstructure of the solid phase, which links the strength to neck growth, solid-phase contiguity, and characteristics of grain boundary [11].

During ESD process, the electrode bumps the surface of substrate resulting in elastic strain and quick heating equivalent strain [13], which are favorable to grain refinement.
In addition, the element Co diffuses significantly into the transition zone and substrate owing to the fact that the atomic number of Co is similar to Fe and easily to form substitutional solid solutions, which causes a higher relative concentration of element Co in the transition region and substrate.
According to Hall-Petch equation, hardness is inversely proportional to the square root of grain size, hence, the inherent hardness of the coating can be improved greatly.
In addition, extra fine particles can increase the grain-boundary activity which plays an important role on the load transfer in the strengthening of the coating.

The improved hydriding kinetics is undoubtedly ascribed to the refinement of the grains incurred by the melt spinning.
Consequently, high densities of crystal defects such as dislocations, stacking faults and grain boundaries are introduced.
The huge number of interfaces and grain boundaries available in the nanocrystalline materials provide easy pathways for hydrogen diffusion and accelerates the hydrogen absorbing/desorbing process [13].

This could be attributed to the formation of secondary mullite through the solution of alumina particles and precipitation of mullite grains [9].
Since no continuous interconnection is observed between graphite-derived pores due to a homogeneous dispersion of graphite particles in the powder compacts, the values of pore size showed in Table 1 actually reflect the size of pore channels between mullite grains or mullite and alumina particles.
Moreover, ceramic grain growth and pore closure of some of smaller pores during sintering are also helpful for the narrowing the pore size distribution. 10 1 0.1 0.01 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 1250℃ 1350℃ 1400℃ 1450℃ Differential Intrusion /mLg-1-µm Pore Diameter /µm 0 10 20 30 40 0 10 20 30 40 50 60 55.935 29.67 54.05 50.64 Open porosity /% graphite /wt% 43.05 Fig. 2.
The pore structure of porous ceramics (a) Open porosities as a function of graphite quantity; (b) pore size distribution; (c) SEM micrograph of a pore resulted from graphite burnout flexural strength The relationship between strength and porosity have been investigated by many researchers [13, 14, 15], and a number of expressions can be used to describe the strength-porosity behavior of porous materials.

Ni-Co alloys can be easily produced by electrodepostion from aqueous solution(Standard electrode potential:Ni,-0.246V;Co,-0.277V).However, it turns out to be anormalous behavior in the codeposition, which leads to a higher mole fraction of Co in the deposit than the ratio Co2+/(Co2++Ni2+) in the bulk solution while Co is considered to be the less noble metal[1].A number of experimental studies have been conducted to analyze this behavior and other characteristics of the Ni-Co system[2-19].Alloy composition is crucial, as it determines the alloy properties.
Simultaneously, the coatings tend to be more compact and the grains size decrease [16].
High diffusion of matal ions with fast depositon rate would result in the rough surface morphology, large grain size and less dense arrangement of atoms.
Wang et al. [16]observed the wear rate of the Co coatings are more than one order of magnitude lower and the friction coefficient are nearly two times smaller than that of Ni coatings with almost the same grain size under the same wear conditions, attributed to the better resistance of hcp structure to adhesion interactions during the wear process.

The grain are coarse and the grain boundary are clear, grain boundary of the substrate extended to the combination belt, the microstructure of transition zone extended to each other, the bonding of the transition zone are metallurgical.
In the cladding process, the melting point of Ti(CN) is higher than the other phase while the density is lower than other phase, during the solidification process of the molten pool , Ti(CN) would float under the stirring of molten pool when Ti(CN) were nucleated and grew up in front of solid-liquid boundary, which resulted that the number of Ti(CN) particle decreased with the distance far away the cladding layer surface. when the surface of the coating was heated by nitrogen arc, the graphite powder, titanium powder and Ti(CN) are burned partially, which made the highest hardness near coating surface area [5].

According to [8-9] the correlation function of the orientation of local anisotropy axes (Eq. 1b) may be written as (1a) (1b) here is the magnetization unit vector, K is the effective anisotropy energy, A is the exchange parameter, kH = (MsH/2A)1/2 is the wave number of exchange correlations, and H is an external magnetic field.
Using analytic theory and numerical calculation and taking into account stochastic domain formation, one can present the field dependence of the magnetization dispersion Km(0) = dm(H) in a form [9]: ((2) Here d is the dimension of exchange–coupled areas in the grain; δ=(A/K)1/2; Ha=2K/Ms is local magnetic anisotropy field and а is the symmetry coefficient, equal to 1/151/2 for uniaxial anisotropy.
The ferromagnetic phase, which was a nitrogen supersaturated bcc alfa-FeN solid solution, is nanocrystalline with the grain size in the bcc phase, depending on the annealing conditions, changes from ~ 3 to ~25 nm.
We assume that each pattern in fig.3 represents a ferromagnetic correlation volume with fluctuating magnetization direction due to the average random magnetocrystalline anisotropy of the grains as it discussed in theoretical background of the paper.

A good casting should meet a number of commonly known requirements, viz. it must be pourable, have high solid concentration and the particles must not settle out, meaning the deflocculation degree has to be controlled.
The grain size and grain shape were also observed with Scanning Electron Microscopy.
The SEM micrograph of the attrition milled powder (Fig.2) revealed non-uniform grains, whose sizes were estimated starting from submicron meter to 3 mm.

Introduction TiC grain has the characteristics of high hardness, high melting point and good thermal stability.
The study on TiC grain reinforcing metallic matrix composite becomes a hot spot recent years[1-4].
TiC grain was dissolved out as fine particles and dispersion in composite material.
(a) 150µm (b) 15µm (c) A C B 5µm Fig. 3 SEM micrographs of composite coating with different magnifications Table 2 EDS composition test result of each point in Fig.3 Elements C Cr Fe Ni Ti A(wt%) 1.69 5.36 88.59 1.29 B(wt%) 5.02 2.63 89.42 1.11 C(wt%) 7.96 1.90 32.61 56.59 3µm (a) (b) 3µm (c) 3µm Fig. 4 EDS area scan of elements (a) original, (b) Fe element, (c) Ti element Fig.4 shows that grainy dispered phase contains a large number of Ti and C elements.