Recent Advances in Interface Modification of Cu/graphite Composites and Layered Ternary Carbides of Modified Layer Candidate

We review the fundamental properties and significant issues related to Cu/graphite composites.In particular,recent research on the interfacial modification of Cu/graphite composites is addressed,including the metal-modified layer,carbide-modified layer,and combined modified layer.Additionally,we propose the use of ternary layered carbide as an interface modification layer for Cu/graphite composites.

Discovery of new MAX-phase-like layered ternary carbide V_(8)P_(6)C:Crystal structure,thermal expansion,and elastic properties

Due to the laminated structure,MAX phases and MAX-phase-like compounds possess outstanding dam-age tolerance capability with good thermal/electrical conductivity and other charming functional prop-erties,showing a bright future for structural-functional uses.Here,a new MAX-phase-like ternary car-bide V_(8)P_(6)C with layered characteristics was discovered.Contrary to the alternate stacking of hexagonal-arranged M/A/X atom layers in MAX phases,V_(8)P_(6)C has a layered structure formed by a repeated stacking of the slabs consisting of V_(6)C-octahedrons and VP 6-distorted-octahedrons in three-atomic layers thick.The thermal expansion anisotropy was revealed,with the thermal expansion coefficients(TECs)along a-axis,c-axis,and the average value,equal toα_(a)=8.55(5)μK^(−1),α_(c)=10.23(5)μK^(−1),andα_(L)=9.14(5)μK^(−1),respectively.The dilation along the c-axis was mainly dominated by out-plane V-P bonds be-tween layered slabs.According to the pressure-dependent lattice parameters,the polycrystalline bulk modulus(B_(0)=185(9)GPa)and high compressibility anisotropy factor(B_(a)/B_(c)=1.64)was found.Mean-while,the second-order elastic constants were calculated,and the elastic moduli,E=303 GPa,B=198 GPa,G=122 GPa,andν=0.246,were obtained.And the weak connection between layer slabs by out-plane V1-P bond was revealed by the bond stiffness model,with a bond stiffness close to the M-A bond in MAX phases.Furthermore,good damage tolerance capability was predicted according to Paugh’s ratio(G/B=0.616)and Cauchy pressure(P_(a)=0 GPa,P_(c)=-7.5 GPa),even better than those of typical MAX phases.The discovery of V_(8)P_(6)C provides a new member of MAX-phase-like damage-tolerant ceramic with relatively low density,moderate thermal expansion,and anisotropic compressibility,and the unique lay-ered structure is inspiring for exploring new layered ternary ceramics.

Enhanced oxidation resistance of low-carbon MgO-C refractories with ternary carbides:a review

The demand for low-carbon MgO–C refractories is ever growing to meet the development of advanced steelmaking technologies and efficient energy conservation.Meanwhile,to improve the oxidation resistance and inhibit the weakness of low-carbon MgO–C refractories,antioxidants are necessary.The application of ternary carbides that focused on improving the oxidation performance of MgO–C refractories has been explored,and the ternary carbides including Al_(4)O_(4)C,Al8B_(4)C_(7),Al_(4)SiC_(4),Ti_(2)AlC,Ti_(3)AlC_(2),and Ti_(3)SiC_(2)have been proved effective.The crystal structure,physical properties,oxidation behavior,and synthesis of these ternary carbides were summarized,and their oxidation mechanism in assisting antioxidation of MgO–C refractories was discussed.In addition,the potential aspects related to the usage and development of ternary carbides in low-carbon MgO–C refractories were proposed.

First-principles calculations of structural, electronic, elastic and thermal properties of phase M_2SiC(M=Ti,V,Cr,Zr,Nb,Mo,Hf,Ta and W)

The structural,electronic and elastic properties of the M_2SiC phases were studied,where M are 3d,4d,and 5d early transition metals.The valence electron concentration(VEC) effect of Ti,V,Cr,Zr,Nb,Mo,Hf,Ta and W on these properties was examined.The C_(44) saturates for a VEC value in surrounding of 8.5 for each serie.Hf-s,Ta-s and W-s electrons mainly contribute to the density of states at the Fermi level,and should be involved in the conduction properties.The distortion increases with increasing VEC and decreasing k_c/k_a factor except for the series M=Ti,V and Cr,where it is lower at the VEC value of 8.5(it follows a parabolic variation).The M_2SiC was characterized by a profound anisotropy for the shear planes(1010) and compressibility in the direction is higher than that along the cone except for W_2SiC,where it is lower.

Incipient low-temperature formation of MAX phase in Cr–Al–C films

Ceramic-metallic MAX phase of chromium aluminium carbide ternary compounds was successfully obtained through deposition by DC sputtering onto Si substrates. A study of the influence of substrate temperature and in-air post-annealing on the film crystallinity and oxidation was undertaken. Scanning electron microscopy （SEM）, wavelength-dispersive X-ray analysis （WDSX）, and X-ray diffraction （XRD） were used for film characterization. It is shown that, at substrate temperature of about 450℃, as-deposited films are amorphous with small nanocrystals. Subsequent annealing in air at 700℃ leads to film crystallization and partial oxidation. WDSX spectroscopy shows that the films oxidise to a depth of around 120 nm, or 5% of total film thickness which amounts at around 2.68 ixm. As a novelty, this demonstrates the possibility of in-air crystallization of Cr2AlC films without significant oxidation. Materials Analysis Using Diffraction （MAUD） software package for a full-profile analysis of the XRD patterns （Rietveld-type） was used to determine that, as a result of annealing, the average crystallite size changes from 7 to 34 nm, while microstrain decreases from 0.79% to 0.24%. A slight tendency of preferential growth along the （10 10） direction has been observed. Such texturing of the microstructure has the potential of inducing beneficial anisotropic fracture behaviour in the coatings, potentially interesting for several industrial applications in load-bearing devices.