[en] Objective: To explore the imaging features and pathological manifestations of solitary fibroma tumor of kidney in order to improve the diagnostic accuracy of this disease. Methods: CT, MRI findings and clinico pathological features of one case with solitary fibroma tumor of kidney were retrospectively analyzed, and related literatures were reviewed. Results: The CT plain scan showed a solid soft tissue mass in the right renal parenchyma protruding into the renal pelvis, showing uniform high density. The CT value on plain scan was about 47 HU. On CT contrast enhanced scan, the enhancement of cortical phase was inhomogeneous, and the mass was further enhanced in parenchymal phase and secretory phase, and tended to be homogeneously enhanced. On the MRI plain scan, the mass showed isointense signal on T₁WI, obviously homogeneous and low signal on T₂WI, and slightly low signal on diffusion-weighted imaging (DWI). On multi-phase contrast enhancement, the mass showed progressive delayed enhancement and tended to be uniform. Microscopically, the tumor tissue was composed of intersecting bundles, the tumor cells were fusiform with no obvious heteromorphism, and mitosis was rare. Immunohistochemical results showed positive expression of CD34, CD99 and Vim. Conclusion: The solitary fibroma of kidney has characteristic imaging features, and should be considered in the differential diagnosis of renal solid tumors. (author)

[en] The crystal structure of NH₃BH₃ was investigated using synchrotron high pressure X-ray diffraction (HPXRD) up to 27 GPa and neutron diffraction up to 5 GPa. Density functional theoretical (DFT) calculations were carried out simultaneously for comparison. The results confirm a pressure induced phase transition from the tetragonal I4mm phase to a high pressure orthorhombic Cmc21 phase around 1.22 GPa. Further increase of pressure above 8 GPa, we observed a second structural transition from Cmc21 to a triclinic P1 phase which are reversible with small hysteresis. The transition pressures and the bulk modulus obtained experimentally are in good agreement with theory.

[en] We have investigated the electronic structure, chemical bonding, and equations of state of Zr₂Al₃C₅ by means of the ab initio pseudopotential total energy method. The chemical bonding displays layered characteristics and is similar to that of nanolaminate ternary aluminum carbides Ti₂AlC and Ti₃AlC₂. Zr₂Al₃C₅ could be fundamentally described as strong covalent bonding among Al-C-Zr-C-Zr-C-Al atomic chains being interleaved and mirrored by AlC₂ blocks. The interplanar cohesion between covalent atomic chains and AlC₂ blocks is very weak based on first-principles cohesion energy calculations. Inspired by the structure-property relationship of Ti₂AlC and Ti₃AlC₂, it is expected that Zr₂Al₃C₅ will have easy machinability, damage tolerance, and oxidation resistance besides the merits of refractory ZrC. Zr₂Al₃C₅ has a theoretical bulk modulus of 160 GPa and illustrates elastic anisotropy under pressure below 20 GPa

[en] The possible crystal structures of transition metal nitrides M₂N₃ (M = V or Nb) were investigated using first principles calculations. We predict that the ground state structures of V₂N₃ and Nb₂N₃ are trigonal and orthorhombic, respectively, over a wide pressure range. Examinations of the thermodynamic stabilities of trigonal V₂N₃ and orthorhombic Nb₂N₃ with respect to phase decomposition suggest that they can be prepared under moderate pressure conditions. Elastic constant calculations indicated that both nitrides were mechanically stable and are potential candidates for hard materials.

[en] The theoretical elastic stiffness of Y₃Si₅N₉O, the only Y-Si-O-N quaternary crystal that contains a framework of corner-sharing SiN₄ and/or SiON₃ tetrahedron in three dimensions, was investigated using the first-principles total energy calculations. The full set of second order elastic coefficients, polycrystalline bulk and shear moduli, and anisotropic elastic moduli were reported and further compared with those of Y₂O₃ and β-Si₃N₄. The equation of state and compressibility of Y₃Si₅N₉O were investigated at pressures up to 50 GPa. The crystal structure is stable up to 50 GPa and exhibits anisotropic compressibility under hydrostatic pressure. The relatively softer YN₆ and/or YN₅O polyhedra are more prone to distort or deform than the SiN₄ and/or SiON₃ tetrahedra. Therefore, although the crystal structure of Y₃Si₅N₉O contains a Si-N-O framework similar to that in β-Si₃N₄, it displays elastic stiffness between those of Y₂O₃ and β-Si₃N₄

[en] In this paper, we predicted the possible mechanical properties and presented the electronic structure of Zr₃Al₃C₅ by means of first-principles pseudopotential total energy method. The equation of state, elastic parameters (including the full set of second order elastic coefficients, bulk and shear moduli, Young's moduli, and Poisson's ratio), and ideal tensile and shear strengths are reported and compared with those of the binary compound ZrC. Furthermore, the bond relaxation and bond breaking under tensile and shear deformation from elasticity to structural instability are illustrated. Because shear induced bond breaking occurs inside the NaCl-type ZrC_x slabs, the ternary carbide is expected to have high hardness and strength, which are related to structural instability under shear deformation, similar to the binary carbide. In addition, mechanical properties are interpreted by analyzing the electronic structure and chemical bonding characteristics accompanying deformation paths. Based on the present results, Zr₃Al₃C₅ is predicted to be useful as a hard ceramic for high temperature applications

[en] Ti₂AlC was predicted to bear Al-vacancy down to a sub-stoichiometry of Ti₂Al_0.5C. The phase instability beyond a critical Al content was attributed to occupation of the Ti-Al anti-bonding orbital, which reduces the coupling strength between Ti₂C slab and Al atomic plane. The migration energy barrier of Al self-diffusion along the (0 0 0 1) plane was low, 0.83 eV, resulting in rapid out-diffusion of Al during oxidation and decomposition of Ti₂AlC at high temperatures

[en] Ti₃AlC₂ suffers severe Na₂SO₄-induced corrosion attacks at temperatures higher than 800 deg. C in air. A convenient and efficient pre-oxidation method is proposed to enhance the corrosion resistance of Ti₃AlC₂. The corrosion weight-changes of the pre-oxidized samples were decreased by about four orders of magnitude compared with those of the untreated specimens. The mechanism on improvement of corrosion resistance was investigated by means of thermogravimetric analysis, X-ray diffraction and scanning electron microscopy/energy-dispersive spectroscopy. A continuous and adherent α-Al₂O₃ scale was prepared by high-temperature pre-oxidation treatment in air. The preformed dense Al₂O₃ scale has good compatibility with the Ti₃AlC₂ substrate, and consequently, can act as an efficient barrier against corrosion. Long-time corrosion tests demonstrate that the Al₂O₃ scale conserves after corrosion attack and is capable of long-term stability

[en] The pressure-volume-temperature measurements were carried out for titanium carbide (TiC) at pressures and temperatures up to 8.1 GPa and 1273 K using energy-dispersive synchrotron x-ray diffraction. Thermoelastic parameters were derived for TiC based on a modified high-temperature Birch-Murnaghan equation of state and a thermal pressure approach. With the pressure derivative of the bulk modulus, K₀^', fixed at 4.0, we obtain: the ambient bulk modulus K₀=268(6) GPa, which is comparable to previously reported value; temperature derivative of bulk modulus at constant pressure (∂K_T/∂T)_P=-0.026(9) GPa K^-1, volumetric thermal expansivity α_T(K^-1)=a+bT with a=1.62(12)x10^-5 K^-1 and b=1.07(17)x10^-8 K^-2, pressure derivative of thermal expansion (∂α/∂P)_T=(-3.62±1.14)x10^-7 GPa^-1 K^-1, and temperature derivative of bulk modulus at constant volume (∂K_T/∂T)_V=-0.015(8) GPa K^-1. These results provide fundamental thermophysical properties for TiC for the first time and are important to theoretical and computational modeling of transition metal carbides.

[en] The mechanical and thermodynamic stabilities of M₄AlC₃ (M = V, Nb and Ta) and Ti₄AlN₃ polymorphs were investigated by means of the first-principles pseudopotential total energy method. All compounds satisfied the Born criteria for mechanical stability, but had different thermodynamic stabilities. Only Ta₄AlC₃ showed a possible polymorphic phase transformation driven by thermodynamic competition. The present theoretical results support the polymorphism of Ta₄AlC₃ in experimental synthesis and explain the underlying thermodynamic mechanism. Polymorphism was excluded from V₄AlC₃, Nb₄AlC₃ and Ti₄AlN₃