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Abstract: We report the synthesis of a new class of Al2O3–WC nanocomposites for the first time by using metal–organic chemical vapor deposition process in a spouted bed followed by spark plasma sintering technique. The microstructure and mechanical properties of these prepared nanocomposites have been analyzed for various sintering parameters. From microstructure observation, it is found that the nanosized WC particles are dispersed within alumina matrix grains and intergrains. The microstructure of transgranular and step-wise fracture surface are found in these nanocomposites. The basic mechanical properties like density, hardness, and toughness also have been analyzed and the results are interpreted by correlating with that of corresponding microstructures. [Copyright &y& Elsevier]

Abstract: The fine grains of Al2O3–Cr2O3/Cr-carbide nanocomposites were prepared by employing recently developed spark plasma sintering (SPS) technique. The initial materials were fabricated by a metal organic chemical vapor deposition (MOCVD) process, in which Cr(CO)6 was used as a precursor and Al2O3 powders as matrix in a spouted chamber. The basic mechanical properties like hardness, fracture strength and toughness, and the nanoindentation characterization of nanocomposites such as Elastics modulus (E), elastic work (W e ) and plastic work (W p ) were analyzed. The microstructure of dislocation, transgranular and step-wise fracture surface were observed in the nanocomposites. The nanocomposites show fracture toughness of (4.8MPam1/2) and facture strength (780MPa), which is higher than monolithic alumina. The strengthening mechanism from the secondary phase and solid solution are also discussed in the present work. Nanoindentation characterization further illustrates the strengthening of nanocomposites. [Copyright &y& Elsevier]

Abstract: The densification behaviors of Al2O3–Cr2O3/Cr3C2 nanocomposites prepared by a Spark Plasma Sintering (SPS) were investigated in this work. The initial powders used for sintering were Al2O3–Cr2O3, which were prepared by metal organic chemical vapor deposition (MOCVD) in a spout bed. Different colors of the compacts such as green, purple and black were observed after densification process at different SPS temperatures from 1200°C to 1350°C. These changes of color were relevant to the existence of secondary phase of green Cr2O3, pink solid solution of Cr2O3–Al2O3 and black Cr3C2, which were formed under the different SPS temperature. The secondary phase of Cr2O3 retarded the processing of densification for spark plasma sintering at 1200°C. The Cr2O3 reacted with Al2O3 to form solid solution of Cr2O3–Al2O3 and with carbon to form Cr3C2 as sintering temperature increased to 1350°C. The characteristics of high heating rate, shorter sintering time for SPS and the formation of secondary phase of Cr3C2 effectively reduced the substrate''s grain growth, making Al2O3–Cr2O3/Cr3C2 nanocomposites with small grain size. [Copyright &y& Elsevier]

Abstract: Nanosized particles dispersed uniformly on Al2O3 particles were prepared from the decomposition of precursor Cr(CO)6 by metal organic chemical vapor deposition (MOCVD) in a fluidized chamber. These nanosized particles consisted of Cr2O3, CrC1−x , and C. A solid solution of Al2O3–Cr2O3 and an Al2O3–Cr2O3/Cr3C2 nanocomposite were formed when these fluidized powders were pre-sintered at 1000 and 1150°C before hot-pressing at 1400°C, respectively. In addition, an Al2O3–Cr2O3/Cr-carbide (Cr3C2 and Cr7C3) nanocomposite was formed when the particles were directly hot pressed at 1400°C. The interface between Cr3C2 and Al2O3 is non-coherent, while the interface between Cr7C3 and Al2O3 is semi-coherent. [Copyright &y& Elsevier]

Nanoscaled Cr2O3 powder with an average particle size of 20–40 nm, coated on alumina particles, has been produced by means of chemical vapor deposition (CVD) in a fluidized chamber, using the pyrolysis of Cr(CO)6 precursor. Amorphous and crystalline Cr2O3 particles were obtained when the temperatures of the pyrolysis were 300 and 400 °C, respectively. To prepare nanoscaled Cr3C2 powder from the nanometer-sized Cr2O3, carbonizing behavior of the Cr2O3 particles was investigated. It was found that, when amorphous Cr2O3 powders were carbonized in graphite furnace at 1150 °C for 2 h in vacuum (10−3 Torr), the powder was transformed into Cr3C2, while the crystalline Cr2O3 was transformed into a mixture of Cr7C3 and Cr3C2. The examinations by x-ray diffraction, transmission electron microscopy, and energy dispersive spectroscopy confirmed the transformation of the nano-sized Cr3C2 powders. The results of thermogravimetry and differential thermal analysis indicated that the transformation temperature was ∼1089 °C for amorphous Cr2O3 and ∼1128 °C for crystalline Cr2O3. [ABSTRACT FROM AUTHOR]

Abstract: Sb/SnO2 bi-layer films were prepared on glass substrates using ion beam sputtering deposition (IBSD) and radio frequency (RF) magnetron sputtering deposition technology. The as-deposited bi-layer films were irradiated with a pulsed ultraviolet (UV) laser beam at 355nm for the characteristic modulation which is expected to receive interest in the subtle transition. The effect of laser irradiation on the optical and electrical behavior and the chemical state of the films was investigated using X-ray photoelectron spectroscopy (XPS). The conductivity of Sb/SnO2 after laser irradiation increased in comparison with that of SnO2 and as-deposited Sb/SnO2 thin films. The optical transmittance of laser irradiated Sb/SnO2 increased from 41% to 47%. [Copyright &y& Elsevier]