Preparation and characterization of organic–inorganic hybrids and coating films from 3‐methacryloxypropylpolysilsesquioxane

3‐Methacryloxypropylpolysilsesquioxane (MA‐PS) was prepared by acid‐ or base‐catalyzed hydrolytic polycondensation of 3‐methacryloxypropyltrimethoxysilane (MAS). MA‐PS coating film was prepared by dip‐coating on organic, metal and inorganic substrates, including poly(ethylene terephthalate), aluminum, stainless steel, and glass. The coating films on poly(ethylene terephthalate) and glass showed high adhesive strength. The hardness of coating films increased with increasing heat treatment temperature, whereas they decreased with increasing H₂O/MAS molar ratio. The refractive index of coating films increased with increasing heat treatment temperature. In addition, flat and transparent free‐standing films (0.24–0.27 mm thickness) were prepared from MA‐PS that were crack‐free after heat treatment at 1000 °C. Copyright © 2001 John Wiley & Sons, Ltd.     

Nanoindentation of biodegradable cellulose diacetate‐graft‐poly(L‐lactide) copolymers: Effect of molecular composition and thermal aging on mechanical properties

Nanoindentation of cellulose diacetate‐graft‐poly(lactide)s (CDA‐g‐PLLAs) synthesized by ring opening graft copolymerization of L ‐lactide in bulk onto the residual hydroxyl positions on CDA were conducted to investigate the effect of the molecular composition and thermal aging on mechanical properties and creep behavior. Continuous stiffness measurement (CSM) technique was used to obtained hardness and elastic modulus. These material properties were expressed as a mean value from 100 to 300 nm depths and an unloading value at final indentation depth. The hardness and elastic modulus in all CDA‐g‐PLLAs were higher than those in pure CDA, indicating that the introduction of PLLA increases the hardness and elastic modulus. With an increase of crystallinity by thermal aging, the hardness and elastic modulus were increased in both CDA‐g‐PLLA and PLLA. The creep test performed by CSM showed that the creep strain of CDA was decreased by the grafting of PLLA. Thermal aging decreased the creep strain of CDA‐g‐PLLA and PLLA. With an increase of holding time, hardness was decreased, whereas elastic modulus was kept almost constant. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1114–1121, 2007     

（Ti（1-x）Alx）N硬质涂层的研究进展

TiAlN作为一种三元复合纳米涂层材料,具有非常好的性能.该涂层克服了TiN涂层所存在的一些缺陷,其硬度远远高于TiN涂层,最高可达47GPa, 并且具有很好的热稳定性,在700℃高温下仍很稳定,而TiN涂层在500℃时就已被氧化.TiAlN涂层还具有抗磨损,摩擦系数小,热膨胀系数及热传导系数低等特性,这些特性与涂层中Al含量的多少有关,Al含量的改变会导致涂层微观结构的改变,从而使其性能发生变化.氮分压和基底温度对TiAlN涂层的性质有着极其重要影响.本文结合国内外对TiAlN涂层的最新研究进展,对TiAlN涂层的应用,制备方法,结构,抗氧化性及硬度作了简要论述.     

Pc-carbon:一种可能的超硬碳材料

基于密度泛函理论计算预测了一种新型碳同素异形体（Pc-carbon）.声子色散谱和弹性常数计算证实了Pc-carbon的动力学和力学稳定性.计算结果显示，Pc-carbon是弹性各向异性的，其维氏硬度达到87.6 GPa.应力应变计算结果表明，Pc-carbon的理想拉伸强度和剪切强度分别为65.8 GPa和56.5 GPa，进一步证实了其超硬特性.电子结构计算结果表明，Pc-carbon是带宽为0.99 eV的半导体.     

Assessment of quantum‐chemical methods for electronic properties and geometry of signaling biomolecules

A reasonable balance between accuracy and feasibility of quantum‐chemical methods depends on the complexity of the molecular system and the scientific goals. Six series of indole‐, naphthalene‐, phenol‐, benzoic‐, phenoxy‐, other auxin‐derivatives, and a test set of similar organic molecules have been chosen for an assessment of 13 density functional and semi‐empirical molecular orbital methods with respect to electronic and structural properties. The accuracy and precision of HOMO/LUMO calculations are determined by comparison with experimental ionization potentials and electron affinities. Further comparison was performed at atomic level by covariance analysis. The methods KMLYP, MSINDO, and PM3 are precise and accurate for the whole set of molecules. The method AM1 offers comparable accuracy with the exception of electron affinities of indole derivatives, where significant deviations from experiment were observed. Geometrical properties were best reproduced with the semi‐empirical method MSINDO. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Stability and elastic properties of Nb_xC_y compounds

Density functional theory(DFT) is applied to investigate the stability and mechanical properties of NbxCy compounds.The structures of NbxCy compounds are optimized, and the results are in good agreement with previous work. The calculated results of the cohesive energy and the formation enthalpy of NbxCy show that they are thermodynamically stable structures, except for Pmc21-Nb2 C. The mechanical properties such as the bulk modulus, Young’s modulus, the shear modulus, and Poisson’s ratio are obtained by Voigt–Reuss–Hill approximation. The results show that the Young’s modulus and shear modulus of NbC are larger than other NbxCy compounds. The mechanical anisotropy is characterized by calculating several different anisotropic indexes and factors, such as universal anisotropic index(AU), shear anisotropic factors(A1, A2,A3), and percent anisotropy(ABand AG). The surface constructions of bulk and Young’s moduli are illustrated to indicate the mechanical anisotropy. The hardness of NbxCy compounds is also discussed in this paper. The estimated hardness for all NbxCy compounds is less than 20 GPa.     

Fabrication of minimal capital-intensive scratch-resistant and hydrophobic tungsten oxide film on stainless steel through spray pyrolysis

In this contribution, a pure and robust tungsten oxide (WO₃) film was accomplished on stainless steel (SS) substrate at 400°C through a minimal capital intensive, simplistic spray pyrolysis method by utilizing a precursor comprising tungsten hexachloride and 2-methoxyethanol. Thermal analysis revealed the precursor's thermal decomposition and crystallization at ~230°C and 255°C, respectively. The fabricated polycrystalline (monoclinic crystal structured) film was uniform and dense in nature, exhibiting surface porosity and average surface roughness of 4.7 % and 15.9 nm, respectively. The average grain size and thickness of film were 360 ± 70 nm and ~3.6 μm, respectively. W, O elemental presence with a close atomic ratio of 1:3 on the film's surface was acquired along with 91 % lattice oxygen. Regardless of applied normal load in the range of 5 to 15 N, an increment of ~22 % in scratch hardness was gained in WO₃-coated SS compared to uncoated one. Hydrophilic natured WO₃ film (water contact angle, WCA, of ~31°) was efficaciously transformed into hydrophobic (WCA, 136°) by chemical modification with octadecyltrichlorosilane to create a self-assembled monolayer on the surface of the film. The hydrophobicity of octadecyltrichlorosilane (OTS)-treated film was found to be preserved even after 100 days.