Titanium carbonitride films on cemented carbide cutting tool prepared by pulsed high energy density plasma

Hard films prepared by pulsed high energy density plasma (PHEDP) are characterized by high film/substrate adhesive strength, and high wear resistance. Titanium carbonitride (TiCN) films were deposited onto YG11C (ISO G20) cemented carbide cutting tool substrates by PHEDP at room temperature. XRD, XPS, SEM, AES, etc. were adopted to analyze the phases (elements) composition, microstructure and the interface of the films, respectively. The results show that, the uniform dense films are composed of grains ranging from 70 to 90 nm. According to the AES result, there is a broad transition layer between the film and the substrate, due to the ion implantation effect of the PHEDP. The transition layer is favorable for the film/substrate adhesion.     

Properties of polystyrene-poly(methylmethacrylate) random and diblock copolymers in dilute and semidilute solutions

Solution properties for random and diblock copolymers of polystyrene (PS) and poly(methyl methacrylate) (PMMA) have been measured by dynamic and total intensity light scattering in solvents of differing quality. The results are compared with the corresponding properties for PS and PMMA homopolymers of similar molecular weight, in order to determine if interactions between unlike monomers are significant. The hydrodynamic radius (R_h) and diffusion second virial coefficient (k_d) for the random copolymer are found to be larger than the corresponding values for the homopolymers in a solvent which is near-theta for the two homopolymers, whereas no such effect is observed for the block copolymer. This suggests that most intrachain interactions occur a relatively short distance along the chain backbone. In a mutual good solvent R_h and k_d of the random copolymer are comparable to the average of the values for the homopolymers, indicating that in a good solvent monomer/solvent interactions dominate over monomer/monomer interactions. For an isolated diblock copolymer in a mutual good solvent, there is no evidence that interactions between unlike monomers lead to additional expansion of the entire molecule, as measured by R_h, nor expansion of the individual blocks as probed by light scattering with one block optically masked. However, at low but finite concentration there is evidence (the coefficients of the binary interaction terms in the viscosity and the mutual diffusion coefficient, and the second and third virial coefficients) that a weak ordering effect may exist in block copolymer solutions, far from the conditions where microphase separation occurs. Finally, measurements of ternary polymer-polymer-solvent solutions show no dependence on monomer composition or monomer distribution for the tracer diffusion of probe PS-PMMA copolymers in a PMMA/toluene matrix. This indicate that the frictional interaction is largely unaffected by interactions between unlike monomers. However, there is evidence that the thermodynamic interaction is more unfavorable between a random copolymer and the homopolymer matrix than between a diblock and the matrix. © 1994 John Wiley & Sons, Inc.     

Dialdehyde starch‐crosslinked chitosan films and their antimicrobial effects

For improved mechanical and water‐swelling properties of chitosan films, a series of transparent films were prepared with dialdehyde starch as a crosslinking agent. Fourier transform infrared and X‐ray analysis results demonstrated that the formation of Schiff's base disturbed the crystallization of chitosan. The mechanical properties and water‐swelling properties of the films were significantly improved. The best values of the tensile strength and breaking elongation were 113.1 MPa and 27.0%, respectively, when the dialdehyde starch content was 5%. All the crosslinked films still retained obvious antimicrobial effects toward S. aureus and E. coli, and they showed potential for biomedical applications. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 993–997, 2003     

Coupled lubrication and Stokes flow finite elements

A method is developed for performing a local reduction of the governing physics for fluid problems with domains that contain a combination of narrow and non‐narrow regions, and the computational accuracy and performance of the method are measured. In the narrow regions of the domain, where the fluid is assumed to have no inertia and the domain height and curvature are assumed small, lubrication, or Reynolds, theory is used locally to reduce the two‐dimensional Navier–Stokes equations to the one‐dimensional Reynolds equation while retaining a high degree of accuracy in the overall solution. The Reynolds equation is coupled to the governing momentum and mass equations of the non‐narrow region with boundary conditions on the mass and momentum flux. The localized reduction technique, termed ‘stitching,’ is demonstrated on Stokes flow for various geometries of the hydrodynamic journal bearing—a non‐trivial test problem for which a known analytical solution is available. The computational advantage of the coupled Stokes–Reynolds method is illustrated on an industrially applicable fully‐flooded deformable‐roll coating example. The examples in this paper are limited to two‐dimensional Stokes flow, but extension to three‐dimensional and Navier–Stokes flow is possible. Copyright © 2003 John Wiley & Sons, Ltd.     

Properties of sol-gel dip-coated zinc oxide thin films

Zinc oxide (ZnO) films were deposited on glass substrates by the sol-gel dip coating method using acrylamide route. The films were characterized by X-ray diffraction studies which indicated wurtzite structure. Optical absorption measurements indicated band gap in the range 3.17-3.32 eV. XPS studies indicated the formation of ZnO. The resistivity of the films were in the range 1000-10,000 ohm cm.     

Thickness dependence of free‐standing thin films

Below a critical thickness, of about 60 nm, the glass transition temperature of polystyrene (PS) films decreases with film thickness, as demonstrated using free‐standing films. A geometrical model is developed here describing this phenomenon in the case of ideal (Gaussian) chains. This model, which can be considered as an application of the free volume model, assumes that the decrease of the glass transition temperature from thick to ultrathin films is due to the modification of the interpenetration between neighboring chains. The theoretical curve deduced from the model is in excellent agreement with the PS experimental results, without using any adjustable parameters. From these results, it can be concluded that new chain motions, usually buried in bulk samples, are expressed by the presence of the surface. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 10–17, 2007     

用电泳技术制备YBCO高温超导厚膜

介绍了电泳技术制备YBCO高温超导厚膜的实验方法和YBCO高温超导厚膜的电学性质测量 ,讨论了在学生小型科研实验或设计实验中开展此实验的学时安排、注意事项和实验内容的扩展 .     

Effect of nonstoichiometry on Raman scattering of VO2 films

We report on Raman scattering of VO2 films prepared by radio frequency magnetron sputtering under different conditions. Our investigations revealed that the dominated Raman peaks shift towards high frequency for both V-rich and O-rich VO2 films, compared with the stoichiometry VO2 films. The experimental evidence is presented and the cause for nonstoichiometry dependence of Raman spectra of VO2 films is discussed.     

Synthesis of side‐chain liquid‐crystalline homopolymers and triblock copolymers with p‐methoxyazobenzene moieties and poly(ethylene glycol) as coil segments by atom transfer radical polymerization and their thermotropic phase behavior

A series of side‐chain liquid‐crystalline (LC) homopolymers of poly[6‐(4‐methoxy‐4′‐oxy‐azobenzene) hexyl methacrylate] with different degrees of polymerization were synthesized by atom transfer radical polymerization (ATRP), which were prepared with a wide range of number‐average molecular weights from 5.1 × 10³ to 20.6 × 10³ with narrow polydispersities of around 1.17. Thermal investigation showed that the homopolymers exhibit two mesophases, a smectic phase, and a nematic phase, and the phase‐transition temperatures of the homopolymers increase clearly with increasing molecular weights. A series of novel LC coil triblock copolymers with narrow polydispersities was synthesized by ATRP, and their thermotropic phase behavior was investigated with differential scanning calorimetry and polarized optical microscopy. The LC coil triblocks were designed to have an LC conformation of poly[6‐(4‐methoxy‐4′‐oxy‐azobenzene) hexyl methacrylate] with a wide range of molecular weights from 3.5 × 10³ to 1.7 × 10⁴ and the coil conformation of poly(ethylene glycol) (PEG) (number‐average molecular weight: 6000 or 12,000) segment. Their characterization was investigated with ¹H NMR, Fourier transform infrared spectra, and gel permeation chromatography. Triblock copolymers exhibited a crystalline phase, a smectic phase, and a nematic phase. The phase‐transition temperatures from the smectic to nematic phase and from the nematic to isotropic phase increased, and the crystallization of PEG depressed with increasing molecular weight of the LC block. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2854–2864, 2003     

Structure and optical properties of lead iodide based two-dimensional perovskite compounds containing fluorophenethylamines

Phenethylammonium-based perovskites, which can be regarded as a semiconductor/insulator multiple quantum well consisting of lead halide semiconductor layers sandwiched between phenethylammonium insulator layers were prepared. To investigate the effects of the electronic state and the orientation of organic insulator layers on the optical properties of layered perovskites, fluorine substituted analogues were also prepared. The structure and optical properties were investigated by the XRD, UV–Vis absorption, and fluorescence measurements. The exciton absorption peak was shifted by the substitution of fluorine atoms in organic ammonium compounds. It became clear that the optical properties of two-dimensional perovskite compounds were controlled by the substitution of fluorine atoms.