强碱-阳极氧化法处理Ti片制备TiO_2薄膜的研究

本文利用强碱-阳极氧化法对钛片进行改性,制备TiO2薄膜;用扫描电镜（SEM）、X射线光电子能谱（XPS）考察了不同电解液浓度下氧化电压对TiO2氧化膜形貌及组成的影响。结果发现,在本实验条件下,该法制得的氧化膜是由三种钛氧化物组成的,主要成分是TiO2,此外还有低价钛氧化物Ti2O3及TiO;氧化电压的不同会对薄膜形貌产生重要的影响,当氧化电压较高时,氧化膜的厚度比较厚且致密;钛表面生成氧化膜大致过程可概括为：Ti→TiO→Ti2O3→TiO2,其中TiO转为为TiO2的几率依靠电势的大小及氧化时间的长短。     

Effect of ultrasound irradiation on polymeric microfiltration membranes

The effect of powerful ultrasound (US) at a frequency of 40 kHz and an intensity of 1.43-3.57 W·cm⁻² on polymeric microfiltration membranes was evaluated. Four different polymers including polyethersulfone, nylon 6(N₆), the mixed ester of cellulose nitrate with cellulose acetate (CN-CA) and polyvinylidenefluoride (PVDF), with an average pore diameter of 0.45 μm, were investigated. The evolution of the polymeric structure exposed to US was followed by the measurements of the water flux and the rejection rate of 1 wt% isolated soybean protein. The result shows that important variations occur on some membranes after irradiation. In addition, microscopic photos of irradiated membranes by field emission scanning electron microscopy were taken in order to directly observe the change on membrane surface. It has been shown that, over the four materials tested, only the PVDF presents no significant change in the measured parameters with increase of the duration at the low intensity of ultrasound irradiation, whereas the others are affected by ultrasound treatment.     

Structural Rietveld refinement and magnetic features of prosademium (Pr) doped Cu nanocrystalline spinel ferrites

Pr doped spinel nanoferrites having following composition Cu Pr_x Fe_2-xO₄ (x?=?0, 0.25, 0.50, 0.75, 1.00) were synthesized using sol-gel route. Prosademium (Pr) which is a rare earth metal was doped to tailor the properties of the Cu spinel nanoferrites. Characterization tools such as FTIR, XRD, FESEM and VSM were employed to investigate the phase, absorption bands, structure, microstructure and magnetic properties. FTIR was used to see the absorption bands and force constants of the Pr doped Cu spinel nanoferrites. Crystallite size, lattice parameters, cell volume and micro strains were determined from XRD data. Bulk density, X-ray density and porosity of the Pr doped Cu spinel nanoferrites were also calculated. Rietveld refinement was applied to investigate the detailed structural parameters of the Pr doped Cu spinel nanoferrites. Unit cell software based on regression diagnostics was also used to determine the structural factors of the prepared nanoferrites. It was noticed that Cu nanoferrite showed the single-phase cubic structure whereas the Pr doped Cu ferrite depicted the orthorhombic structure respectively. FESEM show large amount of agglomerations at x?=?0.00 whereas irregular shape of the particles confirms the nanosized of ferrites as well. Magnetic properties were determined from VSM which elaborated the remanence, coercivity, saturation magnetization, anisotropy constant (K), initial permeability, Bohr magneton and YK (Yafet and Kittel) angles. Magnetic saturation, coercivity, remanence and anisotropy constant were decreased with Pr concentration in Cu spinel ferrite. However, YK angles were increased with Pr doping in Cu spinel nanoferrites. Microwave frequency response was evaluated which confirm the use of these Pr doped Cu spinel nanoferrites in the range of 5.2?Ghz–9.5?GHz respectively. The properties of these Pr doped Cu spinel nanoferrites suggested their used for microwave devices, memory devices and recording media applications.     

Experimental determination of solidified lithium disilicate crystal bandgap energy using EELS and XPS

Lithium disilicate (LS2) has been a crucial parent composition for glass-ceramics since the 1950s because of its excellent chemical and physical durability. In addition, a wide range of electrical properties can be obtained by changing the composition and crystallinity. Bandgap energy is one of the critical electrical properties for designing new lithium silicate-based materials. In this study, the bandgap energy of a synthesized LS2 crystal is evaluated using electron energy-loss spectroscopy and X-ray photoelectron spectroscopy. These two techniques unambiguously establish that the bandgap energy of LS2 is 7.7-7.8 eV, which is in the vacuum ultraviolet region. This confirms the insulating nature of the LS2 crystal.     

On the nature of the active state of silver during catalytic oxidation of methanol

Under the applied high reaction temperatures (900 K) the Ag surface is restructured and a tightly held oxygen species is formed on the surface (O) apart from O atoms dissolved in the bulk (O). Methanol oxidation to formaldehyde proceeds through this O species as demonstrated by application of a variety of spectroscopic techniques.     

Identification of inductive behavior for polyaniline via electrochemical impedance spectroscopy

Polyaniline (PANI) film electrodeposited in HCl medium using cyclic voltammetry (CV) with an upper potential limit of 0.90 V, exhibited an inductive behavior. PANI films deposited with different conditions were subjected to various applied potentials and the impedance characteristics were recorded through electrochemical impedance spectroscopy (EIS). The impedance results clearly reveal the existence of inductive behavior to PANI. Inductive behavior was observed for PANI films deposited with conditions which favor benzoquinone/hydroquinone (BQ/HQ) formation and further evidenced by X-ray photoelectron spectroscopy (XPS). A comparative analysis of the EIS and XPS results of PANI films prepared under similar conditions with the upper potential limits of 0.75 and 0.90 V, respectively, clearly documented that the presence of BQ/HQ, the degradation product of PANI, formed during the electrochemical polymerization at the upper potential limits causes inductive behavior to PANI.     

The Effect of Conditioning on Adhesion to Human Dentin

The effect of conditioning dentin was investigated using ethyleneglycol bis(aminoethylether) tetraacetic acid (EGTA) and three proprietary agents containing ethylenediamine tetraacetic acid (EDTA), maleic acid and dipentaerythritol pentaacrylate phsophoric acid ester (PENTA). Ground dentin was treated with EGTA or one of the three proprietary agents. After adhering composite resin to treated surfaces, the shear bond strength (SBS) was determined with and without thermal stress. Scanning electron and atomic force microscopies were used to assess morphological effects of each of the agents, while low resolution X-ray photoelectron spectroscopy (XPS) was employed to evaluate elemental changes due to treatment. Mean bond strength was greatest for the PENTA-conditioned surfaces. EDTA and maleic acid demineralized the dentin surface while the agent containing PENTA produced an adherent surface film. The XPS survey showed a reduction in Ca and an increase in N for agents containing EGTA, EDTA and maleic acid, while a simultaneous reduction in both these species was observed for PENTA. EGTA did not improve adhesion for systems which were based on smear layer removal and substrate demineralization. For the PENTA-based system, which relied on the development of a molecular overlayer, EGTA degraded bond strength.     

The Effect of Conditioning on Adhesion to Human Dentin

The effect of conditioning dentin was investigated using ethyleneglycol bis(aminoethylether) tetraacetic acid (EGTA) and three proprietary agents containing ethylenediamine tetraacetic acid (EDTA), maleic acid and dipentaerythritol pentaacrylate phsophoric acid ester (PENTA). Ground dentin was treated with EGTA or one of the three proprietary agents. After adhering composite resin to treated surfaces, the shear bond strength (SBS) was determined with and without thermal stress. Scanning electron and atomic force microscopies were used to assess morphological effects of each of the agents, while low resolution X-ray photoelectron spectroscopy (XPS) was employed to evaluate elemental changes due to treatment. Mean bond strength was greatest for the PENTA-conditioned surfaces. EDTA and maleic acid demineralized the dentin surface while the agent containing PENTA produced an adherent surface film. The XPS survey showed a reduction in Ca and an increase in N for agents containing EGTA, EDTA and maleic acid, while a simultaneous reduction in both these species was observed for PENTA. EGTA did not improve adhesion for systems which were based on smear layer removal and substrate demineralization. For the PENTA-based system, which relied on the development of a molecular overlayer, EGTA degraded bond strength.     

Adhesion Between Plasma-Treated Polypropylene Films and Thin Aluminum Films

Polypropylene (PP) film was treated with radio-frequency-induced oxygen plasma, followed by the vacuum deposition of aluminum (Al) thin film, and the peel strength of the Al deposited PP film (Al/PP) was examined. The peel strength of plasma-treated PP film varied widely in the range of 6.7 to 157 N/m depending upon the plasma treatment conditions, whereas that of the untreated PP was 5.2 N/m. The peel strength was minimized at oxygen pressure near 13.3 Pa (0.1 Torr), and decreased with increasing discharge power. The peel strength rapidly increased at the initial stage of plasma treatment (∼ several seconds), decreased at the second stage, and slightly increased again at the third stage. A good agreement was found between the peel strength of Al/PP and the amounts of oxygen introduced onto the PP surface at the initial stage. A short-time treatment was very effective to improve the adhesion of Al/PP. At the end of the second stage, a large amount of carbon was detected by XPS on the Al layer of the peeled interface of Al/PP, which gave a minimum peel strength. Cohesive failure of PP film might have occurred. SEM photograph showed that PP surface was etched by oxygen plasma at the thrid stage. These peel behaviors of Al/PP were explained by the chemical and physical changes of the PP surface caused by oxygen plasma treatment: (1) introduction of O-functional groups onto the PP surface at the initial stage, (2) formation of weak booundary layers resulting from the partial scission of PP molecules at the second stage, and (3) plasma etching of the PP surface at the third stage.     

Adhesion Studies of Fluoropolymers

A comparative study of the treatment of polytetrafluoroethylene (PTFE) and poly(vinyl fluoride) (PVF) with “Tetra-Etch” has been carried out. The treatment of PTFE resulted in extensive changes in surface chemistry and topography, whereas with PVF there was no significant change in topography and the chemical changes were much less marked. However, treatment of both polymers resulted in large increases in bond strength.

Multiple bonding experiments in which samples are repeatedly fractured and re-bonded were carried out with untreated PTFE and PVF. These resulted in moderate increases in bond strength with PTFE and large increases with PVF. The results indicate that weak boundary layer (WBL) removal is a key element in adhesion improvement by “Tetra-Etch” on PVF. With PTFE, WBL removal also improves adhesion, but the chemical and/or topographical changes introduced by the “Tetra-Etch” are required for optimum performance.     

Adhesion Studies of Fluoropolymers

A comparative study of the treatment of polytetrafluoroethylene (PTFE) and poly(vinyl fluoride) (PVF) with “Tetra-Etch” has been carried out. The treatment of PTFE resulted in extensive changes in surface chemistry and topography, whereas with PVF there was no significant change in topography and the chemical changes were much less marked. However, treatment of both polymers resulted in large increases in bond strength.

Multiple bonding experiments in which samples are repeatedly fractured and re-bonded were carried out with untreated PTFE and PVF. These resulted in moderate increases in bond strength with PTFE and large increases with PVF. The results indicate that weak boundary layer (WBL) removal is a key element in adhesion improvement by “Tetra-Etch” on PVF. With PTFE, WBL removal also improves adhesion, but the chemical and/or topographical changes introduced by the “Tetra-Etch” are required for optimum performance.     

Self-Assembled Monolayers of Vinyltriethoxysilane and Vinyltrichlorosilane Deposited on Silicon Dioxide Surfaces

Abstract

This study was aimed at deposition of self-assembled monolayers (SAMs) using vinyltriethoxysilane (VTES) and vinyltrichlorosilane (VTCS) molecules chemisorbed on silicon dioxide surfaces. The kinetics of SAM formation on planar glass substrates and silicon wafers was characterized by contact angle measurements. The surface free energy and its dispersion and polar components enabled to estimate the time of immersion required to deposit compact SAMs. Adsorption of organosilane molecules as a function of immersion time was characterized by X-ray photoelectron spectroscopy. The SAM thickness was evaluated by spectroscopic ellipsometry. Surface topography of deposited layers was investigated by atomic force microscopy (AFM). The VTCS/glass combination exhibited the fastest kinetics but the deposit was not uniform and included local agglomerates. The hydrophobic vinyl groups at deposit surface resulted in a surface free energy of 32 mJ/m².     

Atmospheric Plasma Surface Activation of Poly(Ethylene Terephthalate) Film for Roll-To-Roll Application of Transparent Conductive Coating

An effective surface activation is crucial for high-speed roll-to-roll coating of functional films for printed electronics applications. In this article, we report a study of surface treatment of three types of poly(ethylene terephthalate) (PET) films by an argon/oxygen atmospheric pressure plasma and an ambient air atmospheric pressure plasma to obtain the required wettability for subsequent slot die coating of transparent conductive polymer layer using a poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) ink. Prior to plasma treatment, the PET surfaces, which differ in manufacturing process of their preparation, were characterized by X-ray photoelectron spectroscopy. The surface changes after the plasma treatments were characterized by water contact angle measurement and atomic force microscopy. We found that the water contact angles of the three types of untreated PET surfaces were 80.9°, 75.9°, and 66.3°, respectively, and the water contact angles after argon/oxygen plasma treatment at treatment speed of 1 m · min^?1 decreased to 36.2°, 31.9°, and 40.9°, respectively. These conditions were stable from 1 up to 4 days, which are longer than reported values of 15–60 min and sufficient for roll-to-roll coating processes.     

A facile route for the synthesis of mechanically strong MWCNTs/NDs nanobifiller filled polyacrylate composites

ABSTRACT

We present here the synthesis of novel Nano-Bifiller filled composites with extremely promising material properties. To achieve this goal, initially, poly (methyl methacrylate) (PMMA) and poly (ethylene glycol) (PEG) blend were formed. Later, the matrix was reinforced with purified carbon (P-CNT), amino modified carbon nanotube (PDA-CNT) and amino modified carbon nanotube nanodiamond (PDA-CNT-ND). In this way, three series of nanocomposites, i.e. PMMA/PEG/P-CNT, PMMA/PEG/PDA-CNT, and PMMA/PEG/PDA-CNT-ND were synthesized with varying P-CNT, PDA-CNT and PDA-CNT-ND loading (i.e., 1 wt.%, 3 wt.%, 5 wt.%, 10 wt.%, 30 wt.% and 50 wt.%) by a solution blending route. The reinforcement and loading effect of these three types of nanofillers on the matrix was studied. Studies were performed using Fourier transform infrared spectroscopy (FTIR), mechanical testing, thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM) and X-ray powder diffraction (XRD) to explore the structural, morphological, mechanical and thermal properties of nanocomposites prepared. The inter-association of poly (methyl methacrylate) and poly (ethylene glycol) (PMMA/PEG) due to hydrogen bonding and covalent attachment of matrix to the sidewalls of nanotubes was confirmed by FTIR spectra. The experimental results showed that a loading of 5 wt. % filler in matrix produced a tensile strength and modulus of 26.4 (MPa) and 1255.75 (MPa) in PMMA/PEG/P-CNT nanocomposites, while 28.8 (MPa) and 1411.04 (MPa) in PMMA/PEG/PDA-CNT nanocomposites and 29.4 (MPa) and 1419.41 (MPa) in PMMA/PEG/PDA-CNT-ND nanocomposites as compared to neat PMMA which has tensile strength and modulus of 21.79 (MPa) and 1083.84 (MPa) respectively. These results depict that bifiller nanocomposites showed better mechanical properties as compared to pristine and amine functionalized MWCNT. Scanning electron microscopy revealed granular morphology with few protruding out carbon nanotubes. Thermal stability of PMMA/PEG/PDA-CNT-ND nanocomposites was found higher than PMMA/PEG/PDA-CNT and PMMA/PEG/P-CNT nanocomposites. The T_o (369^°C) and T₁₀ (515^°C) values for PMMA/PEG/PDA-CNT-ND composites was higher than PMMA/PEG/PDA-CNT [T_o (354^°C) and T₁₀ (420^°C)] and PMMA/PEG/P-CNT composites [T_o (312^°C) and T₁₀ (390^°C)]. These results suggest that the bifiller nanocomposites were thermally more stable. The XRD spectra showed a pronounced XRD peak at 25.9^°, corresponding to (002) reflection of the nanotubes indicating that MWCNT structure was not destroyed during composite formation. The peak appeared at 75.3^° were indexed to (220) reflections due to nanodiamond structure.     

Formation of a liquid film of AgNO3 on a silver surface

The behavior of a AgNO₃/Ag₂O/Ag “sandwich” upon heating in vacuum was studied by in situ X‐ray photoelectron spectroscopy (XPS) and ex situ scanning electron microscopy (SEM). The AgNO₃/Ag₂O/Ag “sandwich” was prepared by exposure of a silver foil to a NO : O₂ mixture. The upper layer of the “sandwich” consists of AgNO₃ crystals of a mean size between 0.1 and 0.4 μm. Heating at 550 K in vacuum results in melting of the AgNO₃ crystals. A liquid film of AgNO₃, readily wetting the silver, covers the surface. Cooling below the melting point of AgNO₃ leads to the agglomeration of silver nitrate to long islands with a size reaching a few tens of micrometers (μm). The possible effects of AgNO₃ liquid‐phase formation on surface processes are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

The mechanism for the colour change of iron chromium black pigments in glazes through transmission electron microscopy techniques

Black iron-chromium (Fe-Cr) bearing oxide pigments are generally utilised as effective colourants in a wide variety of applications. However, in the case of their use within ZnO-containing glazes, they yield an undesirable brown colour instead of expected black colour. In order to understand the colour change in this system, we report the use of focused ion beam (FIB) sample preparation technique followed by the use of analytical transmission electron microscopy (TEM) characterisation techniques. According to the results, the formation of a reaction layer between the pigment and glaze was identified with an average composition of Zn_0.48Fe_0.79Cr_1.32O₄. Additionally, the valance of Fe was determined as 3+ in the pigment grain, whereas 2+ in the reaction layer and the glaze, respectively. Therefore, it was concluded that the colour change is occurring as result of the valence variation of Fe, the formation of Zn_0.48Fe_0.79Cr_1.32O₄ compound and the outward diffusion of Fe into the glaze.     

Conductive polymer composites with segregated structures

Conductive polymer composites (CPCs) have generated significant academic and industrial interest for several decades. Unfortunately, ordinary CPCs with random conductive networks generally require high conductive filler loadings at the insulator/conductor transition, requiring complex processing and exhibiting inferior mechanical properties and low economic affordability. Segregated CPC (s-CPC) contains conductive fillers that are segregated in the perimeters of the polymeric granules instead of being randomly distributed throughout the bulk CPC material; these materials are overwhelmingly superior compared to normal CPCs. For example, the s-CPC materials have an ultralow percolation concentration (0.005–0.1 vol%), superior electrical conductivity (up to 10⁶ S/m), and reasonable electromagnetic interference (EMI) shielding effectiveness (above 20 dB) at low filler loadings. Therefore, considerable progress has been achieved with s-CPCs, including high-performance anti-static, EMI shielding and sensing materials. Currently, however, few systematic reviews summarizing these advances with s-CPCs are available. To understand and efficiently harness the abilities of s-CPCs, we attempted to review the major advances available in the literature. This review begins with a concise and general background on the morphology and fabrication methods of s-CPCs. Next, we investigate the ultralow percolation behaviors of and the elements exerting a relevant influence (e.g., conductive filler type, host polymers, dispersion methods, etc.) on s-CPCs. Moreover, we also briefly discussed the latest advances in the mechanical, sensing, thermoelectric and EMI shielding properties of the s-CPCs. Finally, an overview of the current challenges and tasks of s-CPC materials is provided to guide the future development of these promising materials.     

Butanol isomer separation using polyamide-imide/CD mixed matrix membranes via pervaporation

Mixed matrix membranes (MMMs) comprising polyamide-imide (PAI) and α-, β- or γ-cyclodextrin (CD) have been investigated experimentally and computationally for isomeric n-butanol/tert-butanol (n-BuOH/t-BuOH) separation via pervaporation. Consistent with molecular simulation, experimental results show that the CD inclusion ability and butanol discrimination ability are dependent on both CD cavity size and butanol molecular size. The PAI membrane incorporated with α-CD has the smallest cavity and has the highest discrimination ability for the n-BuOH/t-BuOH pair but with a low butanol flux. The mixed matrix membrane embedded with γ-CD has the lowest selectivity and the highest flux. The PAI/β-CD membrane has a comparable selectivity and flux, and exhibits preferential sorption and diffusion selectivity toward n-BuOH. A maximum separation factor of 1.53 with a corresponding flux of 4.4 g/m² h are obtained at an optimal β-CD loading of 15 wt%. Further increments in the CD content eventually lead to a decrease in separation performance because of CD agglomeration and severe phase separation. To better understand the influence of CD on the separation performance of mixed matrix membranes, SEM, FTIR and XRD have been employed for membrane characterizations. The effect of n-butanol/t-butanol ratio in the feed composition has also been studied. It is found that both flux and separation factor decrease with increasing n-butanol content in the feed. The decline is attributed to the change in total vapor pressure at the upstream and the mutual drag effect of isomeric butanol molecules.     

Complex macromolecular architecture design via cyclodextrin host/guest complexes

The design of complex macromolecular architectures has driven macromolecular engineering over the past decades. The introduction of supramolecular chemistry into polymer chemistry provides novel opportunities for the generation of macromolecular architecture with specific functions. Cyclodextrins are attractive design elements as they form supramolecular inclusion complexes with hydrophobic guest molecules in aqueous solution affording the possibility to combine a large variety of building blocks to form novel macromolecular architectures. In the present critical review, the design of a broad range of macromolecular architectures driven by cyclodextrin host/guest chemistry is discussed, including supramolecular block copolymers, polymer brushes, star and branched polymers.