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。     

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.     

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.     

Plasma treatment of polydimethylsiloxane

Plasma treatment of silicone surfaces is a useful way of increasing wettability to improve adhesion and a first step in producing various organosilicon thin-film composites. Despite numerous earlier studies, there is no consensus on the effect of plasma treatment nor on the mechanism of the subsequent hydrophobic recovery. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to study the effect of plasma treatments of polydimethylsiloxane elastomer using four different plasma gases: argon, helium, oxygen, and nitrogen. In each case, the surface was oxidized to produce a thin, wettable, brittle silica-like layer. These surfaces progressively recover their hydrophobicity by diffusion of untreated polymer chains through cracks in the treated layer. Angle-resolved XPS detected the untreated, diffused layer and SEM revealed the common occurrence of cracks in the treated layer, although conditions could be found for each gas where the surface becomes completely wettable by water but is free from cracks.     

Kinetics of Adhesion Interaction of Polyolefins with Metals under Conditions of Contact Thermooxidation. 1. Oxidation Kinetics and Change of Peel Strength

The kinetics of contact thermooxidation (CTO) of a polyethylene layer on a steel surface in connection with the change of peel strength (A) under conditions of free access of oxygen through the polymeric layer was studied. The CTO parameters (oxygen uptake, carbon dioxide evolution, change of carbonyl group content, change of the weight of the layer) and the change in the values of A were found to be kinetically interrelated. The dependence of the rate of change of individual CTO parameters and the magnitude of A on the thickness of the layer being oxidized and temperature can be described by a simple equation. The analysis of constants in this equation allows one to estimate the catalytic effect of the substrate in CTO. The dependence of experimental determined A values on contact time can be satisfactorily described by a simple expression based on the assumption that the magnitudes of A are controlled by two main competitive processes: the accumulation of oxygen-containing groups and oxidative cross-linking, causing the increase of A values, and reactions of oxidative destruction causing the decrease in A.     

Kinetics of Adhesion Interaction of Polyolefins with Metals under Conditions of Contact Thermooxidation. 1. Oxidation Kinetics and Change of Peel Strength

The kinetics of contact thermooxidation (CTO) of a polyethylene layer on a steel surface in connection with the change of peel strength (A) under conditions of free access of oxygen through the polymeric layer was studied. The CTO parameters (oxygen uptake, carbon dioxide evolution, change of carbonyl group content, change of the weight of the layer) and the change in the values of A were found to be kinetically interrelated. The dependence of the rate of change of individual CTO parameters and the magnitude of A on the thickness of the layer being oxidized and temperature can be described by a simple equation. The analysis of constants in this equation allows one to estimate the catalytic effect of the substrate in CTO. The dependence of experimental determined A values on contact time can be satisfactorily described by a simple expression based on the assumption that the magnitudes of A are controlled by two main competitive processes: the accumulation of oxygen-containing groups and oxidative cross-linking, causing the increase of A values, and reactions of oxidative destruction causing the decrease in A.     

Measurement of Adhesion Between Carbon Fibers and Bismaleimide Resins

The adhesion between carbon fibers and bismaleimide resins was evaluated using the microbond single fiber pull-out test. A commercially-available, methylene dianiline-based bismaleimide resin and a novel phosphorus-containing bismaleimide were tested with as-received and plasma-treated polyacrylonitrile-based carbon fibers. The surface chemical composition, topography, tensile strength, and surface free energy of the carbon fibers were studied using x-ray photoelectron spectroscopy, scanning electron microscopy, single fiber tensile tests, and dynamic contact angle analysis. The carbon fiber-bismaleimide adhesion improved when the carbon fiber received an oxidative commercial surface treatment or was exposed to an air or ammonia plasma prior to bonding.     

Measurement of Adhesion Between Carbon Fibers and Bismaleimide Resins

The adhesion between carbon fibers and bismaleimide resins was evaluated using the microbond single fiber pull-out test. A commercially-available, methylene dianiline-based bismaleimide resin and a novel phosphorus-containing bismaleimide were tested with as-received and plasma-treated polyacrylonitrile-based carbon fibers. The surface chemical composition, topography, tensile strength, and surface free energy of the carbon fibers were studied using x-ray photoelectron spectroscopy, scanning electron microscopy, single fiber tensile tests, and dynamic contact angle analysis. The carbon fiber-bismaleimide adhesion improved when the carbon fiber received an oxidative commercial surface treatment or was exposed to an air or ammonia plasma prior to bonding.     

Film Structure and Adhesion

Paint films although attached to a substrate on one side only may be subjected to stresses, comparable to those in structural adhesives. These stresses result from shrinkage during film formation and subsequent ageing, mechanical strains, relative thermal movements of film and substrate and from osmotic pressure due to soluble material under or within the film. The adhesive strength required to prevent detachment varies from very little for weak, highly porous coatings to 10,000 lb/in² for tough coatings of high elastic modulus. Generally, adhesive strength both to the substrate and between coats in a paint system must exceed cohesive strength, under the conditions when failure is likely to develop. Dispersion and other forces, such as hydrogen bridging, between coatings and clean metal substrates should suffice to ensure adhesion but most practical surfaces carry contaminants, which interfere with wetting and intimacy of contact. Solvents and other low molecular weight components may also provide a weak interfacial layer, at least for a period after application. Modification of polymer structure to improve contaminant displacement and to increase polymer/substrate interaction forces, for example by the introduction of polar substituent or end groups will be discussed and potentialities of adhesion-promoting surface treatments reviewed.     

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.     

Adhesion and Surface Analysis

In the last 25 years, surface sensitive analytical techniques have made a major contribution to our understanding of adhesion phenomena and problems. There are several areas where these techniques have provided important information including the identification of failure modes, the chemistry of a substrate before and after pretreatments, the stability of surfaces and interfaces, the identification of surface contaminants, the interaction across an interface and the nature of interphases. X-ray photoelectron spectroscopy (XPS or ESCA), Auger electron spectroscopy (AES) and static secondary ion mass spectrometry (SSIMS) have proved to be especially useful. Many examples of the usefulness of these techniques are given.     

Adhesion to Plasma-Modified LaRC-TPI II. Effect of Plasma Treatment on Peel Strength

LaRC-TPI, an aromatic thermoplastic polyimide, was exposed to oxygen, argon and ammonia plasmas as pretreatments for adhesive bonding. A 180[ddot] peel test with an acrylate-based pressure sensitive adhesive tape as an adherend was utilized to study the interactions of the plasma-treated polyimide surface with another polymeric material. The peel strengths of the pressure sensitive adhesive tape on the plasma-treated LaRC-TPI fell below the level of the non-treated controls, regardless of the plasma treatment used. Failure surface analysis by XPS revealed the presence of polyimide on the pressure sensitive adhesive failure surface, indicating failure in the plane of a weak boundary layer created by plasma treatment. The removal of the weak boundary layer by a solvent rinse restored the peel strength to the level of the control. Comparison with tape adhesion peel strengths of oxygen plasma-treated high density polyethylene showed that the physical condition of a polymer surface following plasma treatment plays an important role in determining the level of adhesion which can be achieved.     

Interrelation of Scanning Electron Micrographs with Flexural Behavior of Ferrite and Nano-Barium Titanate Reinforced Poly-Ether-Ether-Ketone (PEEK) Composites

ABSTRACT

The flexural behavior of ferrite filled poly-ether-ether-ketone (PEEK) composites, with and without reinforcement of nano-barium titanate, was studied and was corroborated through scanning electron microscopy (SEM). In this study, ferrite filled PEEK, and ferrite and nano-barium titanate reinforced PEEK composites were prepared. Ferrite filled PEEK composites showed reduction in flexural strength and increase in flexural modulus with the increase in ferrite content, whereas, with the reinforcement of nano-barium titanate, flexural strength increased and flexural modulus decreased at similar ferrite content. The SEM micrographs corroborated well with flexural behavior, as ferrite particles and smooth topographic surfaces of brittle fracture were evident in the samples having higher ferrite content in ferrite filled PEEK composites, whereas, typical yield pattern of crust and trough on fractured topographic surfaces of ferrite and nano-barium titanate, reinforced PEEK composites, was visible.     

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.     

Hot Melt Adhesive Model: Interfacial Adhesion and Polymer/Tackifier/Wax Interactions

This work continues our study of the hot melt adhesive (HMA) model published earlier [1]. This HMA model was developed based on the pressure sensitive adhesive (PSA) tack model established previously [2]:

P = P₀BD (1)

where P is the adhesive bond strength, P₀ is the interfacial (intrinsic) adhesion term, B is the bonding term and D is the debonding term. The previous paper [1] describes the B and D terms in detail. However, only a brief discussion of the P₀ term was given. The present paper will provide a more in-depth but still rather qualitative study of the P₀ term within the framework of the adhesion model described in Eq. (1). HMAs studied are ethylene/vinyl acetate copolymer (EVA)/tackifier/wax blends. Substrates studied are untreated and corona-discharge-treated polyolefins such as polypropylene (PP) and polyethylene (PE). First, it has been found that the tackifier surface tension could be roughly correlated with one of its thermodynamic parameters: the solubility parameter dispersion component. Secondly, except for EVA/tackifier binary blends, the compatibility of any two of these three components, the EVA polymer, the tackifier and the wax, in a HMA can be estimated from surface tension and X-ray photoelectron spectroscopy (XPS) measurements. Thirdly, based on the study of the EVA/mixed aliphatic-aromatic tackifier/wax model HMA system, it has been observed that the HMA/polyolefin substrate interfacial composition depends on the wax/substrate compatibility. The cause of an inferior peel strength of a HMA containing a high wax content to a polyolefin substrate is possibly due to the formation of a weak boundary layer (WBL) of wax at the interface and/or low dissipative properties of the HMA.

Also, the relationship between EVA/tackifier/wax interactions and HMA peel strength will be discussed. A correlation between the EVA/tackifier compatibility measured by cloud point and viscoelastic experiments to the debonding term, D, in Eq. (1) has been found.     

Modification of Conductive Polymer for Polymeric Anodes of Flexible Organic Light-Emitting Diodes

A conductive polymer, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), was modified with dimethyl sulfoxide (DMSO) in solution state, together with sub-sequential thermal treatment of its spin-coated film. The electrical conductivity increased by more than three orders of magnitude improvement was achieved. The mechanism for the conductivity improvement was studied at nanoscale by particle size analysis, field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). Smaller particle size was observed, resulting in larger contact area and better electrical conductive connections. Connection of conductive PEDOT increased on the surface of the PEDOT:PSS particles, which promoted high conductivity. Flexible anodes based on the modified PEDOT:PSS were fabricated. Flexible organic light-emitting diodes (FOLED) based the polymeric anodes have a comparable performance to those on indium–tin–oxide (ITO) anodes.     

Effects of surface modification by remote hydrogen plasma on adhesion in poly(tetrafluoroethylene)/copper composites

Poly(tetrafluoroethylene) (PTFE) sheet was modified with the remote hydrogen plasma, and the effect of the modification on adhesion between the PTFE sheet and copper metal was investigated. The remote hydrogen plasma was able to make PTFE surfaces hydrophilic without etching. In the modification process, defluorination and oxidation occurred on the PTFE surface. Reactivity of defluorination was 25% (estimated from the concentration of CF₂ component) −39% (estimated from the F/C atom ratio). Surface modification of PTFE surface by remote hydrogen plasma contributed to the adhesion between PTFE and copper metal. Peel strength was improved from 7.5 to 92 mN/5 mm by surface modification by a factor of 12. Failure of the PTFE/copper adhesive joint occurred at the interface between the PTFE and copper metal layers, rather than in the inner layer of the PTFE polymer or copper metal layers. Remote hydrogen plasma treatment is a preferable pretreatment of PTFE surface for the fabrication of PTFE and copper metal composites. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2191–2200, 1999     

Decomposition of soot by ozone and nitrogen oxides

In this work the decomposition of soot by NO _x and ozone at low temperatures was investigated. The assumption of a 3-stage process of the soot decomposition by ozone was proved using XPS (X-ray photoelectron spectroscopy). The supposed decomposition of soot by NO _x was found to be secondary at least in the temperature range of about 160 °C.