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Adhesively bonded titanium alloy joints were prepared through flame-based surface treatment, and their failure behavior and substrate surface properties were investigated. The commercially available ITRO surface treatment technique was applied to Ti-6Al-4 V alloy substrates to modify their surfaces prior to bonding with an epoxy film adhesive. Adhesively bonded single-lap joint specimens were tested under static tensile loading to determine their strength and failure mode. Scanning electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy were employed to observe the morphology and chemistry of the treated titanium alloy surfaces. ITRO treatment significantly increased the strength of the joint specimens. The strength enhancement was probably due to the interactions of the silicon oxide film that was formed on the surface of the titanium alloy substrate with both the adhesive and the substrate. [ABSTRACT FROM AUTHOR]

This paper deals with the interfacial adhesion properties of Ti-6Al-4V alloy substrates, prepared by using different treatment protocols selected on the basis of their different effectiveness, and bonded using a structural, high-strength epoxy adhesive. The alternative pre-bonding treatments were sodium hydroxide anodization and low-pressure-plasma treatment, the effects of which were compared to that of a base preparation via solvent degreasing of the substrates’ surface. The treated surfaces were joined according to standard protocols, and then tested for shear strength. The mechanical results were then correlated to surface characteristics of the substrates such as oxidation state and wettability. Parallel scanning Kelvin-probe measurements allowed us to focus our attention on the possible role of the electrical properties of the substrates. We observed that each treatment entails different behavior of the electrical potential of the surface, which correlates with the mechanical strength of the joints. The results suggest that an evaluation of the surface potential of titanium-alloy substrates might be a promising, indicative supplementary parameter for the evaluation of their pre-bonding surface conditions, allowing correlations with presence/absence of an oxide layer at the resin-substrate interface.

Extensive data reported the influence of the physicochemical properties on the bacterial adhesion in biomaterials, of which surface roughness of titanium (Ti) can dictates methicillin-resistant Staphylococcus aureus (MRSA) adhesion to orthopedic implants. Herein, we investigated the influence of the Yb:YAG laser texturing of titanium-15molybdenum (TiMo-L) surface on the MRSA (ATCC #33591) cells adhesion and viability. The physicochemical properties and antibacterial performance of TiMo-L were compared to samples of laser-irradiated pure titanium (Ti-L). Polished samples (Ti-P and TiMo-P) were used as controls. Laser textured surfaces presented a high degree of hydrophilicity, an irregular-shaped cavity and a typical microstructured pattern, compared to the polished substrates. The laser irradiation reduced the peaks of molybdenum (Mo) in the surface of Ti-15Mo alloy, which is explained, at least in part, by the difference between the melting point of Ti (1.668 ºC) and Mo (2.623 ºC). Laser texturing raised the MRSA cells viability and statistically increased the bacterial adhesion to pure Ti (P < 0.01; Wilcoxon-Signed rank test) and Ti-15Mo alloy (P < 0.001; Paired t test). The TiMo-L surface was significantly less susceptible to MRSA cell adhesion compared to Ti-L substrate (P < 0.001; Paired t test).

Abstract The subject of this paper is the quantitative evaluation of the correlation which exists between the surface characteristics of parts in a titanium alloy, Ti-6Al-4V, and the mechanical strength of the joints, made linking these parts using a structural epoxy adhesive. In particular, the surfaces were prepared by using vacuum plasma as a prebonding treatment with various process gases (air, Ar and O 2). For each of these treatments, tests were performed for the mechanical characterisation of the joints, and surveys on the wettability properties were carried out by using a sessile drop method in order to estimate the surface energy of plasma treated surfaces. The results were related to the morphological and electrical properties of the substrates, defined in parallel through SKPM assessment. Further XPS analyses of their chemical state allowed the evaluation of the effect of vacuum plasma on both contaminant removal and formation of a weak oxide layer. The results obtained highlighted interesting relationships between vacuum plasma surface preparation and mechanical resistance of the bonded joints, as well as synergy between the morphological, electrical and chemical properties present in adhesive phenomena. [ABSTRACT FROM AUTHOR]

This paper presents a study on the effect of surface treatments on the mechanical behavior of adhesively bonded titanium alloy joints. Several different treatments were selected for the preparation of Ti-6Al-4V alloy faying surfaces, and bonded joints were fabricated using surface-treated titanium alloy substrates and a film adhesive. Tensile tests were performed on single-lap specimens to evaluate the joint strength and to assess the failure mode, i.e. cohesive failure, adhesive (interfacial) failure or a mix of both. Contact angle measurements were also carried out, and the surface free energies of titanium alloys and the thermodynamic works of adhesion for the adhesive/titanium alloy interfaces were obtained. A three-dimensional finite element analysis was used to predict the strength of the specimens exhibiting cohesive failure. In addition, an expression of the relationship between the joint strength corresponding to interfacial failure and the thermodynamic work of adhesion was introduced based on the cohesive zone model (CZM) concept. It is shown that two surface treatments, Itro treatment and Laseridge, lead to cohesive failure and a significant increase in the joint strength, and the numerically predicted strength values are fairly close to the experimental values. These surface treatments are possible replacements for the traditional surface treatment processes. For degreasing, emery paper abrasion, atmospheric plasma treatment, sulfuric acid anodizing, nano adhesion technology and high-power lasershot, the specimens fail at the adhesive/substrate interface and the joint strength increases linearly with the thermodynamic work of adhesion as expected from our CZM-based expression. [ABSTRACT FROM PUBLISHER]

This investigation highlights the performance of epoxy-novolac interpenetrating polymer network (IPN) adhesive bonding of surface-modified polyether imide (PEI) to titanium (Ti) under elevated temperatures and an aggressive chemical environment as well as humid conditions. The results of physical and thermomechanical properties reveal that epoxy-novolac (4:1) IPN adhesive is the best combination. X-ray photoelectron spectroscopic (XPS) analysis demonstrates formation of oxide functional groups due to low-pressure plasma treatment onto the surface PEI and formation of oxide as well as nitride functional groups due to anodization and plasma nitriding on the titanium surfaces. Surface energy of the anodized titanium is relatively higher in comparison to plasma-nitrided titanium due to the high polarity of oxygen compared to nitrogen, and it consequently shows higher adhesive joint strength. Epoxy-novolac (4:1) IPN adhesive bonding of polyether imide to titanium reveals that anodized titanium to plasma-treated polyether imide adhesive joints show higher bond strength in ambient conditions. However, when exposed to an aggressive environment, the plasma-nitrided titanium to polyether imide adhesive joint shows higher bond strength because the nitride layer is more stable than the oxide layer and consequently results in a durable interface between titanium and adhesive, leading to cohesive failure of the adhesive joints. [ABSTRACT FROM AUTHOR]

Co-consolidated titanium – carbon fibre reinforced thermoplastic composite hybrid joints show potential for application in aerospace structures. The strength of the interface between the titanium and the thermoplastic composite is crucial for the strength of the entire hybrid joint. Application of a surface treatment on the titanium is an effective way to improve this interfacial strength. This paper evaluates the effect of several titanium surface treatments on the interfacial strength between titanium and carbon fibre reinforced polyetheretherketone (PEEK) or polyetherketoneketone (PEKK). Furthermore, the underlying bonding mechanisms, activated by these surface treatments, are studied. The research result shows that the grit blasted titanium – carbon fibre reinforced PEKK interface outperforms the other interfaces. [ABSTRACT FROM AUTHOR]

The most recent works suggest that the alkaline anodizing process (NaTESi) based in a bath of sodium hydroxide may be an attractive alternative to chromic acid anodizing (CAA) for surface pretreatment of titanium alloys for preparing hybrid adhesive bonds Ti6Al4V/Carbon Fiber Reinforced Composite (CFRC). This work compares several anodizing processes used for surface preparation, such as CAA, NaTESi and two modified NaTESi processes. The surface morphology, roughness, surface free energy and, especially, the initial strength adherence and durability under the wedge crack tests have been characterized. Wedge crack tests were performed in three different ageing media that may be representative of the environment that adhesive joints based upon Ti6Al4V/CFRC have to withstand during aircraft service life environments: hot/wet conditions; CTB3+TS test, that combines wet-dry cycles with exposure to a corrosive environment (CTB3) and thermal shocking (TS); and immersion tests in a Lap Joint Simulant Solution (LJSS). The results indicate that despite the morphological differences of the oxide grown by CAA and NaTESi, the initial adhesive strength with an epoxy adhesive and the durability of the bond are similar for both anodizing processes. Conversely, higher initial adhesive forces are exhibited for both modified NaTESi anodizing processes. [ABSTRACT FROM AUTHOR]

Biological fouling in marine environments creates numerous problems for engineered structures. Microbial attachment to a solid surface and biofilm formation initiates the process of biofouling. Therefore, detecting the initial bacterial attachment and understanding the mechanism of biofilm formation are important for controlling biofouling. In the present study, the mechanisms of bacterial attachment and biofilm formation of two marine isolated bacteria, namely Pseudoalteromonas sp. and Pseudoalteromonas flavipulchra on Ti-coated samples were examined through different electrochemical, surface analysis and thermodynamic methods. The results revealed that the rate of bacterial attachment and mechanism of biofilm formation varied for different species of bacteria. The amount of exopolysaccharide production could affect the bacterial attachment rate. Open circuit potentiometry has been found to be a valid and simple technique for continuous real-time monitoring of the biofilm formation compared to other electrochemical and thermodynamic techniques. Finally, two different models have been suggested to explain initial adhesion and biofilm formation of bacteria of different species. [ABSTRACT FROM AUTHOR]

The growing demand in lighter and safer structures generates the requirement of lighter joining strategies, particularly for lightweight metal alloys, composites, and also joining dissimilar materials together. Titanium alloys stand out as the conventional choice for materials for light weight structures. Adhesive bonding of titanium is an appealing route for joint design, also for the possibility of joining it with dissimilar materials. The realization of a strong joint depends not only on the joint design and type of adhesive, but also on the preparation of the adhering surface. Laser texturing presents advantages compared to common surface preparation processes in terms of eco-compatibility, energetic efficiency, ease of manufacturing, and repeatability. This work presents a preliminary investigation on laser texturing of Ti6Al4 V alloy with a pulsed fiber laser source with the aim to increase surface adhesion for bonding. Particularly, different surface textures are proposed, and laser machining strategies are developed. The results showed that laser texturing provided up to eightfold and 30% higher shear strength compared to plain and sand blasted surfaces, respectively. Failure analysis showed that a margin of improvement is still possible by adapting the surface texture for better cavity filling and reducing surface damage caused by the laser treatment. [ABSTRACT FROM PUBLISHER]

Abstract: In this paper, the effect of pulsed laser irradiation (Nd:YVO4, 1064nm) on the surface morphology and adhesion behaviour of Ti–6Al–4V was investigated. The surfaces were inspected by scanning electron microscopy (SEM), the chemical composition was obtained using X-ray photoelectron spectroscopy (XPS) and the adhesive properties were evaluated by means of wedge tests and floating roller peeling tests. The experiments revealed a homogeneous morphology consisting of a nano-structured oxide layer obtained within a particular set of laser parameters. The chemical investigation showed a considerable decrease of the contamination level on the surface compared to alkaline etching. The wedge test and floating roller peeling test showed that the nano-structured oxide layer formed after the laser process leads to a long-term stable adhesion behaviour. Using the laser pre-treatment the adhesion properties on titanium can be improved as compared to wet chemical pre-treatment processes like alkaline etching (Turco 5578) or anodising (NaTESi). [Copyright &y& Elsevier]

Abstract: This paper evaluates wet-chemical pre-treatments (alkaline etching, anodising) and a plasma treatment for structural bonding of titanium (Ti6Al4V). The main objective of this study is the comparison of the applicability of the plasma pre-treatment to wet-chemical treatments on titanium for structural bonding. In this context, an atmospheric pressure plasma device was used to deposit thin functional films from hexamethyldisiloxane (HMDSO) precursor on titanium. X-ray photoelectron spectroscopy (XPS) was employed to assess the chemical composition of the surface after different pre-treatments on the titanium substrate, while the morphology and the film thickness were investigated with scanning electron microscopy (SEM). The adhesion properties on titanium were evaluated by means of a wedge test in hot/wet conditions. After bonding tests the fracture surface and the failure loci were analysed. Using a long arc plasma generator and HMDSO precursor almost stoichiometric SiO2 coatings were obtained on the titanium substrate. These coatings exhibit good long-term durability and bond strength compared to an alkaline etching in the wedge test. The investigated anodising process leads to oxide layers revealing a highly porous nanostructure. In contrast to the alkaline etching, the plasma derived coatings and the oxide layer produced by the anodising process exhibit a higher micro, respectively nano roughness, and hence a better long-term durability. [Copyright &y& Elsevier]

Abstract: The development of durable bonds using titanium adherens has been investigated from the point of view of surface energy theoretical models measurements. The traditional Chromium Acid Anodization, which provides excellent durability, has to be phased out due to the use of hazardous Cr (VI) in the bath and as a result, special attention is paid to the sodium hydroxide anodizing and other alkaline chemical etchers. There are hardly any references on the surface free energy of adhesive titanium oxide coatings and therefore the objective of this work was to evaluate the surface and interface energy parameters of the various types of alkaline chromate free surface treatments using Neumann, Fowkes and van Oss–Chaudhury–Good methods in order to determine which method provides greatest differentiation between the coatings. Results show that Fowkes method produced the greatest variance in surface energies of the compared surface treatments and hence can be considered as better suited for more accurate discrimination between the oxide surface treatments on Ti–6Al–4V alloy. Although, in the case of model liquids, i.e. water and diiodomethane, the trends obtained for contact angles, surface energies, works of adhesion and solid/liquid interface energies all correlated between each other, a disagreement between the trends of solid/liquid interface energies calculated using Fowkes and van Oss–Chaudhury–Good methods for surface treatment/adhesive resin was obtained. In case of real adhesive systems, the use of work of adhesion appears more adequate in order to discriminate the surface treatments. Based on these findings the anodization in the tested alkaline bath after a previous alkali etching in the same bath is recommended, although adhesion test has to be still performed. [Copyright &y& Elsevier]

Abstract: This article presents the results of the testing of adhesive joint strength of hybrid assemblies consisting of different materials and joints of the same materials. Both experimental testing and numerical FEM analysis of the joints were applied. This type of joint can be found in the aviation industry, for example, where the use of composites as construction materials, including polymer composites with epoxy matrix, is becoming increasingly popular. One frequently used joint type in the aviation industry is the adhesive joint. The literature generally refers to adhesive joints made from the same materials while there is little information on adhesive joints using materials with different geometries and properties (mechanical, physical and chemical), therefore it would be useful to evaluate joint strengths both experimentally and numerically in terms of joint behaviour under various types of load. This paper compares experimental data obtained through numerical analysis for adhesive joints made of titanium sheet, aluminium sheet and aramid–epoxy composite using a number of different joint assemblies. [ABSTRACT FROM AUTHOR]

Abstract: In this investigation, attempts are made to prepare high-performance nanoadhesive bonding of titanium for its essential applications to aviation and space. The high-performance nanoadhesive is prepared by dispersing silicate nanoparticles into the ultra-high-temperature-resistant epoxy adhesive at 10wt% ratio with the matrix adhesive followed by modification of the nanoadhesive after curing under high-energy radiation for 6h in the pool of SLOWPOKE-2 nuclear reactor with a dose rate of 37kGy/h to promote crosslink into the adhesive. Prior to bonding, the surfaces of the titanium sheets are mechanically polished by wire brushing, ultrasonically cleaned by acetone and thereafter the titanium sheets are modified by plasma ion implantation using plasma nitriding. The titanium surface is characterized by X-ray photoelectron spectroscopy (XPS). The thermal characteristics of the epoxy adhesive and the high-performance nanoadhesive are carried out by thermal gravimetric analysis (TGA). The TGA studies clearly shows that for the basic adhesive there is a weight loss of the adhesive, however, in the case of epoxy–silicate nanoadhesive, there is almost 100% retention of weight of the adhesive, when the adhesive is heated up to 350°C. Lap shear tensile strength of the joint increases considerably, when the titanium surface is modified by plasma-nitriding implantation. There is a further massive increase in joint strength, when the plasma-nitriding implanted titanium joint is prepared by nanosilicate–epoxy adhesive and further modification of the adhesive joint under high-energy radiation results a further significant increase in joint strength. In order to simulate with aviation and space climatic conditions, the joints are separately exposed to cryogenic (−196°C) and elevated temperature (+300°C) for 100h and thermal fatigue tests of the joints are carried out under 10 cycles by exposing the joint for 2h under the above temperatures. When the joint completely kept at ambient condition and the joint strength compared with those joints exposed to aviation and space climatic conditions, it is observed that the joint could retain 95% of the joint strength. Finally, to understand the behavior of the high-performance silicate–epoxy nanoadhesive bonding of titanium, the fractured surfaces of the joints are examined by scanning electron microscope. [Copyright &y& Elsevier]

Abstract: The reduction of numerous metal oxides is being investigated by electro-deoxidation in molten salts due to the low-oxygen content advantage these processes offer. One of these processes is the Fray–Farthing–Chen (FFC) process that involves the direct reduction of titanium dioxide to titanium. A model for the multi-stage reduction of titanium dioxide to titanium is reported herein. The modeling approach adopted is based on the porous electrode theory used for studying lithium-ion batteries. [J.S. Newman, C.W. Tobias, J. Electrochem. Soc. 109 (12) (1962) 1183; K.E. Thomas, J.S. Newman, T.M. Darling, in: B. Scrosati, W. van Schalkwijk (Eds.), Advances in Lithium-Ion Batteries, Kluwer Academic Publishers, New York, 2002; J.S. Newman, K.E. Thomas, Electrochemical Systems, 3rd ed., Wiley-Interscience, 2004; V. Srinivasan, J.S. Newman, J. Electrochem. Soc. 151 (10) (2004) A1517; V. Srinivasan, J.S. Newman, J. Electrochem. Soc. 151 (10) (2004) A1530; J. Christensen, V. Srinivasan, J.S. Newman, J. Electrochem. Soc. 153 (3) (2006) A560; J.S. Newman, K.E. Thomas, H. Hafezi, D.R. Wheeler, J. Power Sources 119 (SI) (2003) 838; C.R. Pals, J.S. Newman, J. Electrochem. Soc. 142 (10) (1995) A3274]. The reduction of an individual sintered pellet of TiO2 as it undergoes electro-deoxidation in a molten salt bath of CaCl2 is modeled. This model has been applied to study the effect of physical variables such as the porosity, radius of pellet, radius of grains (particle size) in the pellet and the effect of starting with a partially reduced oxide. The effect of calcium titanate formation on the reduction is also incorporated and it is shown that if the reduction is started with a pellet of partially reduced titanium dioxide, one can avoid titanate formation. Though the FFC process is not completely successful in complete reduction due to titanate formation and needs to be developed further it has succeeded in the reduction of metals that are not as complex as the titanium oxygen system. This model could also be used for studying the reduction of other metal and mixed oxides such as SiO2, NiO, Cr2O3, Nb2O5 and ZrO2 that are simpler to reduce than TiO2. [Copyright &y& Elsevier]

Abstract: The functionality of structural light alloy castings can be improved by inserting into them, upon moulding, local iron base reinforcements. To acquire a better knowledge of such bimetallic assemblies, samples were prepared by immersing a mild steel bar (5mm in diameter) in aluminium base Al–Si alloy melts held at 730°C. After melt solidification, the bimetallic samples were cut into 5mm thick slices and pushout testing was performed on these slices. Characterization of damaging corresponding to different load level before complete debonding allows the determination of the failure mode. Crack initiation occurs at the specimen bottom face in the intermetallic reaction layer, important damage occurs before complete debonding and no brittle failure is observed. The results highlight the necessity of analysing pushout tests with a more integrated approach taking into account shear stress distribution along the interface such as interfacial crack growth. [Copyright &y& Elsevier]

Abstract: The objective of this investigation was to design a joint, suitable for use from low to high-temperatures, by the combination of two adhesives, one for strength at high-temperatures and one for strength at low-temperatures. Such a joint is needed for the fuselage of supersonic aircraft, where aluminium or titanium /composite joints are common and kinetic heating at high speeds can lead to high skin temperatures. The mixed modulus concept described by Hart-Smith is the starting point of the analysis. At high-temperatures, a brittle adhesive (high modulus) in the middle of the joint retains the strength and transfers the entire load. At low-temperatures, a ductile adhesive at the ends of the joint is the load-bearing adhesive. To guarantee that the load is transferred through the low-temperature adhesive, the ends of the overlap can be stiffened. A numerical analysis was carried out using finite element models to study the stress distribution in a mixed adhesive joint so as to find the best possible design of titanium/titanium and titanium/composite double lap joints. It has been shown that, for a joint with dissimilar adherends, the combination of two adhesives gives a better performance (increased load capacity) over the temperature range considered than the use of a high-temperature adhesive alone. [Copyright &y& Elsevier]

Abstract: The authors have previously developed a novel joint that consists of two adhesives, one better at low temperatures (−55°C) and the other for high temperatures (200°C). They have shown that this technique enables the design of a joint with a higher load capacity than a joint with only one adhesive, especially for dissimilar adherends. They studied the case of a double-lap joint where the outer adherends were titanium and the inner adherend was a carbon fibre-reinforced bismaleimide. However, they found that at low temperatures, the joint strength was low because the composite failed first and did not allow the adhesive to develop its full shear strength capacity. This paper presents techniques that were investigated to decrease the transverse stresses in the composite and so to increase the joint strength, particularly at low temperatures, thus making the use of a mixed adhesive joint more justifiable. Experimental tests and a finite-element analysis of double-lap joints have shown that it is more advantageous to have the composite as the outer adherend than having the composite as the inner adherend in conjunction with an internal taper in the external metallic adherends and an adhesive fillet. [Copyright &y& Elsevier]

Abstract: Adhesive joints with dual adhesives to be used over a wide temperature range (−55 to 200°C) were studied theoretically in a previous paper. The joint strength predictions have shown that, for identical adherends, the mixed modulus technique is of little benefit. However, for metal/composite joints, there is a real improvement, especially if the difference of coefficients of thermal expansion is high. The objective of the present study is to investigate experimentally if the use of a mixed adhesive joint is advantageous as predicted. The manufacture is particularly complex, and a way to produce such joints has been described. Experiments are then presented for titanium/titanium and titanium/composite double lap joints. It is shown that, for a joint with dissimilar adherends, the combination of two adhesives gives a better performance (increased load capacity) over the temperature range than a high temperature adhesive alone. Mixed adhesive joints were also cycled thermally to prove that they can be used at low temperatures after a stage at high temperatures, and vice versa. [Copyright &y& Elsevier]

Abstract: Under certain conditions of polymerization, a thick interphase can appear in the epoxy/titanium alloys adhesive bonded joints. The hardener nature change, which created the interphase, changes considerably the mechanical properties and ageing resistance of the assemblies. By measurement of fracture energies and physicochemical analysis of the failure facies, this work shows the interphase effect on the adhesive bonded joints mechanical behaviour. Also the beneficial of the interphase formation on ageing resistance is shown. [Copyright &y& Elsevier]

Abstract: Used as adhesives, epoxy systems can originate, under specific conditions, thick interphases with metallic substrates. Indeed, by interaction with the metallic surface, the amine can be modified. So the adhesive nature changes by diffusion of this modified amine in the bonded joint. In this work, the effect of epoxy viscosity and curing process on the interphase formation is studied. Calorimetric and rheometric tests have been performed, which confirm the amine modification and emphasise the coexistence of two different networks in the adhesive. Also, the importance of the curing cycle in the interphases formation is shown. [Copyright &y& Elsevier]

Abstract: Phenylethynyl (PE) end-capped co-oligomides of molecular weight equal to 4000g/mol based on 4,4′-(hexafluoroisopropylidene) biphthalic anhydride (6FDA) and para and meta phenylene diamine containing 80/20 and 70/30molar ratios of para-to-meta- substituents in the repeat unit were synthesized for thermal, rheological and adhesive properties. On the basis of minimum melt viscosity and glass transition temperature, Tg, several co-oligomides and co-oligomer/reactive blend systems were selected for adhesive measurements. The co-oligomide PE-6F-PDA-4K (70p/30m) (PE-PI-4 joint system) exhibited the highest tensile lap shear strength (3582) psi of all systems investigated, while joint system PE-PI-8a containing a 80/20mole% blend of PE-6F-PDA-4K (80p/20m) with reactive diluent PE-6F-m-PDA exhibited the lowest tensile lap shear strength (2392psi). Optical micrographs showed that bonded specimens containing glass scrim cloth between both titanium adherents fail cohesively at the primer/glass scrim cloth interface, while titanium joints which contained no glass scrim cloth failed mostly at the titanium-primer-adhesive interface region. The results clearly demonstrate that titanium to titanium adhesive joints can be fabricated at low pressure (14.7psi under vacuum) at 370°C for 1h from low-viscosity phenylethynyl end-capped co-oligomides. [Copyright &y& Elsevier]

A study of the effects of grit-blasting and plasma-spraying angles on the adhesion strength of an alloy (Tribaloy 800) that was plasma sprayed on a titanium-base alloy is reported. Five different spray and grit-blast angles were investigated: 45°, 55°, 65°, 75°, and 90°. The surface texture in different directions was characterized by the classic average roughness and by a fractal analysis number using a two-dimensional fractal analysis method. The grit residue was measured by an x-ray spectrometer. The study showed that the maximum adhesion strength was close to a 90° blasting and spraying angle. However, the grit residue reaches its maximum at a 75° blasting angle. From the image analysis of the interface in different directions, it was found that the nonperpendicular grit blasting produces an anisotropic surface. The fractal analysis method showed a rather good correlation with the blasting angle. However, no good correlation between the fractal number and the adhesion strength was found. [ABSTRACT FROM AUTHOR]

In this study, different surface pretreatments were applied to clean and activate titanium alloy surfaces. The samples were subjected to grit blasting treatments using two different pressures and afterwards, a UV/Ozone treatment was applied at different times to study the wettability and surface oxidation of the titanium samples. Scanning electron microscopy and laser confocal microscopy showed the surface morphology and the increased roughness with grit blasting pressure. X-ray Photoelectron Spectroscopy revealed that titanium was increasingly oxidized with increasing UV/Ozone treatment time, which leads to a reduced contact angle and a better adhesive performance in a butt tension test proving the effectivity of this surface treatment for titanium. Furthermore, the addition of sol-gel AC-120 and corrosion inhibition primer BR 6747 showed to be an additional improvement in the initial adhesion and after different degrees of aging by exposure to salt-spray, making the surface treatment techniques used in this research, a promising environmental friendly alternative to improve adhesive bonding performance. [ABSTRACT FROM AUTHOR]