Adhesion titanium alloys

Similarly, Allen, Alsalim and Wake 45,46 determined that alkaline hydrogen peroxide was the best pretreatment for titanium alloys. This pretreatment was found to preferentially etch the P phase, while also undercutting some of the a grains and redepositing needle-like crystals on the P grains. The very rough surfaces that resulted were found to enhance adhesion by mechanical aspects. 

Surface Preparations of Titanium Alloys for Adhesive Bonding... 

If chlorinated solvents are used with titanium surfaces, they must be completely removed prior to bonding. Chlorinated solvents give rise to stress corrosion cracking in the vicinity of welds. Welding of titanium often occurs in the same plant as adhesive bonding, and it is sometimes done on the same parts. So the best practice is to avoid the use of chlorinated solvents completely. Several airframe manufacturers that fabricate titanium alloys no longer permit the use of chlorinated solvents. 

A similar route was taken by Wang et al. (2014), using polydopamine films to induce the growth of hydroxyapatite on titanium alloy to enhance osteoconductiv-ity. BMP-2 was absorbed onto hydroxyapatite for improved osteoinductivity. The results showed that the conjunction of HAp and BMP-2 increases cell adhesion,... 

Heimann, R.B. and Vu, T.A. (1996) Improvement of Adhesion of Bioceramic Coatings on Jaw and Bone Implants Made from Titanium Alloy. Freiberg, Second Interim Report, SMWK-Projekt No. 7541.82-0390/414, February 15, 1996. 

Efficient immobilization of aptamers on surfaces is necessary for the construction of tongh, stable sensors and assay systems as one necessary step to overcome limitations for practical applications (Bini et al., 2007). Bini et al. (2007) have compared thrombin aptamers immobilized on a gold snrface by chemisorption (thiolated aptamer) and by biotin-streptavidin interaction (biotinylated aptamer carrying a linker) on a gold surface modified by a thiol-dextran-streptavidin layer. The linker-modified aptamer immobilized via streptavidin-biotin showed better reproducibility and sensitivity results for the quartz crystal sensor. Aptamers can be used for the functionalization of titanium-alloy surfaces (e.g., implant material, scaffolds) to enhance cell adhesion. The aptamers directed to osteoblasts are fixed electrochemically on the snrface of the alloy and promote cell adhesion (Gno et al., 2005, 2007). 

At elevated temperatures where titanium alloys would be the adherend of choice, a different failure mechanism becomes important. Because the solubility of oxygen in titanium increases with temperature, the oxygen in a CAA or other oxide diffuses or dissolves into the metal, leaving voids or microcracks at the metal-oxide interface and embrittles the metal near the interface (Fig. 7). Consequently, stresses are concentrated over small areas at the interface and the joint fails at low stress levels [75,77]. Such phenomena have been observed for adherends exposed to 600°C for as little as 1 hour or 300°C for 710 hours prior to bonding [75] and for bonds using a high-temperature adhesive cured at 371°C [78] or 400°C [75]. 

Formulations suitable for high strength, high-temperature adhesives based on PAI, have been developed. Excellent bond strengths are observed with stainless steel, aluminum and titanium alloys, and PI films. ... 

The thermal and dynamic mechanical behaviors of triblock copolymers with a styrene/isoprene/styrene architecture were investigated in order to understand their adhesive properties. Both copolymer free films and films bonding together two titanium alloy plates were found to have thermal and mechanical response that was strongly dependent on joint preparation. Microphase separation in the melts of these triblock materials was felt to contribute to the observed phenomena namely, the presence of residual stresses in thin films which had been cooled while under high pressure. 

Lively, G.W. and A.E. Hohman, Development of a mechanical-chemical surface treatment for titanium alloys and adhesive bonding. Proceedings of the 6th National SAMPE Technical Conference, Vol. 5, Materials and Processes for the 70 s, Kiamesha Lake, NY, pp. 145-159, October 9-11, 1973. 

Figure 4. Reflectance infrared spectrum of a failed lap shear titanium alloy adherend bonded with a polyimide adhesive (22).

Figure 13. XPS titanium 2p photopeak of failed lap shear sample of titanium alloy bonded with polyimide adhesive solvent cast from (a) DMAC solution and from (b) diglyme solution (22).

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