Chemical modification of titanium

Figure 5 Chemical modification of titanium alkoxides. (a) = [Ti(OiPr)3 (OAc)]2 (b) = [Ti(OiPr)3(acac)].

Kumar G, Narayan B. Osseointegrated titanium implants requirements for ensuring a long-lasting, direct bone-to-implant anchorage in man. In Banaszkiewicz PA, Kader DF, editors. Classic papers in orthopaedics. (London) Springer 2014. p. 507—9. Nanci A, Wuest JD, Peru L, Brunet P, Sharma V, Zalzal S, et al. Chemical modification of titanium surfaces for covalent attachment of biological molecules. J Biomed Mater Res 1998 40(2) 324-35. 

Sanchez C., Babonneau F., Doeuff S. and Leaustic A. (1988) "Chemical modification of titanium alkoxide precursors" Ultrastructure processing of advanced ceramics 77-87. 

Anderson S., Constable E. C., Dare-Edwards M. P., Goodenough J. B., Hamnett A. and Seddon K. R. (1979), Chemical modification of a titanium(lV) oxide electrode to give stable dye sensitization without a supersensitizer , Nature 280, 571-573. 

C. Chemical modification of the glued surfaces by the formation of passivating layers. The modification technique depends on the nature of the metal. The parts are most often subjected to acid pickling, e.g. aluminum alloys are anodized in sulfuric and chromic acids. It is preferable to anodize aluminum parts in sulfuric acid followed by treatment of the anodic film in a bichromate. There are several methods of pickling carbon and stainless steels, chemical oxidation of magnesium alloys as well as copper and titanium alloys before gluing [4]. 

The goal of chemical modification of phenolics is the improvement of chemical and physical properties and to tailor the polymer to specific applications. Phenolics can be modified during synthesis by use of substituted monomers or monomer mixtures and after synthesis by electrophilic ring substitution, nucleophilic hydroxyl group capping, and reactions with compounds of boron, phosphorous, silicon, and titanium. 

Kelley, S. S., Greenberg, A. R., Filley, J., Peterson, R., and Krantz, W. B. (2002). Chemical modification of cellulose acetate with titanium isopropoxide. Int. J. Polym. Anal. Characterization 1, 162. 

Modification of the metal itself, by alloying for corrosion resistance, or substitution of a more corrosion-resistant metal, is often worth the increased capital cost. Titanium has excellent corrosion resistance, even when not alloyed, because of its tough natural oxide film, but it is presently rather expensive for routine use (e.g., in chemical process equipment), unless the increased capital cost is a secondary consideration. Iron is almost twice as dense as titanium, which may influence the choice of metal on structural grounds, but it can be alloyed with 11% or more chromium for corrosion resistance (stainless steels, Section 16.8) or, for resistance to acid attack, with an element such as silicon or molybdenum that will give a film of an acidic oxide (SiC>2 and M0O3, the anhydrides of silicic and molybdic acids) on the metal surface. Silicon, however, tends to make steel brittle. Nevertheless, the proprietary alloys Duriron (14.5% Si, 0.95% C) and Durichlor (14.5% Si, 3% Mo) are very serviceable for chemical engineering operations involving acids. Molybdenum also confers special acid and chloride resistant properties on type 316 stainless steel. Metals that rely on oxide films for corrosion resistance should, of course, be used only in Eh conditions under which passivity can be maintained. 

Our results clearly show that modification of the electronic state of titanium oxide by metal ion implantation is closely associated with the strong and longdistance interaction which arises between the titanium oxide and the metal ions implanted, as shown in Fig. 13, and not by the formation of impurity energy levels within the band gap of the titanium oxides resulting from the formation of impurity oxide clusters which are often observed in the chemical doping of metal ions, as shown in Figs. 6 and 13. 

Modification of the polymer or the presence of additives can effect the light resistance of a fiber. This is extremely important for textile conservation since fibers being produced currently by the man-made fiber industry may perform differently from those produced in earlier years. For example, a company bulletin, published first in 1960, reported that the resistance to chemical decomposition by fluorescent light or by sunlight of many of the nylons they manufactured had been improved (20). Titanium dioxide, which is used as a delustrant during the manufacture of fibers, can decrease their light resistance (13,15,18, 21, 22, 23). Dyes (18, 24, 25) and finishes (25, 26) are other important factors. 

The effect of the last monomeric unit of the growing polymer chain on the stereospecificity of the olefin addition has been confirmed by the calculation of the energy of non-bonded interactions and by quantum-chemical calculations (see section 5.2). Corradini et al. have analyzed the possibility of the it-complex formation on the octahedral titanium ions located on different faces of a- andy-TiCla. The possibility of the coordination by both faces of the propylene molecule was studied. It was shown that active centers on the lateral faces of a-TiCls and y-TiClj may be regioselective (primary insertion of propylene) ruther than stereospecific (no predominant CjHs coordination by one face). In the case of active centers located on the edges of the layered modifications of TiClj, CsHg is coordinated with the more accessible (outward) coordination sites of the titanium ions predominantly the polymer chain is then located on the less accessible (inward) octahedral site. This position of the polymer chain results in a fixed orientation of the first carbon-carbon bond of the polymer chain due to its non-bonded interaction with the TiClj surface. This may explain the predominant coordination of propylene molecules by one face and the stereospecificity of such type of active centers. 

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