Stabilization of Ti-molecular sieve catalysts used in selective sulfoxidation reactions by ionic liquids

Sulfoxidation reactions of 4,6-dimethyl-2-methylthiopyrimidine have been performed using titanosilicate catalysts in ionic liquids, dioxane and ethanol. The ionic liquid reactions showed superior reactivity compared with molecular solvents. Moreover, on examination of the recycling of the catalyst, a significant increase in the stability of catalyst was found both in terms of recycling activity and leaching of the titanium from the catalyst. The mechanism by which the ionic liquid reduces the solubilisation of the catalysts is explored.

Relationship between microstructure and deformation behaviour during dynamic compression in Ti-3Al-5Mo-5V alloy

The relationship between microstructure and deformation and damage behaviour during dynamic compression in Ti-3Al-5Mo-5V alloy has been studied using several experimental techniques, including optical microscopy, scanning electron microscopy and microhardness measurements. It was found that the deformation behaviour during dynamic compression was closely related to deformation parameters. After dynamic deformation, the deformation shear band that formed in the titanium alloy had microhardness similar to that of the matrix. However, the microhardness of the white shear band was much higher than the matrix microhardness. The effects of deformation parameters, including deformation rate and deformation degree, on deformation localisation were investigated. Based on the results from the present work, the microstructure and deformation processing parameters can be optimised. In addition, treatment methods after dynamic compression were explored to restore alloy properties. Using post-deformation heat treatment, the microstructure and property inhomogeneity caused by shear bands could be largely removed.

Anatase thin films on glass from the chemical vapor deposition of titanium(IV) chloride and ethyl acetate

Thin (50-500 nm) films of TiO2 may be deposited on glass substrates by the atmospheric pressure chemical vapor deposition (APCVD) reaction of TiCl4 with ethyl acetate at 400600 C. The TiO2 films are exclusively in the form of anatase, as established by Raman microscopy and glancing angle X-ray diffraction. X-ray photoelectron spectroscopy gave a 1:2 Ti:O ratio with Ti 2P(3/2) at 458.6 eV and O 1s is at 530.6 eV. The water droplet contact angle drops from 60degrees to

Synthesis and NMR Characterization of Titanium and Zirconium Oxides Incorporated in SBA-15

Single oxides of Ti and Zr incorporated SBA-15 were prepared and characterized by N-2 adsorption, NMR, and XPS techniques. Si-29 MAS NMR results suggest the formation of Si-O-X linkages (X: Ti or Zr) by an increase in the ratio of Q(3)/Q(4) in the presence of Ti or Zr. XPS analysis of Ti-SBA-15 catalysts indicate the presence of Ti-O-Si bonds in addition to Ti-O-Ti and Si-O-Si bonds, supporting the NMR evidence.

Heterogeneous oxidation of pyrimidine and alkyl thioethers in ionic liquids over mesoporous Ti or Ti/Ge catalysts

Heterogeneous catalytic oxidation of a series of thioethers (2-thiomethylpyrimidine, 2-thiomethyl-4,6-dimethyl-pyrimidine, 2-thiobenzylpyrimidine, 2-thiobenzyl-4,6-dimethylpyrimidine, thioanisole, and n-heptyl methyl sulfide) was performed in ionic liquids by using MCM-41 and UVM-type mesoporous catalysts containing Ti, or Ti and Ge. A range of triflate, tetrafluoroborate, trifluoroacetate, lactate and bis(trifluoromethanesulfonyl)imide-based ionic liquids were used. The oxidations were carried out by using anhydrous hydrogen peroxide or the urea-hydrogen peroxide adduct and showed that ionic liquids are very effective solvents, achieving greater reactivity and selectivity than reactions performed in dioxane. The effects of halide and acid impurities on the reactions were also investigated. Recycling experiments on catalysts were carried out in order to evaluate Ti leaching and its effect on activity and selectivity.

PtRuO/Ti anodes with a varying Pt:Ru ratio for direct methanol fuel cells

PtRuO/Ti anodes with a varying Pt:Ru ratio were prepared by thermal deposition of a PtRuO catalyst layer onto a Ti mesh for the direct methanol fuel cell (DMFC). The morphology and structure of the catalyst layers were analyzed by SEM, EDX, and XRD. The catalyst coating layers became porous with increase of the Ru content, and showed oxide and alloy characteristics. The relative activities of the PtRuO/Ti electrodes were assessed and compared using half-cell tests and single DMFC experiments. The results showed that these electrodes were very active for the methanol oxidation and that the optimum Ru surface coverage was ca. 38% for a DMFC operating at 20-60 °C. © 2006 Elsevier B.V. All rights reserved.

Ti mesh anodes prepared by electrochemical deposition for the direct methanol fuel cell

An anode structure based on Ti mesh has been developed for the direct methanol fuel cell (DMFC). This new anode was prepared by electrochemical deposition of a ~ 3 µ m PtRu catalyst layer on ~ 50 µ m Ti mesh. It has a thinner structure compared to that of a porous carbon-based conventional anode. The Ti mesh anode shows a performance comparable to, and exceeding that, of the conventional anode in a DMFC operating with 0.25 or 0.5 M methanol solution and atmosphere oxygen at 90 C. However, it shows a lower performance of the cell when higher concentrations of methanol was employed. This may be attributed to its thin and open structure, which could facilitate the transport of methanol from the flow field to the anode catalyst layer and carbon dioxide in the opposite direction. © 2006 International Association for Hydrogen Energy.

Comparative study of tool life and hole quality in drilling of CFRP/titanium stack using coated carbide drill

The use of hybrid materials including carbon fiber reinforced plastics (CFRPs) and lightweight metals such as titanium are increasing particularly in aerospace applications. Multi-material stacks require a number of holes for the assembly purposes. In this research, drilling trials have been carried out in CFRP, Ti-6Al-4V and CFRP/Ti-6Al-4V stack workpieces using AlTiN coated tungsten carbide drill bit. The effects of process parameters have been investigated. The thrust force, torque, burr formation, delamination, surface roughness and tool wear have been analyzed at various processing condition. The experimental results have shown that the thrust force, torque, burr formation and the average surface roughness increase with the increased feed rate and decrease with the increased cutting speed in drilling of Ti-6Al-4V. In drilling CFRP, delamination and the average surface roughness has similar tendency with the cutting parameters however thrust force and torque rises with the increased cutting speed. The results showed that after making 15 holes in CFRP/Ti-6Al-4V stack, measured thrust forces were increased by 20% in CFRP and by 45% in Ti-6Al-4V. Delamination was found to be much smaller in drilling of CFRP in stack from compared to drilling single CFRP. Tool life was significantly shortened in drilling of stack due to the combination of the wear mechanisms.

Effect of contact pressure on fretting fatigue behavior of Ti-1023

With a new test facility, we have investigated fretting fatigue properties of Ti-1023 titanium alloy at different contact pressure. Both fatigue fracture and fretting scar were analyzed by scanning electron microscopy (SEM). Moreover, the depth of crack initiation area in fatigue fracture has been analyzed quantitatively, to investigate the relationship between the depth of crack initiation area and the fretting fatigue strength. The changing trends of the depth of crack initiation area and fretting fatigue strength with the increase of contact pressure show obvious opposite correlations. The depth of crack initiation area increases rapidly with the increase of contact pressure at low contact pressure (smaller than 10 MPa), and the fretting fatigue strength drops rapidly. At the contact pressure of 10–45 MPa, both the depth of crack initiation area and the fretting fatigue strength do not vary significantly. Contact pressure influences fatigue strength through influencing the initiation of fatigue crack. The main damage patterns are fatigue flake and plow.

Hole-making Process and Its impacts on the Fatigue Response of Ti -6Al-4V Aircraft Alloy

In this work, the impact of conventional drilling and helical milling processes on the fatigue response Ti-6Al-4V (grade 5 titanium alloy) has been presented. Results show that the work pieces produced by helical milling has a 119% longer fatigue life compared with the drilled pieces under dry machining condition, and a 96% longer fatigue life for helical milled piece under lubricated condition. The use of cutting fluid has led to longer fatigue lives – 15% longer for drilling and 3% longer for helical milling. Other results such as the machined surface roughness, alloy surface and sub-surface microstructures have also been studied in details.

Enhancement of Wear and Corrosion Resistance of Beta Titanium Alloy by Laser Gas Alloying with Nitrogen

The relatively high elastic modulus coupled with the presence of toxic vanadium (V) in Ti6Al4 V alloy has long been a concern in orthopaedic applications. To solve the problem, a variety of non-toxic and low modulus beta-titanium (beta-Ti) alloys have been developed. Among the beta-Ti alloy family, the quaternary Ti-Nb-Zr-Ta (TNZT) alloys have received the highest attention as a promising replacement for Ti6Al4 V due to their lower elastic modulus and outstanding long term stability against corrosion in biological environments. However, the inferior wear resistance of TNZT is still a problem that must be resolved before commercialising in the orthopaedic market. In this work, a newly-developed laser surface treatment technique was employed to improve the surface properties of Ti-35.3Nb-7.3Zr-5.7Ta alloy. The surface structure and composition of the laser-treated TNZT surface were examined by grazing incidence x-ray diffraction (GI-XRD) and x-ray photoelectron spectroscopy (XPS). The wear and corrosion resistance were evaluated by pin-on-plate sliding test and anodic polarisation test in Hanks’ solution. The experimental results were compared with the untreated (or base) TNZT material. The research findings showed that the laser surface treatment technique reported in this work can effectively improve the wear and corrosion resistance of TNZT.

Modifications of Surface Properties of Beta Ti by Laser Gas Diffusion Nitriding

Beta-type Ti-alloy is a promising biomedical implant material as it has a low Young’s modulus and is also known to have inferior surface hardness. Various surface treatments can be applied to enhance the surface hardness. Physical vapor deposition and chemical vapor deposition are two examples of this but these techniques have limitations such as poor interfacial adhesion and high distortion. Laser surface treatment is a relatively new surface modification method to enhance the surface hardness but its application is still not accepted by the industry. The major problem of this process involves surface melting which results in higher surface roughness after the laser surface treatment. This paper will report the results achieved by a 100 W continuous wave (CW) fiber laser for laser surface treatment without the surface being melted. Laser processing parameters were carefully selected so that the surface could be treated without surface melting and thus the surface finish of the component could be maintained. The surface and microstructural characteristics of the treated samples were examined using x-ray diffractometry, optical microscopy, three-dimensional surface profile and contact angle measurements, and nanoindentation test.