C.P titanium/Ti-6Al-4V joint by spark plasma welding: Microstructure and mechanical properties.

The welding ability of Ti-6Al-4V alloy is weak due to their two-phase microstructure. On the other hand, friction welding methods lead to significant microstructural changes. In this research, for the first time, pure titanium was successfully joined to the Ti-6Al-4V alloy, without any change in the microstructure and mechanical properties of both alloys, by applying the SPW method. Further, the effects of temperature, pressure, and time of the SPW process on the microstructure and mechanical properties of commercial pure (C.P) titanium joined to the Ti-6Al-4V alloy were investigated. The results indicated that the effect of temperature and pressure on the SPW process was greater than that of time. Further, mechanical properties investigations showed that the yield strength of the joint interface was larger than that of the substrate metal, following which necking and fracture occurred in the pure titanium substrate metal. The alloy (Ti-Ti64) bonded at 800 °C, with a time of 10 min and pressure of 20 MPa, exhibited the superior bonding of 7-9 µm interface thickness, and excellent tensile strength (534 ± 13 MPa) and Vickers micro-hardness (190 ± 5 HV0.1). Investigation of the effect of pressure (normal stress) also showed that with an increase in pressure, because of the reduction of the chemical potential of diffusing species, the joint temperature would drop, and the joint could be created at a temperature below 800 °C.

Removal of nickel and cadmium heavy metals using nanofiber membranes functionalized with (3-mercaptopropyl)trimethoxysilane (TMPTMS).

Functionalized nanofibrous membranes have been produced via electrospinning with a polymer solution of 19% (w/w) of nylon 66 prepared in a formic acid/chloroform mixture (75:25 v/v). The optimum parameters of electrospinning, like voltage, flow rate, tip and collector distances, were achieved and produced nanofiber membranes with a thickness of 287 nm. Then the nanofiber membranes were functionalized by (3-mercaptopropyl)trimethoxysilane (TMPTMS) at various amounts. Three different initial concentrations of metal ions and three different levels of pH were chosen. The effect of filtration process parameters such as the initial concentration of metal solution, pH of the solution, and the amount of functionalizer trimethoxysilane (TMPTMS) on the adsorption was studied. In surveying filtration process parameters, the results showed that metal ion rejection increased by increasing the pH of the solution and decreased by increasing the initial concentration of the effluent. By increasing the amount of functionalizer, removal efficiency increased. The results showed that the maximum efficiency of absorption of cadmium and nickel were 93.0 and 97.6%, respectively, and the filtering mechanism of the membrane is the blocking pores type. The adsorption data of cadmium and nickel ions fitted particularly well with the Freundlich isotherm.