Effect of interlayer configurations on joint formation in TLP bonding of Ti-6Al-4V to Mg-AZ31

YesIn this research work, the transient liquid phase (TLP) bonding process was utilized to fabricate joints using thin (20μm) nickel and copper foils placed between two bonding surfaces to help facilitate joint formation. Two joint configurations were investigated, first, Ti- 6Al-4V/CuNi/Mg-AZ31 and second, Ti-6Al-4V/NiCu/Mg-AZ31. The effect of bonding time on microstructural developments across the joint and the changes in mechanical properties were studied as a function of bonding temperature and pressure. The bonded specimens were examined by metallographic analysis, scanning electron microscopy (SEM), and X-ray diffraction (XRD). In both cases, intermetallic phase of CuMg2 and Mg3AlNi2 was observed inside the joint region. The results show that joint shear strengths for the Ti-6Al-4V/CuNi/Mg- AZ31 setup produce joints with shear strength of 57 MPa compared to 27MPa for joints made using the Ti-6Al-4V/NiCu/Mg-AZ31 layer arrangement.NSERC (Canada

Dissimilar Welding and Joining of Magnesium Alloys: Principles and Application

The growing concerns regarding fuel consumption within the aerospace and transportation industries make the development of fuel-efficient systems a significant engineering challenge. Currently, materials are selected because of their abilities to satisfy engineering demands for good thermal conductivity, strength-to-weight ratio, and tensile strength. These properties make magnesium an excellent option for various industrial or biomedical applications, given that is the lightest structural metal available. The utilization of magnesium alloys, however, requires suitable welding and joining processes that minimizes microstructural changes while maintaining good joint/bond strength. Currently, magnesium are joined using; mechanical fastening, adhesive bonding, brazing, fusion welding processes or diffusion bonding process. Fusion welding is the conventional process used for joining similar metals. However, the application of any welding technique to join dissimilar metals presents additional difficulties, the principal one being; the reaction of the two metals at the joint interface can create intermetallic compounds that may have unfavorable properties and metallurgical disruptions which deteriorates the joint performance. This chapter investigates the welding and joining technologies that are currently used to join magnesium alloys with emphasis on the development of multi-material structures for applications in the biomedical industries. Multi-material structures often provide the most efficient design solution to engineering challenges

Fast Disinfection of Escherichia coli

Water disinfection has attracted the attention of scientists worldwide due to water scarcity. The most significant challenges are determining how to achieve proper disinfection without producing harmful byproducts obtained usually using conventional chemical disinfectants and developing new point-of-use methods for the removal and inactivation of waterborne pathogens. The removal of contaminants and reuse of the treated water would provide significant reductions in cost, time, liabilities, and labour to the industry and result in improved environmental stewardship. The present study demonstrates a new approach for the removal of Escherichia coli (E. coli) from water using as-produced and modified/functionalized carbon nanotubes (CNTs) with 1-octadecanol groups (C18) under the effect of microwave irradiation. Scanning/transmission electron microscopy, thermogravimetric analysis, and FTIR spectroscopy were used to characterise the morphological/structural and thermal properties of CNTs. The 1-octadecanol (C18) functional group was attached to the surface of CNTs via Fischer esterification. The produced CNTs were tested for their efficiency in destroying the pathogenic bacteria (E. coli) in water with and without the effect of microwave radiation. A low removal rate (3–5%) of (E. coli) bacteria was obtained when CNTs alone were used, indicating that CNTs did not cause bacterial cellular death. When combined with microwave radiation, the unmodified CNTs were able to remove up to 98% of bacteria from water, while a higher removal of bacteria (up to 100%) was achieved when CNTs-C18 was used under the same conditions

Enhanced gain saturation model of non-linear semiconductor optical amplifiers

This study proposes an enhanced gain saturation model of non-linear semiconductor optical amplifiers (SOAs) by incorporating material-dependent gain compression factor. The rate equations are utilised with the extra gain compression term for Indium-Gallium-Arsenide material-based SOA to account for the steep relaxation oscillations behaviour of non-linear SOAs. The proposed gain saturation model is verified with experimental results that showed very good agreements with a mean square error of 0.094

System identification and closed-loop control of laser hot-wire directed energy deposition using the parameter-signature-property modeling scheme

Hot-wire directed energy deposition using a laser beam (DED-LB/w) is a method of metal additive manufacturing (AM) that has benefits of high material utilization and deposition rate, but parts manufactured by DED-LB/w suffer from a substantial heat input and undesired surface finish. Hence, monitoring and controlling the process parameters and signatures during the deposition is crucial to ensure the quality of final part properties and geometries. This paper explores the dynamic modeling of the DED-LB/w process and introduces a parameter-signature-property modeling and control approach to enhance the quality of modeling and control of part properties that cannot be measured in situ. The study investigates different process parameters that influence the melt pool width (signature) and bead width (property) in single and multi-layer beads. The proposed modeling approach utilizes a parameter-signature model as F_1 and a signature-property model as F_2. Linear and nonlinear modeling approaches are compared to describe a dynamic relationship between process parameters and a process signature, the melt pool width (F_1). A fully connected artificial neural network is employed to model and predict the final part property, i.e., bead width, based on melt pool signatures (F_2). Finally, the effectiveness and usefulness of the proposed parameter-signature-property modeling is tested and verified by integrating the parameter-signature (F_1) and signature-property (F_2) models in the closed-loop control of the width of the part. Compared with the control loop with only F_1, the proposed method shows clear advantages and bears potential to be applied to control other part properties that cannot be directly measured or monitored in situ.Comment: 28 pages, 14 figures, 4 tables

Effect of multi-wall carbon nanotubes on the mechanical properties of natural rubber

Multi-walled carbon nanotubes (MWNTs) were used to prepare natural rubber (NR) nanocomposites. Our first effort to achieve nanostructures in MWNTs/NR nanocomposites were formed by incorporating carbonnanotubes in a polymer solution and subsequently evaporating the solvent. Using this technique, nanotubess can be dispersed homogeneously in the NR matrix in an attempt to increase the mechanical properties of these nanocomposites. The properties of the nanocomposites such as tensile strength, tensile modulus, tear strength, elongation at break and hardness were studied. Mechanical test results show an increase in the initial modulus for up to 12 times in relation to pure NR. In addition to mechanical testing, the dispersion state of the MWNTs into NR was studied by transmission electron microscopy (TEM) in order to understand the morphology of the resulting system. According to the present study, application of the physical and mechanical properties of carbon nanotubes to NR can result in rubber products which have improved mechanical, physical and chemical properties, compared with existing rubber products reinforced with carbon black or silicone

Novel aluminum oxide-impregnated carbon nanotube membrane for the removal of cadmium from aqueous solution

An aluminum oxide-impregnated carbon nanotube (CNT-Al2O3) membrane was developed via a novel approach and used in the removal of toxic metal cadmium ions, Cd(II). The membrane did not require any binder to hold the carbon nanotubes (CNTs) together. Instead, the Al2O3 particles impregnated on the surface of the CNTs were sintered together during heating at 1400 °C. Impregnated CNTs were characterized using XRD, while the CNT-Al2O3 membrane was characterized using scanning electron microscopy (SEM). Water flux, contact angle, and porosity measurements were performed on the membrane prior to the Cd(II) ion removal experiment, which was conducted in a specially devised continuous filtration system. The results demonstrated the extreme hydrophilic behavior of the developed membrane, which yielded a high water flux through the membrane. The filtration system removed 84% of the Cd(II) ions at pH 7 using CNT membrane with 10% Al2O3 loading. A maximum adsorption capacity of 54 mg/g was predicted by the Langmuir isotherm model for the CNT membrane with 10% Al2O3 loading. This high adsorption capacity indicated that adsorption was the main mechanism involved in the removal of Cd(II) ions. View Full-TextScopu

Relationship Between Osteoporosis and Marginal Bone Loss in Osseointegrated Implants: A 2-Year Retrospective Study

Background: Fitting implants in osteoporotic patients has raditionally been controversial, and there is little scientific evidence relating osteoporosis to marginal bone loss (MBL). The aims of this study are as follows: 1) to evaluate the possibility of a correlation between osteoporosis, as measured by the mandibular cortical index (MCI), and MBL and 2) to assess how various systemic diseases, periodontitis, and placement of implants in regenerated bone are correlated with MBL and MCI. Methods: This retrospective study examines 212 implants inserted in 67 patients. To take a possible cluster failure into account, an implant for each patient was selected (n = 67 implants). MBL was assessed. Osteoporosis was evaluated using the MCI. Both MBL and MCI were assessed from panoramic radiographs. x2 test was performed (Haberman post hoc test). Significance was P <0.05. Results: When the total sample implant (N = 212) was evaluated, a significant association was found between the presence of osteoporosis and MCI (P <0.001) and between the presence of diabetes mellitus and MCI (P <0.01). Significant associations were also found between MBL and placement of implants in regenerated sites (P <0.001) and between MBL and a previous history of periodontitis (P <0.05). When the sample is evaluated only in selected implants (one per patient, n = 67), significant differences appear to relate only to the MBL with the placement of implants in regenerated bone sites (P <0.001). Conclusions: Osteoporosis (as evaluated by MCI) does not pose a risk for the development of greater MBL. Parameters adversely affecting the development of increased MBL are a previous history of periodontitis and especially the placement of implants at sites of bone regeneration