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Mg-based biodegradable alloys for orthopedic implants - A review
No full textTraditional metallic biomaterials for orthopedic implants require materials exhibiting excellent corrosion resistance in human body. Recently, implants made of biodegradable metallic materials are thought to be potential for orthopedic implant applications as they can circumvent revision surgeries. These implants are considered as the third generation implants as they are expected to provide adequate mechanical strength
to support the bone during restoration; have excellent in vivo biocompatibility and controlled degradation rate.
These implants would degrade within the body after completing its mission without leaving any residues within
the body. Biocompatible elements like Mg, Fe and Zn and their alloys have been considered for bone implant
applications due to their biodegradability. Amongst these, Mg alloys are preferred due its high specific strength,
low elastic modulus that are close to human bone and low density minimizing the risk of stress shielding. However,
Mg alloys have fast degradation rate in biological fluids leading to the release of hydrogen which would lead
to premature failure of implants. This paper reviews the research efforts towards the development of Mg-based
biodegradable alloys for orthopedic implants. Concepts followed in designing Mg-based biodegradable alloys,
the mechanical properties of developed Mg-based alloys, degradation mechanism of Mg-based alloys and the efforts to reduce the degradation rate, and status of Mg-based alloys in orthopedic applications are compiled along with the existing problems and future research directions
Electrochemical application of shape and phase dependant copper sulphide for costeffective next generation supercapacitive energy storage: A review
No full textCopper sulphides (Cu2-xS) based chalcogenide materials have received voluminous consideration for supercapacitive energy storage with unique semiconducting properties, nontoxicity and extensive earth abudancy. The existence of Cu2-xS in discrete crystal geometries and morphology liberalizes opportunities to tune them for desired performances. Consequently, the understanding of the phase and morphology dependency on performances can be pivotal in building novel designs for enhanced power and energy delivery. Herein an in-depth recent literature investigation into the synthesis of diverse phases and morphologies of Cu2-xS nano/ microstructures and their super capacitive behaviours has been reported. Given the potent of Cu2-xS as highly efficient supercapacitive electrode as low cost material and their extensive deployment it is imperative to profoundly highlight the recent advances in Cu2-xS based electrode materials directed towards supercapacitive energy storage
Effect of microstructural constituents on mechanical properties and fracture toughness of Inconel 718 with anomalous deformation behavior at 650 degrees C
No full textIn the current work, Inconel 718 superalloy was subjected to five different heat treatment schedules to develop five different microstructures for studying the effect of gamma', gamma '' and delta phases on mechanical properties of IN-718 at room temperature and 650 degrees C as the working temperature of IN-718 is near 650 degrees C. Microstructural characterization was performed with Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Vickers hardness tests, tensile tests and fracture toughness (J(IC)) tests were performed for different heat-treated samples at room temperature. Further tensile tests were carried out at 650 degrees C for all heat-treated specimens and one high-temperature J(IC) test at 650 degrees C was performed for Standard heat-treated compact tension specimen. It had been demonstrated that gamma' and gamma '' phases caused a substantial increase in hardness of the material while delta phase was attributed to low hardness of this superalloy. Also, it was found that gamma '' phase provided maximum strength to IN-718 superalloy followed by gamma' at room temperature but on contrary, gamma' was found to be primarily responsible for higher strength than gamma '' at 650 degrees C. The delta phase furnished poor strength at all temperatures. However, the formation of Nb + Ti carbides and oxides at 650 degrees C caused premature failure of the tensile specimens with lower elongation. In case of fracture toughness test, the maximum value of critical J-integral (J(IC)) and tearing modulus (T) were demonstrated by gamma' phase. A decrease in the J(IC) value of the material was observed at higher temperature (650 degrees C). Both critical J-integral (J(IC)) and tearing modulus (T) were found to be critical parameters for crack growth characterization of this superalloy
Influence of boron on microstructure and mechanical properties of Gleeble simulated heat-affected zone in P91 steel
No full textIn the present endeavor, a Gleeble thermo-mechanical simulator has been used to simulate subzones of the heat-affected zone (HAZ) of boron-free P91 and boron-modified P91B steels to investigate the influence of boron on microstructure and mechanical properties. The prior austenite grain (PAG) size remained similar to that of parent metal in the fine-grained heat-affected zone (FGHAZ) and inter-critical heat-affected zone (ICHAZ) of P91B steel. The microhardness value of simulated specimens, including parent metals was observed to be similar. But impression creep resistance of boron-containing steel was significantly higher than that of the boron-free steel. The presence of boron decreased precipitates size and increased fraction of low energy Σ3 coincident-site lattice (CSL) boundaries that attributed to improvement of creep resistance. However, there was a slight reduction in solid solution hardening due to increased area fraction of precipitates in parent metal and simulated specimens of boron-containing steel. Hindering of alloy element partitioning during impression creep of P91B-ICHAZ was observed, which was possibly due to the presence of boron in soluble form in the iron matrix and the segregated form on grain and sub-grain boundaries (SGBs). Further, the addition of boron was observed to retard M23C6 precipitate coarsening in the P91B-ICHAZ in comparison to its P91 version
Reclamation of Precious Metals from Small Electronic Components of Computer Hard Disks
No full textPresent research work focuses on the recovery of precious metals (Ag, Au, Pd, and Pt) from the leach liquor of small populated chips present in the hard disk of computers. Initially, the hard disks were dismantled to separate the printed circuit boards (PCBs) followed by its depopulation to liberate the mounted small electronic components. The liberated black chips were pulverized to *100 mesh and chemically analysed. The powdered black chips containing *0.6% Ag, *0.3% Au, *0.01% Pd, *0.0003% Pt, and 20% Cu on mass basis were first leached in nitrate medium for maximum dissolution of non-ferrous metals along with Ag leaving Au, Pd, and Pt in the residue. About 99.99% of precious metals
were leached out from the residue using suitable lixiviant. The obtained leach liquor was purified using advanced separation techniques (solvent extraction/ion-exchange/ precipitation) from which marketable products (metals/salts) could be produced
Study of Dry Mineral Separation Behavior in Dry Density Separators
No full textMineral dry density separation behavior (mineral beneficiation) involves segregation of high density particles and low density particles in the feed, i.e., in nutshell, mineral dry density beneficiation is density segregation in physics terms. In dry beneficiation, this density segregation is achieved using air as fluidized medium. Density segregation on dry separators can be achieved in two ways: (1) using minimum fluidization velocity differences and (2) using terminal velocity difference between different density particles. Dry separators based on minimum fluidization velocities follow two steps for dry beneficiation: (1) vertical density stratification and (2) horizontal segregation. Particles due to buoyancy, drag and gravitational forces get vertically density stratified and later frictional, gravity and external (vibrational, etc.) forces horizontally segregate different density particles. Dry separators based on terminal velocities follow single step for dry beneficiation of mineral, and air velocity in this type of dry density separators is maintained between terminal velocity of high density and low density particles. Velocity of air is higher for low density particles, which leads to higher drag and buoyancy forces to get pushed out of system with air and get collected at further distance than high density particles leading to density segregation. Mathematical models have been developed using force balance on particles and simulated in MATLAB for both type of separators to explain the physics of separation. Solutions to the simulated mathematical model equations are the particle trajectories of different density particles in the two dry separators. Iron ore is used as feed for studying separation futures in mathematical modeling on dry separators
Thermodynamic Assessment of Steelmaking Practices for the Production of Re-sulfur Steels
No full textFactSage has become one of the most important modeling tools in simulating the high-temperature metallurgical processes. The usefulness of the FactSage has been demonstrated in this work using several examples of steelmaking processes. Primary steelmaking (basic oxygen furnace) simulation was done with the available process data, and process charts similar to the standard ones were obtained. Ladle refining furnace process for free-cutting steels was simulated and it was observed that absolute non-equilibrium condition exists in steel during casting due to S injection. It was found that non-metallic inclusion formation is thermodynamically possible at final processing stages during Ca and S injection with variable recoveries. A significant change in the nature of non-metallic inclusions formed in re-sulfur steel causes clogging during continuous casting of liquid steel, and its influence on the process has been discussed, for mere 2 ppm of Ca difference in the liquid steel composition
Material and Substance Flow Analysis of Used Lead Acid Batteries in Nigeria: Implications for Recovery and Environmental Quality
No full textBackground: As resources become scarce, information from material and substance flow analysis can help to improve material recovery policy. The flow of toxic substances such as lead (Pb), cadmium (Cd), chromium (Cr), arsenic (As) and antimony (Sb) can be used as a basis for appropriate risk management decisions for optimum environmental quality.
Objectives: The present study examined a material and substance flow analysis of used lead acid batt
Correlating Effect of Temperature on Cyclic Plastic Deformation Behavior with Substructural Developments for Austenitic Stainless Steel
No full textLow-cycle fatigue experiments have been carried out at elevated and sub-zero temperatures. Corresponding
effect on cyclic plasticity characterizing parameters such as cyclic hardening/softening and Masing
behavior is compared for different loading conditions. Disparities in the fatigue life as well as the cyclic
plastic behavior have been attributed to the phase transformations that largely obstruct the dislocation
motion. Further, the changes in strains in the materials matrix have been quantified through misorientation
studies, wherein clear demarcation in strain distributions due to fatigue loading at different temperatures was obtained and further correlated with the substructural alterations observed through transmission
electron microscopy