Kamal Kumar

Challenges and opportunities for biodegradable magnesium alloy implants

Abstract Magnesium (Mg) and its alloys posse’s great potential for the application of biodegradable medical implants. It is due to their unique properties like low density and elastic modulus, good biocompatibility, etc. But still there are many challenges for Mg alloy based implants. Due to rapid degradation of Mg and its alloys in biological fluid, it loses its mechanical integrity and fails to perform before the complete healing of bone fracture (in orthopedics application) or removal of plaque in arteries (in case of vascular implants). Using suitable alloying elements mechanical strength and corrosion resistance of Mg-alloys can be enhanced but cytotoxicity and long term inflammatory consequences of these elements are the major concern. Further modifying the surface characteristics of Mg-alloy through various surface coating, machining, mechanical working, etc., corrosion behaviour can be manipulated. In this field of biodegradable implants, the various opportunities are yet to be explored in detail to improve the clinical performance of Mg alloy implants for orthopedics and vascular applications. This review paper summarises the various challenges and opportunities in design and development of biodegradable Mg alloy implants.

Surface modification of WC-Co alloy using Al and Si powder through WEDM: A thermal erosion process

ABSTRACT This paper presents the surface modification of WC-Co alloy with the use of aluminum and silicon powder in wire electric discharge machining (WEDM) process. A separate attachment with the stirrer is used to mix the metal powder in the dielectric, which is further supplied by a pump at the workplace continuously. The effects of different process parameters like peak current, pulse on-time, pulse off-time and servo-voltage are investigated on the material transfer, crack formation and white-layer formation with the help of Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis. It was observed that silicon powder enhances the surface quality (4 µm white layer) compared with aluminum (6 µm white layer) powder. The white-layer thickness without the use of metal powder was around 14 µm. The cracks density after the addition powders reduces significantly.

Physical and tribological characteristics of porous NiTi SMA fabricated by powder metallurgy

ABSTRACT This paper presents the mechanical and tribological characteristics of the NiTi shape memory alloy (SMA) fabricated by powder metallurgy. This material has prominent applications in micro-electromechanical systems, medical implants, actuator, space and aerospace industries, etc. In every field, wear characteristics plays a dominating role. In present work dry-abrasion wear behavior is determined for NiTi alloy by varying binder percentage. With increasing binder percentage from 2.5 to 15 %, density decreases from 6.5 to 5.3 g/cm3 while porosity increases from 19 % to 51 %. Increasing rotational speed and binder percentage at a constant load the wear rate increases in the NiTi alloy. Due to the presence of hard particles, NiTi exhibits a very small wear rate. The coefficient of friction is also computed for the alloys in present research work. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction were used for the investigation of surface morphology and phases in the NiTi alloy.

Post-Processing of NiTi Alloys: Issues and Challenges

Nitinol (NiTi) exists in an equiatomic phase of Ni and Ti. Nitinol has growing applications in aerospace and medical industries due to its unique properties of pseudoelasticity, corrosion resistance, shape memory effect, and biocompatibility. NiTi can be produced by conventional and nonconventional manufacturing routes and its behavior can be modified by altering the composition, changing the porosity, and shape setting under varying thermal and mechanical treatment. After the fabrication, several post-processing operations are required on NiTi for desired application. This paper presents a brief on post-processing like machining, surface coating, and mechanical and thermal treatment for shape setting of NiTi alloys, and their issues and challenges.

Mechanical characteristics and bioactivity of porous Ni50−xTi50Cux (x = 0, 5 and 10) prepared by P/M

The present research work investigates and analyses the effect of compaction pressure, sintering temperature and time on mechanical characteristics, namely compressive strength and Youngs modulus of Ni50−xTi50Cux (x = 0, 5 and 10) alloys fabricated using powder metallurgy technology. The effect of process parameters on mechanical characteristics was evaluated using the Taguchi method and analysis of variance. Using the Taguchi approach, optimised values of process parameters were found for higher compressive strength and lower Youngs modulus in each set of Ni50Ti50, Ni45Ti50Cu5 and Ni40Ti50Cu10 alloys. With the addition of copper in NiTi alloy, a little improvement in mechanical characteristics was observed, but bioactivity was decreased at 10%of Cu. Therefore, above 5% of Cu in NiTi alloy was not proved successful for biomedical applications.

Estimation of recent changes in thickness and mass balance of the Patsio glacier in the Great Himalayan region using geodetic technique and ancillary data

Abstract An understanding of glacier mass budget in the Himalayas is important for regional water resource management. This study presents a detailed estimation of mass budget of the Patsio glacier (The Great Himalaya) using SRTM-X (2000), Cartosat-1 (2005) and TanDEM-X (2013) DEMs. Geodetic findings indicate an overall mass loss by −0.26±0.11 m.w.e/yr,−0.30±0.10 m.w.e/yr and −0.16±0.11 m.w.e/yr during 2000-2013, 2000-2005 and 2005–2013 respectively. Maximum downwasting was observed in the terminus area of the glacier during the period 2000–2013. The observed lower rate of mass loss between 2005 and 2013 was attributed to declining temperature during that period. However, long-term temperature trends depict warming, so was exhibited by mass loss during 2000–2013. Geodetic based findings were found to be concordant with GPR based estimation. This study confirms the suitability of geodetic mass balance technique for mountainous glaciers, which will be useful to evaluate future changes in the glacial extent and runoff study.