Srinivasa R. Bakshi

Bio: Srinivasa R. Bakshi is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Spark plasma sintering & Carbon nanotube. The author has an hindex of 34, co-authored 99 publications receiving 4515 citations. Previous affiliations of Srinivasa R. Bakshi include Naval Postgraduate School & Indian Institutes of Technology.

The nano-scratch behavior of biocompatible hydroxyapatite reinforced with aluminum oxide and carbon nanotubes

Abstract: Hydroxyapatite (HA) reinforced with sub-micrometer Al2O3 and carbon nanotubes (CNTs) has been synthesized as a coating on the Ti-6Al-4V substrate via plasma spraying. The addition of Al2O3 and CNTs to HA has shown improvement in the hardness and elastic modulus by 65% and 50%, respectively, when compared to HA. Consequently, HA-Al2O3-CNT coatings have been nano-scratched to understand their wear performance. Reinforcement of HA by Al2O3 shows a decrease in the wear volume by more than 13 times, whereas HA-Al2O3-CNT coating demonstrated further wear volume reduction of five times compared to that of HA-Al2O3 coating.

Al-Si-Mn Alloy Coating on Aluminum Substrate Using Cold Metal Transfer (CMT) Welding Technique

Abstract: The cold metal transfer (CMT) process was explored as a weld overlay technique for synthesizing Al-Si-Mn alloy coating on a commercially pure Al plate. The effect of welding speed on the bead geometry, deposition rate, and the dilution were studied and the best parameter was used to synthesize the coatings. The CMT process can be used to produce thick coatings (>2.5 mm) without porosity and with low dilution levels. The Vickers hardness number of the Al substrate increased from 28 in the bulk to 57 in the coating. It is suggested that the CMT process can be an effective and energy-efficient technique for depositing thick coatings and is useful in weld repair of aluminum alloy components.

In-situ synthesis of TiC/SiC/Ti3SiC2 composite coatings by spark plasma sintering

Abstract: Composite coatings consisting of TiC/SiC/Ti3SiC2 phases have been synthesized using spark plasma sintering (SPS) of Ti/SiC/C powder mixture on titanium substrate. The processing of composite coatings was achieved at 1300 °C and 1400 °C with a uniaxial pressure of 90 MPa and holding time of 8 min. Identification and quantification of the phases have been performed using x-ray diffraction (XRD). X-ray elemental maps obtained using EDS have been used to analyze the evolution of various phases and their distribution in the microstructure. A tentative mechanism for phase evolution based on exothermic reactions between various constituent powders has been proposed. Microhardness of the spark plasma sintered coatings was found to be ~ 3 times that of the Ti substrate resulting in ~ 100 times lower wear weight loss in ball-on-disc wear tests.

Carbon nanotube and in-situ titanium carbide reinforced titanium diboride matrix composites synthesized by reactive spark plasma sintering

Abstract: Mechanically milled powder mixtures of Titanium and Boron containing 1, 2, 4 and 6 vol% multi-walled carbon nanotubes (CNT) were consolidated by reactive spark plasma sintering resulting in TiB 2 -TiC-CNT hybrid composites. Addition of CNT was found to affect the reaction rate for TiB 2 formation which results in sudden volume shrinkage. Rod shaped TiC were formed due to reaction between Ti and CNT. TiB 2 -TiC-CNT hybrid composites having more than 96% relative density with nanosized TiB 2 grains were obtained. XRD results revealed TiB 2 and TiC as major and minor phases respectively. Unreacted CNT were observed in SEM and TEM. TiB 2 -TiC-CNT composites showed nanohardness of above 25 GPa and elastic modulus of 520 GPa. Indentation fracture toughness was improved by 55% (3.3±0.1 to 5.11±0.6) by the addition of 4 vol% of CNT. The effect of CNT addition on oxidation and co-efficient of thermal expansion is also presented.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Carbon Nanotubes: Present and Future Commercial Applications

Abstract: Worldwide commercial interest in carbon nanotubes (CNTs) is reflected in a production capacity that presently exceeds several thousand tons per year. Currently, bulk CNT powders are incorporated in diverse commercial products ranging from rechargeable batteries, automotive parts, and sporting goods to boat hulls and water filters. Advances in CNT synthesis, purification, and chemical modification are enabling integration of CNTs in thin-film electronics and large-area coatings. Although not yet providing compelling mechanical strength or electrical or thermal conductivities for many applications, CNT yarns and sheets already have promising performance for applications including supercapacitors, actuators, and lightweight electromagnetic shields.