Srinivasa R. Bakshi
Other affiliations: Naval Postgraduate School, Indian Institutes of Technology, Soochow University (Suzhou) ...read more
Bio: Srinivasa R. Bakshi is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topic(s): Spark plasma sintering & Carbon nanotube. The author has an hindex of 34, co-authored 99 publication(s) receiving 4515 citation(s). Previous affiliations of Srinivasa R. Bakshi include Naval Postgraduate School & Indian Institutes of Technology.
TL;DR: In this paper, a review summarises the research work carried out in the field of carbon nanotube (CNT) metal matrix composites (MMCs), focusing on the critical issues of CNT-reinforced MMCs that include processing techniques, nanotubes dispersion, interface, strengthening mechanisms and mechanical properties.
Abstract: This review summarises the research work carried out in the field of carbon nanotube (CNT) metal matrix composites (MMCs). Much research has been undertaken in utilising CNTs as reinforcement for composite material. However, CNT-reinforced MMCs have received the least attention. These composites are being projected for use in structural applications for their high specific strength as well as functional materials for their exciting thermal and electrical characteristics. The present review focuses on the critical issues of CNT-reinforced MMCs that include processing techniques, nanotube dispersion, interface, strengthening mechanisms and mechanical properties. Processing techniques used for synthesis of the composites have been critically reviewed with an objective to achieve homogeneous distribution of carbon nanotubes in the matrix. The mechanical property improvements achieved by addition of CNTs in various metal matrix systems are summarised. The factors determining strengthening achieved by CNT reinforcement are elucidated as are the structural and chemical stability of CNTs in different metal matrixes and the importance of the CNT/metal interface has been reviewed. The importance of CNT dispersion and its quantification is highlighted. Carbon nanotube reinforced MMCs as functional materials are summarised. Future work that needs attention is addressed.
TL;DR: In this paper, the effects of CNT dispersion, processing technique, degree of deformation and CNT-matrix interface on the elastic modulus, strength and toughness of composites are analyzed.
Abstract: Tensile strength data of Al/CNT composites from the literature is analyzed to understand the effects of CNT dispersion, processing technique, degree of deformation and CNT–matrix interface on the elastic modulus, strength and toughness of composites. Strengthening can be divided in three regimes which show decreasing strengthening effect with an increasing CNT content. The strengthening is highest for CNT content less than 2 vol.%. The applicability of the micromechanics models in predicting the strength and elastic modulus of CNT reinforced metal matrix composites is also analyzed. The rule of mixtures is effective in predicting the elastic modulus of the Al/CNT composites for low CNT content (
01 Sep 2010-Acta Biomaterialia
TL;DR: Results indicate that BNNT is a potential reinforcement for composites for orthopedic applications and interactions of the osteoblasts and macrophages with bare BNNTs prove them to be non-cytotoxic.
Abstract: Biodegradable polylactide-polycaprolactone copolymer (PLC) has been reinforced with 0, 2 and 5wt.% boron nitride nanotubes (BNNTs) for orthopedic scaffold application. Elastic modulus of the PLC-5wt.% BNNT composite, evaluated through nanoindentation technique, shows a 1370% increase. The same amount of BNNT addition to PLC enhances the tensile strength by 109%, without any adverse effect on the ductility up to 240% elongation. Interactions of the osteoblasts and macrophages with bare BNNTs prove them to be non-cytotoxic. PLC-BNNT composites displayed increased osteoblast cell viability as compared to the PLC matrix. The addition of BNNTs also resulted in an increase in the expression levels of the Runx2 gene, the main regulator of osteoblast differentiation. These results indicate that BNNT is a potential reinforcement for composites for orthopedic applications.
•19 Oct 2010
TL;DR: In this article, Meyyappan et al. describe the development of reinforced metal matrix carbon nanotubes (MM-CNT) composites for large-scale applications and provide a roadmap to help researchers develop these composites and choose potential materials.
Abstract: From the Foreword, written by legendary nano pioneer M. Meyyappan, Chief Scientist for Exploration Technology NASA Ames Research Center, Moffett Field, California, USA: "…there is critical need for a book to summarize the status of the field but more importantly to lay out the principles behind the technology. This is what Professor Arvind Agarwal and his co-workers … have done here." Carbon Nanotubes: Reinforced Metal Matrix Composites reflects the authors’ desire to share the benefits of nanotechnology with the masses by developing metal matrix carbon nanotube (MM-CNT) composites for large-scale applications. Multiwall carbon nanotubes can now be produced on a large scale and at a significantly reduced cost. The book explores potential applications and applies the author’s own research to highlight critical developmental issues for different MM-CNT composites—and then outline novel solutions. With this problem-solving approach, the book explores: Advantages, limitations, and the evolution of processing techniques used for MM-CNT composites Characterization techniques unique to the study of MM-CNT composites—and the limitations of these methods Existing research on different MM-CNT composites, presented in useful tables that include composition, processing method, quality of CNT dispersion, and properties The micro-mechanical strengthening that results from adding CNT The applicability of micro-mechanics models in MM-CNT composites Significance of chemical stability for carbon nanotubes in the metal matrix as a function of processing, and its impact on CNT/metal interface and mechanical properties Computational studies that have not been sufficiently covered although they are essential to research and development The critical issue of CNT dispersion in the metal matrix, as well as a unique way to quantify CNT distribution and subsequently improve control of the processing parameters for obtaining improved properties Carbon Nanotubes: Reinforced Metal Matrix Composites paints a vivid picture of scientific and application achievements in this field. Exploring the mechanisms through which CNTs are enhancing the properties of different metal-based composites, the authors provide a roadmap to help researchers develop MM-CNT composites and choose potential materials for use in emerging areas of technology.
TL;DR: In this paper, a multiwalled carbon nanotube (CNT) reinforced aluminum nanocomposite coatings were prepared using cold gas kinetic spraying, which resulted in coatings of the order of 500μm in thickness.
Abstract: Multiwalled carbon nanotube (CNT) reinforced aluminum nanocomposite coatings were prepared using cold gas kinetic spraying. Spray drying was used to obtain a good dispersion of the nanotubes in micron-sized gas atomized Al–Si eutectic powders. Spray dried powders containing 5 wt.% CNT were blended with pure aluminum powder to give overall nominal CNT compositions of 0.5 wt.% and 1 wt.% respectively. Cold spraying resulted in coatings of the order of 500 μm in thickness. Fracture surfaces of deposits show that the nanotubes were uniformly distributed in the matrix. Nanotubes were shorter in length as they fractured due to impact and shearing between Al–Si particles and the Al matrix during the deposition process. Nanoindentation shows a distribution in the elastic modulus values from 40–229 GPa which is attributed to microstructural heterogeneity of the coatings that comprise the following: pure Al, Al–Si eutectic, porosity and CNTs.
01 May 1993
TL;DR: 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.
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.
TL;DR: In this paper, a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) is presented.
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
TL;DR: 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.
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.
01 Jun 2005