Colonel (Dr) Vijay Kumar | Defence Institute of Advanced Technology (DU), Pune, India. (original) (raw)
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Papers by Colonel (Dr) Vijay Kumar
Book Chapter in Macromolecular Engineering: From Precise Synthesis to Macroscopic Materials and Applications, Second Edition, 2022
Composites are the precisely formed multiphase materials, wherein the constituent p... more Composites are the precisely formed multiphase materials, wherein the constituent phases enable desirable amalgamation of the best properties. The composites are usually optimized with a set of properties for the desired range of applications and often used for their structural properties. Ablative composites are highly endothermic sacrificial materials, which undergo ablation wherein the outer surface of the material degrades to form a carbonaceous layer, which isolates the underlying material from intense thermal-heat-flux environs. Ablative materials widely explored for various applications in the space sector
are based on carbon, ceramic, elastomeric, and thermoset matrices. However, from the very beginning of the space activity, polymer composites continue to be the most versatile thermal protection materials. Phenolic resins have emerged as superior charring binders and their ablative performance is further enhanced by modification with ultra-high temperature ceramics (UHTCs). Nanotechnology-enabled new areas of developments make a strong case to articulate high-thermal-ablative characteristics from the interface zone in-between inorganic and organic phases for polymer composites. This article presents an overview of the polymer composites as ablative materials.
Industrial & Engineering Chemistry Research, 2019
Ablative composites are highly endothermic sacrificial thermal protection materials, indispensabl... more Ablative composites are highly endothermic sacrificial thermal protection materials, indispensable from the aerospace industry. Polymeric ablatives are the most versatile and the largest class of thermal protection materials due to their capability to be turned to varied hyper-thermal environment. Carbon/carbon composites have outstanding mechanical properties at higher temperatures but they are susceptible to oxidation, which is addressed by matrix modification or coating ultra-high temperature ceramics (UHTC) and also by the use of nanostructures toughened UHTC coatings as discussed in this article. The article presents a comprehensive review of the science and technology of the four distinct groups of ablative composites (carbon/carbon, carbon/phenolic, carbon/elastomeric and carbon/ceramic). The selection of the best material formulations for a given environment is ratified by the testing techniques, which have also been reviewed along with a brief discussion on the composites recycling technologies and their environmental and economic impacts.
JOURNAL OF APPLIED POLYMER SCIENCE, 2017
In this study, we demonstrated a novel three-dimensional network of thermally stable fumed silica... more In this study, we demonstrated a novel three-dimensional network of thermally stable fumed silica (FS)-resorcinol formal-dehyde (RF) nanocomposites via an ionic-liquid (IL)-assisted in situ polycondensation process. The study involved subjecting the tailored nanocomposites to thermogravimetric analysis and oxyacetylene flame environment as per ASTM test standards for thermal ablative performance. X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, and wettability studies were undertaken to underline the improvement correlation in the microstructure and material properties. Significant reductions in the linear ablation rate (66%) and mass ablation rate (26.6%), along with lower back-face temperature profiles, marked enhanced ablative properties. The increased char yield (33.3%) and higher temperatures for weight losses evinced the improved thermal stability of the modified RF resin. The uniformly dispersed fused nanosilica with a glassy coating morphology on the ablative surface acted as barrier to oxidation. The results signify that the IL-assisted modification of the RF resin with FS significantly enhanced ablative performance. A viable replacement to the conventional phenolic nanocomposites for thermal ablative applications to buy critical time for the containment and suppression of thermal-heat-flux threats is of paramount importance.
Laser shielding characteristics of Fumed Silica (FS)-Resorcinol Formaldehyde (RF) nanocomposites ... more Laser shielding characteristics of Fumed Silica (FS)-Resorcinol Formaldehyde (RF) nanocomposites tailored via a facile in-situ polymerization technique have been investigated. The samples were subjected to Nd:YAG pulsed wave lasers to measure ablation energy for the specimen materials. The modification of RF resin with FS increases the ablation energy (32.6%) compared to pristine RF. The ablation energy significantly increases (73.5%) for the ionic liquid assisted modification. Morphology of the irradiated surface studied along with FTIR, XRD and contact angle measurements to understand the underlying reasons for the improvement in the properties.
Thermal ablation performance, thermal stability and laser shielding characteristics of tailored n... more Thermal ablation performance, thermal stability and laser shielding characteristics of tailored nanoclay (NC)-resorcinol formaldehyde (RF) nanocomposites have been investigated. RF resin was modified with ionic liquid and a range of weight loadings of functionalized nanoclay via a facile in-situ polymerization technique. Thermal ablation testing of the modified resin shows lower back-face temperature profiles and distinct reduction in linear and mass ablation rates while TGA results show enhanced thermal stability. Significant increase in the laser ablation energy and increased d-spacing of the surface modified nanoclay in RF nanocomposite connote favorable polymer intercalation / exfoliation within the silicate layers.
Air plasma spray Electron beam-physical vapor deposition Thermally grown oxide Yttria-stabilized ... more Air plasma spray Electron beam-physical vapor deposition Thermally grown oxide Yttria-stabilized zirconia Thermal conductivity a b s t r a c t Thermal barrier coating is a crucial thermal insulation technology that enables the underlying substrate to operate near or above its melting temperature. Such coatings bolster engineers' perpetual desire to increase the power and efficiency of gas turbine engines through increasing the turbine inlet temperature. Advances in recent years have made them suitable for wider engineering and defense applications, and hence they are currently attracting considerable attention. A thermal barrier coating system is itself dynamic; its components undergo recurrent changes in their composition, microstructure and crystalline phases during its service life. Nevertheless, the performance of multi-layered and multi-material systems tailored for high temperature applications is closely linked to the deposition process. The process improvements achieved so far are the outcome of increased understanding of the relationship between the coating morphology and the operating service conditions, as well as developments in characterization techniques. This article presents a comprehensive review of various processing techniques and design methodologies for thermal barrier coatings. The emphasis of this review is on the particle technology; the interrelationship between particle preparation, modification and the resulting properties, to assist developments in advanced and novel thermal barrier coatings for engineering applications.
Thermal barrier coatings (TBCs) have proved to be a key technology in thermal stability and their... more Thermal barrier coatings (TBCs) have proved to be a key technology in thermal stability and their use to
achieve surface temperature reduction of the underlying super alloys surpass all other achievements in
the field of material technologies that have taken place in last three decades. The technological advances
in TBCs also make them suitable for wider engineering and defense applications. The performance of these multi-layered and multi-material systems, tailored for high temperature applications is closely linked
to their microstructure evolution. The article presents a comprehensive review of various degradation
mechanisms to which the TBC system is subjected during service life viz. hot corrosion, CMAS attack,
oxidation, erosion, foreign object damage, sintering and phase transformations. Strategies to mitigate
the adverse impact of the degradation mechanisms and the recent advances toward reduction in the
thermal conductivity of TBCs have also been discussed. The emphasis of this review is on the relationship
between the properties and the microstructure of TBCs for better understanding of their life limiting
mechanisms to assist developments in advanced and novel TBCs for engineering applications.
Book Chapter in Macromolecular Engineering: From Precise Synthesis to Macroscopic Materials and Applications, Second Edition, 2022
Composites are the precisely formed multiphase materials, wherein the constituent p... more Composites are the precisely formed multiphase materials, wherein the constituent phases enable desirable amalgamation of the best properties. The composites are usually optimized with a set of properties for the desired range of applications and often used for their structural properties. Ablative composites are highly endothermic sacrificial materials, which undergo ablation wherein the outer surface of the material degrades to form a carbonaceous layer, which isolates the underlying material from intense thermal-heat-flux environs. Ablative materials widely explored for various applications in the space sector
are based on carbon, ceramic, elastomeric, and thermoset matrices. However, from the very beginning of the space activity, polymer composites continue to be the most versatile thermal protection materials. Phenolic resins have emerged as superior charring binders and their ablative performance is further enhanced by modification with ultra-high temperature ceramics (UHTCs). Nanotechnology-enabled new areas of developments make a strong case to articulate high-thermal-ablative characteristics from the interface zone in-between inorganic and organic phases for polymer composites. This article presents an overview of the polymer composites as ablative materials.
Industrial & Engineering Chemistry Research, 2019
Ablative composites are highly endothermic sacrificial thermal protection materials, indispensabl... more Ablative composites are highly endothermic sacrificial thermal protection materials, indispensable from the aerospace industry. Polymeric ablatives are the most versatile and the largest class of thermal protection materials due to their capability to be turned to varied hyper-thermal environment. Carbon/carbon composites have outstanding mechanical properties at higher temperatures but they are susceptible to oxidation, which is addressed by matrix modification or coating ultra-high temperature ceramics (UHTC) and also by the use of nanostructures toughened UHTC coatings as discussed in this article. The article presents a comprehensive review of the science and technology of the four distinct groups of ablative composites (carbon/carbon, carbon/phenolic, carbon/elastomeric and carbon/ceramic). The selection of the best material formulations for a given environment is ratified by the testing techniques, which have also been reviewed along with a brief discussion on the composites recycling technologies and their environmental and economic impacts.
JOURNAL OF APPLIED POLYMER SCIENCE, 2017
In this study, we demonstrated a novel three-dimensional network of thermally stable fumed silica... more In this study, we demonstrated a novel three-dimensional network of thermally stable fumed silica (FS)-resorcinol formal-dehyde (RF) nanocomposites via an ionic-liquid (IL)-assisted in situ polycondensation process. The study involved subjecting the tailored nanocomposites to thermogravimetric analysis and oxyacetylene flame environment as per ASTM test standards for thermal ablative performance. X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, and wettability studies were undertaken to underline the improvement correlation in the microstructure and material properties. Significant reductions in the linear ablation rate (66%) and mass ablation rate (26.6%), along with lower back-face temperature profiles, marked enhanced ablative properties. The increased char yield (33.3%) and higher temperatures for weight losses evinced the improved thermal stability of the modified RF resin. The uniformly dispersed fused nanosilica with a glassy coating morphology on the ablative surface acted as barrier to oxidation. The results signify that the IL-assisted modification of the RF resin with FS significantly enhanced ablative performance. A viable replacement to the conventional phenolic nanocomposites for thermal ablative applications to buy critical time for the containment and suppression of thermal-heat-flux threats is of paramount importance.
Laser shielding characteristics of Fumed Silica (FS)-Resorcinol Formaldehyde (RF) nanocomposites ... more Laser shielding characteristics of Fumed Silica (FS)-Resorcinol Formaldehyde (RF) nanocomposites tailored via a facile in-situ polymerization technique have been investigated. The samples were subjected to Nd:YAG pulsed wave lasers to measure ablation energy for the specimen materials. The modification of RF resin with FS increases the ablation energy (32.6%) compared to pristine RF. The ablation energy significantly increases (73.5%) for the ionic liquid assisted modification. Morphology of the irradiated surface studied along with FTIR, XRD and contact angle measurements to understand the underlying reasons for the improvement in the properties.
Thermal ablation performance, thermal stability and laser shielding characteristics of tailored n... more Thermal ablation performance, thermal stability and laser shielding characteristics of tailored nanoclay (NC)-resorcinol formaldehyde (RF) nanocomposites have been investigated. RF resin was modified with ionic liquid and a range of weight loadings of functionalized nanoclay via a facile in-situ polymerization technique. Thermal ablation testing of the modified resin shows lower back-face temperature profiles and distinct reduction in linear and mass ablation rates while TGA results show enhanced thermal stability. Significant increase in the laser ablation energy and increased d-spacing of the surface modified nanoclay in RF nanocomposite connote favorable polymer intercalation / exfoliation within the silicate layers.
Air plasma spray Electron beam-physical vapor deposition Thermally grown oxide Yttria-stabilized ... more Air plasma spray Electron beam-physical vapor deposition Thermally grown oxide Yttria-stabilized zirconia Thermal conductivity a b s t r a c t Thermal barrier coating is a crucial thermal insulation technology that enables the underlying substrate to operate near or above its melting temperature. Such coatings bolster engineers' perpetual desire to increase the power and efficiency of gas turbine engines through increasing the turbine inlet temperature. Advances in recent years have made them suitable for wider engineering and defense applications, and hence they are currently attracting considerable attention. A thermal barrier coating system is itself dynamic; its components undergo recurrent changes in their composition, microstructure and crystalline phases during its service life. Nevertheless, the performance of multi-layered and multi-material systems tailored for high temperature applications is closely linked to the deposition process. The process improvements achieved so far are the outcome of increased understanding of the relationship between the coating morphology and the operating service conditions, as well as developments in characterization techniques. This article presents a comprehensive review of various processing techniques and design methodologies for thermal barrier coatings. The emphasis of this review is on the particle technology; the interrelationship between particle preparation, modification and the resulting properties, to assist developments in advanced and novel thermal barrier coatings for engineering applications.
Thermal barrier coatings (TBCs) have proved to be a key technology in thermal stability and their... more Thermal barrier coatings (TBCs) have proved to be a key technology in thermal stability and their use to
achieve surface temperature reduction of the underlying super alloys surpass all other achievements in
the field of material technologies that have taken place in last three decades. The technological advances
in TBCs also make them suitable for wider engineering and defense applications. The performance of these multi-layered and multi-material systems, tailored for high temperature applications is closely linked
to their microstructure evolution. The article presents a comprehensive review of various degradation
mechanisms to which the TBC system is subjected during service life viz. hot corrosion, CMAS attack,
oxidation, erosion, foreign object damage, sintering and phase transformations. Strategies to mitigate
the adverse impact of the degradation mechanisms and the recent advances toward reduction in the
thermal conductivity of TBCs have also been discussed. The emphasis of this review is on the relationship
between the properties and the microstructure of TBCs for better understanding of their life limiting
mechanisms to assist developments in advanced and novel TBCs for engineering applications.