Browsing by Author "Kumar Thakur, Vijay"

Now showing 1 - 9 of 9
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    4D printing of materials for the future: opportunities and challenges
    (Elsevier, 2019-10-16) Joshi, Siddharth; Rawat, Krishna; Karunakaran, C.; Rajamohan, Vasudevan; Mathew, Arun Tom; Koziol, Krzysztof K. K.; Kumar Thakur, Vijay; Balan, A.S.S
    The concept of 4D printing is its formation of complex three-dimensional structures that have the ability to adopt different shapes and forms when subjected to different environmental stimuli. A few researchers simply view 4D printing as an extended technique of 3D printing or additive manufacturing with the added constraint of time. However, the unique shape change mechanism exhibited in this process is a combination of shape programming and the usage of smart active materials mostly polymers. This review article highlights the various smart materials, activation mechanisms and the shape-changing techniques employed in the 4D printing process. The potential of the shape-changing structures and their current applications in various biomedical and engineering fields is also explored. The article aims to emphasize the potential and viability of 4D printing and focused on providing an in-depth insight into the 4D printing process.
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    'Data sheet of nanocomposites with F/N-doped ZnO'
    (Cranfield University, 2024-02-20 13:07) Chen, Shuyang; Skordos, Alex; Kumar Thakur, Vijay
    The dataset for this research comprises the measurement results for pristine PVDF and PVDF-ZnO nanocomposites with and without fluorine/nitrogen doping. For TGA, DSC and XRD results each file contains the relevant data per experimental technique. Within each file worksheets correspond to the different materials. The column headers specify the variables and their associated units. For dielectric tests, the data is organised in separate files for permittivity, loss and imaginary modulus. The data are organised in worksheets by material in 2D arrays. The rows correspond to spectra at different measured temperatures and the columns to fixed frequency data. The materials nomenclature is as follows: -PVDF: pure PVDF -PVDF+5% ZnO: PVDF with 5% ZnO by weight -PVDF+10% ZnO: PVDF with 10% ZnO by weight -PVDF+15% ZnO: PVDF with 15% ZnO by weight -PVDF+5% F-ZnO: PVDF with 5% Fluorine doped (10% molar fraction) ZnO by weight -PVDF+10% F-ZnO: PVDF with 10% Fluorine doped (10% molar fraction) ZnO by weight -PVDF+15% F-ZnO: PVDF with 15% Fluorine doped (10% molar fraction) ZnO by weight -PVDF+5% N-ZnO: PVDF with 5% Nitrogen doped (10% molar fraction) ZnO by weight-PVDF+10% N-ZnO: PVDF with 10% Nitrogen doped (10% molar fraction) ZnO by weight -PVDF+15% N-ZnO: PVDF with 15% Nitrogen doped (10% molar fraction) ZnO by weight
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    Exploring new horizons for paper recycling: A review of biomaterials and biorefinery feedstocks derived from wastepaper
    (Elsevier, 2018-03-09) Adu, Cynthia; Jolly, Mark R.; Kumar Thakur, Vijay
    Paper is a perfect example of the circular economy as it remains the furthermost recycled product in Europe, creating significant environmental benefits and raw materials resources to the industry. Indeed, maintaining a consistent level of quality whilst limiting the environmental footprint of the product has become a major challenge for the industry. In this direction, paper is proving to be the promising feedstock for biorefinery and biomaterials. The future of paper recycling is slowly going beyond fibre recovery to address the needs of other industries because for the earth's environmental well-being various paper products need to be recycled and reused persistently. In this article, we outline the ambitious use of wastepaper (WP) for high-value applications such as; production of cellulose nanocrystals (CNC), composite reinforcement, high performance electrical components and biofuels.
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    High performance thermosets with tailored properties derived from methacrylated eugenol and epoxy-based vinyl ester
    (Wiley, 2018-01-31) Zhang, Yuehong; Li, Yuzhan; Kumar Thakur, Vijay; Gao, Zhenhua; Gu, Jiyou; Kessler, Michael R.
    A renewable chemical, eugenol, is methacrylated to produce methacrylated eugenol (ME) employing the Steglich esterification reaction without any solvent. The resulting ME is used as a low viscosity comonomer to replace styrene in a commercial epoxy-based vinyl ester resin (VE). The volatility and viscosity of ME and styrene are compared. The effect of ME loadings and temperatures on viscosity of the VE-ME resin is investigated. Moreover, the thermo-mechanical properties, curing extent, and thermal stability of the fully cured VE-ME thermosets are systematically examined. The results indicate that ME is a monomer with low volatility and low viscosity, and therefore the incorporation of ME monomer in VE resins allows significant reduction of viscosity. Moreover, viscosity of the VE-ME resin can be tailored by adjusting ME loadings and processing temperature to meet commercial liquid molding technology requirements. The glass transition temperatures of VE-ME thermosets range from 139 to 199 °C. In addition, more than 95% of the monomer is incorporated and fixed in the crosslinked network structure of VE-ME thermosets. Overall, the developed ME monomer exhibits promising potential to replace styrene as an effective low viscosity comonomer. The VE-ME resins show great advantages for use in polymer matrices for high performance fiber-reinforced composites. This work showed great significance to the vinyl ester industry by providing detailed experimental support.
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    Manufacturing and characterization of regenerated cellulose/curcumin based sustainable composites fibers spun from environmentally benign solvents
    (Elsevier, 2017-12-11) Coscia, Marta Gina; Bhardwaj, Jyoti; Singh, Nandita; Santonicola, M. Gabriella; Richardson, Robert M.; Kumar Thakur, Vijay; Rahatekar, Sameer S.
    We report a novel manufacturing method for bio renewable regenerated cellulose fibres modified with curcumin, a molecule is known for its medicinal properties. Ionic liquid namely 1-Ethyl 3-Methyl Imidazolium diethyl phosphate (emim DEP) was found to be capable of dissolving cellulose as well as curcumin. Regenerated cellulose/curcumin composites fibres with curcumin concentration ranging from 1 to 10 wt% were manufactured using dry jet wet fibres spinning process using three different winding speeds. All the cellulose and curcumin composite fibres showed distinct yellow colour imparted by curcumin. The resultant fibres were characterised using scanning electron microscopy (SEM), infrared spectroscopy, mechanical testing, and X-Ray diffraction studies. Scanning electron microscopy of cellulose/curcumin fibres cross-section did not show curcumin aggregates in cellulose fibres indicating uniform dispersion of curcumin in cellulose matrix. The cellulose chain alignment in cellulose/curcumin composite fibres resulted in tensile strength ranging from 223 to 336 MPa and Young’s modulus ranging from 13 to 14.9 GPa. The mechanical properties of cellulose/curcumin composite fibres thus obtained are better than some of the commercially available regenerated cellulose viscose fibres. The wide-angle X-ray diffraction analysis of cellulose/curcumin composite fibres showed good alignment of cellulose chains along the fibre axis. Thus, our findings are a major step in manufacturing strong cellulose fibres with a pharmacologically potent drug curcumin which in future could be used for medicinal, cosmetic and food packaging applications.
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    On the morphological investigation of Pt dispersion and structure of alumina-platinum composites obtained by thermal oxidation of Al-Pt nano thin layers
    (Elsevier, 2019-01-30) Reszka, Kazimierz; Morgiel, Jerzy; Rydzkowski, Tomasz; Kumar Thakur, Vijay
    This article presents the methodology for the Pt/Al and Pt/Al nanolaminates production as well as Pt + Al composites using two magnetrons by preparing the oxide-metal composites through high temperature oxidation of nanofilms deposited by PVD method on a metal substrate. In this article, we described the nanostructures obtained as a result of PVD technology. The applied layers were oxidized at a temperature of 860°C under Ar + O2 for 48 hours. SEM surface analysis of the obtained nanolaminates showed that the base of the oxidized laminates was covered with a fine wafer and whisker structure with an anisotropic growth orientation. Oxidation of composite layers provided the growth of chaotically oriented and mutually penetrable whiskers and small crystals. Analysis of nanolayers by the TEM technique indicated that the growth of oxide crystals leads to the dissipation of Pt particles. The comparison of oxide layers obtained with the Pt/Al system with oxide layers obtained with Pt + Al composite nanofilms indicates that those obtained through the oxidation of nanofilms shows a greater surface development. This is due to the partial covering of Pt particles through the Al layer, which causes a very strong fragmentation of the Pt nanofilms occurring during oxidation. During the oxidation in the entire volume of nanofilms, strong stresses are created that cause numerous nano-cracks, which promotes the expansion of the surface and its high activity.
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    Progress in hydroxyapatite-starch based sustainable biomaterials for biomedical bone substitution applications
    (American Chemical Society, 2017-09-05) Miculescu, F.; Maidaniuc, A.; Voicu, Stefan Ioan; Kumar Thakur, Vijay; Stan, G. E.; Ciocan, L. T.
    Hydroxyapatite is a calcium phosphate intensively proposed as a bone substitution material because of its resemblance to the constituents of minerals present in natural bone. Since hydroxyapatite’s properties are mainly adequate for nonload bearing applications, different solutions are being tested for improving these properties and upgrading them near the target values of natural bone. On the other hand, starch (a natural and biodegradable polymer) and its blends with other polymers have been proposed as constituents in hydroxyapatite mixtures due to the adhesive, gelling, and swelling abilities of starch particles, useful in preparing well dispersed suspensions and consolidated ceramic bodies. This article presents the perspectives of incorporating starch and starch blends in hydroxyapatite materials. Based on the role of starch within the materials, the review covers its use as (i) a polymeric matrix in hydroxyapatite composites used as adhesives, bone cements, bone waxes, drug delivery devices or scaffolds and (ii) a sacrificial binder for fabrication of porous hydroxyapatite scaffolds. The suitability of these materials for bone reconstruction has becomes a reachable aim considering the recent advancements in ceramic fabrication and the current possibilities of controlling the processing parameters.
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    Progress in lignin hydrogels and nanocomposites for water purification: Future perspectives
    (Elsevier, 2017-08-12) Thakur, Sourbh; Govender, Penny P.; Mamo, Messai A.; Tamulevicius, Sigitas; Kumar Mishra, Yogendra; Kumar Thakur, Vijay
    Lignin is one of the most abundant natural polymers after cellulose and has attracted great attention in academia as well as in industry for miscellaneous applications. Lignin also exhibits very high potential as a renewable sustainable resource for a galaxy of high value biochemicals. Due to the typical structure of lignin, it can be converted into different types of useful products. From a ligno-cellulose bio-refinery prospective point of view, it can be regarded as an economic bio product and can also be used as filler in several polymers to form blends or composites. Recently lignin-based hydrogels have shown excellent performance for removal of various pollutants from water. The adsorption properties of lignin based hydrogels can further be improved by using a combination of nanomaterials and lignin that results in promising hydrogel nanocomposites. In nature, the most abundant structures are formed by the combination of lignin, cellulose and hemicelluloses. In this article, we have attempted to comprehensively review the research work carried out in the direction of usage of lignin-based hydrogel for removal of toxic pollutants including metal ions and dyes.
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    Synthesis and characterization of jellified composites form bovine bone-derived hydroxyapatite and starch as precursors for robocasting
    (American Chemical Society, 2018-01-31) Miculescu, Florin; Maidaniuc, Andreea; Miculescu, Marian; Dan Batalu, Nicolae; Cătălin Ciocoiu, Robert; Voicu, Stefan Ioan; Stan, George E.; Kumar Thakur, Vijay
    Hydroxyapatite–starch composites solidify rapidly via jellification, making them suitable candidates for robocasting. However, many aspects related to hydroxyapatite powder characteristics, hydroxyapatite–starch interaction, and composites composition and properties need to be aligned with robocasting requirements to achieve a notable improvement in the functionality of printed scaffolds intended for bone regeneration. This article presents a preliminary evaluation of hydroxyapatite–starch microcomposites. Thermal analysis of the starting powders was performed for predicting composites’ behavior during heat-induced densification. Also, morphology, mechanical properties, and hydroxyapatite–starch interaction were evaluated for the jellified composites and the porous bodies obtained after conventional sintering, for different starch additions, and for ceramic particle size distributions. The results indicate that starch could be used for hydroxyapatite consolidation in limited quantities, whereas the composites shall be processed under controlled temperature. Due to a different mechanical behavior induced by particle size and geometry, a wide particle size distribution of hydroxyapatite powder is recommended for further robocasting ink development.