IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Addendum of Project Agreement project titled “Additive Manufacturing of Steels by Laser Metal Deposition (LMD),Project No.CLP0208
No full textA Comparative Study on the Moisture Response of Nanoporous gamma-Alumina with Parallel Plate and Micro-Interdigital Electrodes
No full textNanoporous gamma-alumina thick films were prepared from its aqueous sol which in turn was prepared from an organometallic precursor. Ethylacetoacetate was added into the sol as a crack suppressing agent. The sensing behavior of the said film was measured in capacitive mode both in percentage relative humidity (%RH) level as well as parts per million by volume (ppm(v)) level moisture present in the gas phase. Two different electrode designs viz. parallel plate parallel electrode configuration (PEC)] and micro-interdigital (inter-digital configuration) were employed for the sensing study. PEC shows superior sensing behavior over the interdigital electrode. The capacitance of the sensor with PE and ID configuration increase from similar to 17 pF to similar to 153 pF and similar to 15 pF to similar to 24 pF, respectively, as the moisture content increased from 2 ppm to 100 ppm. Further, the capacitance of the sensor with PE and ID configuration increased from similar to 151 pF to similar to 963 pF and similar to 97 pF to similar to 521 pF, respectively, as moisture content increased from 5% to 60%RH. Schematic and equivalent circuit diagrams for both electrode designs were invoked to explain the achieved superior sensitivity. In addition, the fabricated gamma-alumina thick film based capacitive moisture sensor in parallel plate electrode geometry demonstrates low hysteresis (similar to 10 pF at 60%RH and similar to 0.8 pF at 50 ppm(v) moisture content), appreciable repeatability over 15 cycles, prolonged stability for 12 months, robustness, drift-free measurement, impressive resolution, usability at high temperature, magnetic field, radiative and corrosive/toxic gas environment. GRAPHICS]
Improvement of thermal conductivity of carbonaceous matrix in monolithic Al2O3-C refractory composite by surface-modified graphites
No full textThe thermal conductivity of the matrix part of alumina - carbon unshaped refractory has been estimated to accurately interpret its thermophysical and thermomechanical behavior. The properties of precalcined composite matrix containing either as-received or surface-modified graphite in equal quantity (20.0 wt%) have been investigated at three different temperatures (110,550,900 degrees C). The thermal compatibility or degradation of both kinds of carbonaceous matrices had been correlated with respective scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) analyses. The monolithic matrices were also subjected to X-ray diffraction (XRD) studies to distinguish between their phase evolution patterns. A synergestic study on an equivalent graphite-free formulation was also carried out. The thermal shock resistance profile of respective castables had been addressed to confirm the superiority of surface-treated graphites. Nanoengineering at graphite surface was conceived by Rietveld analysis of the (004) peak that substantiated the additional influence of calcium aluminate coating on selective clumping and partial exfoliation of graphite sheets
Densification, microstructure and tribomechanical properties of SPS processed beta-SiAlON bonded WC composites
No full textDensification, microstructure and tribomechanical properties of spark plasma sintering (SPS) processed beta-SiAlON (20-40 wt%) bonded WC matrix composites have been reported. All the specimens achieved almost their theoretical density values after SPS at 1750 degrees C for 25 min under 40 MPa. Incorporation of beta-SiAlON in WC significantly altered the densification trend of the composites resembling that of pure beta-SiAlON. Microstructural investigations using scanning and transmission electron microscopy revealed formation of principally equiaxed, micron sized WC grains surrounded by the sub-micron to micron sized beta-SiAlON phase. The interface region between WC and beta-SiAlON was found to be free of any reaction product. Energy dispersive X-ray spectrum confirmed presence of characteristics elements in both WC and beta-SiAlON phases in the composite. The maximum Vickers hardness (similar to 18 GPa) and fracture toughness (similar to 6.8 MPa-m(0.5)) under 10 kgf were obtained for the 30 wt% beta-SiAlON/WC composite. These were almost 6% and 50% higher, respectively, than those obtained for pure WC. Indentation size effect (ISE) analyses of some selected specimens indicated moderate sensitivity towards ISE (Meyer's exponent = 1.802) of the 30 wt% beta-SiAlON/WC composite and higher true hardness (similar to 15.4 GPa) than those obtained for both the constituent phases. The load dependence of fracture toughness of some selected specimens has also been reported. Unlubricated wear studies under 30 N up to 250 m using ball-on-disc configuration indicated similar to 46-55 times higher specific wear rate of the beta-Si3N4 ball when rubbed against the composites compared to that (similar to 8 x 10(-6) mm(3)/N-m) obtained against pure WC. Formation of compacted flaky tribo-layer within the wear track of the composites was evidenced
Enhancement of optical properties of boron-doped SiC thin film: a SiC QD effect
No full textSilicon carbide quantum dots (SiC-QD) embedded inside the SiC thin film deposited on silicon (111) wafer is directly synthesized by modified chemical vapour deposition technique using boron-doped liquid polycarbosilane as a precursor. Subsequent microscopic characterization of the thin film exhibits the presence of QD, which is theoretically corroborated from the exciton Bohr radius. The film shows interesting visible and near-infra-red photoluminescence at room temperature with enhanced lifetime. In addition to the lifetime, the quantum efficiency in the visible emission was also enhanced substantially than what was reported previously
Mechanical behaviour of additively manufactured bioactive glass/high density polyethylene composites
No full textBioactive glass (BAG) is a well-known biomaterial that can form a strong bond with hard and soft tissues and can also aid in bone regeneration. In this study, BAG is added to a polymer to induce bioactivity and to realize fused filament fabrication (FFF) based printing of polymer composites for potential orthopaedic implant applications. BAG (5, 10, and 20 wt%) is melt compounded with high density polyethylene (HDPE) and subsequently extruded into feedstock filament for FFF-printing. Tensile tests on developed filaments reveal that they are stiff enough to resist forces exerted during the printing process. Micrography of printed HDPE/BAG reveals perfect diffusion of raster interface indicating proper selection of printing parameters. Micrography of freeze fractured prints shows the homogeneous distribution and good dispersion of filler across the matrix. The tensile, flexural, and compressive modulus of FFF-printed HDPE/BAG parts increases with filler addition. BAG addition to the HDPE matrix enhances flexural and compressive strength. The tensile and flexural behaviour of FFF-prints is comparable to injection molded counterparts. Property maps exhibit the merits of present study over the existing literature pertaining to desired bone properties and polymer composites used in biomedical applications. It is envisioned that the development of HDPE/BAG composites for FFF-printing can lead to possible orthopaedic implants and scaffolds to mimic the bone properties in customised anatomical sites or injuries
Silver as solid-state electron mediator in MoS2/Ag-AgVO3 Z-Scheme heterostructures for photocatalytic H-2 generation
No full textHeterostructured photocatalysts have attracted enoromous research interest in H-2 generation through water splitting because of highly efficient interfacial charge-transfer characteristics of nanoarchitectures. Herein, Ag nanoparticles decorated AgVO3 nanorods and MoS2 nanosheets are combined to fabricate MoS2/Ag-AgVO3 heterostructures,in which Ag NPs act as a solid-state electron mediator. Owing to unique nanoarchitecture, MoS2/Ag-AgVO3 exhibited the best H-2 generation (reaches 38.6 mmol g(-1) in 2 h) whichis four times and twenty times higher than Ag-AgVO3 and bare MoS2 under visible light respectively. Transient photocurrent and Nyquist spectra reveal that the enhanced photocatalytic performance of MoS2/Ag-AgVO3 is mainly attributed to its effective carrier separation and transfer through the surfaces. Moreover, the band structures of the materials have been calculated from Mott-Schottky study, demonstrated a Z-scheme interfacial charge-transfer mechanism. This study describes a promising approach for harvesting solar energy to generate H-2 from water by designing an efficient Ag mediated Z-scheme heterostuctures. (C) 2020 Elsevier B.V. All rights reserved
An insight into the structure, composition and hardness of a biological material: the shell of freshwater mussels
No full textThe shell of the freshwater mussel (Mollusca: Bivalvia) is a composite biological material linked with multifunctional roles in sustaining ecosystem services. Apart from providing mechanical strength and support, the shell is an important site for adherence and growth of multiple types of algae and periphyton. Variations in the shell architecture are observed in the mussels both within a species and among different species. Considering the prospective utility of the shell of the freshwater mussels as a biological material, an assessment of the shell characteristics was accomplished usingCorbicula bensoniandLamellidens marginalisas model species. The calcium carbonate (CaCO3) content of the shells, physical features and mechanical strength were assessed along with the morphometric analysis. The CaCO(3)content of the shell (upto 95% to 96% of the shell weight) of both the mussels was positively correlated with the shell length, suggesting increased deposition of CaCO(3)in shells with the growth of the species. The cross sectioned views of FE-SEM images of the shells exhibited distinct layered structure with external periostracum and inner nacreous layer varying distinctly. In the growing region, the growth line was prominent in the mussel shells revealed through the FESEM images. In addition XRD, FTIR and EDS studies on the mussel shells confirmed the existence of both aragonite and calcite forms of the calcium carbonate crystals with the incidence of various functional groups. The mechanical strength of the mussel shells was explored through nanoindentation experiments, revealed significant strength at the nanoparticle level of the shells. It was apparent from the results that the shell of the freshwater musselL. marginalisandC. bensoniqualify as a biological material with prospective multiple applications for human well-being and sustaining environmental quality
Influence of pressure on the transport, magnetic, and structural properties of superconducting Cr0.0009NbSe2 single crystal
No full textWe investigate the superconducting critical current density (J(c)), transition temperature (T-c), and flux pinning properties under hydrostatic pressure (P) for Cr0.0009NbSe2 single crystal. The application of P enhances T-c in both electrical resistivity (similar to 0.38 K GPa(-1): 0 <= P <= 2.5 GPa) and magnetization (similar to 0.98 K GPa(-1): 0 <= P <= 1 GPa) measurements, which leads to a monotonic increase in J(c) and flux pinning properties. The field-dependent J(c) at various temperatures under P is analyzed within the collecting pinning theory and it shows that delta T-c pinning is the crossover to delta l pinning above the critical pressure (P-c similar to 0.3 GPa). Our systematic analysis of the flux pinning mechanism indicates that both the density of pinning centers and pinning forces greatly increase with the application of P, which leads to an enhancement in the vortex state. Structural studies using synchrotron X-ray diffraction under pressure illustrate a stable hexagonal phase without any significant impurity phase and lattice parameter reduction with P shows highly anisotropic nature
Cr+6 Controlled Nucleation in SiO2-MgO-Al2O3-K2O-B2O3-F Glass Sealant (SOFC)
No full textThis study highlights the strong effect of chromium (Cr6+) as a nucleating agent for SiO2-MgO-Al2O3-B2O3-K2O-F glass sealant. In the process, Al2O3 from the base glass was gradually substituted by K2Cr2O7, which considerably tuned the crystallization characteristics, microstructure, thermal, and mechanical properties. The distinctive feature of this study is the induction of nucleation and crystallization in glass matrix on addition of Cr6+ content performing only annealing heat-treatment (600 degrees C). The melt-quenched SiO2-MgO-Al2O3-B2O3-K2O-F glass with zero Cr6+ content is found amorphous, which in presence of Cr6+ content became crystalline with MgCr2O4, K3CrF6, MgF2, and mullite (3Al(2)O(3).2SiO(2)) phases. Glassy features in DSC and dilatometric thermal properties (T-g, T-d, thermal expansion) were attained in glass without Cr- content, but glass-ceramic-like features obtained for Cr- containing glasses. Large thermal expansion (>11 x 10(-6)/K) was achieved for such glasses, and that is compatible with the CTE of solid oxide fuel cell (SOFC) components (electrode, interconnect, etc.) at the operating temperature (700-900 degrees C). FESEM study revealed the development of 200-500 nm sized crystallites in 2 mol% K2Cr2O7-containing glass microstructure and that became more compact sorted with 10-50 mu m sized crystals in higher Cr-doped glasses. Higher crystallinity was thus ascertained for higher Cr-containing glasses, which influenced the corresponding density and mechanical properties. From nano-indentation measurements, the hardness and Young's modulus were estimated to be 0.6 (+/- 0.5) and 25 (+/- 10) GPa, respectively, for base glass and in the range of 3.3 to 8.4 and 58 to 94 GPa, respectively, for Cr-containing glass-ceramics. Hardness measured from micro-indentation tests for the base glass was 3.63 (+/- 0.18) GPa, which increased to 3.94-6.08 GPa for Cr-containing glass-ceramics. Due to the typical microstructure and compatible thermal and mechanical properties, 2 mol% K2Cr2O7-doped SiO2-MgO-Al2O3-B2O3-K2O-F glass can be useable as high temperature sealant (like SOFC)