IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Co-existence of a Cr3+ phase (CaAl2Cr2O7) with hydraulic calcium aluminates at high temperature in the Al2O3-CaO-Cr2O3 system
No full textObtaining a stable Cr3+ phase at higher temperatures in the presence of hydraulic calcium aluminates (the phases found in calcium aluminate cement, CAC) in the Al2O3-CaO-Cr2O3 system remains a significant challenge in many application areas, as the formation of toxic, carcinogenic, and water-soluble Cr6+ compounds often occur. To address the issue, recently, we synthesized a high-temperature stable Cr3+ ternary compound (CaAl2Cr2O7) with space group P3 (143). In the present work, we investigated the formation-stability of CaAl2Cr2O7 with in situ calcium aluminate phases at 1500 degrees C under the CO2 atmosphere in the Al2O3-CaO-Cr2O3 system through solid-oxide reactions route varying Cr2O3 content (at constant Al2O3:CaO ratio). It co-existed with hydraulic calcium aluminates and other phases over the full investigated composition range of 2.76-68.3 mol% Cr2O3 (5-80 wt%). Apart from CAC phases (CaAl2O4, CaAl4O7), major Cr3+-phases are CaAl2Cr2O7 and (Al,Cr)(2)O-3 while (alpha,beta)-CaCr2O4 and Ca(Al,Cr)(12)O-19 formed as minor phases. At a constant Al2O3:CaO ratio of 5.6:4.4 mol% (7:3 wt%), the formation of the CaAl2Cr2O7 phase increases with Cr2O3 content (up to the investigated composition of 26.43 mol%) and then decreases gradually. The solid solubility of Al and Cr in the CaAl2Cr2O7 phase limited over a narrow range, and presumably dependent more on heat treatment condition rather than composition as reflected from the lattice parameter calculations. Though XRD revealed the presence of only Cr(3+)phases in the partial CO2 atmosphere, however, traces of Cr6+ could be detected using XPS and leaching tests. However, leachable Cr6+ content (0.095-1.252 mg/L) were much below the United States Environmental Protection Agency (US-EPA) permissible limit of 5 mg/L. The formation mechanism of the CaAl2Cr2O7 and other phases with plausible reactions were also discussed
Universal sensing of ammonia gas by family of lead halide perovskites based on paper sensors: Experiment and molecular dynamics
No full textIn this paper we show that, high sensitivity and high selectivity room temperature ammonia (NH3) gas sensors with both visual and electrical response can be made from family of lead halide perovskites with different cations and anions. These sensors, based on papers, act as general platforms for new generation of solid state gas sensors for sensitive detection of NH3 gas by simple color change (similar to 10 ppm sensitivity) as well as electrical resistance change with sub ppm sensitivity limited by electrical noise only. The sensors with materials like CH3NH3PbI3 (MAPI), CH3NH3PbBr3 (MAPB) and CH(NH2)(2)PbI3 (FAPI), are grown on paper from solution. MAPB changes color from orange to white and FAPI and MAPI from black to yellow under NH3 gas exposure respectively. For electrical sensor operation, a fixed concentration (20 ppm) of NH3 gas, the sensitivity of MAPI is highest at 96 % followed by MAPB at 82 % and FAPI at 65 %. The sensors with electrical read out could trace NH3 gas well below ppm level with only few nanowatt of power consumption. Based on experiments, a sensing mechanism has been proposed. The proposed mechanism mainly consists of decomposition of the perovskite halides to lead (Pb) halide by preferential adsorption of NH3 gas molecules. The proposed mechanism has also been substantiated by molecular dynamics simulations. These sensors fabricated by simple solution process on paper substrates and operable at ambient temperature, are compatible with very low power (similar to nW) paper electronics
Understanding the sodium-ion dynamics in NASICON (Na3Al2P3O12) glass containing NaF: Scaling of electrical conductivity spectra
No full textQuest for high ion-conducting solid electrolyte materials for sodium-ion batteries has been tremendously increasing. Glass materials are a potential solid electrolyte for high-energy Na-ion batteries. Nevertheless, the effective research on glass materials for their applications in Na-ion batteries is dawdling due to its low ionic DC-conductivity and poor understanding of the dynamics of mobile cations. Herein, we have attempted to address the effect of substitution of NaF for Al2O3 on the conductivity of Na3Al2P3O12 (NAP) glass (mol%: 37.5P(2)O(5)-25.0Al(2)O(3)-37.5 Na2O). Raman spectra reveal that the increase in the substituent NaF concentration significantly affects the coordination of Al3+ and the distribution of sodium cations in the network structure of NAP glass. Impedance spectra reveal that the change in conductivity of NAP glass with an increase in the NaF concentration is highly dependent on a specific temperature range. At a lower temperature range, (10 mol%) have deviated from Summerfield scaling and further indicate that the fraction of sodium-ions responsible for the ionic conductivity is decreasing with an increase in the temperature. Scaling of AC-conductivity curves for all the glass samples using the Ghosh procedure suggests that the number density along with the hopping distance of sodium ions changes with increasing temperature. The Modified random network structural model has been further utilized to explain the variation in the NAP glass conductivity with an increase in the NaF concentrations. The outcome of this work will certainly aid in designing the chemical compositions of glasses for the development of solid electrolyte materials for their applications in Na-ion batteries. (C) 2021 Elsevier B.V. All rights reserved
Elucidating the effect of CaF2 on structure, biocompatibility and antibacterial properties of S53P4 glass (vol 831, 154704, 2020)
No full textReduced graphene oxide (rGO) decorated ZnO-SnO2: A ternary nanocomposite towards improved low concentration VOC sensing performance
No full textA ternary p-n-n heterojunction has been prepared by introducing reduced graphene oxide (rGO) in ZnO-SnO2 nanocomposite and its ppm level volatile organic compounds (VOCs) sensing properties have been exploited. Using a simple, facile sol-gel process, initially, ZnO-SnO2 nanocomposites containing different concentrations of ZnO and SnO2 were prepared and subsequently this was followed by rGO incorporation. The as-synthesized powders were well characterized through XRD, FTIR, Raman spectroscopy, FESEM, TEM, and XPS analyses. The sensing study revealed that, the ternary nanocomposite sensor delineated similar to 91% n type sensing response towards similar to 10 ppm acetone gas at an optimum working temperature of 150 degrees C. Even it could sense similar to 1 ppm acetone with appreciable sensing response of similar to 71%. Additionally, the sensor displayed fast response (similar to 10 s) and recovery time (similar to 100 s) suitable for detection of multiple pulses in short time duration. It also exhibited a considerable similar to 65% sensing response towards similar to 10 ppm ethanol at 150 degrees C. These superior sensing performances of rGO decorated ZnO-SnO2 nanocomposite illustrated with band structure modification. Our results indicated that, the fabricated rGO decorated ZnO-SnO2 sensor, with remarkable high sensing response, minimum interference from other toxic, inflammable gases and profound long term stability, could be considered as a prolific candidate for real time detection of low concentration VOCs in versatile commercial applications. (C) 2021 Elsevier B.V. All rights reserved
Effect of melting time on volatility, OH in glass in microwave processing
No full textGlass comprising of SiO2-B2O3-Na2O-CaO-K2O is melted at 1523 K in the microwave (MW) and conventional heating. Evaporation loss was studied with varying melting time (30 min to 3 h). Assessment of B2O3, a more volatile component in the studied composition, is carried out by adopting wet chemical method like volumetric titrimetry. The rate of evaporation loss (of B2O3) is found similar to 20% less in MW heating. The density of glass increases slightly with increasing melting time. Chemical analysis for other volatile ingredient, K2O using ICP-AES suggests higher yield in glass signifying less loss of K2O in MW heating. A study adopting X-ray photoelectron spectroscopy (XPS) indicates that the ratio of nonbridging oxygen (NBO) to the total oxygen in glass increases with melting time. This signifies a higher loss of glass network former like B2O3. OH content in conventional glass decreases with increasing soaking time at melting temperature whereas it initially increases with time and reduces beyond 120 min of soaking at melting temperature in MW furnace. A significant reduction in energy consumption and time savings in MW heating has been recorded
Looking into the possibilities of cure of the type 2 diabetes mellitus by nanoparticle-based RNAi and CRISPR-Cas9 system: A review
No full textHyperglycemia is the hallmark of T2DM, related to many candidate genes, e.g., MAPK4, GCKR, STAT3, SOCS3, PTPN1 and PEPCK. To detect new variants of the susceptible genes related to T2DM, a genome-wide association study (GWAS) is being undertaken as well. The existing treatments are unable to address the root cause of the disease at the genetic level and in this regard, the concept of RNAi and most recently, the invention of CRISPR-Cas9 system holds a huge promise and paves a new direction in the treatment strategy of the disease at the genetic level, with a possibility for complete cure, although, issues like low efficiency and off-target problems have impeded their applicability. Additionally, the target-specific delivery using viral carriers also poses serious safety issues. Hence, the current scenario underscores the need for suitable nanocarriers for delivery of the above payloads to the target site and in the present narrative review, we attempt to draw the current understanding of RNAi on the T2DM treatment with the help of nanoparticle encapsulated anti-miR, siRNA, shRNA delivery, also nanoparticle-based CRISPR-Cas9 delivery, to explore the prospect of the complete cure of the disease
Facile Preparation of Biocompatible and Transparent Silica Aerogels as Ionogels Using Choline Dihydrogen Phosphate Ionic Liquid
No full textFeatured Application: Ionogels containing bio-ionic liquids help in the area of biomolecule encapsulation. Bio-ionic liquids can retain the stability of biomolecules at room temperature within the pores of ionogels. Ionogels have interesting applications in biosensors, electrochemical devices, super capacitors, batteries, gas sensors, CO2 capture, and so forth. We developed a facile and greener approach for the preparation of silica-aerogel-based ionogels using choline dihydrogen phosphate ionic liquid by the sol-gel approach. A series of silica-based aerogels as ionogels were prepared by varying the ionic liquid concentrations: 0.1, 0.5, 1, 3, 5, and 10 wt %. The as-prepared ionogels were characterized using several analytical techniques, namely, attenuated total reflectance (ATR)/FT-IR, TGA, XRD, and particle size analyses. The role of ionic liquid in the viscoelastic properties of the sol-gel transition was monitored using time-dependent rheological measurements. The addition of ionic liquid to the sol-gel system favored the formation of a more interconnected silica network structure. The formation of a silica network structure during sol-gel hydrolysis and condensation was confirmed from Si-29 solid-state CP/MAS NMR spectra. The effect of the ionic liquid on the morphological properties was investigated using SEM and TEM studies. The cell viabilities of the prepared gel samples were clearly evident from the cytotoxicity assay studies using Swiss and HaCaT cells. The main advantages of using biocompatible ionic liquids for the preparation of these aerogels as ionogels are that they may be used for encapsulating biological molecules and retain their conformational stability for a longer duration
Influence of magnetron configurations on the structure and properties of room temperature sputtered ZnO thin films
No full textUnder the unbalanced magnetron (UBM) sputtering process, not only the plasma is confined near the target like in the conventional balanced magnetron (BM) sputtering process, but also extends towards the substrate and support the ion-assisted deposition (surface of thin films is bombarded by energetic Ar+ ions during the sputtering process). Here, we report the influence of magnetron configurations on the structure and properties of room temperature sputtered ZnO thin films while keeping other process parameters fixed. The UBM configuration has significantly improved various properties of ZnO thin films in comparison to the BM configuration. The crystalline quality with dominant orientation (002) and uniform distribution of grains is observed while an increase in the band gap from 3.25 eV (BM) to 3.33 eV (UBM) is obtained. The lower defects as investigated from Zn2p and O1s core level XPS spectra, which is well supported by Photoluminescence measurements. In addition to that, surface hydrophobicity has been increased from 121.2 degrees (BM) to 125.5 degrees (UBM). Thus, the unbalanced magnetron configuration in the sputtering process significantly enhanced the structural, optical and surface properties of ZnO thin films even at room temperature and low plasma power without any post annealing treatments, which is highly desired for the device fabrication
Recent advancements of copper oxide based nanomaterials for supercapacitor applications
No full textCopper oxides (CuO and Cu2O) have been established as technologically important materials due to their unique advantages of low cost, high chemical stability and remarkable electrochemical performance, particularly, in the fields of catalysis, photovoltaics and energy storage applications. Specifically, promising capacitance availability, noticeable electrochemical response and facile fabrication of copper oxides have driven enormous attention for high energy supercapacitors to meet the high rising demands for efficient electrochemical energy storage systems. This review summarizes the recent advancements of various copper oxide based nanosystems employed to design better electrode materials for advanced supercapacitors. Special emphasis has been given on correlating their capacitive behavior with varying morphology obtained via different synthetic procedures. Electrochemical responses of varied copper oxides nanostructures have been comprehensively discussed. To overcome the issue of high rates of agglomeration, low conductivity and poor electrochemical stability of pristine copper oxides nanomaterials, they have been successfully combined with suitable pseudocapacitive materials like metal oxides, chalcogenides, etc., as well as several carbon-based systems such as conducting polymers, carbon nanotubes and functionalized graphene systems, etc. to fabricate binary/ternary/quaternary nanocomposites with superior features for advanced energy storage applications, have also been outlined. In the course, merits/ demerits of these assorted nanocomposites have been highlighted to delineate clearly the current challenges faced that may promote better strategic designing of smarter nanomaterials for high performance supercapacitor electrodes in the near future