IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Switchable and dual-wavelength self-Q-switched fiber laser based on a homemade Er/Yb double clad fiber and polarization maintaining fiber Bragg grating
No full textWe report an experimental study on the self-Q-switched operation of a linear cavity fiber laser based on a homemade Er/Yb double clad fiber as gain medium. The parameters of the self-Q-switched pulses depend on the active fiber length of 2, 3, and 4 m. With a maximum fiber length of 4 m, stable self-Q-switched pulses are obtained for the whole 976 nm pump range, with a minimum pulse duration of 1.24 mu s and a maximum repetition rate of 92.57 kHz. When the fiber length is shortened to 2 m, the range of the pump power level, at which the self-Q-switched operation is attained, is significantly diminished. Besides, dual-wavelength and switchable single-wavelength laser operations of the fiber laser are achieved by using a polarization maintaining fiber Bragg grating as spectral filter. Laser wavelengths at 1536.7 and 1537.1 nm with a line-width of 0.4 nm are obtained. The maximum average output power for the Q-switched laser operating in the dual-wavelength regime is 472 mW
Single-step process without organic template for the formation of zeolite A from RHA
No full textDice-shaped zeolite A (NaA) was prepared via direct dissolution of rice husk ash (96.5% SiO2) in the presence of NaOH and sodium aluminate solution by autoclave process at 90 degrees C/6 h without using any templating agent. The prepared particles were characterized by DTA/TG, XRD, FTIR, N-2 adsorption-desorption physisorption analysis, FESEM, and TEM. XRD results confirmed crystallization of pure NaA zeolite phase. FTIR study shows the characteristic bands at 554 cm(-1) for double 4 membered ring (D4R) of NaA zeolite. The total BET surface area of the product was found to be 31.6 m(2) g(-1). FESEM and TEM images show dice shaped NaA particles of size around 1 mu m which is formed via oriented crystalline aggregation of primary particles (30-40 nm). A tentative mechanism was proposed for the formation of NaA crystals through direct dissolution of rice husk ash. The synthesized NaA zeolite could be used for purification of alcohol and separation of toxic and radioactive ions from waste water via a cost-effective process
Transparent ultra-low expansion lithium aluminosilicate glass-ceramics: Crystallization kinetics, structural and optical properties
No full textbeta-quartz solid solution phase in the Li2O-Al2O3-SiO2-P2O5 (LAS) glass system has been precipitated by controlled heat-treatment of the parent glass prepared by melt-quench technique. Detailed crystallization kinetics of LAS glass was studied which facilitated in determination of an optimized heat-treatment protocol in order to synthesize highly transparent glass-ceramics of extremely low thermal expansion coefficient. The crystallization kinetic studies indicated a bulk nucleation with linear growth event in the LAS glasses. The LAS glass-ceramics (GCs) containing the beta-spodumene crystalline phase shows extremely low to negative thermal expansion coefficient (K-1) ranging from -0.0029 x 10(-6) to 0.3227 x 10(-6) measured in the temperature range 223 to 423 K. The glass-ceramics exhibited visible light transmittance of nearly 90%, such high transparency was possible by restricting average crystal size to nanometric scale through controlled crystallization. Microstructural characterization of the heat-treated GCs using FESEM and TEM showed nano-crystalline spherical particles of 2-3 nm, which provided a rationale for its high transparency
Al-Mg-Ca-Layered Double Oxides for Efficient Removal of As(V) from Water: The Role of Amides
No full textAl-Mg-Ca-layered double oxides (LDO) were synthesized by solvothermal process at 160 degrees C/24 h in the presence of formamide (F), dimethylformamide (DMF), and diethylformamide (DEF), followed by calcination at 500 degrees C. The role of different amides for the formation of Al-Mg-Ca LDOs in terms of their microstructural behaviors, textural properties, and surface elemental analysis toward the removal of As(V) from groundwater was investigated. Microstructural analysis shows chrysanthemum flower-like morphology (2-4 mu m) with orderly arrangement of nanorod/petal-like particles (10-15 nm). DEF-modified Al-Mg-Ca LDO exhibited the highest surface area of 251 m(2)/g, resulting in the maximum As(V) adsorption capacity of 100 mg/g. The XPS study shows peak shifting of Al-O and Mg-O to a higher binding energy after adsorption of As(V), indicating the change in chemical environment, i.e., sharing of elements with the neighboring atoms. The effects of different parameters, like contact time, dose concentration, pH, and temperature, were investigated for As(V) adsorption. The synthesized Al-Mg-Ca LDOs were used for the removal of As(V) (0.7 ppm) from the groundwater collected from the lower Indo-Gangetic plain area (Hariharpara block at Murshidabad district in West Bengal of India) down to <10 ppb
Strontium doped hydroxyapatite from Mercenaria clam shells: Synthesis, mechanical and bioactivity study
No full textSynthesis of strontium-doped hydroxyapatite from Mercenaria clam shells has been carried out by hydrothermal method. The doping of bioceramic, processed from biogenic resources is mostly unexplored. The objective is to understand the effect of strontium (Sr) incorporation on phase stability, sintering behaviour, mechanical properties and cytotoxicity of hydroxyapatite (HAp) derived from clam shells. The different molar concentrations of Sr, varies from 10, 30, 50, 70% of Ca, were substituted into the HAp. The synthesized powders were sintered at 1200 degrees C in air. The as synthesized powders and sintered specimens were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and high resolution transmission electron microscopy. The crystallite size and cell parameters of sintered specimens were analyzed from XRD. The XRD of hydrothermally synthesized powders mostly matched with HAp with slight shifting due to Sr doping. However, some distinct Sr based compounds were also observed where Sr substitution is more that 50% of Ca. The XRD of sintered specimen showed increasing beta-tricalcium phosphate (beta-TCP) phase with Sr substitution. The sintered density of solid samples gradually increased from 3.04 g/cc to 3.50 g/cc and surface energy decreased with increasing Sr substitution. Similarly, microhardness, fracture toughness and nanohardness of solid samples found to be enhanced with Sr substitution. The elastic modulus gradually increased from 130 to 137 GPa for HAp and Sr substituted HAp (70% of Ca). The in vitro cytotoxicity of sintered specimen against mouse osteoblast cell line showed that all the samples were nontoxic. However cell proliferation found low for the solid samples containing more than 50% Sr substitution
Additive manufacturing of natural fiber reinforced polymer composites: Processing and prospects
No full textThroughout the world there have been alarming concerns over the use of nonrenewable resources during manufacturing of goods and associated environmental legislations. Therefore, the use of natural materials and fabrication of composites therefrom, particularly, development of natural fiber reinforced polymer composites is gaining significant attention. Although natural fiber reinforced composites (NFRCs) show strong application prospects, various materials and processing related challenges needs to be addressed to achieve long-term stability and performance. In this review, we attempted to provide an overview of different types of natural fibers, their characteristics and properties enabling them to be used as reinforcing agents in different polymers. Then the unique requirement of fiber surface modification to achieve enhanced fiber-matrix bonding is discussed. The article also discusses conventional processing routes and critical issues associated with NFRCs processing. The use of different additive manufacturing (AM) technologies in processing polymer composites is also discussed. At the end, we have critically analyzed the challenges and opportunities associated with AM of NFRCs
Determination of half maximal inhibitory concentration of CaAl layered double hydroxide on cancer cells and its role in the apoptotic pathway
No full textIn continuation of our previous work, which proposed a new direction of application of the bare, phase pure CaAl LDH as an active anticancer agent, the efficacy of the system was assessed by determination of half maximal inhibitory concentration (IC50) of the same on human colon cancer (HCT 116) cell line and human breast cancer (MCF 7) cell line. This was in turn established by tracing the involvement of Ca2+ ion with the CAMKII alpha protein- a key player in the Ca2+/Calmodulin pathway which remains overexpressed in human colon cancer cell. CAMKII alpha regulates the reactive oxygen species (ROS) production by decreasing the activity of superoxide dismutase (SOD) enzyme and hence SOD activity was also evaluated in our study. The results exhibit significant involvement of the bare, phase pure CaAl LDH at cellular level to down regulate CAMKII alpha and SOD gene and its active involvement in apoptosis could also be traced
Polyionic Resin Supported Pd/Fe(2)O(3)Nanohybrids for Catalytic Hydrodehalogenation: Improved and Versatile Remediation for Toxic Pollutants
No full textA series of Pd/Fe2O3 nanohybrids with low metal content supported with Amberlite resin formate (Pd/Fe2O3@ARF) was prepared and characterized by FTIR, XRD, XPS, EELS, SEM-EDAX, and HRTEM. The coexistence of mainly crystalline Pd and Fe2O3 nanoparticles (NPs) of average size similar to 4-5 nm in the resin matrix was confirmed. These nanohybrids were used for hydrodehalogenation of polyhaloar-omatics using NaBH4 as a reducing agent in water. Notably, the composite Pd/Fe2O3@ARF-110 exhibits excellent catalytic performance in the hydrodehalogenation of different haloar-omatics. High TOF (in comparison to other related heterogeneous catalysts), recydability, and chemoselectivity between halide and C = C bond make this nanohybrid catalyst very attractive for the degradation of persistent organic pollutants originated from industries. The experimental observations and other analytical studies suggest that the enhanced catalytic activity could be due to strong interactions between Fe2O3 and Pd NPs that facilitate the cleavage of B-H bond and subsequent hydride generation