Synthesis of ZnO based nanopowders via a non-hydrolytic sol gel technique and their densification behaviour and varistor properties

Hexagonal nanocrystalline varistor grade ZnO particles with size 50 nm and the specific surface area of 28 m2/g have been prepared by non-aqueous gelation technique involving diethylene glycol and triethanolamine. The as-prepared varistor nanopowders were analyzed with the support of XRD, TG/DTA, FTIR, TMA, SEM and TEM. Varistor discs were fabricated by pressing and their densification was studied at 850, 950, 1050 and 1150°C. The evolution of varistor microstructures, extent of grain growth and the influence of microstructure on the I-V properties were explored and presented

A facile hydrous mechano-synthesis of magnesium hydroxide [Hy-Mg(OH)2] nano fillers for flame-retardant polyester composites

Scrap metals are a cost-effective secondary resource for producing functional metal oxides/hydroxides. Developing such functional hydroxides from scrap Mg via a low-energy, chemical-free process has high technological importance in the current scenario, as it emphasizes the ‘waste to wealth’ and green motives of production. This study presents an aqueous mechanical milling technique as a facile approach to yield functional grade nano Mg(OH)2 from industrial Mg crumbs. Formation of fiber-like nano Hy-Mg(OH)2 was confirmed on milling of waste metal scraps, by carefully controlling the mechanical parameters viz. the ball to powder mass ratio, milling medium, milling time, and milling speed. The optimized production of Hy-Mg(OH)2 was obtained after 90 h of milling, the evolution was confirmed using standard characterization techniques like XRD, TEM, and EDS. Flame retardant polyester/nano Hy-Mg(OH)2 composites were developed using casting technique. The developed polyester/nano Hy-Mg(OH)2 composites showed good flame retardancy, an oxygen index of ∼ 33% was obtained with 0.3 wf of nano Hy-Mg(OH)2 addition

Mesochanneled Hierarchically Porous Aluminosiloxane Aerogel Microspheres as a Stable Support for pH-Responsive Controlled Drug Release

The molecular-scale self-assembly of a 3D aluminosiloxane (Al–O–Si) hybrid gel network was successfully performed via the cocondensation of hydrolyzed alumina (AlOOH) and (3-aminopropyl)­trimethoxysilane (APS). It was transformed into a microspherical aerogel framework of Al–O–Si containing mesochannels with tunable hierarchically bimodal meso/macroporosities by a subcritical drying technique. Good homogeneity of AlOOH and APS brought during the synthesis guaranteed a uniform distribution of two metal oxides in a single body. A systematic characterization of the aerogel support was carried out using FTIR, SEM, TEM, nitrogen adsorption/desorption analysis, WAXS, SAXS, and ξ-potential measurement in order to explore the material for drug uptake and release. The drug loading and release capacity and chemical stability of an aluminosiloxane aerogel were studied using two nonsteroidal antiinflammatory drugs, ibuprofen and aspirin. A comprehensive evaluation of the aluminosiloxane aerogel with ordered mesoporous MCM-41 was also performed. Aerogel supports showed a high drug loading capacity and a pH-responsive controlled-release property compared to MCM-41. Meanwhile, kinetic modeling studies indicate that the drug releases with a zero-order profile following the Korsmeyer–Peppas model. The biocompatibility of aluminosiloxane aerogels was established via ex vivo and in vivo studies. We also outline the use of aluminosiloxane aerogel as a support for a possible 3D matrix for an osteoconductive structure for bone tissue engineering

Electrical and thermal properties of 10 mol% Gd 3+ doped ceria electrolytes synthesized through citrate combustion technique

Nanocrystalline ceria electrolyte doped with 10 mol% gadolinia [Ce0.9Gd0.1O1.95] was synthesized by citric acid combustion technique involving mixtures of cerium nitrate oxidizer (O) and citric acid fuel (F) taken in the ratio of O/F=1. The as combusted precursors produced crystalline ceria particles upon calcination performed at 700°C for 2h. Ceria pellets were made and sintered at temperatures 1200, 1400 and 1500°C with a dwell time of 2, 4 and 6 h. The sintered microstructures, electrical and thermal conductivities and thermal diffusivity properties were evaluated in addition to the powder properties such as crystalline structure, surface area, particle size and morphology. Sintered ceria samples had 99% theoretical density at 1500°C/6h. The sintered microstructures exhibit dense ceria grains with sizes 500 nm to one micron. The electrical conductivity versus temperature showed conductivity in the order of 10^(-2) and 10^(-1) S·cm-1 at 500 and 700°C, respectively. The ceria sintered at 1500°C has the maximum thermal conductivity of ~2.79 W·m-1K-1 at room temperature

Biocatalytic Conversion Efficiency of Steapsin Lipase Immobilized on Hierarchically Porous Biomorphic Aerogel Supports

Hierarchically porous alumino-siloxane aerogels (ALS-PG) with a rare structural architecture were developed through a biotemplating method using pollen grains of Hibiscus rosa-sinensis. The unique structure of the Hibiscus rosa-sinensis pollen makes it an attractive biotemplate, by replicating all levels of macro- and mesoscale morphological features. The micromorphological analysis exposed funnel-shaped macrochannels between the mesoporous aerogel framework that are difficult to design artificially. The N₂ sorption analyses confirmed hierarchical trimodal pore size distribution with an average mesopores diameter (ca. 3.9, 8.7, 26.6 nm), high BET/Langmuir surface area (497/664 m² g^–1) and large pore volume (1.6788 cm³ g^–1) than the corresponding nontemplated aerogels and xerogels counterpart. Beneficial properties of this sophisticated hierarchical porous structure was examined and confirmed by the immobilization of steapsin lipase. Hierarchically porous ALS-PG showed enhanced loading and immobilization efficiency (32.3 mg g^–1 and 74.21%) when compared to non templated ALS-WO-PG (11.2 mg g^–1 and 41.40%). It was further improved with the methyl (MTMS@ALS-PG) (69.8 mg g^–1 and 96.87%) and amino propyl (APTMS@ALS-PG) (65.1 mg g^–1 and 94.96%) surface modifications. Additionally, it showed enhanced catalytic performance for hydrolytic, esterification, and transesterification reactions. It is anticipated that this hierarchically porous aerogel supports can suitably hold the biocatalyst and can solve critical problems associated with its native state for technological applications

Aqueous Mechanical Oxidation of Zn Dust: An Inventive Technique for Bulk Production of ZnO Nanorods

Metal to bulk metal oxide nanoparticles have been successfully processed via a sustainable, facile, and ecofriendly (green) approach, namely, <i>aqueous mechanical-oxidation.</i> Micron-sized zinc (Zn) dust (∼45 μm) was directly wet-milled using ceramic milling media for 72 h, resulting in the production of bulk monocrystalline ZnO nanorods (aspect ratio ∼5.2, hydrodynamic diameter of 315 nm) and voluminous H₂ gas by catalyst-free water-splitting reaction. The mill-induced surface oxidation and the chemical purity of the synthesized nano ZnO were carefully studied using the XPS analysis. Other standard analytical tools were also employed to understand the crystallinity, phase purity, morphology, and surface area of the final artifact. The photocatalytic activities of these mechanically grown ZnO nanorods were ascertained from two cationic dye-degradation experiments, using the dyes methylene blue and rhodamine 6G. In a nutshell, the study throws a new insight into a cost-effective, zero-effluent, single-step, and parallel-processing approach of two high-value products, bulk nano ZnO and catalyst-free H₂ gas from micronic Zn dust