The poor mechanical strength of graphene oxide (GO) membranes, caused by the weak interlamellar interactions, poses a critical challenge for any practical application. In addition, intrinsic but large-sized 2D channels of stacked GO membranes lead to low selectivity for small molecules. To address the mechanical strength and 2D channel size control, thiourea covalent-linked graphene oxide framework (TU-GOF) membranes on porous ceramics are developed through a facile hydrothermal self-assembly synthesis. With this strategy, thiourea-bridged GO laminates periodically through the dehydration condensation reactions via NH2 and/or SH with OCOH as well as the nucleophilic addition reactions of NH2 to COC, leading to narrowed and structurally well-defined 2D channels due to the small dimension of the covalent TU-link and the deoxygenated processes. The resultant TU-GOF/ceramic composite membranes feature excellent sieving capabilities for small species, leading to high hydrogen permselectivities and nearly complete rejections for methanol and small ions in gas, solvent, and saline water separations. Moreover, the covalent bonding formed at the GO/support and GO/GO interfaces endows the composite membrane with significantly enhanced stability.

Self-Assembly of Thiourea-Crosslinked Graphene Oxide Framework Membranes toward Separation of Small Molecules.

Deep eutectic-solvothermal synthesis of nanostructured Fe3S4 for electrochemical N2 fixation under ambient conditions.

Synthesis and characterization of double-network hydrogels based on sodium alginate and halloysite for slow release fertilizers.

Struvite (MgNH4PO4·6H2O; MAP) precipitation is a viable means of phosphorus (P) recovery from animal and human wastes. The behavior of metal contaminants such as chromium (Cr) during struvite precipitation, however, requires consideration. Here the influence of both Cr concentration and oxidation state on sorption is assessed. The Cr content of struvite precipitated in the presence of 1–100 μM Cr as Cr(III) (22.3–3030.1 mg/kg) was higher than that of solids from Cr(VI) (4.5–5.1 mg/kg) solutions. For 1–20 μM Cr(III) solids, scanning electron microscopy (SEM) revealed etch pit formation on struvite crystal surfaces, indicative of a surface interaction. The formation of an adsorbate was confirmed by X-ray absorption fine structure spectroscopy (XAFS). At initial concentrations ≥20 μM Cr(III), XAFS confirmed the formation of a Cr(OH)3·nH2O(am) precipitate. Fourier transform infrared (FT-IR) spectroscopy revealed that both Cr(III) and Cr(VI) sorption resulted in distortion of the PO43– tetrahedra in the minera...

Sorption of Chromium with Struvite During Phosphorus Recovery

Synthesis, growth and optical studies of novel organometallic NLO crystal: Calcium bis-thiourea chloride

Cobalt zinc ferrite, Co0.8Zn0.2Fe2O4, nanoparticles have been synthesized via autocatalytic decomposition of the precursor, cobalt zinc ferrous fumarato hydrazinate. The X-ray powder diffraction of the ‘as prepared’ oxide confirms the formation of single phase nanocrystalline cobalt zinc ferrite nanoparticles. The thermal decomposition of the precursor has been studied by isothermal, thermogravimetric and differential thermal analysis. The precursor has also been characterized by FTIR, and chemical analysis and its chemical composition has been determined as Co0.8Zn0.2Fe2(C4H2O4)3·6N2H4. The Curie temperature of the ‘as-prepared oxide’ was determined by AC susceptibility measurements.

Synthesis and characterization of Co0.8Zn0.2Fe2O4 nanoparticles

Single crystals of a new nonlinear optical material, bisthiourea-urea have been grown from aqueous solution by slow evaporation technique with a period of 4 weeks. The structure of the grown crystals was confirmed by X-ray diffraction (XRD). The presence of title compound in the crystal lattice has been qualitatively determined by FTIR analysis. The mechanical properties and thermal stability of the grown crystals were evaluated by Vickers microhardness test and TG and DTG, respectively.

Thermal, FTIR and microhardness studies of bisthiourea-urea single crystal

The growth and characterization of a new non-linear organometallic crystal, potassium thiourea thiocyanide (PTT) is reported. The growth of single crystals was accomplished by the slow evaporation solution growth method. The grown crystals were characterized by XRD, TG–DTA, UV, and FTIR spectral analyses. PTT has good optical transmission in the entire visible region which is an essential requirement for a non-linear crystal. TG curve of PTT undergoes complete decomposition between 176 and 1,000 °C in three steps with corresponding three DTA peaks. The high thermal stability of organometallic crystals are due to strong bonding existing between the conjugation layers of thiourea molecule and the potassium ions.

The growth and characterization of a metal organic crystal, potassium thiourea thiocyanide

Mixed crystals of various proportions of urea thiourea were grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterized using thermogravimetry–differential thermal analysis (TG–DTA) and FTIR spectroscopic analyses. A fitting decomposition pattern for the title compound was formulated on the TG curve which shows a two-stage mass loss between 175 and 750 °C. In this temperature range, DTA curves show exothermic peaks supporting the formulated decomposition pattern. The FTIR spectra show the characteristic absorption, vibration frequencies due to urea thiourea. Detailed structural analysis of the compound is under progress.

Thermal and FTIR spectral studies in various proportions of urea thiourea mixed crystal

This paper is devoted to the investigation of the properties of the natural rubber composites prepared using the cation exchanged-montmorillonite fillers. The characteristics of the montmorillonite fillers were studied by Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TG). These characterized fillers were used to preparation of the natural rubber composites, which were submitted to measurements of dynamic-mechanical thermal analysis (DMTA) and vulcanizing characteristics (MH, ML, ts, tc(90), Rv) as well as physico-mechanical properties (tensile strength, modulus at 300 elongation—M300, tensibility).

S. C. Mojumdar

Papers

Synthesis and characterization of Co0.8Zn0.2Fe2O4 nanoparticles

Thermal, FTIR and microhardness studies of bisthiourea-urea single crystal

The growth and characterization of a metal organic crystal, potassium thiourea thiocyanide

Thermal and FTIR spectral studies in various proportions of urea thiourea mixed crystal

Investigation of natural rubber composites with addition of montmorillonite fillers using thermal analysis