Phosphorus- and silicon-containing amino curing agent for epoxy resin

Iranian Polymer Journal - Current research work focuses on the synthesis of phosphorus- and silicon-containing amine curing agent (PSA) for epoxy resins. PSA was synthesized using phenyl phosphonic...     

Novel catechol-derived phosphorus-based precursors for coating applications

Polymer Bulletin - Depletion of the petroleum resources and poor flame-retardant properties of the epoxy resins drive researchers to develop an epoxy resin with good heat stability from...     

Melt Homogenization and Self-Organization in Chalcogenides-Part II

The compositional variation of the non-reversing enthalpy at T_g, ΔH_nr(x), in Ge_xSe_100−x glasses decreases abruptly by an order of magnitude as x increases to x_c(1) = 19.5(5)%, the rigidity transition, and then remains minuscule till x increases to x_c(2) = 26.0(5)%, when the term abruptly increases by an order of magnitude as glasses become stressed-rigid. The rigid but unstressed networks formed in between these two transitions represent the Intermediate Phase (IP). The square-well like variation of ΔH_nr(x), also known as the reversibility window develops sloping walls, then a triangular shape and eventually disappears as glasses of increasing heterogeneity are studied. The ΔH_nr term ages over weeks outside the IP but not inside the IP. Raman line shapes of as-quenched melts are quite similar to those of T_g-cycled glasses for compositions in the IP, but not outside the IP– an optical analog of the thermal reversibility window. Variations of Molar volumes, display a global minimum in the IP and a pronounced increase outside that phase. Physical behavior of dry and homogeneous chalcogenide glasses that leads to sharp elastic and chemical phase transitions remains to be understood theoretically. The physics of network may be even more interesting than hitherto recognized.     

Development of magnetically switchable high permittivity microwave dielectrics using La(Al1-xFex)O3

The introduction of transition metal doping, particularly Fe³⁺, into high-performance microwave dielectrics can make “smart” materials that switch between a high-Q, low loss state and a low-Q, high loss state using a small external magnetic field. In this study, the dielectric and magnetic properties of the high permittivity host material LaAlO₃ (ε_r = 22.5), when doped with Fe³⁺, are reported. Spin losses dominate the loss tangent at cryogenic temperatures and survive up to room temperature. Peaks in the loss tangent versus temperature relation are observed near 40, 75, and 215 K. Additional measurements of samples exposed to annealing in varying environments, combined with Debye analysis and the results of native defect energy predictions from density functional calculations[Phys Rev B. 2009;80:104115], allows us to associate the 40, 75, and 215 K peaks to the following reactions, , , and , respectively.     

Reactive quaternary ammonium antimicrobial agent derived from cardanol for UV curable coating

The current research work presents an attempt to develop an antimicrobial agent from the bioresource cardanol which can be embedded in the polymer matrix to develop a UV curable coating. The brominated cardanol (BC) was synthesized from liquid bromine (Br₂) and cardanol followed by the reaction with triethylamine (TEA) to synthesize quaternary ammonium cardanol (AC). Further, the reaction with glycidyl methacrylate (GMA) gives a UV curable antimicrobial agent (AA). This AA was incorporated in the epoxy acrylate UV curable system in various proportions along with the photoinitiator and coated onto a wooden substrate. The Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies and elemental analysis results revealed that the desired product has been formed. An antimicrobial test was performed with three types of microorganisms viz., bacteria, yeast, and fungi. The test results showed that the antimicrobial performance of the coatings was increased with the significant inhibition percentage values of 81.59% for gram-positive bacteria (Staphylococcus aureus), 77.12% for gram-negative bacteria (E. coli), and 73.82% for yeast (Candida albicans). Also, there was a decrease in the growth% value of the fungi (Aspergillus niger) as the concentration of AA in the system was increased. The mechanical properties of all the coatings were similar. There was a decrease in the T_g as well as in the degradation temperature of the coating films as the concentration of AA was increased, but the char yield got increased, as well. The sample with 20 wt% of AA showed the maximum amount of char yield (11.49%).

     

Sol–gel based layer-by-layer deposits of lanthanum cerium molybdate nanocontainers and their anticorrosive attributes

The present study focuses on the synthesis of novel lanthanum cerium molybdate (LCM) nanoparticles by sol–gel synthesis method and their use in the development of nanocontainers in an anticorrosive coating application. The obtained nanoparticles were used as core material with two different polyelectrolytic shells comprising of polypyrrole (PPY) and polyacrylic acid (PAA) or polyethyleneimine (PEI) and polystyrene sulfonate (PSS) involving the entrapment of benzotriazole (BTA) as the corrosion inhibitor using layer-by-layer (LBL) deposition method. At each step of this nanocontainer synthesis, the thickness of the layers, surface charges and the presence of the functional groups were determined by particle size, zeta potential and Fourier transform infrared spectroscopy (FTIR) analysis, respectively. The X-ray diffractograms (XRD) indicated the change in the crystallinity of the nanoparticles and nanocontainers while thermogravimetric analysis (TGA) showed the thermal degradation behavior of the nanocontainers. The morphological studies conducted using scanning electron microscopy (SEM) exhibited the formation of nanocontainers containing nanoparticles in their cores. The release of BTA from the nanocontainers was evaluated at different pH values. The anticorrosive performance of the nanocontainers was examined by incorporation of the nanoparticles and nanocontainers in a commercial epoxy coating system and to be applied on mild steel and magnesium panels by electrochemical corrosion analysis. Tafel plots demonstrated the decrease in the current density with an increase in the loading percentage of nanocontainers in the epoxy system while Bode plots confirmed the significant improvement in the corrosion protection of the mild steel and magnesium by LCM nanoparticles and nanocontainers.

     

Gas-phase hydroxylation of benzene over H–Ga-FER zeolite

The direct hydroxylation of benzene with N₂O is studied using H–Ga-FER zeolite as catalyst. The H–Ga-FER zeolite was synthesized by using the hydrothermal synthesis route. Pyrrolidine was used as a template. The catalyst was characterized by using XRD and NMR techniques. The gas-phase hydroxylation reaction was carried out using nitrous oxide gas as an oxidant. The reaction was thoroughly studied by changing different parameters like temperature, time, reactant mole ratio and contact time (WHSV). It was observed that by using H–Ga-FER, phenol was formed with 100% selectivity. The deactivation is faster in case of H–Ga-FER as compared with Al-FER and Fe-FER. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of Rheology and Slip on Lubricant Deformation and Disk-to-Head Transfer During Heat-Assisted Magnetic Recording (HAMR)

The high-temperature laser heating during heat-assisted magnetic recording (HAMR) causes the media lubricant to deform and transfer to the head via evaporation/condensation. The ability of the lubricant to withstand this writing process and sufficiently recover post-writing is critical for robust read/write performance. Moreover, the media-to-head lubricant transfer causes a continuous deposition of contaminants originating from the media at the head near field transducer, challenging the reliability of HAMR drives. Most previous studies on the effects of laser exposure on lubricant depletion have assumed the lubricant to be a viscous fluid and have modeled its behavior using traditional lubrication theory. However, Perfluoropolyether lubricants are viscoelastic fluids and are expected to exhibit a combination of viscous and elastic behavior at the timescale of HAMR. In this paper, we introduce a modification to the traditional Reynolds lubrication equation using the linear Maxwell constitutive equation and a slip boundary condition. We study the deformation and recovery of the lubricant due to laser heating under the influence of thermocapillary stress and disjoining pressure. Subsequently, we use this modified lubrication equation to develop a model that predicts the media-to-head lubricant transfer during HAMR. This model simultaneously determines the deformation and evaporation of the viscoelastic lubricant film on the disk, the diffusion of the vapor phase lubricant in the air bearing, and the evolution of the condensed lubricant film on the head. We investigate the effect of viscoelasticity, lubricant type (Zdol vs Ztetraol), molecular weight, slip, and disjoining pressure on the lubricant transfer process.     

Supported NHC-Benzimi@Cu Complex as a Magnetically Separable and Reusable Catalyst for the Multicomponent and Click Synthesis of 1,4-Disubstituted 1,2,3-Triazoles via Huisgen 1,3-Dipolar Cycloaddition

Catalysis Letters - In this paper, we report a novel magnetically separable silica coated copper nano-magnetite NHC-benzimi@Cu complex as heterogeneous catalyst for the multicomponent click...