Thermal properties,induction period,interfacial energy and nucleation parameters of solution grown benzophenone

The kinetic parameters (reaction order, n, activation energy, E, pre-exponential factor, A, constant rate, k) for the dehydration step due to elimination of osmotic water and hydrogen-bounded water with the carboxylic groups, and for the anhydrifying step owing to the dehydration of two neighboring (-COOH) groups, were determined under non-isothermal conditions for some carboxylic resins with acrylic-divinylbenzene (DVB) matrix. The kinetic parameters were evaluated by means of isoconversional methods from (TG/DTG) thermal analysis data. The results show a dependence of the apparent kinetic parameters on the cross-linking degree, granulation, gel/macroporous matrix nature, exchange capacity and heating rate.     

Peracetic Acid Depolymerization of Biorefinery Lignin for Production of Selective Monomeric Phenolic Compounds

Lignin is the largest source of renewable material with an aromatic skeleton. However, due to the recalcitrant and heterogeneous nature of the lignin polymer, it has been a challenge to effectively depolymerize lignin and produce high‐value chemicals with high selectivity. In this study, a highly efficient lignin‐to‐monomeric phenolic compounds (MPC) conversion method based on peracetic acid (PAA) treatment was reported. PAA treatment of two biorefinery lignin samples, diluted acid pretreated corn stover lignin (DACSL) and steam exploded spruce lignin (SESPL), led to complete solubilization and production of selective hydroxylated monomeric phenolic compounds (MPC‐H) and monomeric phenolic acid compounds (MPC‐A) including 4‐hydroxy‐2‐methoxyphenol, p‐hydroxybenzoic acid, vanillic acid, syringic acid, and 3,4‐dihydroxybenzoic acid. The maximized MPC yields obtained were 18 and 22 % based on the initial weight of the lignin in SESPL and DACSL, respectively. However, we found that the addition of niobium pentoxide catalyst to PAA treatment of lignin can significantly improve the MPC yields up to 47 %. The key reaction steps and main mechanisms involved in this new lignin‐to‐MPC valorization pathway were investigated and elucidated.     

Effect of bismuth on liquid-phase epitaxy (LPE) grown GaAs layer using Ga–As–Bi melt

GaAs epitaxial layers of high structural quality have been realised from Ga–As–Bi melt using liquid-phase epitaxy (LPE). LPE grown GaAs epitaxial layer using bismuth solvent on GaAs substrate has been found to be of good structural perfection as compared to layers using gallium solvent. The temperature-dependent PL spectra of GaAs layer, grown from Ga+Bi mixed solvent has shown that the use of bismuth does not change the band energy. ECV depth profile of heavily zinc-doped epitaxial layer shows uniform doping in the GaAs layer grown using gallium solvent as compared to the layer grown using bismuth solvent.     

Sub-boundaries on (002) cleavages of Li2CO3 single crystals

Linear arrays of dislocations (straight, terminating and curved) are observed on etching with 2% citric acid (002) cleavages of lithium carbonate (Li₂CO₃) single crystals, grown by zone melting technique. As the dislocations are non-uniformly spaced and disappear on successive etching, they may not be revealing low-angle grain boundary, nor slip traces as they are terminating and curved meaning crystallographically non-oriented. On the observation of experiments on successive etching and etching of matched pairs, it is concluded that the arrays of etch pits reveal dislocation walls (dislocation density 1.1 × 10⁶ — 1.5 × 10⁷ pits cm⁻²) probably created due to the localized thermal stresses released as a result of high temperature annealing of the crystal during growth. The implications are discussed.     

Crystallization of an organic intercalation compound: cholic acid

Crystals of cholic acid have been grown in silica and tetramethoxy silane gels. Crystals grew with different morphology and Leisegang rings were also seen in some cases. Crystals were analyzed by X-ray, IR and microhardness studies. The grown crystals were found to be monohydrate and the hardness of the crystals were found to decrease with increase of load.     

Improvement in micro-structural and mechanical properties of zinc film by surface treatment with low temperature argon plasma

Nanocrystalline zinc films were deposited on gold coated borosilicate glass substrates by thermal evaporation method using zinc powders as the source material and then treated with argon plasma at various temperatures. From X-ray diffraction study, the as-deposited films are found to be metallic Zn and polycrystalline in nature. The crystalline nature improves with the increase of temperature up to 200 °C and decreases with the further increase of temperature to 300 °C. The binding energy observed for Zn 2p_3/2, and the binding energy separation between Zn 2p_3/2 and Zn 2p_1/2 in the X-ray photoelectron spectrum indicate that the films are metallic zinc films. Transmission electron microscopic study shows hexagonal shaped grains having size ∼58 nm upon treatment with Ar plasma. It is clearly shown the grain growth and distinct grain boundary with the increase in temperature. The average Young's modulus (E) and hardness (H) are measured to be 84 GPa and 4.0 GPa for as-deposited film, whereas 98 GPa and 5.8 GPa for plasma treated film at 200 °C. The enhancement in mechanical properties is attributed to improvement in crystalline nature of the film and better interlinking between grains and boundaries.     

Effect of annealing on natural calcitic crystals—A thermostimulated luminescence (TSL) study

The quality crystals (Calcitic limestone) were selected using the UV–visible methylene blue adsorption method. The thermostimulated luminescence (TSL) glow curve characteristics of six well crystallized limestone samples were analyzed. The glow curves of unannealed sample show only one peak in the range 320–330 °C. The sample irradiated with a gamma dose of 100 Gy shows two additional peaks in the range of 113–125 °C and 242–260 °C when recorded with linear heating rate of 10 °C/s. The annealed sample also shows the same trend as that of irradiated sample. Annealing treatment above 250 °C increases the sensitivity of all TSL peaks except 320 °C. On the other hand, annealing at 750 °C caused a collapse in the TSL sensitivity. The enhancement in TSL sensitivity was found to depend on the annealing temperature and time. Annealing treatment at 650 °C for 4 h followed by quenching in air is the optimum condition for TSL sensitization. The response to gamma irradiation is linear in the range from 0.5 Gy to 10⁴ Gy. The emission spectra of all the samples show an emission at around 610 nm but with different intensities for each TSL peak. With reference to earlier work, it may be assumed that the recombination site always involves Mn²⁺ ions. The observation made through infra-red (IR) and X-ray diffraction (XRD) studies with thermal treatment shows the structural changes of calcite from D_3h to C_s symmetry at 750 °C. The Thermogravimetric-Differential Thermal Analysis (TG-DTA) analysis shows the calcite gets disordered at 760 °C. Hence, the collapse in the TSL sensitivity at 750 °C is due to structural change or structural disorderedness.     

Study of optical and thermal properties in nickel doped ZnS nanoparticles using surfactants

The presence of surfactants polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP), sodium hexameta polyphosphate (SHMP) and tri-octyl phosphine oxide (TOPO) on the surface of Ni²⁺ doped ZnS (ZnS:Ni²⁺) nanoparticles resulted variation in their optical properties. The optical properties of each surfactant-capped ZnS:Ni²⁺ nanoparticles were investigated using UV–visible (UV–Vis) absorption and photoluminescence (PL) techniques. The absorption spectra and fluorescent emission spectra showed a significant blue shift compared to that of the bulk zinc sulfide. The effect of the optical properties in colloidal form (wet) and dry samples were investigated. Enhanced PL emission was observed for the dry samples at 80 °C. Thermal properties of the ZnS:Ni²⁺ was also studied using thermo gravimetric-differential thermal analysis (TG-DTA), Fourier transform infra-red spectrometer (FT-IR) and X-ray diffraction (XRD). The results are presented and discussed.