Thermochemistry and kinetics of the aspect of diammonium hydrogen phosphate precipitation in phosphoric acid solution

Journal of Thermal Analysis and Calorimetry - The thermochemical and kinetic studies of diammonium hydrogen phosphate precipitation in phosphoric acid with ammonia were followed using a...     

Precursor Carboxy-silica for Functionalization With Interactive Ligands. II. Carbodiimide Assisted Preparation of Silica Bonded Stationary Phases with D-glucamine for Hydrophilic Interaction Liquid Chromatography

Chromatographia - A precursor carboxy-silica support was introduced for grafting a retentive polar ligand, namely D-glucamine, for use in hydrophilic interaction liquid chromatography. This support...     

Numerical study of the thermal processes occurring in materials under irradiation with high-energy heavy ions

Numerical simulation of the thermal processes occurring in indium phosphide under the action of a heavy gold ion with the energy E ₀ = 200 MeV is carried out. The problem is solved taking into account phase transitions of the melting and evaporation types. Numerical studies are carried out on the basis of a modified thermal-peak model and the obtained results are analyzed.     

Determination of <Superscript>210</Superscript>Pb in human skeletal remains from Morocco: implications for time since death assessment

In forensic contexts, time since death assessment in human skeletal remains is crucial for identification, and both accuracy and reliability are required. In this paper, we present the possibilities and constraints of the use of ²¹⁰Pb in dating skeletonized human bones in Morocco. The method was tested on recent as well as archaeological bones of known dates of death. A calibration curve was obtained from the available data in the scientific literature. The ²¹⁰Pb initial activity was introduced as an increasing lineal function with time. The ²¹⁰Pb dating approach gives promising results only for recent bones. On the contrary, for archaeological bones, the technique has erroneously led to post-mortem intervals in the range of recent bones which constitute a serious limitation of the method. On the other hand, uranium isotopes content in bones is suggested in this work as a possible indicator in placing a studied bone within either a forensic or archaeological context.     

KINETIC STUDY OF ALKOXIDE PROMOTED DECOMPOSITION OF ORGANIC PHOSPHONIUM COMPOUNDS Evidence for Hexacovalent Intermediate

Abstract

This study reports rate data of the alkoxide promoted decomposition of triphenyl 3-hydroxypropyl phosphonium chloride, diphenyl di(3-hydroxypropyl)phosphonium chloride, and tetraphenyl phosphonium bromide. Comparison of kinetics, rate constants, and activation parameters of the alkoxide promoted decompositions points to different mechanism as compared to the hydroxyl promoted reaction. The alkoxide reaction is believed to proceed via a hexacovalent intermediate. Reasons for the hexacovalent route are discussed.     

Novel Bis-arylPheDOT Synthons for Electrochromic Polymers

Two terthiophenes incorporating the synthon 3,4-(1,2-phenylenedioxy)thiophene (PheDOT) have been developed. Specifically, 2,5-bisthienyl-3,4-(1,2-phenylenedioxy)thiophene (BTh-PheDOT 1) and 2,5-bisethylenedioxythienyl-3,4-(1,2-phenylenedioxy)thiophene (BEDOT-PheDOT 2) were electropolymerized to form electroactive polymer films (P1 and P2) that switched between two highly colored states with the more electron-rich EDOT derivative P2 observed to switch at a lower potential. Additionally, both P1 and P2 displayed moderate to low optical bandgaps of 1.8 and 1.6 eV, respectively. Crystal structures of BTh-PheDOT showed the monomer to be nearly planar with π -stacking observable between monomers. These findings demonstrate the potential of PheDOT as an electroactive synthon for the formation of well-ordered systems.     

Preparation and Characterization of New Optically Active Poly(amide-imide)s from N,N′-(bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetra carboxylic)-bis-L-isoleucine and Aromatic Diamines

Five new optically active aromatic poly(amide-imide)s (PAIs) 5a–e were prepared from a direct polycondensation reaction of a new diacid of N,N′-(bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetra carboxylic)-bis-L-isoleucine 3 with various aromatic diamines 4a–e in a medium consisting of triphenyl phosphite (TPP), calcium chloride (CaCl₂), pyridine (Py) and N-methyl-2-pyrrolidone (NMP). The polycondensation reaction produced a series of novel poly(amid-imide)s 5a–e in quantitative yields with inherent viscosities of 0.39–0.51 dL/g. The resulting polymers were fully characterized by means of ¹H-NMR, FT-IR spectroscopy, elemental analyses, inherent viscosity, solubility test, specific rotation and thermal properties of them were investigated using TGA/DTG and differential scanning calorimeter (DSC). The diacid 4 was synthesized by the condensation reaction of bicyclo[2,2,2]oct-7-ene-2,3,5,6- tetracarboxylic dianhydride 1 with L-isoleucine 2 in acetic acid solution.     

Preparation of activated carbon filled epoxy nanocomposites

Activated carbon derived from oil palm empty fruit bunch (AC-EFB), bamboo stem (AC-BS), and coconut shells (AC-CNS) were obtained by pyrolysis of agricultural wastes using two chemical reagents (H₃PO₄ or KOH). The AC-EFB, AC-BS and AC-CNS were used as filler in preparation of epoxy nanocomposites. Epoxy nanocomposites prepared at 1, 5 and 10 % activated carbons filler loading using KOH and H₃PO₄ chemical agents. Transmission electron microscopy confirms better dispersion of the nano-activated carbons in the epoxy matrix at 5 % activated carbon. The presence of 5 % AC-CNS in the epoxy matrix using H₃PO₄ chemical reagent resulted in an improvement of the thermal stability of epoxy matrix. KOH treated AC filled epoxy nanocomposites were slightly better in thermal stability as compared to H₃PO₄ treated AC filled epoxy nanocomposites, may be due to better interaction of filler with epoxy matrix. Thermal analysis results showed that thermal stability of the activated carbon filled epoxy nanocomposites improved as compared to the neat epoxy matrix. The degree of crystallinity of epoxy matrix was improved by adding the activated carbon due to interfacial interaction between AC and epoxy matrix rather than loading of AC alone. Developed nanocomposites from biomass (agricultural wastes) materials will help to reduce the overall cost of the materials for its demanding applications as insulating material.