Laser synthesis of palladium-alumina composite membranes for production of high purity hydrogen from gasification

This paper describes a special method of laser-based deposition to synthesize palladium-ceramic composite membranes. Thin film Pd was deposited on a ceramic substrate by Nd-YAG laser irradiation of coating precursor PdCl₂ on γ-alumina substrate. The parameters of the laser processing technique were optimized to synthesize metal-ceramic composite membranes. The physical and chemical characteristics of Pd coated γ-alumina membranes were studied and compared with various other alumina membranes referenced in the literature. Hydrogen permeation experiments were performed in a CO + CO₂ + CH₄ + H₂ environment under typical catalytic steam gasifier exit conditions. The Pd-ceramic composite showed good mechanical and thermal stability and resulted in a hydrogen permeability flux of about 0.061 mol/m² s. The activation energy of the Pd membrane was found to be 5.39 kJ/mol in a temperature range of 900-1300 °F.     

Shape evolution in <Superscript>76,78</Superscript>Kr nuclei at high spins in tilted axis cranking Hartree-Fock-Bogoliubov approach

A two-dimensional tilted axis cranking Hartree-Fock-Bogoliubov (CHFB) calculation is performed for ⁷⁶Kr and ⁷⁸Kr nuclei up to high spins J = 30 employing a pairing-plus-quadrupole (PPQ) model interaction Hamiltonian. Intricate details of the evolution of single particle structures and shapes as a function of spin have been investigated. The results show the existence of energy levels with high K quantum numbers lying close to the yrast line in both the nuclei. Such high K states should exhibit isomeric characteristics due to the K-selection rules for the γ-decays. Moreover, in ⁷⁸Kr a new band with J = 20–30 lying below the observed ground band is predicted.      

On a mild generalization of the Schönemann - Eisenstein - Dumas irreducibility criterion

We state a mild generalization of the classical Schönemann and Eisenstein- Dumas irreducibility criterion in ?[x] and provide an elementary proof. In the end of the paper, we also provide a concrete example of a polynomial which is irreducible by the main result of the paper but whose irreducibility does not follow from existing criteria.     

Synthesis,spectral, fluorescence and thermal studies on ionic hafnocene thiopurine complexes

Ionic chelates of hafnocene, with 6-mercaptopurine (HL¹) (A) and 6-thioguanine (HL²) (B) of the type [( ⁵-C₅H₅)₂HfL¹]⁺X^– (C) and [( ⁵-C₅H₅)₂HfL²]⁺X^– (D) (X = CuCl₃, ZnCl₃, CdCl₃, HgCl₃, PhNHNHCS₂) have been prepared and characterized by conductivity measurements and by i.r., electronic, ¹H-n.m.r. and ¹³C-n.m.r. spectra. Fluorescence studies of the complexes containing Hg in the anionic moiety, and relevant photochemical parameters, have been elucidated. Thermodynamic parameters have been calculated using thermogravimetric (t.g.) and differential thermal analytical (d.t.a.) curves and their variations have been correlated with some structural parameters of the complexes. The ligands, as well as their hafnium(IV) complexes, exhibit appreciable antibacterial and antifungal activity against E. coli, S. typhi, P. aeruginosa, Z. mobilis bacterial strains and versus A. awamori, A. niger fungal strains, respectively.     

Determination and locational variations in the quantity of hydroxyanthraquinones and their glycosides in rhizomes of Rheum emodi using high-performance liquid chromatography

Locational variations in the quantity of five hydroxyanthraquinone derivatives (emodin glycoside (1), chrysophanol glycoside (2), emodin (3), chrysophanol (4) and physcion (5)) in the rhizomes of Rheum emodi are described. A simple and reliable method was developed for quantitation of compounds (1-5) in the methanolic extract of rhizomes of R. emodi using reverse-phase high-performance liquid chromatography (HPLC) with photo-diode array detector (PDA). The separation was carried out using a Purospher((R))-Star RP-18 e column (4.6mm i.d.x 250 mm, 5 microm) under the following conditions: acetonitrile:methanol (95:5, v/v) (solvent A) and water:acetic acid (99.9:0.1, v/v) (solvent B) as mobile phase with a linear gradient elution at a flow rate of 0.8 mL/min. The detection wavelength was set at 290 nm. Regression equation revealed a linear relationship (r(2)>0.9901) between the mass of hydroxyanthraquinone derivatives injected and the peak areas. The detection limits (S/N=3) ranged from 0.56 to 3.50 ng/mL and the recoveries ranged from 95.7 to 103.5% for five hydroxyanthraquinone derivatives. Compound 2 was found in maximum quantity (up to 2.23%) in the rhizomes from all the three locations (L(1), L(2) and L(3)) while compound 5 was found in the least quantity (up to 0.19%).     

Dry sliding wear behavior of Al-SiO2 composites

Abstract

Al-base composites with different amount of silica (5, 10, 15 and 20 wt.%) were developed using powder metallurgy route and compacts were sintered at 550 °C for 2 h. XRD analysis of all compositions was conducted for phases and amount of the second phase present. Morphology of the composites shows quite uniform distribution of the SiO₂ particles but at higher percentage of SiO₂ particles the clustering starts. Mechanical properties such as uniaxial compressive strength (UCS) and hardness were evaluated and it is seen that among all compositions, composite with 10 wt.% SiO₂ has maximum UCS and hardness. Wear behavior of all composites was studied with sliding distance, applied loads, sliding velocity and composition. All composites show a linear increase in cumulative wear with distance and load. Wear rate with load increases continuously for all compositions, however, composite with 10 wt.% SiO₂ revealed minimum wear rate with distance, sliding velocity and loads. Wear rate with sliding velocity increases sharply after attaining minima at 3 m/s sliding velocity. SEM analysis of wear tracks is in agreement with wear results. Al-10 wt.%SiO₂ also shows minimum wear coefficient values for all loads, however, wear coefficient decreases with load for all compositions.     

Essential oil composition of three accessions of Dracocephalum heterophyllum Benth. cultivated at Palampur, India

Seeds of three accessions of Dracocephalum heterophyllum growing wild in high altitude locations in the cold desert regions of trans-Himalaya were collected and propagated under polyhouse conditions at IHBT Palampur to evaluate, compare their growth performance and essential oil composition. Three different chemotypes viz., citronellol-rose oxides type, citronellol type and citronellal-trans rose oxide type were identified. Samples of essential oils were distilled separately from leaves and inflorescence of all the three cultivated accessions and characterised by capillary GC and GC-MS techniques, which showed variation in the volatile constituents. In all the three accessions, citronellol was higher in the inflorescence oils as compared to leaf oils. Rose oxides, which are important high odour value cyclic monoterpene ethers were found in the essential oil samples of leaves as well as in the inflorescence of accession II, whereas these constituents were absent in the leaves of other two accessions. The essential oil from the inflorescence part of accession I was devoid of both cis and trans isomers of rose oxide, while accession III contained only one isomer of trans rose oxide. Under polyhouse conditions, seed germination was higher in accession III, whereas aerial biomass was higher in accession I. In comparison to other accessions, yield of volatile oil was higher in both leaf and inflorescence of accessions I, whereas accession II had higher oil yield from inflorescence. This is the first report of volatile oil composition of three accessions of D. heterophyllum cultivated at Palampur having potential as a new source of high valued essential oil for introduction in the perfumery industry.     

Polylactic acid/polypropylene polyblend fibers for better resistance to degradation

Polyblend fibers were produced from five ratios of polylactic acid/polypropylene (PLA/PP) in an effort to improve the resistance to hydrolysis and biodegradation, and to improve the dyeability of PLA. The inherent limitations of PLA such as its relatively poor resistance to hydrolysis have restricted the use of PLA. When made into polyblend fibers, the two polymers, PLA and PP, show partial compatibility and the mechanical properties of the blends are inferior compared to the pure PLA or PP fibers. However, PLA in the blends had substantially better resistance to biodegradation and hydrolysis, and dyeability with disperse dyes, resulting in a polyblend fiber with much better resistance to hydrolysis and similar dyeability to PLA. Blending PP with PLA could be a simple and effective method to create a new fiber with better resistance to hydrolysis and lower price than PLA, and better dyeability, sustainability and faster degradability than PP.     

Thermodynamics of the silver-silver ion electrode and thermodynamic solubility product constants of silver halides and pseudo-halides in urea-water mixtures

The hydration kinetics of tricalcium aluminate, C₃A, with gypsum or anhydrite at 1:3 mole ratio were studied using hydration periods of 5 min up to 7 days. These studies were assessed with the aid of differential thermal analysis, thermogravimetric analysis and X-ray diffractometry as well as chemical analysis.The results revealed that hydration periods of up to 7 days of tricalcium aluminate with gypsum in paste form and in suspension, forms ettringite with unhydrated components of C₃A and gypsum. On the other hand, the only hydration product of the slurry of C₃A with anhydrite is ettringite after 7 days of hydration. The kinetics of hydration were studied by the quantitative determination of ettringite from the TG analysis. The results also illustrate that the rate of ettringite formation is slower in the presence of gypsum than in the presence of anhydrite and also that hydration of the slurry gives more ettringite than the hydration of the paste.