Dehydration,Water Vapor Adsorption and Desorption Behavior of Zn[B3O3(OH)5] · H2O and Zn[B3O4(OH)3]

The dehydration behaviors of two different hydrated zinc borate species, Zn[B₃O₃(OH)₅] · H₂O and Zn[B₃O₄(OH)₃], which are industrially important flame retardants, were studied by thermal gravimetric(TG) analysis and in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Dehydration onset temperatures of Zn[B₃O₃(OH)₅] · H₂O and Zn[B₃O₄(OH)₃] were 129 and 320°C, respectively, at a 10°C/min ramp rate. A very small amount of boric acid was volatilized in addition to water vapor when both samples were heated at 250°C. A significant amount of water vapor was adsorbed by Zn[B₃O₃(OH)₅] · H₂O from air at 25°C. However, Zn[B₃O₄(OH)₃] adsorbed a very small amount of water under the same conditions. Both zinc borates did not have a tendency to cake during storage.     

Evaluating π-π-Interactions as a Method for Isolation of Polycyclic Aromatic Hydrocarbons from Solution

The polycyclic aromatic hydrocarbon (PAH), chrysene, was linked to the solid support TentaGel S-NH₂ via a linker by means of synthesis. The resulting product 4-(chrysene-1-yloxy)-N-(TentaGel S)butanamide (4) was then evaluated for its ability to isolate PAHs from solution by means of π-π-interactions.     

Development of a Four-Channel Potentiostat for Amperometric Detection in Flow Injection Analysis

Abstract

A four-channel multipotentiostat has been developed for simultaneous voltammetric measurements with microelectrode arrays. To reduce the complexity of electrochemical cell, only one reference and one auxiliary electrode are used. The potential ranges of the four working electrodes may be independently controlled, but they are synchronously scanned by only one DAC. This is accomplished through a microcomputer interfaced with a PCL-711B data acquisition board, which allows the continuous monitoring of the currents and actual potentials of the working electrodes.

The system has been applied to the simultaneous determination of ascorbic and uric acids in synthetic samples. The measurements were carried out with gold microelectrodes modified by deposition of noble metals, which enhance the electrocatalysis and provide an anticipation and a better definition of the oxidation potentials. Recuperation of 98.2% and 97.8% for ascorbic and uric acids, respectively, was obtained by using amperometry.     

Stability of the chromia layer on steels in flowing nonequilibrium H2-H2O-CH4-CO mixtures at 950 °C

The stability of the protective oxide layer formed on Fe-12.5 pct Cr, Fe-18 pct Cr-10 pct Ni, and Fe-25 pct Cr-20 pct Ni was investigated in a flowing nonequilibrium H2-H2O-CH4-CO mixture at 950 °C. The samples were preoxidized in H2-H2O, and subsequently the carbon activity was raised in stepwise manner by adding methane. CO formation occurred on the sample surface by the catalytic reaction CH4 + H2O → CO + 3H2. The conversion of oxide to carbide commenced at the end of the sample wherePco has its highest andPH2O its lowest value. Oxidation, conversion, and catalytic reaction were monitored by gravimetric measurements and CO-determination during the experiments. Partial equilibria can be calculated for (ac)1 =K ₁ P _{ch 4}/(Ph2)2, (ac)2 =K2(PcoPh2)ph{2o}and(Po2)1\2 = K3Ph2o/Ph2. The conversion of oxide to carbide started when the steady state ofac and(Po2)1/2 on the surface approached the value for the equilibrium of chromium oxide and chromium carbide. The results show that this steady state value is much nearer to the point(ac)2-(Po2)1/2 in the thermochemical stability diagram than to the point (ac)1 — (Po ₂)^1/2- The oxide layers were stable even at very high values of (ac)₁ which demonstrates that there is only very little interaction of CH₄ with the oxide surface. P. C. Prasannan formerly Research Scientist at the Max-Planck-Institut für Eisenforschung This paper is based on a presentation made at the “Stephen R. Shatynski Memorial Symposium on Surfaces and Interfaces” held at the 114th annual AIME meeting in New York, February 24-28, 1985, under the auspices of the ASM-MSD Thermodynamic Activity Committee.     

HYDRODYNAMICS AND STABILITY OF SLOT-RECTANGULAR SPOUTED BEDS PART II: INCREASING BED THICKNESS

Tests were carried out with rectangular spouted bed columns of different thickness, i.e., front-to-back dimension, while holding the column width and air-entry slot width constant, to investigate the effects on spoul stability and bed hydrodynamics. For the three sizes of glass beads and one size of polyethylene beads examined, increasing the column thickness led to three-dimensional effects, such as formation of multiple spouts, and affected such hydrodynamics variables as the minimum spouting velocity, maximum spoutable bed depth and maximum pressure drop.     

FTIR spectroscopic characterization of irradiated hazelnut (Corylus avellana L.)

Radiation induced molecular changes in macromolecular components of hazelnut tissues were investigated by mid-Fourier transform infrared (FTIR) spectroscopy. Irradiation dose of 1.5 kGy (low) and 10 kGy (high) were applied. The changes in frequency, signal intensity and intensity ratio of IR bands revealed that the unsaturated lipid concentration increased for low dose treated samples whereas it decreased and peroxidation appeared at high dose treatment. The low dose irradiation treatment, slightly increased the total lipid content whereas it dramatically decreased for high dose treatment. A slight increase in the lipid to protein ratio was observed for low dose treatment, whilst this ratio significantly decreased for high dose treatment. In addition, the high dose γ-irradiation caused alterations in the structure of hazelnut proteins, as cross-linking and aggregation occured in protein molecules. These results indicate that FTIR spectroscopy can be successfully used to monitor food irradiation.     

Intentional ρ-type doping by carbon in metalorganic MBE of GaAs

We report on the intentional ρ-type doping of GaAs layers grown in an UHV system from molecular beams of arsine (AsH₃) and mixtures of frimethyl gallium (TMG) and friethyl gallium (TEG). The entire doping range between 10¹⁴ cm^-3 (growth from pure TEG) and 10²⁰ cm^-3 (growth from pure TMG) can be covered by using mixtures of TMG and TEG. As revealed by SIMS and photoluminescence (PL) carbon is the dominant acceptor in the layers. Comparison of the Hall mobility and of the PL spectra shows that the quality of our films equals that of the best LPE and MBE grown ρ-type GaAs layers.     

The effect of microstructure in the hydrogen embrittlement of a gas pipeline steel

Hydrogen embrittlement (HE) tests were carried out on a carbon-manganese pipeline steel having a low sulphur content (<0.01%). It was shown that the susceptibility to HE increased as the microstructures changed from ferrite-pearlite to martensite. In the hydrogenated state the fracture surface of the ferrite-pearlite and ferrite-bainite specimens consisted of small cleavage regions surrounding non-metallic (oxide) inclusions; these were called rosettes and were a characteristic feature of the embrittled state. In hydrogenated martensitic specimens, failure was almost entirely intergranular along prior austenite grain boundaries and cracking of martensitic laths. In the martensitic specimens a relationship between inverse time to failure and prior austenite grain size was established.