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Researchers at ACSION Industries and Oak Ridge Center for Composite Manufacturing Technology have recently achieved a major breakthrough for the composites industry by successfully developing Electron-Beam (EB) curable epoxies and EB curing cycles that reduce processing time and cost while meeting the demanding requirements of high-performance composite structures. These developments make it possible to use a large class of common epoxies to build composite parts without the need for slow, high-temperature, high-pressure curing cycles, the associated expensive fabrication tools, or the toxic chemical hardeners. The pioneering invention and development of EB-curable epoxies and the impact of these materials on EB processing of advanced composites has provided the stimulus for several companies to use these EB-curable epoxies to demonstrate numerous manufacturing advantages for EB-cured composite materials. This research has already highlighted novel composite material design concepts that are feasible only by using this technology. This paper summarizes the important aspects of EB-curable epoxies and the EB-curing process.

(1999). Porosity Measurements of Advanced Composites using Mercury Intrusion Porosimetry – A new quality tool. Materials Technology: Vol. 14, No. 3, pp. 129-132.

Research to develop products and processes tor the electron curing of fibre-reinforced composites is rapidly progressing at several industrial and government laboratories, including AECL Research. Electron curing uses high-energy electrons or X-rays generated from these electrons, rather than thermal energy, to cure selected composite matrix polymers and to enhance their physical and chemical properties. Our recent programs have focussed on resin development, economics and process design. This paper summarizes the recent advances in electron curing technology.

Radiation modification of the gel content and the complex modulus of plastics was used to determine the depth-dose distribution in a solid polyethylene block irradiated with a 10 MeV electron beam, under typical radiation processing conditions. The results indicate that the accumulated charge has no significant effect on the shape of the dose profile. This suggests that, under certain circumstances, intrinsic “dosimeters” could be more appropriate than conventional thin film dosimeters placed inside the material for dose measurements in electrically non-conducting materials.

Iodine-129 and carbon-14 are of lesser importance than many other radionuclides in nuclear waste management because of their relatively low radiotoxicity. Their safe immobilization and disposal, however, is a significant challenge because their chemical properties are quite different from most other components of nuclear fuel waste. The authors have sought thermodynamically defensible inorganic waste forms for both of these radioisotopes. This paper discusses the stability and solubility of inorganic iodides as they relate to the selection of a waste form for iodine-129. The best candidates appear to be silver iodide (AgI), either alone or in combination with silver chloride (AgCl), and a combination of Bi 5 O 7 I and Bi 2 O 3 . Neither is completely satisfactory. The principal drawback of AgI is its relative ease of reduction. High chloride concentrations also increase the solubility of AgI, but it is insensitive to carbonate. The main disadvantage of bismuth oxyiodide is its susceptibility to displacement reactions with dissolved chloride and carbonate; also, it is unstable under strongly reducing conditions.

Recently developed epoxy paste adhesives were electron beam cured and experimentally explored to determine their suitability for use in an aerospace-quality aircraft component. There were two major goals for this program. The first was to determine whether the electron beam-curable past adhesives were capable of meeting the requirements of the US Air Force T-38 supersonic jet trainer composite windshield frame. The T-38 windshield frame`s arch is currently manufactured by bonding thin stainless steel plies using an aerospace-grade thermally-cured epoxy film adhesive. The second goal was to develop the lowest cost hand layup and debulk process that could be used to produce laminated steel plies with acceptable properties. The laminate properties examined to determine adhesive suitability include laminate mechanical and physical properties at room, adhesive tack, out-time capability, and the debulk requirements needed to achieve these properties. Eighteen past adhesives and four scrim cloths were experimentally examined using this criteria. One paste adhesive was found to have suitable characteristics in each of these categories and was later chosen for the manufacture of the T-38 windshield frame. This experimental study shows that by using low-cost debulk and layup processes, the electron beam-cured past adhesive mechanical and physical properties meet the specifications of the T-38 composite windshield frame.

The effect of a magnetic field on the light emission from squalane solutions of fluorene, pulse irradiated at the center of a large electromagnet, is described. The fluorescence intensity following pulse radiolysis was found to be 40 to 50 percent higher in an applied field of 0.3 T (3000 G) and the triplet yield showed a small decrease. The enhancement of the singlet emission is attributed to an increase in the fraction of geminate solute ion recombinations leading to excited singlet fluorene. The magnetic field effect was time dependent, being undetectable during the pulse and reaching a maximum value after about 100 ns. These observations are compared with the theory of Brocklehurst which describes the singlet to triplet conversion of geminate solute ion pairs quantitatively in terms of the electron--nuclear hyperfine interactions in the radical ions. After correction for the large in-pulse fluorescence and its decay, satisfactory agreement between experiment and theory was obtained. The results emphasize the importance of ion recombination in the generation of excited states in radiolysis and confirm the role of the electron--nuclear spin interaction in determining the ratio of singlet and triplet yields.

The effect of an applied magnetic field on the fluorescence from γ-irradiated solutions of perfluorobiphenyl and perfluoronaphthalene has been measured in various solvents. In all the solvents used (cyclohexane, squalane, isooctane) the fluorescence intensity increases with increasing field and tends towards a plateau at high fields (>0.1 T). At low fields, the fluorescence enhancement is smaller for the perfluorocarbons than for the parent hydrocarbons, due to the larger electron–nuclear hyperfine coupling and broader spread of the hyperfine levels in the radical ions of the perfluorocarbons. At high fields the fluorescence enhancement is also smaller for the perfluorocarbons than for the parent hydrocarbons, indicating a larger relative proportion of prompt (field-independent) fluorescence for the perfluorocarbons than for the parent hydrocarbons.

Observations are reported on the interconversion of solid α-Bi2O3, Bi12O17Cl2, BiOCl, and a daubréeite-like phase tentatively identified as Bi2O2(OH)Cl, in aqueous chloride solutions at 25 °C. Equilibrium constants, K, for these interconversions are expressed as anion activity ratios, {Cl−}/{OH−}. Experimental values of K for equilibrium between Bi2O3 and each of the chlorides are 100.56 ± 0.20 for Bi12O17Cl2, 101.5 ± 0.4 for Bi2O2(OH)Cl, and 103.13 ± 0.04 for BiOCl; the fatter two represent metastable equilibria. These equilibrium constants yielded the following estimates of Gibbs energies of formation: Bi12O17Cl2, −3141 ± 6 kJ mol−1;"Bi2O2(OH)Cl", −696 ± 4 kJ mol−1; BiOCl, −321.5 ± 1.3 kJ mol−1. Phase relationships among these solids are discussed, with reference to natural occurrence, other bismuth oxychlorides, and the stability of other basic salts of bismuth.

The decomposition of synthetic hydrocerussite, Pb 3 (OH) 2 (CO 3 ) 2 , and plumbonacrite, Pb 10 O(OH) 6 (CO 3 ) 6 , in both CO 2 and inert atmospheres, was compared using differential thermal analysis and thermogravimetry. The overall weight losses, upon decomposition to PbO, were in good agreement with calculated values. The initial dehydration steps for hydrocerussite and plumbonacrite yielded 2 PbCO 3 ·PbO, and a mixture of 2 PbCO 3 ·PbO and PbCO 3 ·PbO, respectively, consistent with the lower carbonate content of plumbonacrite than hydrocerussite. These differences do not account for discrepancies among the numerous previous reports on hydrocerussite decomposition. Rather, the decomposition route of a lead carbonate seems to be highly sensitive to the nature of its formation.

Four basic lead carbonates were prepared and identified by X-ray powder diffractometry. These were hydrocerussite (Pb3(OH)2(CO3)2), plumbonacrite (Pb10O(OH)6(CO3)6), and the two adducts MOH•2PbCO3 (M = Na, K). New diffraction data are presented for the latter two compounds; they both have primitive hexagonal lattices with two formula units per unit cell. The unit cell dimensions of the sodium and potassium compounds are a = 5.273 ± 0.002 Å, c = 13.448 ± 0.005 Å and a = 5.348 ± 0.002 Å, c = 13.990 ± 0.005 Å, respectively. Six possible space groups are discussed.Raman and infrared spectra are reported for all four compounds, and compared with those of cerussite (PbCO3); assignment of the spectral features is discussed. Vibrational spectra of the two MOH adducts indicate that they are isostructural, and that the structure contains a well-defined lead sub-lattice, consistent with the X-ray data. The spectra of hydrocerussite and plumbonacrite indicate that lead is present as oxygen-bridged polymeric moieties in these solids. The carbonate ions occupy two and three independent sites in hydrocerussite and plumbonacrite, respectively.

We have determined equilibrium conditions for each reaction in the solid interconversion sequence [Formula: see text], in aqueous carbonate solutions near 25 °C. Our data yield the following Gibbs energies of formation from the elements, ΔfG°(298.15 K): plumbonacrite, −5310 ± 31 kJ mol−1; hydrocerussite, −1705 ± 11 kJ mol−1; cerussite, −628.0 ± 3.9 kJ mol−1. Corresponding estimated values of ΔfG°(373 K) are −5120 ± 50, −1643 ± 18, and −612 ± 9 kJ mol−1, respectively. We have demonstrated the existence of a narrow stability field for plumbonacrite, and convenient small-scale preparations of hydrocerussite and plumbonacrite are described. Gibbs energy data for the solids have been combined with selected data for aqueous lead species in a detailed computation of solubility behaviour for this system at 25 °C.

Identification du carbonate (BiO) 4 (OH) 2 CO 3 comme intermediaire dans l'interconversion de α-Bi 2 O 3 et de la bismutite synthetique (BiO) 2 CO 3 . Energies de formation de Gibbs, analyse thermogravimetrique, diffraction RX sur poudre et spectrometries IR et Raman. Parametres cristallins

The spectrum of the solvated electron in D2O has been measured in the temperature range 292–445 K. The results show that Emax varies from 1.80eV at 292 K, to 1.32eV at 445 K, with a temperature coefficient of ∼ 3.2x10-3 eV K-1. The values are consistent with those measured in D2O at higher temperatures and, at low temperatures, do not differ appreciably from those in H2O.

Observations are reported on the interconversion of solid α-Bi2O3, Bi12O17Cl2, BiOCl, and a daubreeite-like phase tentatively identified as Bi2O2(OH)Cl, in aqueous chloride solutions at 25 °C. Equilibrium constants, K, for these interconversions are expressed as anion activity ratios, {Cl−}/{OH−}. Experimental values of K for equilibrium between Bi2O3 and each of the chlorides are 100.56 ± 0.20 for Bi12O17Cl2, 101.5 ± 0.4 for Bi2O2(OH)Cl, and 103.13 ± 0.04 for BiOCl; the fatter two represent metastable equilibria. These equilibrium constants yielded the following estimates of Gibbs energies of formation: Bi12O17Cl2, −3141 ± 6 kJ mol−1;"Bi2O2(OH)Cl", −696 ± 4 kJ mol−1; BiOCl, −321.5 ± 1.3 kJ mol−1. Phase relationships among these solids are discussed, with reference to natural occurrence, other bismuth oxychlorides, and the stability of other basic salts of bismuth.

Four basic lead carbonates were prepared and identified by X-ray powder diffractometry. These were hydrocerussite (Pb3(OH)2(CO3)2), plumbonacrite (Pb10O(OH)6(CO3)6), and the two adducts MOH•2PbCO3 ...

Equilibria between Bi5O7I and Bi2O3 have been measured with the solids in contact with aqueous solutions at 10–60 °C, and with low-pressure oxygen (0.2–100kPa) at 550–800 °C. In the aqueous systems...

Absorption maxima for the solvated electron in 2-propanol have been measured in the temperature range 210–298 K. The value of Emax increases with decreasing temperature in a manner similar to that observed in 1-propanol. However, for a given temperature, Emax is significantly smaller for 2-propanol than for 1-propanol.

The decay of the solvated electron and the relative yields of free and geminate solvated electrons have been measured in ethanol in the range 150–290 °K. The estimated absolute yields at low temperature agree well with sub‐nanosecond values at room temperature, however the yield of solvated electrons appears to be substantially less than the total ionization yield. (AIP)