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- Author or Editor: M. Nakamura x
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Abstract
The effect of network structure on the glass transition temperature (T g) was examined by differential scanning calorimetry, thermomechanical analysis and dynamic thermomechanometry for epoxy resins cured with mixtures of curing agents consisting of an active ester, 1,3,5-triacetoxybenzene (TAB), and a polyfunctional phenol, 1,3,5-trihydroxybenzene (THB). Free hydroxyl groups are formed from THB after curing, whereas acetyl groups are left from TAB. TheT g value of cured epoxy resins decreased with increasing TAB content in the curing agent, which is attributed to the looser network structure induced by the steric hindrance of acetyl groups from TAB in the curing reaction and also to the weaker intermolecular interaction and the internal plasticization of acetyl groups from TAB.
Abstract
The rate constant of radiation induced exchange reaction between thallium(I) and thallium(III) ions has been studied for elucidating the mechanisms which are responsible for (T1(II) intermediates or bridging groups (SO 4 2– ) in sulfuric acid and perchloric acid solutions. It was found that the radiation induced exchange reaction is accelerated by the sulfate ion, and the rate of the thallium(II)-thallium(I) reaction is faster than that of the thallium(II)-thallium(III) process in perchloric acid solution.
Abstract
Japanese iron artifacts contain a small amount of charcoal which was used in manufacturing. We developed a wet method of carbon extraction from the iron samples for AMS radiocarbon dating. The method consists of dissolution of iron with a Cu2+ solution and dissolution of deposited Cu in HCl. High extraction yields (80–90%) and low contamination by modern carbon were achieved by the wet method.
Abstract
Transport of La, Nd, Eu, Tb, Tm and Lu through a supported liquid membrane (SLM) was investigated by using di(2,4,4-trimethylpentyl)phosphinic acid (DTMPPA) as a mobile carrier. Lanthanoid elements in the feed solution were quantitatively transported and concentrated into the product solution of mild acidity. The transport rates increased with increasing atomic number of lanthanoids in the low pH region of the feed solution. Separation factors evaluated from the transport rates for lanthanoids were close to those from the distribution ratios in liquid-liquid extraction.
Abstract
The stability constans,
1, of each monochloride complex of Eu(III) have been determined in the methanol and water mixed system with 1.0 mol·dm–3 ionic strength using a solvent extraction technique. The values of
1 increase with an increase in the mole fraction of methanol (X
S
) in the mixed solvent system when 0
X
S
0.40. The, distance of Eu3+–Cl– in the mixed solvent system was calculated using the Born-type equation and the Gibbs' free energy derived from
1. Calculation of the Eu3+–Cl– distance and the preferential solvation, of Eu3+ by water proposed the variation of the outersphere complex of EuCl2+ as follows: (1) [Eu(H2O)9]3+Cl–, [Eu(H2O)8]3+Cl– and [Eu(H2O)7(CH3OH)3+Cl– inX
S
0.014, (2) [Eu(H2O)8]3–Cl– and [Eu(H2O)7(CH3OH)]3+Cl– in 0.014<X
S
<0.25 and (3) [Eu(H2O)7(CH3OH)]3–Cl– and [Eu(H2O)6(CH3OH)[2
3+Cl– in 0.25<X
S
0.40.
Abstract
The stability constants, β1, of each monochloride complex of Am(III) have been determined in a mixed system of methanol and water at 1.0 mol·dm−3 ionic strength using a solvent extraction technique. The values of β1 of Am(III) decrease up to about 0.1 mole fraction of methanol (X s) in the bulk solutions and then increase with increasingX s when 0.1<X s≤0.4. The distance of Am3+−Cl− in the mixed system was estimated using a Born-type equation. From the estimated distance of Am3+−Cl− (d Am−Cl), it is concluded that AmCl2+ in the aqueous solution is present as a solvent-shared ion-pair. Further, based on the variation of dAm−Cl with increasingX s, the variations of β1 in the system are accounted for by the size-variation of the primary solvation sphere around Am(III) and by an effect due to the presence of a slight covalency in the solvation of Am(III).
Abstract
The stability constants, β1, of each monochloride complex of Ln(III) (Ln=Nd or Tm) have been determined in the mixed system of dimethyl sulfoxide (DMSO) and water with 1.0 mol·dm−3 ionic strength using a solvent extraction technique. The values of β1 of Ln(III) decrease to about 0.2 mole fraction of DMSO (X s) in the mixed solvent system and then increase withX s (>about 0.2). However, the variation mode of β1 of Nd(III) withX s somewhat differs from that of Tm(III). Calculation of Ln3+−Cl− distance using a Born-type equation of the Gibbs' free energy derived from the β1 evealed the followings: (1) For Tm3+ with coordination number 8, the estimated distance between Tm3+ and Cl− (d Tm-Cl) increases linearly withX s in 0.00≤X s≤0.17. This means an enlargement of the primary solvation sphere size of Tm3+ withX s. On the other hand, thed Tm-Cl shows a decrease withX s in 0.17<X s<0.28. (2) The estimatedd Nd-Cl increases linearly withX s in 0.00≤X s<0.06 and 0.06<X s≤0.17, but their slopes are different. The larger slope againstX s in 0.06<X s≤0.17 is attributable to a lowering of the β1 by a coordination of ClO4 − into the secondary solvation sphere of Nd3+ and/or by an increase in the solvation number of the primary solvation sphere of Nd3+.
Abstract
Macro-porous cation exchange resin Diaion CPK-08 and gel type cation exchange resin Dowex 50WX8 were irradiated with γ-rays from60Co, while soaked in distilled water, 0.5M HNO3 or 4M HNO3, and the ion-exchange properties, such as strong- and weak-acid capacities, moisture content and wet resin volume, were examined in relation to absorbed dose. There was no appreciable difference between the radiation stabilities of the two cation exchangers. Increase of HNO3 concentration reduced the loss of strong-acid capacity and increased the decross-linkage and the weak-acid capacity. Elution characteristics of137Cs and90Sr from columns packed with γ-irradiated resin were examined and the column distribution ratio of these radionuclides and the theoretical plate number were calculated. These values decreased with the increase of absorbed dose. Diaion CPK-08 was packed into a pressurized column and irradiated with γ-rays at a dose rate of 2·106 R/hr, while water was passed through the column at a constant flow rate. The greatest change of the resin properties was observed at an upper stream position from the position of the highest radiation dose of 2·106 R/hr.
