Effect Of High-temperature Aging Research Articles

Effects of High-Temperature Aging on the Dispersion of Rh/Al 2O 3

The effects of high-temperature treatment in relatively simple gas mixtures of 1% O 2/N 2, 1% H 2/N 2, and an environment which alternates between these two gases on the dispersion of 0.5 wt% Rh/Al 2O 3 were characterized using temperature-programmed desorption (TPD) of D 2. The TPD data was used to determine the relative changes in the Rh metal dispersion as a result of treatment. These treatments were selected as they are believed to model the oxidation and reduction environments in the typical automotive exhaust. When the fresh catalyst was aged in reducing environments at 600, 700, or 800°C, the dispersion decreased rapidly within the first 2 h of treatment, but more slowly thereafter. The rate of this decrease is directly related to the treatment temperature. When the catalyst was aged in oxygen at 600, 700, or 800°C, the Rh was rapidly and completely oxidized. At the lower aging temperatures, most of the Rh could be recovered to the metallic state using a reduction treatment at 200°C, but at 800°C, only a small amount of the Rh was recovered to the metal using this mild reduction treatment. Subsequent reduction treatments at high temperature resulted in near complete recovery of Rh in the form of large metal particles. Treatment in alternating oxygen/hydrogen environments at low frequency produced Rh 2O 3 after each oxidation treatment and Rh metal particles after each reduction treatment. The higher temperature treatments produced sintered Rh metal particles, even in the alternating environment. Treatment in alternating oxygen/ hydrogen environments at high frequency resulted in incomplete oxidation of Rh after the oxidation cycle, but did result in more rapid sintering of the Rh metal as the treatment temperature was increased. This sintering rate, however, was slower than for treatments in the pure gases at the same temperature.

Synthesis and Properties of Polyacetylene Films Prepared by Ti(OEt)4–AlMe3 Catalyst System

Abstract Novel homogeneous catalyst system of composed tetraethoxytitanium–trimethylaluminum, Ti(OEt)4–AlMe3, is employed for synthesis of polyacetylene film. It is confirmed that the present system has a high catalytic activity for acetylene polymerization, and its activity is comparable to that of the representative Ti(O-n-Bu)4–AlEt3 catalyst system. Experimental conditions, especially for preparation and aging of the catalyst, are optimized in view of properties of polyacetylene film such as cis content, mechanical stretchability, and electrical conductivity. The homogeneity of the present catalyst aged at room temperature enables us to synthesize highly conductive non-stretched and stretched films whose electrical conductivities after iodine doping are 2.0 × 103 and 1.2 × 104 S cm−1, respectively. Discussion has also been made in terms of the effect of high-temperature aging for the catalyst, the role of co-catalyst as a reductant, and the dependence of electrical conductivity on film thickness.

高温時効に伴うHK40及びHP遠心鋳造管の共晶炭化物の形態変化

高温時効に伴うHK40及びHP遠心鋳造管の共晶炭化物の形態変化

Effect of high-temperature ageing on the gas chromatographic properties of porous polymer beads

The effect of column ageing at 200δC under a flow of carrier gas on the gas chromatographic behaviour of porous polymer bead (PPB) stationary phases was investigated by analysing standard mixtures of linear alkanes and polarity “probes”: ethanol, butanol, pyridine, nitromethane, l-nitropropane, benzene, methylethyl ketone and methylpropyl ketones. A linear dependence of the logarithm of the adjusted retention times (log t′ R on the time of ageing was observed for many PPBs, but some of them showed non-linear relationships (Chromosorb 103, 107 and 108). The PPBs showing linear behaviour can be divided into four classes: (1) no variation of log t′ R with ageing (Porapak N, Q and R and Chromosorb 106); (2) linear increase in log t′ R (Porapak P and S and Chromosorb 101, 102 and 104); (3) linear decrease in log t′ R (Porapak T); (4) horizontal, increasing or decreasing log t′ R values depending on the chemical composition of the polarity probes (Chromosorb 105). The variation of retention times and elution order with thermal ageing of the PPBs can explain the differences between retention data reported in the literature and must be taken into account in the determination of the high-temperature polarity of these stationary phases.

Effect of high-temperature aging in vacuum on the creep resistance of alloy 5VMTs

Effect of high-temperature aging in vacuum on the creep resistance of alloy 5VMTs

Effect of high-temperature aging on the endurance of thin-walled joints made of alloy AK4-1T1

Effect of high-temperature aging on the endurance of thin-walled joints made of alloy AK4-1T1

Cr-Niオーステナイト鋼の高温時効組織

Cr-Niオーステナイト鋼の高温時効組織

Alterations of Bovine Sarcoplasmic Proteins as Influenced by High Temperature Aging

SUMMARY— Effects of high temperature aging upon certain characteristics of bovine I. dorsi muscle were studied. Paired wholesale ribs of carcasses were obtained subsequent to slaughter. The left rib of each pair was held at 30°C for 24 hr, then stored at 3°C. Analogous right ribs were immediately stored at 3°C. A sampling schedule of 0, 1, 2, 3, 4, 7 and 10 days was followed.There were minor variations in moisture, pH, tyrosine‐tryptophan indices of non‐protein nitrogenous compounds and expressible moisture ratios between treatments and with time. These differences were not statistically significant.Up to three days storage, extractability of water soluble protein was greatest from muscles held at the elevated temperature. After the third day, however, extractability was greater for muscles held at 3°C.Color differences between muscles treated via the two storage temperatures were marked. Absorbance ratios (422.280 mp) of extracts showed that muscles held at the high temperature had higher extractable levels of oxymyoglobin than ribs held at 3°C. This difference remained apparent throughout the aging period.Results of DEAE‐cellulose ion exchange chromatography of the sarcoplasmic proteins showed only minor variations in profiles between the two aging treatments. Alterations did appear with time. Profile alterations did not appear related to anticipated increases in tenderness.