Water-quenched Samples Research Articles

Charge transfer and short-range order in Cu-Pd and Ni-Mo alloys

Abstract Water-quenched samples of Cu–Pd and Ni–Mo alloys have been studied by electron diffraction and electron-energy-loss spectroscopy. Diffraction patterns from these alloys exhibit pronounced diffuse scattering due to short-range order. Determination of the white-line intensity in the energy-loss spectra from these samples indicated a concentration dependence and the results are discussed in terms of charge transfer associated with short-range order.

Reductilization of an Embrittled Amorphous La<SUB>55</SUB>Al<SUB>25</SUB>Ni<SUB>20</SUB> Alloy by Water Quenching from Supercooled Liquid

A water quenching treatment from supercooled liquid region was found to induce the ductilization of an amorphous La55Al25Ni20 alloy which was embrittled by annealing in a wide temperature range up to the glass transition temperature (Tg). The tensile fracture surface appearance also changed from a shell-like pattern typical for the brittle amorphous alloy to a pattern consisting of smooth and vein regions typical for the ductile amorphous alloy. There is no appreciable difference in the fracture surface appearance between the melt-spun and the ductilized alloys. The embrittled samples exhibit a reversible endothermic reaction resulting from the annihilation of the short-range ordering developed during annealing, accompanied by a significant decrease of an exothermic reaction. On the other hand, the water-quenched sample with good ductility does not have the endothermic reaction and exhibits only the exothermic reaction in the entire temperature range up to Tg. Accordingly, the reductilization caused by water quenching is presumed to destroy the structure stabilized by the annealing-induced structural relaxation so as to rather close to the quenching-induced disordered atomic configuration. This has been supported by the results of X-ray diffraction.

The morphology, character and strength of the interface in glass fibre-polypropylene composites

The interface in clean glass fibre-polypropylene and silane-treated glass fibre-polypropylene pull-out specimens has been studied. The nature of the silane layer on the treated fibres was examined and the influence of agglomerates in the silane layer on the nucleating ability of the fibre surface has been considered. Transcrystalline sheaths of polypropylene were observed in the water-quenched samples but not the air-cooled and 50 °C oven-cooled samples. The nature of the interface and the plane of failure have been determined utilizing optical microscopy and scanning electron microscopy of both the fibre and matrix-failure surfaces. The shrinkage stresses in the air-cooled and oven-cooled clean fibre specimens were relieved by the formation of kink bands. The results suggest the existence of an interphase. The different interfacial strengths in the silane-treated and clean fibre specimens can be explained in terms of the above findings.

銅製錬自溶炉のシャフト内の反応解析 （第２報） 反応シャフトにおける銅精鉱粒子の酸化および衝突挙動

Water-quenched samples were collected from the reaction shaft of a pilot scale flash furnace, in which copper concentrate was processed together with silicious sand. The samples were subjected to size distribution measurements and chemical analyses. Based on the results, the following conclusions have been obtained:(1) The sampling method used in this study can collect not only coarse particles but fine ones equally.(2) The desulfurization reaction of copper concentrate is not completed in the reaction shaft, but proceeds even in the settler to some extent.(3) A copper concentrate particle impinges on other particles about 40 times while falling down 4m from the shaft roof to the bath, and its final diameter becomes more than 250μm or 5 times as large as the original diameter.(4) Such increase in particle diameter is not brought about by the agglomeration of the particles during feeding nor difference in terminal velocity of the particles, but by turbulence in the reaction shaft.

Low-rank coal-water fuel combustion in a laboratory-scale furnace

A detailed study of hot-water dried lignite slurry combustion and the formation of nitrogen-containing pollutants was performed in a vertical, laboratory-scale combustor. Space-resolved local measurements of solid and gaseous combustion products were obtained from throughout the combustion zone using a stainless steel, water-quenched sample probe. Coal burnout (daf) of greater than 99% was achieved without supplementary fuel support, in an estimated residence time of 1.4 s. Flame stability was strongly affected by the atomized droplet size, which is controlled by the atomizing air to slurry mass ratio ( A S ). For A S greater than 0.7, coal burnout was relatively insensitive to further increases in A S , yet burnout decreased rapidly as A S was decreased. Nitric oxide (NO) emissions were not affected greatly by changes in A S . Decreasing stoichiometric ratio (SR) to about 0.8 caused coal burnout to decrease from about 98% to 94% and NO emissions to decrease from around 600 ppm to less than 100 ppm. Changes in secondary air swirl number from 0 to 4.25 had little or no effect on coal burnout or NO emissions for a SR of 1.1 and an A S of 0.75. At low A S (0.24), high secondary air swirl was required to stabilize the slurry flame. Reactor mapping tests showed rapid mixing between the slurry and the combustion air. CO was found only near the slurry inlet at a maximum concentration of 0.3%. No other fuel-rich species were detected in measurable quantities.

The effect of DO3 ordering on the parent ? martensitic transformation in the CuZnAl shape-memory alloy

The character of D03 ordering resulting from different quenching rates and its effect on the characteristic martensitic transformation temperatures and shape-memory effect in the Cu-21.5 at % Zn-12.5 at % Al alloy has been analysed. ln room temperature water-quenched samples with a cooling rate ∼ 1000° C sec−1 showing B2 long-range order and DO3 Short-range order, e significant stabilization of martensite in the reverse transformation was observed. This stabilization was eliminated in the air-cooled samples with a cooling rate ∼20° C sec−1 showing DO3 long-range order. Mechanical tests revealed a more complete shape recovery in the air-cooled samples, when compared to room temperature waterquenched ones.

Entrained flow gasification of coal: 1. Evaluation of mixing and reaction processes from local measurements

Local mixing and reaction processes were studied within a laboratory-scale, entrained coal gasifier at atmospheric pressure, using a Utah high-volatile, low-sulphur bituminous coal at a design flow rate of 24.5 kg h −1. The coal-oxygen-steam feed mass ratio was 1.00:0.91:0.27. A water-quenched sample probe was used to collect radial gas and char samples at seven different axial positions in the 124 cm long reactor for the measurement of gasification products and residual char composition. The observed carbon conversion was 79 ± 3%. Coal hydrogen and oxygen were converted more rapidly and more completely than carbon. Devolatilization, which occurred very rapidly near the inlet, led to most of this carbon conversion; heterogeneous char reactions with CO 2 and steam apparently accounted for the balance. Oxygen was consumed through reaction with volatiles very quickly in the upper gasifier region. These data were used to evaluate mixing and reaction characteristics within the reactor. Agreement of measurements with predictions from a generalized two-dimensional entrained coal gasification model was good.

The enhanced oxidation of SO 2 by NO 2 on carbon particulates

The oxidation of SO 2 on carbon particles in dry air and in air at 65% relative humidity (RH) was found to be greatly enhanced by the presence of gaseous NO 2. Exposures of 20–80 ppm SO 2 + 10 ppm NO 2 on 1 mg samples of commercial carbon black were found to produce both sorption and desorption coverages (weight retained after desorption into N 2) of over one order of magnitude greater than for corresponding SO 2 exposures. Significant agglomeration and wetting were observed to occur progressively during exposures at 65% RH and samples, even after 150 h exposure, rarely reached steady-state weight gain. The wetting may have regenerated fresh reactive carbon surface. Sorptions conducted in nitrogen atmospheres, rather than in air, appeared to produce slightly higher sorptions and weight retentions for equivalent exposure concentrations and times, indicating that NO 2 served as the oxidizer and that molecular oxygen, or some trace constituents in air, may have weakly inhibited the oxidation by NO 2. Wet chemical analysis of the desorbed phase indicated that sulfate, presumably H 2SO 4, accounted for over half of the retained weight. Measurements of pH from water-quenched samples indicated a highly acidic surface phase and suggested the oxidation process could process in an acidic environment.

Flow stress and dynamic strain-ageing of β-transformed Zircaloy-4

The 0.2% yield stress of β-transformed Zircaloy-4 was found to be independent of prior-β grain size but varied as the inverse of the transformed β plate width. A dislocation loop expansion model originally proposed by Langford and Cohen [7] for cold-drawn iron wires is used to explain the inverse plate width dependence. Both air-cooled and water-quenched samples exhibited dynamic strain-ageing effects in approximately the same temperature range of 573 to 673 K: (a) a local minimum in strain-rate sensitivity is associated with a peak or an inflection point in the temperature dependence of the 0.2% yield stress for water-quenched or air-cooled samples respectively, and (b) yield drops were observed in strain rate change tests.

Mount Etna and the 1971 eruption - Oxygen and sulphur fugacities of magmatic gases directly measured in active vents of Mount Etna

Solid-electrolyte sensors were used to measure the oxygen and sulphur fugacities of magmatic gases in vents located at an elevation of about 3170 m on the northeast flank of the NE crater of Mt Etna in July 1970. The temperature of the gas ranged from 773 to 1057 °C. The least-squares fit of 13 measured lgfo2 values yielded the relation: lg/o2 (atm) = 2.175- 15110/T (K), which gives values of 0.9 to 2.2 lgfo2 units higher than those obtained in the Makaopuhi lava lake, Hawaii, within the temperature range measured, the difference increasing with decreasing temperature. Laboratory study of a water-quenched sample of the Etna lava and calculations of gas equilibria indicate that the difference is due partly to the intrinsically higher f 02 of the Etna magma and partly to the mixing of air with the Etna gases. The measured j^2 value was 10-2 4 atm at 860 °C.