Ultrasonic Study of the Ordering of ortho–Hydrogen in Quench–Condensed Films

The ultrasonic attenuation and dispersion of quench–condensed H ₂ films was measured for ortho–concentrations ranging from x = 75% to x = 32%. Orientational ordering was observed for all ortho–H ₂ concentrations. The obtained results are compared to recent specific heat experiments by Birmingham et al.     

Early Stage Morphology of Quench Condensed Ag, Pb and Pb/Ag Hybrid Films

In situ Scanning Tunneling Microscopy (STM) has been used to study the morphology of Ag, Pb and Pb/Ag bilayer films fabricated by quench condensation of the elements onto cold (T = 77 K) inert and atomically flat Highly Oriented Pyrolytic Graphite (HOPG) substrates. All films are thinner than 10 nm and show a granular structure that is consistent with earlier studies of Quench condensed (QC) films. The average lateral diameter, & of the Ag grains, however, depends on whether the Ag is deposited directly on HOPG (&=13 nm) or on a Pb film consisting of a single layer of Pb grains (&=26.8 nm). In addition, the critical thickness for electrical conduction (d_G) of Pb/Ag films on inert glass substrates is substantially larger than for pure Ag films. These results are evidence that the structure of the underlying substrate exerts an influence on the size of the grains in QC films. We propose a qualitative explanation for this phenomenon.     

Quench properties of high current superconductors

A technique has been developed which allows the simultaneous determination of most of the important parameters of a high current superconductor. The critical current, propagation velocity, normal state resistivity, magnetoresistance, and enthalpy are determined as a function of current and applied field. The measurements are made on non-inductive samples which simulate conditions in full scale magnets. For wide, braided conductors the propagation velocity was found to vary approximately quadratically with current in the 2 to 5 kA region. A number of conductors have been tested including some Nb³Sn braids which have critical currents in excess of 10 kA at 5 T, 4.2K.     

Quench modification of aluminium-silicon eutectic alloys

Directional solidification of aluminium-silicon eutectic alloys were carried out in order to investigate the mechanism by which the quench modification takes place. For this purpose a new type of Bridgman furnace was designed which can attain a high temperature gradient and a high interfacial growth velocity up to 1000 m^–1. It is established that the fibrous structure is the result of faceted-non-faceted growth of the coarse silicon particle at high solidification rate. It is observed that refining of the flake structure closely follows the characteristics of normal eutectic.     

Condensed Matter Physics

Gert StroblSpringer-Verlag (2003), 379 pp. ISBN: 3-540-00353-3 $59.95 / $30.50 / €39.95     

Hybridizing Energy Conversion and Storage in a Mechanical-to-Electrochemical Process for Self-Charging Power Cell

Energy generation and energy storage are two distinct processes that are usually accomplished using two separated units designed on the basis of different physical principles, such as piezoelectric nanogenerator and Li-ion battery; the former converts mechanical energy into electricity, and the latter stores electric energy as chemical energy. Here, we introduce a fundamental mechanism that directly hybridizes the two processes into one, in which the mechanical energy is directly converted and simultaneously stored as chemical energy without going through the intermediate step of first converting into electricity. By replacing the polyethylene (PE) separator as for conventional Li battery with a piezoelectric poly(vinylidene fluoride) (PVDF) film, the piezoelectric potential from the PVDF film as created by mechanical straining acts as a charge pump to drive Li ions to migrate from the cathode to the anode accompanying charging reactions at electrodes. This new approach can be applied to fabricating a self-charging power cell (SCPC) for sustainable driving micro/nanosystems and personal electronics.     

Quench factor analysis of aluminium alloys

Abstract

A model was developed almost 20 years ago which described how precipitation during the quench affected the development of properties of aluminium alloys during subsequent aging treatment. This model was the basis for an analytical process, known as quench factor analysis, that was used to predict the effects of quench path on corrosion characteristics and strength. The purpose of this paper is to provide a theoretical basis for the model and to review how quench factor analysis has been used in solving industrial problems. Several investigators have confirmed that quench factor analysis is an effective predictive method for all quenching conditions save one. The exception is when material has been quenched below the knee of the C-curve and subsequently reheated above the knee before the quench is complete. Applications include the design of quench systems, the development of quench practices which optimize combinations of high strength and low residual stress and distortion, and predictions of the magnitude of loss in strength as a result of unsuitable quenching conditions. By combining quench factor analysis with homogeneous nucleation theory, interactions between quenching and aging conditions have been clarified, and aging treatments have been developed which minimize the low and variable strengths caused by less than ideal quenching conditions. Quench factor analysis also adequately describes the rate of loss in toughness of an AA 6000 series extrusion alloy for those cooling conditions which produced commercially significant loss in strength. The latest use of quench factor analysis is in a specification for quenchants for aluminium alloys.

MST/573     

Quench crack behavior of nickel-base disk superalloys

There is a need to increase the temperature capability of superalloy turbine disks to allow higher operating temperatures in advanced aircraft engines. When modifying processing and chemistry of disk alloys to achieve this capability, it is important to preserve the ability to use rapid cooling during supersolvus heat treatments to achieve coarse grain, fineγ′ microstructures. An important step in this effort is an understanding of the key variables controlling the cracking tendencies of nickel-base disk alloys during quenching from supersolvus heat treatments. The objective of this study was to investigate the quench cracking tendencies of several advanced disk superalloys during simulated heat treatments. Miniature disk specimens were rapidly quenched after solution heat treatments. The responses and failure modes were compared and related to the quench cracking tendencies of actual disk forgings. Cracking along grain boundaries was generally observed to be operative. For the alloys examined in this study, the solution temperature, not alloy chemistry, was found to be the primary factor controlling quench cracking. Alloys with high solvus temperatures show greater tendency for quench cracking.     

7085铝合金的淬火敏感性

采用分级淬火法测定了7085铝合金的TTT和TTP曲线,并结合透射电镜对其淬火敏感性进行了研究。结果表明,在等温保温过程中7085铝合金淬火态电导率升高,时效态硬度下降,在中间温度段电导率及硬度变化较快;TTT和TTP曲线的鼻尖温度约为320℃,淬火敏感区间为250~370℃;等温保温过程中,过饱和固溶体分解析出平衡相η,在320℃附近析出速率达到最大,随着等温保温时间的延长,η相聚集并长大,时效后出现大量无沉淀析出区域,导致性能显著下降;在淬火敏感区间,较高的相变驱动力和较大的扩散速率是η相快速析出长大的主要原因。     

Das Karlsruhe Tritium Neutrino Experiment

The Karlsruhe Tritium Neutrino Experiment — The Word's Most Accurate Scale Scale The mass of the neutrino is one of the big open questions in particle physics, astrophysics and cosmology. The Karlsruhe TRItium Neutrino (KATRIN) experiment aims to measure the neutrino mass with a sensitivity of 200 meV/c². This corresponds to an improvement by a factor of 10 compared to predecessor experiments. In order to achieve this improvement, the KATRIN experiment needs to solve technical challenges from various technical fields such as high voltage, cryogenics or vacuum technology. A considerable challenge is the operation of a large spectrometer with a volume of 1240 m³ in a pressure regime of 10^?11 mbar.     

Isotope Exchange of Azidothymidine with Tritium

The following modes of isotope exchange of azidothymidine (3'-azido-3'-deoxythymidine) with tritium were studied: solid- and liquid-phase isotope exchange with gaseous tritium and isotope exchange in solution with tritium water. Catalytic reactions of azidothymidine with gaseous tritium in solution result in virtually complete reduction of the azido group to amino group. This reduction also occurs in the course of solid-phase catalytic hydrogenation; the yield of 3'-amino-3'-deoxythymidine ranges from 20 to 70%. The molar radioactivity of tritium-labeled azidothymidine prepared by solid-phase catalytic isotope exchange with gaseous tritium and by isotope exchange in solution with tritium water does not exceed 0.5 Ci mmol^{- 1}.     

Condensed matter physics journals

On the basis of a citation/reference criterion, 20 core journals are selected in the field of condensed matter physics. Citation data and indicators from 1980Journal Citation Reports reveal their different characteristic features such as applied orientation, communication function and longevity. The manually obtained data for the core journals are written into a matrix in order to determine an appropriate ranking parameter. The method ofPrice is used first to reduce the diagonal elements and then, following the method ofGeller, influence weights are calculated for the core journals. Influence weights are determined also for non-core journals using only the references received from the core.     

Condensed Cesium Indium Phosphates

In the range 250–400°C, the Cs₂O–In₂O₃–P₂O₅(H₂O) system contains the triphosphate CsInHP₃O₁₀and cyclododecaphosphate Cs₃In₃P₁₂O₃₆. The phase relations in this system are similar to those in the analogous Fe and Ga systems, but the transformation of CsInHP₃O₁₀into Cs₃In₃P₁₂O₃₆is much slower. The monoclinic cell parameters in CsInHP₃O₁₀are a= 12.054 Å, b= 8.936 Å, c= 9.432 Å, = 111.77° (sp. gr. C2/c). The structure of Cs₃In₃P₁₂O₃₆, determined by single-crystal techniques, is cubic (sp. gr. Pa3¯), with a= 14.885 Å.     

Variation of Quench Propagation Velocities in YBCO Cables

We show by modelling that the quench propagation velocity is not constant in HTS coils but it changes during the quench. Due to the large temperature margin between the operation and the current sharing temperatures, the normal zone does not propagate with the temperature front. This means that the temperature will rise in a considerably larger volume when compared to the quenched volume. Thus, the evolution of the temperature distribution below current sharing temperature T _{c s} after the quench onset affects the normal zone propagation velocity in HTS more than in LTS coils. This can be seen as an acceleration of the quench propagation velocities while the quench evolves when margin to T _{c s} is high. In this paper, we scrutinize quench propagation in a stack of YBCO cables with an in-house finite element method software which solves the heat diffusion equation. We compute the longitudinal and transverse normal zone propagation velocities at various distances from the hot spot to demonstrate the distance-variation of these velocities. According to the results in our particular simulation case, the longitudinal normal zone propagation velocity is 30 % higher far away from the quench origin compared to its immediate vicinity when T _op=4.2 K and T _{c s} =15 K.     

Tritium Sorption by Modified Natural Aluminosilicates

In connection with problems of interaction of tritium-containing underground waters with clay geological barriers and tritium water treatment, the sorption of tritium by natural and synthetic clays modified with organic compounds was studied. The mechanism of tritium sorption by aluminosilicates, involving the isotope exchange of hydrogen atoms in organic and inorganic compounds, was proposed. Modification of clays with organic compounds shows promise as a way to improve the sorption capacity of clays with respect to tritium.