Showing papers on "Quenching published in 1994"
TL;DR: The dissipation of excess absorbed excitation that is monitored by the main component of nonphotochemical quenching is a process that is necessary if plants are to avoid photoinhibition and photodestruction under conditions of light stress.
Abstract: ce has become one of the most powerful methods for assessing photosynthetic performance in plant physiological experiments (Horton and Bowyer, 1990; Krause and Weis, 1991). This has resulted almost entirely from the development of methods to distinguish photochemical and nonphotochemical quenching of fluorescence. Moreover, it is now clear that the process of nonphotochemical quenching itself indicates important regulatory adjustments in the photosynthetic membrane in response to altered external and internal conditions (Demmig-Adams and Adams, 1992; Horton and Ruban, 1992). In particular, the dissipation of excess absorbed excitation that is monitored by the main component of nonphotochemical quenching is a process that is necessary if plants are to avoid photoinhibition and photodestruction under conditions of light stress. When light is absorbed by the Chl molecules in the thylakoid membrane, the excited state has several alternative and competing fates: a small proportion is emitted as fluorescence, but, under light-limiting conditions, the major pathway of de-excitation is through photosynthetic electron transfer. The effect of photochemical utilization of energy is to quench fluorescence, and it is well known that when photosynthetic electron flow is saturated the yield of fluorescence rises. This photochemical quenching has been termed qP and, using the light-doubling principle as applied with modulated fluorimetry, it is easy to calculate it in leaves, chloroplasts, and cells (Schreiber et al., 1986; Horton and Bowyer, 1990; van Kooten and Snel, 1990). However, qP does not account for all of the quenching observed. Indeed, in light saturating for electron transport, qP tends to zero, yet there can be large amounts of quenching. Such quenching is therefore called nonphotochemical quenching and refers to the difference between the initial, dark-adapted maximum level of fluorescence and that recorded after a period of illumination. This quenching can be calculated in a number of ways, leading to it being termed variously as qN (Schreiber et al., 1986; van Kooten and Snel, 1990), NPQ (Bilger and Bjorkman, 1994), or SV, (Gilmore and Bjorkman, 1994); these all refer to the
282 citations
TL;DR: In this article, the absorption spectra, the luminescence properties, and the electrochemical behavior of six dinuclear heterometallic compounds have been investigated, and it is concluded that the observed energy-transfer processes take placemore via a Dexter (electron exchange) mechanism.
Abstract: The absorption spectra, the luminescence properties (at 293 and 77 K), and the electrochemical behavior of six dinuclear heterometallic compounds have been investigated. The compounds are made of Ru(tpy){sub 2}{sup 2+}- and Os(tpy){sub 2}{sup 2+}-type components (tpy = 2,2{prime}:6{prime},2 inches-terpyridine, which in some cases carries p-tolyl (Meph) or methylsulphone (MeO{sub 2}S) substituents in the 4{prime} position), connected by n phenylene (ph) spacers (n=0,1, and 2). In the resulting rigid rod-like structures of general formula (X{sub 1}tpy)Ru(tpy(ph){sub n}tpy)Os(tpyX{sub 2}){sup 4+} the metal-to-metal distance varies form 11 to 20 {Angstrom}. The absorption spectra of the two components are slightly perturbed in the dinuclear compounds, and metal-metal and ligand-ligand interactions are evidenced by the trends of the oxidation and reduction potentials. The luminescence of the Ru-based unit is quenched by the connected Os-based unit with practically unitary efficiency, regardless of the number of interposed phenylene spacers. Quenching is accompanied by quantitative sensitization of the Os-based luminescence. The rate of energy transfer at 293 K is larger than 10{sup 10} s{sup -1} in all cases. The Foerster (Coulombic) mechanism does not satisfactorily account for such a fast rate, particularly for the species with n=2. It is concluded that the observed energy-transfer processes take placemore » most likely via a Dexter (electron exchange) mechanism. This is consistent with the strong electronic coupling of the Ru-based units in the compound with n=0, and with the relatively small insulating effect expected for the phenylene spacers. 37 refs., 7 figs., 3 tabs.« less
236 citations
TL;DR: In this paper, a 1:1 cyclohexane-propanol-2 suspension with aqueous hydrogen fluoride in the presence of air is described and the temporal changes in the luminescence intensity of the suspension are described.
106 citations
TL;DR: A series of highly ductile, high strength steels exhibiting transformation induced plasticity due to retained austenite was developed by varying the carbon content in the range 0·01 − 0·4 wt-% in 5 wt −%Mn based steel as mentioned in this paper.
Abstract: A series of highly ductile, high strength steels exhibiting transformation induced plasticity due to retained austenite was developed by varying the carbon content in the range 0·01–0·4 wt-% in 5 wt-%Mn based steel. For up to 0·l%C the mechanical properties are insensitive to cooling rate after intercritical heating, but afurther increase in carbon content causes a large sensitivity to the cooling rate, owing to carbide precipitation occurring during slow cooling. By suppressing this carbide precipitation with water quenching after the intercritical holding, an excellent combination of tensile strength (1580 MN m−2) and uniform elongation (21%) was attained at 0·3%C in this series.MST/1964
83 citations
TL;DR: In this paper, the authors present two well known forms of metallurgical damage of ground surfaces involve untempered and overtempered martensite transformations and the special characteristics that pertain in grinding where the time at temperature before quenching is unusually short.
76 citations
TL;DR: In this article, a martensitic transformation from acicular Fe2O3 particles with 10−15 at % MnO2 were prepared by oxidizing Fe++ and Mn++ in alkaline aqueous solution when a quenched sample, which contains martensite, α, Fe, and austenite, was tempered at 200°C for different times, the magnetic moment first increased (transformation of α’‐martensite to α‘‐Fe16N2); the highest magnetic moment was obtained at about 60 min of temper
Abstract: The α‘‐Fe16N2 phase was synthesized by a nitriding, quenching, and tempering process starting from Fe2O3 Acicular γ‐Fe2O3 was first reduced to α‐Fe under H2, then it was converted to γ‐austenite at 650–700 °C by nitriding using a NH3‐H2 mixed gas A martensitic transformation to α’‐martensite occurred when the sample was quenched in liquid nitrogen Finally, the α‘‐Fe16N2 phase was formed from the α’‐martensite by tempering in the temperature range 120–200 °C In order to increase the extent of the martensitic transformation, acicular Fe2O3 particles with 10–15 at % MnO2 were prepared by oxidizing Fe++ and Mn++ in alkaline aqueous solution When a quenched sample, which contains martensite, α‐Fe, and austenite, was tempered at 200 °C for different times, the magnetic moment first increased (transformation of α’‐martensite to α‘‐Fe16N2); the highest magnetic moment was obtained at about 60 min of tempering Using even longer tempering times, the magnetic moment decreased (decomposition of α‘‐Fe16N2 to α‐F
65 citations
TL;DR: In this article, a hydrogen-absorbing alloy with a composition of LaNi 4.55 Al 0.45 through annealing and rapid quenching was investigated to improve its equilibrium characteristics with hydrogen.
61 citations
TL;DR: In this article, a large magnetic induction was reported for Fe16N2 in bulk form by treating Fe powder with NH3/H2 gas mixtures at temperatures in the range 660-670'°C.
Abstract: Using molecular beam epitaxy and ion implantation, Japanese workers have formed Fe16N2 in thin Fe films. They report a large magnetic induction for this nitride, ≥2.8 T. In the present study, Fe16N2 has been prepared in bulk form by treating Fe powder with NH3/H2 gas mixtures at temperatures in the range 660–670 °C. The γ phase alloy, which forms under these conditions, was quenched to room temperature to form the α’‐Fe‐N phase and then heat treated at 120–150 °C to form the α‘‐Fe‐N phase. The α’ phase has been prepared in 80% purity, the other phase being nonmagnetic γ‐Fe‐N. The α‘ phase has been prepared in 50% purity, the impurity phases being α‐Fe and γ‐Fe‐N. Magnetic measurements give saturation magnetizations at room temperature of 250±10 emu/g (2.6μB/Fe) for the α’ phase, 285±10 emu/g (2.9μB/Fe) for the α‘ phase, and essentially zero for the γ phase. Mossbauer measurements confirm that nitrogen austenite is nonmagnetic. The anisotropy of Fe16N2 is small but detectable.
60 citations
TL;DR: In this paper, an experimental and theoretical study of flow and heat transfer regimes during quenching of a heated vertical channel is presented, and the quench front lies in the transition boiling region which spreads into the dry and wet segments.
53 citations
TL;DR: In this article, the thermodynamic parameters of all stable phases in the Ni-Zr system are reported, and the available experimental data are taken into account in deriving the interaction parameters of various phases.
Abstract: The thermodynamic parameters of all stable phases in the Ni-Zr system are reported in this paper. The available experimental data are taken into account in deriving the interaction parameters of various phases. The Ni7Zr2, Ni21Zr8, Ni11Zr9, NiZr, and NiZr2 phases are treated as stoichiometric. The solid solubility of the Ni5Zr, Ni3Zr, and Ni10Zr7 phases are described using a two sublattice model. The calculated thermodynamic properties and the phase diagram are in good agreement with the experimental ones. The thermodynamic parameters, along with the classical nucleation and crystal growth theory, have been used to explain the formation of metastable noncrystalline and crystalline phases upon rapid quenching of the liquid alloys. It has been demonstrated that even without any prior knowledge of the physical property, such as glass transition or crystallization temperature and thermodynamic property, such as the enthalpy of amorphous → crystal transformation of the amorphous alloy, it is possible to make a reasonably good “first order prediction” of the glass-forming range in a binary system. The experimentally determined glass-forming range in the Ni-Zr system is found to be in good agreement with the predicted one.
50 citations
TL;DR: In this article, an Al-4.3 wt% Cu-Mg alloy reinforced with 20 vol% reinforcing fibres was examined after a T7 heat treatment and the expected precipitate phase was equilibrium S′ (Al2CuMg), which was confirmed to form in the monolithic alloy.
Abstract: An Al-4.3 wt% Cu-2.0 wt% Mg alloy reinforced with 20 vol% reinforcing fibres was examined after a T7 heat treatment. The expected precipitate phase was equilibrium S′ (Al2CuMg), which was confirmed to form in the monolithic alloy. However when this Al-Cu-Mg alloy was squeeze-cast into a fibre preform and given an identical T7 heat treatment a number of other phases also nucleated; these included θ′ (Al2Cu), β′ (Mg2Si) and the cubic σ phase (Al5Cu6Mg2). These additional phases were determined to nucleate and grow rapidly during the water-quench following solution treatment. The existence of excess Si (approximately 0.5 wt%) in the matrix was determined to be responsible for nucleation of these additional phases. This extra Si entered the composite matrix during squeeze-casting through breakdown of an SiO2 layer which existed at the fibre interfaces. During quenching Si clusters rapidly form and provide nucleation sites for the σ and θ′ phases. The Si clusters apparently created a compressive strain in the matrix which attracted a high concentration of small Cu atoms to their interface. The σ phase nucleated in this high-Cu region since, on a localized scale, σ became the equilibrium phase. This type of nucleation process may also explain the enhanced precipitate nucleation which occasionally takes place in other alloy systems when trace amounts of certain elements are added.
TL;DR: The theory of light quenching is described and some of its effects on the steady-state and time-resolved intensity and anisotropy decays of fluorophores are described.
TL;DR: In this paper, the authors measured tensile stress and birefringence in polystyrene and polycarbonate melts at various temperatures during constant strain rate elongational flow and found that significant elastic recovery was found at temperatures as low as Tg-30°C, and discussed as a function of the thermomechanical history.
TL;DR: In this paper, the influence of several commonly used heat treatments on the microstructure of TIMETAL 21S was studied using optical and transmission electron microscopy (TEM).
Abstract: A relatively new titanium alloy, TIMETAL 21S (Ti-15Mo-2.7Nb-3Al-0.2Si-0.15O (in wt pct)), is a potential matrix material for advanced titanium matrix composites for elevated temperature use. In order to develop a perspective on the microstructural stability of this alloy, the influence of several commonly used heat treatments on the microstructure of TIMETAL 21S was studied using optical and transmission electron microscopy (TEM). Depending on the specific thermal treatment, a number of phases, includingα,ω- type, and silicide, can form in this alloy. It was found that both recrystallized and nonrecrystallized areas could be present in the microstructure of an annealed bulk alloy, but the microstructure of annealed sheet alloy was fully recrystallized. The mixed structure of the bulk alloy, developed as a result of inhomogeneous deformation, could not be removed by heat treatment alone at 900 °C. Athermalω-type phase formed in this alloy upon quenching from the solution treatment temperature (900 °C). Silicide precipitates were also found in the quenched sample. Thermal analysis was used to determine theβ transus and silicide solvus as close to 815 °C and 1025 °C, respectively. In solution-treated and quenched samples, a high-temperature aging at 600 °C resulted in the precipitation ofα phase. The precipitation reaction was slower in the recrystallized regions compared to the nonrecrystallized regions. During low-temperature aging (350 °C), the ellipsoidalω-type phase persisted in the recrystallized areas even after 100 hours, whereas a high density ofα precipitates developed in the nonrecrystallized areas within only 3 hours. The observed behavior in precipitation may be related to the influence of substructure in the nonrecrystallized areas, providing for an enhanced kinetics during aging. Theα precipitates (formed during continuous cooling from the solution treatment temperature, low-temperature aging, and high-temperature aging) always obeyed the Burgers orientation relationship. With respect to the microstructure, TIMETAL 21S is similar to other solute-lean, metastableβ titanium alloys.
TL;DR: In this paper, the authors performed deep-level transient spectroscopy measurements of electronic defect states in a coincidence Σ = 25 grain boundary (GB) in silicon and found that the most heavily contaminated samples with Cu or with both Cu and Ni exhibit a single interface trap at Ec−0.54 eV.
Abstract: Deep‐level transient spectroscopy measurements of electronic defect states in a coincidence Σ=25 grain boundary (GB) in silicon have been performed after quenching of heat‐treated samples (900 °C, 2 h) containing copper and/or nickel. These elements are usually suspected to be nonintentionally contaminating impurities. The special care supplied to get processed samples free from transition‐metal impurities (particularly copper) has led to the measurement of a continuous distribution of boundary levels between Ec−0.20 eV and Ec−0.38 eV which shift toward deeper energies (between Ec−0.25 eV and Ec−0.42 eV) with a gradual increase of the copper content. The heavily contaminated samples with Cu or with both Cu and Ni exhibit a single interface trap at Ec−0.54 eV. According to transmission electron microscopy (TEM) and energy‐dispersive x‐ray (EDX) analyses, as well as comparable data reported earlier, this interface state seems characteristic of copper precipitates obtained by quenching from 900 °C; however, the incorporation of nickel in a ‘‘copper‐free’’ bicrystal has been found to result in an almost discrete boundary level at Ec−0.50 eV. From TEM, EDX, and electron‐diffraction investigations, the corresponding precipitates were geometrically shaped, intersecting the GB plane, and identified as two types (A and B) of NiSi2 silicide.
20 Oct 1994-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the solidification process of a hypereutectic Al-17wt.%Si-0.31w.%Mg alloy with 15 wt.% SiC particles was investigated by quenching samples through solidification region and by conventional casting of samples from the mechanically stirred composite melts.
Abstract: The solidification process of a hypereutectic Al-17wt.%Si-0.31wt.%Mg alloy with 15 wt.% SiC particles was investigated by quenching samples through the solidification region and by conventional casting of samples from the mechanically stirred composite melts. The nucleation and growth processes of the primary Si phase under both stirred and unstirred conditions were examined, and the Si/SiC P interface was analysed by SEM and EDX with X-ray image analysis. The Si phase of AlSi alloys has a more important role than the α phase in the bonding of the SiC reinforcement with the matrix, because the Si phase nucleates preferentially on the SiC particles even when the spinnel interfacial layer exists. The crystal structures of the phases in the composites were identified by X-ray diffraction, and the factors which influence the heterogeneous nucleation of Si crystal on the substrates are discussed.
TL;DR: In this paper, the authors showed that undoped InP samples annealed in vacuum turn out to be semi-insulating if the cooling after the high temperature treatment (around 900 °C) is sufficiently slow (around 30 °C h−1).
Abstract: We show, for the first time, that undoped InP samples annealed in vacuum turn out to be semi-insulating if the cooling after the high temperature treatment (around 900 °C) is sufficiently slow (around 30 °C h−1). However, the best semi-insulating properties ( ϱ > 10 7 Ω cm ; μ ≈ 4000 cm 2 V −1 s −1 ) are achieved with a double anneal under vacuum of InP with residual carrier concentration less than 4 × 10 15 cm −3 . It is also shown that InP specimens with n ≈ 10 16 cm −3 can exhibit high resistivity, but lower mobility, after sequential thermal treatments. The conductivity conversion is ascribed to the overlap of two phenomena: (i) in-diffusion of deep impurities and (ii) generation-incorporation of “shallow” acceptors. It was also observed that annealed semi-insulating samples resumed the semi-conducting behavior after a second thermal treatment and quenching. This suggests that the concentration of both types of annealing-related levels are dependent on the cooling rate.
TL;DR: In this article, the formation of pure nitride glasses has been demonstrated in the system Li3N-Ca3N2-P3N5, by the rapid quenching of fused mixtures of the nitrides at high pressures.
Abstract: THE incorporation of nitrogen in oxide glasses can lead to improved physical properties such as hardness and refractive index1–4; one might accordingly expect to see a further improve-ment in glasses containing nitrogen as the only anion. But while there are now many examples of non-oxide glasses in the halide and chalcogenide families5–8, the formation of pure nitride glasses has not hitherto been demonstrated. Here we report the formation of glasses in the system Li3N-Ca3N2-P3N5, by the rapid quenching of fused mixtures of the nitrides at high pressures. The use of high-pressure conditions prevents thermal decomposition of the nitride mixtures to gaseous nitrogen. The new nitride glasses are stable in air, have remarkably high refractive indices (1.97–2.0), hardness exceeding that of silica glass, and high glass transition tempera-tures (7g > 700 °C).
01 May 1994-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the structural state and subsequent devitrification behavior of the melt-spun ribbons are found to be particularly sensitive to the quenching conditions and there are inhomogeneities both through the ribbon thickness and along the length.
Abstract: Various Al100−xSmx alloys (10 ⪕ × ⪕ 14) have been rapidly solidified by single-roller melt spinning with careful control of the atmosphere in the quenching device. The structural state and subsequent devitrification behaviour of the melt-spun ribbons are found to be particularly sensitive to the quenching conditions. Except for the thinnest ribbons, there are inhomogeneities both through the ribbon thickness and along the length. Both fully and partially amorphous ribbons have been obtained. The crystallization processes of the amorphous phases have been followed by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry (DSC). Al92Sm8 shows primary crystallization of Al, followed by the formation of metastable phases; Al90Sm10 transforms polymorphically to a metastable intermetallic; Al88Sm12 and Al86Sm14 display eutectic crystallization into Al and a metastable mixture of compounds. For Al90Sm10, the DSC traces involve several overlapping peaks. This may be the result of transformations occurring in distinct parts of the ribbon with different mechanisms. A kinetic analysis of the crystallization processes has been performed by means of isothermal and non-isothermal DSC experiments. A discussion of the kinetic parameters derived from Kissinger and Avrami analyses is provided.
TL;DR: In this article, the authors examined the effect of external quenching by condensed or gaseous extinguishants and by external sources on the extinguishment of Class B flames.
Abstract: Flame quenching by condensed or gaseous extinguishants and by external sources is exam ined. The quenching by extinguishants is due to heat-absorption sinks—dissociation, decompo sition, vaporization, and heat capacity. External quenching by water-cooled metal surfaces or by radiation to surroundings is shown to have common properties with internal quenching by extinguishant particles or molecules.Flame-extinguishing mechanisms are effectively explained with thermal quenching concepts and a flame heat balance. New criteria for the extinguishment of Class B flames are postulated and, then, substantiated by a comprehensive analysis of extinguishment data for a large number of agents. Adiabatic limit temperatures were initially computed with the flame heat balance (Equation 1) using quenching quantities based on heats of formation of extinguishing sub stances at 298 K, but such limits and quenching quantities exhibited no systematic character. However, alternate limits and quenching quantities based on heats...
TL;DR: In this paper, the Tb3+ emission spectrum at room temperature of aluminates and relevant crystals containing Tb ion as a stoichiometric agent was measured for transparent and colorless TbAlO3 single crystals grown by the Czochralski method in a reducing atmosphere.
Abstract: Optical spectra are measured for transparent and colorless TbAlO3 single crystals grown by the Czochralski method in a reducing atmosphere, although those grown in an inert atmosphere show blackbody color due to broadband absorption of Tb4+ ions. This is a report on strong Tb3+ emission spectrum at room temperature of aluminates and relevant crystals which contain the Tb ion as a stoichiometric agent. All fine structures in absorption and emission spectra can be assigned to the intra‐4f transitions of Tb3+ ions. Similar concentration quenching is observed in TbxGd1−xAlO3 system to that in the Nd:YAG crystals; however, the quenching is found to be very small compared with that of the Nd:YAG. An order estimate of the induced emission cross section for the strongest emission line is calculated to be about 6×10−21 cm2.
Patent•
30 Sep 1994TL;DR: A method for producing high density and/or high surface density ferrous powder metal parts has the steps of: compacting a iron-containing powder substantially free of graphite at room temperature and at about 40-50 tsi, sintering the green compact in an inert, non-oxidizing environment at a temperature of about 2050°-2300° F, repressing the sintered compact at room-temperature at about 60 tsi; carburizing the repressed compact at high temperature to form a layer of relatively high carbon concentration to a depth
Abstract: A method for producing high density and/or high surface density ferrous powder metal parts has the steps of: compacting a iron-containing powder substantially free of graphite at room temperature and at about 40-50 tsi; sintering the green compact in an inert, non-oxidizing environment at a temperature of about 2050°-2300° F.; repressing the sintered compact at room temperature at about 60 tsi; carburizing the repressed compact at high temperature to form a layer of relatively high carbon concentration to a depth of at least about 0.010 inches; and immediately quenching the hot carburized compact followed by a tempering treatment.
TL;DR: In this article, the differences between residual stress formation mechanisms for several important polymer processes are studied for free quenching (e.g. in extrusion), constrain, and non-quenching.
Abstract: The differences between residual stress formation mechanisms are studied for several important polymer processes. The most important cases are free quenching (e.g. in extrusion), constrain...
TL;DR: In this article, the authors corroborated the results of Trudeau et al. showing that an Fe-B-Si metallic glass undergoes crystallization during milling in a Spex ball mill, but after milling the partially-crystallized powders could not be fully reverted to a metallic glass by piston-anvil quenching from the liquid state.
01 May 1994-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the quenching of the melt in a quartz tube into water was found to enable the production of bulk amorphous alloy in cylindrical form with a diameter of 16 mm and a length of 150 mm for the Zr 65 Al 7.5 Ni 10 Cu 17.5 Be x alloys with the largest ΔT x of 127 K.
Abstract: The temperature interval of the supercooled liquid region before crystallization in Zr 65 − x Al 7.5 Ni 10 Cu 17.5 Be x alloys is the largest for the x = 0 alloy. It is therefore said that the addition of Be with an extremely small atomic size as compared with those of the other constituent elements is not effective for further extension of the wide supercooled liquid region. The quenching of the melt in a quartz tube into water was found to enable the production of bulk amorphous alloy in cylindrical form with a diameter of 16 mm and a length of 150 mm for the Zr 65 Al 7.5 Ni 10 Cu 17.5 alloys with the largest ΔT x of 127 K. The finding of the extremely large glass-forming ability of the ZrAlNiCu alloy is very important for subsequent development of metallic amorphous alloys.
TL;DR: The increasing availability and use of pulsed laser sources requires consideration of the possible effects of light quenching and offers the opportunity for a new class of two‐p Pulse or multiple‐pulse time‐resolved experiments where the sample is prepared by the excitation pulse and subsequent quenched pulses to modify the excited state population, followed by time‐ or frequency‐domain measurement of the optically prepared excited fluorophores.
Abstract: Experimental studies have recently demonstrated that fluorescence emission can be quenched by laser light pulses from modern high-repetition rate lasers, a phenomenon we call "light quenching." In this overview article, we describe the possible effects of light quenching on the steady-state and time-resolved intensity and anisotropy of fluorophores. One can imagine two classes of experiments. Light quenching can occur within the single excitation pulse, or light quenching can be accomplished with a second time-delayed quenching pulse. The extent of light quenching depends on the amplitude of the emission spectrum at the quenching wavelength. Different effects are expected for light quenching by a single laser beam (within a single laser pulse) or for a time-delayed quenching pulse. Depending upon the polarization of the light quenching beam, light quenching can decrease or increase the anisotropy. Remarkably, the light quenching can break the usual z-axis symmetry of the excited state population, and the measured anisotropy (or polarization) depends upon whether the observation axis is parallel or perpendicular to the propagation direction of the light quenching beam. The polarization can increase to unity under selected conditions. Quenching with time-delayed light pulses can result in step changes in the intensity or anisotropy, which is predicted to result in oscillations in the frequency-domain intensity and anisotropy decays. These predicted effects of light quenching, including oscillations in the frequency-domain data, were demonstrated to occur using selected fluorophores. The increasing availability and use of pulsed laser sources requires consideration of the possible effects of light quenching and offers the opportunity for a new class of two-pulse or multiple-pulse time-resolved experiments where the sample is prepared by the excitation pulse and subsequent quenching pulses to modify the excited state population, followed by time- or frequency-domain measurement of the optically prepared excited fluorophores.
TL;DR: In this article, the basic thermodynamic differences between high energy milling and rapid quenching, associated with a crystallization controlled by elemental diffusion, could explain the structural transformation of amorphous transition metal-metalloid alloys.
Abstract: Recently, it was shown that mechanical deformation processes can completely crystallize some amorphous transition‐metal–metalloid alloys. However, the mechanism is still unclear. We demonstrate here that, for the simpler amorphous Fe90Zr10 alloy, the basic thermodynamic differences between high‐energy milling and rapid quenching, associated with a crystallization controlled by elemental diffusion, could be behind this structural transformation.
TL;DR: Anode and cathode potentials for electrodes of mild steel in stagnant air or flowing argon and CO2 have been obtained both of the voltage distribution during arc quenching and of a measured melting velocity.
Abstract: Anode and cathode potentials for electrodes of mild steel in stagnant air or flowing argon and CO2 have been obtained both of the voltage distribution during arc quenching and of a measured melting velocity. The potentials are independent of arc current in the observed region 40-200 A. The energy for melting a unit length of a wire electrode has been established as the energy input for breaking a short-circuit bridge of the observed wire. The important role of neutral particle flux to melted electrodes has been revealed. A model of rapid arc quenching due to temperature and field emission of electrons has been suggested.