Peak In Temperature Range Research Articles

Thermal optimization of two-terminal SOT-MRAM

While magnetoresistive random-access memory (MRAM) stands out as a leading candidate for embedded nonvolatile memory and last-level cache applications, its endurance is compromised by substantial self-heating due to the high programming current density. The effect of self-heating on the endurance of the magnetic tunnel junction (MTJ) has primarily been studied in spin-transfer torque (STT)-MRAM. Here, we analyze the transient temperature response of two-terminal spin–orbit torque (SOT)-MRAM with a 1 ns switching current pulse using electro-thermal simulations. We estimate a peak temperature range of 350–450 °C in 40 nm diameter MTJs, underscoring the critical need for thermal management to improve endurance. We suggest several thermal engineering strategies to reduce the peak temperature by up to 120 °C in such devices, which could improve their endurance by at least a factor of 1000× at 0.75 V operating voltage. These results suggest that two-terminal SOT-MRAM could significantly outperform conventional STT-MRAM in terms of endurance, substantially benefiting from thermal engineering. These insights are pivotal for thermal optimization strategies in the development of MRAM technologies.

The dependence on displacement rate and temperature of near-surface void-denuding in self-ion irradiated pure polycrystalline and single-crystal iron

Pure iron has been irradiated with Fe2+ ions in a series of studies to identify neutron-atypical physical processes that influence the depth dependence of void swelling, focusing especially on suppression effects arising from injected interstitials and surface proximity. One paper in this series examined the surface influence in single-crystal Fe irradiated to 50 and 100 peak dpa over a range of temperature (425–525 °C) and ion energy (1.0, 2.5, 3.5, 5.0 MeV) while keeping the peak damage rate at 1.2 × 10–3 dpa/s, although the surface dpa rate was lower but increasing with decreasing ion energy, providing a small range of surface dpa rate. The observed denuded width Δx was modified to incorporate sputtering loss. The activation energy governing the denuding process was found to be EΔx4=1.65±0.03eV, higher than the vacancy migration energy EVm known to be 0.67 eV. This difference was attributed to the effect of dissolved carbon (103 appm) which reduces the effective vacancy mobility and thereby increases the effective migration energy.Since the previous study involved a factor of only 2.83 in near-surface dpa rate it is important to confirm that the dependence of EΔx4 on dpa rate is maintained over a larger range of damage rates. In this study polycrystalline Fe with 140 appm carbon was irradiated with 5 MeV Fe2+ ions to 50, 100 and 150 dpa over a range of peak dpa rates (2.0 × 10–4, 1.2 × 10–3, 6.0 × 10–3 dpa/sec) and temperatures (425, 475, 525 °C). At very high dpa levels sputtering and void growth lead to loss of voids via shrinkage, limiting the upper dose level where this technique can be applied. It was found that the single-crystal and polycrystal specimens yielded essentially identical behavior with EΔx4 = 1.65 eV, validating the application of this activation energy over a wider range of dpa, dpa rate, temperature, and crystal form.

The Impact of Multiple Thermal Cycles Using CMT® on Microstructure Evolution in WAAM of Thin Walls Made of AlMg5

Wire Arc Additive Manufacturing (WAAM) of thin walls is an adequate technology for producing functional components made with aluminium alloys. The AlMg5 family is one of the most applicable alloys for WAAM. However, WAAM differs from traditional fabrication routes by imposing multiple thermal cycles on the material, leading the alloy to undergo cyclic thermal treatments. Depending on the heat source used, thermal fluctuation can also impact the microstructure of the builds and, consequently, the mechanical properties. No known publications discuss the effects of these two WAAM characteristics on the built microstructure. To study the influence of multiple thermal cycles and heat source-related thermal fluctuations, a thin wall was built using CMT-WAAM on a laboratory scale. Cross-sections of the wall were metallographically analysed, at the centre of a layer that was re-treated, and a region at the transition between two layers. The focus was the solidification modes and solubilisation and precipitations of secondary phases. Samples from the wall were post-heat treated in-furnace with different soaking temperatures and cooling, to support the results. Using numerical simulations, the progressive thermal cycles acting on the HAZ of one layer were simplified by a temperature sequence with a range of peak temperatures. The results showed that different zones are formed along the layers, either as a result of the imposed thermal cycling or the solidification mode resulting from CMT-WAAM deposition. In the zones, a band composed of coarse dendrites and an interdendritic phase and another band formed by alternating sizes of cells coexisted with the fusion and heat-affected zones. The numerical simulation revealed that the thermal cycling did not significantly promote the precipitation of second-phase particles.

The kinetics and warm flame chemistry associated with radiative extinction of spherical diffusion flames

Several studies have found that microgravity diffusion flames with sufficient heat loss cool until they extinguish at a critical temperature near 1130 K. In this work, the associated chemical kinetics are explored for spherical diffusion flames burning ethylene. The flames are simulated with a transient numerical model with detailed chemistry, transport, and radiation. This incorporates the UCSD mechanism with 57 species and 270 reactions. Species concentrations, reaction rates, and heat release rates are examined. Upon ignition, the peak temperature is above 2000 K, but this decreases until extinction due to radiative losses. This allows the chemistry to be studied over a wide range of peak temperatures for the same fuel and oxidiser. When the peak temperature is high, the dominant chemistry is similar to that for typical normal-gravity ethylene diffusion flames. There are two distinct zones: an ethylene pyrolysis zone and an oxidation zone, and negligible reactant leakage. The ethylene mainly reacts with H and OH. The concentration of OH in the ethylene pyrolysis zone is high due to the long residence times and reactions of CO2 and H2O with H. As the flame cools and the peak temperature approaches the critical extinction temperature, there is increased reactant leakage leading to higher O, OH, and HO2 concentrations on the fuel side. Most reactions shift towards the oxidiser side and there is large overlap between the two zones. Reactions involving HO2 become more significant and the large consumption rates of H by HO2 increase the concentrations of OH and O on the fuel side. The appearance of warm flame chemistry delays extinction but is not sufficiently exothermic to prevent it.

Laser Beam Welding Parametric Optimization for AZ31B and 6061-T6 Alloys: Residual Stress and Temperature Analysis Using a CCD, GA and ANN

Laser beam welding (LBW) is a technology that efficiently joins materials using a concentrated laser beam, providing advantages such as a small heat-affected zone (HAZ), high precision, adaptability to various materials, and seamless integration into automated processes. Precision in LBW is limited by challenges in selecting appropriate process parameters, performing expensive and risky physical experiments, and dealing with materials with high thermal conductivity and low melting temperatures, such as AZ31B and AA6061. This study aims to predict laser welding process parameters, encompassing beam power (4000W-6000W), spot size (0.4mm-0.8mm), welding speed (30mm/s-50mm/s), and segment number (5-15) utilizing the Response Surface Methodology (RSM), Genetic Algorithm (GA) and backpropagation neural networks. Beam power significantly affects peak temperature, leading to deeper laser penetration and a higher maximum temperature, while the segment number plays a crucial role in residual stress by potentially causing uneven cooling and distinct thermal gradients. The ANN results confirm the model's accuracy and the GA-predicted process parameters include a laser power of 4000W, welding speed of 50mm/s, spot size of 0.6mm, segment number of 15, peak temperature range of 888.9°C to 1020.5°C, and a preferred equivalent stress of 1396.62 MPa.

Analysis of the catalytic pyrolysis of shale gas oil‐based drill cuttings via TG‐MS

AbstractBACKGROUNDShale gas oil‐based drill cuttings are receiving increasing attention because of their hazards and contamination. In this study, two catalysts (Fe2(SO4)3 and a synthesised catalyst) were used to study the pyrolysis products, possible reaction mechanisms, and kinetic characteristics via thermogravimetry‐mass spectrometry (TG‐MS) analysis.RESULTSThe results indicate that the synthesised catalyst, YAP‐3, exhibited an improved catalytic effect on the pyrolysis of drill cuttings with a good conversion rate. The reaction activation energy during the pyrolysis was reduced from 9.6 to 1.4 kJ/mol. In addition to hydrocarbons, the pyrolysis products contained nitrogen oxides and other compounds.CONCLUSIONA comparison of the peak temperature range and response intensity of the same substance with the same mass‐to‐charge ratio (m/z) showed that YAP‐3 significantly promoted the formation of pyrolysis products. This study provides theoretical support for the catalytic pyrolysis treatment of shale gas drill cuttings. © 2023 Society of Chemical Industry.

Model for contact formation of novel TeO2 containing Pb-free silver paste on n+ and p+ doped crystalline silicon

Silver (Ag) pastes are widely used in the global market for most solar cell architectures. Thereby, lead (Pb) is no longer wanted in productions for environmental reasons. In this work, a model for the contact formation between Pb-free, tellurium oxide (TeO2) containing screen-printable Ag pastes and silicon is presented. It is shown that Te plays a key role in this model. Te is not only an important part in etching the surface passivation layers with TeO2 dissolving the dielectric layer but also for a formation of the contacts with Te forming a compound consisting of Ag2Te. Using EDX mapping, local contact regions can be examined and interpreted for contact formation. The used paste system enables far more flexible paste mixturing leading to a novel developed commercial paste which is on a par with other pastes used in industry concerning the resulting contact properties. This is also demonstrated in this work by the very low contact resistivity of less than 1 mΩcm2 over a wide range of firing peak temperatures. It is additionally shown that good resistivities can be achieved on both n+- and p+-doped regions.

Thermomechanical Simulation of Heat-Affected Zones in Nickel-Free High Nitrogen Stainless Steel: Microstructural Evolution and Mechanical Property Studies

Three different Heat Affected Zones (HAZ) in hot rolled Nickel Free High Nitrogen Stainless Steels (NFHNSS) based on three different peak temperatures were physically simulated using Gleeble Simulator to investigate microstructural evolution and structure-property correlation. Optical microscopy revealed that the austenite grains are recrystallized in the simulated heat affected zone in the peak temperature range of 750 oC to 1050 oC. Extent of recrystallization of grains and nucleation of precipitates varied with peak temperatures. TEM characterization showed the presence of Cr2N precipitate having an average particle size in the range of 300 nm to 395 nm in the simulated HAZ were confirmed by Selected Area Electron Diffraction (SAED) analysis. Precipitation kinetics of Cr2N were simulated using Thermo-Calc were found to correlate well with experimental values. Mechanical properties of specimens taken from three different HAZ were evaluated for tensile strength and hardness. Variation in strength of the different specimens has been discussed using various strengthening models. Fractography analysis was also carried out to understand the effect of peak temperature on fracture behaviour. Transition in fracture patterns in NFHNSS from ductile to mixed mode was observed for different specimens.

Influence of Alternating Multi-Layered Design on Damping Characteristics of Butyl Rubber Composites and a New Idea for Achieving Wide Temperature Range and High Damping Performance.

This paper investigates the influence of an alternating multi-layered design on the material loss factor and effective temperature range of free/constrained-damping butyl rubber, and then proposes a new method of designing materials with high damping properties and a wide temperature range. First, the wide-temperature rubber IIR-0, the low-temperature rubber IIR-1, the medium-temperature rubber IIR-2, and the high-temperature rubber IIR-3 are prepared and characterized. Second, the influences of an alternating multi-layered design on the damping peak values and temperature range of free damping and micro-constrained damping of the rubber types are investigated. Finally, different methods for broadening the damping temperature range and improving the damping loss factor are discussed. The results show that the loss factor of the alternating multi-layered, constrained damping structure is increased to 0.488, while that of the free-damping structure is increased to 0.845. Their damping-temperature ranges are increased to 89.4 °C and 93.2 °C, respectively. A wide temperature range and high damping performance can be achieved by the alternating multi-layered design of rubber/plastic micro-constrained damping composites.

Formation, cooling history and age of impact events on the IIE iron parent body: Evidence from the Miles meteorite

Most iron meteorites formed in planetary cores during differentiation, but the IIE iron meteorites have chemical and physical features that are inconsistent with this origin. By combining mineral chemistry, mineral modes and three-dimensional petrography, we reconstruct the bulk chemistry of the felsic silicate-bearing Miles IIE iron meteorite and demonstrate that the silicate inclusion compositions are similar to partial melts produced experimentally from an H chondrite composition. We use the reconstructed bulk composition, mineralogy and thermodynamic modelling to show that melting above ∼1200°C under reducing conditions formed metal (Fe-Ni alloy) and felsic silicate partial melts. Upon cooling, the melts crystallized Mg-rich pyroxenes, Na- and K-rich feldspars, and tridymite. Importantly, this mechanism enriches cosmochemically volatile elements (i.e., those with a 50% condensation temperature of ∼430–830°C, like Na and K) to the level found in the felsic silicate inclusions.The presence of crystallographically disordered srilankite (only stable above 1160°C) and an absence of Widmanstätten texture require both high peak temperatures and rapid cooling, which cannot be explained by core formation. Instead they point to small melt volumes, a transient heat pulse, and small thermal mass, and imply efficient physical segregation of silicate and metallic melts through buoyancy separation followed by rapid cooling that arrested the separation of metal and silicate liquid phases. In situ 207Pb/206Pb age of 4542.3 ± 4.0 Ma in Zr-oxide and phosphate minerals dates the melting event that formed the silicate inclusions. This age aligns with the earliest ages found in other IIE iron meteorite silicates and requires a heating event ∼25 million years after the solar system formed. We found 39Ar/40Ar ages of 3495 ± 52 Ma (low-T) and 4303 ± 7 Ma (high-T) in a K-feldspar grain, with the 3495 Ma age aligning with later thermal events recorded in other IIE iron meteorites. Dating reveals the complex petrogenetic and thermal history of Miles and the IIE iron meteorites. This is the first IIE iron meteorite found to record evidence of heating at 4.5 and 3.5 Ga likely from impact events.We propose that high-velocity impact(s) into an iron-rich, porous chondritic parent body at ∼4.54 Ga produced immiscible metal and silicate melts that cooled rapidly and trapped low density silicate inclusions within high density metal. Other IIE irons that formed at lower peak temperatures (900–1000°C) contain chondritic silicate inclusions and relict chondrules, supporting this conceptual model. This petrogenesis is consistent with thermodynamic modelling, experimental data and the wide range of peak temperatures and cooling rates observed in the IIE iron meteorites.

Integrated Starches and Physicochemical Characterization of Sorghum Cultivars for an Efficient and Sustainable Intercropping Model.

Sorghum has good adaptation to drought tolerance and can be successfully cultivated on marginal lands with low input cost. Starch is used in many foods and nonfood industrial applications and as a renewable energy resource. Sorghum starches with different amylose contents affect the different physicochemical properties. In this study, we isolated starches from six sorghum varieties (i.e., Jinza 34, Liaoza 19, Jinnuo 3, Jiza 127, Jiniang 2, and Jiaxian) and investigated them in terms of their chemical compositions and physicochemical properties. All the starch granules had regular polygonal round shapes and showed the characteristic “Maltese cross”. These six sorghum starches showed an A-type diffraction pattern. The highest amylose content of starch in Jinza 127 was 26.90%. Jiaxian had a higher water solubility at 30, 70, and 90 °C. From the flow cytometry analysis based on six sorghum starch granules, Liaoza 19 had a larger and more complex granules (particle percentage (P1) = 66.5%). The Jinza 34 starch had higher peak (4994.00 mPa∙s) and breakdown viscosity (4013.50 mPa∙s) and lower trough viscosity (973.50 mPa∙s). Jinnuo 3 had higher onset temperature, peak temperature, conclusion temperature, gelatinization enthalpy, and gelatinization range. The principal component analysis and hierarchical cluster analysis based on classification of different sorghum starches showed that Jiniang 2 and Jinnuo 3 had similar physicochemical properties and most divergent starches, respectively. Our result provides useful information not only on the use of sorghum starches in food and non-food industries but for the great potential of sorghum-based intercropping systems in maintaining agricultural sustainability.

Influence of pulse TIG welding thermal cycling on the microstructure and mechanical properties of explosively weld titanium/steel joint

The microstructures, interfacial compounds, and mechanical properties evolutions of the Ti/steel explosive welding interface during pulse tungsten inert gas (TIG) welding thermal cycling were studied. A Gleeble-1500D thermomechanical simulator was used to simulate the thermal cycling with the peak temperature (Tm) range of 692–1283 °C. The results show that the thickness of intermetallic compounds increased with the increase of Tm. When Tm is 1283 °C, the explosive welding interface was liquefied during the thermal cycling, which was consisted of α-Fe, α-Fe + Fe2Ti eutectic, Fe2Ti and a trace amount of α-Fe, FeTi, FeTi + β-Ti eutectic, β-Ti and a trace amount of FeTi, β-Ti + α-Ti and α-Ti from the steel side to Ti side. The substantial brittle phases (i.e., Fe2Ti and FeTi) can cause cracks in the interface and deteriorate the combination of the interface. In addition, the tensile and shear strength of the explosive welding interface decreased with the increased Tm. Reductions in strength were mainly attributed to the growth of the interfacial compounds.

Measurement and analysis of welding deformation and residual stress in CMT welded lap joints of 1180 MPa steel sheets

Ultra-high strength steel (UHSS) sheet has been used in automobile structures for light weight and energy efficiency. The objective of this study is to investigate the characteristics of the heat softening phenomenon and its effect on the formation of welding residual stresses and deformation in UHSS lap joints. Firstly, the lap joints of 1180 MPa steel sheets were fabricated using the cold metal transfer (CMT) welding process, and obvious heat softening was observed in the tempered area by hardness measurement. Miniature tensile test shows that the heat softening zone has about 33% reduction in strength comparing with the base metal. To identify the softening temperature, the simulated thermal cycle experiment was performed by applying various thermal cycles to the 1180 MPa sheet. It was found that the softening zone corresponds to the range of peak temperature from 500 °C to 720 °C. Based on the in-house FEM code JWRIAN, heat softening was modeled and included in the numerical models of CMT welded lap joints. By the verification with measured data, more accurate simulation results were obtained by the numerical model considering heat softening behavior. It was found that there exist the compressive or small tensile residual stress in the weld zone due to low temperature solid-state phase transformation and large tensile residual stress in the heat softening zone. A combined out-of-plane deformation was observed in the 1180 MPa steel lap joint. The upper plate has a downward angular distortion and concave longitudinal deflection, while the lower plate is deformed in the opposite manner. The effects of plate thickness on the welding distortion and residual stresses in 1180 MPa steel lap joints were parametrically analyzed using the developed model.

Combined effects of welding heat input and peak temperature on precipitation and mechanical properties of the HAZ for modified austenitic medium manganese steels

We studied the microstructure and mechanical properties of the simulated welding heat-affected zone (HAZ) for modified austenitic medium manganese steels (MAMMS) in the welding peak temperature range of 750 °C to 1050 °C. The precipitation behavior of cementite and VC particle was sensitive to the welding thermal cycle in this temperature range. When the peak temperature increased from 750 °C to 850 °C, the intergranular cementite and VC particle became coarser, leading to deterioration of toughness. However, when the peak temperature raised to 1050 °C, the intergranular cementite disappeared. The sensibility of tensile strength to heat input at high peak temperature was higher than that at low temperature, which implied that it was affected by combined effects of the two factors of heat input and peak temperature, rather than a single factor. This variation tendency was highly related with the coarsening behavior of VC particle depending on the interaction effect of these two factors. The growth rate of VC particle with peak temperature of 850 °C was ∼4 times as high as that with peak temperature of 750 °C. However, it only increased to ∼1.3 times when the peak temperature increased from 850 °C to 1050 °C.

Late Paleozoic Gondwanide deformation in the Central Andes: Insights from RSCM thermometry and thermal modeling, southern Bolivia

A widespread unconformity between Ordovician metasedimentary rocks and nonmetamorphosed Mesozoic sedimentary rocks across the Eastern Cordillera of Bolivia provides evidence for significant pre-Late Cretaceous deformation and erosion. In this paper, we refine the middle to late Paleozoic tectonic history of the central Andean segment of Gondwana's western margin. We combine Raman spectroscopy of carbonaceous material (RSCM) thermometry with semi-quantitative deformation temperature estimates from quartz recrystallization microstructures and published illite crystallinity values from Cambrian-Devonian sedimentary rocks that span the Eastern Cordillera of southern Bolivia at ~21°S. Estimates of peak temperature and deformation temperature range primarily between ~220 and ~ 400 °C and show a general increase with depth that defines a metamorphic field gradient between ~37 and ~ 47 °C/km. Temperatures obtained from Ordovician rocks directly below the unconformity require erosion of a > ~5 km overburden prior to the Late Cretaceous, which was likely accomplished by a combination of distributed cleavage development and Paleozoic folding and thrust faulting revealed from cross-section reconstructions. The peak temperature data are incorporated into thermal models along with published illite KAr, zircon (UTh)/He, and zircon fission-track cooling ages that refine the timing of Paleozoic orogenesis in the central Andes. We interpret shortening-related flexural subsidence driven by cratonward growth of a pre-Andean orogenic wedge along the western margin of Gondwana, with peak temperature conditions attained during eastward advance of a foreland basin between ~420 and ~ 318 Ma during the Devonian-Carboniferous Gondwanide Orogeny. Erosional exhumation between ~352 and ~ 294 Ma was the result of continued growth and eastward expansion of the associated Transpampean tectonic highland across the Eastern Cordillera. The growth of this pre-Andean contractional orogen coincided with global plate reorganization and the reestablishment of subduction and arc magmatism along the western margin of Gondwana, as indicated by a significant influx of Carboniferous arc-related detritus into the foreland basin system.

Spectroscopy of P30 and the abundance of Si29 in presolar grains

The astrophysical $^{29}\mathrm{Si}(p,\ensuremath{\gamma}$) reaction is expected to play a key role in determining the final $^{29}\mathrm{Si}$ yields ejected in nova explosions. Such yields are used to accurately identify the stellar origins of meteoritic stardust and recently, distinctive silicon isotopic ratios have been extracted from a number of presolar grains. Here, the light-ion $^{28}\mathrm{Si}(^{3}\mathrm{He},p$) fusion-evaporation reaction was used to populate low-spin proton-unbound excited states in the nucleus $^{30}\mathrm{P}$ that govern the rate of the astrophysical $^{29}\mathrm{Si}(p,\ensuremath{\gamma}$) reaction. In particular, $\ensuremath{\gamma}$ decays were observed from resonances up to ${E}_{r}=500\phantom{\rule{0.28em}{0ex}}\mathrm{keV}$, and key resonances at 217 and 315 keV have now been identified as ${2}^{+}$ and ${2}^{\ensuremath{-}}$ levels, respectively. The present paper provides the first estimate of the 217-keV resonance strength and indicates that the strength of the 315-keV resonance, which dominates the rate of the $^{29}\mathrm{Si}(p,\ensuremath{\gamma}$) reaction over the entire peak temperature range of oxygen-neon novae, is higher than previously expected. As such, the abundance of $^{29}\mathrm{Si}$ ejected during nova explosions is likely to be less than that predicted by the most recent theoretical models.

Micromagnetic modeling of the heat-assisted switching process in high anisotropy FePt granular thin films

The dynamic process of assisted magnetic switchings has been simulated to investigate the associated physics. The model uses a Voronoi construction to determine the physical structure of the nanogranular thin film recording media, and the Landau–Lifshitz–Bloch equation is solved to evolve the magnetic system in time. The reduction of the magnetization is determined over a range of peak system temperatures and for a number of anisotropy values. The results show that the heat-assisted magnetic recording process is not simply magnetization reversal over a thermally reduced energy barrier. To achieve full magnetization reversal (for all anisotropies investigated), an applied field strength of at least 6 kOe is required and the peak system temperature must reach at least the Curie point (Tc). When heated to Tc, the magnetization associated with each grain is destroyed, which invokes the non-precessional linear reversal mode. Reversing the magnetization through this linear reversal mode is favorable, as the reversal time is two orders of magnitude smaller than that associated with precession. Under these conditions, as the temperature decreases to ambient, the magnetization recovers in the direction of the applied field, completing the reversal process. Also, the model produces results that are consistent with the concept of thermal writability; when heating the media to Tc, the smaller grains require a larger field strength to reverse the magnetization.

An analysis of thermo-mechanical fatigue crack growth in the titanium alloy Ti-6246

Titanium alloys are equipped with impressive high strength and low density, along with other notable mechanical properties. Often the choice for low to intermediate temperature mechanical applications, titanium alloys are well utilised within the aerospace industry, making up 40% of the aero-engine. Within the gas turbine engine, the high transient thermal stresses developed due to variations in power requirements during a typical flight cycle give rise to the phenomenon of thermo-mechanical fatigue (TMF). The lifing models utilised within this research focus on damage tolerance approaches. TMF crack growth test techniques have been developed for high performance titanium alloys, in which diverse phasing (φ) between mechanical loading and temperature have been investigated. In addition, factors affecting the TMF behaviour of Ti-6246, including peak temperature, minimum temperature and temperature range have also been explored.

Grove Mountains (GRV) 020043: Insights into acapulcoite-lodranite genesis from the most primitive member

Although acapulcoites and lodranites played a key role in understanding partial differentiation of asteroids, the lack of samples of the chondritic precursor limits our understanding of the processes that formed these meteorites. Grove Mountains (GRV) 020043 is a type 4 chondrite, with abundant, well-delineated, pyroxene-rich chondrules with an average diameter of 690 μm, microcrystalline mesostasis, polysynthetically striated low-Ca pyroxene, and slightly heterogeneous plagioclase compositions. Similarities in mineralogy, mineral composition, and oxygen isotopic composition link GRV 020043 to the acapulcoite-lodranite clan. These features include a high low-Ca pyroxene to olivine ratio, high kamacite to taenite ratio, and relatively FeO-poor mafic silicates (Fa10.3, Fs10.4) relative to ordinary chondrites, as well as the presence of ubiquitous metal and sulfide inclusions in low-Ca pyroxene and ƒO2 typical of acapulcoites. GRV 020043 shows that evidence of partial melting is not an essential feature for classification within the acapulcoite-lodranite clan. GRV 020043 experienced modest thermal metamorphism similar to type 4 ordinary chondrites. GRV 020043 suggests a range of peak temperatures on the acapulcoite-lodranite parent body similar to that of ordinary chondrites, but shifted to higher temperatures, perhaps consistent with earlier accretion. The mineralogy and mineral compositions of GRV 020043, despite modest thermal metamorphism, suggests that most features of acapulcoites previously attributed to reduction were, instead, inherited from the precursor chondrite. Although partial melting was widespread on the acapulcoite-lodranite parent body, ubiquitous Fe,Ni-FeS blebs in the cores of silicates were not implanted by shock or trapped during silicate melting, but were inherited from the precursor chondrite with subsequent overgrowths during metamorphism.

Thermo-Mechanical Fatigue of SOFC Glass-Ceramic Sealant/Steel Interconnect Joint in a Reducing Atmosphere

Thermo-mechanical fatigue (TMF) behavior of a joint between a solid oxide fuel cell glass-ceramic sealant and an interconnect steel is investigated in a reducing atmosphere (H2–7 vol% H2O) under cyclic shear and tensile loadings combined with cyclic temperature change between 40°C and 800°C. Experimental results indicate TMF life of shear specimen is increased with a decrease in the end stress applied at 800°C which dominates the shear TMF life. The accumulated duration of loading at peak temperature range (795–800°C) in TMF test is comparable with the estimated creep rupture time at 800°C for shear specimens. TMF fracture of the shear specimens mainly occurs at the interface between the glass-ceramic layer and chromia layer. For tensile specimens, TMF life is controlled by the end stresses applied at 800°C and 40°C. For tensile TMF specimens, fracture mostly takes place within the glass-ceramic layer and at the chromia/glass-ceramic interface.