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All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Effect of Deformation Temperature on the Microstructure and Mechanical Properties of High-Strength Low-Alloy Steel During Hot Compression

The microstructure and mechanical properties of high-strength low-alloy steel were investigated at deformation temperatures of 800-1100 °C and strain rates of 0.1-10 s{sup −1} using an MMS-200 thermal mechanical simulator. The results indicated that the increased deformation processes observed between the starting and finishing temperatures during hot compression testing caused a polygonal ferrite transformation in the material. The polygonal ferrite grain sizes increased with increasing transformation temperatures and gradually grew larger at higher deformation temperatures. Widmanstätten ferrite and acicular ferrite were also formed at high temperatures from 1000-1100 °C, which accordingly led to an increase in Vickers microhardness. In addition, the flow stress in the material increased with an increase in the strain and a decrease in the deformation temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Tempering Temperature on the Precipitation Behavior and Mechanical Properties of a Martensite Ferritic Steel

In this investigation, the precipitation of boron-containing M{sub 23}C{sub 6} in the CB2 steel during tempering was investigated. Scanning electron microscopy, energy-dispersive x-ray spectroscopy, transmission electron microscopy and differential scanning calorimetry were used to analyze the influence of temperature on the microstructure and properties of CB2-tempered martensite ferritic steel. The steel was normalized at 1100 °C for 2 h and then tempered at six different temperatures between 690 and 790 °C for 2 h. During air-cooling following austenitization, the precipitation of M{sub 3}C particles occurred in flakes forming with their diameter and thickness of 100 and 20 nm, respectively. The boron-containing M{sub 23}C{sub 6} was formed on the lath boundary after the dissolution of M{sub 3}C within the boundary. When the tempering temperature increased from 690 to 790 °C, the average diameter of boron-containing M{sub 23}C{sub 6} increased from 132 to 198 nm. Owing to the rapid growth of the precipitates, the phenomenon of lath widening as well as the recovery of microstructure would take place at high temperature. With an increase in the temperature, the tensile and yield strengths decreased gradually, while the plasticity increased and the boron-containing M{sub 23}C{sub 6} grew rapidly. Furthermore, when the tempering temperature exceeded 750 °C, the plasticity of CB2 steel was significantly improved.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Microstructural Characterization and Simulation of High Temperature Inelastic Deformation and Fracture of Al-Li 2070

A combined experimental and simulation investigation is carried out to characterize the high temperature deformation behavior of a recently developed Al-Li alloy, AA2070, over a temperature range including typical forging temperatures. Focus is placed on providing explanations for the temperature-dependent plastic and fracture behavior observed for this material using macroscale tensile tests, microscale imaging and analysis, and physics-based micromechanical modeling. It is shown that AA2070 experiences non-monotonic elongation to failure with a rise in temperature. Detailed fractography and microstructural analysis, including dynamic recrystallization analysis, provide insight into this interesting and practically useful behavior. In addition, a validated crystal plasticity model is called upon to explain the unique texture observed in the necked region of the ductile tensile specimen. The insights provided by this investigation will allow improved design of high temperature forming operations for AA2070 and similar alloys which can extend the application of third generation Al-Li alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Elevated temperature ductility dip in an additively manufactured Al-Cu-Ce alloy

The deformation and failure mechanisms of Al-9Cu-6Ce (wt%) based alloys fabricated with laser powder bed fusion were investigated from room temperature to 400°C. The yield and ultimate tensile strengths decreased monotonically with increase in temperature, but the tensile elongation dipped unexpectedly at elevated temperatures and exhibited a minimum at 300°C. The dip in tensile elongation occurred with a concomitant dip in strain-rate sensitivity (SRS) of deformation. The as-fabricated alloy microstructure was heterogeneous, and the heat affected zone (HAZ) underneath the melt pool boundary was prone to strain localization. At 300 °C, the reduced SRS promoted the progression of strain localization in the HAZ leading to failure initiation and the dip in tensile elongation. Furthermore, a higher SRS or strain-hardening rate at other temperatures improved the tensile elongation by slowing the progression of strain localization in the HAZ such that failure initiated by other mechanisms elsewhere in the microstructure. Notably, the tensile elongation was limited by the defect structure only in a narrow temperature range (150 - 200 °C) while at other temperatures it was limited by the inherent microstructural features. This investigation exemplifies unexpected deformation and failure mechanisms possible in heterogeneous microstructures that result from additive manufacturing.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Investigation of heat pump technologies for high-temperature applications above 250 °C

This paper examines heat pump (HP) technologies to achieve heat supply temperatures above 250 °C, referred to as ultra-high-temperature heat pump (UHTHP). UHTHP, as a low-carbon heat delivery and heat augmentation technology, can offer an alternative to traditional combustion heating for decarbonizing high-temperature industrial processes. However, the heat supply temperature of over 250 °C surpasses the temperature range typically covered in the high-temperature HP literature and existing capabilities of commercial HP systems. This paper reviews HP technologies with the potential to evolve into UHTHP. Additionally, UHTHP studies in the literature are analyzed to compare the pros, cons, and technical potentials of various HPs using different thermodynamic cycles and fluids. Furthermore, we then pinpoint the technical gaps and challenges that have hindered widespread adoption of UHTHP in industry, explore potential improvements and solutions, and discuss the feasibility. Current efforts aim to lay the ground for future research, development, and commercial deployment for UHTHP.

32 - ENERGY CONSERVATION, CONSUMPTION, AND UTILIZA↗
DOE OSTI2019

Modeling the effect of temperature gradient on moisture and ionic transport in concrete

Most reinforced concrete structures are under the influence of environmental conditions, such as temperature fluctuations, moisture and chloride variations simultaneously. Thus, the moisture transfer in concrete is driven by the moisture gradient as well as the temperature gradient. Similarly, the ionic transfer in concrete is driven by the concentration gradient of the ion as well as the temperature gradient. This paper developed an analytical solution that can be used for the moisture or the chloride transport in concrete considering the effect of temperature gradient. The effect of mass transfer on the thermal conduction was not considered, so the problem is simplified as a one-way coupled problem. The analytical model was validated by using two CASE studies, in which realistic material parameters of concrete were used, the parameters were obtained from experiments in the literature. The comparisons between analytical results and experimental results showed good agreement. It indicated that the present model can successfully characterize the effect of temperature gradient on moisture transfer and the effect of temperature gradient on chloride transport in concrete.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Combined curing as a novel approach to improve resistance of ultra-high performance concrete to explosive spalling under high temperature and its mechanical properties

Highlights: • The combined curing can significantly enhance the resistance of UHPC to explosive spalling under high temperature. • The combined curing can improve the mechanical properties of UHPC remarkably. • Both further hydration of residual cement and pozzolanic reaction are activated under a high temperature steam condition. - Abstract: The influence of a combined curing composed of precuring in hot water and heating in dry air on mechanical properties and explosive spalling of ultra-high performance concrete (UHPC) subjected to high temperature was investigated in this experiment. Meanwhile, the microstructure of UHPC was determined by means of X-ray diffraction (XRD) with Rietveld method, thermogravimetric analysis (TGA), scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP). The results indicate that the combined curing improves the mechanical properties of UHPC remarkably. More importantly, it is quite efficient to enhance the resistance of UHPC to explosive spalling under high temperature, which should be a novel approach to prohibit spalling occurrence, different from adding polypropylene fiber. During dry air heating in the combined curing, a high temperature steam environment is established in the dense structure framework of UHPC formed in the preceding hot water curing. Both further hydration of residual cement and pozzolanic reaction of mineral admixtures can be activated during the dry air heating, leading to not only the formation of a large amount of dense hydrates (such as C-S-H gels, katoite, tobermorite and xonotlite, etc.), which accumulate in the aforementioned existing framework, but also the consumption of most of internal free water. Therefore, both mechanical properties of UHPC and its resistance to explosive spalling under high temperature can be enhanced significantly.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of the hydration temperature on the pore structure of cement paste: Experimental investigation and micromechanical modelling

The hydration temperature has a considerable effect on the microstructure of cement paste. The microstructural changes with increasing curing temperature result in a significant decrease of cement mechanical properties. The present work aims at studying these phenomena via micromechanical modelling, based on an experimental characterization of cement microstructure. The pore structure of a class G oil-well cement paste (American Petroleum Institute classification) hydrated at different temperatures, between 7 °C and 90 °C is characterized. Then, the influence of the microstructure variations on the elastic properties of the hardened paste is explored through micromechanical modelling. A previous analysis of the microstructure enabled determining the volume fractions of different phases of a class G cement paste hydrated under different temperatures [1]. A multiscale self-consistent homogenization model is used based on these results to simulate the variations of the mechanical properties with hydration temperature. The results are compared with macro-scale elastic properties obtained from uniaxial compression tests. It is shown that the increasing capillary porosity with elevating hydration temperature, is not sufficient to fully explain this drop of elastic properties. The latter originates mainly from the decrease of the elastic properties of the foam composed of the porous C-S-H intermixed with capillary pores. The pore structure analysis coupled with the micromechanical modelling permitted a back-analysis of the intrinsic porosities of high density and low density C-S-H showing an almost constant LD intrinsic porosity and a significantly decreasing HD intrinsic porosity.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Nanostructural evolution of Al(OH)3 gel formed by the cubic and orthorhombic ye'elimite clinkers of calcium sulfoaluminate cements in an ultra-wide hydration temperature range

This paper investigated the influence of hydration temperature on the nanostructure of the AH{sub 3} phase formed in calcium sulfoaluminate cements. Orthorhombic ye'elimite (st-ye'elimite) and cubic ye'elimite (ss-ye'elimite) were hydrated in an ultra-wide temperature range (5–220 °C). Results showed that the AH{sub 3} phase formed by ss-ye'elimite was always microcrystalline in nature at various curing temperatures (5–130 °C), and transformed into the AlOOH phase at 150 °C and above. However, the AH{sub 3} phase formed by st-ye'elimite grew from a microcrystal to a favorable crystal as the temperature increased, and transformed into the AlOOH phase at 170 °C and above. The nanostructure of hydration products was further investigated using TEM/SAED analysis together with FE-SEM images, directly evidencing that the formed AFm-12 phase was single-crystal in nature, and the formed AH{sub 3} phase was microcrystalline at low temperatures and grew into single-crystal hexagonal prisms with the preferred growth direction along [001] direction at high temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Field evaluation of zone temperature response to control actions in cooling systems of small and medium-sized office buildings

The response of zone temperature to control actions in heating, ventilation, and air conditioning (HVAC) systems, known as zone temperature response, has been a central focus of building control research owing to its crucial role in determining control performance. However, existing studies often overlook the representativeness of the buildings being studied, resulting in unclear generalizations. In addition, those studies tend to focus on a single aspect of the response. Furthermore, this paper provides the first comprehensive characterization of zone temperature response applicable to a clearly defined building sector—small and medium-sized office (SMO) buildings (<5000 m 2 ) in the US. Specifically, two representative SMO buildings, selected based on the US Department of Energy’s commercial prototype buildings, were studied. Field tests were conducted over a 2-month period during summer, and the collected data were analyzed with two key metrics—delay time and nonlinearity index—to quantify zone temperature response, capturing both short- and long-term patterns. Beyond this quantitative characterization, the analysis reveals that the HVAC system type, rather than factors like floor area or zone location, is the primary determinant of the zone temperature response. Drawing on the field test results, we recommend that building control strategies monitor zone temperatures at intervals shorter than 10 minutes, configure controls independently for VAV- and RTU-served zones, and implement nonlinear methods at the zone level—particularly for VAV zones—rather than across the entire building.

Building control↗
DOE OSTI2022

Impact of coolant temperature on the combustion characteristics and emissions of a stratified-charge direct-injection spark-ignition engine fueled with E30

The direct injection spark ignition (DISI) engine has received considerable attention due to its potential to increase the power density of traditional spark ignition engines while significantly improving fuel economy through lean, unthrottled combustion. However, the market introduction of DISI engines operated in a lean combustion mode is inhibited by their unsatisfactory emissions, especially during cold start conditions that make proper mixture formation more challenging. Ethanol-blended gasoline, now a widely used fuel, makes the cold start of a DISI engine more difficult, leading to higher HC and soot emissions because of the high latent heat of vaporization of ethanol relative to gasoline. This work investigated the impact of coolant temperature on the characteristics of combustion and emissions in a stratified-charge DISI engine fueled with an E30 fuel (i.e. 30% ethanol in gasoline), while the coolant temperature was alternated between four levels (45, 60, 75, and 90 °C) to simulate different conditions throughout the warm-up process. The experiments showed that the coolant temperature affected the post-spark inflammation time, as well as the speed, intensity, and stability of the combustion process in the engine. When the coolant temperature rose, the engine produced more NOX and less CO, PM and HC. In addition, high-speed direct photography was used to obtain crank-angle resolved images of fuel sprays and flames in the cylinder. As the coolant temperature rose, the liquid spray lengths became shorter, reducing the possibility of wall wetting, and reduced irradiance from soot particles also indicated less nonpremixed combustion. The in-cylinder imaging results are consistent with the observed combustion and emission characteristics and shed light on the underlying processes. Finally, some potential solutions to the emissions challenges faced here could be either raising in-cylinder temperatures by using trapped residuals or modifying the injection schedule, for example by increasing the number of injections or to inject later in the cycle into a higher-density environment.

42 ENGINEERING↗
DOE OSTI2021

Temperature-responsive smart tracers for field-measurement of inter-well thermal evolution: Heterogeneous kinetics and field demonstration

Temperature-responsive smart tracers enable advanced warning of a “premature thermal breakthrough” and may therefore improve reservoir management and reduce financial risk. A successful calculation of inter-well fluid temperatures requires that temperature-dependent kinetics are known, which typically result from homogeneous batch reactor experiments. However, recent meso-scale field experiments at the Altona Field Laboratory involving fluid flow in a discretely-fractured reservoir suggest that silica-fluid interfaces may accelerate hydrolysis kinetics. Here, the Arrhenius parameters of phenyl acetate hydrolysis are investigated under heterogeneous reaction conditions in packed-bed column experiments. The breakthrough curve of the reaction product is compared to an inert reference tracer (carbon-cored nanoparticles). Temperatures experienced during field testing ranging from 10 to 40 °C were studied using a phosphate buffer solution to maintain a near-neutral pH, as found in the reservoir. The empirically-determined pre-exponential factor and activation energy values are subsequently used in a first-order kinetic model to improve calculations of effective reservoir temperatures for these meso-scale field tests. Here, the results suggest that hydrolysis reactions can directly monitor inter-well reservoir temperatures, but only if the influence of solid-fluid interactions are carefully accounted for.

15 GEOTHERMAL ENERGY↗
DOE OSTI2023

Stability study of aqueous foams under high-temperature and high-pressure conditions relevant to Enhanced Geothermal Systems (EGS)

In Enhanced Geothermal System (EGS) hydraulic fracturing is carried out by injecting cold water into deep Hot Dry Rocks (HDR) under carefully controlled conditions to create new or reopen existing fractures. Water-based fracturing fluids demonstrate some challenges including immense quantity of water usage, water sensitivity of the formations, water blocking, and lack of proppant carrying capacity and transportation. Thus, an alternative is to use foam-based fracturing fluid which offers potential advantage over conventional water-based fracturing fluid such as minimum water usage, reduced wellbore damage, high proppant carrying capacity, and less environmental damage. However, foams are complex mixture of gaseous phase and liquid phase which are thermodynamically unstable at downhole conditions, and their stability can decrease over time due to liquid drainage, bubble coarsening, and coalescence. This paper shows laboratory experiments executed to study foam stability at high temperature (200°C) and high pressure (6.9MPa) conditions which simulates the geothermal environment. Foam stability was characterized by half-life of foam, which is defined as the time taken by the foam to decreases by 50% of its original height due to drainage. In this paper, two types of gaseous phases, nitrogen (N 2 ) and carbon dioxide (CO 2 ) were investigated. Also, based on successful practice of foam-based fracturing fluid in oil and gas industries, four surfactants, including Alpha olefin sulfonate (AOS), Sodium dodecyl sulfonate (SDS), Tergitol™ (NP – 40), and Cetyltrimethylammonium chloride (CTAC) at optimum concentration of 1wt.% were tested for best stability performance. In addition, different stabilizing agents including guar gum, bentonite clay, crosslinker, silicon dioxide nanoparticles (SiO 2 ), graphene oxide (GO) were also studied. Experimental results showed that N 2 foams were more stable than CO 2 foams. It was observed that foam half-life decreased with the increase in temperature. Among all the surfactants, AOS foams showed the most promising thermal stability at high temperatures. Moreover, with the addition of stabilizing agents, foam's half-life was enhanced. Stabilizing agents such as crosslinker and GO dispersion showed the most stable foams with half-life recorded at 20min and 17min, respectively, at 200°C and 6.9MPa. Finally, pressure also showed a positive effect on foam stability; with increased pressure, foam half-life was increased. Based on the experimental data, analytical models for the effect of temperature and pressure were developed, considering foam degradation is a first-order kinetic reaction that linearly depends on the foam drainage mechanism. The effect of temperature on foam half-life was studied as an exponential decay model. In this model, foam half-life is a function of drainage rate constant (D A ) and activation energy (E a ) of the foam system. The effect of pressure on foam half-life was found to obey a power-law model where an increase in pressure showed an increase in foam half-life. Furthermore, a linear relation was studied for the effect of pressure on foam activation energy and drainage rate. Then the combined effects of temperature and pressure were studied, which yielded an analytical model to predict the foam stabilities in terms of half-life for different foam compositions. In conclusion, this research indicates that with an appropriate selection of surfactants and stabilizing agents, it is possible to obtain stable foams, which could replace conventional water fracturing fluid under EGS conditions.

15 GEOTHERMAL ENERGY↗
DOE OSTI2019

Temperature and load-ratio dependent fatigue-crack growth in the CrMnFeCoNi high-entropy alloy

Multiple-principal element alloys known as high-entropy alloys have significantly been gaining attention for the vast variety of compositions and potential combinations of properties that remain to be explored. Of these alloys, one of the earliest, the ‘Cantor alloy’ CrMnFeCoNi, demonstrates excellent damage-tolerance with tensile strengths of ~1 GPa and fracture toughness values in excess of 200 MPa√m; moreover, these mechanical properties tend to further improve at cryogenic temperatures. Yet, few studies have explored its corresponding fatigue properties. Here we expand on our previous study to examine the mechanics and mechanisms of fatigue-crack propagation in the CrMnFeCoNi alloy (~7 μm grain size), with emphasis on long-life, near-threshold fatigue behavior, specifically as a function of load ratio at temperatures between ambient and liquid-nitrogen temperatures (293 K–77 K). We discover that Δ K th fatigue thresholds are decreased with increasing positive load ratios, $\mathcal{R}$ between 0.1 and 0.7, but are increased at decreasing temperature. These effects can be attributed to the role of roughness-induced crack closure, which was estimated using compliance measurements. Evidence of deformation twinning at the crack tip during fatigue-crack advance was not apparent at ambient temperatures but seen at higher stress intensities (Δ K ~ 20 MPa√m) at 77 K by post mortem microstructural analysis for tests at $\mathcal{R}$ = 0.1 and particularly at 0.7. Overall, the fatigue behavior of this alloy was found to be superior, or at least comparable, to conventional cryogenic and TWIP steels such as 304 L or 316 L steels and Fe-Mn steels; these results coupled with the remarkable strength and fracture toughness of the Cantor alloy at low temperatures indicate significant promise for the utility of this material for applications at cryogenic environments.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Dendrite-free Al recycling via electrodeposition using ionic liquid electrolytes: The effects of deposition temperature and cathode surface roughness

In this report, the electrodeposition of Al from aluminum scrap alloys (A2020) on copper cathode substrates with varied surface roughness under different deposition temperatures was studied using low-temperature AlCl 3 -1-butyl-3-methyl-imidazolium chloride (BMIC) ionic liquid electrolytes. The bulk electrodeposition of Al was carried out under a voltage of 1.5 V at a stirring rate of 120 rpm using a fixed ionic liquid electrolyte concentration (molar ratio AlCl 3 : BMIC = 2:1). The effects of deposition temperature (range from 80 °C to 140 °C) and surface roughness of Cu cathode substrates (polished by 320, 600, 800, 1200 grits SiC sandpapers and mirror polishing process) on the morphology of deposited Al, current density, current efficiency and energy consumption, were investigated. The Al deposits were characterized using scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), profilometer, and electrochemical measurements for current density, current efficiency, and energy consumption. It is demonstrated that the deposition temperature and surface roughness of Cu electrodes play a critical role in the nucleation and growth of Al deposits. Higher deposition temperature promotes the diffusion and/or migration of Al 2 Cl 7 - ions and then enhances the current density and efficiency during the electrodeposition of Al. Smoother surface of Cu electrodes is preferred for the formation of dendrite-free Al deposits. Typically, on the mirror polished Cu electrode, no Al dendrite structure was observed, and only plate-like Al deposits were formed at the deposition temperature of 100 °C. Pure metallic Al was successfully deposited on Cu electrodes in AlCl 3 + BMIC ionic liquid electrolytes for all experiments with a current efficiency range from 72% to 99% and energy consumption of 4.6–6.3 kW h/kg Al.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Elevated temperature tensile tests on DU–10Mo rolled foils

We report that studies were completed to obtain tensile mechanical properties for uranium-10wt.% molybdenum (U-10Mo) foils which were subjected to four different thermomechanical processing conditions. U-Mo alloy foils are being investigated to support fuel conversion of high power research reactors from their current high enriched fuel form to a low enriched fuel form. Mechanical properties of the fuel foil have an effect on irradiation performance and fuel fabrication and therefore are required to support modeling and qualification of new low-enriched uranium monolithic fuel plate designs. The data contained in this document contributes to fuel qualification by fulfilling the requirement that physical properties related to fuel meat be established. It is expected that depleted uranium-10wt% Mo (DU–10Mo) mechanical behavior is representative of the low-enriched U10-Mo to be used in actual fuel plates; therefore DU–10Mo was studied to simplify material processing, handling, and testing requirements. In this report, the different thermomechanical treatments included variations of wrought hot and cold rolling reduction and post rolling annealing. Each of the four foils was hot rolled. After hot rolling reduction, three of the four foils were further reduced by cold rolling. One of the three was reduced a further 20% by cold rolling, and the remaining two were reduced 50% by cold rolling. Following cold rolling reduction, one of the two foils which had been reduced 50% by cold rolling was annealed at 650?°C. Performing this analysis allows assessment of the impact of foil fabrication history on the resultant tensile properties DU–10Mo fuel foils. Tensile properties of DU–10Mo at room temperature through approximately 400 °C determined from the tests conducted herein suggest the material is stronger and has lower ductility than what has been reported previously in the literature. The explanation for these differences has yet to be determined, but is likely related to differences in grain size and/or impurity content, and variation in fabrication history. At the highest temperatures tested (550 °C) better agreement between the values reported here and available literature was found. As expected, yield and ultimate tensile strength decreased with increasing test temperature. Generally, the yield stress for all foil processing conditions was found to be in the range of 1100 MPa for room temperature tests, and in the range of 200 MPa for tests conducted at 550 °C. Ultimate tensile stress was in the range of 1175 MPa at room temperature, decreasing to approximately 225 MPa at 550 °C. Lastly, elongation increased significantly, from 0 to 2% at room temperature to 50% or more for the tests at 550 °C.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Effect of temperature on silicon-based anodes for lithium-ion batteries

Silicon is considered a promising anode candidate to replace graphite in lithium-ion (Li-ion) batteries for electric vehicle (EV) applications, given its high capacity (approximately 10 times higher than graphite) and, consequently, the higher energy density it can provide. However, to ensure that silicon can be used in EVs, it is necessary to determine whether it can withstand the temperature changes that an EV can experience. For this purpose, we evaluate the electrochemical performance of silicon-graphite (Si-Gr) half-cells at 4 different temperatures and explore the effect of adding fluoroethylene carbonate (FEC) to the electrolyte. We observe that cells cycled without FEC are temperature-sensitive; that is, the specific capacity, cyclability, and coulombic efficiency of Si-Gr vary as a function of the temperature applied. Conversely, the presence of FEC in the cell stabilizes the electrochemical behavior of Si-Gr, diminishing its sensitivity to temperature and providing similar reversible capacity, coulombic efficiency, and cycle-life. In this manuscript, we provide an explanation of the reasons causing this phenomenon along with other side effects of temperature, as proved by several characterization techniques.

25 ENERGY STORAGE↗
DOE OSTI2018

Effects of the rolling temperature on microstructure and mechanical properties of 2Cr13/316L laminated composites prepared by accumulative roll-bonding (ARB)

Highlights: • The rolling temperature affects the grain size and microstructural phases of the composite plates. • The rolling temperature affects tensile strength and bending strength of 2Cr13/316L properties of the composite plates. • The temperature gradient and thermal deformation of center and outside regions are different during rolling process. • Composite plate with higher strength and elongation can be obtained by rolling processes. - Abstract: The microstructure and mechanical properties of 2Cr13/316L composite plates by hot-rolling at different rolling temperatures of 1130 °C, 1180 °C, 1250 °C, 1300 °C are investigated in details. With the increase of the rolling temperature, the tensile strength and bending strength of 2Cr13/316Lwere reduced first and then increased slightly due to the coarsening of grains and the increasing of ferrite content in 2Cr13 layers. The highest tensile elongation is obtained at the composite plate with rolling temperature of 1180 °C. 2Cr13/316L composite plates obtained by hot rolling processes were able to withstand larger bending deformation, and no cracks or interfacial delamination can be found in the bending process because of a strong combined interface.

36 MATERIALS SCIENCE↗

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