SEARCH · Engineering Papers

Results for “phase change composite”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28

All sources NASA NTRS DOE OSTI

DOE OSTI2021

Random copolymer of poly(polyethylene glycol methyl ether)methacrylate as tunable transition temperature solid-solid phase change material for thermal energy storage

Polymer based phase change materials (PCM) for thermal energy storage (TES) applications have gained some attention recently due to their high stability and potential solid to solid phase transition. In this work, we are the first to utilize a simple copolymerization strategy for static tunability transition temperature (T t ) of polymeric PCM. The copolymerization between short and long side chain polyethylene glycol based methacrylate polymers was designed to tune T t with minimum impact on their energy density. Polarized optical microscope and x-ray techniques were also used to understand the relationship between crystal structure and T t of different copolymer composition which was discussed in the context. The solid to solid transition polymeric PCM were successfully developed with tunable T t ranged from 18 °C to 35 °C which is suitable toward building envelop applications.

14 SOLAR ENERGY↗

DOE OSTI2022

Transformation of a ceramic precursor to a biomedical (metallic) alloy: Part I – sinterability of Ta 2 O 5 and TiO 2 mixed oxides

Mixed Ta 2 O 5 – TiO 2 binary system was studied by a combination of differential thermal analysis (DTA), scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), X-ray diffraction (XRD) and in situ high temperature X-ray diffraction (HT-XRD) techniques. Different compositions of the mixed oxide powders were fabricated by ball–milling the powdered compositions, pelletizing the homogenized composite powders, and heating the green pellets in air at different temperatures for fixed time intervals. The sintered pellets were evaluated and characterized with respect to porosity, morphology, and phase distribution. DTA runs of the un-sintered powders indicated the onset temperatures for both exothermic and endothermic changes in the binary system. Significant amount of sintering was observed to take place at temperatures higher than 900 °C. Both room and high temperature X-ray diffraction patterns exhibited consistency in phase formation. A ternary compound (TaTiO 4 ) and a ternary solid solution (Ti 0.33 Ta 0.67 O 2 ) were observed to form in both room and high temperatures in addition to the respective binary phases (Ta 2 O 5 and TiO 2 ). A sintering temperature in the range 900–1000 °C was observed to be adequate to achieve the requisite mechanical strength and optimum internal porosity (40–48%) for subsequent electrochemical polarization experiments.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Arctic Coastal Erosion: Modeling and Experimentation

Increasing Arctic coastal erosion rates have put critical infrastructure and native communities at risk while also mobilizing ancient organic carbon into modern carbon cycles. Although the Arctic comprises one-third of the global coastline and has some of the fastest eroding coasts, current tools for quantifying permafrost erosion are unable to explain the episodic, storm-driven erosion events. Our approach, mechanistically coupling oceanographic predictions with a terrestrial model to capture the thermo-mechanical dynamics of erosion, enables this much needed treatment of transient erosion events. The Arctic Coastal Erosion Model consists of oceanographic and atmospheric boundary conditions that force a coastal terrestrial permafrost environment in Albany (a multi-physics based finite element model). An oceanographic modeling suite (consisting of WAVEWATCH III, Delft3D-FLOW, and Delft3D-WAVE) produced time-dependent surge and run-up boundary conditions for the terrestrial model. In the terrestrial model, a coupling framework unites the mechanical and thermal aspects of erosion. 3D stress/strain fields develop in response to a plasticity model of the permafrost that is controlled by the frozen water content determined by modeling 3D heat conduction and solid-liquid phase change. This modeling approach enables failure from any allowable deformation (block failure, slumping, etc.). Extensive experimental work has underpinned the ACE Model development including field campaigns to measure in situ ocean and erosion processes, strength properties derived from thermally driven geomechanical experiments, as well as extensive physical composition and geochemical analyses. Combined, this work offers the most comprehensive and physically grounded treatment of Arctic coastal erosion available in the literature. The ACE model and experimental results can be used to inform scientific understanding of coastal erosion processes, contribute to estimates of geochemical and sediment land-to-ocean fluxes, and facilitate infrastructure susceptibility assessments.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1983

Apollo 14 very low titanium glasses - Melting experiments in iron-platinum alloy capsules

This paper describes two techniques that have been developed to produce Fe-Pt alloy capsules for hgh-pressure experiments, and reports liquidus-phase relations of the Apollo 14 very low titanium glasses determined using Fe-rich capsules (a/Fe/ approximately 0.6). The liquid is multiply saturated with olivine and clinopyroxene at equal to or greater than 22 kbar. The multiple saturation is at least 3 kbar higher than that determined using pure Fe capsules and corresponds to a source region at least 60 km deeper if olivine and clinopyroxene were the residual phases. However, independent data on iron activity or oxygen fugacity of the glasses are still needed in order to choose a container of optimum composition. Preliminary experiments in Fe-poor alloy capsules suggest that the valence state of iron and the crystallization sequence in the melt have changed, possibly as a result of oxidizing materials entrapped during the iron-plating processes. The FeO content of the charge decreases linearly with increasing run duration in experiments using pure Fe capsules. The observation that iron-rich globules grow with time suggests that the equilibrium Fe (bleb) + Fe2O3 (liq) = 3 FeO (liq) might be established in the liquid at high pressure. If this explanation is correct, an appreciable amount of 'FeO' in the liquid could actually be Fe2O3, and some natural lunar volcanic glasses may contain ferric iron as well.

Chen, H.-K.↗

NASA NTRS1995

Robust Quantitative Measurement of Flows and Transparent or Highly Reflective Objects

The liquid crystal point diffraction interferometer (LCPDI) is a new instrument that has been developed for the measurement of phase objects. The LCPDI uses the compact, robust design of Linnik's point diffraction interferometer and adds to it phase stepping capability for quantitative interferogram analysis. The result is a compact, simple to align, environmentally insensitive interferometer capable of accurately measuring optical wave-fronts. A solid state camera provides very high data density and automated data reduction. The instrument can measure either transparent objects like fluids and lenses, or highly reflective opaque objects like mirrors. In the former case, the refractive index distribution is measured and then related to various properties like temperature, density, chemical composition, or thickness. In the latter case, the measured phase distribution is related to the object shape. The objects measured must be stationary or quasisteady state because the measurement requires the acquisition of several frames of image data during which time the object's properties must not have changed. The data acquisition time depends on the speed of the frame grabber and the required number of data frames. Typically, three to five frames taking 1 to 2 seconds are required. The potential for faster data acquisition exists.

Mercer, Carolyn R.↗

NASA NTRS1994

Shock waves data for minerals

Shock compression of the materials of planetary interiors yields data which upon comparison with density-pressure and density-sound velocity profiles constrain internal composition and temperature. Other important applications of shock wave data and related properties are found in the impact mechanics of terrestrial planets and solid satellites. Shock wave equation of state, shock-induced dynamic yielding and phase transitions, and shock temperature are discussed. In regions where a substantial phase change in the material does not occur, the relationship between the particle velocity, U(sub p), and the shock velocity, U(sub s), is given by U(sub s) = C(sub 0) + S U(sub p), where C(sub 0) is the shock velocity at infinitesimally small particle velocity, or the ambient pressure bulk sound velocity. Numerical values for the shock wave equation of state for minerals and related materials of the solar system are provided.

Ahrens, Thomas J.↗

NASA NTRS2004

Aqueous Alteration of Carbonaceous Chondrites: New Insights from Comparative Studies of Two Unbrecciated CM2 Chondrites, Y 791198 and ALH 81002

Carbonaceous chondrites are an important resource for understanding the physical and chemical conditions in the early solar system. In particular, a long-standing question concerns the role of water in the cosmochemical evolution of carbonaceous chondrites. It is well established that extensive hydration of primary nebular phases occurred in the CM and CI chondrites, but the location where this alteration occurred remains controversial. In the CM2 chondrites, hydration formed secondary phases such as serpentine, tochilinite, pentlandite, carbonate and PCP. There are several textural observations which suggest that alteration occurred before the accretion of the final CM parent asteroid, i.e. preaccretionary alteration. Conversely, there is a significant body of evidence that supports parent-body alteration. In order to test these two competing hypotheses further, we studied two CM chondrites, Y-791198 and ALH81002, two meteorites that exhibit widely differing degrees of aqueous alteration. In addition, both meteorites have primary accretionary textures, i.e. experienced minimal asteroidal brecciation. Brecciation significantly complicates the task of unraveling alteration histories, mixing components that have been altered to different degrees from different locations on the same asteroidal parent body. Alteration in Y-791198 is mostly confined to chondrule mesostases, FeNi metal and fine-grained matrix and rims. In comparison, the primary chondrule silicates in ALH81002 have undergone extensive replacement by secondary hydrous phases. This study focuses on compositional and textural relationships between chondrule mesostasis and the associated rim materials. Our hypothesis is: both these components are highly susceptible to aqueous alteration and should be sensitive recorders of the alteration process. For parent body alteration, we expect systematic coupled mineralogical and compositional changes in rims and altered mesostasis, as elemental exchange between these components occurs. Conversely, for preaccretionary alteration, there should be no clear relationships between the rims and mesostases.

Chizmadia, L. J.↗

NASA NTRS2006

Laboratory Studies on the Formation of Carbon-Bearing Molecules in Extraterrestrial Environments: From the Gas Phase to the Solid State

A detailed knowledge of the formation of carbon-bearing molecules in interstellar ices and in the gas phase of the interstellar medium is of paramount interest to understand the astrochemical evolution of extraterrestrial environments (1). This research also holds strong implications to comprehend the chemical processing of Solar System environments such as icy planets and their moons together with the atmospheres of planets and their satellites (2). Since the present composition of each interstellar and Solar System environment reflects the matter from which it was formed and the processes which have changed the chemical nature since the origin (solar wind, planetary magnetospheres, cosmic ray exposure, photolysis, chemical reactions), a detailed investigation of the physicochemical mechanisms altering the pristine environment is of paramount importance to grasp the contemporary composition. Once these underlying processes have been unraveled, we can identify those molecules, which belonged to the nascent setting, distinguish molecular species synthesized in a later stage, and predict the imminent chemical evolution of, for instance, molecular clouds. Laboratory experiments under controlled physicochemical conditions (temperature, pressure, chemical composition, high energy components) present ideal tools for simulating the chemical evolution of interstellar and Solar System environments. Here, laboratory experiments can predict where and how (reaction mechanisms; chemicals necessary) in extraterrestrial environments and in the interstellar medium complex, carbon bearing molecules can be formed on interstellar grains and in the gas phase. This paper overviews the experimental setups utilized in our laboratory to mimic the chemical processing of gas phase and solid state (ices) environments. These are a crossed molecular beams machine (3) and a surface scattering setup (4). We also present typical results of each setup (formation of amino acids, aldehydes, epoxides; synthesis of hydrogen terminated carbon chains as precursors to complex PAHs and to carbonaceous dust grains in general; nitriles as precursor to amino acids).

Jamieson, C. S.↗

DOE OSTI2020

Fast-current-heating devices to study in situ phase formation in metallic glasses by using high-energy synchrotron radiation

Details of fast-resistive-heating setups, controlled heating ranging from ~10 1 K s –1 to ~10 3 K s –1 , to study in situ phase transformations (on heating and on cooling) in metallic glasses by high-energy synchrotron x-ray diffraction are discussed here. Both setups were designed and custom built at the Leibniz Institute for Solid State and Materials Research Dresden (IFW Dresden) and have been implemented at the P02.1 Powder Diffraction and Total Scattering Beamline and the P21.1 Swedish Materials Science Beamline at PETRA III storage ring, DESY, Hamburg. The devices are interchangeable at both beamlines. Joule heating is triggered automatically and is timed with the incident beam and detector. The crystallization process can be controlled via a feedback circuit by monitoring the change in the time-dependent resistivity and temperature of glasses. Different ambient atmospheres, such as vacuum and inert gases (He and Ar), can be used to control oxidation and cooling. The main focus of these devices is on understanding the crystallization mechanism and kinetics in metallic glasses, which are brittle and for which fast heating gives defined glass–crystal composites with enhanced plasticity. As an example, phase-transformation sequence(s) in a prototyped Cu–Zr-based metallic glass is described on heating, and a crystalline phase beneficial to the plasticity is identified.

47 OTHER INSTRUMENTATION↗

DOE OSTI2021

Passivation-driven speciation, dealloying and purification

Thin passivating surface oxide layers on metal alloys form a dissipation horizon between dissimilar phases, hence harbour an inherent free energy and composition gradient. We exploit this gradient to drive order and selective surface separation (speciation), enabling redox-driven enrichment of the core by selective conversion of low standard reduction potential (E°) components into oxides. Additionally, coupling this oxide growth to volumetric changes during solidification allows us to create oxide crystallites trapped in a metal (‘ship-in-a-bottle’) or extrusion of metal fingerlings on the heavily oxidized particle. We confirm the underlying mechanism through high temperature X-ray diffraction and characterization of solidification-trapped particle states. We demonstrate that engineering the passivating surface oxide can lead to purification via selective dealloying with concomitant enrichment of the core, leading to disparate particle morphologies.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Designing order–disorder transformation in high-entropy ferritic steels

Order–disorder transformations hold an essential place in chemically complex high-entropy ferritic steels (HEFSs) due to their critical technological application. The chemical inhomogeneity arising from mixing of multi-principal elements of varying chemistry can drive property altering changes at the atomic scale, in particular short-range order. Using density-functional theory-based linear-response theory, we predict the effect of compositional tuning on the order–disorder transformation in ferritic steels—focusing on Cr–Ni–Al–Ti–Fe HEFSs. We show that Ti content in Cr–Ni–Al–Ti–Fe solid solutions can be tuned to modify short-range order that changes the order–disorder path from BCC-B2 (Ti atomic-fraction = 0) to BCC-B2-L2 1 (Ti atomic-fraction > 0) consistent with existing experiments. Our study suggests that tuning degree of SRO through compositional variation can be used as an effective means to optimize phase selection in technologically useful alloys.

36 MATERIALS SCIENCE↗

NASA NTRS1997

Modeling of Gallium Nitride Hydride Vapor Phase Epitaxy

A reactor model for the hydride vapor phase epitaxy of GaN is presented. The governing flow, energy, and species conservation equations are solved in two dimensions to examine the growth characteristics as a function of process variables and reactor geometry. The growth rate varies with GaCl composition but independent of NH3 and H2 flow rates. A change in carrier gas for Ga source from H2 to N2 affects the growth rate and uniformity for a fixed reactor configuration. The model predictions are in general agreement with observed experimental behavior.

Meyyappan, Meyya↗

NASA NTRS1979

Technology development for phosphoric acid fuel cell powerplant (phase 2)

The status of technology for the manufacturing and testing of 1200 sq. cm cell materials, components, and stacks for on-site integrated energy systems is assessed. Topics covered include: (1) preparation of thin layers of silicon carbide; (2) definition and control schemes for volume changes in phosphoric acid fuel cells; (3) preparation of low resin content graphite phenolic resin composites; (4) chemical corrosion of graphite-phenolic resin composites in hot phosphoric acid; (5) analysis of electrical resistance of composite materials for fuel cells; and (6) fuel cell performance and testing.

Christner, L.↗

DOE OSTI2025

Coaxial Direct Ink Writing of Cholesteric Liquid Crystal Elastomers in 3D Architectures

Abstract Cholesteric liquid crystal elastomers (CLCEs) hold great promise for mechanochromic applications in anti‐counterfeiting, smart textiles, and soft robotics, thanks to the structural color and elasticity. While CLCEs are printed via direct ink writing (DIW) to fabricate free‐standing films, complex 3D structures are not fabricated due to the opposing rheological properties necessary for cholesteric alignment and multilayer stacking. Here, 3D CLCE structures are realized by utilizing coaxial DIW to print a CLC ink within a silicone ink. By tailoring the ink compositions, and thus, the rheological properties, the cholesteric phase rapidly forms without an annealing step, while the silicone shell provides encapsulation and support to the CLCE core, allowing for layer‐by‐layer printing of self‐supported 3D structures. As a demonstration, free‐standing bistable thin‐shell domes are printed. Color changes due to compressive and tensile stresses can be witnessed from the top and bottom of the inverted domes, respectively. When the domes are arranged in an array and inverted, they can snap back to their base state by uniaxial stretching, thereby functioning as mechanical sensors with memory. The additive manufacturing platform enables the rapid fabrication of 3D mechanochromic sensors thereby expanding the realm of potential applications for CLCEs.

36 MATERIALS SCIENCE↗

DOE OSTI2023

Dynamic Oscillation and Motion of Oil‐in‐Water Emulsion Droplets

Abstract The interplay of interfacial tensions on droplets results in a range of self‐powered motions that mimic those of living systems and serve as a tunable model to understand their complex non‐equilibrium behavior. Spontaneous shape deformations and oscillations are crucial features observed in nature but difficult to incorporate in synthetic artificial systems. Here, we report sessile oil‐in‐water emulsions that exhibit rapid oscillating behavior. The oscillations depend on the nature and concentration of the surfactant, the chemical composition of the oil, and the wettability of the solid substrate. The rapid changes in the contact angle per oscillation are observed using side‐view optical microscopy. We propose that the changes in the interfacial tension of the oil droplets is due to the partitioning of the surfactant into the oil phase and the movement of self‐emulsified oil out of the parent droplets giving rise to the rhythmic variation in droplet contact‐line. The ability to control and understand droplet oscillation can help model similar oscillations in out‐of‐equilibrium systems in nature and reproduce biomimetic behavior in artificial systems for various applications, such as microfluidic lab‐on‐a‐chip and adaptive materials.

Krishna Mani, Sanjana↗

DOE OSTI2023

Dynamic Oscillation and Motion of Oil‐in‐Water Emulsion Droplets

The interplay of interfacial tensions on droplets results in a range of self‐powered motions that mimic those of living systems and serve as a tunable model to understand their complex non‐equilibrium behavior. Spontaneous shape deformations and oscillations are crucial features observed in nature but difficult to incorporate in synthetic artificial systems. Here, we report sessile oil‐in‐water emulsions that exhibit rapid oscillating behavior. The oscillations depend on the nature and concentration of the surfactant, the chemical composition of the oil, and the wettability of the solid substrate. The rapid changes in the contact angle per oscillation are observed using side‐view optical microscopy. We propose that the changes in the interfacial tension of the oil droplets is due to the partitioning of the surfactant into the oil phase and the movement of self‐emulsified oil out of the parent droplets giving rise to the rhythmic variation in droplet contact‐line. The ability to control and understand droplet oscillation can help model similar oscillations in out‐of‐equilibrium systems in nature and reproduce biomimetic behavior in artificial systems for various applications, such as microfluidic lab‐on‐a‐chip and adaptive materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Revisiting metastable immiscibility in SiO 2 –Al 2 O 3 : Structure and phase separation of supercooled liquids and glasses

Understanding and controlling liquid–liquid phase separation in aluminosilicates is crucial for optimizing glass properties. However, the metastable nature of aluminosilicates’ phase separation has made it difficult to study experimentally, and uncertainty persists regarding the compositional and temperature extents of the miscibility gap. Here, we present new experimental evidence that suggests a consolute temperature between 1440 and 1590°C and endmember compositions of 7 and 62 mol.% Al 2 O 3 for the phase-separated glasses. Using containerless melt processing, deeply supercooled liquids over the 0–60 mol.% Al 2 O 3 range are probed with in situ small- and wide-angle X-ray scattering, which simultaneously reveals changes in nanoscale density heterogeneity and atomic structure. Correlations between phase separation and atomic coordination environments are compared for liquids and glasses. Pair distribution function analysis shows mean O–(Si + Al) coordination increases with Al 2 O 3 content and decreases with temperature.

36 MATERIALS SCIENCE↗

NASA NTRS2005

Pressure Vessel with Impact and Fire Resistant Coating and Method of Making Same

An impact and fire resistant coating laminate is provided which serves as an outer protective coating for a pressure vessel such as a composite overwrapped vessel with a metal lining. The laminate comprises a plurality of fibers (e.g., jute twine or other, stronger fibers) which are wound around the pressure vessel and an epoxy matrix resin for the fibers. The epoxy matrix resin including a plurality of microspheres containing a temperature responsive phase change material which changes phase in response to exposure thereof to a predetermined temperature increase so as to afford increased insulation and hear absorption.

Thomas K DeLay↗