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Results for “Polymer-derived ceramic”

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.

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36 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Customized Nanostructured Ceramics via Microphase Separation 3D Printing

To date, the restricted capability to fabricate ceramics with independently tailored nano- and macroscopic features has hindered their implementation in a wide range of crucial technological areas, including aeronautics, defense, and microelectronics. In this study, a novel approach that combines self- and digital assembly to create polymer-derived ceramics with highly controlled structures spanning from the nano- to macroscale is introduced. Polymerization-induced microphase separation of a resin during digital light processing generates materials with nanoscale morphologies, with the distinct phases consisting of either a preceramic precursor or a sacrificial polymer. By precisely controlling the molecular weight of the sacrificial polymer, the domain size of the resulting material phases can be finely tuned. Pyrolysis of the printed objects yields ceramics with complex macroscale geometries and nanoscale porosity, which display excellent thermal and oxidation resistance, and morphology-dependent thermal conduction properties. This method offers a valuable technological platform for the simplified fabrication of nanostructured ceramics with complex shapes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Structural and thermodynamic evolution of an amorphous SiOC ceramic after swift heavy ion irradiation

Radiation induced structural and energetic changes have been widely studied in crystalline materials, but studied to a much lesser extent in amorphous solids. Using a combination of neutron pair distribution function (PDF) analysis and high temperature oxide melt solution calorimetry, we obtained critical insights into the structural and energetic evolution in a swift heavy ion irradiated amorphous SiOC polymer-derived ceramic. The radiation modified SiOC structure becomes energetically less stable by 24.0±1.6 kJ/mol compared to the unirradiated structure. This destabilization is related to decreased connectivity of the Si-O-C network and destruction of free carbon. In comparison with unirradiated SiOC, the irradiated structure is more likely to become phase separated during subsequent thermal annealing. Here, our study has important implications for evaluating amorphous SiOC ceramic as a possible radiation resistant structure for nuclear applications.

36 MATERIALS SCIENCE↗
DOE OSTI2026

The Influence of Residual Copper Catalyst on the Polymer-to-Ceramic Conversion of a Click-Derived Polycarbosilane

Preceramic polymers (PCPs) are a key class of materials for the preparation of advanced ceramic components. Following conventional polymer processing and subsequent pyrolysis, polymer-derived ceramic (PDC) fibers, monoliths, and composites offer novel engineering opportunities for aerospace applications. Despite the rapidly emerging commercial applications of PDCs, many basic scientific questions remain regarding the structural transformation of the polymer to the final ceramic and how processing variables affect PDC materials properties. PCPs prepared using a mild and scalable copper (Cu) catalyzed azide/alkyne “click” reaction have been demonstrated as a unique class of material that can bind with transition metals, ultimately producing ultrahigh temperature ceramics (UHTCs) upon pyrolysis. Unexpectedly, it was found that the removal of residual Cu catalyst from a model click-derived polycarbosilane PCP significantly reduced the ceramic yield during pyrolysis. Herein, we report the influence of Cu impurities on polycarbosilane-derived SiC ceramics and present a mechanistic understanding of the unintended role of Cu in the polymer-to-ceramic conversion process. Synchrotron-based scattering and spectroscopy methods were implemented to track the evolution of different atomic species and local structures as well as the influence of Cu toward atomic-scale structures in the final ceramics. It was determined that Cu impurities catalyze the formation of silicon carbide through the formation of an intermediate molten copper/copper silicide, ultimately increasing the ceramic yield. Overall, this contribution highlights the need to carefully assess the interplay between the chemistries needed for PCP synthesis and their potential influence on final PDCs following processing.

Ponder, Jr., James F. [Air Force Research Laborato↗
DOE OSTI2022

Influence of Thermal Treatment on Preceramic Polymer Grafted Nanoparticle Network Formation: Implications for Thermal Protection Systems and Aerospace Propulsion Components

Preceramic polymer grafted nanoparticles (PCP GNPs) offer potential advantages in the production of polymer-derived ceramic composites compared to neat preceramic polymers (PCPs), such as reduced thermal shrinkage and increased char yield. In comparison to traditional composites (particles + free polymer), PCPs avoid issues of compatibility, agglomeration, and phase separation during processing and provide routes to control nanoparticle arrangement. Prior literature has established that the conversion efficiency of PCPs and PCP GNPs to ceramics and ceramic composites is linked to the thermal pretreatment of these precursor polymers (e.g., curing). In this paper, we investigate the material transformations that occur when exposing PCP GNPs to a low-temperature thermal treatment (≤250 °C) prior to pyrolysis. The PCP GNPs explored in this study possessed silica nanoparticle cores but were distinct in their PCP coronas, having poly(1,1-dimethylpropylsilane) (allyl-GNP)- or poly(1,1-dimethylbenzylethylsilane) (styryl-GNP)-grafted polymers. After undergoing low-temperature thermal treatment, these PCP GNPs exhibited increased char yield at 800 °C; however, unlike commercial PCPs (e.g., allylhydridopolycarbosilane (SMP-10)), obvious cross-linkable sites are not present in the PCP corona structure. Differential scanning calorimetry, oscillatory rheology, and X-ray photon correlation spectroscopy were utilized to elucidate the thermally induced material changes in the allyl- and styryl-GNPs. Thermally induced changes to the structure and behavior of the PCP GNPs were determined to be linked to the chemical structure of the grafted polycarbosilane chains. Styryl-GNPs experienced a curing event between 180 and 250 °C, effecting the formation of a network, which contributed to char yield improvement (at 800 °C). The nanoscale dynamics of this material also shows a transition from diffuse behavior to ballistic behavior because of the cross-linking event. Conversely, the allyl-GNPs did not exhibit a curing event under heat treatment but did show an increase in thermally induced physical cross-linking. The allyl-GNP physical network is stronger after the first cycle of thermal treatment, and it is considered that this contributed to the improvement in char yield post thermal treatment. The advancements in the understanding of the cross-linking behavior of these hybrid materials are expected to advance the application of these materials to turbine engine, advanced friction, and heat-shielding components.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Coal as Value-Added for Lithium Battery Anodes (Final Report)

Graphite is a basic material used for energy storage in lithium-ion (Li-ion) batteries. More than 70% of worldwide graphite production and nearly 50% of the annual graphite supply for the United States comes from China. Potential economic and national security concerns exist because Li-ion batteries are used not only for the fast-growing electrical vehicle market (15.6% compound annual growth rate [CAGR] from 2018 to 2028 in North America), but also for defense applications including unmanned aerial and ground vehicles. Development of an alternative formulation for Li-ion batteries is key. Building upon previous research confirming the ability of silicon alloys to improve the energy density of anodes, Semplastics developed a novel material based on our X-MAT® polymer-derived ceramic (PDC) technology. The X-MAT anode material is a composite of chemically tailored silicon oxycarbide (SiOC) and domestically sourced coal powder, designed to be a drop-in replacement for graphite within Li-ion battery anodes. Preliminary tests of this material showed more than twice the reversible capacity of graphite anodes (1,000 mAh/g vs. 372 mAh/g), with excellent stability and capacity retention, almost 100% coulombic efficiency, low voltage potential, and low thermal expansion. At full adoption in 2024, we expect the coal utilization to reach 27,300 tons. Through this project, Semplastics proposed to complete development and begin commercialization of this material. The objective was to determine the best formulation for technical performance and economic viability. At the end of the project, the X-MAT anode material is ready for implementation into existing battery manufacturing processes and can have a significant impact on the utilization of coal, with positive effects for the mining sector and the mitigation of carbon dioxide (CO 2 ) emissions.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2023

Low Weight, High Strength Coal-Based Building Materials for Infrastructure Products (Rev.A)

Semplastics has developed, tested, and proven the viability of a new class of composite infrastructure components that use coal as the primary component. Phase I resulted in the production of brick and block components, called X-BRIX and X-BLOX, with dimensions comparable to commercially available bricks and concrete blocks, but with superior mechanical strength, lower weight, greater hardness, improved toughness, greater abrasion resistance, and greater chemical resistance than concrete. Multiple samples of full-size (16” × 8” × 8”) X-BLOX and full-size (8” × 4” × 2.5”) X-BRIX were made to demonstrate the technology, and to support the development of mortar or joining techniques. Phase I moved the coal-based composite materials technology from a current Technology Readiness Level (TRL) of 3 to TRL 5. Semplastics’ coal-based composite materials exhibit a number of high-performance characteristics, including high strength (five times the flexure strength of the best commercial brick, and more than twice the compressive strength of construction-grade concrete block), lower density (by 37 to 41%), improved mechanical durability and abrasion resistance, and resistance to chemicals, acids, salts, and chemical wastewater. These properties offer significant improvements over conventional bricks, concrete blocks, and pavers. The coal particles are completely encapsulated and bonded using a specially formulated polymer-derived ceramic (PDC) that is cured to form an “aggregate” of coal and PDC resin. This aggregate can be further processed and lightly pressed (at 10 to 50 psi) to produce a brick. After pyrolyzing (similar to the processing used to make standard clay bricks), the finished coal-based brick is significantly harder and more abrasion-resistant than regular bricks. We have produced prototype X-BRIX and X-BLOX that contain at least 55% coal by weight (71% carbon by weight, due to the controlled carbon content of the PDC) and showed their superior mechanical properties through in-house and contracted testing.

01 COAL, LIGNITE, AND PEAT↗
NASA NTRSDate not supplied

Material Response Analysis of PICA-NuSil at the Hypersonic Materials Environmental Test System

Phenolic impregnated carbon ablator (PICA) is a thermal protection system (TPS) that gained heritage during the Stardust mission and is the baseline TPS material for expeditions to Mars (e.g., Mars Science Laboratory and Mars 2020).1 PICA is friable; therefore, a polysiloxane resin (NuSil CV-1144-0) is deposited onto the surface of flight hardware before assembly, test, and launch operations (ATLO) to mitigate particle shedding. Furthermore, the Mars Science Laboratory (MSL) and Mars 2020 heatshields were instrumented with an array of thermocouple plugs (MEDLI Integrated Sensor Plugs or MISP) designed to measure the in-depth thermal response of PICA during flight. Post-flight analysis of MISP data suggests that recession was lower than predicted, and NuSil is suspected as a reasonable cause. NuSil primarily consists of a copolymer blend of dimethyl and diphenyl-substituted polysiloxane resin. Four decades of research in the field of polymer-derived ceramics demonstrate that polysiloxane resins form oxidation-resistant silicon oxycarbide materials at pyrolysis temperatures as low as 800 °C. -2 Furthermore, silicon oxycarbide materials exhibit excellent thermal stability at relatively high-temperatures (< 1200 °C) but eventually decompose via carbothermal reduction. -3 Therefore, it is reasonable to suggest that NuSil forms an oxidation-resistant thermal barrier coating on the TPS surface and influences the material response during atmospheric entry. Evidence for this notion was observed during prior arc-jet testing at both the Aerodynamic Heating Facility (AHF) and the Panel Test Facility (PTF) at the NASA Ames Research Center. Articles of PICA were subjected to testing in airflow, and a temperature discontinuity was recorded at the surface of coupons coated with NuSil. A glassy coating was observed to form at the surface in shear flow configurations (wedge and panel) under moderate heat fluxes. Furthermore, state-of-the-art material response models have yet to account for the underlying physics and chemistry of the temperature discontinuity. To this end, a pathfinder test campaign was executed at the Hypersonic Materials Environmental Test System (HyMETS) to enhance the fundamental understanding of PICA-NuSil ablation phenomena and provide a preliminary data set to aid in the development of material response models.

PICA↗
DOE OSTI2025

Elucidation of Local Ordering and Atomic-Scale Structure in Polymer-Derived SiOC

Silicon oxycarbide (SiOC) is a versatile ceramic material with tunable microstructure and compositions that can be modulated through precursor chemistry and processing conditions. Though there are several noteworthy uses of SiOC across a range of application spaces, the difficulties in elucidating the short- to medium-range order within these materials have limited the maturation of strategies to precisely control SiC x O 4–x compositions for user-tailored applications. In this contribution, we implement a range of synchrotron scattering and spectroscopy methods coupled with stochastic modeling techniques to elucidate changes in local chemistry and structure associated with the pyrolysis of a commercially available SiOC polymer precursor. Stochastic modeling approaches provide valuable insights into decoupling local Si–O and Si–C environments while confirming predominate heterogeneous phases in materials. Using pyrolysis temperatures between 250 to 800 °C results in a heterogeneous material predominately composed of SiOC and amorphous SiO 2 domains. At 1100 °C, redistribution of Si–C pairs in the SiOC network and Si–O from the SiO 2 domains create a more ordered SiOC phase with local cubic SiC-like ordering. In addition, residual carbon leads to a detectable carbon phases at 1100 °C that persist at higher temperatures. These efforts address the difficulties of obtaining atomic-scale insights into the local structure and nanoscale heterogeneities in SiOC, providing pathways toward establishing structure–property relationships for future materials development.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1992

Approaches to polymer-derived CMC matrices

The use of polymeric precursors to ceramics permits the fabrication of large, complex-shaped ceramic matrix composites (CMC's) at temperatures which do not degrade the fiber. Processing equipment and techniques readily available in the resin matrix composite industry can be adapted for CMC fabrication using this approach. Criteria which influence the choice of candidate precursor polymers, the use of fillers, and the role of fiber architecture and ply layup are discussed. Three polymer systems, polycarbosilanes, polysilazanes, and polysilsesquioxanes, are compared as candidate ceramic matrix precursors.

Hurwitz, Frances I.↗
NASA NTRS1992

Approaches to polymer-derived CMC matrices

The use of polymeric precursors to ceramics permits the fabrication of large, complex-shaped ceramic matrix composites (CMC's) at temperatures which do not degrade the fiber. Processing equipment and techniques readily available in the resin matrix composite industry can be adapted for CMC fabrication using this approach. Criteria which influence the choice of candidate precursor polymers, the use of fillers, and the role of fiber architecture and ply layup are discussed. Three polymer systems, polycarbosilanes, polysilazanes, and polysilsesquioxanes, are compared as candidate ceramic matrix precursors.

Hurwitz, Frances I.↗
NASA NTRS2021

Microstructural, Strength, and Creep Characterization of Sylramic™, Sylramic™-iBN and Super Sylramic™-iBN SiC Fibers

The chemical composition, microstructure, strength, and thermal stability of polymer-derived Sylramic™ SiC fibers fabricated by Dow Corning and COI Ceramics, Inc., and nitrogen-treated Sylramic™ SiC fibers, referred to as Sylramic™-iBN and Super Sylramic™-iBN SiC fibers, were investigated and compared. The baseline Sylramic™ SiC fibers fabricated by both vendors as well as the nitrogen-treated Sylramic™ SiC fibers are composed mostly of β-SiC (~97 wt%) with small amounts of TiB2 (~2 wt%), amorphous carbon (~1 wt%) and trace amounts of B4C. Most of the amorphous carbon is segregated at the core/interior of the fibers. Both baseline and nitrogen-treated Sylramic™ SiC fibers have similar grain size and pore size distribution, except for a thin layer of in-situ grown crystalline BN (30 to 70 nm) on the surface of Sylramic™-iBN and Super Sylramic™-iBN fibers. Wide variation in strength within a batch as well as between batches is observed in both baseline and nitrogen-treated Sylramic™ SiC fibers but both types of fibers are microstructurally stable at temperatures to 1800°C in argon and nitrogen environments compared to Nicalon™-S and Tyranno®-SA SiC fibers. Under the same creep condition, Super Sylramic™-iBN fibers show better creep resistance compared to Sylramic™, Sylramic™-iBN, Hi-Nicalon™-S, and Tyranno®-SA fibers. Possible reasons for strength variability and the mechanism of in-situ BN formation on Sylramic™ SiC fibers are discussed.

SiC fibers↗
DOE OSTI2020

Polymer-derived SiC/C/Al environmental barrier coatings on carbon steel

Carbon steel is a widely used structural material; however, it lacks corrosion resistance in water environments. An alternative approach to overcome this challenge is to implement the deposition of inherently corrosion-resistant ceramic coatings. SiC/C/Al coatings were developed at 700°C, using polycarbosilane in combination with Al and C, which were included as active and passive fillers, respectively. Here, we show that it is necessary to use Al particle sizes below 10 µm for them to function as an active filler below 900°C. Owing to their laminar microstructure, these coatings showed a cohesive delamination with an adhesion strength of 10 MPa. Results demonstrated that these coatings were able to reduce the corrosion of carbon steel in saline water by 99.7%, with corrosion rates of 38.33 mpy for carbon steel, and 0.099 and 0.155 mpy for SiC/C and SiC/C/Al (10 µm) coatings, respectively.

36 MATERIALS SCIENCE↗
NASA NTRS1999

Comparison of the Tensile, Creep, and Rupture Strength Properties of Stoichiometric SiC Fibers

Tensile strength, creep strength, and rupture strength properties were measured for the following types of polymer-derived stoichiometric SiC fibers: Hi-Nicalon Type S from Nippon Carbon, Tyranno SA from Ube, and Sylramic from Dow Corning. Also included in this study were an earlier version of the SA fiber plus two recent developmental versions of the Sylramic fiber. The tensile strength measurements were made at room temperature on as-received fibers and on fibers after high-temperature inert exposure. The creep-rupture property data were obtained at 1400 deg C in air as well as, argon. Some fiber types showed strong effects of environment on their strength properties. These results are compared and discussed in terms of underlying mechanisms and implications for ceramic composites.

Yun, H. M.↗
DOE OSTI2022

Thermal properties of field-assisted-sintered SiCN–Y 2 O 3 composites

Polymer-derived amorphous SiCN has excellent high-temperature stability and properties. To reduce the shrinkage during pyrolysis and to improve the high-temperature oxidation resistance, Y 2 O 3 was added as a filler. In this study, polymer-derived SiCN–Y 2 O 3 composites were fabricated by mixing a polymeric precursor of SiCN with Y 2 O 3 submicron powders in different ratios. The mixtures were cross-linked and pyrolyzed in argon. SiCN–Y 2 O 3 composites were processed using field-assisted sintering technology at 1350°C for 5 min under vacuum. Dense SiCN–Y 2 O 3 composite pellets were successfully made with relative density higher than 98% and homogeneous microstructure. Due to low temperature and short time of the heat-treatment, the grain growth of Y 2 O 3 was substantially inhibited. The Y 2 O 3 grain size was ~1 μm after sintering. The composites’ heat capacity, thermal diffusivity, and thermal expansion coefficients were characterized as a function of temperature. The thermal conductivity of the composites ceramics decreased as the amount of amorphous SiCN increased and the coefficient of thermal expansion (CTE) of the composites increased with Y 2 O 3 content. However, the thermal conductivity and CTE did not follow the rule of mixture. This is likely due to the partial oxidation of SiCN and the resultant impurity phases such as Y 2 SiO 5 , Y 2 Si 2 O 7 , and Y 4.67 (SiO 4 ) 3 O.

36 MATERIALS SCIENCE↗
DOE OSTI2021

AOI [1]: Passive Wireless Sensor Systems Fabricated by Direct-Writing for Temperature and Health Monitoring of Energy Systems in Harsh-Environments (Final Report)

Researchers at West Virginia University (WVU) propose to demonstrate a wireless, high-temperature sensor system for monitoring the temperature and health of energy-system components. The active sensor and electronics for wireless communication will be composed entirely of an electroceramic materials (conductive ceramics) which are capable of withstanding the harsh-environments required for fossil energy-based technologies. This work will focus primarily on the fabrication and testing of temperature (thermocouples and thermistors) and health (strain/stress and crack propagation sensors) that function at extreme temperatures (up to 700-1700ºC). The electronics will accompany the high-temperature sensor, which will include a passive wireless communication circuit that allows the transmission of the data based on the LCR resonance principle to a near-by reader antenna. This passive transmission of data will reduce the need for interconnect wires near the active, and possibly rotating, energy-system component. The research will include process development to permit the 2D/3D direct-writing of the entire sensor and communication circuit onto the energy-system component. The direct-writing will be facilitated by using silicon-based polymer-derived precursors to form the high-temperature, stable electroceramic compositions. In addition, methods for direct-writing the circuit onto a fugitive carrier substrate will be completed, which will permit a “peel-and-stick”-like transfer of the sensor circuit to the energy-system component. This feature will allow the economical and precise placement of the sensor circuit onto components of various shapes and locations, without altering the geometry and active features of the manufactured component, or the removal (or decommissioning) of the component for installation. The proposed work will be directed at the following areas: 1) Investigation of phase formation, sintering/grain growth, and electrical properties of polymer-derived electroceramic composites; 2) Definition of processes to direct-write through ink-jet and robo-casting the polymer-derived electroceramic composites onto oxide and polymer surfaces; 3) Development of methods to form monolithic "peel-and-stick" preforms that will efficiently transfer the sensor circuit to ceramic surfaces after thermal treatment; 4) Design of passive wireless LCR circuits and receiver (reader) antennas for communication and testing at high temperatures; 5) Investigation of the passive wireless sensor system developed (and method of transferring sensor system) for temperature and stress/strain measurements on a SOFC repeat unit and a singular gas turbine blade prototype as example applications.

01 COAL, LIGNITE, AND PEAT↗