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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Glancing Angle Deposition in Gas Sensing: Bridging Morphological Innovations and Sensor Performances

Glancing Angle Deposition (GLAD) has emerged as a versatile and powerful nanofabrication technique for developing next-generation gas sensors by enabling precise control over nanostructure geometry, porosity, and material composition. Through dynamic substrate tilting and rotation, GLAD facilitates the fabrication of highly porous, anisotropic nanostructures, such as aligned, tilted, zigzag, helical, and multilayered nanorods, with tunable surface area and diffusion pathways optimized for gas detection. This review provides a comprehensive synthesis of recent advances in GLAD-based gas sensor design, focusing on how structural engineering and material integration converge to enhance sensor performance. Key materials strategies include the construction of heterojunctions and core–shell architectures, controlled doping, and nanoparticle decoration using noble metals or metal oxides to amplify charge transfer, catalytic activity, and redox responsiveness. GLAD-fabricated nanostructures have been effectively deployed across multiple gas sensing modalities, including resistive, capacitive, piezoelectric, and optical platforms, where their high aspect ratios, tailored porosity, and defect-rich surfaces facilitate enhanced gas adsorption kinetics and efficient signal transduction. These devices exhibit high sensitivity and selectivity toward a range of analytes, including NO2, CO, H2S, and volatile organic compounds (VOCs), with detection limits often reaching the parts-per-billion level. Emerging innovations, such as photo-assisted sensing and integration with artificial intelligence for data analysis and pattern recognition, further extend the capabilities of GLAD-based systems for multifunctional, real-time, and adaptive sensing. Finally, current challenges and future research directions are discussed, emphasizing the promise of GLAD as a scalable platform for next-generation gas sensing technologies.

Chemistry↗
DOE OSTI2019

Deformation Behavior and Microstructure Evolution of Powder Metallurgy Ti6Al4V Alloy During Hot Compression

In order to determine appropriate workability parameters for cross-wedge rolling products of powder metallurgy (PM) Ti6Al4V alloys, thermal compression experiments were carried out within the temperature range of 850-1050 °C, the strain rate range of 0.1-10 s{sup −1}, and with a height decrease of 60%. The compression deformation behavior was investigated. A strain-compensated constitutive model was established based on the flow stress curves corrected by the friction, which can predict the flow behaviors under the entirety of the experimental deformation conditions. Moreover, the processing map was developed, and stable and unstable deformation regimes were established. The microstructure analysis illustrated that globularization and dynamic recrystallization were the main deformation mechanisms. The porosity of the compressed samples was greatly reduced and influenced by the temperature and strain rate. Considering the material flow stress, hot processing map, microstructure and porosity, the appropriate hot deformation parameters for PM Ti6Al4V alloy preforms are suggested.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Investigation of the Mechanical Properties of GdBa{sub 2}Cu{sub 3}O{sub 7−δ} Added with Nanosized Ferrites ZnFe{sub 2}O{sub 4} and CoFe{sub 2}O{sub 4} Using Ultrasonic Measurement

Recently, there is much interest in studying the effect of nanosized ferrites addition on high- T{sub c} superconductors. However, little information is available on the mechanical properties. We have investigated the effect of (CoFe{sub 2}O{sub 4}){sub x} and (ZnFe{sub 2}O{sub 4}){sub x} nanosized ferrites with 0.01 ≤ x ≤ 0.40 on the mechanical properties of the high- T{sub c} superconducting compound GdBa{sub 2}Cu{sub 3}O{sub 7−δ} (Gd-123) prepared by the conventional solid-state reaction technique. Elastic parameters including shear modulus (G), bulk modulus (B), and Young’s modulus (E) of all samples were inspected using ultrasonic measurements and compared with Vickers microhardness results. Furthermore, the porosity of the samples was investigated and correlated to Young’s modulus, which was corrected to zero porosity using different models. The corrected values were correlated with Vickers microhardness. Moreover, the Debye temperature (θ{sub D}) and the electron-phonon coupling factor (λ) were also determined as a function of x. We observed that the different nanoparticles addition has influenced the Gd-123 compound differently. For (ZnFe{sub 2}O{sub 4}){sub x} added samples, the mechanical properties and Debye temperature improved up to x = 0.06, then deteriorated with further addition. However, (CoFe{sub 2}O{sub 4}){sub x} addition improved the mechanical properties for all samples with x up to 0.40. We found that the proportionality constant between the corrected values of E and H{sub v} and G and H{sub v} are strongly dependent on the porosity corrections and the kind of superconducting material. This indicates that the widely used formula E = 81.96 H{sub v} may not be valid for all types of superconducting materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Improvement of the Superconducting Properties of GdBa{sub 2}Cu{sub 3}O{sub 7-δ} with Nano-Sized Ferrite Addition

We have been investigating the effect of (CoFe{sub 2}O{sub 4}){sub x} and (ZnFe{sub 2}O{sub 4}){sub x} (x is the wt%) nano-sized ferrites on the superconducting (SC) properties of the high-T{sub c} SC compound GdBa{sub 2}Cu{sub 3}O{sub 7-δ} (Gd123) prepared by the conventional solid-state reaction technique. In this work, the magnetic hysteresis for pure Gd123 samples and samples added with nano-sized ferrites was measured using a superconducting quantum interference device (SQUID) magnetometer using a dc field up to 30,000 Oe. The magnetic J{sub c} was estimated using the extended Bean model. While a clear increase in J{sub c} values with the addition of (CoFe{sub 2}O{sub 4}){sub x} nano-sized ferrites is observed, a less clear positive effect on the J{sub c} values is observed with the addition of (ZnFe{sub 2}O{sub 4}){sub x} nano-sized ferrites. These results indicate an improvement of grain connectivity, decrease of voids between the grains, and decrease of porosity in Gd123 compound resulting from CoFe{sub 2}O{sub 4} addition consistent with the mechanical properties measured before. (CoFe{sub 2}O{sub 4}){sub x} nano-sized ferrite addition has thus resulted in an improvement in the SC properties of Gd123 high-T{sub c} SC compound making it more convenient for applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Thermophysical Properties of High-Frequency Induction Heat Sintered Graphene Nanoplatelets/Alumina Ceramic Functional Nanocomposites

This paper concerns the thermophysical properties of high-frequency induction heat (HFIH) sintered alumina ceramic nanocomposites containing various graphene nanoplatelets (GNP) concentrations. The GNP/alumina nanocomposites demonstrated high densities, fine-grained microstructures, highest fracture toughness and hardness values of 5.7 MPa m{sup 1/2} and 18.4 GPa, which found 72 and 8%, superior to the benchmarked monolithic alumina, respectively. We determine the role of GNP in tuning the microstructure and inducing toughening mechanisms in the nanocomposites. The sintered monolithic alumina exhibited thermal conductivity value of 24.8 W/mK; however, steady drops of 2, 15 and 19% were recorded after adding respective GNP contents of 0.25, 0.5 and 1.0 wt.% in the nanocomposites. In addition, a dwindling trend in thermal conductions with increasing temperatures was recorded for all sintered samples. Simulation of experimental results with proven theoretical thermal models showed the dominant role of GNP dispersions, microstructural porosity, elastic modulus and grain size in controlling the thermal transport properties of the GNP/alumina nanocomposites. Thermogravimetric analysis showed that the nanocomposite with up to 0.5 mass% of GNP is thermally stable at the temperatures greater than 875 °C. The GNP/alumina nanocomposites owning a distinctive combination of mechanical and thermal properties are promising contenders for the specific components of the aerospace engine and electronic devices having contact with elevated temperatures.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Synthesis of porous Ti–50Ta alloy by powder metallurgy

Highlights: • The proposed preview milling with the next sintering enables the homogeneous porous Ti50Ta (wt).% alloy to be obtained • The α and β nanocrystalline phases were prepared by ball milling. • For the longest sintering time there is complete diffusion of preview milled initial powders • The press and sinter route is proved to be a promising alternative for melted Ti-based biomaterials. - Abstract: The aim of the present study was to assess the possibility of producing porous Ti50Ta (wt%) alloys using powder metallurgy by characterizing the material properties. The influence of the sintering time on the microstructure, mechanical properties, and corrosion behaviour of the produced alloy was investigated. The samples were examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), optic microscopy, X-ray diffraction (XRD) and nanoindentation methods. The XRD results confirmed that nanocrystalline α and β phases were formed during high-energy ball milling. A longer sintering time of 72 h allowed complete interdiffusion of the elements in the pre-milled initial powders. The sintering time significantly influenced the microstructure and porosity. Additionally, the corrosion resistance of the Ti-Ta samples in Ringer's solution was characterized and differences were observed between the samples sintered at different temperatures. The open-circuit potential (E{sub OCP}) and the corrosion potential (E{sub CORR}) of all samples were similar. The sintered Ti50Ta (wt%) alloy showed better corrosion resistance than equivalent Ti or Ta reference samples. We concluded that these alloys had suitable properties for medical implant applications in the future.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Magnetic Mesocellular Foam Functionalized by Curcumin for Potential Multifunctional Therapeutics

The study investigates curcumin/SPIONs hybridized mesocellular foam type silica for potential dual purpose of drug delivery (curcumin) and magnetic resonance imaging. Magnetization capability and curcumin release was assessed for different structured silica such as spherical silica (Q-10), Si-MCM-41, Si-SBA-16, mesocellular foam (MSU-Foam), Si-KIT-6, ULPFDU-12, and silicalite. The phase, textural, and morphological variation was systematically scrutinized using various physico-chemical techniques. Ten weight percent SPIONs loading was found to generate magnetically active SPIONs in the following order: Q-10 (1.44 emu/g) > SBA-16 (0.80 emu/g) > MSU-Foam (0.24 emu/g) > Si-MCM-41 (0.07 emu/g) > Si-KIT-6 (0.07 emu/g) > silicalite (0.08 emu/g), respectively. The iron oxide dispersion, specific surface area, and porosity play a major role in various structured silicas. MSU-Foam with wormhole structure showed highest specific surface area occupation of SPIONs (73%). The presence of interconnected porosity of foam tends to generate external agglomeration of SPIONs (7–18 nm) at the pore surface contributing to expansion of pore sizes from 16.4 to 40.2 nm. The SPIONs over spherical micron-sized silica Q-10 showed the formation of large nanoclusters (10–25 nm). Thirty to 390 μg/ml of curcumin was loaded over silica and SPIONs/silica structured hybrid, and drug release was studied at pH 5.6 for 72 h. SPIONs/MSU-Foam with less magnetization showed the highest cumulative curcumin release (53.2%), while Q-10 spherical silica with high magnetization property showed less cumulative release of curcumin (12%).

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2025

Depolymerization as a Design Strategy: Depolymerization Etching of Polymerization-Induced Microphase Separations

Thermally triggered depolymerization has traditionally been viewed through the lens of sustainability and recycling, not as a constructive tool for materials design. Herein, we show that selective, thermally triggered depolymerization to gaseous monomer serves as a solvent-free strategy for generating porosity in nanostructured polymer materials, offering a means to bypass the mass transport limitations inherent in conventional solution-based etching. As a demonstration platform, we employed polymerization-induced microphase separation (PIMS) to generate disordered bicontinuous block copolymer structures with embedded depolymerizable domains. By incorporating a methacrylate block susceptible to thermal depolymerization within a cross-linked, depolymerization-resistant styrenic matrix, we developed a process we term depolymerization etching of polymerization-induced microphase separations (DEPIMS). This approach enables highly selective and efficient domain removal via reversion to monomer to produce mesoporous materials with high surface areas (>200 m 2 /g). Subsequent surface functionalization yielded mesoporous adsorbents with tunable uptake kinetics and among the highest dye adsorption capacities reported for PIMS-derived materials, demonstrating the adaptability of the DEPIMS platform for chemical separations. DEPIMS can also be extended to a gram-scale, one-pot approach to yield mesoporous materials with recoverable monomer in under 12 h. These findings reposition thermal depolymerization from a sustainability tool to a broadly enabling strategy for scalable, on-demand fabrication of functional nanostructured materials.

Depolymerization↗
DOE OSTI2025

Machine learning approaches for intentional materials engineering

In this article, the development of nanoporous metals and metallic composites through dealloying processes presents significant opportunities in materials engineering. However, designing multicomponent precursor alloys and establishing corresponding processing methods that yield predictable compositions and nanostructures remain a complex challenge. This article explores how machine learning (ML)-augmented computational and experimental methodologies can tackle these challenges by predicting precursor alloy compositions, final nanoporous structures, and mechanical properties, while integrating ML-enabled autonomous experimentation for material design and quantification. We highlight recent advancements in applying ML to nanostructured materials design via dealloying and discuss how techniques from other nanomaterial designs can be adapted for improved control over morphological and compositional outcomes in nanoporous and nanocomposite materials. Furthermore, we explore the role of ML in autonomous synchrotron x-ray experimentation, enabling real-time feedback between modeling and experimental setups. ML-driven approaches to microstructure characterization and mechanical property prediction are also examined, with a focus on modeling and advanced imaging techniques such as three-dimensional nanotomography. Finally, this article outlines future directions for ML-enhanced materials science, emphasizing the exploration of high-dimensional parameter spaces and the incorporation of materials kinetics into processing and property evaluation, ultimately advancing the design of nanoporous structures and materials science.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Green Synthesis of Fe{sub 3}O{sub 4}/Cellulose/Polyvinyl Alcohol Hybride Aerogel and Its Application for Dye Removal

A novel Fe{sub 3}O{sub 4}/cellulose–polyvinyl alcohol (PVA) aerogel was successfully synthesized by an eco-friendly and facile method in this work. Cellulose/PVA matrix was prepared through an environmental friendly physical cross-linking process and further in-situ decorated with Fe{sub 3}O{sub 4}. Series of Fe{sub 3}O{sub 4} decorated aerogels were prepared and the effects of Fe{sub 3}O{sub 4} nanoparticles (NPs) on the aerogels were systematic investigated. As-prepared aerogels exhibited desirable properties including nanostructure, relatively high porosity, improved mechanical and superparamagnetism. The TEM results showed that Fe{sub 3}O{sub 4} NPs were integrated in the three-dimensional matrix of cellulose/PVA with a diameter of 9–12 nm. Furthermore, the mechanical strength of the aerogels was significantly enhanced after the introduction of Fe{sub 3}O{sub 4} NPs. Meanwhile, the obtained Fe{sub 3}O{sub 4}/cellulose/PVA aerogel exhibited excellent adsorption performance toward methyl blue dye, and can be reused through fenton-like catalysts oxidative degradation of organic dye in H{sub 2}O{sub 2} solution. Therefore, they will have a great potential application as eco-friendly and economical adsorbents.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Structural Changes during the Conversion Reaction of Tungsten Oxide Electrodes with Tailored, Mesoscale Porosity

In-plane tungsten oxide nanostructures, including hexagonally patterned cylinders and holes in a matrix, were fabricated via sequential infiltration synthesis (SIS) on self-assembled block copolymer templates. Using the tailored morphology and porosity of these model electrodes with in situ grazing incidence small angle X-ray scattering, the intrinsic structural change of nanoscale active materials during the conversion reaction of WO 3 + 6Li ↔ W + 3 Li 2 O was investigated at controlled electrochemical conditions. Reversible electrode volume expansion and contraction was observed during lithiation and delithiation cycles, respectively. The potential where electrode’s thickness expansion started was ~1.6 V, which is close to thermodynamically expected one for conversion reaction of WO 3 with lithium (1.65 V). The temporal evolution of the electrode volume at constant electrode potentials revealed high overpotential for bulk lithiation and slow conversion reaction kinetics, despite the tailored porosity of the SIS electrodes. Oxide cylinders showed smaller overall electrode thickness change, likely due to unconstrained lateral volume change, as compared to a matrix with holes. On the other hand, better connectivity and guided volume change of the latter electrode morphology provided improved cycling stability. Additionally, heterogeneity in an electrode, from internal pores and density gradients, was found to aggravate the fragmentation of the electrode during conversion reaction. Insights into oxide conversion reaction kinetics and the relationship between electrode mesostructure and cycling behavior obtained from this study can help guide the more rational design of conversion electrode for high performing batteries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Carbon coated hierarchical porous MoO2 nanoflowers as high-performance anodes in lithium-ion batteries

Highlights: • Carbon-coated hierarchical porous MoO{sub 2} are synthetized via a template-free solvothermal technique. • Synthesizing hybrid porous materials provides potential to achieve superior performance in energy application. • This hierarchical structure can be extended to design for other materials in view of their application in LIBs. - Abstract: Carbon-coated hierarchical porous MoO{sub 2} nanoflowers are synthetized via a template-free solvothermal technique and investigated as anodes in lithium-ion batteries (LIBs). Such hybrid porous materials possess high porosity and a conductive layer, which have superior lithium ion/electron transport. The voids inside the structure can accommodate huge volume expansion and relieve the stress. The relative MoO{sub 2} electrodes present a high reversible capacity of 784.7 mA h g {sup −1} after 60 cycles (707.7 mA h g{sup −1} after 120 cycles for 200 mA g{sup −1}) and high coulumbic efficiency (above 98% over 120 cycles). Our study can easily be extended to other materials with a similar hierarchical structure in view of their application in LIBs.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2018

Graphene foam supported LiFePO4 nanosheets composite as advanced cathode for lithium ion batteries

Highlights: • Construct self-supported porous LiFePO{sub 4}/GF composite film. • Porous LiFePO{sub 4}/GF composite film show superior cycling life. • Hierarchical porous nanosheets structure boost fast electron/ion transfer. - Abstract: Smart design of advanced cathode plays a significantly important role for the development of high-performance lithium ion batteries (LIBs). In this work, we synthesized a new kind of LiFePO{sub 4}/Graphene foam (LFP/GF) integrated binder-free cathode via chemical vapor deposition (CVD) + hydrothermal method. The LFP is composed of interconnected LiFePO{sub 4} nanosheets with numerous nanopores of 50–500 nm. High porosity and good adhesion endow LiFePO{sub 4}/GF film superior electrochemical properties with remarkable high-rate capacities, small polarization and stable cycling life. A high-rate capacity of 110 mAh g{sup −1} at 24 C is obtained for the LiFePO{sub 4}/GF composite. Moreover, a high capacity retention of 95% is acquired after 160 cycles. This enhancement is due to the unique integrated porous LiFePO{sub 4} nanosheets and good support of graphene foam providing fast ion/electron transfer. Our work displays a new insight in constructing integrated cathode for application in high-performance LIBs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Nanosized carriers for hydrophobic compounds based on mesoporous silica: synthesis and adsorption properties

MCM-41 type mesoporous silica particles were obtained using a template method in an alkaline medium and cetyltrimethylammonium bromide as a matrix. The structural and adsorption characteristics of the mesoporous material were studied by dynamic light scattering, scanning electron microscopy, low-temperature adsorption—desorption of nitrogen, IR spectroscopy, and simultaneous thermal analysis. It was shown that the obtained mesoporous material possesses high porosity with the specific pore volume in excess of 1 cm{sup 3} g{sup −1}. It was established that the size of silica particles does not exceed 200 nm, which is a value acceptable for the penetration of drugs through cell membranes. The optimal compositions of aqueous dispersions of MCM-41 with minimal sedimentation processes were determined. A drug (indomethacin) was encapsulated into the silica pores using the precipitation method at various temperatures (40 and 60 °C), the quantitative parameters of loading efficiency were calculated. The infl uence of temperature on the encapsulation ability was demonstrated.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Integrated carbon cloth supported LiFePO4/N-C films as high-performance cathode for lithium ion batteries

Highlights: • Construct carbon cloth supported LiFePO{sub 4}/N-C films via hydrothermal. • The LiFePO{sub 4}/N-C films show high capacity and good cycles. • Carbon cloth and N-C layer work together to provide fast ion/electron transfer. - Abstract: Fabricating advanced cathode is critical for the development of high-performance lithium ion batteries (LIBs). In this work, we develop a facile hydrothermal method for construction of LiFePO{sub 4}/N-C films on the carbon cloth forming integrated binder-free cathode. The LiFePO{sub 4}/N-C films are composed of interconnected nanoscale LiFePO{sub 4}/N-C particles with diameters of 100–200 nm. High porosity and good adhesion are obtained in the carbon cloth supported LiFePO{sub 4}/N-C films (CC + LiFePO{sub 4}/N-C films). As compared to the LiFePO{sub 4}/C powder nanoparticles, the CC + LiFePO{sub 4}/N-C films show much better electrochemical properties with higher capacities, smaller polarization and better high-rate cycling life. A high capacity of 169 mAh g{sup −1} at 1C is achieved for the carbon cloth supported LiFePO{sub 4}/N-C films, superior to the LiFePO{sub 4}/C powder nanoparticles (154 mAh g{sup −1} at 5C). This enhancement is owing to the unique integrated porous architecture and N-C coating. Our work shows a new way to construct integrated cathode for application in LIBs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Study on Nanocellulose Properties Processed Using Different Methods and Their Aerogels

In this paper the effects of different mechanical methods including homogenization, ultrasonication and grinding on the properties of the nanocellulose materials and their aerogels, were investigated. The cellulose nanocrystal products, (CNC-H) and (CNC-U), were prepared by homogenization and ultrasonication of the acid hydrolyzed pulps, respectively. The aerogel products were produced by solvent exchanging of nanocellulose hydrogels with tertiary butyl alcohol and followed by freeze drying. The nanocellulose materials were studied using transmission electron microscopy, field emission scanning electron microscopy (FE-SEM), Fourier transformed infrared spectroscopy (TEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA). Size distribution and surface charges of the nanocellulose suspensions were measured by zetasizer. Also, the morphology, the porosity properties and surface area of the CNCs and CNF aerogels were investigated via FE-SEM and nitrogen adsorption–desorption isotherms. The results showed that CNC-H has higher surface charge, suspension stability (− 41.8 mV), crystallinity index (74.7%) and better size dispersion than CNC-U and CNF with an average particle size of 122 nm. CNC-H microstructures demonstrated homogeneous network structure with smaller nanometer dimensions (15–30 nm width and 60–400 nm length). However, the CNC-H showed lower thermal stability compared to CNC-U and CNF. Larger average pore size (16.32 nm), pore volume (0.42 cc/g) and high specific surface area (> 100 m{sup 2} g{sup −1}) in CNC-H aerogel were obtained. Graphical Abstract: Suspensions of nanocellulose (NC) were prepared by different mechanical methods: Homogenizing, Ultrasonic and grinding. The NC products were investigated and their differences in morphology and other characteristics were studied. The aerogels were prepared from the nanocellulose hydrogels. The nitrogen physisorption was used to study the pore characteristics of the aerogels. .

36 MATERIALS SCIENCE↗
DOE OSTI2018

One-pot synthesis of porous g-C3N4 nanomaterials with different morphologies and their superior photocatalytic performance

Highlights: • g-C{sub 3}N{sub 4}, liking a yolk-shell cake, was prepared. • The shell region is porous nanosheets and the yolk region is hollow particles. • The surface area and pore volume of two types of g-C{sub 3}N{sub 4} could be controlled. • The as-prepared porous g-C{sub 3}N{sub 4} nanomaterials exhibit improved photocatalytic activity. - Abstract: Graphitic carbon nitride (g-C{sub 3}N{sub 4}), liking a yolk-shell cake, was successfully prepared via a gas-bubble template method with the assistance of NH{sub 4}Cl. In this special structure, the shell region consists of numerous thin sheets with rich porosity, while the yolk region consists of a lot of cross-linked large hollow particles. The formation mechanism of yolk-shell structure was investigated via adjusting the mass ratio of NH{sub 4}Cl to melamine, and calcination temperature. The surface area and pore volume of the two types of porous g-C{sub 3}N{sub 4} nanomaterials significantly depend on the mass ratio of NH{sub 4}Cl to melamine in a certain extent. The as-prepared porous g-C{sub 3}N{sub 4} nanomaterials exhibit improved photocatalytic activity compared to bulk g-C{sub 3}N{sub 4}. Moreover, the porous thin sheets in shell region possess larger specific surface area, higher light utilization, higher charge separation and transfer efficiency, than the hollow particles in yolk region, leading to the superior photocatalytic performance. We believe that this simple, economical, and nontoxic approach for the preparation of g-C{sub 3}N{sub 4} nanomaterials opens new possibilities for scalable synthesis of g-C{sub 3}N{sub 4}-based materials with more controllable structures.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Study on the Carbon Nanostructures for Nanosized Si Electrodes

Silicon (Si) has been considered as a next-generation anode material due to natural abundance, low operating potential (<0.5 V vs. Li/Li+), and high theoretical specific capacity of 4200 mAh g-1.[1] However, the electrochemical alloying reaction of Si involves large volume changes of 400% during lithiation and delithiation, causing cracking and pulverization of Si.[1] In addition, solid electrolyte interface (SEI) of Si anode experiences constant changes due to unstable SEI reactivity.[2] Considerable efforts have been made to design nanostructured Si materials to address the issues because nanostructuring can relieve the mechanical strain.[3] However, when compared to micrometer-sized active materials having sufficient electrolyte pathway through interparticle space, the nanoparticle (NP)-based electrodes tend to be densely packed. As mass loading is higher and electrode is thicker, ion transport issue can become more severe in the densely packed electrodes.[4] In this work, we will present studies on engineered porosity impacts performance in Si NP electrodes by altering carbon nanostructures. We explore the extreme limit of effectively non-porous electrodes using quasi-spherical, Si NPs, which result in densely packed electrodes when slurry is prepared with conventional carbon black. We engineer porosity using carbon nanostructures including multi-walled carbon nanotubes and carbon nanorods in place of conventional carbon black to create pore structure in Si NP-based electrodes. These experiments provide a correlation between mass loading, porosity and silicon utilization in Si NP-based electrodes. References: [1] C. K. Chan, H. Peng, G. Liu, K. Mcllwrath, X. F. Zhang, R. A. Huggins, Y. Cui, "High-performance lithium battery anodes using silicon nanowires", Nat. Nanotechnol., 2008, 3, 31, [2] J. D. McBrayer, M.-T. F. Rodrigues, M. C. Schulze, D. P. Abraham, C. A. Apblett, I. Bloom, G. M. Carroll, A. M. Coclasure, C. Fang, K. L. Harrison, G. Liu, S. D. Minteer, N. R. Neale, G. M. Veith, C. S. Johnson, J. T. Vaughey, A. K. Burrel, B. Cunningham, "Calendar aging of silicon-containing batteries", Nat. Energy, 2021, 6, 1164, [3] H. Wu, G. Zheng, N. Liu, T. J. Carney, Y. Yang, Y. Cui, "Engineering Empty space between Si Nanoparticles for Lithium-Ion Battery Anodes", Nano Lett., 2012, 12, 904, [4] X. Zhang, Z. Ju, Y. Zhu, K. J. Takeuchi, E. S. Takeuchi, A. C. Marschilok, G. Yu, "Multiscale Understanding and Architecture Design of High Energy/Power Lithium-Ion Battery Electrodes", Adv. Energy Mater., 2021, 11, 2000808

carbon nanostructure↗