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Wang, Xiaodong

Publications and source records attributed to Wang, Xiaodong.

6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Achieving 19% efficiency in non-fused ring electron acceptor solar cells via solubility control of donor and acceptor crystallization

Non-fused ring electron acceptors (NFREAs) potentially have lower synthetic costs than their fused counterparts. However, the low backbone planarity and the presence of bulky substituents adversely affect the crystallinity of NFREAs, impeding charge transport and the formation of bicontinuous morphology in organic solar cells. Here we show that a binary solvent system can individually control the crystallization and phase separation of the donor polymer (for example, D18) and the NFREA (for example, 2BTh-2F-C 2 ). We select solvents such as chloroform and o -xylene that evaporate at different temperatures and rates and have different solubility for D18. Upon evaporation of chloroform, D18 starts to assemble into fibrils. Then, the evaporation of o-xylene induces the rapid formation of a fibril network that phase segregates 2BTh-2F-C 2 into pure domains and leads to a bicontinuous morphology. In conclusion, the well-defined interpenetrating network morphology affords an efficiency of 19.02% on small-area cells and 17.28% on 1 cm 2 devices.

14 SOLAR ENERGY↗
DOE OSTI2024

Enabling thermal energy storage in structural cementitious composites with a novel phase change material microcapsule featuring an inorganic shell and a bio-inspired silica coating

Phase change material (PCM) microcapsules offer a promising approach for integrating PCM into building materials for efficient thermal energy storage. Here, this study presents the development of a novel PCM microcapsule specifically designed for incorporation into cementitious materials. The microcapsule consists of a low-cost PCM core derived from vegetable oil by-products and a durable inorganic shell made from cenosphere, a hollow fly ash generated from coal burning power plants. A novel process is developed to apply a silica coating to these cenosphere-based PCM microcapsules (CPCM), resulting in bioinspired-silica-coated CPCM microcapsules (BCPCM). This coating process draws inspiration from marine microorganism-based silica production and utilizes low-cost sodium silicate as a precursor, enabling eco-friendly and cost-effective manufacturing at ambient temperature and mild pH conditions. The morphology, chemical stability, and thermal properties of the BCPCM along with its thermo-mechanical performance in cementitious composites were comprehensively analyzed. Experimental results demonstrate successful silica deposition on BCPCM, leading to enhanced latent heat properties of the produced BCPCM. With the silica coating, BCPCM exhibits a 50 °C delay in thermal decomposition compared to CPCM, enhancing fire resistance and preventing premature PCM leakage of the microcapsule. The bioinspired silica coating effectively restores over 10% of the strength loss for each percent increase in CPCM incorporated into the mortar. The thermal performance experiments reveal that increasing the BCPCM content reduces temperature peaks and rates of temperature increase, indicating an improved capacity for thermal energy storage. This new PCM microcapsule provides a cost-effective solution to integrate thermal energy storage to cementitious material, as evidenced that over 30% of aggregates (in volume) can be replaced by the microcapsule without a drastic loss of strength.

25 ENERGY STORAGE↗
DOE OSTI2023

All-polymer nanocomposites having superior strength, toughness and ultralow energy dissipation

Toughening polymers has attracted significant interest. Traditionally, polymer toughness is enhanced by constructing polymer networks or introducing sacrificial bonds into the chains between crosslink points. These strategies, though, introduce pronounced energy dissipation and associated heat, both of which are undesirable under long-term cyclic loading, for example at the interface of implants in the human body. By incorporating single-chain nanoparticles (SCNPs) into linear polymer chains to generate all-polymer nanocomposites (APNCs), we have been able to achieve high strength, high toughness with low energy dissipation. Using a combination of simulation and experimental results, we are advancing a “SCNPs effect” where tightly cross-linked SCNPs produce a modulus contrast to achieve strengthening and toughening. Benefitting from the soft interface, the penetrable and deformable SCNPs cause the surrounding polymer chains to move in concert, significantly reducing the interfacial friction to achieve low energy dissipation. The intramolecular cross-linking of the SCNPs and adhesion between the SCNPs and polymer matrix are critical for realizing such high-performance systems. Based on a Gaussian regression model and back propagation (BP) neural network, the mechanical strength can be predicted and is supported by simulations. Finally, the APNC concept described can be applied to elastomers and gels, broadening its utilization in high-cycle and low-dissipation applications, like soft robots, flexible sensors and cartilage replacements, and artificial heart valves.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Mars-Ward Ion Flows in the Martian Magnetotail: Mars Express Observations

In this work, we investigate Mars-ward planetary ions (O + and O 2 + ) in the Martian magnetotail that potentially reduce the amount of escaping ions. The global properties of Mars-ward flows in the Martian magnetotail are characterized, based on over 13-years of ion data (May 2007–December 2020) collected by the Analyzer of Space Plasma and Energetic Atoms instrument on Mars Express. We find that Mars-ward flows are frequently observed in the vicinity of the crustal fields, implying that crustal fields may play a key role in producing such flows. The occurrence rate and sunward flux are found higher during solar maximum than solar minimum. However, the occurrence rate and flux of Mars-ward flows are relatively low. This is different from the case at Venus, where the planetward flows can significantly decrease the total escape rates of ions.

58 GEOSCIENCES↗
DOE OSTI2020

Temperature-induced structural evolution in liquid Ag-Ga alloys

Temperature-dependent atomic structural evolutions of liquid Ag 60 Ga 40 and Ag 70 Ga 30 alloys have been studied by in situ high-energy x-ray-diffraction (HEXRD) experiments combined with ab initio molecular-dynamics simulations. The experimental data show a reversible structural crossover at about 1050 ~ 1100 (± 50) K in both liquid Ag 60 Ga 40 and Ag 70 Ga 30 alloys. Obvious changes of the electrical resistivity, absolute thermoelectric power, and atomic diffusivity around the similar temperature range for both Ag-Ga liquids strongly support the HEXRD results. The origin of the liquid-to-liquid crossover in both Ag-Ga liquids was suggested to link with the rearrangements of Ag and Ga atoms, i.e., Ag and Ga atoms prefer to associate with themselves in the higher temperature range above 1100 K, consistent with the accelerated increase of the strong covalently bonded Ga–Ga dimers in both Ag-Ga liquids. In addition, more studies from the energy aspect are still desirable to understand the rearrangements of Ag and Ga atoms in the higher temperature range in both Ag-Ga liquids.

36 MATERIALS SCIENCE↗