@article{sultana_yang_xu_monroe_el-ghannam_2024, title={Synthesis and characterization of functionally graded SiC-mullite thermal material}, volume={330}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2023.124414}, abstractNote={SiC-mullite is considered for high temperature applications due to its high mechanical strength and thermal shock-resistance. However, maintaining these properties is challenged by the high processing temperature requirement for the formation and densification of the mullite phase which leads to abundant surface oxidation of SiC into cristobalite. Cristobalite has relatively poor mechanical strength and thermal properties compared to SiC. Herein, we report on using coal fly ash as a source of alumina (Al2O3) that reacts in situ with the silica (SiO2) oxidation product of SiC. The instantaneous mullite formation on the surface of SiC facilitated due to presence of minor concentrations of metal oxides in coal fly ash, resulted in a strong bonding zone between the two phases at relatively low temperature. In this work, SiC was mixed with coal fly ash at weight ratios 90SiC/10ash, 85SiC/15ash, 80SiC/20ash and 75SiC/25ash and sintered at 1400 °C. Measurements of mechanical properties showed that the 85SiC/15ash composition has the highest mechanical strength among samples. XRD analysis showed the phase composition of thermally treated 85SiC/15ash to be 81.8 wt% SiC, 11.4 wt% mullite, and 6.8 wt% cristobalite. SEM-EDX revealed a concentration gradient of Al in the cristobalite which enhanced formation of functionally graded bonding zones between phases and resulted in SiC-mullite composite with high thermomechanical properties. The compressive strength, nanoindentation elastic modulus, Vickers hardness were 434 ± 20 MPa, 370.9 ± 22.6 GPa, 11.5 ± 1.2 GPa respectively. The thermal shock resistance test showed high dimensional and mechanical stabilities after quenching in liquid nitrogen (−196 °C) from 1400 °C. The SiC-mullite composite showed low thermal expansion co-efficient from 3.17 × 10−7/K to 5.615 × 10−6/K when the sample was heated from 182 K to 354 K. The specific heat capacity, thermal diffusivity, and thermal conductivity were 7.83 ± 0.0014 J/g.K, 1.04 ± 0.013 mm2/s, and 17 W/m.K at 100 °C, respectively. The SiC-mullite composite exhibited moderate electrical conductivity of 3.48 × 10−2 S/m at 1000 °C.}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Sultana, Farjana and Yang, Ni and Xu, Chengying and Monroe, James and El-Ghannam, Ahmed}, year={2024}, month={Feb} }
 @article{yang_xu_2023, title={An ultrathin polymer-derived UHTCs coating on CFRP substrate: Effective electromagnetic wave absorber}, volume={43}, ISSN={["2452-2139"]}, DOI={10.1016/j.coco.2023.101713}, abstractNote={The utilization of carbon fiber-reinforced polymer (CFRP) materials in electronic equipment encounters notable challenges of electronic warfare operations and the risk of detection by various sensors. A novel ceramic coating comprising TiC/SiOC with added Al2O3 adhesive was formulated to address these issues. The TiC/SiOC-50 wt% Al2O3 coating demonstrated exceptional microwave-effective absorption bandwidth (EAB) of 13.5 GHz, effectively covering the entire Ka-band, while maintaining a thin thickness of 0.60 mm. The TiC/SiOC-80 wt% Al2O3 system exhibited remarkable EM characteristics, including a minimum reflection loss (RLmin) of −58.26 dB, an EAB of 10.74 GHz, and an ultra-thin thickness of 0.38 mm, which sets a new record as the thinnest reported coating in the existing literature. The outstanding electromagnetic performance, coupled with their lightweight and thin characteristics, positions these coatings as highly viable solutions for various electromagnetic shielding and absorption applications in extreme environments.}, journal={COMPOSITES COMMUNICATIONS}, author={Yang, Ni and Xu, Chengying}, year={2023}, month={Nov} }
 @article{jia_yang_xu_snyder_patrick_kumar_zhang_xu_2023, title={Polymer-derived SiOC reinforced with core-shell nanophase structure of ZrB2/ZrO2 for excellent and stable high-temperature microwave absorption (up to 900 degrees C)}, volume={13}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-023-27541-3}, abstractNote={Abstract}, number={1}, journal={SCIENTIFIC REPORTS}, author={Jia, Yujun and Yang, Ni and Xu, Shaofan and Snyder, Alexander D. D. and Patrick, Jason F. F. and Kumar, Rajan and Zhang, Dajie and Xu, Chengying}, year={2023}, month={Jan} }
 @article{yang_zhang_reynolds_kumah_xu_2023, title={The Role of Carbon Content: A Comparison of the Nickel Particle Size and Magnetic Property of Nickel/Polysiloxane-Derived Silicon Oxycarbide}, volume={1}, ISSN={["1527-2648"]}, url={https://doi.org/10.1002/adem.202201453}, DOI={10.1002/adem.202201453}, abstractNote={A facile and novel processable method to synthesize the Ni nanoparticles (Ni NPs) by tailoring their size in the matrix of the silicon oxycarbide (SiOC) ceramic system is reported. This method is based on polymer‐derived ceramics (PDCs), instead of the conventional powder route. The specific structural characteristics and magnetic properties of the various Ni NPs/SiOC composites as a function of carbon content are systematically investigated. The magnetic properties are experimentally investigated as a function of NP size and measurement temperature. It is demonstrated that the change in the size of Ni NPs (average from ≈4 to ≈ 19 nm) determines the magnetic nature of superparamagnetism. Zero‐field‐cooled (ZFC) and field‐cooled (FC) magnetization studies under magnetic fields of 100 Oe are performed. The saturated M versus H (M–H) loops (saturation magnetization) increase and the coercivity decreases with the size reduction of Ni NPs. It is an indicator of the presence of superparamagnetic behavior and single‐domain NP for ceramic materials.}, journal={ADVANCED ENGINEERING MATERIALS}, author={Yang, Ni and Zhang, Xuanyi and Reynolds, Lewis and Kumah, Divine and Xu, Chengying}, year={2023}, month={Jan} }
 @misc{kenion_yang_xu_2022, title={Dielectric and mechanical properties of hypersonic radome materials and metamaterial design: A review}, volume={42}, ISSN={["1873-619X"]}, DOI={10.1016/j.jeurceramsoc.2021.10.006}, abstractNote={This review paper examines ten current ceramic radome materials under research and development and provides a comprehensive overview of available high temperature and high frequency data from literature. An examination of metamaterials for radio-frequency transparent radomes is given and our preliminary experimental results of a high-temperature metamaterial design are presented. The next-generation hypersonic vehicles’ radome temperatures will exceed 1000℃ and speeds will exceed Mach 5. An ideal radome material will have a high flexural strength, low dielectric constant and loss tangent, and high resistance to thermal shock and corrosion. The microstructural effect on the dielectric and mechanical properties and the effects of environmental factors such as rain are discussed. The impact of metamaterial structure on key radome factors such as boresight error, gain, and polarization is examined. After examining the associated benefits with the use of metamaterials, our preliminary results for a potential high-temperature metamaterial design are presented.}, number={1}, journal={JOURNAL OF THE EUROPEAN CERAMIC SOCIETY}, author={Kenion, Taylor and Yang, Ni and Xu, Chengying}, year={2022}, month={Jan}, pages={1–17} }
 @article{pasagada_yang_xu_2022, title={Electron beam sintering (EBS) process for Ultra-High Temperature Ceramics (UHTCs) and the comparison with traditional UHTC sintering and metal Electron Beam Melting (EBM) processes}, volume={48}, ISSN={["1873-3956"]}, DOI={10.1016/j.ceramint.2021.12.229}, abstractNote={Ultra-high temperature ceramics (UHTCs) are refractory materials with unusual properties making them strong contenders for applications involving adverse and chemically aggressive environments. This paper presents an effort to process UHTCs using an additive manufacturing method, specifically Electron Beam Sintering (EBS) - adoption of the Electron Beam powder-bed fusion (PBF) process. Such a process shows that the processing and consolidation phenomenon of UHTCs are different from what is observed in the traditional sintering process of UHTCs and Electron Beam Melting (EBM) of typical metals or alloys. In this article, the EBS process of UHTCs is studied. The differences between EBS and the two aforementioned traditional processing methods are analyzed. The scientific hypotheses have been backed by experimental results on a ZrB2 – 30 vol% ZrSi2 UHTC mixture using an electron beam via Liquid Phase Sintering (LPS) theory. Efforts to develop processing conditions to fabricate dense and defect-free UHTC components are explored with the help of finite element (FE) simulations. Characterization of the EBS processed samples using Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD) revealed unique needle-like patterned grains of ZrB2 in a ZrSi2 matrix. Our findings demonstrate the feasibility of the EBS process to produce dense layers of UHTCs for coatings, potential three-dimensional, as well as complex-shaped applications.}, number={7}, journal={CERAMICS INTERNATIONAL}, author={Pasagada, Venkata Keerti Vardhan and Yang, Ni and Xu, Chengying}, year={2022}, month={Apr}, pages={10174–10186} }
 @article{yang_2022, title={Special Issue "Functionalities of Polymer-Based Nanocomposite Films and Coatings"}, volume={12}, ISSN={["2079-6412"]}, DOI={10.3390/coatings12091245}, abstractNote={Polymer-based coatings are the thin film of polymer applied to any type of flat or irregular surfaces (e [...]}, number={9}, journal={COATINGS}, author={Yang, Ni}, year={2022}, month={Sep} }
 @article{yang_xu_zhang_xu_2022, title={Super-Wideband Electromagnetic Absorbing TiC/SiOC Ceramic/Glass Composites Derived from Polysiloxane and Titanium Isopropoxide with Low Thickness (<1 mm)}, volume={12}, ISSN={["1527-2648"]}, DOI={10.1002/adem.202201508}, abstractNote={Herein, TiC/SiOC ceramic/glass composites with excellent electromagnetic wave (EMW) absorbing performance are fabricated by pyrolysis of polycarbosiloxane and titanium (IV) isopropoxide (TTIP). By taking advantage of the polymer‐derived route, the phase compositions and microstructures are easily tuned. The composites are investigated by X‐ray diffraction (XRD) analysis, scanning electron microscope, and transmission electron microscopy/energy dispersive spectroscopy. Nanoscaled TiC is formed and uniformly distributed without clustering within the SiOC matrix. Thermogravimetric Analysis (TGA) and in situ XRD results revealed good thermal stability and oxidation resistance mechanism. The presented material system (TiC/SiOC) shows a super‐wide microwave absorption bandwidth (EAB) of 13.5 GHz, including the entire Ka‐band (26.5–40 GHz) with a low thickness requirement (<1 mm). The superior EMW absorption properties of the ceramics are attributed to the optimal interface polarization, as well as the ordering, concentration, and interconnectivity of the conductive network, which all determine the electrical conductivity in the composites.}, journal={ADVANCED ENGINEERING MATERIALS}, author={Yang, Ni and Xu, Shaofan and Zhang, Dajie and Xu, Chengying}, year={2022}, month={Dec} }