A. James Clark School of Engineering

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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.

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Author: search.filters.author.Ren, Shenqiang

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    Flame retardant biogenic building insulation materials from hemp fiber
    (Wiley, 2023-12-27) Jadhav, Porus Sunil; Sarkar, Arpita; Zhu, Long; Ren, Shenqiang
    Biogenic thermal insulation materials are in high demand because of its carbon-sequestration nature. However, high flammability, moisture condensation, and relatively high thermal conductivity of biogenic material are major concerns for sustainable building applications. In this study, we report the fire-retardant cellulose xerogel insulation nanocomposites derived from hemp fiber recycling and silica xerogel, in which the boric acid treatment improves its fire retardancy. The as-prepared materials show a low thermal conductivity of 31.3 mW/m K, high flexural modulus of 665 MPa, hydrophobicity with the water contact angle of 115°, and fire retardancy with 30% weight loss over a period of burning time 10 min. Overall, this work provides an effective method for the synthesis of fire-retardant biogenic thermal insulation materials and shows a promising way for next-generation bio-based insulation materials.
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    Additive Manufacturing of High-Temperature Hybrid Electronics via Molecular-Decomposed Metals
    (Wiley, 2023-10-20) Khuje, Saurabh; Alshatnawi, Firas; Smilgies, Detlef; Alhendi, Mohammed; Islam, Abdullah; Armstrong, Jason; Yu, Jian; Poliks, Mark; Ren, Shenqiang
    As the modern electronic technology extends into operating in harsh working conditions, it calls for a system that is capable of uncompromising performance in extreme environments, thus providing a strong motivation to look for advanced materials and electronics with the capability of high-throughput and rapid prototyping. Coupled with additive manufacturing, molecular decomposition metals bypass the challenging oddities of traditional material-limited and thermally initiated metalworking, enabling high throughput and rapid prototyping of stoichiometry and composition-controlled metals. Here, a new paradigm for the design and additive manufacturing of copper metallic alloy materials onto ceramics is described by printing molecular decomposable metal materials, capable of withstanding thermo-mechanical loading, operating in extreme environments in static and dynamic conditions. The resulting printed hybrid electronics are electrically stable for 25 h of aging at 1000 °C. This curious fact paves a way for printed antenna and sensor electronics that reliably operate up to 1000 °C. These results can be further extended to establish other printable molecular decomposable materials as a platform for rapid prototyping of high temperature electronics that are suitable for harsh environments.
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    Additive Manufacturing of High-Temperature Preceramic-Derived SiOC Hybrid Functional Ceramics
    (Wiley, 2023-09-22) Li, Zheng; Khuje, Saurabh; Islam, Abdullah; Ren, Shenqiang
    High-temperature capable materials, metals, and ceramics are attracting significant interest for applications in extreme environmental conditions. Herein, a hybrid metal-reinforced ceramic matrix material consisting of preceramic-derived high-temperature SiOC and copper nanoplates is reported, enabling the manufacturing of high-temperature sensing electronics. The preceramic polymer precursors including polydimethylsiloxane and polydimethylsilane, together with copper nanoplates, are thermally converted into durable copper-reinforced SiOC ceramics. The presence of copper in SiOC ceramics enhances its electrical conductivity, while SiOC suppresses oxygen uptake and acts as a shield for oxidation to achieve high-temperature thermal resistance and negative temperature coefficient at high temperatures. A comprehensive electric and sensing performance, combined with cost-effectiveness and scalability, can facilitate the utilization of hybrid Cu and SiOC composites in high-temperature electronics.
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    Bottom-Up Multiferroic Nanostructures
    (2009) Ren, Shenqiang; Wuttig, Manfred; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Multiferroic and especially magnetoelectric (ME) nanocomposites have received extensive attention due to their potential applications in spintronics, information storage and logic devices. The extrinsic ME coupling in composites is strain mediated via the interface between the piezoelectric and magnetostrictive components. However, the design and synthesis of controlled nanostructures with engineering enhanced coupling remain a significant challenge. The purpose of this thesis is to create nanostructures with very large interface densities and unique connectivities of the two phases in a controlled manner. Using inorganic solid state phase transformations and organic block copolymer self assembly methodologies, we present novel self assembly "bottom-up" techniques as a general protocol for the nanofabrication of multifunctional devices. First, Lead-Zirconium-Titanate/Nickel-Ferrite (PZT/NFO) vertical multilamellar nanostructures have been produced by crystallizing and decomposing a gel in a magnetic field below the Curie temperature of NFO. The ensuing microstructure is nanoscopically periodic and anisotropic. The wavelength of the PZT/NFO alternation, 25 nm, agrees within a factor of two with the theoretically estimated value. The macroscopic ferromagnetic and magnetoelectric responses correspond qualitatively and semi-quantitatively to the features of the nanostructure. The maximum of the field dependent magnetoelectric susceptibility equals 1.8 V/cm Oe. Second, a magnetoelectric composite with controlled nanostructures is synthesized using co-assembly of two inorganic precursors with a block copolymer. This solution processed material consists of hexagonally arranged ferromagnetic cobalt ferrite (CFO) nano-cylinders within a matrix of ferroelectric Lead-Zirconium-Titanate (PZT). The initial magnetic permeability of the self-assembled CFO/PZT nanocomposite changes by a factor of 5 through the application of 2.5 V. This work may have significant impact on the development of novel memory or logic devices through self assembly techniques. It also demonstrates a universal two-phase hard template application. Last, solid-state self assembly had been used recently to form pseudoperiodic chessboard-like nanoscale morphologies in a series of chemically homogeneous complex oxide systems. We improved on this approach by synthesizing a spontaneously phase separated nanolamellar BaTiO3-CoFe2O4 bi-crystal. The superlattice is magnetoelectric with a frequency dependent coupling. The BaTiO3 component is a ferroelectric relaxor with a Vogel-Fulcher temperature of 311 K. Since the material can be produced by standard ceramic processing methods, the discovery represents great potential for magnetoelectric devices.