Publications by authors named "Hyungho Park"

Achieving low thermal conductivity and high mechanical strength presents a material design challenge due to intrinsic trade-offs, such as the aerogel's porosity, impeding applications in construction, industry, and aerospace. This study presents a composite that incorporates a silica aerogel within a thermally expanded 2D layered vermiculite matrix. This design overcomes limitations imposed by van der Waals bonding lengths, typically less than 10 Å, which hinder aerogel integration with van der Waals crystals.

View Article and Find Full Text PDF

Household air purifiers are widely used to enhance indoor air quality. However, limited information exists regarding the factors that influence their long-term performance. This study investigates the impact of various residential environments on the long-term efficacy of air purifiers.

View Article and Find Full Text PDF

Due to their high surface area and low weight, silica aerogels are ideally suited for several uses, including drug delivery, catalysis, and insulation. Oil-water-oil () double emulsion is a simple and regulated technique for encasing a volatile oil phase in a silica shell to produce hollow silica (SiO) aerogel particles by using hydrophilic and hydrophobic emulsifiers. In this study, the oil-water-oil () double emulsion method was implemented to synthesize surface-modified hollow silica (SiO) aerogel particles in a facile and effective way.

View Article and Find Full Text PDF

A facile reduction and doping process is employed with the supercritical ethanol drying method to form RuNi alloy aerogels. The optimized heterostructure comprising RuNi metal, RuO, and NiO phases is synthesized through partial oxidation. When applied to the surface of Ni foam, the multiphase aerogels form a morphology of highly porous 0D colloidal aerogel networks on the surface.

View Article and Find Full Text PDF

High-nickel cobalt-free layered cathode is regarded as a highly potential cathode material for the next generation lithium ion batteries (LIBs) because of its high energy density, low cost and environmentally benign. However, the poor cycle performance caused by its intrinsic unstable structure and chemo-mechanical instability frustrates its practical applications. Herein, we have developed a new core-shell high-nickel cobalt-free layered LiNiMgAlO@LiZrO (LZO-NMA9523) cathode for high-performance LIBs.

View Article and Find Full Text PDF

Electrode materials must be rationally designed with morphologies and electroactive sites manipulated through cations' synergy in bimetal compounds in order to maximize the performance of energy storage devices. Therefore, the present study emphasizes binder-free scalable preparation of cobalt nickel vanadate (CNV) thin films by a facile successive ionic layer adsorption and reaction (SILAR) approach with specific cations (Co:Ni) alternation. Increasing the Ni cation content in the CNV notably transforms its microflower structure comprising nanoflakes (252 nm) into nanoparticles (74 nm).

View Article and Find Full Text PDF

The layered fibers of carbon-fiber-reinforced polymer (CFRP) composites exhibit low thermal conductivity (TC) throughout their thickness due to the poor TC of the polymeric resin. Improved heat transmission inside the hydrogen storage tank during the filling process can reduce further compression work, and improved heat insulation can minimize energy loss. Therefore, it is crucial to understand the thermal properties of composites.

View Article and Find Full Text PDF

In recent decades, aerogels have attracted tremendous attention in academia and industry as a class of lightweight and porous multifunctional nanomaterial. Despite their wide application range, the low mechanical durability hinders their processing and handling, particularly in applications requiring complex physical structures. "Mechanically strengthened aerogels" have emerged as a potential solution to address this drawback.

View Article and Find Full Text PDF

The lack of crystallinity of the aerogel materials has limited their significance which otherwise have found huge potential in wide variety of applications. In current work, we have developed TiO aerogels by solid-state gelation method using commercially available P25 and ST-01 (commercial Ishihara TiO Powder). The lack of crystallinity in the aerogel framework was resolved via utilizing crystalline TiO nanoparticles and the phase transformation was assessed as a function of phase composition.

View Article and Find Full Text PDF

Biomass-derived value-added materials such as levulinic acid (LA) are favorable natural resources for producing ester-based biolubricants owing to their biodegradability, nontoxicity, and excellent metal-adhering properties. However, highly active catalysts must be developed to carry out efficient esterification of LA with aliphatic alcohols, especially long-chain aliphatic alcohols. In this study, we developed a novel porous covalent organic polymer catalyst (BPOP-SOH) with dual acid sites, phosphate and sulfonic acid sites, for the esterification of LA.

View Article and Find Full Text PDF

Silica aerogels and their derivatives have outstanding thermal properties with exceptional values in the thermal insulation industry. However, their brittle nature restricts their large-scale commercialization. Thus, enhancing their mechanical strength without affecting their thermal insulating properties is essential.

View Article and Find Full Text PDF

Sulfur dioxide (SO) gas at trace levels challenges the consumption of fuel gases and cleaning of flue gases originating from diverse anthropogenic sources. We have demonstrated Zn-Al layered double hydroxide (LDH) and layered double oxide (LDO) as low-cost and effective adsorbents in removing lowly concentrated SO gas at room temperature. Water in the adsorbent bed significantly improved the performance, where the maximum adsorption capacity of 38.

View Article and Find Full Text PDF

Aerogels are highly porous materials with fascinating properties prepared using sol-gel chemistry. Due to their unique physical and chemical properties, aerogels are recognized as potential candidates for diverse applications, including thermal insulation, sensor, environmental remediation, etc. Despite these applications, aerogels are not routinely found in our daily life because they are fragile and have highly limited scale-up productions.

View Article and Find Full Text PDF

The binary as well as ternary nanocomposites of the square-facet nanobar Co-MOF-derived CoO@Co/N-CNTs (N-CNTs: nitrogen-doped carbon nanotubes) with Ag NPs and rGO have been synthesized via an easy wet chemical route, and their supercapacitor behavior was then studied. At a controlled pH of the precursor solution, square-facet nanobars of Co-MOF were first synthesized by the solvothermal method and then pyrolyzed under a controlled nitrogen atmosphere to get a core-shell system of CoO@Co/N-CNTs. In the second step, different compositions of CoO@Co/N-CNT core-shell structures were formed by an method with Ag NPs and rGO moieties.

View Article and Find Full Text PDF
Article Synopsis
  • * The resulting F-SnO@Pt hybrid boasts a large surface area and high porosity, demonstrating significantly improved hydrogen evolution performance with a remarkably low overpotential of just 42 mV and a turnover frequency 22 times higher than traditional Pt/C catalysts.
  • * Strong interactions between Pt and F-SnO enhance the catalyst's activity and stability against corrosion, while theoretical analysis indicates that this hybridization improves hydrogen atom adsorption, boosting reaction kinetics for better performance in electrochemical
View Article and Find Full Text PDF

In this study, inverse spinel cubic ferrites MFeO (M = Fe, and Co) have been fabricated for the high-capacity adsorptive removal of Hg(II) ions. The PXRD analysis confirmed ferrites with the presence of residual NaCl. The surface area of FeO (Fe-F) and CoFeO (Co-F) material was 69.

View Article and Find Full Text PDF

To implement artificial neural networks (ANNs) based on memristor devices, it is essential to secure the linearity and symmetry in weight update characteristics of the memristor, and reliability in the cycle-to-cycle and device-to-device variations. This study experimentally demonstrated and compared the filamentary and interface-type resistive switching (RS) behaviors of tantalum oxide (TaO and TaO)-based devices grown by atomic layer deposition (ALD) to propose a suitable RS type in terms of reliability and weight update characteristics. Although TaO is a strong candidate for memristor, the filament-type RS behavior of TaO does not fit well with ANNs demanding analog memory characteristics.

View Article and Find Full Text PDF

Following the global corona virus pandemic and environmental contamination caused by chemical plastic packaging, awareness of the need for environmentally friendly biofilms and antibacterial coatings is increasing. In this study, a biodegradable hybrid film, comprising of green-synthesized zinc oxide nanoparticles (ZnO NPs) with a chitosan (CS) matrix, was fabricated using a simple casting procedure. The ZnO NPs were synthesized using extract, and the synthesized NPs and films were characterized using different approaches.

View Article and Find Full Text PDF

The present study pioneered an oxygen migration-driven metal to insulator transition Mott memory, a new type of nonvolatile memory using lanthanum titanium oxide (LTO). We first show the reset first bipolar property without an initial electroforming process in LTO. We used oxygen-deficient ZnO as an interlayer between LTO and a W electrode to clarify whether oxygen migration activates LTO as the Mott transition.

View Article and Find Full Text PDF

2D-2D lattice engineering route is used to synthesize intimately coupled nanohybrids of layered double hydroxide (LDH) and potassium hexaniobate. The 2D-2D lattice engineering route is based on the electrostatically derived self-assembly of delaminated zinc-chromium-layered double hydroxide (ZC-LDH) nanosheets and potassium hexaniobate (HNb) nanosheets (ZCNb nanohybrids). The 2D-2D lattice-engineered ZCNb nanohybrids display expanded surface area, mesoporous anchored nanosheets network morphology, and intimate coupling between nanosheets.

View Article and Find Full Text PDF

Emerging energy-efficient neuromorphic circuits are based on hardware implementation of artificial neural networks (ANNs) that employ the biomimetic functions of memristors. Specifically, crossbar array memristive architectures are able to perform ANN vector-matrix multiplication more efficiently than conventional CMOS hardware. Memristors with specific characteristics, such as ohmic behavior in all resistance states in addition to symmetric and linear long-term potentiation/depression (LTP/LTD), are required in order to fully realize these benefits.

View Article and Find Full Text PDF

The one-step hydrothermal method was used to synthesize Sn-doped TiO (Sn-TiO) thin films, in which the variation in Sn content ranged from 0 to 7-wt % and, further, its influence on the performance of a dye-sensitized solar cell (DSSC) photoanode was studied. The deposited samples were analyzed by X-ray diffraction (XRD) and Raman spectroscopy, which confirmed the existence of the rutile phase of the synthesized samples with crystallite size ranges in between 20.1 to 22.

View Article and Find Full Text PDF

In the present study, cobalt manganese phosphate (H-CMP-series) thin films with different compositions of Co/Mn are prepared on stainless steel (SS) substrate via a facile hydrothermal method and employed as binder-free cathode electrodes in a hybrid supercapacitor. The XRD study reveals a monoclinic crystal structure, and the FE-SEM analysis confirmed that H-CMP-series samples displayed a nano/microarchitecture (microflowers to nanoflakes) on the surface of SS substrate with excess available surfaces and unique sizes. Interestingly, the synergy between cobalt and manganese species in the cobalt manganese phosphate thin film electrode demonstrates a maximum specific capacitance of 571 F g at a 2.

View Article and Find Full Text PDF
Article Synopsis
  • Researchers developed high-efficiency quantum dot light-emitting diodes (QLEDs) using lithium-doped titanium dioxide nanoparticles (TiO NPs) as an electron transport layer (ETL) to enhance device performance.
  • The addition of lithium improves charge balance by raising the conduction band minimum, which helps manage electron injection effectively.
  • A green QLED with 5% Li-doped TiO NPs achieved record performance metrics, including maximum luminance of 169,790 cd/m², an external quantum efficiency of 10.27%, and a current efficiency of 40.97 cd/A, demonstrating the potential of Li-doped TiO NPs for future QLEDs.
View Article and Find Full Text PDF

Turbomachine components used in aerospace and power plant applications preferably require continuous structural health monitoring at various temperatures. The structural health of pristine and damaged superalloy compressor blades of a gas turbine engine was monitored using real electro-mechanical impedance of deposited thick film piezoelectric transducers at 20 and 200 °C. IVIUM impedance analyzer was implemented in laboratory conditions for damage detection in superalloy blades, while a custom-architected frequency-domain transceiver circuit was used for semi-field circumstances.

View Article and Find Full Text PDF