• Journal of the Korean Ceramic Society
• /
• v.55 no.1
• /
• pp.1-20
• /
• 2018

Semiconducting nanomaterials have attracted considerable interest in recent years due to their high sensitivity, selectivity, and fast response time. In addition, for portable applications, they have low power consumption, lightweight, simple in operation, a low maintenance cost. Furthermore, it is easy to manufacture microelectronic sensor structures with metallic oxide sensitive thin layers. The use of semiconducting metal oxides to develop highly sensitive chemiresistive sensing systems remains an important scientific challenge in the field of gas sensing. According to the sensing mechanisms of gas sensors, the overall sensor conductance is determined by surface reactions and the charge transfer processes between the adsorbed species and the sensing material. The primary goal of the present study is to explore the possibility of using semiconducting mixed metal oxide nanostructure as a potential sensor material for selective gases.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.27 no.5
• /
• pp.243-248
• /
• 2017

In this study copper glaze samples were prepared with varying amount of tin oxide, and the chromatic characteristics of glazes were explained on the results of spectrophotometric, crystalline phase, and microstructural analyses. The red color of copper glaze was dissipated with the addition of tin oxide and turned into achromatic color due to the decrease of CIEab values. Tin oxide homogeneously distributed in the glaze layer interfered with the red color generation coming from the growth of Cu nuclei, and formed an alloy with metal copper around bubbles. This resulted in the decrease of metal copper peak intensity with minor $Cu_2O$ peak. With the 3.79 % tin oxide addition the glaze was appeared as gray due to the black color CuO and Cassiterite $SnO_2$ phases.

• Ceramist
• /
• v.22 no.1
• /
• pp.70-81
• /
• 2019

Breath analysis is rapidly evolving as a non-invasive disease recognition and diagnosis method. Metal oxide gas sensors are one of the most ideal platforms for realizing portable, hand-held breath analysis devices in the near future. This paper reviewed the recent developments in metal oxide gas sensors detecting exhaled biomarker gases such as nitric oxides, acetone, ammonia, hydrogen sulfide, and hydrocarbons. Emphasis was placed on strategies to tailor sensing materials/films capable of highly selective and sensitive detection of biomarker gases with negligible cross-response to ethanol, the major interfering breath gas. Specific examples were given to highlight the validity of the strategies, which include optimization of sensing temperature, doping additives, utilizing acid-base interaction, loading catalysts, and controlling gas reforming reaction. In addition, we briefly discussed the design and optimization method of gas sensor arrays for implementing the simultaneous assessment of multiple diseases. Breath analysis using high-performance metal oxide gas sensors/arrays will open new roads for point-of-care diagnosis of diseases such as asthma, diabetes, kidney dysfunction, halitosis, and lung cancer.

• Applied Chemistry for Engineering
• /
• v.18 no.6
• /
• pp.618-624
• /
• 2007

thermochemical methane reforming consisting of two steps on Cu/Fe/Zr mixed oxide media was carried out using a fixed bed infrared reactor. In the first step, the metal oxide was reduced with methane to produce CO, $H_2$ and the reduced metal oxide in the temperature of 1173 K. In the second step, the reduced metal oxide was re-oxidized with steam to produce $H_2$ and the metal oxide in the temperature of 973 K. The reaction characteristics on the added amounts of Cu in Cu/Fe/Zr mixed oxide media and the cyclic tests were evaluated. With the increase of the added amount of Cu in Cu/Fe/Zr mixed oxide media, the conversion of $CH_4$, the selectivity of $CO_2$ and the $H_2/CO$ molar ratio were increased, while the selectivity of CO was decreased in the first step. On the other hand, the evolved amount of $H_2$ was decreased with increasing the added amount of Cu in the second step. The $Cu_xFe_{3-x}O_4/ZrO_2$ medium added with Cu of x = 0.7 showed good regeneration properties in the 10th cyclic tests indicating that the medium had high durability. In addition, the gasification of the deposited carbon in the water splitting step was promoted with the addition of Cu in the media.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.302.1-302.1
• /
• 2016

Solution-processed amorphous metal-oxide thin-film transistors (TFTs) are considered as promising candidates for the upcoming transparent and flexible electronics due to their transparent property, good performance uniformity and possibility to fabricate at a low-temperature. In addition, solution processing metal oxide TFTs may allow non-vacuum fabrication of flexible electronic which can be more utilizable for easy and low-cost fabrication. Recently, for high-mobility oxide TFTs, multi-layered oxide channel devices have been introduced such as superlattice channel structure and heterojunction structure. However, only a few studies have been mentioned on the bias illumination stress in the multi- layered oxide TFTs. Therefore, in this research, we investigated the effects of bias illumination stress in solution-processed bilayer oxide TFTs which are fabricated by the deep ultraviolet photochemical activation process. For studying the electrical and stability characteristics, we implemented positive bias stress (PBS) and negative bias illumination stress (NBIS). Also, we studied the electrical properties such as field-effect mobility, threshold voltage ($V_T$) and subthreshold slop (SS) to understand effects of the bilayer channel structure.

• Journal of Powder Materials
• /
• v.8 no.3
• /
• pp.186-191
• /
• 2001

Several fabrication processes, corresponding nanostructural features and multifunctionality as well has been investigated for oxide ceramic based nanocomposites with metal nanodispersion (i.e., ceramic/metal nanocomposites). Transition metal (Ni, Co, etc) dispersed alumina and zirconia based nanocomposites have been synthesized by reducing and hot-press sintering of ceramic and metal oxide mixtures prepared by several method. Improved fracture strength (1.1 and 1.9 GPa for $Al_2O_3/Ni$ and $ZrO_2/Ni$ nanocomposites, respectively) of these composites have been achieved according to their nanostructures. In addition, ferromagnetic characteristic has been kept. The variation of magnetization with an applied stress has found to be more sensitive as smaller as the magnetic metal dispersion is. This result thus suggests the possibility of fracture and/or stress sensing of the composites by simple magnetic measurement.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.26 no.2
• /
• pp.119-138
• /
• 2016

Objectives: The purpose of this study is to review size, shape, and crystal structure-dependent toxicity of major metal oxide particles such as silicon dioxide, tungsten trioxide, aluminum oxide, and titanium dioxide as byproducts generated in semiconductor fabrication facility. Methods: To review the toxicity of major metal oxide particles, we used various reported research and review papers. The papers were searched by using websites such as Google Scholar and PubMed. Keyword search terms included '$SiO_2$(or $WO_3$ or $Al_2O_3$ or $TiO_2$) toxicity', 'health effects $SiO_2$(or $WO_3$ or $Al_2O_3$ or $TiO_2$). Additional papers were identified in references cited in the searched papers. Results: In various cell lines and organs of human and animals, cytotoxicity, genotoxicity, hepatoxicity, fetotoxicity, neurotoxicity, and histopathological changes were induced by silicon dioxide, tungsten trioxide, aluminium oxide, and titanium dioxide particles. Differences in toxicity were dependent on the cell lines, organs, doses, as well as the chemical composition, size, surface area, shape, and crystal structure of the particles. However, the doses used in the reported papers were higher than the possible exposure level in general work environment. Oxidative stress induced by the metal oxide particles plays a significant role in the expression of toxicity. Conclusions: The results cannot guarantee human toxicity of the metal oxide particles, because there is still a lack of available information about health effects on humans. In addition, toxicological studies under the exposure conditions in the actual work environment are needed.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.36D no.3
• /
• pp.34-40
• /
• 1999

Recently, the gate oxide damage induced by the plasma processes has been one of the most significant reliability issues as the gate oxide thickness falls below 10 nm. The plasma-induced damage was studied with the metal antenna test structures. In addition to the electron trapping, the hole trapping in a 10 nm thick gate oxide due to the plasma-induced charging was observed in the NMOS's with a metal antenna. The hole trapping caused the transconductance (gm) to be reduced like the case of the electron trapping, but to the extent much less than the electron trapping. It would be because the electrical stress that the plasma-induced charging forced to the gate oxide for the devices with the hole trapping was much smaller than for those with the electron trapping. This hypothesis was strongly supported by the measured characteristics of the Fowler-Nordheim current in the gate oxide.

• Transactions of the Korean hydrogen and new energy society
• /
• v.18 no.2
• /
• pp.140-150
• /
• 2007

Thermochemical 2-step methane reforming, involving the reduction of metal oxide with methane to produce syngas and the oxidation of the reduced metal oxide with water to produce pure hydrogen, was investigated on ferrite-based metal oxide mediums. The mediums, CoFZ, CuFZ, or MnFZ, were composed of the mixture of M(M=Co, Cu or Mn)-substituted ferrite as an active component and $ZrO_2$ as a binder, respectively. The WZ medium, composed of the mixture of $WO_3$ and $ZrO_2$, was also prepared to compare. With an addition of $ZrO_2$, the surface area of the mediums was slightly increased and the sintering of active components was greatly suppressed during the reduction. The higher reactivity of the reduced mediums for water splitting was confirmed by the temperature programmed reaction. From the results of the thermochemical 2-step methane reforming, the reactivity of $CH_4$ reduction and water splitting with ferrite-based metal oxide mediums was relatively higher than that with WZ, and the order of reactivity of the mediums was MnFZ>CoFZ>CuFZ>WZ.

• Journal of Korea Foundry Society
• /
• v.10 no.2
• /
• pp.154-161
• /
• 1990

The microstructures of sintered products of $Fe_2O_3$or $Fe_3O_4$-Oxide added cast iron powder was investigated. And the effects of particle size distribution was investigated too. As the result, the structures of sintered products did not related to the species of Fe-Oxide. Th porosity of sintered products was decreased in size and spherodized with increasing sintering temperature, decreasing Fe-Oxide quantity. Fe-Oxide itself did not hinder sintering of cast iron powder particularly, therefore sintering could be occurred without termination of reduction of it. And the sintered products of finer particle size distribution had finer and more spherodized porosity, and had minimized the deviation of size and shape of porosity.