• Journal of Sensor Science and Technology
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• v.24 no.3
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• pp.151-154
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• 2015

The gas sensing characteristic of $MoS_2-MoO_2$ composite yolk-shell spheres were investigated. $MoO_3$-carbon composite spheres were prepared by ultrasonic spray pyrolysis of aqueous droplets containing Mo-source and sucrose in nitrogen, which were converted into $MoO_3$ yolk-shell spheres by heat treatment at $400^{\circ}C$ in air. Subsequently, $MoS_2-MoO_2$ composite yolk-shell spheres were prepared by the partial sulfidation of $MoO_3$. The $MoS_2-MoO_2$ composite yolk-shell spheres showed relatively low and irreversible gas sensing characteristics at < $200^{\circ}C$. In contrast, the sensor showed high and reversible response (S=resistance ratio) to 5 ppm $NO_2$ (S=14.8) at $250^{\circ}C$ with low cross-responses (S=1.17-2.13) to other interference gases such as ethanol, CO, xylene, toluene, trimethylamine, $NH_3$, $H_2$, and HCHO. The $MoS_2-MoO_2$ composite yolk-shell spheres can be used as reliable sensors to detect $NO_2$ in a selective manner.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.1
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• pp.52-58
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• 2004

Magneto-Impedance(MI) sensor is a highly sensitive sensor, which was able to detect a weak geomagnetic field. It also has a merit to be able to build in the low power system. In this study, their magnetic permeability and anisotropy field(H$\sub$k/) as a function of some different thickness of sputtered amorphous CoZrNb films with zero-magnetostriction and soft magnetic property are investigated. In order to make a uniaxial anisotropy, film was subjected to the post annealing in a static magnetic field with 1KOe intensity at 250, 300, and 320$^{\circ}C$ respectively for 2 hours. Magnetic properties of films are measured by using a M-H loop tracer. Magnetic permeability of a film is measured over the frequency range from 1 ㎒ to 750㎒. By thickening a CoZrNb film relatively, magnetic permeability and impedance are examine to design the. MI sensor which drives at 50㎒, and thereof fabricated the MI sensor which drives at the 50㎒.

• Journal of the Korean Ceramic Society
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• v.23 no.5
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• pp.1-8
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• 1986

This paper is concerned with a gas sensor composed of semi-conducting ${\gamma}$-$Fe_2O_3$ ceramics made by oxidizing $Fe_2O_3$ sintered body. Acicular $\alpha$-FeOOH powder prepared by precipitation of $FeSO_4$.$7H_2O$ solution was transformed to $FeSO_4$ sintered at 700$^{\circ}$-850$^{\circ}$C for 1 hr. and then oxidized to ${\gamma}$-$Fe_2O_3$ The gas sensitive properties of ${\gamma}$-$Fe_2O_3$ ceramic bodies based on the lectrical resistance change was measured in 0.5-2 vol% $H_2$ and $C_2$ $H_2$ gas at 35$0^{\circ}C$ The specific surface area of sintered specimen largely dependent on the sintering temperature and grain shape directly affected the gas sensitive pro-perties of ${\gamma}$-$Fe_2O_3$gas sensor. Specimens having larger specific surface area showed better sensitivity which means the electrical resistance change due to oxidation and reduction process occurs on ly at the surface of grains microscopically in the ${\gamma}$-$Fe_2O_3$ceramics. Micropores made in $Fe_2O_3$ powder during dehydration of $\alpha$-FeOOH can not prompt the gas sensitive properties of sintered ${\gamma}$-$Fe_2O_3$ because they are sintered or closed in the grains during sintering process and dose not affect the specific surface area of sintered body.

• Journal of Sensor Science and Technology
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• v.28 no.4
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• pp.231-235
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• 2019

We investigated the facile and effective strategy for sensitive and selective $C_2H_5OH$ sensors based on the In-decorated NiO nanoigloos. The In-decorated NiO nanoigloos is fabricated by RF sputtering using 750 nm-diameter polystyrene beads using a soft-template. The morphological evolution based on the Van der Drift model was generated through a heterojunction between In metal and NiO, resulting in a pyramidal rough surface. Upon decorating the In on the NiO surface, high sensitivity and selectivity to $C_2H_5OH$ were observed, and gas sensing mechanism was demonstrated by a high surface-to-volume and double Schottky barrier. We are confident that the method presented in this study will have a significant impact on the fabrication of effective nanostructures and their application for the gas sensors.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.2
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• pp.105-110
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• 2000

The $\alpha$-$Fa_{2}O_{3}/SnO_{2}$ thin film gas sensor was fabricated by APCVD and heat treated. The gas sensitivity to flammable gases ($CH_4$, $H_2$, LPG) was measured. This device was to heat treatment at $400^{\circ}C$, $450^{\circ}C$, $500^{\circ}C$, $550^{\circ}C$, $600^{\circ}C$ for 2 h to enhance the gas sensitivity. The heat treated device at $500^{\circ}C$ for 2 h had the best properties and especially it shows high sensitivity to H2 gas. The sensitivity to gases was studied in the temperature range from lOoC to $300^{\circ}C$ in order to find the optimum detection temperature. In the range of detection from 500 ppm to 10,000 ppm at $175^{\circ}C$ the fabricated device showed that the gas sensitivity to $H_2$ was from 62%~76% and to $CH_4$ was from 16 %~58% and to LPG was from 8%~37 %. The sensitivity difference between heat treated device and as fabricated one was about 10 8 The long-term stability to LPG at 1,000 ppm was converged to sensitivity of 30 %.

• Electronics and Telecommunications Trends
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• v.37 no.2
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• pp.30-41
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• 2022

As the society is superaging, the number of patients with movement disabilities due to musculoskeletal or nervous system illness is rapidly increasing. To improve public health and reduce medical expenses, it is essential to develop rehabilitation systems that allow patients to resume their daily-life activities. However, the existing musculoskeletal illness diagnosis and rehabilitation method is limited in terms of precision and efficiency because it is based on an empirical diagnosis and prescription without regard for individual characteristics. To overcome these limits, it is critical to design a novel concept of routine rehabilitation therapy device that is capable of inducing musculoskeletal balance by the precise analysis of musculoskeletal usage patterns via the motion and the muscle activity tracking of linked muscles. This study introduces the trend of on-skin sensor device technology for routine musculoskeletal monitoring and therapy. For on-skin rehabilitation systems, skin-adhesive and stretchable motion/posture, electromyography, pressure sensors, small-size and low-power wireless sensor interfaces, and user-friendly rehabilitation contents based on new algorithms are combined.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.236-236
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• 2009

This paper describes the fabrication and characteristics of Schottky micro hydrogen sensors for high temperatures by using polycrystalline(poly) 3C - SiC thin film grown on Si substrates with thermal oxide layer using APCVD. Pd/poiy 3C-SiC Schottky diodes were made and evaluated by I-V and C-V measurements. Electric current density and barrier height voltage were $2\times10^{-3}\;A/cm^2$ and 0.58 eV, respectively. These devices could operate stably at about $400^{\circ}C$. According to $H_2$ concentrations, their barrier height($\Phi_{Bn}$) were changed 0.587 eV, 0.579 eV, 0.572 eV and 0.569 eV, respectively. the current was increased. Characteristics of implemented sensors have been investigated in terms of sensitivity, linearity of response, response rate and response time. Therefore, from these results, Pd/poly 3C-SiC Schottky devices have very high potential for high temperature chemical sensor applications.

• Bulletin of the Korean Chemical Society
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• v.32 no.9
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• pp.3433-3436
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• 2011

Some of metal nanoparticles have the potential for use as colorimetric assays for estimating solution properties, such as pH and temperature due to localized surface plasmon (LSP) phenomena. This report describes the use of silver nanoparticles (AgNP) conjugated with cytochrome c (Cyt c) for the colorimetric determination of solution pHs. When the pH of a solution decreases, the Cyt c immobilized on the AgNP undergoes a conformational change, leading to a decrease in the interparticle distance between Cyt c-AgNP probes and consequent red-shift in LSP. As a result, the color of the Cyt c-AgNP probe solution changes from yellow to red and finally to a grayish blue in the pH range from 11 to 3. This gradual color change can be used to determine the pH of a solution over a wide pH range, compared to other colorimetric methods that use gold nanoparticles.

• Journal of Powder Materials
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• v.13 no.3 s.56
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• pp.192-198
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• 2006

The nanostructured cerium oxide powders were synthesized by spray thermal decomposition process for the use as the raw materials of resistive oxygen sensor. The synthesis routes consisted of 1) spray drying of water based organic solution made from cerium nitrate hydrate ($Ce(NO_3){_3}6H_2O$) and 2) heat treatment of spray dried precursor powders at $400^{\circ}C$ in air atmosphere to remove the volatile components and identically to oxidize the cerium component. The produced powders have shown the loose structure agglomerated with extremely fine cerium oxide particles with about 15 nm and very high specific surface area ($110m^2/g$). The oxygen sensitivity, n ($Log{\propto}Log (P_{O2}/P^o)^{-n}$ and the response time, $t_{90}$ measured at $600^{\circ}C$ in the sample sintered at $1000^{\circ}C$, were about 0.25 and 3 seconds, respectively, which had much higher performances than those known in micron or $100{\sim}200nm$ sized sensors.

• Journal of Sensor Science and Technology
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• v.15 no.3
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• pp.168-172
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• 2006

Potentiometric $CO_{2}$ sensors were fabricated using a NASICON ($Na_{1+x}Zr_{2}Si_{X}P_{3-X}O_{12}$, 1.8 < x < 2.4) thick film and auxiliary layers. The powder of a precursor of NASICON with high purity was synthesized by a sol-gel method. By using the NASICON paste, an electrolyte was prepared on the alumina substrate by screen printing and then sintered at $1000^{\circ}C$ for 4 h. A series of $Na_{2}CO_{3}-CaCO_{3}$ auxiliary phases were deposited on the Pt sensing electrode. The electromotive force (emf) values were linearly dependent on the logarithm of $CO_{2}$ concentration in the range between 1,000 and 10,000 ppm. The device attached with $Na_{2}CO_{3}-CaCO_{3}$ (1:2 in mol.%) showed good sensing properties in the low temperatures.