• Proceedings of the KIEE Conference
• /
• 2001.07c
• /
• pp.1399-1401
• /
• 2001

We studied on structure and resistivity, temperature coefficient of resistance (TCR) of NiCr and NiCr-N thin resistor films prepared by do reactive magnetron sputtering of NiCr target. It is found that while pure NiCr films are polycrystalline, an addition of nitrogen (N2/(Ar+N2) ratios are between 10% and 70%) into the film is changed into amorphous structure and sheet resistance of films is increased. Measurement temperatures of TCR are ratios of $5^{\circ}C$ per 15min from $25^{\circ}C$ to $130^{\circ}C$. TCR for an as-deposited NiCr-N thin film is varied from positive to negative.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1995.11a
• /
• pp.347-350
• /
• 1995

In this paper, we fabricated fuel shortage detecting sensor, utilizing NTC thermistor concerned with Mn-Ni-Co system. We would be obtained B constant value of 1930∼2080 and resistivity 387∼430(ohm-cm) additive Bi$_2$O$_3$0∼0.5 wt% to Mn$_3$O$_4$:9wt%, Co$_3$O$_4$:61wt%, NiO:28wt% under 1150∼1250$^{\circ}C$ of sintering temperature. In sensor, we obtained characteristics, which we want, in resistance range 850∼l150$\Omega$, B constant 2000${\pm}$5%. we can see 15 multiplied differences between gasoline and heat dissipation coefficient of air condition.

• Proceedings of the KIEE Conference
• /
• 1998.11c
• /
• pp.861-863
• /
• 1998

As-casted high nitrogen alloys (Fe-25%Mn-12%Cr-1%Ni) have been investigated to study core material. Nitrogen concentration in molten alloys was increased with increasing the square root of nitrogen gas pressure in melting chamber. This result can be explained by Sievert's law. Nitrogen that dissolved as a interstital solid solution element in austenite stainless steel increased lattice parameter and hardness. Electric resistivity($\rho$) was increased with increasing nitrogen concentration and was about $80{\mu}{\Omega}cm$ at room temperature. Coefficient of linear thermal expansion of the nitrogen steel was about $22{\times}10^{-6}/^{\circ}C$.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2005.11a
• /
• pp.71-74
• /
• 2005

In this paper, the effects of the MWCNTs on the PTC characteristics of the conventional CB/polymer nanocomposites were investigated. For the uniform dispersion of the MWCNTs in the polymer matrix., nitricacid-treated MWCNTs were dispersed with the dissolved HOPE in the solvent. After evaporating solvent, the dried master batches in the oven were melt blended mixed with CB and HDPE to obtain the PTC materials. The initial resistivity of PTC materials decreased and the PTC intensity increased with the MWCNTs. During three repeated heating and cooling cycles, the PTC materials containing MWCNTs showed a great reproducibility due to the conductive network structures of CB particles and MWCNTs.

• Journal of the Korean Ceramic Society
• /
• v.29 no.10
• /
• pp.779-784
• /
• 1992

In producing cordierite glass-ceramics by sintering, following experiments were conducted in order to determine the optimum heat-treatment schedule for high-crystallinity and dense sintered body. The glass composition of 11.67MgO-29.46Al2O3-52.88SiO2-5P2O5-1B2O3 (wt%) was selected on the basis of the early experiment. The 3-step heat treatment schedule was determined by the results of DTA, Dilatometric measurement and high-temperature XRD, where the particle-size-controlled glass powder was used. The degree of densification and the crystallinity were evaluated by the measurement of the bulk density and X-ray scattering intensity. The specimen fired with the optimum conditions showed ${\alpha}$-cordierite phase, relative density ∼98%, crystallinity ∼92%, thermal expansion coefficient ∼30${\times}$10-7/$^{\circ}C$, dielectric constant ∼5.5 and resistivity ∼1.0${\times}$1012 {{{{ OMEGA }}cm, respectively.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.11
• /
• pp.2701-2706
• /
• 2009

The polymer blends containing polypyrrole (PPy) and the sulphonic acids such as β-naphthalene sulfonic acid (NSA), camphor sulfonic acid (CSA), and dodecylbenzenesulfonic acid (DBSA) were synthesized by in situ deposition technique in an aqueous media using ammonium per sulfate (APS) as an initiator. The obtained films were characterized by scanning electron microscopy (SEM), and the thermal behavior of these polymer blends was analyzed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The temperature-dependent (DC) conductivity of the obtained films shows a semiconducting behavior with a negative temperature coefficient of resistivity (TCR). The conductivity data were also analyzed through Mott’s equation, which provides the variable range hopping model in three dimensions. The parameters such as density of states at the Fermi energy, hopping energy, and hopping distance were calculated for PPy, PPy-NSA, PPy-CSA, and PPy-DBSA films, and the data were compared.

• Journal of Korean Vacuum Science & Technology
• /
• v.6 no.1
• /
• pp.12-15
• /
• 2002

The physical properties, including magneto-optical and transport ones, of Ni$_2$MnG$_2$ alloy in the martensitic and austenitic states were investigated. The dependence of the temperature coefficient of resistivity on temperature shows kinks at the structural and ferro-para magnetic transitions. Electron-magnon and electron-phonon scattering are analyzed to be the dominant scattering mechanisms of the Ni$_2$MnG$_2$ alloy in the martensitic and austenitic states, respectively. The experimental real parts of the off-diagonal components of the dielectric function present two sharp peaks, one at 1.9 eV and the other at 3.2 eV, and a broad shoulder at 3.5 eV, all are identified by the band-structure calculations. These peak positions are coincident with those in the corresponding optical-conductivity spectrum, which is thought to originate from the single-spin state in Ni$_2$MnG$_2$ alloy.

• Proceedings of the KIEE Conference
• /
• 1999.07d
• /
• pp.1989-1991
• /
• 1999

This paper presents characteristics of CrN thin-film strain gauges, which were deposited on glass by DC reactive magnetron sputtering in an argon-nitrogen atmosphere(Ar-$(5{\sim}25%)N_2$). The physical and electrical characteristics of these films investigated with the thickness range $3500{\AA}$ of CrN thin films, annealing temperature $(100{\sim}300^{\circ}C)$ and annealing $(24{\sim}72hr)$. The optimized condition of CrN thin-film strain gauges were thickness range of $3500{\AA}$ and annealing condition($300^{\circ}C$, 48 hr) in Ar-10 %$N_2$ deposition atmosphere. Under optimum conditions, the CrN thin-films for strain gauge is obtained a high resistivity, ${\rho}=1147.65{\mu}{\Omega}cm$, a low temperature coefficient of resistance, TCR=$-186ppm/^{\circ}C$ and a high temporal stability with a good longitudinal, 11.17. And change in resistance after annealing for the CrN thin-films were quitely linear and stable.

• Journal of Sensor Science and Technology
• /
• v.18 no.4
• /
• pp.301-306
• /
• 2009

This paper describes the design and fabrication of 16$\times$16 microbolometer infrared focal plane arrays based on iMEMS technology. Amorphous silicon was used for infrared-sensitive material, and it showed the resistance of 18 Mohm and the temperature coefficient of resistivity of -2.4 %. The fabricated sensors exhibited responsivity of 78 kV/W and thermal time constant of 8.0 msec at a bias voltage of 0.5 V. The array performances had satisfactory uniformity less than 5 % within one-sigma. Also, 1/f noise of pixel was measured and the noise factor of $6\times10^{-11}$ was extracted. Finally, we obtained detectivity of $1.27\times10^9cmHz^{0.5}/W$ and noise equivalent temperature difference of 200 mK at a frame rate of 30 Hz.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.142-142
• /
• 2007

Micro thermoelectric generator has been attractive for the alternative power source to operate the wireless sensor node. In this paper, we designed the column-type micro thermoelectric device and their device characteristics were measured. n-type Bi2Te3 and p-type BiSbTe3 thermoelectric thin films were grown on (001) GaAs substrates by metal organic chemical vapour deposition (MOCVD) and they were pattemed. The height of thermoelectric film were controlled by the deposition time, temperature and MO-x gas pressure. Seebeck coefficient was measured at room temperature and hole concentration and electrical resistivity of thermoelectric film were also characterized.