• Journal of the Korean Ceramic Society
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• v.49 no.1
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• pp.124-129
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• 2012

An M-shaped SiC gas igniter was fabricated by a reaction sintering followed by nitrogen doping. The igniter showed both resistivity at room temperature and NTC to PTC transition temperature values that were lower than those of commercial igniters. It was deduced that the doped nitrogen reduces the electrical resistivity at room temperature, while, at high temperature, the doped nitrogen and a trace of $Si_3N_4$ phase work as scattering centers against electron transfer, resulting in a lowered NTC-to-PTC transition point (below $650^{\circ}C$). Such characteristics were correlated to the fast heating speed (as compared to the commercial models) and to the prevention of the high temperature overshooting of the nitrogen-doped SiC igniter.

• Journal of the Korean Society of Safety
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• v.18 no.3
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• pp.101-108
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• 2003

Polymeric positive temperature coefficient(PTC) composites have been prepared by incorporating carbon black(CB) into high density polyethylene(HDPE), polyphenylene sulfide(PPS) and polybutylene terephthalate(PBT) matrices. A PTC effect was observed in the composite, caused by the large thermal expansion due to He consecutive melting of HDPE, PPS and PBT crystallites. This theory is based upon the premise that the PTC phenomenon is due to a critical separation distance between carbon particles in the polymer matrix at the higher temperature. The influence of PTC characteristics of the PPS/CB composite can be explained by DSC result. HDPE, one of prepared composition, exhibit the higher performance PTC behavior that decreaseing of negative temperature coefficient(NTC) effect and improved reproducibility by chemically crosslinking. Also, PBT/CB and PPS/CB composites exhibit the higher PTC peack temperature than HDPE/CB PTC composite, individually $200^{\circ}C$ and $230^{\circ}C$. These PTC composite put to good use in a number of safety application, such as self$.$controlled heater, over-current protectors, auto resettable switch, high temperature proctection sensor, etc.

• International Journal of Internet, Broadcasting and Communication
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• v.7 no.1
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• pp.57-61
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• 2015

The level of change in distant PTC, near PTC, distant NTC, and near NTC was measured divided by before and after viewing 3D images. The 50 examinees were categorized into Low/ Middle/ High groups according to the level of change by test subject. Among all the entries, the exophoria group showed the highest change distribution, and in the distant and near NTC entries showed statistically significant differences in variation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.236-237
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• 2006

We have investigated volume resistivity showed by changing the content of Carbon nanotube and carbon black which is the component parts of semiconducting shield in underground power transmission cable. Specimens were made of sheet form with the six of specimens for measurement. Volume resistivity of specimens was measured by volume resistivity meter after 10 minutes in the preheated oven of both $23{\pm}1[^{\circ}C]$ and $90{\pm}1[^{\circ}C]$. The volume resistivity decreased by adding Carbon nanotube and carbon black. Also the volume resistivity had different properties because of PTC/NTC tendencies at between $23[^{\circ}C]$ and $90[^{\circ}C]$. We experimented with electric properties of semiconducting components with fewer Carbon nanotube than carbon black.

• Polymer(Korea)
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• v.27 no.4
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• pp.275-284
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• 2003

The positive temperature coefficient (PTC) effects of high density polyethylene (HDPE)/carbon black composite materials were investigated by enhancing adhesive characteristics of electrodes and controlling HDPE chemical crosslinking. When the silver paste was used as an electrode for the same 45 wt% HDPE/carbon composites, the resistance was over 1 $\Omega$, which should be compared with the resistance of 0.2 $\Omega$ for the dendritic copper electrode. In general, the silver-paste electrode exhibited higher electrical resistance than cupper electrode due to the interfacial resistance between the electrode and PTC composites. The HDPE/carbon composite exhibited typical PTC characteristics maintaining a constant resistance up to vicat point and showing a maximum at the melting point of HDPE. The crosslinked HDPE significantly decreased the negative temperature coefficient (NTC) phenomena, and desirably showed a constant or slightly increasing feature of electrical resistance in the high temperature region.

• Composites Research
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• v.16 no.1
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• pp.19-25
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• 2003

In this paper, electrical properties of nanostructured carbon blacks (CB)-filled high density polyethylene (HDPE) composites were investigated as a function of temperature, which were prepared by the conventional melt-mixing method. The composites were irradiated with electron beam in a dosage of 30∼150 kGy to enhance an electronical reproducibility and to reduce a negative temperature coefficient (NTC) phenomenon. And, gel contents (%) of irradiated CB/HDPE composites were estimated by solvent extraction method. From the experimental results. the positive temperature coefficient (PTC) intensity of the composites was strongly depended on the CB content and particle size. And, the increase of gel contents (%) and disappearance of NTC behavior of the composites were identified at a dosage of 60 kGy. It was also found that the electron beam irradiation made an improvement of electrical reproducibility of the composites. This result was probably due to the reduction of the freedom of CB movement at above the melting temperature of the polymer crystalline, resulting in increasing the crosslinking structure of the composites.

• Journal of the Korean Chemical Society
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• v.47 no.2
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• pp.147-154
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• 2003

In this study, the fluorinated carbon blacks(CB) were used to reduce the negative temperature coefficient (NTC) phenomenon of the CB-filled high density polyethylene(HDPE) compounds in the fluorination pressure of 0.1-0.4 MPa. The changes in surface properties of the CB were investigated by using FT-IR, XPS and contact angle measurements. From the FT-IR results, the fluorinated CB showed the C-F absorption peak at 1400-1000 cm$^{-1}$ and the peak intensity was increased with increasing the fluorination pressure. Also, the analysis of XPS spectra of the fluorinated CB indicated that fluorine content was increased with increasing the fluorination pressure. Meanwhile, the surface free energy of the fluorinated CB was decreased with increasing the fluorination pressure. Consequently, the increase of fluorine contents on CB made a disappearance of NTC behaviors of CB/HDPE compounds, which was probably due to the reduction of CB reaggregation after melting point of the HDPE, resulting from decreasing the surface free energy of CB particles.

• Polymer(Korea)
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• v.29 no.1
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• pp.32-35
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• 2005

In this paper, the carbon nanotubes (CNTs) were ozonized and the positive temperature coefficient (PTC) behaviors of CNTs-filled high-density polyethylene (HDPE) conductive composites were studied. The results of element analysis (EA) and FT-IR indicate that the oxygen-containing functional groups on the CNTs surfaces, such as O-H, C-O, and C＝O groups, were increased with the ozonization. Electrical resistivities of the CNTs/HDPE composites were measured by using a digital multimeter. The resistivity of the composites was increased abruptly near the crystalline melting temperature of the HDPE used as matrix, which could be attributed to the destruction of conductive network by the thermal expansion of HDPE. And, the PTC intensity of the CNTs/HDPE composites was increased with the increase of the ozone treatment time. It was probably due to the growing of maximum volume resistivity of the composites induced by the increased oxygen-containing functional groups in the CNTs surfaces.

• 전기의세계
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• v.41 no.3
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• pp.38-42
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• 1992

써미스터(THERMLISTOR)는 Thermally Sensitive Resistor의 약칭으로 온도변화에 대한 저항치의 변화가 극히 크게 변화하는 특징을 갖는 감온반도체이다. 이중에는 부특성 또는 NTC(Negative Temperature Coeffient) THERMISTOR와 정특성 또는 PTC(Positive Temperature Coeffient)THERMISTOR의 두종류와 NTC와 동일한 부의 온도계수이지만 어떤 온도영역에서 저항치가 급격히 감소하는 CTR로 분류한다. 이렇게 3가지 종류로 분류되는 THERMISTOR중 우리주변에서 가장 널리 보급되고 가정생활에서 실제로 흔히 볼수 있는 가전기기의 온도검출용 sensor로 많이 사용되고 있는 THERMISTOR SENSOR에 대해서만 기초지식을 알아보기로 하고 다음기회에는 응용기술에 대해서 알아보기로 하겠다.

• Carbon letters
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• v.2 no.3_4
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• pp.159-164
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• 2001

In this study, the effects of carbon black (CB) content and anodic oxidation treatment with $AgNO_3$ on positive temperature coefficient (PTC) behavior of CB/HDPE nanocomposites were investigated. Also, the addition of elastomer as a toughing agent was studied. The 20~50 wt% of CB, 0~5 wtt% of elastomer, and 1 wt% of $AgNO_3$-filled HDPE nanocomposites were prepared using the internal mixer in 60 rpm at $160{\circ}C$ and the compression-molded at $180{\circ}C$ for 10 min. As a result, the room temperature resistivity and PTC intensity of the composites were dependent, to a large extent, on the content of CB, addition of elastomer, and surface chemical properties that were controlled in the relative arrangements of the carbon black aggregates in a polymeric matrix. Moreover, the composites with relatively low room temperature resistivity and suitable PTC intensity could be achieved by treatment of $AgNO_3$. Consequently, it was noted that PTC effect was due to the deagglomeration or the breakage of the conductive networks caused by thermal expansion or crystalline melting of the polymeric matrix.