• Proceedings of the Materials Research Society of Korea Conference
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• 1997.10a
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• pp.75-75
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• 1997

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.05a
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• pp.115-115
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• 1996

• Proceedings of the Materials Research Society of Korea Conference
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• 1998.11a
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• pp.49-49
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• 1998

• Proceedings of the Membrane Society of Korea Conference
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• 1996.10a
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• pp.60-61
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• 1996

염색폐수를 처리하기 위하여, 일반적으로 물리.화학적 공정과 호기성 생물학적 공정을 조합한 방법들을 사용하고 있다. 하지만 호기성 생물학적 공정은 난분해성 물질의 제거능력이 낮고, 염색폐수의 주된 오염원인 염료분자가 호기성 미생물에 대한 에너지원으로 적합하지 않아 분해되기 어려우며, 물리.화학적 공정을 이용한 처리방법으로도 높은 처리효율을 얻을 수가 없다. 이러한 문제점을 극복하기 위하여 염색폐수 처리에 혐기-호기공정을 이용하며, 혐기성 공정에서 생물학적으로 분해되기 어려운 고분자 물질들을 가수분해하여 생물학적으로 분해가능한 저분자물질로 전환시키고, 호기성 공정에서 저분자 물질을 효과적으로 처라할 수 있기때문에 기존의 염색폐수 처리공정에 비하여 훨씬 높은 처리효율을 얻을 수 있다. 특히, 혐기성 미생물은 호기성 미생물에 비하여 난분해성 물질에 대한 분해력이 높고, 생물독성 물질에 대한 내성이 강하기 때문에 수중생물에 유해한 염료를 함유한 염색폐수의 색도제거에 효과적인 것으로 기대된다. 또한, 막분리 공정은 유기물 및 미생물이 막표면에 축적, 증식함으로써 막세공에 막힘현상을 초래하여 역세척 등의 물리적인 방법이나 화학약품을 이용한 화학적 세척 방법으로도 투과플럭스의 회복이 불가능한 상태를 유발함으로 막의 수명을 단축시키는 원인이 된다. 따라서, 혐기-호기공정과 조합하면 색도성분 제거 및 막 오염의 원인이 되는 유기물 및 용존성 고형물을 제거하고, 막 오염의 억제를 통한 후 수염의 연장은 물론, 처리수의 수질향상에 활용될 수 있을 것으로 사료된다.1로 강구와 함께 공구강 vial에 장입 후, Spex mixer/mill을 이용하여 기계적 합금화 하였다. 기계적 합금화 공정으로 제조한 분말에 대한 X-선 회절분석과 시차 열분석으로 합금화 정도를 분석하였다. (Bi1-xSbx)2Te3 및 Bi2(Te1-ySey)3 합금분말을 10-5 torr의 진공중에서 300℃∼550℃의 온도로 30분간 가압소결하였다. 가압소결체의 파단면에서의 미세구조를 주사전자현미경으로 관찰하였으며, 상온에서 가압소결체의 열전특성을 측정하였다. (Bi1-xSbx)2Te3의 기계적 합금화에 요구되는 공정시간은 Sb2Te3 함량에 따라 증가하여 x=0.5 조성에서는 4 시간 45분, x=0.75 조성에서는 5 시간, x=1 조성에서는 6 시간 45분의 vibro 밀링이 요구되었다. n형 Bi2(Te1-ySey)3 합금분말의 제조에 요구되는 밀링시간 역시 Bi2Se3 함량 증가에 따라 증가하였으며 Bi2(Te0.95Se0.05)3 합금분말의 제조에는 2시간, Bi2(Te0.9Se0.1)3 및 Bi2(Te0.85Se0.15)3 합금분말의 형성에는 3시간의 bivro 밀링이 요구되었다. 기계적 합금화로 제조한 p형 (Bi0.2Sb0.8)2Te3 및 n형 Bi2(Te0.9Se0.1)3 가압 소결체는 각기 2.9x10-3/K 및 2.1x10-3/K 의 우수한 성능지수를 나타내었다.ering)가 필수적이다. 그러나 침전법에서 얻게 되는 분말은 매우 미세하여 colloid를 형성하게 되며, 이러한 colloid 상태의 미세한 침전입자가 filte

• Journal of the Microelectronics and Packaging Society
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• v.18 no.4
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• pp.55-61
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• 2011

The n-type $Bi_2(Te_{0.9}Se_{0.1})_3$ powers were fabricated by mechanical alloying, mixed with tungsten(W) powders, and hot-pressed at $550^{\circ}C$ for 30 minutes. Thermoelectric properties of the hot-pressed $Bi_2(Te_{0.9}Se_{0.1})_3$ were characterized as a function of the volume percent of tungsten-powder addition. The power factor of the hot-pressed $Bi_2(Te_{0.9}Se_{0.1})_3$ was $21.9{\times}10^{-4}$ $W/m-K^2$, and was improved to $30.5{\times}10^{-4}$ $W/m-K^2$ by dispersion of 1 vol% W powders. While the dimensionless figure-of-merit of the $Bi_2(Te_{0.9}Se_{0.1})_3$ hot-pressed without dispersion of W powders was measured as 0.52 at room temperature, it became substantially enhanced to 0.95 with addition of 1 vol% W powders.

• Korean Journal of Materials Research
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• v.22 no.6
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• pp.280-284
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• 2012

Bismuth antimony telluride (BiSbTe) thermoelectric materials were successfully prepared by a spark plasma sintering process. Crystalline BiSbTe ingots were crushed into small pieces and then attrition milled into fine powders of about 300 nm ~ 2${\mu}m$ size under argon gas. Spark plasma sintering was applied on the BiSbTe powders at 240, 320, and $380^{\circ}C$, respectively, under a pressure of 40 MPa in vacuum. The heating rate was $50^{\circ}C$/min and the holding time at the sintering temperature was 10 min. At all sintering temperatures, high density bulk BiSbTe was successfully obtained. The XRD patterns verify that all samples were well matched with the $Bi_{0.5}Sb_{1.5}Te_{3}$. Seebeck coefficient (S), electric conductivity (${\sigma}$) and thermal conductivity (k) were evaluated in a temperature range of $25{\sim}300^{\circ}C$. The thermoelectric properties of BiSbTe were evaluated by the thermoelectric figure of merit, ZT (ZT = $S^2{\sigma}T$/k). The grain size and electric conductivity of sintered BiSbTe increased as the sintering temperature increased but the thermal conductivity was similar at all sintering temperatures. Grain growth reduced the carrier concentration, because grain growth reduced the grain boundaries, which serve as acceptors. Meanwhile, the carrier mobility was greatly increased and the electric conductivity was also improved. Consequentially, the grains grew with increasing sintering temperature and the figure of merit was improved.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.9
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• pp.561-565
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• 2014

Thermoelectric materials have been the topic of intensive research due to their unique dual capability of directly converting heat into electricity or electrical power into cooling or heating. Bismuth telluride ($Bi_2Te_3$) is the best-known commercially used thermoelectric material in the bulk form for cooling and power generation applications In this work we focus on the large scale synthesis of nanostructured undoped bulk nanostructured $Bi_2Te_3$ materials by employing a novel bottom-up solution-based chemical approach. Spark plasma sintering has been employed for compaction and sintering of $Bi_2Te_3$ nanopowders, resulting in relative density of $g{\cdot}cm^{-3}$ while preserving the nanostructure. The average grain size of the final compacts was obtained as 200 nm after sintering. An improved NS bulk undoped $Bi_2Te_3$ is achieved with sintered at $400^{\circ}C$ for 4 min holding time.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.5
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• pp.443-447
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• 2009

Bismuth-antimony-telluride based thermoelectric thin film materials were prepared by metal organic vapor phase deposition using trimethylbismuth, triethylantimony and diisopropyltelluride as metal organic sources. A planar type thermoelectric device has been fabricated using p-type $Bi_{0.4}Sb_{1.6}Te_3$ and n-type $Bi_{2}Te_{3}$ thin films. Firstly, the p-type thermoelectric element was patterned after growth of $5{\mu}m$ thickness of $Bi_{0.4}Sb_{1.6}Te_3$ layer. Again n-type $Bi_{2}Te_{3}$ film was grown onto the patterned p-type thermoelectric film and n-type strips are formed by using selective chemical etchant for $Bi_{2}Te_{3}$. The top electrical connector was formed by thermally deposited metal film. The generator consists of 20 pairs of p- and n-type legs. We demonstrate complex structures of different conduction types of thermoelectric element on same substrate by two separate runs of MOCVD with etch-stop layer and selective etchant for n-type thermoelectric material. Device performance was evaluated on a number of thermoelectric devices. To demonstrate power generation, one side of the device was heated by heating block and the voltage output was measured. The highest estimated power of 1.3 ${\mu}m$ is obtained at the temperature difference of 45 K.

• Journal of Powder Materials
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• v.31 no.1
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• pp.50-56
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• 2024

We report the effect of plastic deformation on the thermoelectric properties of n-type Bi₂Te_2.5Se_0.5 compounds. N-type Bi₂Te_2.5Se_0.5 powders are synthesized by an oxide-reduction process and consolidated via spark-plasma sintering. To explore the effect of plastic deformation on the thermoelectric properties, the sintered bodies are subjected to uniaxial pressure to induce a controlled amount of compressive strains (-0.2, -0.3, and -0.4). The shaping temperature is set using a thermochemical analyzer, and the plastic deformation effect is assessed without altering the material composition through differential scanning calorimetry. This strategy is crucial because the conventional hot-forging process can often lead to alterations in material composition due to the high volatility of chalcogen elements. With increasing compressive strain, the (00l) planes become aligned in the direction perpendicular to the pressure axis. Furthermore, an increase in the carrier concentration is observed upon compressive plastic deformation, i.e., the donor-like effect of the plastic deformation in n-type Bi₂Te_2.5Se_0.5 compounds. Owing to the increased electrical conductivity through the preferred orientation and the donor-like effect, an improved ZT is achieved in n-type Bi₂Te_2.5Se_0.5 through the compressive-forming process.

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.05a
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• pp.111-111
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• 1996