We report the effect of plastic deformation on the thermoelectric properties of n-type Bi2Te2.5Se0.5 compounds. N-type Bi2Te2.5Se0.5 powders are synthesized by an oxide-reduction process and consolidated via sparkplasma 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 hotforging 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 donorlike effect of the plastic deformation in n-type Bi2Te2.5Se0.5 compounds. Owing to the increased electrical conductivity through the preferred orientation and the donor-like effect, an improved ZT is achieved in n-type Bi2Te2.5Se0.5 through the compressive-forming process.

Thermoelectric materials and devices are energy-harvesting devices that can effectively recycle waste heat into electricity. Thermoelectric power generation is widely used in factories, engines, and even in human bodies as they continuously generate heat. However, thermoelectric elements exhibit poor performance and low energy efficiency; research is being conducted to find new materials or improve the thermoelectric performance of existing materials, that is, by ensuring a high figure-of-merit (zT) value. For increasing zT, higher σ (electrical conductivity) and S (Seebeck coefficient) and a lower к (thermal conductivity) are required. Here, interface engineering by atomic layer deposition (ALD) is used to increase zT of n-type BiTeSe (BTS) thermoelectric powders. ALD of the BTS powders is performed in a rotary-type ALD reactor, and 40 to 100 ALD cycles of ZnO thin films are conducted at 100oC. The physical and chemical properties and thermoelectric performance of the ALD-coated BTS powders and pellets are characterized. It is revealed that electrical conductivity and thermal conductivity are decoupled, and thus, zT of ALD-coated BTS pellets is increased by more than 60% compared to that of the uncoated BTS pellets. This result can be utilized in a novel method for improving the thermoelectric efficiency in materials processing.

High-temperature and high-pressure post-processing applied to sintered thermoelectric materials can create nanoscale defects, thereby enhancing their thermoelectric performance. Here, we investigate the effect of hot isostatic pressing (HIP) as a post-processing treatment on the thermoelectric properties of p-type Bi0.5Sb1.5Te3.0 compounds sintered via spark plasma sintering. The sample post-processed via HIP maintains its electronic transport properties despite the reduced microstructural texturing. Moreover, lattice thermal conductivity is significantly reduced owing to activated phonon scattering, which can be attributed to the nanoscale defects created during HIP, resulting in an ~18% increase in peak zT value, which reaches ~1.43 at 100oC. This study validates that HIP enhances the thermoelectric performance by controlling the thermal transport without having any detrimental effects on the electronic transport properties of thermoelectric materials.

수도권 중심의 국가발전 전략이 한계에 다다른 가운데, 주요국들은 지 방을 발전시키기 위한 다양한 전략이 제시되어 왔다. 2000년대 이후 유 럽, 일본 등 주요국들은 광역경제권 형성을 통한 지방 대도시권 발전방 향의 전략을 채택해 온 가운데, 최근 한국에서도 부울경 지역연합이 출 범한 경험이 있다. 본 논문에서는 프랑스의 지방분권 개혁 및 문제점, 과 제에 관하여 고찰하였다. 특히 본고에서는 프랑스의 광역경제권 형성 과 정을 통해 부·울·경 메가시티 전략에 대한 시사점을 얻고자 하였다. 1970년대 중앙집권적 행정체제로는 경제발전과 지역협력 대응에의 한계 가 있음을 직시한 프랑스는 지방분권을 추진해 왔다. 지방분권 추진에 많은 어려움을 겪어 왔던 프랑스 정부는 2012년 이후 최근까지 지방분 권의 효율성과 민주주의의 조화를 위한 분권발전 정책을 제시해 왔다. 프랑스는 지방분권 추진 과정에서 지역 광역화와 생활권의 이격에서 발 생하는 문제점들을 해결하기 위해, 도시지역계획(PLU), 코뮌 토지이용구 분도(CC), 국토의 일관성 계획(SCOT) 등을 제시하였다.

During the treatment of spent nuclear fuel, radioactive iodine is generated in a liquefied or gaseous form in a specific process. In the case of iodine 129, it is a long-lived nuclide with a very long halflife and has high groundwater mobility under repository conditions. Despite showing a low radioactivity value, research on the management of radioactive iodine from a long-term perspective is continuously being performed. Although research has been conducted using borosilicate glass as a medium for solidifying iodine, compatibility of I in borosilicate glass is very small and the volatility is high in the solidification process. So it is not suitable as a solidified substance of iodine. Therefore, studies on other solidification media to replace them are continuously being conducted. Our research team tried to develop a new medium that can contain iodine in a solidified body stably through a simple heat treatment process and can improve problems such as volatility and waste loading. Iodine is captured as AgI in the Ag ion-exchanged zeolite. So, TeO2, Ag2O, and Bi2O3 having a high AgI loading rate were used as main components. It was named TAB after taking the first letter of each element. In previous studies, the physical properties, structure, and chemical stability of TAB materials were confirmed. PCT (Product Consistent test) was performed to confirm chemical stability. It is mainly used to compare the chemical stability of glass materials with other glass materials, but there are limitations in evaluating the long-term chemical stability of materials. In this experiment, we tried to evaluate the long-term stability of TAB and compare it with borosilicate, which is conventionally used to treat radioactive waste. In addition, we tried to understand the leaching behavior inside the TAB medium. For this purpose, ASTM C1308 test was performed for 365 days, and distilled water and KURT groundwater were used as leachates to examine the effect of ions in the groundwater on the solidified body. To analyze the leaching behavior, ICP-MS and ICP-OES analyses were performed, and the cross-section of the sample after leaching was observed through SEM.

Zintl compound Mg3Sb2 is a promising candidate for efficient thermoelectric material due to its small band gap energy and characteristic electron-crystal phonon-glass behavior. Furthermore, this compound enables fine tuning of carrier concentration via chemical doping for optimizing thermoelectric performance. In this study, nominal compositions of Mg3.8Sb2-xTex (0 ≤ x ≤ 0.03) are synthesized through controlled melting and subsequent vacuum hot pressing method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) are carried out to investigate phase development and surface morphology during the process. It should be noted that 16 at. % of excessive Mg must be added to the system to compensate for the loss of Mg during melting process. Herein, thermoelectric properties such as Seebeck coefficient, electrical conductivity, and thermal conductivity are evaluated from low to high temperature regimes. The results show that Te substitution at Sb sites effectively tunes the majority carriers from holes to electrons, resulting in a transition from p to n-type. At 873 K, a peak ZT value of 0.27 is found for the specimen Mg3.8Sb1.99Te0.01, indicating an improved ZT value over the intrinsic value.

2017년 9월 23일, ITLOS는 가나와 코트디부아르 간 해양경계획정 분쟁에 대한 판결을 내렸다. 그 이전 2015년 4월 25일에는 분쟁 수역에 대한 ITLOS의 잠정조치 명령이 있었다. 잠정조치 명령에서 코트디부아르의 주장이 받아들여진 것과 달리 본안 판결에서는 가나에게 유리한 결과가 나왔다. ITLOS 특별재판부는 코트디부아르의 잠정조치 신청을 일부 수용하여 가나의 새로운 시추행위를 금지하는 잠정조치 명령을 내렸다. 코트디부아르가 해양환경 보호와 관련하여 신청한 것은 기각하면서도, 가나에게 해양환경에 대한 중대한 손해를 방지하기 위해 시추와 관련된 모든 활동들을 엄격히 감시하도록 명령한 것이다. 이것은 당사국 모두에게 분쟁수역의 해양환경에 대한 중대한 손해를 방지할 의무를 부과한 것이다. 이 사건의 또 다른 시사점은 본안 판결의 법적 구속력을 확인한 사건이라는 것이다. ITLOS 특별재판부가 정한 원칙을 적용해 양국간 해양경계를 획정하니 종래의 경계선과 큰 차이가 없었다. 이러한 결과에 대해 가나는 만족스러워한 반면, 코트디부아르도 승복할 수밖에 없었다. 그 이유는 물론 이 재판이 국제법의 원칙에 따라 진행되었기 때문이다. 이처럼 국제재판은 그 결과가 나오면 돌이킬 수 없기 때문에 국제재판을 통한 분쟁의 해결은 신중한 접근이 필요하다.

In this study, Bi-Sb-Te thermoelectric materials are produced by mechanical alloying (MA) and spark plasma sintering (SPS). To examine the influence of the milling atmosphere on the microstructure and thermo-electric (TE) properties, a p-type Bi-Sb-Te composite powder is mechanically alloyed in the presence of argon and air atmospheres. The oxygen content increases to 55% when the powder is milled in the air atmosphere, compared with argon. All grains are similar in size and uniformly, distributed in both atmospheric sintered samples. The Seebeck coefficient is higher, while the electrical conductivity is lower in the MA (Air) sample due to a low carrier concentration compared to the MA (Ar) sintered sample. The maximum figure of merit (ZT) is 0.91 and 0.82 at 350 K for the MA (Ar) and MA (Air) sintered samples, respectively. The slight enhancement in the ZT value is due to the decrease in the oxygen content during the MA (Ar) process. Moreover, the combination of mechanical alloying and SPS process shows a higher hardness and density values for the sintered samples.

Bi2Te3 powders are recovered by wet chemical reduction for waste n-type thermoelectric chips, and the recovered particles with different morphologies are prepared using various surfactants such as cetyltrimethylammonium bromide (CTAB), sodium dodecylbenzenesulfonate (SDBS), and ethylenediaminetetraacetic acid (EDTA). When citric acid is added as the surfactant, the shape of the aggregated particles shows no distinctive features. On the other hand, rod-shaped particles are formed in the sample with CTAB, and sheet-like particles are synthesized with the addition of SDBS. Further, particles with a tripod shape are observed when EDTA is added as the surfactant. The growth mechanism of the particle shapes depending on the surfactant is investigated, with a focus on the nucleation and growth phenomena. These results help to elucidate the intrinsic formation mechanism of the rod, plate, and tripod structures of the Bi2Te3 recovered by the wet reduction process.

In this work, p-type Bi−Sb−Te alloys powders are prepared using gas atomization, a mass production powder preparation method involving rapid solidification. To study the effect of the sintering temperature on the microstructure and thermoelectric properties, gas-atomized powders are consolidated at different temperatures (623, 703, and 743 K) using spark plasma sintering. The crystal structures of the gas-atomized powders and sintered bulks are identified using an X-ray diffraction technique. Texture analysis by electron backscatter diffraction reveals that the grains are randomly oriented in the entire matrix, and no preferred orientation in any unique direction is observed. The hardness values decrease with increasing sintering temperature owing to a decrease in grain size. The conductivity increases gradually with increasing sintering temperature, whereas the Seebeck coefficient decreases owing to increases in the carrier mobility with grain size. The lowest thermal conductivity is obtained for the bulk sintered at a low temperature (603 K), mainly because of its fine-grained microstructure. A peak ZT of 1.06 is achieved for the sample sintered at 703 K owing to its moderate electrical conductivity and sustainable thermal conductivity.

We fabricate fine (<20 μm) powders of Bi0.5Sb1.5Te3 alloys using a large-scale production method and subsequently consolidate them at temperatures of 573, 623, and 673 K using a spark plasma sintering process. The microstructure, mechanical properties, and thermoelectric properties are investigated for each sintering temperature. The microstructural features of both the powders and bulks are characterized by scanning electron microscopy, and the crystal structures are analyzed by X-ray diffraction analysis. The grain size increases with increasing sintering temperature from 573 to 673 K. In addition, the mechanical properties increase significantly with decreasing sintering temperature owing to an increase in grain boundaries. The results indicate that the electrical conductivity and Seebeck coefficient (217 μV/K) of the sample sintered at 673 K increase simultaneously owing to decreased carrier concentration and increased mobility. As a result, a high ZT value of 0.92 at 300 K is achieved. According to the results, a sintering temperature of 673 K is preferable for consolidation of fine (<20 μm) powders.

A thin film thermoelectric generator that consisted of 5 p/n pairs was fabricated with 1 μm-thick n-type In3Sb1Te2 and p-type Ge2Sb2Te5 deposited via radio frequency magnetron sputtering. First, 1 μm-thick GST and IST thin films were deposited at 250 oC and room temperature, respectively, via radio-frequency sputtering; these films were annealed from 250 to 450 oC via rapid thermal annealing. The optimal power factor was found at an annealing temperature of 400 oC for 10 min. To demonstrate thermoelectric generation, we measured the output voltage and estimated the maximum power of the n-IST/ p-GST generator by imposing a temperature difference between the hot and cold junctions. The maximum output voltage and the estimated maximum power of the 1 μm-thick n-IST/p-GST TE generators are approximately 17.1 mV and 5.1 nW at ΔT = 12K, respectively.

Identification of specific marker proteins in cells is useful for isolating cells and determining their cellular characteristics and functions. Based on our previous study showing that matrix metalloproteinase 9 (MMP-9) can be used as a marker for porcine spermatogonia, the expression pattern of MMP-9 was determined in both pre- (5-month old) and post-pubertal (11–month old) bovine testes. Histological analysis revealed that spermatogonia were located near the basement membrane in both testes, while spermatozoa were not detected in the 5-month old pre-pubertal bovine testes and epididymides. Mature spermatozoa were observed in the 11-month bovine testes and epididymides, and MMP-9 expression in 11-month old bovine testes was lower than 5-month old testes, according to reverse transcription-PCR and real-time-PCR data. To determine the specific expression sites of MMP-9 in the bovine testes, immunohistochemistry was performed. Expression of MMP-9 was observed in cells near the basement membrane of seminiferous tubules in both 5- and 11-month old testes. Furthermore, MMP-9 positive cells expressed protein gene product 9.5 (PGP9.5) and deleted in azoospermia (DAZL) that are already known as bovine spermatogonial stem cells markers. In the present study, MMP-9 expression was identified in both pre- and post-pubertal bovine spermatogonia expressing PGP9.5 and DAZL, and located near the basement membrane of seminiferous tubules. Thus, MMP-9 can be used as a marker for bovine spermatogonia, and may provide useful platforms for understanding the interaction between germ cells and extracellular matrix during spermatogenesis in the seminiferous tubules.

The recent rise in applications of thermoelectric materials has attracted interest in studies toward the fabrication of thermoelectric materials using mass production techniques. In this study, we successfully fabricate n-type Bi2Te2.7Se0.3 material by a combination of mass production powder metallurgy techniques, gas atomization, and spark plasma sintering. In addition, to examine the effects of hydrogen reduction in the microstructure, the thermoelectric and mechanical properties are measured and analyzed. Here, almost 60% of the oxygen content of the powder are eliminated after hydrogen reduction for 4 h at 360°C. Micrographs of the powder show that the reduced powder had a comparatively clean surface and larger grain sizes than unreduced powder. The density of the consolidated bulk using as-atomized powder and reduced atomized powder exceeds 99%. The thermoelectric power factor of the sample prepared by reduction of powder is 20% better than that of the sample prepared using unreduced powder.

Bi2Te3 related compounds show the best thermoelectric properties at room temperature. However, n-type Bi2Te2.7Se0.3 showed no improvement on ZT values. To improve the thermolectric propterties of n-type Bi2Te2.7Se0.3, this research has Cu-doped n-type powder. This study focused on effects of Cu-doping method on the thermoelectric properties of n-type materials, and evaluated the comparison between the Cu chemical and mechanical doping. The synthesized powder was manufactured by the spark plasma sintering(SPS). The thermoelectric properties of the sintered body were evaluated by measuring their Seebeck coefficient, electrical resistivity, thermal conductivity, and hall coefficient. An introduction of a small amount of Cu reduced the thermal conductivity and improved the electrical properties with Seebeck coefficient. The authors provided the optimal concentration of Cu0.1Bi1.99Se0.3Te2.7. A figure of merit (ZT) value of 1.22 was obtained for Cu0.1Bi1.9Se0.3Te2.7 at 373K by Cu chemical doping, which was obviously higher than those of Cu0.1Bi1.9Se0.3Te2.7 at 373K by Cu mechanical doping (ZT=0.56) and Cu-free Bi2Se0.3Te2.7 (ZT=0.51).

In this study, we report the sintering behavior and properties of a Ge2Sb2Te5 alloy powders for use as asputtering target by spark plasma sintering. The effect of various sintering parameters, such as pressure, temperature andtime, on the density and hardness of the target has been investigated in detail. Structural characterization was performedby scanning electron microscopy and X-ray diffraction. Hardness and thermal properties were measured by differentialscanning calorimetry and micro-vickers hardness tester. The density and hardness of the sintered Ge2Sb2Te5 materialswere 5.8976~6.3687 g/cm3 and 32~75 Hv, respectively.

Carbon nanotube-dispersed bismuth telluride matrix (CNT/Bi2Te3) nanopowders were synthesized by chem- ical routes followed by a ball-milling process. The microstructures of the synthesized CNT/Bi2Te3 nanopowders showed the characteristic microstructure of CNTs dispersed among disc-shaped Bi2Te3 nanopowders with as an average size of 500 nm in-plane and a few tens of nm in thickness. The prepared nanopowders were sintered into composites with a homogeneous dispersion of CNTs in a Bi2Te3 matrix. The dimensionless figure-of-merit of the composite showed an enhanced value compared to that of pure Bi2Te3 at the room temperature due to the reduced thermal conductivity and increased electrical conductivity with the addition of CNTs.

The present study was focused on the analysis of the electric and thermal properties of spark plasma sintered thermoelectric material. The crystal structure, microstructure, electric and thermal properties of the sintered body were evaluated by measuring XRD, SEM, electric resistivity, Hall effect and thermal conductivity. The sintered body showed anisotropic crystal structure. The c-axis of the crystal aligned in a parallel direction with applied pressure during spark plasma sintering. The degree of the crystal alignment increased with increasing sintering temperature and sintering time. The electric resistivity and thermal conductivity of the sintered body showed anisotropic characteristics result from crystal alignment.