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.

The effects of an excess of Bi on the piezoelectric and dielectric properties of 0.60Bi1+xFeO3-0.40BaTiO3 (x = 0, 0.01, 0.03, 0.05, 0.07) were investigated. The ceramics were processed through a conventional solid state reaction method and then quenched after sintering at different temperatures in the range of 980~1070 oC. A single perovskite structure without any secondary phase was confirmed for all compositions and temperatures. It was found that excess Bi reduced the sintering temperatures, acted as a sintering aid and enhanced the properties in combination with quenching. Curie temperature (TC) was found to slightly increase due to the presence of excess Bi; electrical properties were also improved by quenching. At x = 0.03 and 1030 oC, remnant polarization (2Pr) was as high as 45.4 μC/cm2 and strain at 40 kV/cm was up to 0.176 %.

Membrane distillation (MD) is a hydrid membrane process using the temperature difference as a driving force. In order to enhance the performance (flux) of the MD process, various membrane structures (asymmetric or bi-composite) and materials (PP, PVDF or PTFE) have been suggested. In this study, the support layer of the commercial PTFE/PP bi-composite membrane is modifed by forming the macro punctures in it. The size and location of macro punctures were varied according to the designed support layer porosities (50, 60, 70 and 80 %). The modified membrane test was conducted by using the DCMD configuration. The flux of a modified membranewas enhanced up to 27 % compared with that of pristine membrane when the size of the macro puncture and overall porosity of the support layer were larger than 20 mm2 and 60 %, respectively.

Aquatic ecosystems are receiving various harmful effects due to anthropogenic chemical pollutions. To protect wildlife, risk assessments of the chemicals are conducted using reference indexes of toxicity estimated by species-level laboratory tests and/or micro-/mesocosm community-level studies. However, the existing micro-/mesocosm communities are structurally too complicated, and it is also difficult to compare the experimental results directly with those from species-level tests. Here, we developed a procedure of a simple bi-trophic microcosm experiment which contains the common species (a green algae, Pseudokirchneriella subcapitata and a cladoceran, Daphnia magna) for testing chemical toxicities. For the proper operation of bitrophic microcosm experiment, the minimum required concentration of primary producer (P. subcapitata) is 5×105 cells mL-1. The microcosm system showed higher stability when the initially introduced D. magna population was composed of neonates (<24-h old) than adults and those mixture. This simple microcosm system would be an applicable tool to estimate the disturbing impacts of pollutants on plant-herbivore interactions, and linking the species- and population-/community level risk assessments in the future studies.

This study carried out fiber damage detections of laminated GFRP plate structures using a modified bi-variate Gamma function. The effects of different layup sequences of composites on the fiber damage detection are studied using the finite element commercial package and genetic algorithm. Four unknown parameters are considered to determine the shape of the damage distribution, which is a modified form of the bivariate Gamma density distribution function. The sample studies show the excellence of the proposed method from the standpoints of its computation efficiency as well as its ability to determine the complex shape of an arbitrary stiffness degradation distribution.

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.

This study performed an inverse detection of fiber stiffness degradation that occurs due to damages in free vibrating composite structures. Five unknown parameters are considered to determine the fiber stiffness which is a modified form of the bivariate Gaussian distribution function. The proposed approach is more feasible than the conventional element-based damage detection method from the computational efficiency because a finite element analysis coupled with a genetic algorithm using a small number of unknown parameters is performed. The numerical examples show that the proposed technique is a feasible and practical method, which can prove the location of a damaged region as well as inspect the distribution of deteriorated fiber stiffness although there is a small difference in dynamic characteristics between damaged and undamaged structures.

Bi0.5Na0.5TiO3 (BNT) based ceramics are considered potential lead-free alternatives for Pb(Zr,Ti)O3(PZT) based ceramics in various applications such as sensors, actuators and transducers. However, BNT-based ceramics have lower electromechanical performance as compared with PZT based ceramics. Therefore, in this work, lead-free bulk 0.99[(Bi0.5Na0.5)0.935Ba0.065](1-x)LaxTiO3-0.01SrZO3 (BNBTLax-SZ, with x = 0, 0.01, 0.02) ceramics were synthesized by a conventional solid state reaction The crystal structure, dielectric response, degree of diffuseness and electric-field-induced strain properties were investigated as a function of different La concentrations. All samples were crystallized into a single phase perovskite structure. The temperature dependent dielectric response of La-modified BNBT-SZ ceramics showed lower dielectric response and improved field-induced strain response. The field induced strain increased from 0.17% for pure BNBT-SZ to 0.38 % for 1 mol.% La-modified BNBT-SZ ceramics at an applied electric field of 6 kV/mm. These results show that Lamodified BNBT-SZ ceramic system is expected to be a new candidate material for lead-free electronic devices.

흰가루병에 저항성이 있는 절화장미 품종을 육성하기위하여 2007년 수량이 많고 절화수명이 긴 다홍색의 스탠다드 ‘Aladin’ 품종과 화형이 우수하고 흰가루병에 저항성이 있는 적색 스탠다드 ‘Red Queen’ 품종을 각각모본과 부본으로 인공교배를 실시하였다. 2008년 획득한종자를 파종하여 219개의 실생 개체를 얻었으며 꽃잎수가 5개 미만인 것을 제외하고 2009-2011년까지 3차에 거쳐 특성평가를 실시한 후 ‘원교 D1-179’를 최종 선발하여 ‘Antique Curl’로 명명하였다. ‘Antique Curl’은 복색으로 노랑색(Y2C) 분홍색(R49A)이 혼합되어 있으며, 화형은 고심형, 꽃잎수는 56.7장으로 대조품종인 ‘MoonLight’보다 약 20장 더 많다. 화폭은 12.3cm로 대조품종보다 약간 작았다. 1m2당 연간 채화 가능한 수량은 135.5본이며 절화장은 65.8cm, 절화경경은 5.8mm의 절화 특성을 보였다. 또한 절화수명은 16.8일이며 흰가루병 저항성을 가지고 있으며 기호도 평가에서도 4.0을 획득하여 대조품종 보다 1.0 높은 기호도를 보였다. ‘Antique Curl’의품종보호권(품종보호: 제4456호)은 2013년 4월에 국립종자원을 통해 정식 등록되었다.

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).

New lead-free piezoelectric ceramics 0.96[{Bi0.5 (Na0.84 K0.16)0.5}1-xLax(Ti1-y Nby)O3]-0.04SrTiO3 (BNKT-ST-LN, where x = y = 0.00 ≤ (x = y) ≤ 0.015) were synthesized using the conventional solid-state reaction method. Their crystal structure, microstructure, and electrical properties were investigated as a function of the La and Nb (LN) content. The X-ray diffraction patterns revealed the formation of a single-phase perovskite structure for all the LN-modified BNKT-ST ceramics in this study. The temperature dependence of the dielectric curves showed that the maximum dielectric constant temperature (Tm) shifted towards lower temperatures and the curves became more diffuse with an increasing LN content. At the optimum composition (LN 0.005), a maximum value of remnant polarization (33 C/cm2) with a relatively low coercive field (22 kV/cm) and high piezoelectric constant (215 pC/N) was observed. These results indicate that the LN co-modified BNKT-ST ceramic system is a promising candidate for lead-free piezoelectric materials.