중앙분리대 콘크리트 방호울타리(Concrete Median Barriers, CMB)는 마주 달리는 차량과의 정면충 돌을 예방할 뿐만 아니라 탑승자의 상해 및 차량의 파손까지 최소화하는 중요한 안전시설 중 하나이 다. 현재 국내의 CMB는 설계속도에 따라 등급이 정해지고, 이에 맞는 성능 평가를 실시하게 된다. 현 재 국내의 특수구간을 제외한 저속구간 및 일반구간(60~80km/hr)에서는 SB4등급 이하의 CMB가 사 용되고 있으며, 고속구간(100km/h 이상 도로)에서는 SB5등급 이상의 CMB가 사용된다. 그중 고속국 도에 시공되는 SB5등급 이상의 CMB에 대한 연구는 지속해서 수행되는 반면 일반국도에 대한 CMB 연구는 비교적 부족한 실정이다. 따라서 본 연구에서는 일반국도에 시공되는 SB4등급의 효율적인 단 면을 찾기 위한 해석적 연구가 수행되었다. 단면 형상은 1, 2차 충돌에 큰 영향을 미치는 단면의 높이 와 최하단부의 곡률 반경이 고려되었다. 유한요소 해석에 사용된 차량은 미국 교통부(U.S Department of Transportation)에서 제공한 16톤 트럭을 국내 차량과 비슷한 형태로 개선한 차량이었다. 해석 결과 로, 트럭의 충돌 후 단면 형상에 따라 발생한 트럭의 거동, 콘크리트 비산량, 소성변형이 비교되었다.

In this study, we report the microstructural evolution and shear strength of an Sn-Sb alloy, used for die attach process as a solder layer of backside metal (BSM). The Sb content in the binary system was less than 1 at%. A chip with the Sn-Sb BSM was attached to a Ag plated Cu lead frame. The microstructure evolution was investigated after die bonding at 330 °C, die bonding and isothermal heat treatment at 330 °C for 5 min and wire bonding at 260 °C, respectively. At the interface between the chip and lead frame, Ni3Sn4 and Ag3Sn intermetallic compounds (IMCs) layers and pure Sn regions were confirmed after die bonding. When the isothermal heat treatment is conducted, pure Sn regions disappear at the interface because the Sn is consumed to form Ni3Sn4 and Ag3Sn IMCs. After the wire bonding process, the interface is composed of Ni3Sn4, Ag3Sn and (Ag,Cu)3Sn IMCs. The Sn-Sb BSM had a high maximum shear strength of 78.2 MPa, which is higher than the required specification of 6.2 MPa. In addition, it showed good wetting flow.

In this study, we investigated the microstructure and piezoelectric properties of 0.96(K0.456Na0.536)Nb0.95Sb0.05-0.04 Bi0.5(Na0.82K0.18)0.5ZrO3 (KNNS-BNKZ) ceramics based on one-step and two-step sintering processes. One-step sintering led to significant abnormal grain (AG) growth at temperatures above 1,085 °C. With increasing sintering temperature, piezoelectric and dielectric properties were enhanced, resulting in a high d33 = 506 pC/N for one-step specimen sintered at 1,100 °C (one-step 1,100 °C specimen). However, for one-step 1,115 °C specimen, a slight decrease in d33 was observed, emphasizing the importance of a high tetragonal (T) phase fraction for superior piezoelectric properties. Achieving a relative density above 84 % for samples sintered by the one-step sintering process was challenging. Conversely, two-step sintering significantly improved the relative density of KNNS-BNKZ ceramics up to 96 %, attributed to the control of AG nucleation in the first step and grain growth rate control in the second step. The quantity of AG nucleation was affected by the duration of the first step, determining the final microstructure. Despite having a lower T phase fraction than that of the one-step 1,100 °C specimen, the two-step specimen exhibited higher piezoelectric coefficients (d33 = 574 pC/N and kp = 0.5) than those of the one-step 1,100 °C specimen due to its higher relative density. Performance evaluation of magnetoelectric composite devices composed of one-step and twostep specimens showed that despite having a higher g33, the magnetoelectric composite with the one-step 1,100 °C specimen exhibited the lowest magnetoelectric voltage coefficient, due to its lowest kp. This study highlights the essential role of phase fraction and relative density in enhancing the performance of piezoelectric materials and devices, showcasing the effectiveness of the two-step sintering process for controlling the microstructure of ceramic materials containing volatile elements.

This study reports an analytical investigation on the development of SB4-grade separated concrete median barriers. The proposed barrier sections comprise three designs, with heights of 810, 1000, and 1270 mm and upper widths of 90, 120, and 120 mm, respectively. Before conducting collision analyses on the proposed sections, the considered collision analysis model was validated using real collision test results; the model was found to accurately predict the real collision test results. The proposed cross-sections were modeled to perform collision analysis according to SB4-grade collision conditions. Results indicated that increasing the cross-section height increased the damaged area and decreased the strength, while the occupant protection performance remained mostly unaffected. Furthermore, the proposed cross-sections met the strength and occupant protection performance criteria specified in domestic guidelines, suggesting their suitability as a separated concrete median barrier for bridges.

Infrared radiation (IR) refers to the region of the electromagnetic radiation spectrum where wavelengths range from about 700 nm to 1 mm. Any object with a temperature above absolute zero (0 K) radiates in the infrared region, and a material that transmits radiant energy in the range of 0.74 to 1.4 um is referred to as a near-infrared optical material. Germanatebased glass is attracting attention as a glass material for infrared optical lenses because of its simple manufacturing process. With the recent development of the glass molding press (GMP) process, thermal imaging cameras using oxide-based infrared lenses can be easily mass-produced, expanding their uses. To improve the mechanical and optical properties of commercial materials consisting of ternary systems, germanate-based heavy metal oxide glasses were prepared using a melt-cooling method. The fabricated samples were evaluated for thermal, structural, and optical properties using DSC, XRD, and XRF, respectively. To derive a composition with high glass stability for lens applications, ZnO and Sb2O3 were substituted at 0, 1, 2, 3, and 4 mol%. The glass with 1 mol% added Sb2O3 was confirmed to have the optimal conditions, with an optical transmittance of 80 % or more, a glass transition temperature of 660 °C, a refractive index of 1.810, and a Vickers hardness of 558. The possibility of its application as an alternative infrared lens material to existing commercial materials capable of GMP processing was confirmed.

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.

This research investigated how adding Sb (0.75, 1.0, 2.0 and 5.0 wt%) to as-extruded aluminum alloys affected their microstructure, mechanical properties, electric and thermal conductivity. The addition of Sb resulted in the formation of AlSb intermetallic compounds. It was observed that intermetallic compounds in the alloys were distributed homogenously in the Al matrix. As the content of Sb increased, the area fraction of intermetallic compounds increased. It can be clearly seen that the intermetallic compounds were crushed into fine particles and homogenously arrayed during the extrusion process. As the Sb content increased, the average grain size decreased remarkably from 282.6 μm (0.75 wt%) to 109.2 μm (5.0 wt%) due to dynamic recrystallization by the dispersed intermetallic compounds in the aluminum matrix during the hot extrusion. As the Sb content increased from 0.75 to 2.0 wt%, the electrical conductivity decreased from 61.0 to 59.8 % of the International Annealed Copper Standard. Also, as the Sb content increased from 0.75 to 2.0 wt%, the ultimate tensile strength did not significantly change, from 67.3 to 67.8 MPa.

본 연구에서는 유리섬유보강근(GFRP rebar)를 적용한 SB6 등급 콘크리트 방호벽의 비선형 동적 해석을 수행하였다. ACI 설계기준에 근거한 새로운 방호벽 구조에 대하여 소형차와 트럭의 충돌에 대한 유한요소 모델링을 수행하였다. 트럭 충돌 에 대하여 제안한 모델은 기존의 철근을 적용한 모델과 비교하였을 때 구조적으로 만족할 만한 성능을 보였다. 또한, 소형차 충 돌 해석으로부터 산출한 탑승자 보호지수는 한계기준 범위 안에서 만족하였다. 이러한 결과로부터, 제안한 방호벽 구조는 기존 철근을 적용한 방호벽을 대체하여 실용적으로 적용이 가능할 것으로 기대된다.

This study demonstrates a different approach method to fabricate antimony selenide (Sb2Se3) thin-films for the solar cell applications. As-deposited Sb2Se3 thin-films are fabricated via electrodeposition route and, subsequently, annealed in the temperature range of 230 ~ 310oC. Cyclic voltammetry is performed to investigate the electrochemical behavior of the Sb and Se ions. The deposition potential of the Sb2Se3 thin films is determined to be -0.6 V vs. Ag/AgCl (in 1 M KCl), where the stoichiometric composition of Sb2Se3 appeared. It is found that the crystal orientations of Sb2Se3 thin-films are largely dependent on the annealing temperature. At an annealing temperature of 250 oC, the Sb2Se3 thin-film grew most along the c-axis [(211) and/or (221)] direction, which resulted in the smooth movement of carriers, thereby increasing the carrier collection probability. Therefore, the solar cell using Sb2Se3 thin-film annealed at 250 oC exhibited significant enhancement in JSC of 10.03 mA/cm2 and a highest conversion efficiency of 0.821 % because of the preferred orientation of the Sb2Se3 thin film.

One disadvantage of deep cycle flooded lead-acid batteries is increasing water loss caused by use of (+) Pb-Sb / () Pb-Sb alloy grid. Water loss is generated by the emission of hydrogen gas from the () electrode during battery charging. In this paper, we maintain cycle life aspect through the development of hybrid flooded lead-acid batteries to which a (+) Pb- Sb / () Pb-Ca grid is applied and deal with the improvement of water loss. The amount of water loss compared to that of the () Pb-Sb grid decreased when Ca was added to the () Pb grid. For the () Pb-Ca grid, it was confirmed that the time to reach 0.0 V, at which water decomposition occurs, was increased compared to that of the () Pb-Sb grid at the NPV (Negative Potential Voltage). In the cycle life test conducted with the BCI (Battery Council International) standard, compared to the (+) Pb-Ca grid, the (+) Pb-Sb grid increased the life cycle of the batteries and the (+) Pb-Ca grid showed an early end of life due to PbO corrosion layer generation, as determined through SEM / EDS and Tear Down analysis. In conclusion, by addition of Sb to (+) Pb grid and Ca to () Pb grid, we developed a hybrid flooded lead-acid battery that meets user requirements to improve water loss characteristics and preserve cycle life characteristics.

Zintl phase Mg3Sb2 is a promising thermoelectric material in medium to high temperature range due to its low band gap energy and characteristic electron-crystal phonon-glass behavior. P-type Mg3Sb2 has conventionally exhibited lower thermoelectric properties compared to its n-type counterparts, which have poor electrical conductivity. To address these problems, a small amount of Sn doping was considered in this alloy system. P-type Mg3Sb2 was synthesized by controlled melting, pulverizing, and subsequent vacuum hot pressing (VHP) method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate phases and microstructure development during the process. Single phase Mg3Sb2 was successfully formed when 16 at.% of Mg was excessively added to the system. Nominal compositions of Mg3.8Sb2-xSnx (0 ≤ x ≤ 0.008) were considered in this study. Thermoelectric properties were evaluated in terms of Seebeck coefficient, electrical conductivity, and thermal conductivity. A peak ZT value ≈ 0.32 was found for the specimen Mg3.8Sb1.994Sn0.006 at 873 K, showing an improved ZT value compared to intrinsic one. Transport properties were also evaluated and discussed.

This study is an experimental study to evaluate the vehicle-protection performance of the reinforced F section of a concrete median barrier. To reinforce the strength performance and durability of the F section, the design strength of concrete was increased and a wire mesh was added. The reinforced F section was tested in an actual collision to verify the protection performance of the SB4 class(Impact Severity: 160kJ) concrete barrier. In the truck-crash test for strengthperformance evaluation, no damage or no sufficient scattering occurred to cause damage to a third party. In addition, the truck smoothly moved through an escape box after the collision. THIV and PHD, which are criteria for evaluating the occupant-protection performance, were measured at 75% and 64% of the limit, respectively, and were confirmed to provide good occupant-protection performance. The vehicle rotations after the collision were 12%–19% of the allowed limits.

This study investigates the effect of MnO2 and CuO as acceptor additives on the microstructure and piezoelectric properties of 0.96(K0.5Na0.5)0.95Li0.05Nb0.93Sb0.07O3-0.04BaZrO3, which has a rhombohedral-tetragonal phase boundary composition. MnO2 and CuO-added 0.96(K0.5Na0.5)0.95Li0.05Nb0.93Sb0.07O3-0.04BaZrO3 ceramics sintered at a relatively low temperature of 1020 oC show a pure perovskite phase with no secondary phase. As the addition of MnO2 and CuO increases, the sintered density and grain size of the resulting ceramics increases. Due to the difference in the amount of oxygen vacancies produced by B-site substitution, Cu ion doping is more effective for uniform grain growth than Mn ion doping. The formation of oxygen vacancies due to B-site substitution of Cu or Mn ions results in a hardening effect via ferroelectric domain pinning, leading to a reduction in the piezoelectric charge coefficient and improvement of the mechanical quality factor. For the same amount of additive, the addition of CuO is more advantageous for obtaining a high mechanical quality factor than the addition of MnO2.

Sb-doped SnO2 (ATO) transparent conducting films are fabricated using horizontal ultrasonic spray pyrolysis deposition (HUSPD) to form uniform and compact film structures with homogeneously supplied precursor solution. To optimize the molar concentration and transparent conducting performance of the ATO films using HUSPD, we use precursor solutions of 0.15, 0.20, 0.25, and 0.30 M. As the molar concentration increases, the resultant ATO films exhibit more compact surface structures because of the larger crystallite sizes and higher ATO crystallinity because of the greater thickness from the accelerated growth of ATO. Thus, the ATO films prepared at 0.25 M have the best transparent conducting performance (12.60±0.21 Ω/□ sheet resistance and 80.83% optical transmittance) and the highest figure-of-merit value (9.44±0.17 × 10-3 Ω-1). The improvement in transparent conducting performance is attributed to the enhanced carrier concentration by the improved ATO crystallinity and Hall mobility with the compact surface structure and preferred (211) orientation, ascribed to the accelerated growth of ATO at the optimized molar concentration. Therefore, ATO films fabricated using HUSPD are transparent conducting film candidates for optoelectronic devices.

PURPOSES: In this research, an SB3-level roadside barrier for a highway transition zone that meets the newly established guide Installation and Management Guide for Roadside Safety Appurtenance is developed. Its performance is evaluated by a numerical simulation and real-scale vehicle impact testMETHODS: The commercial explicit dynamic software LS-DYNA is utilized for impact simulation. An FE model of a passenger vehicle developed and released by the National Crash Analysis Center (NCAC) at George Washington University and a heavy goods vehicle (HGV) model developed by the TC226/CM-E Work Group are utilized for impact simulation. The original vehicle models were modified to reflect the conditions of test vehicles. The impact positions of the passenger vehicle and truck to the transition guardrail were set as 1/2 and 3/4 of the transition region, respectively, according to the guide.RESULTS : Based on the numerical simulation results of the existing transition barrier, a new structural system with improved performance was suggested. According to the result of a numerical simulation of the suggested structural system, two sets of transition barriers were manufactured and installed for real-scale vehicle impact tests. The tests were performed at a test field for roadside safety hardware of the Korea Highway Corporation Research Institute.CONCLUSIONS: The results of both the real-vehicle impact tests and numerical simulations of the developed transition barrier satisfied the performance criteria, and the results of numerical simulation showed good correlation with the test results.

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.

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.