Search

We investigated the operating characteristics of solid oxide carbon fuel cells (SO–CFCs) integrated with a steam gasifier that used carbonaceous fuels, including activated carbon and biomass driven charcoal. Steam gasification was carried out in a specially designed gasifier, which was directly integrated with a solid-oxide based carbon fuel cell. We studied the effects of gasification temperature, steam flow rate and catalyst addition on the electrochemical performance of SO–CFC, and the results showed that among the three tested fuels, activated carbon with a K 2 CO 3 catalyst performed the best. At 850 °C, maximum power density values of 108 mW/cm 2 , 161 mW/cm 2 and 181 mW/cm 2 were achieved when the SO–CFC was operated using activated carbon, biomass driven charcoal and activated carbon with a K 2 CO 3 catalyst, respectively. The SO–CFC operated continuously for 100 h and it showed relatively stable performance. This study suggests that by using a catalytic steam gasifier integrated with the SO–CFC, solid carbon fuel resources can be used for power generation with higher efficiency and minimal carbon footprint.

This letter considers the downlink of a cellular network with an asymmetric antenna configuration, where virtual multiple-input multiple-output (MIMO) is formed with receive cooperation over out-of-band or in-band overlay device-to-device (D2D) links. The objective of this work is to determine the best pairing and resource sharing configuration of the cooperative devices such that the overall network utility is optimized and the devices achieve their best available rate larger than that without D2D cooperation. A distributed algorithm is developed via an algorithmic-game-theoretic message-passing framework to obtain a solution at a low computational cost and without reporting the D2D link qualities to the base station. We show that the algorithm converges to an optimal point through analysis and its performance is validated by simulation. In addition, the virtual MIMO network enabled by the D2D receive cooperation is shown to provide a significant gain over the network without the D2D receive cooperation.

We propose a two-way multi-hop relaying scheme improving the throughput as well as enlarging the coverage for ship-to-ship communications in multi-ship marine networks. The proposed scheme reduces the time slots required for the data exchange by designing data transmission and network coding procedures in a sophisticated way based on two-phase digital network coding. Simulation results show that the proposed two-way multi-hop relaying scheme improves the throughput of the conventional one about 5/3 times. ※ 본 연구는 미래창조과학부 및 정보통신산업진흥원의 IT융합 고급인력과정 지원사업(NIPA-2014-H0401-14-1009)과 정부(교육부) 및 한국연구재단의 일반연구자지원 사업으로 (2012R1A1A2040091) 수행된 연구임. First Author : Kyung Hee University, Department of Electronics and Radio Engineering, dopthinh@gmail.com, 학생회원 ° Corresponding Author : Kyung Hee University, Department of Electronics and Radio Engineering, yheekim@khu.ac.kr, 종신회원 * 경희대학교 전자전파공학과, chrisdr84@khu.ac.kr, 학생회원 ** 목포대학교 정보전자공학과, srlee@mokpo.ac.kr, 정회원 *** 목포대학교 컴퓨터공학과, majung@mokpo.ac.kr, 정회원 논문번호:KICS2014-05-160, Receved May 2 2014; Revised July 9, 2014; Accepted July 9, 2014 I. 서 론 최근 다양한 육상 무선 통신의 발전과 함께 해양 환경을 고려한 해상 통신에 대한 연구가 활발히 진행 되고 있다. 해상에서는 전송거리가 긴 MF/HF 대역의 모뎀과 VHF 대역의 AIS(automatic identification system)을 주로 사용 중이다. AIS는 VHF 대역 중 156MHz, 162MHz 에서 SOTDMA (self-organized TDMA) 방식을 사용하여 선박관련 정보와 항해 안전 정보 등을 주고받아 선박간의 충돌 회피 및 원활한 항 해를 가능하게 하는 시스템이다 . MF/HF 대역의 모뎀은 전송거리가 길다는 장점을 가지지만, 낮은 전 송 속도로 인해 효율적인 서비스를 제공하기에 부족 함이 있다. 항만의 경우 기존의 육상 통신 시스템 기 지국을 해안에 설치하여 최대 15km에 이르는 지역까 지 고속 무선 통신을 제공하는 서비스를 제공할 수 있 지만, 연안과 대양의 경우 육상의 기지국으로 네트워 크를 구성하는 것이 불가능하다. 이러한 한계를 극복 하기 위해 해상 위성통신(inmarsat)을 이용하기도 하 지만 , 이는 많은 비용이 들기 때문에 중소형 선박 논문 / 다중-홉 선박간 통신을 위한 네트워크 부호화 기법 567 그림 1. -홉 해상 통신 시스템. Fig. 1. -hop ship-to-ship communication system. 에 사용하기 어렵다. 따라서 군집해 있는 선박들이 저 비용으로 상호 통신을 가능하게 하고 통신 서비스 영 역을 넓힐 수 있는 새로운 방법이 필요하다. 본 논문에서는 선박 간 통신 가능 영역을 확장하여 통신 연결성을 높이는 다중-홉 릴레이 통신 방식을 고 려한다. 다중-홉 릴레이 통신은 송신 노드가 최종 목 적 노드까지 데이터를 전달할 때 송신 노드와 목적 노 드 사이에 위치한 다른 노드가 신호를 전달함으로써 전송 반경을 넓힐 수 있다. 이러한 다중-홉 릴레이 통 신 방식에 대한 연구는 대부분 증폭-후-전달 (amplify-and-forward) 또는 복호-후-전달(decodeand-forward) 방식을 기반으로 한 단방향 통신에 집중 되었다 . 그러나 이러한 단방향 다중-홉 릴레이 방 식은 릴레이 전송 시 시간 슬롯이 추가로 소요되기 때 문에 주파수 효율이 저하되는 문제가 발생한다. 이러한 주파수 효율 저하 문제를 극복하는 방법으 로 이중-홉 환경에서 양방향 통신을 위한 두 단계 아 날로그 네트워크 부호화 , 세 단계 디지털 네트워크 부호화 , 두 단계 디지털 네트워크 부호화 기법 등이 제안되어 활발한 연구가 진행되었다. 이에 최근 에는 상기 방식을 다중-홉 환경에 적용하는 연구가 발 표되고 있다. 먼저 두 단계 아날로그 네트워크 부호화 를 다중-홉 릴레이 네트워크에 적용한 연구에서는 [14,15] 복잡성으로 인해 4-홉 환경에서 제한적으로 연 구되었다. 이 방법은 홉 수가 증가하면 신호 증폭 효 율이 나빠지고 다른 홉의 채널상태정보를 모두 알아 야 간섭을 소거할 수 있기 때문에 실제적인 적용이 어 렵다. 이러한 문제를 극복하기 위해 복호-후-전달 기 반 방식이 [16-17] 제안되었는데, 세 단계 디지털 네트워 크 부호화를 기반으로 한 [17]의 제안 기법이 [16] 의 제안 기법보다 향상된 전송률을 제공하였다. 이에 본 논문에서는 [17]보다 향상된 성능을 제공 하도록 두 단계 디지털 네트워크 부호화를 [12,13] 다중홉 환경에 알맞게 확장한 방식을 제안한다. 이후 논문 의 구성은 다음과 같다. II장에서는 고려하는 다중-홉 해양 통신 시스템 모형과 기존 및 제안 기법에 필요한 네트워크 부호화 기법을 설명한다. III장에서는 제안하 는 다중-홉 양방향 릴레이 기법을 기존 기법과 비교 설명하고, IV장에서 레일리 페이딩 채널에서의 성능을 비교한다. 마지막으로 V장에서 결론을 맺는다.

The nanopowder for the Ni-YSZ anode functional layer (AFL) was prepared by ammonium carbonate co-precipitation method. The electrolyte thickness of the Ni-YSZ-based cell with the anode functional layer was about 16 μm. The anode functional layer coated 2times by dip-coating method was 18 μm in thickness. Compared to the Ni-YSZ cell without AFL, the cell performance was greatly increased in the cell with AFL, showing above 0.6 Wcm-2 at 800 °C. This result exceeds 0.35 W cm-2 of the cell without AFL at the same temperature by approximately two times. Thus, the anode functional layer synthesized by co-precipitation method can be a promise for the performance improvement of YSZ-based solid oxide fuel cells in intermediate temperature range.

We consider user pairing and resource allocation for the uplink of cellular systems employing virtual multiple input multiple output (MIMO). As a multiple access scheme, discrete Fourier transform spread orthogonal frequency division multiple access (DFTS-OFDMA) is adopted for more flexible resource allocation than single carrier (SC)-OFDMA adopted in the Long Term Evolution (LTE) system. We formulate the optimization problems of user pairing and resource allocation to maximize the throughput of the DFTS-OFDMA system under different constraints. The DFTS-OFDMA allowing non-contiguous subcarrier allocation and redundant user assignment provides a better throughput than the SC-FDMA at lower complexity in finding the optimal solution but at the cost of the increased control information indicating the allocated resources.

A mathematical investigation of a normal mode helical antenna (NMHA) is presented to provide an equivalent model. The vector potential of a single-turn NMHA using a developed helix line is flrst derived. To avoid complexity in the vector potential, a useful relationship between the source point and the helix line is established. Employing this relationship, the integral of the vector potential can be calculated as that of a linear current antenna, and the result leads to an equivalent model that is a combination of the electric dipole and the magnetic dipole, i.e., exactly the same as assumed in previous work. A helix line of several turns can be regarded as a combination of the turns. Thus a general NMHA can be analysed as the sum of the vector potentials of the turns in the helix. To verify the obtained formulas, the calculated radiation characteristics are compared with the results of the commercial simulation, showing good agreement.

A normal-mode helical antenna with open-ended and center-fed configurations is investigated. The investigation is twofold. First, explicit formulas are derived by employing the vector potential with the triangular current distribution for a normal-mode helical antenna. These give straightforward results when compared to previous numerical analysis. Second, the equivalent circuit model is proposed to obtain the input impedance. The proposed equivalent circuit model consists of a parasitic capacitance, an effective self-capacitance, an effective inductance, and a radiation resistance in a series combination. The radiation characteristics are compared to the commercial simulation to verify whether the obtained formulas and the equivalent circuit model achieve a good agreement.

A tubular segmented-in-series (SIS) solid oxide fuel cell (SOFC) sub module for intermediate temperature (700–800 °C) operation was fabricated and operated in this study. For this purpose, we fabricated porous ceramic supports of 3 YSZ through an extrusion process and analyzed the basic properties of the ceramic support, such as visible microstructure, porosity, and mechanical strength, respectively. After that, we fabricated a tubular SIS SOFC single cell by using dip coating and vacuum slurry coating method in the case of electrode and electrolyte, and obtained at 800 °C a performance of about 400 mW cm–2. To make a sub module for tubular SIS SOFC, ten tubular SIS SOFC single cells with an effective electrode area of 1.1 cm2 were coated onto the surface of the prepared ceramic support and were connected in series by using Ag + glass interconnect between each single cell. The ten-cell sub module of tubular SIS SOFC showed in 3% humidified H2 and air at 800 °C a maximum power of ca. 390 mW cm–2.

Gadolinia-doped ceria (GDC, Gd0.1Ce0.9O1.95) powders with high sinterability are prepared by carbonate coprecipitation and applied in the fabrication of Ni–YSZ (yttria-stabilized zirconia)-supported tubular solid oxide fuel cells (SOFCs) with a cell configuration of Ni–YSZ/Ni/Ni–GDC/GDC/LSCF(La0.6Sr0.4Co0.2Fe0.8O3−δ)–GDC/LSCF. A high power density (594 mW cm−2) at 600 °C is achieved using the cell (diameter: 6 mm) prepared by sintering of the electrolyte at 1400 °C. This result is attributed to the dense electrolyte and good adherence between GDC and the electrode. The carbonate-derived GDC powders can be sintered to 97% of the theoretical density even at 1050 °C, which demonstrates that the fabrication temperature of tubular SOFCs can potentially be lowered by using cost-effective Ni–YSZ supports.

An interconnect in an anode-supported flat-tubular solid oxide fuel cell (SOFC) electrically connects unit cells and separates fuel and oxidant gases in a stack. An anode-supported flat-tubular SOFC with a highly conductive and dense interconnect film is developed. The dense interconnect film having an n-type conducting layer on the reducing side and a p-type conducting layer on the oxidizing side is fabricated on a porous anode support by a simple and cost-effective screen-printing process, followed by co-sintering with the anode and the electrolyte. The interconnect exhibits low resistance and high stability in a dual atmosphere. The anode-supported flat-tubular cell with the ceramic interconnect shows a power density as high as 360 mW cm −2 at 850 °C.

A novel design of tubular segmented-in-series(SIS) solid oxide fuel cell (SOFC) sub module was presented in this paper. The tubular ceramic support was fabricated by the extrusion technique. The NiO-YSZ anode and the yttria-stabilized zirconia (YSZ) electrolyte were deposited onto the ceramic support by dip coating method. After sintering at for 5 h, a dense and crack-free YSZ film was successfully fabricated. Also, the multi-layered cathode composed of LSM-YSZ composite, LSM and LSCF were coated onto the sintered ceramic support by dip coating method and sintered at . The performance of the tubular SIS SOFC cell and sub module electrically connected by the Ag-glass interconnect was measured and analysed with different fuel flow and operating temperature.

An interconnect layer in an anode-supported flat-tubular solid oxide fuel cell connects electrically unit cells and separates fuel from oxidant in the adjoining cells. Nano-sized La-doped SrTiO 3 for the interconnect is synthesized in this study by the Pechini method using citric acid. The materials with stoichiometric and Sr-deficient compositions are prepared and sintered in an oxidizing atmosphere. The synthesized fine powders exhibit high sinterability, leading to near-full densification. The Sr deficiency plays a crucial role in mechanical, electrical and thermal expansion properties. The interconnect is coated using the synthesized powder on a porous flat-tubular anode support by a screen printing process. The thin and dense layer is obtained after co-sintering in air, and the interconnect/anode interface remains intact upon reduction.

>> This paper presents the characterization of micro-tubular SOFCs using three different anode currentcollecting methods of inlet current collection (IC), both current collection (BC) and total current collection (TC).The maximum power densities of SOFCs at 750℃ using IC, BC and TC were 56 mW/cm 2 (0.43 V, 0.13 A/cm 2 ),236 mW/cm 2 (0.43 V, 0.55 A/cm 2 ) and 261 mW/cm 2 (0.43 V, 0.61 A/cm 2 ) respectively. It was confirmed byimpedance spectroscopy that both the polarization resistance and the ohmic resistance were dramatically increasedat SOFC with IC. Key words : Tubular SOFC(원통형 SOFC), Anode-support(연료극 지지체), Current collection(전류 집전) † Corresponding author : sblee@kier.re.kr [ 접수일 : 2012.1.26 수정일 : 2012.2.15 게재확정일 : 2012.2.24 ]Copyright ⓒ 2012 KHNES 1. 서 론 고체산화물 연료전지(Solid Oxide Fuel Cell: SOFC)는 고체상의 세라믹을 전해질로 사용하여 600℃∼1000℃의 고온에서 운전함으로써 값비싼 귀금속 촉매를 사용하지 않고도 반응을 가속화시킬 수 있으며, 연료극 측에서의 내부 개질 반응이 가능하여 개질기를 간략화 할 수 있을 뿐만 아니라, 수소 이외에 천연가스 및 석탄가스 등의 다양한 연료를 사용할 수 있다. 또한, 온도 상승에 따라 이론 효율(등온 변화로 화학에너지에서 전기에너지로 변환할 수 있는 최대값)은 감소하지만, 반면에 온도 상승에 따라 전기 저항, 전극반응 저항(electrode polarization resistance)은 작아지므로, 온도 상승에 따른 이론 효율의 감소를 보충할 수 있다. 따라서 다른 저온형 연료전지에 비해 높은 효율을 나타낸다.고체산화물 연료전지는 그 형태에 따라 크게 원통형(tubular type) SOFC와 평판형(planar type) SOFC로 구분되며, 각각 형태에 따른 장단점 특성을 갖게 된다. 그중 원통형 SOFC의 구조는 기체 밀봉이 최소화되고, 내구성이 우수한 SOFC 구조로 평가받고 있

In order to estimate the possibility of applying electrolytes generally used in solid oxide fuel cells(SOFCs) to direct carbon fuel cells(DCFCs), properties of YSZ(yttria stabilized zirconia) electrolyte were evaluated. In this study, vacuum slurry coating method was adapted to coat thin layer on anode support substrate. After sintering the electrolyte at for 5hrs, microstructure was analyzed by using SEM image. Also, gas permeability and ionic conductivity were measured to find out the potential possibility of electrolyte for DCFCs. The YSZ electrolyte represented dense coating layer and low gas permeability value. The ionic conductivity of YSZ electrolyte was high over . After measurement of the electrolyte properties, direct carbon fuel cell was fabricated and its performance was measured at .

The management of complicated crown-root fractures is a challenge. Intentional replantation with 180° rotation may be a useful procedure to overcome this problem. In Case 1, a 23-year-old woman with complicated crown-root fractured teeth #11, #21, and #22 was referred for treatment. All fractured teeth were extracted, rotated 180°, and replanted in a slightly extruded position. After 3 months, root canal treatment was completed and the final restorations fabricated. At the 18-month follow up, the patient was asymptomatic, the tooth was functional, and no root resorption was observed radiographically. At the 90-month follow up, slight cervical root resorption of tooth #11 was noted. In Case 2, a 27-year-old woman with a crown-root fractured tooth #21 was referred for treatment. Despite immediate repositioning of the coronal fragment and a 2-week stabilization with a wire splint, the coronal fragment remained separated from the apical tooth segment. The apical segment was extracted, rotated 180°, and replanted in a slightly extruded position. After 1 and 4 weeks, the root canal treatment was completed and the final restoration fabricated, respectively. At the 24-month follow up, the patient was asymptomatic and apical healing was completed.

In order to improve the sintering ability and electrical conductivity of La0.8Ca0.2CrO3 (LCC), LCC/glass composite interconnect materials for high temperature solid oxide fuel cells (SOFCs) were studied in this paper. Glass is known as a sintering aid for improving sintering ability. It promotes liquid phase sintering and improves densification during the sintering process. The components of the glass used in this study are B2O3, SrO, La2O3, SiO2 and Al2O3.The phase stability, microstructure, electrical conductivity and thermal expansion coefficient (TEC) were measured to determine the optimal glass content in the composite materials. All of the tested composite materials showed perovskite structures and dense microstructures. It was found that the addition of up to 5 wt.% glass increased the sintering ability and the electrical conductivity in both air and hydrogen atmospheres. The glass powder enhances the sintering behavior because it acts as a liquid phase sintering aid and the Sr2+ ion in glass powder generates [ S r L a ′ ] and [ C r C r • ] . These lead to improvement in the electrical conductivity of the material. The TEC of the composites indicated compatibility with other cell components. The above results present that LCC/glass composite materials are suitable to be used as interconnects for SOFCs.

A novel design of tubular segmented-in-series solid oxide fuel cell (SOFC) unit bundle was presented in this paper. The tubular ceramic support was fabricated by the extrusion technique. The anode functional layer and the yttria-stabilized zirconia (YSZ) electrolyte are deposited onto the ceramic support by dip coating method. Also, the multi-layered cathode composed of LSM/8YSZ composite, LSM and LSCF were coated onto the co-sintered ceramic support by dip coating method and sintered at 1150°. The performance of first cell in the unit bundle at 800oC showed maximum power of 30.6mW/cm2.

An anode-supported flat tubular SOFC stack for intermediate temperature (700~800oC) operation was fabricated and operated in this study. For this purpose, we fabricated anode-supported flat tubular cells by optimization of the current collecting method and the induction brazing process. After that, we designed a compact fuel and air manifold by adopting a simulation technique to uniformly supply fuel and air gas into the stack and a unique seal and insulation method to make a more compact stack. To assemble the stack, the prepared anode-supported flat tubular cells with an effective electrode area of 90 cm2 were connected in series to 30 bundles, in which one unit bundle consists of two flat tubular cells connected in parallel. The performance of the stack in 3 % humidified H2 and air at 750oC showed a maximum electrical power of 921 W.

Sub-micrometer powders for ceramic interconnects of solid oxide fuel cells were synthesized by the aqueous combustion process. The materials were prepared from the precursor solutions with different glycine (fuel)-to-nitrate (oxidant) ratios (). Single-phase powders with a perovskite structure were obtained after combustion when was equal to or larger than 0.480. Especially, the stoichiometric precursor with

Redox behavior of a Ni–Y 2 O 3 -stabilized ZrO 2 (YSZ) composite anode support and the performance degradation of an anode-supported tubular solid oxide fuel cell (SOFC) were studied under complete oxidation and reduction conditions (degrees of oxidation and reduction = 100%). Materials characterization studies showed that the exposure time in oxidizing and reducing atmospheres played a critical role in the degradation of the porous structures and the physical properties of the anode support. In particular, the redox cycling with an 8 h exposure time resulted in the cracking of YSZ network, leading to significant decay of the mechanical strength. The polarization experiments on the redox-cycled anode-supported tubular cell showed serious performance degradation as a result of the decreases of open-circuit potential and power density. The ac-impedance measurements combined with microstructural observations indicated that the performance degradation resulted mainly from (i) the degradation of anode support, (ii) microcracks across the whole cell, and (iii) interface delamination.

The nickel based brazing alloys (BNi 2, BNi 4) modified by reactive TiH 2 have been studied for their gas sealing properties of anode-supported tubular SOFCs to ferritic stainless steel by induction brazing process. BNi 2 and BNi 4 are not wetted on YSZ electrolyte, but the brazing alloy with TiH 2 showed good wettability with YSZ electrolytes due to a formation of TiO x layer. Among the tested brazing alloys (BNi 2, BNi 4, modified BNi 2, modified BNi 4), all except modified BNi 4 did not join with YSZ. The modified BNi 4 showed the lowest gas leak rate. The gas tightness of a brazed cell was confirmed by open circuit voltage, which was nearly the same as a theoretical value. Based on these experimental results, it is concluded that the BNi 4 modified by TiH 2 is suitable as a sealing material in SOFCs operating at 750 °C.

This study reports the high temperature oxidation kinetics, area specific resistance (ASR), and interfacial microstructure of metallic interconnects coated by (La 0.8 Sr 0.2 ) 0.98 MnO 3 (LSM) in air atmosphere at 800 °C. An efficient LSM conductive layer was fabricated on metallic interconnects for solid oxide fuel cells (SOFCs) by using a wet spray coating method. The optimum conditions for slurries used in the wet spray coating were determined by the measurement of slurry viscosity and coated surface morphology. The surface roughnesses of the substrates were increased through sandblast treatment. The adhesive strength of the interface between the coated layer and the metal substrate increased with increased surface roughness of the metallic interconnects. The electrical conductivities of the coated substrates were measured by using a DC two-point and four-wire method under air atmosphere at 800 °C. Of note, the Crofer22APU treated at 1100 °C in N 2 with 10 vol.% H 2 showed long-term stability and a lower ASR value than other samples(heat-treated at 800 °C and 900 °C). After an 8000-h oxidation experiment the coated Crofer22APU substrate, the ASR showed a low value of 23 mΩ cm 2 . The thickness of the coated conductive oxide layer was about 10-20 μm. These results show that a coated oxide layer prevents the formation and the growth of scale (Cr 2 O 3 and (Mn, Cr, Fe) 3 O 4 layer) and enhances the long-term stability and electrical performance of metallic interconnects for SOFCs.

A Crofer 22 APU mesh coated with a conductive ceramic material was developed as an alternative cathode current collector to Ag-based materials for solid oxide fuel cells. (LSM) layer was deposited onto the Crofer mesh using a spray-coating technique, in an attempt to mitigate the degradation of electrical properties due to surface oxidation at high temperatures. The oxidation experiments at in air indicated that the areaspecific resistance (ASR) of the LSM-coated Crofer mesh was strongly dependent on the wire diameter and the contact morphology between mesh and cell. In addition, the post-heat-treatment in resulted in a reduced thickness of Cr-containing oxide scales at the interface between Crofer mesh and LSM layer, leading to a decreased ASR.

The process of vacuum slurry coating for the fabrication of a dense and thin electrolyte film on a porous anode tube is investigated for application in solid oxide fuel cells. 8 mol% yttria stabilized zirconia is coated on an anode tube by vacuum slurry-coating process as a function of pre-sintering temperature of the anode tube, vacuum pressure, slurry concentration, number of coats, and immersion time. A dense electrolyte layer is formed on the anode tube after final sintering at 1400 °C. With decrease in the pre-sintering temperature of the anode tube, the grain size of the coated electrolyte layer increases and the number of surface pores in the coating layer decreases. This is attributed to a reduced difference in the respective shrinkage of the anode tube and the electrolyte layer. The thickness of the coated electrolyte layer increases with the content of solid powder in the slurry, the number of dip-coats, and the immersion time. Although vacuum pressure has no great influence on the electrolyte thickness, higher vacuum produces a denser coating layer, as confirmed by low gas permeability and a reduced number of defects in the coating layer. A single cell with the vacuum slurry coated electrolyte shows a good performance of 620 mW cm−2 (0.7 V) at 750 °C. These experimental results indicate that the vacuum slurry-coating process is an effective method to fabricate a dense thin film on a porous anode support.

A MnCo2O4 powder was synthesized via a glycine nitrate process (GNP) from manganese and cobalt nitrates. Single phase spinel was obtained by calcining an ash at 800oC and almost fully densified MnCo2O4 was fabricated at 1100oC. It was found that the sintering at higher temperature than 1100oC leads to the decomposition of the MnCo2O4. The MnCo2O4 showed compatible thermal expansion coefficient and good electrical conductivity. However, the phase stability under the reducing environments was proved to be poor.

We investigated the influences of metallic coating of cobalt deposited on the ferritic stainless steel, SUS 444, by electrodeposition. Cobalt electrodeposited sample revealed a lower area specific resistance value than that of uncoated at 800°in air and showed efficient retention capability of chromium evaporation. Also, cobalt was oxidized to CoCo2O4 and mixed oxide spinels after 1000h at 800° in air.

This article reviews recent R&D trends in SOFC development with an emphasis on industries that can produce the SOFC stack and power generation system. SOFC is an electrochemical device that can convert the chemical energy of fuel into the electrical energy with environment friendly system and high efficiency. SOFC power generation system could be classified as the portable power generation system, auxiliary power unit(APU), residential power generation(RPG) and large size distributed power generation. In the case of more than 10kW system, the major R&D trends are focused on the tubular type SOFC system with high efficient and long term stability to meet the commercialization of SOFC power generation system.

La0.8Sr0.2Ga0.8Mg0.2O2.8 (LSGM8080) powder, showing the highest electrical conductivity among LSGMs of various compositions, is synthesized using the glycine nitrate process (GNP) and used as the electrolyte for an intermediate-temperature solid oxide fuel cell (IT-SOFC). The LDC (Ce0.55La0.45O1.775) powder is synthesized by a solid-state reaction and employed as the material for a buffer layer to prevent the reaction between the anode and electrolyte materials. The LDC also serves as the skeleton material for the anode. An anode-supported single cell with an active area of 1 cm2 is constructed for performance evaluation. A single-cell test is performed at 750 and 800 °C. The maximum power density of the cell 459 and 664 mW cm−2 at 750 and 800 °C, respectively.

A 700 W anode-supported micro-tubular solid-oxide fuel cell (SOFC) stack for use as an auxiliary power unit (APU) for an automobile is fabricated and characterized in this study. For this purpose, a single cell was initially designed via optimization of the current collecting method, the brazing method and the length of the tubular cell. Following this, a high-power single cell was fabricated that showed a cell performance of 0.54 W / cm 2 at 0.7 V and 800 ∘ C using H 2 (fuel utilization = 45 % ) and air as fuel and oxidant gas, respectively. Additionally, a fuel manifold was designed by adopting a simulation method to supply fuel gas uniformly into a single unit cell. Finally, a 700 W anode-supported micro-tubular SOFC stack was constructed by stacking bundles of the single cells in a series of electrical connections using H 2 (fuel utilization = 49 % ) and air as fuel and oxidant gas, respectively. The SOFC stack showed a high power density of 0.38 W / cm 2 ; moreover, due to the good thermo-mechanical properties of the micro-tubular SOFC stack, the start-up time could be reduced by 2 h, which corresponds to 6 ∘ / min .

A dual-band RF switch that utilizes composite right/left handed (CRLH) transmissions-lines(TLs) and PIN diodes is proposed. The design method of RF switch is based on the phase characteristic of the CRLH-TL, which can be adjusted arbitrary, and employed conventional type-II; filter structure. The use of multiple PIN diodes as switching element offers prominent performance such as low insertion loss, low power consumption, and high isolation. Theoretical performance of RF switch is verified through the circuit simulations and the measurement of a fabricated prototype at 0.8 GHz and 1.6 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2074–2077, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23591

KIER has been developing the anode-supported flat tubular solid oxide fuel cell unit bundle for the intermediate temperature() operation. Anode-supported flat tubular cells have Ni/YSZ cermet anode support, 8 moi.% stabilized thin electrolyte, and cathode multi-layer composed of Sr-doped , LSM-YSZ composite, and . The prepared anode-supported flat tubular cell was joined with ferritic stainless steel cap by induction brazing process. Current collection for the cathode was achieved by winding Ag wire and paste, while current collection for the anode was achieved by using Ni wire and felt. For making stack, the prepared anode-supported flat tubular cells with effective electrode area of connected in series with 12 unit bundles, in which unit bundle consists of two cells connected in parallel. The performance of unit bundle in 3% humidified and air at shows maximum power density of (@ 0.7V). Through these experiments, we obtained basic technology of the anode-supported flat tubular cell and established the proprietary concept of the anode-supported flat tubular cell unit bundle.

The characteristics of La0.8Sr0.05Ca0.15CrO3 interconnect material synthesized by modified pechini method, USP, and GNP was investigated. The powder synthesized by Pechini method exhibited somewhat aggregated shape. The precursor synthesized by USP had spherical shape and their particle size decreased somewhat after calcining procedure at 1000oC. In the case of GNP, the precursor formed agglomerated particles. The average particle size of powders synthesized by Pechini method, USP, and GNP were 0.4+m, 0.6+m, and below 10nm, respectively. The La0.8Sr0.05Ca0.15CrO3 powder had a single perovskite phase and orthorhombic structure. After sintering at 1400oC and 1500oC, the relative density of samples synthesized by pechini method was approximately 95% and that of samples synthesized by USP was slightly small. However, that of the samples synthesized by GNP was approximately 92%.

The effect of ScSZ - YSZ composite on stabilization and electrical conductivity has been investigated. Composite of (8YSZ)x(10ScSZ)(1-x)(x=0~1) were mixed by wet milling process and sintered at 1400°C for 5h and characterized by XRD, SEM, dilatometry and impedance spectroscopy. the long-term stability of the electrolyte materials was examined at 900°C for up to 1000h. The cubic phase shifts from an YSZ character to a ScSZ character with increase in percentage of ScSZ. The conductivity of composite with increasing ScSZ content is slightly higher than YSZ. Especially, above 50wt% ScSZ composition exhibited higher electrical conductivity. All compositions showed conductivity degradation after annealing at 900°C for 1000h.

The performance of anode-supported tubular SOFC was investigated in terms of the thickness of anode support. Considering the geometry of single cell, it can be readily known that the concentration polarization across the anode- support is the most significant factor to determine the performance of the cell. For this purpose, we fabricated single cells having different anode-support thickness of 1mm and 2mm for both cells the cathode layer ((La0.85Sr0.15)0.98MnO3) and electrolyte layer (8mol%yttria-stabilized zirconia) were coated at the same condition. The cell performance was increased with decreasing anode-support wall thickness. The single cell having wall thickness of 1mm showed a power density of 0.42mW/cm2 at 0.7V and 700oC. From the analysis of impedance spectra, it was concluded that the total polarization of the anode supported tubular SOFC was mainly governed by the concentration polarization caused by the mass transport though the anode- support.

KIER has been developing the anode supported flat tubular SOFC stack for the intermediate temperature (700~800oC) operation. For this purpose, we have first fabricated anode supported flat tubular cells by the optimization between the current collecting method and the induction brazing process. After that we designed the compact fuel & air manifold by adopting the simulation technique to uniformly supply fuel & air gas and the unique seal & insulation method to make the more compact stack. For making stack, the prepared anode-supported flat tubular cells with effective electrode area of 90 cm2 connected in series with 12 modules, in which one module consists of two cells connected in parallel. The performance of stack in 3 % humidified H2 and air at 800 oC shows maximum power of 507 W. Through these experiments, we obtained basic & advanced technology of the anode-supported flat tubular cell and established the proprietary concept of the anode-supported flat tubular SOFC stack in KIER

We developed a 700W anode-supported tubular SOFC stack for APU application. For this purpose, we have first designed single cell by optimization of current collecting method, brazing method and the length of tubular cell, and then we have fabricated high power single cell. After that we designed fuel manifold by adopting simulation method to uniformly supply fuel gas and oxygen gas to the inside and to the outside of single cells, respectively. Finally, by stacking the bundles of cells in series electrical connection, we can construct a 700W anode-supported micro-tubular SOFC stack having power density of 0.38W/cm2 at 750oC

Nano-sized LSM–YSZ composite was co-synthesized by a glycine–nitrate process (GNP). Transmission electron microscopy revealed that the as-prepared LSM–YSZ particles consist of nano-sized powders with a dominant YSZ phase. Backscatter electron image shows that LSM and YSZ phases were regularly dispersed within the composite. Alternating current impedance measurement revealed that the co-synthesized LSM–YSZ electrode shows lower polarization resistance and activation energy than the physically mixed LSM–YSZ electrode. This electrochemical improvement would be attributed to the increase in three-phase boundary and good dispersion of LSM and YSZ phases within the composite.

LSGM (La1 − xSrxGa1 − yMgyO3 − δ) powders of four different compositions (x, y = 0.1 or 0.2) (a symbolic system such as LSGM9191 for x = 0.1 and y = 0.1 or LSGM9182 for x = 0.1 and y = 0.2 is used hereafter) were synthesized using the GNP (glycine nitrate process) as the electrolyte material of the intermediate temperature solid oxide fuel cell (IT-SOFC). They were then calcined at 1000 °C for 2 h, compacted into a disc or a rod, and sintered at 1400 °C for 4 h in preparation for structural, electrical and thermomechanical characterizations. The reactivity of the LSGM with the cathode material of LSM (La0.85Sr0.15MnO3) or with the anode material of Ni–YSZ was analyzed by sintering an LSGM/LSM, LSGM/NiO or LSGM/YSZ powder mixture at 1400 °C for 4 h and then searching for possible reaction products in its XRD pattern. The sinters of LSGM9191, LSGM9182 and LSGM8282 consisted of a single LSGM phase. On the other hand, the sinter of LSGM8291 contained the second phases of LaSrGa3O7 and LaSrGaO4 as well in addition to the main LSGM phase. The electrical conductivity of LSGM8282 (0.105 S cm−1 at 800 °C) turned out to be the highest among those of the four LSGMs and more than twice as high as that of YSZ (∼0.045 S cm−1). The linear thermal expansion coefficient was measured to be 12.1 × 10−6 K−1 for LSGM8282 which was very close to that of LSM (11.7 × 10−6 K−1). The phase stability of LSGM8282 in contact with LSM was fairly good. LSGM8282, however, reacted quite extensively with Ni–YSZ.

We synthesized and investigated by Glycine Nitrate Process(GNP) method used as cathode materials for SOFC(solid oxide fuel cell). Optimized amount of glycine is 3.17 mol. ICP elemental composition analysis indicated that the stoichiometry of the synthesized powders have nearly nominal values. SEM images and XRD patterns reveal that the synthesized powder has uniform size distribution and high degree of crystallinity. The sample powders were isostatically pressed to form a pellet. The green body was sintered at and the relative density of the sintered specimens were measured by Archimedes mettled. We measured electrochemical performance of LSF by AC impedance spectroscopy. Resistance of LSF shows lower value than that of LSM throughout all temperature region. The anode-supported solid oxide fuel cell showed a performance of at . The electrochemical characteristics of the single cell were examined by at impedance method.

Pore-size controlled porous carbons were prepared for the catalyst-supporting materials of direct methanol fuel cell (DMFC) from the naphthalene-based mesophase pitch. Porous carbon was synthesized by etching the silica sphere from the carbon/silica mixture. The pore size of the porous carbon was controlled by the size of silica sphere. 60wt% Pt-Ru/porous carbons catalysts were prepared by using impregnation method. Physical and electrochemical properties of the catalyst were characterized by using XRD, cyclic voltammetry (CV) and unit cell test.

In this paper, An active antenna of T-DMB was developed to equip to handhold gadgets by using LNA and a parasitic element allowing to miniature. The size of the fabricated active antenna is and FR4 is used for the substrate. The size of the proposed antenna is reduced by 38.8% at the operating frequency compared to one without a parasitic element, and a short stub. The proposed antenna shows improved performance at the measurement especially in the ratio of S/N compared with conventional monopole of 300 mm. The proposed antenna is well able to adapt into handhold gadgets for receiving T-DMB.

The ceramic interconnect,La0.8Sr0.05Ca0.15(Cr1 −x , Bx)O3 (B = Cu, Ni, V, x = 0.02, 0.1, 0.5) (LSCCB) powders were prepared by Pechini method, Ultrasonic Spray Pyrolysis (USP) and Glycine Nitrate Process (GNP). Nano sized powders were synthesized by GNP and their chemical compositions were confirmed by ICP analysis. The electrical conductivities of LSCCCu, LSCCNi, and LSCCV samples were 34 S/cm, 48 S/cm, and 22 S/cm at 800∘C in air, respectively. Among the LSCCB powders, the LSCCNi sample shows highest relative density and electrical conductivity. In a low oxygen partial pressure, however, LSCCV sample was more stable. The perovskite phase of the composition LSCCV sample is of large practical interest for interconnects in SOFC because of the stability in low oxygen partial pressure.

Synthesis and sintering properties of the (La0.8Ca0.2−x Sr x )CrO3 samples doped by two alkaline earth metals in comparison to the doped only by one alkaline earth metal were evaluated by phase analysis, sintering properties, thermal expansion behaviors, and electrical conductivity. The sintered (La0.8Ca0.2−x Sr x )CrO3 (x = 0, 0.05, and 0.1) and (La0.8Ca0.2−x Sr x )CrO3 (x = 0.2) were found to have orthorhombic and rhombohedral symmetries, respectively. Relative density of the (La0.8Sr0.2)CrO3 sample sintered at 1500∘C for 5 h was lower than that of the (La0.8Ca0.2−x Sr x )CrO3 (x = 0, 0.05, and 0.1) sample. TECs of the (La0.8Ca0.2−x Sr x )CrO3 (x = 0, 0.05, 0.1, and 0.2) in air were 11 × 10−6/∘C, 11.2 × 10−6/∘C, 11.2 × 10−6/∘C, and 11.3 × 10−6/∘C, respectively. The electric conductivity of the (La0.8Ca0.2−x Sr x )CrO3 sample was determined.