The effects of low-Co AB_5 type hydrogen storage alloys prepared by quenchingand annealing on the performances of MH-Ni batteries were investigated, and the characteristics ofthe low-Co AB_5 type hydrogen storage allo...The effects of low-Co AB_5 type hydrogen storage alloys prepared by quenchingand annealing on the performances of MH-Ni batteries were investigated, and the characteristics ofthe low-Co AB_5 type hydrogen storage alloys were compared with those of the high-Co AB_5 typehydrogen storage alloy as well. The results showed that the faster the cooling of the low-Cohydrogen storage alloy is, the better homogeneity of the chemical composition for the alloy and thelonger cycle life of the battery are, but the electrochemical discharge capacity and high-ratedischarge ability are reduced. The high-rate discharge ability and charge retention of MH-Nibatteries for the conventional as-cast annealed low-Co hydrogen storage alloy were superior to thosefor the rapidly quenched low-Co hydrogen storage alloy and the high-Co hydrogen storage alloy, buta little inferior in the cycle life.展开更多
To remove the scalar ambiguity in conventional blind channel estimation algorithms, totally blind channel estimation （TBCE） is proposed by using multiple constellations. To estimate the unknown scalar, its phase is ...To remove the scalar ambiguity in conventional blind channel estimation algorithms, totally blind channel estimation （TBCE） is proposed by using multiple constellations. To estimate the unknown scalar, its phase is decomposed into a fractional phase and an integer phase. However, the maximum-likelihood （ML） algorithm for the fractional phase does not have closed-form solutions and suffers from high computational complexity. By ex- ploring the structures of widely used constellations, this paper proposes a low-complexity fractional phase estimation algorithm which requires no exhaustive search. Analytical expressions of the asymptotic mean squared error （MSE） are also derived. The theo- retical analysis and simulation results indicate that the proposed fractional phase estimation algorithm exhibits almost the same performance as the ML algorithm but with significantly reduced computational burden.展开更多
In order to further reduce the cost of AB5 type rare earth-based hydrogen storage alloy, a low-Co AB5 type hydrogen storage alloy were by substituting Co with Cu and Fe.The characteristics of these alloys have been in...In order to further reduce the cost of AB5 type rare earth-based hydrogen storage alloy, a low-Co AB5 type hydrogen storage alloy were by substituting Co with Cu and Fe.The characteristics of these alloys have been investigated by means of XRD, PCT, and measurement of electrochemical capacity and cycle life.The test results show that the effect of these two kinds of substituting elements on discharge capacity is Cu ＞ Fe, and the cycle life is on the contrary.Both of them have no distinct influence on activity speed, but activity speed increases with the decrease of Co.By the order way, the high discharge rate characteristics rise with the addition of Cu and decreasing of Co.展开更多
The reduction of low-concentration carbon dioxide with water to organic fuels is still a huge challenge. In this study, we successfully designed the partially oxidized cobalt nanoparticles coated by the nitrogendoped ...The reduction of low-concentration carbon dioxide with water to organic fuels is still a huge challenge. In this study, we successfully designed the partially oxidized cobalt nanoparticles coated by the nitrogendoped carbon layer(Co@NC) of 2-8 nm via a facile method and then interspersed with different amount of Pt nanoparticles. The Co@NC decorated with 1 wt% Pt exhibits the best ability for COreduction to CHand a CHproduction rate of 14.4 μmol·g·his achieved. It is worth noting that the system is carried out under low-concentration CO(400 ppm) circumstance without any sacrificial agent, which could be meaningful to the design of catalysts for atmospheric COreduction.展开更多
On the basis of typical high Co MI(Lanthanum rich mischmetal) based hydrogen storage alloy, a series oflow Co or Co free alloys have been prepared by means of partial or full replacement of Co by a combination of othe...On the basis of typical high Co MI(Lanthanum rich mischmetal) based hydrogen storage alloy, a series oflow Co or Co free alloys have been prepared by means of partial or full replacement of Co by a combination of other elements. The microstructures, p c T (pressure concentration temperature) characteristics and electrochemical propertiesunder different charge discharge conditions of the alloys have been investigated. Compared with the high Co alloy, thelow Co or Co free alloys have the lower hydrogen equilibrium pressure and discharge capacity, but have the nearly samehigh rate and high temperature discharge capability, and better charge discharge cycling stability. The reason is revealedby SEM, XPS and XRD results. \[展开更多
在集成散热微流道的低温共烧陶瓷(low-temperature co-fired ceramics,LTCC)封装基板中引入内嵌金属柱(embedded metal columns,EMCs)作为导热增强结构,是提升封装体散热性能的重要改进措施。基于已有的理论分析与试验研究结果,结合工...在集成散热微流道的低温共烧陶瓷(low-temperature co-fired ceramics,LTCC)封装基板中引入内嵌金属柱(embedded metal columns,EMCs)作为导热增强结构,是提升封装体散热性能的重要改进措施。基于已有的理论分析与试验研究结果,结合工艺条件,分析内嵌金属柱截面形状、长度、直径和流体入口流速对其散热性能的影响。通过正交试验设计,在有限元仿真软件中建立带有内嵌金属柱的LTCC微流道基板的热仿真模型,并对得到的热仿真数据进行极差与方差分析。研究结果表明,影响内嵌金属柱散热性能的因素由大到小依次为流体流速、内嵌金属柱截面形状、内嵌金属柱直径以及内嵌金属柱长度;在置信度为90%的情况下,流体入口流速、内嵌金属柱截面形状和直径均对其散热性能有显著影响,内嵌金属柱长度对其散热性能无显著影响。展开更多
Lithium-rich layered oxides (LLOs) are increasingly recognized as promising cathode materials for nextgeneration high-energy-density lithium-ion batteries (LIBs).However,they suffer from voltage decay and low initial ...Lithium-rich layered oxides (LLOs) are increasingly recognized as promising cathode materials for nextgeneration high-energy-density lithium-ion batteries (LIBs).However,they suffer from voltage decay and low initial Coulombic efficiency (ICE) due to severe structural degradation caused by irreversible O release.Herein,we introduce a three-in-one strategy of increasing Ni and Mn content,along with Li/Ni disordering and TM–O covalency regulation to boost cationic and anionic redox activity simultaneously and thus enhance the electrochemical activity of LLOs.The target material,Li_(1.2)Ni_(0.168)Mn_(0.558)Co_(0.074)O_(2)(L1),exhibits an improved ICE of 87.2%and specific capacity of 293.2 mA h g^(-1)and minimal voltage decay of less than 0.53 m V cycle-1over 300 cycles at 1C,compared to Li_(1.2)Ni_(0.13)Mn_(0.54)Co_(0.13)O_(2)(Ls)(274.4 mA h g^(-1)for initial capacity,73.8%for ICE and voltage decay of 0.84 mV/cycle over 300 cycles at 1C).Theoretical calculations reveal that the density of states (DOS) area near the Fermi energy level for L1 is larger than that of Ls,indicating higher anionic and cationic redox reactivity than Ls.Moreover,L1 exhibits increased O-vacancy formation energy due to higher Li/Ni disordering of 4.76%(quantified by X-ray diffraction Rietveld refinement) and enhanced TM–O covalency,making lattice O release more difficult and thus improving electrochemical stability.The increased Li/Ni disordering also leads to more Ni^(2+)presence in the Li layer,which acts as a pillar during Li+de-embedding,improving structural stability.This research not only presents a viable approach to designing low-Co LLOs with enhanced capacity and ICE but also contributes significantly to the fundamental understanding of structural regulation in high-performance LIB cathodes.展开更多
低温共烧陶瓷(Low Temperature Co-fired Ceramics,LTCC)具有优异的介电性能、热稳定性和多功能集成能力,在5G/6G通信、毫米波雷达、卫星载荷、系统级封装等领域得到广泛应用。然而,传统工艺存在两方面显著局限:一是受成型方式制约,难...低温共烧陶瓷(Low Temperature Co-fired Ceramics,LTCC)具有优异的介电性能、热稳定性和多功能集成能力,在5G/6G通信、毫米波雷达、卫星载荷、系统级封装等领域得到广泛应用。然而,传统工艺存在两方面显著局限:一是受成型方式制约,难以实现曲面多层基板的高精度制造;二是工艺流程复杂且对批次规模依赖性强,难以满足单件、小批基板的快速验证需求。增材制造基于逐层堆叠、按需沉积的独特技术路径,为突破上述瓶颈提供了创新性解决方案。文中系统综述了LTCC增材制造所涉及的材料制备、成型工艺方面的研究动态,分析了当前存在的关键问题,并展望了未来发展方向。展开更多
文摘The effects of low-Co AB_5 type hydrogen storage alloys prepared by quenchingand annealing on the performances of MH-Ni batteries were investigated, and the characteristics ofthe low-Co AB_5 type hydrogen storage alloys were compared with those of the high-Co AB_5 typehydrogen storage alloy as well. The results showed that the faster the cooling of the low-Cohydrogen storage alloy is, the better homogeneity of the chemical composition for the alloy and thelonger cycle life of the battery are, but the electrochemical discharge capacity and high-ratedischarge ability are reduced. The high-rate discharge ability and charge retention of MH-Nibatteries for the conventional as-cast annealed low-Co hydrogen storage alloy were superior to thosefor the rapidly quenched low-Co hydrogen storage alloy and the high-Co hydrogen storage alloy, buta little inferior in the cycle life.
基金supported by the National Science and Technology Major Project of China(2013ZX03003006-003)
文摘To remove the scalar ambiguity in conventional blind channel estimation algorithms, totally blind channel estimation （TBCE） is proposed by using multiple constellations. To estimate the unknown scalar, its phase is decomposed into a fractional phase and an integer phase. However, the maximum-likelihood （ML） algorithm for the fractional phase does not have closed-form solutions and suffers from high computational complexity. By ex- ploring the structures of widely used constellations, this paper proposes a low-complexity fractional phase estimation algorithm which requires no exhaustive search. Analytical expressions of the asymptotic mean squared error （MSE） are also derived. The theo- retical analysis and simulation results indicate that the proposed fractional phase estimation algorithm exhibits almost the same performance as the ML algorithm but with significantly reduced computational burden.
文摘In order to further reduce the cost of AB5 type rare earth-based hydrogen storage alloy, a low-Co AB5 type hydrogen storage alloy were by substituting Co with Cu and Fe.The characteristics of these alloys have been investigated by means of XRD, PCT, and measurement of electrochemical capacity and cycle life.The test results show that the effect of these two kinds of substituting elements on discharge capacity is Cu ＞ Fe, and the cycle life is on the contrary.Both of them have no distinct influence on activity speed, but activity speed increases with the decrease of Co.By the order way, the high discharge rate characteristics rise with the addition of Cu and decreasing of Co.
基金financially supported by the National Natural Science Foundation of China(Nos.51772312 and 51472260)the Environmental Functional Materials Innovation Team of Ministry of Education(IRT 16R49)the International Joint Laboratory on Resource Chemistry(IJLRC)
文摘The reduction of low-concentration carbon dioxide with water to organic fuels is still a huge challenge. In this study, we successfully designed the partially oxidized cobalt nanoparticles coated by the nitrogendoped carbon layer(Co@NC) of 2-8 nm via a facile method and then interspersed with different amount of Pt nanoparticles. The Co@NC decorated with 1 wt% Pt exhibits the best ability for COreduction to CHand a CHproduction rate of 14.4 μmol·g·his achieved. It is worth noting that the system is carried out under low-concentration CO(400 ppm) circumstance without any sacrificial agent, which could be meaningful to the design of catalysts for atmospheric COreduction.
文摘On the basis of typical high Co MI(Lanthanum rich mischmetal) based hydrogen storage alloy, a series oflow Co or Co free alloys have been prepared by means of partial or full replacement of Co by a combination of other elements. The microstructures, p c T (pressure concentration temperature) characteristics and electrochemical propertiesunder different charge discharge conditions of the alloys have been investigated. Compared with the high Co alloy, thelow Co or Co free alloys have the lower hydrogen equilibrium pressure and discharge capacity, but have the nearly samehigh rate and high temperature discharge capability, and better charge discharge cycling stability. The reason is revealedby SEM, XPS and XRD results. \[
文摘在集成散热微流道的低温共烧陶瓷(low-temperature co-fired ceramics,LTCC)封装基板中引入内嵌金属柱(embedded metal columns,EMCs)作为导热增强结构,是提升封装体散热性能的重要改进措施。基于已有的理论分析与试验研究结果,结合工艺条件,分析内嵌金属柱截面形状、长度、直径和流体入口流速对其散热性能的影响。通过正交试验设计,在有限元仿真软件中建立带有内嵌金属柱的LTCC微流道基板的热仿真模型,并对得到的热仿真数据进行极差与方差分析。研究结果表明,影响内嵌金属柱散热性能的因素由大到小依次为流体流速、内嵌金属柱截面形状、内嵌金属柱直径以及内嵌金属柱长度;在置信度为90%的情况下,流体入口流速、内嵌金属柱截面形状和直径均对其散热性能有显著影响,内嵌金属柱长度对其散热性能无显著影响。
基金National Natural Science Foundation of China (No.52202046)Natural Science Foundation of Shaanxi Province (No.2021JQ-034)。
文摘Lithium-rich layered oxides (LLOs) are increasingly recognized as promising cathode materials for nextgeneration high-energy-density lithium-ion batteries (LIBs).However,they suffer from voltage decay and low initial Coulombic efficiency (ICE) due to severe structural degradation caused by irreversible O release.Herein,we introduce a three-in-one strategy of increasing Ni and Mn content,along with Li/Ni disordering and TM–O covalency regulation to boost cationic and anionic redox activity simultaneously and thus enhance the electrochemical activity of LLOs.The target material,Li_(1.2)Ni_(0.168)Mn_(0.558)Co_(0.074)O_(2)(L1),exhibits an improved ICE of 87.2%and specific capacity of 293.2 mA h g^(-1)and minimal voltage decay of less than 0.53 m V cycle-1over 300 cycles at 1C,compared to Li_(1.2)Ni_(0.13)Mn_(0.54)Co_(0.13)O_(2)(Ls)(274.4 mA h g^(-1)for initial capacity,73.8%for ICE and voltage decay of 0.84 mV/cycle over 300 cycles at 1C).Theoretical calculations reveal that the density of states (DOS) area near the Fermi energy level for L1 is larger than that of Ls,indicating higher anionic and cationic redox reactivity than Ls.Moreover,L1 exhibits increased O-vacancy formation energy due to higher Li/Ni disordering of 4.76%(quantified by X-ray diffraction Rietveld refinement) and enhanced TM–O covalency,making lattice O release more difficult and thus improving electrochemical stability.The increased Li/Ni disordering also leads to more Ni^(2+)presence in the Li layer,which acts as a pillar during Li+de-embedding,improving structural stability.This research not only presents a viable approach to designing low-Co LLOs with enhanced capacity and ICE but also contributes significantly to the fundamental understanding of structural regulation in high-performance LIB cathodes.
文摘低温共烧陶瓷(Low Temperature Co-fired Ceramics,LTCC)具有优异的介电性能、热稳定性和多功能集成能力,在5G/6G通信、毫米波雷达、卫星载荷、系统级封装等领域得到广泛应用。然而,传统工艺存在两方面显著局限:一是受成型方式制约,难以实现曲面多层基板的高精度制造;二是工艺流程复杂且对批次规模依赖性强,难以满足单件、小批基板的快速验证需求。增材制造基于逐层堆叠、按需沉积的独特技术路径,为突破上述瓶颈提供了创新性解决方案。文中系统综述了LTCC增材制造所涉及的材料制备、成型工艺方面的研究动态,分析了当前存在的关键问题,并展望了未来发展方向。
