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本文利用广义常微分方程理论,得到了线性脉冲微分方程的通解公式,并利用ω-周期解的定义和线性代数方程的性质,得到了线性脉冲微分方程初值问题的ω-周期解. 相似文献
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通过直流四端法研究了钙钛矿型混合导体La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF)和La0.6Sr0.4Co0.2Fe0.8O3-δ-Ce0.9Gd0.1O1.95(LSCF-GDC)复合材料的高温电学性质.通过电导率测试得出单相LSCF和LSCF-GDC的小极化子导电活化能分别为Ea1=9.72kJ/mol和Ea2=10.64kJ/mol.突然改变氧分压条件进行电导弛豫测试,进而研究了二者的氧表面交换性质.测定了温度范围在600~800℃、氧分压在21~34kPa之间变化时两种样品的表面交换系数为kchem为2.87×10-6~6.91×10-6cm/s.讨论认为GDC对氧表面交换过程的催化作用与引入GDC对材料微结构的影响共同促进了复合材料中的氧输运过程.根据两种样品氧表面交换系数和温度的关系估算了氧表面交换过程活化能. 相似文献
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本文对Co基非晶Fe_(5.3)Co_(61.3)Ni_(7.4)Si_(10)B_(16)及Fe_(5)Co_(58)Ni_(11)Si_(10)B_(16)合金用不同方法进行了热处理后得出:退火使合金磁性恶化,纵向磁退火有效地消除了应力,局部感生各向异性和畴壁钉扎,形成感生单轴各向异性,静态磁性获得显著提高。Fe_(5.3)Co_(61.3)Ni_(7.4)Si_(10)B_(16)合金最好静态磁性μ_m高达169×10~4Gs/Oe,Hc为4.3mOe,μ_(0.002)为94000G/0e,Br/Bs=0.895,磁滞损耗减小。但由于形成粗大180°畴使反常涡流损耗增加。倾斜磁场退火使180°畴数目增多,在一定频段内有效的降低反常涡流损耗。对提高初始导磁率有一定作用。 相似文献
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采用d-HDDR(室温吸氢后"氢化—歧化—脱氢—再复合")工艺制备Nd12.5Fe68.9-xCo12GaxZr0.1B6.5(x=0,0.1,0.3,0.5,0.7)永磁磁粉,研究了歧化氢压、脱氢再复合温度、脱氢再复合真空度及合金元素Ga对Nd12.5Fe68.9-xCo12GaxZr0.1B6.5合金磁性能的影响规律,利用X射线衍射仪(XRD)对磁粉的相结构进行表征。结果表明,d-HDDR工艺中,合金的相变过程为:Nd2(Fe,Co)14B+2H22NdH2+12α-(Fe,Co)+(Fe,Co)2B;0.03MPa的歧化氢压是NdFeB磁粉产生磁各向异性的关键,脱氢再复合阶段采用高温,低真空与高真空相结合的制度是NdFeB磁粉获得高各向异性的保证;添加Ga元素有益于提高磁粉的矫顽力和各向异性,其最佳添加量为0.3%(原子分数),Nd12.5Fe68.6Co12Ga0.3Zr0.1B6.5磁粉的典型性能为:(BH)max=218.3kJ/m3,Br=1.22T,jHc=751.2kA/m,DOA=0.52。 相似文献
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Quanmin YANG Yongquan LEI+ Changpin CHEN Jing WU Qidong WANG Dept. of Mater. Sci. Eng. Zhejiang Univresity Hangzhou China 《材料科学技术学报》1993,9(2):125-128
The thermal stability of amorphous ternary hydrides Mg_(50)Ni_(50)H_(54) and Mg_(30)Ni_(70)H_(45) and their corre-sponding amorphous binary alloys Mg_(50)Ni_(50) and Mg_(30)Ni_(70) were studied with X-ray diffraction(XRD) and differential scanning calorimetry(DSC). Samples of the amorphous alloys were preparedby mechanical alloying and the amorphous hydrides were obtained by charging the alloys with gas-eous hydrogen at 3.0 MPa and 423 K. It was found that the amorphous hydrides released most oftheir hydrogen before the crystallization of the essentially hydrogen depleted amorphous alloy. Thecrystallization temperature of amorphous Mg_(50)Ni_(50)H_(54) elevated and that of amorphousMg_(30)Ni_(70)H_(45) did not change in relation to the original binary amorphous alloy. This is very excep-tional for amorphous hydrides. The reason for the effects of hydrogen absorption/desorption on thecrystallization of amorphous alloys was discussed. 相似文献
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采用流延–共压–共烧结法制备了具有多孔|致密|多孔Zr_(0.84)Y_(0.16)O_(2–δ)-La_(0.8)Sr_(0.2)Cr_(0.5)Fe_(0.5)O_(3–δ)(YSZ-LSCF)结构的透氧膜和多孔YSZ-LSCF|致密YSZ-LSCF|致密YSZ|致密YSZ-LSCF|多孔YSZ-LSCF结构的固体氧化物燃料电池。采用浸渍法在多孔层内壁上沉积了具有高催化活性的LaNi_(0.6)Fe_(0.4)O_(3–δ)(LNF)纳米颗粒,随着LNF浸渍量的提高,会在多孔层内壁上形成连续的导电网格,增加电化学反应活性位点,进而显著改善电极性能。当LNF浸渍量为12wt%时,电极性能达到最优,在800℃时阴极和阳极极化阻抗分别为0.26和0.08?·cm~2,在空气/CH_4梯度中氧渗透速率为7.6 mL/(cm~2·min),比未浸渍前提高了14倍。阻抗谱分析表明空气侧氧还原反应中的电荷转移反应是氧渗透过程的速率控制步骤。 相似文献
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Natural Passivity of Amorphous Fe_(40)Ni_(40)P_(14)B_6 and Fe_(54.6)Ni_(38)Si_(4.1)B_(2.3)V_1 Alloys
The natural passive films forrned on Fe_(40)Ni_(40)P_(14)B_6 and Fe_(54.6)Ni_(38)Si_(4.1)B_(2.3)V_1 amorphous alloys long-term exposed in air have been studied by X-ray photoelectron spectroscopy (XPS) and Auger electron (including Ar+ ion depth profiling) spectroscopy (AES). The following aspects have been investigated: (1) chemical states of the elements in the films. binding energies and the chemical shifts measured by XPSf (2) structure and composition of the films fand (3) thickness of the passive films determined by AES depth profiling and XPS analysis. 相似文献
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《化工新型材料》2016,(4)
采用机械混合和凝胶包覆法制备10%(wt,质量分数,下同)BaZr_(0.9)Y_(0.1)O_(2.95)-90%BaCe_(0.86)Y_(0.1)Zn_(0.04)O_(2.91)(BZY-BCYZn)复相电解质,研究这两种制备方法对BZY-BCYZn复相电解质的结构和导电性能的影响。结果表明:凝胶包覆法制备的纳米BZY-BCYZn颗粒的平均晶粒尺寸为50nm,在1350℃烧结5h获得致密复相电解质材料(致密度达到96%),在600℃湿润Ar条件下的电导率为7.3mS/cm,比机械混合法制备的BZY-BCYZn复相电解质具有更加优异的烧结性能和导电性能。 相似文献
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采用溶胶-凝胶工艺制备了Sr_(1-x)La_xCo_(0.3)Ti_(0.3)Fe_(11.4)O_(19)铁氧体,利用XRD和微波网络矢量分析仪对其相成分和吸收特性进行研究,实验发现:适量的掺杂稀土镧时能够增大吸收频带宽度,改善吸收性能;当x=0.3时,最大吸收可达42.37dB,10dB带宽达2.90GHz,20dB带宽达2.33GHz,这非常有利于作为高频吸波材料。通过对Sr_(0.7)La_(0.3)Co_(0.3)Ti_(0.3)Fe_(11.4)O_(19)铁氧体烧结温度的分析,发现在800℃烧结,晶粒只有40nm左右,吸收性能最好。 相似文献
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《中国标准化(英文版)》2014,(6)
正Themed on"quality,innovation,development",the first China Quality Conference(Beijing)was held in the Great Hall of the People on September 15.Chinese Premier Li Keqiang delivered an important speech at the conference.State Councilor Yang Jing and Wang Yong attended the conference with over 600 domestic and international representatives from foreign,regional and international quality organizations 相似文献
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