Based on three different kinds of conductive paths in microstructure of soil and theory of electrochemical impedance spectroscopy(EIS), an integrated equivalent circuit model and impedance formula for soils were propo...Based on three different kinds of conductive paths in microstructure of soil and theory of electrochemical impedance spectroscopy(EIS), an integrated equivalent circuit model and impedance formula for soils were proposed, which contain 6 meaningful resistance and reactance parameters. Considering the conductive properties of soils and dispersion effects, mathematical equations for impedance under various circuit models were deduced and studied. The mathematical expression presents two semicircles for theoretical EIS Nyquist spectrum, in which the center of one semicircle is degraded to simply the equivalent model. Based on the measured parameters of EIS Nyquist spectrum, meaningful soil parameters can easily be determined. Additionally, EIS was used to investigate the soil properties with different water contents along with the mathematical relationships and mechanism between the physical parameters and water content. Magnitude of the impedance decreases with the increase of testing frequency and water content for Bode graphs. The proposed model would help us to better understand the soil microstructure and properties and offer more reasonable explanations for EIS spectra.展开更多
采用两步法制备了(1-x)NiCo_(0.2)Mn_(1.8)O_(4)-xBaBiO_(3)(x=0.1、0.2、0.3、0.4)系列负温度系数(Negative Temperature Coefficient,NTC)复相陶瓷材料。系统研究了BaBiO_(3)(BB)含量对NiCo_(0.2)Mn_(1.8)O_(4)(NCM)基复相陶瓷的相结...采用两步法制备了(1-x)NiCo_(0.2)Mn_(1.8)O_(4)-xBaBiO_(3)(x=0.1、0.2、0.3、0.4)系列负温度系数(Negative Temperature Coefficient,NTC)复相陶瓷材料。系统研究了BaBiO_(3)(BB)含量对NiCo_(0.2)Mn_(1.8)O_(4)(NCM)基复相陶瓷的相结构、显微结构及电学性能的影响。结果表明,当x=0.1时,复相陶瓷内部均为细小均匀的三棱锥结构的尖晶石NiCo_(0.2)Mn_(1.8)O_(4)相。当x=0.2时,钙钛矿BaBiO_(3)相开始增多,且尖晶石晶粒开始长大、棱边开始变得圆润。当x达到0.3及以上时,内部晶粒继续长大,而且晶界明显增宽和变得模糊,呈现液相烧结特征,此外有第二相BaMnO_(3)开始生成并增多。阻抗分析表明,复相陶瓷的电阻主要决定于内部的晶界电阻。电阻分析表明室温电阻率ρ_(25℃)、温度敏感常数B、电导活化能E_(a)均呈现出随着BaBiO_(3)含量先降低后升高的趋势,且极小值出现在x=0.2时。该体系复合陶瓷的B值、ρ_(25℃)和E_(a)分别在4151~4374 K、4930~26206Ω·cm和0.357~0.376 eV的范围可调,拓宽了尖晶石体系热敏陶瓷的应用范围。展开更多
基金Projects(5120833351078253)supported by the National Natural Science Foundation of China+4 种基金Projects(2014011036-12014131019TYUT2014YQ017OIT2015)supported by the Natural Science Foundation of Shanxi ProvinceChina
文摘Based on three different kinds of conductive paths in microstructure of soil and theory of electrochemical impedance spectroscopy(EIS), an integrated equivalent circuit model and impedance formula for soils were proposed, which contain 6 meaningful resistance and reactance parameters. Considering the conductive properties of soils and dispersion effects, mathematical equations for impedance under various circuit models were deduced and studied. The mathematical expression presents two semicircles for theoretical EIS Nyquist spectrum, in which the center of one semicircle is degraded to simply the equivalent model. Based on the measured parameters of EIS Nyquist spectrum, meaningful soil parameters can easily be determined. Additionally, EIS was used to investigate the soil properties with different water contents along with the mathematical relationships and mechanism between the physical parameters and water content. Magnitude of the impedance decreases with the increase of testing frequency and water content for Bode graphs. The proposed model would help us to better understand the soil microstructure and properties and offer more reasonable explanations for EIS spectra.
文摘电池内部温度相比于表面温度对电池性能影响更大,更能表征电池工作状态,但是电池内部温度难以直接获取。文中基于电化学阻抗谱(electrochemical impedance spectroscopy,EIS)法提出一种预测电池内部温度的新算法,该算法利用电池表面温度和环境温度对内部温度进行一次估计得到的值选择频率,然后基于EIS对内部温度进行二次估计,相比于使用单频率测量法具有精度高,可测量范围广的优点。首先,研究电池内部温度、荷电状态(state of charge,SOC)对电池阻抗的影响,在不考虑SOC影响下得到电池内部温度与阻抗实部的关系;然后,进行温度估计。与文献实验数据进行对比发现,发现所估计的温度与实际温度最大误差为8.77%,比单一频率下的预测误差低了3%,能够更准确地预测电池内部温度,对电池内部温度估计策略具有一定的指导意义。
文摘采用两步法制备了(1-x)NiCo_(0.2)Mn_(1.8)O_(4)-xBaBiO_(3)(x=0.1、0.2、0.3、0.4)系列负温度系数(Negative Temperature Coefficient,NTC)复相陶瓷材料。系统研究了BaBiO_(3)(BB)含量对NiCo_(0.2)Mn_(1.8)O_(4)(NCM)基复相陶瓷的相结构、显微结构及电学性能的影响。结果表明,当x=0.1时,复相陶瓷内部均为细小均匀的三棱锥结构的尖晶石NiCo_(0.2)Mn_(1.8)O_(4)相。当x=0.2时,钙钛矿BaBiO_(3)相开始增多,且尖晶石晶粒开始长大、棱边开始变得圆润。当x达到0.3及以上时,内部晶粒继续长大,而且晶界明显增宽和变得模糊,呈现液相烧结特征,此外有第二相BaMnO_(3)开始生成并增多。阻抗分析表明,复相陶瓷的电阻主要决定于内部的晶界电阻。电阻分析表明室温电阻率ρ_(25℃)、温度敏感常数B、电导活化能E_(a)均呈现出随着BaBiO_(3)含量先降低后升高的趋势,且极小值出现在x=0.2时。该体系复合陶瓷的B值、ρ_(25℃)和E_(a)分别在4151~4374 K、4930~26206Ω·cm和0.357~0.376 eV的范围可调,拓宽了尖晶石体系热敏陶瓷的应用范围。
