Effects of manganese and chromium doping on the surface properties of alumina insulators

Bulk doping was taken into consideration to improve the surface voltage hold-off performance of alumina insulators in vacuum. The as-blended 95% alumina powder was selected as initial powder to be doped with proper Cr₂O₃ and MnCO₃. The results of properties measurements and experiments showed that samples doped with proper Cr₂O₃ and MnCO₃ possessed better surface properties compared with original 95% alumina insulators. The doped samples displayed higher surface breakdown strength and performed better metallization properties after being metallized through a newly designed method. Both the surface resistivity and the secondary electron emission coefficient of alumina were decreased significantly after manganese and chromium doping, which resulted in the improvement of surface insulating performance. In addition, some points concerning the influences of manganese and chromium doping on the structures and properties of alumina insulators were also briefly discussed upon analyses on composition and structure of ceramic samples.     

Correlation between dielectric properties and sintering temperatures of polycrystalline CaCu/sub 3/Ti/sub 4/O/sub 12/

Dielectric properties of polycrystalline CaCu/sub 3/Ti/sub 4/O/sub 12/ (CCTO) pellets sintered in the temperature range 1000-1200/spl deg/C were evaluated with impedance spectroscopy at frequency range of 10/sup 2/ to 10/sup 7/ Hz from 90 K to 294 K. A correlation has been established between the pair values of low frequency limit dielectric constant and the total resistivity and the sintering temperature. For example, the sample sintered at 1100/spl deg/C demonstrates higher value of low frequency limit dielectric constant and lower value of total resistivity, while the sample sintered at 1000/spl deg/C demonstrates lower values of low frequency limit dielectric constant and higher value of total resistivity. This correlation has been successfully explained by relating with the difference in grain size and grain volume resistivities of these two polycrystalline CCTO samples. Further, it is suggested that donor doping of oxygen vacancies Vo' and Vo" may be the reason to cause the difference in the grain volume resistivities of these two samples.     

稀土金属对碱性锌锰电池性能的影响

通过将不同含量的3种稀土金属添加到正极活性物质中，探讨其对碱性锌锰电池的影响。结果表明：稀土a加入量小于1．5％时，电池的放电容量会提高，超过2％时，放电容量会降低，最适宜的添加量为0．5％；而稀土b、稀土c不宜添加在碱性锌锰电池中。     

正极中添加氧化银对碱锰电池性能的影响

通过在正极活性物质中加入不同数量的氧化银 ,探讨其对碱性锌锰电池性能的影响。结果表明 :在正极活性物质中 ,随着氧化银含量的增加 ,电性能也随之提高。     

Widely tunable Al/sub 2/O/sub 3/-GaAs DBR filters with variable tuning characteristics

We demonstrate an optical tunable filter using Al/sub 2/O/sub 3/-GaAs layers as the top distributed Bragg reflector mirror. The mechanical properties and spectral response versus voltage are characterized. The tuning characteristics can be changed by removing the tensile-stressed Si/sub 3/N/sub 4/ on the mirror and legs. An integrated optical-mechanical model is used to analyze the result. Axial nitride and initial residual stress are incorporated into the model to obtain accurate fit. A 64-nm tuning range with 12-V tuning voltage is measured, a significant improvement over previous designs.     

Influence of sintering temperature on the flashover performance of alumina insulators in vacuum

This paper reports on the influence of sintering conditions on the flashover/pre-flashover characteristics of alumina insulators in vacuum under an impulse voltage. Four kinds of alumina insulator were studied, which were prepared using the same formula with different sintering conditions. The surface pre-flashover and flashover phenomena of different samples in vacuum have been observed under impulse voltage. Based on the experimental results, the characteristics of pre-flashover and flashover vary with different kinds of test samples. It was found that the insulators with a higher sintering temperature had a lower flashover voltage, and more active preflashover. From a scanning electron microscope (SEM) analysis of alumina insulators, we conclude that the methods of preparing alumina samples can affect their microstructure resulting in a change in the pre-flashover and flashover performance as alumina insulators.     

MnO_2的预处理对LiMn_2O_4正极材料的影响

研究了对前躯体MnO2(EMD)进行不处理、去离子水处理和LiOH处理对合成LiMn2O4正极材料的性能影响。测试结果表明,LiOH处理得到的MnO2杂质含量少,结构稳定,制备的LiMn2O4X射线衍射峰增强,结晶性变好。LiOH处理MnO2制备的LiMn2O4的电化学性能优于去离子水处理MnO2制备的LiMn2O4和不处理MnO2制备的LiMn2O4。LiOH处理、去离子水处理及不处理MnO2制备的LiMn2O4在0.5C的放电比容量分别为115.56mAh/g、109.98mAh/g和100.67mAh/g;1C充放电90次循环下所对应的容量保持率分别为86.79%、86.56%、57.30%。     

Effect of Cr2O3 addition on the microstructure and electrical properties of Mn-Ni-Co oxides NTC thermistors

The as-sintered Mn_1.1Ni_1.4Co_0.5O₄ crystallized in the solid solution of cubic spinel Mn-Ni-Co oxides, along with a small amount of the cubic spinel Ni-rich oxide phase. On the other hand, the Cr-substituted Mn_1.1Ni_1.4 Co_{0.5− x} Cr _x O₄ (0.07 ≤x ≤q 0.35) showed a single phase of cubic spinel Mn-Ni-Co-Cr oxides. This indicates that the substituted Cr suppressed the decomposition in the oxides. In addition, the Cr hindered the grain growth during sintering and increased the porosity. The electrical resistivity, the B _25/85 constant, and the activation energy of the Mn_1.1Ni_1.4Co_{0.5− x} Cr _x O₄ NTC thermistors increased with increasing Cr content. It is demonstrated that the Cr-substituted Mn_1.1Ni_1.4Co_{0.5− x} Cr _x O₄ NTC thermistors provided a variety of electrical properties, depending on the composition.     

0.5Li_2MnO_3-0.5LiMn_(1/3)Ni_(1/3)Co_(1/3)O_2正极材料的制备与性能

采用球磨流变相辅助高温固相反应法制备0.5Li_2MnO_3-0.5LiMn_(1/3)Ni_(1/3)Co_(1/3)O_2材料,利用恒流充放电、循环伏安、SEM和X射线能谱(EDS)等技术对产物进行分析。材料属于R-3m空间群的α-NaFeO_2型层状结构,颗粒结晶完整,95%的颗粒粒径在18.39μm以内。在4.8~2.0 V充放电,材料的0.05 C首次放电比容量为250.9 mAh/g,库仑效率为70.1%,并在首次充电过程中完成结构重整;0.20 C首次放电比容量为214.4 mAh/g,2.00 C放电比容量为136.2 mAh/g。     

铋改性二氧化锰在电化学电容器中的应用

采用液相沉淀法合成二氧化锰并在其表面包覆氧化铋,以期改善二氧化锰的电容性能。X射线衍射(XRD)测试表明合成的二氧化锰为无定形结构,包覆Bi2O3后材料转变为结晶度较差的α-Mn O2;扫描电镜(SEM)和X射线能谱(EDX)测试结果显示其为无规则颗粒状且表面覆盖着疏松的Bi2O3。循环伏安、恒电流充放电和电化学阻抗谱测试表明包覆5%(质量分数)Bi2O3的二氧化锰具有最好的电容性能。在电流密度分别为200、400和600 m A/g时,电极比电容分别为352.8、307.2和277.2 F/g,相比未包覆Mn O2分别提高了17.1%、15.0%和9.5%。     

铬掺杂对LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2电化学性能的影响

以乙酸盐为原料,采用高温固相法制备正极材料Li1.1(Ni1/3Co1/3Mn1/3)1-xCrxO2,采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对材料的结构和形貌进行表征,用恒电流充放电测试系统测试材料的电化学性能和循环性能。结果表明:合成的Li1.1(Ni1/3Co1/3Mn1/3)0.95Cr0.05O2样品具有典型的空间群为R-3m的六方层状α-Na Fe O2结构,且结构完整,阳离子混排程度较低。颗粒大小分布比较均匀,粒径大小在300~900 nm。该样品在0.1 C、2.6~4.6 V下的首次放电比容量为187.6 m Ah/g,并表现出良好的循环性能。适当的Cr掺杂可以提高Li Ni1/3Co1/3Mn1/3O2正极材料的晶体结构稳定性,使其具有良好的电化学性能。     

The influence of the dielectric strength of the N/sub 2//SF/sub 6/-insulation by conducting particle on the spacer surface

This paper investigates the dielectric properties of various N/sub 2//SF/sub 6/ gas mixtures based upon a cylindrical spacer model with adhering particle on the surface tinder homogeneous field conditions. The investigation involves a comparison with pure SF/sub 6/. The flashover field strength for clean and particle contaminated spacer surface under AC and LI stress is determined. The results of the investigations show the sensitivity of N/sub 2//SF/sub 6/ gas mixtures to conducting particles on spacer surfaces for gas pressures up to 800 kPa. Moreover, the correspondence between pure SF/sub 6/ at pressure range from 100 to 400 kPa and N/sub 2//SF/sub 6/ gas mixtures for AC and lightning impulse (LI) flashover field strength range from 50 to 178 kV/cm is determined. Conclusions are drawn about the ability of SF/sub 6/ gas mixtures to serve as technically efficient media for GIS/GITL. The results shed light on the issue of the SF/sub 6/ reduction and particle detectability in GIS/GITL.     

Effects of Al2O3 on the piezoelectric properties of Pb(Mn1/3Nb2/3)O3-PbZrO3-PbTiO3 ceramics

Piezoelectric properties of Al₂O₃-doped Pb(Mn_1/3Nb_2/3)O₃-PbZrO₃-PbTiO₃ ceramics were investigated. The constituent phases, microstructure, electromechanical coupling factor, dielectric constant, piezoelectric charge and voltage constants were analyzed. Diffraction peaks for (002) and (200) planes were identified by X-ray diffractometer for all the specimens doped with Al₂O₃. The highest sintered density of 7.8 g/cm³ was obtained for 0.2 wt% Al₂O₃-doped specimen. Grain size increased by doping Al₂O₃ up to 0.3 wt%, and it decreased by more doping. Electromechanical coupling factor, dielectric constant, piezoelectric charge and voltage constants increased by doping Al₂O₃ up to 0.2 wt%, and it decreased by more doping. This might result from the formation of oxygen vacancies due to defects in O^{2 −} ion sites and the substitution of Al³⁺ ions.     

Low temperature sintering of Ba0.91Ca0.09Ti0.916Sn0.084O3 lead-free piezoelectric ceramics with the additives of ZnO and MnO2

The objective of this work is to lower the sintering temperature of Ba_0.91Ca_0.09Ti_0.916Sn_0.084O₃ (BCTS) ceramics without sacrificing the piezoelectric performance. The low-temperature sintering technique has been conducted to prepare the BCTS ceramics by adding two additives of ZnO and MnO₂. The ceramics endure a phase transition from a ferroelectric tetragonal phase to a pseudo-cubic relaxor ferroelectric with increasing MnO₂ content. The addition of ZnO and MnO₂ decreases the sintering temperature greatly, positively affecting their dielectric and piezoelectric properties. An enhanced electrical behavior of d ₃₃?～?495 pC/N, k _p?～?43.0 %, ε _r?～?5429, and tan δ?～?1.54 % has been observed in the ceramic with x?=?0.1 wt% when sintered at ~1315 °C. As a result, the method to dope two additives of ZnO and MnO₂ can effectively improve the piezoelectric properties of BaTiO₃-based ceramics sintered at a low temperature.     

Co2O3或/和V2O5掺杂对NiZn铁氧体磁性能的影响

一定量的V2O5掺杂有利于NiZn铁氧体烧结温度的降低，且在一定范围内起始磁导率升高；而Co2O3掺于Nizn铁氧体，起始磁导率降低，但损耗特性可得到改善。我们采用Co2O3-V2O5复合掺杂，发现选择适当的配比，在起始磁导率没有大的下降的情况下，烧结温度和损耗特性等其他磁特性可得到较好的改善。     

The Influence of Bi2O3 and Sb2O3 on the Electrical Properties of ZnO-Based Varistors

This work presents a study of the influence of both Bi content and Sb/Bi ratio on the electrical characteristics of a commercial-type ZnO varistor. In contrast to previous studies two nonlinear coefficients, the breakdown fields and energy absorption abilities were measured after sintering at 970°C or 930°C. The Bi-content was varied from 0.9 to 1.8 at% while the Sb/Bi ratio was varied from 0.8 to 1.5, leading to values of up to 104 for the nonlinear coefficient 1, 1100 V mm^–1 for the breakdown field and 1137 J cm^–3 for the energy absorption ability. The highest value was measured for the highest Bi-content and the lowest Sb/Bi ratio and vice versa. The breakdown field E _V increased with lower sintering temperature, increased Sb/Bi ratio (at a given Bi-content) and increased Bi-content (at a given Sb/Bi ratio). The energy absorption coefficient increased at the higher sinter temperature and with lower Sb and Bi concentrations.The observed effects were related to the amount of spinel phase (Zn₇Sb₂O₁₂) formed during the sintering process and the amount of liquid phase present during early stages of the sintering process.     

Oxygen permeation properties and surface modification of acceptor-doped CeO2/MnFe2O4 composites

The preparation and oxygen permeation properties of the (Ce_0.8Pr_0.2)O_2−δ − x vol% MnFe₂O₄ composites, where x = 0 to 35, have been investigated. The samples were prepared by the Pechini method. In the case of Ce_0.8Pr_0.2O_2−δ, an oxygen flux density of 6 μmol⋅cm⁻²⋅s⁻¹ (L = 0.0247 cm) and the maximum methane conversion of 50% were attained at 1000^∘C. Unlike composites consisting of Gd-doped CeO₂ and MnFe₂O₄, the oxygen permeability of the (Ce_0.8Pr_0.2)O_2−δ – x vol% MnFe₂O₄ composites was almost constant regardless of the volume fraction of MnFe₂O₄; however, the optimum volume fraction of MnFe₂O₄ was determined to be 5 to 25 in the context of the chemical and mechanical stabilities under methane conversion atmosphere. In addition, the surface modification of the (Ce_0.8Gd_0.2)O_2−δ – 15 vol% MnFe₂O₄ composite was performed by using the FePt nanoparticles. The catalyst loading of 2.8 mg/cm² on the both side of the 0.3 mm-thick (Ce_0.8Gd_0.2)O_2−δ – 15vol% MnFe₂O₄ composite increased the oxygen flux density from 0.30 to 0.76 μmol⋅cm⁻²⋅s⁻¹ in the case of He/air gradients; however, the effect seems to be reduced in the case of high oxygen flux density caused by a large pO₂ gradient. Moreover, the Langmuir-Blodgett film of the FePt nanoparticles were successfully prepared on the tape-cast (Ce_0.8Gd_0.2)O_2−δ – 15vol% MnFe₂O₄ composite. Hydrophobic treatments for the surface of the composite were crucial to achieve high transfer ratio for the deposition of the LB film.     

BNS-Na对碱锰电池放电性能的影响

研究了在锌膏中加入BNS-Na对碱性锌锰电池放电性能的影响.锌膏中加入BNS-Na后,新制和储存电池在小电流放电下性能没有提高,中等电流放电下放电高压段有所提高,当BNS-Na含量为10%时,大电流放电性能提高约10%.     

退火时间对FeGaB/Al2O3多层薄膜性能的影响

现代电子元器件的高速发展,以及磁性元器件小型化、集成化需求日益增长,推动了纳米级磁性功能薄膜材料的研究。以高饱和磁致伸缩系数、低矫顽力的FeGaB薄膜材料为研究基础,以提高薄膜软磁性能为目标,使用脉冲激光沉积系统制备了FeGaB/Al2O3复合多层薄膜,发现在350℃的生长环境下,未退火的样品成膜质量较好,但软磁性能一般。为了提高磁性能,进行一组不同退火时间下的退火实验,实验发现样品的铁磁共振线宽较大,且退火时间对吸收峰强度影响较大。