ViCo0.98-xTi0.02LaxO2的高温固相法合成及其电化学性能

以Li2CO3、Co3O4为原料,采用高温囿相法制备了钮离子电池正极材料LiCo0.98-xTi0.02LaxO2(x=0,0.01,0.03,0.05).采用扫描电镜(SEM)、恒流充放电研究了材料的表面形貌和电化学性能,结果表明:掺杂La后材料的D50略有增大,放电平台电压升高;在2.75～4.20 V电位范围内,LiCo0.97Ti0.02La0.01O2的首次1 C放电比容量达到143.86 mAh/g,50次循环后容量保持率为97.0%,且具有很好的倍率性能.     

Microwave dielectric properties of Na<Superscript>+</Superscript> and M<Superscript>3+</Superscript>-doped Ba(Mg<Subscript>0.5</Subscript>W<Subscript>0.5</Subscript>)O<Subscript>3</Subscript> ceramics

In this study, phase evolution, microstructure, and microwave dielectric properties of (Ba_0.98Na_0.02)(Mg_0.48M³⁺_0.02W_0.5)O₃ (M³⁺?=?Al, Ga, Sc, In, Yb, Y, Dy, Gd, and Sm) ceramics sintered at 1700 °C for 1 h were investigated. All the compounds exhibited an ordered cubic perovskite structure. Regardless of the ionic radius of the doped M³⁺ ions, BaWO₄ was detected as the secondary phase in all the compounds. The field emission scanning electron microscopy (FE-SEM) images revealed a dense microstructure in all the compounds, except in the Al-doped compound, which exhibited an insufficient grain growth. The large and irregularly shaped grains indicated that the liquid phase sintering occurred. Splitting of the A_1g(O) mode was observed in the Raman spectra of large M³⁺ ion-doped compounds. Splitting of the F_2g modes did not occur and the bands were sharp, indicating that the cubic symmetry was retained. As the ionic radius of the doped M³⁺ ions increased, the dielectric constant (ε_r) increased slightly. The compounds doped with M³⁺?=?Sc, In, Yb, and Y exhibited a very high quality factor (Q?×?f₀) in the range of 250,000 ~ 280,000 GHz. In the case of the compounds doped with M³⁺?=?Al, Ga, Sc, In, Yb, Y, and Dy, the value of the temperature coefficient of resonant frequency (τ_f) was in the range of ?24 ~ ?19 ppm/°C, while the Gd and Sm-doped compounds exhibited positive values of 2.8 and 31.2 ppm/°C, respectively. The dielectric constant, quality factor, and temperature coefficient of resonant frequency of the In-doped compound, i.e., (Ba_0.98Na_0.02)(Mg_0.48In_0.02W_0.5)O₃, were 18.7, 286,557 GHz, and???24.4 ppm/°C, respectively.     

Li(Ni1/3Co1/3Mn1/3)1-ySnyO2材料的合成及性能研究

采用碳酸盐共沉淀法制备Li(Ni1/3Co1/3Mn1/3)1-ySnyO2(y=0,0.01,0.02,0.05,0.10)。通过XRD、SEM测试对其晶型结构、组织形貌进行了分析,交流阻抗法(AC)和充放电性能测试对其电化学性能进行了研究。实验表明,制备的样品均具有较好的层状结构,其中Li(Ni1/3Co1/3Mn1/3)0.98Sn0.02O2性能最佳,以0.5C循环充放电时,首次放电比容量达到173.31mAh/g,30次循环后,放电比容量为149.55mAh/g,容量保持率为86.29%。     

溶胶-凝胶法制备La1-xSrxCoO3-δ导电陶瓷

采用溶胶-凝胶法制备了单相的La1-xSrxCoO3-δ系列导电陶瓷,对其结构性能进行了表征,并探讨了La1-xSrxCoO3-δ导电陶瓷在电接触材料中应用的可能性。结果表明,随着样品中Sr掺杂量的增加,La1-xSrxCoO3-δ样品的衍射峰峰位向大角度方向略有偏移,衍射峰峰值减小,并发生宽化。溶胶-凝胶法制备的La1-xSrxCoO3-(δx=0.1~0.7)陶瓷普遍具有较好的导电性,其中La0.4Sr0.6CoO3-δ样品在1 000℃热处理条件下,会部分转变为La0.5Sr0.5CoO2.91,同时生成La2O3、Co3O4、SrCoLaO4等氧化物并释放出O2,这与AgC-dO电接触材料中CdO的特性有类似之处,在电接触材料领域具有潜在的应用价值。     

Thermoelectric properties of n-type Ca1-xBixMnO3-δ (0.00, 0.02, and 0.05) system

Polycrystalline samples of Ca_1-xBi_xMn_yO_3-δ (x?=?0.00, 0.02, and 0.05) are prepared by the conventional solid-state reactions. Thermoelectric properties are measured at 300 K–700 K. All the samples are single phase with an orthorhombic structure. Thermopower of all the samples is negative, indicating that predominant carriers are electrons over the entire temperature range. Among the samples, Ca_2.95Bi_0.05MnO_3-δ has the highest dimensionless figure of merit of 0.047 at 300 K, representing an improvement of about 487 % with respect to the parent compound of CaMnO_3-δ.     

纳米CoO的制备及对MH-Ni电池正极性能的影响

CoO添加剂可以有效地提高MH-Ni电池正极活性材料Ni(OH)2的放电深度,改善正极的综合放电性能.采用真空分解棒状超微CoCO3前驱体制备了粒度均匀的短棒状CoO纳米颗粒,并研究了纳米CoO对氢镍电池正极性能的影响.研究发现,纳米CoO代替普通亚微米CoO,可以使电极内部的CoOOH导电网络更均匀、更完整,并抑制γ-NiOOH的生成,从而缩短电池制备的静置时间,提高正极的放电比容量和放电中值电压,并缓解电池放电比容量和放电中值电压的退化速度.     

高温固相法合成锂、铁位掺杂的LiFePO4/C

用高温固相法合成锂、铁位掺杂的Li0.98M0.02Fe0.9Ti0.1PO4/C(M=Na、Mg和Al),并用XRD、SEM、能量色散谱、循环伏安和恒流充放电等方法进行分析.Li0.98Al0.02Fe0.9Ti0.1PO4/C的振实密度为1.48g/cm3;在2.4～4.2 V循环,0.2 C、5.0 C首次放电比...     

Mg2+不同取代位对LiFePO4/C性能的影响

以蔗糖为碳源,用高温固相法制备了Li0.98Mg0.02FePO4/C、LiFe0.98Mg,0.02PO4,/C和不确定掺杂位的样品LiFePO/C+Mg2+的正极材料.用XRD,SEM、恒流充放电测试、循环伏安和交流阻抗谱方法,研究了样品的结构、形貌及电化学性能.研究发现,样品均为单一规则的橄榄石型的LiFeP0,...     

锂离子电池正极材料LiFePO_4的复合改性研究

为了提高LiFePO4的充放电性能,通过高温固相法合成了Li0.98M0.02FePO4/C(M=Cr、W)及Li1.03M0.02Fe0.98PO4/C(M=Zr、Ni)两类橄榄石型正极材料。运用X射线衍射光谱法(XRD)、扫描电子显微镜法(SEM)、能量散射X射线谱(EDX)和电化学测试对合成产物的晶体结构、颗粒形貌和电化学性能进行了表征。结果表明:Li0.98Cr0.02FePO4/C的放电比容量最高达到157.3mAh/g,且多次循环后容量几乎无衰减;在大电流充放电倍率下,材料依然能保持优良的循环性能,Li0.98W0.02FePO4/C首次放电比容量可达130.2mAh/g,10次循环后容量保持率为97%。离子掺杂和碳包覆改性能有效地提高LiFePO4的比容量和循环性能。     

Bi_2O_3含量对NiCuZn旋磁铁氧体基板材料性能的影响

采用氧化物法制备了NiCuZn铁氧体材料,研究了Bi2O3掺杂对其旋磁性能的影响。结果表明,在1～4wt%的范围内,随着Bi2O3含量的提高,铁磁共振线宽△H和介电损耗角正切tgδε都呈现出先减小后上升的趋势;并且在掺杂量为3wt%、烧结温度为900℃时,△H15kA/m、tgδε=6.5×10-4、Ms300kA/m,可用于低温共烧旋磁铁氧体基板的制备。     

Varistors Based on Doped SnO2

When tin oxide is doped with either Sb₂O₃ and CoO or Ta₂O₅ and CoO, it shows highly nonlinear current (I)–voltage (V) characteristics. Addition of CoO leads to creation of oxygen vacancies and helps in sintering of SnO₂. Both tantalum and antimony act as donors and increases the conductivity. The change in nonlinear coefficient (α) and the breakdown voltage (E _B) are studied as function of the quantity of the donor introduced. The magnitudes of grain size and grain boundary barrier height (Φ _B ) are calculated as a function of duration of sintering. The observed nonlinear coefficient (α) is in the range of 3–34 and the breakdown voltage varies from 110 V/cm to 4400 V/cm. Incorporation of 5 mole% titanium leads to increase in both α and E _B values. All the samples show single phase as found by X-ray diffraction. These samples exhibit low breakdown voltages as compared to commercial ZnO varistors.     

A、B位掺杂改性BaCoO_3基透氧膜材料的进展

介绍了通过A、B位掺杂改性BaCoO3基钙钛矿型透氧膜材料的研究进展.A位掺杂的材料主要有Ba0.5Sr0.5Co0.8Fe0.2O3-δ和La0.2Ba0.8Co0.8Fe0.2O3-δ等,它们的透氧量较高,稳定性较好;B位掺杂的材料主要有BaCo0.4Fe0.4Zr0.2O3-δ、BaCo0.7Fe0.2Nb0.1O3-δ和BaBi0.2Co0.2Fe0.6O3-δ等,它们的A位完全由Ba占据,不但具有较高的透氧量,而且能在长期工作后保持稳定的结构.     

高温固相法合成Li0.98M0.02Fe0.99Mg0.01PO4/C及其电化学性能

通过高温固相法合成以Fe2O3为铁源,Li2CO3为锂源,柠檬酸为碳源的Li0.98M0.02Fe0.99Mg0.01PO4/C(M=Al,Ti,V)锂离子电池正极材料,利用了X射线衍射光谱法(XRD)、循环伏安(CV)、电化学阻抗谱(EIS)和恒流充放电等实验方法研究了在铁位固定掺杂摩尔分数为1%的Mg的情况下,变换锂位掺杂金属对产物结构和电化学性能的影响。结果表明,少量金属掺杂后的产物Li0.98M0.02Fe0.99Mg0.01PO4/C其充放电容量和循环性能都比未掺杂的纯相要高。在室温下,Li0.98Al0.02Fe0.99Mg0.01PO4/C材料以0.1倍率放电时,首次比容量达到156 mAh/g,循环几次后达到160.2 mAh/g,循环性能良好,晶胞系数c/a的值与其他掺杂材料相比较高,结晶度好。     

溶胶-微波干燥法制备Nd_(0.6)Ca_(0.4)CoO_3及其电化学性能

研究用溶胶-微波干燥法制备钙钛矿型氧化物Nd0.6Ca0.4CoO3,通过XRD、TEM对制备的产物进行表征。结果表明,得到的产物为Nd0.6Ca0.4CoO3,平均粒径为65nm。以该氧化物为催化剂,酸处理的碳黑为载体,制备了用于碱性介质中氧还原反应的气体扩散电极,利用极化曲线(LSV)和交流阻抗(EIS)方法测试了其在碱性介质中(6mol/LKOH)对氧还原的催化性能。该催化剂在空气气氛下,电极电位在-0.2V(vs.Hg/HgO)时催化氧还原的电流密度达到160mA/cm2,有显著的氧还原催化效果。微波加热功率、微波加热时间对催化剂的催化氧还原性能有较大的影响。     

Mg掺杂对LiNi_(0.6)Co_(0.15)Mn_(0.25)O_2电化学性能的影响

以氢氧化钠为沉淀剂,氨水为络合剂,通过氢氧化物共沉淀法制得前驱体,然后高温煅烧,合成锂离子电池正极材料Li(Ni_(0.6)Co_(0.15)Mn_(0.25))_(1-x)Mg_xO_2(x=0、0.01、0.02、0.03和0.04)。通过XRD、循环伏安、电化学阻抗谱(EIS)和恒流充放电等测试,研究Mg掺杂对材料性能的影响。适量的Mg掺杂可降低材料阳离子混排度,提高材料的循环性能及倍率性能。Li(Ni_(0.6)Co_(0.15)Mn_(0.25))_(0.98)Mg_(0.02)O_2的电化学性能较好,以0.1 C在2.7~4.3 V循环,首次放电比容量高达190.9 mAh/g;1.0 C循环30次的容量保持率为90.07%。     

纳米Gd2O3掺杂对WO3基陶瓷电学行为的影响

采用传统电子陶瓷工艺制备纳米Gd2O3掺杂的WO3陶瓷,对其电学行为进行研究,分析了显微结构与其电学行为的关系。结果表明,小剂量的纳米Gd2O3掺杂能明显改善WO3陶瓷的非线性电学特性,这种影响被认为是元素替代和由此而引起的晶粒尺寸减小共同作用的结果。当掺杂量为50(摩尔分数,下同)时,Gd2O3和WO3发生固相反应生成Gd2(WO4)3相,该相导致WO3相减少甚至消失,这是导致WO3陶瓷非线性电学行为消失的主要原因。     

贮氢合金的表面处理研究

对贮氢合金粉ＭｍＮｉ３．５５Ｃｏ０．７５Ｍｎ０．４Ａｌ０．３进行了添加氧化亚钴的热碱还原处理的实验研究工作。实验结果表明,该方法可以显著提高 ＭＨ／Ｎｉ电池的活化性能和循环特性,降低电池内压,提高电池的耐过充能力。其效果优于单纯的热碱还原处理,但后者又优于贮氢合金粉不处理。     

CoO膜厚对磁控溅射Co/CoO薄膜结构和磁性能的影响

为了探究FM/AFM双层膜中的交换偏置现象,利用磁控溅射法制备Co/Co O薄膜,通过改变沉积时间获得了不同Co O层厚度的Co/Co O双层膜系。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、交变梯度磁强计(AGM)、超导量子干涉仪(SQUID)分别对样品的物相结构、表面形貌及磁性能进行分析和表征。结果表明,AFM层厚度对表面形貌有一定的影响,但表面成分不随AFM层厚度的变化而变化。所有样品的XRD谱均出现Co O(002)衍射峰,说明薄膜为晶态。不同厚度的Co/Co O双层膜样品表现出不同的矫顽力和偏置场,低温下样品的磁滞回线表现出明显的交换偏置效应,并且磁偏移量随膜层厚度增加呈现逐渐增大的趋势。当Co O厚度为62.5nm时,偏置场最大可达到420k A/m。     

氢氧化镍和粘结式氢氧化镍电极

在pH值8—11,添加钴和钡,采用一次阶梯烘干,可以制得高活性、高堆积密度的Ni(OH)_2。胶体石墨和乙炔黑为3:1作导电材料,2％的CMC(3％)和6.86％的PTFE(60％)作粘结剂,添加CoO或Co(Ac)_2可以制得柔性很好的高体积比容量粘结式镍电极。TG—DTA给出Ni(OH)_2的烘干温度不得高于170℃。XRD证实高活性Ni(OH)_2有晶格缺陷。IR证实了Ni(OH)_2的同质多晶现象。SEM观察到Ni(OH)_2的球形、类球形和无定形外貌。     

Influence of the calcium excess in the structural and spectroscopic properties of the complex perovskite Ba3CaNb2O9

The effects of the change in the Ca/Nb ratio in the structure and spectroscopic properties of the solid solution Ba₃Ca_1+xNb_2-xO_9-δ with x?=?0–0.25 are investigated. The solid solution undergoes a transition from an hexagonal phase (2:1 order) to a cubic phase (1:1 order) with increasing calcium content as indicated by X-Ray diffraction and Raman. The calcium excess matches with a gradual increase in blue colour due to a reduction at the high temperatures of sintering. Optical absorption experiments showed that there are different absorption bands in the region 0.45–4.5?eV corresponding tentatively to OH vibrations, polarons and monovalent oxygen vacancies. The series properties change gradually with calcium excess with the exception of Ba₃Ca_1.18Nb_1.82O_9-δ that showed a slight change attributable to the presence of protons in the lattice. These changes can be used to quantify protons in complex perovskites.