Depolarization temperature and piezoelectric properties of (Bi1/2Na1/2)TiO3–(Bi1/2Li1/2)TiO3–(Bi1/2K1/2)TiO3 lead-free piezoelectric ceramics

The phase transition temperature and piezoelectric properties of x(Bi_1/2Na_1/2)TiO₃–y(Bi_1/2Li_1/2)TiO₃–z(Bi_1/2K_1/2)TiO₃ [x + y + z = 1] (abbreviated as BNLKT100y–100z) ceramics were investigated. BNLKT100y–100z ceramics were prepared by conventional ceramic fabrication. The depolarization temperature T_d was determined by the temperature dependence of the dielectric and piezoelectric properties. This study focuses on the effect of Li¹⁺ and K¹⁺ ions on T_d and the piezoelectric properties of BNT ceramics. BNLKT100y–100z (y = 0–0.08) has a morphotropic phase boundary (MPB) between rhombohedral and tetragonal phases at z = 0.18–0.20, and high piezoelectric properties were obtained at the MPB composition. The piezoelectric constant d₃₃ increased with increasing y; however, T_d decreased above y = 0.06. The d₃₃ and T_d values of BNLKT4-20 and BNLKT8-20 were 176 pC/N and 171 °C, and 190 pC/N and 115 °C, respectively.     

6 1/2井眼下4 1/2套管固井技术及应用

6?井眼下4?套管井的固井是一个新领域,给固井工艺提出了一些问题。为了解决问题,对固井难点进行分析,对低密度水泥浆体系、防漏压稳工艺、提高顶替效率等方面进行研究,形成了一套6?井眼下4?套管的固井技术,投入现场应用后,固井质量良好。     

厚壁容器1 1/4Cr-1/2Mo钢的焊接

本文简要地介绍了SA387Gr11C12钢焊接工艺试验,通过两种焊接方法的比较,说明双丝窄间隙自动焊是厚壁容器的最佳工艺。     

Bi1/2Na1/2TiO3无铅压电陶瓷的研究进展

近年来,随着环境保护和人类社会可持续发展的需求,作为环境友好的铁电压电陶瓷典型代表的Bi1／2Na1／2TiO3(BNT)基无铅压电陶瓷,已成为世界发达国家致力研发的热点材料之一。本文结合目前有关BNT基无铅压电陶瓷的报道,探讨了BNT压电瓷的压电机理及其相变过程,着重介绍了BNT压电陶瓷制备工艺以及改性研究和目前的应用,并对BNT基无铅压电陶瓷未来的发展趋势作了展望。     

锂离子电池正极材料LiNi1/2Co1/6Mn1/3O2的制备与性能

采用Co2+浓度递增的金属离子混合溶液分次共沉淀方法制备Ni1/2Co1/6Mn1/3(OH)2,以其为前驱体,通过高温固相反应得到具有Co含量梯度的层状LiNi1/2Co1/6Mn1/3O2,探讨了焙烧温度及Co含量梯度对材料的结构和电化学性能的影响. 通过X射线衍射、扫描电镜、热重分析及恒电流充放电测试对合成的样品进行了表征. 结果表明,700℃合成产物即具有类LiNiO2的六方层状结构,800和850℃合成产物阳离子排列有序度高,层状结构显著. 材料结晶度好,粒度均匀,粒径在亚微米级. 合成温度800℃的梯度材料具有最佳的电化学性能, 2.5~4.2 V, 0.1 C倍率充放电50次后,梯度材料的容量仍保持在171.2 mA×h/g. 相同的焙烧温度,梯度材料比均匀材料的电化学性能更加优异.     

Li[Ni1/2Mn1/2]O2的制备及电化学性能研究

介绍了一种采用前驱体碳酸盐共沉淀法制备锂离子电池正极材料Li[Ni1/2Mn1/2]O2的工艺路线。通过对样品进行X射线衍射(XRD)测试,可知产品具有类似钴酸锂的层状结构。通过对产品进行扫描电镜(SEM)观察可以看出,产品具有规则的球形形貌,且粒径在5~10μm;电化学测试表明,材料的首次放电比容量大于170 mA.h/g,循环20次后容量保持率大于98%。     

0.7Li2MnO3-0.3LiNi1/2Mn1/2O2的共沉淀制备及电化学性能

本文通过共沉淀法合成了0.7Li2MnO3-0.3LiNi1/2Mn1/2O2这种正极材料,并对这种材料的结构、相组成和微观形貌进行了表征,并且进行了电化学性能测试。结果表明这种电极材料在循环测试中比容量能达到100mAh.g-1,后续循环稳定性较好。     

La(Mg1/2Ti1/2)O3–La2/3TiO3 microwave dielectric ceramics

Structure and microwave dielectric properties were studied in the (1−x)La(Mg_1/2Ti_1/2)O₃–xLa_2/3TiO₃ system. Ceramics with this composition in the 0⩽x⩽0.5 range were processed from powders obtained by a citrate-based chemical route. Structure of these perovskite solid solutions changed from orthorhombic for x=0.1 and 0.3 to pseudocubic for x=0.5. Microwave and radio frequency measurements revealed increase in permittivity and temperature coefficient of the resonant frequency τ_f with increasing of La_2/3TiO₃ content. Close to zero τ_f value was found near to x=0.5 composition of (1−x)La(Mg_1/2Ti_1/2)O₃–x La_2/3TiO₃.     

(1-x)(Bi1/2Na1/2)0.900Ba0.088Sr0.012TiO3-x(Bi1/2K1/2)TiO3无铅压电陶瓷的电学和力学性能

利用常规烧结方法制备出了多种A位离子掺杂的钛酸铋纳[(Bi1/2Na1/2)TiO3,BNT]无铅压电陶瓷.对BNT基陶瓷的电学性能和力学性能进行了研究.在(1-x)(Bi1/2Na1/2)0.900Ba0.088Sr0.012TiO3-x(Bi1/2K1/2)TiO3(x=0-0.14)陶瓷体系中,当x=0.10时,可获得最大压电常数(168pC/N).在1 kHz,这种陶瓷的介电常数、介电损耗和平面机电耦合系数分别为1 221,0.0361和0.2281.Curie温度随x的增加先增加,当x=0.12时,达到最高值(300℃),随后,当x值进一步增加,Curie温度降低.该种无铅压电陶瓷的Vickers硬度和断裂韧性分别为5.0GPa和2.0MP·m1/2,均高于Pb(Zr,Ti)O3陶瓷.     

(Na1/2Bi1/2)TiO3系无铅压电陶瓷材料研究进展

概述了近年来国内外(Na1/2Bi1/2)TiO3(BNT)基无铅压电陶瓷的研究近况。主要介绍BNT陶瓷及BNT基陶瓷的研究工作。通过非化学计量掺杂及A位空位的存在，使BNT基陶瓷的电性能得到了较大的提高。     

The effect of Fe-acceptor doping on the electrical properties of Na1/2Bi1/2TiO3 and 0.94 (Na1/2Bi1/2)TiO3–0.06 BaTiO3

Na_1/2Bi_1/2TiO₃ (NBT) based ceramics are amongst the most promising lead-free ferroelectric materials. It was expected that the defect chemistry and the effect of doping of NBT would be similar to that observed for lead based materials, however, acceptor doping does not lead to ferroelectric hardening. Instead, high oxygen ionic conductivity is induced. Nevertheless, for solid solutions with BaTiO₃ (BT), which are more relevant with respect to ferroelectric applications, such a drastic change of electrical properties has not been observed so far. To rationalize the difference in defect chemistry between NBT and its solid solution 94(Na_1/2Bi_1/2TiO₃)–0.06 BaTiO₃ (NBT–6BT) compositions with different concentrations of Fe-dopant were investigated. The study illustrates that the materials exhibit very similar behavior to NBT, and extraordinarily high oxygen ionic conductivity could also be induced in NBT–6BT. The key difference between NBT–6BT and NBT is the range of the dependence of ionic conductivity with dopant concentration. Previous studies of NBT–6BT have not reached sufficiently high dopant concentrations to observe high conductivity. In consequence, the same defect chemical model can be applied to both NBT and its solid solutions. This will help to rationalize the effect of doping on ferroelectric properties of NBT-ceramics and defect chemistry related degradation and fatigue.     

MgF2包覆对正极材料LiNi1/3Co1/3Mn1/3O2性能的影响

通过浸渍法在正极材料LiNi1/3Co1/3Mn1/3O2的表面包覆MgF2,通过XRD、SEM、交流阻抗（EIS）分析、充放电测试研究了不同量MgF2包覆对LiNi1/3Co1/3Mn1/3O2正极材料的结构与电化学性能的影响。结果表明,MgF2以非晶态形式包覆于LiNi1/3Co1/3Mn1/3O2材料颗粒的表面,当包覆量为3%（物质的量分数,下同）时,三元正极材料具有优良的电化学性能,在3.0~4.6 V充放电范围内0.1C充放电倍率下,首次放电比容量为196.3 mA·h/g,1C循环50次后容量保持率为95.7%,55 ℃高温下1C循环50次后容量保持率为93.3%。     

锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2研究进展

层状结构材料LiNi1/3Co1/3Mn1/3O2具有高比容量、高循环性能、低成本和环保等优点,有望取代LiCoO2成为新一代锂离子电池正极材料。在介绍LiNi1/3Co1/3Mn1/3O2的结构特点和电化学反应特性的基础上,对其主要合成方法进行了详细评述,总结了该正极材料的阴阳离子掺杂、复合离子掺杂以及表面包覆改性等技术,指出国内外目前锂离子电池材料研究中存在的问题和未来的发展方向。     

O1/A1/O2/A2工艺处理焦化废水试验研究

通过对短程硝化反硝化工艺的研究,开发了好氧/厌氧/好氧/缺氧(O1/A1/O2/A2)生物脱氮新工艺并用于焦化废水的处理。考察了NH4+-N、COD、TN对反应器运行效果影响。结果表明,当进水COD平均为3 012.9 mg/L,NH4+-N、TN、挥发酚、总氰平均质量浓度分别为590.5、608.4、361.8、34.5 mg/L;出水COD平均为81.7 mg/L,出水NH4+-N、TN、挥发酚、总氰的平均质量浓度分别为0.1、9.9、0.1、0.1 mg/L,出水指标达到国家污水综合排放一级标准,A/O工艺处理这种焦化废水TN偏高,而用O1/A1/O2/A2工艺可以解决这一问题,实现了TN脱除。考察了温度、DO、pH对短程硝化影响。结果表明,在DO质量浓度为1.0～1.5 mg/L、温度在30～35℃、pH 7.5～8.0,系统能够进行稳定短程硝化反硝化。     

Al2O3包覆LiNi1/3Co1/3Mn1/3O2锂离子电池正极材料

综述了Al2O3包覆LiNi(1/3)Co(1/3)Mn(1/3)O2锂离子电池正极材料的研究现状与进展,并评述了其制备方法和包覆改性;讨论了包覆改善该正极材料性能的机理;提出了这种正极材料的研发过程中的一些问题并对其未来的发展前景作了展望。     

Microwave dielectric characteristics of 0.75(Al1/2Ta1/2)O2–0.25(Ti1−xSnx)O2 ceramics

The microwave dielectric characteristics of 0.75(Al_1/2Ta_1/2)O₂–0.25(Ti_1−xSn_x)O₂ ceramics were investigated. The microwave dielectric properties of 0.75(Al_1/2Ta_1/2)O₂–0.25TiO₂ sintered at 1450 °C exhibited a dielectric constant (ϵ_r) of 31.2, a Q·f₀ of 54,590 GHz, and the temperature coefficient of resonant frequency (τ_f) of +12.8 ppm/°C. To control of the τ_f and enhance the Q·f₀ for 0.75(Al_1/2Ta_1/2)O₂–0.25TiO₂, Sn⁴⁺ was substituted for Ti⁴⁺. With an increase of Sn content from 5 to 50 mol%, the ε_r slightly decreased, the Q·f₀ increased and the τ_f shifted from positive to negative value. The τ_f within ±10 ppm/°C of zero was realized for the Sn content below 30 mol% and the microwave dielectric properties had the ε_r value of 31.2–26.3, the Q·f₀ of 54,600–70,700 GHz, and τ_f of +12.8–−9.3 ppm/°C for this compositions. The relationship between microstructure and microwave dielectric characteristics was investigated.     

环氧树脂辅助制备LiNi1/3Co1/3Mn1/3O2及其储锂性能

采用环氧树脂来均匀分散Li~+,Co~(2+),Mn~(2+)和Ni~(2+),并通过环氧树脂低温固化来维持离子均匀分散,续以空气中充分煅烧制备LiNi1/3Co_(1/3)Mn_(1/3)O2材料。电化学研究显示,850℃下制得的材料具有更好的充放电性能,0.2℃倍率下的首次充放电容量分别达到186.4和135.1mAh·g~(-1)。     

Bi1/2Na1/2TiO3–BaTiO3 based thick-film capacitors for high-temperature applications

Thick films with compositions (1 − x)(0.94Bi_1/2Na_1/2TiO₃–0.06BaTiO₃)–x(K_0.5Na_0.5NbO₃) (x = 0, 0.03, 0.09 and 0.18) have been prepared and their structural and electrical properties have been investigated. Dielectric properties show that these films are well suited for high-temperature applications due to their low variance in permittivity (<15%) over large temperature ranges. The thick film with x = 0.18 offers an operational temperature range from room temperature to 350 °C. Films with x = 0.03 and 0.09 also possess a stabile permittivity up to 400 °C. The improvement in the thermal stability of the permittivity is attributed to the addition of K_0.5Na_0.5NbO₃ which leads to breaking of the long-range order in the materials. However, the polarizability of the materials was found to decrease possibly due to the clamping effect of the substrate. The characteristics of each film are discussed based on dielectric and electrical properties.