锂离子电池正极材料LiNi0.8Co0.15Al0.05O2的制备及电化学性能

首先以AlO2-为铝源,采用三元共沉淀法制备前驱体Ni_(0.8)Co_(0.15)Al_(0.05)(OH)_2。对前驱体进行500℃高温处理,随后与过量的锂盐混合均匀,在氧气气氛下700℃煅烧12 h制得LiNi_(0.8)Co_(0.15)Al_(0.05)O_2(NCA)材料。采用X射线衍射仪(XRD)测试可知,所得的NCA材料呈典型的α-NaFeO_2层状结构,属于R-3m空间群。扫描电子显微镜(SEM)测试显示,NCA为粒径5～6μm的球状颗粒。材料在电流倍率为0.1C下首次放电容量为167.1mAh/g,循环200次以后容量保持率为96.2%。倍率测试表明,0.1、10 C下NCA的容量分别为184.0、112.7 mAh/g,到恢复到0.1 C时,容量仍可达179.7mAh/g,具有比较好的倍率性能。     

锆盐原料不同对LiZr2(PO4)3锂离子固体电解质结构及性能的影响

以不同的锆盐为原料,采用固相法及液相法制备LiZr_2(PO_4)_3锂离子固体电解质,通过无压烧结的方式制备得到固体电解质片,并通过X射线衍射(XRD),扫描电子显微镜(SEM),电化学交流阻抗(EIS)对LiZr_2(PO_4)_3锂离子固态电解质进行表征,通过测试结果对比分析,研究锆盐原料的不同对LiZr_2(PO_4)_3锂离子固态电解质结构及性能的影响。结果表明:当以醋酸锆为锆盐原料时,合成的LiZr_2(PO_4)_3以高电导率的菱方相于室温下稳定存在,而其他3种锆盐作原料时合成的LiZr_2(PO_4)_3室温下以三斜相存在。制备的菱方相LiZr_2(PO_4)_3电解质样品片室温锂离子总电导率最大,为2.25×10~(-5) S/cm,且激活能值最小,为0.28 eV。     

CeN3O9.6H2O对镁空气电池负极性能的影响

通过动电位极化法和电化学阻抗谱法,研究了在8%NaCl电解液中,六水合硝酸铈(CeN_3O_9·6H_2O)对AZ31负极抗腐蚀性能的影响。结果表明:电解液中加入Ce N_3O_9·6H_2O,在AZ31镁合金表面形成Ce(OH)_3保护膜,提高镁合金的耐腐蚀性。随着CeN_3O_9·6H_2O浓度的增大,Ce(OH)_3保护膜逐渐致密,AZ镁合金的腐蚀速率降低。当Ce N_3O_9·6H_2O浓度达到1.0 g/L时,镁合金的腐蚀速率最低,其缓蚀率为70.4%。然而当加入的Ce N_3O_9·6H_2O浓度大于1.0 g/L时,由于Ce(OH)3保护膜被溶解而导致镁合金的腐蚀速率增大。由浸泡50 h AZ合金的SEM图发现CeN_3O_9·6H_2O的添加在镁合金表面形成Ce(OH)_3保护膜,抑制阳极反应。从等效电路图得到Mg~(2+)电荷转移阻力增大了69.5?,改善了镁合金的耐腐蚀性能。通过放电测试得到加入CeN_3O_9·6H_2O提高电池的放电性能,放电时间延长40 min。     

三元共晶成分Al2O3/YAG/ZrO2粉体及陶瓷的制备与组织性能研究

本文采用醇水共沉淀法制备了三元共晶成分Al₂O₃/YAG/ZrO₂粉体,在600-1350_oC温度范围煅烧后研究其物相转变过程。经1300_oC煅烧后Al₂O₃/YAG/ZrO₂共晶成分粉体的物相由α-Al₂O₃、c-ZrO₂和YAG构成,且具有α-Al₂O₃相包裹c-ZrO₂相的特殊结构。将煅烧粉体在1550_oC下热压烧结,制备具有内晶型结构的共晶成分Al₂O₃/YAG/ZrO₂复相陶瓷,其致密度、室温抗弯强度、断裂韧性和高温(1000_oC)抗弯强度分别为98.8%、420 MPa、3.69 MPa.m_1/2和464 MPa,并对复相陶瓷组织结构的形成机理进行了探讨。     

CaO-Bi2O3-MoO3-xNb2O5复合掺杂对高磁导率Mn-Zn铁氧体的微观结构和电磁性能的影响

采用高温固相反应制备了CaO-Bi_2O_3-MoO_3-XNb_2O_5(X=0.000%~0.075%,质量分数,步长:0.015%)复合掺杂的高磁导率Mn-Zn铁氧体材料,利用XRD、SEM、四探针电阻测试仪、阻抗分析仪、和软磁测试仪等分析测试手段对材料结构和性能进行表征,研究了复合掺杂剂中Nb_2O_5掺杂量对高磁导率Mn-Zn铁氧体材料的结构和电磁性能的影响。结果表明:当Nb_2O_5少量掺杂时,Nb_2O_5可以改善材料的微观结构,提高其密度、频率稳定性和品质因数,提高其电阻率,降低其体积功耗;当Nb_2O_5过量掺杂时,Nb_2O_5将恶化材料的微观结构,导致材料的电磁性能变差。当Nb2O5掺杂量为0.030%时材料的综合电磁性能最佳。     

高容量锂离子电池正极材料LiNi0.5Co0.2Mn0.3O2的制备与工艺优化

采用氢氧化物共沉淀法合成前驱体Ni_0.5Cc_0.2Mn_0.3H(OH)₂,进一步用高温固相法与锂源共混煅烧得到LiNi_0.5Co_0.2Mn_0.3O₂。初步探讨了前驱体与锂源在高温煅烧过程中的质量变化及煅烧工艺对材料结构和性能的影响。热重分析(TGA)表明在煅烧过程中750℃后材料质量几乎没有变化。X射线衍射(XRD)对750℃-900℃的材料进行结构分析,结果表明所有材料具有良好的α-NaFeO₂层状结构和较小的阳离子混排度。扫描电镜(SEM)分析表明材料具有表面光滑,分布均匀的球形结构。横流充放电测试结果表明在850℃煅烧的材料具有最好的电学性能,在0.2C,2.5-4.6V测试条件下,其具有193.7mAh/g的首次放电容量,循环30次后的容量保持率为94.2%,并且具有最好的倍率性能。     

废旧锂离子电池中Li, Fe和V的回收及xLiFePO4-yLi3V2(PO4)3的制备

由于LiFePO_4和Li_3V_2(PO_4)_3材料的特征相近,制备方法类似,提供了一种从废旧LiFePO_4和Li_3V_2(PO_4)_3混合电池中回收Li、Fe和V,再制备xLiFePO_4-yLi_3V_2(PO_4)_3的方法。在空气气氛中600℃热处理1h后,去除粘结剂PVDF使活性物质与集流体分离。调节Li、Fe、V和P摩尔比,球磨、锻烧,配制不同比例的xLiFePO_4-yLi_3V_2(PO_4)_3(x:y=5:1,7:1,9:1)复合电极材料。表征了其形貌、结构和电化学性能,结果表明,回收制备的复合材料将同时具备LiFePO_4和Li_3V_2(PO_4)_3两种材料的电化学性能,能显著改善LiFePO_4的倍率性能。     

低热固相法合成镁铝尖晶石

以分析纯碱式乙酸铝、硝酸镁为原料,柠檬酸为配合剂,采用低热固相反应制备前驱体,然后通过煅烧的方式获得了MgAl_2O_4粉体.研究了煅烧温度、柠檬酸用量对MgAl_2O_4粉体性能的影响.结果表明,可在全固相条件下通过低热固相反应得到Mg和Al分子级混合的前驱体,该前驱体煅烧到700 ℃保温3 h形成含有部分阳离子缺陷的尖晶石晶相,随温度升高,逐渐转化为结晶完整的尖晶石.柠檬酸使用量符合化学计量比n(C_6H_8O_7):n(Mg+Al)为1:1时能够获得比表面积达到166 m~2/g的MgAl_2O_4粉体.     

α-(Al,Cr,Fe)_2O_3相稳定性和力学性能的第一性原理计算

采用第一性原理分别对α-Al_2O_3、α-(Al_(0.75)Cr_(0.25))_2O_3、α-(Al_(0.75-x)Cr_(0.25)Fe_x)_2O_3和α-(Al_(0.75)Cr_(0.25-x)Fe_x)_2O_3相晶胞体积、结合能、态密度和力学性能的变化进行计算。研究表明:α-(Al_(0.75-x)Cr_(0.25)Fe_x)_2O_3四元相的晶胞体积随着Fe原子置换数量的增加而缓慢增大,α-(Al_(0.75)Cr_(0.25-x)Fe_x)_2O_3四元相晶胞的体积随着Fe原子数量的增加而迅速减小;相结合能结果显示,α-Al_2O_3、α-(Al_(0.75)Cr_(0.25))_2O_3、α-(Al_(0.75-x)Cr_(0.25)Fe_x)_2O_3和α-(Al_(0.75)Cr_(0.25-x)Fe_x)_2O_3相均为稳定结构,其中α-Al_2O_3相的结合能最低,随着置换原子种类和数量的增加,结合能增大,相稳定性下降;当Fe元素原子数量占金属元素总原子数0～3 at.%时,α-(Al_(0.75-x) Cr_(0.25)Fe_x)_2O_3和α-(Al_(0.75)Cr_(0.25-x)Fe_x)_2O_3四元相的硬度、H/E和H3/E*2较α-(Al_(0.75)Cr_(0.25))_2O_3相有明显提升,但均低于α-Al_2O_3相,仅α-(Al0.63Cr_(0.25)Fe0.12)_2O_3相的H/E和H~3/E~(*2)值高于α-Al_2O_3相。     

Ba(Mg1/3Ta2/3)O3热障涂层的制备及抗热震性能研究

本文以BaCO₃、MgO、Ta₂O₅为原料,采用固相反应法合成了Ba(Mg_1/3Ta_2/3)O₃(简称BMT)陶瓷粉末,利用大气等离子喷涂技术制备了BMT/YSZ双层陶瓷涂层。利用XRD、SEM和金相显微镜检测了BMT粉体及涂层的物相组成和显微结构。采用水淬法考核了涂层的抗热震性能。结果表明：1450℃下煅烧4h可合成出具有复合钙钛矿结构的BMT粉末,粉末具有良好的高温相结构稳定性。等离子喷涂制备的BMT/YSZ涂层组织致密,涂层系统中各界面结合紧密。涂层在室温至1150℃间热震9次后发生片状剥落,剥落位置位于BMT层间,BMT材料低的断裂韧性和第二相Ba₃Ta₅O₁₅的存在是导致涂层失效的主要原因。     

Al2O3包覆LiNi0.03Co0.05Mn1.92O4正极材料的制备及其电化学性能

以Al(NO3)3?9H2O为包覆原料,通过燃烧法制备得到LiNi0.03Co0.05Mn1.92O4@Al2O3正极材料。通过X射线衍射(XRD),场发射扫描电子显微镜(FESEM)和透射电镜(TEM)等表征手段对材料的结构和形貌进行分析,并通过恒电流充放电、循环伏安(CV)、交流阻抗(EIS)等测试分析材料的电化学性能。结果表明,Al2O3包覆没有改变LiNi0.03Co0.05Mn1.92O4的尖晶石型结构,包覆层厚度约10.6nm。LiNi0.03Co0.05Mn1.92O4@Al2O3正极材料电化学性能得到了明显改善,1 C和10 C倍率下初始放电比容量分别为119.9 mAh?g-1和106.3 mAh?g-1,充放电循环500次后容量保持率分别为88.4%和78.2%,而未包覆的LiNi0.03Co0.05Mn1.92O4在1 C和10 C倍率下初始放电比容量分别为121.2 mAh?g-1和104.0 mAh?g-1,500次循环后容量保持率分别为84.1%和67.6%。LiNi0.03Co0.05Mn1.92O4@Al2O3活化能为32.92 kJ?mol-1,而未包覆材料的活化能为36.24 kJ?mol-1,包覆有效降低了材料Li+扩散所需克服的能垒,提高了材料的电化学性能。     

Ni42Cr6Fe合金在高温湿氢中的氧化膜组织结构及生长过程研究

用ＴＥＭ、Ｘ射线衍射、ＳＥＭ等技术研究了Ｎｉ４２Ｃｒ６Ｆｅ玻封合金在高温湿氢中的氧化膜生长过程。氧化初期，Ｃｒ＿（２）Ｏ＿３和尖晶石氧化物同时形核长大，前者在晶界处形核长大，后者在晶内处形核长大。随后由于Ｃｒ的选择氧化，氧化膜主要以Ｃｒ２Ｏ３生长为主．当氧化进行到一定程度后，由于表面层Ｃｒ的贫化，氧化膜生长转化以（Ｆｅ，Ｍｎ）Ｃｒ２Ｏ４尖晶石氧化物生长为主．最后形成表层以粗大晶粒（Ｆｅ，Ｍｎ）Ｃｒ２Ｏ４为主，底部以较小晶粒Ｃｒ２Ｏ３为主，中部由大晶粒（Ｆｅ，Ｍｎ）Ｃｒ２Ｏ４围绕小晶粒Ｃｒ２Ｏ３的稳态氧化膜组成     

Indication of Chromium Oxide Hydroxide Evaporation During Oxidation of 304L at 873 K in the Presence of 10% Water Vapor

The oxidation of type 304L stainless steel wasinvestigated at 873 K in the presence of O₂and O₂ + 10% H₂O. Oxidation timevaried between 1 and 672 hr. The oxidized samples wereinvestigated by a number of surface-analytical techniques includinggrazing-angle XRD, SEM/EDX, auger spectroscopy, SIMS andXPS. Oxidation in dry oxygen results in the formation acorundum-type oxide (Me₂O₃) withadditional formation of spinel oxides after prolonged exposure. Theoxide layer contained mainly chromium, with smalleramounts of Fe and Mn. Oxidation in the presence of watervapor results in an oxide that contains more Fe and less Cr, the outer part of the oxide beingdepleted in Cr. In the presence of water vapor, a massloss is detected after prolonged exposure. We show thatthe mass loss is caused by chromium evaporation. The volatile species is suggested to beCrO₂(OH)₂.     

纳米Cr2O3微粒对2024-T4微弧氧化膜结构及耐磨性能的影响

摘 要: 在含有不同浓度纳米Cr2O3微粒的硅酸盐体系电解液中对2024-T4铝合金进行微弧氧化处理,使用SEM观察陶瓷膜的表面形貌和截面形貌,使用EDS能谱仪分析膜层中各主要成分沿截面方向的分布,使用XRD分析陶瓷膜的相结构,使用纳米压痕硬度计测量陶瓷膜的硬度,使用粗糙度仪测量陶瓷膜的表面粗糙度,使用摩擦磨损试验机测量陶瓷膜的摩擦系数,使用激光共聚焦显微镜测量磨痕体积,评估磨损率,使用SEM观察磨痕形貌,结果表明：在电解液中加入纳米Cr2O3微粒后,制备的陶瓷膜中出现了Cr2O3相,电解液中纳米Cr2O3微粒浓度达到2.4g/L时,陶瓷膜的硬度最高,摩擦系数最小,磨损率最低,耐磨性最好。     

Pd/ZrO2-Al2O3催化剂中载体制备对CH4转化活性的影响

为推动ZrO2-Al2O3在天然气汽车尾气净化催化剂中的实际应用,并阐明其制备条件对负载催化剂转化活性的影响机制,文章以ZrO2-Al2O3复合氧化物为载体,采用等体积浸渍法制备了Pd/ZrO2-Al2O3催化剂,并在连续流动固定床反应器上研究了ZrO2-Al2O3复合氧化物的制备对催化剂低温CH4氧化活性的影响。结果表明：制备方法中,相比于浸渍法和胶溶法,沉淀法更能提高催化剂活性;锆源、铝源优选中,以Zr(NO3)4为锆源、拟薄水铝石为铝源时能获得较高的催化活性;组分配比中,以w (ZrO2): w (Al2O3)=10:90的催化活性最高。XRD、低温N2吸附、CO脉冲吸附的结构表征表明,ZrO2-Al2O3复合氧化物的大的比表面积、孔容、孔径是促进贵金属Pd分散,提升催化剂低温CH4转化活性的关键因素。     

Li4SiO4 氚增殖陶瓷的制备及其与14Cr-ODS钢的腐蚀界面行为

Li₄SiO₄小球与ODS钢的化学相容性对聚变反应器的安全运行具有重要意义。研究了在500、600、700 ℃的氩气环境中保温300 h后ODS钢与小球接触界面组织和成分的变化。结果表明,在600~700 ℃时,Li₄SiO₄小球与ODS钢的界面发生了严重的元素互扩散和反应。在Li₄SiO₄小球表面,由于ODS钢中Fe和Cr的扩散,出现了一层薄薄的反应层,这也导致了密度的增加,破碎负荷从51 N （500 ℃）下降到32 N（700 ℃）。XRD图谱显示,ODS钢表面出现了LiCrO₂和LiFeO₂新相,说明Li₄SiO₄小球中的Li和O原子可以扩散到ODS中,与Fe、Cr元素在高温下发生反应形成腐蚀层。在700 ℃时,腐蚀层可分为2个氧化层。最外层是LiFeO₂和LiCrO₂的混合物,下一层主要是LiFeO₂。在ODS钢的表面,700 ℃/300 h条件下氧扩散系数为2.2×10^-14 cm²/s,这说明ODS钢作为一种包层结构材料,在未来的包层设计中需要一层耐腐蚀涂层。     

Photocatalytic performance of nano-photocatalyst from TiO2 and Fe2O3 by mechanochemical synthesis

Nano-particles of homogeneous solid solution between TiO₂ and Fe₂O₃ (up to 10 mol%) have been prepared by mechanochemical milling of TiO₂ and yellow Fe₂O₃/red Fe₂O₃/precipitated Fe (OH)₃ using a planetary ball mill. Such novel solid solution cannot be prepared by conventional co-precipitation technique. A preliminary investigation of photocatalytic activity of mixed oxide (TiO₂/Fe₂O₃) on photo-oxidation of different organic dyes like Rhodamine B (RB), Methyl orange (MO), Thymol blue (TB) and Bromocresol green (BG) under visible light (300-W Xe lamp; λ > 420 nm) showed that TiO₂ having 5 mol% of Fe₂O₃ (YFT1) is 3-5 times higher photoactive than that of P25 TiO₂. The XRD result did not show the peaks assigned to the Fe components (for example Fe₂O₃, Fe₃O₄, FeO₃, and Fe metal) on the external surface of the anatase structure in the Fe₂O₃/TiO₂ attained through mechanochemical treatment. This meant that Fe components were well incorporated into the TiO₂ anatase structure. The average crystallite size and particle size of YFT1 were found to be 12 nm and 30 ± 5 nm respectively measured from XRD and TEM conforming to nanodimensions. Together with the Fe component, they absorbed wavelength of above 387 nm. The band slightly shifted to the right without tail broadness, which was the UV absorption of Fe oxide in the Fe₂O₃/TiO₂ particle attained through mechanochemical method. This meant that Fe components were well inserted into the framework of the TiO₂ anatase structure. EPR and magnetic susceptibility show that Fe³⁺ is in low spin state corresponding to μ_B = 1.8 BM. The temperature variation of μ_B shows that Fe³⁺ is well separated from each other and does not have any antiferromagnetic or ferromagnetic interaction. The evidence of Fe³⁺ in TiO₂/Fe₂O₃ alloy is also proved by a new method that is redox titration which is again support by the XPS spectrum.     

Effects of protecting layer [Li,La]TiO3 on electrochemical properties of LiMn2O4 for lithium batteries

A sample of LiMn₂O₄ spinel oxide was surface-modified with lithium lanthanum titanate ([Li,La]TiO₃), which was developed as a lithium ionic conductor, by means of hydrothermal processing and subsequent heat treatment at 400 °C. The surface coating layers were analyzed by morphology observation using a transmission electron microscopy. Energy-dispersive spectrometry and X-ray photoelectron spectroscopy were used for element investigation. The surface modification effects on rate capability during cycling and capacity retention for the LiMn₂O₄ spinel oxide were confirmed. Then Mn dissolution during storage at elevated temperatures of the pristine, coated sample was characterized. The Mn dissolution characterization was based on the idea that Mn dissolution is one of the most significant reasons for capacity loss for LiMn₂O₄ spinel oxide, and this phenomenon is especially severe at elevated temperatures. Our experimental results indicate that the surface-modified sample shows much a better initial capacity and rate capability compared with the pristine sample. The [Li,La]TiO₃ coating effectively enhances the structural stability of LiMn₂O₄ at elevated temperatures, most likely because the [Li,La]TiO₃-modifying layers play a definitive role in suppressing Mn dissolution in the electrolyte during storage.