尖晶石LiMn2O4的表面改性研究

采用化学镀包覆方法对尖晶石LiMn2O4进行表面改性。通过XRD和SEM等方法对改性后的尖晶石LiMn2O4表面进行了研究。电化学测试结果表明,化学镀包覆方法能改善尖晶石LiMn2O4的充放电性能,特别是能大幅度提高Li／LiMn2O4电池的高温性能。     

合成温度与时间对尖晶石LiMn2O4性能的影响

采用高温固相合成法制备尖晶石LiMn2O4锂离子电池正极材料,研究合成温度与合成时间对尖晶石LiMn2O4晶体结构和电化学性能的影响。结果表明,尖晶石LiMn2O4晶体结构和电化学性能随合成温度和时间的增加而提高,但合成时间超过24h后对材料结构与性能的影响不大。     

纳米LiMn2O4的制备

以硝酸锂、硝酸锰为原料,柠檬酸作为络合剂,采用溶胶一凝胶法获得前驱体,然后将前驱体在空气气氛中焙烧制备了纳米LiMn2O4。采用DTA-TG对前驱体的热分解行为进行了研究,用XRD考察了合成产物的结构和纯度,用SEM对合成产物进行了形貌观察和尺寸测量,并采用氧化一还原返滴定方法测定了合成产物中锰的平均化合价。试验结果表明,在300℃时已有明显的尖晶石LiMn2O4相出现;经300℃预处理后产物的质量明显提高;合成产物的粒度和晶格常数随温度升高而增加;预处理后合成产物的形貌呈球形,颗粒尺寸在30nm左右且分布均匀;锰的平均化合价为3．498与理论值吻合的较好。     

Al2O3包覆LiMn2O4正极材料的合成和电化学性能研究

研究了在锂离子电池尖晶石LiMn2O4正极材料上包覆Al2O3来改善材料在循环过程中的容量衰减问题。通过SEM和X射线衍射研究材料的表观形貌和晶体结构，在电化学性能测试中，发现包覆Al2O3可以减少材料与电解液的直接接触，阻止了电解液对尖晶石的侵蚀，抑制锰离子在电解液中的溶解和由此带来材料结构的改变，以及与电解液中微量的HF反应，避免了HF对锰离子溶解的加速作用。从电化学循环测试后材料的X射线图谱上可以发现，LiMn2O4材料包覆Al2O3后，可以在很大程度上抑制循环过程中MN5O8杂相峰的出现。     

用第一原理研究LiMn2O4及掺杂化合物的结构与稳定性

为了从理论方面研究Al^3＋、Co^3＋、Y^3＋掺杂对尖晶石型LiMn2O4电子结构的影响,采用基于密度泛函理论的第一原理,对LiMn2O4及掺杂化合物的电子结构进行了研究。通过对晶格常数、能带结构和态密度的分析,发现掺杂Al^3＋、Co^3＋、Y^3＋都能有效地抑制Jahn-Teller畸变;掺Al^3＋、Co^3＋后,晶格常数变小,材料的循环性能有所提高;掺Co^3＋、Y^3＋能提高正极材料的导电率,改善了材料的导电性能,掺Al^3＋后,材料的电导率下降。     

高尺寸稳定性的MgAl2O4/MgO复合陶瓷型芯的制备

本文以镁铝尖晶石(MgAl2O4)为原料,制备了新型MgAl2O4/MgO复合陶瓷型芯。用X射线衍射仪(XRD)分析了样品的相组成,并用扫描电子显微镜(SEM)观察了陶瓷型芯的表面和断面微观形貌。结果表明,陶瓷型芯中的主晶相为镁铝尖晶石,次晶相为方镁石,镁铝尖晶石为陶瓷型芯骨架,骨架大颗粒之间填充有细方镁石颗粒。性能测试证实,添加镁铝尖晶石可抑制氧化镁的液相烧结,降低收缩率,同时可以显著提高陶瓷型芯的显气孔率和高温尺寸稳定性。含有60wt%镁铝尖晶石的MgAl2O4/MgO复合陶瓷型芯显气孔率为38.24%、收缩率为1.99%、室温抗弯强度为25.9 MPa、热膨胀率仅为1.61%。溶出实验结果表明,所制备的MgAl2O4/MgO复合陶瓷型芯能在温和条件下溶出,不对铸件造成化学腐蚀及机械损伤：在溶出液为20wt%有机弱酸乙酸溶液中,90 ℃溶出6 h后,型芯能够完全塌陷成粉末。     

TiCl4水溶液强水解合成Li4Ti5O12的研究

在高LiOH浓度下,以TiCl4和LiOH.H2O为原料,水解并合成Ti(OH)62-,控制条件,让Li+嵌入Ti-O八面体中,直接合成了Li4Ti5O12前躯体。对粉体进行了DSC-TGA、XRD分析,结果表明,热处理温度和时间对合成材料的组成和性能影响较大,在700~800℃热处理前驱体即可得到纯尖晶石相Li4Ti5O12。SEM分析及电性能检测表明,经过800℃热处理6 h的样品结晶度好,颗粒分布较均匀,平均粒径约为1μm;在0.1 C充放电倍率下,首次可逆比容量达158.8 mA.h/g,11次循环后,仍有133.8 mA.h/g。     

水热合成纳米NiFe_2O_4粉体

通过水热法采用Ni(N03)2·6H2O和FeCl3·6H2O合成纳米NiFe2O4粉体。利用X射线衍射(XRD)、扫描电镜(SEM)对样品进行表征。结果表明,不同PEG和反应温度对合成纳米NiFe2O4粉体有影响。通过扫描电镜分析,不加PEG、加PEG-400和PEG-2 000对近似于球体颗粒粒度大小有影响,而加入PEG-20000,纳米NiFe2O4粉体形状变成了纳米线,均匀分布;不同反应时间对合成纳米NiFe2O4粉体没有明显的影响;而不同反应温度对合成纳米NiFe2O4粉体形状有影响,其影响是从纳米线变化到出现少量颗粒与纳米线混合,再到大量球形颗粒混合纳米线。水热过程是溶解再结晶的过程,部分晶体经高温后结晶成颗粒。     

掺杂SnO2对NiFe2O4陶瓷电导率的影响

采用冷压-烧结粉末冶金技术制备了NiFe2O4陶瓷,并对其进行SnO2掺杂.对光谱纯石墨和所制备的试样进行的不同温度下电导率测试研究表明:用直流四端电极法改进的高温电导率测试仪测定结果重现性和准确性良好;NiFe2O4陶瓷材料的导电性能随着温度升高而提高,且呈现半导体材料特性;掺杂少量SnO2有利于降低材料的活化能,提高其电导率,而不影响陶瓷基体材料的半导体特性.     

二维纳米氧化铝涂层包覆锰酸锂材料电化学性能的研究

以无机铝盐Al(NO3)3·9H2O为原料,氨水为沉淀剂,通过溶胶-凝胶法在Li Mn2O4表面包覆一层二维纳米状Al2O3。通过XRD、SEM、TEM和电化学测试对样品的晶体结构、表面形貌和电化学性能进行了表征。结果表明,此方法合成的锰酸锂表面均匀包覆了一层二维纳米氧化铝,呈蓬松无序状,厚度约为50 nm。电化学测试结果表明:该复合材料的首次放电比容量为112.7 m Ah/g(0.1C),1C倍率循环400周容量保持率为78.35%。     

Effect of additive V2O5 on sintering mechanism and properties of inert anodes of NiFe2O4 spinel

In order to improve the properties of NiFe2O4 spinel based inert anode, some additive MnO2 were added to raw materials. NiFe2O4 spinel with MnO2 was made by solid-phase reaction at 1200℃for 6 h. XRD were carried out and the effects of MnO2 on density, conductivity and corrosion resistance were measured. XRD shows when MnO2 was added no new phases exist and MnO2 and NiFe2O4 formed solid solution; Mn4+ replaced parts of Fe3+ and the sample still had the structure of NiFe2O4 spinel. The crystal lattice of NiFe2 O4 spinel became aberrated when MnO2 was added, which can promote sintering, and improve density. Because Mn4+ replaces parts of Fe3+ and produces conduction electron, which can improve conductivity.The corrosion resistance of the samples was enhanced. When MnO2 is 1.0%, the sample‘s corrosion rate is 1/5 of that of the sample without MnO2. The reason is that Al2 O3 in the melt reacts with Mn4+ in the sample to produce MnAl2O4. MnAl2 O4 forms a dense protecting coat, which can prevent melt from eroding further.Because the key problem with inert anodes is anode corrosion, so we consider the optimal amount of MnO2 is 1.0%.     

Effect of MnO2 on properties of NiFe2O4 spinel based inert anode

In order to improve the properties of NiFe2O4 spinel based inert anode, some additive MnO2 were added to raw materials. NiFe2O4 spinel with MnO2 was made by solid-phase reaction at 1200℃for 6 h. XRD were carried out and the effects of MnO2 on density, conductivity and corrosion resistance were measured. XRD shows when MnO2 was added no new phases exist and MnO2 and NiFe2O4 formed solid solution; Mn4+ replaced parts of Fe3+ and the sample still had the structure of NiFe2O4 spinel. The crystal lattice of NiFe2 O4 spinel became aberrated when MnO2 was added, which can promote sintering, and improve density. Because Mn4+ replaces parts of Fe3+ and produces conduction electron, which can improve conductivity.The corrosion resistance of the samples was enhanced. When MnO2 is 1.0,, the sample''s corrosion rate is 1/5 of that of the sample without MnO2. The reason is that Al2 O3 in the melt reacts with Mn4+ in the sample to produce MnAl2O4. MnAl2 O4 forms a dense protecting coat, which can prevent melt from eroding further.Because the key problem with inert anodes is anode corrosion, so we consider the optimal amount of MnO2 is 1.0,.     

Effect of additive V2O5 on sintering mechanism and properties of inert anodes of NiFe2O4 spinel

In order to improve the properties of inert anode of NiFe2O4 spinel, some additive V2O5 was added to raw materials-powders of NiO and Fe2O3. The powders of NiO, Fe2O3 were mixed with slight amount of V2O5, then they are moulded and sintered at 1200℃ for 6h. The sintering mechanism of powders of NiO and Fe2O3 with some additive V2 O5 was researched. The effect of V2O5 on density, electrical conductivity and corrosion resistance of inert anode of NiFe2O4 spinel was studied at the same time. The results show that the sintering mechanism for powders of NiO and Fe2O3 with some additive V2O5 is liquid-phase sintering. Additive V2O5 can increase the density of the samples, especially it improves the corrosion resistance of the samples remarkably. When the amount of V2 O5 is 1.5 ,, the sample''s corrosion rate is 1/80 of that of sample without V2 O5. But the electrical conductivity of the samples with V2O5 is lower than that of the sample without V2O5.     

砂岩型铀矿CO2+O2地浸过程中浸出铀浓度与HCO-3浓度关系分析

以新疆某砂岩铀矿采区为研究对象,对所有抽注单元的浸出液铀浓度与HCO-3浓度变化关系进行了分析。结果表明:HCO3^-浓度与浸出液铀浓度有着密切的变化关系,大体上可分为6种类型;水动力、水化学、矿化条件、钻孔工程等因素是铀浓度与HCO3^-浓度关系呈现不同特征的主要原因。在生产中充分挖掘和利用铀浓度、HCO3^-变化特征所蕴含的信息是提高CO2+O2地浸采铀精益化管理的重要途径。     

LiFePO4-Na2CO3体系焙烧过程物相变化及Li、Fe回收研究

LiFePO4作为正极材料在电动汽车动力电池中获得广泛使用,其报废后再利用理论和工艺是当前研究的热点问题。本文提出了一种采用碱性焙烧联合酸性浸出从LiFePO4中提取Li、Fe的新型回收方法,并对LiFePO4-Na2CO3体系焙烧过程中的物相变化进行了研究。研究结果表明：LiFePO4-Na2CO3作用体系以质量比1:0.67混合在800~950 ℃焙烧,过程是包含化合物分解反应、氧化反应及化合物生成反应等反应类型的复杂反应,焙烧产物的物相组成为Fe2O3、Fe3O4、NaLi2PO4、LiNa5(PO4)2。浸出液使用磷酸溶液(pH=0)、浸出温度50 ℃、浸出时间60 min、液固比为20 mL/g,并用磷酸控制浸出终止pH=1的条件下,焙烧产物中Li的浸出率均大于98%,Fe的浸出率低于9%。