铝电解惰性阳极基体材料的研究

本论文选用ZnO和Fe2O3、Ni2O3和Fe2O3与NiO和Fe2O3等不同氧化物，采用高温固相烧结法制备铝电解惰性阳极基体材料，通过对其烧结性能、导电性能及耐蚀性能的综合分析，得出试验结论为：采用NiO和Fe2O3合成的NiFe2O4尖晶石材料，其综合性能最好，且试样理论尖晶石含量为85％左右时，其热腐蚀率最低。     

NiFe2O4基金属陶瓷惰性阳极的腐蚀研究进展

综述了近年来国内外铝电解用NiFe2O4基金属陶瓷惰性阳极在阳极组元的溶解与分布、腐蚀率的预测与测定以及氧化物和金属相对阳极腐蚀的影响三个方面所做的研究工作。     

铝电解用NiFe2O4-Cu金属陶瓷惰性阳极的制备

以高温固相合成法合成的NiFe2O4陶瓷粉体和金属Cu粉为原料, 采用冷压-烧结法制备了Cu含量在5%～20%之间的NiFe2O4-Cu金属陶瓷惰性阳极, 研究了烧结气氛和烧结温度对其物相组成、微观形貌和基本物理性能的影响. 结果表明 通过控制烧结气氛中氧分压在NiO和Cu2O的离解反应平衡氧分压之间, 可以制备出具有目标物相组成的NiFe2O4-Cu金属陶瓷; 烧结温度和保温时间对所得NiFe2O4-Cu金属陶瓷的相对密度有较大影响; NiFe2O4和Cu之间的不润湿性限制了NiFe2O4-Cu金属陶瓷烧结温度的提高和保温时间的延长, 在保证金属相分布均匀且不溢出的前提下, 所制备的NiFe2O4-Cu金属陶瓷的相对密度较小; 金属相Cu含量越高, NiFe2O4-Cu金属陶瓷最高烧结温度越低、最长保温时间越短, 从而相对密度越低、孔隙率越高; 除了尽量降低金属相含量外, 还可向NiFe2O4-Cu金属陶瓷中添加其他金属如Ni和Co等, 以改善陶瓷相与金属相之间的润湿性, 以提高烧结温度, 进而提高其相对密度和耐腐蚀性能.     

铝电解用NiFe2O4-10NiO基金属陶瓷惰性阳极的耐腐蚀性能

制备铝电解用NiFe2O4-10NiO基金属陶瓷惰性阳极,并在实验室电解槽中考察其电解腐蚀性能。结果表明,电解过程中虽然惰性阳极在960°C熔盐电解质中表现出优异的耐腐蚀性能,但采用XRD、SEM/EDX和金相分析其物相组成和微观结构后发现,电解后阳极中的金属相发生了优先腐蚀,在阳极表面产生大量孔洞。NiFe2O4相中的 Fe 元素的优先溶解可能导致 NiFe2O4晶粒的不均匀腐蚀。溶解在电解液中的 Al2O3与阳极中的 NiO 或FeO 发生反应生成的 NiFe2O4-NiAl2O4-FeAl2O4相对 NiO 相的吞并以及体积膨胀,阳极表面形成致密的NiFe2O4-NiAl2O4-FeAl2O4保护层。因此,致密的NiFe2O4-NiAl2O4-FeAl2O4保护层可以阻挡阳极表面金属相的损失和陶瓷相的腐蚀。     

NiFe2O4基金属陶瓷惰性阳极腐蚀组元在电解质中的传质研究

通过计算铝电解用NiFe2 O4基金属陶瓷惰性阳极腐蚀组元Fe、Ni和Cu在铝电解质中的传质系数,讨论了不同过热度下不同阳极腐蚀组元在电解质中的传质行为.结果表明,过热度对不同腐蚀组元的影响不明显,Cu的抗腐蚀性能最好,Ni次之,而Fe最差.     

NiFe2O4基惰性阳极粉体颗粒配比的研究

NiFe2O4尖晶石粉料的颗粒配比对惰性阳极制品的机械强度、导电性及耐蚀性有重要影响。依据颗粒的堆积原理，建立了尖晶石颗粒堆积充填的简化模型。根据模型，将尖晶石中的颗粒分成粗、中颗粒和细粉三等级，并对级配颗粒粗细范围进行了界定划分。同时．对各颗粒的质量百分含量进行理论计算。在此基础上，进行振实密度试验。试验结果表明．当粗颗粒占45％、中颗粒占15％、细粉占40％时体系的振实密度最大。此外．振实试验也验证了颗粒堆积充填模型的合理性。     

高能球磨法制备NiFe2O4基惰性阳极

本文以NiO和Fe2O4为主要原料,采用机械化合两步烧结法制备NiFe2O4基金属陶瓷试样。研究了球磨时间、助磨剂含量、球磨转速对制备前驱体粒度的影响,并利用X射线衍射和扫描电子显微镜等进行表征。结果表明,球磨参数越好,粉体颗粒越细,提高冷等静压压坯的致密度、降低试样烧结温度,最终提高惰性阳极试样密度,改善试样的导电性和抗腐蚀性等性能并达到保护环境、节约能源的效果。本实验制备惰性阳极球磨阶段最佳球磨条件为：助磨剂含量150ml、球磨时间6h、球磨转速300r／min,此条件下制得了体积密度为5．68g／ml的阳极试样。     

惰性阳极基体材料NiFe2O4尖晶石的研制

本文用Ni2O3和Fe2O3为原料制备了铝电解用惰性阳极基体材料NiFe2O4尖晶石,详细介绍了整个制备过程。通过对NiFe2O4尖晶石的含量、真密度以及开口孔隙率等重要指标进行研究比较,最终得出了制备NiFe2O4尖晶石最佳工艺条件,并用最佳工艺条件重新制取试样进行热腐蚀实验。     

Nb2O5掺杂NiFe2O4陶瓷材料的显微结构和导电性能

以NiO、Fe2O3和Nb2O5为原料,采用固相烧结法合成陶瓷粉体,通过等静压-气氛烧结法制备Ni1-xNbxFe2O4(x=0,0.02,0.05,0.07,0.10,0.20)陶瓷试样,并对其进行导电性能测试。通过XRD、SEM、EDX、FTIR和XPS等分析手段对材料的物相组成、显微结构和微区成分进行表征,研究Nb2O5掺杂对陶瓷材料显微结构和导电性能的影响。结果表明:Nb2O5掺杂抑制NiFe2O4基体中NiO相的出现,过量时生成FeNbO4相;适量掺杂(x=0.05)有利于消除晶界孔隙,提高陶瓷的烧结密度;与未掺杂试样相比,掺杂Nb2O5的NiF2O4陶瓷材料的导电性均得到很大改善,其中掺杂量x=0.05的Ni0.95Nb0.05Fe2O4陶瓷试样在1 233 K的电导率较纯NiFe2O4的提高60%。     

纤维/NiFe2O4复合陶瓷惰性阳极的制备及性能

以高温固相合成法,采用两步烧结法制备镀铜碳纤维增强的纤维/NiFe2O4复合陶瓷惰性阳极,即先以NiO、Fe2O3、微量V2O5和MnO2为原料制备NiFe2O4尖晶石基体材料,然后以该NiFe2O4尖晶石基体材料和镀铜碳纤维为原料,采用冷压烧结法制备纤维/NiFe2O4复合陶瓷惰性阳极.研究镀铜碳纤维添加量对NiFe2O4复合陶瓷惰性阳极体积密度、气孔率和抗弯强度的影响.结果表明:添加镀铜碳纤维可以显著改善NiFe2O4复合陶瓷材料的性能,当镀铜碳纤维添加量为3%(质量分数)时,其体积密度比不添加镀铜碳纤维试样的体积密度提高约12%,其抗弯强度比不添加镀铜碳纤维的提高约22%.     

新型炼铝电极材料

研制了一种新型铝电解金属陶瓷惰性阳极,阳极基体由Fe-Ni-Co-Al-O构成.在电解温度960℃,氧化铝质量浓度为6.0%,阳极电流密度为1.0 A/cm2,分子比为2.6的电解质中对其进行了10 h的电解.电解过程平稳,电解铝产品纯度达到96%～99%,阳极气体中氧气的含量为98%,反电动势为2.45 V,高于理论值0.25～0.35 V.此阳极具备较好的导电性、抗氧化和耐腐蚀性.采用X射线衍射和电子探针微分析仪(EPMA)对电解后的阳极进行分析,发现阳极表面存在铁酸镍、铝酸铁等尖晶石型化合物,阳极表面下层为铝酸铁、钴酸镍等陶瓷相以及金属相;金属相和陶瓷相相互弥散分布构成结构致密的金属陶瓷层.     

Effect of Ni content on corrosion behavior of Ni/（10NiO-90NiFe2O4） cermet inert anode

Ni/（10NiO-90NiFe2O4） cermet inert anodes with metal Ni content of 0, 5, 10, 15 and 20 （mass fraction, %） were prepared and their corrosion behavior in Na3AlF6-Al2O3 melts was investigated in laboratory electrolysis tests. The results indicate that the content of metal Ni in anodes has little effect on the steady-state concentration of impurities Ni and Fe in electrolyte and the values range in （114-173）×10^-6 and （287-385）×10^-6, but the content of impurities in the metal aluminum manifolds. There is preferential corrosion for metal Ni in NiO-NiFe2O4 based cermet anodes. Considering the corrosion resistance and electrical conductivity, the cermet containing 5%Ni （mass fraction） behaves best among NiO-NiFe2O4 based cermet anodes studied, and should be further studied.     

Effect of additive on corrosion resistance of NiFe2O4 ceramics as inert anodes

In order to improve the corrosion resistance of NiFe2O4 ceramics as inert anode, additive V2O5 was added to raw materials NiO and Fe2O3. The inert anodes of nickel-ferrite ceramics were prepared by powder metaUurgic method and the static corrosion rate in Na3AlF6-Al2O3 was determined by mass loss measurement. The effect of V2O5 on sintering property and corrosion resistance was studied. The results show that V2O5 can promote the grain to develop completely and improve sintering property. EDS results show the reaction product Ni2FeVO6 distributes along the grain boundary. The corrosion tests show that V2O5 is beneficial to improving corrosion resistance remarkably. The reasons that V2O5 can improve the corrosion resistance must be V2O5 promoting the gains to develop completely and Ni2FeVO6 distributes along the grain boundary. The stable structure can control the chemical dissolution of ceramics anode and the reinforced grain boundary can control the grain-boundary corrosion rate.     

Nanostructured MgFe2O4 as anode materials for lithium-ion batteries

Transition metal oxides in the nano size region are enormous attention as a new generation of anode materials for high energy density Li-ion batteries. MgFe₂O₄ is used for the first time as active electrode vs. lithium metal in test cells. The research has been focused on the effect of grain size of MgFe₂O₄ and their electrochemical performance studied. In this studies, nanostructured milled MgFe₂O₄ (grain size 19 nm) sample have been compared with relatively large-sized as-prepared sample (grain size 72 nm). From the result, the 19 nm grain size sample delivered an improved discharge capacity of around 850 mAh/g, whereas it is only 630 mAh/g for as-prepared sample (72 nm). These values are two times higher than that of a carbon anode (372 mAh/g). The anomalous capacity may be associated with the formation of oxygen rich MgFe₂O₄ samples.     

Preparation and preliminary testing of cermet inert anode for aluminum electrolysis

1　INTRODUCTIONAluminumhasthelargest productivityamongthenonferrousmetals ,2 4Mtperyearintheworld .Whilegreatprogresshavebeenmadeintheprimaryaluminum production ,theindustrycontinuestopur sueresearchtosolvesomeformidablechallenges ,suchas quitealargeenergyintensity(14 0 0 0 15 0 0 0kW·hpertonaluminum) ,highcon sumptionofcarbonanode(5 0 0 6 0 0kgpertonalu minum) ,significantemissionsofgreenhousegas(1.71tpertonaluminum )andotherdetrimentalgases ,highcapitalinvestmentandcost[1] .Inertelectr…     

小型金属陶瓷惰性阳极的低温铝电解实验

本实验采用自行研制的小型镍铁尖晶石基惰性阳极 (直径 43mm)与冰晶石 -氧化铝系低温电解质 ,在 85 0℃下进行电解实验 ,保持阳极电流密度lA/cm2 ,实验共进行 11小时 ,得到了少量的金属铝。实验结果表明 ,在此电解温度下 ,构成惰性阳极的金属陶瓷材料抗电解质腐蚀的能力较强 ;阳极在实验后出现的裂纹说明材料的抗热震性有待进一步提高 ,而且本实验中惰性阳极与金属导杆的连接方式也需更深入研究。     

Magnetic study of Ti-substituted NiFe2O4 ferrite

The Ni_1+xTi_xFe_2−2xO₄ (0 ≤ x ≤ 0.1) ferrite systems prepared by a semi-chemical route, have been studied by electron paramagnetic resonance (EPR) at X-band, Mössbauer spectroscopy and magnetization measurements at various temperatures. EPR spectra of these samples comprise generally a broad and asymmetric EPR signal. The variation of g_eff and peak-to-peak line width ΔH_pp, with Ti concentration and temperature are attributed to the variation of dipole–dipole interaction and the superexchange interaction. Mössbauer spectra comprise two sets of sextet attributed to Fe³⁺ at two distinct sites-A and -B. Ti⁴⁺ ions are concluded to occupy the octahedral B-sites. Magnetic moment is found to decrease with the increase of Ti⁴⁺ concentration. The effective magnetic field H_eff at the A-sites also follows a similar trend. The reason is attributed to the canted structure of spins in the Ti-doped samples. An anomalous behavior at x = 0.015 is observed in the properties studied here and some sort of phase change is believed to occur at 473 K in these ferrites.     

铝电解金属陶瓷惰性阳极的机械加工及大型化研究

本文用普通钻头和设计的专用走具,采用传统机械加工方法对金属陶瓷铝电解惰性阳极钻孔,同时也研究了金属陶瓷惰性阳极的磨削、抛光等加工方法。用这些方法成功地解决了金属陶瓷铝电解惰性阳极的机械加工和大型化问题。     

Preliminary testing of NiFe_2O_4-NiO as ceramic matrix of cermet inert anode in aluminum electrolysis

1　INTRODUCTIONTheideaofusinginertanodes(alsocallednon consumableoroxygen evolvinganodes)inaluminumproductionisasoldastheHall H啨ｒｏｕｌｔｐｒｏｃｅｓｓ ,dat ingbacktothediscoveryofoneoftheinventors ,Hall[1] .Inertanodesareintendedtoreplacethecon sumablecarbonanodethatiscurrentlyused .Withacarbonanode ,thecellreactionisAl2 O3+ 3/ 2C =2Al+ 3/ 2CO2 (1)where　acryolite basedmelt(Na3AlF6 AlF3 CaF2 )atnear 96 0℃servesassolventforthealumina .Withaninertanode ,thecellreactionwillbeAl2 …