Al2O3微粉添加量对镁合金微弧氧化膜特性影响研究

为了研究添加Al₂O₃微粉对AZ31A镁合金微弧氧化膜特性影响,在不同浓度Al₂O₃微粉电解液中对其进行了微弧氧化处理。利用扫描电镜(SEM)观察微弧氧化膜形貌,能谱仪(EDS)分析了膜层表面Ca、Mg、O、Al元素分布,X射线衍射仪(XRD)分析了相组成,测定了膜厚、硬度和氧化液中Al₂O₃表面电荷,讨论了掺杂改性机理。结果表明,加入Al₂O₃微粉后,氧化电压随Al₂O₃添加量增加先增加后降低;氧化膜表面孔洞数量和尺寸减小,膜层表面Ca元素分布逐渐减少,成膜效率降低,膜层致密度和表面疏松层硬度提高,氧化膜主要由MgO和MgO₄等相组成。     

Al_2O_3微粉添加量对镁合金微弧氧化膜特性影响

为了研究添加Al_2O_3微粉对AZ31A镁合金微弧氧化膜特性影响,在不同浓度Al_2O_3微粉氧化液中对其进行了微弧氧化处理。利用扫描电镜(SEM)观察了微弧氧化膜形貌,能谱仪(EDS)分析了膜层表面Ca、Mg、O、Al元素分布,X射线衍射仪(XRD)分析了相组成,测定了膜厚、硬度和氧化液中Al_2O_3表面电荷,讨论了改性机理。结果表明,加入Al_2O_3微粉后,氧化电压随Al_2O_3添加量增加先增加后降低;氧化膜表面孔洞数量和尺寸减小,膜层表面Ca元素分布逐渐减少,成膜效率降低,膜层致密度和表面疏松层硬度提高,氧化膜主要由MgO和MgO_4等相组成。     

铝合金微弧氧化的研究进展

综述了微弧氧化技术的发展历程、成膜机理,论述了铝合金微弧氧化的特点。基于铝合金微弧氧化工艺研究现状,详细阐述了氧化时间、占空比、电压、电流密度、电解液浓度、基体粗糙度、纳米颗粒添加剂以及复合工艺等对铝合金微弧氧化膜层的组织与性能的影响。如电流密度会影响涂层的生长机理,使膜层的表面结构和内部缺陷产生较大的差异;采用不同的电解液所得到的膜层的厚度和粗糙度有明显的区别;在不同的电压参数下膜层的均匀性及膜层中微孔的尺寸大不相同;制备微弧氧化复合涂层以及采用纳米增强颗粒可使膜层的结构和性能有大幅提升。通过改变以上影响因素对铝合金微弧氧化膜层组织和结构加以调控,从而实现了对膜层性能的优化,如膜层的硬度、耐磨性、耐腐蚀性、抗疲劳性能的提高。最后对铝合金微弧氧化的发展方向提出了展望。     

电流密度对铈掺杂铝合金微弧氧化膜性能的影响

在不同电流密度下制备了铈掺杂ZL108合金的微弧氧化膜,研究了电流密度对铈掺杂铝合金微弧氧化膜性能的影响。利用扫描电镜观察微弧氧化膜的表面形貌,采用能谱仪分析膜层元素,利用极化曲线评定耐蚀性,并对微弧氧化膜的厚度、表面硬度进行了测定。结果表明,随着电流密度的增加,氧化电压、膜层厚度均增加,而硬度先上升后降低;微弧氧化膜表面微孔数量及尺寸不断增加,最后出现块状凸起并有裂纹产生。Ce元素在微弧氧化膜表面的分布随电流密度增加而不断均匀。当电流密度为10 A/dm~2时Ce含量最高,此时微弧氧化膜耐蚀性最好。     

ZL系列铸铝合金的微弧氧化

对含硅量为 8 %～ 12 %的ZL系列铸铝合金的微弧氧化工艺条件、膜层结构以及成膜过程进行了研究。结果表明 :采用不对称交变电压和在以硅酸钠为主要成分的复合电解液体系中 ,铸铝合金表面可获得一层性能优异的微弧氧化膜层。电子能谱 (EDS)和X射线衍射 (XRD)分析结果表明微弧氧化膜主要由Al,Si和O元素组成 ,膜的相结构主要为 η Al2 O3 ,α Al2 O3 和SiO2 ,并含有γ Al2 O3 和Mg ,W ,Cu等元素的氧化物。扫描电镜 (SEM)分析表明微弧氧化膜由致密层 (内层 )和疏松层 (外层 )构成 ,疏松层表面存在许多气孔 ,而致密层完整光滑 ,具有较高的显微硬度和优异的耐磨耐蚀性能     

复合氧化制备TC4钛合金表面多孔生物陶瓷膜层

研究了复合氧化工艺在Ti-6Al-4V(TC4)钛合金表面制备多孔TiO_2氧化膜层的工艺和性能。在乙酸钙和磷酸二氢钾电解体系中,运用阳极氧化法、微弧氧化和复合氧化方法在TC4钛合金表面制备了多孔生物陶瓷TiO_2氧化膜层,并讨论了电解液浓度(Ca/P)、成膜电压和成膜时间等参数对膜层膜厚、硬度及粗糙度等性能的影响。采用X射线衍射仪、显微硬度计、便携式粗糙度仪、扫描电镜和电化学工作站等仪器分析了表面TiO_2膜层的物相组成、显微硬度、粗糙度、耐腐蚀性和显微形貌及其结构。研究结果表明:采用恒压阳极氧化技术,在TC4表面可形成一层光滑致密氧化膜层,该膜层粗糙度比预处理过的钛合金表面大0.05μm,厚2~10μm,显微硬度为3200MPa(HV)左右,比钛合金显微硬度3100MPa(HV)略大。再在阳极氧化膜层的基础上进行复合氧化,可以在TC4表面形成具有良好耐腐蚀性的多孔TiO_2膜层。膜层的硬度可以达到7000MPa(HV),厚度达到64μm。     

微弧氧化对铸铝合金在乙二醇水溶液中的耐蚀性能的影响

分别采用自然氧化和微弧氧化方法在AlSi10Mg(a)铸造铝合金表面获得氧化膜层,利用失重法、扫描电镜、交流阻抗、极化曲线等研究了微弧氧化对铸铝合金在38%乙二醇水溶液中的耐蚀性能的影响。结果表明,通过微弧氧化工艺可在砂型铸造铝合金AlSi10Mg(a)材质表面形成连续致密的膜层;相比铸铝合金的自然氧化成膜,微弧氧化成膜显著提高了铸铝合金表面在溶液中的膜层电阻和电荷转移电阻,也提高了铸铝合金的自腐蚀电位和击穿电位,降低了自腐蚀电流密度和膜层维钝电流密度。AlSi10Mg(a)铸造铝合金经微弧氧化后在38%乙二醇溶液中具有良好的耐蚀性能和膜层稳定性。     

添加Ce(SO_4)_2对ZL108铝合金微弧氧化膜特性影响

在Ce(SO_4)_2添加量为0.5 g/L的氧化液中对ZL108铝合金进行了微弧氧化处理,研究了添加Ce(SO_4)_2对微弧氧化膜特性的影响。利用扫描电镜(SEM)观察了微弧氧化膜形貌,能谱仪(EDS)分析了膜层元素,X射线衍射仪(XRD)分析了膜层相组成,测试了膜层厚度、硬度和氧化电压变化曲线。结果表明,添加Ce(SO_4)_2后有利于微弧氧化膜生长,导致氧化电压和硬度增加,Ce元素进入膜层并改变了微弧氧化膜形貌,使膜层γ-Al_2O_3相含量增加。     

TiO2纳米粒子对铝锂合金微弧氧化膜结构及性能的影响

为改善微弧氧化膜层的耐蚀性及力学性能,向电解液中添加TiO₂纳米粒子后对2297铝锂合金进行了微弧氧化。利用SEM、XRD、EDS、辉光放电表征技术及电化学测试技术,分析了TiO₂纳米粒子对微弧氧化膜结构、力学性能及耐蚀性的影响。结果表明：添加TiO₂纳米粒子后,微弧氧化膜层变得平坦致密。随着TiO₂纳米粒子添加量的提高,膜层表面放电通道的孔径逐渐减小,数量逐渐增多。TiO₂纳米粒子会抑制熔融Al₂O₃与电解液中$ {\rm{SiO}}_{\rm{3}}^{{\rm{2 ^- }}}$的接触,所以膜层中Si元素的含量随TiO₂纳米粒子添加量的增加而逐渐下降(原子数分数从初始的10.27%下降到了3.10%)。显微硬度测试结果表明,TiO₂纳米粒子的引入增加了膜层的致密度及平整度,所以膜层的硬度得到了提升(添加1 g/L TiO₂纳米粒子后硬度提高了15%)。电化学测试结果显示,当微弧氧化的其它条件相同时,TiO₂纳米粒子的适量添加会提升膜层的耐蚀性,但过量添加时,由于膜层放电通道数量的增多等原因,其耐蚀性下降。     

LY12铝合金微弧氧化膜层的形成与生长机制

在硅酸钠电解液中利用交流脉冲微弧氧化电源对LY12铝合金进行表面处理,研究微弧氧化初期成膜和后期生长膜层的微观结构差异,探讨铝合金微弧氧化陶瓷层的形成与生长机制。结果表明:初期成膜过程中发生电化学沉积反应,形成电解液中溶质元素的氧化物,增大铝合金表面的阻抗值;后期生长过程中,基体铝与OH-放电所产生的活性氧发生化合反应,形成Al2O3陶瓷层,溶质元素消耗极少;铝合金样品表面获取的预制备膜重新参与陶瓷层的生长,可明显缩短微弧氧化起弧时间、降低起弧电压,同时提升击穿电压的稳定值。     

改进型镁扩散法制备高临界电流密度MgB2超导体性能研究

本文采用一种改进型镁扩散法成功制备出密度达到1.95g/cm₃的MgB₂超导块材。论文研究了不同的热处理条件对MgB₂块材的超导转变温度(T_c)和临界电流密度(J_c)性能的影响。采用最佳热处理条件制备的MgB₂超导体T_c和J_c分别达到了38.1K和0.53MA/cm₂(10K,自场)。为了改进镁扩散法MgB₂超导体中弱的高场磁通钉扎性能,本文还研究了nano-Pr₆O₁₁和C掺杂对MgB₂超导体的临界电流密度和不可逆场(H_irr)的影响。结果表明C掺杂的MgB₂超导体临界电流密度在10K,6T下达到了10₄A/cm₂,该结果比未掺杂MgB₂超导体在同样条件下性能提高了两个量级,甚至比固态反应法制备的nano-C掺杂MgB₂超导体性能更好。利用该方法制备的nano-Pr₆O₁₁掺杂的MgB₂超导体在10K,2T下也比未掺杂样品J_c提高达9.4倍。根据大量的实验结果和理论分析我们提出基于改进型镁扩散法和化学掺杂,包括纳米粒子和C掺杂,很有可能是一种制备高性能MgB₂超导体非常有效的途径。     

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。     

Improved capacity and rate capability of Ru-doped and carbon-coated Li4Ti5O12 anode material

Pure Li₄Ti₅O₁₂, modified Li₄Ti₅O₁₂/C, Li₄Ru_0.01Ti_4.99O₁₂ and Li₄Ru_0.01Ti_4.99O₁₂/C were successfully prepared by a modified solid-state method and its electrochemical properties were investigated. From the XRD patterns, the added sugar or doped Ru did not affect the spinel structure. The results of electrochemical properties revealed that Li₄Ru_0.01Ti_4.99O₁₂/C showed 120 and 110 mAh/g at 5 and 10 C rate after 100 charge/discharge cycles. Li₄Ru_0.01Ti_4.99O₁₂/C exhibited the best rate capability and the highest capacity at 5 and 10 C charge/discharge rate owing to the increase of electronic conductivity and the reduction of interface resistance between particles of Li₄Ti₅O₁₂.It is expected that the Li₄Ru_0.01Ti_4.99O₁₂/C will be a promising anode material to be used in high-rate lithium ion battery.     

Preparation and characteristic of spherical Li3V2(PO4)3

Spherical Li₃V₂(PO₄)₃ was synthesized by using N₂H₄ as reducer. The products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that single-phase, spherical and well-dispersed Li₃V₂(PO₄)₃ has been successfully synthesized in our experimental process. Electrochemical behaviors have been characterized by charge/discharge measurements. The initial discharge capacities of Li₃V₂(PO₄)₃ were 123 mAh g⁻¹ in the voltage range of 3.0–4.3 V and 132 mAh g⁻¹ in the voltage range of 3.0–4.8 V.     

Alloyed W–(Co,Ni,Fe)–C phases for reaction sintering of hardmetals

It has been shown that W–Co–C phases could dissolve a substantial amount of metals such as V, Cr and Ta, which are known to positively influence the microstructure of hardmetals with respect to uniform grain size distribution and fine grain size. This offers a tool to circumvent the conventional doping of hardmetals with individual carbides. In the present study we used double- and triple-alloyed κ-W₉Co₃C₄ (i.e. κ-(W,V,Cr)₉Co₃C₄ and κ-(W,V,Cr,Ta)₉Co₃C₄) and applied a variety of sintering experiments to obtain WC–Co, WC–(Ti,Ta,Nb)C–Co and WC–(Ti,Ta,Nb)(C,N)–Co hardmetals. We also prepared κ-W₉Fe₃C₄, alloyed κ-W₉Ni₃C₄, and κ-W₉(Fe/Ni)₃C₄, and used the latter for sintering.     

The high-temperature corrosion behavior of Nb-Al alloys in a H2/H2S/H2O gas mixture

The corrosion behavior of pure Nb and three Nb Al alloys containing 12.5, 25, and 75 at.% Al was studied over the temperature range of 800–1000°C in a H₂/H₂S/H₂O gas mixture. Except for the Nb-12.5Al alloy consisting of a two phase structure of -Nb and Nb₃Al, other alloys studied were single phase. The corrosion kinetics followed the parabolic rate law in all cases, regardless of temperature and alloy composition. The parabolic rate constants increased with increasing temperature, but fluctuated with increasing Al content. The Nb-75Al alloy exhibited the best corrosion resistance among all alloys studied, whose corrosion rates are 1.6–2.2 orders of magnitude lower than those of pure-Nb (depending on temperature). An exclusive NbO₂ layer was formed on pure Nb, while heterophasic scales were observed on Nb-Al alloys whose compositions and amounts strongly depended on Al content and temperature. The scales formed on Nb-12.5Al consisted of mostly NbO₂ and minor amounts of Nb₂O₅, NbS2, and -Al₂O₃, while the scales formed on Nb-25Al consisted of mostly Nb₂O₅ and some -Al₂O₃. The scales formed on Nb-75Al consisted of mostly -Al₂O₃ and Nb₃S₄ atT 900°C, and mostly -Al₂O₃ , Nb₃S₄ and some AlNbO₄ at 1000°C. The formation of -Al₂O₃ and Nb₃S₄ resulted in a significant reduction of the corrosion rates.     

Effects of Mo and Al Additions on the Sulfidation Behavior of 310 Stainless Steel

The high-temperature sulfidation behavior of 310stainless steel (310SS) with Mo and Al additions (up to10 at.%) was studied over the temperature range700-900°C in pure-sulfur vapor over the range of 10^-3 to 10^-1 atm. Thecorrosion kinetics followed the parabolic rate law inall cases and the sulfidation rates increased withincreasing temperature and sulfur pressure. Thesulfidation rates decreased with increasing Mo and Al contents and it wasfound that the addition of 10 at.% Mo resulted in themost pronounced reduction among the alloys studied. Thescales formed on 310SS with Mo additions were complex, consisting of an outer layer of ironsulfide (with dissolved Cr), (Fe,Ni)₉S₈, andCr₂S₃/Cr₃S₄(with dissolved Fe), and an inner heterophasic layer ofFe_1-xS,Cr₂S₃/Cr₃S₄,NiCr₂S₄,Fe_1.25Mo₆S_7.7, FeMo₂S₄, andMoS₂. The scales formed on 310SS with Mo andAl additions had a similar mixture as above, except thatAl_0.55Mo₂S₄ was alsoobserved in the inner layer. The formation ofMoS₂ andAl_0.55Mo₂S₄ partly blocked the transport of cations throughthe inner scale, resulting in the reduction of thesulfidation rates compared to 310SS.     

Effects of K2O-Li2O doping on surface and catalytic properties of Fe2O3/Cr2O3 system

The effects of K₂O and Li₂O-doping (0.5, 0.75 and 1.5 mol%) of Fe₂O₃/Cr₂O₃ system on its surface and the catalytic properties were investigated. Pure and differently doped solids were calcined in air at 400-600 °C. The formula of the un-doped calcined solid was 0.85Fe₂O₃:0.15Cr₂O₃. The techniques employed were TGA, DTA, XRD, N₂ adsorption at −196 °C and catalytic oxidation of CO oxidation by O₂ at 200-300 °C. The results revealed that DTA curves of pure mixed solids consisted of one endothermic peak and two exothermic peaks. Pure and doped mixed solids calcined at 400 °C are amorphous in nature and turned to α-Fe₂O₃ upon heating at 500 and 600 °C. K₂O and Li₂O doping conducted at 500 or 600 °C modified the degree of crystallinity and crystallite size of all phases present which consisted of a mixture of nanocrystalline α- and γ-Fe₂O₃ together with K₂FeO₄ and LiFe₅O₈ phases. However, the heavily Li₂O-doped sample consisted only of LiFe₅O₈ phase. The specific surface area of the system investigated decreased to an extent proportional to the amount of K₂O and Li₂O added. On the other hand, the catalytic activity was found to increase by increasing the amount of K₂O and Li₂O added. The maximum increase in the catalytic activity, expressed as the reaction rate constant (k) measured at 200 °C, attained 30.8% and 26.5% for K₂O and Li₂O doping, respectively. The doping process did not modify the activation energy of the catalyzed reaction but rather increased the concentration of the active sites without changing their energetic nature.     

固相-水热法制备LiFePO4-Li3V2（PO4）3复合材料及其电化学性能（英文）

分别采用固相-水热法和球磨法制备磷酸亚铁锂-磷酸钒锂复合正极材料(LiFePO4-Li3V2(PO4)3)。电化学性能测试表明,LiFePO4-Li3V2(PO4)3复合正极材料的电化学性能远远高于 LiFePO4和 Li3V2(PO4)3单独作为正极材料的性能,并且以固相-水热法制备的复合材料性能优于以球磨法制得的复合材料。研究发现 LiFePO4-Li3V2(PO4)3复合材料有 4 个氧化还原峰,相当于 LiFePO4 和 Li3V2(PO4)3 氧化还原峰的叠加。采用固相-水热法制备的LiFePO4-Li3V2(PO4)3 复合材料形貌较为规则,且有新相物质产生,这是导致其电化学性能较好的原因。     

Synthesis of lanthanum carbonate nanoparticles via sonochemical method for preparation of lanthanum hydroxide and lanthanum oxide nanoparticles

Lanthanum carbonate nanoparticles were synthesized from the reaction of lanthanum acetate and Na₂CO₃ under sonication via sonochemical method. Lanthanum hydroxide nanoparticles were prepared by facial hydrothermal processing from the resulted product at 110 °C for 24 h. The role of surfactant, calcination temperature and sonication time were investigated on the morphology and particle size of the products. Products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrum (XPS), and Fourier transform infrared (FT-IR) spectra. La₂O₃ nanoparticles were obtained by calcinations of the nanoparticles of lanthanum carbonate at 600 °C.