Ti基准晶合金电化学性能及表面修饰

发布时间：2018-02-03 18:42

本文关键词： Ti-V-Ni 储氢合金电化学性能表面包覆化学镀 PECVD　出处：《吉林大学》2016年博士论文　论文类型：学位论文

【摘要】：Ti基准晶合金由于具有极高的气态储氢量而备受关注,但难活化、室温容量低、循环稳定性差等问题制约了其在电化学领域中的应用。而且Ti基准晶复相合金的电化学活化性能以及容量衰退机制还有待于深入研究。为此,本论文中,重点研究了Ti基准晶复相合金的电化学储氢活化性能以及影响因素,并针对其循环稳定性进行了一系列的表面改性,主要研究内容及结果如下:分别采用机械合金化和急冷甩带法制备了Ti40.83Zr40.83Ni18.34准晶合金,发现急冷甩带法制备的合金具有更好的结晶性,为纯二十面体准晶相。合金的室温放电容量只有50 m Ah g-1,即使经过热碱活化也没有得到改善。针对合金的电化学活性差以及表面容易生成致密的氧化层等因素,将合金颗粒球磨粉碎后进行氧化石墨烯包覆处理,发现用干磨或湿磨都会降低合金的放电容量,但用乙醇为分散剂湿磨对合金结构破坏较弱而且能得到尺寸适合包覆的粒径,可以保证电极在室温下具有良好的放电性能。用急冷甩带法制备了Ti1.4V0.6Ni合金,合金晶体结构中除了二十面体准晶相还有Ti Ni相或非晶相的存在。用置换还原法对合金进行了表面化学镀铜处理,通过控制Cu2+的浓度得到了不同质量比的镀层。通过电化学测试发现,合金在充放电循环过程中的容量衰减主要是由于活性物质V在碱性电解液中的溶解以及合金粉化造成的。而且V的溶解过程分为两步,第一步是在活化过程中的一次性溶解,第二步是在循环过程中的缓慢溶解。合金表面镀铜对第二步溶解具有了明显的抑制作用,当镀铜含量为10 wt.%时,第二步中的V溶解几乎被完全抑制。合金经过100次充放电测试,容量保持率较空白合金提升了23%。包覆层也可以有效抑制合金的表面氧化和粉化。采用液相还原法在Ti1.4V0.6Ni合金表面化学镀镍,通过控制Ni2+的浓度以及反应条件可以获得质量可控的镀层。经过100次循环放电测试,镀镍合金的容量保持率提升了35%。镀镍层比镀铜层更稳定,可以有效的抑制氧化膜的产生、合金颗粒的粉化以及V的溶解,其原因是合金富Ni层与镀镍层同时在循环过程中对合金起到了保护作用。采用等离子体气相沉积(PECVD)在Ti1.4V0.6Ni合金电极表面制备了不同厚度的非晶碳膜。碳膜平整、致密,主要由sp2和sp3杂化碳组成,随着膜厚度增加,sp3碳含量上升。电化学测试表明,碳膜可以有效降低合金电极的电荷转移电阻,但是随着sp3碳含量的增加会导致电极极化增大。碳膜对活性物质的溶解起到很好的抑制作用,而且其结构经过100次循环后还能保持稳定包覆的状态。采用电化学沉积在Ti1.4V0.6Ni合金电极表面实现了还原氧化石墨烯的包覆,制备的包覆层平整而且缺陷很少。从测试结果中发现,用HI作为还原剂可以得到还原效果很好的石墨烯膜,而且处理过程中不存在劣化合金放电性能的副反应。在电化学测试中,包覆层减小了合金电极的阻抗和电压极化,经过50次循环测试后,石墨烯包覆的电极保持有145 m Ah g-1的放电容量,比未包覆电极的放电容量高出13.8%。
[Abstract]:Ti base amorphous alloys have attracted much attention because of the gaseous hydrogen storage capacity is high, but difficult to activate, room temperature low capacity, poor cycling stability problems restricting its application in the field of electrochemistry and electrochemical Ti quasicrystal multiphase alloy activation performance and capacity degradation mechanism also needs to be further researched. Therefore, this thesis in the focus on the electrochemical hydrogen storage of Ti quasicrystal multiphase alloy activation properties and influence factors, and the cycle stability of a series of surface modification, the main research contents and results are as follows: using mechanical alloying and quenching rejection of Ti40.83Zr40.83Ni18.34 quasicrystal alloy prepared, the crystallinity was found sharp cold rejection alloy belt prepared has better, pure twenty icosahedral quasicrystal phase at room temperature. The discharge capacity was 50 m Ah g-1 alloy, even after heat alkali activation has not been improved. Aiming at the The difference and the factors of electrochemical activity of gold surface is easy to generate a dense oxide layer, the alloy particle grinding after the graphene oxide coating, found by wet or dry will reduce the discharge capacity of the alloy, but the use of ethanol as dispersant wet milling alloy structure damage is weak and can get the particle size for coating the size, can ensure that the electrode has good discharge performance at room temperature. With a quenching rejection Ti1.4V0.6Ni alloy prepared alloy, crystal structure of icosahedral quasicrystal phase in addition to twenty and Ti Ni phase and amorphous phase. The alloy was treated by electroless copper plating on the surface displacement reduction method, by controlling the concentration of Cu2+ the coatings with different mass ratio. Electrochemical tests showed that the capacity of the alloy in the charge discharge cycle in the process of decay is mainly due to the dissolution of active material V in alkaline electrolyte and alloy Gold powder caused by V. And the dissolution process is divided into two steps, the first step is one-time dissolved in the activation process, the second step is slowly dissolved in the circulation process. Copper alloy surface has obvious inhibitory effect on the second steps of dissolution, when the copper content was 10 wt.%, in the second step the dissolution of V was almost completely inhibited. The alloy after 100 charge discharge test, the capacity retention rate compared with blank surface oxidation and improve the alloy powder coating 23%. alloy can be effectively restrained. The liquid phase reduction method on the surface of Ti1.4V0.6Ni alloy chemical nickel plating, by controlling the concentration of Ni2+ and reaction conditions can get quality control coating. After 100 cycles the discharge test, the capacity retention rate of nickel alloy promoted 35%. nickel plating copper layer is more stable than the oxide film, can inhibit the generation of effective, alloy particles powder and V solution, The reason is that the Ni rich layer and nickel alloy layer at the same time in the circulation process of alloy plays a protective role. By plasma chemical vapor deposition (PECVD) on the surface of Ti1.4V0.6Ni alloy electrode was prepared by amorphous carbon films with different thickness. The carbon film is smooth, dense, mainly composed of SP2 and SP3 hybrid carbon membrane with. The increase of the thickness of SP3 increased carbon content. The electrochemical tests show that carbon membrane can effectively reduce the charge transfer resistance of the alloy electrode, but with the increase of SP3 carbon content will lead to polarization increases. Dissolved carbon film on active substances play a good inhibitory effect, and its structure after 100 cycles can maintain stable coating state. By electrochemical deposition on the surface of Ti1.4V0.6Ni alloy coated electrodes to achieve reduction of graphene oxide, preparation of coated flat and rarely found defects. From the test results, using HI as a reductant In order to get the reduced graphene film effect is very good, and side effects of discharge performance deterioration alloy does not exist in the process. In the electrochemical test, the coating resistance of the alloy electrode and the voltage polarization decreases after 50 cycles after the test, the graphene coated electrode discharge has a capacity of 145 m Ah g-1 that is 13.8%. higher than the discharge capacity of the uncoated electrode

【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG139.7

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