Performance of electrical double layer capacitors with porous carbons derived from rice husk

The porous structure and electrochemical double layer capacitance of porous carbons prepared from rice husks by using alkali hydroxide as activating agents were investigated. Three samples of carbons prepared by NaOH-activation, three samples prepared by KOH-activation and two samples of commercial carbons have been studied. The porosity of the carbons was characterized by nitrogen adsorption isotherms at 77 K and electrochemical constant current cycling method was used to measure the double layer capacitance. The specific capacitance of the carbons is not linearly proportional to the surface area. Additionally, the double layer capacitance strongly depends on the pore structure and the functional groups. A specific capacitance larger than 200 F g⁻¹ was achieved by using the porous carbon prepared with NaOH (activation temperature: 750 °C; activation time: 30 min). All the carbons prepared with rice husk in this study have larger double layer capacitance (125–210 F g⁻¹) than the commercial grade carbons (78–100 F g⁻¹).     

微反射镜和光纤自对准V型槽的制作

用纯KOH水溶液和KOH +IPA混合水溶液在 ( 1 0 0 )硅片上沿 <1 0 0 >方向上腐蚀所暴露的平面是不同的。纯KOH水溶液中总是能暴露与衬底垂直的 {1 0 0 }面 ,在KOH +IPA溶液中 ,随着KOH的浓度不同将暴露 {1 1 0 }和 {1 0 0 }面。使用KOH浓度为 50 %的KOH +IPA溶液 ,在 ( 1 0 0 )硅片上一次掩模制作微反射镜和光纤自对准V型槽 ,微镜的表面粗糙度低于 1 0nm。     

Microstructural analysis of the ageing of pseudo-binary (Ti,Zr)Ni intermetallic compounds as negative electrodes of Ni-MH batteries

Ageing of Ti_1.02−xZr_xNi_0.98 (0 ≤ x ≤ 0.48) compounds during the electrochemical cycling in aqueous KOH electrolyte has been investigated. Microstructural and chemical characterisation, mostly conducted by transmission electron microscopy, show that for all electrodes their activation results from calendar KOH corrosion. After activation, Zr substituted compounds attain much higher capacity (∼350 mAh g⁻¹) than the binary TiNi compound (∼150 mAh g⁻¹) but their cycle-life is poor. The mechanism of electrode degradation differs for the binary and the substituted compounds. For TiNi, degradation is due to KOH corrosion whereas, for substituted compounds, it mainly results from the loss of electrical contact due to particle pulverisation. For all electrodes, KOH corrosion produces a double surface layer formed by an inner two-phase (Ni-NiO) nanocrystalline layer and an outer (Ti,Zr)O₂ amorphous layer.     

电极浸渍电解液方式对双电层电容器的影响

以活性碳纤维(ACF)电极为研究对象,用质量分数为0.2的氢氧化钾(KOH)作为电解液制作KOH-ACF浸渍电极,研究了浸泡时间、搅拌、真空度、温度等的影响因素,目的使电解液能更有效的进入ACF电极,研究发现,浸泡时间长、真空度高和温度低都有利于电解液进入电极,搅拌可以加快浸泡吸附的速度,制成的双电层电容器比电容可达70F／g。     

Enhanced alkaline stability and performance of alkali‐doped quaternized poly(vinyl alcohol) membranes for passive direct ethanol fuel cell

Direct ethanol fuel cells (DEFCs) emerge as the new research energy field since fast production of electricity, high efficiency conversion, and simple fabrication process. The production cost, conductivity properties, and ethanol permeability of membrane were the main problem that limited the DEFC performance and commercialization. In this study, a low cost, good ionic conductivity and low ethanol permeability of an anion exchange membrane based on incorporation KOH‐doped quaternized poly(vinyl alcohol) (QPVA) membrane (designed as QPVA/KOH) is synthesized and cross‐linked with glutaraldehyde solution. The membrane is expected to cut the production cost and enhance the performance. In this work, an optimum of alkali‐doped concentration has influence the membrane performance. The membrane has reveal high chemical stability even doped with 8‐M KOH solution in 100°C. The morphology of membranes remained unbreakable and achieved high range of ionic conductivity (~10^?2 S cm^?1). The membranes present maximum ionic conductivity 1.29 × 10^?2 S cm^?1 at 30°C and 3.07 × 10^?2 S cm^?1 at 70°C. The ethanol permeability of membrane is lower compared with the commercial membranes. Power density of alkaline DEFCs with platinum‐based catalyst by using cross‐linked QPVA/KOH membrane is 5.88 mW cm^?2, which is higher than commercial membranes at 30°C temperature. At 70°C, power density has increased up to 11.28 mW cm^?2 and significantly increased up to 22.82 mW cm^?2 via the nonplatinum‐based catalyst. Moreover, according to the durability test, the performance of passive alkaline DEFC by using cross‐linked QPVA/KOH membrane has maintained at 36.2% level. With such efficiency, the stack current density has been able to stay above 120 mA cm^?2 for over 1000 hours, at 70°C.     

微粒嵌布难选金红石矿煤基深度还原热力学

关键词：金红石矿;深度还原;配碳比;KOH;K2CO3     

阵列光开关驱动结构制作工艺的研究

采用KOH溶液湿法腐蚀制作阵列光开关的微反射镜上电极.腐蚀表面的不平整影响了光开关的驱动扭臂结构的制作.采用合理配比的HF,HNO3和CH3COOH腐蚀剂对制作的微反射镜阵列硅片进行抛光处理,抛光后微反射镜表面和腐蚀的(110)面均有较大的改善,并且抛光不影响器件的结构,最后制作出了均匀一致的光开关阵列扭臂驱动结构.     

Optimizing the conditions of multi-walled carbon nanotubes surface activation and loading metal nanoparticles for enhanced hydrogen storage

In this study, the effect of surface activation of multi-walled carbon nanotubes (MWCNTs) by KOH along with loading of cobalt and lithium nanoparticles on the surface of MWCNTs are investigated. In the first step, surface activation parameters, i.e. MWCNT/KOH weight ratio, activation temperature, and activation time are optimized to give the highest hydrogen uptake. According to obtained results, the optimum synthesis conditions are MWCNT/KOH weight ratio of 1:5, 800 °C, and 1 h of activation duration. Afterward, cobalt and lithium metal nanoparticles are doped discretely on the surface of activated nanotubes. It is demonstrated that amounts of loaded cobalt and lithium metals are 5.5 and 1.9% wt, respectively. In addition, it is revealed that the amount of hydrogen storage capacity for cobalt-loaded and lithium-loaded MWCNTs are 1.06% wt. and 1.33% wt., respectively (at 278 K) which are higher than the capacity of pristine and activated MWCNT samples.