Thermally oxidized aluminum as catalyst-support layer for vertically aligned single-walled carbon nanotube growth using ethanol

Characteristics and role of Al oxide (Al-O) films used as catalyst-support layer for vertical growth of single-walled carbon nanotubes (SWCNTs) were studied. EB-deposited Al films (20 nm) were thermally-oxidized at 400 oC (10 min, static air) to produce the most appropriate surface structure of Al-O. Al-O catalyst-support layers were characterized using various analytical measurements, i.e., atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and spectroscopy ellipsometry (SE). The thermally-oxidized Al-O has a highly-roughened surface, and also has the most suitable surface chemical states compared to other type of Al-O support layers. We suggest that the surface of thermally-oxidized Al-O characterized in this work enhanced Co catalyst activity to promote the vertically-aligned SWCNT growth

Electrochemical Analyses of Carbon Nanotube Based Supercapacitor in 1M LiPF6 Organic Electrolyte

Excellent electrical conductivity, high mesoporosity, and high electrolyte accessibility of carbon nanotube (CNT) ensure a high charge transport capability and hence a high power density for the capacitor. However, performance of the supercapacitors should be improved to satisfy the increasing demands for various applications. In this article, commercial CNT was used as active material and a non-aqueous solution, LiPF6 was used as electrolyte to fabricate electrodes for EDLC-type supercapacitor. Electrochemical measurements such as BET analysis and cyclic voltammetry were performed to determine the capacitance behavior of the device. As results, specific surface area of the CNTs was found to be 609 m2 g-1, and specific capacitance was calculated to be 42 F g-1

Synthesis of Fe catalyst nanoparticles by solution process towards carbon nanotube growth

The iron catalyst nanoparticles were prepared on silicon wafers by solution process, which first spins coat the solution of iron (III) nitrate nonahydrate and colloidal solution, and then are heated to obtain the formation of iron nanoparticles. The effects of different spin speed and heat treatment parameters during the solution process were investigated. As a result, the smallest thickness of the Fe catalyst thin films is 78 nm, and the smallest Fe catalyst nanoparticles, i.e. 9.67 nm, were obtained at the highest spin speed of 8000 rev min-1 and 500oC. The uniformity of the thin films was also found to increase with increasing spin speed. The particle and thickness analysis was performed by means of field emission scanning electron microscopy

Systematic review of catalyst nanoparticles synthesized by solution process: towards efficient carbon nanotube growth

Nano-field research has been expanded rapidly since those tiny materials such as carbon nanotubes (CNTs), cobalt catalyst and iron catalyst can give huge impact to the application products with their extraordinary properties. The scientific discovery of these materials can be defined as a magic key to solve the raw materials shortage and unlock the limitation performance of the devices. CNTs have been found to be one of the new nanomaterials that can improve different kind of devices’ performance. CNT can be grown on the substrates with the presence of active metal catalysts. Since small metal catalyst particles (diameter <10 nm) are crucial in growing CNTs, the deposition method of metal catalyst on the substrates has been studied. The optional processes using solutions to produce catalyst nanoparticles will be discussed in this review. Sol–gel process along with spin coating is the most suitable deposition method with low cost of production and the easiness to control particle size deposited on the substrates

Understanding the structural properties of feasible chemically reduced graphene

The production of pristine graphene materials for industrialization, often limited by the complicated synthesis route, has introduced other graphene derivatives with a workable and facile synthesis route, especially for mass production. For the chemical exfoliation process, the synthesis involves oxidants and reducing agents to exfoliate the graphene layer from the 3D graphite and remove excess oxygen-containing functional groups yielding graphene-like materials known as reduced graphene oxide (rGO). This work feasibly produces rGO with nanoplatelet morphology through the green solution-processable method. Upon reduction, the crystallite size for the a-axis (La) is more prominent (22.50 Å) than the crystallite size for the c-axis (Lc) (11.50 Å), suggesting the nanoplatelets structure of the end product, which is also confirmed by the morphology. The integrated intensity (ID/IG) ratio and average defect density (nD) of as-prepared rGO confirmed the sp2 restoration in the graphitic structure. Overall, the Raman and X-ray diffraction (XRD) characterization parameters validate the production of rGO nanoplatelets, especially with four graphene layers per domain, suggesting that high-quality rGO are achievable and ready to be implemented for the large-scale production

Direct growth of vertically aligned single-walled CNTs on conducting substrate and its electrochemical performance in ionic liquids

We report fabrication of vertically-aligned single-walled carbon nanotube (VA-SWCNT) electrodes for a symmetric electrochemical capacitor using a simple ethanol-based CNT growth system. From the CNT direct growth technique, the electrode was easily prepared, and consequently assembled with ionic liquid as electrolyte. VA-SWCNTs were directly grown on conducting SUS 310S foils in which the binder material was not incorporated in the capacitor structure. This capacitor demonstrated excellent gravimetric capacitance and a high rate capability. From the cyclic voltammetric analysis, the capacitance was contributed not only from the ideal double layer capacitance, but also from faradaic processes that might have occurred during charge-discharge. Other than the capacitance, the VA-SWCNT capacitor was also measured by using frequency response (impedance) and charge-discharge analyses

Development of High Performance Electrochemical Capacitor: A Systematic Review of Electrode Fabrication Technique Based on Different Carbon Materials

Increasing demand for energy requirement has attracted considerable attention among researchers to develop efficient energy storage device. Among energy storage devices, electrochemical capacitor (EC) has great potential for its capability to deliver more power than batteries and store more energy than conventional capacitors. The electrode or active material is the most crucial factor in determining the device properties. Recently, carbon based materials play significant roles as electrode materials and possesses remarkably significant achievements toward the development of sustainable energy storage applications. Electrode fabrication technique is another important factor to be considered. Hence, this article reviews the electrode fabrication techniques for EC based on different types of carbon as electrode materials, and their EC performances measured by techniques such as cyclic voltammetry and charge discharge characteristics are also discussed

Formation of Cr23C6 During the Sensitization of AISI 304 Stainless Steel and its Effect to Pitting Corrosion

The metallic carbide precipitation was observed after the sensitization of AISI 304 stainless steel specimens in neutral flame by using oxy-fuel and slowly cooled in the air. Correlation between corrosion and X-Ray Diffraction (XRD) shows that the enrichment of Cr23C6 in the microstructure of AISI 304 worsens the pitting corrosion resistance properties as the sensitization time increases from 5 to 60 s. However, the precipitation dissolved and corrosion resistance properties improved after the specimens treated in solution quenching treatment at 1130 oC, soaked from 24 – 120 min, then rapidly cooled in water

Nanostructuring Ultra-thin Co Films to Active Catalyst Particles for Vertically Aligned Single-Walled CNT Growth

In the field of material synthesis using chemically-derived technique, nanostructuring metal catalyst particles towards high quality production of carbon nanotubes (CNTs) has been very attractive. In this work, cobalt (Co) which used as catalyst for vertical growth of CNTs were studied by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Aluminum (Al) films (20 nm) were thermally-oxidized to form aluminum oxide (Al-O) as to support 0.5 nm Co catalyst during CNT growth. In growing CNTs by using chemical vapor deposition (CVD) technique, the role and characters of all involving materials are crucial to the growth result. From the Co/Al-O substrate and at 650 oC of CVD temperature, 33-m thick of vertically aligned single-walled CNT (VA-SWCNT) forest was grown. TEM particle analysis revealed that the Co particles have an average of 3.50 nm which experimentally and in principle favored the growth of highly demanded VA-SWCNTs. The as-prepared Co particles are suggested chemically active for the CNT growth. In addition, XPS analysis confirmed the surface chemical state of Co particles prior to the VA-SWCNT growth using ethanol based CVD system