•Flame-synthesized TiO2/carbon composite particles were used for anode materials.•TiO2 and carbon determine capacity retention and discharge capacity, respectively.•Optimal synthesis condition was ...found regarding capacity and retention of the cells.
A flame-synthesized TiO2-based anode material was developed by conducting in-situ composition of TiO2 particles and amorphous carbon particles in a flame. The particle characteristics of the collected composite particles were subsequently examined, and the performances of lithium-ion secondary batteries that used these composite particles as anode materials were measured and evaluated. The aggregates of synthesized and collected particles were confirmed through SEM, EDS, and XRD analysis, revealing a mixture of amorphous carbon particles and TiO2 particles with ranging in size from about 40 to 80 nm. Analysis of the charge/discharge test results on these coin cells indicates that TiO2 and amorphous carbon determine capacity retention and discharge capacity, respectively. Considering both capacity and retention of the cells, optimal flame synthesis conditions were found.
Abstract
Recently, some studies have utilized silicon (Si) as an anode material of lithium ion battery by recycling Si from the slurry of wafer slicing dust. The filtration of Si particles condensed ...from Si vapors that were exhausted from the ingot growing furnace could propose another method of Si recycling. In this study, we investigated the possibility of using such collected silicon oxides (SiO
x
) particles as an anode material. After collecting SiO
x
particles, FE-SEM, TEM, EDS, XRD, XPS analysis, and charge/discharge test were carried out to investigate characteristics and usability of these particles. FE-SEM and FE-TEM images showed that these particles mainly consisted of spherical primary particles with a diameter of 10 nm or less. Agglomerates of these primary particles were larger than 300 nm in diameter. In TEM image and EDS analysis, crystalline particles were observed along with amorphous particles. As a result of XRD analysis, amorphous silica (SiO
2
) and crystalline Si were observed. Charge/discharge tests were carried out to determine the feasibility of using these particles as an anode material for lithium ion batteries. A cycle efficiency of 40.6% was obtained in the test in which the total number of charge/discharge cycle was 100 under the condition of C-rate 0.2 for the first three times and C-rate 1.0 for the remaining 97 times. Results showed that these collected particles could be used as an anode material for lithium ion batteries.
This study involves the investigation of mechanical damping and thermal stability of hybrid epoxy composites with two types of fillers, graphitized carbon nanofiber (CNF) and micron size silicon ...dioxide (SiO2) particles. While viscoelastic properties of the composites were characterized for the study of mechanical damping, the linear coefficient of thermal expansion (CTE) was evaluated for investigation of thermal stability of the hybrid composites. The effect of filler loading was investigated with respect to both mechanical and thermal stability of the hybrid composite materials. It has been found that the addition of 3% weight fraction of SiO2 particles along with 3% weight fraction of CNF can improve damping loss factors by up to 15.6% at room temperature while at the same time improving thermal stability with up to 15% reductions in CTE. This study also presents semi-empirical models which can account for both the fillers in prediction of viscoelastic properties and CTE of the hybrid composites. It is observed that there is reasonable agreement in both mechanical damping and CTE for the hybrid composites between the experimental data and the predicted data.
A foldable and cuttable sheet heater was fabricated using single-walled carbon nanotubes (SWCNTs) and aramid nanofibers (ANFs). SWCNTs are particularly well suited for Joule heating based on their ...high thermal stability, electrical properties, high current density, and aspect ratio. When the SWCNT/ANF composite reaches a high temperature during Joule heating, ANFs will endure this temperature due to their impressive thermal stability, derived from aramid fibers. With the aim of achieving a synergistic effect between the SWCNTs and ANFs, 0–100 wt% SWCNT/ANF composite sheets were fabricated by tip-type sonication and vacuum filtration. After assessing the thermal stability and electrical properties of the composite sheets, the Joule heating effect was analyzed. TGA showed that our sheet had high thermal stability in an air condition up to around 500 °C. The electrical conductivity of the composite sheet was improved as the amount of SWCNT added rose to 790.0 and 747.5 S/cm in the 75 and 100_SWCNTs/ANF, respectively. The maximum heating temperature, up to 280 °C, reached by Joule heating was measured as a function of SWCNT content and input voltage, and the relationship among SWCNT content, input voltage, heating temperature, and electric power was described. Mechanical properties were also measured in a temperature range similar to the heating temperature of 300 °C reached by Joule heating. Ultimately, we obtained a foldable and cuttable composite sheet with a stretchable structure, capable of being molded into a variety of shapes. This energy-efficient material can potentially be employed in any device in which a heater is required to deliver high temperatures.
We designed and tested a manufacturing process that resulted in the formation of composites with maximized electrical conductivity and optimized electromagnetic interference (EMI) shielding ...effectiveness (SE) properties. Single-walled carbon nanotube (SWCNT) paper, which is a microscopic aggregate of van der Waals force interaction, was impregnated with semi-cured epoxy to make SWCNT prepregs. These prepregs were completely cured into SWCNT/epoxy composites. Fabricating and curing processes were executed under proper temperature cycle depending on the time. We inspected SWCNT paper and the interfacial state between the SWCNTs and epoxy in the composite with a field emission-scanning electron microscopy and calculated the SWCNT weight fraction through thermogravimetric analysis measurements. Using these observations, electrical conductivity and EMI SE were investigated according to thickness which could be controlled by the suggested manufacturing process as 1-, 5- and 10-layer composites. Finally, we determined ideal composite thickness and the associated number of prepreg layers using skin depth theory.
Numerical analysis using CFD facilitates the problem of investigating lean methane-air mixtures on the Pt-coated catalytic walls, involving homogeneous gaseous species and heterogeneous catalytic ...surface reactions. Parametric studies on the inlet velocity and temperature alter the location of the commencement of surface reactions, and as a result, the prudent selection of appropriate flow configurations in the catalytic combustion process can be determined. The results show that the temperature is regulated by the stable combustion process attaining an adiabatic flame temperature, while on the other hand, immediately after the occurrence of flame ignition, sharp rises of gaseous species are observed, proving that the gas reactions are induced by the catalytic surface activity. In addition, this work analogized the Navier-Stokes model with the 1-D plug-flow reactor model to reveal the range of validity of various approximations.
This study was conducted to investigate the characteristics of silicon nanoparticles using waste vapors generated from a single-crystal silicon ingot growth furnace and to study their potential ...applications. The silicon vapors generated in the silicon ingot growth furnace were collected in the form of nanoparticles, and SEM, EDS, BET and XRD analyzes were performed to analyze the characteristics of the collected particles. The particles were in the form of agglomerated nanoparticles with a specific surface area of 176 m2 / g and were amorphous SiOx particles with low crystallinity. In the future, we plan to study the application fields of the collected nanoparticles.
Carbon fibers are commonly used in many specialized, high-performance applications such as race cars and aircraft due to their lightweight and high durability. The most important stage in the ...production of carbon fibers is the carbonization process. During this process, carbon fibers are subjected to high temperatures in the absence of oxygen to prevent fibers from burning. Labyrinth seals are attached to a carbonization furnace to prevent airflow into the furnace and to assist in the elimination of off-gases. This study investigated flow characteristics inside a carbonization furnace and the effects of different geometric parameters of labyrinth seals such as labyrinth tooth shape, number of teeth, and tooth clearance. Varying carbonization furnace operating conditions were also studied in regard to flow behavior, including fiber movement and outlet vacuum pressure. A high working gas flow rate at the furnace inlet resulted in recirculation zones. Properly regulated gas flow from the main and labyrinth inlets enabled uniform flow around the fibers’ inlet and outlet which prevented air from being trapped in the reactor. Flow behavior was minimally effected by changes to labyrinth seal geometry such as tooth length, tooth clearance, and outlet pressure. However, the movement of fibers had a clear effect on flow characteristics in the furnace.
In this study, epoxy composites were reinforced with multi-walled carbon nanotubes and fused silica particles, dispersing the fillers within the epoxy resin based on a simple physical method using ...only shear mixing and ultrasonication. The hybrid composite specimens with 0.6 wt% of carbon nanotubes and 50 wt% of silica particles showed improved mechanical properties, with increase in tensile strength and Young’s modulus up to 12 and 37%, respectively, with respect to those of the baseline specimens. The experimental results showed that the low thermal expansion of the silica particles improved the thermal stability of the composites compared with that of the baseline specimen, whereas the thermal expansion slightly increased, due to the increased heat transfer from the exterior to the interior of specimens by the carbon nanotube filler. The coefficient of thermal expansion of the hybrid composite specimen reinforced with 0.6 wt% of carbon nanotubes and 50 wt% of silica particles was decreased by 25%, and the thermal conductivity was increased by about 84%, compared with those of the baseline specimen.
In this article, TiO₂ nanoparticles were synthesized by using O₂-enriched coflow, hydrogen, diffusion flames. We investigated the thermal stability of the flame-synthesized TiO₂ nanoparticles by ...examining the crystalline structures of the nanoparticles and by analyzing the photocatalytic degradations of methylene blue solutions. Also, the results were compared with those of commercial P-25 nanoparticles. The maximum centerline temperature of the flame was measured to be 1,743 °C. Under this synthesis condition, TiO₂ nanoparticles, which were spherical with diameters approximately ranging from 30 to 60 nm, were synthesized. From the XRD analyses, about 96 wt.% of the synthesized nanoparticles were anatase-phase. After the heat-treatment at 800 °C for 30 min, the synthesized TiO₂ nanoparticles showed no significant changes of their shapes and crystalline phases. On the other hand, most of the commercial particles sintered with each other and changed to the rutile-phase. Whereas the photocatalytic ability of heat-treated commercial particles deteriorated, that of the flame-synthesized particles improved. On the basis of the improved result of photocatalytic degradation of methylene blue by using the heat-treated flame-synthesized nanoparticles, it is believed that the flame-synthesized TiO₂ nanoparticles have higher thermal stability at 800 °C than the commercial particles.
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