Scientific Research Paper Nloc.pdf

Synthesis and Structural Properties of Carbon Nanofibers (CNFs) Using Alcohol Catalytic Chemical Deposition (ACCVD) Tengku D.A1, Muhammad I.R2 and Maisarah R3 1)

MRSM Kepala Batas, Penang 2)

3)

MRSM Pasir Salak, Perak

MRSM Tun Ghafar Baba, Melaka

Keywords: CNFs, ACCVD

Abstract. This study is to synthesis and determine the structural properties of carbon nanofibers using alcohol catalytic chemical vapour deposition (ACCVD) using iron as a catalyst and ethanol as a carbon source. 1.0 g of iron(II,III) oxide is placed in a alumina boat which was positioned in a sintering furnace and heated at 400°C for 2 hours to reduce magnetite,Fe3O4 to hematite, Fe2O3. The sample is then placed in ACCVD and heated to 600°C before the ethanol (boiled at 80°C) is flowed into the chamber. After 30 minutes, the ethanol flow was stopped and the furnace was allowed to cool down before collecting the sample. The sample is characterised using X-ray diffraction (XRD) for phase analysis and Field Emission Scanning Electron Microscope (FESEM) for structure and morphology analysis. Introduction and Background Carbon nanofibers (CNFs) are cylindrical nanostructures with graphene layers arranged as stacked cones, cups or plates. Carbon nanostructures have been intensively investigated due to their unique one-dimensional structure with adjustable electronic conductivity and unusual mechanical strength. Since their discovery in 1991, carbon nanofibers (CNFs) have attracted a deal of interests due to their own unique characteristics and potential applications such as separation, gas sensing, catalyst support, energy storage, and environmental protection [1]. There are three main techniques that are generally used to produce carbon nanofibers which are arc discharge, laser ablation and chemical vapor deposition (CVD). CVD is the best technique to be used because it produce carbon nanostructures that have a larger diameter range and can be created in a larger quantity. It also required lower cost compare to others [2]. Usually the catalyst used are a form of transition metal such as nickel (Ni), copper (Cu) and Iron (Fe). In this study, we synthesised carbon nanofibers using alcohol catalytic chemical deposition (ACCVD) using iron (Fe) as a catalyst and ethanol as a carbon source.

Experimental Methods 1) Iron oxide, Fe3O4 with 50-100nm of particle size is weighed with a weighing scale to obtain initial weight. 2) The weight of the catalyst, Fe3O4 is estimated so that it is suitable to be put in the alumina boat, in our case, the weight of the catalyst was approximately 1.0 g. 3) The alumina boat is placed inside the sintering furnace and then the furnace was set to a temperature of 400°C with the holding time of 2 hours. 4) The reduced iron oxide is weighed to obtain the final weight after sintering. 5) The sample is collected for ACCVD process. 6) During the ACCVD process, the sample is placed in a quartz tube located in a horizontal tube furnace. 7) While the furnace is still at room temperature, argon gas is flowed into the chamber for 15 minutes to excess unwanted gaseous. 8) After that, the sample is heated from room temperature until it reaches 400°C. 9) When the temperature is 400°C, the flow of Argon gas is stopped and replaced with hydrogen gas for 30 minutes. 10) After 30 minutes, the flow of hydrogen gas is stopped and the temperature of the furnace is then raised up to 600°C. 11) Ethanol vapour is flowed into the chamber along with argon gas with the holding time of 30 minutes as the temperature reached 600°C. 12) After 30 minutes, the flow of ethanol vapour is stopped and argon gas is flowed into the chamber until the furnace is completely cooled. 13) The sample is collected and weighed to obtain yield percentage of catalyst after ACCVD then sent for characterizations through XRD and FESEM.

Results and Discussion Yield analysis After doing ACCVD, the percentage of yield is calculated by using the formula as shown in equation (1): Percentage of yield=

𝑚𝑎𝑠𝑠 𝑜𝑓 𝑝𝑟𝑜𝑑𝑢𝑐𝑡−𝑀𝑎𝑠𝑠 𝑜𝑓 𝑐𝑎𝑡𝑎𝑙𝑦𝑠𝑡 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑐𝑎𝑡𝑎𝑙𝑦𝑠𝑡

× 100%

(1)

Table 1: Percentage of yield obtained by using iron oxide catalyst and ethanol as carbon source Catalyst

Iron oxide

Mass before

Mass after

ACCVD (g)

ACCVD (g)

0.7053

0.7106

% of yield

1.07

Figure 1: The XRD’s profile of CNFs synthesized using ACCVD Figure 1 shows the result obtained from XRD for CNFs synthesized via ACCVD. The result shows that the sample is graphite at 27° with hexagonal structure. It has been proved carbon exists at the peak 26.7° [3].

a)

b)

c)

Figure 2: Field Emission Scanning Electron Microscope (FESEM) images of synthesised CNFs at a) 50000x Magnification b) 100000x Magnification c) 200000x Magnification Figure 2 shows the information for the CNFs morphology was obtained by FESEM result. The range of diameter size of the CNFs is 18-30 nm. Based on the images, tiny fibres indicating the beginning of the formation of carbon nanofiber are found at the magnification of 50000x which shows in figure 2(a). Long, medium size and irregular shaped fibres are shown at the magnification of 100000x in figure 2(b). A long strand like fibre is shown at magnification of 200000x in figure 2(c). Conclusion Synthesis of CNFs via ACCVD using iron as the catalyst and ethanol as the carbon source was successfully performed. XRD data indicates that the element obtained is graphite while the crystal structure of the element is hexagonal. The morphology obtained by FESEM indicates formation of carbon nanofibers with a diameter ranging from 18-30 nm.

The carbon nanofiber obtained is widely used to replace the expensive metal platinum in a myriad of functions most notably as a platinum substitute in fuel cells. Carbon nanofibers’ strength and durability in acidic and alkaline mediums closely mimics those of platinum enables the CNFs to be used as a protective layer around the electrode to prevent it from corrosion or contamination. They are also used in the medical field to treat diseased tissue. Its microscopical size allows the fibres to easily penetrate diseased cells and deliver therapeutic drugs. In outline, carbon nanofibers are an ingenious scientific invention which helps humans to live their lives more easily at a low and practical cost.

Acknowledgement As MRSM students, we would like to express our utmost respect and gratitude towards University Putra Malaya for giving us the opportunity to take part in the Noble Laureate Outreach Camp (NLOC). This whole experience means a lot to us and we are so grateful for the permission to use the laboratory equipment necessary to conduct our experiment. A special thank you to our advisor Miss Nuzul Fatihin Izatil Azman for your useful guidance on how to implement the steps in the synthesis of Carbon Nanofibers. Not forgetting Dr.Md Shuhazlly Bin Mamat for your immense knowledge in guiding us through this experiment. Our sincere gratitude also goes to MARA for organizing this wonderful program. Without this program, we would not have obtained knowledge on Carbon Nanofibers. Last but not least, we would like to extend our appreciation towards all of the people who had helped us to ensure that this experiment was carried out triumphantly.

References [1] S. Iijima, “Helical microtubules of graphitic carbon,” Nature, vol. 354, no. 6348, pp. 56–58, 1991.

[2]Margez et al.,(2010) Magrez,a.,Seo,J.,Smajda,R.Mionić,M., & Forrό,L.(2010). Catalytic CVD Synthesis of Carbon Nanotubes : Towards High Yield and Low Temperature Growth.Materials,3(11),4871-4891.doi:103390/ma3114871

[3]Owner Societies (2015) Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics.