Global Engineering for Development, Environment and SocietyInternship Report

TAIST Exchange Program for NSTDA
2016/8/15 ～ 2016/9/19

Masaya Kobayashi
Hanaoka Lab

-IntroductionI took part in the TAIST-Tokyo tech exchange program during this summer vacation.
TAIST is established as international cooperation between NSTDA(National Scienceand Technology Development Agency) is the Thailand of advanced research institutions,Thai university groups and Tokyo institute of Technology.
TAIST has three programs for students.
1.

Automotive Engineering(AE)2.

Information and Communication Technology for Embedded Systems(ICTES)

3.

Advanced and Sustainable Environmental Engineering(EnvE)

I participated EnvE program. Thai student can get master degree from these programs.
Also, Tokyo-tech students can take part in these program partially.

Figure1: Map of Thailand Science Park
NSTDA is placed in Thailand Science Park. NSTDA has four departments. These are
NECTEC(Electronics and Computer science), BIOTEC(Biotechnology), MTEC(Metalmaterials) and NANOTEC(Nanotechnology). I studied in NANOTEC.
The reason why I take part in this internship, I have the background of physics field, I
want to challenge for internship to research agency. Actually, I graduated from facultyof science. Also, in current laboratory, I don’t have any chances to do experiment. I
guessed this is the rare opportunity for me. I wanted to learn the application ofnanotechnology and improve my English skills through this internship.

Figure2: Instructors (Dr.Paiboon, Dr.Jedsada) and me
They are instructors. Dr.Jedsada is my main instructor. He always conducted
experiment with me. Dr.Jedsada research about Graphene/MnO2 materials forSuper-capacitor electrode. He has already known some making methods, but he hasn’t
try it yet. I partially contributed to his research. My mission is “Making the electrodeusing GO/MnO2” and “Using some analysis methods of electrode materials”.
-InternshipBy the way, I have to explain about Super-capacitor. It is Eco-friendly electrical storage
device. It has construction using electrolyte and aluminum/carbon as materials.

Figure3: Principle of Super-capacitor
There is some particles, such as Positive ion, Negative ion, Electron and Hole on thesurface of Super-capacitor. They made the double layers like Figure3. This is the samesituation with the series of two capacitors. In this double layers, electric charge isaccumulated. Then, we can see the charge and discharge. Super-capacitor has somecharacteristics. Merit is that it has quicker charge and discharge and longer life thannormal capacitor. In other hands, Super-capacitor is weak to high voltage. And it’s too
expensive.

Figure4: Outline of my research process
At first, we read some papers as reference. From these papers, we decided methods ofexperiment for Super-capacitor. Pre-Experiment is Electrophoretic deposition andGO/MnO2 synthesis. Using Pre-experiment result, finally we made electrode materials
for super-capacitor. After that, we confirmed quality of our sample and calculatedcapacitance.
-ExperimentAs pre-experiment in order to decide materials for synthesis GO/MnO2, we prepared
two sets. Set 1 is ①GO(0.4 mg/mL) + KMnO4(1.968g) and ②GO(0.4 mg/mL) +KMnO4(1.968g)+Mn(CH3COO)2(1.408g). I warmed up this composite in thehydrothermal on 160℃ during 12 hours. After centrifuge, we could get powders.

Figure5: ①&② powder
Set 2 is ③GO(0.4mg/mL) + KMnO4(20mM) and ④GO(0.4mg/mL) + KMnO4(10mM).
The difference between ③ and ④ is concentration of KMnO4. In the same way withSet 1, we made the powder and suspension.

Figure6: ③&④ powder

Figure7: ③&④ suspension

I analyzed samples ① to ④ using some analysis device. At first, we observed surfaceof ① and ② powders using SEM. SEM means Scanning Electron Microscope. We canfocus on smaller nano-level materials on the surface. From SEM results, we caninvestigate morphology if the composite.

Figure8&9: SEM image of ①&② powder

SEM image of ① shows 2-D surface. ② shows nanorod. Existence of nanostructure isbetter for high conductivity. Also, we conducted XRD analysis. XRD means X-ray
diffraction. We used XRD method to investigate structure of composite.
50① powder② powder45Intensity [a.u.]403530252015100102030

402θ[°]

5060

Figure10: XRD result of ①&② powder

Figure11: Reference of XRD peak(GO/MnO2)

7080

In Figure10, we can recognize structure of GO/MnO2 using Figure11 reference. β&δface is usually observed recent research of Super-capacitor.

Figure12&13: SEM image of ③&④ powder

Figure14&15: SEM image of ③&④ suspension
Figure12 shows nanostructures as well as Figure9. It is called nanowire. The difference
between nanowire and nanorod is length of structure. Figure13 is difficult to maintainwhat it is. Because it usually shows nanostructure, but it doesn’t have any structures.
Probably, I mistook focusing on appropriate sample. Figure14&15 are suspension
images. It shows a lot of nanostructure. If we choose this method to make electrodematerials, it is possible.
We can’t use XRD method in this situation because XRD can be used just solid sample
cases. In this case, we appropriated to measure “zeta potential”. Zeta potential ispotential difference between interface of charged particle and sufficiently distant point.
Sample Name Zeta Potential [mV]③-50④-32.4

Table1: Zeta potential result of ③&④

Figure16: Zeta potential when particle has negative charge
High zeta potential has high density of negative charge. Figure16 shows results of oursamples. It can be said ③ sample is high zeta potential. High zeta potential is better tomake the good Super-capacitor.
After we conducted experiment to synthesize GO/MnO2, we tried to do coating method.
It is called electrophoretic deposition. This method means phenomenon that charged
particles move in the electric field in order to Al with GO.

Figure17: Image of electrophoretic deposition

Using this method, we could make the Al sheet coating with GO.

Figure18: Al sheet coating with GOWe checked surface of Al sheet we made by SEM, we could get Figure20.

Figure19: SEM image of GO/Al
This figure shows flat surface. Flat surface is better for good Super-capacitor too.
Because electrolyte can go through inside of electrode materials. We guessed thiscoating method is possible for making electrode materials.
We decide samples to make electrode materials. That is GO(2mg/mL) +KMnO4(20mM). We conducted same way with ③ experiment. We made a suspension ofGO + KMnO4 and warmed up this suspension in hydrothermal on 140℃ during
12hours. After that, we used electrophoretic deposition again to coat Al with GO/MnO2.
In this way, we made the capacitor electrode. In order to analyze, we used SEM, XRD
and measuring zeta potential.

Figure20: SEM image of GO/MnO2 on Al
This picture shows some particles on the surface. Also, it has flat surface. Based on thissample surface, we made an electrode materials for Super-capacitor.

Table2: Zeta potential results of GO/MnO2 on Al
This zeta potential is high as well as ③. Because this value is similar to ③ data.

Figure21: XRD result of GO/MnO2 on Al
In our previous prediction, this picture will show the β face. However, this XRD
pattern doesn’t fit with any MnO2 literature(Figure11). I can’t explain enough detail.

As another analysis method, we conducted Cyclic Voltammetry method. From thismethod, we could get cyclic voltammogram.
2.50E-08
2.00E-08

Current(A)1.50E-08
1.00E-08
5.00E-09

0.00E+00-5.00E-09-1.00E-08
-0.4

-0.2

00.2

0.4

0.6

0.8

1Potential applied(V)Figure22: Cyclic voltammogram of our sample
Figure22 shows hysteresis curve. In calculating area of hysteresis curve, we cancalculate area capacitance of our sample. The formula of capacitance is following;

Carea  I (V )dV

mr  2(V f  Vi )From these way, our capacitance has,Carea  50nF / cm 2
Actually, this is quite small capacitance. I guessed there are some problems.
Probably, the coating layer is too thin. And, accessibility of electrolyte is not good.
As the summary of experiment, I could make electrode materials through the synthesis

GO and MnO2 and electrophoretic deposition method. I wanted more time in order toconduct an experiment.

0.0030.0025
0.002

Current(A)0.00150.001
0.00050-0.0005-0.001-0.0015-0.002
-0.4

-0.2

0

0.2
0.4
0.6
Potential applied(V)

0.81

Figure23: Cyclic Voltammogram of General Super-capacitor(5F)Figure23 shows the example of cyclic voltammogram of general Super-capacitor. It’s acommercial one. It has 0.4F/cm2 capacitance. This figure has a more symmetric area
than our sample. Generally speaking, the larger the integral area, the higher
capacitance.
-OthersDuring internship in Thailand, I could feel Thai culture from many things. From here,
I’d like to explain about my days in Thailand.

Figure24: My parent come Bangkok

Figure25:TAIST student

In August 19-20, My parent came Bangkok to meet with me. They said “We come tocheck whether you didn’t do bad things”. They are just parents even if time passed.
I took part in TAIST classes partially as exchange student. Then, I met some Thaistudents. Figure25 shows my best Thai friend! He taught me Thai language. The paper
I have, but it is hard to see, shows my mane in Thai. Also, some TAIST students
planned short trip to Ayutthaya for me.

Figere26: Ayutthaya
Ayutthaya is historical place in Thailand. Ayutthaya is close to Bangkok. If you go toAyutthaya from Bangkok by bus, you take 2hours. Easy to access, most of traveler visit
here.
-ConclusionFrom this exchange program, I learned the advanced scientific knowledge. And I hadcourage to speak English than previous me. I felt that Thai culture and kindness of thepeople. I want to challenge more international program or project. This internship hasphysics and chemistry field. It’s not directly related to my master research. However, I
believe this experience will be useful in my future.