3D Graphene foam from glucose by chemical blowing

[trujafar]

I'm a third year physics undergraduate and I want to make 3D Graphene - without spending a fortune.

This is my background:

I found this review article by Jiang and Fan (Design of advanced porous graphene materials: from graphene nanomesh to 3D architectures) to be very helpful. From what I've understood, the main methods are hydrothermal and CVD. CVD involves using nickel foam, and at $250 a sheet Marketech Intl, Inc. - Nickel Foam is a no-no. However, hydrothermal methods such as this one Porous 3D graphene-based bulk materials with exceptional high surface area and excellent conductivity for supercapacitors which use graphene oxide and surcose seems more promising.

In line with this, I've done research on graphene oxide (a precurser to many graphene-based products), and have read about the Hummer's method, the Improved Hummer's Method (http://pubs.acs.org/doi/abs/10.1021/nn1006368) and have also watched Robert Murray-Smith's videos (www.youtube.com/user/RobertMurraySmit[/URL]).

Now for my question:

I read this article [URL="http://www.nature.com/ncomms/2013/131216/ncomms3905/full/ncomms3905.html"]Three-dimensional strutted graphene grown by substrate-free sugar blowing for high-power-density supercapacitors[/URL] which has a seemingly simple and interesting method for synthesis of 3D graphene foam, which I would very much like to make. But upon reading the article, I'm facing a couple of problems:

1) In the Methods section of the paper use argon gas is used for the ambient gas in the tube furnace. Under what pressure does this take place? Does it have to be a tube furnace, or will any other furnace with programmable temperature work?

2) Is the glucose mixed directly with amonnium salt, or is it dispersed in a solution?

3) In the diagram, glucose is converted to meldonin at ~250C, then it is heated to ~1350C. Is the melanoidin conversion carried out in ambient conditions, and then the sample cooled to room temprature, or is this a one step process? What exactly happens? Can I carry this out in lower temprature, say ~ 900C at the cost of lower quality?

[URL]http://www.nature.com/ncomms/2013/131216/ncomms3905/images/ncomms3905-f4.jpg

I've sent a email to Dr Yoshio Bando a couple of days ago, but I haven't yet got an answer. I'm worried that I wasn't very polite.

 

[Greg Bernhardt]

I'm sorry you are not generating any responses at the moment. Is there any additional information you can share with us? Any new findings?

 

[trujafar]

1) In the Methods section of the paper use argon gas is used for the ambient gas in the tube furnace. Under what pressure does this take place? Does it have to be a tube furnace, or will any other furnace with programmable temperature work?

The pressure is 1 atm. There is nothing special about a tube furnace, but the fact that it is easy to create a specified atmosphere. This is really important since for the pyrolosis of carbon to take place, an inert gas is needed, otherwise the glucose will burn. According to their paper, 4C/min is the optimal temprature ramp for strutted graphene production.

2) Is the glucose mixed directly with amonnium salt, or is it dispersed in a solution?

Both are in solid form, and the solid white glucose powder is directly mixed with the amonnium salt in a 1:1 ratio in weight.

3) In the diagram, glucose is converted to meldonin at ~250C, then it is heated to ~1350C. Is the melanoidin conversion carried out in ambient conditions, and then the sample cooled to room temprature, or is this a one step process? What exactly happens? Can I carry this out in lower temprature, say ~ 900C at the cost of lower quality?

The shown diagram states that in the while it is being heated to 1350C, glucose is converted to meladonin, and then graphene. However, as far as the experimental procedure needs to cencern itself, it is a one-step process. What exactly happens is not known. At a lower temprature, to quote directly from Dr Wang "will be something similar to strutted graphene, just with a lower crystalline degree, lower conductance and lower specific surface area."

My understanding of the above is thanks to Dr Xuebin Wang. Any errors are due to misunderstanding on my part.

 

[R14]

so regarding 2), do you mix glucose and ammonium salts in solid form and bring them to 200 deg 4deg/min to form the foam, and that is done at room atmosphere?
Would you get a brown "caramel" foam or a white glucose form? at around 160 deg glucose start caramelizing.

any recipes to get white glucose foams?

 

[trujafar]

The synthesis of the grapheme foam is a one-step process from room temperature to 1350C with a temperature step of about 5C/min.
It is important that it is performed in a inert atmosphere. A tube furnace is generally used for these purposes.
However, the heating element, tube material and thermocouple will limit the maximum temperature that you can go up to. Due to these limitations, I was only able to go up to 1000C. Below is the sample.

 

[trujafar]

I'd suggest that you would take a look at Dr Wang's recent papers. He has further optimized and examined the bubbling process. Of particular interest is his paper titled "High-throughput fabrication of strutted graphene by ammonium-assisted chemical blowing for high-performance supercapacitors". Study the section titled "Growth process of ammonium-assisted chemical blowing for SG". It will give you a greater insight into the process.