# Effective Fiber Sieving

• posted
I need to sieve fiber-shaped silica powder according to their lenght
(L) or diameter (D) distributions. The fibers have L distribution of
100 micron - 1 cm, and D distribution of 5-25 microns. Normal rotap
sieving does not seem to fulfill my objective to obtain this product in
specific L or D portions. Any sueggestions on this regard?
• posted
The most obvious method is flotation or settling in a fluid.
say you've got a fluid moving smoothly upwards in an inverted cone; the velocity decreases as height increases. A unique fiber diameter will be suspended at each height (where the downwards gravitational force is balanced by the upwards drag force.)
There are many variations on this theme.
The biggest practical problem is that the fibers must be separated so they don't tangle. I can't imagine a method that can possibly work if the fibers are tangled.
Dave
• posted
----- Original Message ----- From: "ScottV" To: Sent: Saturday, January 07, 2006 4:01 PM Subject: Re: Invention Idea
• posted
was using a new newsreader and didn't realize that this didn't get to the group;
----- Original Message ----- From: ScottV To: Hatem Alsyouri Sent: Sunday, January 08, 2006 2:05 AM Subject: Re: Effective Fiber Sieving
Shouldn't be too difficult to get an electrostatic charge on the fibers. But strategies for sorting them once you do have a charge on them can take different paths. The more I think of it the better they should sort.
One path - charged fibers falling through a constant magnetic field will deflect by a combination of mass and surface charge.
Another would be an inner and outer drum of opposite charge that will tend to orient the fibers in a radial direction. Extra electrons on the fiber surface will gather towards the corners of the ends where the surface energy is highest. A positvely charged outer drum could have an intermediate filter drum to sort by diameter as the fibers are pulled to the outer drum. Or parallel belt instead of drum so you could just wipe the belt to collect the diameter sorted fibers.
maybe both - sort by diameter and then by charge/mass ratio to get length. Or if lucky charge/mass might be enough.
Worry about build up of charge on filter and possibility of identical charge/mass ratios for particular shapes.
ScottV
----- Original Message ----- From: Hatem Alsyouri To: ScottV Sent: Saturday, January 07, 2006 11:02 PM Subject: Re: Effective Fiber Sieving
Thanks Scott fir your feedback. This strategy could be a good starting point. So to simplify it, you are suggesting to place the fibers in an electric field and vary the potential until the fibers orient and sort according to their surface charge (as a function of L/D ratio). I am not quite sure about the electric properties of the silica fibers but I have a feeling it might work. I will give it a try.
Best
Hatem A.
ScottV wrote: I'm imagining that getting an electrostatic charge on them and sorting them by mass would be a start. It seems that the would be a correlation between L/D ratio and charge distribution that would help. Though I don't quite imagine how you would differentiate two identical charge distributions of different Lengths.
Should be at least a way to orient the fibers using that strategy.
Just brainstorming here. Any other ideas?
ScottV
----- Original Message ----- From: Newsgroups: sci.materials Sent: Thursday, January 05, 2006 10:59 PM Subject: Effective Fiber Sieving

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