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ref: -1977 tags: polyethylene surface treatment plasma electron irradiation mechanical testing saline seawater accelerated lifetime date: 04-15-2017 06:06 gmt revision:0 [head]

Enhancement of resistance of polyethylene to seawater-promoted degradation by surface modification

  • Polyethylene, when repeatedly stressed and exposed to seawater (e.g. ships' ropes), undergoes mechanical and chemical degradation.
  • Surface treatments of the polyethlyene can improve resistance to this degradation.
  • The author studied two methods of surface treatment:
    • Plasma (glow discharge, air) followed by diacid (adipic acid) or triisocyanate (DM100, = ?) co-polymerization
    • Electron irradiation with 500 kEV electrons.
  • Also mention CASING (crosslinking by activated species of inert gasses) as a popular method of surface treatment.
    • Diffuse-in crosslinkers is a third, popular these days ...
    • Others diffuse in at temperature e.g. a fatty acid - derived molecule, which is then bonded to e.g. heparin to reduce the thrombogenicity of a plastic.
  • Measured surface modifications via ATR IR (attenuated total reflectance, IR) and ESCA (aka XPS)
    • Expected results, carbonyl following the air glow discharge ...
  • Results:
    • Triisocyanate, ~ 6x improvement
    • diacid, ~ 50 x improvement.
    • electron irradiation, no apparent degradation!
      • Author's opinion that this is due to carbon-carbon crosslink leading to mechanical toughening (hmm, evidence?)
  • Quote: since the PE formulation studied here was low-weight, it was expected to lose crystallinity upon cyclic flexing; high density PE's have in fact been observed to become more crystalline with working.
    • Very interesting, kinda like copper. This could definitely be put to good use.
  • Low density polyethylene has greater chain branching and entanglement than high-density resins; when stressed the crystallites are diminished in total bulk, degrading tensile properties ... for high-density resins, mechanical working loosens up the structure enough to allow new crystallization to exceed stress-induced shrinkage of crystallites; hence, the crystallinity increases.

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ref: -0 tags: parylene plasma ALD insulation long-term saline PBS testing date: 04-02-2014 21:32 gmt revision:0 [head]

PMID-23024377 Plasma-assisted atomic layer deposition of Al(2)O(3) and parylene C bi-layer encapsulation for chronic implantable electronics.

  • This report presents an encapsulation scheme that combines Al(2)O(3) by atomic layer deposition with parylene C.
  • Al2O3 layer deposited using PAALD process-500 cycles of TMA + O2 gas.
  • Alumina and parylene coating lasted at least 3 times longer than parylene coated samples tested at 80 °C
    • That's it?
  • The consistency of leakage current suggests that no obvious corrosion was occurring to the Al2O3 film. The extremely low leakage current (≤20 pA) was excellent for IDEs after roughly three years of equivalent soaking time at 37 °C.
    • Still, they warn that it may not work as well for in-vivo devices, which are subject to tethering forces and micromotion.

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ref: -0 tags: polyimide adhesion oxygen nitrogen plasma surface energy date: 03-10-2014 22:33 gmt revision:0 [head]

Adhesion Properties of Electroless-Plated Cu Layers on Polyimide Treated by Inductively Coupled Plasmas

  • O2 then N2/H2 ICP treatment of polyimide surfaces dramatically lowers the surface energy (as measured by contact angle), and increases the adhesion of palladium-catalyzed electroless copper.
  • Particularly, C-N bonds are increased as revealed by XPS.
  • No peel-strength measurements given.

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ref: -0 tags: plasma etch removal parylene DRIE date: 05-28-2013 18:47 gmt revision:2 [1] [0] [head]

Plasma removal of Parylene C

  • Ellis Meng, Po-Ying Li and Yu-Chong Tai USC / Caltech
  • Technics O2 plasma etch works, as do DRIE / RIE etch; all offer varying degrees of anisotropy, with the more intricate processes offering straighter sidewalls.
  • Suggested parameters for O2 etch is 200sccm / 200W.
  • Etch will be somewhat isotropic -- top of photoresist will be etched away, leading to ~15deg sloped sidewalls.
    • Hence, small parylene features will be narrowed by the 02 plasma.

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ref: physics notes-0 tags: plasma mercury vapor lamp electron ozone date: 04-03-2007 15:23 gmt revision:3 [2] [1] [0] [head]

ok, so i just (19 Feb 2007) did some simple experiments with the small (100W) mercury vapor lamp that i have + a hard-drive magnet + a solenoid.

  1. magnet splits the plasma into two paths, depending on the direction of the AC plasma current. The split is strongest when at the transition between north and south poles on the HD rare-earth magnet, as here the field lines are going in short loops with the vertical part approximately intersecting the plasma, and hence exerting the lorentz force towards or away from the magnet.
    1. it is possible to extinguish the bulb by moving the plasma too close! I think that this forces the electrons to collide with the quartz tube, cooling them too much.
  2. I also built a solenoid out of a small spool of 14 gauge magnet wire attached to my buzz box arc welder. The current was set at ~50 amps, (not sure how accurate that setting was) - enough to get the small coil pretty hot rather quickly. When placed inside the AC-energized coil, the plasma arc was forced to spiral around the walls of the quartz tube.
    1. This is most likely because the mean velocity of the electrons is pretty low, hence the lamour radius is high in the relatively-weak magnetic field. I notice that at the beginning of igniting the mercury-vapor lamp, far more ozone is produced (as gauged by smell) than is produced when it is hot and the plasma current is high. This accompanies a shift from a very blue emission spectra to a whiter emission, I think this is because the pressure becomes higher inside the tube, hence the mean free path of the electrons is lower, hence they have less energy to excite the hard-UV bands of mercury ions once the lamp is hot. http://en.wikipedia.org/wiki/Planck's_constant --> E=hv, where v is the frequency --> 250nm approximately equals 5 eV. lamour radius: mv/qB. 5ev ~= 1.33e6 m/s. @ B= 0.1T, lamour radius = 7.5e-5m = 0.07mm (what?) ok, more reasonable: B = 0.005T, r = 1mm - still smaller than observed! Need to check this magnetic field. B=mu n I. I = 50A, n = 3 * 2/0.064) = 93 turns, mu (air) = 4*pi*10^-7 --> B ~= 0.005T. (as a first approximation). If the electron velocity is lower, then the radius will be smaller; it is the opposite for the magnetic field strength.
    2. of course, we are disregarding thermal interactions, as well as drift - will have to look at the textbook for this.
  3. Feb 23 2007 - I made a larger-diameter solenoid out of the 14 gauge copper wire & turned the buzz-box welder current up to 100A (or so it says, don't know how much in practice) - enough to get the coil very hot very quickly. I put this current loop around the broken 400W metal-halide lamp - the one originally from the blacklight cannon. As it is still being driven from the same low-wattage power supply, it remains cool, the bulb voltage is low (21V) and much UV (and ozone) is produced - generally indicating that the pressure in the bulb is low and the electron velocity/mean free path is higher.
    1. well, actually: when the blub pressure is low, much energy below 240nm is produced. Apparently this is what is required for ozone production:
    2. HBO lamps do not generate ozone, because owing to the self-absorption in the cooler outer arc regions, all radiation below 240nm is trapped within the discharge. However during run-up before pressure increases, some ozone is produced.
    3. When I turned the solenoid on around the ignited bulb, the concentration of plasma in the center noticably increased, and the luminous intensity increased also. I'm not sure if this was due to AC pumping of plasma current; I doubt it, as most of the magnetic flux should have went around the plasma.
    4. The bulb voltage went to 23 - 24V; I do not know the current, I will have to measure it (perhaps with an oscilloscope?)
    5. The plasma became less uniform, too, perhaps because the solenoid was not aligned to the E-field with any accuracy.

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ref: physics notes-0 tags: plasma LDX dipole confinement fusion date: 02-24-2007 17:55 gmt revision:0 [head]

First Experiments to test plasma confinement by magnetic dipole

  • Beta is limited by the background pressure of lower-temperature gas - more gas = more stable & trapped electrons. presumably this is due to the presence of positive charges? I don't know, need to read more.
    • this is in the presence of 2-5Kw of microwave electron-cynchrotron radiation heating.
  • this is not levitated - it is the superconducting dipole held up with supports (steel cables? - looks pretty heavy!)
  • want to do catalyzed D-D fusion in the ultimate device
  • do say how they are going to get longer-term containment of the hot plasma.

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ref: physics notes-0 tags: plasma physics electromagnet tesla coil copper capillary tubing calculations date: 02-23-2007 16:01 gmt revision:0 [head]

calculations for a strong DC loop magnet using 1/8" copper capillary tubing:

  1. OD .125" = 3.1.7mm^2; ID 0.065 -> copper area = 23.2mm^2 ~= AWG 4
  2. AWG 4 = 0.8 ohms/km
  3. length of tubing: 30' ~= 40 turns @ 9" each (windings packed into a torus of major radius 1.5"; minor radius 0.5")
  4. water flow rate through copper capillary tubing: 1 liter/min; assuming we can heat it up from 30C -> 100C, this is 70KCal = 292 KJ/min = 4881 W total. (better pipe it into our hot water heater!)
  5. 4.8kw / 9m of tubing = 540 W/m
  6. 540W/m / 8e-4 = 821 A ; V = 821 * 9 * 8e-4 = 5.9V (!!! where the hall am i going to get that kind of power?)
  7. 821A * 40 turns = 32.8KA in a loop major radius 1.5" = 3.8cm
  8. magnetic field of a current loop -> B = 0.54T
  9. lamour radius: 5eV electrons @B = 0.54T : 15um; proton: 2.7cm; electrons @1KeV ~= 2.66e8 (this is close to the speed of light?) r = 3mm.