Apparatus for indirect atmospheric pressure plasma processing

Abstract

Apparatus for plasma processing of a continuous fiber, comprising a first and a second plasma torch. Each plasma torch comprises oppositely arranged electrodes to define a plasma discharge chamber between the electrodes. The plasma discharge chamber comprises an inlet and an outlet for passing a plasma forming gas between the electrodes. The apparatus further comprises an afterglow chamber in fluid communication with the outlets of the plasma discharge chambers, which comprises a substrate inlet and a substrate outlet arranged at opposite sides of the outlets of the plasma discharge chambers. A transport system is configured to continuously transport the fiber from the substrate inlet to the substrate outlet through the afterglow chamber. The substrate inlet comprises an aperture having a cross-sectional size substantially smaller than a cross-sectional size of the afterglow chamber. The outlets of the plasma torches face each other and exhaust plasma activated species into the afterglow chamber.

What is claimed is: 
     
         1 . An apparatus for plasma processing of a continuous fiber, comprising a first plasma torch and a second plasma torch,
 wherein each of the first plasma torch and the second plasma torch comprises:
 a first electrode and a second electrode, wherein the first electrode and the second electrode are spaced apart and are concentric on an axis, and 
 a plasma discharge chamber between the respective first and second electrodes, wherein the plasma discharge chamber comprises an inlet and an outlet for passing a plasma forming gas between the first and second electrodes, 
   wherein the apparatus further comprises:
 an afterglow chamber in fluid communication with the outlets of the plasma discharge chambers of the first and second plasma torches, wherein the afterglow chamber comprises a substrate inlet and a substrate outlet, and 
 a transport system configured for continuous transport of the continuous fiber from the substrate inlet to the substrate outlet through the afterglow chamber and such that the continuous fiber is kept remote from the plasma discharge chambers while being processed by plasma activated species flowing from the outlets of the plasma discharge chambers into the afterglow chamber, 
   wherein the outlets of the plasma discharge chambers of the first plasma torch and the second plasma torch are arranged opposite one another, with the afterglow chamber interposed between the outlets of the plasma discharge chambers of the first and second plasma torches,   wherein the outlets of the plasma discharge chambers of the first and second plasma torches are interposed between the substrate inlet and the substrate outlet,   wherein the substrate inlet comprises an inlet aperture having a cross-sectional size substantially smaller than a cross-sectional size of the afterglow chamber at the outlet of the plasma discharge chamber of the first plasma torch.   
     
     
         2 . The apparatus of  claim 1 , wherein the first and second plasma torches are axially aligned. 
     
     
         3 . The apparatus of  claim 1 , wherein the inlet aperture is aligned with a delimiting wall of the outlet of each of the plasma discharge chambers along a transport direction of the continuous fiber, such that the afterglow chamber is made to extend only at a downstream side of the outlets of the plasma discharge chambers. 
     
     
         4 . The apparatus of  claim 1 , wherein a cross-sectional size of the inlet aperture is equal to or smaller than 50% of a cross-sectional size of the afterglow chamber. 
     
     
         5 . The apparatus of  claim 1 , wherein the substrate inlet ensures contactless entrance of the continuous fiber into the afterglow chamber. 
     
     
         6 . The apparatus of  claim 1 , wherein the inlet aperture has dimensions to minimise air entrainment by the continuous fiber into the afterglow chamber. 
     
     
         7 . The apparatus of  claim 1 , wherein the substrate inlet is tubular comprising a first lumen, the transport system being operable for transporting the continuous fiber through the first lumen, and wherein the inlet aperture corresponds to the first lumen. 
     
     
         8 . The apparatus of  claim 7 , wherein the first lumen has a length in a transport direction of the continuous fiber equal to or larger than twice a cross sectional size of the first lumen. 
     
     
         9 . The apparatus of  claim 7 , wherein the afterglow chamber is tubular comprising a second lumen, wherein the second lumen fluidly communicates with the first lumen, wherein the transport system is operable for transporting the continuous fiber through the second lumen, and wherein a cross sectional size of the second lumen is at least twice a cross-sectional size of the first lumen. 
     
     
         10 . The apparatus of  claim 9 , wherein the second lumen comprises a longitudinal axis extending between the substrate inlet and the substrate outlet. 
     
     
         11 . The apparatus of  claim 9 , wherein the afterglow chamber is cylindrical. 
     
     
         12 . The apparatus of  claim 11 , wherein the first lumen has a circular cross section having a diameter substantially smaller than a diameter of the afterglow chamber. 
     
     
         13 . The apparatus of  claim 1 , comprising a device operable to inject an inert gas on a surface of the continuous fiber at the substrate inlet. 
     
     
         14 . The apparatus of  claim 1 , wherein each of the plasma discharge chambers defines an axis of flow of the plasma forming gas, the axis of flow being perpendicular to a transport direction of the continuous fiber in the afterglow chamber. 
     
     
         15 . The apparatus of  claim 1 , wherein the outlets of the plasma discharge chambers of the first and second plasma torches face one another and exhaust plasma activated species into the afterglow chamber. 
     
     
         16 . The apparatus of  claim 1 , wherein the first and second electrodes are cylindrical. 
     
     
         17 . The apparatus of  claim 1 , wherein the afterglow chamber comprises a transparent wall. 
     
     
         18 . The apparatus of  claim 1 , comprising a control unit coupled to the first electrode of each of the first plasma torch and the second plasma torch, wherein the control unit is operable to sustain an atmospheric pressure plasma discharge in the plasma discharge chambers of the first and second plasma torches. 
     
     
         19 . A method of atmospheric pressure plasma processing of continuous carbon fibers, comprising transporting the carbon fiber through the apparatus of  claim 1 .