Application of Plasma Surface Treatment to Solid‐State Microscopic Particulates

Abstract

The plasma‐assisted improvement of wettability and flowability of fine powders is described. The plasma down‐stream reactor designed for an adequate treatment of particulates allows efficient surface modification and functionalization of particulates. It is discussed that the resulting rapidity of the processes is due to the homogeneous dispersion of particulates in the reactor. This enables intense particle/plasma interaction presumably due to the formation of floating potential sheaths around each single particle immersed in the plasma. Thus, although the overall energy influx applied is in the range of 10 to 100 J · m−2 of the particulate surfaces, the treatment time in the order of a tenth of a second instead of hours compared to conventional processes.

Improvement of polymer properties for powder bed fusion by combining in situ PECVD nanoparticle synthesis and dry coating

“…Table 5 provides a comparison of the parameter used and the results obtained in this study with those of the studies of Sonnenfeld et al [ 23 ] and Roth et al [ 25 ] where PE‐HD powders were treated in a downstream plasma reactor using Ar/O 2 /HMDSO mixtures as a plasma gas. This comparison is relevant as PE‐HD and PP powders present similar properties (e.g., only carbon and hydrogen in the backbone chain, density, and mean particle size, among others).…”

“…Sonnenfeld et al, [ 22,23 ] Spillmann et al, [ 14,24 ] and Roth et al [ 25 ] presented an alternative process to DPC. This process consists of the simultaneous production and deposition of nanoparticles on the surface of the substrate particles by a homogenous gas phase reaction in a dusty plasma‐enhanced chemical vapor deposition (PECVD) process.…”

“…The achieved results in terms of powder flowability for lactose (particle size = 6.7 µm) were very close to the ones achieved by conventional DPC. [ 23 ] In the case of PE‐HD, the dusty plasma treatment led to an increase of the flowability of 57%–80% with respect to the untreated material after process times of about 0.1 s. [ 23,25 ] Roth [ 26 ] analyzed the effect of the different process parameters (e.g., plasma power, process pressure, gas composition, silicon precursor, mass flow of precursor, powder, etc.) on the plasma properties, the synthesis of nanoparticles, and the modification of the flowability of lactose powders.…”

Simulation study of nanoparticle coating in a low pressure plasma reactor

“…Sonnenfeld et al showed that due to the formation of floating potential sheath around each particle a homogeneous distribution of particle is established in the reactor which results in the surface treatment time of the order of a tenth of a second instead of hours compared to conventional processes. 11 Roth et al used a two stage plasma processing approach to enhance the flowability and dissolution of salicylic acid powder for pharmaceutical applications. 14 In the first step, the surface of salicylic acid particle was coated with SiO x nanostructures which act as spacers and reduce the prevailing interparticle van der Waals forces, such that the particles can easily flow.…”

Wettability and Adhesion of Polyethylene Powder Treated with Non-Equilibrium Various Gaseous Plasma in Semi-Industrial Equipment

“…That comprehensive paper describes both laboratory research and industrial applications. Sonnenfeld et al [16] used a capacitively coupled radio-frequency (RF) plasma reactor to improve the wettability and flowability of fine powders made from high-density PE. The formation of floating potential sheaths around each single particle immersed in the plasma enabled intense particle/plasma interaction and thus improved wettability in a treatment time of only 0.12 s. The O/C ratio after this treatment was 0.15.…”