A.S. da Silva Sobrinho

Argon-Oxygen Post-Discharge Treatment of Hexatriacontane: Heat Transfer between Gas Phase and Sample

Characterization of the interaction between an argon-oxygen post-discharge and hexatriacontane (C36H74) is carried out. Optical emission spectroscopy using the atmospheric band O2 (b1Σg +, v=0 X3Σg −, v’=0) at 760 nm gives simultaneously the evolution of the O(3P) concentration above the surface and the gas temperature by simulation of the rotational spectrum of the transition. Surface reactions contribute to the heating in the sample and to a substantial increase in the gas temperature. Finally, a strong correlation between the time evolutions of the transition intensity and the sample temperature is observed, suggesting that O(3P) is the main reactive species that produces the heating and the chemical changes in the HTC.

Surface improvement of EPDM rubber by plasma treatment

The surface of ethylene-propylene-diene monomer (EPDM) rubber was treated in N2/Ar and N2/H2/Ar RF plasmas in order to achieve similar or better adhesion properties than NBR (acrylonitrile-butadiene) rubber, nowadays used as thermal protection of rocket chambers. The surface properties were studied by contact angle measurements and by x-ray photoelectron spectroscopy (XPS). The treated surfaces of the EPDM samples show a significant reduction in the contact angle measurement, indicating an increase in the surface energy. XPS analyses show the incorporation of polar nitrogen- and oxygen-containing groups on the rubber surface. After plasma treatment the presence of oxygen is observed due to surface oxidation which occurs when the samples are exposed to the air. Atomic force microscopy and scanning electron microscopy analyses indicate a decrease in the EPDM rubber surface roughness, promoted by surface etching during the plasma treatment. Strength tests indicate improvement of about 30% and 110% in the adhesion strength for the plasma treated EPDM/polyurethane liner interface and for the EPDM/epoxy adhesive interface, respectively. The adhesion strength of the EPDM/liner is similar to that obtained for the NBR/liner, which indicates that EPDM rubber can safely be used as thermal protection of the solid propellant rocket chamber.

Study of residual gas formed during plasma debinding of powder injection moulded parts

Mass spectrometry (MS) and optical spectroscopy have been used to study the residual gas formed during hydrogen plasma debinding of polypropylene from powder injection moulded parts. Mass spectra show that the residual gas formed during the debinding process presents a large number of aliphatic compounds and a certain difficulty in their identification. However, it was possible to identify the presence of propylene, methane, acetylene and ethane. Optical spectroscopy also shows the presence of CH radicals. The end point of the debinding process can easily be monitored by following the temporal evolution of the CH radical and the different ions by optical spectroscopy and MS, respectively.

Plasma processed carbon thin films applied to dye-sensitized solar cells

AbstractPlasma-treated carbon thin films are investigated as counter electrodes for dye-sensitized solar cells. The films were grown onto fluorine-doped tin oxide (FTO) substrates by magnetron sputtering using pure graphite target and argon atmosphere and subsequently annealed at 600xa0°C for 30xa0min in vacuum. These films were then submitted to a plasma texturing process in a reactive ion etching reactor using three different gas combinations: sulfur hexafluoride/argon (SF6 + Ar), sulfur hexafluoride/hydrogen (SF6 + H2), and sulfur hexafluoride/oxygen (SF6 + O2). The morphology and structure of the obtained films were characterized by scanning electron microscopy and Raman spectroscopy. Cyclic voltammetry technique allowed accessing the improvements in their catalytic properties, while the photocurrent-voltage curves under simulated solar illumination AM 1.5G (100xa0mW/cm2) evaluated the performance of the respective assembled solar cells. The results show that photovoltaic performance is significantly affected by the different plasma texturing conditions used. The carbon counter electrode obtained after SF6 + O2 plasma texturing achieved the best power conversion efficiency of 2.23%, which is comparable to the 2.31% obtained using the commercial platinum counter electrode.n Graphical abstractReactive Ion Etching reactor for plasma texturing process of carbon thin films

Correction to: Plasma processed carbon thin films applied to dye-sensitized solar cells

The authors regret an error in the Experimental section of the published article:

Optical Characterization of Glow and Afterglow Regions of Ar/O2 Microwave Plasma: Effect of Applied Power and Gas Flow

In this work, the effect of microwave power and gas flow on formation of atomic oxygen (O) was investigated by actinometry method in the two different regions of Ar/O2 microwave plasma: the glow and afterglow regions. The experiments were performed keeping constant the Ar/O2 gas flow ratio at proportion of 3/2 and varying the microwave power from 200 to 1100 W and the total gas flow from 50 to 300 sccm. The results showed that the production of O depends on both discharge parameters investigated and that the microwave power has the greater influence in the production of O. At afterglow region the production of O tends to be uniform and not dependent on the gas flow and microwave power. This may be due to homogenization of the processes of recombination and loss in the gas phase and to the walls along the afterglow region.