Assessment of plasma torches as innovative tool for cleaning of historical stone materials

The Adverse Effects of TiO2 Photocatalycity on Paraloid B72 Hybrid Stone Relics Protective Coating Aging Behaviors under UV Irradiation

“…Although a great many techniques have been developed to protect the stone relics from environment weathering [ 16 , 17 , 18 ], many challenges still need to be solved. Coating, especially polymer hybrid coating with superhydrophobicity and self-cleaning property is regarded as one of the most effective approaches to improve anti-pollution and reduce water penetration performances by [ 19 , 20 , 21 , 22 , 23 ].…”

The inhibition of biodegradation on building limestone by plasma etching

“…In the literature, the possible use of plasma cleaning for the restoration and preservation of various materials such as wood, paper, fabric, metals, glasses, ceramics and stones has been reported. Plasma etching, for instance, was used in an attempt to remove: a) varnish (lacquer) coating on paintings using oxygen plasma [6]; b) epoxy / acrylic resin on stones by using compressed air or mix of oxygen and argon plasma [7], [8]; c) cleaning patinas on metal artefacts using hydrogen plasma [9]. It was proved that plasma can successfully remove the above-mentioned contaminations without damaging the substrate.…”

“…The type of plasmas applied for cleaning can be classified into several categories depending on their operating principle: a) dielectric barrier discharge (DBD), in which the discharge is generated in a cylindrical system at the atmospheric pressure: it consists of a tube made with dielectric material (fused silica), the high voltage electrode (brass) is a ring placed over the tube and the rod ground electrode is placed in the middle of this tube with gas inlet, driving the plasma to the environmental air [12]; b) corona discharge initiates the plasma between the internal pinshaped electrode and the cylinder/truncated cone shaped external electrode (nozzle) which is made with stainless steel and is replaceable, when the nozzle is open, coronal filaments brings out a gas flow with the leaving plasma flowing freely [13]. c) arc discharge generates thermal plasma by compressed air, it can reaches working temperature exceeding 300 °C ~ 400°C, with short treating time [8], [14]; d) capacitive coupled plasma has a vacuum chamber, with inlet for selective gas (inert, oxidic or reductive) that generates ions and react with the sample, two discal-shaped electrodes are placed at the top and the bottom, with sample placed in between [15]. Atmospheric plasma treatment has been shown to be able to remove biofilms on artificial substrates such as polystyrene wafers and stainless steel [16], [17], while He/O2 plasma jet was found to have antimicrobial effects on some bacterial biofilms [18].…”

In vitro characterization of two different atmospheric plasma jet chemical functionalizations of titanium surfaces

“…Plasma torches offer the possibilities to treat surfaces that are not placed between the electrodes, deleting size constraint and allowing local treatments on 3D shapes. The most common technology for plasma torches is the arc discharge, which allows the introduction of functional groups [26,27], but cannot avoid a quite high processing temperature and the cathode erosion with the possibility that metal particles are deposited on the sample surface [28,29]. Nanopulse technology has been recently introduced to overcome plasma heating, as the nanosecond voltage pulse rise permits the formation of high energy reactive species, while the few tens of nanoseconds pulse length prevent the transition to arc discharge.…”