Matteo Gherardi

Three-Dimensional Time-Dependent Large Eddy Simulation of Turbulent Flows in an Inductively Coupled Thermal Plasma Torch With a Reaction Chamber

A 3-D time-dependent simulation of a laboratory-scale inductively coupled thermal plasma torch system has been carried out to investigate unsteady turbulent flow patterns, which may arise in the reaction chamber as a consequence of a sharp expansion of the gas at the torch outlet. A large eddy simulation model has been used to predict the instantaneous flow field without any time filtering, as done in the Reynolds averaged Navier-Stokes models (for example, κ-ε or Reynolds stress model).

Cleaning of 19 th century daguerreotypes by means of atmospheric pressure cold plasma jet

Summary form only given. Daguerreotypes represent the first practical form of photographs, particularly in vogue between 1840 and 1860, before becoming outdated due to the development of alternative and faster techniques. In daguerreotypes, the image results from the distribution of silver/mercury microcrystals of varying size and density on a silver-coated copper sheet. Through years, several 19th century daguerreotypes have suffered several corrosion phenomena, which have greatly reduced their historic and artistic value.

Fluid-dynamic characterization of atmospheric pressure non-equilibrium plasma sources for biomedical applications

Summary form only given. The complexity of plasma interaction with biological material and the stiff requisites imposed by biomedical treatments put a premium on diagnostics as a means to investigate process feasibility and to develop plasma sources tailored for specific applications. Among the several diagnostic techniques adopted in the field of cold non-equilibrium atmospheric pressure plasmas, optical emission spectroscopy (OES), high speed imaging (HSI) and Fourier transform infrared spectroscopy (FTIR) are widely used.

Synthesis of Copper-Based Nanostructures in Liquid Environments by Means of a Non-equilibrium Atmospheric Pressure Nanopulsed Plasma Jet

The influence of the liquid composition on the chemical and morphological properties of copper-based nanostructures synthesized by a non-equilibrium atmospheric plasma treatment is investigated and discussed. The synthesis approach is simple and environmentally friendly, employs a non-equilibrium nanopulsed atmospheric pressure plasma jet as a contactless cathode and a Cu foil as immersed anode. The process was studied using four distinct electrolyte solutions composed of distilled water and either NaClu2009+u2009NaOH, NaCl only or NaOH only at two different concentrations, without the addition of any copper salts. CuO crystalline structures with limited impurities (e.g. Cu and Cu(OH)2 phases) were produced from NaClu2009+u2009NaOH containing solutions, mainly CuO and CuCl2 structures were synthesized in the electrolyte solution containing only NaCl and no synthesis occurred in solutions containing only NaOH. Both aggregated and dispersed nanostructures were produced in the NaClu2009+u2009NaOH and NaCl containing solutions. Reaction pathways leading to the formation of the nanostructures are proposed and discussed.

Plasma treatment of tooth root canal for enhancement of bond strength of dental adhesive system

The adhesive-dentin interface has been well recognized as the weaker area for dental composite resin restoration and an improvement of its characteristic is essential to extend the longevity of dental restorations. Nowadays, the enhancement of bond strength of dental adhesive system is still a hot topic and a huge research effort is being spent to develop new materials and techniques.

Design oriented modelling for the synthesis of copper nanoparticles by a radio-frequency induction thermal plasma

Summary form only given. Radio-frequency inductively coupled plasma (RF-ICP) technology has proven to be a viable means for continuous production of nanoparticles (NP), thanks to its distinctive features, such as high energy density, high chemical reactivity, high process purity, large plasma volume, long residence time of precursors and the high cooling rate (104-105 Ks-1) in the tail of the plasma, and its large number of process variables, e.g. frequency, power, process gases, phase of the precursor and system geometry. Nonetheless, this high versatility comes at a price, as process optimization (in terms of yield and size distribution of the NP) is a challenging process that can hardly rely on try and fail experimental approaches due to equipment costs and to the limited amount of information that can be obtained from conventional diagnostic techniques. Therefore, process optimization of the NP synthesis process in RF-ICP systems has to rely extensively on modelling techniques.

Effective decontamination of soft reline-based oral cancer obturators by means of cold atmospheric plasma

Severe oral cancer might require patients to undergo surgical removal of soft tissues of the oral cavity; in order to replace these tissues, patients are required to wear removable oral palatal obturators, generally patient custom-made, as it is necessary to mold as much as possible the prosthesis to the lacking tissue. Among the large number of materials suitable for this purpose, soft reline holds a relevant position since it is easily moldable and possesses, thanks to its sponge-like return, the mechanical characteristics required to sustain the typical values of the compressive oral forces. Unfortunately, because of the sophistication of the raw material and the custom-made production process, soft reline oral palatal obturators are very expensive. Therefore, an eventual implant failure might be severely resource-(because of the implants cost) and time-(because of the long production process) consuming, prompting the desire for novel means for limiting implant failures, which are primarily caused by severe bacteria biofilm contaminations. Cold atmospheric plasma (CAP) processes represent a very promising strategy to decontaminate soft reline shutters, given its strong antibacterial potential, related to the killing activity of the several and synergic biologically active agents.

Characterization and evaluation of bactericidal effect and cytocompatibility of a low power ICP source for biomedical applications

The widespread use of antibiotics has led to emergence of multi-drug resistant organisms. This poses steep challenges in patients with extensive burns, which are particularly susceptible to opportunistic pathogens; since an effective treatment by means of antibiotics is not always achievable, new treatment alternatives are strongly in demand. Cold atmospheric plasmas as a source of reactive species, radicals, UV light, heat and charged particles are a promising technology to reduce bacterial load in chronic wounds.

Crosslinking of water-soluble pullulan nanofibrous mats through atmospheric plasma treatment

Summary form only given. Water soluble polymers may display interesting properties (e.g. thermal, mechanical, biocompatibility, etc.) that make them useful in different fields where, however, the stability of the material in a aqueous environment is often required. Chemical modification of the polymer molecular chains are commonly applied to introduce interchain bridging (crosslinks) that impart water resistance to the material. However, these methods are time-consuming and often make use of toxic chemical agents. Recently, it has been reported that non-equilibrium plasma treatments, commonly used to modify the chemical structure and the reactivity of polymer surfaces, are able to induce formation of radicals, which may recombine, producing unsaturation and crosslinking1. In this work we focus on the use of atmospheric pressure non-equilibrium plasmas to crosslink pullulan. Pullulan is a water soluble polysaccharide whose biodegradability, biocompatibility, low oxygen permeability and high temperature resistance make it very attractive for food technology, pharmaceutical application, environmental remediation and filtration. Results will be presented concerning the treatment of pullulan in form of electrospun mat with a Dielectric Barrier Discharge plasma source, inserted in a properly designed chamber, operated in environment air at atmospheric pressure and driven by a HV amplifier connected to a function generator with a microsecond rise time. In order to evaluate the effects of electrical parameters and treatment time on the degree of crosslinking in pullulan, several operating conditions were investigated. The crosslinking degree of plasma treated electrospun samples was evaluated: (i) from the capability of the pullulan fibers to preserve their morphology upon water exposure; (ii) through weight loss and swelling degree measurements; (iii) by monitoring the change of mechanical properties of electrospun mat after plasma treatment.Results show a relevant enhancement of electrospun pullulan mats water resistance after plasma treatment, demonstrating that this treatment is an environmental friendly crosslinking approach. First conclusions on the correlation between plasma operating parameters and crosslinking degree will be presented. The in situ one-step crosslinking by plasma can be easily extended to other water-soluble polymers.

An experimental and computational study of the interaction between the jet of an ICP torch and a cylidrical substrate

Summary form only given. Several industrial and research and development processes can possibly make use of Inductively Coupled Plasma (ICP) torches in the interaction with either a static or a rotating cylindrical substrate; like for high purity silica overcladding of preforms for optical fiber production, as well as in some calibration procedure for high precision measurement of physical properties of materials and, generally, in the frame of thermal treatment techniques, with or without chemical synthesis and deposition of materials. The investigation of thermo-fluid-dynamic phenomena in the downstream plasma region of interaction with the substrate is important in order to optimize these processes, also taking advantage of the many operating and geometric parameters intrinsic in the use of ICP plasmas. The interaction between cylindrical rods of different diameters (4, 8, 16 mm) and materials (stainless steel and quartz), placed at different distances (30 and 40 mm) from the exit region of an ICP torch operated in Ar at 13.56 MHz and 500 W at atmospheric pressure has been investigated using Schlieren Imaging (SI) with a Z-type setup; substrate temperature measurements have been obtained using infrared temperature sensors. Two different points of view of the same experimental set-up have been used for SI: one with the camera axis coaxial with the rod axis, while another one with the camera axis perpendicular to both rod and torch axis, as shown in Fig. 1. Hot-spot temperature on the surface of the substrate has been measured with infrared sensors (Optris LTCF1); results are compared with T distribution obtained with 3D simulation of the region where the substrate interacts with the impinging jet; axisymmetric 2D simulation of the volumetric region where plasma is generated has been used. Experimentally derived temperatures are also used to validate the simulation model and to “tune” it with the aim of choosing the best physical description of the turbulent phenomena occurring downstream the torch. Future studies will concern the analysis of substrate under rotation and/or translation.