Effects of Cold Plasma Treatment on Interlayer Bonding Strength in Fused Filament Fabrication (FFF) Process

Fused Filament Fabrication (FFF) is the most popular additive manufacturing method because of its numerous capabilities and relatively low cost. This comes with a trade off as FFF printed parts are typically weak in the layer deposition direction due to insufficient interlayer bonding. This research adopts the method of cold plasma treatment and investigates the potential enhancement of interlayer bonding by altering the printed surface prior to the deposition of the next layer. Polylactic acid (PLA) is used as the printing material, due to its ubiquity in industry. The bonding strength is measured by the shear bond strength test. The results show that bond strength improved over 100% with 30 s of treatment and over 50% with 300 s of treatment. A mechanically polished surface is also included in the comparison for the high surface wettability, but the result shows no improvement. This indicates that wettability may not be the dominant mechanism for enhanced bonding after treatment

Functional thin films synthesized from liquid precursors by combining mist chambers and atmospheric-pressure plasma polymerization

For the creation of thin films, the use of precursors in liquid phase offers a viable alternative when these chemicals are sensitive to high temperatures and phase changes. However, it requires appropriate liquid handling and deposition technologies capable of dispensing the fluid homogeneously to produce a uniform thin film. We report different tailor-made mist chamber designs integrated in an atmospheric-pressure plasma polymerization process for the synthesis of functional thin polymer films from liquid precursors. A systematic investigation, evaluated by performance indicators, is presented on the characteristics and suitability of metallic 3D-printed mist chambers depending on inner volume, geometry and surface post-treatment, for the deposition of a thin liquid monomer film. To assess the quality of the subsequently obtained plasma-polymerized (pp) films, their properties were characterized in terms of thickness, chemical composition, surface morphology and stability in aqueous environment. It was found that the specification of the mist chambers along with the plasma process parameters influences the pp film’s thickness, surface morphology and degree of monomer conversion. This study is one of the first demonstrations of a controllable process able to tune the cross-linked polymeric chains of plasma-polymers at atmospheric pressure, highlighting the opportunities of using mist chambers and plasma technology to discover tailored organic thin films to materials sciences and life sciences

Advances in optical surface figuring by reactive atom plasma (RAP)

In this thesis, the research and development of a novel rapid figuring procedure for large ultra-precise optics by Reactive Atom Plasma technology is reported. The hypothesis proved in this research is that a metre scale surface with a form accuracy of ~1 μm PV can be figure corrected to 20 – 30 nm RMS in ten hours. This reduces the processing time by a factor ten with respect to state-of-the-art techniques like Ion Beam Figuring. The need for large scale ultra-precise optics has seen enormous growth in the last decade due to large scale international research programmes. A bottleneck in production is seen in the final figure correction stage. State-of-the-art processes capable of compliance with requisites of form accuracy of one part in 108 (CNC polishing, Magneto-Rheological Finishing and Ion Beam Figuring) have failed to meet the time and cost frame targets of the new optics market. Reactive Atom Plasma (RAP) is a means of plasma chemical etching that makes use of a Radio Frequency Inductively Coupled Plasma (ICP) torch operating at atmospheric pressure. It constitutes an ideal figuring alternative, combining the advantages of a non-contact tool with very high material removal rates and nanometre level repeatability. Despite the rapid figuring potential of this process, research preceding the work presented in this manuscript had made little progress towards design and implementation of a procedure for metre-class optics. The experimental work performed in this PhD project was conducted on Helios 1200, a unique large-scale RAP figuring facility at Cranfield University. Characterisation experiments were carried out on ULE and fused silica surfaces to determine optimum process parameters. Here, the influence of power, surface distance, tool speed and surface temperature was investigated. Subsequently, raster-scanning tests were performed to build an understanding on spaced multiple passes ... [cont.].SAS Prize winne

The emerging role of cold atmospheric plasma in implantology: A review of the literature

In recent years, cold atmospheric plasma (CAP) technologies have received increasing attention in the field of biomedical applications. The aim of this article is to review the currently available literature to provide an overview of the scientific principles of CAP application, its features, functions, and its applications in systemic and oral diseases, with a specific focus on its potential in implantology. In this narrative review, PubMed, Medline, and Scopus databases were searched using key words like “cold atmospheric plasma”, “argon plasma”, “helium plasma”, “air plasma”, “dental implants”, “implantology”, “peri‐implantitis”, “decontamination”. In vitro studies demonstrated CAP’s potential to enhance surface colonization and osteoblast activity and to accelerate mineralization, as well as to determine a clean surface with cell growth comparable to the sterile control on both titanium and zirconia surfaces. The effect of CAP on biofilm removal was revealed in comparative studies to the currently available decontamination modalities (laser, air abrasion, and chlorhexidine). The combination of mechanical treatments and CAP resulted in synergistic antimicrobial effects and surface improvement, indicating that it may play a central role in surface “rejuvenation” and offer a novel approach for the treatment of peri‐implantitis. It is noteworthy that the CAP conditioning of implant surfaces leads to an improvement in osseointegration in in vivo animal studies. To the best of our knowledge, this is the first review of the literature providing a summary of the current state of the art of this emerging field in implantology and it could represent a point of reference for basic researchers and clinicians interested in approaching and testing new technologies

White paper on the future of plasma science and technology in plastics and textiles

This is the peer reviewed version of the following article: “Uros, C., Walsh, J., Cernák, M., Labay, C., Canal, J.M., Canal, C. (2019) White paper on the future of plasma science and technology in plastics and textiles. Plasma processes and polymers, 16 1 which has been published in final form at [doi: 10.1002/ppap.201700228]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."This white paper considers the future of plasma science and technology related to the manufacturing and modifications of plastics and textiles, summarizing existing efforts and the current state‐of‐art for major topics related to plasma processing techniques. It draws on the frontier of plasma technologies in order to see beyond and identify the grand challenges which we face in the following 5–10 years. To progress and move the frontier forward, the paper highlights the major enabling technologies and topics related to the design of surfaces, coatings and materials with non‐equilibrium plasmas. The aim is to progress the field of plastics and textile production using advanced plasma processing as the key enabling technology which is environmentally friendly, cost efficient, and offers high‐speed processingPeer ReviewedPostprint (author's final draft

Plasma chemical driven biomedical applications with a radio frequency driven atmospheric pressure plasma jet

2012 Fall.Includes bibliographical references.We present radio frequency driven atmospheric pressure plasma jet for various biomedical applications such as tissue removal, bacterial sterilization, and tooth whitening. Two different types of plasma assisted electrosurgery, remote electrode plasma jet and plasma jet surrounding monopolar electrosurgical electrode, were employed to enhance tissue removal in terms of less heat damage on contiguous tissue and fast removal rate. Chlorine based chemical (CHxClx) additives in argon plasma jet enhanced tissue removal rate, proportional to the Cl radical density in the plasma jet. Pulsed RF provided another knob to control the removal profile, heat damage, and removal rate. Hydrogen peroxide (H2O2) additive provided abundant OH generation in the helium plasma jet. It not only enhanced tissue removal rate but also reduced heat damage on the contiguous tissue. The tissue removal mechanism of helium-H2O2 plasma is explained based on the FTIR measurement of the tissue samples, and optical emission and absorption spectra. Hydrogen peroxide addition to argon plasma jet was employed for bacterial inactivation. Observed OH density by optical emission and absorption was proportional to the number of deactivated microorganism. Argon plasma jet in DI water also provided abundant OH on the interface of water and gas plasma. The OH radicals applied on porcine tooth sample selectively removed the stain without damaging the underlying enamel

Advances in Laser Materials Processing

Laser processing has become more relevant today due to its fast adaptation to the most critical technological tasks, its ability to provide processing in the most rarefied and aggressive mediums (vacuum conditions), its wide field of potential applications, and the green aspects related to the absence of industrial cutting chips and dust. With the development of 3D production, laser processing has received renewed interest associated with its ability to achieve pointed to high-precision powder melting or sintering. New technologies and equipment, which improve and modify optical laser parameters, contribute to better absorption of laser energy by metals or powder surfaces and allow for multiplying laser power that can positively influence the industrial spread of the laser in mass production and advance the existing manufacturing methods. The latest achievements in laser processing have become a relevant topic in the most authoritative scientific journals and conferences in the last half-century. Advances in laser processing have received multiple awards in the most prestigious competitions and exhibitions worldwide and at international scientific events. The Special Issue is devoted to the most recent achievements in the laser processing of various materials, such as cast irons, tool steels, high entropy alloys, hard-to-remelt materials, cement mortars, and post-processing and innovative manufacturing based on a laser

Effects of Cold Plasma Treatment on Interlayer Bonding Strength in Fused Filament Fabrication (FFF) Process

Fused Filament Fabrication (FFF) is the most popular additive manufacturing method because of its numerous capabilities and relatively low cost. This comes with a trade off as FFF printed parts are typically weak in the layer deposition direction due to insufficient interlayer bonding. This research adopts the method of cold plasma treatment and investigates the potential enhancement of interlayer bonding by altering the printed surface prior to the deposition of the next layer. Polylactic acid (PLA) is used as the printing material, due to its ubiquity in industry. The bonding strength is measured by the shear bond strength test. The results show that bond strength improved over 100% with 30 s of treatment and over 50% with 300 s of treatment. A mechanically polished surface is also included in the comparison for the high surface wettability, but the result shows no improvement. This indicates that wettability may not be the dominant mechanism for enhanced bonding after treatment

Long-term Adhesion Study Of Self-etching Systems To Plasma-treated Dentin

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Purpose: To determine the influence of atmospheric pressure plasma (APP) treatment on the microtensile dentin bond strength of two self-etching adhesive systems after one year of water storage as well as observe the contact angle changes of dentin treated with plasma and the micromorphology of resin/dentin interfaces using SEM. Materials and Methods: For contact angle measurements, 6 human molars were sectioned to remove the occlusal enamel surface, embedded in PMMA resin, and ground to expose a flat dentin surface. Teeth were divided into two groups: 1) argon APP treatment for 30 s, and 2) blown air (control). For the microtensile test, 28 human third molars were used and prepared similarly to contact angle measurements. Teeth were randomly divided into 4 groups (n = 7) according to two self-etching adhesives and APP treatment (with/without). After making the composite resin buildup, teeth were sectioned perpendicular to the bonded interface to obtain beam specimens. The specimens were tested after 24 h and one year of water storage until failure. Bond strength data were analyzed by three-way ANOVA and Tukey's post-hoc test (a = 0.05%). Three beam specimens per group that were not used in the bond strength test were prepared for interfacial SEM analysis. Results: APP application decreased the contact angle, but increased the bond strength only for one adhesive tested. SEM evaluation found signs of degradation within interfacial structures following 1-year aging in water. APP increased the dentin surface energy, but the effects of APP and 1-year water storage on dentin bond strength were product dependent. Conclusion: APP increased the dentin surface energy. It also increased the bond strength for Scotchbond Universal, but storage for one year negated the positive effect of APP treatment.173227233Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CAPES [3110/2010]CNPq [305777-2010-6

Mechanical and metallurgical properties of two-layered diamalloy 4010 and 2002 HVOF coating

Diamalloy 4010, which is iron/molybdenum blend, is resistive to wear and Diamalloy 2002 is resistive to corrosion and wear. However, combination of these powders in layered structure, may offer advantages over the individual powders. In this case, mechanical properties of the resulting layered structure could be improved. Consequently, investigation into mechanical and metallurgical properties of the resulting structure is necessary. High Velocity Oxy-Fuel coating of Diamalloy 2002 [(WC12Co)50,Ni33Cr9Fe3.5Si2B2C0.5] powders and Diamalloy 4010 [Fe68Mo30Cr1.8Mn0.2] powders as well as two-layered coatings consisting of these powders was carried out. In the two-layered structure, Diamalloy 4010 was sprayed at the substrate surface while Diamalloy 2002 was sprayed on the top of Diamalloy 4010 coating. The coating microstructure and morphology were examined using optical microscope, Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS). The indentation tests were carried out to evaluate the microhardness and surface elastic modulus of the resulting coatings. The mechanical properties of the coatings were examined through tensile and three-point bending tests. It was found that the coating produced for Diamalloy 2002 resulted in higher hardness than that corresponding to Diamalloy 4010. The failure mechanism of coating during tensile and three-point bending tests was mainly crack formation and propagation in the coating. The elastic modulus of coating produced from Diamalloy 2002 was higher than that of Diamalloy 4010 coating, which was due to the presence of 12% WC in the coating. The irregularities observed in the elastic limit of the curves indicated the formation of cracks in the coatings, which was particularly true for two layered coating. The shear stress developed at interface of the two-layered coating was responsible for the crack initiation in the coating. The deep cracks were also formed in the coatings after the tensile tests. This was attributed to the local stress centers, which increased the stress intensity under the tensile load