Yukihiro Kusano

Danish Technological Institute

Silicon oxide (SiOx) coatings are attracting significant attention and are widely used in industrial applications. They can be prepared by plasma-assisted chemical vapor deposition (PACVD). PACVD at atmospheric pressure (AP-PACVD) is often employed to synthesize SiOx coatings, but it has generally not been scaled up to an industrially viable level....

Plasmas are reactive ionised gases, which enable the creation of unique reaction fields. This allows plasmas to be widely used for a variety of chemical processes for materials, recycling among others. Because of the increase in urgency to find more sustainable methods of waste management, plasmas have been enthusiastically applied to recycling pro...

Plastic is commonly used for food packaging, of which plastic polymer polyethylene terephthalate (PET) is widely used in the food and beverage industry. Furthermore, PET is the most suitable and recyclable plastic polymer used in food contact applications due to its functional properties: inertness and low diffusion of gases and migrants. However,...

Hybrid plasmas have been reported in various areas of research over the last 40 years. However, a general overview of hybrid plasmas has never been presented or reported. In the present work, a survey of the literature and patents is carried out to provide the reader with a broad view of hybrid plasmas. The term refers to several different configur...

Surface tensions of solid materials have been studied over 200 years and widely used for industrial or engineering applications. The surface tensions and surface tension components can be calculated using measured contact angles, for example, by the model studied by Owens and Wendt. The model is often represented in an asymmetric linear form, calle...

Polyethylene‐terephthalate (PET) films were treated using an air‐to‐air type atmospheric pressure dielectric barrier discharge (DBD) plasma in helium with ultrasonic irradiation, particularly for aiming at improving wettability. Airborne ultrasound was irradiated to the plasma using a pneumo‐acoustic stem‐jet Hartmann's generator. The wettability w...

Leading edge erosion on a wind turbine blade from Vindeby offshore wind farm is characterized by X‐ray tomography, and air bubbles within the top coat are observed. Similar coating systems with and almost without air bubbles within the top coat are tested on a R&D Test Systems style whirling arm rain erosion tester (RET) and found to have different...

Fibre-reinforced polymer composites are gaining increasing attention in various applications for constructing mechanical structures such as wind turbine blades. The interface between fibres and a polymer matrix should be optimally designed to promote the mechanical performance of the composites. Plasma treatment shows obvious advantages over conven...

Bundles or fabrics of sized glass fibres were treated by a dielectric barrier discharge plasma in a He/CF 4 gas mixture at atmospheric pressure with and without ultrasonic irradiation. The plasma treatment introduced fluorine both inside and outside of the fibre bundle, decreasing wetting of glycerol. Ultrasonic irradiation markedly increased the f...

Single-layer films from cellulose nanofibrils on a plastic support were coated with sol–gel coated with inorganic–organic copolymers (ORMOCER®s), consisting of inorganic Si–O–Si-based networks combined with ceramic (Al–O– and Zr–O–) groups and special organic fluoroalkyl chain containing functional groups. Sol–gel coatings decreased the surface hyd...

Micromechanisms of leading edge erosion of wind turbine blades are studied with the use of X‐ray tomography and computational micromechanics simulations. Computational unit cell micromechanical models of the coatings taking into account their microscale and nanoscale structures have been developed and compared with microscopy studies. It was observ...

Sized glass fibre bundles were treated using atmospheric pressure plasma in a helium/tetrafluoromethane gas mixture. X-ray photoelectron spectroscopy showed that fluorine was introduced onto the sizing surface. A new analysis method (dynamic micro-wetting) to determine the wetting rate of the plasma-treated fibre bundles is presented. The dynamic m...

Cellulose nanofibre coatings were treated by a dielectric barrier discharge plasma in a He/NH3 gas mixture at atmospheric pressure. Ultrasound was optionally irradiated during the treatment. The treatment enhanced the wetting of deionized water, glycerol, and uncured epoxy. Irradiation of ultrasound did not significantly change optical emission fro...

A novel method is proposed to maximize the value of operating fleet of wind turbines suffering leading edge erosion. This method will ensure longer lifetime and reduce repair cost. The challenge is to balance the cost of repair, downtime of wind turbines and loss of energy production due to leading edge erosion. Current practice is to inspect the t...

The interfacial shear strength (IFSS) is commonly used for evaluating the adhesion at the interface between fibre and matrix. A glass fibre/epoxy matrix system was investigated. The surface coatings applied to glass fibres may result in a discrepancy in the amine:epoxide group ratio between the interface and the bulk matrix, consequently moving the...

A method to determine the orientation and diameter distributions of mineral wool fibre networks using X-ray tomography and image analysis is presented. The method is applied to two different types of mineral wool: glass wool and stone wool. The orientation information is obtained from the computation of the structure tensor, and the diameter is est...

Impact fatigue caused by rain droplets, also called rain erosion, is a severe problem for wind turbine blades and aircraft. In this work, an assessment of impact fatigue on a glass fibre reinforced polymer laminate with a gelcoat is presented and the damage mechanisms are investigated. A single point impact fatigue tester is developed to generate i...

Repeated impacts can cause damage to not only a surface but also inside the material. Mechanisms include stress-wave propagation into the material, reflection of the waves at the back surface, and subsequent repeated reflections in the vicinity of the impact and the back surface. Impact damage performance was observed for polyurethane-coated fibre...

Fluoropolymer coated alanine films are treated by a dielectric barrier discharge and a gliding arc at atmospheric pressure as well as with gamma irradiation. The film surfaces and the underlying bulk materials are characterized before and after each treatment. The fluorine content decreases and the oxygen content increases at the fluoropolymer surf...

Translational, rotational, vibrational and electron temperatures of a gliding arc discharge in atmospheric pressure air were experimentally investigated using in situ, non-intrusive optical diagnostic techniques. The gliding arc discharge was driven by a 35 kHz alternating current (AC) power source and operated in a glow-type regime. The two-dimens...

Dielectric barrier discharge plasma treatment was applied to modify cellulose nanofibre (CNF) surfaces with and without ultrasonic irradiation. The plasma treatment improved the wetting by deionised water and glycerol, and increased the contents of oxygen, carbonyl group, and carboxyl group on the nanofibre surface. Ultrasonic irradiation further e...

A gliding arc discharge was generated in a turbulent air flow at atmospheric pressure driven by a 35 kHz alternating current (AC) electric power. The spatiotemporally resolved characteristics of the gliding arc discharge, including glow-type discharges, spark-type discharges, short-cutting events and transitions among the different types of dischar...

A gliding arc discharge can be generated between two diverging electrodes and extended by a turbulent gas flow to form a plume of stable non-thermal plasmas sustained at atmospheric pressure. Gliding arc discharge is rather complicated since it involves plasma chemistry, flow dynamics and discharge-turbulence interaction. Optical techniques, especi...

The theme of the 37th Risø International Symposium is the scientific basis for understanding the performance of composite materials. Specifically, the Symposium focuses on the underlying mechanisms that control the properties of composites, which will lead to better and more reliable model predictions. This will serve to support and further promote...

Surfaces of carrot nanofibre coatings were modified by a gliding arc in atmospheric pressure air. The treatment strengthened wetting of deionized water and glycerol, increased an oxygen content, C-O and C=O, and moderately roughened the surfaces. In the perspective of composite materials, these changes to the nanofibres can potentially improve thei...

Two types of E-glass fibres, a conventional and a high modulus where the last one in the following will be denoted as ECR-glass fibre, were investigated regarding density, diameter, stiffness and strength. The fibres were analysed as pristine and after sizing removal treatments. The sizing was removed by either burning at 565°C or soxhlet extractio...

An alternating current (AC) gliding arc can be conveniently operated at atmospheric pressure and efficiently elongated into the ambient air by an air flow and thus is useful for surface modification. A high speed camera was used to capture dynamics of the AC gliding arc in the presence of polymer surfaces. A gap was observed between the polymer sur...

A non-thermal gliding arc discharge was generated at atmospheric pressure in an air flow. The dynamics of the plasma column and tracer particles were recorded using two synchronized high-speed cameras. Whereas the data analysis for such systems has previously been performed in 2D (analyzing the single camera image), we provide here a 3D data analys...

Rapid transition from glow discharge to thermal arc has been a common problem in generating stable high-power non-thermal plasmas especially at ambient conditions. A sustained diffusive gliding arc discharge was generated in a large volume in atmospheric pressure air, driven by an alternating current (AC) power source. The plasma column extended be...

A gliding arc is a quenched plasma that can be operated as a non-thermal plasma at atmospheric pressure and that is thus suitable for large-scale plasma surface treatment. For its practical industrial use the discharge should be extended stably in ambient air. A simple analytical calculation based on Ohm's law indicates that the critical length of...

We demonstrate a plasma discharge which is generated between two diverging electrodes and extended into a gliding arc in non-equilibrium condition by an air flow at atmospheric pressure. Effects of the air flow rates on the dynamics, ground-state OH distributions and spectral characterization of UV emission of the gliding arc were investigated by o...

Atmospheric pressure plasma processing has attracted significant interests over decades due to its usefulness and a variety of applications. Adhesion improvement of polymer surfaces is among the most important applications of atmospheric pressure plasma treatment. Reflecting recent significant development of the atmospheric pressure plasma processi...

Atmospheric pressure plasma treatment is useful for adhesion improvement, because cleaning, roughening and addition of polar functional groups can be expected at the surfaces. Its possible applications in the wind energy industry include plasma treatment of fibres and fibre-reinforced polymer composites before assembling them to build wind turbine...

Understanding the mechanical properties of fibrous network as complex as stone wool materials requires a relevant description of their microstructure and architecture. In this study, different methods have been proposed to characterize the fibre orientation, diameter and length of fibres as well as the number density of fibre contacts. The methods...

A gliding arc is a plasma that can be operated at atmospheric pressure and applied for plasma surface treatment for adhesion improvement. In the present work, glass-fibre-reinforced polyester plates were treated using an atmospheric pressure gliding arc discharge with an air flow to improve adhesion with a vinylester adhesive. The treatment improve...

Glass-fiber-reinforced polyester (GFRP) plates are treated using a 50 Hz dielectric barrier discharge at a peak-to-peak voltage of 30 kV in helium at atmospheric pressure with and without ultrasonic irradiation to study adhesion improvement. The ultrasonic waves at the fundamental frequency of around 30 kHz with the sound pressure level of approxim...

Dynamic processes in a gliding arc plasma generated between two diverging electrodes in ambient air driven by 31.25 kHz AC voltage were investigated using spatially and temporally resolved optical techniques. The life cycles of the gliding arc were tracked in fast movies using a high-speed camera with framing rates of tens to hundreds of kHz, showi...

A non-equilibrium quenched plasma is prepared using a gliding-arc discharge generated between diverging electrodes and extended by a gas flow. It can be operated at atmospheric pressure and applied to plasma surface treatment to improve adhesion properties of material surfaces. In this work, glass-fibre-reinforced polyester plates were treated usin...

A dielectric barrier discharge in a gas mixture of tetrafluoromethane (CF4) and O2 was used for tailoring the surface properties of nanofibrillated cellulose (NFC) films. The surface chemical composition of plasma-modified NFC was characterized by means of X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry, while su...

An atmospheric pressure dielectric barrier discharge (DBD) was generated in an N2/O2 gas mixture at room temperature with and without ultrasonic irradiation to investigate ozone production. Powerful ultrasonic irradiation with the sound pressure level of approximately 150 dB into the DBD can enhance ozone production especially when the DBD was driv...

A numerical model for NxOy remediation in humid air plasma produced with a dielectric barrier discharge at atmospheric pressure is presented. Special emphasis is given to NO2 and N2O reduction with the decrease of O-2 content in the feedstock gas. A detailed reaction mechanism including electronic and ionic processes, as well as the contribution of...

Efficiency of atmospheric pressure plasma treatment can be highly enhanced by simultaneous high power ultrasonic irradiation onto the treating surface. It is because ultrasonic waves with a sound pressure level (SPL) above ∼140 dB can reduce the thickness of a boundary gas layer between the plasma and the material surface, and thus, many reactive s...

Electrostatic charging, discharging, and consequent surface modification induced by sliding dissimilar surfaces have been studied. The surface-charge related phenomena were monitored by using a home-built capacitive, non-contact electrical probe, and the surface chemistry was studied by X-ray photoelectron spectroscopy (XPS). The experiments were p...

Carbon fibres and ultra-high-molecular-weight polyethylene (UHMWPE) fibres are extensively used for improving mechanical properties of fibre reinforced polymer (FRP) composites. Strong adhesion between the fibre surfaces and the polymer matrix is one of the key issues for improving the longitudinal tensile strength of FRP composites. However, adhes...

Glass fibre reinforced polyester (GFRP) composites exhibit high strength-weight ratio and corrosion resistance, and are therefore used for a variety of applications in civil engineering, aerospace and automobile industry as well as medical and dental applications. Adhesives are often required for joining these materials to components fabricated fro...

Ozone production has been investigated using an atmospheric pressure dielectric barrier discharge in pure O2 at room temperature with and without ultrasonic irradiation. It was driven at a frequency of either 15 kHz or 40 kHz. The ozone production was highly dependent on the O2 flow rate and the discharge power. Furthermore, powerful ultrasonic irr...

The decontamination of objects (food) in a sealed container by means of atmospheric pressure plasmas is investigated. The target is Listeria monocytogenes, a bacterium which causes listeriosis and can be found in plants and food. The non-pathogenic species, Listeria innocua, is used for the experiments. Glass slides were inoculated with L. innocua....

A glass-fibre-reinforced polyester (GFRP) plate was treated with dielectric barrier discharge (DBD) at atmospheric pressure in air for adhesion improvement. The effects of ultrasonic irradiation using a high-power gas-jet generator during the treatment were investigated. The optical emission spectrum of the discharge remained almost unchanged by th...