Flame Treatment Research Articles

Use of flame activation of surfaces to bond PDMS to variety of substrates for fabrication of multimaterial microchannels

Silicones are widely used in industry as sealants, insulation, gaskets, coatings, seals and molds. One variety of silicone, poly dimethyl siloxane (PDMS), has been widely used for rapid prototyping of microfluidic and nanofluidic devices. The bonding of PDMS to other substrates is required to create a sealed microfluidic network. This can be achieved either by using dry bonding (e.g. oxygen plasma treatment) or wet bonding (e.g. microcontact printing) processes. Flame treatment has been used for surface activation of other polymeric materials (e.g. Poloylefin) and wood. This can increase the wettability and improve the adhesion of the coating (e.g. paints, inks and adhesives) with these substrates. In this paper, we present a universal method to bond silicones to other substrates by using flame treatment. We find that the flame treatment could allow one to simply bond PDMS to a variety of substrates including glass, silicon, epoxy (SU8), silicones, polyethylene and even metals such as aluminum. We fully characterize this bonding and find that it is due to the changes in surface property as well as topography on the surface.

Facile synthesis of α-Fe2O3 pyramid on reduced graphene oxide for supercapacitor and photo-degradation

We report a novel method to synthesize a novel α-Fe2O3 pyramid interspersed reduced graphene oxide composite by continuous 20-second flame treatment. The structural and morphological characteristics of the obtained composites were investigated by Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Raman spectrum, and Field-emission scanning electron microscopy. Pyramid-type α-Fe2O3 is found to be successfully decorated on reduced graphene oxide. Such a unique composite not only gives a high specific capacitance (965.7 F/g at 5 mV/s) and a good cycling performance, but also shows a strong, stable photo-degradation capacity of Rhodamine-B under simulation solar light (with 100% of degradation rate within 10 min). It is worthy of note that the content of graphene oxide in precursors is found to highly affect the formation of the crystal structure of α-Fe2O3, thus intensely affecting the electrochemical behaviors and photo-degradation capacity.

Surface energy modification for coating adhesion improvement on polypropylene

Polypropylene (PP) has poor superficial properties making a pre-treatment before coating the paint film necessary. The pre-treatment related to surface improvement most widely used in the industry is the flame treatment due to its capacity to achieve the necessary level of surface energy. This work is to study the effect of the flame treatment in the adhesion increase for painting films applied on polypropylene substrates. Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), dyne test inks, contact angle, resistance to adhesion by engraving and washing were employed to evaluate the flame treatment. The morphological, chemical and physical analysis presented superficial modification, the formation of new functional groups and improvements on adhesion between substrates and paint film, respectively. These results proved the efficacy of the flame treatment in the increase of the surface energy and in the adherence of the coatings applied to the PP substrates.

A bioinspired structured graphene surface with tunable wetting and high wearable properties for efficient fog collection.

Inspired by the fog harvesting ability of the spider net and the interphase wetting surface of Namib desert beetles, we designed a kind of special bioinspired hybrid wetting surface on a Cu mesh by combining polydimethylsiloxane (PDMS) and graphene (G). A surface containing hydrophobic and superhydrophobic areas is prepared by a combination of laser etching and ultrasonic vibration. Thus, this as-prepared hybrid wetting surface can quickly drive tiny water droplets toward more wettable regions, which makes a great contribution to the improvement of collection efficiency. Moreover, the PDMS/G surface not only is tolerant to many stresses such as excellent anti-corrosion ability, anti-UV exposure and oil contamination, but also shows self-healing simply by burning the worn areas, which thus endows the surface with tunable-wettability change between flame treatment and abrasive wear. This study offers a novel insight into the design of burned healed materials with interphase wettability that may enhance the fog collection efficiency in engineering liquid harvesting equipment and realizes renewable materials in situ cheaply and rapidly by processes that can be easily scaled and automated.

Research progress of biomimetic superhydrophobic surface characteristics, fabrication, and application

The biomimetic superhydrophobic surface derived from lotus effect is one of the hotspot issues in recent years and also a specific application case of biomimetic in modern industry. Based on the excellent characteristics of bionic superhydrophobic surface, such as self-cleaning, anti-icing, drag reduction, and anti-corrosion, it has great application value in the fields of industry, military, and biomedicine. Based on the effect of water contact angle and water sliding angle of superhydrophobic surface on the hydrophobicity, we discussed the wetting behavior of biomimetic superhydrophobic surface, the important properties of biomimetic superhydrophobic surface were reviewed in detail, and we provided the necessary theoretical basis for the application of superhydrophobic surface. The methods of fabrication of biomimetic superhydrophobic surface were summarized and elaborated three kinds of low-cost and simple methods of spraying, chemical etching, and flame treatment, and the development trend of biomimetic superhydrophobic surface was also prospected.

Hydroxyapatite Nanowire-Based All-Weather Flexible Electrically Conductive Paper with Superhydrophobic and Flame-Retardant Properties.

How to survive under various harsh working conditions is a key challenge for flexible electronic devices because their performances are always susceptible to environments. Herein, we demonstrate the novel design and fabrication of a new kind of the all-weather flexible electrically conductive paper based on ultralong hydroxyapatite nanowires (HNs) with unique combination of the superhydrophobic surface, electrothermal effect, and flame retardancy. The superhydrophobic surface with water repellency stabilizes the electrically conductive performance of the paper in water. For example, the electrical current through the superhydrophobic paper onto which water droplets are deposited shows a little change (0.38%), and the electrical performance is steady as well even when the paper is immersed in water for 120 s (just 3.65% change). In addition, the intrinsic electrothermal effect of the electrically conductive paper can efficiently heat the paper to reach a high temperature, for example, 224.25 °C, within 10 s. The synergistic effect between the electrothermal effect and superhydrophobic surface accelerates the melting and removal of ice on the heated electrically conductive paper. Deicing efficiency of the heated superhydrophobic electrically conductive paper is ∼4.5 times that of the unheated superhydrophobic electrically conductive paper and ∼10.4 times that of the heated superhydrophilic paper. More importantly, benefiting from fire-resistant ultralong HNs, thermally stable Ketjen black, and Si-O backbone of poly(dimethylsiloxane), we demonstrate the stable and continuous service of the as-prepared electrically conductive paper in the flame for as long as 7 min. The electrical performance of the electrically conductive paper after flame treatment can maintain as high as 90.60% of the original value. The rational design of the electrically conductive paper with suitable building materials and structure demonstrated here will give an inspiration for the development of new kinds of all-weather flexible electronic devices that can work under harsh conditions.

Steaming and Flaming for Converting Cool-season Turfgrasses to Hybrid Bermudagrass in Untilled Soil

Turfgrass species can be classified into two main groups: cool-season and warm-season species. Warm-season species are more suited to a Mediterranean climate. Transplanting is a possible method to convert a cool-season to a warm-season turfgrass in untilled soil. It generally requires the chemical desiccation of the cool-season turfgrass. However, alternative physical methods, like flaming and steaming, are also available. This paper compares flaming, steaming, and herbicide application to desiccate cool-season turfgrass, for conversion to hybrid bermudagrass (Cynodon dactylon x C. transvaalensis) in untilled soil, using transplanting. Two prototype machines were used, a self-propelled steaming machine and a tractor-mounted liquefied petroleum gas flaming machine. Treatments compared in this work were two flaming treatments and two steaming treatments performed at four different doses together with two chemical treatments with glufosinate-ammonium herbicide applications. The cool-season turfgrass species were tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne). The desiccation effect of the various treatments on cool-season turf was assessed by photographic survey 15 days after treatment. The percentage cover of hybrid bermudagrass was visually assessed at 43 weeks after planting. Steaming and flaming effects on both parameters were described by logistic curves. The highest doses of steaming and flaming almost completely desiccated cool-season turf, and similar hybrid bermudagrass cover was established by both the methods as the chemical application (50% to 60%). Thus both flaming and steaming may be considered as valid alternatives to herbicides aimed at turf conversion.

Motion of water droplets in the counter flow of high-temperature combustion products

This paper presents the experimental studies of the deceleration, reversal, and entrainment of water droplets sprayed in counter current flow to a rising stream of high-temperature (1100 K) combustion gases. The initial droplets velocities 0.5–2.5 m/s, radii 10–230 μm, relative volume concentrations 0.2·10−4–1.8·10−4 (m3 of water)/(m3 of gas) vary in the ranges corresponding to promising high-temperature (over 1000 K) gas-vapor-droplet applications (for example, polydisperse fire extinguishing using water mist, fog, or appropriate water vapor-droplet veils, thermal or flame treatment of liquids in the flow of combustion products or high-temperature air; creating coolants based on flue gas, vapor and water droplets; unfreezing of granular media and processing of the drossed surfaces of thermal-power equipment; ignition of liquid and slurry fuel droplets). A hardware-software cross-correlation complex, high-speed (up to 105 fps) video recording tools, panoramic optical techniques (Particle Image Velocimetry, Particle Tracking Velocimetry, Interferometric Particle Imagine, Shadow Photography), and the Tema Automotive software with the function of continuous monitoring have been applied to examine the characteristics of the processes under study. The scale of the influence of initial droplets concentration in the gas flow on the conditions and features of their entrainment by high-temperature gases has been specified. The dependencies Red = f(Reg) and Red’ = f(Reg) have been obtained to predict the characteristics of the deceleration of droplets by gases at different droplets concentrations.

Robust and Low-Cost Flame-Treated Wood for High-Performance Solar Steam Generation

Solar-enabled steam generation has attracted increasing interest in recent years because of its potential applications in power generation, desalination, and wastewater treatment, among others. Recent studies have reported many strategies for promoting the efficiency of steam generation by employing absorbers based on carbon materials or plasmonic metal nanoparticles with well-defined pores. In this work, we report that natural wood can be utilized as an ideal solar absorber after a simple flame treatment. With ultrahigh solar absorbance (∼99%), low thermal conductivity (0.33 W m-1 K-1), and good hydrophilicity, the flame-treated wood can localize the solar heating at the evaporation surface and enable a solar-thermal efficiency of ∼72% under a solar intensity of 1 kW m-2, and it thus represents a renewable, scalable, low-cost, and robust material for solar steam applications.

Flyweight 3D Graphene Scaffolds with Microinterface Barrier-Derived Tunable Thermal Insulation and Flame Retardancy.

In this article, flyweight three-dimensional (3D) graphene scaffolds (GSs) have been demonstrated with a microinterface barrier-derived thermal insulation and flame retardancy characteristics. Such 3D GSs were fabricated by a modified hydrothermal method and a unidirectional freeze-casting process with hierarchical porous microstructures. Because of high porosity (99.9%), significant phonon scattering, and strong π-π interaction at the interface barriers of multilayer graphene cellular walls, the GSs demonstrate a sequence of multifunctional properties simultaneously, such as lightweight density, thermal insulating characteristics, and outstanding mechanical robustness. At 100 °C, oxidized GSs exhibit a thermal conductivity of 0.0126 ± 0.0010 W/(m K) in vacuum. The thermal conductivity of oxidized GSs remains relatively unaffected despite large-scale deformation-induced densification of the microstructures, as compared to the behavior of reduced GSs (rGSs) whose thermal conductivity increases dramatically under compression. The contrasting behavior of oxidized GSs and rGSs appears to derive from large differences in the intersheet contact resistance and varying intrinsic thermal conductivity between reduced and oxidized graphene sheets. The oxidized GSs also exhibit excellent flame retardant behavior and mechanical robustness, with only 2% strength decay after flame treatment. In a broader context, this work demonstrates a useful strategy to design porous nanomaterials with a tunable heat conduction behavior through interface engineering at the nanoscale.

Normal spectral emissivity measurement on five aeronautical alloys

Aeronautical alloys have a good performance on resisting oxidization, corrosion and fatigue in high temperature environments. Therefore, they are not only widely employed in aero-engine but also in nuclear and petroleum industries. The normal spectral emissivity of five alloys in the wavelength ranging 1–15 μm at moderate and high temperature (400–1200 K) is measured. It is found that the emissivity decreases with the increasing of wavelength and increases when temperature rises. The effects of oxidation and flame treatment process are also studied. The results of the oxidized samples indicate that oxidation can enhance the emissivity significantly and alter the wavelength dependent trend. The results of the flame treatment processed samples show that the impurities and defects caused by the flame treatment process moderately increase the emissivity. The experimental data presented in this paper can be used directly to improve the accuracy of radiation computation and other relevant applications.

Tribological and Oxidative Behavior of Thermally Sprayed NiCrBSi Coatings

The behavior of NiCrBSi coatings deposited by three different spraying techniques was studied: flame spray with a subsequent flame treatment (FS + Flame), flame spray with post-laser treatment (FS + Laser) and laser cladding (LC). The coating responses under wear and oxidation conditions were analyzed. Although the microstructure of the coatings deposited by the three different techniques showed similar phases and precipitates, some changes in the size and distribution of these constituents were observed. The pin on disk configuration was used to determine the friction coefficients and wear rates. LC coatings showed the highest wear resistance, with plastic deformation being the main wear mechanism identified for all of the coatings analyzed. Tests under aggressive environments were also performed to determine the oxidation kinetics.

Normal spectral emissivity of GH536 (HastelloyX) in three surface conditions

The normal spectral emissivity of GH536, a nickel-based superalloy, is measured using a FT-IR spectrometer in the wavelength range 1–15μm at moderate and high temperature (400–1200K), as well as the samples with partially oxidized and flame treatment processed. It is found that the emissivity of GH536 decreases with the increasing of emission wavelength, which is well predicted by the electromagnetic wave theory, and increases linearly when the temperature rises. The emissivity of the other two samples with partially oxidized and flame treatment processed is also investigated in details. The results of the partially oxidized sample indicate that oxidation can enhance the emissivity significantly and alter the wavelength dependence trend. And the results of the flame treatment processed sample shows that the impurities and defects caused by the fire treatment process moderately increase the emissivity. The experimental data of GH536 is compared with the results calculated using Hagen-Rubens equation, which shows an inconsistence at high temperature condition. Therefore, a modified emissivity model is proposed, which has a good agreement in measured wavelength range at moderate and high temperature condition.

Effect on Surface Roughness of Laser AblatedSS 321 Material Coated with Graphene and SiC

Objectives: SS 321 is an austenitic stainless steel material which finds application in many fields. The coating on SS 321 by Graphene and SiC are used to improve the thermal resistance and strength of SS 321. Methods/Statistical Analysis: Coating of Graphene and SiC on SS 321 was done by spin coating and drop casting. The coated samples were subject to laser ablation followed by flame treatment. Then treated and untreated samples were characterized by SEM, EDX and Surface roughness measurement. Findings: From the SEM images the coating was found to be uniform and from the EDX measurement, the composition of the samples has been calculated and no observable impurities found. From the surface roughness measurement, it is evident that the roughness parameter changes from untreated to treated samples but there were no sign of cracks, which proves that the coating by Graphene and SiC on SS 321 is viable and increases the strength of the material. Application/Improvement: By doing Atomic Force Microscopy and thermal resistance and strength measurements on Graphene SiC coated SS 321 can give further authentic result or by choosing CNT like materials for coating, may improve the performance of SS 321.

Sterilization of beehive material with a double inductively coupled low pressure plasma

American Foulbrood is a severe, notifiable disease of the honey bee. It is caused by infection of bee larvae with spores of the gram-positive bacterium Paenibacillus larvae. Spores of this organism are found in high numbers in an infected hive and are highly resistant to physical and chemical inactivation methods. The procedures to rehabilitate affected apiaries often result in the destruction of beehive material. In this study we assess the suitability of a double inductively coupled low pressure plasma as a non-destructive, yet effective alternative inactivation method for bacterial spores of the model organism Bacillus subtilis on beehive material. Plasma treatment was able to effectively remove spores from wax, which, under protocols currently established in veterinary practice, normally is destroyed by ignition or autoclaved for sterilization. Spores were removed from wooden surfaces with efficacies significantly higher than methods currently used in veterinary practice, such as scorching by flame treatment. In addition, we were able to non-destructively remove spores from the highly delicate honeycomb wax structures, potentially making treatment of beehive material with double inductively coupled low pressure plasma part of a fast and reliable method to rehabilitate infected bee colonies with the potential to re-use honeycombs.

Fabrication of biomimetic superhydrophobic surfaces by a simple flame treatment method

A simple flame treatment method was explored to construct micro/nanostructures on a surface and then fabricate a biomimetic superhydrophobic surface at a relatively low cost. SiO2-containing polydimethylsiloxane (PDMS) was used as a substrate. The PDMS replicas with various micropatterned surfaces were fabricated using grass leaf, sand paper, and PET sheet with parallel groove geometry as templates via PDMS replica molding. The PDMS replica surfaces with micron structures and the surface of a flat PDMS sheet as a control sample were further treated by flame. The fabricated surfaces were characterized by scanning electron microscopy and water contact angle measurements. The effect of surface microstructures on the transparency of PDMS was also investigated. The studies indicate that the fine nanoscale structures can be produced on the surfaces of PDMS replicas and a flat PDMS sheet by a flame treatment method, and that the hierarchical surface roughness can be adjusted and controlled by varying the flame treatment time. The flame-treated surfaces of PDMS replicas and a flat PDMS sheet possess superhydrophobicity and an ultra-low sliding angle reaching a limiting value of 1°, and the anisotropic wettability of the PDMS replica surface with oriented microgroove structures can be greatly suppressed via flame treatment. The visible light transmittance of the flame-treated flat PDMS surface decreases with prolonged flame treatment times. Copyright © 2016 John Wiley & Sons, Ltd.

Development of the fire retardant glass fabric/carbonized phenolic composite

Because fiber reinforced polymeric composite materials have the advantages of high specific strength and stiffness, their potential for replacing concrete, aluminum and steel. However, the poor fire resistance of fiber reinforced polymeric composite materials is one of the obstacles for their applications.In this study, a fire retardant glass fabric/carbonized phenolic composite was developed using the carbonization of the phenolic resin. Although the glass fiber is not combustible, it melts at approximately 800°C on exposure to fire, whereas the phenolic resin has good fire resistance with minimum smoke levels, excellent dimensional stability and thermal strength. Moreover, the phenolic resin is carbonized at high temperature (above 500°C), which prevents the spread of flames. However, shrinkage during the carbonization process weakens its strength and stiffness.To improve the pristine- and post-fire mechanical properties of the glass fabric/phenolic composite, flame and silane treatments were applied to the glass fabrics. The carbonization and impregnation of the phenolic resin matrix of the composite was repeated several times to develop the glass fabric/carbonized phenolic composite, from which the post-fire tensile strength and the carbonized phenol matrix ratio were measured with respect to the number of carbonization processes.

The effect of four methods of surface activation for improved adhesion of wood polymer composites (WPCs)

Wood Polymer Composites (WPCs) have attracted a lot of interest in recent years as materials with a high renewable content. However the adhesion between WPC components is problematic because of low surface energy and the hydrophobic nature of the most widely used polymer matrices, i.e. polyolefins. Thus this paper has looked at four surface activation pretreatment methods to improve adhesion properties for bonding using epoxy adhesives, namely: hydrogen peroxide solution; hot air; a gas flame; and halogen heating lamps. The treatments were applied to WPC materials made from 60% wood flour in a polypropylene matrix, and lap joint shear strength was measured.Shear strength values showed that all treatments except the halogen heating lamps increased the bond strength and the best results were achieved with hydrogen peroxide treatment at a pH of 7.5 (37% improvement); a two pass hot air treatment at a pass speed of 75mms−1 (44% improvement); and a gas flame treatment at a pass speed of 175mms−1(41% improvement).The bond strength was increased to values that caused failure within the material, rather than at the interfaces of the bond line.

Flame treatment of graphene oxides: cost-effective production of nanoporous graphene electrode for Lithium-ion batteries.

A facile production of highly porous graphene foam by using flame treatment of graphene oxide (GO) is proposed. Highly porous architectures with randomly distributed micro-crack and micro-slit were produced due to the high temperature induced ruinous reduction and rapid expansion of GO. Synchronously, abundant oxygen-containing groups (OCGs) on GO sheets could be effectively removed after flame treatment, which renders significantly increased conductivity to the resultant flame reduced GO (FR-GO). The synergistic effect of micro/nanostructuring and the OCGs removal makes FR-GO a promising candidate for electrode materials. Compared with chemically reduced GO (CR-GO), FR-GO delivers much higher specific capacity. It gives us some hints that flame treatment of graphene-based material is a smart strategy for cost-effective production of anode materials for commercial application.

Effect of surface treatments on the bond strength between resin cement and differently sintered zirconium-oxide ceramics

PurposeThis study investigated the effects of surface treatments on bond strength between resin cement and differently sintered zirconium-oxide ceramics. Methods220 zirconium-oxide ceramic (Ceramill ZI) specimens were prepared, sintered in two different period (Short=Ss, Long=Ls) and divided into ten treatment groups as: GC, no treatment; GSil, silanized (ESPE-Sil); GSilPen, silane flame treatment (Silano-Pen); GSb, sandblasted; GSbSil, sandblasted+silanized; GSbCoSil, sandblasted+silica coated (CoJet)+silanized; GSbRoSil, sandblasted+silica coated (Rocatech-Plus)+silanized; GSbDSil, sandblasted+diamond particle abraded (Micron MDA)+silanized; GSbSilPen, sandblasted+silane flame treatment+silanized; GSbLSil, sandblasted+Er:Yag (Asclepion-MCL30) laser treated+silanized. The composite resin (Filtek Z-250) cylinders were cemented to the treated ceramic surfaces with a resin cement (Panavia F2.0). Shear bond strength test was performed after specimens were stored in water for 24h and thermo-cycled for 6000 cycles (5–55°C). Data were statistically analyzed with two-way analysis of variance (ANOVA) and Tamhane's multiple comparison test (α=0.05). ResultsAccording to the ANOVA, sintering time, surface treatments and their interaction were statistically significant (p<0.05). The highest bond strengths were obtained in GSbCoSil (Ss=13.36/Ls=11.19MPa) and lowest values were obtained in GC (Ss=4.70/Ls=4.62MPa) for both sinter groups. ConclusionsSintering time may be effective on the bond strength and 30μm silica coating (Cojet) with silane coupling application technique increased the bond strength between resin cement and differently sintered zirconium-oxide ceramics.