Search

Students in secondary vocational education often have to learn and practice their skills in potentially dangerous situations, operating complex machinery or working in hazardous conditions. As a consequence, they need to be trained on how to work safely, to respect safety regulations, to wear protective gear and related equipment, to consider ergonomics, and to follow emergency procedures. However, this is difficult in current teaching on hazard perception due to a lack of authentic and real-life learning conditions, and due to learning materials often not being adapted to secondary vocational students. To address these challenges, we adopted an Educational Design Approach in which we designed, developed, and tested a low-cost, mobile immersive virtual reality serious game, teaching hazard perception to secondary vocational students. We engaged 8 teachers and 50 students from 5 secondary vocational schools to co-design and test the prototype serious game. Final test results demonstrate both students and teachers valued the learning experience positively, in terms of spatial presence, involvement, design, interest/enjoyment and value/usefulness. During several iterations, we were also able to identify critical design elements, which were valued positively in terms of both enjoyment and perceived usefulness. The design elements are discussed in a detailed way to support both researchers and practitioners in their future design of immersive virtual reality learning experiences. Finally, directions for future research are presented.

Abstract Sulfur particles coated by activation of metal alkoxide precursors, aluminum–sulfur (Alu–S) and vanadium–sulfur (Van–S), were produced by dielectric barrier discharge (DBD) plasma technology under low temperature and ambient pressure conditions. We report a safe, solvent‐free, low‐cost, and low‐energy consumption coating process that is compatible for sustainable technology up‐scaling. NMR, XPS, SEM, and XRD characterization methods were used to determine the chemical characteristics and the superior behavior of Li–S cells using metal oxide‐based coated sulfur materials. The chemical composition of the coatings is a mixture of the different elements present in the metal alkoxide precursor. The presence of alumina Al2O3 within the coating was confirmed. Multi‐C rate and long‐term galvanostatic cycling at rate C/10 showed that the rate capability losses and capacity fade could be highly mitigated for the Li–S cells containing the coated sulfur materials in comparison to the references uncoated (raw) sulfur. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) confirm the lower charge‐transfer resistance and potential hysteresis in the electrodes containing the coated sulfur particles. Our results show that the electrochemical performance of the Li–S cells based on the different coating materials can be ranked as Alu‐S > Van‐S > Raw sulfur.

A one-dimensional (1-D) fluid model is developed for an RF acetylene discharge. In total, 24 species (neutrals, radicals, electrons, and ions) are considered. For every species, a mass balance equation is solved. Further, the electron energy equation and the Poisson equation are also considered. Reactions taken into account include 19 electron-neutral, one ion-neutral, and 17 neutral-neutral reactions. The reaction rate coefficients of the ion-neutral and neutral-neutral reactions are taken from literature. The rate coefficients of the electron-neutral reactions depend strongly on the average electron energy, and are, therefore, obtained from a simplified Boltzmann equation. The 1-D fluid model yields, among others, information about the densities of the different species in the plasma. The most important neutral species in an acetylene plasma are [C.sub.2][H.sub.2] and [H.sub.2]. Further, the radicals [C.sub.4][H.sub.2], [C.sub.6][H.sub.2], and [C.sub.8][H.sub.2] (to a minor extent) are also present at high densities. These higher order carbon radicals are mainly formed in neutral-neutral reactions with [C.sub.2]H. Other radical species present at high densities are H, [C.sub.2][H.sub.3], [CH.sub.2], and [C.sub.x]H (with x equal to 2, 4, and 6). The most important ionic species are found to be [C.sub.4][H.sup.+.sub.2], [C.sub.2] [H.sup.+.sub.2], and [C.sub.6][[H.sub.+.sub.2]. Finally, a comparison is made between an acetylene and a methane plasma. Index Terms--Acetylene discharges, plasma modeling.

Li‐ion batteries (LIBs) are currently the most preferred energy storage devices in portable applications. Recent surge in the production of electric vehicles in the wake of the current global warming scenario has strongly increased the demand for LIBs, thereby reinforcing the need for new battery chemistries as well as making the existing production chain more efficient and sustainable. Several new technologies are explored to achieve these goals. Among them, plasma technology has the potential to simplify the synthesis and modification of battery materials, enable 'dry' and 'green' processing that eliminate the need for solvents that are often toxic, expensive, flammable, and energy‐intensive. In this review, we have attempted to provide an overview of state‐of‐the‐art (scientific) research and development with respect to the application of plasma‐based processes in the synthesis and modification of materials for battery components. We have explored various applications wherein plasma‐based processes have been demonstrated in the processing of electrode materials, electrolytes, and separators in addition to the recent developments in the context of solid‐state and flexible batteries. Our analysis shows that plasma‐based technologies are slowly but steadily gaining attention in these areas. Several technical and conventional issues remain, which require innovations at the conceptual as well as engineering levels. Technical issues include the selection of appropriate plasma type and precursors, plasma density, selectivity, and a preferable shift from vacuum to atmospheric conditions. The conventional issues include the practical difficulties in converting or adapting the assembly lines to plasma‐based technology. From a business perspective, all that matters is the cost per mAh g−1 of energy produced, for which, unfortunately, we do not have sufficient quantitative data yet with regard to the materials processed by plasma‐based technologies. However, the battery manufacturing sector is now open for innovations like never before. Therefore, it remains to be seen how plasma technologies embrace this opportunity and penetrate the battery production sector, where the key parameters are efficiency and cost‐effectiveness. Would 'giving it the plasma touch' bring added value to the battery manufacturing processes? That is the question we try to address in this review. [ABSTRACT FROM AUTHOR]

The electric field emission behavior of vertically aligned few-layer graphene was studied in a parallel plate–type setup. Few-layer graphene was synthesized in the absence of any metallic catalyst by microwave plasma enhanced chemical vapor deposition with gas mixtures of methane and hydrogen. The deposit consists of nanostructures that are several micrometers wide, highly crystalline stacks of four to six atomic layers of graphene, aligned vertically to the substrate surface in a high density network. The few-layer graphene is found to be a good field emitter, characterized by turn-on fields as low as 1 V/μm and field amplification factors up to several thousands. We observe a clear dependence of the few-layer graphene field emission behavior on the synthesis parameters: Hydrogen is identified as an efficient etchant to improve field emission, and samples grown on titanium show lower turn-on field values and higher amplification factors when compared to samples grown on silicon. [ABSTRACT FROM AUTHOR]

A comparison is made between a one-dimensional (1D) and a two-dimensional (2D) self-consistent fluid model for a methane rf plasma, used for the deposition of diamond-like carbon layers. Both fluid models consider the same species (i.e., 20 in total; neutrals, radicals, ions, and electrons) and the same electron-neutral, ion-neutral, and neutral-neutral reactions. The reaction rate coefficients of the different electron-neutral reactions depend strongly on the average electron energy, and are obtained from the simplified Boltzmann equation. All simulations are limited to the alpha regime, hence secondary electrons are not taken into account. Whereas the 1D fluid model considers only the distance between the electrodes (axial direction), the 2D fluid model takes into account the axial as well as the radial directions (i.e., distance between the electrodes and the radius of the plasma reactor, respectively). The calculation results (species densities and species fluxes towards the electrodes) obtained with the 1D and 2D fluid model are in relatively good agreement. However, the 2D fluid model can give additional information on the fluxes towards the electrodes, as a function of electrode radius. It is found that the fluxes of the plasma species towards both electrodes show a nonuniform profile, as a function of electrode radius. This will have an effect on the uniformity of the deposited layer. [ABSTRACT FROM AUTHOR]

Advances in the synthesis of porous microspheres and in their functionalization are increasing the interest in applications of alumina. This paper deals with coatings plasma deposited from 3-aminopropyltriethoxysilane by means of dielectric barrier discharges on alumina porous microspheres, shaped by a vibrational droplet coagulation technique. Aims of the work are the functionalization of the particles with active amino groups, as well as the evaluation of their surface coverage and of the penetration of the coatings into their pores. A multi-diagnostic approach was used for the chemical/morphological characterization of the particles. It was found that 5 min exposure to plasma discharges promotes the deposition of homogeneous coatings onto the microspheres and within their pores, down to 1 μm. [ABSTRACT FROM AUTHOR]

Lignocellulose represents a potential supply of sustainable feedstock for the production of biofuels and chemicals. There is, however, an important cost and efficiency challenge associated with the conversion of such lignocellulosics. Because its structure is complex and not prone to undergo chemical reactions very easily, chemical and mechanical pretreatments are usually necessary to be able to refine them into the compositional building blocks (carbohydrates and lignin) from which value-added platform molecules, such as glucose, ethylene glycol, 5-hydroxymethylfurfural, and levulinic acid, and biofuels, such as bioderived naphtha, kerosene, and diesel fractions, will be produced. Conventional (wet) methods are usually polluting, aggressive, and highly energy consuming, so any alternative activation procedure of the lignocellulose is highly recommended and anticipated in recent and future biomass research. Lignocellulosic plasma activation has emerged as an interesting (dry) treatment technique. In the long run, in particular, in times of fairly accessible renewable electricity, plasma may be considered as an alternative to conventional pretreatment methods, but current knowledge is too little and examples too few to guarantee that statement. This review therefore highlights recent knowledge, advancements, and shortcomings in the field of plasma treatment of cellulose and lignocellulose with regard to the (structural and chemical) effects and impact on the future of pretreatment methods. [ABSTRACT FROM AUTHOR]

Reductive hydrolysis of cellulose to hexitols is a promising technology to valorize cellulose streams. Several catalytic systems have been reported to successfully process commercially available purified cellulose powders according to this technology. Ruthenium-loaded USY zeolites in the presence of minute amounts of HCl previously showed very high hexitol yields. This contribution first investigates into more detail the impact of several cellulose accessibility-related properties like cellulose crystallinity, particle size and degree of polymerization on the conversion rate and hexitol selectivity. Therefore, a series of commercial cellulose samples and several mechano- and chemotreated ones were processed with the Ru/H-USY–HCl catalytic system under standard hot liquid water conditions. The results reveal that the polymerization degree has a large impact on both the conversion rate and selectivity, but its impact fades for DPs lower than 200. From then on, the dominant parameters are the particle size and crystallinity. A second part addresses the influence of cellulose purity. Therefore, organosolv pulps of three lignocellulosic substrates (wheat straw, spruce and birch wood), optionally followed by a bleaching procedure, were processed under the same catalytic circumstances. Here factors like residual lignin content and acid buffer capacity appeared crucial, pointing to the necessity of a dedicated delignification and purification procedure step in order to form the most reactive cellulose feedstock for hexitol production. Complete removal of non-glucosic components is not required since processing of ethanol organosolv birch cellulose and bleached ethanol organosolv wheat straw cellulose, both containing about 6 wt% of lignin and minor contents of ashes and proteins, showed a similar hexitol yield, viz. 34–39%, to that derived from pure microcrystalline cellulose. [ABSTRACT FROM AUTHOR]

Protein adsorption on inorganic surfaces involves a complex mechanism which could be controlled by surface functionalization methods. A dry surface functionalization method for powders could be beneficial as compared to wet-chemical methods, since aspects like suspension preparation and subsequent drying can be avoided. This paper focuses on atmospheric pressure plasma technology for surface activation of hydroxyapatite powder as a carrier in oral administration applications, aiming at increasing the loading capacity of proteins. Hydroxyapatite powder is treated in N2 and N2H2 atmospheric plasma processes within a static and a dynamic reactor. The influence of plasma activation on the protein adsorption isotherms, powder characteristics: particle morphology, specific surface area, and particle size distribution; have been discussed. The nature and amount of functional groups are studied by zeta potential measurements, thermogravimetric analysis, and titration analysis. Atmospheric plasma treatment increases the protein loading up to 37% when hydroxyapatite powder is treated in pure N2 plasma whereas that of powder activated using N2H2 plasma increased by 13%. The increased protein loading can be attributed to the creation of nitrogen and oxygen containing moieties which cause an increased hydrophilicity after plasma treatment. [ABSTRACT FROM AUTHOR]

This study addresses complex daily activity-travel routines of households with young children and their proper representation in a computational process model of travel demand using family skeletons expressed as family sequence patterns. Building on qualitative interview research findings, an a priori classification of family types is defined according to the distribution of care and work responsibilities in the household on a typical weekday. Enriched census data are examined to calculate the share of each family type in the region of Flanders in Belgium. Next, individual activity-travel sequence patterns are drawn for children and adults. Finally, these individual sequences are combined to family sequence patterns, yielding a concise representation of skeletal information in activity-travel patterns of household members and their interrelationships. This process is tested and the method offers a promising approach to both household activity-travel analysis and travel demand modelling. [ABSTRACT FROM AUTHOR]

Proposes a one-dimensional fluid model for a radio frequency acetylene discharge. Description of the one-dimensional fluid model; Results of the model; Comparison of the results obtained for an acetylene and a methane plasma.

A promising method for the production of few-layer graphene (FLG) is microwave plasma-enhanced chemical vapour deposition (MW PECVD). However, the growth mechanism of PECVD-synthesized FLG is not completely understood. The aim of this work was to investigate the initial stages of the growth process of FLG deposited by MW PECVD on several substrates (quartz, silicon, platinum). The deposited thin films were characterized by angle-resolved x-ray photoelectron spectroscopy (ARXPS), electron backscattered diffraction (EBSD), scanning electron microscopy (SEM) and x-ray diffraction (XRD). It was found that the initial stages of the deposition were different for the three chosen substrate materials. However, the fully grown FLG layers were similar for all substrates. [ABSTRACT FROM AUTHOR]

If graphene is ever going to live up to the promises of future nanoelectronic devices, an easy and cheap route for mass production is an essential requirement. A way to extend the capabilities of plasma-enhanced chemical vapour deposition to the synthesis of freestanding few-layer graphene is presented. Micrometre-wide flakes consisting of four to six atomic layers of stacked graphene sheets have been synthesized by controlled recombination of carbon radicals in a microwave plasma. A simple and highly reproducible technique is essential, since the resulting flakes can be synthesized without the need for a catalyst on the surface of any substrate that withstands elevated temperatures up to 700 °C. A thorough structural analysis of the flakes is performed with electron microscopy, x-ray diffraction, Raman spectroscopy and scanning tunnelling microscopy. The resulting graphene flakes are aligned vertically to the substrate surface and grow according to a three-step process, as revealed by the combined analysis of electron microscopy and x-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

A two-step catalyst annealing process is developed in order to control the diameter of nickel catalyst particles for the growth of carbon nanotubes (CNTs) by microwave plasma-enhanced chemical vapour deposition (MW PECVD). Thermal annealing of a continuous nickel film in a hydrogen (H2) environment in a first step is found to be insufficient for the formation of nanometre-size, high-density catalyst particles. In a second step, a H2 MW plasma treatment decreases the catalyst diameter by a factor of two and increases the particle density by a factor of five. An x-ray photoelectron spectroscopy study of the catalyst after each step in the annealing process is presented. It is found that the catalyst particles interact with the substrate during thermal annealing, thereby forming a silicate, even if a buffer layer in between the catalyst and the substrate is intended to prevent silicate formation. The silicate formation and reduction is shown to be directly related to the CNT growth mechanism, determining whether the catalyst particles reside at the base or the tip of the growing CNTs. The catalyst particles are used for the growth of a high-density CNT coating by MW PECVD. CNTs are analysed with electron microscopy and Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: An atmospheric pressure plasma jet is adapted in order to treat polymeric powders. Nitrogen is used as the main operating gas. Ultra high molecular weight polyethylene powder particles are treated in this modified plasma jet reactor. In order to have a reasonable contact time between particles and plasma, the powder is passed 10 times through the reactor. Treated powders are characterized with XPS and some quick tests for the assessment of the wettability of the powder, like a dispersion test in water. After plasma-treatment, about 7at.% oxygen and 1at.% nitrogen are incorporated at the particle surface. An improved dispersability of treated PE in water is observed and the treatment is found to be stable in time. The amount of oxygen groups at the particle surface can be increased by adding CO2 in the afterglow of the plasma jet. In order to increase the efficiency of the treatment, the reactor is enlarged and an improved wettability can be achieved by 1 pass through this enlarged system. [Copyright &y& Elsevier]

Abstract: Carbon nanowalls (CNWs) are functionalized with short DNA strands. CNWs are a network of upstanding carbon flakes consisting of 4–6 graphene layers packed together. The biological modification of these structures is carried out via the photochemical attachment of an unsaturated fatty acid linker molecule, followed by an EDC-mediated reaction to bind amino-modified DNA strands to the linker. Hybridization experiments are done using complementary and mismatch DNA strands. Fluorescence microscopy shows a clear difference between EDC-negative and EDC-positive samples, supporting the covalent nature of the DNA attachment. Furthermore, we demonstrate that the hybridization is highly selective and reproducible. [Copyright &y& Elsevier]

Abstract: BC x N y thin films deposited at 250°C by pulsed reactive magnetron sputtering of a B4C target in an Ar/N2 plasma were studied by elastic recoil detection analysis, Fourier transform infrared, Raman, and photoelectron spectroscopy, electron microscopy, and nanoindentation. In the concentration range of 6% to 100% N2 in the sputter plasma the segregation into nanocrystalline hexagonal boron nitride and amorphous sp2 carbon is the dominant process during the film growth. The stoichiometric ratio and structural details of the major phases depend on the N2 concentration in the plasma and have significant influence on the Young′s modulus and the elastic recovery of the BC x N y thin films. [Copyright &y& Elsevier]