Editorial
Environmental & Green Materials
Ashutosh Tiwari
Abstract
Climate neutrality has turned out to be crucial in policy and state relationships. In lines of green actions, many capitals have declared aspiring climate neutrality goals to establish their net-zero infrastructures and inhabitants. The increasing emission of greenhouse gases paves the way to enhance ...
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Climate neutrality has turned out to be crucial in policy and state relationships. In lines of green actions, many capitals have declared aspiring climate neutrality goals to establish their net-zero infrastructures and inhabitants. The increasing emission of greenhouse gases paves the way to enhance the earth temperature, which are resulting to endangering lives mainly due to dry up of water reserves. Thus, abrupt climate change is adversely affecting the world-wide ecosystems and biodiversity. The common effects of climate change are causing through droughts, forest fires, cloudbursts, cyclones, earthquakes, heavy rains, snow, cold and hot waves etc. From north to south America and from east to west Asia are experiencing frequently extreme weather events. This interns to fast moving of the global warming. The impact of extreme weather conditions needs to urgently normalise with adopting ecological practices, green scientific protocols, time bound government strategies and comprehensive climate actions.
Research Article
Composite Materials
Daniel Dubecky; Vincent Kvocak; Michala Weissova
Abstract
Composite polymer-concrete beams represent new modern structures that can take an advantage of the polymer's practical tensile properties and combine them with the concrete's favourable compressive properties. Drawing on this knowledge, a set of polymer beams acting compositely with a concrete slab was ...
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Composite polymer-concrete beams represent new modern structures that can take an advantage of the polymer's practical tensile properties and combine them with the concrete's favourable compressive properties. Drawing on this knowledge, a set of polymer beams acting compositely with a concrete slab was designed and manufactured. The aim of the research was to utilise the low weight and high strength of the polymer I-sections and combine them with the high stiffness of the concrete slab, which forms the upper part of the cross-section. The advantage of fibre-reinforced polymer (FRP) beams is their anisotropy, where the strength of the material is increased by placing the fibres uniformly in one direction, and the composite elements are then stressed in the most reinforced direction. To ensure the interaction between the polymer element and the concrete slab, strip shear connectors of a precisely defined shape were developed and utilised. The designed composite beam simulates a pre-cast component that can be applied in bridge structures for short and medium spans. The pre-cast beams were subjected to four-point bending. Apart from the overall deflections of the structure, the stresses in the cross-section of the composite material and the relative deformations/strains on the surface of the concrete part of the cross-section were monitored during the test. The whole experiment yielded new results in both laboratory and theoretical respects, not only regarding the interaction of materials with distinct characteristics but also the properties of composites per se.
Research Article
Structural & Engineering Materials
Beata Stankiewicz
Abstract
Depending on the type of the load which affects the durability and design life glass fibre reinforced polymer (GFRP) structures should be designed so as to take into account as first of all the chemical-physical conditions in which the structure is used including: ultraviolet (UV) radiation, temperature ...
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Depending on the type of the load which affects the durability and design life glass fibre reinforced polymer (GFRP) structures should be designed so as to take into account as first of all the chemical-physical conditions in which the structure is used including: ultraviolet (UV) radiation, temperature influences, humidity, water and chemicals. The results presented herein provide a predictions regarding of the mechanisms involved in the ageing of GFRP pultruded bridge profiles and predicting the property micro scale changes with time and remaining service life of GFRP under real environmental degradation impacts and during simulation laboratory conditions. The outermost layers of FRP (fibre reinforced polymer) composites are damaged mostly because of UV radiation. Radiation also induces remarkable microstructural changes depending on wavelength and intensity, and oxygen availability, eventually leading to polymer chain scission. A scanning electron microscope (SEM) was used to investigate the degradation mechanism of the GFRP samples subjected among others to UV radiation and water vapor condensation. Glass fibre-reinforced polymer GFRP pultruded profiles have great potential in the construction industry, presenting several advantages comparing with traditional materials, among which, the potentially improved durability under environmental influents.
Research Article
Carbon Materials and Technology
Zacharias Fthenakis; Antonios Fountoulakis; Ioannis Petsalakis; Nektarios Lathiotakis
Abstract
This work is part of a systematic study on the energy barriers for the permeation of several molecules, like He, H2, CO, CO2, H2O, NH3, CH4 etc, through nanoporous single layer graphene, having pores with different shape, size, and type. In the present work, we focus on the permeation of CO2 through ...
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This work is part of a systematic study on the energy barriers for the permeation of several molecules, like He, H2, CO, CO2, H2O, NH3, CH4 etc, through nanoporous single layer graphene, having pores with different shape, size, and type. In the present work, we focus on the permeation of CO2 through graphene pores which are constructed when neighboring carbon atoms of the graphene layer are removed from the structure, and nitrogen atoms have replaced the carbon atoms in the boundary of the pore. The energy barriers for each different pore are calculated using 2 different ReaxFF potentials along a path which the molecule would ideally follow in order to pass from the one side of the membrane to the other through the pore. Using the calculated values of the energy barriers, we estimate permeances by employing the kinetic theory of gasses. We give estimates for the preferable sizes and structures of the pores for permeability and demonstrate the ability of nanoporous graphene for CO2 separation.
Research Article
Composite Materials
Miranda Benavides; Denis Leonardo Mayta; Fernando Alonso Cuzziramos; Gerhard Paul Rodriguez; Fredy Alberto Huaman-Mamani
Abstract
The traditional method of manufacturing SiC compounds is associated with a serious environmental problem, mainly due to the need for large amounts of energy (generally derived from oil) to reach processing temperatures (typically above 2500 ºC). In addition, the chemical reaction that gives rise ...
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The traditional method of manufacturing SiC compounds is associated with a serious environmental problem, mainly due to the need for large amounts of energy (generally derived from oil) to reach processing temperatures (typically above 2500 ºC). In addition, the chemical reaction that gives rise to the formation of SiC has CO and CO2 as by-products. Therefore, in this work an alternative method to manufacture SiC/Si composites using waste from the wood industry as the main raw material was developed. SiC/Si composites were fabricated by infiltration of molten silicon into carbon preforms at 1500 °C. The carbon preforms were obtained by pyrolysis (in an inert Ar atmosphere) of four types of resin-carbon mixtures. The carbon used in the mixtures was obtained by pyrolysis of sawdust powder.The mechanical and thermomechanical behavior in uniaxial compression was studied at a constant compression rate of 0.05 mm/min at different temperatures (ambient, 1100 °C and 1400 °C). The maximum resistance values found were in the range of 58 and 384 MPa, while the Young's modulus values were between 40 and 120 GPa. The porosity found in the materials was between 1 and 4%. Finally, the fabricated compounds presented a homogeneous microstructure of interconnected silicon carbide in gray contrast and dispersed and unconnected whitish phases of uniformly distributed silicon.
Research Article
Experimental Techniques
Khaled Saad; Andras Lengyel
Abstract
This research presents a parametric three-dimensional finite element study on the effects of closely spaced knots and related fibre deviations on the flexural failure mechanism of wood. The model considers the effects of the position of the knots along the beam's longitudinal and vertical axis. The numerical ...
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This research presents a parametric three-dimensional finite element study on the effects of closely spaced knots and related fibre deviations on the flexural failure mechanism of wood. The model considers the effects of the position of the knots along the beam's longitudinal and vertical axis. The numerical models were validated by bending tests performed on six beams. The actual three-dimensional geometry of knots and related fibre deviations were determined accurately based on an algorithm proposed previously by the authors. The elastic-plastic constitutive law of Nordic Spruce wood was considered based on the Hill anisotropic model. The failures were numerically predicted with the help of the Tsai-Wu failure criterion. The validated numerical models can also be used based on visual inspections. The user needs only to define the position and size of the knots and the space between them. Moreover, the model allows defining different fibre patterns in the knot vicinity. The model considers a fixed knot located in the tension zone at the mid-span of the beam and a moving knot adjusted at horizontal and vertical centre-to-centre distances d and v from the fixed one. Results revealed that regardless of the distance d (where v = 0), the failure will initiate at the same load levels for both knots. However, moving the adjacent knot diagonally (v not equal to 0) causes shear failure between the knots. The part of the clear wood between the knots is ineffective if the knots' centre-to-centre distance is less than three times the knot diameter.
Research Article
Composite & Ceramic Materials
Vithal Muga; Vaishnavi Kammara; Venkataswamy Perala; Manasa Sunku; Ramaswamy Kadari; Hima Bindu Gaddameedi; Sudhakar Reddy Chandiri
Abstract
Doping of cations into wide bandgap semiconductors is an effective method of increasing photocatalytic activity. This work aims to find out how dopant ions like Ag+, Cu2+ and Sn2+ affect the structural, optical and photocatalytic properties of Li2GeTeO6. The parent Li2GeTeO6 (LGTO) was synthesized by ...
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Doping of cations into wide bandgap semiconductors is an effective method of increasing photocatalytic activity. This work aims to find out how dopant ions like Ag+, Cu2+ and Sn2+ affect the structural, optical and photocatalytic properties of Li2GeTeO6. The parent Li2GeTeO6 (LGTO) was synthesized by conventional solid-state method, whereas the Ag+, Cu2+ and Sn2+-doped Li2GeTeO6 were prepared by a simplistic ion-exchange method. Techniques such as XRD, FT-IR, SEM-EDS, N2 adsorption-desorption analysis, UV-Vis DRS, XPS, and PL were employed to examine the physico-chemical properties of the as-prepared materials and their photocatalytic activities on the degradation of methyl violet (MV) under visible light irradiation. The acquired photocatalytic activity results revealed that all doped samples displayed enhanced photocatalytic performance compared with parent LGTO. The Ag-LGTO had the best photocatalytic activity for MV degradation, with 68.6% degradation efficiency in 180 min of irradiation. Scavenging experiments were carried out to determine the role of various active species generated on the surface of Ag-LGTO during the photocatalytic degradation of MV. The reusability and stability of Ag-LGTO up to five cycles against MV degradation were also investigated. A photocatalytic mechanism for MV degradation over the Ag-LGTO sample was also proposed based on the findings described above.
