Surface properties of new green building material after TiO2–SiO2 coatings deposition

The aim of this study was the surface functionalization of a new green ceramic material, obtained using packaging glass waste (PGW), to improve its cleanability. This objective was reached through the deposition by air-brushing of a nanostructured coating based on titania–silica sol–gel suspension. The coatings were deposited on both glazed and unglazed ceramic substrates and the thermal treatment conditions (temperature) were optimized. The obtained results suggest that the applied coatings are transparent and show a good scratch resistance and photocatalitic activity under the tested conditions. The photodegradation process and the mechanical properties are clearly affected by the thermal treatment and thus by the sample surface roughness. The best surface properties were obtained with a thermal treatment at temperature of 150 °C. These coatings do not exhibit either cracks from the substrate. All in all, the developed surface modified ceramic material is attractive as potential sustainable building material.     

Improvement of nanoparticle filtration efficiency through synthesis of SiC whisker on graphite felt by the VS CVD mechanism

This study examines the synthesis of SiC whisker on graphite felt through the non-catalytic VS CVD (Vapor Solid Chemical Vaporized Deposition) mechanism in order to investigate its potential as a filter to replace the conventional DPF (Diesel Particulate Filer). Since the CVD process is conducted mostly in high temperature exceeding 1000 °C, many restrictions exist in selecting the substrate. Graphite felt is a filter form of non-woven fabric. The graphite felt was selected as a suitable substrate material for this study based on the VS CVD mechanism due to its relatively low cost, high heat resistance, and high flexibility. The appropriate SiC whisker structure of the nanoscale was grown on the graphite felt that exhibited the fore-mentioned characteristics. This enhanced the filtration performance of the bare graphite felt filter more than two times without compromising the gas permeability. Additionally, thermal oxidation resistance was elevated by at least 200 °C more than the bare graphite felt, thereby indicating the transfer of a part of the desirable chemical properties of the SiC.     

Characterization system based on image mapping for field emission devices

Field Emission devices (FE) have been proposed as efficient electron sources for several applications such as electron microscopy and vacuum sensors. Evidently, characterization methods applied during development phase of FE devices are crucial to evaluate aspects related with their working stability, homogeneity, and efficiency. However, the traditional methods provide only overall information about such characteristics, which difficult to improve the performance of these devices and their integration with electronics. To overcome this problem, this work presents an alternative system to characterize FE devices through electron emission imaging in real-time. The proposed system acquires I-V features of FE devices, while a video camera captures the emission image from a phosphor screen. Virtual instrumentation based on LabVIEW manages the whole system including measurement instruments, image capture, and data processing. As a result, histograms, 3D maps, and other FE analyses provide information about emitting characteristics of selected regions of interest. The main contribution of this work is to offer an important tool for the analyses of electron emission, by the association of captured images with the localized emission current. The extracted information from our system can efficiently support the characterization and the development of FE devices.     

Cellular glass obtained from non-powder preforms by foaming with steam

Cellular glass, or foamed glass, has been obtained as a result of the heating (to 700–800 °C) of heavy and strong preforms formed due to the binding properties of the silicate additives. Durability of the preforms reached 6 MPa at the density of 1.8 g/cm³. The main expanding agent in the composition is steam, which can also be a carbon oxidizer and increase the amount of the evolved gases and decrease the density of the foamed glass obtained. As a result of changing the initial composition structure, the density of the obtained foamed glass varied from 0.14 to 0.6 g/cm³, its breaking strength - from 0.6 to 5.0 MPa. and heat conductivity – from 0.045 to 0.15 W/(m·К), respectively. The speed of expansion of the preforms had an extreme character with the induction period typical for topochemical reactions. The obtained cellular materials possessed a distinct crystalline structure. The experiments showed the possibility of obtaining cellular materials with acceptable properties from different types of glass for the solution of environmental tasks. Various technological methods of obtaining cellular material blocks from preforms of various forms were tested to use them for thermal insulation and facing materials.     

Effect of sintering temperature on mechanical properties of magnesia partially stabilized zirconia refractory

The optimized sintering conditions for a 3.5 wt% magnesia partially stabilized zirconia (Mg-PSZ) refractory were proposed in our recent research. The influence of the sintering temperature on the development of phase composition, microstructure, densification, thermal expansion and mechanical strength was studied in detail by X-ray diffraction (XRD), scanning electron microscope (SEM), He-pycnometer, high temperature dilatometry and three-point bending test. The samples sintered at 1670 °C had the highest bend strength, the maximum densification, the lowest thermal expansion coefficient (CTE), a homogeneous microstructure and a linear change in thermal expansion.     

Modeling of continuous ultrasonic impregnation and consolidation of thermoplastic matrix composites

Ultrasonic propagation was used to provide heat and pressure in order to perform impregnation and consolidation during production of thermoplastic matrix composites. For this purpose, a new experimental set-up, integrating a laboratory filament winding machine with a horn and a compaction roller, was developed.The heat transfer phenomena occurring during continuous impregnation and consolidation were simulated solving by finite element (FE) analysis the energy balance equations in 2D accounting for the heat generated by ultrasonic waves, the melting characteristics of the matrix and the movement of the thermoplastic commingled roving.The temperature distribution in the composite, predicted by the numerical simulations, was validated by temperature measurements during the production of E-glass/polypropylene cylinders, with the optimized parameters obtained by the FE analysis. The ultrasonic consolidated composite cylinders were characterized by low void content and a shear modulus comparable with that obtained by the micromechanical analysis.     

Experimental and finite element studies on hot sizing process for L-shaped composite beams

This work aims at developing a hot sizing process on composite materials to correct the profiles of composite structures during manufacture. Hot sizing experiments were carried out at 150 °C with different sizing loads and hot sizing periods for L-shaped composite beams made of carbon fiber plain-weave fabric and epoxy resin. To predict the springback in hot sizing process, a corresponding finite element simulation method was developed using stress relaxation equations determined at the same temperature. Excellent agreements between the predicted and observed results were obtained. The effects of the component thickness and 45° ply percentage on the springback rate were investigated by simulation. Springback rate in hot sizing process on composite materials ranges from 60% to 95%. In conclusion hot sizing process is proved to be a valid method for compensation for the process-induced deformation (PID) of L-shaped composite beams.     

Influence of the order-disorder transition on the magnetic properties of Fe75Al25-xSix alloys

The influence of the different crystal structures and the variation of the lattice parameter on the evolution of the magnetism in the order-disorder transition produced by crushing and mechanical milling in the intermetallic Fe₇₅Al_25-xSi_x alloys (x = 7.5, 12.5, 17.5, 25) has been systematically studied by means of XRD measurements, Mössbauer spectroscopy and magnetic measurements. The results indicate that with the addition of Si to binary Fe₇₅Al₂₅ alloy the mechanical deformation needed to disorder the alloys increases. At the same time the variation of the lattice parameter due to the disorder is reduced as Si is added. The magnetic measurements indicate that there is a complex behaviour in ternary alloys with an opposite influence of Si and Al during the order-disorder transition. However, when the transition is fulfilled there is a linear relationship between structural and magnetic parameters.     

Semi-rigid biopolyurethane foams based on palm-oil polyol and reinforced with cellulose nanocrystals

In this study, water-blown biopolyurethane (BPU) foams based on palm oil were developed and cellulose nanocrystals (CNC) were incorporated to improve the mechanical properties of the foams. In addition, the foams were compared with petroleum polyurethane (PPU) foam. The foam properties and cellular morphology were characterized. The obtained results revealed that a low-density, semi-rigid BPU foam was prepared using a new formulation. CNC as an additive significantly improved the compressive strength from 54 to 117 kPa. Additionally, cyclic compression tests indicated that the addition of CNC increased the rigidity, leading to decreased deformation resilience. The dimensional stability of BPU foams was increased with increasing CNC concentration for both heating and freezing conditions.Therefore, the developed BPU nanocomposite foams are expected to have great potential as core material in composite sandwich panels as well as in other construction materials.     

Interlaminar fracture of CF/EP composite containing a dual-component microencapsulated self-healant

We present an experimental study of the self-healing ability of carbon fibre/epoxy (CF/EP) composite laminates with microencapsulated epoxy and its hardener (mercaptan) as a healing agent. Epoxy- and hardener-loaded microcapsules (average size large: 123 μm; small: 65 μm) were prepared by in situ polymerisation in an oil-in-water emulsion and were dry-dispersed at the ratio 1:1 on the surface of unidirectional carbon fabric layer. The CF/EP laminates were fabricated using a vacuum-assisted resin infusion (VARI) process. Width-tapered double cantilever beam (WTDCB) specimens were used to measure mode-I interlaminar fracture toughness of the CF/EP composites with a pre-crack in the centre plane where the microcapsules were placed. Incorporation of the dual-component healant stored in the fragile microcapsules provided the laminates with healing capability on delamination damage by recovering as much as 80% of its fracture toughness. It was also observed that the recovery of fracture toughness was directly correlated with the amount of healant covering the fracture plane, with the highest healing efficiency obtained for the laminate with large capsules.