This work reports on the fabrication and characterization of Al2O3-based composites reinforced with NiAl + 30 wt% Al2O3 pre-alloyed powder, synthesized via mechanical alloying. Two composite series were prepared using slip casting: Series I with 2.5 vol.% and Series II with 5.0 vol.% of the reinforcement phase. The samples were sintered at 1450 degrees C in a reducing H2/N2 atmosphere. X-ray diffraction revealed that, in both series, after sintering, no NiAl was observed; only Ni was detected. SEM and EDS analyses showed uniform dispersion of the reinforcement. Mechanical testing revealed that increasing the metallic phase reduced the hardness from 17.01 +/- 0.61 GPa (Series I) to 15.73 +/- 1.51 GPa (Series II), while the fracture toughness slightly improved from 5.14 +/- 0.30 to 5.20 +/- 0.37 MPa & centerdot;m0.5. The compressive strength reached 25 kN and 17 kN for Series I and II, respectively. The results demonstrate that a tailored reinforcement content enables control over the microstructure and mechanical performance in Al2O3-NiAl composites.
Ensuring the reliable operation of structural elements using modern materials places increasingly high demands on the accuracy of assessing their key characteristics. One of the most important of these is the elastic modulus of the material. An analysis of methods for determining this modulus was carried out. It has been shown that the main methods, developed at the beginning of the 19th century, are still used today as basic methods without taking into account the characteristics of modern composite materials. It is also shown that the simplifications previously adopted in determining elastic moduli from tensile experiments are not justified. They lead to fictitious values of elastic moduli even for isotropic materials. Analytical dependencies are proposed for obtaining reliable values for this class of materials, which are well confirmed experimentally. It has been proven that these dependencies are unacceptable for determining the elastic moduli of anisotropic materials without taking into account the characteristics of the latter. The methods for determining the elastic moduli for two types of composite materials are presented: monotropic and orthotropic. These methods provide good agreement with experimental values. It is shown that the methods used to date for determining the elastic moduli of structural materials give significantly overestimated values of the determined characteristics compared to the actual ones. In the paper a proposal for determining a modified Young's modulus is presented, which could be more precise and, thus the spread of experimental data could be reduced.
The innovative solid state step-sintering reaction technique was used to fabricate lanthanum doped bismuth-nickel ferrite perovskite oxide (Bi1.7La0.3Ni2Fe2O8). The physical features, surface shape, grain dispersion topography, spatial frequency spectrum and temperature-frequency dependent dielectric properties were investigated. By means of X-ray diffraction, the W-H approach, SEM morphology, histograms and EDAX color mapping, the attributes of the produced material concerning crystallite size (47.5 nm), strain (0.00152), dislocation density(4.43 & times;1014 m-2), polycrystalline grain (0.01 mu m-2 mu m) orientations, uniformly aligned grain texture, modest isotropy (50.45 %) and elemental compositions were evaluated. Impedance spectroscopy analysis of this material provides insight into the dielectric dispersion. The low dielectric loss in the high frequency regime signifies negligible dielectric energy dissipation. The findings support the idea that Bi1.7La0.3Ni2Fe2O8 might be a promising mixed metal oxide-based ceramic component for potential multifunctional electronic device applications.
The standard specimens used to determine the compressive strength of unidirectional (UD) composites are of a relatively small cross-section. The compressive strength of such materials depends on the volume of the tested material and decreases with its increase. Therefore, the results of tests carried out using such specimens may have limited applicability to the design of actual structures, and larger ones should replace standard-sized specimens. The performance of a hybrid holder designed for non-standard specimens of relatively large cross-sections, intended to determine the compressive strength of UD composites, was investigated numerically. Selected numerical results were compared against preexisting experimental data. The holder consisted of a metal cup filled with resin surrounding a specimen. The results showed that (i) concentrations of longitudinal stress occurred in two locations: at the tip of the specimen touching the bottom of the cup and in the resin meniscus plane, (ii) the proportion between them could be controlled by (a) the presence or absence of adhesion between the resin and specimen, and the resin and cup wall, (b) by friction at the mentioned interfaces, and (c) by the specimen immersion depth. Eliminating adhesion and friction at the specimen/resin/cup interfaces reduced the differences in the values of the stress concentration factor present at the end of the specimen and in the meniscus plane, indicating the possibility of optimizing the holder design.
The growing demands related to sustainable development and the need to reduce the environmental impact of the materials industry are leading to a search for alternatives to classic thermosetting resins. Vitrimers - polymers containing covalent adaptive networks, combine the good mechanical properties and thermal stability of cross-linked materials with the possibility of recycling and reprocessing. This study presents epoxy compositions obtained from epoxidized vegetable oil, an acid and anhydride hardener, as well as a transesterification catalyst. The mechanical properties, thermal stability and recyclability of the vitrimers were evaluated, indicating their potential for use in composite materials in line with the rules of the circular economy.
This article presents the results of analyses of aircraft emergency state changes during flight (S1 ... S4 in section 1.1), which will help refine the models of aircraft technical operation processes at airports within a given airline network to enable continued flight. Therefore, in-flight aircraft state changes are eliminated because equipment failures (i.e. aircraft state changes) occur at each stage of the aircraft's flight, requiring fault resolution. Hence, the aircraft's transition through the states during a single flight is presented in the form of a graph. The operational management circuit of the airline's aircraft fleet is represented as a sequence of flights, each consisting of a series of segments between airports within the airline's network within the calendar timeframe of the aircraft's presence in that circuit. The model allows assessment of the aircraft's ability to recover, if necessary, at airports within the airline's network, utilizing the probabilistic and temporal characteristics of the recovery processes employed by airports, which pose a risk of flight delays. Recovery time must be considered to assess the probability and duration of flight delays.
This paper presents a technological sequence of the fabrication process and test results of composite coatings with a nanocrystalline copper matrix including a dispersion phase in the form of graphene flakes deposited by electrochemical reduction on electrical equipment components. The conducted research included the development of solution compositions and process parameters for the deposition of Cu/graphene composite coatings, in addition to adaptation of the coating deposition process to a larger scale on a pilot electroplating line. The innovative aspect presented in the work (a key challenge) was the transfer of the positive results of the work from the laboratory scale to the semi-technical scale. The described work involved running the process in a plating drum and on hangers on a pilot plating line. The surface morphology, and roughness and the structure of the produced composite coatings were characterized. The thickness and bonding of the produced coatings to the substrate material were evaluated. Hardness tests of the produced coatings were carried out. The properties of the Cu/graphene composite coatings produced on the hangers and in the electroplating drum on the pilot electroplating line were compared. The key research challenge was the development of a technology for the fabrication of composite coatings on electrical equipment components, involving the application of Cu/graphene composite coatings by electroplating techniques at on a laboratory scale and then transferring the work to the pilot electroplating line.
The aim of this work is to develop an ultrasonic technique employing phased array probes to detect structural defects in type IV low-pressure tanks used for the storage of hazardous chemicals. Ultrasonic testing was performed by means of an OmniScan MX2 phased-array ultrasonic flaw detector with appropriate probes, and numerical simulations were conducted utilizing CIVA software. Attenuation coefficients were measured for a composite layer excised from a two-layer low-pressure tank. Based on these results, a centre frequency of 5 MHz was selected as optimal. The determined parameters, such as the attenuation coefficient and the structural noise level, were implemented in the CIVA model. The detection criteria were established and color-coded: defects with a signal-to-noise ratio (SNR) < 0 dB were labelled white (undetectable); those 0-10 dB were labelled yellow (limited detectability); and those > 10 dB were labelled green (optimal detectability). The simulation results were validated by testing the composite samples with polytetrafluoroethylene (PTFE) inserts of varying sizes and depths. The defect detectability determined from the simulations was consistent with that obtained from testing reference samples.
Composite materials play a crucial role in the development of lightweight and innovative industry. For high-performance structures such as composite pressure vessels, tubes and pipelines, filament-winding technology is used as a highly automated and reliable manufacturing method. In this study, the mechanical investigation of composite tubes is performed. The analysis consists of a comparison of basalt and glass fibre reinforced plastics (BFRP and GFRP) under axial compression loading. The tubes were manufactured with one layer wound using a 55 degrees winding angle and additional hoop reinforcement in the gripping area. During axial compression loading, the acoustic emission method was used to identify the damage modes occurring in the two groups of materials. Post-failure observations were conducted to assess the crack type and geometry. The results showed that GFRP exhibited superior performance over BFRP in terms of compressive strength (41% higher) and absorbed energy (20% higher).
This work examines the influence of fused deposition modelling (FDM) and hybrid reinforcement with glassy carbon (GC) and nano alumina (n-Al2O3) on the wear behaviour of HDPE composites. The composites containing only n-Al2O3 showed the highest wear and unstable friction due to dominant abrasive mechanisms. The GC-filled HDPE exhibited reduced wear, associated with carbon transfer film formation. The hybrid GC/n-Al2O3 composite demonstrated a synergistic effect, combining surface hardening with self-lubrication, which markedly reduced wear and stabilized the coefficient of friction. Although the FDM-printed samples had higher wear rates than the compression-moulded ones, their coefficients of friction remained similar. The results highlight that hybrid reinforcement can effectively suppress abrasive wear and improve the tribological stability of FDM-processed HDPE composites.
The catalytic electrolysis of water enables this process to be performed at low over-potential, and therefore at a lower energy expenditure. Materials like Ni, Mo or W could substitute costly Pt in this role, especially when applied in the form of coatings. Experiments conducted to date have shown that the efficiency of electrolysis is still increasing in the case of metal nano-rods separated by carbon sheets. The present work is aimed at assessing the temperature stability of such a coating obtained by the magnetron sputtering of an AISI 316L (Fe69Cr18Ni11Mo2, in wt%) target in an atmosphere of Ar and C2H2. The use of in-situ TEM (transmission electron microscopy) heating allowed the start of crystallization of the so-produced coating to be determined, which occurred at similar to 400 degrees C. Isothermal annealing at this temperature for 1 hour resulted in the predominant precipitation of alpha-Fe in parallel with a smaller amount of Ni, Fe, C rich nano-particles, while Cr was distributed relatively uniformly throughout the whole coating. Simultaneously, the amorphous carbon underwent transformation to graphite. The experiment showed that the amorphous metal-carbon composite coatings developed for the hydrogen evolution reaction (HER) may be liable to crystallize in the case it was used in the catalytic electrolysis of superheated steam.
Non-destructive testing (NDT) is gaining increasing importance in the marine industry, with its application expanding beyond aviation into composite yacht manufacturing. This paper presents selected case studies using ultrasonic pulse-echo, infrared thermography, and laser shearography, performed on representative GFRP samples as well as real-world marine structures. The discussed examples highlight the challenges specific to thick composite sections, diverse defect locations, and the need for image-based evaluation systems. The selected cases address problems encountered by yacht manufacturers and attempt to indicate possible solutions.
The paper presents the production technology and properties of layered metallic composites in view of their use for the creation of highly efficient phase-change heat exchangers. It discusses the experimental results of the boiling heat transfer of distilled water and ethanol under atmospheric pressure on copper substrates on which a metal mesh layer, which augments heat transfer via boiling, was applied by sintering. The sintering technology enables durable bonds to be obtained between the joined elements, which results in proper strength properties. The meshes used in the experiments were made of bronze, brass and copper. The heat transfer results indicate that all the samples with the additional layer showed better performance - they dissipated more heat at the same temperature difference in comparison to the smooth surface without any mesh applied onto it, while the copper mesh outperformed the others. It seems to be linked to the highest thermal conductivity of this material in relation to the copper alloys considered in the study.
Stiffness characteristics are often decisive in the choice of material for structural parts. At the same time, the process of their determination for anisotropic materials does not fully satisfy the requirements in terms of reliability and reproducibility. This work is devoted to the development of an approach for determining the moduli of elasticity. An analysis of the Timoshenko approaches developed to estimate the shear component of deflection in transverse bending is presented. The drawbacks preventing their use as a basis for modern methods of determining the elastic components of structural materials are noted. An approach for determining the elastic moduli is proposed, the basis of which are the maximum values of deflections and angles of rotation of the cross-sections of a specimen under three-point transverse bending. The relationship between angular and linear displacements under the considered type of loading is established, which allows stable and reliable values of elasticity moduli to be obtained from the data of angular displacements. The acceptability of the proposed approach for determining the elastic moduli of both isotropic materials and composites is shown.
The distinctive solid state mixed oxide-based step-sintering technique was used to fabricate nickel cobaltite (NiCo2O4) material from Ni2O3 and Co3O4. The material's attributes, namely crystallite size of 40.06 nm with minimal strain of 0.0024, dislocation density 8.4 x 1014 m-2 and cubic crystal structure were revealed by means of X-ray diffraction and the W-H method. SEM micrographs of the microstructure reveal polycrystalline grains of different sizes with clear grain boundaries and an evenly aligned grain texture. This material has been proven to be a suitable capacitive component for advanced electronic applications with the aid of experimentally investigated structural features, grain distribution topography, polar histogram and temperature dependent frequency dispersion dielectric spectra. This material is a desirable candidate for device designs since it exhibits relatively high dielectric permittivity and low dielectric loss at high frequencies, indicating minimum energy dissipation. The results and analysis affirm the dielectric properties, lending credence to the idea that nickel cobaltite could be a viable oxide-based ceramic entity for appropriate device applications.
This article focuses on the glass-ceramic composite structure of glazes with photoluminescent properties. In this study the luminescent glaze is based on phosphor: SrAl2O3:Eu3+, Dy3+ (called GS). The study investigated the effect of the phosphor concentration in the glaze within the range of 10-30 wt% and the effect of annealing time within the range of 0-60 minutes. Changes in phase composition were observed as a function of the process parameters (annealing time) and changes in the photoluminescent properties (excitation spectrum, emission spectrum, and quantum yield) to determine the optimal annealing time during glazing. The study found that with increasing glazing time, the luminescent properties deteriorated due to degradation of the crystalline structure.
In order to distinguish the fabricated lanthanum doped bismuth-nickel ferrite perovskite oxide material (BI(1.7)LA(0.3)NI(2)FE(2)O(8)) as a competitive ferroelectric component, the material's ferroelectric and electrical properties were investigated. Complex impedance spectroscopy, electric modulus spectroscopy, P-E hysteresis loop measurement, capacitance-temperature measurement, FTIR absorption spectroscopy and UV-Visible spectroscopy were carried out to delineate its multifunctional properties. This La substituted material is characterized by excellent frequency-temperature stability, a semiconducting nature, non-Debye thermal relaxation, ferroelectric property (polarization 0.4 mu C/cm(2)), temperature dependent capacitance maximum sensitivity (58.7nF/degrees C) and a stable optical band gap (similar to 3.32 eV), which are the major attributes of this ceramic to substantiate it as a promising ferroelectric entity for advanced technological applications.
With the growing global demand for wollastonite, its potential as a supplementary cementitious material has been explored by inducing carbonation. This study investigates the impact of partially replacing cement with varying amounts of carbonated wollastonite (10-50 wt%) while maintaining a constant proportion of limestone (15 wt%) and gypsum (5 wt%). The developed mixes of blended Portland cement (PC) composites were evaluated for mechanical performance in terms of compressive and flexural strength. The results indicate that the mix containing 20 wt% wollastonite, along with 15 wt% limestone and 5 wt% gypsum, exhibited an approximately 30% higher compressive strength compared to conventional mortar, along with a significant increase of about 62% for the flexural strength. X-ray diffraction (XRD) analysis was performed to assess the phase composition, while thermogravimetric analysis (TGA) quantified the portlandite content and chemically bound water. Microstructural analysis further revealed the formation of the main hydration products such as ettringite, portlandite, and anhydrite enhanced structural integrity. The findings highlight the potential of carbonated wollastonite along with limestone and gypsum in enhancing the mechanical and microstructural properties of the cementitious composites. The mixes with 20 wt% wollastonite along with 15 wt% limestone and 5 wt% gypsum exhibited superior performance compared to other the mixes. However, excessive incorporation resulted in a weakened mechanical performance and microstructure. The findings demonstrate the potential for utilizing carbonated wollastonite in the development of eco-friendly binders, contributing to the reduction in the environmental impact caused by the construction industry.
Wet filament winding is a well-established process to manufacture fibre reinforced polymer (FRP) pressurised vessels. However, due to the large number of process parameters and their interaction, it is difficult to achieve the best component properties from the material system used. For this reason, this article presents an optimisation sequence for setting the individual process parameters, taking into account and prioritising the interactions that occur in each case. The methods employed to optimise the individual process parameters are presented in detail and corresponding production tests were carried out with an exemplary material system. In the course of evaluating the component quality achieved by varying the process parameters using NOL ring tests and analysing micrographs of test specimens, the corresponding optimum process settings for the material system were defined and the achievable component quality was documented.
