Influence of Iron on the Mullite Formation
Influence of iron on the crystallization mechanism of mullite obtained from the hybrid gels and doped with different concentrations of iron was examined. DTA analysis showed that iron addition had a beneficial effect on the mullite formation leading to the temperature decreasing as the amount of iron increased. X-ray diffraction and Mössbauer spectroscopy confirmed the increased iron content in the mullite lattice, which led to an increase in the unit parameter and was related to the higher iron content in regular octahedra, disordered octahedra, and tetrahedra with oxygen vacancies. Plate-like morphology observed by SEM suggests the two-dimensional crystal growth (n = 2). The most prominent kinetic models were used to estimate n and Ea from the DTA curves. Ea values increases as iron content increase, indicating that mullitization slows down due to iron incorporation. The Ea values for the undoped mullite sample ranged from 820 to 860 kJ/mol, from 820 to 890 kJ/mol for the irondoped mullite sample containing 6.0 wt% of Fe2O3, and from 960 to 1060 kJ/mol for the irondoped mullite sample containing 12 wt% of Fe2O3.
Influence of Iron on the Mullite Formation-Supplementary
Thermal Stability and Leaching Behavior of Alkali-Activated Slag Doped with Electric Arc Furnace Dust
The study presented in this paper explores the simultaneous valorization of electric arc furnace slag (EAFS) and electric arc furnace dust (EAFD) through an alkali activation process, as well as the thermal stability of the resulting product. Moreover, environmental fingerprints of alkali activated slag doped with EAFD, before and after thermal treatment, were evaluated. The results demonstrated the feasible alkali activation of EAFS in the presence of EAFD yielding a product that met the criteria which enables its application in a civil engineering at ambient and at elevated temperatures (1000 ºC). Moreover, the EN12457-2 leaching test results, demonstrated that unheated alkali-activated slag with addition of 5% EAFD met the criteria for disposal at non-hazardous landfills as per European Directive 2003/33/CE. However, environmental fingerprints of alkali activated slag with 5% EAFD after heating to 1000 °C, is of concern since chromium release exceeded the permissible concentration requiring disposal in hazardous waste landfills.
Red Mud-Fly Ash-Based Geopolymers as an Eco-Friendly Material for Immobilization of Toxic Pollutants (Pb and Cu) from Wastewater
The use of waste materials as a precursor for synthesizing geopolymer materials is increasingly being utilized. This research aimed to examine the potential use of red mud-fly ash geopolymers to remove toxic pollutants such as copper and lead ions from wastewater. Samples of different ratios of red mud (RM) and fly ash (FA) were synthesized through alkaline activation. Based on compressive strength a geopolymer (RMFAGP1) with the highest value of 29.54 MPa, was chosen for further research. The physical-chemical characterization of RMFAGP1 in terms of mineral composition and structure was performed using XRD, DRIFT and SEM analysis. BET analysis was used to define porosity, as well as the specific surfaces necessary for efficient adsorption. The batch equilibration method was used to determine the PZC value, which serves as a guide for predicting the adsorption process. The best adsorption efficiency was achieved at pH =4 (88.5%) i.e. at pH=5 (99.4%) for Cu and Pb, respectively. The performed analyses indicate that waste materials, such as red mud and fly ash, can be used as raw materials for obtaining a geopolymer that can effectively immobilize Pb and Cu from wastewater, offering a low-cost and eco-friendly solution.
Room Temperature Mössbauer Characterization of Ferrite with Spinel Structure
Cobalt ferrite (CoFe2O4) nanoparticle were obtained by different synthesis methods: coprecipitation (CO), ultrasonically assisted coprecipitation (US-CO), coprecipitation followed by mechanochemical treatment (MC-CO), microemulsion (ME) and microwave assisted hydrothermal synthesis (MW-HT). The structure and cation distribution are investigated by XRD diffraction analysis and Raman spectroscopy. The parameters such as chemical shift, quadruple splitting and hyperfine field and site occupancy of Fe3+ were determined by Mössbauer spectroscopy. The 57Fe-Mössbauer spectrа of the CoFe2O4 wеrе measured at room temperature in ± 12 mm s-1 Doppler velocity range. The 57Fe-Mössbauerspectrа of the CoFe2O4 samples wеrе fitted with the extended Voigt-based fitting method.
Effects of Soda Lime Glass Waste on the Physical, Mechanical and Aesthetics Properties of Sanitary-Ware Glazes
Recycling some waste industrial products in the traditional ceramics is a sustainable and environmentally friendly approach. This work focused on the incorporation of soda lime glass waste (SLGW) in the manufacturing of sanitary ware glazes. Eleven formulations were made under industrial conditions and compared to a reference industrial glaze. The findings revealed that the use of SLGW instead of dolomite (7 wt.%) leads to a significant improvement of the whiteness from 87.0 to 93.26 %. While the use of 20 wt. % SLGW instead of feldspar and 17 wt.% in place of the mixture (10 wt.% feldspar - 7 wt.% dolomite) results in an increased whiteness of 88.58 % and 89.42 %, respectively. The structural and morphological characterizations of the obtained glazes were identified by XRD, Raman spectroscopy and SEM analysis. However, the thermal analyses of the glazes were determined by DTA and TG techniques. Rheological behavior of the slip glazes; both physical and mechanical properties of the fired glazes have been also measured. This study revealed that soda lime glass wastes are good alternative materials, and the corresponding formulations were shown to be viable in the industry of the ceramic glazes. The most remarkable conclusion from this study was that the addition of SLGW improved the aesthetic aspect (whiteness and brightness) of sanitary ceramic glazes.
Determining Threaded Machine Element Fabrication Technology by Pulsed Thermography
Non-destructive testing methods, including pulsed infrared thermography, have become quite common in materials evaluation. The method is suitable for checking the quality of the surface treatment of the material structure up to a certain depth and is increasingly applied in the areas of system maintenance and condition assessment of machine elements. Thus, when installing spare parts (screws) for military purposes, for example in airplanes, helicopters, tanks, or armored vehicles, as well as for commercial purposes, for example, excavators or other machines, it is necessary to inspect these parts additionally to be sure of their quality. The paper discusses the applicability of pulse infrared thermography in the quality control of screws, through the determination of the technology of making standard threaded joints (by rolling or cutting), as well as the technology of the final surface treatment of screws with a cadmium layer.
Investigation of the Effects of Surface Oxide Layer on Wear and Corrosion in NiTi Alloys: A Mechanical and Chemical Perspective
Nickel-Titanium (NiTi) alloys are widely applied in biomedical and industrial domains, mainly because of their unique superelastic characteristics and biocompatibility. However, their performance is often constrained by their tendency to wear and corrode, particularly under repetitive mechanical loading, harsh environmental conditions, and high friction coefficients. This study aims to reduce the wear rate and friction coefficient of NiTi alloys by forming oxide layers on the surface through heat treatment, while also increasing their corrosion resistance. It also examines the effects of high-temperature and prolonged heat treatments on surface performance. NiTi alloys were subjected to heat treatments at 900, 1000, and 1100 °C for 2 and 4 hours. Wear tests were conducted using the ball-on-disc method under three different loads (5N, 10N, and 15N), three different test durations (30, 60 and 90 min), and at a constant speed of 0.05 m/s, to measure the friction coefficient and wear rates. Additionally, the alloys mechanical and corrosion performance was evaluated through microhardness and electrochemical corrosion tests. The results showed that samples treated at 1100 °C for 4 hours exhibited a 146% increase in microhardness, reaching 640 HV, with the oxide layer thickness increasing to 462 μm. This oxide layer reduced the wear rate by 60%, bringing it down to 150x10-6 mm³/Nm during a 30 min test under a 15N load, while the friction coefficient decreased by 58%, dropping to 0.30 μ. In contrast, nonheattreated samples exhibited lower hardness (260 HV), higher friction coefficients (0.72 μ), and greater wear rates (370x10-6 mm³/Nm) under a 5N load over a 90 min test. Corrosion analyses indicated that samples treated at higher temperatures showed more positive corrosion potentials and significantly improved corrosion resistance, with the best performance observed in samples treated at 1100 °C for 4 hours. These findings suggest that the thick oxide layers formed during high-temperature, long-duration heat treatments significantly improve the wear resistance, reduce the friction coefficient, and enhance the corrosion resistance of NiTi alloys, making them more durable for industrial and biomedical applications.
Influence of Grinding, Pressing and Sintering of the Powder 50.0 wt% Fe, 47.0 wt% BaTiO3 and 3.0 wt% TiO2 on Morphology, Microstructure, Magnetic and Electric Properties
A mixture of 50.0 wt% Fe, 47.0 wt% BaTiO3, and 3.0 wt% TiO2 powders is milled and then pressed and sintered. Samples sintered from ground powders have a structure consisting of plates. They consist of the crystalline phase BaFe12O19 and crystalline and amorphous phases Fe, BaTiO3, and TiO2. Samples sintered from powders ground for more than 180 min are compact and composed of BaFe12O19 crystals embedded in an amorphous matrix consisting of amorphous BaTiO3 and TiO2 phases. Magnetization of a sample ground for 220 min gradually decreases with increasing temperature up to 440 °C. This decrease results from the transition of ordered domains into chaotically directed domains. Above 440 °C, the thermal energy is sufficiently large to destroy ordered paramagnetic ferromagnetic and weakly ferromagnetic domains. During sample cooling in the absence of an external magnetic field, the temperature dependence of magnetization is the same as that obtained during heating in the magnetic field. However, during the sample cooling in the magnetic field, substantially higher values of magnetization are obtained. Considerably higher magnetization of the cooled sample remains even after switching off the external magnetic field. The sintered sample, previously pressed in the magnetic field, has a higher dielectric constant than the sample pressed in the absence of the magnetic field. The dielectric constant decreases with increasing frequency.
Effects of Rice Husk Ash Particles on Tribological Properties of Bronze Matrix Composite Brake Pads
The objective of this study was to examine and compare the physical, mechanical,and tribological properties of hybrid bronze metal matrix composite brake pads reinforced with fly ash and rice husk ash (RHA). To this end, metal matrix brake pad samples with various ratios of rice husk were prepared by hot pressing method. Density, hardness, friction coefficient, friction stability, and specific wear rate values were ascertained for the produced samples. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were employed to analyses the microstructure and wear surface. Results indicated that with the increase in rice husk ratio, the hardness value increased, whereas the density decreased. Furthermore, an augmentation in the friction coefficient values was attained by increasing the ratio of rice husk. The highest friction coefficient among all the samples produced was determined in the RHA-8 sample, with a value of 0.462. However, the lowest specific wear value was obtained in the RHA-6 sample, with 4.33 x 10-6 cm3/Nm. The coefficient of friction values obtained from all the samples produced were measured to be in the range of 0.3-0.6, which is the desired range for use as a brake pad material in automotive applications. This study demonstrated that RHA, an agricultural byproduct, may be utilized effectively in brake pads, thereby reducing production costs and enhancing the performance of the pads.
Analyzing the Variations in the Composition and Properties in Zirconia Alumina Composite Ceramics
The effect of unstabilized zirconium dioxide on the processes of formation of composite ceramics from industrial corundum powders heat-treated at temperatures of 1430 and 1580°C, changes in its microstructure and physical and mechanical properties have been investigated. It was shown that due to the rigid corundum matrix, unstabilized ZrO2 is preserved mainly in the tetragonal phase. When ceramics are sintered during heat and self-diffusion, zirconium particles are located along the grain boundary of the corundum matrix and fill the pore space. The sintering effect of amorphous SiO2 also contributes to the increased density of ceramics. A two-stage sintering mode provides a finer-grained microstructure of ceramics. It was shown that due to the presence of a larger number of ZrO2 grains capable of t-m-transformation at the Al2O3 boundaries, the resistance of composite ceramics to mechanical and thermal loads increases. Ceramics obtained at 1580°C and containing 6.0 wt.% t-ZrO2 possesses the maximum hardness of 17 GPa. Dilatometric characteristics and the values of the relative shrinkage of composite samples are given.
Preparation of Magnetic Surface Molecularly Imprinting Polymers Based on Glycidyl Methacrylate as Selective Sorbents for Aniline Removal from Aqueous Medium
In this paper, two molecularly imprinted polymers (MIPs) based on glycidyl methacrylate were synthesized by radical suspension polymerization and surface imprinting method in the presence of silica-coated magnetic nanoparticles. Ethylenediamine (eda) and triethylentetramine (teta) were used for surface imprinting. The samples were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and mercury porosimetry. The sorption and desorption behaviors of two MIPs as an aniline sorbent from aqueous solutions were evaluated. Sorption studies were carried out in the pH range of 2.0 - 10.0 and maximum sorption capacities were attained at pH 6.0. Also, the effect of different desorption agents were examined and acetonitrile was chosen as the best desorbing eluent for aniline. The obtained MIPs were regenerated in four sorption/desorption cycles, and the results show that these two MIPs could be reusable as sorbents for removing aniline from polluted wastewater.
Solid-state Synthesis of a Luminescent Material Based on Strontium Aluminate Doped with Rare Earths
In this study, the processing of a luminescent ceramic material based on strontium aluminate doped with rare earths (Europium and Dysprosium) was carried out. For this purpose, an intense mixing of the precursor materials (Al, Al2O3 and SrCO3) was carried out, with the addition of Europium and Dysprosium. After mechanical milling, precursor powders have sizes smaller than 1 micrometer, and there is a good distribution of powder size. The presence of aluminum in the precursor materials is explained by the desire to obtain nanometric alumina from it, according to the aluminum oxide bonding reaction process (RBAO). The progress of Al2O3 and SrAl2O4 formation was monitored by XRD analysis of the formation of intermediate phases during heat treatment through interrupted tests at different temperatures. Thermogravimetric analysis was also carried out to determine the oxidation temperatures of Al and decomposition of SrCO3. Finally, the analysis by optical emission spectroscopy indicates wavelengths in agreement with the electronic structure of the elements in the SrAl2O4:EuDy.
Sintered Magnesium Ferrite Particles in Decolorization of Anthraquinone dye AV 109: Combination of Adsorption and Fenton Process-Supplementary material
Magnesium ferrite (MgFe2O4) particles were synthetized by sol-gel method and used in the decolorization of the Acid Violet 109 (anthraquinone dye, AV109) water solutions' by combination of adsorption and heterogeneous Fenton process. The material's morphology and elemental analysis of the surface were revealed by Scanning electron microscopy and Energy Dispersive Spectroscopy (SEM/EDS). The X-Ray Diffraction (XRD) technique was used to analyze the crystallographic phase. In the first part of the decolorization experiment, the adsorption ability of the synthesized particles was investigated. During the adsorption study influence of pH was investigated. In the second part of the decolorization experiment, the effects of the various parameters on the Fenton process were studied such as the initial concentrations of hydrogen peroxide, dye, and magnesium ferrite particles. Influence of magnesium ferrite particles structure, pH value and reaction temperature were also investigated. The decolorization reaction was followed by UV-Visible (UV-Vis) spectrophotometry. At optimal conditions, the dye decolorization was 99.1% (55.4% by adsorption and 43.7% by the Fenton process). Both the adsorption and the Fenton process obey second-order kinetics.
Development of Low Carbon and Energy-Efficient Geopolymer-Based Paving Blocks
The development of energy-efficient and low-carbon geopolymer-based paving blocks made from waste, as an environmental-friendly material, was evaluated. Ground concrete (GC) and solid brick (SB) powder, as the representatives of construction and demolition waste (C&DW), with the addition of fly ash (FA) and silica fume (SF), were used. Waste samples were characterized in terms of surface functional groups and radioactivity. The FT-IR spectra showed the required amorphous or semi-crystalline alumino-silicate structure. The gamma spectrometry confirmed waste samples' radiological safety. Hardened geopolymer samples were subjected to physical-mechanical investigation comprising of density, water content, compressive and flexural strengths determination. Based on strength characteristics, the three best prototype mixtures were selected and subjected to further compressive strength determination and durability assessment. Prototype sample SBFASFp1, with a compressive strength of 18.7 MPa, was shown the highest value of all samples, almost the same as the corresponding SBFASF1 sample. Freeze-thaw and the subsequent carbonation tests, as durability indicators, showed that the SBFASF1 sample had the slightest strength decrease, making it most durable in these conditions. These satisfactory test results showed the favorable effects of alternatives to cementitious materials, encouraging their utilization and contributing to the sustainability of the construction sector.
Sintered Magnesium Ferrite Particles in Decolorization of Anthraquinone dye AV 109: Combination of Adsorption and Fenton Process
Shortening of Fast Firing in the Ceramic Tile Production by Inorganic Additives – An Upscale to the Industry
The paper discusses the usage of additives that are protected by the European patent to enhance the features of ceramic tiles. Under laboratory conditions, various types of additives in different concentrations (0.15, 0.30 and 0.50%) were added to the ceramic mass, and changes in shrinkage, modulus of rupture and water absorption were observed. After selecting the appropriate additive and its concentration, a series of industrial tests is performed. The characteristics of regular ceramic mass and mass with the selected additive were monitored without adjusting process parameters in the industrial conditions. Furthermore, utilizing additives allowed for shortening of the fire time without distorting the characteristics of the final products. The application of additives in industrial settings has demonstrated that floor tiles can be produced with improved characteristics and increased production capacity by 6.8%. Thus, significant energy savings and a lowered CO2 footprint can be provided.
Enhanced Microstructural and Mechanical Properties of Alumix 13 Matrix Hybrid Composites Reinforced with B4C and SiC
This study produced B4C and SiC reinforced hybrid/composite samples using powder metallurgy with pre-alloyed Alumix 13 matrix (Al-4.5% Cu-0.5% Mg-0.05% Si). B4C and SiC were added at 5% by weight and mixed in a two-dimensional ball mill for 60 min to ensure homogeneous distribution. The mixed powders were compressed at 700 MPa and sintered at 575°C for 60 min. Hardness values were compared with the highest in samples containing 5% hybrid composite materials. Microstructural characterization of B4C and SiC particles in the Alumix 13 matrix was performed. Alumix 13 matrix was chosen for its favorable mechanical properties and compatibility with reinforcement particles. Ball milling ensured adequate mixing for uniform dispersion while pressing at 700 MPa created dense samples necessary for successful sintering. Hardness analysis showed a significant improvement with 5% hybrid, and microstructural investigation provided information on particle distribution and bonding quality. This work demonstrates the potential of B4C and SiC-reinforced Alumix 13-based hybrid/composites for applications requiring enhanced hardness. It provides valuable data for future research in powder metallurgy and hybrid composite manufacturing.
Exploring the Use of Iron Ore and Pellet Dusts in Sinter Production: A Comprehensive Evaluation
Silico-ferrite of calcium and aluminum (SFCA), a significant equilibrium crystalline phase in the Fe2O3-CaO-Al2O3-SiO2 ternary structure, is an effective bonding form in the sintering process of fine iron ore. The current study investigates the effects of using pellet dust instead of iron ore in sinter blend in SFCA phases. Investigation of the internal structure of the sinter is critical in terms of its physical and metallurgical properties. In this study, the sinter pot experimental conditions were simulated to the actual sinter mill situation. The chemical structure of SFCA compounds was defined as both SFCA and SFCA-I phases in the SiO2-CaO-Fe2O3 and Si-Ca-Fe ternary-phase system. The comparison of the sinter samples with each other revealed that the sinter mixture with a pellet dust fraction of 13.53% in the Sin-3 probably achieved the best similarity in reaction rate and formed the larger ratios in SFCA and SFCA-I. This approach ensures that all sintering parameters are controlled, thereby enhancing the mechanical and technological quality of the sinter, which will result in a more stable charge to the Blast Furnace.
AlFeCoNiCu High-Entropy Alloys Formed by Spark Plasma Sintering of a Powder Mixture and a Deposited Layer
This investigation focuses on the structural characteristics of AlFeCoNiCu high-entropy alloys (HEAs) fabricated using two approaches. The alloys were obtained by the spark plasma sintering (SPS) or hot pressing (HP) treatment of layers deposited by detonation spraying of a mixture of the elemental powders. The feedstock powder mixture used for the spraying was also directly consolidated by SPS under the same conditions (without any pre-alloying treatment). The goal of this work was to conduct a comparative analysis of the compositional and structural features of AlFeCoNiCu HEAs formed by different methods. The SPS treated deposited layer showed a more uniform structure and composition than the alloy obtained directly by SPS of the powder mixture. All alloys processed by SPS or HP were face-centered cubic solid solutions. The alloys obtained from the deposited precursors showed deviations from the nominal composition of the powder mixture. However, the compositional differences and non-uniformities did not affect the hardness of the alloys or the influences of these factors compensated each other. This work shows that, for practical applications, thick samples of AlFeCoNiCu can be produced by SPS of the elemental powder mixtures, while for thin layers and coatings detonation spraying followed by SPS/HP can be applied.
Effect of Heat Treatments on Microstructural and Tribological Properties of 3D Printed 18Ni-300 Maraging tool steel made by Selective Laser Sintering Process
dry atmospheric conditions through sliding wear tests at varying loads and speeds while maintaining a fixed distance. Studies utilizing spectrographic have unveiled that the material's structure is predominantly layered, consisting primarily of dense acicular martensite, along with recycled austenite and intermetallic components. The highest hardness was recorded in sample S1 with 49.7 HRC, while the lowest hardness was measured in sample S3 with 19.5 HRC. In terms of wear resistance, the lowest wear loss, at 0.098 g, was seen in the S1 sample, whereas the S3 sample displayed the highest wear loss at 0.209 g. With these findings, it can be concluded that the appropriate heat treatment significantly enhanced the tribological properties of 18Ni-300 steel.
Comparative Analysis of In-Situ Ionic Activators for Increased Energy Efficiency Process in Alkaline Electrolysers
Electrodeposition of selected d-metals by in-situ electrodeposition as a method for improvement of electrocatalytic activity of conventional electrodes for alkaline hydrogen evolution has been attracting the attention of researchers for about two decades. The modification of metal electrodes by ionic activators as a combination of two (binary systems) or three (ternary systems) d-metal complexes added in electrolytic solution were represented in many studies. Better catalytic performances and higher energy efficiency compared to the common electrodes is provided by a number of affordable and inexpensive solutions resulting from this research. Based on the combinations of selected d-metal complexes added in-situ to the electrolyte during electrolysis, this work provides a systematic overview of the binary and ternary systems of ionic activators, that contribute to energy savings in alkaline electrolysers, with the particular attention paid to the discussion of similarities and universal principles. Theoretical background and the fundamental properties that lay beyond the observed improvements of electrode performance upon activation by ionic activators is also represented.
Transforming Volcanic Rocks from Lichadonisia Island, Greece, into Advanced Luminescent Nanostructures for Potential Solar Concentrator Applications
As the demand for environmentally sustainable materials rises, particularly in applications like luminescent solar concentrators (LSCs) for urban environments, this study investigates the potential of volcanic rock-derived nanostructures from Lichadonisia Island, Greece. These nanostructures are designed to absorb sunlight and convert it to longer wavelengths efficiently. By grinding volcanic rocks and inducing nanostructure formation, followed by enrichment with FeO, enhanced luminescent properties were achieved. Comprehensive characterization using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), and Energy Dispersive X-ray Spectroscopy (EDS) confirmed the crystalline nature of the volcanic rocks and the presence of FeO in an amorphous state. FTIR analysis revealed characteristic peaks of volcanic rocks and additional vibrations from FeO, as well as modifications of Si-O-Al vibrations. FESEM-EDS observations indicated plate-like nanoparticle structures with FeO nanoforms on modified surfaces. Luminescence properties, assessed via Photoluminescence Excitation-Emission (PLE-PL) spectroscopy, showed that while pure nanostructures exhibited luminescence at 470 nm, FeO-enriched nanostructures demonstrated enhanced intensity and an additional emission peak at approximately 425 nm. These findings suggest that volcanic rock-derived nanostructures, particularly when enriched with FeO, offer significant potential for use in eco-friendly LSCs.
Developing Thermal Insulation Cement-Based Mortars with Recycled Aggregate in Accordance with Net Zero Principles
The performance of thermo-insulation rendering mortars with alternations in ratios of powdered cordierite and talc was examined. The goal was to confirm that recycled kilnware cordierite can be reapplied in the mortar design without significant deterioration in performance in comparison with OPC mortar. Differential thermal analysis was employed for examining thermally induced reactions. The cavitation erosion, in testing sequences ranging from 30 to 120 minutes, was used to assess the compactness of the mortar structure. The physico-mechanical properties of experimental mortars were investigated. The morphologies of the mortar tablets upon cavitation were studied using a scanning electron microscope. It was established that cordierite and talc filler in amounts up to 20% enhance microstructural packing and mechanical strengths due to improved cementation and therefore contribute to cavitation erosion resistance. Higher amounts of talc cause structural degradation and mass loss during cavitation tests. Reducing manufacturing costs, energy consumption, and greenhouse gas emissions are the main objectives of the production of this waste-based construction composite, as the reuse of waste materials can help achieve a number of Sustainable Development Goals.
Oxone® Induced Textile Dyes Degradation using Cobalt-doped Alumina Catalyst
Cobalt-doped alumina catalyst calcined at 500 ºC (CoA-500) was investigated in the degradation of anionic textile dye Orange G in the presence of Oxone®. Different reaction parameters were altered in order to study their influence on Orange G degradation. The increase of the Oxone® dosage, mass of the catalyst and temperature was beneficial for the dye degradation rate. The best catalytic performance was obtained in the range of the initial solution pH = 6–8. Simultaneous degradation of both Orange G and cationic textile dye Basic blue 41, was also tested. The degradation of the Basic blue 41 did not occur while Orange G was present in the system. CoA-500 was found to be efficient catalyst in the Oxone® induced catalytic degradation of textile dyes.
The Effect of Particle Size on the Crystallization LiGe2(PO4)3 Phase from Glass
The glass was prepared by the standard melt-quenching technique. The crystallization of powder glass from the system Li2O-Al2O3-GeO2-P2O5 was studied. The investigations were performed under non-isothermal and isothermal conditions using the AAS, DTA, XRD and FTIR methods. The aim of this research was to study the ease of glass formation, crystallization and crystal structure of obtained phases. The results showed that the glass crystallizes by primary crystallization. LiGe2(PO4)3 was formed as the primary phase, until detectable traces of GeO2 were formed as secondary. The influence of particle size of the glass powder samples in the range 0-1 mm on the temperature of the DTA crystallization peak, Tp, the peak height (δT)p and the parameter Tp2/(δT)p was studied. It was demonstrated that for the particle size in the range of 0.05-0.35 mm surface and volume crystallization were significant, while the particle size >0.35 mm according to the volume crystallization was dominant.
The Influence of Alumina Type on the Immobilization of Ascorbate Oxidase and Ascorbic Acid Detection
Two alumina types (trihydrate (T) and anhydrous (G)) were used for the immobilization of ascorbate oxidase (AO) by the adsorption procedure. The samples were characterized by FTIR analysis and EPR spectroscopy to confirm the presence of enzyme in the composite and the activity of immobilized enzyme. The samples of alumina with and without AO were used as modifer of carbon paste electrode and tested by Fe(CN6)3-/4- redox probe using cyclic voltammetry at different scan rates. The response of investigated electrodes toward ascorbic acid was tested in the Britton-Robinson buffer at pH range of 2 to 5. Direct detection of ascorbic acid was tested at G and G+AO electrodes and the calibration curves were constructed by square wave voltammetry under the optimized conditions. The immobilization of AO at anhydrous alumina increased the concentration range and the sensitivity from 0.00617 µM/µA for G to 0.01693 µM/µA for G+AO in the concentration range from 10 µM to 200 µM.
Synthesis of Y2O3 and Graphite-Added Copper-Based Hybrid Composites by Powder Metallurgy: Mechanical Properties and Tribological Behavior
In the presented study, Y2O3 and graphite-reinforced Cu matrix hybrid composite materials were prepared using the powder metallurgy method. The aim is to compare the microstructure, density, hardness, and wear behavior of composites with different yttria contents (5, 10, and 15 wt%) and graphite (2 wt%) reinforcements. An increase in the Y2O3 ratio, along with the addition of graphite, resulted in an observed increase in the hardness values of the composites. Additionally, it was observed that Y2O3 and graphite are homogeneously distributed in the copper matrix in the SEM-EDX spectra. Upon examining the microstructures of the composites, it was determined that with the increase in yttrium oxide content, partially yttrium oxide agglomerations formed in some regions. The addition of Y2O3 resulted in a copper sample that is 1.34 times harder than pure copper. Addition of Y2O3 -graphite, samples with 3.301–22.3 % higher wear resistance were obtained.