Preparation and Characteristics of High-Performance, Low-Density Metallo-Ceramics Composite.

By applying the physical vapour deposition method, hollow ceramic microspheres were coated with titanium, and subsequently, they were sintered using the spark plasma sintering technique to create a porous ceramic material that is lightweight and devoid of a matrix. The sintering process was carried out at temperatures ranging from 1050 to 1200 °C, with a holding time of 2 min. The samples were subjected to conventional thermal analyses (differential scanning calorimetry, thermogravimetry, dilatometry), oxidation resistance tests, and thermal diffusivity measurements. Phase analysis of the samples was performed using the XRD and the microstructure of the prepared specimens was examined using electron microscopy. The titanium coating on the microspheres increased the compressive strength and density of the resulting ceramic material as the sintering temperature increased. The morphology of the samples was carefully examined, and phase transitions were also identified during the analysis of the samples.

High-Temperature, Lightweight Ceramics with Nano-Sized Ferrites for EMI Shielding: Synthesis, Characterisation, and Potential Applications.

The present study focuses on the synthesis and characterisation of a lightweight ceramic material with electromagnetic interference (EMI) shielding properties, achieved using mullite containing micrometre-sized hollow spheres (cenospheres) and CoFe2O4 nanoparticles. This research explores compositions with varying CoFe2O4 contents ranging from 0 up to 20 wt.%. Conventional sintering in an air atmosphere is carried out at a temperature between 1100 and 1300 °C. The addition of ferrite nanoparticles was found to enhance the process of sintering cenospheres, resulting in improved material density and mechanical properties. Furthermore, this study reveals a direct correlation between the concentration of ferrite nanoparticles and the electromagnetic properties of the material. By increasing the concentration of ferrite nanoparticles, the electromagnetic shielding effect of the material (saturation magnetisation (Ms) and remanent magnetisation (Mr)) was observed to strengthen. These findings provide valuable insights into designing and developing lightweight ceramic materials with enhanced electromagnetic shielding capabilities. The synthesized ceramic material holds promise for various applications that require effective electromagnetic shielding, such as in the electronics, telecommunications, and aerospace industries.

The Effect of Zinc Oxide on DLP Hybrid Composite Manufacturability and Mechanical-Chemical Resistance.

The widespread use of epoxy resin (ER) in industry, owing to its excellent properties, aligns with the global shift toward greener resources and energy-efficient solutions, where utilizing metal oxides in 3D printed polymer parts can offer extended functionalities across various industries. ZnO concentrations in polyurethane acrylate composites impacted adhesion and thickness of DLP samples, with 1 wt.% achieving a thickness of 3.99 ± 0.16 mm, closest to the target thickness of 4 mm, while 0.5 wt.% ZnO samples exhibited the lowest deviation in average thickness (±0.03 mm). Tensile stress in digital light processed (DLP) composites with ZnO remained consistent, ranging from 23.29 MPa (1 wt.%) to 25.93 MPa (0.5 wt.%), with an increase in ZnO concentration causing a reduction in tensile stress to 24.04 MPa and a decrease in the elastic modulus to 2001 MPa at 2 wt.% ZnO. The produced DLP samples, with their good corrosion resistance in alkaline environments, are well-suited for applications as protective coatings on tank walls. Customized DLP techniques can enable their effective use as structural or functional elements, such as in Portland cement concrete walls, floors and ceilings for enhanced durability and performance.

Physical, Thermal, and Chemical Properties of Fly Ash Cenospheres Obtained from Different Sources.

Cenospheres are hollow particles in fly ash, a by-product of coal burning, and are widely used as a reinforcement when developing low-density composites called syntactic foams. This study has investigated the physical, chemical, and thermal properties of cenospheres obtained from three different sources, designated as CS1, CS2, and CS3, for the development of syntactic foams. Cenospheres with particle sizes ranging from 40 to 500 µm were studied. Different particle distribution by size was observed, and the most uniform distribution of CS particles was in the case of CS2: above 74% with dimensions from 100 to 150 µm. The CS bulk had a similar density for all samples and amounted to around 0.4 g·cm-3, with a particle shell material density of 2.1 g·cm-3. Post-heat-treatment samples showed the development of a SiO2 phase in the cenospheres, which was not present in the as-received product. CS3 had the highest quantity of Si compared to the other two, showing the difference in source quality. Energy-dispersive X-ray spectrometry and a chemical analysis of the CS revealed that the main components of the studied CS were SiO2 and Al2O3. In the case of CS1 and CS2, the sum of these components was on average from 93 to 95%. In the case of CS3, the sum of SiO2 and Al2O3 did not exceed 86%, and Fe2O3 and K2O were present in appreciable quantities in CS3. Cenospheres CS1 and CS2 did not sinter during heat treatment up to 1200 °C, while sample CS3 was already subjected to sintering at 1100 °C because of the presence of a quartz phase, Fe2O3 and K2O. For the application of a metallic layer and subsequent consolidation via spark plasma sintering, CS2 can be deemed the most physically, thermally, and chemically suitable.

Industry 4.0 and Digitalisation in Healthcare.

Industry 4.0 in healthcare involves use of a wide range of modern technologies including digitisation, artificial intelligence, user response data (ergonomics), human psychology, the Internet of Things, machine learning, big data mining, and augmented reality to name a few. The healthcare industry is undergoing a paradigm shift thanks to Industry 4.0, which provides better user comfort through proactive intervention in early detection and treatment of various diseases. The sector is now ready to make its next move towards Industry 5.0, but certain aspects that motivated this review paper need further consideration. As a fruitful outcome of this review, we surveyed modern trends in this arena of research and summarised the intricacies of new features to guide and prepare the sector for an Industry 5.0-ready healthcare system.

Dynamic Alloying of Steels in the Super-Deep Penetration Mode.

The dynamic effects observed in collisions represent a specific area of high-energy interaction located at the boundary of mechanics, hydrodynamics, shock wave physics, and alternating high-pressure regions. The paper shows that in the volume of a solid metal body, as a result of dynamic alloying by a high-speed stream of powder particles in the super-deep penetration mode (SDP), fiber structures of altering material arise, forming the framework of the composite material. The stream of powder particles in the metal obstacle following the path of least resistance and the impact of shock waves on particles results in a volumetric framework from the products of interaction between the injected and matrix materials. When using SDP, defective structural elements (channeled)-germs of reinforcing fibers arise. At the subsequent heat treatment, there is an intensive diffusion. The growth process of reinforcing fibers shifts to higher temperatures (as compared to the standard mode), leading to an increase in the bending strength of the fiber material up to 13 times for W6Mo5Cr4V2 high-speed tool steel. As a result of the completion of the growth of reinforcing fibers in the volume of the W6Mo5Cr4V2 high-speed tool steel, the material's bending strength in 1.2 times is realized. Simultaneously, it provides an increase of wear resistance 1.7-1.8 times.

Application of Granular Biocomposites Based on Homogenised Peat for Absorption of Oil Products.

Among the various methods for collecting oil spills and oil products, including from the water surface, one of the most effective is the use of sorbents. In this work, three-component bio-based composite granular adsorbents were produced and studied for oil products' pollution collection. A bio-based binder made of peat, devulcanised crumb rubber from used tyres, and part fly ash as cenospheres were used for absorbent production. The structure, surface morphology, porosity, mechanical properties, and sorption kinetics of the obtained samples were studied. Composite hydrophobicity and sorption capacity to oil products, such as diesel fuel (DF) and motor oil (MO), were determined. The obtained pellets are characterised by a sufficiently pronounced ability to absorb oil products such as DF. As the amount of CR in the granules increases, the diesel absorption capacity increases significantly. The case of 30-70-0 is almost three times higher than the granules from homogenised peat. The increase in q is due to two factors: the pronounced surface hydrophobicity of the samples (Θ = 152°) and a heterogeneous porous granule structure. The presence of the cenosphere in the biocomposite reduces its surface hydrophobicity while increasing the diesel absorption capacity. Relatively rapid realisation of the maximum saturation by the MO was noted. In common, the designed absorbent shows up to 0.7 g·g-1 sorption capacity for MO and up to 1.55 g·g-1 sorption capacity for diesel. A possible mechanism of DF absorption and the limiting stages of the process approximated for different kinetic models are discussed. The Weber-Morris diffusion model is used to primarily distinguish the limiting effect of the external and internal diffusion of the adsorbate on the absorption process.

Spent Coffee Grounds Valorization in Biorefinery Context to Obtain Valuable Products Using Different Extraction Approaches and Solvents.

The valuable products that can be isolated from spent coffee ground (SCG) biomass consist of a high number of bioactive components, which are suitable for further application as raw materials in various production chains. This paper presents the potential value of the SCG obtained from large and local coffee beverage producers, for the production of valuable, biologically active products. Despite its high potential, SCG has not been utilized to its full potential value, but is instead discarded as waste in landfills. During its decomposition, SCG emits a large amount of CO2 and methane each year. The main novelty of our work is the implementation of sequential extraction with solvents of increased polarity that allows for the maximal removal of the available extractives. In addition, we have compared different extraction techniques, such as conventional and Soxhlet extraction, with more effective accelerated solvent extraction (ASE), which has seen relatively little use in terms of SCG extraction. By comparing these extraction methods and highlighting the key differences between them in terms of extraction yield and obtained extract composition, this work offers key insights for further SCG utilization. By using sequential and one-step accelerated solvent extraction, it is possible to obtain a significant number of extractives from SCG, with a yield above 20% of the starting biomass. The highest yield is for coffee oil, which is obtained with n-hexane ranging between 12% and 14% using accelerated solvent extraction (ASE) according to the scheme: n-hexane→ethyl acetate→60% ethanol. Using single-stage extraction, increasing the ethanol concentration also increases the total phenolic content (TPC) and it ranges between 18.7-23.9 Gallic acid equivalent (GAE) mg/g. The iodine values in the range of 164-174 using ASE and Soxhlet extraction shows that the hexane extracts contain a significant amount of unsaturated fatty acids; coffee oils with a low acid number, in the range of 4.74-6.93, contain few free fatty acids. The characterization of separated coffee oil has shown that it mainly consists of linoleic acid, oleic acid, palmitic acid, stearic acid and a small number of phenolic-type compounds.

Solutions of Critical Raw Materials Issues Regarding Iron-Based Alloys.

The Critical Raw Materials (CRMs) list has been defined based on economic importance and supply risk by the European Commission. This review paper describes two issues regarding critical raw materials: the possibilities of their substitution in iron-based alloys and the use of iron-based alloys instead of other materials in order to save CRMs. This review covers strategies for saving chromium in stainless steel, substitution or lowering the amounts of carbide-forming elements (especially tungsten and vanadium) in tool steel and alternative iron-based CRM-free and low-CRM materials: austempered ductile cast iron, high-temperature alloys based on intermetallics of iron and sintered diamond tools with an iron-containing low-cobalt binder.

Towards Next-Generation Sustainable Composites Made of Recycled Rubber, Cenospheres, and Biobinder.

The utilisation of industrial residual products to develop new value-added materials and reduce their environmental footprint is one of the critical challenges of science and industry. Development of new multifunctional and bio-based composite materials is an excellent opportunity for the effective utilisation of residual industrial products and a right step in the Green Deal's direction as approved by the European Commission. Keeping the various issues in mind, we describe the manufacturing and characterisation of the three-component bio-based composites in this work. The key components are a bio-based binder made of peat, devulcanised crumb rubber (DCR) from used tyres, and part of the fly ash, i.e., the cenosphere (CS). The three-phase composites were prepared in the form of a block to investigate their mechanical properties and density, and in the form of granules for the determination of the sorption of water and oil products. We also investigated the properties' dependence on the DCR and CS fraction. It was found that the maximum compression strength (in block form) observed for the composition without CS and DCR addition was 79.3 MPa, while the second-highest value of compression strength was 11.2 MPa for the composition with 27.3 wt.% of CS. For compositions with a bio-binder content from 17.4 to 55.8 wt.%, and with DCR contents ranging from 11.0 to 62.0 wt.%, the compressive strength was in the range from 1.1 to 2.0 MPa. Liquid-sorption analysis (water and diesel) showed that the maximum saturation of liquids, in both cases, was set after 35 min and ranged from 1.05 to 1.4 g·g -1 for water, and 0.77 to 1.25 g·g-1 for diesel. It was observed that 90% of the maximum saturation with diesel fuel came after 10 min and for water after 35 min.

Using circular economy principles to recycle materials in guiding the design of a wet scrubber-reactor for indoor air disinfection from coronavirus and other pathogens.

An arduous need exists to discover rapid solutions to avoid the accelerated spread of coronavirus especially through the indoor environments like offices, hospitals, and airports. One such measure could be to disinfect the air, especially in indoor environments. The goal of this work is to propose a novel design of a wet scrubber-reactor to deactivate airborne microbes using circular economy principles. Based on Fenton's reaction mechanism, the system proposed here will deactivate airborne microbes (bioaerosols) such as SARS-CoV-2. The proposed design relies on using a highly porous clay-glass open-cell structure as an easily reproducible and cheap material. The principle behind this technique is an in-situ decomposition of hydrogen peroxide into highly reactive oxygen species and free radicals. The high porosity of a tailored ceramic structure provides a high contact area between atomized oxygen, free radicals and supplied polluted air. The design is shown to comply with the needs of achieving sustainable development goals.

Novel hybrid method to additively manufacture denser graphite structures using Binder Jetting.

This study introduces two hybrid processes integrating an additive manufacturing technique with post-processing treatments namely (i) Binder Jetting Printing (BJP) + Cold Isostatic Pressing (CIP) + cycle and (ii) BJP + cycle where cycle refers to a sequence of Impregnation-Drying-Pyrolysis. These two new processes yielded additively manufactured parts with higher density and reduced defects/porosities. As a testbed, we used these new processes to fabricate graphite structures. The samples produced by both methods were compared with each other and benchmarked to the samples produced by (a) BJP alone and (b) Traditional uniaxial pressing like compaction moulding. Various characterisation methods were used to investigate the microstructure and mechanical properties which showed that the porosity of hybrid manufactured samples reduces from 55% to a record 7%. This technological pathway is expected to create a new avalanche of industrial applications that are hitherto unexplored in the arena of hybrid additive manufacturing with BJP method.

Influence of Glass Additions on Illitic Clay Ceramics.

A mixture of an illitic clay and waste glass was prepared and studied during the sintering process. The illitic clay, from the Liepa deposit (Latvia), and green glass waste (GW) were disintegrated to obtain a homogeneous mixture. The addition of disintegrated GW (5-15 wt% in the mixture) led to a reduction in the intensive sintering temperature, from 900 to 860 °C, due to a significant decrease in the glass viscosity. The addition of GW slightly decreased the intensities of the endo- and exothermic reactions in the temperature range from 20 to 1000 °C due to the reduced concentration of clay minerals. GW reduced the plasticity of the clay and reduced the risk of structural breakage. The increase in sintering temperature from 700 to 1000 °C decreased the apparent porosity and water uptake capacity of the ceramics from 35% and 22%, down to 24% and 13%, respectively. The apparent porosities of all the sintered mixtures showed a decrease of between 6% to 9% after the addition of GW with concentrations from 5 up to 15 wt% respectively, while the water uptake capacities decreased from between 4% and 10%. The addition of GW led to an increase in the apparent density of the ceramic materials, up to 2.2 g/cm3. Furthermore, the compressive strength increased by more than two times, reaching a highest value of 240 MPa after the sintering of the 15 wt% GW-containing mixture at 1000 °C.

Investigation of Melts of Polybutylcarbosilane Dendrimers by 1H NMR Spectroscopy.

Melts of polybutylcarbosilane (PBC) dendrimers from third (G3) up to sixth (G6) generations are investigated by 1H NMR spectroscopy in a wide temperature range up to 493 K. At room temperature, NMR spectra of G3-G5 dendrimers exhibit resolved, solution-like spectra ("liquid" phase). In contrast, the spectrum of the G6 dendrimer is characterized by a single unresolved broad line at whole temperature range, which supports the presence of an anomalous phase state of G6 at temperatures higher than glass transition temperature. For the first time, an unexpected transition of G5 dendrimer from a molecular liquid state to an anomalous state/phase upon temperature increase has been detected using NMR data. Specifically, an additional wide background line appears in the G5 spectrum above 473 K, and this line corresponds to a G5 state characterized by restricted molecular mobility, i.e., a state similar to the "anomalous" phase of G6 melt. The fraction of the G5 dendrimers in "anomalous" phase at 493 K is approximately 40%. Analysis of the spectral shapes suggests that changes in the G5 dendrimers are reversible with temperature.

Effect of Fly-Ash Cenospheres on Properties of Clay-Ceramic Syntactic Foams.

A low-density clay ceramic syntactic foam (CSF) composite material was successfully synthesized from illitic clay added by fly ash cenospheres (CS) using the semi-dry formation method. The content of CS varied in the range of 10, 30, 50 and 60 vol %. Furthermore, reference samples without cenospheres were produced for property comparison. The materials comprising different amount of the additives were fired at temperatures of 600, 950, 1000, 1050, 1100, 1150 and 1200 °C. Firing times were kept constant at 30 min. Processing characteristics of the materials were evaluated in terms of density achieved and shrinkage observed as functions of both the CS content and the sintering temperature. The compressive strength and water uptake were determined as application-oriented properties. Except for the reference and the low CS level samples, the materials show an increase in strength with the increase in firing temperature, and a decrease of mechanical reliability with a decrease in density, which is typical for porous materials. Exceptions are the samples with no or low (10 vol %) content of cenospheres. In this case, the maximum strength is obtained at an intermediate sintering temperature of 1100 °C. At a low density (1.10 and 1.25 g/cm³), the highest levels of strength are obtained after sintering at 1200 °C. For nominal porosity levels of 50 and 60 vol %, 41 and 26 MPa peak stresses, respectively, are recorded under compressive load.