Search Results (46)

Excessive blood loss is a leading cause of mortality among soldiers and accident victims. The wound healing process typically ranges from three weeks to several months, with disruptions in healing stages potentially prolonging recovery time. Chronic wounds may persist for years, creating a favorable environment for microbial growth. Chitosan, a derivative of chitin—the second most abundant biopolymer in nature—is obtained through deacetylation and exhibits mucoadhesive, analgesic, antioxidant, biodegradable, non-toxic, and biocompatible properties. Due to its hemostatic and regenerative support capabilities, chitosan is widely applied in the food, cosmetic, and agricultural industries; environmental protection; and as a key component in dressings for chronic wound healing. Notably, its antibacterial properties make it a promising candidate for novel biomaterials to replace traditional antibiotics and prevent the emergence of drug-resistant strains. The primary aim of this study was the chemical cross-linking of chitosan with the amino acids L-aspartic and L-glutamic acid in the presence of periclase (magnesium oxide) under microwave radiation conditions. Subsequent research stages involved the analysis of the samples’ physicochemical properties using SEM, FT-IR, XPS, atomic absorption spectrometry, swelling behavior (in water, SBF, and blood), porosity, and density. Biological assessments included biodegradation, cytotoxicity, and antibacterial activity against Escherichia coli and Staphylococcus aureus. The obtained results confirmed the high potential of the newly developed hemostatic agents for effective hemorrhage management under non-sterile conditions. Full article

Prosthetics, a rapidly advancing field in dentistry, aims to improve patient comfort and aesthetics by addressing the challenge of replacing missing teeth. A critical obstacle in dental implantation is the condition of the jawbone, which often necessitates reconstruction prior to implant placement. Guided bone regeneration (GBR) and guided tissue regeneration (GTR) techniques utilize membranes that act as scaffolds for bone and tissue growth while serving as barriers against rapidly proliferating cells and pathogens. Commonly used membranes, such as poly(tetrafluoroethylene) (PTFE) and collagen, have significant limitations—PTFE is non-bioresorbable and requires secondary removal, while collagen lacks adequate mechanical strength and exhibits unpredictable degradation rates. To overcome these challenges, nanofiber membranes produced via electrospinning using polylactic acid (PLA) were developed. The novel composites were functionalized with bioactive additives, including periclase (MgO) nanoparticles and polydopamine (PDA), to enhance osteoblast adhesion, antibacterial properties, and tissue regeneration. This study comprehensively evaluated the biological, mechanical, and physicochemical properties of the prepared nanofibrous scaffolds. Experimental results revealed controlled degradation rates and improved hydrophilicity due to surface modifications with PDA and MgO. Moreover, the nanofibers exhibited enhanced swelling behavior, which promoted nutrient exchange while maintaining structural integrity over prolonged periods. The incorporation of bioactive additives contributed to superior osteoblast proliferation, antibacterial activity, and growth factor immobilization, supporting bone tissue regeneration. These findings suggest that the developed nanofibrous composites are a promising candidate for GBR and GTR applications, offering a balanced combination of biological activity, mechanical performance, and degradation behavior tailored for clinical use. Full article

Magnesia-spinel multicomponent materials have been used as refractories for a long time. In addition to a few binary systems, the influence of spinel phases on the thermal expansion ($\alpha$) of MgO or the resulting compound has not been studied so far. As $\alpha$ is critical for refractories in application, this work investigates the thermal expansion of complex MgO-based spinel systems using X-ray diffraction (XRD) in combination with Rietveld refinement in the temperature range between 30 °C and 1200 °C. All studied periclase solid solutions, in contact with spinels of the systems Mg_1.01(Al_0.23Cr_1.64Fe_0.13)O₄, ${\mathrm{Fe}}_3{\mathrm{O}}_4$–${\mathrm{MgFe}}_2{\mathrm{O}}_4$, NiFe₂O₄–NiAl₂O₄, MgAl₂O₄–MgFe₂O₄, Fe₃O₄–FeAl₂O₄ and ${\mathrm{Fe}}_3{\mathrm{O}}_4·{\mathrm{NiFe}}_2{\mathrm{O}}_4·2{\mathrm{MgAl}}_2{\mathrm{O}}_4$ showed $\alpha$ trends below plain MgO, or even decreasing values above 1000 °C. Many spinels showed large negative thermal expansion coefficients. It was found that the structural change in spinels is constrained, leading to a common analytical expression to calculate the lattice parameter of spinels with temperature, which was used to study the nature of the investigated spinels in more detail. The work highlights that Cr-free MgO-spinel systems show similar or even better high-temperature behaviour than commonly used magnesia–chrome aggregates. Full article

Thermal decomposition (pyrolysis) of coal bottom ash (collected after lignite combustion in coal-fired power plant TEKO-B, Republic of Serbia) was investigated, using the simultaneous TG-DTG techniques in an inert atmosphere, at various heating rates. By using the XRD technique, it was found that the sample (CBA-TB) contains a large amount of anorthite, muscovite, and silica, as well as periclase and hematite, but in a smaller amount. Using a model-free kinetic approach, the complex nature of the process was successfully resolved. Thermodynamic analysis showed that the sample is characterized by dissociation reactions, which are endothermic with positive activation entropy changes, where spontaneity is achieved at high reaction temperatures. The model-based method showed the existence of a complex reaction scheme that includes two consecutive reaction steps and one single-step reaction, described by a variety of reaction models as nucleation/growth phase boundary-controlled, the second/n-th order chemical, and autocatalytic mechanisms. It was established that an anorthite I1 phase breakdown reaction into the incongruent melting product (CaO·Al₂O₃·2SiO₂) represents the rate-controlling step. Autocatalytic behavior is reflected through chromium-incorporated SiO₂ catalyst reaction, which leads to the formation of chromium(II) oxo-species. These catalytic centers are important in ethylene polymerization for converting light olefin gases into hydrocarbons. Adiabatic T_D24 prediction simulations of the process were also carried out. Based on safety analysis through validated kinetic parameters, it was concluded that the tested sample exhibits high thermal stability. Applied thermal treatment was successful in promoting positive changes in the physicochemical characteristics of starting material, enabling beneficial end-use of final products and reduction of potential environmental risks. Full article

This study considers the regularities in the formation of amorphous–crystalline coatings with zinc oxide and wollastonite particles via micro-arc oxidation (MAO) on metal substrates made from a Mg-0.8 wt.% Ca alloy. The combination of components with increased antibacterial and osteogenic properties made it possible to obtain a unique bioactive and corrosion-resistant coating that slowed down the bioresorption of a magnesium implant and stimulated the processes of osteointegration. The coating was examined using various methods, including scanning and transmission electron microscopy, X-ray crystallography, scratch testing, energy-dispersive X-ray spectroscopy, and potentiodynamic polarization testing. As a result of plasma-chemical interactions between electrolyte components and the magnesium substrate, a porous amorphous–crystalline coating comprising wollastonite (CaSiO₃), zinc oxide (ZnO), forsterite (Mg₂SiO₄), and periclase (MgO) was formed at varying voltages (350–500 V) during the MAO process. The protective properties of the coating were exceptional, as evidenced by the mass loss values of the coated samples (1.4–2.3%) in 0.9% NaCl solution, which were significantly lower than the mass loss of the uncoated alloy (8.9%). The coating synthesized at a voltage of 500 V was characterized by a maximum zinc content of 8 at.%, which was responsible for the highest antibacterial activity against Staphylococcus aureus (99.1%). Full article

Changes in the phase composition of serpentinite from the Zhitikarinsky deposit (Kazakhstan) were studied during heat treatment in the temperature range of 105–800 °C in order to determine the phase that leads to an increase in the reactivity of serpentinite during interactions with acids. In accordance with this, the task was set to consider the influence of temperatures (105 °C, 600 °C, 660 °C, 725 °C, 750 °C and 800 °C), selected according to the extreme points of the main transformations from its derivatogram, on changes in the phase composition. The effects of heat treatment on the phase composition and reactivity of serpentinite during interactions with sulfuric acid were studied and discussed using the diffraction patterns of serpentinite heat treated at selected temperatures for 1 h and using methods of thermodynamic evaluation of the possible reactions in the temperature range of 350–750 °C, as well as establishing the nature of their interaction with sulfuric acid under identical conditions. It has been shown that, in the range of 600–750 °C, the crystal lattice of the structural composition of serpentinite is completely destroyed with the formation of not only magnesium silicates but possibly also magnesium oxide, which leads to the thermal activation of serpentinite in relation to interactions with acids and the improvement of the technological process of extracting magnesium from it. The greatest increase in reactivity was found in serpentinite samples heat treated at temperatures of 725 °C and 750 °C, which can be recommended for the thermal activation of serpentinite before using acid methods to improve the technological performance of the process of extracting magnesium from serpentinite. Full article

This study investigated the effects of substituting magnesium oxide (MgO) with dolomitic limestone (DL) on the mechanical and physical properties of magnesium oxysulfate (MOS) cement. Additionally, the hydration formation phases and the influence of the molar ratio on the MOS cement’s performance were examined. The corresponding action mechanisms were identified and explored by compressive strength tests, scanning electron microscopy (SEM), X-ray diffraction (XRD), isothermal calorimetry, and a thermogravimetric analysis (TGA). The results showed that replacing MgO with DL decreased the reaction speed and heat release rate generated in the hydration process of the MOS cement. This substitution also reduced the quantity of non-hydrated MgO particles and delayed the formation of Mg(OH)₂. The diminished formation of Mg(OH)₂ contributed to an increase in the apparent porosity of pastes containing DL, thus alleviating internal stresses induced by Mg(OH)₂ formation and enhancing their mechanical strength after 28 days of curing. Conversely, the increased porosity improved the CO₂ diffusion within the structure, promoting the formation of magnesium carbonates (MgCO₃). Through the characterization of the cement matrix (XRD and TGA), it was possible to identify phases, such as the brucite, periclase, and 318 phases. The obtained results revealed the potential of incorporating mineral fillers like limestone as a promising approach to producing MOS cement with a reduced environmental impact and better properties at higher curing ages. Full article

A series of M(x)CoCeMgAlO mixed oxides with different transition metals (M = Cu, Fe, Mn, and Ni) with an M content x = 3 at. %, and another series of Fe(x)CoCeMgAlO mixed oxides with Fe contents x ranging from 1 to 9 at. % with respect to cations, while keeping constant in both cases 40 at. % Co, 10 at. % Ce and Mg/Al atomic ratio of 3 were prepared via thermal decomposition at 750 °C in air of their corresponding layered double hydroxide (LDH) precursors obtained by coprecipitation. They were tested in a fixed bed reactor for complete methane oxidation with a gas feed of 1 vol.% methane in air to evaluate their catalytic performance. The physico-structural properties of the mixed oxide samples were investigated with several techniques, such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), elemental mappings, inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction under hydrogen (H₂-TPR) and nitrogen adsorption–desorption at −196 °C. XRD analysis revealed in all the samples the presence of Co₃O₄ crystallites together with periclase-like and CeO₂ phases, with no separate M-based oxide phase. All the cations were distributed homogeneously, as suggested by EDX measurements and elemental mappings of the samples. The metal contents, determined by EDX and ICP-OES, were in accordance with the theoretical values set for the catalysts’ preparation. The redox properties studied by H₂-TPR, along with the surface composition determined by XPS, provided information to elucidate the catalytic combustion properties of the studied mixed oxide materials. The methane combustion tests showed that all the M-promoted CoCeMgAlO mixed oxides were more active than the M-free counterpart, the highest promoting effect being observed for Fe as the doping transition metal. The Fe(x)CoCeMgAlO mixed oxide sample, with x = 3 at. % Fe displayed the highest catalytic activity for methane combustion with a temperature corresponding to 50% methane conversion, T₅₀, of 489 °C, which is ca. 40 °C lower than that of the unpromoted catalyst. This was attributed to its superior redox properties and lowest activation energy among the studied catalysts, likely due to a Fe–Co–Ce synergistic interaction. In addition, long-term tests of Fe(3)CoCeMgAlO mixed oxide were performed, showing good stability over 60 h on-stream. On the other hand, the addition of water vapors in the feed led to textural and structural changes in the Fe(3)CoCeMgAlO system, affecting its catalytic performance in methane complete oxidation. At the same time, the catalyst showed relatively good recovery of its catalytic activity as soon as the water vapors were removed from the feed. Full article

Thermoacid behavior of serpentinite from the Zhitikarinsky field (g. Zhitikara, Kazakhstan). The character of dissolution of heat-treated serpentinite in a narrow temperature range of 600–750 °C is investigated, where the crystal lattice of the structural structure of chrysotile in sulfuric acid is destroyed. The X-ray and chemical analysis of the products of dissolution of heat-treated serpentinite at 600 °C, 725 °C and 750 °C in sulfuric acid solution show that the reason for the increase in the reactivity of heat-treated serpentinite at 725 °C and 750 °C with respect to the acidic medium and the degree of magnesium extraction into sulfate solution is the formation of periclase (MgO) in the serpentinite composition after heat treatment of them within a temperature range of 600–750 °C. The results were discussed using data obtained by conducting a thermodynamic evaluation of probable reactions during the thermoacid treatment of serpentinite, phase compressions of heat-treated serpentinite at 600–750 °C, and after its acid treatment at 1.0 M H₂SO₄. Full article

Magnesium oxide is typically white and can be colorized with transition metal insertion by doping. We present the preparation of a green-colored hydroxide by the exchange of Mg²⁺ on the crystalline lattice with Ni²⁺ in MgO, using three nickel salts. MgO_st was prepared by the colloidal starch suspension method, using cassava starch. The oxides and hydroxides, before and after, were characterized by X-ray diffraction (XRD), and show that a phase change occurs: a transition from periclase (MgO) to brucite (Mg(OH)₂) due to the incorporation of nickel ions from different salts (acetate, chloride, and nitrate), resulting in the solid solution [Ni_xMg_1−x(OH)₂]. The FTIR spectrum corroborates the crystallographic structure identified through XRD patterns, confirming the formation of a crystal structure resembling brucite. The new samples present a green color, indicative of the incorporation of the Ni²⁺ ions. The antimicrobial activity of products resulting from the doping of magnesium oxide with nickel and the precursor MgO_st was assessed through the minimum inhibitory concentration (MIC) test. The evaluation included three bacterial strains: Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), Salmonella gallinarum (ATCC 9184), and a yeast strain, Candida albicans (ATCC 10231). The obtained results were promising; the tested samples exhibited antimicrobial activity, with a MIC ranging from 0.312 to 0.625 μg.μL⁻¹. The nickel compound, derived from the precursor chloride salt, demonstrated superior MIC activity. Notably, all tested samples displayed bactericidal activity against the S. aureus strain and exhibited a broad spectrum of inhibition, encompassing both Gram-positive and Gram-negative strains. Only the nickel compounds derived from precursors with acetate and nitrate anions demonstrated antimicrobial activity against C. albicans, exhibiting a fungistatic behavior. Based on the conducted studies, [Ni_xMg_1−x(OH)₂] has emerged as a promising antimicrobial agent, suitable for applications requiring the delay or inhibition of bacterial growth. Full article

This study aimed to synthesize magnesium oxide (MgO) using a colloidal starch method for two primary purposes: the removal of chromium (III) ions from synthetic wastewater and the subsequent use of the chromium-containing material as synthetic inorganic pigments (SIPs) in commercial paints. The synthesis used to obtain the oxide (St-MgO) is a promising method for using plants, such as cassava, as green fuels due to their abundance, low cost, and non-toxicity. With this, the oxide showed greater porosity and alkalinity, compared to commercial magnesium oxide (Cm-MgO). The MgO samples were subjected to structural characterization using XRD and FTIR, surface area and pore volume study by B.E.T. and SEM, and chemical composition by ICP-OES and thermogravimetric analysis (TGA). The crystalline periclase phase was identified for both samples, but the brucite phase was shown to be a secondary phase for the commercial sample. After the removal of chromium ions, the brucite crystalline phase became the majority phase for the samples, regardless of the concentration of ions removed. The pigments were characterized by color measurements and discussed in terms of colorimetric parameters using the CIELab method and electron spectroscopy (VIS-NIR). This study also evaluated the colorimetric stability of green pigments in aggressive environments (acidic and alkaline) over a 240 h exposure period, demonstrating minimal color difference. This study aims to develop materials for the decontamination of wastewater containing chromium and its reuse as a synthetic inorganic pigment, using an innovative and sustainable synthesis method. Full article

Recycling of industrial waste into useful materials is a crucial aim for achieving sustainable development in materials science. The use of production waste in the manufacture of construction materials contributes to improving the environmental situation and reducing the cost of the final product. This article examines the utilization of coal combustion waste recycled into foamed geopolymers and ways of enhancing their strength properties through the introduction of strengthening additives. Eight compositions of foamed geopolymers containing different strengthening additives were synthesized. Inorganic substances (CaO, MgO, ZnO, TiO₂, Al₂O₃, SiC, and ZrO₂) were chosen as strengthening additives that were introduced in an amount of 3% (over 100%). The physical and mechanical properties (density, compressive strength, porosity, and pore size distribution) of the obtained samples were studied and compared. Magnesium oxide MgO and aluminum oxide Al₂O₃ were chosen as the best strengthening additives. Magnesium oxide allows geopolymer materials with the lowest density to be obtained. Aluminum oxide can significantly increase the strength of geopolymers. The phase composition of the samples contains new crystalline phases in the form of α-alumina and periclase. The porous structure is homogeneous and meets the requirements for foamed thermal insulation materials. The strengthening effect of the chosen additives was verified using geopolymers based on different waste from Novocherkassk SDPP. Full article

In order to raise the utilization rate of industrial waste and mitigate issues involving land resource occupation and environmental damage, in this study, industrial-waste-based artificial aggregates (IWAAs) were fabricated using steel slag powders, fly ash, and cement. They were processed under accelerated carbonation and were utilized in a bitumen mixture. During the experiment, the micromorphology, internal structure, and phase composition of IWAAs before and after accelerated carbonation were characterized using X-ray phase analysis, thermal analysis, and scanning electron microscopy (SEM); concurrently, the possibility of IWAAs being used as a partial substitute for natural aggregate to prepare bituminous mixture was qualitatively and quantitatively analyzed based on Marshall’s design procedure in combination with road performance tests and microcosmic analyses. The results indicated that the presence of carbonate crystals brought about by accelerated carbonation was the main phase composition inside the IWAAs, enhancing the microstructure densification and diminishing the immersion expansion and crushing values; this is due to the depletion of the interior Ca-based (e.g., f-CaO and Portlandite) and Mg-based (e.g., periclase and brucite) compounds together with the formation of cement hydration products. Additionally, the 12 h carbonation time obtained the optimum CO₂-sequestration efficiency on the premise of satisfying the performance standard. The expansion rate and crushing value of the IWAAs decreased by 82.21% and 41.58%, respectively, whilst the anti-rutting properties, the moisture damage resistance, and the skid resistance rose by 31.92%, 5.59%, and 10.00%, respectively, in the IWAAs–bituminous mixture. This study lays a foundation for research on the CO₂ sequestration and resource utilization of industrial wastes in bitumen mixtures. Full article

Magnesium oxysulfate (MOS) cement features potential advantages, including light weight, green and environmental protection, low thermal conductivity, and high frost- and fire-resistance, but its poor mechanical strength limits the extensive utilization in the architectural engineering. In this study, low-cost quartz (Q) was used as a mineral admixture to increase the mechanical strength of MOS pastes. The impact of the filler Q on the early and later mechanical strength of MOS cement was investigated, in which also had an impact on fluidity, setting times, volume stability, hydration processes, phase transformations, and microstructure. The results show that hydration of periclase to form 5Mg(OH)₂·MgSO₄·7H₂O (phase 5-1-7) in this system was a multi-stage reaction process. 3Mg(OH)₂·MgSO₄·8H₂O was the first sediment in this system and was converted into phase 5-1-7. The dilution and dispersion effects of the filler Q increased the early hydration rate, shortened the setting time, and increased the content and crystallite size of phase 5-1-7, increasing the early mechanical strength of MOS cement, while the volume-filling effect of the filler Q reduced the content of large pore and total pore volume, and improved the pore structure of the MOS cement, improving the later mechanical strength of MOS cement. MOS cement containing 15 wt.% of filler Q exhibited the highest early and later mechanical strength, and the lowest volume shrinkage, which is more suitable for application in architectural engineering. Based on these results, filler Q can be used as an enhancer in MOS cement, however its enhancement mechanisms are effective only when the content of filler Q is no more than 20 wt.%. Full article

This research combines technical, environmental, and economic aspects regarding the utilization of Bege Bahia marble waste (BB) in clinker production. Three different eco-friendly clinkers were produced, investigated, and compared with one that is commercially available. BB was used to replace 49.2%, 77%, and 80.3% of the limestone by total amount of clinker. Two clinkers were selected to produce cement pastes, and their impact on compressive strength at 28 days was examined. The results suggest that substituting limestone with BB does not adversely affect the compressive strength of cement paste. Moreover, employing 77% or 80.3% BB in clinker production does not significantly influence the alite and belite contents but slightly increases the tricalcium aluminate and ferrite phases while reducing the periclase content. A life cycle analysis was conducted to assess the effects of replacing limestone with marble waste. The results revealed a substantial decrease in abiotic depletion, leading to conservation of substantial natural resources. Consequently, the utilization of BB in clinker production makes a significant contribution to environmental preservation while providing an effective alternative to limestone. In addition, the resulting clinkers serve as useful repositories, providing a permanent and sustainable destination for waste that is currently deposited in landfills. Finally, the economic viability was also examined under various scenarios based on the distance between marble and cement plants. The results highlight the transport distance of marble waste as the primary determinant of economic feasibility in utilizing this residue as a limestone replacement. Full article