Dicalcium phosphate dihydrate (CaHPO4·2H2O, DCPD, brushite) crystals were synthesised within Scots pine sapwood via a wet-chemistry route from aqueous solutions of Ca(CH3COO)2 and NH4H2PO4 salts. SEM/EDS analysis was used to assess the saturation of the wood cell lumina and cell wall as well as morphological features and elemental composition of the co-precipitated mineral. Brushite mineral crystallization and crystallite growth within the wood matrix was studied by in situ XRD. The chemical composition of the mineral before and after the dissolution was evaluated using FTIR spectroscopy. The overall impact of brushite on the thermal behaviour of wood was studied by TGA/DSC and TGA/DTA/MS analysis under oxidative and pyrolytic conditions. Bending and compression strength perpendicular and parallel to the fibre directions as well as bending strengths in longitudinal and transverse directions of the mineralised wood were also evaluated. Results indicate the viability of the wet-chemistry processing route for wood reinforcement with crystalline calcium phosphate (CaP)-based minerals, and imply a potential in producing hybrid bio-based materials that could be attractive in the construction sector as an environmentally friendly building material.

The end-of-life recycling of crystalline silicon photovoltaic (PV) modules and the utilisation of waste is of fundamental importance to future circular-economy societies. In the present work, the wet-chemistry synthesis route – a low-temperature dissolution–precipitation process – was explored to produce aluminosilicate minerals from waste c-Si solar cells. Nanostructured crystals were produced in an alkaline medium by increasing the reaction temperature from room temperature to 75 °C. The morphology of the produced crystals varied from nanolayered aggregates to rod-shaped crystals and was found to be dependent on the temperature of the reaction medium. Chemical and phase composition studies revealed that the synthesised compounds consisted of structurally different phases of aluminosilicate minerals. The purity and elemental composition of produced crystals were evaluated by energy dispersive spectroscopy (EDS) and micro X-ray fluorescence (μXRF) analysis, confirming the presence of Al, O, and Si elements. These results give new insights into the processing of aluminosilicate minerals with sustainable attributes and provide a possible route to reducing waste and strengthening the circular economy.

Modification of Scots pine (Pinus sylvestris L.) sapwood using aqueous formulations of Na₂SiO₃ via vacuum-pressure technique and subsequent treatment with cashew nut-shell liquid (CNSL) is reported. Morphology, elemental distribution within wood matrix, and structural properties of wood-composites were investigated by FE-SEM/EDS, FTIR analysis. Microstructure and density of modified wood blocks were further assessed by X-ray computed tomography. The flammability of Na₂SiO₃-CNSL-wood composites was evaluated simultaneously performing thermogravimerical (TG) and FTIR gas analysis; the results showed that maximum weight loss for the modified wood was obtained at up to 70 °C lower temperatures compared to the untreated wood, whilst substantially reducing terminal weight losses. The coefficient of friction significantly increased after the CNSL treatment compared to that of untreated wood, but addition of Na₂SiO₃ to CNSL eliminated most of the friction increase. Enhanced tribological properties along with industrial wood-impregnation method suggest that wood modification using Na₂SiO₃ in combination with CNSL has a potential for the exploration of a broader range of wood material properties in agreement with sustainable material management.

Optimising the exploitation of available waste resources for the recovery of their intrinsic value will be vital in the future circular economy society. Recovery of energy, nutrients and metals from waste streams is in focus today. This study aimed to evaluate the use of an aquaculture waste, i.e. the dried-solid waste discharge that generates by cleaning the fishing-nets, as a potential fire-retardancy promoter for Scots pine sapwood. As-received dried-solid waste from salmon-farming was calcined at different temperatures to evaluate material phase transformation and achieve homogeneous phase distribution. Thermal degradation of waste powders was studied by TG-FTIR gas analysis when annealing the material to temperatures up to 800°C, and the crystallinity, phase composition, morphology, elemental composition and particle sizes of as-received and calcined-waste materials at different temperatures were evaluated by XRD, FTIR, SEM/EDS, and TEM analyses. The flammability studies using cone calorimeter of Scots pine sapwood blocks treated with as-received and processed material is also reported and discussed. Results were promising, indicating that the aquaculture waste could be employed as an effective fire-retardant. The possibility of value-creation from waste discharges is enforced in this study so to promote the way towards waste valorisation and circular economy.

The objective of this study was to explore an effect of the combined inorganic materials on the wood hardness and flame-retardancy properties in a concept of sustainable material management. Herein, the reinforcement of Scots pine (Pinus sylvestris L.) sapwood with sodium silicate and TiO2 nanoparticles via vacuum-pressure technique is reported. Pyrolysis of modified wood was studied by TG-FTIR analysis; the results showed that maximum weight loss for the modified wood was obtained at 40–50 °C lower temperatures compared to the reference untreated wood. The Gram–Schmidt profiles and spectra extracted at maxima absorption from Gram–Schmidt plots indicated chemical changes in wood–inorganic composites. SEM/EDS analysis revealed the presence of Na–O–Si solid gel within the wood-cell lumen and showed that TiO2 was homogeneously distributed within the amorphous Na–O–Si glass-forming phase to form a thin surface coating. EDS mapping further revealed the higher diffusivity of sodium into the cell wall compared to the silicon compound. The presence of amorphous sodium silicate and nano-TiO2 was additionally confirmed by XRD analysis. FTIR spectra confirmed the chemical changes in Scots pine sapwood induced by alkalization. Brinell hardness test showed that the hardness of the modified wood increased with the highest value (44% increase in hardness) obtained for 10% Na2SiO3–nTiO2 modified wood. The results showed good correlation between TG and flammability test; limiting oxygen index (LOI) values for the wood–inorganic composites increased by 9–14% compared to the untreated wood.

This work presents a rapid and facile way to access the cell wall of wood with magnetic nanoparticles (NPs), providing insights into a method of wood modification to prepare hybrid bio-based functional materials. Diffusion-driven infiltration into Scots pine (Pinus sylvestris L.) sapwood was achieved using colloidal Fe₃O₄ nanoparticles. Optical microscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray powder diffraction analyses were used to detect and assess the accessibility of the cell wall to Fe₃O₄. The structural changes, filling of tracheids (cell lumina), and NP infiltration depth were further evaluated by performing X-ray microcomputed tomography analysis. Fourier transform infrared spectroscopy was used to assess the chemical changes in Scots pine induced by the interaction of the wood with the solvent. The thermal stability of Fe₃O_4-modified wood was studied by thermogravimetric analysis. Successful infiltration of the Fe₃O₄ NPs was confirmed by measuring the magnetic properties of cross-sectioned layers of the modified wood. The results indicate the feasibility of creating multiple functionalities that may lead to many future applications, including structural nanomaterials with desirable thermal properties, magnetic devices, and sensors. 

Various types of scaffolds made of synthetic polymers have been widely studied for bone-tissue applications due to their mechanical strength, biocompatibility and biodegradability, but the hydrophobic nature of synthetic polymers and frequent absence of pores within the scaffolds inhibit cellular attachment, infiltration, and tissue ingrowth. In this study, multi-composite scaffolds composed of dipentaerythritol hexa-acrylate (DPHA), ethylene glycol dimethacrylate (EGDMA), gelatin, and carbonated hydroxyapatite (cHAP) have been made. Percentage ratio of polymer matrix to gelatin was varied 50/50, 75/25, and 95/5 to change the porosity of the resultant scaffolds. The structure, crystallinity, and phase composition of the cHAP were confirmed by FTIR, Raman, XRD and Rietveld analyses, TG/DSC was used to evaluate the distribution of ceramics within the polymer matrix, and FTIR-ATR was used to confirm the molecular structure of composites. SEM/EDS analysis of the scaffolds revealed cavities and irregularities in the surface, and that cHAP was indistinctly exposed on the composite surface, computed tomography (CT) was used to estimate the density and homogeneity of the scaffolds, and the cHAP distribution within the scaffolds was evaluated by conventional radiography. The hydrophilicity of the multi-composite scaffolds was investigated using an aqueous solution of methylene blue dye which showed that the acrylate(75%)–gelatin(25%)–cHAP composite had the highest hydrophilicity. The results suggest that acrylate–gelatin–cHAP scaffolds have a potential for bone-tissue engineering. 

For the first time to the best of our knowledge, cobalt-chromium spinels CoCr_2−xGa_xO₄ with different amounts of gallium (x = 0–2 with a step of 0.5) were synthesized via the aqueous sol–gel route as ceramic pigments. The phase composition, crystallite size, morphological features, and color parameters of new compositions and their corresponding ceramic glazes were investigated using XRD, CIELab, SEM, and optical microscopy. It was demonstrated that the formation of single-phase CoCr_2−xGa_xO₄ samples was problematic. Full substitution of Cr³⁺ by Ga³⁺ ion in the spinel resulted in the formation of light blue powders, which yielded violetish blue color for the corresponding ceramic glaze.

In the present work, three different Mn²⁺-doped calcium pyrophosphate (CPP, Ca₂P₂O₇) polymorphs were synthesized by wet co-precipitation method followed by annealing at different temperatures. The crystal structure and purity were studied by powder X-ray diffraction (XRD), Fourier-transform infrared (FTIR), solid-state nuclear magnetic resonance (SS-NMR), and electron paramagnetic resonance (EPR) spectroscopies. Scanning electron microscopy (SEM) was used to investigate the morphological features of the synthesized products. Optical properties were investigated using photoluminescence measurements. Excitation spectra, emission spectra, and photoluminescence decay curves of the samples were studied. All Mn-doped polymorphs exhibited a broadband emission ranging from approximately 500 to 730 nm. The emission maximum was host-dependent and centered at around 580, 570, and 595 nm for γ-, β-, and α-CPP, respectively.

In this review article the available results about application of sol–gel synthesis method for the preparation of different calcium phosphates and composite materials are summarized. The attention is paid to calcium phosphate-containing compounds which show the biological properties and could be used as potential phosphate bioceramics in medicine. It was demonstrated that the sol–gel synthesis method is a powerful tool for the synthesis of calcium hydroxyapatite and other phosphates, and different calcium phosphate-based composites at mild synthetic conditions resulted in high reproducibility, high phase purity, and desired morphology. Thus, the sol–gel synthesis method enables the researchers to develop biomaterials with superior features in terms of biomedical applications.

In the present work, gadolinium substitution effects on the properties of yttrium manganite Y_xGd_1−xMn_0.97Fe_0.03O₃ (x from 0 to 1 with a step of 0.2) synthesized by an aqueous sol–gel method have been investigated. Partial substitution of Mn³⁺ by ⁵⁷Fe³⁺ in the manganite was also performed in order to investigate deeper the structural properties of synthesized compounds applying Mössbauer spectroscopy. It was demonstrated that substitution of Y³⁺ by Gd³⁺ ions leads to the changes of structural, magnetic and morphological properties of investigated system. The crystal structure gradually transformed from hexagonal to orthorhombic with an increase of Gd³⁺ content in the crystal lattice. The mixed phase was obtained when x = 0.6, whereas other compounds were determined to be monophasic. Magnetization measurements revealed paramagnetic behavior of all specimens, however magnetization values were found to be dependent on chemical composition of the samples. Solid solutions with orthorhombic structure revealed higher magnetization values compared to those of hexagonal samples. The highest magnetization was observed for pure GdMn_0.97Fe_0.03O₃. Structural properties were investigated by powder X-ray diffraction, Mössbauer, FTIR and Raman spectroscopies. Morphological features of the synthesized specimens were studied by scanning electron microscopy (SEM).

The objective of the work was to improve the leaching resistance of fire-retardant (FR) modified wood by the incorporation of a thermoset resin. Here, Scots pine (Pinus sylvestris L.) sapwood was impregnated with melamine formaldehyde (MF) resin and hydrophilic FRs guanyl-urea phosphate/boric acid by a vacuum-pressure treatment. Resistance to leaching of FR-modified wood was evaluated, after conducting an accelerated aging test according to European standard EN 84. Inductively coupled plasma analysis showed that the incorporation of MF resin significantly reduced the leachability of FRs. Scanning electron microscopy/energy-dispersive X-ray spectrometry revealed that the mechanism of water resistance was by doping the FRs into MF resin microspheres. Fourier transform infrared spectra showed the chemical functionality changes of FR-modified wood such as the formation of methylene bridges by drying the modified wood specimens. An increase in the thermal stability of FR-modified wood was confirmed by thermal gravimetric analysis. Excellent fire performance of FR-modified wood after leaching was affirmed by the limiting oxygen index and cone calorimeter tests.

Tungsten trioxide (WO₃) and molybdenum-doped tungsten trioxide (WO₃:Mo) films were deposited on stainless steel surface by a chemical aqueous solution approach using dip-coating technique. The deposited 5, 10 and 15-layer films were homogeneous and continuous. The surface morphology and crystallinity of the produced films were dependent on the metal cation species and concentration of PVA in the solution. FE-SEM analysis revealed the formation of textured WO₃ film surfaces having spike-like nanostructures. The values of the static water contact angle measured on the film surface showed that deposited WO₃ films can exhibit both hydrophilic and hydrophobic nature, while WO₃:Mo films showed hydrophilic behavior. Tribological properties of the deposited films were evaluated in deionized water. All three coatings retained a lubricating layer much better than original steel, demonstrating major reduction in friction and wear. Particularly effective were PVA-free WO₃ films, whose friction coefficient stayed under 0.2 for over 2000 cycles. Excellent tribological, hydrophobic and hydrophilic properties along with simple deposition methods suggest very promising potential of WO₃ and WO₃:Mo coatings in industrial applications.

A simple chemical solution-based synthesis route has been developed to prepare uniform and shape-controllable Ag3PO4 crystals. Tetrapod- and cube-shaped crystals having a size of about 9–10 μm were prepared from AgNO3 and NH4H2PO4 precursors, and pseudo-octahedral (equiaxial) crystals were prepared from AgNO3 and (NH4)2HPO4. TEM analysis revealed Ag3PO4 crystals to be electron beam sensitive materials, which under a voltage of 200 kV decompose to the metallic Ag, thereby demonstrating the difficulty in determining crystal facets and structural defects using conventional electron diffraction studies. UV–Vis diffuse reflectance spectroscopy was used to study the correlation between structural and optical properties of surfaces of Ag3PO4 crystals. Furthermore, a spatial 3-dimentional (3D) reconstruction of Ag3PO4 surface structures was performed from SEM images. The reconstruction produced realistic 3D mesh models, insomuch that the 3D reconstructed structures provided extra information about the examined crystals. Results suggested that the proposed synthesis route and performed spatial reconstruction of Ag3PO4 had the potential for simulating processing conditions to produce various microcrystals and explore material surface structures and reconstruction of microstructures.