Brushite mineralised Scots pine (Pinus sylvestris L.) sapwood - revealing mineral crystallization within a wood matrix by in situ XRD.

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.

Synthesis, structural and luminescent properties of Mn-doped calcium pyrophosphate (Ca2P2O7) polymorphs.

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-, ß-, and α-CPP, respectively.

The Accessibility of the Cell Wall in Scots Pine (Pinus sylvestris L.) Sapwood to Colloidal Fe3O4 Nanoparticles.

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 Fe3O4-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.

Approaching Highly Leaching-Resistant Fire-Retardant Wood by In Situ Polymerization with Melamine Formaldehyde Resin.

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.

Study of gadolinium substitution effects in hexagonal yttrium manganite YMnO3.

In the present work, gadolinium substitution effects on the properties of yttrium manganite YxGd1-xMn0.97Fe0.03O3 (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 GdMn0.97Fe0.03O3. 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).

Surface hardness and flammability of Na2SiO3 and nano-TiO2 reinforced wood composites.

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.

Correction: Surface hardness and flammability of Na2SiO3 and nano-TiO2 reinforced wood composites.

[This corrects the article DOI: 10.1039/C9RA05200C.].

Feasibility evaluation of low-crystallinity ß-tricalcium phosphate blocks as a bone substitute fabricated by a dissolution-precipitation reaction from α-tricalcium phosphate blocks.

Although sintered ß-tricalcium phosphate blocks have been used clinically as artificial bone substitutes, the crystallinity of ß-tricalcium phosphate, which might dominate biocompatibility, is extremely high. The objective of this study is to evaluate the feasibility of fabricating low-crystallinity ß-tricalcium phosphate blocks, which are expected to exhibit good biocompatibility via a dissolution-precipitation reaction of α-tricalcium phosphate blocks as a precursor under hydrothermal conditions at 200°C for 24 h. Although ß-tricalcium phosphate is a metastable phase, the presence of Mg2+ in the reaction solution inhibits the formation of its corresponding stable phase and induces ß-tricalcium phosphate formation under acidic conditions. It was found that low-crystallinity ß-tricalcium phosphate blocks could be fabricated from α-tricalcium phosphate blocks immersed in 1.0 mol/L MgCl2 + 0.1 mol/L NaH2PO4 solution while maintaining the shape of the α-tricalcium phosphate blocks. The crystallite size of the fabricated ß-tricalcium phosphate blocks was 42 nm, which was substantially smaller than that of the sintered ß-tricalcium phosphate blocks. When the fabricated ß-tricalcium phosphate blocks were implanted into bone defects in rabbit femurs, they exhibited excellent tissue responses. In particular, the initial osteoconductivity (two and four weeks) was substantially greater than that of sintered ß-tricalcium phosphate blocks.