Sol-gel preparation and electrical behaviour of Ln: YAG (Ln = Ce, Nd, Ho, Er)

A sol-gel method has been developed to prepare pure yttrium aluminum garnet, Y3Al5O12 (YAG), and rare-earth substituted (Ce-Y3Al5O12, Nd-Y3Al5O12, Ho-Y3Al5O12, and Er-Y3Al5O12) samples. The XRD patterns of the polycrystalline powders sintered at 1000ºC showed the formation of monophasic garnet materials. The micro-structural features in the polycristalline samples were studied by scanning electron microscopy. A homogeneous distribution of rare-earth dopants in the YAG lattice was achieved in all of the cases. Electrical conductivity measurements were also performed on the compacts of sol-gel derived Ln-YAG samples. In contrast to the expected dielectric behaviour, the conducting properties of the examined specimens indicate metallic behaviour with the resistivity increasing gradually with increasing temperature

Sol–gel synthesis of calcium phosphate-based biomaterials : A review of environmentally benign, simple, and effective synthesis routes

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.Validerad;2020;Nivå 2;2020-05-11 (johcin)</p

Original scientific paper Sol-gel preparation and electrical behaviour of Ln:

Abstract: A sol-gel method has been developed to prepare pure yttrium aluminum garnet, Y3Al5O12 (YAG), and rare-earth substituted (Ce-Y3Al5O12, Nd-Y3Al5O12, Ho-Y3Al5O12, and Er-Y3Al5O12) samples. The XRD patterns of the polycrystalline powders sintered at 1000 ºC showed the formation of monophasic garnet materials. The micro-structural features in the polycristalline samples were studied by scanning electron microscopy. A homogeneous distribution of rare-earth dopants in the YAG lattice was achieved in all of the cases. Electrical conductivity measurements were also performed on the compacts of sol-gel derived Ln-YAG samples. In contrast to the expected dielectric behaviour, the conducting properties of the examined specimens indicate metallic behaviour with the resistivity increasing gradually with increasing temperature

The Use of Heating to Change the Crystallinity and Structure of Carbonated Calcium Hydroxyapatite

Previous synthesis routes created apatite in low crystallinity and high crystallinity states, but a wider range will extend the design capabilities of apatities for hard tissue replacements. While high crystallinity apatites are more conventional, this work investigated lower crystallinity variations from an amorphous 10 state to low crystallinity apatite. Carbonated hydroxyapatite was prepared by precipitating an amorphous phase followed by crystallization at 650 ºC after a slow (5 ºC/min) and fast heating rate (60 ºC/min). The effect of processing conditions on crystallinity and structure changes was evaluated by thermal analysis, X-ray diffraction, transmission electron microscopy, Fourier transform infra-red and Raman spectroscopy. Furthermore, peak deconvolution of IR and Raman spectra resolved carbonate and 15 phosphate bands and revealed the carbonate and crystalline phase content in CHAp. Similar to precipitation of crystalline apatite, the crystallization at elevated temperature led to carbonate in both the phosphate and hydroxyl positions. Heating at 650 ºC provided a nanosized spherical hydroxyapatite containing carbonate controlled by the heating rate. This creates a mechanism for creating a large range in crystallinity with a greater resorption capability for regenerative medicine

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

The study was partially funded by the Swedish Research Council FORMAS project “Utilization of solid inorganic waste from the aquaculture industry as wood reinforcement material for flame retardancy” (grant no. 2018-01198). Vilnius University is highly acknowledged for financial support from the Science Promotion Foundation (MSF-JM-5/2021). This project has also received funding from European Social Fund (project No 09.3.3-LMT-K-712-19-0069) under grant agreement with the Research Council of Lithuania (LMTLT). The authors acknowledge the Center of Spectroscopic Characterization of Materials and Electronic/Molecular Processes ("SPECTROVERSUM" www.spectroversum.ff.vu.lt ) at the Lithuanian National Center for Physical Sciences and Technology for the use of spectroscopic equipment. Institute of Solid State Physics, University of Latvia, Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2.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. © 2022, The Author(s).Swedish Research Council FORMAS grant no. 2018-01198; Vilnius University Science Promotion Foundation MSF-JM-5/2021; ESF project No 09.3.3-LMT-K-712-19-0069; Institute of Solid State Physics, University of Latvia, Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2

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.Validerad;2019;Nivå 2;2019-09-18 (johcin)</p

Brushite mineralised Scots pine (Pinus sylvestris L.) sapwood – revealing mineral crystallization withina 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.Validerad;2023;Nivå 2;2023-02-16 (hanlid);Funder:  FCT/MEC (PIDDAC) (UIDB/50011/2020,UIDP/50011/2020, LA/P/0006/2020)</p

Acrylate–gelatin–carbonated hydroxyapatite (cHAP) composites for dental bone-tissue applications

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. Godkänd;2021;Nivå 0;2021-02-09 (johcin)FORMAS "Utilization of solid inorganic waste from the aquaculture industry as wood reinforcement material for flame retardancy 2018-01198