| 1. |
- Garskaite, Edita, et al.
(author)
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Surface hardness and flammability of Na2SiO3 and nano-TiO2 reinforced wood composites
- 2019
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In: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 9:48, s. 27973-27986
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Journal article (peer-reviewed)abstract
- 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.
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| 2. |
- Garskaite, Edita, et al.
(author)
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The Accessibility of the Cell Wall in Scots Pine (Pinus sylvestris L.) Sapwood to Colloidal Fe3O4 Nanoparticles
- 2021
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In: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 6:33, s. 21719-21729
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Journal article (peer-reviewed)abstract
- 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.
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| 3. |
- Golubevas, Ricardas, et al.
(author)
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Acrylate–gelatin–carbonated hydroxyapatite (cHAP) composites for dental bone-tissue applications
- 2020
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In: Materials Advances. - : Royal Society of Chemistry. - 2633-5409. ; 1:6, s. 1675-1684
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Journal article (peer-reviewed)abstract
- 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.
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| 4. |
- Grazenaite, Egle, et al.
(author)
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Ga-Substituted Cobalt-Chromium Spinels as Ceramic Pigments Produced by Sol–Gel Synthesis
- 2020
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In: Crystals. - : MDPI. - 2073-4352. ; 10:12
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Journal article (peer-reviewed)abstract
- For the first time to the best of our knowledge, cobalt-chromium spinels CoCr2−xGaxO4 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 CoCr2−xGaxO4 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.
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| 5. |
- Griesiute, Diana, et al.
(author)
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Synthesis, structural and luminescent properties of Mn-doped calcium pyrophosphate (Ca2P2O7) polymorphs
- 2022
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In: Scientific Reports. - : Springer Nature. - 2045-2322. ; 12:1
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Journal article (peer-reviewed)abstract
- 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.
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| 6. |
- Ishikawa, Kunio, et al.
(author)
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Sol–gel synthesis of calcium phosphate-based biomaterials : A review of environmentally benign, simple, and effective synthesis routes
- 2020
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In: Journal of Sol-Gel Science and Technology. - : Springer. - 0928-0707 .- 1573-4846. ; 94:3, s. 551-572
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Research review (peer-reviewed)abstract
- 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.
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| 7. |
- Karoblis, Dovydas, et al.
(author)
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Study of gadolinium substitution effects in hexagonal yttrium manganite YMnO3
- 2021
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In: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11
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Journal article (peer-reviewed)abstract
- 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).
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| 8. |
- Raudoniene, Jolanta, et al.
(author)
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Wet-chemistry synthesis of shape-controlled Ag3PO4 crystals and their 3D surface reconstruction from SEM imagery
- 2019
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In: Powder Technology. - : Elsevier. - 0032-5910 .- 1873-328X. ; 345, s. 26-34
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Journal article (peer-reviewed)abstract
- 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.
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| 9. |
- Tuomela, Anu, et al.
(author)
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Luminescence and vacuum ultraviolet excitation spectroscopy of samarium doped SrB4O7
- 2020
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In: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388. ; 826
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Journal article (peer-reviewed)abstract
- Sm2+ and Sm3+ co-doped SrB4O7 could be utilized in several high-level optical devices and fundamental knowledge about the optical behavior of these materials benefits the development of luminescent applications. Herein, we report luminescence and its vacuum ultraviolet (VUV) excitation spectra in samarium doped SrB4O7. Both, Sm2+ and Sm3+ luminescence centers have been examined and distinguished in the emission and the excitation spectra investigated under synchrotron radiation. The contribution of either Sm2+ or Sm3+ emission lines into the emission spectra heavily depended on the excitation energy, and strong f-f transitions of both Sm2+ and Sm3+ were detected. At 10 K, a broad intrinsic luminescence in the UV range was detected and attributed to the radiative transition of either bound or self-trapped exciton in SrB4O7. The optical behavior, including e.g. inter-configurational f-d transitions of Sm(n+) were elucidated with first-principles calculations. Partial density of states well represents the changes of the electronic states that are related to the samarium doping, which in turn explains the emerging features in excitation spectra. In summary, the obtained results clarify the excitation and emission behavior of samarium doped SrB4O7.
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