Search Results (6)

Structural features of new mixed bismuth-containing samarium iron–aluminium borate single crystals Sm_1−xBi_xFe_3−yAl_y(BO₃)₄ (x = 0.05–0.07, y = 0–0.28) were studied using X-ray diffraction analysis based on aluminium content and temperature in the range 25–500 K. The crystals were grown using the solution-in-melt technique with Bi₂Mo₃O₁₂ in a flux. The composition of the single crystals was analyzed using energy-dispersive X-ray fluorescence and energy-dispersive X-ray elemental analysis. Temperature dependencies of Sm_1−xBi_xFe_3−yAl_y(BO₃)₄ unit-cell parameters were studied. Negative thermal expansion was identified below 100 K and represented by characteristic surfaces of the thermal expansion tensor. (Sm,Bi)–O, (Sm,Bi)–(Fe,Al), (Fe,Al)–(Fe,Al), and (Fe,Al)–O interatomic distances decreased with the addition of aluminium atoms. An increase in the (Fe,Al)–(Fe,Al) intrachain bond length at low temperatures in the magnetically ordered state weakened this bond, whereas a decrease in the (Fe,Al)–(Fe,Al) interchain distance strengthened super-exchange paths between different chains. It was found that the addition of aluminium atoms influenced interatomic distances in Sm_1−xBi_xFe_3−yAl_y(BO₃)₄ much more than lowering the temperature from 293 K to 25 K. The effect of aluminium doping on magnetoelectric properties and structural symmetry of rare-earth iron borates is also discussed. Full article

The doping of magnesium on lithium aluminium borate phosphor is reported in this study. A solid-state sintering technique was employed as the borate samples were synthesized. This report focuses on the structural, optical, thermoluminescence, and kinetic analyses of the main glow peak. The structural properties of lithium aluminium borates improved due to the magnesium dopants used. Differences in the crystallite size and particle size were 38.85–67.35 nm and 50–60 nm, respectively, and these results were obtained from the analyzed X-ray diffractogram and scanning electron spectroscopy. The energy band gaps obtained from the direct transition of borate phosphor materials were within the range of 3.00–4.40 eV, and the doped samples gave a higher energy band gap. A decrease in the TGA (%) exhibited a weight loss or water loss for the undoped, 0.1% Mg, and 0.3% Mg-doped lithium aluminium borate materials. The glow curve measured at a heat rate of 1 °C·s⁻¹ after irradiation to 50 Gy revealed four peaks related to the magnesium doped lithium aluminium borate. The main glow peak was observed at 86 °C. Activation energy was extracted from the main glow peak by using kinetic analysis which involves the initial rise, deconvolution, and variable heating rate approach, and it was approximately 0.67 ± 0.03 eV. A shift in the main glow peak curve from 86 to 110 °C was recognized for the magnesium-doped lithium aluminium borate when it was irradiated from 1 to 300 Gy. Full article

Wettability at the metal-ceramic interface is highly important for the development of modern composite materials. Poor wettability by metal melts restricts the use of alumina in protective metal matrix composite (MMC) coatings. In the present experimental study, the possibility to modify wetting properties of alumina by thermochemical surface boronizing was investigated. The results of SEM, EDS, XRD and XPS characterisation of surfaces revealed the formation of oxygen containing Al–B compounds identified as aluminium borates (Al₁₈B₄O₃₃/Al₄B₂O₉); no signs of non-oxide Al–B compounds were observed. The shape of the single splats deposited on the boronized alumina surface by the thermal spray and re-melted in the furnace revealed that significant wetting improvement by self-fluxing nickel alloy did not occur. However, the improvement of adhesion between the nickel/nickel alloy and Al₂O₃ surface was obtained due to formation of an intermediate layer consisting of B, O, Al and Si between the metal and ceramic surfaces at the presence of some silicon at the modified surfaces. The presented study demonstrates that the thermochemical boronizing of alumina in amorphous boron medium is a simple method to obtain a thin aluminium borate layer consisting of oriented nano-rod-like crystals, whose growing direction is predetermined by the orientation of the alumina grains’ faces at surface. Full article

In this study we present an NIR carbon dioxide gas sensor based on an inner filter process that includes an ionic liquid (IL), 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF₄), to improve its stability, dynamic behavior and lifetime, which are usually the main drawbacks with these sensors. The presence of CO₂ causes a displacement of a simple boron-dipyrromethene-type fluorophore, azaBODIPY, as the pH indicator towards its acid form. This increases the emission intensity of Cr(III)-doped gadolinium aluminium borate (GAB) as the luminophore. The characterization of the prepared sensor was carried out and a discussion of the results is presented. The response and recovery times improved considerably, 23 and 49 s, respectively, with respect to the sensor without IL, at 60 and 120 s, respectively,. Additionally, the measurement range is extended when using IL, able in this case to measure in the complete range up to 100% CO₂; without IL the measurement range is limited to 60% CO₂. The detection limit ranges from 0.57% CO₂ without IL to 0.26% CO₂ when IL is added. The useful lifetime of the sensing membrane was 20 days for membranes with IL and only 6 days for membranes without IL, with the sensor always kept in the dark and without the need to maintain a special atmosphere. Full article

In this study, a series of Li₂O-Al₂O₃-B₂O₃ glasses doped with various concentrations of Dy₂O₃ (where x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0 mol%) were prepared by using a conventional melt-quenching technique. The structural, physical and optical properties of the glasses were examined by utilising a variety of techniques instance, X-ray diffraction (XRD), UV–Vis-NIR spectrometer, Fourier transform infrared (FTIR) and photoluminescence (PL). The XRD spectra demonstrate the amorphous phase of all glasses. Furthermore, the UV-vis-NIR spectrometers have registered optical absorption spectra a numbers of peaks which exist at 1703, 1271, 1095, 902, 841, 802, 669, 458, 393 and 352 nm congruous to the transitions from the ground of state (⁶H_15/2) to different excited states, ⁶H_11/2, ⁶F_11/2 + ⁶H_9/2, ⁶F_9/2 + ⁶H_7/2, ⁶F_7/2, ⁶F_5/2, ⁶F_3/2, ⁴F_9/2, ⁴I_15/2, ⁴F_7/2 and ⁶P_7/2, respectively. The spectra of emission exhibit two strong emanation bands at 481 nm and 575 nm in the visible region, which correspond to the transitions ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2. All prepared glass samples doped with Dy₂O₃ show an increase in the emission intensity with an increase in the concentration of Dy³⁺. Based on the obtained results, the aforementioned glass samples may have possible applications, such as optical sensor and laser applications. Full article

Bonding between polycrystal alumina and sapphire with (0001), (10 $\overline{1}$ 0), (11 $\overline{2}$ 0), (1 $\overline{1}$ 02) orientations is successfully achieved by growing aluminium borate whiskers in the joint. The morphology of the whiskers in the joint is characterised by (Scanning Electron Microscopy) SEM. The relationship between the growing direction of the aluminium borate whiskers and the orientation of the sapphire substrate is investigated. The effect of the growing direction of the aluminium borate whiskers on the mechanical properties of the joint is discussed. The results show that the whiskers on the sapphire with (10 $\overline{1}$ 0) orientation grow perpendicular to the surface of the substrate while the whiskers show a random growth on the other substrates. It is found that there is an orientation relationship between the whiskers (220) and sapphire (10 $\overline{1}$ 0) and the morphology of the whiskers has great influence on the mechanical properties of the joint. The joint between polycrystal alumina and sapphire with (10 $\overline{1}$ 0) orientation exhibits the highest strength, which reaches 26 MPa. Full article