Papers by Keyword: Combustion Synthesis

Abstract: In this study, a simple combustion synthesis was utilized to obtain the SrLaAlO₄ (SLAO) host sample and SrLaAlO₄: Ce (SLAO:Ce) phosphors with different Ce concentrations (1.0, 3.0, 5.0 and 7.0 mol.%). Also, the as-synthesized samples were subjected to a post-annealing treatment at 1200 °C in air. X-ray diffraction (XRD) patterns for the SLAO and SLAO:Ce phosphors correspond to pure tetragonal phase (JCPDS No 24-1125). The photoluminescence spectra of the SLAO:Ce phosphors (under 254 nm excitation) showed a blue emission peak at 470 nm attributed to the 5d → 4f Ce³⁺ transition. The SLAO:Ce phosphors doped with 1 mol.% of Ce showed the highest emission and quenching of photoluminescence was produced when the Ce dopant concentration increases (3.0-7.0 mol.%). The CCT and color purity are in the range of 6456 -8276 K and 49.1 -55.9 % respectively. Due to its strong blue emission, the SLAO:Ce phosphor could be a good candidate for UV phosphor converted LED or for solid state lighting applications.

Abstract: In this study Barium Lanthanum Aluminate BaLaAlO₄ and BaLaAlO₄:xEu red phosphors were produced at different x at.% Eu concentration (x = 0,1,3,5 and 7 at.% of Eu) by combustion synthesis method and post-annealing. The X-ray diffraction (XRD) patterns shows that all samples present the orthorhombic phase (JCPDS # 44-0164). Scanning electron microscopy (SEM) shows that the grains size diminished and then increases as a function of Eu-doping concentration addition. Photoluminescence spectra of the samples, under UV excitation, show a maximum strong red emission at l_em= 615 nm attributed to the ⁵D₀®⁷F₂ Eu³⁺ ion transition. The Eu-doped BaLaAlO₄ sample that present the highest luminescence intensity was with the x= 1.0 at.% of Eu doping concentration. The quenching in photoluminescence spectra was detected for the Eu doping concentrations of x= 5 and 7 at%, which was ascribed to due to dipole-quadrupole (d-q) interactions. Because the strong red emission of Eu-doped BaLaAlO₄ phosphor it could be used UV activated LEDs.

Abstract: Acetylcholine (ACh) is a main neurotransmitter functioning in smooth muscle and cardiovascular system control. It also plays a key role in memory and learning. While excessive acetylcholine level results in decreased heart rates, depleted level of acetylcholine in human brains can lead to Alzheimer disease. Therefore, detection of acetylcholine is clinically vital. This study aimed at examining potential usage of titanium dioxide (TiO₂) doped with 2.5 mol% Zn as electrochemical sensors for acetylcholine detection. Zn-doped TiO₂ powder was synthesized by a solution combustion technique. Phase identification, microstructural examination, as well as electrocatalytic activity evaluation of the synthesized powder were conducted. The synthesized powder showed anatase phase with fine particle sizes ranging from 9.3 to 11.4 nanometers on average. Specific surface area of 75.48 m²/g was observed. Electrocatalytic activities of the powder in cholin acetate solutions with concentrations ranging from 0.05 to 0.1 μM and 1 to 10 μM were evaluated via cyclic voltammetry technique. At applied voltage of 0.05 V, peak currents corresponding to oxidation reactions between ACh and Zn-doped TiO₂ were detected. Sensitivity values of 3.13x10^-4 and 1.32 μA/(μMmm²), which is in an acceptable range, were evident.

Abstract: Ni-Al-Ti system is one of the intermetallic systems that attract wide interest for high-temperature application. In this work, combustion synthesis was used to produce intermetallic materials prepared by Ni/Al with varied Ti content using 3%, 10%, 20%, and 30%. The reactant mixtures were compressed in a steel die to form compacted pellets. The ignition of the combustion process was conducted using an arch flame. Sequential tests of SEM, EDS, and XRD were conducted to characterize the microstructure of the synthesized products, whereas the mechanical properties of the product were measured using a Vickers microhardness test and wear test. The result shows that the phases formed in the product were dominated by Ni-Al and Ti-Ni systems. An increase in the Ti content from 3% to 20% increases the hardness. The formation of several intermetallic phases was responsible for the harder products. An increase of Ti content decreases the wear rate. This work shows that the content of 10% Ti can be used to achieve the optimized properties of hardness and wear resistance.

Abstract: In this work, a ternary system prepared by Ni-Al-Ti mixed powder was synthesized using self-propagation high-temperature synthesis (SHS) process. The weight of the reactant was varied using 3%, 10%, 20% and 30% of the Ti content. The mixtures were compressed in a steel die to form compacted pellets, and subsequently ignited using an external heat source to initiate the combustion process. The synthesized products were characterized using SEM, EDS, and XRD, whereas the mechanical property of the product was measured using a Vickers microhardness test. The identification of the formed phase indicates that Ni-Al, Ti-Al and Ti-Ni systems were formed during the reaction. An increase of Ti content from 3% to 10% improves the density of the synthesized product. Further increase of Ti content to 20% results in the generation of cracks. The addition of Ti with 30% leads to the formation of a porous product. The heat released by the SHS process due to the formation of several intermetallic phases was responsible for the formation of defect products. The highest hardness of the product was achieved in the product prepared by 20% Ti content. However, the higher Ti content than 20% results in hardness reduction. This work shows that the content of 10% of Ti produced a dense and hard product.

Abstract: Calcium titanate (CaTiO₃) was synthesized through combustion in air from calcium sources of raw minerals (lime-stone and calcite), anatase titanium dioxide (A-TiO₂) and magnesium (Mg). The syntheses were divided into two reactant systems (lime-stone/A-TiO₂/Mg and calcite/A-TiO₂/Mg. Before synthesis, the raw minerals and A-TiO₂ were high-energy milled for 30 min. These powders were then separately mixed with Mg by ball milling. After synthesis, the as-combusted products were leached with 2 M HCl solution to remove by-products and impurities. A sequential mechanism for the in-situ combustion was proposed by using data from simultaneous thermal analysis (STA) together with thermodynamic values calculated with HSC^ software. XRD results showed that the as-leached products from both reactant systems mainly contained CaTiO₃. FT-IR spectroscopy indicated that the as-leached products had Ca-Ti-O and Ti-O functional groups. In addition, SEM observation of the as-leached products revealed cuboid-like crystals with a particle size of about 100 nm.

Abstract: Electric current assisted sintering of β-Si₅AlON₇-TiN ceramic composites from raw materials prepared by combustion synthesis was investigated. A high level of relative density (92% and higher) was achieved by using of two types of electric current assisted sintering technique: high voltage electric discharge consolidation, as well as spark plasma sintering. While only spark plasma sintering, it may be considered as promising technique for obtaining ceramic composites and items with high level of strength properties.

Abstract: MgO/Graphene ceramic composites were fabricated by combining combustion synthesis with spark plasma sintering. MgO/Graphene mixture powders were prepared by the combustion reaction between Mg powders and CO₂ gas. Dense MgO/Graphene composites were fabricated by spark plasma sintering (SPS) using LiF as the sintering additive. The effect of the sintering temperature on microstructure and mechanical properties of the prepared MgO/Graphene ceramics was discussed. The sintering temperature of the MgO/Graphene mixture powders increased from 900°C to 1300°C. The highest density of 3.43g/cm³ and hardness of 2133MPa were obtained at 1100°C. Compared with monolithic MgO ceramics, the hardness of MgO/Graphene ceramics at the same sintering temperature was increased from 840MPa to 2133MPa.

Abstract: This work is focused on preparation of Nb-doped Ti–Al material (Ti–29.3Al–17.6Nb wt %) by centrifugal SHS. Results of studying of combustion and synthesis regularities of intermetallic material on γ-TiAl base from oxide materials under high gravity are presented in the article. For the first time is used a reduction mixture on Al/Ca base which markedly increases the yield of Ti–Al–Nb and decreases the amount of non-metallic impurities (oxygen, nitrogen, carbon) in target product.

Abstract: Formation of the Ti₃(Al,Sn)C₂ solid solutions was studied by combustion synthesis from elemental powder compacts with Al₄C₃ and TiC additions. Combustion temperatures of 1590–1700 °C and flame-front speeds of 14.2–18.8 mm/s were measured for the Al₄C₃-added samples. Due to the dilution effect of TiC, the combustion temperature and flame velocity were significantly reduced to 1220–1280 °C and 7.1–9.6 mm/s, respectively, for the TiC-adopted samples. The XRD analysis indicated that MAX solid solutions Ti₃(Al_1–xSn_x)C₂ with x = 0.2, 0.4, and 0.6 were produced from the Al₄C₃-adopted samples. Because of the low reaction temperature, the extent of Sn substitution for Al in Ti₃(Al_1–ySn_y)C₂ was narrowed down to y = 0.4 for the TiC-containing samples. The as-synthesized Ti₃(Al,Sn)C₂ grains were plate-like and closely stacked into a laminated microstructure.