Salt-assisted Spray Pyrolysis Research Articles

Synthesis and magnetic properties of Sm2Co17 particles using salt-assisted spray pyrolysis and a reduction-diffusion process

Sm2Co17 particles, with several hundreds of nanometers to a few micrometers in diameter, were synthesized by a combination of salt-assisted ultrasonic spray pyrolysis and a reduction-diffusion (R-D) process. It was found that NaCl plays a decisive role toward the suppression of particle coalescence during R-D process. By optimizing a reductant contents, the single-phased and non-agglomerated Sm2Co17 particles were obtained. In addition, particle size was controlled by varying calcination temperature from 800 °C to 1100 °C and size-dependent magnetic properties were observed. The optimum magnetic properties were achieved at a calcination temperature of 900 °C: coercivity of 5.3 kOe, a saturation magnetization of 99.33 emu/g, and a remanence of 56.53 emu/g.

CO2 assisted deposition of R/S-ibuprofen on different porous carrier materials: Influence of carrier properties on loading and dissolution behavior

With regard to bioavailability of poorly water-soluble drugs a big goal in research is to improve their dissolution behavior in the gastrointestinal tract. One suitable way to enhance the bioavailability is the use of drug loaded carrier materials. However, the effect of carrier properties such as specific surface area, pore size and pore volume on the dissolution of drugs is not well known yet. To investigate this, carrier materials with defined properties were produced by Salt Assisted Spray Pyrolysis (SASP) and loaded with racemic ibuprofen by the Controlled Particle Deposition (CPD) process. Their loadings and dissolution rates were compared to those of MCM-41 and SBA-15. It was found that the ibuprofen loading on the SASP carrier materials is lower due to their smaller specific surface areas, whereas their dissolution rates were higher in comparison to CPD processed MCM-41 and SBA-15. Furthermore, it was observed that pore size and pore volume influence the loading capacity of carrier materials. Wider mesopores lead to multilayer formation where crystalline ibuprofen structures were detected by XRD analysis. N2-adsorption/desorption experiments at T = 77 K on the CPD processed carriers lead to the assumption that the small mesopores of MCM-41 or SBA-15 were occupied by ibuprofen due to the shift of the typical capillary condensation step at p/p0 = 0.3–0.4 (untreated material) towards lower relative pressures of the CPD processed carriers.

Synthesis of hollow cobalt oxide nanopowders by a salt-assisted spray pyrolysis process applying nanoscale Kirkendall diffusion and their electrochemical properties.

A new concept for preparing hollow metal oxide nanopowders by salt-assisted spray pyrolysis applying nanoscale Kirkendall diffusion is introduced. The composite powders of metal oxide and indecomposable metal salt are prepared by spray pyrolysis. Post-treatment under a reducing atmosphere and subsequent washing using distilled water produce aggregation-free metal nanopowders. The metal nanopowders are then transformed into metal oxide hollow nanopowders by nanoscale Kirkendall diffusion. Co3O4 hollow nanopowders are prepared as first target materials. A cobalt oxide-NaCl composite powder prepared by spray pyrolysis transforms into several Co3O4 hollow nanopowders by several treatment processes. The discharge capacities of the Co3O4 nanopowders with filled and hollow structures at a current density of 1 A g(-1) for the 150th cycle are 605 and 775 mA h g(-1), respectively. The hollow structure formed by nanoscale Kirkendall diffusion improves the lithium-ion storage properties of Co3O4 nanopowders.

Preparation and Dielectric Property of BaTiO<sub>3</sub> Nanoparticles by Salt-Assisted Spray Pyrolysis

BaTiO3 nanopowders were prepared by salt-assisted spray pyrolysis using a flux of KNO3 and NaNO3. Compounds of metal sources are thermally decomposed in the melting flux. Some flux mixtures make a eutectic composition because of the reduced melting point of the flux. The optimum temperature for the preparation of BaTiO3 nanoparticles was 700 °C. When both KNO3 and NaNO3 were used as the flux, the average particle size of the BaTiO3 powders was 40 nm, and the particle distribution was broad. On the other hand, when only KNO3 was used, the average size of BaTiO3 powders was 60 nm, and the particle distribution was narrow. This suggested that the sodium ions in the BaTiO3 nanoparticles led to a broad particle distribution. X-ray diffraction (XRD) revealed that all the diffraction peaks were in agreement with the crystal phase of BaTiO3. The relative density of the sintered body of BaTiO3 powders was 87 %. The relative dielectric constant of the sintered body was 1180, and the dielectric loss (tanδ) was 0.023 at room temperature. This suggested that the residual potassium ions in the BaTiO3 nanoparticles led to a reduction in the relative density and dielectric constant.

Integration of Spin‐Coated Nanoparticulate‐Based La0.6Sr0.4CoO3–δ Cathodes into Micro‐Solid Oxide Fuel Cell Membranes

AbstractThin cathodes for micro‐solid oxide fuel cells (micro‐SOFCs) are fabricated by spin‐coating a suspension of La0.6Sr0.4CoO3–δ (LSC) nanoparticulates obtained by salt‐assisted spray pyrolysis. The resulting 250 nm thin LSC layers exhibit a three‐dimensional porous microstructure with a grain size of around 45 nm and can be integrated onto free‐standing 3 mol.% yttria‐stabilized‐zirconia (3YSZ) electrolyte membranes with high survival rates. Weakly buckled micro‐SOFC membranes enable a homogeneous distribution of the LSC dispersion on the electrolyte, whereas the steep slopes of strongly buckled membranes do not allow for a perfect LSC coverage. A micro‐SOFC membrane consisting of an LSC cathode on a weakly buckled 3YSZ electrolyte and a sputtered Pt anode has an open‐circuit voltage of 1.05 V and delivers a maximum power density of 12 mW cm–2 at 500 °C.

Synthesis and characterization of nanoparticulate La0.6Sr0.4CoO3−δ cathodes for thin-film solid oxide fuel cells

Nanocrystalline La0.6Sr0.4CoO3−δ (LSC) powder with an ultrafine microstructure is synthesized via salt-assisted spray pyrolysis and subsequently stabilized in water-based dispersions. Nanoparticulate cathode thin films of LSC and LSC–GDC (gadolinium doped ceria) nanocomposites (with 10–40 wt% of GDC) are prepared via single step spin coating on yttria stabilized zirconia (YSZ) substrates. In order to prevent the chemical reaction between the cathode and the electrolyte, a thin buffer layer of GDC is deposited using spin coating on the YSZ substrates. The electrochemical performance of the thin film cathodes is measured by impedance spectroscopy on symmetrical cells in the temperature range of 450–650 °C. LSC cathode thin films (250 nm thick) with 30 wt% GDC content exhibit the lowest area specific resistance (ASR) values of 0.32, 0.78 and 2.04 Ω cm2 in ambient air at 650, 600 and 550 °C, respectively.

Synthesis and luminescence properties of Pr3+ doped Ca x Ba1−x TiO3 (0.3⩽x

Ca x Ba1−x TiO3 (CBT) fine particles doped with red luminescence center of Pr3+ ions (Pr: CBT) were successfully synthesized by salt assisted spray pyrolysis (SASP) process. Scanning electronic microscope (SEM) and laser scattering analysis demonstrate that salt can be removed from the surface of particles by washing with Milli-Q water and the particles can be further separated by ball-milling to get well-dispersed Pr3+ ions doped CBT fine particles. The luminescence properties, such as photoluminescence (PL) and mechanoluminescence (ML), of as-synthesized Pr: CBT particles were investigated. For Pr: CBT fine particles with different Ca molar ratios, all the samples show one emission at 612 nm, with increasing Ca molar ratio, PL intensity of Pr: CBT fine particles become stronger and stronger. When pressure was loaded on the Pr: CBT pellet, mechanoluminescence(ML) emission was measured. The results show that the ML intensity is proportional to the applied pressure.

Synthesis of nanocrystalline GaN from Ga 2O 3 nanoparticles derived from salt-assisted spray pyrolysis

Gallium nitride (GaN) nanoparticles were successfully produced from nano-sized gallium oxide (Ga 2O 3) particles under a flow of ammonia gas. The gallium oxide nanoparticles were prepared by salt-assisted spray pyrolysis (SASP). Highly crystalline Ga 2O 3 nanoparticles with an average diameter of approximately 10 nm were obtained at various temperatures when a flux salt (LiCl, 5 mol/l) was added to the precursor solution. The effects of the crystallinity of the Ga 2O 3 particles and nitridation time on transformation to GaN were characterized using X-ray diffraction and scanning/transmission electron microscopy. Highly crystalline GaN nanoparticles with a mean size of 23.4 nm and a geometric standard deviation of 1.68 nm were obtained when Ga 2O 3 nanoparticles with relatively low crystallinity were used as the starting material. The resulting GaN nanoparticles showed a photoluminescence peak at 364 nm under UV excitation at 254 nm.

Colour Tuning of Single Host Phosphors for White Light by AlAddition

We report a newly found strong disturbing effect of Al addition tothe intensity ratios of blue and green emissions from single hostfull-colour phosphor ofBa3MgSi2−xAlxO8:0.02Eu2+, 0.1Mn2+ fornear-UV excited white light. The phase-pure silicatephosphor in the size of around 4 μm is prepared by salt-assisted spraypyrolysis route, having three-colour emissions at thewavelength peak values of 437 nm, 500 nm and 608 nm simultaneously underthe excitation of 375 nm. The amount variation of Al ion added to thephosphor host results in a drastic change of the intensity ratiobetween green and blue emissions, while the intensity of red lightkeeps unchanged. As a consequence, the combination of three colourslies in the white light region and can be tuned by precisely controlledaddition of Al content. The Raman spectroscopy verifies the modifyingeffect of Al ion to the tetrahedral network in silicate hosts. Weassume that by addition of Al ion, the amount of those two kinds ofEu2+ substituting for those two kinds of Ba2+ lattice siteswith distinct energy levels of blue and green featured emissions can beadjusted to contribute to diversification of the ratios of blue and greenemissions.

Direct Preparation of Nonagglomerated Indium Tin Oxide Nanoparticles using Various Spray Pyrolysis Methods

Indium tin oxide particles were prepared using three different spray synthetic techniques: conventional, salt-assisted, and low pressure. Optimum conditions for the preparation of small size, nonagglomerated particles were investigated for these three methods. The use of the conventional spray pyrolysis method resulted in only larger particles (submicrometer order). Salt-assisted spray pyrolysis (SASP) and low-pressure spray pyrolysis (LPSP) produced highly crystalline, dense, homogeneous, and nearly nonagglomerated nanoparticles that were less than 25 nm in size. The size of the particles was in the range 12–24 nm for the SASP method and 8–14 nm for the LPSP method. In addition, the LPSP method led to the production of single nanometer-size multicomponent particles in a single step with less heating time without the need for any post heat treatment and additives.

Synthesis of Single Crystalline ZnO Nanoparticles by Salt-Assisted Spray Pyrolysis

LiNO3 was used as a shield in the preparation of single crystalline ZnO particles by a spray pyrolysis process in order to prevent agglomeration and enhance the crystallinity of the ZnO. LiNO3 was added to a precursor solution of zinc acetate dihydrate prior to its atomization by means of an ultrasonic transducer. Agglomerate-free particles having a mean particle size of 26 nm were successfully obtained after washing the product. X-ray diffractometry, field-emission scanning electron micrograph and transmission electron micrograph data indicate that the size and morphology of ZnO were strongly influenced by the operating temperature used and the residence time of the particle in the reactor.

Preparation of Agglomerate-Free and Highly Crystalline (Ba0.5, Sr0.5)TiO3 Nanoparticles by Salt-Assisted Spray Pyrolysis

Optimum conditions for the synthesis of non-agglomerated barium strontium titanate (BST) nanoparticles were examined. The effects of salt concentration, operating temperature, and droplet/particle residence time in the hot zone as a function of carrier gas flow rate and heating zones on particle size, crystallinity, and chemical composition of BST nanoparticles were investigated. Highly crystalline, dense BST nanoparticles in a size range of 17-60 nm with a narrow size distribution (σ g =1.2) were prepared using a salt-assisted spray pyrolysis (SASP) method without the need for post-annealing or for controlling of initial excess of barium and strontium in the solution, relative to titanium. The particle size decreased with decreasing salt concentration, operating temperature and droplet/particle residence time in the hot zones. The chemical homogeneity of the resulting particles was analyzed using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). The chemical composition of the resulting powder completely reflected the initial solution composition. SASP can be used to produce highly crystalline (Ba 1-x , Sr x )TiO 3 (x=0.5) nanoparticles in sizes as small as 30 nm in a single step.

Size Tunable Synthesis of Highly Crystalline BaTiO 3 Nanoparticles using Salt-Assisted Spray Pyrolysis

Highly crystalline, dense BaTiO3 nanoparticles in a size range from 30 to 360nm with a narrow size distribution (σg = 1.2–1.4) were prepared at various synthesis temperatures using a salt-assisted spray pyrolysis (SASP) method without the need for post-annealing. The effect of synthesis temperature on particle size, crystallinity and surface morphology of the nanoparticles were characterized by X-ray diffraction and scanning/transmission electron microscopy. The nature of the crystalline structure was analyzed by Rietveld refinement and Raman spectroscopy. The particle size decreased with decreasing operation temperature. The crystal phase was transformed from tetragonal to cubic at a particles size of about 50nm at room temperature. SASP can be used to produce high weight fraction of tetragonal BaTiO3 nanoparticles down to 64nm in a single step.

Agglomerate-free BaTiO3 particles by salt-assisted spray pyrolysis

Optimum conditions for the synthesis of nonagglomerated BaTiO3 particles by salt-assisted spray pyrolysis (SASP) were investigated. The effect of particle residence time in the reactor and salt concentration on the crystallinity and surface morphology of BaTiO3 was examined by x-ray diffraction and scanning electron microscopy. Mixtures of a metal chloride or nitrate salt, dissolved in aqueous precursor solutions, were sprayed by an ultrasonic atomizer into a five-zone hot-wall reactor. By increasing the salt concentration or the particle residence time in the hot zone, the primary particle size was increased, and its surface texture was improved compared to BaTiO3 particles prepared by conventional spray pyrolysis. The SASP-prepared BaTiO3 crystal was transformed from cubic to tetragonal by simply increasing the salt concentration at constant temperature and residence time. Further thermal treatments such as calcination or annealing are not necessary to obtain nonagglomerated tetragonal BaTiO3 (200–500 nm) particles with a narrow size distribution. Increasing the carrier gas flow rate and decreasing the residence time in the hot zone resulted in cubic BaTiO3 particles about 20 nm in diameter.