Pesquisadores em todo o mundo buscam métodos alternativos que minimizem o tempo de deposição de filmes finos semicondutores cotados como promissores candidatos em aplicações médicas como detectores de raios-X em radiografias digitais. O iodeto de chumbo (PbI2) é considerado, entre outros, como um bom candidato para a fabricação de detectores usados à temperatura ambiente. Outros pesquisadores fabricaram protótipos de detectores usando esse material. Seus experimentos mostraram alta resolução e sensibilidade para imagens em tempo real, mostrando que o material possui potencialidade para aplicações médicas futuramente. Não obstante, uma das desvantagens de seus métodos é o longo tempo necessário para a deposição na fabricação de filmes finos. Este trabalho apresenta uma nova metodologia usada para a deposição de filmes finos de iodeto de chumbo (PbI2). O método alternativo de crescimento dos filmes é chamado de spray pyrolysis. A técnica possui uma vantagem intrínseca pelo fato de a deposição ser facilmente expandida para grandes áreas de substrato que é desejado nas linhas de produção industrial. O pó de iodeto de chumbo foi dissolvido em água deionizada a 100ºC (água em ebulição) onde a solubilidade é maior que à temperatura ambiente. Após a dissolução do pó...
Ultasonic spray pyrolysis (SP) has been investigated for the production of the barium strontium titanate (BST) powders from the polymeric precursors. The processing parameters, such as flux of aerosol and temperature profile inside the furnace, were optimized to obtain single phase BST. The powders were characterized by the methods of X-ray diffraction analysis, SEM, EDS and TEM. The obtained powders were submicronic, consisting of spherical, polycrystalline particles, with internal nanocrystalline structure. Crystallite size of 10 nut, calculated using Rietveld refinement, is in a good agreement with results of HRTEM. (c) 2005 Elsevier B.V. All rights reserved.
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); The Spray Pyrolysis (SP) process has been employed at moderate temperature (470-970 K) for the synthesis of micro- and nano-particles of hydrated metal oxides and of related nanocomposites. It has been applied to iron nitrate solutions, without or with the addition of sodium chloride as a flux. After removal of the flux, nanocomposites of ferrihydrite (5Fe2O3,9H2O) / hematite (α- Fe2O3) / and an amorphous Fe2O3 are obtained, with surface area 140 m²/g. It has been applied also to a sol of Aluminum-tri-sec-butoxide, without or with activation by europium or terbium ions. Boehmite (γ-AlOOH) powders are synthesized at 470 K, with surface area equal to 180 m²/g. Transition alumina (γ-Al2O3) are synthesized at 970 K. Nanocomposites made by reaction of the boehmite or γ-Al2O3 particles with the amino acid asparagin (ASN) have been prepared and characterized. The luminescence of the Eu3+ or Tb3+ doped nanocomposites has been investigated: they can be considered as bio-compatible luminescent nanoparticles.
Boehmite (gamma-AlOOH) synthesis have been investigated using a spray pyrolysis (SP) device starting from a stable sol of Al-tri-sec-butoxide peptized by nitric acid. Free spherical particles from 100 to 500 nm have been elaborated. Particles sub-structure is made of nano-crystalline boehmite with very small average crystallite size (one crystal cell along the b axis). The nano-crystalline boehmite synthesized by SP at low temperature (200 degrees C) is spontaneously dispersible in water without any surface treatment. Boehmite powder may be transformed to transition gamma-alumina by heat post-treatment. Powders of sub-micrometric and spherical gamma-alumina particles may also be synthesized by SP at 700 degrees C. (C) 2008 Elsevier B.V. All rights reserved.
The broadband inter-configurational (4f(1)5d(1)-->4f(2)) emission of Pr(3+) doped in lanthanum orthophosphate (LaPO(4)) and in calcium pyrophosphate (Ca(2)P(2)O(7)) has been investigated under plasma excitation. The synthesis by spray pyrolysis at moderate temperature followed by a controlled annealing proves to be a very efficient way to produce good quality UVC emitting phosphor Ca(1.92)Pr(0.04)Na(0.04)P(2)O(7) (alpha phase). The emission of this phosphor in the wavelength range 200-350 nm has been measured with a prototype device, which can be employed for anti-microbial testing. (C) 2010 Elsevier B.V. All rights reserved.
Mossbauer spectroscopy was used in this study to investigate magnetite nanoparticles, obtained by spray pyrolysis and thermal treatment under H-2 reduction atmosphere. Room temperature XRD data indicate the formation of magnetite phase and a second phase (metallic iron) which amount increases as the time of reduction under H2 is increased. While room temperature Mossbauer data confirm the formation of the cubic phase of magnetite and the occurrence of metallic iron phase, the more complex features of 77 K-Mossbauer spectra suggest the occurrence of electronic localization favored by the different crystalline phase of magnetite at low temperatures which transition to the lower symmetry structure should occur at T similar to 120 K (Verwey transition).
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Pós-graduação em Ciência dos Materiais - FEIS; Neste trabalho foram depositados em substrato vítreo, filmes finos de Óxido de Zinco puro (ZnO) e dopados com alumínio (ZnO:Al) e manganês (ZnO:Mn), utilizando a técnica spray-pirólise. Foram investigadas as propriedades estruturais, ópticas e elétricas dos filmes, assim como, a dependência com a temperatura de deposição e concentração. As temperaturas utilizadas para deposição dos filmes finos foram 400 ºC e 450 ºC, e a concentração de dopantes variaram de 1 a 5 átomo por cento (at%). As técnicas de difração de raios-X e espectroscopia por refletância no infravermelho foram utilizadas para avaliar as características estruturais dos filmes. A Espectroscopia de transmitância na região do UV-Vis foi utilizada como uma das técnicas no estudo das propriedades ópticas, fornecendo valores da banda proibida. A técnica do ângulo de Brewster, foi utilizada com o intuito de avaliar o índice de refração e a espessura dos filmes finos. A avaliação da resistividade foi realizada com a finalidade de estudar a propriedade elétrica, e medidas do efeito Hall para investigar a densidade dos portadores de carga e mobilidade dos filmes semicondutores. A análise dos difratogramas de raio-X...
Highly transparent and conductive thin films of SnO2:F and In2O3:Sn (ITO) have been prepared on glass substrates using the simple pyrolitic (spray) method. Through an exhaustive parameter study and using as diagnostic method for the film quality a figure of merit defined as a function of both, the transmittance and the electric resistivity, the conditions to prepare the SnO2:F and ITO films, with adequate properties to be used as transparent front contact for solar cells, were achieved. A relevant contribution of this work is related with the deposition of SnO2:F and ITO films with the mentioned characteristics, using a solution synthesized in our laboratory by dissolving the precursor metals in HCl. Transparent conducting oxide (TCO) thin films were obtained, with transmittances greater than 80% and resistivities smaller than 7x10- 4 omega·cm, results which are comparable with those obtained using commercial reactants. Results concerning the influence of the synthesis parameters on the optical, electrical and structural properties of the TCO films are reported.
The Spray Pyrolysis (SP) process has been employed at moderate temperature (470-970 K) for the synthesis of micro- and nano-particles of hydrated metal oxides and of related nanocomposites. It has been applied to iron nitrate solutions, without or with the addition of sodium chloride as a flux. After removal of the flux, nanocomposites of ferrihydrite (5Fe2O3,9H2O) / hematite (α- Fe2O3) / and an amorphous Fe2O3 are obtained, with surface area 140 m²/g. It has been applied also to a sol of Aluminum-tri-sec-butoxide, without or with activation by europium or terbium ions. Boehmite (γ-AlOOH) powders are synthesized at 470 K, with surface area equal to 180 m²/g. Transition alumina (γ-Al2O3) are synthesized at 970 K. Nanocomposites made by reaction of the boehmite or γ-Al2O3 particles with the amino acid asparagin (ASN) have been prepared and characterized. The luminescence of the Eu3+ or Tb3+ doped nanocomposites has been investigated: they can be considered as bio-compatible luminescent nanoparticles.
Low-temperature method for the synthesis of novel morphology of needle-like nanoparticles of disodium dimolybdate (Na2Mo2O7) in the process of ultrasonic spray pyrolysis (USP) using aqueous solutions of thermodynamically stable molybdenum (VI) oxide clusters as precursor is described. Needle-like Na2Mo2O7 particles were obtained and collected in toluene, while centrifugation was employed to isolate solid material from solution. The scanning electron microscopy (SEM) confirmed that the morphology of the synthesized Na2Mo2O7 particles is needle-like collected into bundles. The X-ray Powder Diffraction (XRPD) analysis revealed appearance of orthorhombic Na2Mo2O7, synthesized at 300 °C. By comparing the XRPD pattern of the synthesized needle-like Na2Mo2O7 powder obtained in the process of USP with the XRPD pattern simulated for randomly-distributed crystallites by planes, the most prefered growth plane of needle-like nanoparticles were found.
Scanning-Transmission and Transmission Electron Microscopy techniques (STEM and TEM) have been applied to the characterization of nanostructured gadolinium oxides doped with europium synthesized by spray pyrolysis. The High Angle Annular Dark Field (HAADF) &- Scanning Transmission Electron Micros-copy (STEM) tools have been used to perform a tomographic study to identify morphological character-istics of nanostructured particles, and to differentiate them according to the heat treatments to which these have been subjected. With these techniques it has been possible to conﬁrm the hollowness and por-ous nature of samples subjected to low temperature annealing (900 ºC). Moreover, the beginning of the densiﬁcation and sintering processes in samples subjected to thermal treatment at higher temperature (1100 ºC) have been evaluated. Chemical analysis by electron energy loss spectroscopy (EELS) and X ray energy dispersive spectroscopy (EDS) carried out in STEM mode have allowed to conﬁrm the high uni-formity and the expected chemical composition. The high resolution tools either allowed to conﬁrm the presence of a cubic (Ia3 symmetry) and the monoclinic (c2/m symmetry) phases in the nanostructured particles.; This work has been supported by the Advanced Structural Materials Program- ESTRUMAT (S2009/MAT-1585) and MAT2010-19837-C06-05. Thanks are extended to NanoPort (FEI)- Eindhoven...
This paper presents a CMOS-compatible wafer-level fabrication process for monolithic CMOS/MEMS sensor systems coated with sensitive layers directly deposited by means of flame spray pyrolysis (FSP). Microhotplate (νHP)-based devices, featuring an FSP dir
Article in Press, Accepted Manuscript.; In the field of materials for Lithium ion batteries, the lithium iron phosphate LiFePO4 has been proven for use as a positive electrode due to its good resistance to thermal degradation and overcharge, safety and low cost. The use of nanostructured materials would improve its efficiency. This work shows the results of the synthesis of nanostructured materials with functional properties for Lithium batteries through aerosol techniques. The Spray Pyrolysis method allows synthesizing nanostructured particles with spherical geometry, not agglomerates, with narrow distribution of particle size and homogeneous composition in respect to a precursor solution. Experimental techniques were focused on the morphological (SEM and TEM), structural (XRD and HRTEM-SAED), chemical (EDS) and electrochemical characterization.; The authors gratefully appreciate the financial support of the Ministry for Education and Science of Spain in the project “Advanced materials for Lithium batteries through alternative synthesis” (PIROLION project-PROFIT 2007-2008), MAT2007-64486-C07-05 (FEDER) and the Juan de la Cierva program JCI-2005-1892-13 (M.I. Martín). We thank I. Boyano for helpful discussions and A. Lago for experimental aid. The assistance in TEM characterization of the Electron Microscopy and Citometry Center...
Ultrafine particles or nanoparticles (ranging between a few nanometers to 100 nm) are of considerable interest for a wide variety of applications, ranking from catalyst to luminescence ceramics, due to their unique and improved properties primarily determined by size, composition and structure. This study presents the preparation and characterization of nanostructured spherical alumina particles by the Spray Pyrolysis method for the application in reinforcements of metal-matrix composites (MMCs). Synthesis procedure includes aerosol formation ultrasonically from alumina nitrate water solution and its decomposition into a tubular flow reactor at 700 ºC. The obtained particles are spherical, smooth, amorphous and in non-agglomerated state. Microstructural and morphological analyses were carried out using X-ray powder diffraction (XRD), scanning electron microscopy (SEM/EDS) and analytical and high resolution transmission electron microscopy (TEM/HRTEM).
Keywords: Spray Pyrolysis; Alumina; Nanostructured Particles; Isothermal Treatment; The authors gratefully appreciate the financial support of the Ministry for Education
and Science of Spain, Juan de la Cierva Program JCI-2005-1892-13 (M.I. Martín),
MAT2006-02458 project, Sabatic Grant SAB 2004-0035 and Project142010...
Cadmium sulphide (CdS) thin films were prepared by means of the chemical spray pyrolysis technique. The substrate temperature was varied in the range from 200 to 400°C. The structural properties of the semiconductor were characterized by X-ray diffraction; XRD patterns indicated the presence of single-phase hexagonal CdS. Direct band gap values of 2.37-2.41 eV were obtained. The refractive index is reported on depending on the substrate temperature, and was obtained from transmission spectra and from spectroellipsometry measurements. As a consequence, the optical parameters of the films were determined using the Swanepoel, Cauchy, Sellmeier and Wemple models. The resistivity of the films was found to vary in the range 10³ 10(5)Ω.cm, depending on the substrate temperature.
Thin films of zirconium oxynitride were deposited on stainless steel 316L and characterized through ultrasonic spray pyrolysis-nitriding (UPS-N). Initially, thin films of ZrO2 are deposited using ultrasonic spray pyrolysis, and later ZrO2 films were nitrided in a NH3 atmosphere. We analyzed the effect of some variables, such as substrate temperature, flow ratio, and time of the production of coatings and their influence on the structure of the films. The characterization was carried out using X-ray diffraction (XRD) spectroscopy, X-ray photoelectron (XPS), and scanning electron microscopy (SEM). Films that were grown using the UPS method exhibited a tetragonal zirconia polycrystalline structure with preferential orientation in plane (101). These films, after being nitrided in an atmosphere of anhydrous ammonia at 1023 K, go through two processes: a phase transition from tetragonal to monoclinic, and later the formation of zirconium oxynitride rhombohedral ZrOxNy.
A two-step synthesis process was performed to obtain TlBa2Ca2Cu3Ox (Tl-1223) superconductor films. The synthesized films were obtained under different thallium diffusion conditions in a two-zone furnace precursor films were deposited at 550° C on silver substrates using the spray pyrolysis technique from acetylacetonates (2, 4-pentanedionates) as reagents. Second, a thallium diffusion process is carried out to incorporate Tl in the films. For this task Tl2O3 pellets, as a Tl source, were used at 750°C. Different oxygen flow rates at atmospheric pressure were used in order to get the thallous oxide p (Tl2O) partial pressure in the range of 6.9 x 10-4 to 6.1 x 10-2 atm. The Tl-1223 phase was obtained in all cases, though for a low p (Tl2O), the films presented the BaCuO2 phase mixed with the Tl-1223 one. Critical temperature (T C) values for these films were in the range of 90 to 102 K.
We studied the crystallinity, morphology, and surface composition of Nd-doped molybdenum oxide films grown on glass slides through spray pyrolysis. After fabrication, the films were subjected to thermal treatment in oxygen for periods ranging from 2 to 20 hours. The films were structurally characterized through X-ray diffraction (XRD), their bulk chemical composition was determined using Energy-Dispersive X-ray analysis (EDX), and their surface composition was determined using X-ray Photoelectron Spectroscopy (XPS). The XRD results show that the films obtained from different dissolution volumes and at substrate temperature of 300° C exhibit the characteristics of the oxygen-deficient molybdenum trioxide Mo9 O26 phase. The films subjected to different thermal treatments exhibit a mixture of Mo9O26 and Mo17O47 phases. EDX study shows the energy belonging to the L line of Nd. Finally, films doped with Nd and subjected to a thermal treatment of 20h were analyzed through XPS, showing the binding energies at the crystalline lattice correspond to Nd2 (MoO4)3 and Nd2Mo2O7.
Physical and chemical properties of ceramic powders are highly dependent on the morphology and chemical composition of the precursor powders. Therefore, properties of ceramic powders are expecting to be improved by controlling the most important parameters of morphology such as composition of precursors, temperature and airflow. Promising techniques to produce ceramic powders with controlled morphology are sol-gel, coprecipitation, and pyrolysis. Among these techniques, spray pyrolysis is one of the most suitable to control the morphology and the chemical composition of the particles, because the spray pyrolysis technique integrates the evaporation, precipitation, decomposition and sintering stage of powder synthesis into a single continuos process. Spherical powders were prepared from acetylacetonate of zirconium and acetate calcium hydrated solutions by pneumatic spray pyrolysis. The morphology and size of the powders change with variation of airflow, temperature, and solution concentration.
Atomic Force Microscopy (AFM) was used to observe the growth stages of both buffer layers and Y-Ba-Cu-O films on three different substrates: Si (100) and MgO (100) for crystalline ones and fused silica for the amorphous type. In order to compare the benefits of buffer layers, YSZ was grown on the three different substrates and AFM topographies were made at each stage of growth: Bare substrate, YSZ films on bare substrates, Y-Ba-Cu-O/YSZ films and Y-Ba-Cu-O on bare substrates. An Ultrasonic Spray Pyrolysis system was used to deposit all the films and layers. Films grown on buffer layers present smoother surfaces than those grown on bare substrates.