922 resultados para mineral particle size


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Cells the solid oxide fuel are systems capable to directly convert energy of a chemical reaction into electric energy in clean, quiet way and if its components in the solid state differentiate of excessively the techniques for having all. Its more common geometric configurations are: the tubular one and to glide. Geometry to glide beyond the usual components (anode, cathode and electrolyte) needs interconnect and sealant. E the search for materials adjusted for these components is currently the biggest challenge found for the production of the cells. The sealants need to present chemical stability in high temperatures, to provoke electric isolation, to have coefficient of compatible thermal expansion with the excessively component ones. For presenting these characteristics the glass-ceramics materials are recommended for the application. In this work the study of the partial substitution of the ZrO2 for the Al2O3 in system LZS became it aiming at the formation of system LZAS, this with the addition of natural spodumene with 10, 20 and 30% in mass. The compositions had been casting to a temperature of 1500°C and later quickly cooled with the objective to continue amorphous. Each composition was worn out for attainment of a dust with average diameter of approximately 3μm and characterized by the techniques of DRX, FRX, MEV, dilatometric analysis and particle size analysis. Later the samples had been conformed and treated thermally with temperatures in the interval between 700-1000 °C, with platform of 10 minutes and 1 hour. The analyses for the treated samples had been: dilatometric analysis, DRX, FRX, electrical conductivity and tack. The results point with respect to the viability of the use of system LZAS for use as sealant a time that had presented good results as isolating electric, they had adhered to a material with similar α of the components of a SOFC and had presented steady crystalline phases

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Continuous Synthesis by Solution Combustion was employed in this work aiming to obtain tin dioxide nanostructured. Basically, a precursor solution is prepared and then be atomized and sprayed into the flame, where its combustion occurs, leading to the formation of particles. This is a recent technique that shows an enormous potential in oxides deposition, mainly by the low cost of equipment and precursors employed. The tin dioxide (SnO2) nanostructured has been widely used in various applications, especially as gas sensors and varistors. In the case of sensors based on semiconducting ceramics, where surface reactions are responsible for the detection of gases, the importance of surface area and particle size is even greater. The preference for a nanostructured material is based on its significant increase in surface area compared to conventional microcrystalline powders and small particle size, which may benefit certain properties such as high electrical conductivity, high thermal stability, mechanical and chemical. In this work, were employed as precursor solution tin chloride dehydrate diluted in anhydrous ethyl alcohol. Were utilized molar ratio chloride/solvent of 0,75 with the purpose of investigate its influence in the microstructure of produced powder. The solution precursor flux was 3 mL/min. Analysis with X-ray diffraction appointed that a solution precursor with molar ratio chloride/solvent of 0,75 leads to crystalline powder with single phase and all peaks are attributed to phase SnO2. Parameters as distance from the flame with atomizer distance from the capture system with the pilot, molar ratio and solution flux doesn t affect the presence of tin dioxide in the produced powder. In the characterization of the obtained powder techniques were used as thermogravimetric (TGA) and thermodiferential analysis (DTA), particle size by laser diffraction (GDL), crystallographic analysis by X-ray diffraction (XRD), morphology by scanning electron microscopy (SEM), transmission electron microscopy (TEM), specific surface area (BET) and electrical conductivity analysis. The techniques used revealed that the SnO2 exhibits behavior of a semiconductor material, and a potentially promising material for application as varistor and sensor systems for gas

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The study aimed at the treatment of attapulgite for the development and characterization of composite recycled low density polyethylene - PEBD_rec embedded with natural attapulgite - ATP_NAT, sifted - ATP_PN and attapulgite treated with sulfuric acid - ATP_TR in different compositions (1, 3 and 5%) and compared with the PEBD_rec. The atapulgitas, natural, screened and treated, were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), particle size analysis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and determining the area specific surface (BET). The composites were characterized by thermogravimetry (TG), differential scanning calorimetry (DSC), Xray diffraction (XRD), torque rheometry, scanning electron microscopy (SEM) and traction. The composite PEBD_rec / ATP (natural, sieved and treated) were produced by mixing in the molten state in a single screw extruder matrix wire with subsequent reprocessing matrix tape. It was found that the screening of attapulgite not reduce the quantity of quartz and the acid treatment completely extracted dolomite aggregate impurities of the channels attapulgite, and increase their surface area. The addition of attapulgite in PEBD_rec acts as a catalyst, reducing the thermal stability of the polymer. The increased concentration of attapulgite, increases resistance and reduces the elongation at break and modulus of elasticity of the composite PEBD_rec / attapulgite

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Nickel alloys are frequently used in applications that require resistance at high temperatures associated with resistance to corrosion. Alloys of Ni-Si-C can be obtained by means of powder metallurgy in which powder mixtures are made of metallic nickel powders with additions of various alloying carriers for such were used in this study SiC, Si3N4 or Si metal with graphite. Carbonyl Ni powder with mean particle size of 11 mM were mixed with 3 wt% of SiC powders with an average particle size of 15, 30 and 50 μm and further samples were obtained containing 4 to 5% by mass of SiC with average particle size of 15 μm. Samples were also obtained by varying the carrier alloy, these being Si3N4 powder with graphite, with average particle size of 1.5 and 5 μm, respectively. As a metallic Si graphite with average particle size of 12.5 and 5 μm, respectively. The reference material used was nickel carbonyl sintered without adding carriers. Microstructural characterization of the alloys was made by optical microscopy and scanning electron microscopy with semi-quantitative chemical analysis. We determined the densities of the samples and measurement of microhardness. We studied the dissociation of carriers alloy after sintering at 1200 ° C for 60 minutes. Was evaluated also in the same sintering conditions, the influence of the variation of average particle size of the SiC carrier to the proportion of 3% by mass. Finally, we studied the influence of variation of the temperatures of sintering at 950, 1080 and 1200 ° C without landing and also with heights of 30, 60, 120 and 240 minutes for sintering where the temperature was 950 °C. Dilatometry curves showed that the SiC sintered Ni favors more effectively than other carriers alloy analyzed. SiC with average particle size of 15 μm active sintering the alloy more effectively than other SiC used. However, with the chemical and morphological analyzes for all leagues, it was observed that there was dissociation of SiC and Si3N4, as well as diffusion of Si in Ni matrix and carbon cluster and dispersed in the matrix, which also occurred for the alloys with Si carriers and metallic graphite. So the league that was presented better results containing Si Ni with graphite metallic alloy as carriers, since this had dispersed graphite best in the league, reaching the microstructural model proposed, which is necessary for material characteristic of solid lubricant, so how we got the best results when the density and hardness of the alloy

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Polymer matrix composites offer advantages for many applications due their combination of properties, which includes low density, high specific strength and modulus of elasticity and corrosion resistance. However, the application of non-destructive techniques using magnetic sensors for the evaluation these materials is not possible since the materials are non-magnetizable. Ferrites are materials with excellent magnetic properties, chemical stability and corrosion resistance. Due to these properties, these materials are promising for the development of polymer composites with magnetic properties. In this work, glass fiber / epoxy circular plates were produced with 10 wt% of cobalt or barium ferrite particles. The cobalt ferrite was synthesized by the Pechini method. The commercial barium ferrite was subjected to a milling process to study the effect of particle size on the magnetic properties of the material. The characterization of the ferrites was carried out by x-ray diffraction (XRD), field emission gun scanning electron microscopy (FEG-SEM) and vibrating sample magnetometry (VSM). Circular notches of 1, 5 and 10 mm diameter were introduced in the composite plates using a drill bit for the non-destructive evaluation by the technique of magnetic flux leakage (MFL). The results indicated that the magnetic signals measured in plates with barium ferrite without milling and cobalt ferrite showed good correlation with the presence of notches. The milling process for 12 h and 20 h did not contribute to improve the identification of smaller size notches (1 mm). However, the smaller particle size produced smoother magnetic curves, with fewer discontinuities and improved signal-to-noise ratio. In summary, the results suggest that the proposed approach has great potential for the detection of damage in polymer composites structures

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This work aims at obtaining nanoparticles of iron oxide, the magnetite one (Fe3O4), via synthesis by thermal decomposition through polyol. Thus, two routes were evaluated: a simple decomposition route assisted by reflux and a hydrothermal route both without synthetic air atmosphere using a synthesis temperature of 260ºC. In this work observed the influence of the observe of surfactants which are generally applied in the synthesis of iron oxide nanoparticles decreasing cluster areas. Further, was observed pure magnetite phase without secondary phases generally found in the iron oxide synthesis, a better control of crystallite size, morphology, crystal structure and magnetic behavior. Finally, the introduction of hydroxyl groups on the nanoparticles surface was analyzed besides its employment in the polymer production with OH radicals. The obtained materials were characterized by XRD, DLS, VSM, TEM, TG and DSC analyses. The results for the magnetite obtainment with a particle size greater than 5 nm and smaller than 11 nm, well defined morphology and good magnetic properties with superparamagnetic behavior. The reflux synthesis was more efficient in the deposition of the hydroxyl groups on the nanoparticles surface

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The industrial production of ornamental rocks and the burning of coffee husk generate waste that is discarded into the environment. However, with the study of the incorporation of these residues in ceramic products, may be found an alternative to reducing environmental impacts and detrimental effects on human health caused by its indiscriminate disposal of waste in nature. Thus, this work aimed to study the addition of ashes of the coffee husk and granite residue in matrix of red ceramic. The raw materials were dry milled and sieved to mesh 100. To characterize the raw materials were carried out analyzes of X-ray diffraction (XRD), X-ray fluorescence (XRF), particle size analysis (PSA), differential thermal analysis (DTA) and thermogravimetric analysis (TG). Six formulations were prepared where the clay content was kept constant (70%wt) and ashes contents and granite residue varied from 10, 15, 20 and 30%. Dilatometrics analyzes were performed at four selected formulations, containing them: 100% clay (A100); 70% clay and 30% ashes (A70C30); 70% clay and 30% granite residue (A70G30); and 70% clay, 15% granite residue and 15% ashes (A70G15C15). The samples were prepared by uniaxial compaction with pressure of 25 MPa, and fired at temperatures of 800°C, 850ºC, 900ºC, 950ºC, 1000ºC and 1100°C. Assays were performed to determine the linear shrinkage of burning (LSB), water absorption (WA), apparent porosity (AP), density (D) and tensile bending. Also were performed analyzes of X-ray diffraction (XRD) and scanning electron microscopy (SEM) of the samples fired. The formulations incorporating granite residue and/or ashes reached the required limits of water absorption according to NBR 15270-1 and NBR 15310 and tensile bending according to classical literature (SANTOS, 1989) necessary for the production of tiles and ceramic block for masonry sealing

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The refractory metal carbides have proven important in the development of engineering materials due to their properties such as high hardness, high melting point, high thermal conductivity and high chemical stability. The niobium carbide presents these characteristics. The compounds of niobium impregnated with copper also have excellent dielectric and magnetic properties, and furthermore, the Cu doping increases the catalytic activity in the oxidation processes of hydrogen. This study aimed to the synthesis of nanostructured materials CuNbC and niobium and copper oxide from precursor tris(oxalate) oxiniobate ammonium hydrate through gas-solid and solid-solid reaction, respectively. Both reactions were carried out at low temperature (1000°C) and short reaction time (2 hours). The niobium carbide was produced with 5 % and 11% of copper, and the niobium oxide with 5% of copper. The materials were characterized by X-Ray Diffraction (XRD), Rietveld refinement, Scanning Electron Microscopy (SEM), X-Ray Fluorescence Spectroscopy (XRF), infrared spectroscopy (IR), thermogravimetric (TG) and differential thermal analysis (DTA , BET and particle size Laser. From the XRD analysis and Rietveld refinement of CuNbC with S = 1.23, we observed the formation of niobium carbide and metallic copper with cubic structure. For the synthesis of mixed oxide made of niobium and copper, the formation of two distinct phases was observed: CuNb2O6 and Nb2O5, although the latter was present in small amounts

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The production of waste from urban and industrial activities is one of the factors of environmental contamination and has aroused attention of the scientific community, in the sense of its reuse. On the other hand, the city of Salvador/Ba, with approximately 262 channels, responsible for storm water runoff, produces every year, by the intervention of cleaning and clearing channels, a significant volume of sediments (dredged mud), and thus an appropriate methodology for their final destination. This study aims to assess the influence of incorporation of these tailings in arrays of clay for production of interlocked block ceramic, also known as ceramic paver. All the raw materials from the metropolitan region of Salvador (RMS) were characterized by x-ray fluorescence, x-ray diffraction, thermal analysis (TG and TDA), particle size analysis and dilatometry. With the use of statistical experimental planning technique, ternary diagram was defined in the study region and the analyzed formulations. The specimens were prepared with dimensions of 60x20x5mm³, by uniaxial pressing of 30 MPa and after sintering at temperatures of 900°, 1000º and 1100ºC the technological properties were evaluated: linear shrinkage, water absorption, apparent porosity, apparent specifies mass, flexural rupture and module. For the uniaxial compression strength used cylindrical probe body with Ø 50 mm. The standard mass (MP) was prepared with 90% by weight of clay and 10% by weight of Channel sediment (SCP), not being verified significant variations in the properties of the final product. With the incorporation of 10% by weight of manganese residue (PFM) and 10% by weight of the Ceramic waste (RCB) in the mass default, in addition to adjusting the plasticity due to less waste clay content, provided increased linear firing shrinkage, due the significant concentration of K2O, forming liquid phase at low temperature, contributing to decreased porosity and mechanical resistance, being 92,5 MPa maximum compressive strength verified. After extract test leachate and soluble, the piece containing 10% of the PFM, was classified as non-hazardous and inert material according to NBR10004/04 ABNT. The results showed the feasibility on using waste, SCP, RCB and PFM clay mass, at temperatures above 900ºC, paver ceramic production, according to the specifications of the technical standards, so that to exceed the 10% of the PFM, it becomes imperative to conduct studies of environmental impacts

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To produce porcelain tiles fluxing agents are used in order to obtain a liquid phase during firing. This liquid phase fills the pores decreasing porosity, water absorption and contributes to material densification. In the porcelain tiles industry, feldspar is the main flux material used, with quantities ranging between 35 and 50%. Studies focus on the discovery of materials with flux characteristics that can reduce the consumption of feldspar by porcelain tiles industry. In this context, the coffee husk ashes, a residue obtained when coffee husks are burned to produce heat for the dryers during the processing of the green fruit, have as main chemical constituents potassium, calcium and magnesium, giving them characteristics of fluxing material. Brazil is the largest coffee producer in the world and is responsible for over 30% of the world s production. In this work a physical treatment of coffee husk ash was carried out in order to eliminate the organic matter and, after this, two by-products were obtained: residual wastes R1 and R2. Both residues were added separately as single fluxes and also in association with feldspar in mixtures with raw materials collected in a porcelain industry located in Dias d Ávila-Ba. The addition of these residues aimed to contribute to the reduction of the consumption of feldspar in the production of porcelain tiles. Specimens were produced with dimensions of 60 mm x 20 mm x 6 mm in an uniaxial die with compacting pressure of 45 MPa. The samples were heated to a temperature of 1200 °C, for 8 minutes. Tests were performed to characterize the raw materials by XRF, XRD, particle size analysis, DTA and TGA and, additionally, the results of the physical properties of water absorption, apparent porosity, linear shrinkage, density, dilatometry, flexural strength and SEM of sintered body were analyzed. Additions of less than 8% of the residue R1 contributed to the decrease of porosity, but the mechanical strength of the samples was not satisfactory. Additions of 5% the R2 residue contributed significantly to decrease the water absorption and apparent porosity, and also to increase the mechanical strength. Samples with addition of feldspar associated with the R2 residue, in proportions of 6.7% of R2 and 6.7% of feldspar, led to results of water absorption of 0.12% and mechanical strength of 46 MPa, having parameters normalized to the manufacture of porcelain stoneware tiles

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The coatings mortars are essential elements of building structures because they execute an important role in protecting walls and are particularly exposed to aggressive action responsible for its degradation over time. The importance of wall coverings has been the subject of discussion and analysis in the conservation and rehabilitation of old buildings. Are sometimes removed and replaced with inappropriate solutions of constructive point of view or architecture. The most commonly used coatings on walls of old buildings is based on traditional hydraulic lime mortars. The present study aims at the formulation of new lime- based mortars and aerial fine aggregate, in order to contribute to a better field of conservation and restoration mortar coating of old buildings. Residue was used for polishing porcelain as fine aggregate, replacing the aggregate (sand), in percentages 05-30% by mass. We conducted a thorough evaluation of the mortar properties in fresh and hardened state by comparing the performance of the same with a reference mortar. The residue used was characterized as the density, bulk density, and particle size laser, scanning electron microscopy, X-ray diffraction and X-ray fluorescence. Formulations were produced 7, 6 with residue and one commonly used formulation, which served as a reference. In the formulations of lime mortars air (hydrated lime powder CH-I) has been adopted a stroke volume (1:3) with constant binder, was varied and the water / binder and aggregate and waste. For evaluation of mortars fresh, proceeded to consistency analysis, specific gravity, water retention and air content embedded. In the hardened state assays were performed in specific gravity, water retention, modulus of elasticity, tensile strength in bending, compressive strength, water absorption by capillary action, adhesion, tensile strength, resistance to shrinkage and salts by of crystallization trials with resources chloride solution, nitrate and sulfate all sodium in prismatic at 90 days of age, in addition to the micro structural analysis of mortars. Based on the results we can see that the mortar formulated with 10% content of waste and the reference free retraction feature more stable closer to neutrality. The composition of 10% was obtained better performance against the action of the salt crystallization. The mortar with 15% residue obtained better density, lower air content embedded and high capacity for water retention developing good workability. The replacement of 20% of waste generates a satisfactory utilization of resistance to compression, flexion and traction grip the base. And, finally, it can be seen that the mortar with 10, 15 and 20% residual show, in principle, good suitability as coatings, thus enabling a final result consistent with durability, workability and aesthetics developing therefore a material with better performance to repair or replace existing mortars in old buildings

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The development of new materials to fill the demand of technological advances is a challenge for many researchers around the world. Strategies such as making blends and composites are promising alternatives to produce materials with different properties from those found in conventional polymers. The objective of this study is to evaluate the effect of adding the copolymer poly(ethylene methyl acrylate) (EMA) and cotton linter fibers (LB) on the properties of recycled poly(ethylene terephthalate) (PETrec) by the development of PETrec/EMA blend and PETrec/EMA/LB blend composite. In order to improve the properties of these materials were added as compatibilizers: Ethylene - methyl acrylate - glycidyl methacrylate terpolymer (EMA-GMA) and maleic anhydride grafted polyethylene (PE-g-MA). The samples were produced using a single screw extruder and then injection molded. The obtained materials were characterized by thermogravimetry (TG), melt flow index (MFI) mensurements, torque rheometry, pycnometry to determinate the density, tensile testing and scanning electron microscopy (SEM). The rheological results showed that the addition of the EMA copolymer increased the viscosity of the blend and LB reduces the viscosity of the blend composite. SEM analysis of the binary blend showed poor interfacial adhesion between the PETrec matrix and the EMA dispersed phase, as well as the blend composite of PETrec/EMA/LB also observed low adhesion with the LB fiber. The tensile tests showed that the increase of EMA percentage decreased the tensile strength and the Young s modulus, also lower EMA percentage samples had increased the elongation at break. The blend composite showed an increase in the tensile strength and in the Young`s modulus, and a decrease in the elongation at break. The blend formulations with lower EMA percentages showed better mechanical properties that agree with the particle size analysis which showed that these formulations presented a smaller diameter of the dispersed phase. The blend composite mechanical tests showed that this material is stronger and stiffer than the blend PETrec/EMA, whose properties have been reduced due to the presence of EMA rubbery phase. The use of EMA-GMA was effective in reducing the particle size of the EMA dispersed phase in the PETrec/EMA blend and PE-g-MA showed evidences of reaction with LB and physical mixture with the EMA

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Ionic oxides with ABO3 structure, where A represents a rare earth element or an alkaline metal and B is a transition metal from group VIII of the periodic table are potential catalysts for oxidation and good candidates for steam reforming reaction. Different methods have been considered for the synthesis of the oxide materials with perovskite structure to produce a high homogeneous material with low amount of impurities and low calcination temperatures. In the current work, oxides with the LaNiO3 formula had been synthesized using the method of the polymeric precursors. The thermal treatment of the materials took place at 300 ºC for 2h. The material supported in alumina and/or zirconia was calcined at 800 ºC temperature for 4h. The samples had been characterized by the following techniques: thermogravimetry; infrared spectroscopy; X-ray diffraction; specific surface area; distribution of particle size; scanning electron microscopy and thermo-programmed reduction. The steam reforming reaction was carried out in a pilot plant using reducing atmosphere in the reactor with a mixture of 10% H2-Argon, a mass about 5g of catalyst, flowing at 50 mL.min-1. The temperature range used was 50 - 1000 oC with a heating rate of 10 oC.min-1. A thermal conductivity detector was used to analyze the gas after the water trapping, in order to permit to quantify the consumption of hydrogen for the lanthanum nickelates (LaNiO3). The results showed that lanthanum nickelate were more efficient when supported in alumina than when supported in zirconia. It was observed that the methane conversion was approximately 100% and the selectivity to hydrogen was about 70%. In all cases were verified low selectivity to CO and CO2

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This research was motivated by the requirement of asbestos s replacement in building systems and the need to generate jobs and income in the country side of the state of Bahia, Brazil. The project aimed at using fibers from licuri leaves (syagrus coronata), an abundant palm in the region, to produce composites appropriate for the sustainable production of cement fibre reinforced products in small plants. The composites were produced in laboratory using Portland cement CP-II-F32, sand, water, licuri palm fiber contents of 1.0, 1.5 and 2.0% by weight of binder (two different fiber length) and metakaolin. The latter was chosen as an additional binder for its efficiency to reduce the alkalinity of cementitious matrixes therefore preventing the degradation of vegetable fibers. The characterization of the composite components was carried out by sieving and laser particle size analyses, thermal analysis, fluorescence and X-ray diffraction. The composites performance was evaluated by 3- point-bending tests, compressive strength, ultrasound module of elasticity, free and restrained shrinkage, water capillarity absorption and apparent specific gravity. It has been found that the addition of fibers increased the time to onset of cracking over 200.00% and a 25% reduction in cracks opening in the restrained shrinkage test. The capillary absorption reduced about 25% when compared to fiber-free composites. It was also observed with regard to flexural strength, compressive strength and specific gravity, that the addiction of fibers did not affect the composite performance presenting similar results for compounds with and without fibers. In general it can be stated that the reinforced composite fibers of palm licuri presents physical and mechanical characteristics which enable them to be used in the intended proposals of this research

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In this work was used a plasma torch of non transferred arc with argon as work gas, using a power supply with maximum DC current of 250 A and voltage of 30 V to activate the plasma and keep it switched on. The flame temperature was characterized by optical emission spectroscopy, through Boltzmann-plot-method. The torch has been used like igniter in the aluminothermic reduction of the mixture tantalum oxide and aluminum, seeking to obtain metallic tantalum. In heating of the reagents only one particle will be considered to study interactions between plasma-particle, seeking to determinate its fusion and residence time. The early powders were characterized by laser granulometry, scanning electron microscopy (SEM) and X-ray diffraction analysis. The final product of this reaction was characterized by SEM and X-ray diffraction. Crystallite size was calculated by the Scherrer equation and microdeformation was determined using Willamsom-Hall graph. With Rietveld method was possible to quantify the percentile in weight of the products obtained in the aluminothermic reaction. Semi-quantitative chemical analysis (EDS) confirmed the presence of metallic tantalum and Al2O3 as products of the reduction. As was waited the particle size of the metallic tantalum produced, presents values in nanometric scale due the short cooling time of those particles during the process