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Sintering and Microwave Properties of Zirconium Tin Titanate Doped with Select Oxides

Arantes, Vera Lúcia
Fonte: SPRINGER; NEW YORK Publicador: SPRINGER; NEW YORK
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
38.50809%
Zirconium tin titanate (ZST) is often used as a dielectric resonator for the fabrication of microwave devices. Pure compositions do not sinter easily by solid state sintering; therefore, sintering ZST requires sintering aids capable of creating defects that could improve diffusion processes and/or promote liquid phase sintering. The mechanisms by which the additives influence the microstructure and, consequently, the ZSTs dielectric properties are not very clear. The effects of ZnO, Bi2O3, and La2O3, on the stoichiometry and dielectric properties of ZST sintered at different temperatures were investigated in this study.; Coordination for Improvement of PostGraduationCAPES; Coordination for Improvement of Post-Graduation-CAPES; Sao Paulo Research Foundation (FAPESP); Sao Paulo Research Foundation-FAPESP

Conventional and microwave sintering of CaCu(3)Ti(4)O(12)/CaTiO(3) ceramic composites: non-ohmic and dielectric properties

Ramirez, M. A.; Bueno, P. R.; Longo, Elson; Varela, José Arana
Fonte: Iop Publishing Ltd Publicador: Iop Publishing Ltd
Tipo: Artigo de Revista Científica Formato: 5
ENG
Relevância na Pesquisa
48.54143%
The non-ohmic and dielectric properties as well as the dependence on the microstructural features of CaCu(3)Ti(4)O(12)/CaTiO(3) ceramic composites obtained by conventional and microwave sintering were investigated. It was demonstrated that the non-ohmic and dielectric properties depend strongly on the sintering conditions. It was found that the non-linear coefficient reaches values of 65 for microwave-sintered samples and 42 for samples sintered in a conventional furnace when a current density interval of 1-10 mA cm(-2) is considered. The non-linear coefficient value of 65 is equivalent to 1500 for samples sintered in the microwave if a current interval of 5-30 mA is considered as is shortly discussed by Chung et al (2004 Nature Mater. 3 774). Due to a high non-linear coefficient and a low leakage current (90 mu A) under both processing conditions, these samples are promising for varistor applications. The conventionally sintered samples exhibit a higher relative dielectric constant at 1 kHz (2960) compared with the samples sintered in the microwave furnace (2100). At high frequencies, the dielectric constant is also larger in the samples sintered in the conventional furnace. Depending on the application, one or another synthesis methodology is recommended...

Electrical and microstructural properties of microwave sintered SnO2-based varistors

Furtado, P. S.; Oliveira, M. M.; Vasconcelos, J. S.; Rangel, J. H. G.; Longo, Elson; Sousa, V. C de
Fonte: Associação Brasileira de Cerâmica Publicador: Associação Brasileira de Cerâmica
Tipo: Artigo de Revista Científica Formato: 151-157
ENG
Relevância na Pesquisa
48.176987%
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Foi feito um estudo das propriedades microestruturais e elétricas de varistores à base de SnO2, sinterizados por microondas a 1200 ºC, com uma taxa de aquecimento de 120 ºC/min e tempos de tratamento de 10, 20, 30, 40, 50 e 60 min. O sistema utilizado neste estudo foi de (98,95-X) %SnO2.1,0%CoO.0,05%Cr2O3.X%Ta2O5, onde X corresponde a 0,05 e 0,065 mol%. A sinterização foi feita em um forno de microondas doméstico (2,45 GHz), equipado para uso em laboratório. Carbeto de silício foi colocado em um recipiente refratário para formar uma câmara de aquecimento em torno do suporte da amostra. As amostras foram analisadas por microscopia eletrônica de varredura, difração de raios X, medições de corrente dc e espectroscopia de impedância. Os seguintes parâmetros foram analisados: densidade, tamanho médio de grão, coeficiente de não-linearidade, campo de rigidez dielétrica, corrente de fuga, e altura e largura da barreira de potencial.; An investigation was made of the microstructural and electrical properties of SnO2-based varistors microwave sintered at 1200 ºC, applying a heating rate of 120 ºC/min and treatment times of 10...

Influence of microwave energy on structural and piezoelectric response of Bi 4Ti 3O 12 ceramics

Aguiar, Ederson Carlos; Simões, Alexandre Zirpoli; Longo, Elson; Varela, José Arana
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 209-216
ENG
Relevância na Pesquisa
47.94111%
Bismuth titanate ceramics (Bi 4Ti 3O 12) with 10 wt% in excess of bismuth (BIT10) were prepared by the polymeric precursor method and sinterized in microwave (MW) and conventional furnaces (CF). The effect of microwave energy on structural and electrical behavior of BIT10 ceramics was investigated by means of X-ray diffraction (XRD), Scanning electron microscopy (SEM) and electrical measurements. The results of the BIT10 ceramics processed in the microwave furnace (MW) showed a high structural organization compared to conventional treatment (CF). Size of grains and dieletrical properties are influenced by annealing conditions while coercitive field is not dependent on it. The maximum dielectric permittivity (12000) was obtained for the sample sintered in the microwave furnace. Piezoelectric force microscopy images reveals that in-plane response may not change its sign upon polarization switching, while the out-of-plane response does with the influence of microwave energy. Copyright © 2010 American Scientific Publishers All rights reserved.

Sintering temperature influence on microwave dielectric properties of TiO2-ZrO2 ceramics

Souza, José Vitor C.; Castro, Pedro J.; Nono, Maria C. A.; Mineiro, Sergio L.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 646-651
ENG
Relevância na Pesquisa
38.759424%
Dielectric ceramics have been widely investigated and used for microwave applications such as resonators and filters. The present study deals with the influence of sintering temperature on microwave dielectric properties of TiO2 ceramics with 10, 20, and 30 wt% ZrO2. Three compositions have been developed through mixing procedures and then tested for each sintering temperature: 1500 and 1400°C. X-ray diffraction and scanning electron microscopy are carried out aiming to explain the ceramic behavior of each sample. The dielectric constants of different ceramics for both temperatures varied from 85.4 to 62.6, while their quality factor due to dielectric losses varied from 3110 to 1630. The Q decrease is attributed to the non uniform grain growth and to the obtained crystalline phases. The best microwave parameters were obtained for the ceramics sintered at 1400°C, which can be applied in microwave circuits as dielectric resonators. © (2010) Trans Tech Publications.

SnO 2 ceramics with low electrical resistivity obtained by microwave sintering

Gasparotto, Gisane; Bordignon, M. A N; Foschini, C. R.; Gasparotto, Gisele; Aguiar, E. C.; Zaguete, M. A.; Perazolli, L.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 193-200
ENG
Relevância na Pesquisa
69.1797%
The main aim of this study was to develop dense and conducting SnO 2 ceramics without precipitated phases on the grain boundaries, which was verified using field emission scanning microscopy (FE-SEM) coupled with an energy-dispersive X-ray spectroscopy (FE-SEM/EDS). Two sample groups were investigated, where the first sample group was doped with zinc while the second one was doped with cobalt. The ceramics were prepared using the oxides mixture method and the sintering was carried out in a conventional muffle oven as well as in microwave oven. The results obtained were found to be similar regarding the relative density for the two sintering methods while time and temperature gains were observed for the microwave sintering method. The relative densities obtained were nearly 95%, for the two sintering methods. Concerning the electrical characterization measurements-electric field x current density as well as the environment temperature, the ceramics obtained through the conventional sintering method presented non-ohmic behavior. For the microwave sintered ceramics, we observed an ohmic behavior with electrical resistivity of 1.3 Ωcm for the samples doped with ZnO/Nb 2O 5 and 2.5 Ωcm for that of the samples doped with CoO/Nb 2O 5. The FE-SEM/EDS results for the microwave sintered ceramics indicated a structure with a reduced number of pores and other phases segregated at the grain boundaries...

SnO2 dense ceramic microwave sintered with low resistivity

Perazolli, Leinig Antonio; Gasparotto, Gisane; Jaomaci, Natalia; Ruiz, Miguel; Zaghete, Maria Aparecida; Foschini, Cesar Renato; Aguiar, Ederson Carlos; Varela, José Arana
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 272-280
ENG
Relevância na Pesquisa
48.176987%
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aprefeiçoamento de Pessoal de Nível Superior (CAPES); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); The Hall-Héroult process is used for alumina reduction by the use of graphite anodes even though it involves a high emission of carbon dioxide (CO2) and several other organic compounds. Proposals have been made aiming at substitut- ing graphite for a single-phase SnO2-based ceramic with low resistivity and chemical resistance to cryolite, which is characterized as an inconsumable anode, reducing pollutant emissions. To this end, a wide range of studies were carried out on SnO2-based ceramics modified with ZnO as a densification aid doped with the promoters of electrical conduc- tivity such as Nb2O5, Al2O3 and Sb2O3 through a mixture of oxides and hybrid sintering in a microwave oven. The pressed pellets were sintered in a microwave oven up to 1050°C under a constant heating rate of 10°C/min. After sin- tering, the density was determined by the Archimedes method, the phases were then characterized by X-ray diffraction, the microstructure and chemical composition resulting from the sintered SnO2-based ceramics were also investigated by field emission scanning electron microscopy (FE-SEM) coupled with an energy-dispersive X-ray spectroscopy (EDS) and the electrical properties were determined by the measurements of the electric field × current density. A single-phase ceramic was obtained with a relative density of above 90% and electrical resistivity of 6.1 Ω·cm at room temperature. The ceramics obtained in this study could be a potential candidate as an inconsumable anode to replace the current fused coke used in the reduction of alumina.

Impacto da energia de micro-ondas na sinterização da zircônia odontológica

Luz, Júlio Nogueira
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Dissertação de Mestrado Formato: 57 f. : il.
POR
Relevância na Pesquisa
38.918318%
Pós-graduação em Odontologia Restauradora - ICT; The objective of this study was to evaluate the impact of the sintering method, conventional and through microwave energy on the microstructural characteristics and mechanical properties of ceramics based on Y- TZP zirconia. The null hypothesis is that sintering is carried out by microwave oven has no effect on the biaxial flexural strength Y- TZP disc, both discs aged by means of a thermo cycler, and in the non- cycled groups. One hundred samples in the form of VIPI Block Zirconn ceramic discs (12 x 1.2 mm) were machined in accordance with ISO 6872 standards for biaxial bending test and were divided into groups according to the method of sintering and thermomechanical aging: Group I: conventional and without mechanical cycling sintering ; Group II : conventional + thermomechanical cycling sintering ; Group III: microwave sintering and without thermomechanical cycling ; Group IV: in microwave sintering + thermomechanical cycling . The specimens were subjected to biaxial bending after sintering for non-cycled groups and after cycling for groups which were submitted to aging ( 1,200,000 cycles, 45 N load and frequency of 2.8 Hz, biaxial, immersed in water 37 °C). Qualitative analysis was performed on samples using a scanning electron microscope and X-ray diffraction samples in eight samples(n = 2) for all groups. For statistical analysis the Weibull modulus (m) was used...

Sintering response and mechanical properties of microwave sintered 316L Powder Blends

Mascarenhas, João; Marcelo, Teresa
Fonte: EUROPM 2007 Publicador: EUROPM 2007
Tipo: Conferência ou Objeto de Conferência
Publicado em 24/10/2007 ENG
Relevância na Pesquisa
58.68867%
Microwave sintering can be an efficient, economic and valuable approach for the processing of some PM materials. Recent findings on the ability of powdered metals to absorb and dissipate microwave radiation, opened new opportunities for the PM world. Being the particle size of the metallic powders one of the key parameters that rules the heating rate and the temperature performance during microwave sintering, work has been carried out on compacts of 316L powder blends with 60, 50, 25 and 7 m mean particle sizes, at 1150ºC for 30 minutes in a 2.45 GHz-1000 W microwave oven. Green and sintered densities and corresponding transverse rupture strength (TRS) are reported as well as hardness and porosity. Densities in excess of 95% were attained for the finer powders. TRS tests were performed on all but the 7 m powder specimens, being the highest value of 630 MPa obtained for the 25 m powder specimens

Effect of particle size of starting oxide powders on the performance of doped-lanthanum oxyapatite produced by mechanical alloying followed by microwave sintering

Oliveira, F. A. Costa; Marcelo, Teresa; Alves, Cátia; Santos, Mário João dos; Mascarenhas, João; Trindade, B.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2014 ENG
Relevância na Pesquisa
47.61291%
La9.33Si2Ge4O26 oxyapatite powders were synthesized at room temperature through mechanical alloying of La2O3, GeO2 and SiO2 precursor powders with different particle sizes as well as crystal structure in the case of silica powder (crystalline/amorphous). The mechanical alloyed mixtures were subsequently sintered by microwave heating at 1350 C for 1 h in order to obtain dense and homogeneous materials. All sintered materials consisted of the target apatite phase although minor amounts of secondary phases (e.g.La4GeO8) were also present only in samples obtained from micrometric SiO2 powders with a crystalline structure. The microstructure of the materials obtained from nanometric SiO2 with an amorphous structure was found to be more homogenous than the ones obtained from micrometric/crystalline silica. The mechanical behavior of the samples was slightly dependent on the particle size of the precursors and on the SiO2 crystallinity.

Alumina ceramics obtained by chemical synthesis using conventional and microwave sintering

Thomazini,D.; Gelfuso,M. V.; Chinelatto,A. S. A.; Chinelatto,A. L.; Sanson,F. K.; Teixeira Neto,F.
Fonte: Associação Brasileira de Cerâmica Publicador: Associação Brasileira de Cerâmica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2011 EN
Relevância na Pesquisa
58.828105%
It is well known that the heating mechanism and powder precursor define the microstructural characteristics of ceramics. Especially abnormal grain growth of pure alumina ceramics developed during conventional sintering method suggests that this material is a potential candidate to be treated in microwave sintering process. Alumina ceramics produced with commercial (A1K) and chemically synthesized powders were sintered in conventional and microwave furnaces. Two methods were employed to prepare the chemically synthesized nanosized powders: Pechini method and emulsification with oleic acid. The microwave sintered samples were characterized by apparent density and scanning electron microscopy and compared with the samples sintered in a conventional furnace. Alumina ceramics sintered in the microwave furnace had fine grained microstructure, not related with the starting powders. This characteristic was achieved in a sintering time shorter than those produced in the conventional furnace. However, satisfactory densification was observed only to A1K ceramics (3.95 g/cm³) sintered during one hour in microwave furnace.

Electrical and microstructural properties of microwave sintered SnO2-based varistors

Furtado,P. S.; Oliveira,M. M.; Vasconcelos,J. S.; Rangel,J. H. G.; Longo,E.; Sousa,V. C de
Fonte: Associação Brasileira de Cerâmica Publicador: Associação Brasileira de Cerâmica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
Relevância na Pesquisa
48.176987%
An investigation was made of the microstructural and electrical properties of SnO2-based varistors microwave sintered at 1200 ºC, applying a heating rate of 120 ºC/min and treatment times of 10, 20, 30, 40, 50 and 60 min. The system used in this study was (98.95-X) %SnO2.1.0%CoO.0.05%Cr2O3.X%Ta2O5, where X corresponds to 0.05 and 0.065 mol%. Sintering was carried out in a domestic microwave oven (2.45 GHz) fitted for lab use. Silicon carbide was placed in a refractory vessel to form a heating chamber surrounding the sample holder. The pellets were examined by scanning electron microscopy, X-ray diffractometry, direct current measurements and impedance spectroscopy. The parameters of density, medium grain size, coefficient of nonlinearity, breakdown electrical field, leakage current, and height and width of the potential barrier were analyzed.

Microwave fast sintering of submicrometer alumina

Menezes,Romualdo Rodrigues; Souto,Pollyane Marcia; Kiminami,Ruth Herta Goldschmidt Aliaga
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2010 EN
Relevância na Pesquisa
38.563494%
Commercially available alumina powder with high-purity submicrometer particle size and narrow particle size distribution was fully densified by a microwave hybrid fast firing technique. The alumina compacts were surrounded by susceptor material, which helped the heating of the samples, and sintered in a microwave oven at a frequency of 2.45 GHz and a power level of 1.8 kW. The sintered samples reached densities of 99% in sintering cycles of 30 to 40 minutes, a much shorter time than conventional sintering processes. The sintered samples showed uniform microstructures with powder particle size/average grain size rations higher than 1:2.

The effect of voltage on the arc stud welding of microwave sintered Fe+Al powder mixture

Talaş,Şükrü; Doğan,Mustafa; Çakmakkaya,Mehmet; Kurt,Adem
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2014 EN
Relevância na Pesquisa
47.61291%
The joining of powder metallurgy products is of importance because of high demand in many industrial applications. In this study, the effect of welding voltage on the joint quality has been investigated using discharge arc stud welding, a low heat input welding method, without gas protection to join steel stubs to microwave sintered compacts containing a powder mixture of 26 atomic % Al and Fe (balance). It has been shown that welds with steel stubs are prone to side cracking in the weld zone and they also suffer from the oxidation of metal powders adjacent to weld zone. The forms of oxides are continuous and laminar type in welds with steel stubs and the composition of weld zone changes with increasing arc voltage.

Microwave sintering of mullite-Al2O3 from kaolin precursor

Navarro,Lilian Cecilia Reinoso; Menezes,Romualdo Rodrigues; Kiminami,Ruth Herta Goldschmidt Aliaga
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2014 EN
Relevância na Pesquisa
48.636177%
In the present work the effect of the microwave hybrid fast sintering of mullite-Al2O3 with non-stoichiometric mullite composition was investigated. Samples were fast sintered using a range of microwave power from 1.2 to 2.1 kW. The mullitization process of the silica-rich composition was faster than that of the alumina-rich composition. Alumina-rich mullite showed higher densities and smaller grain size than alumina-poor mullite. It was concluded that the microwave hybrid sintering of mullite was very sensitive to composition.

Microwave Assisted Synthesis and Sintering of Ba0.5Sr0.5Co0.8Fe0.2O3-δ Perovskite

Nuernberg,Rafael Bianchini; Morelli,Márcio Raymundo
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2015 EN
Relevância na Pesquisa
58.86045%
Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) perovskite-type oxide is currently one of the most promising materials for applications in solid-oxide fuel cells (SOFCs), protonic ceramic fuel cells (PCFCs), oxygen separation membranes, and catalytic membranes for methane conversion. BSCF powder synthesis has received considerable attention and new synthesis methods have been proposed to obtain nanoscale powders with high chemical homogeneity. In this study, BSCF perovskite powder has been successfully prepared by microwave assisted combustion in aqueous solution. The synthesized powder was characterized by DSC, BET, XRD, and SEM. BSCF powder presented phase homogeneity, high specific surface area (9.93 g/m2) and nanometric crystallite size (23nm). The microwave sintering has been conducted in different conditions of dwell time and temperature. The influence of the temperature and the dwell time on microstructure was evaluated by optical microscopy. The results showed that microwave sintering could achieve the same densification compared to conventional sintering with only 10% of processing time. This shorter processing time has resulted in a reduction of grain size of up to 46.5%, compared to conventional sintering.

Microwave Sintered 3D Printed Tricalcium Phosphate Scaffolds for Bone Tissue Engineering

Tarafder, Solaiman; Balla, Vamsi Krishna; Davies, Neal M.; Bandyopadhyay, Amit; Bose, Susmita
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
38.636177%
We report here the fabrication of three dimensional (3D) interconnected macro porous tricalcium phosphate (TCP) scaffolds with controlled internal architecture by direct 3D printing (3DP), and high mechanical strength by microwave sintering. TCP scaffolds with 27%, 35% and 41% designed macro porosity having pore sizes of 500 μm, 750 μm, and 1000 μm, respectively, have been fabricated via direct 3DP. These scaffolds are then sintered at 1150 °C and 1250 °C in conventional electric muffle furnace as well as microwave furnace. Total open porosity between 42% and 63% is obtained in the sintered scaffolds due to the presence of intrinsic micro pores along with the designed pores. A significant increase in compressive strength, between 46% and 69%, is achieved by microwave sintering as compared to conventional sintering as a result of efficient densification. A maximum compressive strength of 10.95 ± 1.28 MPa and 6.62 ± 0.67 MPa is achieved for scaffolds with 500 μm designed pores (~400 μm after sintering) sintered in microwave and conventional furnaces, respectively. An increase in cell density with a decrease in macro pore size is observed during in vitro cell-material interactions using human osteoblast cells. Histomorphological analysis reveals that the presence of both micro and macro pores facilitated osteoid like new bone formation when tested in the femoral defect on Sprague-Dawley rats. Our results show that bioresorbable 3D printed TCP scaffolds have great potential in tissue engineering applications for bone tissue repair and regeneration.

Comparative sintering of zirconia and hydroxyapatite-zirconia composites

Reidy, Colin
Fonte: University of Limerick Publicador: University of Limerick
Tipo: Doctoral thesis; all_ul_research; ul_published_reviewed; ul_theses_dissertations; none
ENG
Relevância na Pesquisa
39.15919%
peer-reviewed; Hydroxyapatite [Ca10(PO4)6OH2, HA] is the major constituent of the mineral phase of bone and exhibits desirable properties as a bone graft, such as biocompatibility, bioactivity, osteoconductivity and direct bonding to bone tissue. However, due to its limited mechanical properties, in particular low fracture toughness (KIC) and tensile strength, HA is limited to non-load bearing applications and metal implant surface coatings. Zirconia (ZrO2) based materials exhibit high fracture toughness due to the stress induced martensitic transformation of tetragonal to monoclinic ZrO2. In theory, a composite material composed of HA and a reinforcing ZrO2 phase, combining the inherent bioactivity of HA with reinforcement from the ZrO2 is an attractive proposition in terms of load bearing bone replacement. The work contained herein attempts to improve the mechanical properties of HA through the addition of a ZrO2 phase and consolidation through two comparative sintering techniques, microwave and conventional sintering. The first objective was to investigate the effect of microwave sintering on physical, mechanical and chemical properties of Y2O3 (2-5 mol%) doped ZrO2 compositions compared with conventional sintering. Y2O3 content was altered through the attrition milling of commercial undoped monoclinic ZrO2 powders with co-precipitated Y2O3-doped ZrO2 powders and these were characterized using X-ray diffraction (XRD)...

WC-Co Particles Reinforced Aluminum Matrix by Conventional and Microwave Sintering

Ghasali,Ehsan; Pakseresht,Amir Hossein; Agheli,Maryam; Marzbanpour,Amir Hossein; Ebadzadeh,Touradj
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2015 EN
Relevância na Pesquisa
68.788413%
Metal matrix composites of Al-WC (10, 15 and 20 wt%) were prepared by microwave (without holding) and conventional sintering (held for 1 hour) processes at various temperatures between 650-950 °C. The results indicated that the highest density of conventional and microwave sintering corresponds to 97.4 ± 1.2% and 98.6 ± 0.8 of theoretical density, respectively; The highest bending strength of conventional and microwave sintered samples were 223 ± 12 and 256 ± 12 MPa, respectively. XRD patterns showed the decomposition of WC particles and formation of Al5W and Al12W interfacial reaction product phases in both processes. SEM studies showed that WC reinforcement particles were more likely to be agglomerated in microwave compared to conventional sintering process.

3D Online Submicron Scale Observation of Mixed Metal Powder's Microstructure Evolution in High Temperature and Microwave Compound Fields

Kang, Dan; Xu, Feng; Hu, Xiao-fang; Dong, Bo; Xiao, Yu; Xiao, Ti-qiao
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
Publicado em 11/03/2014 EN
Relevância na Pesquisa
38.663237%
In order to study the influence on the mechanical properties caused by microstructure evolution of metal powder in extreme environment, 3D real-time observation of the microstructure evolution of Al-Ti mixed powder in high temperature and microwave compound fields was realized by using synchrotron radiation computerized topography (SR-CT) technique; the spatial resolution was enhanced to 0.37 μm/pixel through the designed equipment and the introduction of excellent reconstruction method for the first time. The process of microstructure evolution during sintering was clearly distinguished from 2D and 3D reconstructed images. Typical sintering parameters such as sintering neck size, porosity, and particle size of the sample were presented for quantitative analysis of the influence on the mechanical properties and the sintering kinetics during microwave sintering. The neck size-time curve was obtained and the neck growth exponent was 7.3, which indicated that surface diffusion was the main diffusion mechanism; the reason was the eddy current loss induced by the external microwave fields providing an additional driving force for mass diffusion on the particle surface. From the reconstructed images and the curve of porosity and average particle size versus temperature...