共查询到20条相似文献,搜索用时 484 毫秒
1.
A. Sarmiento Santos J. Roa Rojas D. Martínez E. Vera C. A. Parra Vargas U. Fuentes Guerrero 《Journal of Superconductivity and Novel Magnetism》2013,26(6):2247-2251
The abnormal glow discharge applied to the sintering process is a recent technique used for processing both metallic and ceramic materials. In this paper, we use the abnormal glow discharge as an alternative method for the sintering step of the YBa2Cu3O7?δ superconductor material. The physical properties of the sintered samples by glow discharge were compared with the properties of sintered samples in resistive furnace, which is commonly used for production of high temperature superconductor ceramics. The structural analysis of the YBa2Cu3O7?δ samples was carried out by the X-ray diffraction technique, microstructural analysis by Scanning Electron Microscopy and electrical resistivity by the four probes method (resistance measurements as a function of temperature). The experimental results permitted to establish the similar structure and morphology for all samples: produced by plasma and resistive furnace sintering. The superconducting behavior was corroborated for both sintering processes. 相似文献
2.
Hydroxyapatite (HA) coating with nanoparticles like nanorice is fabricated on chemically pretreated titanium (Ti) surface, through an electrochemical deposition approach, for biomaterial applications. The Ti surface was chemically patterned with anatase TiO2 nanofibers. These nanofibers were prepared by in situ oxidation of Ti foils in a concentrated solution of H2O2 and NaOH, followed by proton exchange and calcinations. Afterward, TiO2 nanofibers on Ti substrate were coated with HA nanoparticles like nanorice. The obtained samples were annealed at high temperature to produce inter diffusion between TiO2 and HA layers. The resultant layers were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), Infrared Spectroscopy (FTIR), corrosion tests in SBF solution, and Electron Probe Micro Analysis (EPMA). It was found that only Ti from the titanium substrate diffuses into the HA coating and a good corrosion resistance in simulated body fluid was obtained. 相似文献
3.
The densification behaviour of highly ordered SiO2 compacts sintered at 1000° C in H2O (g) + N2, static air, N2 and 5% HCl + N2 atmospheres was investigated. Densification rate was found to be atmosphere dependent. Surface tension to viscosity ratios
were obtained for various sintering atmospheres using available sintering models. Scanning electron microscopy observations
were employed to describe the different stages in the sintering of ordered compacts and to show the effects of various atmospheres
on the microstructural development of ordered compacts. 相似文献
4.
《Materials Science & Technology》2013,29(8):1062-1064
AbstractNd:YAG ceramics with CaF2 and tetraethoxysilane (TEOS) as sintering additives were fabricated by vacuum sintering at 1750°C for 5 h and the microstructures were characterised using X-ray diffraction and scanning electron microscopy. Scanning electron microscopy result shows that the sintered bulk doped with TEOS contains many pores in the grains. The bulk doped with CaF2 displays uniform microstructure. The average size of the grains is 10 mm and few pores can be detected in this sintered bulk. The maximum transmittance of the sintered Nd:YAG ceramics were 44% doped with CaF2 and 14% doped with TEOS. 相似文献
5.
James T. Joseph Shyla Joseph Annamma John J. K. Thomas V. S. Prasad Sam Solomon 《Journal of Materials Science: Materials in Electronics》2011,22(3):228-232
Microwave dielectric ceramics of the type (Sm0.5Y0.5)Ti(Nb1−x
Ta
x
)O6 were prepared for x = 0, 0.2, 0.4, 0.6, 0.8 and 1 through the conventional solid state ceramic route. The ball-milled compositions were calcined
at 1,250 °C. The cylindrical pellets were sintered at temperatures between 1,385 and 1,450 °C. The densities were determined
by Archimedes method. The structure was analyzed using X-ray diffraction method. The microwave dielectric properties of the
polished pellets were measured using cavity resonator method. The morphological studies were done using Scanning Electron
Microscopy and Transmission Electron Microscopy. The Raman spectra were recorded and analyzed to confirm the structural change.
The photoluminescence spectra were also taken and the emission lines were identified. A correlation study was done among the
measured properties and parameters. Most of the samples have high dielectric constant, high quality factor and low temperature
coefficient of resonant frequency and hence suitable for microwave applications. 相似文献
6.
Hamed Heidari Houshang Alamdari Dominique Dubé Robert Schulz 《Advanced Engineering Materials》2012,14(9):802-809
The development of a proper processing method for the fabrication TiB2‐based wettable cathodes for aluminum electrolysis has been challenging for more than half a century. In this work, TiB2‐based ceramics were consolidated via pressureless sintering using Ti, Fe, and Ti–Fe additives. The microstructure, physical and mechanical properties as well as the interaction and the stability of the material in liquid aluminum were investigated. It was shown that specimens sintered with a Ti–Fe additive have excellent stability in liquid aluminum as the solid TiB2 skeleton maintained its integrity and strength after 5 days of exposure in liquid aluminum at 960 °C. Transmission electron microscopy analysis revealed that the formation of inter‐particle bridges of pure TiB2 is responsible for the good resistance of the material in molten aluminum. A sintering mechanism was proposed for the consolidation of TiB2 with a Ti–Fe additive. TiB2‐based ceramic sintered with a Ti–Fe alloy is suggested as a potentially reliable material for application as wettable cathode for aluminum electrolysis. 相似文献
7.
On the disappearance of Mo2C during low-temperature sintering of Ti(C,N)-Mo2C-Ni cermets 总被引:1,自引:0,他引:1
In order to seek a better understanding of the mechanisms leading to the disappearance of Mo2C during the sintering of Ti(C,N)-based cermets at or below 1200 °C, the sintering reactions occurring in ternary phase mixtures Ti(C,N)-Mo2C-Ni and their associated binary counterparts Ni-Mo2C, Ti(C,N)-Mo2C and Ni-Ti(C,N) at 1200 °C were investigated by X-ray diffraction analysis. It was shown that the decrease and disappearance of Mo2C during the sintering of Ti(C,N)-MoC-Ni cermet composites at or below 1200 °C are dictated by the relative amount of Mo2 to Ni, through enhanced dissolution of Mo2C in Ni by the presence of Ti(C,N). The reprecipitation of (Ti,Mo)(C,N) onto Ti(C,N) grains does not occur to a large extent under these conditions. On average, when the ratio of Mo2C to Ni is below or around 0.3, all of the Mo2C phases present in the Ti(C,N)-Mo2C-Ni alloys can be dissolved in Ni after 1 h at 1200 °C. However, when the ratio is well over 0.3, only partial dissolution of Mo2C can be observed even when the alloys are sintered at 1200 °C for 10 h. Both Mo2C and Ti(C,N) can be dissolved in Ni in the solid state, but the dissolution of Mo2C in Ni in the Ti(C,N)-Mo2C-Ni alloys is enhanced by the presence of Ti(C,N), hence N, compared to the dissolution of Mo2C in the Ni-Mo2C alloys. Negligible phase interactions are detected between Ti(C,N) and Mo2C when sintered at 1200 °C for up to 5 h, either with or without Ni presence. 相似文献
8.
Thin films of TiO2 doped with vanadium and palladium, prepared by the magnetron sputtering method, were studied by means of X-ray diffraction (XRD), Scanning Electron Microscopy with Energy Disperse Spectrometer (SEM-EDS) and Atomic Force Microscopy (AFM). Investigations have brought important information about microstructure due to dopant incorporation in the TiO2 host lattice. Directly after deposition thin films were XRD-amorphous and SEM investigations did not reveal details on the microstructure. Analysis of the topography of prepared thin films required application of Atomic Force Microscope. The AFM images show that as-deposited sample was dense with grain sizes varied in the range of 5.5 nm-10 nm, that indicated high quality nanocrystalline behavior. Additional annealing results in the formation of three phases in the thin film, e.g. (Ti,V)O2 — solid solution, PdO and metallic inclusions of Pd. SEM-EDS system allowed analysis of the elemental composition, especially the V one, which lines have not been evidenced in the XRD diffraction pattern. EDS maps show homogenous distribution of elements Ti, O, V, Pd in prepared thin films. 相似文献
9.
TiO2氧空位形成的影响因素 总被引:1,自引:0,他引:1
为了研究TiO2氧空位形成的影响因素,用管式电阻炉在空气、Ar及不同温度下对TiO2烧结.采用扫描电子显微镜(SEM)、X射线衍射(XRD)和X射线光电子能谱(XPS)对烧结TiO2样品的微观形貌、物相组成、元素及价态进行了表征,研究了烧结温度、烧结气氛和Ar+刻蚀对TiO2样品氧空位形成的影响.结果表明:相同气氛下,随着烧结温度的升高,TiO2氧空位浓度逐渐增大;相同温度下,惰性气氛有利于TiO2氧空位的产生;Ar+刻蚀有利于TiO2氧空位的形成. 相似文献
10.
L. O. O. Costa S. M. R. Vasconcelos A. L. Pinto A. M. Silva L. V. Mattos F. B. Noronha L. E. P. Borges 《Journal of Materials Science》2008,43(2):440-449
Hydrogen production for fuel cells from ethanol partial oxidation was evaluated on 1% Rh/CeO2 catalyst. Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) were used to analyze carbon formation
and the possible sintering of the metallic phase. X-ray fluorescence (XRF), nitrogen adsorption, and temperature-programmed
reduction (TPR) were also used for catalyst characterization. Two groups of rhodium particles of different sizes were observed.
By SEM/EDS analysis, no residual chloride was identified. TEM made it possible to identify the presence of rhodium in small
clusters. On the other hand, products distribution was affected by reaction temperature. At 473 K, only traces of acetaldehyde
were detected for the Rh/CeO2 catalyst. In the reaction conditions, no deactivation of the catalyst due to carbon deposition or sintering of the metal
was observed. Overall, our results show that the performance of Rh/CeO2 catalyst points to promising applications in terms of H2 production for fuel cells technology by ethanol partial oxidation. 相似文献
11.
Ki Beom Park Jaeho Choi Sung Yong Lee Jae-Young Park Tae-Wook Na Jong-In Choi 《Materials Science & Technology》2020,36(12):1372-1380
The present study investigated the sintering behaviour of Nb–16Si–25Ti–8Hf–2Cr–2Al alloy powders. The alloy powders were produced using ahydrogenation–dehydrogenation method and featured an irregular morphology. Powders sintered at 1500°C and 1600°C exhibited pores in their microstructures, while powders sintered at 1700°C for 4?h were fully densified and poreless. The cast ingot and powders were composed of three phases: Nbss, Nb5Si3, and Nb3Si. However, the Nb3Si phase was not observed, while HfO2 oxides formed in the sintered compact. The hafnium and oxygen reacted to form an HfO2 oxide during the high-temperature sintering process. From the result of the thermodynamic calculation, Hf oxide formed after sintering because Hf has the highest driving force for oxidation among the elements constituting the alloy. 相似文献
12.
《材料与设计》2015
The influence of various synthesis techniques on the dispersion and evolution of multi-walled carbon nanotubes (MWCNTs) in titanium (Ti) metal matrix composites (TMCs) prepared via powder metallurgy routes has been investigated. The synthesis techniques included sonication, high energy ball milling (HEBM), cold compaction, high temperature vacuum sintering and spark plasma sintering (SPS). Powder mixtures of Ti and MWCNTs (0.5 wt.%) were processed by HEBM in two batches: (i) ball milling of the mixtures (Batch 1) and (ii) ball milling of Ti powder alone, followed by a further ball milling with sonicated MWCNTs (Batch 2). Both batches of the powder mixtures were pressed at 40 MPa into green compacts and then sintered in vacuum. Batch 2 powder mixtures were also consolidated using SPS. The crystallinity and sp2 carbon network of the MWCNTs were characterized through analyzing the characteristic Raman peak ratio (ID/IG) of each processed sample. X-ray diffraction (XRD) was used for phase identification. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the morphology of the MWCNTs in the powder mixtures. The evolution of MWCNTs during the fabrication process and mechanical properties of the sintered compacts were discussed in conjunction with the formation of nano-crystalline TiC. 相似文献
13.
《Thin solid films》2005,471(1-2):100-104
Thin films of CeO2–TiO2–ZrO2 with 23 mol% of Ce, 45 mol% of Ti and 32 mol% of Zr were obtained by the sol–gel method. The precursor sol was prepared from a mixture of Ce(NH4)2 (NO3)6, Ti(OPri)4 and Zr(OPri)4 solubilized in isopropanol and then sonicated. Xerogels were characterized by Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA) and X-ray diffraction. The films were deposited by dip-coating technique on a glass plate coated with an indium tin oxide film (ITO) and thermally treated at 80 °C for 15 min. and heated at 450 °C for 15 min in an oxygen atmosphere. By means of the addition of a lithium salt (LiCF3SO3) to the precursor solution, films with different electrochemical performances were obtained. Their possible use as ion storage (counter-electrode) in electrochromic devices (ECD) was analyzed by spectroelectrochemical measurements using cyclic voltammetry and chronoamperometry coupled to spectrometric measurements. 相似文献
14.
A.F. Habibe L.D. Maeda R.C. Souza M.J.R. Barboza J.K.M.F. Daguano S.O. Rogero C. Santos 《Materials science & engineering. C, Materials for biological applications》2009,29(6):1959-1964
The objective of this work was to evaluate the influence of bioglass additions on the sintering and mechanical properties of yttria-stabilized zirconia ceramics, Y-TZP. Samples containing different bioglass additions, varying between 0 and 30 wt.%, were cold uniaxial pressed at 80 MPa and sintered in air at 1200 °C or 1300 °C for 120 min. Sintered samples were characterized by X-ray Diffractometry and Scanning Electron Microscopy. Hardness and fracture toughness were determined using Vickers indentation method. As a preliminary biological evaluation, in vitro cytotoxicity tests by Neutral Red Uptake method (using mouse connective tissue cells, NCTC clone L929 from ATCC bank) were realized to determine the cytotoxicity level of ZrO2-bioglass ceramics. The increasing of bioglass amount leads to the decreasing of relative density due to martensitic (tetragonal-monoclinic) transformation during cooling of the sintered samples. Y-TZP samples sintered at 1300 °C containing 5 wt.% of bioglass presented the best results, with high relative density, hardness and fracture toughness of 11.3 GPa and 6.1 MPa m1/2, respectively. Furthermore, the un-cytotoxic behavior was observed in all sintering conditions and bioglass amounts used in this study. 相似文献
15.
X. Zhao F. Neves J. B. Correia K. Liu F. M. Braz Fernades V. Koledov S. von Gratowski S. Xu J. Huang 《Journal of Materials Science》2018,53(19):13432-13441
This work reports on an efficient powder metallurgy method for the synthesis of NiTi alloys, involving mechanical activation of pre-alloyed NiTi2 and elemental Ni powders (NiTi2–Ni) followed by a press-and-sinter step. The idea is to take advantage of the brittle nature of NiTi2 to promote a better efficiency of the mechanical activation process. The conventional mechanical activation route using elemental Ti and Ni powders (Ti–Ni) was also used for comparative purposes. Starting with (NiTi2–Ni) powder mixtures resulted in the formation of a predominant amorphous structure after mechanical activation at 300 rpm for 2 h. A sintered specimen consisting mainly of NiTi phase was obtained after vacuum sintering at 1050 °C for 0.5 h. The produced NiTi phase exhibited the martensitic transformation behavior. Using elemental Ti powders instead of pre-alloyed NiTi2 powders, the structural homogenization of the synthesized NiTi alloys was delayed. Performing the mechanical activation at 300 rpm for the (Ti–Ni) powder mixtures gave rise to the formation of composite particles consisting in dense areas of alternate fine layers of Ni and Ti. However, no significant structural modification was observed even after 16 h of mechanical activation. Only after vacuum sintering at 1050 °C for 6 h, the NiTi phase was observed to be the predominant phase. The higher reactivity of the mechanically activated (NiTi2–Ni) powder particles can explain the different sintering behavior of those powders compared with the mechanically activated (Ti–Ni) powders. It is demonstrated that this innovative approach allows an effective time reduction in the mechanical activation and of the vacuum sintering step. 相似文献
16.
In this research a nano-composite structure containing of an intermetallic matrix with dispersed Al2O3 particles was obtained via mechanical activation of TiO2 and Al powder mixture and subsequent sintering. The mixture has been milled for different lengths of time and then as a subsequent process it has been sintered. Phase evolutions in the course of milling and subsequent sintering of the milled powder mixture were investigated. Samples were characterized by XRD, SEM, DTA and TEM techniques.The results reveal that the reaction begins during milling by formation of Al2O3 and L12 Al3Ti and further milling causes partial amorphization of powder mixture. DTA results reveal that milling of the powder mixture causes solid state reaction between Al and TiO2 rather than liquid–solid reaction. Also, it was observed that the exothermicity of aluminothermic reduction is reduced by increasing the milling time and the exothermic peak shifts to lower temperatures after partial amorphization of powder mixture during milling. Phase evolutions of the milled powders after being sintered reveal that by increasing the milling time and formation of L12 Al3Ti in the milled powder, intermediate phase formed at 500 °C changes from D022 Al3Ti to Al24Ti8 phase. 相似文献
17.
Z. Khakpour A. Maghsoudipour A. A. Youzbashi K. Ahmadi 《Journal of Materials Science: Materials in Electronics》2012,23(3):786-794
The densification behavior of nanocrystalline Gd-doped ceria electrolyte, synthesized via mechanical alloying process, was
investigated by means of the conventional pressure less sintering and the two-step sintering methods. The effect of the heating
rate and the amounts of dopant on the sinterability of Ce1−x
Gd
x
O(2−δ)
x = 0.2 (2GDC) and x = 0.3 (3GDC) oxides was studied, which indicated that the gadolinium retards densification and grain growth in the final
state of the conventional sintering and 2GDC samples reach 94% density at 1,550 °C. Subsequent investigation on the grain
growth in the fully densified ceramics showed that lowering of the heating rate and increasing of the soaking time reduce
the effect of dopant and cause samples to be densified to the higher theoretical density (97%) at lower temperatures (1,400 °C).
Fully dense Gd-doped ceria ceramics with finest grain size (900–1,100 nm) can be obtained by two-step sintering method. Electrical
conductivity measurement in the GDC samples was studied by impedance spectroscopy. The grain boundary conductivity in these
specimens obtained by two-step sintering method was compared with normal sintered specimens. It is concluded that the reduced
conductivity observed in the two-step sintering specimen is attributable to the microstructure changes obtained by increased
of grain boundary resistivity. 相似文献
18.
19.
Wein-Duo Yang 《Journal of Materials Science》1999,34(14):3533-3544
X-ray photoelectron spectroscopy has been used to investigate the existence of Ti3+ on the surface of La2O3-doped strontium titanate and to determine its surface characteristics. The surfaces, having Sr/Ti ratios significantly varying from the stoichiometric ratio, revealed the presence of carbon and suggested the presence of hydroxyl groups on the surface, whose concentration largely decreased in the bulk. Ti3+ species existed as a function of the sintering conditions and were detected on the surface of (La, Sr)TiO3 sintered in air or in N2 by natural cooling. These samples had a lower electrical resistivity, especially when sintered in a N2 atmosphere. The surfaces of air oxidized SrTiO3 and quenched from high temperature contained no detectable amount of Ti3+, resulting in higher resistivity. However, the N2-sintered samples were dark blue in color and exhibited lower resistivity, semiconductivity, and lower valence oxidation state Ti existed when sintered above 1350°C. 相似文献
20.
《Materials Science & Technology》2013,29(10):1252-1256
AbstractTernary carbide Ti3 SiC2 was first synthesised through a pulse discharge sintering (PDS) technique from mixtures of Ti, SiC, and C with different molar ratios. Sintering processes were conducted at 1200 – 1400°C for 15 – 60 min at a pressure of 50 MPa. The phase constituents and microstructures of the synthesised samples were analysed by X-ray diffraction (XRD) technique and observed by scanning electron microscopy (SEM). The results showed that, for samples sintered from 3Ti/SiC/C powder at 1200 – 1400°C, TiC is always the main phase and only little Ti3 SiC2 phase is formed. When the molar ratios Ti : SiC : C were adjusted to 3 : 1.1 : 2 and 5 : 2 : 1, the purity of Ti3 SiC2 in the synthesised samples was improved to about 93 wt-%. The optimum sintering temperature for Ti3 SiC2 samples was found to be in the range 1250 – 1300°C and all the synthesised samples contain platelike grains. The relative density of Ti3 SiC2 samples was measured to be higher than 99% at sintering temperatures above 1300?C. It is suggested that the PDS technique can rapidly synthesise ternary carbide Ti3 SiC2 with good densification at lower sintering temperature. 相似文献