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1.
Y2O3 + Nd2O3 co-stabilized ZrO2-based composites with 40 vol% WC were fully densified by pulsed electric current sintering (PECS) at 1350 °C and 1450 °C.
The influence of the PECS temperature and Nd2O3 co-stabilizer content on the densification, hardness, fracture toughness and bending strength of the composites was investigated.
The best combination of properties was obtained for a 1 mol% Y2O3 and 0.75 mol% Nd2O3 co-stabilized composite densified for 2 min at 1450 °C under a pressure of 62 MPa, resulting in a hardness of 15.5 ± 0.2
GPa, an excellent toughness of 9.6 ± 0.4 MPa.m0.5 and an impressive 3-point bending strength of 2.04 ± 0.08 GPa. The hydrothermal stability of the 1 mol% Y2O3 + 1 mol% Nd2O3 co-stabilized ZrO2-WC (60/40) composites was compared with that of the equivalent 2 mol% Y2O3 stabilized ceramic. The double stabilized composite did not degrade in 1.5 MPa steam at 200 °C after 4000 min, whereas the
yttria stabilized composite degraded after less than 2000 min. Moreover, the (1Y,1Nd) ZrO2-WC composites have a substantially higher toughness (~9 MPa.m0.5) than their 2Y stabilized equivalents (~7 MPa.m0.5). 相似文献
2.
Based on the structure characteristic of Ti3AlC2 and the easy formation of Ti3Al1 − x
Si
x
C2 solid solution, a Si interlayer was selected to join Ti3AlC2 layered ceramic by diffusion bonding method. Joining was performed at 1,300–1,400 °C for 120 min under 5 MPa load in an Ar
atmosphere. The phase composition and interface microstructure of the joints were investigated by XRD, SEM and EPMA. The results
revealed that Ti3Al(Si)C2 solid solution formed at the interface. The mechanism of bonding is attributed to silicon diffusing inward the Ti3AlC2. The strength of joints was evaluated by a 3-point bending test. The jointed specimens exhibit a high flexural strength of
285 ± 11 MPa, which is about 80% of that of the Ti3AlC2; and retain this strength up to 1,000 °C. The high mechanical performance of the joints indicates that diffusion bonding
via a Si interlayer is effective to bond Ti3AlC2 ceramic. 相似文献
3.
X. H. Zheng J. Xiao X. Huang D. P. Tang X. L. Liu 《Journal of Materials Science: Materials in Electronics》2011,22(8):1116-1119
The formation behavior of CaCu3Ti4O12 (CCTO) had been investigated via solid state reaction from CaTiO3, CuO and TiO2 powders. In the temperature range from 750 to 1,200 °C, the reaction sequence was traced by XRD, and the microstructure evolution
of calcined powders was also investigated by SEM. CCTO began to form owing to the reaction between CaTiO3, CuO and TiO2 at around 850 °C, and became the major phase at 1,000 °C. Finally, the single phase CCTO was obtained at 1,150 °C. However,
CCTO was decomposed at CaTiO3, CuO and TiO2 when the temperature increased to 1,200 °C. In addition, no other intermediate phases occurred in the synthesized process.
The formation behaviors indicated that CaTiO3 prevented the formation and growth of CCTO. 相似文献
4.
Xibao Li Gangqin Shao Xiaohua Yu Jian Wang Hongxing Gu 《Journal of Materials Science: Materials in Electronics》2011,22(2):189-192
Ce0.8Sm0.2O1.9 (SDC) powder was synthesized by spray pyrolysis at 650 °C. XRD results showed that phase-pure SDC powder with an average
crystallite size of 11 nm was synthesized. SDC electrolyte film was prepared by tape casting and sintered at different temperatures
of 1,300, 1,400 and 1,500 °C for 2 h, respectively. The SDC electrolyte film was relatively denser and showed finer microstructure
at relatively lower temperature of 1,400 °C, which might be due to the high sintering activity of the spray pyrolysis SDC
powder. The ionic conductivity of the SDC electrolyte film sintered at 1,400 °C reached a maximum value of 9.5 × 10−3 S cm−1 (tested at 600 °C) with an activation energy for conduction of 0.90 eV. 相似文献
5.
ZrB2 (zirconium diboride)-based ceramics reinforced by 15vol.% SiC whiskers with high density were successfully prepared using MoSi2 as sintering aids. The effects of sintering condition and MoSi2 content on densification behavior, phase composition, and mechanical properties of SiCw/ZrB2 composites were studied. Nearly, fully dense materials (relative density >99%) were obtained by hot-pressing (HP) at 1700°C–1800°C in flow argon atmosphere. The grain size of ZrB2 phase in the samples sintered by HP at 1700°C–1800°C were very fine, with mean size below 5 μm. Mechanical properties (such as flexural strength, fracture toughness, and Vickers hardness) of the sintered samples were measured. The sample with 15vol.% MoSi2 addition sintered by HP at 1750°C displayed the best mechanical properties. 相似文献
6.
Oktar FN Agathopoulos S Ozyegin LS Gunduz O Demirkol N Bozkurt Y Salman S 《Journal of materials science. Materials in medicine》2007,18(11):2137-2143
Biologically derived hydroxyapatite from calcinated (at 850 °C) bovine bones (BHA) was doped with 5 wt% and 10 wt% of SiO2, MgO, Al2O3 and ZrO2 (stabilized with 8% Y2O3). The aim was to improve the sintering ability and the mechanical properties (compression strength and hardness) of the resultant
BHA-composites. Cylindrical samples were sintered at several temperatures between 1,000 and 1,300 °C for 4 h in air. The experimental
results showed that sintering generally occurs at 1,200 °C. The BHA–MgO composites showed the best sintering performance.
In the BHA–SiO2 composites, extended formation of glassy phase occurred at 1,300 °C, resulting in structural degradation of the resultant
samples. No sound reinforcement was achieved in the case of doping with Al2O3 and zirconia probably due to the big gap between the optimum sintering temperatures of BHA and these two oxides. 相似文献
7.
Huanfu Zhou Xiuli Chen Liang Fang Changzheng Hu Hong Wang 《Journal of Materials Science: Materials in Electronics》2010,21(9):939-942
Ba5Nb4O15 powders were synthesized by molten-salt method in NaCl–KCl flux at a low temperature of 650–900 °C for 2 h, which is lower
than that of the conventional solid-state reaction. This simple process involved mixing of the raw materials and salts in
a certain proportion. Subsequent calcination of the mixtures led to Ba5Nb4O15 powders at 650–900 °C. XRD and SEM techniques were used to characterize the phase and morphology of the fabricated Ba5Nb4O15 powders, respectively. After sintering at 1,300 °C for 2 h, the densified Ba5Nb4O15 ceramics with good microwave dielectric properties of εr = 39.2, Q × f approximated as 27,200 GHz and τ
f
= 72 ppm/°C have been obtained. 相似文献
8.
Hiroshi Maiwa 《Journal of Materials Science》2008,43(19):6385-6390
Ba(Zr0.2Ti0.8)O3 (BZT) ceramics are prepared from spray-dried powder by spark plasma sintering (SPS) and by normal sintering. By the application
of SPS, ceramics with >96% relative densities could be obtained by sintering at 1,100 °C for 5 min in air atmosphere. The
pellet as sintered by SPS at 1,100 °C was black and conductive. Although SPS was carried out in air atmosphere, the samples
were deoxidized by heating the carbon die. By post-annealing at 1,000 °C for 12 h in air, the pellet was oxidized and became
white and insulating. Grain growth was suppressed in the ceramics prepared by SPS, and the average grain size was 0.52 μm.
The starting powder contained 1.90% carbon, mainly as binder, and the SPS-prepared ceramics and ordinary prepared ceramics
contained 0.15 and 0.024% carbon, respectively. The BZT ceramics obtained by SPS and the subsequent annealing at 1,000 °C
for 12 h exhibited a mild temperature dependence of their dielectric constant. The field-induced displacement of the BZT ceramics
was less hysteretic and smaller than that of the ceramics sintered by the conventional method. 相似文献
9.
Guo-Hua Chen 《Journal of Materials Science》2007,42(17):7239-7244
The effects of replacement of MgO by CaO on the sintering and crystallization behavior of MgO–Al2O3–SiO2 system glass-ceramics were investigated. The results show that with increasing CaO content, the glass transition temperature
firstly increased and then decreased, the melting temperature was lowered and the crystallization temperature of the glass-ceramics
shifted clearly towards higher temperatures. With the replacement of MgO by less than 3 wt.% CaO, the predominant crystalline
phase in the glass-ceramics fired at 900 °C was found to be α-cordierite and the secondary crystalline phase to be μ-cordierite.
When the replacement was increased to 10 wt.%, the predominant crystalline phase was found to be anorthite and the secondary
phase to be α-cordierite. Both thermal expansion coefficient (TCE) and dielectric constant of samples increases with the replacement
of MgO by CaO. The dielectric loss of sample with 5 wt.% CaO fired at 900 °C has the lowest value of 0.08%. Only the sample
containing 5 wt.% and10 wt.% CaO (abbreviated as sample C5 and C10) can be fully sintered before 900 °C. Therefore, a dense
and low dielectric loss glass-ceramic with predominant crystal phase of α-cordierite and some amount of anorthite was achieved
by using fine glass powders (D50 = 3 μm) fired at 875–900 °C. The as-sintered density approaches 98% theoretical density. The flexural strength of sample
C5 firstly increases and then decreases with sintering temperature, which closely corresponds to its relative density. The
TCE of sample C5 increases with increasing temperature. The dielectric property of sample C5 sintered at different temperatures
depends on not only its relative density but also its crystalline phases. The dense and crystallized glass-ceramic C5 exhibits
a low sintering temperature (≤900 °C), a fairly low dielectric constant (5.2–5.3), a low dielectric loss (≤10−3) at 1 MHz, a low TCE (4.0–4.25 × 10−6 K−1), very close to that of Si (∼3.5 × 10−6 K−1), and a higher flexural strength (≥134 MPa), suggesting that it would be a promising material in the electronic packaging
field. 相似文献
10.
Junji Zhang Jumei Yu Mingju Chao Erjun Liang Mingyu Li Dechuan Li 《Journal of Materials Science》2012,47(3):1554-1558
Textured poly crystalline barium dititanate BaTi2O5 (BT2) ceramics with a preferred 〈010〉 orientation were synthesized by laser rapid solidification method, with a CO2 laser. The 〈010〉 orientation of the BT2 is along the laser incident direction, and the orientation factor (f) and relative density of the unannealed BT2 sample are 0.40 and 96.2%, respectively. The two quantities increase with increasing
annealing time, and reach the maximum values of 0.42 (annealed at 1,000 °C for 12 h) and 97.5% (annealed at 1,000 °C for 24 h),
respectively. The images of scanning electron microscopy reveal that the BT2 are composed of flake-like microstructures with
the maximum thickness of 20 μm and dimension of 0.6 mm, which are parallel to the laser incident direction. The measured Curie
temperature (T
c) and the maximum dielectric constant (εmax) are 443 and 6,000 °C, respectively. 相似文献
11.
O. Ozturk 《Journal of Materials Science: Materials in Electronics》2012,23(6):1235-1242
In this study we have investigated the influence of iron diffusion and diffusion-annealing time on the mechanical and the
superconducting properties of bulk Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy superconductors by performing X-ray diffraction (XRD), scanning electron microscopy (SEM), Vickers hardness, dc resistivity
(ρ-T) and critical current density (Jc) measurements. The samples are prepared by the conventional solid-state reaction method. Doping of Bi-2223 was carried out
by means of iron diffusion during sintering from an evaporated iron film on pellets. Then, the Fe layered superconducting
samples were annealed at 830 °C for 10, 30 and 60 h. The mechanical properties of the compounds have been investigated by
measuring the Vickers hardness (Hv). The mechanical properties of the samples were found to be load dependent. The load independent Vickers hardness (H0), Young’s modulus (E), yield strength (Y), and fracture toughness (KIC) values of the samples are calculated. These all measurements showed that the values of the Vickers hardness, critical current
density, and critical transition temperature and lattice parameter c increased with increasing Fe doping and diffusion-annealing time. 相似文献
12.
Mohammad Maleki Shahraki Seyyed Ali Shojaee Ali Nemati Mohammad Ali Faghihi Sani 《Journal of Materials Science: Materials in Electronics》2010,21(2):199-205
In this study, SnO2-based varistors were prepared from mechanically activated nanocrystalline powders. Nanocrystalline powders were derived by
subjecting the initial powders to intensive high-energy activation with different times and ball to powder ratio. The effect
of activation parameters on the powder properties and sintering temperature, as well as microstructural, micro-electrical
and macro-electrical properties of the final specimens was evaluated. Varistors derived from high-energy mechanical activation
exhibit a higher density (98.3% relative density) and more refined microstructure upon sintering at 1,300 °C in comparison
varistors prepared from conventional powders. Breakdown voltage and nonlinear coefficient were increased up to 24 kV/cm and
45 respectively. 相似文献
13.
Xiumin Yao Shouhong Tan Xiangyu Zhang Zhengren Huang Dongliang Jiang 《Journal of Materials Science》2007,42(13):4960-4966
SiC reticulated porous ceramics (SiC RPCs) was fabricated with polymer replicas method by using MgO–Al2O3–SiO2 additives as sintering aids at 1,000∼1,450 °C. The MgO–Al2O3–SiO2 additives were from alumina, kaolin and Talc powders. By employing various experimental techniques, zeta potential, viscosity
and rheological measurements, the dispersion of mixed powders (SiC, Al2O3, talc and kaolin) in aqueous media using silica sol as a binder was studied. The pH value of the optimum dispersion was found
to be around pH 10 for the mixtures. The optimum condition of the slurry suitable for impregnating the polymeric sponge was
obtained. At the same time, the influence of the sintering temperature and holding time on the properties of SiC RPCs was
investigated. According to the properties of SiC RPCs, the optimal sintering temperature was chosen at 1,300 °C, which was
lower than that with Al2O3–SiO2 additives as sintering aids. 相似文献
14.
Choon-W. Nahm 《Journal of Materials Science: Materials in Electronics》2011,22(8):1010-1015
The microstructure, electrical properties, and DC-accelerated aging behavior of the ZnO-V2O5-Mn3O4 ceramics were investigated at different sintering temperatures of 850–925°C. The microstructure of the ZnO-V2O5-Mn3O4 ceramics consisted of ZnO grain as a primary phase, and Zn3(VO4)2 which acts as a liquid-phase sintering aid, in addition to Mn-rich phase as secondary phases. The maximum value (3,172 V/cm)
and minimum value (977 V/cm) of breakdown field were obtained at sintering temperature of 850 and 900°C, respectively. The
nonlinear coefficient exhibited the highest value, reaching 30 at 925°C and the lowest value, reaching 4 at 850°C. The optimum
sintering temperature was 900°C, which exhibited not only high nonlinearity with 24 in nonlinear coefficient, but also the
high stability, with %ΔE1mA = −0.9% and %∆α = −12.5% for DC-accelerated aging stress of 0.85 E1mA/85°C/24 h. 相似文献
15.
Hai-Long Wang Chang-An Wang De-Liang Chen Hong-Ling Xu Hong-Xia Lu Rui Zhang Lun Feng 《材料科学前沿(英文版)》2010,4(3):276-280
ZrB2-SiC ultra-high temperature ceramic composites reinforced by nano-SiC whiskers and SiC particles were prepared by microwave sintering at 1850°C. XRD and SEM techniques were used to characterize the sintered samples. It was found that microwave sintering can promote the densification of the composites at lower temperatures. The addition of SiC also improved the densification of ZrB2-SiC composites and almost fully dense ZrB2-SiC composites were obtained when the amount of SiC increased up to 30vol.%. Flexural strength and fracture toughness of the ZrB2-SiC composites were also enhanced; the maximum strength and toughness reached 625 MPa and 7.18 MPa·m1/2, respectively. 相似文献
16.
Yunfeng Hua Litong Zhang Laifei Cheng Zhengxian Li Jihong Du 《Journal of Materials Science》2010,45(2):392-398
37.2 vol.% SiCP/SiC and 25.0 vol.% SiCW/SiC composites were prepared by chemical vapor infiltration (CVI) process through depositing SiC matrix in the porous particulate
and whisker preforms, respectively. The particulate (or whisker) preforms has two types of pores; one is small pores of several
micrometers at inter-particulates (or whiskers) and the other one is large pores of hundreds micrometers at inter-agglomerates.
The microstructure and mechanical properties of 37.2 vol.% SiCP/SiC and 25.0 vol.% SiCW/SiC composites were studied. 37.2 vol.% SiCP/SiC (or 25.0 vol.% SiCW/SiC) consisted of the particulate (or whisker) reinforced SiC agglomerates, SiC matrix phase located inter-agglomerates and
two types of pores located inter-particulates (or whiskers) and inter-agglomerates. The density, fracture toughness evaluated
by SENB method, and flexural strength of 37.2 vol.% SiCP/SiC and 25.0 vol.% SiCW/SiC composites were 2.94 and 2.88 g/cm3, 6.18 and 8.34 MPa m1/2, and 373 and 425 MPa, respectively. The main toughening mechanism was crack deflection and bridging. 相似文献
17.
Guo-hua Chen Jun-tao Liu Hua-rui Xu Chang-rong Zhou Min-hong Jiang Xin-yu Liu 《Journal of Materials Science: Materials in Electronics》2011,22(8):915-919
Ultrafine strontium barium niobate (Sr0.3Ba0.7Nb2O6, SBN30) powders were prepared by urea method starting from a precursor solution constituting of Sr (NO3)2, Ba (NO3)2, NbF5, urea and polyvinyl alcohol (PVA) as surfactant. Their structural behavior and morphology were examined by means of X-ray
diffractometry (XRD) and Scanning electron microscopy (SEM). The results showed that the SBN30 powders crystallized to a pure
tetragonal phase at annealing temperatures as low as 750 °C. The average particle size of SBN powders subjected to 750 °C
was of the order of 150–300 nm. With increasing calcination temperature,however, the average particle size of the calcined
powders increased. The SBN30 ceramic prepared from urea method can be sintered at temperature as low as 1,225 °C. The transition
temperature from the ferroelectric phase to the paraelectric phase and the relative dielectric permittivity of the SBN30 powder
were less than the corresponding values of the bulk ceramic. The permittivity and loss tangent (tan δ) at room temperature
(1 kHz) was found to be 930 and below 0.025. 相似文献
18.
Wubian Tian ZhengMing Sun Hitoshi Hashimoto Yulei Du 《Journal of Materials Science》2009,44(1):102-107
The compressive properties of ternary compound Cr2AlC at different temperatures and strain rates were studied. When tested at a strain rate of 5.6 × 10−4 s−1, the compressive strength decreases continuously from 997 ± 29 MPa at room temperature to 523 ± 7 MPa at 900 °C. The ductile-to-brittle
transition temperature is measured to be in the range of 700 to 800 °C. When tested in the strain rate range of 5.6 × 10−5 to 5.6 × 10−3 s−1, Cr2AlC fails in a brittle mode at room temperature, whereas the deformation mode changes from a brittle to a ductile as the strain
rate is lower than 5.6 × 10−4 s−1 when compressed at 800 °C. The compressive strength increases slightly with increasing strain rate at room temperature and
it is less dependent on strain rate when tested at 800 °C. The plastic deformation mechanism of Cr2AlC was discussed in terms of dislocation-related activities, such as kink band formation, delamination, decohesion of grain
boundary, and microcrack formation. 相似文献
19.
Xiuli Chen Huanfu Zhou Liang Fang Dongjin Chu Changda Li Ruili Guo Hong Wang 《Journal of Materials Science: Materials in Electronics》2011,22(4):371-375
The influences of B2O3 and CuO (BCu, B2O3: CuO = 1:1) additions on the sintering behavior and microwave dielectric properties of LiNb0.6Ti0.5O3 (LNT) ceramics were investigated. LNT ceramics were prepared with conventional solid-state method and sintered at temperatures
about 1,100 °C. The sintering temperature of LNT ceramics with BCu addition could be effectively reduced to 900 °C due to
the liquid phase effects resulting from the additives. The addition of BCu does not induce much degradation in the microwave
dielectric properties. Typically, the excellent microwave dielectric properties of εr = 66, Q × f = 6,210 GHz, and τ
f
= 25 ppm/oC were obtained for the 2 wt% BCu-doped sample sintered at 900 °C. Chemical compatibility of silver electrodes and low-fired
samples has also been investigated. 相似文献
20.
Polycrystalline samples of (Pb0.25Sr0.75)TiO3 (PST75) were prepared by the solid-state reaction method. The effects of firing temperatures and excess PbO on PST75 ceramics
were investigated. The PST75 was calcined between 600 and 1000 °C for 3 h and the sintering temperature ranged between 1050
and 1250 °C for 2 h. The optimized calcination and sintering conditions were identified as 950 and 1250 °C, respectively.
The lattice parameter c increased, while the lattice parameter a decreased with increased firing temperatures. The average particle size and average grain size increased with increased firing
temperatures. After the addition of PbO—excess 0, 1, 3, 5, and 10 wt%—in the PST75 samples, the lattice parameter a decreased. The average particle size and the average grain size increased with the increase of PbO. The porous microstructure
slightly decreased with an increasing amount of PbO—up to 3 wt%—then slightly increased with the higher excess PbO. The density
was improved by adding 3 wt% of excess PbO. A low dielectric loss was observed from the 3 wt% excess PbO sample. 相似文献