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1.
Joining of composite, Al2O3-TiC, with heat-resistant 9Cr1MoV steel, was carried out by diffusion brazing technology, using a combination of Ti, Cu and
Ti as multi-interlayer. The interfacial strength was measured by shear testing and the result was explained by the fracture
morphology. Microstructural characterization of the Al2O3-TiC/9Cr1MoV joint was investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM) with energy-dispersion
spectroscopy (EDS). The results indicate that a Al2O3-TiC/9Cr1MoV joint with a shear strength of 122 MPa can be obtained by controlling heating temperature at 1130°C for 60 min
with a pressure of 12 MPa. Multi-interlayer Ti/Cu/Ti was fused fully and diffusion occurred to produce interfacial layer between
Al2O3-TiC and 9Cr1MoV steel. The total thickness of the interfacial layer is about 100 μm and Ti3AlC2, TiC, Cu and Fe2Ti are found to occur in the interface layer. 相似文献
2.
Jürgen G. Heinrich André Gahler Jens Günster Martin Schmücker Jingxian Zhang Dongliang Jiang Meiling Ruan 《Journal of Materials Science》2007,42(14):5307-5311
The microstructural evolution during direct laser sintering of LSD (Layerwise Slurry Deposition)—samples in the Al2O3–SiO2 system has been investigated. Slurries with a water content of 34 wt.% and a SiO2/Al2O3—ratio of about 3:1 have been used to manufacture layers which—after consecutive drying—have been sintered and laminated by
laser treatment. Densified samples can be obtained with laser irradiances from 190 to 270 kW/cm2 and scan velocities between 35 and 65 mm/s. Elemental mappings of the layers’ cross sections suggest an inhomogeneous phase
distribution in the laser sintered LSD samples with a slight alumina concentration gradient. A lower degree of particle melting
in the bottom region of the layers is plausible due to attenuation of the laser beam intensity. SEM and HRTEM micrographs
show that after a few seconds of laser treatment relictic starting phase, crystalline alumina plus amorphous silica, occur
together with needle like mullite, the latter formed within an amorphous aluminosilicate phase. The resulting phase assemblage
reflects the non-equilibrium conditions which can be expected for short time laser treatments. Mullite nucleation within the
bulk of the liquid phase rather than in the vicinity of the parent alumina phase suggests that dissolution of alumina is the
rate controlling step. Subsequent thermal post treatment in air in a conventional sintering furnace causes an increase of
density to about 96% and leads to additional phase reactions. Amorphous silica transforms into cristobalite and the amount
of alumina is reduced by additional mullite formation. By both coalescence of individual crystals and grain growth the morphology
of the newly formed mullite changes during post heat treatment. 相似文献
3.
A series of glass comprising of SiO2–MgO–B2O3–Y2O3–Al2O3 in different mole ratio has been synthesized. The crystallization kinetics of these glasses was investigated using various
characterization techniques such as differential thermal analysis (DTA), thermo gravimetric analysis (TGA), X-ray diffraction
(XRD), and scanning electron microscopy (SEM). Crystallization behavior of these glasses was markedly influenced by the addition
of Y2O3 instead of Al2O3. Addition of Y2O3 increases the transition temperature, T
g, crystallization temperature, T
c and stability of the glasses. Also, it suppresses the formation of cordierite phase, which is very prominent and detrimental
in MgO-based glasses. The results are discussed on the basis of the structural and chemical role of Y3+ and Al3+ ions in the present glasses. 相似文献
4.
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
5.
Using electrophoretic deposition (EPD), we have produced YSZ individual ceramic coatings and YSZ/Al2O3 composite coatings for a wide range of applications in modern materials research. YSZ and Al2O3 nanopowders were prepared by high-energy physical dispersion techniques, namely, by a laser evaporation–condensation process and electroexplosion of wire, respectively. Stable nonaqueous suspensions for the EPD process have been prepared using YSZ and Al2O3 nanopowders with an average particle size of 11 and 22 nm, respectively. The YSZ/Al2O3 composite coating produced by sintering at 1200°C has been shown to have higher density in comparison with the YSZ individual coating produced at the same temperature. X-ray diffraction characterization showed that the YSZ/Al2O3 composite coating consisted of two crystalline phases: α-Al2O3 (corundum) (42 wt %) and cubic ZrO2〈Y2O3〉 (58 wt %). Quantitative analysis of electron micrographs of the surface of the films showed that the YSZ individual coating produced by sintering at 1200°C had a loose structure and contained pores (9%), as distinct from the composite coating, which had a dense, porefree grain structure. 相似文献
6.
Natsuki Yamasaki Hideaki Miyazawa Manshi Ohyanagi Zuhair A. Munir 《Journal of Materials Science》2012,47(8):3577-3584
The effect of the addition of Al2O3 (50 wt%) on the dehydrogenation of MgH2 was investigated. Composites of the oxide and the hydride were prepared in two ways: by milling the components separately
or by co-milling them together in a gear-driven planetary ball mill for 10 min. The co-milled composite (MgH2–Al2O3) released approximately 90% of the maximum hydrogen storage capacity within 30 min under a pressure of 0.003 MPa at 250 °C.
In contrast, the composite of the separately milled components did not release hydrogen even after 2 h under the same conditions.
BET measurement with nitrogen gas showed a negligible difference in the specific surface areas between the co-milled and separately
milled composites. However, the saturation amount of hydrogen gas for the co-milled composite was 30% larger than that of
the mixture of separately milled hydride and oxide. The activation energy for hydrogen desorption from the co-milled composite,
calculated on the basis of the surface-controlled model was 80 kJ mol−1, a value that is 50 kJ mol−1 lower than that of mixture of the separately milled MgH2 and Al2O3. 相似文献
7.
PVA(Polyvinyl alcohol)/chromium nitrate/aluminum nitrate composite nanofibers were prepared by using sol–gel processing and
electrospinning technique. By high temperature calcinating the above precursor fibers, Cr2O3/Al2O3 composite nanofibers were successfully obtained. The fibers were characterized by XRD, IR, and SEM, respectively. The results
showed that the crystalline phase and the morphology of the fibers depended on the calcination temperatures. 相似文献
8.
L. A. Trusov D. D. Zaitsev P. E. Kazin Yu. D. Tret’yakov M. Jansen 《Inorganic Materials》2009,45(6):689-693
Glasses with nominal compositions 11SrO · 5.5Fe2O3 · 4.5Al2O3 · 4B2O3 (1) and 15SrO · 5.5Fe2O3 · 4.5Al2O3 · 4B2O3 (2) were prepared by rapidly quenching oxide melts between counterrotating steel rollers. The glasses were then heat-treated in the range 650–950°C to produce glass-ceramic samples. The samples were characterized by X-ray diffraction, electron microscopy, and magnetic measurements. The phase composition of the glass-ceramics was determined, and their microstructure and magnetic properties were studied. The annealing temperature was shown to have a strong effect on the coercivity of the materials, which reaches 650 and 570 kA/m for compositions 1 and 2, respectively. 相似文献
9.
Potential multiferroic material, (BiNa)1/2(FeV)1/2O3, synthesized using solid-state route is investigated. The phase formation was confirmed by X-ray diffraction and surface
morphology by scanning electron microscopy (SEM). Structural data reveal the single phase formation corroborated by SEM. The
grain distribution is uniform with an average grain size of 3·6 μm. Electrical properties were investigated in a frequency range (1 kHz–1 MHz) by complex impedance spectroscopy (CIS) technique.
The material showed negative temperature coefficient of resistance (NTCR) reflecting semiconductor behaviour. A.C. conductivity
was found to obey Johnscher’s law. Conductivity mechanism is discussed and activation energy estimated (1·17 eV) for the conduction
process is associated with Fe3 + → Fe2 + variable state. The M–H curve showed the presence of ferromagnetism in the studied material. 相似文献
10.
Dense Al2O3/TiC composite ceramic materials are synthesized using the SHS compaction of mixtures based on TiO2 + Al + C. Mineralizing and heating additives are introduced into compounds. The phase composition and microstructure of combustion products are investigated by x-ray phase analysis, electron microscopy, and microprobe techniques. Two Al2O3 modifications are revealed. Special attention is devoted to the presence of residual graphite. The mechanisms of phase formation and formation of the microstructure of combustion products are considered. 相似文献
11.
E. V. Dudnik A. V. Shevchenko A. K. Ruban V. P. Red’ko L. M. Lopato 《Inorganic Materials》2010,46(2):172-176
We have studied the properties of nanocrystalline ZrO2〈3 mol % Y2O3〉 and 90 wt % ZrO2〈3 mol % Y2O3〉-10 wt % Al2O3 powders prepared via hydrothermal treatment of coprecipitated hydroxides at 210°C. The results demonstrate that Al2O3 doping raises the phase transition temperatures of the metastable low-temperature ZrO2 polymorphs and that the structural transformations of the ZrO2 and Al2O3 in the doped material inhibit each other. 相似文献
12.
Tarcisio E. AndradeJr Carlos Renato Rambo Heino Sieber Antonio E. Martinelli Dulce Maria A. Melo 《Journal of Materials Science》2007,42(14):5426-5430
Al2O3 fibers with a hollow morphology were produced by Al-vapor infiltration-reaction and subsequent oxidation from pyrolysed fibers
of natural sisal. Following pyrolysis, the bio-fiber template was reacted with gaseous Al at 1,400 °C–1,600 °C in vacuum to
form Al4C3. After an oxidation/sintering process at 1,550 °C, the biomorphic Al4C3 fibers were fully converted into Al2O3, maintaining the microstructural features of the native sisal. Phase and microstructural characterization during processing
were evaluated by high temperature X-ray diffractometry and scanning electron microscopy, respectively. Thermo-analyses were
performed in the Al4C3 samples in order to estimate the reactions and the weight change during the oxidation step. 相似文献
13.
R. Awad A. I. Abou Aly M. Kamal M. Anas 《Journal of Superconductivity and Novel Magnetism》2011,24(6):1947-1956
Cu0.5Tl0.5Ba2Ca2−x
Pr
x
Cu3O10−δ
superconducting samples, with 0≤x≤0.15, were prepared by a single-step solid state reaction on a form of rectangular bar. The prepared samples were characterized
using X-ray powder diffraction (XRD) and scanning electron microscope (SEM). The room temperature Vickers microhardness was
measured at different loads (0.25–3 N). The experimental results were analyzed using Meyer’s law, Hays–Kendall approach, elastic/plastic
deformation model, proportional specimen resistance model, and the indentation-induced cracking (IIC) model. Surprising results
were obtained and showed that all samples in the form of rectangular bars exhibited reverse indentation size effect in contrary
with those in the form of discs. Vickers microhardness values were decreased as Pr-content increased that consisting with
the porosity results. Furthermore, the Young’s modulus was determined using the dynamic resonance technique. A relation between
Young’s modulus (E) and Vickers microhardness (H
V) was obtained. 相似文献
14.
W. Skoneczny 《Materials Science》2010,46(2):276-281
The paper presents the characterization of obtaining Al2O3 oxide layers on AlMg2 aluminum alloy as a result of hard anodizing by the electrolytic method in a three-component electrolyte. The Al2O3 layers obtained on the AlMg2 alloy in the three-component SBS electrolyte were subjected to detailed microstructural investigations (by means of a scanning
electron microscope). By using X-ray diffraction, the phase compositions of obtained oxide layers were examined. It was found
that the Al2O3 oxide layers obtained via hard anodizing in a three-component electrolyte are amorphous. The chemical composition of the
Al2O3 layers is presented and compared with the results of stechiometric calculations for the Al2O3 layer. Surface morphologies of the obtained oxide layers are characterized and discussed in nano- and microscopic scales.
The surface morphologies of the layers obtained have a significant influence on their properties, including their susceptibility
to further modification (e.g., to incorporation of graphite), their wear resistance, and the capacity for sorption of lubricants. 相似文献
15.
Hogyoung Kim Dong Ha Kim Sungyeon Ryu Byung Joon Choi 《Journal of Materials Science: Materials in Electronics》2017,28(20):14974-14980
Using the temperature dependent current–voltage (I–V) measurements, the electrical properties of Au/nonpolar m-plane ZnO Schottky diodes with an Al2O3 interlayer prepared by atomic layer deposition (ALD) was investigated. With an Al2O3 interlayer, it was found to have higher barrier heights and higher rectifying ratio. Modified Richardson plots produced effective Richardson constants of 30.0 and 37.6 Acm?2K?2 for the samples with and without Al2O3 interlayer, respectively, which are similar to the theoretical value of 32.0 Acm??2K??2 for n-ZnO. Scanning transmission electron microscope (STEM) results showed that the oxygen-contained layer on ZnO surface degraded the film quality of subsequently deposited Al2O3 layer. In addition, the inter-diffusion of Au and Al atoms into ZnO subsurface region also modulated the electrical properties of Au/ZnO contacts. 相似文献
16.
Abhijit Kar Sudipta Mandal Rabindra N. Ghosh Tamal K. Ghosh Ajoy Kumar Ray 《Journal of Materials Science》2007,42(14):5556-5561
Diffusivities of Ti, Cu, Al and Ag in the interface of Al2O3–Al2O3 braze joints using Ag–Cu–Ti active filler alloy, have been calculated by Matano–Boltzman method. The Matano plane has been
identified for each elemental diffusion at various brazing temperatures. The diffusivities of Ag, Cu and Al are almost insignificant
on formation of interface during brazing, whereas the diffusivity of Ti changes significantly with the brazing temperature
and controls the formation of different reaction product in the interface. Presence of TiO and Ti3Cu3O phases in the interface has been confirmed by transmission electron microscopy (TEM). 相似文献
17.
Haibo Yang Jingjing Dai Ying Lin Ning Han Xiao Liu Jingjing Wang 《Journal of Materials Science: Materials in Electronics》2017,28(15):10853-10861
Polyaniline (PANI)/CoFe2O4/Ba3Co2Fe24O41 composite was prepared by an in-situ polymerization method. The phase structure, morphology and magnetic properties of the as-prepared PANI/CoFe2O4/Ba3Co2Fe24O41 composite were characterized by XRD, FT-IR, SEM, TEM, and VSM, respectively. The microwave absorption properties of the composite were investigated by using a vector network analyzer in the 2–18 GHz frequency range. The results show that the maximum reflection loss value of the PANI/CoFe2O4/Ba3Co2Fe24O41 composite reaches ?30.5 dB at 10.5 GHz with a thickness of 3 mm and the bandwidth of reflection loss below ?10 dB reaches up to 1.2 GHz. The excellent microwave absorption properties of the as-prepared PANI/CoFe2O4/Ba3Co2Fe24O41 composite due to the enhanced impedance match between dielectric loss and magnetic loss. 相似文献
18.
A novel method was introduced to prepare open-cell Al2O3–ZrO2 ceramic foams with controlled cell structure. This method used epispastic polystyrene (EPS) spheres to array ordered templates
and centrifugal slip casting in the interstitial spaces of the EPS template to obtain cell struts with high packing density.
Aqueous Al2O3–ZrO2 slurries with up to 50 vol.% solid contents were prepared and centrifuged at acceleration of 2,860g. The effect of the solid contents of slurries on segregation phenomena of different particles and green compact uniformity
were investigated. In multiphase system, the settling velocities of Al2O3 and ZrO2 particles were calculated. Theory analysis and calculated results both indicated segregation phenomenon was hindered for
slurries with 50 vol.% solid content. The cell struts of sintered products had high green density (61.5%TD), sintered density
(99.1%TD) and homogeneous microstructures after sintered at 1,550 °C for 2 h. The cell size and porosity of Al2O3–ZrO2 ceramic foams can be adjusted by changing the size of EPS spheres and the load applied on them during packing, respectively.
When the porosity increased from 75.3% to 83.1%, the compressive strength decreases from 3.82 to 2.07 MPa. 相似文献
19.
This article reports on the preparation, characterization and experimental investigation of polyamide 6 (PA6) reinforced with alumina oxide (Al2O3) and graphite composites. The test specimens were prepared in an injection-moulding machine by varying the weight proportions of Al2O3 and graphite particles blended with PA6. The tribological properties of the composites were observed by using pin-on-disc wear test rig under dry sliding conditions. The worn surfaces of the composites were examined using scanning electron microscope. The addition of Al2O3 and graphite significantly enhanced the tribological properties of PA6. The PA6 containing 30 wt% Al2O3 and 20 wt% graphite revealed the best tribological behaviours due to the stronger interfacial bonding characteristics with improved wear resistance. Further, the thermal stability of Al2O3 and graphite particles was studied through thermogravimetric analysis test. It was also found that further addition of Al2O3 and graphite in PA6 had no significant improvement in wear resistance, the co-efficient of friction and heat generation. 相似文献
20.
An as-received ultrafine-grained Cu powder and four nanostructured Cu–(2.5–10) vol%Al2O3 composite powders produced by high-energy mechanical milling of mixtures of the Cu powder and an Al2O3 nanopowder were consolidated using warm powder compaction followed by open die powder compact forging. The circular discs
produced in the experiments achieved full densification. Tensile testing of the specimens cut from the forged discs showed
that the Cu-forged disc had a fairly high yield strength of 330 MPa, UTS of 340 MPa and a plastic strain to fracture of 15%,
but the Cu–Al2O3 composite-forged discs did not show any macroscopic plastic yielding. The fracture strength of the composite-forged discs
decreased almost linearly with the increase of the volume fraction of Al2O3 nanoparticles. This study shows that a high level of consolidation of the ultrafine-grained Cu powder and the nanostructured
Cu–2.5 vol%Al2O3 composite powder has been achieved by warm powder compacting at 350 °C and powder compact forging at 500 and 700 °C. However,
this is not true for the nanostructured Cu–(5, 7.5 and 10) vol%Al2O3 composite powders, possibly due to their higher powder particle hardness at elevated temperatures in the range of 350–800 °C. 相似文献