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1.
Porous anodic alumina (PAA) template is widely used to prepare ordered nanostructure materials. But conventional PAA templates have been restricted for application in micro-electro-mechanical systems (MEMS) technology due to limitations such as shape and brittleness. In this article, a novel process of fabricating alumina porous template based on silicon wafer is described. Porous alumina films were formed by two-step anodization of aluminum layers sputter deposited on silicon wafer. The pore diameters range from 80 to 100 nm. The Pilling–Bedworth ratio of Al/Al2O3 was measured and calculated. Thickness of PAA template can be precisely controlled. This research provides an effective tool to nanofabrication in MEMS technology. 相似文献
2.
Dongdong Li Chuanhai Jiang Jianhua Jiang Xin Ren 《Materials Chemistry and Physics》2008,111(1):168-171
A simple and cost effective method for fabricating long-range ordered porous anodic alumina (PAA) membranes is presented, which explores a self-ordering regime with controllable interpore distances over a large scale (300–360 nm). The cohesive force at the hemi-spherical scallop/cell wall (HS/CW) interface is weaker than the other locations. When the PAA membranes were immersed in H3PO4 solution, regular cheese-like hexagonal patterns have been propagated at the cell boundaries. With increased etching time, numerous pores were observed at triple points where three cells met. The distinct fracture and etching behaviors in PAA can be ascribed to the intense ionic transport accompanied by the volume expansion in the barrier region under high electric field. 相似文献
3.
The poor hardness of zirconia-toughened alumina (ZTA) with 5?wt-% CeO2 (ZTA5CeO2) ceramic has limited its applications as a cutting insert. Therefore, in this work, the possibility of MgO nanoparticles (20?nm) as reinforcement to ZTA5CeO2 ceramics was investigated. Mgo nanoparticles with different weight percentages (0-2?wt-%) were added to ZTA5CeO2 ceramics. ZTA5CeO2 with 0.5?wt-%MgO showed the highest fracture toughness of 9.14?MPa.√m. The addition of 0.5?wt-%MgO nanoparticles showed the excellent role of MgAl11CeO19 grains as a crack deflector, which consequently produced a reasonable hardness value of 1591?HV and lowered the wear areas to 0.0528?mm2. 相似文献
4.
The effect of calcination on the characteristics and sintering behaviour of zirconia-toughened alumina (ZTA) composite powders has been investigated. TiO2 was selected as an additive to promote the sinterability of ZTA powders. The starting materials were Al2O3 powder, Zr(OC3H7)4 and Ti(OC3H7)4, and homogeneous ZTA powder containing Zr-O-Ti bonding was prepared. Calcination affected the tetragonalmonoclinic phase transformation temperature of ZrO2 crystallizing from the gels. Calcination improved the densification rate of ZTA powder compact during sintering, which was attributed to the optimal ZrO2 particle size and distribution on the surface of alumina. A ZTA specimen with high bulk density and high tetragonal ZrO2 content was obtained under the conditions of 850°C/1 h calcination and 1500°C/1 h sintering. 相似文献
5.
Juanjian Ru Han He Yehua Jiang Rong Zhou Yixin Hua 《Advanced Powder Technology》2019,30(10):2160-2168
In order to solve the cast-infiltration difficulty and low interface bonding strength of ZrO2-toughened Al2O3 (ZTA) powders reinforced high manganese steel (HMS) matrix composite, uniform and continuous Ni-encapsulated ZTA powders (ZTAp@Ni) as reinforced phase are fabricated by electroless deposition assisted with ionic liquid additive. The effects of Ethaline concentration, temperature, ZTA concentration and deposition times on the morphology of ZTAp@Ni have been investigated. Experimental results show that the thickness of Ni coating is about 7–10 μm, and there is no casting crack or shrink on the composite, so compact bonding between ceramic and matrix is obtained. In addition, the impact abrasive wear resistance testing demonstrates that the performance of ZTAp@Ni reinforced HMS composite is superior to that of matrix. On the basis of experimental analysis, a schematic illustration of the cast-infiltration process is put forward. It implies that Ni-encapsulated ZTA can be wetted with molten HMS matrix to form a ZTA/Al2NiO4-Al2MnO4/Fe interface layer through Ni diffusion and reactive wetting. The interdiffusion of Ni and other elements at ZTA interface layer can reinforce the interfacial bonding strength to form an interface layer between metal and hard phases. 相似文献
6.
M. Ksiazek N. Sobczak B. Mikulowski W. Radziwill B. Winiarski M. Wojcik 《Journal of Materials Science》2005,40(9-10):2513-2517
The subject of the work was to study the effect of Ti thin film on alumina ceramic on mechanical strength and fracture character of Al2O3/Al/Al2O3 joints. The joints were formed by liquid state bonding of alumina substrates covered with titanium thin film of 800 nm thickness using Al interlayer of 30μm thickness at temperature of 973 K in a vacuum of 0.2 mPa for 5 min. The bend strength was measured by four–point bending test at room temperature. Scanning and transmission electron microscopy were applied for detailed characterization of interface structure and failure character of fractured joint surfaces. Result analysis has shown that application of the Ti thin film on alumina leads to decrease of bond strength properties of Al2O3/Al/Al2O3 joints along with the change either of structure and chemistry of interface or of failure character. 相似文献
7.
Nai-Qin Zhao Xiao-Xue Jiang Chun-Sheng Shi Jia-Jun Li Zhi-Guo Zhao Xi-Wen Du 《Journal of Materials Science》2007,42(11):3878-3882
In this paper, two-step anodization was used to obtain porous anodic alumina (PAA) films, which are widely used as the temples
to fabricate nanomaterials. Effects of anodizing conditions such as anodizing voltage and the concentration of electrolyte
on steady current density (I
s) and anodic alumina structure were investigated for oxalic acid as an electrolyte. The result shows that I
s is dependent on anodizing voltage exponentially. The relationship between the concentration of electrolyte and the pore diameter
is almost linear, while there is no effect on inner-pore distance. At different anodizing voltage, the effect degree of the
concentration of oxalic acid on the pore diameter is various. In oxalic acid electrolyte with given concentration matching
with a specifically anodizing voltage, optimal nano-pores arrangements can be obtained. The higher voltage induces the collapse
of thin inner wall and disordered alumina nanowires (ANWs) were formed. 相似文献
8.
《Science and Technology of Advanced Materials》2003,4(4):269-276
New processes for the preparation of nanostructure on glass surfaces have been developed through anodic oxidation of sputtered aluminum. Aluminum thin film sputtered on a tin doped indium oxide (ITO) thin film on a glass surface was converted into alumina by anodic oxidation. The anodic alumina gave nanometer size pore array standing vertically on the glass surface. Kinds of acids used in the anodic oxidation changed the pore size drastically. The employment of phosphoric acid solution gave several tens nanometer size pores. Oxalic acid cases produced a few tens nanometer size pores and sulfuric acid solution provided a few nanometer size pores. The number of pores in a unit area could be changed with varying the applied voltage in the anodization and the pore sizes could be increased by phosphoric acid etching. The specimen consisting of a glass substrate with the alumina nanostructures on the surface could transmit UV and visible light. An etched specimen was dipped in a TiO2 sol solution, resulting in the impregnation of TiO2 sol into the pores of alumina layer. The TiO2 sol was heated at ∼400 °C for 2 h, converting into anatase phase TiO2. The specimens possessing TiO2 film on the pore wall were transparent to the light in UV–Visible region. The electro deposition technique was applied to the introduction of Ni metal into pores, giving Ni nanorod array on the glass surface. The removal of the barrier layer alumina at the bottom of the pores was necessary to attain smooth electro deposition of Ni. The photo catalytic function of the specimens possessing TiO2 nanotube array was investigated in the decomposition of acetaldehyde gas under the irradiation of UV light, showing that the rate of the decomposition was quite large. 相似文献
9.
Zirconia-toughened alumina (ZTA) ceramics 总被引:2,自引:0,他引:2
In the previous decade, a considerable amount of work has been done on the alumina-zirconia ceramic composite system with
a particular emphasis on improving the mechanical properties utilizing the recognized toughening mechanisms. Zirconia-toughened
aluminas (ZTA) can be regarded as a new generation of toughened ceramics; for example, a toughness of >12 MPa m0.5 has been obtained, compared with 3 MPa m0.5 for commercial alumina ceramics. The fracture strength of ZTA is also greatly in excess of that for alumina. The mechanical
properties of ZTA are critically dependent on their microstructures, which can be designed in terms of specific applications
and controlled by means of powder preparation and densification processes. This review also includes details of the possible
future development of ZTA; these are expected to involve the development and measurement of the mechanical properties for
high-temperature engineering applications. 相似文献
10.
Satoru Inoue Song-Zhu Chu Kenji Wada Di Li Hajime Haneda 《Science and Technology of Advanced Materials》2013,14(4):269-276
New processes for the preparation of nanostructure on glass surfaces have been developed through anodic oxidation of sputtered aluminum. Aluminum thin film sputtered on a tin doped indium oxide (ITO) thin film on a glass surface was converted into alumina by anodic oxidation. The anodic alumina gave nanometer size pore array standing vertically on the glass surface. Kinds of acids used in the anodic oxidation changed the pore size drastically. The employment of phosphoric acid solution gave several tens nanometer size pores. Oxalic acid cases produced a few tens nanometer size pores and sulfuric acid solution provided a few nanometer size pores. The number of pores in a unit area could be changed with varying the applied voltage in the anodization and the pore sizes could be increased by phosphoric acid etching. The specimen consisting of a glass substrate with the alumina nanostructures on the surface could transmit UV and visible light. An etched specimen was dipped in a TiO2 sol solution, resulting in the impregnation of TiO2 sol into the pores of alumina layer. The TiO2 sol was heated at ~400 °C for 2 h, converting into anatase phase TiO2. The specimens possessing TiO2 film on the pore wall were transparent to the light in UV–Visible region. The electro deposition technique was applied to the introduction of Ni metal into pores, giving Ni nanorod array on theglass surface. The removal of the barrier layer alumina at the bottom of the pores was necessary to attain smooth electro deposition of Ni. The photo catalytic function of the specimens possessing TiO2 nanotube array was investigatedin the decomposition of acetaldehyde gas under the irradiation of UV light, showing that the rate of the decomposition was quite large. 相似文献
11.
《材料科学技术学报》2015,(8)
Instrumented and Vickers indentation testing and microstructure analysis were used to investigate zirconia toughened alumina(ZTA) and silicon carbide(SiC).Several equations were studied to relate the Vickers indentation hardness,Young's modulus and crack behavior to the fracture toughness.The fracture in SiC is unstable and occurs primarily by cleavage leading to a relatively low toughness of 3 MPa m~(1/2),which may be inappropriate for multi-hit capability.ZTA absorbs energy by plastic deformation,pore collapse,crack deviation and crack bridging and exhibits time dependent creep.With a relatively high toughness around 6.6 MPa m~(1/2),ZTA is promising for multi-hit capability.The higher accuracy of mediar equations in calculating the indentation fracture toughness and the relatively high c/a ratios above 2.5suggest median type cracking for both SiC and ZTA.The Young's modulus of both ceramics was most accurately measured at lower indentation loads of about 0.5 kgf,while more accurate hardness and fracture toughness values were obtained at intermediate and at higher indentation loads beyond 5 kgf respectively.A strong indentation size effect(ISE) was observed in both materials.The load independent hardness of SiC is 2563 HV,putting it far above the standard armor hardness requirement of 1500 HV that is barely met by ZTA. 相似文献
12.
A low temperature and low pressure bonding process for alumina and 316L austenitic stainless steel has been developed using a titanium/molybdenum laminated interlayer. The intermetallic compounds of Ti3Al (or Ti2/Al) and TiAl were formed at the alumina/titanium interface on bonding at above 1273 K. The activation energy of the layer growth was about 142 kJ mol–1. The construction of Al2O3/Ti/Mo/steel gave the most stable joints. The highest tensile strength was above 60 MPa with a titanium 0.4 to 0.6mm thick/molybdenum 0.4 to 0.5 mm thick interlayer on bonding at 1273 K for 3 h under pressure of 12 MPa. 相似文献
13.
地质聚合物因其优异的力学性能、化学稳定性、耐高温等性能,在建筑、耐火、有毒有害离子固化等领域备受关注。本研究通过压汞法(MIP)、FT-IR、SEM测试分析了粉煤灰-偏高岭土基地质聚合物的孔径分布、凝胶结构及断裂方式,探讨了偏高岭土掺量对其结构与性能的影响。结果表明:地质聚合物的孔径分布随水灰比的调整存在大范围的变化,最可几孔径由几个纳米到100nm。当水灰比固定时,偏高岭土掺量由25%(质量分数)增加至60%(质量分数),地质聚合物中气孔均以凝胶孔为主,最可几孔径由40nm减小至26nm,总气孔率无显著变化,但有害孔的孔隙率明显由3.6%降至0.09%。偏高岭土掺量的增加,提高了凝胶相多元环结构中[AlO_4]的数目,使材料呈均匀化、致密化结构,尤其是改善了未反应粉煤灰颗粒与凝胶相之间的界面结合。偏高岭土掺量为60%时,裂纹在粉煤灰颗粒堆积气孔或薄弱界面周围的快速扩展得到有效控制,抗压强度显著提高,7d龄期时强度达到75.5 MPa。 相似文献
14.
A novel growth method for diamond nano-tips on porous anodic alumina (PAA) by hot filament chemical vapor deposition has been investigated for the first time. Before diamond film deposition could be carried out, nano-diamond particles were deposited onto the pore surface of PAA by electrophoretic deposition at the nucleation sites. Diamond nano-tips were then successfully formed by the shape of porous alumina. The results show that a diamond nano-tip with a smaller radius has superior effects of field emission. Its threshold field and current density are 1.2 V μm(-1) and 4.0 mA cm(-2), respectively, for the case of a tip radius of about 20-30 nm. 相似文献
15.
Joints of Al2O3/Al/Al2O3 are formed by liquid-state bonding of alumina substrates covered with thin titanium film of 800 nm thickness using an Al interlayer of 30 or 300 μm at 973 K under a vacuum of 0.2 mPa for 5 min and an applied pressure of 0.01 MPa. The bond strength of the joints is examined by a four-point bend testing at room temperature coupled with optical, scanning and transmission electron microscopy. Results show that: (i) bonding occurs due to the formation of a reactive interface on the metal side of the joint with the presence of Al3Ti precipitates (ii) a decrease in Al layer thickness leads to stronger Al2O3/Al/Al2O3 bonds accompanied by a change of both the distribution of reaction products (Al3Ti) in the region of the interface and the failure surface characteristics. 相似文献
16.
《Nanostructured Materials》1996,7(8):835-845
Nanoscaled Al2O3-powders can be employed for diffusion bonding of alumina ceramics. In order to accomplish bonding of the ceramics, Al2O3-nanopowder with a median particle size of 14 nm in diameter is sandwiched between two commercial microcrystalline corund discs, followed by uniaxially hot compressing of the assembly in vacuum at 80 MPa and 1100 °C for 2 h. Scanning electron microscopic investigations reveal a nanocrystalline structure of the joint with a mean grain size of about 50 nm in diameter and extensive consolidation of the powder without substantial shrinkage void formation. Microhardness measurements across the interface yield a value of 200 HV. In order to achieve complete densification and strength enhancement of the joint material, the sample is subsequently sintered at 1500 °C and 1600 °C for several hours in air. It was found that the hardness of the joint depends strongly on the porosity content and/or grain size and that a hardness of 1700 HV is obtained when both a mean particle size of about 1 μm and complete densification of the joint is achieved. The results show for the first time that Al2O3-nanopowders are suitable for diffusion bonding of alumina ceramics. Possible mechanisms are discussed. 相似文献
17.
Terbium doped YAlO3 composites were fabricated by the co-precipitation method in a porous anodic alumina (PAA) films grown on silicon at three different Tb concentrations: 0.23, 0.87 and 2.11 at.%. To investigate the emission thermal quenching for all samples, we measured the emission spectra as a function of temperature in the range from 10 up to 500 K at 266 and 488 nm excitation wavelengths. Based on obtained results we proposed the physical model explaining the mechanism of Tb3+ emission quenching in YAlO3 composites deposited into PAA film. 相似文献
18.
通孔氧化铝模板的强脉冲电化学剥离研究 总被引:5,自引:0,他引:5
利用0.3mol·L-1的草酸电解液,采用二步恒压阳极氧化法(30-50V)在高纯铝片上获得了高度有序的多孔氧化铝模板,利用HClO4-CH3OH混合溶液为电解液,利用还原反应产生的气体压力将多孔氧化铝膜从铝基底上剥离,获得了大面积(2cm×2cm)均匀无裂的多孔氧化铝的通孔模板,厚度为30-100μm;分析了影响孔径和阻挡层的因素和模板电化学剥离的机理;与其他剥离方法相比,该方法具有工艺简单、周期短、模板溶解少、无污染、模板韧性好, 可获得大面积均匀无裂膜,在纳米结构组装体系研究方面具有重要的实用价值. 相似文献
19.
《Composites》1994,25(10):906-912
Fracture in particulate-reinforced metal-matrix composites is initiated by particulate cracking and interface decohesion, and crack propagation occurs through the matrix, particulate and interface. A ‘critical stress partition’ model is described which considers the proportions of matrix, particulate and interface for which the fracture stress is exceeded. Tensile tests and microhardness measurements are reported for SiC/Al metal-matrix composites having particulate volume fractions of 0–20%. Measurements of the fractions of cracked and interface-debonded particulate before and after final fracture are combined with the fracture model to calculate the interface strength, σint′. The values of σint′ obtained are 469 MPa for uncoated SiC particulate and 438 MPa for particulate coated with a thin layer of Al2O3 to prevent interface reaction. The tensile results indicate that the weaker interfaces promote interface debonding and increase percent elongation. 相似文献
20.
Microstructure and fracture toughness of nickel particle toughened alumina matrix composites 总被引:4,自引:0,他引:4
Al2O3-Ni composite materials have been made by a hot pressing technique. Two composite microstructures, i.e. a dispersive distribution of nickel particles and a network distribution of nickel particles in an alumina matrix, have been produced. The fracture toughness of the composite materials has been measured by a double cantilever beam method. Both composites are tougher than the virgin alumina matrix. The fracture toughness of the composite with a network microstructure is much higher and has a more desirable R-curve behaviour than the composite with a microstructure of dispersed particles. For the particulate dispersion microstructure, the main limitation to toughening is the lack of plastic deformation of the ductile nickel due to the pull out of nickel particles, indicating weak bonding at the Al2O3/Ni interface. For the network microstructure composite, the gauge length of the ductile phase is much larger, allowing the ductile nickel to stretch to failure between the crack faces. A large extent of nickel plastic deformation has been observed, and the weak bonding at the Al2O3/Ni interface can promote partial debonding and contribute further to toughening. 相似文献