Al2O3 Fibers Research Articles

Bio-inspired fabrication of hierarchically porous Mg–Al composites for enhanced BSA adsorption properties

In this paper, hierarchically porous LDHs/Al2O3 composites are successfully fabricated in a large scale by combining the biological template method (for morph-Al2O3) and hydrothermal method (for LDHs). The morph-Al2O3 with fiber structure is prepared by template-directed synthesis employing cotton fibers as bio-templates. Then, the 2D LDHs nanoplatelets are fabricated into complex 3D architectures by in situ growth on surface Al2O3 fibers in a closed hydrothermal system, forming the hierarchical macro-mesoporous LDHs/Al2O3 composites. The N2 sorption analyses confirmed that the calcined composites have uniform mesochannels (7.58 nm), high surface area (292.51 m2/g), and large pore volume (0.55 cm3/g). Meanwhile, the macroporous structures fabricated by LDH nanoplatelets can be directly observed in morphology analysis. In LDHs crystal growth process, the controlling mechanism was discussed in detail according to the crystal growth kinetics and thermodynamics. As compared to calcined LDHs particles, the calcined composites have excellent adsorption properties. The efficient adsorption (90.27%) of BSA from solution suggests that the composites are potentially useful in BSA bioseparation.

Manufacturing and damage analysis of filler reinforced epoxy-based composites

Epoxy matrix composites reinforced with very fine particles were developed and scratch resistance (dynamic tests) was evaluated. Fracture test results were compared depending on the composition (static compression tests). They were conducted for their designed life. In order to improve the toughness of the composites while maintaining a constant volume fraction of different reinforcements, three basic different epoxy matrix composites were manufactured using basically fine Al2O3 and glass fibre as reinforcements (<1 µm) and fine rubber powder (variable between 5–10 µm), respectively. All of the composites were fabricated by mixing the filler particles and epoxy together stirring for 4 h and then placed in an ultrasonic dispersion for 1 h. Microstructural evolution and other detailed damage analyses are carried out on the scanning electron microscope (SEM).

Preparation and Properties of (SiCp+Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3f&lt;/sub&gt;)/7075Al Composites by Pressure Infiltration

(SiCp+Al2O3f)/7075Al composites as potential friction materials were prepared in this paper by pressure infiltration and some related properties were compared with traditional friction materials. The addition of Al2O3 fiber to SiC preform could contribute to enhance compressive strength of the preform as well as tensile strength of the composites. The tensile strength of as-fabricated composites with 35vol%SiCp + 15vol% Al2O3f could reach 402MPa and the friction coefficient is about 0.4 and the thermal conductivity is higher than 120W/mK. Compared with traditional materials such as nodular cast iron, the composites exhibit better comprehensive properties and are suitable as brake materials for automobile.

Modeling of the mechanical behavior of fiber-reinforced ceramic composites using finite element method (FEM)

Modeling of the mechanical behavior of fiber-reinforced ceramic matrix composites (CMC) is presented by the example of Al2O3 fibers in an alumina based matrix. The starting point of the modeling is a substructure (elementary cell) which includes on a micromechanical scale the statistical properties of the fiber, matrix and fiber-matrix interface and their interactions. The numerical evaluation of the model is accomplished by means of the finite element method. The numerical results of calculating the elastic modulus of the composite dependance on the quantity of the fibers added and porosity was compared to experimental values of specimens having the same composition.

Optical and spectroscopic characterization of Er3+–Yb3+co-doped tellurite glasses and fibers

Abstract Optical and spectroscopic properties of Er 3+ –Yb 3+ co-doped TeO 2 –WO 3 –Nb 2 O 5 –Na 2 O–Al 2 O 3 glasses and fibers were investigated. Emission spectra and fluorescence lifetimes of 4 I 13/2 level of Er 3+ ion as a function of rare earth concentration and fiber length were measured in glasses. Results show that the self-absorption effect broadens the spectral bandwidth of 4 I 13/2 → 4 I 15/2 transition and lengthens the lifetime significantly from 3.5 to 4.6 ms. Fibers were fabricated by the rod-in-tube technique using a Heathway drawing tower. The emission power of these Er 3+ –Yb 3+ co-doped Step Index Tellurite Fibers (SITFs; lengths varying from 2 to 60 cm) were generated by a 980 nm diode laser pump and then the emission power spectra were acquired with an OSA. The maximum emission power spectra, within the 1530–1560 nm region, were observed for fiber lengths ranging from 3 to 6 cm. The highest bandwidth obtained was 108 nm for 8 cm fiber length around 1.53 µm.

Template-controlled fabrication of hierarchical porous Zn–Al composites with tunable micro/nanostructures and chemical compositions

The properties of materials are largely determined by the microstructures and components of materials. The design of layered double hydroxide (LDH) based composites has garnered much interest as a way of fabricating novel multiscale architectures with tunable micro/nanostructures and chemical compositions. The present study aims at exploiting the Zn–Al composites for controlled synthesis of multi-scale structures and multi-component materials. Firstly, microscaled Al2O3 fibers are successfully fabricated via a simple, convenient, and cost-effective biotemplate method employing paper fibers as bio-templates. Then, the multi-scale architectures are designed by an in situ growth method, which involves direct growth of nanoscaled LDH platelets on the surfaces of Al2O3 fibers. Finally, the multi-component LDH based materials are prepared based on the controlled crystal growth of LDHs and ZnO. The microstructure, morphology, and textural properties of the as-prepared samples are characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption/desorption. The experimental results show that the longer reaction times are favorable for the crystal growth of LDHs, and the higher hydrothermal temperatures are favorable for the formation of ZnO. This study shows that the design of multi-scale structures and multi-components Zn–Al composites can be extended for the preparation of other hierarchical LDH based materials with controlled morphological and tunable chemical compositions for separation, catalysis, adsorption, sensor, and optical applications.

Porous YSZ Ceramics Reinforced by Different Kinds of Fibers

Porous YSZ ceramics reinforced by different fibers were prepared by gel‐casting with 15% solid content and pressureless sintering. The four kinds of fibers (mullite, aluminosilicate, Al2O3, and YSZ fibers) were added into the YSZ ceramics with the same 10% vol content. After sintered at 1500°C for 2 h, aluminosilicate and mullite fibers could not be found in the samples of porous YSZ ceramics, which showed they reacted with YSZ ceramics at high temperature, while YSZ and Al2O3 fibers still kept perfect after sintering. Furthermore, the influences of fiber content, sintering temperature, porosity of matrix materials on compressive strength and porosity of the porous YSZ ceramics were studied. The results showed that Al2O3 fiber showed more obvious reinforcing effect than YSZ fiber on porous YSZ ceramics. The fiber‐reinforcing effects depend on fiber content, sintering temperature, and porosity of matrix materials. The fiber addition can improve the shrinkage behavior of porous ceramics during sintering and strengthen the skeleton of porous ceramics.

Effect of SiO2 amount on microstructures and tensile properties of alumina short fiber-reinforced composites by low-pressure infiltration method

The tensile properties of two types of alumina (Al2O3 and Al2O3–SiO2) and short fiber-reinforced A366 alloy composite created by low-pressure infiltration have been studied. The applied pressure and temperature of molten alloy are 0.4 MPa and 1073 K, respectively. The composite containing 10 vol.% of fiber preform was sectioned and the microstructure was observed by scanning electron microscopy and energy dispersive X-ray spectroscopy. Tensile properties of Al2O3 fiber-reinforced A366 alloy composites were investigated, in conjunction with investigation of effects of amounts of SiO2 sol added as binder to fabricated preform and effects of changed chemical composition of Al2O3 fiber. The composite with SiO2 sol of 8 mass% has higher relative density in comparison with composite with SiO2 sol of 2 mass%. SiO2 sol raised the relative density of composite by the reaction with aluminum. In addition, the ultimate tensile strength of composite which has Al2O3 fiber-reinforced A366 alloy composite containing SiO2 sol of 8 mass% was approximately 20% higher than that of Al2O3–SiO2 fiber-reinforced A366 alloy composite containing SiO2 sol of 8 mass%.

Mechanism of Synthesizing Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;/Fe-Al Composites with Nano Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Fibers by &lt;i&gt;In Situ&lt;/i&gt; Process

In-situ composite of Al2O3/Fe-Al with Al2O3 fibers were prepared by partial oxidation of oxygen to Fe powder and Al power, crystal phase composition and elemental composition were analyzed by XRD, NORAN. The results indicated that, the crystal composition is determined by Aluminum content, when the content is enough, FeAl3, Al and Al2O3 will be gain, on the contrary, Fe2Al, FeAl, Fe3Al and Al2O3 will be gain; Al2O3 fibers were synthesized via VLS process, the quantity of Al2O3 fibers increased with the Al content, the whisker’s diameter was improved with increasing of sintering temperature.

Study of biomorphic alumina fibers derived from natural silk template and their heat-insulating properties

Many natural materials possess unique and aesthetic microstructures following a long-term evolutionary process. In this study, we succeeded in utilizing these microstructures, i.e., using natural silk fibers as a template to produce biomorphic Al2O3 fibers. Silk fibers were first immersed in an AlCl3 solution and then sintered in air at high temperatures to produce the final Al2O3 fibers. Their microstructures and thermal conductivity were then analyzed. The results showed that these synthesized fibers retained the original morphologies of silk. These Al2O3 fibers were hollow and hence possessed better heat-insulating properties than did Al2O3 fibers prepared by traditional methods.

Aliphatic Polyamide-66 Filled with Alumina Fibers

Two-component compositions of aliphatic polyamide-66 and Al2O3 fibers were investigated. It was found that the components mutually affected their crystalline structures in manufacturing composites by the method of thermal compaction. A decrease in the roentgen degree of crystallinity was revealed upon crystallization of polyamide from a melt in the presence of Al2O3 fibers. By using the methods of infrared spectroscopy and differential thermal analysis, it was established that the physical and chemical interaction at the filler-polymer interface led to the formation of a rigidly bonded structure of polyamide in the boundary zone. It was found that the content of Al2O3 fibers in the polyamide matrix affected the deformation, electric, and physicomechanical properties of the pressed composites ambiguously. The sharp increase in the mechanical characteristics of the composites observed upon filling the polyamide-66 with Al2O3 fibers in the amount of ≥ 30 wt.% reached its maximum at 70 wt.%, when practically the entire polymer was in the surface layer.

Preparation and corrosion resistance of the micro-arc oxidation coating on Al2O3f/ZL109 composites

A ceramic layer was prepared on the surface of Al2O3f/ZL109 composites by means of micro-arc oxidation (MAO) technique. The surface morphology and phase constituent of the ceramic layer were analyzed using scanning electron microscope and X-ray diffraction. The polarization curves of the composites before and after MAO treatment were measured and analyzed. The results showed that after Al2O3f/ZL109 composites were treated using MAO technique in silicate solution, the ceramic layer formed, and it was composed of Al, Si, and mullite phase. Al and Si came from Al alloy matrix of the composites, and the mullite phase formed in process of MAO. Al2O3 fiber in the composites affects the electric conductivity of the composites, the MAO reaction is promoted, and the ceramic layer forming on the composite material side is slightly thicker than that on the Al alloy side. After Al2O3f/ZL109 composites were treated using MAO technique, the corrosion resistance of the composites is significantly improved. A ceramic layer was prepared on the surface of Al2O3/ZL109 composites by means of micro-arc oxidation (MAO) technique. Al2O3 fibers in the composites affect the electric conductivity of the composites during MAO and inhibit the inward growth of MAO ceramic layer. Therefore, the outward growth speed of the ceramic layer is quicker than the inward growth speed.

Analysis of the stresses intensity factor in alumina–Pyrex composites

In this investigation, a numerical model was developed to study the effects of applied loading in Al2O3 fiber–reinforced ceramic–matrix composites. The finite element technique was used to calculate the stress intensity factors for crack growth in ceramic matrix composites and at the interface matrix/fiber. Influences of the applied load on the stress intensity factors for crack in matrix have been investigated. The behaviour of inclined cracks have been also analyzed. The effects of the applied load and the existence of defects (pore and micro-crack) near the interface fiber/matrix on the crack growth were analyzed.

Sliding wear mechanisms of magnesium composites AM60 reinforced with Al2O3 fibres under ultra-mild wear conditions

Abstract Mg alloy based composites were fabricated using Al 2 O 3 fibre preforms incorporated in a squeeze cast Mg–6% Al alloy (AM60). AM60– x % (Al 2 O 3 ) f , where x =9, 11, and 26, samples were subjected to boundary lubricated sliding contact at 25 °C and 100 °C against AISI 52100 counterface within a load range of 1.0–5.0 N. The test parameters emulated ultra-mild wear (UMW) corresponding to wear conditions observed in automotive engine blocks. Wear rates of Mg composites were 10 4 times less than that of the unreinforced alloy. AM60–9% (Al 2 O 3 ) f showed the highest rate of material loss compared to AM60–11% (Al 2 O 3 ) f and AM60–26% (Al 2 O 3 ) f . In the UMW regime, damage to the composites occurred in the following sequence: (i) fibre fracture and fragmentation; (ii) sinking in of the fragmented fibres; (iii) damage to Mg matrix causing high rate of material loss. Contact stress calculations, based on a micromechanical model that considered the fibres as asperities, indicated that at 1.0 N the initial contact pressure (2.8 GPa) exceeded the fibre fracture strength in compression. The normal stress on fractured fibres increased as they continued to be fragmented during sliding and became embedded into the matrix causing plastic deformation and localised pile up formation around the fractured fibres. For AM60–26% (Al 2 O 3 ) f the initial matrix hardness was high due to a large dislocation density created by thermal mismatch during fabrication and led to a greater degree of fragmentation compared to AM60–9% (Al 2 O 3 ) f revealing that the composite with high Al 2 O 3 fibre volume percentage less wear resistant than expected. FIB and TEM analyses of the worn surfaces of AM60–9% (Al 2 O 3 ) f tested at 100 °C indicated the formation of a tribolayer (oil-residue layer)- that mitigated the damage to Mg matrix tested for high sliding cycles making the AM6O-Al 2 O 3 composites suitable for applications at these temperatures.

Preparation of continuous alumina gel fibres by aqueous sol–gel process

Continuous alumina gel fibres were prepared by sol–gel method. The spinning sol was prepared by mixing aluminum nitrate, lactic acid and polyvinylpyrrolidone with a mass ratio of 10:3:1· 5. Thermogravimetry–differential scanning calorimetry (TG–DSC), Fourier transform infrared (FTIR) spectra, X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to characterize the properties of the gel and ceramic fibres. The Al2O3 fibres with a uniform diameter can be obtained by sintering gel fibres at 1200 °C.

Hydroxyapatite Matrix Composites by Hot Isostatic Pressing: Part 1. Alumina Fibre Reinforced

Fracture Toughness Improvement of the Hydroxyapatite Matrix Composite, to a Level Comparable to that of Natural Bone for in Vivo Applications, Was the Aim of the Present Work. Hot Isostatic Press Using a Graphite/stainless Steel Encapsulation System Enabled the Production of Fully Dense Decomposition-Free Hap with Toughness Improvements of: 2.4 Times (Al2O3 Fibres, Optimally 20 Vol%). Glass Encapsulation of Fibre-Reinforced Hap Resulted in Aeration from Sample Volatilization. Further, it Was Found that the Hap Decomposition Temperature Was Higher at 100 Mpa (the Hiping Pressure) than for Pressureless Sintering. the Toughening Effect of the Al2o3 Fibre Additive Induced Plastic Deformation and Ductile Fracture.

Synthesis and Thermal Conductivities of the Biomorphic Al2O3 Fibers Derived from Silk Template

Silk was used as the template to prepare biomorphic Al2O3 fibers. Silk fibers were first immersed into an AlCl3 solution and then sintered at high temperatures to produce the final Al2O3 fibers. Their microstructures, phases, synthesis process, infrared absorption spectra, and thermal conductivity were analyzed. The results show that these Al2O3 fibers retained the morphologies of silk. Different from the traditional Al2O3 fibers, these biomorphic fibers exhibit hollow and possess a good ability of absorbing infrared got from the silk, so that they possessed better heat‐insulating property than the traditional Al2O3 fibers.

Fabrication of electrospun Al2O3 fibers with CaO–SiO2 additive

Alumina fibers were fabricated by the sol–gel method combined with an electrospinning process using aluminum chloride hexahydrate (AlCl3·6H2O) and aluminum powder as raw materials in water solvent. Calcium oxide–silica (CaO–SiO2) was applied as two-component additive to retard the phase transformation of alumina and control the size of the grains during sintering. With the addition of the CaO–SiO2 in the system, the size of the particles that composed the fibers calcined at 1300 °C significantly decreased compared to that without additive, which might be due to the formation of θ-alumina in the samples. In addition, the fiber had low thermal conductivity and good flexibility, which favored its application in insulation.

The Effects of Density on Thermal Conductivity of Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Fiber Composite Papers

In this study, Al2O3 fiber composite papers with a certain strength and flexibility were prepared by pressure filtration. Microstructure and pore size of the composite papers with different density were investigated and thermal conductivities were measured by plane table thermo-conductivity meter at 600°C to 1200°C. Then the relationship between density ρ and thermal conductivity λ was studied, and the optimum density of Al2O3 fiber composite papers at different temperature was determined.

The strain amplitude-controlled cyclic fatigue behavior of Al2O3 fiber reinforced Al–Si alloy composite at elevated temperatures

Abstract The strain amplitude-controlled fatigue characteristics of an Al–Si casting alloy and its composite reinforced with 17 vol% Al2O3 fibers (Al–Si/Al2O3) are studied at three different temperatures. Both the alloy and the composite showed different degrees of cyclic softening at elevated temperatures. Increasing the temperature, fatigue damage of either the alloy or the composite occurred with varying mode from brittle fracture of silicon particles to their separation from the aluminum matrix. This is explained by the different thermal expansion coefficients of silicon particles and the aluminum matrix. The reinforcement Al2O3 fibers in the composite showed a similar damage behavior with those silicon particles despite temperature variation.