Al2O3 Hybrid Research Articles

Enhancement of tensile and thermal properties of epoxy nanocomposites through chemical hybridization of carbon nanotubes and alumina

This paper presents the properties of epoxy nanocomposites, prepared using a synthesized hybrid carbon nanotube–alumina (CNT–Al2O3) filler, via chemical vapour deposition and a physically mixed CNT–Al2O3 filler, at various filler loadings (i.e., 1–5%). The tensile and thermal properties of both nanocomposites were investigated at different weight percentages of filler loading. The CNT–Al2O3 hybrid epoxy composites showed higher tensile and thermal properties than the CNT–Al2O3 physically mixed epoxy composites. This increase was associated with the homogenous dispersion of CNT–Al2O3 particle filler; as observed under a field emission scanning electron microscope. It was demonstrated that the CNT–Al2O3 hybrid epoxy composites are capable of increasing tensile strength by up to 30%, giving a tensile modulus of 39%, thermal conductivity of 20%, and a glass transition temperature value of 25%, when compared to a neat epoxy composite.

Effect of poly(amid–imide)/Al2O3 hybrid with various ratios on the physicochemical properties of poly(vinyl alcohol) nanocomposites films

To study the effect of the various ratios of poly(amide–imide)/Al2O3 nanocomposites (PANC)s on the mechanical and thermal properties of nanocomposites films, poly(vinyl alcohol) (PVA)/PANCs based on various ratios of 2, 4, and 6 wt% were prepared and characterized. In the first step, the surface of alumina nanoparticles was treated with 15 wt% of biosafe diacid and consequently, about 10 wt% of these modified nanoparticles were loaded into the poly(amide–imide) matrix. Then, various contents of the obtained PANCs were incorporated into a PVA solution using a sonochemical treatment. The effects of PANC on the structure and morphology of PVA matrix were studied using powder X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, atomic force microscopy (AFM), and thermal gravimetric analysis (TGA). The results show that the tensile strength and decomposition temperature were improved as the portion of PANC into PVA matrix are increased from 2 to 6 wt%. Also, AFM pictures of the fracture surfaces of PVA/PANCs showed a significantly rougher surface than the neat PVA.

In situ damage sensing in the glass fabric reinforced epoxy composites containing CNT–Al2O3 hybrids

Abstract Damage sensing of the fiber-reinforced structural composites have attracted a lot of attention. In this work, a small amount of carbon nanotubes (CNT)-Al 2 O 3 hybrids are introduced into the woven glass fabric reinforced epoxy composites and serve as in situ sensor to monitor the damage initiation and propagation under mechanical loading. The hybrids with CNTs grown on the Al 2 O 3 micro-spheres are synthesized by chemical vapor deposition. The addition of 0.5 wt.% CNT–Al 2 O 3 increased ac electrical conductivity of the glass fabric/epoxy composites at 10 3 Hz 4–5 orders of magnitude in both in-plane and through-thickness directions. The electrical resistance of the composites was in situ measured under quasi-static tensile testing. With the increase of strain, the resistance response could be classified into three distinguished stages, corresponding to various damage modes (microcracks, fiber/matrix interfacial debonding, transverse cracks, delamination, fiber breakage, etc.).

PEG/SiO2–Al2O3 hybrid form-stable phase change materials with enhanced thermal conductivity

The thermal conductivity of form-stable PEG/SiO2 phase change material (PCM) was enhanced by in situ doping of Al2O3 using an ultrasound-assisted sol–gel method. Fourier transform infrared spectroscopy (FT-IR) was used to characterize the structure, and the crystal performance was characterized by the X-ray diffraction (XRD). Differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA) were used to determine the thermal properties. The phase change enthalpy of PEG/SiO2–Al2O3 reached 124 J g−1, and thermal conductivity improved by 12.8% for 3.3 wt% Al2O3 in the PCM compared with PEG/SiO2. The hybrid PCM has excellent thermal stability and form-stable effects.

Fischer–Tropsch Synthesis Catalyzed by Solid Nanoparticles at the Water/Oil Interface in an Emulsion System

Fischer–Tropsch synthesis (FTS) was carried out in a water/oil mixture medium, using a Ru catalyst supported on a multi-walled carbon nanotube/MgO–Al2O3 hybrid as a catalyst support. The nanohybrid particles at the water/oil interface facilitated and stabilized the formation of water-in-oil emulsion, giving rise to an oil/emulsion/water trilayer liquid structure. FTS occurred at the emulsion phase with much higher conversion rates than those in oil single-phase reactions, yielding products with Anderson–Schulz–Flory distribution. Alkane-enriched hydrocarbons migrate to the top oil phase, while short alcohols remain in the bottom water phase. Thus, this multiphase liquid structure facilitates the separation of products according to their solubility in different phases. This significant advantage of combined reaction and separation is unique to the multiphasic system. In addition, differences in solubility could be used to enhance tolerance against impurities and catalyst poisons in the syngas feedstock. As...

High temperature friction and wear behaviour of Ni–P–Ag–Al2O3 hybrid nanocomposite coating

Codeposition of silver and alumina particles has been performed within an Ni–P coating on carbon steel samples by electroless deposition to form an Ni–P–Ag–Al2O3 hybrid nanocomposite coating. The structure of heat treated coatings was evaluated by XRD analysis. Tribological properties of the coatings were investigated by a pin-on-disc test method using a 52100 steel pin as counter body at high temperature. A 3D optical profiler was employed to measure the wear rate of the deposits. Surface morphology, cross section and wear scars of the coatings were studied by using SEM equipped with EDS analysis. The results showed that tribological properties of Ni–P–Ag–Al2O3 hybrid coating are similar to Ni–P–Ag conventional composite coating. Moreover, friction coefficient and wear resistance of the hybrid coating are strongly influenced by self-lubricating silver thin layers formed between mating surfaces during high temperature sliding wear.

Preparation of PVDF/Al2O3 hybrid membrane via alkaline modification and chemical coupling process

Polyvinylidene fluoride (PVDF)/Al2O3 hybrid membrane (PAHM) was prepared via alkaline modification and chemical coupling using PVDF modified by KOH in the solution of methanol as a membrane-forming polymer, using vinyl-trimethoxy-silicane as a coupling agent and aluminum isopropoxide (AIP) as an inorganic precursor, respectively. PAHM, linking PVDF and Al2O3 with chemical bond, was obtained by sol–gel method. FT-IR spectroscopy, surface contact angle testing, differential scanning calorimetry, and atomic force microscope were applied to characterize the PAHM. The effects of the coupling agent on the structure and properties of the hybrid membrane were also investigated. The results showed that the hydrophilicity of the modified PVDF were the best with 5 wt% of KOH solution at 60°C for 30 min. When PAHM is prepared with 1% coupling agent, the average pore size and the pure water flux decreased compared to PAHM without coupling agent, while the rejection rate significantly increased. Along with the increase in AIP concentration, the tensile strength and elongation at break of PAHM gradually improved, but both of them have a reduction when AIP concentration reached to 10% by weight. Compared with the original PVDF membrane, the flux attenuation coefficient of PAHM prepared by alkali-coupling agent modification declined from 45 to 27%, which means the antifouling performance of membrane improved markedly.

Novel investigation on tribological properties of Ni–P–Ag–Al2O3 hybrid nanocomposite coatings

In this research, silver and alumina particles were co-deposited within Ni–P matrix to obtain Ni–P–Ag–Al2O3 hybrid coating. The structure of coatings was analyzed by X-ray diffraction and the tribological properties of deposits were evaluated by pin on disc tribometer. 3D optical profiler and scanning electron microscopy were used to study wear rate and worn surfaces. The results showed that Ni–P–Ag and Ni–P–Ag–Al2O3 coatings have the self-lubrication property and maximum hardness (∼1310 HV) and wear resistance were obtained for Ni–P–Al2O3 coating. Also, Ni–P–Ag–Al2O3 hybrid nanocomposite coating had higher wear resistance than Ni–P and Ni–P–Ag coatings. Moreover, the best conditions was achieved for heat treated hybrid coating in the concentration of 30mg/L silver and 150mg/L alumina in the plating solution.

In vitro cytotoxicity and in vivo osseointergration properties of compression‐molded HDPE‐HA‐Al2O3 hybrid biocomposites

The aim of this study was to investigate the in vivo biocompatibility in terms of healing of long segmental bone defect in rabbit model as well as in vitro cytotoxicity of eluates of compression-molded High density polyethylene (HDPE)-hydroxyapatite (HA)-aluminum oxide (Al2O3) composite-based implant material. Based on the physical property in terms of modulus and strength properties, as reported in our recent publication, HDPE-40 wt % HA and HDPE-20 wt % HA-20 wt % Al2O3 hybrid composites were used for biocompatibility assessment. Osteoblasts cells were cultured in conditioned media, which contains varying amount of composite eluate (0.01, 0.1, and 1.0 wt %). In vitro, the eluates did not exhibit any significant negative impact on proliferation, mineralization or on morphology of human osteoblast cells. In vivo, the histological assessment revealed neobone formation at the bone/implant interface, characterized by the presence of osteoid and osteoblasts. The observation of osteoclastic activity indicates the process of bone remodeling. No inflammation to any noticeable extent was observed at the implantation site. Overall, the combination of in vitro and in vivo results are suggestive of potential biomedical application of compression-molded HDPE- 20 wt % HA- 20 wt % Al2O3 composites to heal long segmental bone defects without causing any toxicity of bone cells.

High-Temperature Oxidation Kinetics for Recovery of Mechanical Strength on Nano-Ni Dispersed Al2O3 Hybrid Materials

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Fabrication of ZrO2–Al2O3 hybrid nano-porous layers through micro arc oxidation process

Zirconia-alumina layers, with a pores size of 40–300nm, were fabricated via micro arc oxidation method for the first time. The layers were grown under alternative current in the electrolytes of ZrOCl2 salt. They consisted of α-Al2O3, γ-Al2O3, monoclinic ZrO2, tetragonal ZrO2. Increasing the voltage resulted in higher zirconium concentrations in the layers. A porous structure was obtained when the layers were grown under intermediate voltages. Microcracks were observed to appear when the applied voltage increased. Finally, a formation mechanism was proposed with emphasis on the chemical and the electrochemical foundations.

The Effects of Coupling Agents on the Properties of Polyimide/Nano‐Al2O3 Three‐Layer Hybrid Films

PI/nano‐Al2O3 hybrid films were prepared by ultrasonic‐mechanical method. Before addition, nano‐Al2O3 particles were firstly modified with different coupling agents. The micromorphology, thermal stability, mechanical properties, and electric breakdown strength of hybrid films were characterized and investigated. Results indicated that nano‐Al2O3 particles were homogeneously dispersed in the PI matrix by the addition of coupling agents. The thermal stability and mechanical properties of PI/nano‐Al2O3 composite films with KH550 were the best. The tensile strength and elongation at break of PI composite film were 119.1 MPa and 19.1%, which were 14.2% and 78.5% higher than unmodified PI composite film, respectively.

Preparation and characterization of polyimide/Al2O3 hybrid films by sol–gel process

AbstractA sol–gel process has been developed to prepare polyimide (PI)/Al2O3 hybrid films with different contents of Al2O3 based on pyromellitic dianhydride (PMDA) and 4,4′‐oxydianiline (ODA) as monomers. FESEM and TEM images indicated that Al2O3 particles are relatively well dispersed in the polyimide matrix after ultrasonic treatment of the sol from aluminum isopropoxide and thermal imidization of the gel film. The dimensional stability, thermal stability, mechanical properties of hybrid PI films were improved obviously by an addition of adequate Al2O3 content, whereas, dielectric property and the elongation at break decreased with the increase of Al2O3 content. Surprisingly, the corona‐resistance property of hybrid film was improved greatly with increasing Al2O3 content within certain range as compared with pure PI film. Especially, the hybrid film with 15 wt % of Al2O3 content exhibited obviously enhanced corona‐resistance property, which was explained by the formation of compact Al2O3 network in hybrid film. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Mechanical activation-assisted solid-state combustion synthesis of in situ aluminum matrix hybrid (Al3Ni/Al2O3) nanocomposites

Aluminum-based metal matrix composites reinforced with in situ Al3Ni and Al2O3 hybrid reinforcements are prepared by the mechanically activated, self propagating, high temperature synthesis (MASHS). The composites are fabricated from the powder blends consisting of aluminum and nickel oxide with different amounts of excess aluminum following the reaction scheme (2 + X)Al + 3NiO → XAl + Al2O3 + 3Ni (where X = 0, 5, 10 and 15 moles). The onset temperature for the displacement reaction is brought down below the melting temperature of the mechanically activated powder blends by a high energy ball milling (HEBM). The solid-state displacement reaction can effectively preserve the nanostructure of the matrix with ultra fine reinforcements formed by the in situ reaction. It is demonstrated that the composite properties can be tailored by altering the stoichiometry of reactants.

Critical behaviors of the conductivity and dielectric constant of Ti3SiC2∕Al2O3 hybrids

Ti 3 Si C 2 ∕ Al 2 O 3 hybrids were prepared by a spark plasma sintering process. The effective dc conductivity of the hybrids was measured at room temperature, which agrees with the percolation theory and follows the power law around the percolation threshold. The ac conductivity and dielectric constants of the hybrids were also characterized and follow the power law when the concentration of the conductive phase is close to the percolation threshold; meanwhile, the dielectric constant could increase over three orders of magnitude compared with Al2O3.

Compound growth and microstructure of carbon nanotube

The compound growth of single-walled carbon nanotube (SWCNT) and multiwalled carbon nanotube (MWCNT), which formed a nanotube cable, was achieved by the chemical vapor deposition of natural gas on an Fe catalyst supported on SiO2–Al2O3 hybrid materials at 950 °C. The microstructure of nanotubes was characterized by high-resolution transmission electron microscopy (HRTEM). The SWCNTs encapsulated inside MWCNTs can be two, three, or even more in quantity with a diameter range from 1.0 nm to 2.0 nm. The diameter of SWCNT is controlled by the size of the catalyst nanoparticles. Some bundles of SWCNT and double-walled nanotubes were also found. The possible mechanism of compound growth is briefly discussed.

Fabrication of W-1%ThO2 Reinforced Fe-25Cr-8Al-0.5Y Superalloy Matrix Composite

Four different aligned W-1%ThO2 reinforced Fe-25Cr-8Al-0.5Y matrix fiber reinforced superalloy [FRS] material billets were produced by powder metallurgical processing. Three materials differed only in reinforcing fiber aspect ratio, while one material included a small diameter, misoriented Al2O3 hybrid reinforcement. Tensile and thermal cycling specimens were fabricated from the composite billets by using abrasive waterjet and turning processes. Finally the specimens were protected from high temperature oxidation by a FeCrAlY thermal spray coating. Metallurgical and mechanical properties were evaluated and discussed.

Al<SUB>2</SUB>O<SUB>3</SUB>繊維およびSiCウイスカ強化した6061Al合金の機械的性質および摩耗特性

The mechanical properties and wear resistance of Al2O3 fiber and hybrid of Al2O3 and SiC whisker reinforced AA6061 were investigated.The elastic modulus of T6 heat treated Al2O3/6061 and Al2O3-SiC/6061 composites can be expressed as(This article is not displayable. Please see full text pdf.) \ oindentrespectively. The fiber arrangement coefficient α is found to be 0.7 for Al2O3 and 0.45 for SiC whisker.The wear resistance of Al2O3/6061 composites is inferior to that of SiC/6061 composites. The addition of small volume fractions of SiC whisker to Al2O3/6061 composites gives rise to remarkable improvement of the wear resistance which is, on the contrary, superior to that of SiC/6061 composistes.