Al2O3 Whiskers Research Articles

Fabrication of Cu/Al–Al2O3 laminar composites using squeeze casting and roll bonding techniques: Evaluation of microstructure, mechanical properties and wear characteristics

The influence of Al2O3 whiskers addition on the microstructure, tensile, hardness, and wear characteristics of Cu/Al–Al2O3 composites were examined. The squeeze casting was used to fabricate Al–Al2O3 composites with different volume fractions of whiskers. Then, they were bonded to Cu layers. The microstructural and morphological examination were carried out by using SEM, XRD, and EBSD analyses. For the as-cast composites, the agglomeration of whiskers was observed which was then decreased by the following roll bonding process. For the roll bonded composites, the tensile strengths of composites were 210 MPa, 233 MPa, and 250 MPa For Cu/Al-(5 % vol) Al2O3, Cu/Al-(15 % vol) Al2O3, and Cu/Al-(25 % vol) Al2O3, respectively. The wear rate decreased versus volume fraction of whiskers which is correlated with the enhanced hardness of layers in composites. Less material loss and less debris were observed in composites with a higher volume fraction of whiskers.

Role of Cr on the interfacial bonding, mechanical, and electrochemical corrosion properties of Cu matrix composites co-reinforced by Al2O3 whisker and graphene: combined experiments and first-principles calculations

Role of Cr on the interfacial bonding, mechanical, and electrochemical corrosion properties of Cu matrix composites co-reinforced by Al2O3 whisker and graphene: combined experiments and first-principles calculations

Durable Design of Superhydrophobic Coatings with TiO2 Particles and Al2O3 Whiskers for the Enhanced Anti-icing Performance

Durable Design of Superhydrophobic Coatings with TiO2 Particles and Al2O3 Whiskers for the Enhanced Anti-icing Performance

Effect of Al2O3 whiskers on forming accuracy, mechanical and tribological performances of translucent glass-ceramics formed by 3D printing

A method of Al2O3 whiskers addition is provided to simultaneously enhance the forming accuracy, and mechanical and tribological performances of translucent glass-ceramics manufactured through vat photopolymerization 3D printing. Al2O3 whiskers (0–15wt%) were added to a self-prepared fluorapatite glass-ceramic as a raw material. The results demonstrated that the addition of Al2O3 whiskers significantly improved the forming accuracy, mechanical and tribological performances of fluorapatite (FAp) glass-ceramics. The dimensional error of the formed samples decreased by approximately 56% with the addition of 15wt% Al2O3 whiskers. The glass-ceramics containing 10wt% Al2O3 whiskers exhibited a flexural strength and fracture toughness of 220.3±13.7MPa and 1.81±0.18MPa·m1/2, respectively, representing a 44.1% and 111.8% increase compared to pure FAp glass-ceramics. Furthermore, the addition of Al2O3 whiskers led to reduced wear volume in both the glass-ceramics and titanium balls used as counterparts, indicating improved tribological compatibility.

High mechanical strengthened CNTs/Al composite concepts with robust interface and intragranular reinforcement achieved via interfacial thermite reaction

In this work, we develop a novel strategy to simultaneously manipulate robust “Al-Al2O3-CNTs” interface and intragranular nano-sized Al2O3 whiskers and CuAl2 particles in the Cu2[email protected]/Al composite via combining surface modification strategy with interfacial thermite reaction, which contributes to the superior mechanical properties. It was demonstrated that the interfacial thermite reaction between Cu2O and Al would effectively promote the formation of Al2O3 nanolayer at CNTs-Al interface, thus emphasizing to address the enhanced load transfer and interfacial plastic stability. Further, the long-distance diffusion of Cu and O atoms imposed by the intense thermal effect facilitates the in-situ generation of intragranular Al2O3/Al2Cu with good interface compatibility. These intragranular reinforcements could render sustainable strain hardening by trapping dislocation loops. Such interfacial thermite reaction-induced intragranular reinforcements and strong interfacial adhesion are supposed to provide a new perspective for achieving strength-ductility synergy in CNTs/Al systems.

Mechanical strength and microwave dielectric properties of Al2O3 doped Li2MgTi3O8 ceramics with high temperature stability

A temperature stability microwave dielectric ceramic with composition of Li2MgTi3O8 (LMT) and Al2O3 with high flexural strength is synthesized by a conventional solid-state reaction method. The effects of Al2O3 (particles and whiskers) doping on the mechanical and dielectric properties of LMT ceramics are studied. A single spinel structure, without any secondary phases, is detected in the Al2O3 particles and Al2O3 whiskers doped LMT ceramics. The maximum flexural strengths of 152.5 MPa and 166.73 MPa are delivered in LMT +0.3 wt% Al2O3 (p) ceramics and LMT + 0.3 wt% Al2O3 (w) ceramics, respectively, which are enhanced by 53.21% and 67.52% over those of unmodified LMT ceramics. Pinning and grain refinement contribute to the enhanced flexural strength of the system. The intrinsic factors of Q × f change are analyzed by calculating the packing fraction and lattice energy. In addition, ceramics exhibit excellent comprehensive microwave properties at 1050 °C: (LMT + 0.2 wt% Al2O3 (p):Q × f = 67056 GHz, τf = −8.25 ppm/°C, εr = 24.34, σf = 133.3 MPa; LMT + 0.1 wt% Al2O3(w): Q × f = 68670 GHz, τf = −8.94 ppm/°C, εr = 24.32, σf = 122.7 MPa) The results indicate that Al2O3 particles and Al2O3 whiskers are decent reinforcing agents for LMT ceramics.

Preparation of Al3Ti-Al2O3/Al Inoculant and Its Inoculation Effect on Al-Cu-Mn Alloy.

The grain size plays a pivotal role in determining the properties of the alloy. The grain size can be significantly decreased by adding inoculants. Aiming to address the shortcomings of existing inoculants, the Al3Ti-Al2O3/Al inoculant was successfully prepared using Al-Ti master alloy and Al2O3 whiskers as raw materials. With the aid of ultrasonic energy, the Al2O3 whiskers were uniformly dispersed within the inoculants. Under the combined action of ultrasonic and titanium, the Al2O3 whiskers were broken into small particles at high temperature. To enhance the morphology of Al3Ti and achieve even particle dispersion throughout the matrix, vacuum rapid quenching treatment was applied to the inoculant. The SEM test results indicated a significant reduction in particle size after vacuum rapid quenching. The Al3Ti-Al2O3/Al inoculants exhibited excellent grain refinement effects on the weldable Al-Cu-Mn alloy. Crystallographic calculations and HRTEM analysis revealed that Al2O3 and Al have orientation relationships, indicating their potential as effective heterogeneous nucleation sites. The mechanical properties of the Al-Cu-Mn alloy were obviously improved after the Al3Ti-Al2O3/Al inoculant was added.

Microstructures and interfacial interactions of Al2O3 whiskers and graphene nano-platelets co-reinforced copper matrix composites

The mechanical properties and microstructures of Al2O3 whiskers and graphene nano-platelets (GNPs) co-reinforced Cu-matrix composites were studied. Cu-matrix composites with a variation of GNPs amount were fabricated by mechanical alloying followed by vacuum hot-pressing sintering and hot isostatic pressing. The Cu-matrix composite with 0.5 wt.% GNPs (GNPs-0.5) suggests a good interfacial bonding of both Cu/C and Cu/Al2O3 interfaces. Both the hardness and compressive strength of Cu-matrix composites show a consistent tendency that firstly increases to a critical value and then decreases with increasing GNPs amount. It is suggested that the most possible strengthening mechanisms of both GNPs and Al2O3 whisker working in the Cu-matrix composites involve energy dissipating and load transfer, as well as grain refinements for GNPs. The synergetic effect of GNPs and Al2O3 whiskers is highlighted that the embedded GNPs would hinder the crack path generated at the Al2O3/Cu interface and enhance the already outstanding strengthening effect that Al2O3 whiskers provide.

Colloidal co‐assembly of dual‐phased ceramic/metal particles toward lightweight, hierarchically structured, and mechanically robust alumina foam

AbstractCeramic foams constructed by aqueous‐based foam templating have demonstrated great potential in industrial and research applications. However, a multiple‐phased suspension with inherently improved complexity inevitably leads to a severe deterioration of foam stability. Herein, we proposed a colloidal co‐assembly strategy that introduces Al–Al2O3 dual‐phased particles for constructing ultralight yet mechanically robust cellular ceramics. Owing to the Al2O3 oxidation layer on Al particles, both of Al and Al2O3 suspensions demonstrated similar zeta potential and rheological properties, enabling a stable foam structure after colloidal co‐assembly. High‐temperature oxidation of Al particles contributed to the reinforcement of cell wall and formation of Al2O3 whiskers. The calcined products demonstrated a lightweight structure (0.31 g cm−3), a robust compressive strength (3.64 MPa) at a porosity level of 88.5%, and a relatively high specific surface area (14.7 m2 g−1). The current strategy paves the way for the construction of high‐performance ceramic foams for a broad range of applications.

Microstructure and properties of nano-C and in-situ Al2O3 reinforced aluminum matrix composites processed by high-pressure torsion

ABSTRACT In this study, Al-Si matrix composites reinforced with In situ Al2O3, C nanotubes (CNTs), and graphene nanoplatelets (GNPs) were prepared by ball milling, hot-isostatic pressing (HIP), and subsequent high-pressure torsion (HPT). Microstructures, interfacial bonding, and electrical and mechanical properties of the composites were analysed. In situ Al2O3 particles and whiskers were formed via reaction between Al powder and SiO2 powder. Grains of the composites were significantly refined and reinforcements were well dispersed in the matrix by HPT. A sub-micron equiaxed grain structure with an average grain size of 0.60 μm was obtained. Interface between the CNTs and the matrix was narrow and had no brittle phase. With an increase in the number of HPT cycles, microhardness and electrical conductivity of the composites increased. Strengthening mechanism of the Al matrix composites was mainly fine-grain strengthening. Dislocation accumulation and grain boundary evolution caused by HPT were examined.

Phenomenon of Whiskers Formation in Al2O3−C Refractories

Pure alumina (Al2O3) and carbon‐bonded alumina (Al2O3−C) are used to investigate their interaction with iron (Armco) at 1625 °C, applying the sessile drop method. The investigations are conducted inside a heating microscope for 1 h under argon atmosphere with low oxygen partial pressure. No whiskers formation is observed from the experiments with pure Al2O3 and molten iron. In the case of Al2O3−C/Fe system, several phenomena including the decarburization of Al2O3−C, Al2O3−C dissolution in molten iron, Al2O3 layer formation on the iron droplet, and Al2O3 whiskers formation are observed. To clarify the possible influence of iron on Al2O3 whiskers formation, blank Al2O3−C samples without the presence of iron are heated and held in a half‐sealed platinum crucible at 1550 °C for 2 h. Thereby, the Al2O3 whiskers formation is detected. Finally, the experimental investigations are supported with thermodynamic simulations.

Preparation and growth mechanism of the flower-like whiskers of γ-, θ-, and α-Al2O3 phases by homogeneous precipitation/calcination method

The different alumina whiskers phases are extensively used to reinforce high-performance composite materials. The understanding of the mutual relationship of the different phases is key for simulating Al2O3 whiskers containing systems and is of general interest for the metal oxide and ceramic communities. In this paper, we used homogeneous precipitation to synthesized flower-like boehmite whisker precursors from aluminum sulfate and urea. The synthesized precursors were calcined at 600, 900, and 1200 °C to obtain flower-like whiskers of γ-, θ-, and α-Al2O3 phases, respectively. The precursor boehmite crystals prepared in closed, semi-closed, and open reactor systems were qualitatively analyzed using SEM. The results showed that the usea hydrolysis, which serves as a source of OH− ions, is slow under closed-reactor conditions, which favors the growth of the boehmite crystal nuclei into whiskers. We adopted the L16 (43) orthogonal design of experiment to analyze the influence of reaction temperature, time, and the amount of urea (relative to the amount of Al2(SO4)3) in the closed system. Synthesis temperature of 160 °C and the processing time of 8 h yielded optimal boehmite flower-like whiskers. Physicochemical properties of the precursor and series of alumina phases were characterized using thermogravimetric/differential thermal analysis (TG/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) methods. Finally, the obtained results and the thorough analysis of the growth mechanism suggested the step-growth model of boehmite flower-like whiskers.

Influence of alumina whisker or nano-carbon contents on the microstructure and mechanical properties of CuZrTiAlNi refractory high entropy alloy composites

Abstract High-entropy alloy composites were fabricated by ball milling, cold isostatic pressing and microwave sintering to which were added varied contents of Al2O3 whiskers, La-Ce, and carbon nanotubes-graphene, respectively. The structure and mechanical properties of the composites were investigated by X-ray diffraction, scanning electron microscopy and a microhardness tester. The high-entropy alloy and composites show amorphous phases and some crystalline phases. Accordingly, the addition of the reinforcement phase can refine the grain size. The formation mechanism of the phase is mainly related to the factors of mixing entropy, enthalpy, differences in atomic size, and the structure and property of the elements. The hardness of the composites is higher than that of the alloy (437.5 HV), and those composites reinforced by 0.5 wt.-% nanotubes- 0.5 wt.-% graphene are the highest (593.99 HV). The fracture morphology of the Al2O3 whisker reinforced composite shows a river pattern, indicating brittle cleavage. According to the research results, it can be concluded that the strengthening mechanism of the high entropy alloy composites mainly reflects fine grain strengthening and load transfer, and the toughening mechanism mainly crack bridging and a pulling out of the reinforcing phase.

Comparison of sintering behavior and reinforcing mechanisms between 3Y-TZP/Al2O3(w) and 12Ce-TZP/Al2O3(w) composites: Combined effects of lanthanide stabilizer and Al2O3 whisker length

The densification behavior, microstructural development, toughening and strengthening mechanisms of Al2O3 whisker-reinforced 3Y-TZP and 12Ce-TZP composites were systematically and comparatively investigated with varying whisker lengths. Compared with 3Y-TZP/Aw composites, the presence of a Ce-Al-Si-O amorphous phase, caused by the addition of Al2O3 whiskers, promoted the densification and grain growth of 12Ce-TZP/Aw composites. Crack deflection and bridging are proposed as the primary toughening mechanisms for 3Y-TZP/Aw composites, while the t-m martensitic transformation would dominate the toughening and strengthening processes of 12Ce-TZP/Aw composites. Changes in Al2O3 whisker length would vary the distributions of internal stress and amorphous phase within the ceria-stabilized ZrO2 matrix, and hence affect the toughening and strengthening results. It indicates that effective toughening and strengthening of the Al2O3 whisker-reinforced TZP composites can be achieved by taking advantage of collaborative engineering control on the reinforcement morphology and the interface chemistry/structure.

Influence of alumina whisker or nano-carbon contents on the microstructure and mechanical properties of CuZrTiAlNi refractory high entropy alloy composites

Abstract High-entropy alloy composites were fabricated by ball milling, cold isostatic pressing and microwave sintering to which were added varied contents of Al2O3 whiskers, La-Ce, and carbon nanotubes-graphene, respectively. The structure and mechanical properties of the composites were investigated by X-ray diffraction, scanning electron microscopy and a microhardness tester. The high-entropy alloy and composites show amorphous phases and some crystalline phases. Accordingly, the addition of the reinforcement phase can refine the grain size. The formation mechanism of the phase is mainly related to the factors of mixing entropy, enthalpy, differences in atomic size, and the structure and property of the elements. The hardness of the composites is higher than that of the alloy (437.5 HV), and those composites reinforced by 0.5 wt.-% nanotubes- 0.5 wt.-% graphene are the highest (593.99 HV). The fracture morphology of the Al2O3 whisker reinforced composite shows a river pattern, indicating brittle cleavage. According to the research results, it can be concluded that the strengthening mechanism of the high entropy alloy composites mainly reflects fine grain strengthening and load transfer, and the toughening mechanism mainly crack bridging and a pulling out of the reinforcing phase.

Influence of cBN content, Al2O3 and Si3N4 additives and their morphology on microstructure, properties, and wear of PCBN with NbN binder

Polycrystalline cubic boron nitride (PCBN) tool materials with NbN binder without additives and PCBN with Al2O3 or Si3N4 micropowder and whisker additives were manufactured and compared. PCBN materials with Si3N4 whisker reinforcement have the best mechanical properties of all the evaluated materials. Composites reinforced with Al2O3 whiskers have the lowest fracture toughness. However, Al2O3 whisker-reinforced tools outperform both commercial and Si3N4 reinforced tools when machining hardened steel. Thus Al2O3 whisker-reinforced PCBN materials are promising for industrial applications, likely due to their higher resistance to oxidation and diffusional wear mechanisms during cutting operations.

Study on corrosion resistance of copper matrix composites reinforced by Al2O3 whiskers

The corrosion behavior of copper matrix composites with different Al2O3 whisker content in NaCl solution (3.6 wt%) at different temperatures was studied by electrochemical test and electron microscope. The results showed that with the increase of Al2O3 whisker content, the corrosion tendency of the composites first increases and then decreases. The charge-transfer resistance (Rct) value and corrosion current density tend to decrease first and then rise slowly. The whiskers can cause huge differences in performance in different directions so that it is easy to agglomerate and entangle in the matrix, which can increase the heterogeneity of materials in copper matrix alloys, hence, the addition of whiskers will cause the increase of corrosion phenomenon. As the whisker content continues to increase, a large number of reinforcing phases will form a natural protective layer when exposed on the metal surface, which will slow down the corrosion situation. As the temperature increases, the corrosion resistance decreases first and then increases. When the temperature increases from 25 °C to 50 °C, the electrochemical reaction is accelerated, the free electrons between the metal atoms obtain external energy, the ion migration rate is accelerated, and the corrosion reaction is more likely to occur. When the temperature increases from 50 °C to 75 °C, the corrosion reaction rate is mainly controlled by the diffusion of oxygen. As the temperature increases, the solubility of oxygen decreases and the cathode reaction requires oxygen to participate, consequently, the corrosion rate decreases. For the microstructure of the corrosion specimen, corrosion mainly occurred at or around the reinforcement phase/matrix interface. Intermetallic compound particles often appear near corrosion initiation points along the reinforcement phase/matrix interface, and the corrosion behavior of composites is mainly determined by copper. Copper is used as the anode of the battery, and the corrosion products are mainly copper chloride salts.

The Influence of SiC and Al2O3 Whiskers on the Properties of Whisker-Reinforced cBN-Based Composites

Three types of cBN-based composites with TaN binder—without whiskers, with Al2O3 whiskers, and with SiC whiskers—have been produced by the high pressure-high temperature (HPHT) sintering. Density, hardness, Poisson ratio, and fracture toughness of the composites have been studied. The whisker-reinforced cBN-based composites exhibit a higher level of mechanical properties (hardness, fracture toughness) in comparison with the non-reinforced materials.

Fabrication, microstructure and mechanical properties of Al2O3 whiskers reinforced Ti-46Al-4Nb alloy

TiAl alloy refined by Al2O3 whiskers was prepared by suction casting control technology. With the whisker toughening of initial whiskers and the intracrystalline strengthening of detached Al2O3 nanoparticles (NPs), the strength of the sample was increased to 3017 MPa. The refining mechanism, the strengthening and toughening effect of alumina whiskers and NPs on TiAl alloy are discussed.

Microstructures and mechanical properties of alumina whisker reinforced copper matrix composites prepared by hot-pressing and hot isostatic pressing

The single crystal α-Al2O3 fibre is an excellent reinforcement material for their excellent elastic modulus, high chemical and thermal stability. Copper matrix composites containing fixed amount alloys (Sn, Ni, Fe, etc) and different amounts of alumina whisker are prepared through mechanical alloying, hot-pressing and hot isostatic pressing. The results show that a solid solution structure is formed between the alloying elements and copper in which alumina whisker are uniformly distributed in the copper matrix. The compressive strength increases with the increase of Al2O3 whisker when the Al2O3 whisker content changes from 0.0 wt% to 1.5 wt%, and the maximum value reaches 288.26 MPa. The strengthening mechanism is fine grain strengthening and solid solution strengthening; besides, the dispersion mechanism and the mechanism of dislocation strengthening can also be exerted.