Al2O3 ZrO2 Research Articles

A generalized master sintering curve based on nucleation-limited densification kinetics

The master sintering curve was developed assuming diffusion-limited coarsening and densification kinetics. A key limitation of the model is that it is only valid for a single set of initial conditions, i.e., grain size and density. Recent in situ sintering experiments suggest that densification follows nucleation-limited kinetics. A model for sintering can be formulated based on a thermodynamic energy balance between interfacial energy dissipation and work required to overcome the nucleation barrier. A feature of this model is that it inherently relates coarsening and densification, providing a basis for formulating a generalized master sintering curve that is not sensitive to initial conditions. This paper develops the model and demonstrates its practical application to several oxide systems, including ZnO, Al2O3, and Y2O3-doped tetragonal ZrO2.

Kinetic investigation of dry reforming of methane reaction over Ni–Rh/ZrO2–Al2O3 catalyst using Langmuir-Freundlich isotherm

The study involved conducting kinetic measurements for the dry reforming of methane (DRM) over a Ni–Rh/Al2O3 (85%)-ZrO2(15%) catalyst under a wide range of operating conditions (temperature: 500–900 °C, total flow rate of the inlet feed: 50–100 mL/min). The support material was prepared using the sol-gel method, followed by impregnation of Ni–Rh catalyst on the incipient wetness of the Al2O3–ZrO2 support. The calcined, reduced and spent samples were characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA), inductively coupled plasma atomic emission spectrometer (ICP-AES), N2 adsorption/desorption and CHNS analyzer, and tested for activity, yield and stability in DRM reaction. Furthermore, kinetic behavior of Ni–Rh/Al2O3–ZrO2 catalyst in DRM process was investigated by assuming DRM and reverse water-gas shift (RWGS) reactions take place on two kinds of different active sites. Experimental data were fitted using rate expressions based on the Langmuir-Freundlich (LF) isotherm for DRM and RWGS reactions. The activation energy for the DRM reaction was optimized at 43.62 kJ/mol, falling within the reported literature range of 24.73–108.9 kJ/mol. Statistical indices indicated that the kinetic model accurately predicted CO2 conversion compared to other responses, with an error of 12.054%. The computed and experimental trends for CH4 and CO2 conversions, H2 and Co yield in terms of temperature were similar with each other and the difference between the calculated and experimental trends was lower for conversions compared to yields.

Additive Manufacturing of Composite Materials and Functionally Graded Structures Using Archerfish Hunting Technique

ABSTRACTThis paper proposes an optimisation method for fabricating composite materials and functionally graded structures. Using the proposed method, 3D printing of copper (Cu)–polyethylene (PE) composite, Al2O3–ZrO2 ceramic composite and functionally graded CuO foams are utilised. This work aims to advance the capabilities of additive manufacturing by leveraging nature‐inspired approaches to create complex, tailored structures with enhanced performance across various industries. The major objective of the proposed method is to reduce the feed rate and increase the airflow rate and airflow temperature for the heat transfer process. Using the proposed technique in the advanced preparation conditions, Cu–PE composites with unreliable Cu substances are fabricated. The PE binder particle is melting as well as forming thick composites by means of soft surfaces. Using the proposed AHO approach, functionally graded materials with common distributions can be efficiently optimised. By then, the proposed model is implemented on the MATLAB platform, and its execution is calculated using the current procedures. The proposed technique displays superior outcomes in all existing methods like wild horse optimiser, particle swarm optimisation and heap‐based optimiser. The proposed method shows a throughput of 57 mm3. The existing method shows the throughput of 32, 27 and 45 mm3. The results show that the proposed method has higher throughput compared with existing methods.

Phase evolution of Al–Al2O3–ZrO2 refractories at 1300 °C under N2 flowing

In order to obtain Al–Al2O3–ZrO2 composite refractories with excellent oxidation resistance, erosion resistance and thermal shock stability, metallic aluminium and fused Al2O3–ZrO2 were used as the raw materials, while phenolic resin was used as the binding agent. The microstructure was characterised by means of X-ray diffraction and scanning electron microscopy tests. Based on the reaction between zirconia and metallic aluminium under N2 flowing at 1300 °C, the reaction mechanism of zirconia and metallic aluminium in-situ reaction at 1300 °C to generate (Al2OC) x(AlN)1− x solid solution, zirconium nitride, and aluminium–zirconium alloy was revealed, and a model for the evolution of the phases in the aluminium-added Al–Al2O3–ZrO2 specimen was constructed to realise the Al–Al2O3–ZrO2 composite refractories phase controlling. Based on the good corrosion resistance of ZrO2 to CaO and the excellent results of the in-situ reaction of metallic aluminium to generate a large number of non-oxide reinforcing phases capable of replacing elemental C, this work is of great significance for the study of refractory in erosion-heavy environments, such as calcium-treated steel.

Structure Formation of a Ceramic Composite of the Al2O3–ZrO2 System During Strontium Hexaaluminate Synthesis During Firing

Structure Formation of a Ceramic Composite of the Al2O3–ZrO2 System During Strontium Hexaaluminate Synthesis During Firing

Determination of gamma radiation shielding efficiency by radiation-resistant composite ZrO2–Al2O3 – TiO2–WO3 – Nb2O5 ceramics

This work examines the prospects of using composite ZrO2–Al2O3 – TiO2–WO3 – Nb2O5 ceramics as shielding and radiation-resistant materials as structural materials in conditions of heightened radiation background, including gamma radiation and exposure to heavy ions. The key objective of the study is to determine the impact of the variation in composite ceramic composition on resistance to radiation damage caused by exposure to heavy ions comparable to nuclear fuel fission fragments, and to establish the effect of the radiation damage accumulation on the shielding characteristics of these ceramics, the maintenance of which determines the stability of the operation of nuclear materials by eliminating the ionization factor caused by the interaction of gamma quanta. During the studies, it was found that alterations in the phase composition of composite ceramics associated with the formation of ZrTiO4, AlWO3 and Nb2W3O14 phases in the structure lead not only to strengthening of the ceramics, but also to a rise in resistance to radiation damage, and associated changes in the damaged layer degradation, having an adverse impact on the shielding characteristics.

Parametric Optimization of Al2O3–ZrO2 (Y2O3) Based Self-Lubricating Composite Cutting Tools for Increasing Shear Angle and Tool Wear Reduction Using Grey-Taguchi Analysis

Parametric Optimization of Al2O3–ZrO2 (Y2O3) Based Self-Lubricating Composite Cutting Tools for Increasing Shear Angle and Tool Wear Reduction Using Grey-Taguchi Analysis

Ni decorated three-dimension hierarchical pyramidal ZrO2–Al2O3 nanoporous sheets for methane production

ZrO2–Al2O3 nanocomposites were synthesized by a modified co-precipitation method and loaded with 5%Ni as catalysts for methane production via n-heptane cracking. The as-synthesized nanocomposites were characterized by several techniques such as XRD, N2 adsorption-desorption, XPS, TEM, SEM, AFM, TGA, DTG, NH3 -TPD and Raman analysis. The XRD results confirmed the synthesis of amorphous γ alumina and hexagonal phase of zirconium alumina oxide (Zr5Al3O0.5) solid solution. XRD and SEM analyses showed additional small size Related to monoclinic phase of ZrO2 particles loaded on the Al2O3 surface. BET analyses confirmed the ZrO2–Al2O3 formation in mesoporous sheets structure. TEM images of the neat alumina, 10 ZA and their corresponding Ni loaded samples (Ni@10 ZA) revealed well-defined 3D hierarchical pyramidal structures with a height about 200 nm. All catalysts under this study exhibited high tendency to favor methane production via n-heptane cracking. At higher reaction temperatures, Ni@10 ZA catalyst exhibited higher cracking activity compared to the other prepared catalysts under this investigation which confirmed by NH3 -TPD analysis. A promising yield of methane was achieved at about 88 % coupled with 94.71 % selectivity at reaction temperature of 400 °C. Herein, the data collected through this research work revealed that Ni@10 ZA is a promising candidate for methane production via n-heptane cracking.

Controllable preparation and slag corrosion resistance of novel MgO–MgAl2O4–ZrO2 refractory

Brine magnesia and fused Al2O3–ZrO2 powder were used as raw material to prepare MgO–Al2O3–ZrO2 (MAZ) refractory brick which was sintered at 1690 °C for 8 h in a tunnel kiln. Its resistance to slag corrosion of non-ferrous metallurgy was investigated. The phase and microstructure of the samples before and after corrosion were characterized by XRD, SEM and EDS. The results show that MAZ ternary metastable phase was formed during sintering, which then decomposes to finely dispersed MgO, MgAl2O4, and ZrO2. Thus, highly uniform distribution of ultra-fine MgAl2O4 and ZrO2 in the matrix was achieved. The non-ferrous metallurgical slag is mainly composed of FeO and SiO2. At high temperatures, when the material is subjected to slag corrosion, both (Mg, Fe)Al2O4 and 2MgO·SiO2 with high-temperature melt point were formed in the corrosion layer, effectively preventing further infiltration and corrosion of MAZ samples by slag. A model for the formation process of high dispersion of MAZ was explained, and a model for the corrosion mechanism between non-ferrous metallurgical slag and MAZ samples was established.

Effect of nano-oxides on corrosion resistance of Al2O3–ZrO2–C material

The Al2O3–ZrO2–C material was prepared using tabular alumina aggregates and fines, zirconia-corundum, zirconia-mullite, flake graphite, B4C powder, Si powder and different nano-oxides (nano-ZrO2, nano-TiO2, and nano-Al2O3) as raw materials, the effects of different nano-oxides on the corrosion resistance and microstructure evolution of Al2O3–ZrO2–C material were investigated. The results showed that the high reactivity nano-ZrO2, nano-TiO2, and nano-Al2O3 particles reacted with CaO to generate high melting point phases of CaZrO3, CaTiO3, CaO·6Al2O3 (CA6) at high temperature, which forms a protective layer at the interface between corroded media and samples, inhibiting CaO penetration into the material. Additionally, nano-oxides can fill the pores and increase the density of material, thereby contributing to improving the penetration resistance and corrosion resistance of material.

Effects of He irradiation on the microstructures and mechanical properties of Al2O3–ZrO2–ZrC ceramic composites

In this study, the irradiation response of Al2O3–ZrO2–ZrC ceramic composites under 500 keV He ion irradiation at room temperature has been investigated. The microstructure evolution was studied by grazing incidence X-ray diffraction (GIXRD) and transmission electron microscopy (TEM), while the hardness was assessed using the nanoindentation method. The results showed that the composites consisted of α-Al2O3, t-ZrO2, and ZrC phases, and no phase transformations were observed. However, a marginal degradation of structural crystallinity and lattice swelling occurred after irradiation. The aggregation of He bubbles was observed at grain/phase boundaries near the damage peak region. He bubbles were mainly distributed in the α-Al2O3 grains, with only a few in the t-ZrO2 grains. Although no significant presence of He bubbles was discovered in the ZrC grains. the defects clusters mixed “black dot” defects, dislocation loops were observed. The nanoindentation hardness increased with the irradiation fluences up to 1.0 × 1017 ions/cm2, but decreased at a fluence of 2.0 × 1017 ions/cm2. In the peak damage region, He bubble bands were formed in some α-Al2O3 and t-ZrO2 grains at the fluence of 2.0 × 1017 ions/cm2. The bubble bands are responsible for the weakened irradiation hardening effect.

Growth mechanism of Al2O3 on surface of ZrO2 inclusions: experimental and first principles investigation

Zr has been widely used in high-quality steel due to its strong deoxidizing capacity and ability of improve performance of steel. ZrO2–Al2O3 inclusions with core-shell structure were observed in this study. The structure, electronic properties, and energy changes of ZrO2 and ZrO2–Al2O3 systems were studied based on first principles calculation. It indicates that ZrO2 can be used as the heterogeneous nucleation core of Al2O3. Al atoms were preferentially adsorbed on the bridge site of ZrO2 (001) and then form the ZrO2–Al2O3 interface. The template effect of ZrO2 was nine adsorption atomic layers, among which layers 1–5 was a coherent epitaxial layer, layers 5–9 was the transition layer, and the atomic ratio was 3:2. The growth mechanism of Al2O3 on ZrO2 surface was discussed. The results help understand the formation of inclusion at atomic scale and find ways to control the characteristics of inclusion in steel with Zr treatment.

Optimization of stir casting parameters for the tensile behavior of nano Al2O3 and ZrO2 reinforced Al-Mg-Si alloy metal composites

Stir casting is a frequently used method in the metallurgical process of casting aluminium composites. The microstructure and performance of the composites are influenced by the stirring casting parameters. The majority of research conducted in this area focused on producing composites using stir casting parameters that were predetermined, without utilizing an optimization method. This work aims to optimize the stir casting parameters for the manufacturing of Al-Mg-Si (Al6061) alloy reinforced with hybrid nano Al2O3 and nano ZrO2 in order to enhance its performance. The Taguchi optimization technique was employed to analyze the important effects of stir casting parameters on the ultimate tensile strength of a hybrid metal matrix composite. The composites were produced by the ultrasonic aided stir casting method, employing a set of process parameters determined by the Taguchi L16 orthogonal array. The S/N (Signal to Noise ratio) and Regression model were utilized to determine the optimal values and assess the influence of process parameters on the tensile qualities. The Minitab 21 software was utilized to perform simultaneous optimization of the attributes. The findings indicated that the composition of the nano reinforcement, stirring temperature, stirring speed, and stirring time all had a substantial impact on improving the UTS (Ultimate Tensile Strength) of the material.

Characterization of Zr-bearing crystalline phases from Rb-bearing model matrix materials

As part of the synthesis of new matrix materials for vitrifcation of highly active radioactive wastes, the crystalline phases formed during rapid cooling from melts of the Na2O–Rb2O–SrO(Ba)–B2O3– SiO2–Al2O3–ZrO2 system with a high Rb and Zr content (up to 10 mol. %) are found and studied. The presence of numerous Zr and Rb-bearing crystals in samples is established by electron microscopy, X-ray diffraction and Raman spectroscopy; their morphology, chemical composition and spectral characteristics are studied. It is concluded that these crystalline phases form due to the excessive content of individual components of the melt and their formation is responsible for the undesirable fnal local heterogeneity and crystallization of matrix materials.

Using the zirconium­containing binders for obtaining refractory concretes

Now the creation of new heat­resistance and refractory binding materials contributing towards reliable and durable service of high­temperature plants is paid great attention. To develop the physical and chemical principles of such materials technology first of all it is necessary to study the high­melting oxide systems and as a consequence, to obtain refractory products in terms of ones. Taking into consideration all mentioned above, the multicomponent zirconium­oxide systems are of potential interest.
 As a result of our investigations new compositions of high­strength, heat­resistance, and refractory zirconium­containing binders on the basis of different sections of the quaternary system CaO—Al2O3—ZrO2—SiO2 are obtained. Refractory concretes in terms of zirconium­containing cement and various aggregates, both natural (corundum, baddeleyite) and artificial (calcium zirconate), have been elaborated. It is revealed that the kind and granulometric composition of aggregates, molding methods, as well as cement­aggregate relation influence the physical and mechanical properties of concrete developed. Concretes obtained are characterized by high strength (50—60 MPa) and service property stability: refractoriness — more than 1700 °C thermal shock resistance — more than 30 cycles; thermal linear expansion coefficient — 4.8×10–6 ÷ 5.6×10–6 deg.–1, initial strain point under load of 0.2 MPa — 1400—1500 °C Materials developed comply with requirements to refractory materials and can be applied for monolithic linings of heat density parts of high­temperature plants.

Modification of Quartz Ceramics by Applying a Sol-Gel Composition of MgO–Al2O3–ZrO2–SiO2 System

Composite sol-gel materials of the MgO–Al2O3–ZrO2–SiO2 system were synthesized and the processes of their thermal evolution and crystallization were studied. Application of sol-gel compositions of the MgO–Al2O3–ZrO2–SiO2 system to the surface of quartz ceramics leads to a significant increase in the mechanical strength of the material. The processes of thermal evolution of the sol-gel composition were studied using IR spectroscopy, X-ray diffraction, electron microscopy, and energy dispersive analysis. It was shown that the formation of the oxide composite structure of materials begins at the stage of wet gels. Treatment of quartz ceramics with composite sols followed by drying and heat treatment up to 1200°C results in modification of the surface layers of the material, which makes it possible to increase the mechanical strength of the material by more than 20%. Sol-gel modifying compositions, upon drying and subsequent heat treatment, form polycrystalline structures bonded to quartz ceramic particles and consisting of various oxide crystals.

Aero acoustic levitation to unveil the solidification of complex oxides: Case study of the system Al2O3–ZrO2

Binary or multi-component phase mixtures are of particular technical importance. Despite the wide field of application of Al2O3 and ZrO2 composites, the literature reveals contradictions about the liquidus region. Containerless processing avoids typical problems of conventional techniques like melt contamination or lack of suitable container materials. Composition ranging from 0–80 mol% ZrO2 were melted and solidified in an aero acoustic levitator. A high-speed camera recorded the crystallization, allowing a direct correlation with the observed microstructures. Due to homogeneous nucleation, all samples exhibited significant undercooling before crystallization. The nucleation temperature of the different compositions roughly followed the slope of the liquidus line. Undercooling, solidification kinetics, and local reheating played a considerable role in microstructure formation. A lamellae eutectic microstructure was created over a large compositional range from 36–48 mol% ZrO2. On the hypoeutectic side, the effect was attributed to solidification within the coupled zone. However, hypereutectic samples also exhibit a zirconia-rich eutectic as well. We assume impaired ZrO2 nucleation or growth favors alumina precipitation from the melt. Aero acoustic levitation proved to be an excellent technique for studying complex high melting oxide systems, enabling a better understanding of their crystallization process.

Morphology and formation mechanism of cracks in Al2O3–ZrO2 eutectic ceramics fabricated via laser powder bed fusion

AbstractThe cracks in Al2O3–ZrO2 eutectic ceramics produced by laser powder bed fusion (LPBF) have a significant impact on their practical applications in various industries. In order to understand the factors influencing crack formation, a systematic study of the characterization and propagation of cracks in single‐track, multi‐track, and bulk samples by varying the process parameters has been carried out in this research. The results showed that parallel cracks can be healed by reducing the scanning spacing and scanning length. Additionally, it was found that using a modest scanning speed and a shorter length can minimize the accumulation of thermal stress, resulting in the suppress crack formation. Based on this conclusion, a crack‐free Al2O3–ZrO2 eutectic ceramic sample was finally obtained under the optimized parameters with the power of 100 W, the scanning speed of 100 mm/s, the hatch spacing of 100 μm, the scanning length of 3 mm, and the layer thickness of 50 μm. Additionally, three typical microstructures, including eutectic, cellular, and dendritic structures, were identified in the LPBF‐fabricated Al2O3–ZrO2 samples. The cellular microstructure showed improved crack inhibition capability due to the deflection and pinning effects. Cracks expand more easily in dendritic and eutectic microstructures, where anisotropy is more prominent.

Impact of thermal shock on the R-curve and subcritical damage behaviour of flame-sprayed alumina compounds

An alumina rich Al2O3–ZrO2–TiO2 compound was used for the preparation of self-supporting parts via the rod flame spraying technology. The as-sprayed material was compared to self-supporting parts, fabricated from commercially available alumina rods. For both materials, the flexural strength, the fracture resistance, and the behaviour under subcritical loading was evaluated and compared, either before as well as after cold thermal shock. While the flexural strength and the subcritical damaging of both materials were basically affected through thermal shock in a similar manner, the Al2O3–ZrO2–TiO2 compound showed an outstanding behaviour in terms of its fracture resistance, which was only barely reduced after thermal shock quenching.

Synthesis of Precursors of Complex Oxide Systems Al2O3–ZrO2–MxOy (M = La, Y, Ce) Using Electrogenerated Reagents and Their Physical and Chemical Properties

Synthesis of Precursors of Complex Oxide Systems Al2O3–ZrO2–MxOy (M = La, Y, Ce) Using Electrogenerated Reagents and Their Physical and Chemical Properties