Al2O3 Ceramic Materials Research Articles

Study on the wear characteristics of a 3D printed tool in flat lapping of Al2O3 ceramic materials

Widespread and popular use of ceramic products in various industry sectors necessitates the search for methods of their efficient processing. Lapping technology, which enables obtaining high dimensional and shape accuracy and high surface flatness, is one of the basic methods of finishing hard and brittle technical ceramics with a porous structure. This study analyzed the characteristics and wear value of an SLS-printed abrasive tool intended for single-sided lapping of Al2O3 technical ceramics. As earlier research demonstrated, introduction of a 3D printed lapping plate by selective laser sintering (SLS), leads to a significant development in the field of precision machining technology. This method showed not only efficient machining performance on oxide technical materials, but was also characterized by relatively low abrasive wear. Straightness errors were evaluated with the use of a least-squares method (LSQ) and minimum zone method based on control line rotation scheme (CLRS). The proposed model proved the experimental results by identifying a similar location of a higher contact density on the lapping tool, where this location is expected to be the one for bigger wear. Surface topography of the lapping tool depends on the tool wear intensity and as a consequence on its shape error. An SLS-printed lapping plate, by obtaining good technological effects, revealed its potential ability in machining hard and brittle technical ceramics.

The Effect of Laser Power and Laser Exposure Time for Cavity Created on Al2O3 Ceramic Surface

Al2O3 ceramic materials have many industrial applications, especially because they are wear-resistant. In this study, dimples of different sizes were formed on the surface of ceramic plates with a CO2 laser. The effects of laser power and laser exposure time on the dimensions of the cavity were investigated. For this purpose, laser powers of 40, 52, 65, 78, 91, and 105 W were applied to the ceramic material for 10 seconds. In addition, 80 W laser power was kept constant and the laser beam was sent to the material for 1, 5, 10, 15, 20, 25, and 30 seconds. High-resolution images of the resulting cavities were taken with an optical microscope. Using the images, the dimensions of the cavities were measured and the effects of laser power and laser exposure time on the cavity geometry were observed. The effects of both laser power and laser exposure duration on the cavity and Heat Affected Zone (HAZ) regions showed similar characteristics. The size of the cavities and HAZ increased almost linearly as laser power increased. However, when the effect of laser exposure duration was analyzed, the increase in cavity sizes slowed down after the exposure duration exceeded 10 s. When the laser exposure duration exceeded 15 seconds, it was observed that the dimensions of the cavities did not change.

Modulating mechanism on the temperature dependent resistivity of ceramic dielectrics and its advantage over polymer insulation

Volume resistivity of polymer dielectrics reduces significantly with the increase of temperature. As a result, in direct current (DC) power apparatus or electronic device, temperature gradient over the material can result in considerable electric field distortion which greatly threats the polymer insulation. Advanced ceramic dielectrics are promising to be alternative to polymer insulation to deal with this issue. In this paper, Al2O3 and Si3N4 ceramic materials with different ion doping concentrations have been manufactured. Temperature dependent resistivity characteristics of the ceramics are obtained and compared with typical polymer dielectrics. Conduction models of the ceramic dielectrics are applied to understand their temperature dependent resistivity and its modulating mechanism. Effect of ion doping on the temperature dependent resistivity has been obtained and analyzed which agrees well with their charge trapping property acquired by thermal stimulation depolarization current measurement, based on which the method to modulate the temperature stability of material resistivity have been proposed. Finally, a comprehensive comparison between ceramics and polymers in high voltage DC applications have been made which further proves the advantage of ceramic dielectrics.

Structurally characterized aluminum alkoxide derivatives for aerosol spray materials production

The synthesis of a family of aluminum alkoxides was undertaken via the reaction of trimethyl aluminum (Al(CH3)3) using a series of sterically varied ortho-substituted phenols (H-OAr), including: 2-methyl phenol (H-oMP), 2-isopropyl phenol (H-oPP), 2-phenyl phenol (H-oPhP), 2,6-di-methyl phenol (H-DMP), 2,6-di-isopropyl phenol (H-DIP), and 2,6-di-phenyl phenol (H-DPhP). The products isolated using the least sterically encumbered phenoxides proved to generate the homoleptic compounds: [(oMP)Al((μ-oMP)2Al(oMP)2)2] (1), and [Al(μ-oPP)(oPP)2]2 (2), [Al(μ-oPP)(oPP)2(THF)]2 (2-THF), and [Al(μ-oPhP)(oPhP)2]2 (3). As the steric bulk was increased only partial substitution was achieved forming the alkyl, alkoxide compounds: [Al(μ-OAr)(CH3)(OAr)]2 (OAr = trans-DMP (4a), cis-DIP (5a), trans-DPhP (6a)). Sub-stoichiometric metathesis reactions for the smaller OAr ligands were undertaken to produce a series of [Al(CH3)3-x(OAr)x]2 where × = 2: OAr = trans-oMP (1a); x = 1, OAr = oMP (1b), and DMP (4b). Alternatively, the use of neo-pentanol (H-ONep) led to the homoleptic species [(ONep)Al((μ-ONep)2Al(ONep)2)2] (7) and heteroleptic [Al(μ-ONep)(CH3)2]2 (7b). Efforts to generate 7 from [Al(OPri)3]4 resulted in the production of the mixed ligated species [Al4(μ-OPri)6(ONep)6] (8). The compounds were fully characterized using a variety of analytical tools as well as multinuclear NMR (1H, 13C, 27Al) spectroscopy. Select species were used for aerosol spray pyrolysis for the anticipated production of alumina (Al2O3) materials. The final products from 1, 1b, 7, and 7b proved to generate amorphous mesoparticles of size 2.1(0.1), 2.6(0.2), 2.7(0.2), and 2.5(0.2) μm, respectively as determined by SEM and pXRD analyses. Data collected using Single Particle Aerosol Mass Spectrometry (SPAMS) revealed that Al0 particles had been produced instead of the expected Al2O3 ceramic materials.

Effect of graphene nanoplatelets on the mechanical properties and cutting performance of alumina nanocomposite ceramic tools prepared using the SPS-HF dual sintering method

Al2O3/graphene nanoplatelets (GNPs) materials were prepared using the spark plasma sintering-high-frequency (SPS-HF) dual sintering method. The mechanical properties and microstructure of the composites were observed, and the effects of the sintering process and GNPs on the composites were analyzed. Under the sintering condition of a temperature of 1350 °C, pressure of 35 MPa and holding time of 8 min, the optimal mechanical properties of Al2O3 ceramic tool materials were obtained. The addition of GNPs had a positive effect on the mechanical properties of Al2O3 materials. Results show that the SPS-HF dual-sintering method shortens sintering time significantly. Compared to Al2O3 ceramic material, the composite material with 0.5 vol% GNPs had better mechanical properties than the Al2O3 ceramic material, with its flexural strength and fracture toughness being increased by 15.3% (617 MPa) and 63.4% (6.7 MPa m1/2), respectively. The toughening mechanisms of Al2O3/GNPs ceramic nanocomposites are graphene pull-out, graphene breaking, crack deflection, and crack branching. Dry machining tests of 40Cr hardened steel were carried out using an Al2O3/GNP ceramic tool and an Al2O3 ceramic tool. Compared with the Al2O3 ceramic tool, the life of the Al2O3/GNPs ceramic tool was increased by 16.3%, the workpiece roughness was decreased by 9.2%, and the friction coefficient was reduced by 12.8%, confirming the improvement of cutting performance by adding GNPs to ceramic tool materials.

The brazing of Al2O3 ceramic and other materials

The brazing of Al2O3 ceramic and other materials

Compound connection mechanism of Al2O3 ceramic and TC4 Ti alloy with different joining modes

In this paper, laser welding-brazing of TC4 Titanium (Ti) alloy and Al2O3 ceramic dissimilar material was carried. The results showed that the Ti alloy and Al2O3 were joined by melting filler metal when the laser was concentrated in the Ti alloy side of the joint. The joint with one fusion weld and one brazed weld separated by remaining unmelted Ti alloy. Laser beam offset the Ti alloy 1.5 mm, Ti alloy would not be completely melted in joint. Through heat conduction, the filler metal melted occurred at the Ti-ceramic interface. A brazed weld was formed at the Ti-ceramic interface with the main microstructure of β-CuZn + Ti2Zn3, β-CuZn and Al2Cu + β-CuZn. The joint fractured at the brazed weld with the maximum tensile strength of 169 MPa.

Microstructural characterization and mechanical properties on Al2O3–TiO2 materials obtained by uniaxial pressing and extrusion

The present investigation compares for the first time the effect of the addition of TiO2 on Al2O3 ceramic materials prepared by uniaxial pressing and extrusion technique. The properties of the disc- and tubular-shaped materials were investigated using different experimental tests, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Archimedes porosity, linear shrinkage, mechanical performance and scanning electron microscopy (SEM). The XRD analysis revealed the formation of Al2TiO5 phase at 1400 °C for discs and tubes, and became more evident when the sintering was performed at 1500 °C. The increase of TiO2 loading did not affect the open porosity at a given temperature for the tubular- and disc-shaped samples. The addition of 1 wt% TiO2 led to a remarkable increase of tensile strength for the disc-shaped materials heat treated at all temperatures due to the formation of aluminum titanate. However, a further addition on the TiO2 loading appears to decrease the tensile strength of the disc-shaped samples heat treated at 1400 °C and 1500 °C. For instance, the flexural strength of the tubes improved with increasing TiO2 loading and sintering temperature from 1300 °C to 1500 °C. This effect was attributed to the occurrence of a more effective formation of Al2TiO5 on the ceramic tubes. Furthermore, the addition of TiO2 played a key role in controlling the open porosity and the microstructure as confirmed by the SEM images in ceramics obtained by uniaxial pressing and extrusion processing.

Wear of electroplated diamond tools in lap-grinding of Al2O3 ceramic materials

Current development of modern products, together with ever-increasing demands for their operation and usage, necessitate the search for new processing methods. Abrasive machining is widely used in many industrial areas, especially for processing difficult-to-machine materials such as advanced ceramics. Grinding with lapping kinematics, also called lap-grinding, is still one of the innovative methods of abrasive processing being under continuous development. It combines the advantages of grinding and lapping, allowing for meeting high design requirements and, at the same time, ensuring efficient and safe machining. This paper presents experimental and modelling results on the application of electroplated wheels with diamond grains (D107 and D64) in the lap-grinding of Al2O3 ceramic materials in a single-disc lapping machine configuration. The grain size along with the thickness of the nickel bond influenced the material removal rate and surface roughness obtained. The relationship between the material removal and the processing time was approximated by asymptotic mathematical functions. Moreover, the empirical models were modified according to the Preston's equation when the unit pressure increased. The linear and nonlinear regression models enabled accurate curve fitting to the surface roughness data. Microscopic images of the active surface of electroplated diamond tools were analyzed in the aspects of the resultant tool wear and technological effects. In addition, the results were referred to the analysis of microscopic images of the suspension taken from the active surface of the tool after subsequent tests. The suspension consisted of particles of fragmented abrasive grains as well as chips removed from the machined surface.

Nano-graphene toughened Al2O3 ceramic materials: 3D simulation of the fracture behaviour

A 3D simulation model of graphene toughened Al2O3 ceramic materials had been developed to study the fracture behaviour. Voronoi tessellation was used owing to its high similarity to the ceramic grain distribution. In addition, a new method to automatically generate nano-graphene along the Al2O3 grain boundaries was proposed. The Al2O3/graphene interface properties were characterised by the cohesive zone method, wherein cohesive elements along grain boundaries and in grains were generated using Python. Furthermore, the effects of phase interface bonding strength and graphene content on the fracture behaviour were analysed. The results clearly showed the occurrence of both intergranular and transgranular fractures. In addition, some toughening mechanisms induced by nano-graphene such as crack guiding, crack bridging, crack branching, microcracks, and pull-out of graphene have been discussed. The finite element simulation results were consistent with the experimental ones. Therefore, the results presented in this study would be beneficial for improving the design efficiency of Al2O3/graphene ceramic materials.

Effect of graphite addition on mechanical properties of Al2O3 ceramics by directed laser deposition

In this article, graphite-reinforced Al2O3 ceramic materials were prepared by directed laser deposition. The effects of graphite addition (3–12 wt.%) on the phase composition, microhardness and fracture toughness of Al2O3 ceramics were studied. The results showed that the process was beneficial for maintaining uniform mixing of graphite and ceramics and thus could avoid the delamination caused by the difference in their densities. When adding 6% and 9% graphite, there were fewer internal defects in the samples, and no obvious new phase was generated after adding more graphite. The microhardness of 6% and 9% graphite-reinforced Al2O3 ceramics reached 18.84 and 18.86 GPa, respectively, and it was close to that of pure Al2O3 ceramics. The microhardness of all graphite-reinforced Al2O3 materials was lower than that of pure Al2O3 ceramics, but the value increased first and then decreased with addition of more graphite. The change in microhardness was similar to the trend of the number of defects, thus, these newly forming defects were an important factor affecting the microhardness. With an increase in graphite addition, the fracture toughness increased gradually. Furthermore, the fracture toughness reached 5.89 MPa m1/2 at 12% graphite addition, which was higher than 4.82 MPa m1/2 of pure Al2O3 ceramics. Adding more graphite was beneficial in enhancing the deflection and pinning of the graphite particles against cracks, resulting in higher fracture toughness. Graphite can improve the fracture toughness of Al2O3 ceramic, prepared by directed laser deposition, and the method can solve the uneven distribution caused by the difference in densities between the two powders. This also provides a new idea for the rapid manufacture of high-toughness ceramic parts at lower cost.

Increasing the Sintering Rate and Strength of ZrO2–Al2O3 Ceramic Materials by Iron Oxide Additions

We have prepared powders and ceramic composite materials in the ZrO2–Al2O3 system containing 10 and 20 wt % Al2O3 and examined the effect of ferric oxide additions on the linear shrinkage, phase composition, porosity, microstructure, and mechanical properties of the ZrO2–Al2O3 ceramic materials. The results demonstrate that the addition of ferric oxide leads to a considerable increase in linear shrinkage and ensures porosity as low as under 1% even at a sintering temperature of 1450°C in both composite materials. Moreover, small amounts of the additive stabilize the tetragonal phase of ZrO2, whereas increasing the Fe content to 3 mol % leads to an increase in the amount of the monoclinic phase. We have obtained densely sintered ZrO2–10% Al2O3 and ZrO2–20% Al2O3 ceramic materials at 1450°C, with a bending strength of up to 760 and 475 MPa, respectively.

Cohesive Element Model for Fracture Behavior Analysis of Al2O3/Graphene Composite Ceramic Tool Material

The microstructure model of Al2O3/graphene (AG) composite ceramic tool material is established based on Voronoi tessellation. The cohesive element method was used to simulate the crack growth of AG. The effect of cohesive parameters at the grain boundary of Al2O3 and graphene on the crack propagation was investigated. The results show that the grain strength of graphene is too high, the crack propagation to graphene grains will be hindered and cannot propagate forward. Cracks tend to spread along the paths where the crack propagation drive force was high and the resistance was low. When the interface strength between Al2O3 and graphene was at the weak interface, the crack propagation path and length were relatively straight and short. The average energy release rate G C is 1.042 × 10−3 J/m2, which is 2.4% higher than that of single-phase Al2O3 ceramic tool materials. However, if the interface strength between Al2O3 and graphene was at the strong interface, the crack propagated along graphene particles for a short distance, consuming a large amount of fracture energy. Furthermore, the crack will deflect around graphene grains, which increases the crack propagation length. The average energy release rate G C is 1.039 × 10−3 J/m2, which is 2% higher than that of single-phase Al2O3 ceramic tool materials.

Electrical Discharge Machining of Al2O3 and Si3N4 Ceramics; A Research

Ceramic materials which have high hardness and brittleness cannot be machined by traditional machining process because of their low efficiency and feasibility. But in non-traditional machining process, it overcomes these limitations proving it to be very useful in manufacturing process. In this review paper we are discussing about electrical discharge machining (EDM) process on Al2O3 and Si3N4 ceramic materials which are machine able. EDM parameters like material removal rate (MRR), tool wear rate (TWR), surface finish are discussed. EDM is very much suitable for ceramic materials because of its high surface finish, accuracy and efficiency.

Thermal and technological aspects of double face grinding of Al2O3 ceramic materials

Abstract Double face grinding with planetary kinematics is a process to manufacture workpieces with plan parallel functional surfaces, such as bearing rings or sealing shims. In order to increase the economic efficiency of this process, it has to be advanced permanently. The temperature in the contact zone of most grinding processes has a huge influence on the process efficiency and the workpiece qualities. In contrast to most grinding processes these influences are unknown in double face grinding with planetary kinematics. The application of standard measuring equipment is only possible with high effort due to the inaccessibility of the working space during the machining process. Furthermore, measurement of the workpieces temperature in the considered machining system is not reported. Due to that fact, the intensive cooling has so far been the only method to avoid the occurrence of thermal defects especially in case of brittle ceramic materials. The influence of the mean cutting speed, the tools’ cutting performance and the coolant flow on the temperature change of the workpieces made of Al2O3 ceramic materials was investigated with the use of a newly developed method. The first empirical approach to predict the change in temperature of the ceramic workpieces while processing is proposed. The developed measuring method can be used for obtaining experimental temperature data in other processes, such as polishing and lapping for which only theoretical models exist.

Optimization of process parameters by using Taguchi Techniques in abrasive air jet machining of Al2O3 ceramic material

Abstract Quality surface finish of Al2O3 work piece present variety of issues such as non conventional machine is one of the foremost often times used material process in machining of Al2O3 work material to produce outlined surface finish, surface finish associated good characteristics of the work material and input parameters used. The quality of the surface, dimensional precision greatly has an effect and the elements through their useful life. This project introduces a new technique of investigating the P, AFR, SOD and T on abrasive air jet machining of Al2O3 work material. Investigating of process parameters was done by Taguchi Technique. Experiments were conducted on Al2O3 work piece, the parameters of machining such as P, AFR, SOD and T of SiO2 particles impinged on the Al2O3 Materials are optimized by responded concerns particularly Material removing rate. The optimum levels of parameters investigated by using Taguchi method.

Research on Performance Analysis of Art Ceramics Based on Different Composition Contents

Objective: To analyze the mechanical properties of ceramics and the effect of wear resistance after adding different amounts of ZrO2 in Al2O3 ceramic materials, so as to obtain the optimum amount of ZrO2 in Al2O3 ceramics. METHODS: Al2O3 ceramics were prepared by hot pressing bantering. The first group used 99.6 vol% Al2O3, the second group used 15 vol% ZrO2 in Al2O3, and the third group used 25 vol% ZrO2 in Al2O3. In order to meet the memo-mechanical theory of materials and fully consider the phase transition characteristics of ZrO2, a mechanical structure model between the two is established. RESULTS: After the addition of refined zircon crystals to the alumina material, the compactness of the ceramic material was significantly improved. The mechanical properties of the ceramic materials produced in the three experiments showed a linear relationship of stress-strain curves. The fracture toughness of the first group of ceramics is 5.38 MPa⋅m0.5, and the fracture toughness of the second group of ceramics is 8.37 MPa⋅m0.5, which is about 50% higher than the fracture toughness of the previous set of experiments; the third group of experimental sites the fracture toughness of the obtained ceramic material was 10.53 MPa⋅m0.5. Conclusion: Further explanation, accompanied by an increase in the increase in ZrO2. The elastic modulus of ceramics decreases and the fracture toughness increases. This trend is in good agreement with the experimental results. The wear form without increasing the ZrO2 material layer is mainly abrasive wear, and the wear of the ZrO2 material layer is mainly adhesive wear.

Analysis of Gas Leakage and Current Loss of Solid Oxide Fuel Cells by Screen Printing

One of the biggest advantages of SOFC (solid oxide fuel cell) is the probable use of methane as fuel. However, when the actual SOFC stack is operating with CH4 as fuel, due to the catalytic action of metal nickel, carbon will deposit on SOFC anode and nickel foam, which directly shorten the SOFC operating life and lead to performance degradation. The planar anode-supported Ni-YSZ|YSZ|LSCF SOFC was chosen as the research object, with the cell size of 12cm×12cm and the effective area of 100cm2, and the holder is made of 99% purity of Al2O3 ceramic material, in order to eliminate the influence of Cr in stainless steel. The one-cell stack operated at 750℃, and the maximum power density was 0.35W/cm2 when the fuel is 0.5slm/min pure hydrogen. The stability experiment was conducted first under pure H2 for 100h, then fuel was switched into pure methane, and another 100h of voltage stability was tested. In this work, the temperature distribution of the stack was monitored, whose relationship with the weight gain and the micro-structure of the nickel foam was established, and a possible explanation of the carbon deposition distribution and process on the nickel foam was put forward.

Microstructural Effect on Crack Propagation Behavior of Ceramic Tool Materials via Cohesive Zone Modeling

A systematic and parametric study of the effect of grain size and volume fraction of secondary phase on crack propagation behavior of Al2O3 based ceramic tool materials was carried out. Two-dimensional centroid V toughness oronoi tessellations were generated with random grain orientations. Cohesive Zone Method (CZM) was utilized to simulate crack propagation behavior. Zero-thickness cohesive elements were embedded on grain boundaries and inside grains. Crack initiation and propagation in ceramic tool materials microstructure were simulated without predefined crack. Simulation results revealed that crack initiated at the maximum stress position and propagated along the direction perpendicular to external load. Decreasing the grain size or increasing the volume fraction of secondary phase can improve the fracture stress of Al2O3 ceramic tool materials.

An Investigation of Phase Stability of a Composite ATZ Ceramic Material

An investigation of phase transformations, taking place in a composite ZrO2(Y)–Al2O3 ceramic material sintered from ultrafine powders manufactured by a plasmochemical process, is performed during its storage and subsequent thermal heating. The composite low-porosity ceramics based on zirconium dioxide is found to be stable in interactions with the environment during long-term storage under standard conditions and thermal heating. A high efficiency of a spontaneous t→m phase transformation is observed in the composite ceramics with an open porosity of more than 6%. The composite ceramics, in which low porosity is combined with a reduced content of the stabilizing yttrium impurity in the crystal lattice of zirconium dioxide, is characterized by the lowest phase stability.