Ceramic Processing Research Articles

Design and fabrication of an aluminium oxide cutting insert with an internal cooling channel

This paper presents the design and fabrication of an aluminium oxide cutting insert with an internal cooling channel formed through an additive manufacturing method. The formed insert is subjected to a controlled densification process and analysed through a series of characterisation investigations. The purpose of the study is to develop the design concept and analyse the forming and sintering parameters used in the lithographic ceramic manufacturing process. The results validated the feasibility of the geometrical design, providing the required structural conformity with the integrated internal feature using conditional specifications. It is confirmed that the forming parameters would affect the material properties of the green body. Furthermore, the results indicate that the heating rate and temperature variance of the de-binding and thermal treatment regime influences the microstructural growth kinetics and the quality of the densified insert. Using a novel application of liquid gallium as an internal coolant, experimental results showed a decrease in tool wear difference of 36% at Vc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$V_{{\ ext{c}}}$$\\end{document} = 250 m/min, and 31% in tool wear difference at Vc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$V_{{\ ext{c}}}$$\\end{document} = 900 m/min between cooling and non-cooling conditions. When external cooling was applied, the results showed at Vc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$V_{{\ ext{c}}}$$\\end{document} = 250 m/min, the difference between the tool wear rates with the internal coolant relative to the external coolant was 29%. Increasing to Vc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$V_{{\ ext{c}}}$$\\end{document} = 900 m/min, the results revealed a 16% tool wear difference. The results clearly indicate the potential of liquid gallium as a heat transfer agent in internal cooling applications for cutting inserts, and by extension demonstrable reduction in tool wear.

Effect of La3+and Al3+ doping on the crystal structure and magnetic properties of strontium hexaferrites

Modification of crystal structure and magnetic properties of M-type strontium hexaferrites (SrM) doped with foreign ions (Al3+, La3+) was studied, focusing on the distortion of the lattice. Incorporation of Al3+ ions contracted the lattice of SrM and hardened lattice vibration modes with lattice disorders. X-ray diffraction examined the lattice distortion of FeO5 trigonal bipyramidal sites (TBP) revealing that off-center displacement (z0) was reduced to z0 = 0 by heavy Al3+ doping. This reduction of z0 was attributed to stabilization of single-well potential in the positioning of Fe3+ ions in TBP. Furthermore, La3+ doping led to a more significant contraction of the lattice and restored a non-zero off-center displacement of Fe3+ ion in TBP. The polycrystalline ceramics with high coercivity exceeding 21 kOe through the conventional ceramic processing route with concomitant La3+ and Al3+ doping.

Flash sintering of potassium-sodium niobate-based piezoceramics: Refining (micro)structure for properties enhancement

Low-consumption ceramics processing routes are expected to replace conventional ones due to environmental concerns. In this context, flash sintering is garnering interest because it allows dense ceramics to be obtained in just a few minutes and at relatively low temperatures. This is particularly interesting for sintering alkaline-based compounds due to the easy volatilization of these elements. In this work, current-controlled flash sintering is used to obtain potassium-sodium niobate (KNN)-based piezoceramics with refined microstructure and suitable stoichiometry, leading to improved functional properties. KNN-based materials are currently outstanding lead-free piezoceramics, with their properties highly sensitive to the proper construction of the polymorphic phase boundary, as in the case of the first promising composition (K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3. Results of this work show that sintering parameters may determine the polymorphic behavior of this system, thereby evincing flash sintering allows polymorphic phase boundary to be fine-tuned. It is demonstrated that the convergence of microstructure refinement and compositional control holds the potential for enhancing properties through a proper electric current control during flash sintering.

Numerical simulation of heat transfer during spark plasma sintering of porous SiC

The strong covalent bonding of SiC makes it difficult to be fully sintered using conventional sintering techniques. Therefore, electrical current-assisted sintering techniques such as spark plasma sintering are needed to sinter SiC. The finite numerical simulations have been generally used to predict and guide sintering processes of ceramics (i.e.TiC,AlO3). In this work, the numerical simulations of the temperature distribution, electrical field and thermal field on the porous SiC cylindrical samples by Comsol were investigated in details. The influence of porosity on the temperature distribution and electrical field distribution of the SiC samples were analyzed. Both the maximum current density (1.19 × 107A/m2) and the maximum temperature (2030 °C) of the SPS device occurred at the punch/spacer interface. The temperature values at the centre of the samples were proportional to the porosity, and the temperatures at the center of the samples increased from ∼1960 °C to ∼2010 °C at t = 2000s, with the porosity increasing from 1% to 60%. The uniformity of the temperature distribution deteriorated as the porosity increases, and the temperature gradients between the center and edge of the samples with the porosity of 1% and 60%, were ∼80 °C and ∼130 °C at t = 2000s, respectively.

Magnetic Supraparticles Capable of Recording High‐Temperature Events

AbstractSuperparamagnetic iron oxide nanoparticles (SPIONs) are prone to oxidation at elevated temperatures (>300 °C) and lose their magnetizability upon transition from magnetite/maghemite (γ‐Fe2O3 / Fe3O4) to hematite (α‐Fe2O3). Silica (SiO2) shells can effectively prevent this undesired effect up to ≈1000 °C. Herein, the study shows how to utilize SPIONs with varying SiO2 shell thickness and thus, different oxidation susceptibility, and how to combine them in micrometers sized assemblies – so‐called supraparticles (SPs), to create a structurally emerging magnetic temperature recording functionality. The desired oxidation of non or weakly‐protected SPIONs within SPs upon temperature events reduces dipole–dipole interactions of well‐protected SPIONs in the confined SP entity. The resulting change of magnetic interactions therefore contains information on the thermal history of the SP, which can be spectrally read out via magnetic particle spectroscopy within seconds. Their working range can be tuned from 400 to 1000 °C on two independent structural hierarchy levels, namely the SiO2 shell thickness and the freely selectable ratios of different building blocks in the SP. The application of such SPs as particulate additives for magnetic recording of high‐temperature events, especially relevant in metal, alloy, and ceramic processing, representing a yet unexplored and optically‐independent option for bulk temperature recording is proposed.

Cellulose nanocrystals engineered TPS/PBAT granulation through extrusion process and application for compostable carry bags

An economical and scalable process route has been developed for preparation of bio nanofillers, cellulose nanocrystals (CNCs) using acid hydrolysis and ceramic membrane-based continuous neutralization process alternative to conventional dialysis process. Optimized process achieved 42 % yield with crystallinity index of 91.3 % and average size 20–50 nm as confirmed by TEM analysis. Solid-state NMR result shows that the CNCs lateral dimension is comparable to elementary cellulose crystallites. Prior optimized composition of CNCs (Kesari et al., 2022) in TPS was used to prepare bio-nanocomposite with aim to reduced Poly (butylene adipate co-terephthalate) (PBAT) content in packaging films. A strong evolution in the mechanical and rheological properties of the CNCs reinforced blends was observed with increase in PBAT content with optimum blending ratio of 70/30. The composite attained tensile strength and young’s modulus of 11.01 ± 0.15 and 1200.94 ± 16 MPa, respectively with water vapor transmission rate (WVTR) of 63.96 ± 1.02 g/m2/day than neat PBAT (124.56 ± 6.89) which has higher vapor permeation. The thermal analysis confirms with bio nanofillers addition reduced the processing temperature of the polymeric blend. Thus, this work provides an economical and sustainable pathway for high content of biobased carbon (>70 %) for biodegradable packing industry.

Function optimization of ceramic firing process and reduction of energy consumption based on CFD simulation

Microwave sintering, as an efficient and energy-saving advanced sintering method, has advantages that traditional sintering methods cannot match, such as promoting ion diffusion and refining grains. This paper uses microwave heating equipment and solid-phase reaction method combined with microwave sintering technology to prepare ceramics. The treatment process of powders and the influence of microwave sintering parameters on the reduction of energy consumption in the ceramic firing process were studied, and the microwave sintering process was optimized. This article also uses computational fluid dynamics (CFD) as a tool to establish a numerical model of hydrodynamic sedimentation based on the Euler multiphase flow model, and it uses the established numerical model to conduct engineering scale research on the classification treatment process of processing waste. Finally, this article elaborates on the process of multi-process planning and optimizes relevant process parameters. This article builds on previous research by employing a BP neural network (BPNN) to determine the correlations between the many variables involved in the production of functional ceramics and their respective quality metrics. The experimental findings demonstrate the efficacy of the proposed methodology in performing intelligent tasks like process decision-making and optimizing process parameters.

Eutectic Additive Influence in the Li2O–B2O3 System on the Sintering Process and Properties of Li2MgTi3O8 Ceramics

Eutectic Additive Influence in the Li2O–B2O3 System on the Sintering Process and Properties of Li2MgTi3O8 Ceramics

Effect of yttrium nitrate coating on the vat photopolymerization forming process and sintering properties of aluminum nitride ceramics

In this study, a ball-milling method was successfully used to coat yttrium nitrate on the surface of aluminum nitride (AlN) powder and the effects of yttrium nitrate content on the AlN powder particle size, viscosity and curing behavior of the AlN suspension, and performance and microstructure of the sintered AlN bodies were investigated. The results indicated that the AlN powder surface coating significantly reduced the viscosity of the suspension and enhanced the cure depth while increasing the powder particle size, which in turn reduced the stability of the suspension. By studying the performance of sintered bodies, it was found that as the yttrium nitrate content increased, the AlN thermal conductivity and flexural strength initially increased and then decreased. Microstructural analysis results revealed that the second phase in samples with 9.23 and 14.49 wt% yttrium nitrate exhibited an island-like distribution, whereas in samples with 19.18 wt% yttrium nitrate, the second phase exhibited a continuous distribution. Finally, the heat-dissipation performance of AlN components with different structures was also studied, and testing was conducted on the driving chip of a 3D printing device. The results indicated that complex-structured AlN ceramic components exhibited an excellent heat-dissipation performance.

The morphological analysis as approach to ceramic design process

The morphological analysis as approach to ceramic design process

Understanding the consolidation mechanism of selective laser sintering/powder bed selective laser process of ceramics: Hydroxyapatite case

PurposeThe consolidation process and morphology evolution in ceramics-based additive manufacturing (AM) are still not well-understood. As a way to better understand the ceramic selective laser sintering (SLS), a dynamic three-dimensional computational model was developed to forecast thermal behavior of hydroxyapatite (HA) bioceramic.Design/methodology/approachAM has revolutionized automotive, biomedical and aerospace industries, among many others. AM provides design and geometric freedom, rapid product customization and manufacturing flexibility through its layer-by-layer technique. However, a very limited number of materials are printable because of rapid melting and solidification hysteresis. Melting-solidification dynamics in powder bed fusion are usually correlated with welding, often ignoring the intrinsic properties of the laser irradiation; unsurprisingly, the printable materials are mostly the well-known weldable materials.FindingsThe consolidation mechanism of HA was identified during its processing in a ceramic SLS device, then the effect of the laser energy density was studied to see how it affects the processing window. Premature sintering and sintering regimes were revealed and elaborated in detail. The full consolidation beyond sintering was also revealed along with its interaction to baseplate.Originality/valueThese findings provide important insight into the consolidation mechanism of HA ceramics, which will be the cornerstone for extending the range of materials in laser powder bed fusion of ceramics.

Synthesized by coprecipitation method for controlled phase structures of 5YSZ

Yttria-stabilized zirconia (YSZ), which exhibits a tetragonal phase, finds widespread application in the realm of high-temperature solid electrolytes. In the context of this research endeavor, a concerted effort was undertaken to procure a stable and controlled tetragonal phase structure within 5 mol% yttria-stabilized zirconia (5 YSZ) by modulating the precipitation rate of YSZ sols in three distinct precipitation environments, namely acidic (AC), near to neutral (NE), and alkaline (AL) conditions. Through the characterization of 5 YSZ compounds synthesized in these various environments, encompassing an assessment of their elemental composition, phase structure, local structure, and microscale morphology, it was discerned that under acidic conditions, the product exhibited non-uniform elemental distribution, pronounced agglomeration, and an abundance of hydroxyl groups, all of which proved detrimental to the stability of the tetragonal phase, resulting in the presence of 40.63% monoclinic phase. Conversely, under alkaline conditions, substantial agglomeration and hydroxyl group presence were also noted, with 34.7% monoclinic phase in the product. In stark contrast, under the condition which is near to neutral, the product demonstrated uniform elemental distribution, excellent dispersion characteristics, and a virtual absence of hydroxyl groups. The tetragonal phase structure remained stable and homogeneous, with almost negligible monoclinic phase content. Subsequent ceramic processing resulted in the highest attainable density (99.7%), coupled with the highest ionic conductivity at 850 °C (35.2 mS/cm). This study underscores that pH control during coprecipitation reactions stands as a robust and effective methodology for achieving a stable tetragonal phase structure.

A Novel Nondestructive Testing Probe Using AlN-Based Piezoelectric Micromachined Ultrasonic Transducers (PMUTs).

Ultrasonic nondestructive testing (NDT) usually utilizes conventional bulk piezoelectric transducers as transceivers. However, the complicated preparation and assembly process of bulk piezoelectric ceramics limits the development of NDT probes toward miniaturization and high frequency. In this paper, a 4.4 mm × 4.4 mm aluminum nitride (AlN) piezoelectric micromachined ultrasonic transducer (PMUT) array is designed, fabricated, characterized, and packaged for ultrasonic pulse-echo NDT of solids for the first time. The PMUT array is prepared based on the cavity silicon-on-insulator (CSOI) process and packaged using polyurethane (PU) material with acoustic properties similar to water. The fabricated PMUT array resonates at 2.183 MHz in air and at around 1.25 MHz after PU encapsulation. The bandwidth of the packaged PMUT receiver (244 kHz) is wider than that of a bulk piezoelectric transducer (179 kHz), which is good for axis resolution improvement. In this work, a hybrid ultrasonic NDT probe is designed using two packaged PMUT receivers and one 1.25 MHz bulk transmitter. The bulk transmitter radiates an ultrasonic wave into the sample, and the defect echo is received by two PMUT receivers. The 2D position of the defect could be figured out by time-of-flight (TOF) difference, and a 30 mm × 65 mm detection area is acquired. This work demonstrates the feasibility of applying AlN PMUTs to ultrasonic NDT of solids and paves the way toward a miniaturized NDT probe using AlN PMUT technology.

Repair and Maintenance of Ceramic Mould Pressing Machine

This study delves into the critical maintenance and repair procedures for ceramic pressing machines, integral to ceramic tile production. Through a comprehensive review of techniques and best practices, the research aims to optimize machine efficiency and quality output. Employing a methodical approach involving regular cleaning, component inspection, and timely part replacement, the study underscores the significance of skilled technicians proficient in diagnosing and rectifying issues before they escalate. Furthermore, emphasis is placed on the necessity of rigorous training for maintenance personnel and machine operators to ensure seamless operations and minimal production disruptions. The implications of these findings extend to the broader manufacturing sector, offering insights into enhancing machinery longevity and productivity. highlight : Proper maintenance ensures smooth operation and prevents unexpected breakdowns. Trained technicians are essential for effective repair and troubleshooting. Rigorous training for maintenance staff and operators optimizes machine performance and minimizes production downtime. Keywords: Ceramic pressing machines, Maintenance, Repair, Efficiency, Training

One-step synthesis and low-temperature rapid sintering of alumina-zirconia ceramics by flash sintering combined with phase transformation

High-performance alumina-zirconia ceramics are generally sintered above 1500 °C and consume lots of energy; rapid sintering at low temperature is an ideal technique due to its economy and low-energy consumption. For the first time, flash sintering combined with phase transformation-assisted sintering techniques was reported in this work. The alumina-zirconia amorphous precursor powder was used to replace the final product powder for ceramic processing, and the one-step synthesis and rapid sintering densification of alumina-zirconia ceramics at low temperature of 849 °C for 60 s were realized. The effects of electric field on the low-temperature sintering of amorphous powders are summarized into three aspects. Firstly, the electric field reduces the viscosity of the amorphous powder and promotes liquid phase sintering. Secondly, the electric field promotes the phase transition of the amorphous powder from metastable to stable phase, and accelerates the atomic migration. Thirdly, Joule heating and defect generation in the flash sintering promotes more effective material transport. Overall, this work reduces the energy for calcination of amorphous powders, reduces the sintering temperature of ceramics, well hinders the grain coarsening and shows excellent mechanical properties.

Synthesis of flexible, strong, and lightweight oxide ceramic nanofibers via direct electrospinning of inorganic sol for thermal insulation

Oxide ceramic nanofibers are widely used in aerospace and civil facilities due to their superior thermal stability and fire resistance. Currently, electrospinning, one of the important methods for preparing oxide ceramic nanofibers, must rely on adding organic polymers to impart spinnability to inorganic sols. However, these organic polymers will inevitably leave hole flaws in the ceramic nanofibers due to thermal decomposition during the subsequent ceramization process, seriously damaging their mechanical properties. Here, a direct electrospinning strategy for inorganic sol through hydrolyzation–polycondensation rate modulation is proposed, which gets rid of the dependence of spinnability of inorganic sol on organic polymer. Taking silica nanofibers as an example, it exhibits excellent flexibility and mechanical strength (tensile stress up to 1.4 MPa), as well as thermal insulation properties (thermal conductivity as low as 0.0551 W m−1 K−1 at 300 °C). This work provides new insights into developing other high–performance oxide ceramic materials.

Structure modification and electrical properties by Mn2O3 dopant addition to SnO2 varistor system

This work aims to study the effect of Mn2O3 additions on the electrical properties and microstructure characteristics of a SnO2-based ceramic varistor system doped additionally with Sb2O5, Cr2O3, and CoO. The specimens were prepared using conventional ceramic processing and homogenized by a high-energy ball milling system using the following composition: (98.99-X) % SnO2 – 0.05% Cr2O3 – 0.05% Sb2O5 – 1.00% CoO – X% Mn2O3 where X = 0.00, 0.05, 0.10, 0.20, 0.50 and 1% mol. Characterization by TG-DSC/DTA, XRD, XPS, and SEM/EDS, and the proposed chemical and defect-formation reactions allowed the conclusion that Mn2O3 additions produce alterations of the microstructure consisting of the in situ formation of the spinel Co2MnO4 secondary phase and modification of the potential barriers in the intergranular regions, where, in addition, oxygen vacancies are formed. With the 0.05 mol % Mn2O3, the grain size (average in the range of 2–3 μm) drops by 20 %, thus augmenting the grain boundaries. Altogether, this leads to a decrease in the nonlinearity coefficient (α) and an advantageous displacement of the breakdown electric field (EB). The 0.05 mol % Mn2O3 specimen compares favorably with the reference material by surpassing the EB value by a factor of 8. Elucidation of Mn2+ and Co2+ in 1 mol % Mn2O3 specimens by XPS suggests the role of MnO and CoO as intermediate phases, essential for Co2MnO4 formation. The pathway for in situ formation of Co2MnO4 is set forth based on the above characterization techniques in conjunction with proposed chemical and defect-formation reactions.

Improving multifunctional performance of Dy-doped (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 ceramics via tailoring Dy-doping amount and ceramic processing

[(Ba0.85Ca0.15)1-xDyx](Zr0.1Ti0.9)O3 (x mol% Dy-BCZT, x = 0.05, 0.2, 0.5, 1 and 3 mol%) multifunctional lead-free ceramics were prepared by traditional solid-state reaction method, where the influence of Dy doping amount and sintering condition was investigated. All sintered x mol% Dy-BCZT ceramics exhibit pure perovskite structure, large density, and high resistivity, which are affected greatly by Dy doping amount and sintering temperature. The phase structure changes from mainly tetragonal phase to pseudo-cubic phase with the increase of Dy doping amount, and presents irregular change on sintering temperature. Most samples have excellent dielectric, ferroelectric and stain, piezoelectric and fluorescent properties, which can be improved by changing Dy doping amount and tailoring sintering condition. Maximum piezoelectric-fluorescent coupling effect is obtained by selecting composition, optimizing Dy doping amount, and tailoring sintering condition due to morphotropic phase boundary effect and concentration quenching effect, which provides broad application prospect in the field of optoelectronics.

Influence of the pulse duration at the laser processing of nitride ceramics

This paper presents results on laser ablation of AlN and Si3N4 ceramics by laser pulses with different duration. Three types of laser systems, a Nd:YAG one, operated at wavelength of 1064 nm and pulse duration of 15 ns, a Nd:YAG, operated at wavelength of 1064 nm and pulse duration of 10 ps, and a femtosecond laser system, operated at 800 nm, with a pulse duration of 75 fs, are used for experiments. Details on the ablation efficiency, surface morphology, and the chemical composition of the irradiated zones as a function of the pulse duration are given and discussed. It is demonstrated that the ablation rate (ablation depth per pulse) is highest for processing with nanosecond pulses and it is lowest for the femtosecond regime. The laser ablation results in significant change of the surface morphology, as its characteristics are influenced by the pulse duration. For all pulse durations conditions for formation of ripples structures are found. The ablation process is realized by decomposition of the ceramics and the composition of the remaining surface layer is governed by oxidation and carbonization.

Evaluation of zirconia surfaces and shear bond strength after acid–etching with ultrasonic vibration

To evaluate the effect of surface reaction process after hydrofluoric (HF) acid etching using ultrasound and the shear bond strength (SBS) of resin cement to zirconia polycrystal (Y-TZP) ceramic. Y-TZP ceramic sheets were divided into rinsing group (Group P), ultrasonic cleaning group (Group C), and ultrasonic reaction + rinsing group (Group CP), and all the groups were treated for 5, 10, 20, 30, 40, 50, and 60 min, respectively. The surface morphology, elements distribution, roughness, and wettability of the ceramic sheets in each group were observed. The SBS of ceramic-resin bonding specimens was tested after immersion and after cooling-heating cycles, respectively. Octahedral and spiculate products were observed on the surface of Y-TZP that was etched with HF acid in Group P. The amount of these products increased over time. In contrast, only a few octahedral products remained on the surface of Y-TZP in Groups C and CP. Within the same reaction time, the surface reaction of the CP group was stronger than that of the other two groups, accompanied by a more uniform morphology. The shear force in Group C was the lowest, and the shear force reduction in Group CP was the least after cooling-heating cycling, with statistically significant differences (P< 0.05). After the reaction time exceeded 30 min, the shear force in each group decreased instead of increasing. Octahedral and spiculate acid etching products on the surface of HF acid-etched Y-TZP can enhance the bonding force of zirconia. Ultrasonic cleaning would drive the exfoliation of acid etching products from the sample surface, leading to the decrease of the bonding force. The acid etching with ultrasonic vibration can accelerate the HF acid etching process of Y-TZP ceramics, which is conducive to improving the bond strength to resin and durability.