Ceramic Structures Research Articles

The Significance and Usage Strategies of Macromolecules in 3D Printed Ceramic Composites.

3D printing technology enables the creation of complex ceramic structures and enhances the efficiency of customized ceramic production. Polymers play a crucial role in 3D-printed ceramic composites due to their unique processability, yet their significance and application strategies remain underexplored. These polymers not only enable rapid and precise 3D shaping but also offer additional advantages due to their unique and adjustable physicochemical properties. Therefore, the appropriate selection and utilization of polymers are expected to drive new breakthroughs in the field of 3D-printed ceramic composites. This review provides an overview of relevant additive manufacturing technologies and processes, with a specific focus on the strategies for using polymers in 3D-printed ceramic composites, including their roles as binders, templates, preceramics, and matrices. Highlighting the critical functionalities and potential value of these ceramic composites from a practical application perspective.

Simulation and theoretical studies on the influence of removable panel deformation on the seal characteristics of ceramic wafer seal

Purpose The purpose of this study is to investigate the influence of geometric parameters of removable panels on the sealing characteristics of ceramic wafer seal structure subjected to high-temperature gas flow. Design/methodology/approach Based on the laminar flow Reynolds equation, the theoretical and numerical calculation models were constructed to investigate the influence of external convex deformation of removable panel on leakage rate. The theoretical formula for leakage rate after deformation of the removable panel was derived, and the flow field and leakage characteristics of ceramic wafer seal under different operating parameters were studied. Findings The leakage rate exhibits consistent trends between theoretical calculation, numerical simulation and experimental value, with a maximum discrepancy of 8.9%. This validates the accuracy of both the theoretical model and numerical simulation. As the deformation angle of the removable panel increases, the sealing gap gradually widens, resulting in a compromised sealing effect. Moreover, the leakage rate in the central region of the sealing area is lower compared to that at both ends. Originality/value The leakage of the ceramic wafer seal structure under the removable panel with different deformation angles can be monitored based on Reynolds equation. The pseudo-transient numerical calculation method can be used to determine the leakage value of the micro-state ceramic wafer seal structure. These research findings provide a theoretical foundation and numerical investigation approach for studying ceramic wafer seal structures.

Immobilization of simulated cesium wastes in ceramic matrices derived from some natural minerals

Nuclear waste, a result of nuclear energy production, is of great importance because it requires long-term and safe management solutions. The aim of this study is to immobilize radioactive waste in a ceramic matrix to prevent the spread of radioactive waste to the environment during storage in underground storage areas. Ceramic matrices with high chemical resistance, low leaching rate and low cost, which meet the basic expectations for the immobilization of Cs, one of the important fission products, were developed in a ceramic matrix consisting of natural minerals. For this purpose, natural analog minerals, zeolite and bentonite, were preferred as the main matrix in ceramics for the immobilization and permanent storage of cesium waste due to their adaptability to the geological formation of radioactive waste storages. How the phases are formed after the sintering process in waste immobilized ceramics and how cesium is incorporated into the structure of two different mineral types were investigated. The chemical durability of waste immobilized ceramics produced using chemically stable cesium salts was tested. Structural analyses of the prepared ceramics were also performed. Considering the results, it was determined that ceramic structures prepared using minerals are suitable for use in the immobilization of radioactive waste.

Predicting fracture strength of polarized GaN semiconductive ceramics under combined mechanical-current loading

Gallium nitride (GaN) piezoelectric semiconductor ceramics (PSCs) structures are often subjected to combined mechanical and electrical fields in engineering applications, leading to complex deformation and fracture challenges. This paper presents a fracture predictive model for PSCs under combined mechanical and electrical loading, developed using the boundary effect model rather than relying solely on data fitting. By introducing a current parameter that influences the characteristic crack length, the model effectively predicts the quasi-brittle fracture characteristics of GaN PSCs. Additionally, the model reveals how electric current affects the quasi-brittle fracture behavior of PSCs, providing crucial theoretical support for the reliable design of GaN intelligent semiconductor structures in complex environments.

ABOUT THE SINTERING OF HISTORICAL “YELLOW BRICKS” OF SOFIA

The historical “yellow cobblestones” of Sofia are a very well sintered ceramic clinker with practically zero water absorption. However, the high amount of crystal phase formed, which explains the extraordinary mechanical properties of this remarkable material, is in formal contradiction with its low final porosity. In fact, in the modern ceramics clinkers the crystallinity is similar or inferior, but the reached degree of sintering is lower; as a result, the mechanical properties are reduced. The aim of this report is to elucidate some peculiarities of the densification process of “yellow ceramics bricks” because such information is essential for the eventual successful production of replica of this emblematic pavement. The chemical and phase compositions of original “yellow paving bricks” together with those of modern clinker from “Vitosha” boulevard in Sofia were evaluated by XRF and XRD analysis, respectively. The structures of both ceramics were investigated with density measurements and SEM.Their densification behaviour was estimated by re-sintering of milled original samples by Hot Stage Microscopy (HSM) tests. The results elucidate that the sintering temperature of the historical clinker is inferior, and their sintering interval is significantly narrow. This peculiarity is explained by the rapid decreasing of apparent viscosity with temperature rise.Finally, by secondary holding at the sintering temperatures and subsequent fast quenching of a “yellow brick” sample, it is demonstrated that some phase formation occurred during the industrial cooling step. This result explains both the good degree of densification and the better properties of the “yellow cobblestones”.

Ballistic characteristics of ceramic core sandwich structures

The ceramic core sandwich structure (CCSS) is a lightweight material with advantages of high anti-ballistic impact performance, high energy absorption and high specific strength. The ballistic performances of the CCSS with metal face plates hit vertically by projectiles with the nose shapes of conical, flat, and hemispherical are studied analytically and numerically in this paper. Based on the principle of energy conservation, an analytical model of ballistic characteristics of the sandwich ceramic core structure is developed. Numerical calculations are conducted, and the numerical model has been verified by experimental results from references by others. In addition, the analytical results agree well with finite element results. The effects of shape of projectile head, the thickness ratio of three plates of CCSS, and the ratio of shear strength of ceramic core to yield strength of metal face plates on the ballistic characteristics of the CCSS are discussed. It is shown that the conical-nosed projectile achieved the highest ballistic limit velocity (BLV) and the sharper nose increases the normal stress at the impact area thereby enhancing the BLV. The thickness of the ceramic core significantly influences the resistance of the CCSS and the thicker ceramic core enhances the ability of CCSS to absorb kinetic energy from the projectile. Furthermore, an appropriate increase in the yield strength of face plates can enhance the anti-ballistic impact performance of the CCSS. These insights have practical implications for the design of protective systems in military and civilian applications, where optimizing materials for impact resistance is crucial.

Machine learning-assisted design of CaBi2Nb2O9-based ceramics with high piezoelectricity and thermal stability

Calcium bismuth niobate CaBi2Nb2O9 (CBN)-based ceramics are promising candidates for high-temperature piezoelectric applications due to its high Curie temperature. However, the traditional trial-and-error method cannot realize fast design of high-temperature piezoceramics over a wide range of composition space. Based on small sample datasets, a machine learning model was proposed to accelerate the design of CBN-based ceramics with high piezoelectricity and thermal stability. Using the trained gradient boosting regression model, the piezoelectric coefficients are predicted for CBN-based ceramics with different compositions. Based on the machine learning prediction results, we prepared the co-doped Ca1-2x(NaCe)xBi2Nb2-x(W0.75Mn0.25)xO9 (CBNCWM-x) by solid phase reaction method. The results show that co-doping changes the lattice distortion, grain size and domain structures of CBN-based ceramics, realizing the enhanced piezoelectric properties. CBNCWM-0.03 ceramics exhibit an optimum piezoelectric coefficient (d33 ∼ 17.2 pC/N) that is quite close to the predicted result by machine learning model. Moreover, the CBNCWM-0.03 ceramics possess a Curie temperature of 913 °C and maintain 90.7 % of its original d33 value after annealing at 900 °C for 2 h, demonstrating excellent thermal stability. The present work not only provides an approach for the rapid discovery of CBN-based ceramics with high piezoelectricity but also obtains excellent thermally stable ceramics for high-temperature applications.

Enhancement of an intumescent fire shield paint from the nanotube rutile mineral for the fire performance of steel structures

Building and construction fire safety is an important issue for the protection of people and property. Research investigates nano-rutile minerals' synergistic role in intumescent fire shield paint (IFSP). A synergistic ingredient was introduced to intumescent fire shield paint to evaluate its impact on char morphology, fire protection test, fire propagation test, and compare it with current market products. A hydrothermal process was used to create a rutile mineral, with various techniques used to describe its structure, size, and composition. Intumescent char was found in a furnace using FESEM and X-ray fluorescence. The results showed that rutile minerals contain a rutile phase and a nanotube structure. The surface of the sample IFSP A's char showed layer and foam structures with homogenous voids during a fire test, indicating a high porosity structure. Large holes and recurring gaps were observed in the char of the IFSP B, C, and D. Sample IFSP A took more time at the structural critical temperature (about 550 o C) than other intumescent fire shield paint samples, making it a barrier layer that effectively shields the metal substrate from heat. The intumescent char residue had the highest C/O ratio of 0.57, indicating the best char yield degree and anti-oxidation abilities. The IFSP A had a phosphorous content of 36.2%, which could combine with phosphorus and TiO2 to form a ceramic barrier. The increased TiO2 in IFSP A suggests that char layers with TiO2 may still contain strong ceramic structures and function as effective thermal protection layers.

Porosity and pore morphology characteristics of zirconia-alumina bioceramics

AbstractManufacturing ceramic green structures using starch consolidation casting is an established process that is simple, non-hazard, and low-cost. In this study, starch consolidation casting is used to prepare ceramics based on submicron monoclinic zirconia with additions of alumina and magnesia. Scanning electron microscopy results indicate that the size of pores decreased and the morphological irregularity increased when the tapioca starch content increased. The sample with 30 wt.% tapioca starch in a 55 wt.% slurry concentration had the highest estimated apparent porosity (around 56%), whereas the sample with 10 wt.% in a 68 wt.% suspension concentration had the lowest (about 35%).

Photo‐cationic polymerizable ceramic slurry for the fabrication of ceramic structures in three‐dimensional printing

AbstractCycloaliphatic epoxides exhibit post‐light irradiation heat‐induced polymerization, creating warp‐resistant green bodies during sintering. However, their use in light polymerization three‐dimensional (3D) printing is limited by slow photo‐curing speeds. In this study, a photo‐cationic polymerizable ceramic slurry was developed for 3D printing by mixing oxetane with cyclo‐aliphatic epoxide. This mixture improved photo‐curing speed, reduced resin viscosity, and enhanced the ceramic slurry's solid content. Additionally, we optimized the slurry by considering the specific and content ratio of photosensitizers and light absorbers. The optimized slurry polymerized unreacted functional groups in the polymer, improving the fracture strength of the green bodies through enhanced crosslinking density and uniformity in each layer. Ultimately, a sintered body without warpage was produced by the improved green bodies. This approach provides a solution related to controlling the photocuring speed and expands the potential applications of 3D printing in areas where the precision and stability of the printing material are required.

Failure Behavior and Mechanism of Vat Photopolymerization Additively Manufactured Al2O3 Ceramic Lattice Structures

Vat photopolymerization additive manufacturing produces lightweight load-bearing ceramic lattice structures that have flexibility, time-efficiency, and high precision, compared to conventional technology. However, understanding the compression behavior and failure mechanism of such structures under loading remains a challenge. In this study, considering the correlation between the strut angle and bearing capacity, body-centered tetragonal (BCT) lattice structures with varying angles are designed based on a body-centered cubic (BCC) structure. BCT Al2O3 ceramic lattice structures with varying angles are fabricated by vat photopolymerization. The mechanical properties, deformation process, and failure mechanism of the Al2O3 ceramic lattice structures are characterized through a combination of ex- and in-situ X-ray computed tomography (X-CT) compression testing and analyzed using a finite element method (FEM) at macro- and micro-levels. The results demonstrate that as the angle increases, the stress concentration gradually expands from the node to the strut, resulting in an increased load-bearing capacity. Additionally, the failure mode of the Al2O3 ceramic lattice structures is identified as diagonal slip shear failure. These findings provide a greater understanding of ceramic lattice structure failures and design optimization approaches.

Cost-effective option for improving the smile area (a clinical case)

We have presented a clinical case of successful restoration of the frontal group of teeth by the method of aesthetic restoration using the universal nanogibrid composite. The experience of applying direct restoration allows us to ensure high quality restoration of carious teeth, aesthetics of the dentition with minimal time costs — 1 day. Compared to the manufacture of ceramic structures, the time spent on the manufacture of structures is 7 days. The applied method is economically more favorable by an average of 50% compared to the last specified method.

Unlocking enhanced piezoelectric performance through 3D printing of particle-free ceramic piezoelectric complex structures and metamaterials

Piezoelectric materials have found widespread use in miniaturized sensors and actuators due to their ability of mutual conversion of mechanical and electric energy. However, current fabrication techniques for these materials are limited to either bulky structures or thin films, restricting the potential that could arise from developing devices with more intricate geometries. Here, we have developed particle-free piezoelectric ink and successfully employed in 3D printing complex barium titanate (BTO) devices using Digital Light Processing technology. The sol–gel process overcomes the viscosity and light scattering issues associated with the slurry traditionally used in 3D printing of piezoelectric ceramic materials. Printed BTO exhibits a remarkable piezoelectric coefficient of 50 pm/V and is utilized to create 3D micrometric structures for applications as both active devices, such as actuators, and passive devices, including displacement sensors and energy harvesters. Furthermore, the flexibility in device fabrication enabled us to 3D print metamaterial piezoelectric structures, designed to concentrate mechanical stress, thereby enhancing the electrical response compared to conventional bulk structures. This research not only advances the field by overcoming fabrication challenges but also opens avenues for creating innovative devices. The design freedom afforded by additive manufacturing technology further underscores the potential for groundbreaking developments in this domain.

Generalized Background Vector Method for Tailored Three-Dimensional Nonperiodic Woven Composite Designs

In critical aerospace applications such as Ceramic Matrix Composite structures, novel three-dimensional nonperiodic textile composite preforms hold great promise for creating advanced composite structures with strategically aligned fiber tows. However, the inherently challenging nature of determining tow locations, a large-scale combinatorial problem, presents a significant obstacle in textile architecture design. This study generalizes the previously developed Background Vector Method (BVM) to address diverse design requirements and constraints, effectively circumventing combinatorial design complexities via a game theoretic approach. This approach allows for the creation of tunable designs for woven architectures with complex geometries, such as channels and tapering features, through simple control parameter adjustments. The method demonstrates exceptional computational efficiency, making it suitable for large-scale nonperiodic textile structures. Case studies including woven sandwich and airfoil structures highlight the generalized BVM’s versatility and effectiveness in addressing complex design challenges within the aerospace sector.

In-situ monitoring of multi-physical dynamics in ceramic additive manufacturing

Ceramic additive manufacturing is an innovative technology for developing complex ceramic structures, while a direct understanding of the physical phenomena occurring in sequential layers remains challenging, affected by the material design such as the presence of inorganic particles and their contents. This study provides a direct analysis of how the ceramic particles influence fabrication behavior utilizing an in-situ monitoring system. The force profile provides immediate feedback on fractures and geometric design, with the fluctuation in force directly corresponding to specific structural characteristics and stability during the fabrication. Furthermore, the multi-physical dynamics was investigated with a unit signal based on the effect of ceramic on the rheological-curing-mechanical behavior. For example, the mechanical behavior was characterized in real-time, as shown through an intensified peak of 6.6 kPa during the manufacturing of a ceramic composite, a 5.6 times increase compared to pure resin. The monitored data quantified the geometric dynamics and the multi-physical mechanism in real-time, achieved from the data on the overall fabrication status and the unit signal analysis of continuous manufacturing. This method can improve the reliability of ceramic additive manufacturing by providing insight into how ceramics impact fabrication behavior on sequential layers in real-time.

Ceramic Nanotubes—Conducting Polymer Assemblies with Potential Application as Chemosensors for Breath Ammonia Detection in Chronic Kidney Disease

This paper describes the process of producing chemosensors based on hybrid nanostructures obtained from Al2O3, as well as ZnO ceramic nanotubes and the following conducting polymers: poly(3-hexylthiophene), polyaniline emeraldine-base (PANI-EB), and poly(3, 4-ethylenedioxythiophene)-polystyrene sulfonate. The process for creating ceramic nanotubes involves three steps: creating polymer fiber nets using poly(methyl methacrylate), depositing ceramic films onto the nanofiber nets using magnetron deposition, and heating the nanotubes to 600 °C to burn off the polymer support completely. The technology for obtaining hybrid nanostructures from ceramic nanotubes and conducting polymers is drop-casting. AFM analysis emphasized a higher roughness, mainly in the case of PANI-EB, for both nanotube types, with a much larger grain size dimension of over 5 μm. The values of the parameter Rku were close or slightly above 3, indicating, in all cases, the formation of layers predominantly characterized by peaks and not by depressions, with a Gaussian distribution. An ink-jet printer was used to generate chemiresistors from ceramic nanotubes and PANI-EB structures, and the metallization was made with commercial copper ink for printed electronics. Calibration curves were experimentally generated for both sensing structures across a wider range of NH3 concentrations in air, reaching up to 5 ppm. A 0.5 ppm detection limit was established. The curve for the ZnO:PANI-EB structure presented high linearity and lower resistance values. The sensor could be used in medical diagnosis for the analysis of breath ammonia and biomarkers for predicting CKD in stages higher than 1. The threshold value of 1 ppm represents a feasible value for the presented sensor, which can be defined as a simple, low-value and robust device for individual use, beneficial at the patient level.

Formation trajectory of core-rim structures in BiFeO3-BaTiO3 ceramics

Microstructural characterizations and manipulations of BiFeO3-BaTiO3 (BF-BT) ceramics are attracting extensive attention, since they provide a fertile field for functionality explorations. However, for the widely existed core-rim structures with chemical inhomogeneity, the formation mechanism has not been fully understood yet. Here, we carefully tracked the formation trajectory of the core-rim structures in pseudo-cubic 0.64BiFeO3-0.36BaTiO3 ceramics prepared by solid-state reaction methods. In contrast to the popular belief, the core-rim structures characterized by BF-rich@BT-rich@average-composition triple microstructures universally appear in the ceramics with different cooling rates, suggesting that they do not form during the cooling process. Microscopic characterizations of the calcined powders demonstrate the inhomogeneous compositions and surface segregations. Subsequently, the surface BT-rich phases exhibit liquid-like behaviors promoting the diffusion of elements in the sintering process, which were blocked up during the further grain growth and left as the outer cores and nanoparticles at the triple junctions. Our results reveal the formation mechanism of the core-rim structures, and are expected to provide a necessary basis for the microstructure regulation of BiFeO3-BaTiO3 ceramics.

A solar air receiver with porous ceramic structures for process heat at above 1000 °C – Heat transfer analysis

Abstract Concentrated solar energy can be used as the source of heat at above 1000 °C for driving key energy-intensive industrial processes, such as cement manufacturing and metallurgical extraction, contributing to their decarbonization. The cornerstone technology is the solar receiver mounted on top of the solar tower, which absorbs the incident high-flux radiation and heats a heat transfer fluid. The proposed high-temperature solar receiver concept consists of a cavity containing a reticulated porous ceramic (RPC) structure for volumetric absorption of concentrated solar radiation entering through an open (windowless) aperture, which also serves for the access of ambient air used as the heat transfer fluid flowing across the RPC structure. A heat transfer analysis of the solar receiver is performed by means of two coupled models: a Monte Carlo (MC) ray-tracing model to solve the 3D radiative exchange and a computational fluid dynamics (CFD) model to solve the 2D convective and conductive heat transfer. Temperature distributions computed by the iteratively coupled models were compared with experimental data obtained by testing a lab-scale 5 kW receiver prototype with a silicon carbide RPC structure exposed to 3230 suns flux irradiation. The receiver model is applied to optimize its dimensions for maximum efficiency and to scale up for a 5 MW solar tower.

Study on Two Inorganic Consumables in PMMA Electrochromic Devices Based on Work Function Differences

In electrochromic devices, the dielectric layer is not only an electrode dielectric, but also can provide compensating ions for electrochromism. In this paper, three composite porous materials, PMMA/SiO2, PMMA/TiO2, and PMMA/SiO2/TiO2, were prepared and assembled using polymethyl cellulose (PMMA) as the polymer matrix, impurity medium (SiO2) and titanium dioxide (TiO2) inorganic polymers, and the effect of doping two inorganic porous materials on the electrochromic performance was studied. The optical recovery and cycle stability of electrochromic wear of the PMMA/SiO2/TiO2 composite structure are significantly improved compared with the loss of other ceramic structures. Cyclic voltammetry analysis shows that the lithium ion diffusion coefficient of the electrochromic device using the PMMA/SiO2/TiO2 composite ceramic structure is the largest, which is 2.5 × 10−14 cm2​ s−1 . The improvement of electrochromic performance is mainly due to the difference in work function between SiO2 and TiO2 on the figure of merit diagram, which leads to the directional movement of the resonator, accelerates the transmission rate of Li+ and further optimizes the electrochemical properties of the composite ceramic. This study provides an effective method to improve the performance of electrochromic devices.

Damage Assessment of 3-D Printed Ceramic Sandwich Structures with an Auxetic Honeycomb Core Subjected to Quasistatic Indentation Loading

Abstract Ceramic sandwich structures (CSS) have become an important material in the aerospace industry because of their high strength and excellent thermal insulation properties. However, the brittle nature of ceramic makes them vulnerable to damage from foreign objects, which can reduce their load-bearing capacity. In this paper, a series of tests were designed to investigate the response of CSS to impacts from foreign objects. To realize the damage characteristics and failure modes under the indentation force, a quasistatic indentation (QSI) test was conducted on CSS. Additionally, an acoustic emission device was used to capture damage signals during the QSI testing. Thereafter the extent of damage was evaluated by analyzing the damaged area and the compression after indentation properties. The results of these tests revealed the failure mechanism maps and indicated that the compressive strength of the damaged CSS had a stronger correlation with damage to the honeycomb core than to the face sheet.