Edwin Francis Cárdenas Correa, Edgar Absalón Torres Barahona, J. B. Carda Castelló
In additive manufacturing technologies, the use of pastes and inks based on materials such as clay to create three-dimensional objects layer by layer has opened new possibilities in fields such as engineering and biomedicine. This review article aims to provide a comprehensive understanding of 3D printing of ceramic pastes through Direct Ink Writing (DIW), also referred to as Robocasting. DIW offers specific advantages for ceramic 3D printing, including the ability to extrude highly loaded pastes with customized rheological properties to accommodate a broad spectrum of ceramic compositions, varying from conventional clays to advanced ceramics. It is characterized by filament deposition control, which facilitates the fabrication of complex, porous, or customized architectures while simultaneously minimizing material waste. Through a bibliometric analysis of the literature published between 2020 and 2024, the most relevant studies regarding printing system architectures, ceramic paste formulations, and adjustment of parameters to obtain high-quality parts were identified. This work presents relevant and accurate explanations of the DIW technology, supporting researchers and industry professionals seeking to initiate or improve ceramic 3D printing processes for a wide range of applications.
The main objective of this study is to determine the prospects for using multilayer CrN/MoN ceramic coatings as protective sacrificial coatings providing increased resistance of steels to the complex destructive effects of hydrogen and aggressive environments due to the synergistic effect of alternating nitride layers and the formation of a dense, defect-resistant structure with highly effective diffusion barriers that restrain the diffusion of atomic hydrogen deep into the materials. The influence of hydrogenation processes on the wear and corrosion of the coating surface was determined using the scanning electron microscopy method, which was used to visualize surface defects formed as a result of external influences. Based on the data obtained, an analysis of the resistance of the coatings to degradation was conducted, and the role of the coatings in restraining destruction to wear and corrosion processes was determined. Moreover, it was found that increasing the number of layers from 4 to 20 inhibits degradation of strength properties by more than 2.2 times. Such changes in coating hardness and wear resistance are due to the barrier effect associated with the increased number of layers in the coating, which inhibits hydrogen diffusion into the coating. Tests of the resistance of samples after hydrogenation to an aggressive environment showed that the decrease in resistance to aggressive environments for coatings subjected to hydrogenation is most pronounced for samples subjected to hydrogenation for 100 h. In this case, the reduction in wear resistance (friction coefficient) is more than 1.5 to 2 times for coating samples subjected to hydrogenation compared to the original samples. According to an assessment of changes in the adhesive strength of coating samples after exposure to an aggressive environment, it was found that in the case of the original samples (not subjected to hydrogenation), an increase in the number of layers from 4 to 20 leads to a decrease in surface delamination from 1.51% to 0.95%. Moreover, for samples subjected to hydrogenation for 100 h, in the case of 4-layer coatings, the change in adhesion strength is more than 11.4%, and in the case of 20-layer coatings, the decrease in adhesion strength is approximately 6.9%, which is more than 1.5 times lower. The novelty of the study lies in determining the role of variation in the number of layers on resistance to degradation processes caused by hydrogenation and subsequent exposure to an aggressive environment, as well as determining the mechanisms of restraint due to variation in the number of layers and the barrier effects they create, which slow down the degradation processes of mechanical and strength properties.
Plenty of traditional and novel sintering techniques have been utilized to enhance the performance of perovskite materials. Among several sintering methods, electric field-assisted spark plasma sintering (SPS) is a modern category and has been effective for the excellent functionalities of perovskite compounds. The state-of-the-art SPS systems, perovskite materials development, and corresponding design are focused. This article will highlight the parameters of this technique, the advanced procedure of sintering, and their respective effects on the densification and dielectric performance of ABO3 perovskite materials. No such work has been reported to relate the crystalline nature of the various functional perovskites with the spark plasma sintering procedures. This review illustrates a good compilation of recently reported few perovskite materials processed by spark plasma sintering and relationships between thermal effects, density, and dielectric performance. The enhanced density, high dielectric permittivity, and low dielectric loss were achieved due to SPS.
Lithium-doped Li0.66La1.12(Ti0.2Zr0.2Hf0.2Sn0.2Nb0.2)2O7 (LLTNO), Li0.66La1.12(Ti0.2Zr0.2Hf0.2Sn0.2Ta0.2)2O7 (LLTTO) high-entropy pyrochlore and Li0.5Sr0.5(Ti0.2Zr0.2Hf0.2Sn0.2Ta0.2)O3 (LSTTO), Li0.5Ba0.5(Ti0.2Zr0.2Hf0.2Sn0.2Nb0.2)O3 (LBTNO) high-entropy perovskite ceramics were synthesized by solid state reaction method and sintered. Crystal structure, microstructure and electrical properties of these high entropy ceramics were studied. The LLTNO and LLTTO pellets sintered at 1300 °C present a pyrochlore structure, while LSTTO and LBTNO pellets sintered at 1350 °C present a perovskite structure. The LBTNO ceramics has a total conductivity of 1.25 × 10−7 S•cm−1 at room temperature while the LSTTO sample exhibits the highest conductivity of 2.11 × 10−7 S•cm−1 among all samples. Both LSTTO and LBTNO ceramics present negligible electronic conductivity. Relative densities of the LLTNO, LLTTO, LSTTO and LBTNO ceramics were 82, 88, 86 and 87%TD, respectively, which is the reason for low conductivity of these high entropy ceramics. The activation energies of the LSTTO and LBTNO samples were 0.39 and 0.38 eV, respectively, which is close to the traditional Li+-type conducting solid electrolytes.
Youssef Arkame, Achraf Harrati, Yassine Et-Tayea
et al.
This work focuses on the characterization of lizardite and studying the technological and dielectric features of ceramics based on this geomaterial by experimental measurements. Note that, the physical evaluation (dielectric properties) of magnesian clay has never been studied. Natural lizardite was extracted from the Beni Boussera massif (Rif, Morocco), and was characterized in terms of chemical, physical, mineralogical and thermal aspects. A purification process was carried out to identify the mineral phases present in this material. The results showed that the studied material is mainly composed of silica (47.16 wt%) and magnesia (31.21 wt%), it is also richer in clay minerals such as lizardite and chlorite. The ceramic specimens were prepared by the uniaxial pressing method, followed by sintering to different temperatures (i.e., 900, 1000, 1100, and 1200 °C). The influence of the sintering temperature on porosity, density, shrinkage, water absorption, mechanical and microstructural properties of ceramics was evaluated, as well as chemical resistance and dielectric properties were studied. The evaluation of the optimized ceramic materials shows that good dielectric properties are obtained when sintered at a temperature of 1100 °C with a dielectric constant of 1.33, a dielectric loss of around 0.08, and a conductivity of 4.86 E−8 S/cm, at high frequency. Furthermore, the obtained ceramic specimen has a porosity of 17%, a density of 2.02 g/cm3, a water absorption of 9.86%, and a mechanical strength of 19.3 MPa. As a consequence, the results obtained have provided ceramics based on a natural resource with favorable technological and mechanical properties, and very interesting dielectric properties.
In this paper, the concept of incorporating core–shell structured units as secondary phases to toughen Al2O3 ceramics is proposed. Al2O3 composite ceramics toughened by B4C@TiB2 core–shell units are successfully synthesized using a combination of molten salt methodology and spark plasma sintering. The synthesis of B4C@TiB2 core–shell toughening units stems from the prior production of core–shell structural B4C@TiB2 powders, and this core–shell structure is effectively preserved within the Al2O3 matrix after sintering. The B4C@TiB2 core–shell toughening unit consists of a micron-sized B4C core enclosed by a shell approximately 500 nm in thickness, composed of numerous nanosized TiB2 grains. The regions surrounding these core–shell units exhibit distinct geometric structures and encompass multidimensional variations in phase composition, grain dimensions, and thermal expansion coefficients. Consequently, intricate stress distributions emerge, fostering the propagation of cracks in multiple dimensions. This behavior consumes a considerable amount of crack propagation energy, thereby enhancing the fracture toughness of the Al2O3 matrix. The resulting Al2O3 composite ceramics display relative density of 99.7%±0.2%, Vickers hardness of 21.5±0.8 GPa, and fracture toughness 6.92±0.22 MPa·m1/2.
Abstract This work employed an inductively coupled plasma wind tunnel to study the dynamic oxidation mechanisms of carbon fiber reinforced SiC matrix composite (Cf/SiC) in high-enthalpy and high-speed plasmas. The results highlighted a transition of passive/active oxidations of SiC at 800–1600 °C and 1–5 kPa. Specially, the active oxidation led to the corrosion of the SiC coating and interruption of the SiO2 growth. The transition borders of active/passive oxidations were thus defined with respect to oxidation temperature and partial pressure of atomic O in the high-enthalpy and high-speed plasmas. In the transition and passive domains, the SiC dissipation was negligible. By multiple dynamic oxidations of Cf/SiC in the domains, the SiO2 thickness was not monotonously increased due to the competing mechanisms of passive oxidation of SiC and dissipation of SiO2. In addition, the mechanical properties of the SiC coating/matrix and the Cf/SiC were maintained after long-term dynamic oxidations, which suggested an excellent thermal stability of Cf/SiC serving in thermal protection systems (TPSs) of reusable hypersonic vehicles.
Waste valorization is of utmost importance due to the scarcity of natural raw materials. In Europe, up to 150 kton/y of eggshells waste are generated and, usually, landfilling is the only option. This work aims to develop eco-ceramic wall tiles using bio-calcium carbonate from eggshells waste as a raw material. Several pastes were prepared by replacing limestone, the natural raw material used nowadays, with eggshell waste (0, 25, 50, 75 and 100 wt%). Through specimens’ characterization, the total substitution by bio-calcium carbonate with the same granulometry leads to an increase, of 19%, in the flexural strength, without affecting the other properties (linear thermal coefficient, weight loss, firing shrinkage, water absorption, density, colour coordinates), and all values are within industrial limits. Therefore, this work proved that limestone can be totally substituted by eggshell waste. The developed eco-ceramic wall tiles consume less natural raw materials and promote a decrease in the landfilled wastes quantity.
Abstract A well‐known model of stress–strain behavior in continuous‐fiber ceramic composites was expanded, corrected, and coded in a popular programming language. Four versions of the code with differing output plot formats are included. They can be pasted into a program file and used without editing. One of them allows observing the changes in the stress–strain curve while varying nearly any of the input properties. The ability to observe or quickly plot and compare curves using different parameters can aid in understanding the roles of constituent and interface properties in composite behavior. It can also aid in inferring unmeasurable properties in actual composites. Comparisons of model output to experiment are presented and discussed.
Clay samples from selected part of Edda were analyzed to identify the clay mineral types present, their chemical and physical properties with a view to appraising their industrial suitability as ceramic materials. The mineralogical and geochemical analyses were done using the principles of X-Ray diffraction and X-ray fluorescence respectively. A total of seven clay samples were used for the study, other tests such as plasticity, bulk density, shrinkage, loss on ignition (LOI) and water absorption capacity was carried out to determine the amount of water absorbed under specified conditions. The basic industrial properties assessment showed that more than 70% of the clays are fine-grained. The clays exhibited low to moderate plasticity, moderate shrinkage and bulk density, low to moderate values of both loss on ignition and water absorption capacity. The clays are buff to yellowish in colour. The results of x-ray fluorescence revealed that the mean concentration of major oxide in the clays is shown as follows: SiO2 (62.78%), Al2O3 (20.25%), total Fe (6.09%), CaO (0.56%), MgO (3.21%), Na2O (0.47%), K2O, (1.44%) and TiO2 (0.52%). The samples have high silica content, low alumina and low oxide content. The results of x-ray diffraction revealed that kaolinite is the dominant clay mineral with illite and montmorillonite occurring in subordinate amounts, while quartz and feldspar are the non-clay components present. The characteristics of the clays for each parameter were compared with industrial standards. These properties are appropriate for the Afikpo clays to be useful in the manufacturing of ceramics. However, since the silica content of the clays is high further beneficiation is recommended.
Mohamed Nawwar, Rakesh P. Sahu, Ishwar K. Puri
et al.
We investigate the pseudocapacitive properties of ferrimagnetic NiFe2O4 ceramics in a 0.5 M Na2SO4 aqueous electrolyte. These ceramics have a high capacitance of 2.33 Fcm−2 since a more efficient colloidal technique is applied, which enhances the current response of the electrode in the negative potential range. NiFe2O4 is co-dispersed with multiwalled carbon nanotubes (MWCNTs) using Celestine Blue (CB) dye as a multifunctional co-dispersant. The capacitance measurements are performed by cyclic voltammetry, impedance spectroscopy and galvanostatic charge-discharge. The experiments reveal the synergistic effects of NiFe2O4 and conductive MWCNTs additives and the benefit they provide through co-dispersion with CB, which acts as an electron transfer mediator, enhancing pseudocapacitance. The mass ratio of NiFe2O4 and MWCNTs in the composite electrodes is varied to optimize the capacitance enhancement, lower electrical resistance at a high active mass loading of 40 mg cm−2, and achieve favorable capacitance retention at high charge-discharge rates. The results reveal a path for the development of pseudocapacitive ferrimagnetic ceramic composites that have advanced functionality.
The objective of this work is the development of a composite material of clay doped with copper powder and with thermal properties likely to give it a great importance in the ceramic industry, has been the subject of increased attention in recent decades because of their multiple uses as thermal insulators in the fields of ceramics and heterogeneous catalysis. Indeed, this study is based on a global approach of the properties of the material, accompanied by a thorough analysis of the thermophysical characteristics. The thermal conductivity of this material was determined as a function of copper content and temperature. Experiments have shown that thermal conductivity increases with the copper content and decreases with temperature, the experience made by an apparatus called CT-METRE. A theoretical model of the composite material allowing to approach more finely the heat transfers and also to validate the experimental results obtained
Sujith Vijayan, Praveen Wilson, K. Prabhakaran
et al.
An emulsion-based injection molding process has been reported for the preparation of ceramic foam spheres from kaolin and alumina. The foam spheres produced from kaolin alone cracked during sintering due to extensive shrinkage and an excessive glass phase. Incorporation of a minimum of 10 wt% alumina in kaolin prevented the cracking of foam spheres during sintering by promoting secondary mullite growth, which decreases both the glass phase concentration and sintering shrinkage. Foam spheres with an interconnected cellular structure having open porosities, average cell sizes and diametrical compressive strengths in the ranges of 76.5 to 82.7 vol.%, 6.8 to 9.2 μm and 1.65 to 0.93 MPa, respectively, were produced from emulsions prepared from hydrogenated vegetable oil and aqueous clay slurries. The interconnected open cell structure and small cell size enabled fast absorption and 100% retention of urea solution for N2O4 scrubber application. The urea solution absorption capacity (71.5 to 80 vol.%) of the foam spheres was much higher than the capacity (45.6 vol.%) of the porous clay ceramic media currently used in N2O4 scrubbers.
Danielle C.S. Spínola, A. D. Miranda, D. Macedo
et al.
Abstract The high production of drill cuttings during oil well drilling operations is one of the main causes of the huge amount of waste created by the oil industry. Meanwhile, large amount of kaolin waste is produced during the kaolin mining processes. These wastes are usually deposited in landfills with no specific use. Thus, recycling of solid wastes by their incorporation in ceramics has been considered an attractive way to obtain high added value technical solutions, enhancing the culture of reuse. Glass-ceramics have been receiving this same approach with the advantage of obtaining a high-performance product from recycled raw materials. The current study proposes the synthesis of glass-ceramics of the SiO 2 -Al 2 O 3 -CaO-Na 2 O-K 2 O-MgO system from a mixture of kaolin and oil well drilling wastes. A mixture of the recycled raw materials (wastes) and Na 2 CO 3 (a commercial material used to adjust the glass composition) was melted at 1500 °C for 1 h to obtain a glass-ceramic precursor material. The resulting vitreous powder was studied by thermal, chemical and structural characterization techniques, pressed into pellets and further sintered at 850 °C. The microstructural analysis of the obtained glass-ceramics showed the attainment of dendritic-like crystals combined with an amorphous phase.
ABSTRACT Cathode ray tube (CRT) glass contains significant amounts of alkali and alkaline earth oxides, making it a useful by-product for use in the ceramics industry. Among the various alkali oxides present, those of strontium (SrO), calcium (CaO), and magnesium (MgO) are well known flux materials used widely in the ceramics industry. The most effective flux, SrO, is also a limited resource. In this study, we aimed to develop an environmentally friendly, low-cost method for recycling CRT waste by using it to produce transparent ceramic frits on an industrial scale. Four different samples were fabricated containing between 13 and 25 wt.% CRT panel glass. The color values, sintering behaviors, phases, and microstructural properties of the corresponding samples were analyzed and compared. The results indicate that a composition containing 25 wt.% CRT panel glass could pass the ISO 10545 test. Thus, the results confirm that CRT glass can be used to inexpensively produce transparent ceramic frits at an industrial scale. Implications: The recycling of electronic waste (e-waste), including CRT waste, has increased by high rates of computer and TV consumption. This increase in consumption is likely to increase the rate at which CRTs are discarded. However, CRTs cannot be recycled in the desired amount. Owing to the high silicate, barium and strontium content of CRTs, it has great potential for glass ceramics such as frits. CRT panel glass to produce commercial transparent frit at low cost through an industrial production route for use in single-fire sintered products. Thus, CRT wastes can be recycled cost-effective, sustainable and environmentally friendly.
The design of the structural glass for the Manchester Town Hall Link (completed 2015) was carried out by engineering consultancy Eckersley O’Callaghan (EOC). The glass facade forms an enclosed shell which supports a steel roof and acts monolithically to resist lateral loads. The project collates the latest advances in glass technology combined with innovative design methods. In the absence of explicit codes of practice for structural glass, EOC performed a first principles approach in using empirical data, acquired through previous projects, and analytical methods, including FEM and parametric modelling, to justify an elegant and efficient structure which was approved by building control authorities. The result has reduced glass joints and less visible metalwork to meet the architects’ aspirations. This paper describes the approaches and innovations in designing the structural glass for this project.