Fabrication Of Ceramics Research Articles

TSL, OSL and scintillation properties of Tb-doped barium fluoride translucent ceramics

We report on the fabrication of Tb-doped barium fluoride translucent ceramics, and their scintillation and dosimetric characteristics. The Tb-doped barium fluoride ceramics were fabricated by spark plasma sintering. Scintillation derived from the 4f→4f transitions of Tb3+ under X-rays was observed from the Tb-doped barium fluoride ceramics. Their decay times under X-rays were about 10 ms. Further, thermally-stimulated luminescence originating from the transitions was detected, and their dose responses were observed in the range of 0.1–100 mGy. Moreover, the Tb-doped barium fluoride ceramics exhibited optically-stimulated luminescence (OSL), and three exponential decay components were detected in the OSL decay curves.

Effect of polystyrene addition on properties of porous Si3N4 ceramics fabricated by digital light processing

Porous Si3N4 ceramics with high strength and high transmittance have been widely used in the field of defense and military. Additive manufacturing (AM) technology is one of the effective means to fabricate porous Si3N4 ceramics. Nevertheless, it is difficult to prepare porous Si3N4 ceramics by using digital light processing (DLP) because of the large refractive index difference between Si3N4 powders and photosensitive resin. In this study, the effects of the amount of polystyrene (PS) powders on the properties of Si3N4 ceramic slurries and sintered ceramics were systematically discussed. The addition of PS reduced the overall refractive index of powders and increased the average particle size of powders, thus improving the cure depth of Si3N4 ceramic slurries from 11.0 ± 2.0 μm to 55.7 ± 1.8 μm. With the increase of PS content, the shrinkage and porosity of Si3N4 ceramics gradually increased, and the bulk density and flexural strength showed the opposite trend. The slurry with low viscosity (2.38 Pa٠s at a shear rate of 30 s−1) and high cure depth (51.2 ± 4.6 μm) was obtained when the content of PS was 15 wt%, which met the thickness requirements for printing. The total porosity of Si3N4 ceramics reached the maximum values at 28.21 ± 2.58%. The addition of PS solved the problem of low cure depth of slurries, and PS as a pore-forming agent could help Si3N4 ceramics form porous structure. This research provides valuable insights into the fabrication of non-oxide ceramics with high refractive index using DLP technology.

Microstructure and permeability of porous YSZ ceramics with aligned and gradient pore channels fabricated by freeze casting

Porous yttria-stabilized zirconia (YSZ) ceramics with aligned and gradient pore channels were fabricated by the unidirectional freezing of aqueous suspensions with distinct solid loadings under different sintering temperatures. The results indicate that the microstructure and response properties could be tailored by adjusting the solid loading and sintering temperature. The pore channel size increased with the increase of solid loading or the decrease of sintering temperature, regardless of microstructure changes in an individual sample. With increasing the solid loading and sintering temperature, the compressive strength (7.18–30.76 MPa) increased owing to the lower porosity of individual samples. The fabricated samples had increasing Darcian and non-Darcian constants along the freezing direction due to the enhanced pore size and open porosity. The Darcian and non-Darcian constants in this paper were in the range of 7.06 × 10−13 to 5.92 × 10−12 m2 and 1.66 × 10−7 to 8.83 × 10−7 m, respectively. These results are of practical value for the fabrication and optimization of porous ceramics in the applications of filters and membrane supports.

Local optimization of low power laser machining of MgO at the green state enables cost- and energy-efficient benchtop fabrication

Laser machining of ceramics at the green state offers a low-cost route to the near-net fabrication of ceramics. A matrix of laser machining (i.e., laser cutting and scanning) parameters were tested on 5 mm-thick green bodies of magnesium oxide (MgO) using a CO2 laser with a maximum power capacity of 130 W. The input parameters were feed rate and power; we scanned the feed rate of 3–14 mm/s and power of 23–31 W for laser cutting, and 10–60 mm/s and 16–27 W for laser scanning. The quality of the laser-cut and -scanned surfaces was tracked through SEM. Thermal damage along the laser path was assessed to optimize laser cutting. High laser power and/or long dwell time resulted in partial sintering. At both cutting and scanning operations, low feed rates induced thermal damage, while high feed rates provided better edge retention and surface smoothness. However, very high feed rates failed to generate complete cuts and through-holes due to insufficient transfer of the excitation energy. Various combinations of the feed rate and power produced completely cut 5 mm cubes with smooth surfaces via laser cutting in a single pass. The most energy-efficient combination of 12 mm/s and 28 W rendered the highest surface quality with minimum thermal damage. This parameterization set provides a practical roadmap for choosing process parameters for the laser machining of MgO at the green state.

Mechanism of porous ceramic fabrication using Second Aluminum Dross assisted by corn stalk as pore-forming agent

Second Aluminum Dross (SAD), a byproduct of aluminum dross extraction with both resource and pollutant properties, requires harmless treatment and full-component utilization. This study focuses on using corn stalks as a pore-forming agent to create porous ceramics with SAD. The role of corn stalk in pore formation was investigated, and the influence of stalk particle size, content, pyrolysis, and calcination conditions on pore formation in porous ceramics was analyzed. Sample analysis using XRD, XRF, BET, TEM, and SEM revealed the phase composition, component content, and microstructure of the ceramics. The results indicate two forms of pores: micron-sized pores produced by the reaction between corn stalk and oxygen at high temperatures and nano-sized pores left by water vapor in the colloid channel. The porous ceramics had a polycrystalline structure consisting of numerous crystals ranging from 15–50 nm in size, and the polycrystalline component was Al2O3. Corn stalk promotes pore formation, creating a loose and uniform sample with a specific surface area of 174.83m2/g, a porosity of 0.58 cm 3/g, and an average pore size of 124.65 nm. The paper outlines a process for the harmless treatment and high-value utilization of SAD as a raw material, which significantly reduces the cost of raw materials and solves the solid waste disposal problem in the aluminum industry.

Fabrication and investigation of novel hafnium-zirconium carbonitride ultra-high temperature ceramics

By a combination of mechanical activation, combustion synthesis, and spark plasma sintering methods, bulk materials in the Hf-Zr-C-N system with various Hf/Zr atomic ratios were produced. The mechanical activation process in a low-energy mode (350 rpm) for 90 min resulted in the formation of layered Hf/Zr/C composite particles 10–30 μm in size, depending on the Hf/Zr ratio. The diffraction spectra of the as-synthesized powders were described by several isomorphic (Hf,Zr)(C,N)ss cubic phases with different nitrogen content. Spark plasma sintering contributed to the homogenization of the chemical composition and allowed production of the dense (∼98%) single-phase hafnium-zirconium carbonitrides with an FCC structure. The bulk ceramics exhibited superior hardness (∼17 GPa) and fracture toughness (∼5 MPa m1/2), relative to (Hf,Zr)C carbides prepared by similar methods.

A review on magneto-optical ceramics for Faraday isolators

As a promising magneto-optical material applied in Faraday isolators, magneto-optical ceramics possess excellent comprehensive properties and have attracted much attention these years. Herein, we review the fabrication and properties of magneto-optical ceramics including garnet, sesquioxide, and A₂B₂O₇ceramics. Some of the ceramics have been proved to possess applicable performance, while further studies are still needed for most of the magneto-optical ceramics. Aiming at the application for isolators, the research status, existing problems, and development trends of magneto-optical ceramics are shown and discussed in this review.

Who venerated the ancestors at the Petit-Chasseur site? Examining Early Bronze Age cultic activities around megalithic monuments through the archaeometric analyses of ceramic findings (Upper Rhône Valley, Switzerland, 2200–1600 BC)

Through the analyses of recovered pottery, this study explores the social dimension of an ancestor cult developed at the Petit-Chasseur megalithic necropolis (Upper Rhône Valley, Switzerland) during the Early Bronze Age (2200–1600 BC). The jar votive offerings and domestic pottery from settlement sites were characterized using a range of spectroscopic and microscopic techniques. Acquired archaeometric data allowed identification of six ceramic fabrics and two types of clay substrate—illite- and muscovite-based—which were used in pottery production. The present article discusses the pottery composition in the light of natural resources available in the region, thus shedding light on raw material choices and paste preparation recipes. The Early Bronze Age people that lived in the Upper Rhône Valley seem to have shared a common ceramic tradition, partly inherited from the previous Bell Beaker populations. The compositional correspondence between the jar offerings and domestic pottery revealed that the majority of the known Early Bronze Age groups partook in cultic activities at the Petit-Chasseur megalithic necropolis.

Biosynthesis-Based Al2O3 Nanofiller from Cymbopogon citratus Leaf/Jute/Hemp/Epoxy-Based Hybrid Composites with Superior Mechanical Properties.

Metallic nanoparticles (NPs) manufactured by ecofriendly strategies have also received much interest because of their elastic scattering properties and performance in nanomaterials. Aluminium oxide nanomaterials stand out among nanomaterials due to their tremendous uses in ceramic products, fabrics, therapeutic agents, catalyst supports, sewage sludge, and biosensors. The current paper investigates the effect of the nanoparticle composition and layer sequential on the mechanical characteristics of jute (J)-hemp (H) incorporated with an aluminium oxide polymer composite. NaOH is used to change the physical aspects of both plant fibres. A total of 20 specimens were tested with varying stacking sequences and padding weight ratios. Mechanical properties like a nanocomposite's tension, bending, and ILSS was measured. Stacked series and flowability substantially impact the nanocomposite. The Group 3 nanocomposite with 2% Al2O3 has the highest tensile strength, 54.28% of the Group 1 and 2 combinations. The stack series significantly influences the material properties of nanomaterials. Because of the alternating layers of natural fabrics, Group 4 specimens have the maximum flexural strength. Group 3 composite materials have the highest ILSS because they have hemp on the outermost surface. It has been discovered that Group 4 material with a 2% Al2O3 concentration is possibly the most substantial material. The existence of Al2O3 nanoparticles in the green synthesis was confirmed by XRD analysis.

One-Step Crystallization of Gahnite Glass-Ceramics in a Wide Thermal Gradient

The glass crystallization regime plays a crucial role in the fabrication of glass ceramics: it affects both phase composition and microstructure, and thus the properties of the final product. In the search for new glass-ceramic materials, the development of a proper heat-treatment schedule involves the utilization of numerous glass samples that need to be thermally treated and then investigated to determine the values of the target characteristics. In this study, we evaluated the effect of crystallization temperature on the glass structure, phase composition, and hardness of glass ceramics in the ZnO-MgO-Al2O3-SiO2 system containing TiO2 and ZrO2 as nucleators. To maximize the number of heat treatments, we performed polythermal crystallization of the glass in a wide temperature range with the help of a gradient furnace. Using X-ray diffraction, Raman spectroscopy, and transmission electron microscopy, we showed the precipitation of gahnite nanocrystals as the main phase in the bulk of a single glass sample and observed a gradual change in its microstructure, transparency, and hardness. The dependence of Vickers hardness values on heat treatment temperature was found to follow a non-linear trend, revealing the optimal thermal range for glass crystallization.

Mechanical properties of binderless tungsten carbide enhanced via the addition of ZrO2-20 wt% Al2O3 composite powder and graphene nanosheets

As an alternative to conventional tungsten carbide materials, binerless tungsten carbide (BTC) can be used in a variety of applications, such as high-speed cutting tools, rock drilling and extraction, and wear-resistant components. The absence of the metallic bonding phases solves the problems of oxidative corrosion and softening of the material during high-speed cutting process. However, the fabrication of high strength and toughness BTC ceramics remains a huge challenge. In this paper, ZrO2-20 wt% Al2O3 composite powder and graphene nanoplatelets (GNPs) were used as the reinforced phases to fabricate high performance BTC ceramics. The influence of GNPs contents on the densification, microstructure and mechanical properties of oscillatory pressure sintered BTC ceramics with 8 wt% composite powder was evaluated. The synergistic effect of ZrO2-20 wt% Al2O3 composite powder and GNPs exerted a critical role on the densification process and microstructural evolution. The produced BTC ceramics had the densest microstructure and optimal mechanical characteristics when the GNPs content reached up to 0.2 wt%; the flexural strength, Vickers hardness, fracture toughness and relative density were up to 1480 MPa, 23.72 GPa, 8.68 MPa·m1/2 and 99.8%, respectively.

Preparation of thick dense ceramic films of dielectric BaTaO2N through electrophoretic deposition

Sintering of the ferroelectric perovskite oxynitride, BaTaO2N is still a big challenge, because nitrogen is partially released from the crystal lattice during high-temperature sintering. Post-sintering annealing under an NH3 flow is essential in order to compensate for this nitrogen loss and to recover the electrically insulating properties of the ceramic. However, fully densified bulk ceramics are nitrided only on their outer surface, while their interior remains semiconducting. In this work, thick ceramic films of the perovskite oxynitride with a high relative density close to 90% were fabricated using electrophoretic deposition and high-temperature sintering. The nitrogen loss was fully recovered during annealing under an NH3 flow, owing to the thickness of the sintered films being less than 100 μm. After annealing, the BaTaO2N ceramics consisted of 200 nm-sized particles with a dense microstructure. This is the first report of the fabrication of BaTaO2N ceramics with a relative density of 89%. The dielectric constant and dielectric loss were approximately 320 and 0.05 at 1 MHz, respectively.

New Strategy for Preparation of Yttria Powders with Atypical Morphologies and Their Sintering Behavior

A modified precipitation method was used to prepare yttria powers for the fabrication of yttria ceramics in this study. The precipitation behavior, phase evolution, and shape of the yttria precursor were all examined in the presence or absence of an electric field. The findings demonstrate that the phases of the yttria precursor were Y2(CO3)3·2H2O with and without an electric field, while the morphology changed from flake to needle-like under the action of the electric field. After calcining both yttria precursors at 750 °C, yttria powders with similar morphologies were obtained and then densified via conventional sintering (CS) and spark plasma sintering (SPS). The densification and thermal shock resistance of the yttria ceramics were investigated. The yttria ceramics sintered using SPS had higher bulk density and thermal shock resistance than the samples sintered using CS. When the sintering process for the ceramics sintered from needle-like yttria powder was switched from CS to SPS, the bulk density increased from 4.44 g·cm-3 to 5.01 g·cm-3, while the number of thermal shock tests increased from two to six. The denser samples showed better thermal shock resistance, which may be related to the fracture mechanism shifting from intergranular fracture to transgranular fracture.

Correction to: Structural and electrical property characterization of thermoelectric (Ca3Co4O9±δ) ceramic oxide fabrication by various reducing agent method

Correction to: Structural and electrical property characterization of thermoelectric (Ca3Co4O9±δ) ceramic oxide fabrication by various reducing agent method

Porous acicular mullite ceramics produced from well and poorly crystallized kaolinite

This work studies how the crystallinity of a raw kaolinite clay affects the properties of mullite ceramics produced from it. To this purpose, two well and poorly crystallized kaolinite samples from the repository of the Clay Mineral Society were assessed. Also, other two samples were produced in which the growth of mullite acicular grains were promoted by addition of a MoO3 precursor. The role of the kaolinite crystallinity and the MoO3 precursor on the properties of the final ceramics was studied. For each sample, the microstructure and the textural, crystalline, and mechanical properties were analyzed.The poorly crystallized kaolinite is more reactive than the well crystallized one and promotes better mullitization. In addition, when the MoO3 precursor is used, the formation of grains with acicular shape inhibits the ceramic shrinkage and promotes higher porosities. On the other hand, the flexural strength is slightly lower for the mullite produced from poorly crystallized kaolinite. Nevertheless, when this property is extrapolated to the case of zero porosity it is found that in such cases the ceramic solid fraction presents higher flexural strength, indicating that the porous mullite with the acicular grain morphology is a reinforced lightweight ceramic. The obtained results show that the crystallinity of the starting clay should be considered in the ceramic fabrication process due to its effects on the properties of the final product.

CHEMICAL AND MINERALOGICAL ANALYSES OF THE LATE NEOLITHIC CERAMICS FROM ŞAH VALLEY (SINGUBER), TURKEY

Numerous settlements have been identified during the surveys in Şırnak province (Turkey) since the beginning of the 19th century. The potsherds found in the central of such settlements have been thought to be affected by Mesopotamian culture, and the ones from the hillside of the Şah Valley were considered as the most eastern examples of the Hassuna Samara culture. This study presents the results regarding one of the first detailed archaeometric investigations carried out for the Late Neolithic ceramic findings unearthed from Şah Valley (Şırnak province, Turkey). The ceramics were initially characterized by means of portable X-ray florescence (p-XRF) and X-ray diffraction (XRD) in order to enlighten the chemical and mineralogical features of the samples, respectively. The results indicated use of calcareous raw material sources and a low firing temperature range (ca. 700-800oC). The potsherds were also investigated through petrography which showed the presence of quartz, opaque minerals, plagioclase and biotite as the minerals, and clay, claystone and marl rock contents as the rock types for the samples, in general. Fourier transformed infrared (FTIR) spectroscopy was additionally applied for the potsherds. This complementary technique provided information about the vibrations of the chemical bands in the ceramics which displayed the characteristic bond vibrations of decisive minerals in the ceramic fabrics, such as calcite, clay minerals and quartz. Considering the whole archaeometric data, it can be deduced that the Neolithic ceramics of the Şah Valley have been subjected to low firing temperatures which could be assigned to a basic production procedure presumably claiming daily-use wares.

Influence of ink rheology and post processing in the structural performance of silicon nitride-based ceramics fabricated by robocasting

The fabrication of complex shaped Si3N4 parts by conventional methods is challenging due to its high hardness and mechanical strength. Additive manufacturing (AM) appeared as a competitive way to attain three-dimensional complexity at lower costs. However, most of AM technologies still present limitations in producing high dense ceramics, mainly due to several difficulties in developing proper feedstock. This work presents the fabrication of dense silicon nitride-based ceramics by using an extrusion based additive manufacturing technique (direct ink writing, also known as robocasting) and cold isostatic pressing (CIP) as a post processing step. Silicon-nitride aqueous based inks containing different amounts of solids loading (36, 38 and 39 vol%) and proper rheological characteristics for the printing process were studied. The use of CIP (200 MPa) is suggested to reduce or even eliminate defects and porosity and consequently, to improve mechanical performance of the final parts. Relative density, microhardness and flexural strength increased as solids loading in the inks increased and were further improved when CIP pressing was used. Parts produced by robocasting with an ink containing 39 vol% and cold isostatic pressed at 200 MPa exhibited an average relative density around 99%, 1475 HV2 microhardness value and 650 MPa flexural strength, values similar to those of silicon nitride ceramics fabricated by conventional processing.

Investigation of temperature field for the in-situ fabrication of particle-reinforced alumina ceramics coating via laser induction

Laser-induced aluminum thermal reaction was used to prepare a new iron particle reinforced alumina ceramic coating on the surface of TC4 titanium alloy. The aluminum thermal reaction heat generation in the on-line laser melting and coating process is fast and not easy to control, and its effect on the coating quality is unknown and usually neglected in the preparation process. In this paper, a numerical simulation model of a dual heat source containing the reaction heat is established. The temperature field of the new Al2O3-Fe composite coating and the thermal stress distribution pattern of the components were investigated. The effects of different laser parameters on the maximum molten pool temperature, thermal deformation and coating morphology of TC4 titanium alloy substrates were also discussed. The accuracy of the model is verified by the joint temperature acquisition experiment, which provides a reference for the selection of laser cladding process parameters. The simulation results show that the maximum temperature and volume of the melt pool increase significantly due to the coupling of the induced reaction heat, and the maximum temperature is not inversely proportional to the laser scanning speed, but directly proportional. The residual stress analysis shows that the residual stress on the coating is mainly the tensile stress along the laser cladding direction, which is the main reason for the transverse crack of the single layer coating after laser cladding.

Application of Carbon Fiber-Reinforced Ceramic Composites in Active Thermal Protection of Advanced Propulsion Systems: A Review.

Thermal protection is one of the crucial issues for the advanced propulsion systems of Reusable Launch Vehicles. New service requirements for materials, such as high strength, low density, low thermal expansion, high thermal stability, etc., are raised for the thermal structure with the increasing demand of flight Mach numbers and thrust-to-weight ratio. Carbon fiber-reinforced ceramic composites, which generally meet the aforementioned requirements, show great potential for various applications and they have been widely applied in the thermal protection for hypersonic vehicles. This paper gives a comprehensive and systematic review of current research status for carbon fiber-reinforced ceramic composites applied in the thermal structure of advanced propulsion systems. Three aspects are presented and discussed: the ceramic composites fabrication and the property characterization, the thermal performance of composite thermal structure used in practical engines, and the numerical methods for predicting mechanical and thermal properties of composites as well as the physicochemical phenomenon in the cooling channels. Firstly, the main manufacturing processes for the carbon-reinforced ceramic composites are presented and the corresponding advantages and disadvantages are analyzed. The high-temperature oxidation and ablation behaviors of composites are demonstrated and the improvement of oxidation and ablation resistance by introducing the ultra-high-temperature ceramics into C/C composites is discussed in detail. Then, several typical applications of carbon fiber-reinforced ceramic composites (mainly C/SiC), including the work of RCI, JAXA and NASA, have been reviewed and analyzed. After that, the current research status of macroscale equivalent and multiscale numerical methods for predicting the mechanical and thermal properties of composites as well as the complex physicochemical phenomenon occurring in hydrocarbon fuels are sorted out. Finally, several potential prospects are pointed out for the future research on the thermal protection of advanced propulsion systems based on the carbon fiber-reinforced ceramic composites.

Fabrication of Ceramics Using a Fused Deposition Modeling (FDM) Type 3D Printer - High Density Alumina and Ni-Zn-Cu Ferrites, and a Hydroxyapatite (HAP) Scaffold -

Dense alumina and Ni-Zn-Cu ferrites, and porous hydroxyapatite (HAP) have been fabricated using a fused deposition modeling (FDM) type 3D printer, so-called “Additive Manufacturing (AM)”. Green bodies of the former two were consisted of the laminated layer filaments from ceramics/resin = 60/40 vol% kneaded bodies to obtain dense ceramics. On the other hand, the latter was composed of 50/50 or 55/45 vol% filaments for porous scaffold. Binder-out process was performed in air with the selected temperature range/heating rate and final 673~723 K for 1.08~18.0 • 105 s, corresponding to each material. Hot Isostatic Pressed fine grained alumina after microwave sintering with an apparent relative density of 94%, substantially more than 98% by looking at the microstructure, revealed a bending strength of 562 MPa. Permeability µ of dense Ni-Zn-Cu ferrite sintered in air was nearly the same as that of conventional one; at low frequencies µ of “AM” ferrite surpassed the latter. Porous two kinds of HAP ceramics were fabricated from the different calcining temperatures 1223 and 1248 K, and biotested in terms of the cell culture at 310 K for 8.64 and 25.9 • 104 s. The cells on HAP produced from 1223 K calcined grew twofold in comparison with those of control glass.