Conventional Ceramic Processing Research Articles

Preparation, microstructure studies and mechanical properties of glazes ceramic sanitary ware based on kaolin

In this paper, the use of local kaolin coming from Djebel Debbagh (denoted DD1) in the composition of ceramic glazes for sanitary ware was examined. Because of its natural abundance, low price and good characteristics, this kaolin represents an interesting economic alternative to other mineral clays. The chemical composition showed that this kaolin contains 38.49 wt.% Al2O3 and 44.85 wt.% SiO2. Two glazes based on kaolin DD1 denoted as GaDD1 and GbDD1 were prepared with conventional ceramic processing techniques at temperature 1250 oC. As a reference, another glaze (Gref) based on kaolin Remblend was also prepared in the same conditions. The samples were characterized with X-ray diffraction and Scanning Electron Microscope. The results revealed that zircon and quartz are the crystalline phases present in these glazes. In the sample GaDD1, it was found that the degree of whiteness is very high and reaches 93.30 %. However, the water absorption coefficient is low which is about 0.19 ? 0.04 %. In addition, the flexural strength and the Vickers microhardness are respectively, about 56.07 ? 5.61 MPa and 7952.80 ? 101.76 MPa. These properties are compatible with those of the glaze reference Gref and commercial sanitary ware glazes, indicating the potential use of kaolin DD1 in the production of glazed ceramic for sanitary ware applications.

Low-temperature fabrication of calcium deficient hydroxyapatite bone scaffold by optimization of 3D printing conditions

We herein propose a novel low-temperature fabrication process of calcium deficient hydroxyapatite (CDHA) 3D scaffolds for bone tissue regeneration through a combination of material extrusion type 3D printing process and bone cement chemistry. The CDHA scaffolds with high porosity of 70% showed excellent mechanical property of 25 MPa (compressive strength), without any sintering process after 3D printing. By using this method, the final structures do not show size shrinkage, which must be considered in conventional ceramic sintering processes. We could therefore achieve both size- and 3D architecture-controlled porous CDHA scaffolds with high accuracy. In addition, the resulting ceramic cement scaffolds were not brittle and could be machined without chipping or fracturing the scaffold. The complete process takes place at physiological conditions (37 °C, pH=7), and heat sensitive drugs and biomolecules could be directly loaded onto the raw powder and achieve homogeneous distribution throughout the CDHA scaffold. In this study, we discuss various key factors to complete this low-temperature 3D printing fabrication of calcium phosphate, such as the pre-treatment conditions of particles, liquid-to-powder ratio, relationships between strut sizes, infill of structures, setting temperatures and the properties of 3D printed scaffolds. The low-temperature fabrication process of calcium phosphate scaffolds developed in this study has excellent potential for use in bone tissue engineering.

Dependence of the nonlinear behaviour stability of a ZnO nanoparticle-Bi2 O3 -Mn2 O3 -based varistor system on cooling rates during ceramic processing.

A conventional ceramic processing method was applied to manufacture high-density 20-nm ZnO-Bi2 O3 -Mn2 O3 varistor ceramics. Different cooling rates in the range of 135-540°C/h led to a relatively slight influence on the microstructure, varistor voltage, and leakage current. In contrast, these rates strongly affected the nonlinear exponent. The specific surface area of the 20-nm ZnO nanoparticle may have led to an intense solid-state reaction even at a low cooling rate. Superior nonlinearity, with 59.7 μA nonlinear current leakage and 273.5 μA leakage current, was achieved at the 135°C/h cooling rate. The differences in the cooling rates led to a remarkable change in the material's stability under direct current (DC)-accelerated aging stress in the following order: 135°C/hr ˃ 270°C/hr˃405°C/hr ˃ 540°C/hr.

Capacitive behavior of lead free BiNdMnNiO6 double perovskite electronic material

Abstract An effective and simple method has been developed to synthesize the lead free BiNdMnNiO6 double perovskite material. The synthesis has been carried out through the conventional high-temperature solid-state ceramic processing method. The crystal structure formation has been confirmed with the help of the powder X-ray diffraction method which shows that at room temperature the ceramic exhibits a monoclinic structure. Dielectric and impedance spectroscopy methods have been used to study the significances of frequency and temperature on the conduction mechanism of the ceramic material. The variations of tangent loss and dielectric at different frequencies have been carried out to study the capacitive behavior of the ceramic material. From its impedance study, the existence of a negative temperature coefficient has been affirmed. The important physiochemical properties associated with this compound may be very much essential in the development of next-generation electronic devices.

Tailoring dielectric properties of cordierite-mullite ceramics through Ceramic Injection Moulding

Cordierite-mullite ceramics have been processed by Ceramic Injection Moulding (CIM) for the first time. The comparison with cordierite-mullite ceramics obtained by conventional ceramic process (CP) proves the effect of processing on the structure, microstructure, thermal and dielectric properties. CIM processing favours formation of larger content of mullite phase, a more homogeneous microstructure and reduced porosity than by conventional processed ceramics. These factors strongly condition the dielectric behaviour, which is analyzed by complex impedance formalism up to 850 °C and 1 MHz. The conduction mechanism is thermally activated and the activation energy is ~2.5 times larger in CP than in CIM ceramics. Thermal expansion coefficient is tuned by processing method, ranging from 3.9·10−6 °C−1 to 4.6·10−6 °C−1. All these findings show the strong influence of processing in cordierite-mullite ceramic composites. This work shows that tailoring composition and CIM parameters allow cordierite-mullite composites to precisely fulfill the requirements for future electronic applications.

Fabrication and Characterization of Ice Templated Membrane Supports from Portland Cement.

Porous ceramic membranes for aqueous microfiltration and ultrafiltration processes suffer from the high-costs of material and processing. The latter is mainly due to the high-temperature sintering step. In this work, cement-based membrane supports from ultrafine Portland cement are studied as a low-cost alternative to traditional oxidic ceramic supports. An environmentally friendly freeze-casting fabrication route is applied for the fabrication of porous membrane supports. Cement membrane supports are becoming mechanically stabile after hydration reaction of cement with water, which does not require any high-temperature sintering step as in a conventional ceramic membrane fabrication process. This fabrication route, which is sintering-free, decreases the cost and environmental impact of the membrane fabrication process by eliminating extra energy consumption step during sintering. The Archimedes method, scanning electron microscopy (SEM), micro-computed tomographic (µCT), and mercury porosimetry characterize the membrane supports in respect to open porosity, pore size distribution, morphology, and connectivity. The flexural strength of the 3 mm thick membranes is in the range from 1 to 6 MPa, as obtained by the ring-on-ring tests. The obtained membrane supports possess porosity in the range between 48 and 73% depending on fabrication conditions (cooling rate and the solid content, as determined by Archimedes method enabling water flux in the range between 79 and 180 L/(h·m2) at 0.5 bar transmembrane pressure difference and 3 mm membrane thickness.

Structural and dielectric properties of double perovskite lead free BiGdMnNiO6 electronic system

An effective as well as a simple method has been adopted to formulate a lead free BiGdMnNiO6 double perovskite electronic material. The synthesis has been carried out through the conventional high temperature ceramic processing route. The crystal structure realization has been confirmed with the help of powder X-ray diffraction method which shows that at room temperature the ceramic exhibits a monoclinic structure. To study the consequences of frequency and temperature on the conduction mechanism impedance spectroscopy methods have been used. The variations of tangent loss and dielectric at different frequencies have been carried out to study the capacitive behaviour of the ceramic material. The impedance analysis of the material signifies the existence of negative temperature coefficient. The important physiochemical properties associated with this compound may be very much essential in the development of next generation electronic devices.

Preparation and electrical performance of BCHT lead-free piezoelectric ceramics via powder injection molding

(Ba0.85Ca0.15)(Hf0.10Ti0.90)O3 (BCHT) lead-free piezoelectric ceramics were synthesized via the powder injection molding process sintered at several temperatures, in which the BCHT ceramics were prepared by the conventional ceramic processing sintered at the optimized temperature 1450 °C for comparison. All the synthesized BCHT ceramics exhibit rather pure perovskite phase structure, where the BCHT ceramics prepared via the powder injection molding process present more apparent multiphases coexistence characteristic. The electrical properties of the BCHT ceramics prepared via the powder injection molding process are slightly better than those prepared by the solid-state sintering method, which correlate with the increase of ceramics densification and the change of grains micro-morphology. The powder injection molding technique provides a feasible way to synthesize irregular shaped piezoelectric ceramics with excellent electrical performance.

Improved Multilayered (Bi,Sc)O3-(Pb,Ti)O3 Piezoelectric Energy Harvesters Based on Impedance Matching Technique.

As a piezoelectric material, (Bi,Sc)O3-(Pb,Ti)O3 ceramics have been tested and analyzed for sensors and energy harvester applications owing to their relatively high Curie temperature and high piezoelectric coefficient. In this work, we prepared optimized (Bi,Sc)O3-(Pb,Ti)O3 piezoelectric materials through the conventional ceramic process. To increase the output energy, a multilayered structure was proposed and designed, and to obtain the maximum output energy, impedance matching techniques were considered and tested. By varying and measuring the energy harvesting system, we confirmed that the output energies were optimized by varying the load resistance. As the load resistance increased, the output voltage became saturated. Then, we calculated the optimized output power using the electric energy formula. Consequently, we identified the highest output energy of 5.93 µW/cm2 at 3 MΩ for the quadruple-layer harvester and load resistor using the impedance matching system. We characterized and improved the electrical properties of the piezoelectric energy harvesters by introducing impedance matching and performing the modeling of the energy harvesting component. Modeling was conducted for the piezoelectric generator component by introducing the mechanical force dependent voltage sources and load resistors and piezoelectric capacitor connected in parallel. Moreover, the generated output voltages were simulated by introducing an impedance matching technique. This work is designed to explain the modeling of piezoelectric energy harvesters. In this model, the relationship between applied mechanical force and output energy was discussed by employing experimental results and simulation.

$$\hbox {Bi}_2\hbox {O}_{3}\hbox {-doped}$$ $$\hbox {SnO}_{{2}}$$ varistors with low breakdown electric fields

This work presents $$\hbox {Bi}_{{2}}\hbox {O}_{\mathrm {3}}\hbox {-doped SnO}_{{2}}$$ ceramic varistors prepared through conventional ceramic processing in the sintering temperature range of 1290–1320°C. The sample sintered at 1300°C exhibits a breakdown electric field as low as 11.6 V $$\hbox {mm}^{\mathrm {-1}}$$. Scanning electron microscopy images reveal that all the samples have a compact structure, and energy dispersive spectroscopy results for the sample sintered at 1300°C indicate that Bi distributes homogeneously along the grain boundaries and aggregates inhomogeneously on the grain surfaces. With increasing sintering temperature, the grain boundary barrier height remains nearly constant at 0.80 eV. In both the dielectric loss and electric modulus spectra of the sample sintered at 1300°C, obvious relaxations were observed and the activation energies obtained from the respective spectra were 0.33 and 0.15 eV, which are expected to be related to oxygen vacancies and interstitial ions, respectively. Complex impedance spectra are employed to develop a non-typical equivalent circuit model for the $$\hbox {Bi}_{{2}}\hbox {O}_{\mathrm {3}}\hbox {-doped SnO}_{{2}}$$ ceramic varistors at low voltage that yields an excellent fit to the data.

Complex SiOC ceramics from 2D structures by 3D printing and origami

Manufacturing of ceramic components with a geometrically complex 3D architecture and highly detailed features for use in a variety of practical applications is still a challenge. In our investigation, we adopted a synergistic strategy for fabricating SiOC ceramics with intricate 3D morphologies by additive manufacturing and origami technique or assemblage, taking advantage of the high printability and flexibility of a commercially available silicone elastomer. Secondary shaping using origami of different 2D layers with varied design allowed the manufacturing of spiral, flower-like and polyhedron architectures, which are difficult to fabricate without adding supports or by any conventional ceramic fabrication processes. Produced samples showed no cracks or pores and fully retained the given shape after pyrolysis.

Comparison between the use of Co3O4 or CoO on microstructure and electrical properties in a varistor system based on SnO2

This comparative study pursues to clarify the differences between the addition of CoO or Co3O4 as a dopant on the non-linear electrical behavior and microstructure characteristics of a varistor system based on SnO2. The samples were fabricated according to the conventional ceramic processing using the nominal composition: (99.99-X)%SnO2 – 0.05%Cr2O3 – 0.05%Sb2O5 – X%CoO/Co3O4 where X = 0, 1, 3 and 5 mol%. The TGA-DTA analysis revealed essential differences in the thermal stability of CoO and Co3O4 during the sintering process, being CoO the oxide that induced the most visible changes. SEM micrographs, supported by EDS and XRD, showed remarkable grain growth even with a slight addition of cobalt oxide in comparison with the reference sample. The use of CoO holds the average grain size (6.7 μm), composition (SnO2), and shape homogeneity. In the case of Co3O4, a decreasing tendency in the average grain size and an increase in the residual porosity due to the in-situ formation of Co2SnO4 phase is observed. The electrical analysis revealed similarities on the alpha value for all molar percentages of both cobalt oxides: ∼9.6 and ∼8.1 units for CoO and Co3O4, respectively. In contrast, the breakdown electrical field shows notable differences: 1.08–1.16 kV cm−1 for CoO and 1.08–2.46 kV cm−1 for Co3O4. The evidence of this study confirms previous findings and suggests the existence of an essential role for the phase transitions of cobalt oxide on the final performance of SnO2-based varistors.

Sintering and dielectric behavior for doped cordierite by xCuO within MgO (1-x)–Al2O3–SiO2 ceramics

Crystalline structure, morphology, quantitative chemical constitution and dielectric properties of pure cordierite ceramic (CC) bodies and these doped with xCuO in formula MgO(1-x)Al2O3SiO2 (x = 0, 0.02, 0.04 and 0.06 wt%), prepared by a conventional solid state ceramic process, were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray fluorescence (XRF) and broadband dielectric spectrometer (BDS), respectively. Experimental results showed that doping with CuO results in lowering sintering temperature, lowering porosity, increasing bulk density and formation of copper magnesium silicate (CuMgSi2O) phase. CuMgSi2O which was formed with the highest content of CuO (0.06 wt %) increases the glassy phase, i.e. crystalline phase decreases of CC. Accordingly, the dielectric properties of CC found to be affected by CuO content. For instance, the permittivity and loss tangent slightly increased upon doping with 0.02 wt % CuO and then considerably decreased for sample doped with 0.06 wt % CuO due to formation of CuMgSi2O phase. Particularly, the loss tangent attained much lower values (0.003 at 25 °C) upon doping with 0.06 wt% CuO. Interestingly, such materials of very low loss can be used as candidates for wireless communication systems as well as in several electronic devices.

The effect of SiO2 addition on dielectric properties and microstructure of ZnNiO2: based ceramics

The present work attempted to investigate the effect of SiO2 addition on the dielectric properties and microstructure of the ZnNiO2—ceramics. The content of added SiO2 is in the range 5–40 wt%, while that of the other additives keeps constant. The given samples were sintered at 1000–1300 °C for 120 min, with conventional ceramic processing method. By X-ray diffraction, Zinc silicate, Nickel silicate, Quartz, Nickel Zinc Oxide, Zinc Oxide and Nickel oxide were found in all the samples, and no extra phases were identified in the detection limit. Minimum water absorption was present in specimens fired at 1300 °C for 120 min. The DTA pattern shows a clear indication of five maxima happening at the point 104.1 °C, 112 °C, 109.5 °C, 106 °C, and 117.9 °C, respectively. SEM studies show that the increase of SiO2 wt% had significant influence on grain growth and microstructural characteristics of the sintered specimens. There are agglomerated fine particles of NiO, because it has high surface tension. The electrical properties of the samples varied with the increase content of SiO2. The capacitance (pF) and, dielectric constant (ɛ−), decrease when SiO2 content increase and with increasing frequency whereas, conductivity increased with increase content of SiO2.

Dense garnet-type electrolyte with coarse grains for improved air stability and ionic conductivity

Abstract Garnet-type electrolytes with high ionic conductivity and chemical stability against lithium metal show promise as solid-state electrolytes for lithium-ion batteries. However, a high concentration of pores and grain boundaries in air-processed polycrystalline electrolytes makes them prone to dendrite formation and reaction with atmospheric moisture, leading to electrochemical and mechanical instability. In this work, we illustrate that abnormal grain growth, an often-avoided phenomenon in conventional ceramic processing, can be employed as a unique approach to obtain extraordinarily large oligo crystals for minimal grain boundaries. Here we report a straightforward approach to develop a robust Ga-doped garnet, Li6.25Ga0.25La3Zr2O12 (LGLZO) electrolyte with conventional solid-state sintering in air. By preparing nanopowders without agglomeration through ball milling and freeze drying, we can control the microstructure of air-sintered electrolytes for desirable properties of a high density (98% of theoretical density) and an average grain size of 460 µm. The robust air-processed LGLZO electrolytes demonstrate high ionic conductivity, stability in air, and mechanical robustness relative to other garnet electrolytes offering promise as cost- and performance-competitive solid-state electrolytes for safe lithium-ion batteries.

RF complex permeability spectra of Ni-Cu-Zn ferrites prepared under different applied hydraulic pressures and durations for wireless power transfer (WPT) applications

Frequency dispersion of RF complex permeability of Ni-Cu-Zn ferrites prepared under different amplitudes and durations of applied hydraulic pressure have been thoroughly investigated. The Ni0.35Cu0.19Zn0.46Fe2O4 ferrites were prepared by conventional ceramic synthesis process. The obtained ferrite powders were pressed under different hydraulic pressures (4 MPa, 8 MPa, 12 MPa) of different durations (30 s, 2 min, 3 min and 5 min). It was noted that the complex permeability spectra change considerably with respect to the application of different amplitudes and durations of hydraulic pressure before sintering. Porosity and grain size play an important role in affecting the permeability and magnetic loss of the sintered ferrite samples. A significant increase of the real part of the complex permeability from 96 to 151 was achieved due to the application of hydraulic pressure of 8 MPa for 30 s as compare to manually pressed sample. The magnetic loss tangent also increased from 0.01 to 0.02 as the imaginary part of the complex permeability increased, which is still acceptable for most of the wireless power transfer (WPT) applications. It is postulated that the hydraulic pressure applied before sintering of ferrite powder-based specimen increases the real part of permeability while influencing magnetic loss tangent much less severely.

Varistor and electrical properties of MgO.(Fe2O3)1−x(Bi2O3)x ceramics

In this study, MgO.(Fe2O3)1−x(Bi2O3)x (x = 0.01, 0.02, 0.04, 0.08) samples were prepared by the conventional ceramic process. Microstructure studies revealed that the samples contain MgFe2O4 grains surrounded by insulating Bi2O3-rich phases. DC electrical resistivity of the samples was increased by Bi2O3 content up to 1.1 MΩ.cm for the sample with x = 0.08. Current density- electric field investigations suggested that the samples with x = 0.01, 0.02 and 0.04 exhibited varistor properties. The sample with x = 0.01 showed excellent varistor properties with a non-linear coefficient of 45 and a threshold electric field value of 160 V/cm. Variation of D.C electrical conductivity versus temperature indicated that the activation energy values for the conduction were increased by Bi2O3 content from 0.334(5) eV to 0.857(5) eV. A.C electrical conductivity spectra of the samples obey the universal power law and the charge transport mechanism is based on electron hopping via sudden translational motion between the ferric and ferrous ions.

Ca2+ doping effects in (K, Na, Li)(Nb0.8Ta0.2)O3 lead-free piezoelectric ceramics

Lead-free (K0.5-x/2Na0.5-x/2Lix)(Nb0.8Ta0.2)O3 (KNLNT) and (K0.49-x/2Na0.49-x/2-LixCa0.01)(Nb0.8Ta0.2)O3 (KNLNT-Ca) ceramics were prepared by a conventional ceramic processing. Structural analysis shows that the Ca2+ doping takes the A site of ABO3 perovskite and decreases the phase transition temperature. Property measurements reveal that as a donor dopant, the Ca2+ doping results in higher room-temperature dielectric constant, lower dielectric loss, and lower mechanical quality factor. In addition, the Ca2+ doping does not change the positive piezoelectric coefficient d33, but increases the converse piezoelectric coefficient d33* significantly. This is likely due to the increase in the relaxation, as well as the appearance of (CaNa/K·-VNa/K’) defect dipoles.

Non-volatile immobilization of iodine by the cold-sintering of iodosodalite

A cold-sintering process at a very low temperature (300 °C) achieved stable immobilization of simulated radioiodine waste incorporated in sodalite (iodosodalite). The reported sintering temperature was much lower than conventional ceramic waste form processing temperatures (600−1100 °C) and had no effect on the stability of the loaded iodine waste. Excellent iodine retention (>93%) with relative sintered density 91% were achieved by the cold-sintering at 300 °C, respectively. The sintered body exhibited a micro-hardness value of 3.9 ± 0.1 GPa and compressive strength of 198 ± 11 MPa. The seven-day product consistency test found iodine leaching rates on order of the magnitude 10-4 g/m2⋅d. These results are the first example of the low temperature consolidation of iodine-bearing sodalite without using any additional material (e.g. glass, cement, etc.). High retention of the loaded simulated radioiodine without volatilization warrants the cold-sintering process for the environmental-friendly disposal of radioiodine.

Magneto-electro-optical multifunctional coupling effect in lead-free BaTiO3(Yb/Er)-CoFe2O4 ceramics

A multifunctional material 0.65Ba0.955Yb0.025Er0.005TiO3–0.35CoFe2O4, owning superior piezoelectric, photoluminescence and magnetostrictive effects, was prepared via the conventional solid-state ceramic fabrication process. The ferroelectric, piezoelectric, dielectric, photoluminescence, as well as magnetic properties were characterized. Furthermore, in-situ magneto-electric, electro-photoluminescence and magneto-photoluminescence coupling effects were studied. A relatively larger magneto-electric coupling coefficient αE33 was determined to be 11 mV/Oe•cm@1 kHz, while the reversible electric and magnetic modulation ratio of integral intensity of green emission reached 16%@15 kV/cm and 2%@2 kOe, respectively. The underlying mechanism was discussed by PFM results, and the present work provides an alternative material to design devices with multiple functions.