Ceramic Technique Research Articles

Effect of carbon and oxygen on the high-temperature properties of silicon carbide–hafnium carbide nanocomposite fiber

The polymer-derived ceramics (PDCs) technique enables relatively low-temperature fabrication of Si-based ceramics, with silicon carbide fiber as a representative product. Polycarbosilane (PCS) has Si-C backbone structures and can be converted to silicon carbide. In the PDCs method, residual or excess carbon is generated from the precursor (C/Si ratio = 2 for polycarbosilane). Because of the non-stoichiometry of SiC, the physicochemical properties of polymer-derived SiC are inferior to those of conventional monolithic SiC. Herein, a silicon carbide-hafnium carbide nanocomposite fiber was optimized by crosslinking oxygen into the PCS fiber by regulating the oxidation curing time. During pyrolysis, carbothermal reduction, and sintering, carbon was removed by reaction with hydrogen and cross-linked oxygen. Non-destructive techniques (X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and high-temperature thermomechanical analysis) were used to investigate the effects of excess carbon. The microstructure of the near-stoichiometric SiC-HfC nanocomposite fiber was more densified, with superior high-temperature properties.

SnO2 Doping Effect on the Microstructural and Electrical Behavior of ZnO nanoparticles-Bi2O3 Based Varistor Ceramics

In the current study, ZnO-Bi2O3 varistors manufactured from ZnO nanoparticle size and doped with SnO2 were processed by the ceramic industrial technique. The impact of the various SnO2 concentration upon the sintering, microstructural improvement and nonlinearity characteristic of the varistor system was investigated. Different SnO2 concentration was found to possess considerable influences on the varistors, particularly on improving ZnO grains growth at a lower SnO2 amount. But, the adding of greater contents of SnO2 leads to inhibit the ZnO grain growth via the raising percentage of Zn2SnO4 type spinel phase. In discs with a Sn/Bi less than 1.5 mol%, the pyrochlore phase forms and bounds all the SnO2, whereas excess Bi2O3 leads to the formation of a liquid phase at 740 °C which promotes sintering process. For Sn/Bi more than 1.5 mol%, all the Bi2O3 is bounded in Bi2Sn2O7 pyrochlore phase and sintering process is prevented. X-ray diffraction investigated that additive of SnO2 to the ZnO-Bi2O3 varistor sample caused the structure of the Bi2Sn2O7 type pyrochlore phase and the Zn2SnO4 type spinel phase during the sintering step. The SnO2 adding furthermore noticeably affected the electrical behaviors of the sample with a significant rise in the breakdown voltage with increasing the SnO2 doping more than 1.5 mol%. The resistivity also achieved an obvious increase with increase the SnO2 doping contents. Moderate SnO2 doping enhanced the nonlinear properties of the ZnO-Bi2O3 varistor system, while a significant amount of SnO2 causing its deterioration.

High-strength lithography-based additive manufacturing of ceramic components with rapid sintering

Additive manufacturing technology enables the fabrication of technical ceramics and multi-materials with unprecedented geometrical accuracy and complexity, opening the path to new functionalities for engineering applications. A crucial step to consolidate 3D-printed ceramic parts is “sintering”, a time and energy (temperature) intensive densification process. Here we present a strategy for rapid sintering (∼ 300–450 °C/min) of lithography-based additively manufactured alumina ceramics enabling consolidation of ceramic components of complex shapes within minutes. Highly dense, fine-grained microstructures were achieved by controlling densification and limiting grain growth through rapid radiation heat transfer. The high mechanical strength and toughness measured in additively manufactured alumina (∼ 810 MPa and ∼ 4.3 MPa m 1/2 ) sintered at 1600 °C within 2 min was superior to that of conventionally sintered reference parts. This study opens the path for rapid sintering of complex shaped ceramic architectures of high density with tailored microstructure and properties. • 3D-printed ceramics with complex geometry can be sintered within minutes. • Rapid radiation using a customized Spark Plasma Sintering system promotes densification. • Controlling the dwell sintering time allows tailoring of grain size in refined microstructures. • Dense and exceptionally high strength 3D-printed alumina were achieved. • Our sintering protocol may be applied to other 3D printed ceramic materials.

Fabrication of a lead-free ternary ceramic system for high energy storage applications in dielectric capacitors.

The importance of electroceramics is well-recognized in applications of high energy storage density of dielectric ceramic capacitors. Despite the excellent properties, lead-free alternatives are highly desirous owing to their environmental friendliness for energy storage applications. Herein, we provide a facile synthesis of lead-free ferroelectric ceramic perovskite material demonstrating enhanced energy storage density. The ceramic material with a series of composition (1-z) (0.94Na0.5Bi0.5TiO3-0.06BaTiO3)-zNd0.33NbO3, denoted as NBT-BT-zNN, where, z = 0.00, 0.02, 0.04, 0.06, and 0.08 are synthesized by the conventional solid-state mix oxide route. Microphases, microstructures, and energy storage characteristics of the as-synthesized ceramic compositions were determined by advanced ceramic techniques. Powder X-ray diffraction analysis reveals pure single perovskite phases for z = 0 and 0.02, and secondary phases of Bi2Ti2O7 appeared for z = 0.04 and 0.08. Furthermore, scanning electron microscopy analysis demonstrates packed-shaped microstructures with a reduced grain size for these ceramic compositions. The coercive field (Ec) and remnant polarization (Pr) deduced from polarization vs. electric field hysteresis loops determined using an LCR meter demonstrate decreasing trends with the increasing z content for each composition. Consequently, the maximum energy storage density of 3.2J/cm3, the recoverable stored energy of 2.01J/cm3, and the efficiency of 62.5% were obtained for the z content of 2mol% at an applied electric field of 250kV/cm. This work demonstrates important development in ceramic perovskite for high power energy storage density and efficiency in dielectric capacitors in high-temperature environments. The aforementioned method makes it feasible to modify a binary ceramic composition into a ternary system with highly enhanced energy storage characteristics by incorporating rare earth metals with transition metal oxides in appropriate proportions.

Strong and Tough Alumina Ceramic from the Particle‐Stabilized Foam

Strength and toughness are two vital and contradictory properties, especially in alumina structural ceramics. This mutual exclusion limits the widespread application of advanced alumina ceramics in harsh environments. To deal with this issue, self‐toughening alumina bulk ceramics without any ductile phase and with a unique combination of excellent toughness and reliable strength by combining the foam ceramics with hot‐pressing sintering are prepared. Foam ceramics with honeycomb cellular structures are prepared by particle‐stabilized foaming. Then, the foam ceramics is directly hot pressed sintered, in which the cellular structure is fractured into fragments and completely dense under pressure. Equiaxed grains that constituting the fragments grow anisotropically into plate‐like grains with a large diameter–thickness ratio during hot‐pressing sintering. Plate‐like grains improve the material's fracture toughness by exerting a toughening mechanism similar to that of fibers. The self‐toughening alumina ceramics exhibit a unique combination of high flexural strength (874 ± 31 MPa) and high fracture toughness (6.2 ± 0.1 MPa m1/2). The Vickers hardness also can reach 21 GPa. Herein, a new strategy with relatively simple processing to fabricate high‐performance ceramics based on the widespread ceramic processing techniques are provided.

Smelting copper in decorated pottery: communities of practice in the Niari Basin, Republic of the Congo, fifteenth–seventeenth centuries CE

This paper considers copper production in the Niari Basin, Republic of the Congo, during a period dated to the mid-fifteenth–mid-seventeenth centuries CE. Using a combination of pXRF, OM, SEM–EDS, and FTIR, it assesses the microstructure and composition of slags and technical ceramics from sites associated with two different regional pottery traditions: Moubiri-type at the site of Kingoyi near Mindouli and Kindangakanzi-type at Kindangakanzi near Boko-Songho. Both sites are characterised by the use of refractory domestic pottery as crucibles for copper smelting. Moubiri-type pottery is alumina-rich, while Kindangakanzi-type pottery is formed from a magnesia-rich clay, a crucible type unique in sub-Saharan Africa. Similarities in chaînes opératoires at Kingoyi and Kindangakanzi suggest sharing of knowledge at mining and smelting sites, interactions we reconstruct as a metallurgical constellation of practice comprised of the distinct potting communities of practice (see Supplementary information for abstract in Lingala and French).

Sensitivity of electrical behaviours of ZnO nanoparticle–Bi2O3–Mn2O3 varistor system to various La2O3 doping compositions

The effects of La2O3 on the behaviours of ZnO nanoparticle–Bi2O3–Mn2O3 varistors were determined. The discs with various La2O3 compositions (0.0–3.0 mol%) were prepared via traditional ceramic techniques and their characteristics were investigated. The results demonstrate that La2O3 remarkably affects the varistor samples, in which the size of grain diminished from 29.3 to 8.5 µm according to increasing La2O3 content from 0.0 to 3.0 mol%. The significant response within the varistor sample fabricated from ZnO nanoparticles through sintering process at 1200oC perhaps caused by the surface properties of the powdered ZnO nanoparticles. X-ray diffraction results show that the addition of La2O3 to the varistor resulted in additional peaks, which can be attributed to the construction of La-based phases through the sintering process at high temperature. The spinal phases of the (Bi48ZnO73) and (Mn3O4) diminish with the 3.0 mol% content of La2O3. The varistor samples with 2.0 mol% La2O3 show a superior spinal phase construction of (Bi48ZnO73) and (Mn3O4) and La-based phases, resulting in homogeneous grain size. La2O3 doping substantially enhanced the electrical behaviours of the disc sample with a notable increase in breakdown voltage from 2614.8 to 5730.7 V/mm caused by the increase in La2O3 doping concentration from 0.0% to 3.0 mol%. The improvement was associated with the potential lanthanide ion segregation caused by its greater ionic radius to the boundaries between ZnO grains, thus enhancing its electrical properties. Moderate La2O3 doping concentration at 1.0 mol% improved the non-linear characteristics of the sample (α = 66) and 4400 V/mm breakdown voltage was introduced, while a significant amount of La2O3 doping concentration (more than 1.0 mol%) caused its deterioration (α = 35). The increase in donor concentration Nd to 2.1 × 1020 cm−3 for the varistor doped with 1.0 mol% La2O3 is accompanied by a decrease of interfacial states density NIS to 2.2 × 1012 cm−2 eV−1, in addition to decrease in depletion layer ω to 3.9 nm. The leakage currents of the sample decreased from 0.473 to 0.310 mA/cm2 with the increase of La2O3 doping contents from 0.0% to 2.0 mol% and then increased to 0.596 mA/cm2 at 3.0 mol% La2O3 doping concentration. Therefore, La2O3 may be added to dominate the microstructural characteristics and electrical behaviours of ZnO–Bi2O3–Mn2O3 varistor manufactured using powdered ZnO nanoparticles.

Iron Age and Roman metallurgical activities at the Spasovine placer tin deposit, West Serbia

Spasovine, on the south flank of Mt. Cer in West Serbia, is one of the rare localities where Late Bronze Age placer tin mining activities have been documented. Archeological pedestrian surveys on this river terrace recovered ceramic fragments with metal-rich coatings, thought to be fragments of technical ceramics. The physical characteristics of the “petrol” gray-bodied ceramics are consistent with Roman Period ca. 200-300AD production, while black-bodied sherds are most consistent with Iron Age ceramics of western Serbia. SEM-EDS analysis of polished thin-sections and rough surfaces has shown that the fragments are enriched in various metallic residues (Zn, Sn, Cu, Pb in various combinations). Of the fourteen sherds studied, nine Roman samples contain Zn-rich coatings on the inner surfaces as well as deeper penetration of zinc enrichment into the ceramic interior, consistent with Zn cementation for brass. Three of these also contained younger addition of Sn, indicating that they were repurposed for bronze production at Spasovine. The prehistoric sherds contain tin along with Cu and Pb, consistent with the production of leaded tin bronze, which is not known from the area until the Iron Age (ca. 800-600BC). Thus, Spasovine was the site of itinerant mining and metallurgical activity, at least sporadically, over a period of 1700 years from the Late Bronze Age (14th century BCE) to the Roman Period (2nd-3rd century CE). This demonstrates that small deposits of placer tin could have had long-term impact on regional tin economies in ancient Europe.

THE EFFECTS OF KOREAN POTTERS AFTER THE IMJIN WAR ON JAPANESE CERAMIC CULTURE

The Imjin War was fought between Japan and Korea between 1592 and 1598. The process that started with Japan's invasion of Korea resulted in the capture of skilled Korean craftsmen and about 800 Korean potters, among them, after the war. Captive Korean potters were settled in areas of western and southern Japan ruled by the Lords of the time. Korean potters, who have a deep-rooted ceramic tradition, developed ceramic production techniques in the Japanese regions where they were placed and became the creators of products such as Satsuma-yaki, Hagi and Karatsu ceramics, and Arita porcelain, which are known today as Japanese ceramics. As a result of the effects of Korean potters captured as a kind of war booty on Japanese ceramic art and culture, the Imjin War in the literature of ceramic art history; is called the “Tea Bowl War”, “The Pottery War” and the “Ceramic War”. In this study, a brief history of the Imjin War is given, the Korean ceramic tradition and culture, which reached its peak during the pre-war Joseon Dynasty, is evaluated through examples, and finally, technical and formal transformations and new formations in post-war Japanese ceramic production are examined. Keywords: Imjin War, Tea Bowl War, Pottery War, Korean Ceramics, Japanese Ceramics

THE EFFECTS OF KOREAN POTTERS AFTER THE IMJIN WAR ON JAPANESE CERAMIC CULTURE

The Imjin War was fought between Japan and Korea between 1592 and 1598. The process that started with Japan's invasion of Korea resulted in the capture of skilled Korean craftsmen and about 800 Korean potters, among them, after the war. Captive Korean potters were settled in areas of western and southern Japan ruled by the Lords of the time. Korean potters, who have a deep-rooted ceramic tradition, developed ceramic production techniques in the Japanese regions where they were placed and became the creators of products such as Satsuma-yaki, Hagi and Karatsu ceramics, and Arita porcelain, which are known today as Japanese ceramics. As a result of the effects of Korean potters captured as a kind of war booty on Japanese ceramic art and culture, the Imjin War in the literature of ceramic art history; is called the “Tea Bowl War”, “The Pottery War” and the “Ceramic War”. In this study, a brief history of the Imjin War is given, the Korean ceramic tradition and culture, which reached its peak during the pre-war Joseon Dynasty, is evaluated through examples, and finally, technical and formal transformations and new formations in post-war Japanese ceramic production are examined. Keywords: Imjin War, Tea Bowl War, Pottery War, Korean Ceramics, Japanese Ceramics

Microstructure, dielectric response and impedance spectroscopy of SrCu3Ti4O12 ceramics prepared by a sol-gel technique

SrCu3Ti4O12 ultrafine powders and ceramics were successfully prepared using sol-gel and ceramic techniques. DTA/TG, XRD, HRTEM, SAED, SEM, and XPS were employed to characterize the samples' thermal decomposition, phase composition, microstructure, and element valence. During calcination, the dry precursors gradually decompose into oxides and recombine into SrCu3Ti4O12 polycrystalline above 620 °C. Simultaneously, the prepared ceramics sintered at 1025 °C for 8 h exhibited a colossal permittivity at room temperature (εr = 8.5 × 104, 1 kHz) and good temperature stability. XPS result confirms that Cu+/Cu2+ and Ti3+/Ti4+ coexist in ceramics, and Impedance analysis indicates a low-resistance region originating from inhomogeneity in the grain interiors. Finally, the relevance between defect formation and dielectric properties in SrCu3Ti4O12 materials is discussed.

Influence of Ni on the structural evolution of polymer-derived SiOC ceramics

Polymer derived ceramics (PDCs) technique is an advanced method for preparing high performance ceramics, in which pyrolysis process is an important step. In order to study the effect of the Ni transition metal on the pyrolysis process of polysiloxane, different contents of Ni acetate tetrahydrate (Ni(ac)2·4H2O)-impregnated polysiloxane (PSO) precursors were pyrolyzed in argon atmosphere between 1000 °C and 1300 °C. The organic-inorganic conversion behavior of precursors, the elemental and structural characterization of the Ni-free and Ni-containing SiOC ceramics were investigated. The results revealed that the presence of Ni not only enabled the growth of carbon nanotubes (CNTs) but also promoted the crystallization of carbon and SiC phase during the pyrolysis process. Additionally, high Ni content and pyrolysis temperature raised the diameters of CNTs and crystallinity of turbostratic layer carbon and SiC.

Characterization of Chalcolithic Ceramics from the Lisbon Region, Portugal: An Archaeometric Study

The Chalcolithic period in the Lisbon region, Portugal, is usually divided into three phases chronologically: the Early Chalcolithic, characterized by cylindrical corrugated cups, Full Chalcolithic by so-called acacia-leaf decoration, and Late Chalcolithic by Bell Beaker pottery. The aim of this research is to determine if Chalcolithic ceramic raw materials and production techniques have remained the same over time and whether the pottery is locally produced. Regarding the Lisbon region, 149 ceramic samples from four Chalcolithic settlements (Vila Nova de São Pedro, Penedo do Lexim, Espargueira and Baútas) were evaluated concerning textural, chemical and mineralogical compositions. Textural analysis was performed using optical microscopy, chemical characterization was achieved using micro-energy dispersive X-ray fluorescence spectrometry and mineralogical characterization was undertaken using X-ray powder diffraction and petrographic microscopy as main techniques. Results suggest that production techniques may have remained similar throughout all the Chalcolithic period, with firing temperatures between 700 and 800 °C. Multivariate analysis of results from chemical and mineralogical analyses suggests that multiple sources of raw materials must have been used in the manufacture of the pottery collected at the four Chalcolithic settlements.

Stable garnets in the Er2O3–Sc2O3–Al2O3 oxide system for optical ceramics application

Erbium-scandium-aluminum garnets (ErSAG) with the maximum possible concentrations of scandium cations in the dodecahedral and octahedral positions of the crystal lattice have been synthesized. It has been established that in ErSAG at a temperature of 1600 °C the maximum possible concentration of scandium in the dodecahedral and octahedral position reaches 64.7 ± 2.0 at. % and 92.0 ± 2.0 at. %, respectively. The maximum possible concentrations of scandium cations in the dodecahedral position and the set of range of possible ErSAG compositions decrease at increasing of calcination temperature. It was shown that ceramics technique allow to produce the optical ceramics with compositions {Er1.5Sc1.5}[Sc0.2Al1.8](Al3)O12 (SAG: Er 50 at%) and {Y1.57Er0.03Sc1.4}[Sc0.2Al1.8](Al3)O12 (YSAG: Er 1 at%), which can be considered as analogs of yttrium-aluminum garnet single crystals (YAG: Er 50 at% and YAG: Er 1 at%).

Effect of sintering temperature on the structural properties for CaBi4Ti4O15 compound

Polycrystalline CaBi4Ti4O15 (CBT) ceramics were successfully prepared by traditional ceramic technique. The X-ray diffraction spectrum of produced powder was studied at different temperatures (650 C, 850 C, and 1050C. The sintering temperature is very effective factor to obtained high crystallinity with very pure for CBT compound. The product structures analyzed using X-ray diffraction, it confirms, high purity polycrystalline phase formation revealed the existence of bismuth layered perovskite phase Aurivillius orthorhombic crystal structure at 1050ᶹ C. The produced samples' A field emission scanning electron microscope was used to analyze the morphologies (FESEM). It shows crystallites particles in the range about 149-349 nm for the product sintered at1050ᶹ C, it shows a dense microstructure with the presence of large orthorhombic distortion. The dielectric constant and dielectric loss were measured at room temperature as a function of frequency. The dielectric constant of CBT increases in sintering temperature. Moreover, the samples sintered at 1050 ᶹC exhibits good dielectric properties and lower value of tan .

Electrical and dielectric properties of polycrystalline VO2 discriminating between bulk and grain boundary conduction

Electrical and dielectric properties were measured on polycrystalline VO2 samples in the neighborhood of the metal → insulator transition (MIT) temperature of ∼340 K, prepared with the ceramic sintering technique. It is shown that in certain temperature ranges in the monoclinic semiconducting M1-phase below the MIT, bulk and grain boundary (GB) effects can be distinguished applying the method of impedance spectroscopy. An enormous literature has accumulated, dealing with electrical properties of VO2 small films and nanowires, with the aim to prepare various kinds of micro-devices for technology. Evidently, investigations to separate bulk from GB effects are largely missing, although many small films and nanowires are polycrystalline. The structure of their GBs doubtless differs from that in macroscopic samples, nevertheless valuable information might be supplied concerning electrical conduction across and along GBs, compared with conduction in the bulk. GB processes in our VO2 samples could be measured between room temperature and the MIT, bulk properties along with GB conduction could only be studied at low temperatures.

Actors, knowledge and path transformations in a declining cluster

We contribute to the literature on cluster dynamics to show that the outcome for declining industrial clusters are not necessarily restricted to death or renewal or replacement. We do so by considering upward and downward causation pressures in the evolution of the North Staffordshire’s ceramics cluster and the role of actors, their visions and the modification of their assets as influenced by both local knowledge sharing and exposure to ‘global buzz’ at international trade fairs. Efforts by cluster-level actors to reinvigorate the cluster appear to be having an effect, and we highlight the types of knowledge being infused into the cluster through these activities. We find the cluster is experiencing two different pathways simultaneously: the first is one of renewal, where traditional ceramicware firms have been supported by cluster-level actors to find new knowledge and make incremental innovations to support the aesthetic appeal of their product offerings and market reach; the second is a form of cluster exaptation where technical ceramics firms have moved onto a pathway with radical innovative potential associated with the properties of ceramics as advanced materials. We conclude with some policy suggestions for the revival of declining clusters.

Forging a New World Order? Interdisciplinary Perspectives on the Management of Metalworking and Ideological Change in the Late Bronze Age Carpathian Basin

The Carpathian Basin was a highly influential centre of metalworking in the 2nd mil. BC. Nevertheless, despite the abundance of metal objects from the Late Bronze Age, the scarcity of contextually associated metalworking remains representing distinct phases of the metalworking cycle from this region is striking. Here, we explore Late Bronze Age metalworking through the lens of a uniquely complete metalworking assemblage from the site of Șagu from contexts spanning the sixteenth to early thirteenth century BC. This material provides insights into changes in craft organisation following socio-political change after the collapse of Middle Bronze Age tell-centred communities. Our approach combines analytical and experimental data together with contextual analysis of technical ceramics (crucible, mould, and furnace fragments) to reconstruct the metalworking chaîne opératoire and place Șagu in its broader cultural context. Analyses demonstrate clear technological choices in ceramic paste recipes and strong interlinkages between metallurgy and other crafts practised on site, from domestic pottery production to building structures. Experimental replications reveal important intrinsic and experiential aspects of metallurgical activities at Șagu. Evidence on the spatial organisation of metallurgical workflows (routine sequence of actions and decisions) suggests they incorporated a high degree of visibility, which marks a distinct change in the use of craft space compared to the context of densely occupied Middle Bronze Age tells nearby. Combined, our archaeometric, experimental, and contextual results illustrate how changes in metalworking activities in the Late Bronze Age Carpathian Basin were deeply embedded in an ideological shift in the aftermath of the breakdown of Middle Bronze Age tells and the emergence of new social structures.

3D-printing of polymer‐derived SiCN ceramic matrix composites by digital light processing

In this study, we present a DLP 3D-printing strategy for the fabrication of SiCN ceramic matrix composites (CMCs). The polysilazane-based preceramic polymer containing inert fillers was UV-cured into a green body and then converted to SiCN CMCs after pyrolysis. The introduced fillers (Si3N4 particles and Si3N4 whiskers) as reinforcements are well dispersed in the matrix, which can not only effectively reduce the linear shrinkage and weight loss, but also greatly improve the mechanical properties of the SiCN CMCs. The bending strength of the SiCN CMCs reinforced with 10 wt% Si3N4 whiskers (without surface polished) reached 180.7 ± 15.6 MPa. Furthermore, the effect of fillers content on microstructure and porosity of the SiCN CMCs are discussed, and it was found that the excessive fillers led to increased pore defects and decreased continuity of the matrix, thereby reducing the mechanical properties of the SiCN CMCs. This strategy provides a promising ceramic manufacturing technique to fabricate polymer‐derived CMCs with complex-shaped and high-performance for potential demanding applications.

Printing Technical Ceramics in Industrial Sizes

Printing Technical Ceramics in Industrial Sizes