The role of ceramic and glass science research in meeting societal challenges: Report from an NSF‐sponsored workshop

Under the sponsorship of the U.S. National Science Foundation, a workshop on emerging research opportunities in ceramic and glass science was held in September 2016. Reported here are proceedings of the workshop. The report details eight challenges identified through workshop discussions: Ceramic processing: Programmable design and assembly; The defect genome: Understanding, characterizing, and predicting defects across time and length scales; Functionalizing defects for unprecedented properties; Ceramic flatlands: Defining structure‐property relations in free‐standing, supported, and confined two‐dimensional ceramics; Ceramics in the extreme: Discovery and design strategies; Ceramics in the extreme: Behavior of multimaterial systems; Understanding and exploiting glasses and melts under extreme conditions; and Rational design of functional glasses guided by predictive modeling. It is anticipated that these challenges, once met, will promote basic understanding and ultimately enable advancements within multiple sectors, including energy, environment, manufacturing, security, and health care.     

复合陶瓷的应用发展是未来新材料市场的主题

陶瓷基复合材料不是传统意义上的陶瓷,它是以陶瓷为基体与各种纤维复合的一类复合材料。其主要基体有玻璃陶瓷、氧化铝、氮化硅等,具有高温强度好、高耐磨性、高耐腐蚀性、低膨胀系数、隔热性好及低密度等特性,而且资源也比较丰富,有广泛的应用前景。针对陶瓷基复合材料成为争夺国际市场的制高点,分析了陶瓷基复合材料的研发受到重视,阐述了复合陶瓷材料的特点,介绍了陶瓷基复合材料的应用领域,同时指出了节能环保的车用陶瓷基结构复合材料大有作为。     

Phase-separation engineering in fluorozirconate glass for designing and fabricating of transparent perfluorinate glass ceramic

Perfluorinate glass ceramics with ultra-low phonon energy are very important optical and photonic materials. Unfortunately, there is no suitable method to obtain transparent perfluorinate glass ceramics due to poor thermal stability of fluoride glass. As a result, wide applications of glass ceramics in advanced infrared systems are restricted. Here, an effective method based on phase-separation engineering is used to develop transparent perfluorinate glass ceramics. In this article, a novel transparent Er³⁺-doped ZnZrF₆-Ba₆Zn₇F₂₆ perfluorinate glass ceramic was designed and fabricated by phase-separation engineering. The sample exhibits low phonon energy (564 cm⁻¹), ultra-wide transmission range (0.33–8.2 μm, T ≥ 50 %), and strong infrared emission, which is better than that of ZBLAN glass, oxide-, and oxyfluoride-glass ceramics. These good properties of the perfluorinate glass ceramic demonstrate that phase-separation engineering not only offers an effective approach to obtain perfluorinate glass ceramics but also provides wide-ranging opportunities for advanced infrared optical and photonic materials.     

复合陶瓷的应用发展是未来新材料市场的主题

陶瓷基复合材料不是传统意义上的陶瓷,它是以陶瓷为基体与各种纤维复合的一类复合材料。其主要基体有玻璃陶瓷、氧化铝、氮化硅等,具有高温强度好、高耐磨性、高耐腐蚀性、低膨胀系数、隔热性好及低密度等特性,而且资源也比较丰富,有广泛的应用前景。针对陶瓷基复合材料成为争夺国际市场的制高点,分析了陶瓷基复合材料的研发受到重视,阐述了复合陶瓷材料的特点,介绍了陶瓷基复合材料的应用领域,同时指出了节能环保的车用陶瓷基结构复合材料大有作为。     

Development of ceramic fiber reinforced glass ceramic sealants for microtubular solid oxide fuel cells

Ceramic fibers in various forms with different fiber sizes are tested to improve the sealing performance of glass ceramic seals for microtubular solid oxide fuel cell applications. In this regard, several sealing pastes are prepared by mixing each ceramic fibers type with glass ceramics at 1.25 wt %. Five layered microtubular anode supported cells are also fabricated by extrusion and dip coating methods to evaluate the sealing performance of the composite sealants. The pastes are applied between the cells and gas manifolds made of Crofer22 APU. The electrochemical and sealing performances at an operating temperature of 800 °C under hydrogen are investigated after the glass forming process. Microstructures of the sealants are also examined by a scanning electron microscope. Experimental investigations reveal that the cells sealed by the pastes with ceramic bulk fiber and ceramic fiber rope gasket show acceptable open circuit potentials close to the theoretical one. These cells can be also pressurized up to around 150 kPa back pressure in the sealing performance tests. On the other hand, the pastes without any filler, with ceramic rope and with ceramic blanket exhibit poor sealing performance due to gas leakage originated from flowing of the main glass ceramic matrix from the joints. Therefore, ceramic bulk fiber and ceramic fiber rope gasket are found to behave as a stopper and can be used to prevent glass ceramics from flowing for microtubular solid oxide fuel cells or similar applications.     

Structural ceramic and fibrous materials based on quartz glass

Ceramic and fibrous materials based on quartz glass with controlled porosity (0 to 90%) and technologies for fabrication of complex-shaped components developed at the Tekhnologiya Research and Production Enterprise are described. Properties of structural ceramic and heat-protecting fibrous radio transparent materials for use in aerospace and aircraft technologies are reported. Techniques for improving the strength of thin-walled ceramic shells operating under heavy-duty conditions are described.Translated from Novye Ogneupory, No. 10, pp. 13 – 18, October, 2004.     

EAFD-loaded vitreous and glass–ceramic materials

SiO₂, Na₂O and CaO were mixed and co-melted with electric arc furnace dust waste. The resulting vitreous materials, produced by quenching at ambient atmosphere, were transformed into glass–ceramics by two-stage heat treatment, under thermal conditions that were determined by differential thermal analysis. X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry and transmission electron microscopy were employed to investigate the physical properties of all products. It was found that whilst wollastonite (CaSiO₃) separates from the parent matrix as the dominant crystalline phase in all glass–ceramic products, the crystallization mode depends on the batch composition. Leaching tests evidenced that vitreous products were chemically durable. Devitrification did not significantly affect leach resistance so glass–ceramic materials retain the leach resistance that was achieved by vitrification.     

Highly transparent and color-adjustable Eu2+ doped SrO-SiO2-Al2O3 multilayered glass ceramic prepared by controlling crystallization from glass

Multilayered inorganic transparent materials have been widely used as laser materials, scintillators and phosphors due to their excellent combined properties or functions. However, owing to the limitation of the current preparation technology, only the ceramics with cubic crystal structure could be fabricated into multilayered transparent materials, which has greatly obstructed the diversity of multilayered transparent materials. Here we report a novel non-cubic multilayered transparent phosphor with a ceramic/glass/ceramic sandwich-like structure prepared by controlling crystallization from Eu₂O₃-SrO-Al₂O₃-SiO₂ bulk glass. The ceramic thicknesses, total transmittances, emission colors and the fluorescence quantum yields of the samples can be adjusted continuously within a certain range. The multilayered transparent phosphor could be used as a potential candidate for the white LEDs with high color rendering index. It can be anticipated that the controlled crystallization from bulk glass method is a simple, fast, cost-effective and promising synthesis approach to prepare non-cubic transparent materials with ceramic/glass/ceramic structures.     

Shear strength tests of glass ceramic sealant for solid oxide fuel cells applications

Different approaches are used for the integration of ceramic components in solid oxide fuel cells stacks, where dissimilar materials (ceramics and metals) have to be joined and coupled for a reliable long term operation. This work focuses on the mechanical characterisation of a glass ceramic sealant used for the joining of Crofer22APU metallic interconnect samples as well as the interaction with a preoxidised Crofer22APU. Crofer22APU–glass ceramic sealant joined samples are tested by two different mechanical tests. Hourglass samples with different geometries were tested using an in-house developed torsion test machine at room temperature. In addition, their mechanical strength was also evaluated according to the ISO?13124 standard. The comparison of the two different testing methods, with particular focus on the shear strength of the joined samples, are reviewed and discussed.     

Additive manufacturing of ceramic materials for energy applications: Road map and opportunities

Among engineering materials, ceramics are indispensable in energy applications such as batteries, capacitors, solar cells, smart glass, fuel cells and electrolyzers, nuclear power plants, thermoelectrics, thermoionics, carbon capture and storage, control of harmful emission from combustion engines, piezoelectrics, turbines and heat exchangers, among others. Advances in additive manufacturing (AM) offer new opportunities to fabricate these devices in geometries unachievable previously and may provide higher efficiencies and performance, all at lower costs. This article reviews the state of the art in ceramic materials for various energy applications. The focus of the review is on material selections, processing, and opportunities for AM technologies in energy related ceramic materials manufacturing. The aim of the article is to provide a roadmap for stakeholders such as industry, academia and funding agencies on research and development in additive manufacturing of ceramic materials toward more efficient, cost-effective, and reliable energy systems.     

Porcelain—Raw Materials, Processing, Phase Evolution, and Mechanical Behavior

Porcelain represents the foundation of the ceramics discipline and one of the most complex ceramic materials. Composed primarily of clay, feldspar, and quartz, porcelains are heat-treated to form a mixture of glass and crystalline phases. This review focuses on raw materials, processing, heat treatment, and mechanical behavior. Because of the complexities of the porcelain system and despite the substantial amount of research already conducted within the field, there remain significant opportunities for research and study, particularly in the areas of raw material understanding, processing science, and phase and microstructure evolution.     

Hertzian crack propagation in graded glass/ceramic composites

In literature, the concept of material gradation is shown to inhibit surface crack initiation in glass/ceramic composites subjected to Hertzian indentation. However, surface cracks could yet initiate due to relatively higher loadings or in the presence of surface flaws/defects. Hence, characterization of graded composites concerning the resistance against Hertzian crack initiation and propagation manifests itself as a prominent matter. In this study, axisymmetric Hertzian cracks evolving in graded glass/ceramic composites propelled by a rigid cylindrical punch are investigated employing a novel recursive method, called the stacked-node propagation procedure. Crack trajectories and their propagation susceptibilities are predicted via the minimum strain energy density (MSED) criterion regarding the crack growth resistance (R-curve) of ceramics. The stress trajectory approach is also considered for a homogeneous glass to reveal the reliance and effectiveness of the MSED criterion in the present crack problems. The Mori–Tanaka relations are adopted to model the elastic modulus and Poisson's ratio variations through the composites, which are implemented on the simulations via the homogeneous finite element approach. Hertzian crack problem of a practically producible graded composite comprised of oxynitride glass and a fine-grained silicon nitride ceramics (Si₃N₄) is treated as a case study. The degree of material gradation is assessed for the mitigation of surface crack initiation and propagation risks.     

Sol–gel based fabrication and characterization of new bioactive glass–ceramic composites for dental applications

The fabrication of a new composite glass–ceramic with potential application in dental restoration was investigated. The developed material aims to modify the surface of dental ceramics creating bioactive surfaces able to improve material–cell interaction enhancing the bonding of the marginal gap between restoration and tooth. The application of the sol–gel method led to a microporous homogeneous glass–ceramic which can be applied as coating on commercial dental ceramic substrates. The microstructural, thermal, mechanical and biological properties of the fabricated coatings were studied and compared to the respective results of a previously investigated glass–ceramic composite. The material–cell interaction on these two sol–gel dental composites was studied in detail. The attachment and proliferation of both periodontal ligament and gingival fibroblast cells confirmed the bioactive behavior of the new materials and their ability to be potentially applied in dental restorations for soft tissue regeneration and sealing of the marginal gap.     

Matching correlation study of titanium-based ceramics with glass based on dissolution characteristics

Glass-ceramics are ideal candidates in Low-temperature Cofired Ceramic (LTCC) technology. The “dissolution-precipitation” mechanism ensures the sintering compactness of glass-ceramics at low temperatures. The ceramics must be dissolved and precipitated in the liquid phase with the assistance of glass additives. In this case, the characterization of dissolution behaviors that should be highly valued has rarely been emphasized. This study puts forward a simple, repeatable, and efficient design for characterizing the dissolution behaviors of several titanium-based ceramics in glass frits under variable temperature conditions. Interestingly, a glass frit with good wettability does not ensure the low-temperature sintering process of a ceramic matrix. In contrast, the dissolution characteristics of ceramics in the glass should be seriously considered. Hopefully, the study of dissolution behaviors could strengthen the fundamental understanding of the low-temperature sintering of ceramics and offer a glass-ceramic design strategy for developing high-performance.     

PVD hard coatings on ceramic tiles for aesthetic applications: surface characterisation and corrosion properties

The development of innovative ceramic tiles looks for materials with improved mechanical and tribological properties as well as a higher corrosion resistance (high relative humidity, daily watering, household chemical cleaners). In addition, a greater durability leads to lower environmental impact. Along with their improved functionality and recyclability, ceramic tiles should also provide aesthetic properties. Ceramic tiles can be treated to modify the physico-chemical properties of the surface by metal coatings or metallic compounds, also providing an attractive metallic sheen appearance. In the present paper, titanium nitride (TiN) and zirconium nitride (ZrN) coatings were deposited on glazed porcelain stoneware by an industrial PVD multicathode arc deposition system under a reactive nitrogen atmosphere. After the process, the tiles showed a gold-like colour, a smooth surface and a coating thickness between 0.7 and 1.6 μm. The coating composition, scratch resistance and corrosion behaviour have been evaluated. It can be concluded that both coatings are suitable for use in domestic environments due to their stability and resistance to aggressive conditions. Few references have been found regarding these coatings on ceramic tiles for domestic and industrial applications, but it has been proved that they bring added value to traditional ceramics, giving new functional properties of ceramics both decorative and highly corrosion and mechanical resistance.     

Utilization of by-products from western coal combustion in the manufacture of mineral wool and other ceramic materials

The ash by-products from combustion or gasification of western U.S. coals have chemical and mineralogical characteristics that lend themselves to utilization in ceramic materials. Laboratory and pilot-scale fabrication of four such materials has been studied. Cyclone slag from four lignite-fired power plants and a dry scrubber ash have been fabricated into mineral wool insulation in a pilot-scale cupola. Extruded and fired mixtures of fly ash, clay and ground glass have produced ceramics with extraordinary high flexural strength. Ceramic glazed wall tile that utilize fly ash in place of clay have been prepared and shown to meet most specifications for fired clay tile. Both fired and unfired dry-pressed brick containing 100% western fly ash have met ASTM specifications for fired clay brick.     

Cutting characteristics of dental glass ceramics during in vitro dental abrasive adjusting using a high-speed electric handpiece

Machinability is an important characteristic of dental ceramics for restorative dentistry because machining is not only commonly employed in dental CAD/CAM systems but also essential in dental adjustments for occlusal fitting and restorative quality. This paper reports on an in vitro study on machinability of dental ceramics by quantifying cutting characteristics of feldspar and leucite glass ceramics in simulated dental adjusting using a high-speed electric handpiece and diamond burs. Cutting forces, force ratio, energy, surface integrity and bur topography were evaluated as functions of clinically relevant cutting conditions. The results indicate that tangential and normal forces and specific cutting energy for both materials exhibited significant dependences (p<0.01) on both the bur depth of cut and the bur feed rate. Surface roughness showed a weak influence by the choice of the material (0.05>p>0.01) but no correlations with the cutting conditions applied (p>0.05). At the slower feed rates or smaller depths of cut the cutting behaviors for the two materials were very similar in terms of cutting forces and specific cutting energy. At the deeper depths of cut or faster feed rates, normal forces for leucite glass ceramic were significantly higher than those for feldspar glass ceramic (p<0.01). However, leucite glass ceramic produced better cutting surfaces with less fracture areas compared with feldspar ceramic due to its lower index of brittleness and higher force threshold for brittle–ductile transition. This research provides a methodological qualification in evaluating cutting characteristics of dental ceramics and quality control in clinical dentistry.     

Influence of reduced graphene oxide (rGO) on phase development and porosity of SiOC/rGO ceramic composites

Ceramic materials based on silicon oxycarbide (SiOC) and reduced graphene oxide (rGO) were produced by polymer pyrolysis and evaluated in terms of phase development and porosity. Carbonaceous phase, initially prepared from graphite oxide, was incorporated into silicone dihydroxy terminated in different amounts (0, 5, 15 and 25 wt%) and submitted to pyrolysis at 1500 °C to obtain SiOC/rGO ceramics. Higher ceramic yields and more thermally stable materials were obtained after rGO addition, whose results were associated to the chemical interaction degree between rGO and polymer structure. C_graphite and SiC phases were generated in rGO-containing ceramics and a mixture of α- and β-SiC was achieved from 15 wt% rGO, enhancing their crystallinity with increasing of rGO content. Porosity features were influenced by the carbonaceous phase amount and different rGO-polymer interaction degrees. SiOC/rGO ceramics demonstrated desirable structural characteristics for future investigations in electrical and/or electrochemical applications.     

Novel design of YIG/MTC heterogeneous joint bonded by glass ceramic after amorphous glass cladding

A new method of pre-cladding amorphous glass and glass-ceramic brazing was invented to obtain a high-reliability bonding of yttrium iron garnet ferrite (YIG) and magnesium titanate ceramic (MTC) at a relatively low temperature of 725^oC. The amorphous glass cladding could alleviate the stress generated by thermal expansion difference between the glass ceramic and base materials. The microstructure shows that micron-scale and nanoscale CoFe₂O₄ phases were dispersed in the glass seam. The joint shear strength reached 117 ± 6.6 MPa due to the enhancement of CoFe₂O₄ phases, which was twice as that of the joint directly brazed by amorphous bismuth glass. Correspondingly, the joint weak area was transferred from the glass matrix to the vicinity of the interface and the base material, providing a direct evidence that the glass seam was strengthened by the glass ceramic. It is significant for improving high reliability of the microwave devices for long-term service.     

An environmentally friendly process for preparing commercial ceramic foam composites based on frit/glass wastes

Considering the size of the amount of energy consumption in ovens during the production of gas ceramic foam materials in the ceramic industry, it can be stated that natural gas is one of the highest energy resources. Natural gas consumption during the production has been evaluated and financial analyses were made for saving consumption amounts. Raw materials and glass/frit wastes obtained from different regions were investigated and their chemical compositions were determined by X-Rays fluorescence spectrometry (XRF) analysis. Compared to their current alternatives, glass foams with homogenous structure and low density were developed by adding frit/glass wastes in the amount of 80%-90%. X-Ray diffraction (XRD) analysis has been conducted for mineralogical investigation of the samples. Also, to analyze the pore sizes and examine the surface morphology of foams, SEM images were obtained. With the addition of glass/frit wastes, natural gas consumption decreased (ca. 20%-25%) in firing process.