Use Of Ceramic Materials Research Articles

Push-to-pull tensile testing of ultra-strong nanoscale ceramic–polymer composites made by additive manufacturing

The search for light yet strong materials recently benefited from novel high resolution 3D-printing technologies, which allow for fabricating lightweight porous materials with optimally designed micro-topologies. Architectural design improves mechanical properties significantly compared to stochastic porosity, as in foams. Miniaturization of the architectures offers to exploit material strengthening size-effects occurring at the nanoscale. However, these effects and their interaction with structural behavior are not yet well understood. We present tensile experiments of nanoscale alumina–polymer composite bars and cellular microarchitectures, applying 3D-printed push-to-pull mechanisms. The strength of alumina is found to strongly increase as the material thickness decreases. Below 50 nm thickness a plateau at about 5.5 GPa is reached, which is in the range of the theoretical strength. The characteristic low tensile strength of ceramics and its high variability seem not to hold at the nanoscale. Thus, when designed and fabricated appropriately, microarchitectures will facilitate carrying these size-effects beyond scales in future, allowing the use of ceramic materials far beyond what is possible to date.

The Features of Wollastonite in Balikesir and its Use in Ceramic Materials as an Alternative Raw Material

In this work, the influences of wollastonite in Balikesir (Turkey) on ceramic sanitaryware properties were investigated. Samples of wollastonite were collected from the Serceoren deposit in Balikesir. Their characterizations were carried out with the determination of petrographic, physical, mechanical and chemical composition, and by TG-DTA, XRD and SEM. In a second part of the work, tests in sanitaryware compositions were conducted in order to evaluate the suitability of the addition of wollastonite instead of albite in the sanitaryware compositions used in the production of ceramic sanitaryware. The rheological, physical and firing tests of developed sanitaryware bodies were done with the Creavit® new body development test procedure and, results were compared with each other. After evaluating test results it was seen that wollastonite can be used in ceramic sanitary ware bodies as an alternative raw material.

Use of ceramic materials in the restoration of posterior teeth.

Use of ceramic materials in the restoration of posterior teeth.

Near‐Net‐Shaped Porous Ceramics for Potential Sound Absorption Applications at High Temperatures

We present an interesting processing route for obtaining alumina/mullite‐based ceramics with controlled porosity and airflow resistance leading to promising microstructures for application as sound absorbers. The use of ceramic materials aims for potential applications where high temperatures or corrosive atmospheres are predominant, e.g., in combustion chambers of gas turbines. For the production of the porous ceramics we combined freeze gelation and sacrificial templating processes to produce near‐net‐shaped parts with low shrinkage (<3%) based on environmental‐friendly and low cost conditions. The obtained microstructure presents a bimodal pore size distribution, with small pores derived from the freeze gelation process (~30 μm) connecting large pores (2–5 mm diameter) originated from the expanded polystyrene template particles. These connections, called “windows” in this study, show a significant impact on the sound absorption properties, allowing the pressure diffusion effect to take place, resulting in a significant improvement of the sound absorption coefficient. By varying the template particle content and the slurry solid content, it is possible to control the sound absorption behavior at different frequencies of the open‐celled ceramics. These ceramics feature a high open porosity, from 77% to 82%, combined with sufficient compressive strength ranging from 0.27 to 0.68 MPa and sound absorption coefficients of 0.30–0.99, representing a highly promising combination of properties for noise control and reduction at corrosive environments and high temperatures.

ELECTRICAL RESISTIVITY MEASUREMENTS: A REVIEW

World-wide interest on the use of ceramic materials for aerospace and other advanced engineering applications, has led to the need for inspection techniques capable of detecting unusually electrical and thermal anomalies in these compounds. Modern ceramic materials offer many attractive physical, electrical and mechanical properties for a wide and rapidly growing range of industrial applications; moreover specific use may be made of their electrical resistance, chemical resistance, and thermal barrier properties. In this review, we report the development and various techniques for the resistivity measurement of solid kind of samples.

The Dragon Project origins, achievements and legacies

The lineage of the Dragon Project can be traced back to 1955 when the United Kingdom launched a nuclear power programme which involved the construction of large graphite moderated reactors fuelled with natural uranium and cooled by carbon dioxide. Not long afterwards the European Nuclear Energy Agency (ENEA) of the then newly formed Organisation for European Economic Cooperation (OEEC), in the spirit of the time, sought to encourage the construction of nuclear power stations and the development of joint nuclear undertakings. The United Kingdom Atomic Energy Research Establishment (AERE) had, since 1949, been studying possible long term improvements in energy conversion efficiency resulting from higher coolant gas temperatures and the use of ceramic materials. A 1955 paper on gas-cooled reactors using the U-233/thorium cycle attracted interest and this progressed to the definition of an initial programme. The high temperature work led to a proposal for a 20MW(Th) Reactor Experiment and one important consequence of the ENEA/OEEC initiative was the setting up in April 1959 of the international Dragon Project Agreement.Initial experiments at Harwell in 1957 had involved the coating of small spheroidal particles of uranium carbide or oxide with pyrolytic carbon which were then bonded with carbonaceous material. But experiments demonstrated that fission products such as caesium, strontium or barium could diffuse through such coatings. This led in 1961 to the modification of the coated particle design by the addition of an intermediate layer of silicon or zirconium carbide. The small size of the particles necessitated a statistical approach to quality during manufacture and effort was concentrated on the minimisation of the broken or defective particle fraction.The subsequent operation of the Dragon Reactor for over 10 years confirmed the benign nature of a HTR. It also proved that fuel bodies made with coated particles were capable of maintaining a high degree of fission product containment at high temperatures and for high burn-ups. What is remarkable is the speed with which the particle design evolved. The success of the choices that were made resulted in the High Temperature Gas Cooled Reactor system being studied in its various forms by many countries.Irrespective of the particular core design, the basic component of HTR fuel is the coated particle. In the intervening years since the early HTRs were launched it has been realised worldwide that there are now even more factors favouring the use of high temperature reactors. They enable more efficient use of fissile isotopes as well as providing inherent reactor safety. Unlike most other reactor designs, the HTR can take economic advantage from operation at high gas outlet temperatures, whilst maintaining the good retention of fuel and fission products within the fuel elements. The fuel cycle can use uranium, thorium or plutonium. In addition the burn-up can be high, permitting safe disposal of spent fuel without the need for reprocessing. Fast reactors based on coated particle fuel may be a future possibility.The Dragon Project was a successful political collaboration and a technical triumph in demonstrating a new type of reactor. However, overstretched resources coupled with a world-wide trend in that era to favour water reactors caused work on Dragon to be terminated in March 1976. By then the main objectives for the Dragon Project had been successfully achieved and extensively reported. The progression from the 20MWE(Th) Dragon to a 1200MW(e) power station as a single jump in technology was too large a step for the time. The experiences of the other major civil HTR projects of the same period in Germany and the United States of America resulted in the high temperature reactor system being studied in its various forms by many countries as is evidenced by the large number of papers presented at the biennial HTR conferences. In the intervening years since the early HTRs were launched it has been realised that there are now even more factors favouring the use of high temperature reactors.

Environmental effects of using clay bricks produced with sewage sludge: Leachability and toxicity studies

Use of sewage sludge from wastewater treatment plants as a raw material for making clay bricks has been analyzed to be an option to dumping sludges into landfills. This alternative has been shown feasible and interesting due to the high rate of use of ceramic materials in the building sector. However, it meets with some environmental issues and some prejudices on the part of users.This work shows some leachability and toxicity tests (outgassing and offgassing) which demonstrate the environmental compatibility of these ceramic products to be used as building materials and even in deconstruction of the building once its useful life is ended.

Vanadium‐Tin Oxide Nanoparticles with Gas‐Sensing and Catalytic Activity

Nanopowders of vanadium‐tin oxides were prepared by a co‐precipitation process and characterized for their bulk structures, chemical state, sensing capability, and surface reactivity. The solid solutions (cassiterite) were evaluated as sensing elements in a carbon monoxide gas sensor and as catalysts for methanol oxidation in a fixed‐bed reactor. Sensing and catalytic properties were observed dependent upon doping concentration and oxidation state of vanadia species. The sensor response was favored for lower vanadium loadings (V/Sn = 0.05−0.1), related to the reduced vanadium sites. The catalytic activity for methanol conversion was favored for higher vanadium loadings (V/Sn = 0.15−0.2), related to the oxidized vanadium sites. Results demonstrate that the V–O–Sn structure provides redox activity to facilitate oxygen activation for CO gas‐sensing response and promote methanol partial oxidation to formaldehyde. Mechanistic aspects that elucidate the redox pathways are discussed. These oxide nanostructures are promising ceramic materials for use in sensing and catalysis fields involving electron transfer.

Zirconia implant abutments: A review

An increasing aesthetic demand within developed populations conducted to the fabrication of metal-free restorations and to a wide use of ceramic materials, due to its excellent characteristics of biocompatibility and aesthetics. With the incessant increase of commercial labels involved in this technological advance, a review is imposed on ceramic abutments, specifically on zirconia. We made a search of articles of peer-reviewed Journals in PubMed/Medline, crossing the terms "Dental Abutments", "Dental Porcelain" and "Zirconia". The review was divided by subtopics: zirconia physical and mechanical properties, precision fit in the implant-abutment interface, zirconia abutments strength and, finally, bacterial adherence and tissues response. Several studies demonstrate that zirconia abutments offer good results at all the levels but relevant issues need further studies and evaluation. One of the most important is the clinical long term success of zirconia abutments on implants, given that in the literature there are no sufficient in vivo studies that prove it.

An Original Method for the Evaluation of in Vivo Controlled Release of the Ceramic Materials

In recent years, the use of ceramic materials in orthopaedics and dentistry is becoming increasingly popular. However, it is important to know their biological and mechanical properties to optimize their use. The aim of this study is to describe a specific method to assess in vivo the effects of chronic release of ceramic materials implanted, in relation also to the type of material, pellets or powders. This was achieved by implanting ceramic powders and pellets, formed by low cohesion grains, in the patellar tendon of 48 New Zealand adult rabbits (24 with powders and 24 with pellets). The motion of the joint allowed easily and progressively the release of grains, detached from surface of the pellets and released to the joint space. Animals were sacrificed at different intervals (1, 3, 6, 12 months). Retrieved knee joints underwent X-Ray, histological and ultrastructural analysis.

Ceramics and ceramic matrix composites for heat exchangers in advanced thermal systems—A review

Abstract In air-conditioning and energy-recovery applications, heat exchangers are very important to the overall efficiency, cost, and size of the system. Current heat exchanger designs rely heavily on fin-and-tube or plate heat exchanger designs, often constructed using copper and aluminum. Recent developments in material science—in particular, advances in ceramics and ceramic matrix composites—open opportunities for new heat exchanger designs. Some research directed toward using these materials for heat exchangers in other applications has been reported; however, there has not been a comprehensive study of the use of these emerging materials in both conventional HVAC&R systems and emerging energy technologies. This review reports the current state-of-the-art of ceramic materials for use in a variety of heat transfer systems.

A Computational Approach to Design High Reliability Ceramic Laminates

A numerical design approach for ceramic multilayer laminates with predetermined stress profiles is here pro- posed and compared with a well established theoretical method. The design procedure allows for the optimization of layer composition, in order to obtain high reliability and at the same time control composition and stress state of each layer. The proposed approach is used to design alumina-mullite-zirconia laminates with high toughness, meeting at the same time the particular functional requirements of a pure alumina surface layer with residual compressive stresses with the aim to increase tribological properties. The main limitation to the use of ceramic materials in structural applications is owed to their low reliability, i.e. their high scatter in failure strength and low fracture tough- ness. This behavior is directly related to the presence of flaws originated during the production processes and the service. Although improvements in material quality, manu- facturing methods and component design have resulted in a drastic reduction of structure failures, the low fracture toughness of ceramics, coupled with their susceptibility to failure by slow crack growth under stresses well below their fracture strength, remains a concern for the reliability of ce- ramic bearings in many engineering applications (1). Many efforts have been made with the purpose to in- crease the reliability of ceramic materials: a promising ap- proach is the design and manufacturing of multilayered structures with a tailored residual stress field. Layers of ce- ramic composites with different composition are stacked, obtaining a graded ceramic, with the purpose to develop a specific residual stress profile as a result of the sintering process. The thermal stresses are due to the mismatch of the mean coefficient of thermal expansion between the layers and between the different grains in the same layer (2, 3). It was shown that in ceramic multilayer laminates with alumina surface layer, a compressive residual stress at the surface has beneficial effects on the wear and friction behav- ior, as a consequence of the reduction of crack nucleation and propagation and the formation of thinner and smoother tribolayers (4). Similarly, a compressive layer placed at a certain depth can significantly increase the toughness of the material (5).

Bioceramics: Past, present and for the future

There have been a number of major advances made in the field of bioactive ceramics, glasses and glass ceramics during the past 30–40 years. From initial work on the development of materials that are tolerated in the physiological environment, emphasis has now shifted towards the use of ceramic materials that interact with bone tissue by forming a direct bond. It is now possible to choose, by compositional control, whether these materials are biologically stable once incorporated within the skeletal structure or whether they are resorbed over time. This paper reviews the ground-breaking work that was performed during the 1970s and 1980s in the field of bioceramics in the production and characterisation of bioactive and bioresorbable glasses, glass ceramics and calcium phosphates. The review then explores the influence of the original concepts and ideas on the more recent development of ceramic scaffolds, composites and coatings with enhanced bioactivity for bone tissue engineering.

Inorganic Materials for Bone Repair or Replacement Applications

In recent years, excipient systems have been used increasingly in biomedicine in reconstructive and replacement surgery, as bone cements, drug-delivery vehicles and contrast agents. Particularly, interest has been growing in the development and application of controlled pore inorganic ceramic materials for use in bone-replacement and bone-repair roles and, in this context, attention has been focused on calcium-phosphate, bioactive glasses and SiO2- and TiO2-based materials. It has been shown that inorganic materials that most closely mimic bone structure and surface chemistry most closely function best in bone replacement/repair and, in particular, if a substance possesses a macroporous structure (pores and interconnections >100 microm diameter), then cell infiltration, bone growth and vascularization can all be promoted. The surface roughness and micro/mesoporosity of a material have also been observed to significantly influence its ability to promote apatite nucleation and cell attachment significantly. Pores (where present) can also be packed with pharmaceuticals and biomolecules (e.g., bone morphogenetic proteins [BMPs], which can stimulate bone formation). Finally, the most bio-efficient - in terms of collagen formation and apatite nucleation - materials are those that are able to provide soluble mineralizing species (Si, Ca, PO(4)) at their implant sites and/or are doped or have been surface-activated with specific functional groups. This article presents the context and latest advances in the field of bone-repair materials, especially with respect to the development of bioactive glasses and micro/mesoporous and macroporous inorganic scaffolds. It deals with the possible methods of preparing porous pure/doped or functionalized silicas or their composites, the studies that have been undertaken to evaluate their abilities to act as bone repair scaffolds and also presents future directions for work in that context.

Near-application testing of ceramics under proportional and non-proportional loading*

Abstract The use of ceramic materials in machine parts with multiaxial and non-proportional stresses requires near-application testing to gather parameters for proper strength and lifetime prediction and to reduce the costly testing of prototypes. Therefore, experimental procedures have been developed for testing ceramic specimens with natural flaws under proportional and non-proportional stresses. Testing rings of different diameter ratios under internal pressure allows the estimation of short-term strength, crack growth parameters and of multiaxial failure criteria even with surfaces in “as-fired”-conditions. Assessment numbers, which quantify the influence of failure criteria on test results, are used to compare different experimental setups regarding their ability to reveal failure criteria. An additional setup allows testing with non-proportional stresses and different load sequences. A cylindrical specimen with a necked-down portion is loaded by alternating torque and compressive force to achieve variable mixed-mode-loading on natural cracks in the necking. Test series with alumina and zirconia are in progress and preliminary results are presented.

Status quo of ceramic material for metal halide discharge lamps

Polycrystalline alumina is an excellent ceramic material for use as the envelope for metal halide discharge lamps. Although this material was introduced in the mid-1960s, and is thus already known for several decades, recent years have seen considerable effort aimed at further development of these ceramic envelope materials.Developments are not only in the field of ceramic shaping technologies, but are also concentrated on the material properties of the ceramic material itself. Optical, mechanical as well as the chemical properties of the ceramic envelope are strongly controlled by the shape as well as the microstructure of the ceramics used.

Ceramic components for high pressure gasoline fuel injection pumps

AbstractIn the present project the use of ceramic materials in piston‐cylinder‐systems of high pressure pumps for gasoline direct injection is investigated. The aim is to generate injection pressures of 300 bar with low friction and wear despite of gasoline's poor lubricity and low viscosity. The high resistance of ceramic materials against wear is used to realise these aims.

The beneficiation of Bitlis Massif kyanite ore for use in ceramic materials

A beneficiation procedure for possible refractory uses of Bitlis Massif (Turkey) kyanite ore has been developed and involves grinding to d80 = 0˙106 mm, de-sliming, mica flotation, iron oxide flotation and kyanite flotation. A concentrate containing 56˙5% Al2 O3, 39˙01% SiO2, 0˙8% Fe2 O3, 0˙18% TiO2, 0˙09% Na2 O, 0˙1% K2 O and 0˙02% MgO was obtained at a mass recovery of 51˙14% ± 0˙25%. This conforms to both the chemical and size specifications for ceramic uses required to meet American and Chinese standards.

Ceramic gap‐fills for ceramic restoration

Abstract The use of substitute materials to fill missing areas in ceramic objects is well established in ceramic conservation and restoration. Substitute materials such as plaster of Paris and acrylic‐based fillers are generally used to fill voids in soft and porous ceramic objects, and epoxy and polyester resins in the case of dense, vitreous ceramics such as porcelain (Buys and Oakley 2000). The use of ceramic material to conserve and restore ceramic objects is less well established. This article describes a methodology to create ceramic replacements that overcomes the technical difficulties connected with the shrinkage of clay during drying and firing. The advantages, disadvantages and ethical considerations of using ceramic replacements are discussed. Two different methods for making ceramic replacements are presented for porous and vitreous ceramics, respectively. The technical problems of creating ceramic fills for porous ceramics can largely be eliminated, which offers the possibility of using a relatively simple method for creating ceramic fills. A different technique is required for making fills in vitreous ceramics because of the extensive shrinkage during firing.

Characterization of Ceramic Materials For Use In The Manufacture Of AZS Refractory Bricks.

(2004). Characterization of Ceramic Materials For Use In The Manufacture Of AZS Refractory Bricks. Materials Technology: Vol. 19, No. 4, pp. 234-236.