Use Of Ceramic Materials Research Articles

2.5 MeV electron irradiation effect of alumina ceramics

In order to choose an alumina ceramic material for use as a vacuum beam duct in a rapid cycling synchrotron, several kinds of alumina ceramics, having different microstructures, were examined under radiation fields of 2.5 MeV electrons. Since a long ceramic duct can only be manufactured by glazing duct segments, the mechanical strength and deterioration not only of the ceramics but also in the glazing joint were measured after irradiation. These ceramics have a sufficiently high flexural strength of more than 300 MPa before electron beam irradiation, and the experimental results showed no deterioration of the flexural strength after 1000 MGy electron beam irradiation. Also no noticeable changes could be seen in the measured tensile strength of Ti-ceramic brazed samples after 1000 MGy electron beam irradiation.

Investigation of the use of ceramic materials in innovative light water reactor — fuel rod concepts

A new major version of the European severe accident integral code ASTEC, developed by IRSN with some GRS support, was delivered in November 2015 to the ASTEC worldwide community.Main modelling features of this V2.1 version are summarised in this paper. In particular, the in-vessel coupling technique between the reactor coolant system thermal-hydraulics module and the core degradation module has been strongly re-engineered to remove some well-known weaknesses of the former V2.0 series. The V2.1 version also includes new core degradation models specifically addressing BWR and PHWR reactor types, as well as several other physical modelling improvements, notably on reflooding of severely damaged cores, Zircaloy oxidation under air atmosphere, corium coolability during corium concrete interaction and source term evaluation.Moreover, this V2.1 version constitutes the back-bone of the CESAM FP7 project, which final objective is to further improve ASTEC for use in Severe Accident Management analysis of the Gen.II–III nuclear power plants presently under operation or foreseen in near future in Europe. As part of this European project, IRSN efforts to continuously improve both code numerical robustness and computing performances at plant scale as well as users’ tools are being intensified.Besides, ASTEC will continue capitalising the whole knowledge on severe accidents phenomenology by progressively keeping physical models at the state of the art through a regular feed-back from the interpretation of the current and future experimental programs performed in the international frame.

Plasticity and an inverse brittle-to-ductile transition in strontium titanate.

The use of ceramic materials is often restricted by a transition from ductile behavior to brittle fracture with decreasing temperature. For example, strontium titanate ( SrTiO3) is known to be extremely fragile and brittle below 1300 K. It is therefore surprising to find that SrTiO3 single crystals can be deformed in compression below 1050 K again. Extensive plastic deformation up to 7% strain at low yield stresses of the order of only 120 MPa is possible at room temperature. Low temperature plasticity is carried by the same [110] [110] dislocations as the high temperature deformation along the [001] axis. From this we conclude that these dislocations must exist in two different core configurations.

Processing, Microstructure, and Thermomechanical Behavior of Ceramics

A global approach to ceramics, including the effect of processing on microstructure and of microstructure on final properties, is needed in order to extend the use of ceramic materials. The application of such an approach is demonstrated to different types of ceramics. It deals with ceramic processing, from the first step of powder synthesis to the final sintering stage, and it covers important work that has been carried out in order to understand the effect of interfacial properties and their evolution during fatigue of ceramic matrix composites.

Anatase‐to‐Rutile Transformation in Titania Powders

Titania (TiO2) is an important electronic ceramic material for use in diverse applications such as gas sensors, catalysts, dielectrics, and ceramic membranes. TiO2 exists as several polymorphic phases, most commonly as rutile or anatase. This paper investigates the microstructural evolution of anatase‐based commercial TiO2 powders, with an average size of 100 nm, at high temperatures. These powders transform to the rutile structure at 1000°C. The characteristics of the anatase‐to‐rutile transformation have been studied using transmission electron microscopy analysis, and new information regarding the nature and mechanisms of this polymorphic reaction has been revealed.

Investigation of the use of ceramic materials in innovative light water reactor – fuel rod concepts

The RWTH Aachen and the TU Dresden have undertaken a joint research effort, the goal of which is the development of innovative fuel rods which would constitute a high-melting reactor core. An additional sintered silicon carbide (SSiC)-encasement of the UO 2 pellets within the zircaloy cladding was planned. Various designs for the construction of the absorber rods were developed in order to achieve a failure temperature in excess of 1200°C. At the RWTH Aachen, a series of depleted UO 2 pellets were enclosed in gastight SSiC capsules through reaction sintering. The capsules were checked for leaks, and their thermomechanical behavior was analyzed after thermal strain; the capsules were heated to 1800°C (maximally 2070°C) in oxidizing water vapor as well as in air. Further series of experiments were conducted in order to examine the chemical behavior of the SSiC pellets in the presence of various reactor component materials at high temperatures. SSiC was heated to 1800°C while in contact with the following substances: zircaloy, steel, corium material, UO 2, Ag–In–Cd-alloy, HfO 2, Dy 2O 3, Gd 2O 3, Sm 2O 3, BN, and B 4C. With the exception of steel and corium material containing steel, the substances proved relatively inert in reactions with SSiC, such that their use in combination with SSiC can be judged to be favorable.

Preparation of Yttria-Stabilized Tetragonal Zirconia Ceramics for Optical Ferrule

Yttria-stabilized zirconia ceramics are considered to be one of the most important ceramic materials for use in structural applications, because of the high strength and toughness of yttria-stabilized tetragonal zirconia polycrystals. In this work, in order to prepare dense and compact yttria-stabilized tetragonal zirconia body after sintering at 1400°C, we used various raw materials with different particle properties, such as crystallinity, particle size distribution, and particle shape. Crystallinity and tetragonal percentage of the sintered samples were analyzed by X-ray diffraction. Microstructure of the sintered samples was evaluated by field emission-scanning electron microscopy.

00/02128 Kyanite from Minas Gerais, Brazil: characterization for use in ceramic materials

00/02128 Kyanite from Minas Gerais, Brazil: characterization for use in ceramic materials

High Power Characteristics of Piezoelectric Ceramics in Pb(Mn1/3Nb2/3)O3–PbTiO3–PbZrO3 System

As one of high power characteristics of the piezoelectric ceramics in Pb(Mn1/3Nb2/3)O3–PbTiO3–PbZrO3 system, the limit vibration velocity (vmax ), is defined as the vibration velocity that generate the fixed temperature rise was evaluated. From this system, a new material with a higher vmax of 0.79 m/s which is 1.7 times larger than conventional Pb(Mn1/3Sb2/3)O3–PbTiO3–PbZrO3 system was found. By using this new material, piezoelectric transformers were made and the output electric power (P) of the transformers were measured at RL=(ω·Cd2)-1 [load resistance (RL), resonant angular frequency (ω), output damping capacitance (Cd2)] and at other fixed resistances. The P of the piezoelectric transformer was measured on this condition, however, measured values of P were smaller than that of the conventional material. In order to clarify this phenomenon, an equivalent circuit including stray capacitance (Cf) of the load circuit was proposed. Simulation results by using this equivalent circuit showed that; 1. The load resistance giving the maximum output power decreases, as Cf increases. 2. The maximum output power decreases, as Cf increases. 3. When Cd2 of the piezoelectric transformer is small, the effect of Cf on the piezoelectric transformer becomes large. Therefore, a high dielectric constant (ε) is a required characteristic of the piezoelectric ceramic materials for use in the piezoelectric transformer, except for the usually high vmax and high electromechanical coupling coefficient (K).

Ceramic materials for use in microwave electronics

A study is reported of the structure and electrical properties of BaLn2Ti4O12 compositions (BLT), where Ln=La, Nd, or Sm, with calcium, strontium, or lead substituted for barium, and bismuth for the lanthanide. The BLT compound is shown to be characterized by a broad isomorphicity region, at the edge of which form solid solutions with the highest dielectric permittivity reached thus far, up to about 170. A number of thermally stable ceramic materials with a high dielectric permittivity of 80 to 120, which permit construction of microwave dielectric resonators with Q factors of up to 600 for ɛ=120 and up to 3000 for ɛ=80 at f=4 GHz, have been developed based on BLT solid solutions.

Reliability of a Conceptual Ceramic Gas Turbine Component Subjected to Static and Transient Thermomechanical Loading

A three year program to evaluate the feasibility of using monolithic silicon nitride ceramic components in gas turbines was conducted. The use of ceramic materials may enable design of turbine components which operate at higher gas temperatures and/or require less cooling air than their metal counterparts. The feasibility evaluation consisted of the following three tasks: (1) expand the materials properties database for candidate silicon nitride materials; (2) demonstrate the ability to predict ceramic reliability and life using a conceptual component model; and (3) evaluate the effect of proof testing on conceptual component reliability. The overall feasibility goal was to determine whether established life and reliability targets could be satisfied for the conceptual ceramic component having properties of an available material. Fast and delayed fracture reliability models were developed and validated via thermal shock and tensile experiments. A creep model was developed using tensile creep data. The effect of oxidation was empirically evaluated using four-point flexure samples exposed to flowing natural gas combustion products. The reliability and life-limiting failure mechanisms were characterized in terms of temperatures, stress, and probability of component failure. Conservative limits for design of silicon nitride gas turbine components were established.

97/02258 Advanced ceramic materials for use in high-temperature particulate removal systems

97/02258 Advanced ceramic materials for use in high-temperature particulate removal systems

Tensile and dynamic mechanical behaviour of polymer blends based on PVDF

This work reports on tensile property measurements and a dynamic mechanical study of polymer blends, varying in composition and obtained from three conventional polymers: polyvinylidene fluoride (PVDF), polyvinyl acetate (PVA) and polymethyl methacrylate (PMMA). It is the aim of this research to demonstrate that polymer systems with potentially good pyro-piezoelectric properties are capable of obviating the difficulties which arise from the use of ceramic materials, which have been traditionally employed to achieve pyro-piezoelectric materials, i.e. materials capable of adopting complex shapes, which possess good mechanical properties and which, in addition, are inexpensive. All these are prerequisites for the determination of their pyro-piezoelectric properties. The results obtained from measurements of these properties are interpreted in terms of component compatibility in the different blends, as component behaviour is well known to play an important role in the properties of the end-product.

97/01411 Advanced ceramic materials for use in high-temperature particulate removal systems

97/01411 Advanced ceramic materials for use in high-temperature particulate removal systems

Ingenieurkeramik in der Verfahrenstechnik — Alternativen für konventionelle Werkstoffe

AbstractThe use of ceramic materials in chemical engineering is on the increase. They have a number of advantageous properties which prove technically and economically beneficial. Realization of these benefits requires cooperation between component manufacturers and users, with due attention to appropriate design. Example of successful use are discussed.

The Development of Life Prediction Techniques for Structural Ceramics

One of the major challenges involved in the use of ceramic materials in advanced vehicular heat engines is ensuring adequate strength and durability. This Department of Energy supported activity has developed methodologies to predict the structural behavior of ceramic components. The effort involved the characterization of injection-molded and hot isostatic pressed PY6 silicon nitride and the development of analytical life prediction techniques. Three failure modes are addressed: fast fracture, slow crack growth, and creep rupture. The technique deals with surface as well as internal component failures. The life prediction methodologies for fast fracture and slow crack growth have been verified using two types of confirmatory specimens: (1) flat circular disks subjected to bending stresses, and (2) high-speed rotating spin disks. Correlation was achieved for a variety of test conditions and failure mechanisms. The predictions associated with surface failures proved to be optimistic, requiring re-evaluation of the components’ initial fast fracture strength. Correlation was achieved for the spin disks that failed in fast fracture from internal flaws. Time-dependent, elevated-temperature spin disk failures were also successfully predicted.

The 1995 Bakerian Lecture Composite materials

Examples of engineering artefacts made with modern composite materials are given, followed by a brief discussion of the range of physical properties attainable by fibre composites. Physical properties are usually simply additive but the strength properties are not. Multiple fracture is discussed in detail to show how cracks can be used to confer microductility and to provide energy absorbing structures. This opens the way for the use of ceramic materials as high temperature substitutes for metals. A possible microstructure for very high temperature creep resistance is discussed in detail; it consists of alternate layers of single crystals of differing lattice constant and elastic modulus. Finally the concept of a smart material is discussed showing how structures may be monitored with fibres and their mechanical response controlled or modified.

The Use of Ceramic Materials for Femoral Head Replacement

The Use of Ceramic Materials for Femoral Head Replacement

Advanced Ceramic Materials for Use in High-Temperature Particulate Removal Systems

First-generation monolithic porous ceramic filter materials have experienced thermal fatigue, high-temperature creep, and a loss of material strength when operated for extended periods of time in advanced coal-fired combustion and gasification systems. Fiber-reinforced and advanced ceramic composites potentially provide a means to mitigate the degradation mechanisms encountered by monolithic filter matrices and ultimately extend operating life. In this paper we will review advancements which have recently been made during the development of the second-generation porous ceramic filter materials and provide insight into the performance of the filter elements during bench-scale qualification testing and operation in demonstration plant test facilities.

A new far-infrared pyrometer for radiation temperature measurement on semitransparent and absorbing materials in an arc-heated wind tunnel

The use of ceramic materials in scientific research and industry has been growing in the past few years. The scope of this article is to describe the specification, design and calibration of a far-infrared pyrometer suited to measure surface temperatures on semitransparent materials such as alumina and silica and on coated composite materials. The specific problem being discussed is that the materials to be tested are heated by means of a plasma jet through which the temperature has to be measured.