Gathering information on the evolution of small cracks in ceramic matrix composites used in hostile environments such as in gas turbines and hypersonic flights has been a challenge. It is now shown that sequences of microcrack damage in ceramic composites under load at temperatures up to 1,750 °C can be fully resolved with the use of in situ synchrotron X-ray computed microtomography.

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Real-time quantitative imaging of failure events in materials under load at temperatures above 1,600 °C

A novel high-entropy material, (Yb0.2Y0.2Lu0.2Sc0.2Gd0.2)2Si2O7 ((5RE0.2)2Si2O7) was prepared by the sol-gel method and investigated as a promising environmental barrier coating (EBC) for SiC-based composites. The results of X-ray diffraction and transmission electron microscopy indicated that rare-earth elements were distributed homogeneously in the single monoclinic phase. Moreover, it was found that the new material (5RE0.2)2Si2O7 had good phase stability, well-matched coefficient of thermal expansion with SiC-based composite, and excellent resistance to water-vapor corrosion. The water-vapor corrosion test of (5RE0.2)2Si2O7 coated Cf/SiC composites further confirmed that (5RE0.2)2Si2O7 was suitable for application as EBC material and could provide effective protection to Cf/SiC composites from water-vapor damage.

High-entropy environmental barrier coating for the ceramic matrix composites

The production and the supply of high quality laboratory animals have fundamental importance for the accomplishment of vanguard scientific research, with reproducibility and universality. The quality of those animals depends, largely, of the available facilities for their production and lodging, to assure the demanded sanitary control and animals’ welfare, in agreement with the ethical principles that control the activity. The facilities also have to fill out other requirements, such as: the functionality of the environments to make possible the suitable and efficient handling of the animals, facilitating the execution of the routine activities; the respect to ergonomic principles to provide a safe environment and the operators’ well being. The facilities design is of vital importance so that the mentioned requirements can be reached. The project of the Nuclear and Energy Research Institute (IPEN) Animal House Facilities was accomplished in the year of 1964. However, by that time there were not the current recommendations with respect to the sanitary, genetic and environmental controls. The facility was planned with the objective of being a production unit and a local for keeping of defined animals from sanitary, genetic and environmental point of view. Nevertheless, the original unit drawing presents an unsuitable distribution of the area where animals are stocked and also different activities are performed. The Animal House Facilities occupy an area of 840 m, with one pavement, where the production areas and the stock of original animal models of the own Institution are distributed, as well as the maintenance of animals from other national or foreigner institutions. It supplies rats and mice for biological tests of radiopharmaceutical lots, produced in IPEN, before they be sent to hospitals and clinics spread out in Brazil, for use in Nuclear Medicine. It also supplies rats and mice for tests of odontological materials, for tests with growth hormones and for researches of new pharmaceuticals and radiopharmaceuticals, among others applications. Many of the animals models produced in IPEN are unique in Brazil and they constitute, therefore, an important patrimony that should be preserved. This paper describes the activities that have been executed in Animal House Facilities of IPEN, including the refurbishment project and the adaptation of the facilities.

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Instituto de Pesquisas Energéticas e Nucleares

Rare earth silicate environmental barrier coatings: Present status and prospective

Machining of SiC ceramic matrix composites: A review

Advanced ceramic matrix composite materials for current and future propulsion technology applications

Various technology programs in Europe are concerned, besides developing reliable and rugged, low-cost, throwaway equipment, with preparing for future reusable propulsion technologies. One of the key roles for realizing reusable engine components is the use of modern and innovative materials. One of the key technologies that concerns various engine manufacturers worldwide is the development of fiber-reinforced ceramics—CMCs (ceramic matrix composites). The advantages for the developers are obvious–the low specific weight, the high specific strength over a large temperature range, and their great damage tolerance compared with monolithic ceramics make this material class extremely interesting as a construction material. Over the past few years, the EADS-ST Company (formerly DASA) has, together with various partners, worked intensively on developing components for hypersonic engines and liquid rocket propulsion systems. In the year 2000, various hot-firing tests with subscale (scale 1:5) and full-scale nozzle extensions were conducted. In this year, a further decisive milestone was achieved in the sector of small thrusters, and long-term tests served to demonstrate the extraordinary stability of the C/SiC material. Besides developing and testing radiation-cooled nozzle components and small-thruster combustion chambers, EADS-ST worked on the preliminary development of actively cooled structures for future reusable propulsion systems. In order to get one step nearer to this objective, the development of a new fiber composite was commenced within the framework of a regionally sponsored program. The objective here is to create multidirectional (3D) textile structures combined with a cost-effective infiltration process. Besides material and process development, the project also encompasses the development of special metal/ceramic and ceramic/ceramic joining techniques as well as studying and verifying nondestructive investigation processes for the purpose of testing components.

Ceramic Matrix Composites: A Challenge in Space-Propulsion Technology Applications

A two-layer ceramic composite material, wherein the first predominantly load-bearing layer is an oxidic, carbon-free fiber-reinforced ceramic layer which is made by a colloidal process. The second predominantly thermally insulating layer is an oxide-ceramic foam. The colloidal process produces carbon-free oxide ceramics which, because of their high purity, have low dielectric losses in the entire usage temperature range. In addition, the colloidal process provides a simple and cost-effective production method.

Multi-layer ceramic composite material with a thermal-protective effect

A ceramic composite material consists of a carbon fiber-reinforced SiC+C matrix coated with a lower protective layer of one or more compounds of Si, C, B and O, a middle protective layer based on transition metal borides and/or silicides and an upper protective layer of one or more of SiC, SiO2, MoSi2, Mo3Si, Mo5Si3, ZrB, ZrB2, ZrB12, Si3N4, ZrO2, Y2O3, Al2O3, Al2O3-SiO2 mixed oxide and SiOC. A ceramic composite material, for use at up to 1600 degrees C, consists of a basic material which comprises 30-60 vol.% C fibers, 10-55 vol.% matrix of SiC and C in a wt. ratio of 2-20:1 and 5-40 vol.% porosity and which is coated with (a) a 20-150 mu thick lower protective layer of one or more compounds of Si, C, B and O; (b) a 50-250 mu thick middle protective layer of transition metal borides and/or silicides in combination with SiC, SiO2 or SiOC; and (c) a 20-250 mu thick upper protective layer of one or more of SiC, SiO2, MoSi2, Mo3Si, Mo5Si3, ZrB, ZrB2, ZrB12, Si3N4, ZrO2, Y2O3, Al2O3, Al2O3-SiO2 mixed oxide and SiOC. Independent claims are also included for (i) increasing the effectiveness of the oxidation protection system of the above ceramic composite material by an oxidative pretreatment at 900-1400 degrees C to activate the crack sealing mechanisms before use; and (ii) production of the coating layers (a), (b) and (c) by applying slips of inorganic fillers, organic binder and solvent and firing such that the organic binder is converted into inorganic components of the layers.

Ceramic composite reinforced with carbon fibers

Multiple layer ceramic composite material comprises a first layer (1) made from an oxidic carbon-free fiber-reinforced ceramic consisting of at least 30 volume % high strength oxide-ceramic full fibers and an oxidic carbon-free matrix, in which the composite ceramic has a tensile strength of 140 MPa, a heat conductivity of 2 W/mK, a dielectric constant of 6, and a loss factor of 0.002, and a second layer (2) made from a thermal insulating layer consisting of a pure oxidic foam having a density of 0.2-1.4 g/cm 3>, a heat conductivity of 0.25 W/MK, a dielectric constant of 1.5-2.5, and a loss factor of 0.01.

Helmut Knabe

Papers

Advanced ceramic matrix composite materials for current and future propulsion technology applications

Ceramic Matrix Composites: A Challenge in Space-Propulsion Technology Applications

Multi-layer ceramic composite material with a thermal-protective effect

Ceramic composite reinforced with carbon fibers

Multilayered ceramic coposite material having thermal protection properties