Showing papers on "Ceramic published in 1997"
TL;DR: In this article, a methodology is introduced for predicting the effective thermal conductivity of arbitrary particulate composites with interfacial thermal resistance in terms of an effective medium approach combined with the essential concept of Kapitza thermal contact resistance.
Abstract: A methodology is introduced for predicting the effective thermal conductivity of arbitrary particulate composites with interfacial thermal resistance in terms of an effective medium approach combined with the essential concept of Kapitza thermal contact resistance. Results of the present model are compared to existing models and available experimental results. The proposed approach rediscovers the existing theoretical results for simple limiting cases. The comparisons between the predicted and experimental results of particulate diamond reinforced ZnS matrix and cordierite matrix composites and the particulate SiC reinforced Al matrix composite show good agreement. Numerical calculations of these different sets of composites show very interesting predictions concerning the effects of the particle shape and size and the interfacial thermal resistance.
1,638 citations
TL;DR: Three groups of materials-biomaterials, ceramics, and semiconductors-have been selected to illustrate the concept of organic manipulators as used by nature and by synthetic laboratories exploring its potential in materials technology.
Abstract: Organic molecules can alter inorganic microstructures, offering a very powerful tool for the design of novel materials. In biological systems, this tool is often used to create microstructures in which the organic manipulators are a minority component. Three groups of materials-biomaterials, ceramics, and semiconductors-have been selected to illustrate this concept as used by nature and by synthetic laboratories exploring its potential in materials technology. In some of nature's biomaterials, macromolecules such as proteins, glycoproteins, and polysaccharides are used to control nucleation and growth of mineral phases and thus manipulate microstructure and physical properties. This concept has been used synthetically to generate apatite-based materials that can function as artificial bone in humans. Synthetic polymers and surfactants can also drastically change the morphology of ceramic particles, impart new functional properties, and provide new processing methods for the formation of useful objects. Interesting opportunities also exist in creating semiconducting materials in which molecular manipulators connect quantum dots or template cavities, which change their electronic properties and functionality.
775 citations
TL;DR: In this paper, structural ceramic nanocomposites are reviewed with emphasis on the Al 2 O 3 SiC and Si 3 N 4 SiC systems, and it is shown that the strength increase can best be related to a reduction in processing defect size.
Abstract: Structural ceramic nanocomposites are reviewed with emphasis on the Al 2 O 3 SiC and Si 3 N 4 SiC systems. The incorporation of a nanosized second phase, such as SiC, into a ceramic matrix can lead to an improvement in mechanical properties. It is still unclear, however, whether those improvements can directly be related to an intrinsic ‘nanocompossite effect’ or to other factors. This review is divided into three parts. First, basic processing routes for nanocomposites, namely conventional powder processing, sol-gel processing and polymer pyrolysis are presented in detail. Second, the mechanical properties of different nanocomposites are compared. Finally, models which attempt to explain the improvements in these properties are explored. It will be shown that the strength increase can best be related to a reduction in processing defect size. For applications the most interesting properties of nanocomposites are their wear, creep and high temperature performance.
432 citations
TL;DR: In this article, a Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy, machined into 7 mm wide, 38 mm thick compact-tension specimens and fatigue precracked following standard procedures, revealed fracture toughnesses in the fully amorphous structure of K(lc)similar to 55 MPa root m, i.e., comparable with that of a high-strength steel or aluminum ahoy.
Abstract: The recent development of metallic alloy systems which can be processed with an amorphous structure over large dimensions, specifically to form metallic glasses at low cooling rates (similar to 10 K/s), has permitted novel measurements of important mechanical properties. These include, for example, fatigue-crack growth and fracture toughness behavior, representing the conditions governing the subcritical and critical propagation of cracks in these structures. In the present study, bulk plates of a Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy, machined into 7 mm wide, 38 mm thick compact-tension specimens and fatigue precracked following standard procedures, revealed fracture toughnesses in the fully amorphous structure of K(lc)similar to 55 MPa root m, i.e., comparable with that of a high-strength steel or aluminum ahoy. However, partial and full crystallization, e.g., following thermal exposure at 633 K or more, was found to result in a drastic reduction in fracture toughness to similar to 1 MPa root m, i.e., comparable with silica glass. The fully amorphous alloy was also found to be susceptible to fatigue-crack growth under cyclic loading, with growth-rate properties comparable to that of ductile crystalline metallic alloys, such as high-strength steels or aluminum alloys; no such fatigue was seen in the partially or fully crystallized alloys which behaved like very brittle ceramics. Possible micromechanical mechanisms for such behavior are discussed.
423 citations
TL;DR: The hardness and brittleness of ceramic materials are interrelated as mentioned in this paper, and a new index of britteness is proposed by means of extensive Vickers hardness testing, which examines the interrelationship between hardness and fracture processes.
Abstract: The hardness and brittleness of ceramic materials are interrelated. Hard materials are more apt to fracture in the vicinity of an indentation during a hardness test, while softer materials tend to plastically deform to the indenter shape without fracturing. Measured hardness, in turn, is affected by both specimen deformation and fracture processes. This interrelationship is examined by means of extensive Vickers hardness testing. A new index of brittleness is proposed.
423 citations
TL;DR: In this article, the authors describe a strong ceramic composite with a different kind of microstructure, made by unidirectional solidification of an Al 2 O 3 / GdAlO 3 eutectic mixture.
Abstract: Monolithic ceramics are not widely used as structural materials because of their brittleness. Ceramic matrix composites, in which whiskers 1-3 or fibres 4-7 of strong ceramics such as silicon carbide or silicon nitride are embedded in a ceramic matrix, offer improved toughness and strength because the energy of cracks may be dissipated at the whisker/matrik interface. Here we describe a strong ceramic composite with a different kind of microstructure, made by unidirectional solidification of an Al 2 O 3 / GdAlO 3 eutectic mixture. This composite has a microstructure in which continuous networks of single-crystal Al 2 O 3 and single-crystal GdAlO 3 interpenetrate without grain boundaries. Rather than brittle fracture, the material displays plastic deformation at 1,873K owing to dislocation motion, as in metals. The high strength and resistance to brittle failure of this material at such high temperatures augurs well for applications in mechanical engineering.
412 citations
TL;DR: In this paper, the authors reported the synthesis of a tough α-Si3N4 solid solution with this kind of microstructure, which is 40% harder than β-Si 3N4 and is equally strong and tough.
Abstract: Silicon nitride (Si3N4) is a light, hard and strong engineering ceramic1,2. It can withstand harsh environments and support heavy loads at temperatures beyond those at which metals and polymers fail. It can also be manufactured reliably at a reasonable cost and in large quantities. There are two forms of silicon nitride3: α-Si3N4 and β-Si3N4. The former is harder, but only the latter is currently used in engineering applications, because only this form can be given a microstructure resembling a whisker-reinforced composite1,2,4, which gives it the necessary toughness and strength. Here we report the synthesis of a tough α-Si3N4 solid solution with this kind of microstructure. This material is 40% harder than β-Si3N4 and is equally strong and tough. Its hardness (22 GPa) is exceeded only by boron carbide and diamond (which are both brittle). These properties mean that this form of α-Si3N4 should be preferred over β-Si3N4 for all engineering applications, and it should open up new potential areas in which the ceramic can be applied.
385 citations
TL;DR: In this article, a self-consistent, single-valued representation of the major physical, mechanical, and thermal properties of a sintered α-SiC is presented by focusing on a narrowly defined material specification in which boron and carbon are used as sintering aids to produce a dense ceramic (⩾98% of the theoretical maximum density) with a grain size of (6±2) μm.
Abstract: A self-consistent, single-valued representation of the major physical, mechanical, and thermal properties of a sintered α-SiC is presented. This comprehensive set of properties is achieved by focusing on a narrowly defined material specification in which boron and carbon are used as sintering aids to produce a dense ceramic (⩾98% of the theoretical maximum density) with a grain size of (6±2) μm. Such a representation is highly desirable in applications of concurrent engineering practices and for the increasing use of electronic processing of product specifications.
377 citations
TL;DR: Gelcasting as discussed by the authors is a combination of polymer chemistry with slip processing and represents minimal departure from standard ceramic processing and has attracted industrial partners and by collaboration between them and the developers, the process is being advanced from the laboratory toward industrial production.
Abstract: Gelcasting, a ceramic forming process, was developed to overcome some of the limitations of other complex-shape forming techniques such as injection molding and slip casting. In gelcasting, a concentrated slurry of ceramic powder in a solution of organic monomers is poured into a mold and then polymerized in situ to form a green body in the shape of the mold cavity. Thus, it is a combination of polymer chemistry with slip processing and represents minimal departure from standard ceramic processing. The simplicity of the process has attracted industrial partners and by collaboration between them and the developers, the process is being advanced from the laboratory toward industrial production.
326 citations
TL;DR: In this paper, lead zirconate titanate (PZT) films 60 μm in thickness have been fabricated using a new sol gel based process, where PZT powders are dispersed in a sol gel matrix to form a 0-3 ceramic/ceramic composite.
Abstract: Lead zirconate titanate (PZT) films 60 μm in thickness have been fabricated using a new sol gel based process. PZT powders are dispersed in a sol gel matrix to form a 0–3 ceramic/ceramic composite. The dielectric properties of these films have been studied as a function of powder concentration, frequency, and temperature. The characteristic Curie point is observed at 420 °C. The ferroelectric behavior measured in terms of the remanant polarization (Pr=35 μC/cm2) and coercive field (Ec=20 kV/cm) was an improvement over values quoted for thin PZT films but lower than that of bulk ceramic. The piezoelectric properties d33 (325 pC/N) and d31 (−80 pC/N) were comparable with those of the bulk ceramic.
282 citations
TL;DR: A range of increasingly important chemical syntheses for ceramic materials are described in this article, where common themes relating the syntheses are outlined and their advantages over conventional solid-state reactions are described.
Abstract: A range of increasingly important chemical syntheses for ceramic
materials are described. These syntheses are coprecipitation, molten
salts, sol–gel processes, hydrothermal techniques, liquid-phase and
gas-phase reactions, polymer pyrolysis, the Pechini and citrate gel
methods, aerosols and emulsions. Common themes relating the syntheses are
outlined and their advantages over conventional solid-state reactions are
described. The scope for further chemical studies on ceramic synthesis is
discussed.
TL;DR: In this article, the chemical phase behavior of the ceramic powders with varying stoichiometries was studied by high-temperature in-situ X-ray diffraction (XRD) as a function of oxygen partial pressure.
15 Nov 1997-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, an electrostatic precipitator collected the plasma synthesized ceramic particles at a rate of 0.2 mg s −1, with ~5-20% collection efficiency.
Abstract: Conventional plasma spraying was used to process atomized liquid droplets of precursor solutions to produce alumina, zirconia and yttria stabilized zirconia nanoparticles and deposits. An electrostatic precipitator collected the plasma synthesized ceramic particles at a rate of ~0.2 mg s −1 , with ~5–20% collection efficiency. Spray processing produced 1–50 nm size ceramic particles. The size, shape and phase composition of the nanomaterials depend on the spray feedstock. Organo-metallic precursors gave rise to a narrow range of fine-grained material, while aqueous solutions produced wider distributions of larger size grains. Spray processing of liquid feedstock produced nanodeposits with a powdery morphology. Plasma spraying of liquid precursors is a viable technique to produce nanoparticles and deposits.
TL;DR: A survey of the most important contributions to those preparative routes starting from the pioneering work in the 1960s and the 1970s can be found in this article, where a certain emphasis is placed on the concepts that have applied to the preparation of multinary, nonoxide materials and amorphous inorganic networks.
Abstract: Materials research is an interdisciplinary field in which engineers and physical scientists work together. Since the major binary oxides, nitrides, and carbides, which are currently used as high-performance ceramics, were discovered in the last century, the role of chemistry in the development of materials has become barely noticeable. This has changed only in the recent past as, for example, purity and defined morphology of starting powders were recognized as crucial parameters for enhancing the reliability of ceramic workpieces. While the application of chemical methods led to gradual–though significant–improvements, the true potential of chemistry lies rather in the exploitation of new chemical systems and the development of new preparative routes to already known materials. Such an approach is the preparation of ceramics from molecular or polymeric precursors. Herein we survey the most important contributions to those preparative routes starting from the pioneering work in the 1960s and the 1970s; a certain emphasis is placed on the concepts that we have applied to the preparation of multinary, nonoxide materials and amorphous inorganic networks. The name “amorphous high-performance ceramics” is in fact a contradiction in terms. Such materials are thermodynamically unstable with respect to the transformation or decomposition to crystalline phases, thus excluding their application in sensitive areas at high temperatures. However, the selection of element combinations for which the binding energies are derived from strong, local covalent bonds and which are therefore less dependent on a long-range crystalline order, can yield amorphous materials of remarkable thermal and mechanical durability. This is exemplified by novel quaternary ceramics in the Si/B/N/C system, for which an efficient synthesis, starting from raw materials suitable for industrial production, has been developed. For instance, a material of the composition SiBN3C remains amorphous up to 1900°C, which is unique, and, with respect to oxidation, is the most stable nonoxide ceramic known to date. Another advantage of this in several respects unsurpassed material is the simple way, in which the viscosity of the polymeric precursors can be adjusted to various methods of shaping. So far infiltrations and coatings have been realized. Most developed is the preparation of fibers, which in terms of their performance characteristics are significantly better than those currently available.
TL;DR: In this article, various composites of barium strontium titanium oxide (BSTO) combined with other nonelectrically active oxide ceramics have been formulated for application in phased array antennas.
Abstract: Various composites of barium strontium titanium oxide (BSTO) combined with other nonelectrically active oxide ceramics have been formulated for application in phased array antennas. In general, the composites have adjustable electronic properties which can be tailored for use in phased array antennas and other phase shifting devices. The dielectric constant and the loss tangents have been reduced to enhance the overall impedance matching and thereby lowering the insertion loss of the device. In addition, the overall tunability, the change in the dielectric constant with applied voltage, is maintained at a sufficiently high level. In order to address a broad frequency range in the microwave region, the composites have been fabricated in bulk ceramic, thick film, and thin film form. This article discusses the processing, material characterization, and electronic properties of the composites in MHz and GHz frequencies.
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18 Jul 1997TL;DR: In this paper, the internal electrodes formed in the interior of a ceramic laminate of a monolithic ceramic capacitor comprise metal conductor parts and semiconductor parts, which are exposed at both end surfaces of the laminate to be electrically connected with external electrodes.
Abstract: Internal electrodes formed in the interior of a ceramic laminate of a monolithic ceramic capacitor comprise metal conductor parts and semiconductor parts. The semiconductor parts are exposed at both end surfaces of the ceramic laminate to be electrically connected with external electrodes. The external electrodes comprise baked layers of silver formed on the end surfaces of the ceramic laminate and metal plated films formed thereon. In formation of the metal plated films, a plating solution which may reach the end surfaces of the ceramic laminate through the baked layers is blocked by the semiconductor parts and prevented from infiltration into the metal conductor parts of the internal electrodes.
TL;DR: Experimental results are presented showing that the size and distribution of small subsurface defects can be determined with depth and lateral resolutions of 10 and 4 microm, respectively.
Abstract: We use optical coherence tomography with a new configuration to determine the size and location of subsurface defects in solid ceramic and composite ceramic materials. Cross-sectional subsurface regions either parallel or perpendicular to the surface were examined. We present experimental results showing that the size and distribution of small subsurface defects can be determined with depth and lateral resolutions of 10 and 4 microm, respectively.
TL;DR: In this article, a phenomenological model involving distortion of the band structure is proposed to explain the results of kinetic measurements of a highly dense transparent YAG: Ce-ceramic.
TL;DR: In this article, it was shown that the critical current densities are determined by the grain boundary misorientation distributions (GBMDs), and that a percolative networks of low-angle boundaries with fractions consistent with the active cross-sectional area of the conductor exist in each of these conductors.
Abstract: Much of the conductor development effort in the last decade has focused on optimizing the processing of (Bi, Pb)2Sr2Ca2Cu3Ox oxide-powder-in-tube conductors and (Bi, Pb)2Sr2CaCu2O8 (Bi-2212) and TlBa2Ca2Cu3Ox thick film conductors. It is demonstrated that in each of these conductors, critical current densities are dictated by the grain boundary misorientation distributions (GBMD’s). Percolative networks of low-angle boundaries with fractions consistent with the active cross-sectional area of the conductor exist in each of these conductors. Further enhancements in the properties require increased numbers of small-angle grain boundaries. Given the processing methods used to fabricate these materials, no clear route employing a simple modification of the established processing method is apparent. To address this need, conductors with controlled or predetermined GBMD’s are necessary. Development of biaxial texture appears to be the only possible way to increase the number of small-angle boundaries in a practical and controllable manner. We summarize in this paper recent results obtained on epitaxial superconducting films on rolling-assisted-biaxially-textured-substrates (RABiTS). This technique uses well established, industrially scalable, thermomechanical processes to impart a strong biaxial texture to a base metal. This is followed by vapor deposition of epitaxial buffer layers (metal and/or ceramic) to yield structurally and chemically compatible surfaces. Epitaxial YBa2Cu3O7–δ films grown using laser ablation on such substrates have critical current densities exceeding 106 A/cm2 at 77 K in zero field and have a field dependence similar to epitaxial films on single crystal ceramic substrates. Deposited conductors made using this technique offer a potential route for the fabrication of the next generation high temperature superconducting (HTS) wire capable of carrying high currents in high magnetic fields and at elevated temperatures.
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IBM1
TL;DR: In this article, an aluminum or copper heat sink is attached to a ceramic cap or exposed semiconductor chip using an adhesive of silicon or flexible-epoxy adhesive, which is especially useful for flip chip attachment to flexible or rigid organic circuit boards or modules such as CQFP, CBGA, CCGA, CPGA, TBGA, PBGA, DCAM, MCM-L.
Abstract: An aluminum or copper heat sink is attached to a ceramic cap or exposed semiconductor chip using an adhesive of silicon or flexible-epoxy adhesive. The aluminum may be coated by anodizing or Chromate conversion or the copper may be coated with nickel or gold Chromium. Such structures are especially useful for flip chip attachment to flexible or rigid organic circuit boards or modules such as CQFP, CBGA, CCGA, CPGA, TBGA, PBGA, DCAM, MCM-L, and other chip carrier packages in which the back side of chips are connected directly to heat sinks. These adhesive materials withstand wet or dry thermal cycle tests of -65 to 150° C. for 1,000 cycles and 85° C. and 85% relative humidity for 1000 hours while maintaining a tensile strenth of at least 500 psi. The adhesive contains materials having high thermal conductivity and a low coefficient of thermal expansion (CTE) in order to provide increased thermal performance and a CTE between that of the silicon metal die and the metal of the heat sink.
TL;DR: The main effects of the active fillers are to form a stabilizing network of the filler reaction products, increase ceramic yield of the polymer, and to provide internal surface for material transport during polymer decomposition reactions.
Abstract: Pyrolytic conversion of preceramic polymers loaded with active filler particles offers the possibility of near net shape manufacturing of bulk ceramic components from polymers. Active fillers based on elements (B, Si, Al, Ti, Mo, etc.), intermetallics (CrSi2, MoSi2, etc.) or ceramic compounds (AlN, B4C, etc.) which react with the solid and gaseous decomposition products of the preceramic polymer (polysilane, -carbosilane, -silazane, siloxane, etc.) during pyrolysis may form carbide, nitride or oxide reaction products in the polymer derived amorphous or microcrystalline matrix. The main effects of the active fillers are to form a stabilizing network of the filler reaction products, increase ceramic yield of the polymer, and to provide internal surface for material transport during polymer decomposition reactions. Thus, dimensional change, porosity formation as well as material properties can be tailored in a wide range by combination of a variety of polymers, fillers and reaction atmospheres.
TL;DR: In this article, surface analysis of the Magneli phase titanium oxides with the general formula TixO2x-1 has been performed using X-ray photoelectron spectroscopy in order to determine the surface composition.
Abstract: The electrochemical behaviours of the Magneli phase titanium oxides with the general formula TixO2x-1 have been investigated. Surface analysis of these ceramic materials was performed using X-ray photoelectron spectroscopy in order to determine the surface composition. It was shown that the surface layers contain mainly TiIV. When these materials are used as an anode for oxygen evolution, in sulfuric acid, the XPS spectrum shows considerable modification in the O1s region, due to an important contribution of hydroxyl groups and the adsorption of sulfate anions.
02 May 1997-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the basic mechanisms of thin film growth under ion irradiation in the ion energy range below 1 keV are described on an atomic level, with the dependence of the microstructure, such as grain size and orientation, and density of films on the process parameters ion-to-atom arrival ratio, angle of incidence, average deposited energy, and ion energy.
Abstract: Low-energy ion bombardment during growth of thin films from the vapour phase exerts a strong influence on the properties of the films, particularly their microstructure. The basic mechanisms of film growth under ion irradiation in the ion energy range below 1 keV are described on an atomic level. The dependence of the microstructure, such as grain size and orientation, and density of films on the process parameters ion-to-atom arrival ratio, angle of incidence, average deposited energy, and ion energy is discussed with recent results from the literature with silver as an example for a metal, germanium as a semiconductor and titanium nitride as a ceramic compound film.
TL;DR: In this article, the structure, thermal expansion and ionic conductivity of solid electrolytes based on samarium doped cerium oxide, Ce1−xSmxO2−x2 (x = 0−0.30), prepared by the sol-gel method were systematically investigated in a wide range of temperature of 200-650 °C.
TL;DR: In this paper, the effect of substrate surface roughness and coating thickness on the adhesion and tribological behaviour of TiN deposited by reactive ion plating on steel substrates was studied.
Abstract: We have studied the effect of substrate surface roughness and coating thickness on the adhesion and tribological behaviour of TiN deposited by reactive ion plating on steel substrates. Three coating thicknesses (1.5, 3 and 5 μm) and three substrate surface finishes ( R a = 0.02, 0.15 and 0.35 μm) were tested. Scratch tests show that coatings on substrates with a poor surface finish show worse adhesion than on those with a smooth surface. Sliding friction tests were conducted with a pin-on-disc tribometer. The pin was a ball of 100C6 steel or alumina. The results show that adhesion takes place at the TiN coating/steel interface followed by metal transfer onto the ceramic. Wear of the steel increases with increasing TiN coating thickness and substrate surface roughness. Adhesion also occurs when TiN is in sliding contact against alumina. The latter did not suffer any wear while the TiN coating suffered adhesive wear. Large TiN transfer was detected on alumina. The results show that, for a given coating thickness, the wear of the coating is as important as the roughness of the substrate is high. In addition, the coating thickness of 3 μm shows better resistance to wear compared to the two other thicknesses.
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24 Jul 1997TL;DR: In this paper, the erbia atom has an atomic mass greater than the average atomic mass of the zirconium, the yttrium, calcium, magnesium or indium and the oxygen atoms to reduce phonon thermal conductivity of the ceramic thermal barrier coating (18).
Abstract: A metallic article (10) comprises a bond coating (14,16) on the metallic article (10) and a ceramic thermal barrier coating (18) on the bond coating (14,16). The ceramic thermal barrier (18) coating comprises zirconia stabilized with yttria, calcia, magnesia or india, and erbia to reduce the thermal conductivity of the ceramic thermal barrier coating (18). The ceramic thermal barrier coating (18) is at least 100 microns thick. The erbium atom has an atomic mass greater than the average atomic mass of the zirconium, the yttrium, calcium, magnesium or indium and the oxygen atoms to reduce phonon thermal conductivity of the ceramic thermal barrier coating (18). The ceramic thermal barrier coating (18) comprises 4 to 20 wt % of yttria, 5 to 25 wt % of erbia and the balance is zirconia plus incidental impurities. The erbia absorbs energy in the 0.3 microns to 5 microns waveband to reduce photon thermal conductivity. Other suitable additions besides erbia are dysprosia, europia, gadolinia, praseodymia, urania or ytterbia.
TL;DR: In this paper, a review of in situ metal/ceramic composite materials with a greater emphasis on directed melt oxidation and nitridation is presented, and the mechanical properties, toughening mechanisms and potential applications are briefly reviewed.
TL;DR: In this paper, two kinds of oxidation (passive and active) and active-to-passive transition of silicon-based ceramics were discussed thermodynamically, and the rate constants of passive/active oxidation and active topassive oxygen potentials for SiC and Si 3 N 4 were reviewed.
Abstract: Oxidation behavior of silicon-based ceramics such as SiC and Si 3 N 4 at high temperatures is important for their practical applications to structural or electronic materials. In the present paper two kinds of oxidation (passive and active) and active-to-passive transition of silicon-based ceramics were discussed thermodynamically, and the rate constants of passive/active oxidation and active-to-passive transition oxygen potentials for SiC and Si 3 N 4 were reviewed. Passive and active oxidation behavior depended on the microstructure of oxide films and SiO gas pressure on silicon-based ceramics, respectively. Wagner model, volatility diagram and solgasmix-based calculation were used to estimate the active-to-passive transition.
TL;DR: In this article, a review of recent progress in the field of mechanical behavior of layered ceramics is reviewed, including various laminar design approaches for achieving improvements in strength, toughness, work of fracture, R-Curve behavior, and contact damage resistance.
Abstract: ▪ Abstract Recent progress in the field of mechanical behavior of layered ceramics is reviewed. Several processing techniques are described with reference to the fabrication of ceramic laminates. These include tape-casting, centrifugal casting, slip-casting, electrophoretic deposition (EPD), and the production of fibrous monolith materials. The review discusses various laminar design approaches for achieving improvements in strength, toughness, work of fracture, R-Curve behavior, and contact damage resistance. Examples of effective strategies include manipulation of residual stresses, the incorporation of weak interlayers to induce crack deflection, and promotion of synergistic effects between layer materials that exhibit intrinsically different responses.