Results for ceramic  
Title: Improving Ceramic Armor Performance
Abstract:
Recent advances in powder processing and manufacturing technigues are improving the performance of hot-pressed ceramic armor while also reduting costs.

Sources: Mendeley
Keywords: ceramic,
Title: Ceramic Nanocomposites for Solid Oxide Fuel Cells
Abstract:
AbstractSolid oxide fuel cells (SOFCs) are considered as prospective technology for direct conversion of the energy of chemical fuels into electricity. The development of highly efficient SOFC capable to operate in a range of operational temperature with various fuels, however, needs improvements in the microstructural and physical properties of the cell individual parts including electrodes, electrolytes, and current collectors. It is well understood that electrochemical function of the SOFC individual parts strongly depend on microstructural properties including porosity and pore-size distribution, particle size and size distribution, composition and spatial distribution of the constituent phases, and the length of the so-called triple-phase boundaries (TPBs) in the electrodes. Therefore, performing a control over the particle size and shape of the powders (the nanocomposite precursors) used for fabrication of SOFCs as well as controlling the other processing parameters (such as sintering temperature, shrinkage, ceramic to pore-former loading ratio) offer a capability to fabricate both SOFCs with desired electrochemical, mechanical, and thermal performance. Synthesis of nanomaterial has significantly considered as an important and hot field because it offers fast redox reactions, high specific surface areas, and shortened diffusion paths in the solid phase. Reviewing the literature in the past few years shows that optimizing the microstructural properties of SOFC through combination of advanced nanostructured materials in order to improve the electrochemical performance of the cell has still remained as a significant challenge in developing efficient SOFCs. In this chapter we review the articles in the field of synthesis and application of nanocomposite material for SOFCs and present some significant contributions from many research groups who are working in this area. The SOFC nanocomposite material in this chapter is mainly classified into three categories—electrolyte, anode and cathode that are followed by two operational ranges of temperature including high and low temperature.

Sources: Springer
Keywords: ceramic,fuel_cell,fuel-cells,
Title: Ceramic laser gelling
Abstract:
This paper presents a novel layered manufacturing method, ceramic laser gelling (CLG), for forming ceramic green part. This process involves mixing ceramic powder with an inorganic binder to form ceramic slurry. Owing to evaporation of water in a portion of slurry layer caused by laser exposure, the ceramic slurry is gelled locally to form 3D ceramic green part layer by layer. A series of experiments was conducted to obtain suitable laser and scanning parameters for layers of 140-440 ??m thickness and to obtain the smallest pave-able layer thickness of 80 ??m on a self-made experimental rapid prototyping machine. The feasibility of this process was demonstrated by manufacturing an intricate fan blade. In comparison with SLA and SLS, CLG has an advantage of using environmental compatible water-soluble inorganic binder. It needs lower laser power and has faster production rate than ceramic laser fusion (CLF). Futhermore, it can fabricate green parts composed of almost 100% pure silica. ?? 2004 Elsevier Ltd. All rights reserved.

Sources: Mendeley
Keywords: ceramic,
Title: In situ formation of metal-ceramic microstructures, including metal-ceramic composites, using reduction reactions
Abstract:
Partial reduction reactions were used to form a metallic phase either around or inside oxide grains in polycrystals in the FeMnO system. By suitable choice of oxide composition, partial pressure of oxygen, annealing time and temperature, it is possible to control the nucleation and growth of the metallic phase to produce a wide range of metal-ceramic microstructures. These include ceramic grains with a thin layer of metallic phase at their boundaries; ceramic grains with a thick layer of metallic phase at their boundaries -essentially, a metal-ceramic composite; and ceramic grains containing a fine distribution of metal particles-essentially, a ductile phase toughened ceramic. The presence of the metallic phase increases the fracture toughness of all the metal-ceramic microstructures with respect to that of the pure ceramic, with the largest increase observed for the metal-ceramic composite. It is believed that the principles established by studying the FeMnO system can be used on more practical mixed oxide systems to produce metal-ceramic microstructures, which in some cases are unique, and in particular, if the starting oxide material is in the form of plate- or rod-shaped crystals, to produce metal-ceramic composites in situ. ?? 1993.

Sources: Mendeley
Keywords: metal-ceramic,
Title: The effect of ceramic thickness and resin cement shades on the color matching of ceramic veneers in discolored teeth
Abstract:
AbstractThe objective of this study was to analyze the effects of ceramic material thickness and resin cement shade on the color matching of ceramic veneers at the gray tooth structures. Seventy-two artificial maxillary right central incisor teeth (C2 shade) were prepared according to veneer tooth preparation in practice. Ceramic materials (LT, A2 shade, IPS e.max Press) were selected to fabricate the 0.50- and 0.75-mm thick veneers at the body region. The ceramic veneer specimens were bonded to the artificial teeth by the 6 shades of resin cements (Variolink Veneer: shades of HV+3, LV-2, LV-3; and RelyXTM Veneer: shades of WO, TR, A3). A clinical spectrophotometer (Crystaleye, Olympus) was used to measure the color parameters. The color differences (ΔE values) of ceramic veneers and A2 shade tab (Vitapan Classical, Vita) and C*abvalues were calculated. The results of three-way ANOVA indicated that the ΔE values of ceramic veneer and A2 shade tab were significantly different in the thickness of ceramic materials, shades of resin cements, and measuring regions (p < 0.001). There were significant differences in 0.50-mm-thick ceramic veneers that exhibited higher ΔE values compared with veneers that were 0.75-mm thick. Tukey’s HSD test showed that the average ΔE values in body region were significantly smaller than that in cervical and incisal regions. The color matching of ceramic veneers was significantly influenced not only by the ceramic thickness and the resin cement shades but also the tooth regions.

Sources: Springer
Keywords: ceramic,cemented,
Title: Fracture in metal-ceramic composites
Abstract:
This research focuses on fracture mechanisms in metal-ceramic composites. Two co-continuous composites, Cu/Al 2O 3 and Al/Al 2O 3 and a metal-matrix composite Al/SiC were studied. It was found that each composite displayed a different fracture mechanism. The crack propagation inside the metal-matrix composite was dominated by the Al matrix characteristics. However, crack propagation inside both the co-continuous composites was influenced by their microstructure, thermal residual stresses and contiguity. This unique fracture characteristic of co-continuous composites has been elucidated in the present research by experimentation as well as computational modeling. In situ three-point bend tests were performed inside an environmental scanning electron microscope chamber to observe crack growth at the microstructural scale. Finite element modeling was performed by using global-local approach to simulate crack propagation and understand the effects of the microstructure and thermal residual stresses. It was shown that the crack propagated inside the metallic phase and at the interface for the Cu/Al 2O 3 composite due to a high level of tensile thermal stresses inside the metallic phase, as well as due to low contiguity of ceramic phase. However, in the case of Al/Al 2O 3 composite, the crack propagated inside the ceramic due to significantly smaller thermal stresses inside the metallic phase as well as higher contiguity of ceramic phase. ?? 2003 Elsevier Ltd. All rights reserved.

Sources: Mendeley
Keywords: metal-ceramic,
Title: Metal-Ceramic Composite Transducer, the "Moonie"
Abstract:
A new type of metal-ceramic composite transducer, the "moonie,' has been developed by sandwiching a poled lead zirconate titanate (PZT) ceramic between two specially designed metal end caps. Piezoelectric coefficients an order of magnitude larger than PZT itself are obtained. The metal-ceramic composites are being developed as fish finders, hydrophones, actuators, and transducers with integrated sensing and actuating capabilities. This paper describes the moonie principle, optimization of the moonie design using finite element analysis, and the performance of the device for several different applications.

Sources: Mendeley
Keywords: metal-ceramic,
Title: Advances in Ceramic Matrix Composites
Abstract:
Ceramic matrix composites (CMCs) are composite materials and technical ceramics. They consist of ceramic fibres embedded in a ceramic matrix, forming a ceramic fibre-reinforced material. Although their constituents are brittle, CMCs are tough due to the effective design of the fibreImatrix interface, which arrests and deflects cracks in the matrix, preventing failure of the fibrous reinforcement. CMCs are used in extreme conditions, making their tribological responses an important topic. This chapter considers tribological aspects for ceramics and CMCs, including friction, lubrication and wear. Future trends are discussed. The intention is to summarise the state of the art for CMCs and lay the foundation for their future use.

Sources: Mendeley
Keywords: ceramic,
Title: Metal-ceramic composites via in-situ methods
Abstract:
To overcome some of the inherent problems that are associated with conventional processes, several in situ methods have been developed to obtain metal/ceramic composite materials. In this paper recently developed processes have been reviewed with a greater emphasis on directed melt oxidation and nitridation. These methods offer microstructures with varying metal/ceramic combinations. In some processes, metal matrix composites dispersed with controlled quantities of ceramic phase(s) are possible whereas in other ceramic composites with isolated/interconnected metallic dispersions are obtained. They could be varied by controlling the processing variables, i.e. temperature, time, reactant phases and filler materials. The properties of in situ processed materials primarily depend on the matrix and the volume fraction of the constituent phase. The mechanical properties, toughening mechanisms and potential applications are briefly reviewed.

Sources: Mendeley
Keywords: metal-ceramic,
Title: Metal-Ceramic Composite Actuators
Abstract:
A new type of actuator composed of metal (brass) end caps and piezoelectric ceramics has been developed as a displacement transducer. Shallow cavities positioned between the metal caps and the central ceramic disk convert and amplify the radial displacement of the piezoelectric ceramic into a large axial motion of the metal end caps. Large d33 coefficients exceeding 2500 pC/N are obtained with the composite actuators. The behavior of the electrically induced strain with geometric variables, such as the thickness of the metal end caps, and with pressing force and driving frequency has been evaluated. Sizeable strains are obtained with both PZT (piezoelectric lead zirconate titanate) and PMN (electrostrictive lead magnesium niobate) ceramics.

Sources: Mendeley
Keywords: metal-ceramic,
Title: Assessment of an indirect metal ceramic repair system
Abstract:
PURPOSE: This study was designed to compare an alternative indirect treatment to repair fractured or chipped veneering metal ceramic using recently developed ultra-low-fusing ceramics.\n\nMATERIALS AND METHODS: One conventional feldspathic ceramic, Vita Omega, and three ultra-low-fusing ceramics (ULFC), Finesse, Duceram LFC, and Vision-low, were used. Forty ceramic specimens were prepared and divided into two groups. Group I (n = 20) was designed for bond strength testing. It comprised four subgroups (A, B, C, D): one Ceramic-resin (A) and three Ceramic-ULFC disc specimens of different diameters (B, C, D). Group II was composed of repaired ceramic discs using direct and indirect repair methods for biaxial testing. It was comprised of five subgroups: the fractured discs from subgroup A; Omega discs (n = 20) formed the repaired specimens of the four remaining subgroups: B, C, D, E. Data were presented as means and standard deviation (SD) values. One-way analysis of variance (ANOVA) was used for comparison between means. Tukey's post hoc test was used for pairwise comparison between the means when ANOVA test was significant. The significance level was set at p
Sources: Mendeley
Keywords: metal-ceramic,
Title: Metal Ceramic and All-Porcelain Restorations : Current Considerations
Abstract:
A review of the state of the art of metal ceramic and all-porcelain restorations is made. Metal ceramic systems are discussed relative to current fabrication techniques, porcelain margin techniques, marginal adaptation, and esthetics. The material properties, marginal adaptation, and esthetics of all-porcelain restorations are reviewed. Additionally, observations of metal ceramic and all-porcelain restorative systems currently in development are presented.

Sources: Mendeley
Keywords: metal-ceramic,
Title: An overview of ballistic testing methods of ceramic materials
Abstract:
An overview of impact testing techniques used to characterize or evaluate engineering structural ceramics for armor applications is presented. The required brevity of this paper restricts the detail to a listing of the commonly used testing methods, a categorization of ballistic techniques, and an extensive, but far from complete, listing of key references appears in alphabetical order, and we apologize for any omissions. Individual speakers have been invited to this conference, and they will provide greater detail of the testing techniques, the evaluation procedures, and of the armor system design methodologies. In addition, the presentation provides typical testing configurations, typical results, and test objectives. A similar presentation and companion paper on ceramic armors by Gooch also provides information on how this data is typically used to construct armor systems. A categorization of the testing techniques is provided to classify testing methods into those that attempt to characterize a particular ceramic material's properties, those that attempt to evaluate and rank a ceramic material's performance for armor applications, and those techniques that actually evaluate the ceramic in configurations more representative of armor systems. Finally, we discuss some of the difficulties in utilizing these testing techniques for ranking ceramic materials, particularly due to the fairly recent discovery of dwell, which has had profound effects on data evaluation. Dwell describes the behavior of an eroding penetrator prior to penetration and in certain circumstances a penetrator can completely erode on the ceramic surface without penetration.

Sources: Mendeley
Keywords: ceramic,
Title: Metal-ceramic bond: how to improve?
Abstract:
Metal-ceramic restorations include the positive features of metal (strength, durability and stability) and ceramics (esthetics). The strong bond on the metal-ceramic interface is the basic prerequisite for the durability of the metal-ceramic restoration. The heating of metal construction results in the diffusion of certain atoms (tracers) on the surface. There they react with atmospheric oxygen creating in oxides which remain on the cast surface, because the reversible diffusion is prevented. Atoms of silica in ceramic are bound with these oxides as a result of which a metal-tracer-ceramic compound is formed and a chemical bond is realised. In addition to forming an oxide layer, the oxidation heat treatment (OHT) is applied for all alloys in order to remove the entrapped gas and eliminate surface contaminants. Surface metal preparation before porcelain application may also affect the bond strength of metal and ceramics. Roughened surface by sandblasting enables mechanical interlocking and an increased surface for bonding metal and ceramics. Applying a bonding agent may improve the quality of the bond of certain metal-ceramic restorations. Due to the continued oxidation of titanium and creation of a non-adherent oxide layer, the bond strength between titanium and ceramics is weak, which is attempted to be resolved by firing in an argon atmosphere.

Sources: Mendeley
Keywords: metal-ceramic,
Title: Evaluation of marginal adaptation of all-ceramic crowns and metal ceramic crowns
Abstract:
The marginal adaptation of Renaissance crowns is compared with that of the widely used metal ceramic and Dicor crowns. This investigation shows that Dicor and metal ceramic crowns fit better than Renaissance crowns. Clinical implications of all three restorations are discussed. ?? 1991.

Sources: Mendeley
Keywords: metal-ceramic,
Title: Colloidal Forming of Metal/Ceramic Composites
Abstract:
Metal/Ceramic composites have very attractive properties as either structural or electronic materials. For certain applications, complex microstructures and shapes are required. Colloidal processing of ceramics has proved to provide better properties and allows to obtain near net complex shaped parts. However colloidal processing has not received a similar attention in powder metallurgy. This work deals with the colloidal approach to the forming of metallic and metal/ceramic composites in an aqueous medium. Rheological behaviour of concentrated pure nickel, nickel/alumina and nickel/zirconia suspensions is studied and optimized for obtaining fiat surfaces or near net shaped parts by tape casting and gel casting respectively. In each case the influence of the processing additives (acrylic binders for tape casting and carrageenans for gel casting) on the rheological behaviour of the slurries is determined. Pure nickel and nickel/ceramic composites with different compositions have been prepared. Static and dynamic sintering studies were performed at different conditions in order to control the porosity and microstructure of the final bodies, which were characterized by optical microscopy.

Sources: Mendeley
Keywords: metal-ceramic,
Title: Novel Metal-Ceramic Joining for Planar SOFCs
Abstract:
A novel method of ceramic-to-metal joining, referred to as reactive air brazing, was investigated as a potential method of sealing planar solid oxide fuel cells (SOFCs). In the present study, yttria stabilized zirconia (YSZ) and Fecralloy were selected as subject materials to simulate the cell-to-frame seal in planar SOFC. YSZ plates were joined with Fecralloy foils, using a range of CuO-Ag and CuO-Ag-TiO2 braze compositions. Metallographic analysis revealed that a majority of the CuO in the braze preferentially migrates to the braze/Fecralloy interface, indicating a stronger affinity and interaction between the CuO and the alumina scale that had formed on the Fecralloy than with the YSZ substrate. The addition of TiO2 to the braze had no significant effect on the microstructure or mechanical properties of the YSZ/Fecralloy joints, unlike what had been observed previously in YSZ/YSZ joining. Four-point bend tests indicated that joint strength improves with increasing CuO content up to 8 mol % CuO, the maximum concentration of copper oxide tested, likely due to the concomitant improvement in braze wettability. A maximum bend strength of 101 MPa was achieved using the 8 mol % CuO braze composition, demonstrating the feasibility of this joining technique for sealing planar SOFCs. © 2005 The Electrochemical Society. All rights reserved.

Sources: Mendeley
Keywords: metal-ceramic,
Title: Residual stresses in metal-ceramic crowns
Abstract:
Residual stresses in metal-ceramic crowns were examined in three different ways. First, a mathematical formula was used to calculate the stresses in the cervical part of a crown. Second, plastic models was used where the strains were measured with strains-gauges. Third, real crowns were used and strain gauges were attached on them. The results indicated that compressive stresses appeared in the porcelain-metal interface. Compressive stresses were also found on the surfaces of the crowns and tensile stresses perpendicular to the interface.

Sources: Mendeley
Keywords: metal-ceramic,
Title: EVALUATING CERAMIC-CERAMIC BOND STRENGTHS USING METAL-CERAMIC CHARACTERIZATION TECHNIQUES
Abstract:
Objectives: To evaluate the applicability of the ISO 9693 Schwickerath bond strength test, developed for metal ceramic bond strength evaluation, in the case of ceramic-ceramic bonds with transformation toughened zirconia ceramics. Methods: To date, metal ceramic bond strength tests have not been applicable to the evaluation of ceramic bond strength, due to the high stiffness and brittle nature of ceramic core materials. The introduction of transformation toughened zirconia ceramics with a relatively low elastic modulus (200 GPa, comparable to stainless steel) offers an opportunity to evaluate the applicability of this test. Samples of transformation toughened zirconia (Cercon, Dentsply Prosthetics) were prepared with three commercially available veneering porcelain materials - Ceramco PFZ (Dentsply Prosthetics), Cercon Ceram S (Dentsply DeguDent) and Cerabien CZR (Noritake Dental). The ISO 9693 procedure was then used to test the bond strengths in flexure. Results: Bond strengths comparable to those for porcelain fused to metal (PFM, ~ 25 MPa) were achieved with the ceramic-ceramic systems. However significantly different behavior was observed due to the higher elastic modulus, even compared to stiff nonprecious alloys. The effect of surface preparation of the ceramics was significant. Conclusions: Though initial results are encouraging, more refinement related to elastic modulus behavior may be necessary before the ISO 9693 test is applicable to zirconia ceramic systems.

Sources: Mendeley
Keywords: metal-ceramic,
Title: The versatile and esthetic metal-ceramic crown
Abstract:
The predictability, many advantages and remarkable adaptability of metal-ceramic crowns account for their frequent use. Metal-ceramic crowns will continue to be one of the most widely used dental restorations.

Sources: Mendeley
Keywords: metal-ceramic,