Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 11
    Electronic Resource
    Electronic Resource
    Effect of the Amount of Additives and Post-Heat Treatment on the Microstructure and Mechanical Properties of Yttrium–α-Sialon Ceramics (2003)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 86 (2003), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The yttrium–sialon ceramics with the composition of Y0.333Si10Al2ON15 and an excess addition of Y2O3 (2 or 5 wt%) were fabricated by hot isostatic press (HIP) sintering at 1800°C for 1 h. The resulting materials were subsequently heat-treated in the temperature range 1300–1900°C to investigate its effect on the α→β-sialon phase transformation, the morphology of α-sialon grains, and mechanical properties. The results show that α-sialons stabilized by yttrium have high thermal stability. An adjustment of the α-sialon phase composition is the dominating reaction in the investigated Y–α-sialon ceramics during low-temperature annealing. Incorporation of excess Y2O3 could effectively promote the formation of elongated α-sialon grains during post-heat-treating at relatively higher temperature (1700° and 1900°C) and hence resulted in a high fracture toughness (KIC= 6.3 MPa·m1/2) via grain debonding and pullout effects. Although the addition of 5 wt% Y2O3 could promote the growth of elongated α grains with a higher aspect ratio, the higher liquid-phase content increased the interfacial bonding strength and therefore hindered interface debonding and crack deflection. The heat treatment at 1500°C significantly changed the morphology of α-sialon grains from elongated to equiaxed and hence decreased its toughness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03621.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    Contribution from Ferroelastic Domain Switching Detected Using X-ray Diffraction to R-Curves in Lead Zirconate Titanate Ceramics (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In Pb(Zr,Ti)O3 ceramics, which are characterized by different magnitudes of coercive tensile stress, the ferroelastic domain switching induced during crack growth was measured using X-ray diffraction, and was compared with the R-curve behavior. The following correlation was established: material with smaller coercive stress has a larger amount of domain switching, and a higher toughness increment in the R-curve. The half-width of the process zone was determined for one of the four studied compositions from the spatial distribution of domain switching measured using X-ray diffraction from synchrotron source. Its value, 60–80 μm, was in good agreement with the estimate from fracture mechanics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb01116.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    Electronic Resource
    Electronic Resource
    Correlation between Surface Texture and Chemical Composition in Undoped, Hard, and Soft Piezoelectric PZT Ceramics (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The electrical and mechanical properties of piezoelectric lead zirconate titanate (PZT) ceramics are strongly influenced by domain-wall motion, which can be tailored via the substitution of ions within the perovskite structure. Different domain mobilities are achieved by lead and/or oxygen vacancies, according to the valency and ionic radius of the dopants. To quantify the surface near domain mobility, hard (silver-doped), soft (lanthanum-doped), and undoped PZT ceramics have been prepared. An applied mechanical stress after sintering causes texturing near the surface, because of the ferroelastic behavior of the 90° domains. The texture is quantified via X-ray diffractometry (XRD) analysis of the tetragonal FT(002)- and FT(200)-peak intensities, using least-squares refinement with Gaussian profile functions. The samples are subsequently annealed to remove the surface texture and again characterized via XRD measurements. However, annealed samples still reveal a preferred domain orientation that can be removed only by a second annealing of the pulverized samples. A comparison of the tetragonal additive systems clearly reveals the greatest domain mobility for lanthanum-doped PZT ceramics, whereas the silver-doped and undoped samples have similar ferroelastic behavior. Furthermore, the surface texture of all the compositions is dependent on the applied mechanical stress and cannot be removed completely by heat treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02397.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    Preparation of β-Silicon Nitride Seeds for Self-Reinforced Silicon Nitride Ceramics (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper describes a method for the preparation of silicon nitride (Si3N4) seeds that have an average aspect ratio of ∼4. The seeds are prepared via heat treatment of a powder mixture that contains alpha-phase-rich Si3N4 and 0.5 wt% Y2O3 at a temperature of 1800°C and a nitrogen pressure of 35 kPa. A Y-Si-O-N liquid forms during heat treatment; this liquid acts as a flux for seed precipitation. During cooling, the Y-Si-O-N liquid transforms to a thin intergranular grain-boundary phase and causes strong agglomeration of the seeds. The seeds can be isolated by dissolving the grain-boundary phase in hot phosphoric acid, followed by an ultrasonic treatment (for 30 min). The method can be used to produce large quantities of seeds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb01969.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Thermodynamic Analysis of Grain Aspect Ratio in Fibrous Microstructures of Silicon Nitride (1997)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Needlelike, free-floating ß-crystals of silicon nitride, precipitated within a supersaturated Y-Si-Al-O-N oxynitride glass, apparently approach an equilibrium value of the aspect ratio. An expression that relates this aspect ratio to the anisotropy in the interfacial energies of the longitudinal and transverse interfaces of the crystal is derived. The prediction agrees reasonably well with theoretical estimates of the interfacial energies. Kinetic and stearic effects that often lead to nonequilibrium values of the aspect ratio are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03262.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    Long-Term Behavior and Application Limits of Plasma-Sprayed Zirconia Thermal Barrier Coatings (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Investigations of changes in phase composition, mechanical properties, and microstructure of ZrO2-based plasma-sprayed thermal barrier coatings (TBCs) with 8 mol% CeO2, 19.5 mol% CeO2/1.5 mol% Y2O3, 35 mol% CeO2, and 4.5 mol% Y2O3 after long-term heat treatments at typical operation temperatures (1000°–1400°C) are presented. Experimental studies include X-ray diffractometry, mechanical testing, and scanning electron microscopy. Thermal cycling experiments also have been performed. TBCs with 8 mol% CeO2 contain mainly the tetragonal equilibrium phase and, therefore, show rapid failure because of the high amount of tetragonal → monoclinic phase transformation, even after relatively short heat treatments (1250°C/1 h). In the case of the other systems that consist mainly of the tetragonal or cubic nonequilibrium phases, TBCs with 19.5 mol% CeO2/1.5 mol% Y2O3 or 35 mol% CeO2 reveal a smaller amount of monoclinic phase after long-term heat treatments (1250°C/1000 h) compared with TBCs containing 4.5 mol% Y2O3. TBCs containing 35 mol% CeO2 show a higher degree of sintering than the TBCs with 19.5 mol% CeO2/1.5 mol% Y2O3 and, therefore, a greater increase of the elastic modulus. Among the systems investigated, TBCs containing 4.5 mol% Y2O3 exhibit the highest resistance to failure in thermal-cycling experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00833.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    Electronic Resource
    Electronic Resource
    Preparation of Multiple-Cation alpha-SiAlON Ceramics Containing Lanthanum (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Until recently, it was accepted that Ce3+ cations, with an ionic radius (r) of 1.03 Å, were too large to form an α-SiAlON structure. However, more-recent studies have shown that cerium cations can be incorporated into α-SiAlON via quenching at a rate of 600°C/min, after sintering at 1800°C. Thus far, no α-SiAlON formation has been observed for La3+ cations with r= 1.06 Å. In the present work, the possibility of having the La3+ species as a dopant cation in α-SiAlON has been investigated by using La2O3 alone or in equimolar mixtures with CaO or Yb2O3. The resulting materials have been heat-treated at a temperature of 1450°C for up to 720 h to devitrify the grain-boundary glass into crystalline phases and also to observe the α→β SiAlON transformation. X-ray diffractometry on samples that were densified with single cations revealed that the La3+ cation alone does not form an α-SiAlON; rather, it forms the N-phase (La3Si8O4N11) with a ß-SiAlON phase. In the case of multiple cations, α-SiAlON was observed only as a matrix phase. Energy-dispersive X-ray measurements have proven that La3+ cations can be accommodated into the α-SiAlON structure and this structure also does not transform to β-SiAlON at lower temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb01750.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 18
    Electronic Resource
    Electronic Resource
    Sintering Model for Mixed-Oxide-Derived Lead Zirconate Titanate Ceramics (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The properties of lead zirconate titanate (PZT) ceramics are determined by the microstructure and chemical homogeneity of Zr, Ti, and dopants within the grains as well as the presence of secondary grain boundary phases. Stoichiometric 53/47 PZT and compositions with 3 mol% PbO excess were prepared by the mixed-oxide process, and were densified by pressureless sintering in oxygen. The influence of PbO content and different La concentrations on the densification behavior was analyzed by dilatometric measurements. Quantitative image analysis showed a different relative density and grain size dependence for samples containing 〉0.5 mol% additives compared to samples with 〈0.5 mol% La. On the basis of a model experiment and by using different analytical methods (microprobe analysis, HRTEM, STEM, and Auger spectroscopy) three types of inhomogeneities could be detected in conventionally prepared PZT ceramics: the existence of Ti and La enrichment in the core of PZT grains, and PbO-rich secondary phases in triple junctions as well as in grain boundary films. The results of the microstructural characterization and the analysis of the densification behavior were finally combined to deduce a sintering model based on a Pb-vacancy concentration gradient within the PZT grains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02768.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 19
    Electronic Resource
    Electronic Resource
    Transient Growth Bands in Silicon Nitride Cooled in Rare-Earth-Based Glass (1997)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Silicon nitride (Si3N4) particles embedded in various R-SiAl-O-N glasses (R = La, Nd, Gd, Yb) have been systematically studied by high-resolution transmission electron microscopy and by analytical electron microscopy. The particles typically show an internal growth band, which is attributed to the enhanced growth of the particles in the supersaturated silicate liquid during cooling and reheating. The electron energy-loss spectroscopy and energy-dispersive X-ray spectroscopy analysis reveal that the growth band typically contains lanthanide elements. This trapping, especially of the lighter lanthanide elements, within the lattice of the β-SiAlON is obviously beyond the general expectation that the lighter lanthanide ions hardly form solid solutions with either α- or β-Si3N4. This ultimately provides some clues regarding the mobility of the lanthanide ions in the liquids and also revives interest in the general question of the possible effect of a cooling stage on the structures and compositions of the intergranular film and of the grain/glass interface in the Si3N4-based polycrystalline ceramics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb02997.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 20
    Electronic Resource
    Electronic Resource
    Influence of the Rare-Earth Element on the Mechanical Properties of RE–Mg-Bearing Silicon Nitride (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Silicon nitride bulk ceramics with varying compositions of the grain boundary phase but similar grain sizes were developed, which allows to analyze the influence of the grain boundary chemistry on mechanical properties. Micrographs of the crack path reveal a much weaker interface when the rare-earth element in the grain boundary phase changes from a small to a large rare-earth cation (RE3+). Room temperature measurements of toughness and bending strength show that weaker grain boundaries result in a higher toughness, but in a decreased strength of the bulk material. This investigation demonstrates that the mechanical behavior of silicon nitride can be readily tuned by chemical composition changes of the grain boundary phase, but that a compromise between toughness and strength has to be found when designing the material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00421.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...