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  • 1
    Electronic Resource
    Electronic Resource
    Microwave-Assisted Synthesis and Sintering of NZP Compounds (2004)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 87 (2004), 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: We have identified the high microwave susceptibility of the sodium di-hydrogen phosphate monohydrate (NHPM), NH2PO4·H2O. This acid phosphate of sodium can be heated to 〉900°C when exposed to 2.45 GHz microwave radiation. Using NHPM and microwave energy, a novel single-step synthesis of many important crystalline NZP compounds has been accomplished in a very short time. Interestingly, the combination of microwaves and nonstoichiometric oxide precursors for the preparation of NZP materials is found to reduce the reaction temperatures and enhance the reaction kinetics further. The microwave synthesis method is found to be simple and fast, minimizing the loss of volatile chemical species from the reaction. A microwave-assisted procedure for the rapid sintering of NZP compounds has also been demonstrated. Densification (〉97%) has been achieved in 〈30 min at sintering temperature much lower than normally required in conventional processes. Finer microstructure and better densification are the main advantages of the microwave sintering in this study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2004.00834.x
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  • 2
    Electronic Resource
    Electronic Resource
    Microwave Sintering of Alumina at 2.45 GHz (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 sintering kinetics and microstructural evolution of alumina tubes (∼17 mm length, ∼9 mm inner diameter, and ∼11 mm outer diameter) were studied by conventional and microwave heating at 2.45 GHz. Temperature during microwave heating was measured with an infrared pyrometer and was calibrated to ±10°C. With no hold at sintering temperature, microwave-sintered samples reached 95% density at 1350°C versus 1600°C for conventionally heated samples. The activation energy for microwave sintering was 85 ± 10 kJ/mol, whereas the activation energy for conventionally sintered samples was 520 ± 14 kJ/mol. Despite the difference in temperature, grains grew from ∼1.0 μm at 86% density to ∼2.6 μm at 98% density for both conventionally sintered and microwave-sintered samples. The grain size/density trajectory was independent of the heating source. It is concluded that the enhanced densification with microwave heating is not a consequence of fast-firing and therefore is not a result in the change in the relative rates of surface and grain boundary diffusion in the presence of microwave energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2003.tb03467.x
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  • 3
    Electronic Resource
    Electronic Resource
    Preparation of Titanium Nitride: Microwave-Induced Carbothermal Reaction of Titanium Dioxide (2002)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), 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: Carbothermal reduction and nitridation of TiO2 was performed in a 2 kW, 2.45 GHz microwave furnace. Carbon, generally added for the removal of oxygen from TiO2 lattice also served as the low-temperature susceptor in these experiments. At temperatures 〉1200°C, the mixtures started reacting vigorously (self-burn), which was never observed with the respective pure compounds. In the self-burning state, the minimum duration required for complete titanium nitride transformation was ∼20 min with stoichiometric amounts of carbon. With excess C, the transformation duration dropped to just 1 min. CO removal and subsequent Ni fixation occur more directly in microwave-induced reactions than in conventional nitridation procedures. Intermediate formation of successive Magneli phases (Ti2nO2n−1) was not found in the microwave-induced reactions. The combination of microwave processing and combustion makes this route of economical interest.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00051.x
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  • 4
    Electronic Resource
    Electronic Resource
    Microwave Effects in Lead Zirconium Titanate Synthesis: Enhanced Kinetics and Changed Mechanisms (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: A novel, simple, and fast solid-state procedure has been demonstrated for the synthesis of Pb(Zr,Ti)O3 (PZT), using microwave radiation. The process consists of starting with the respective oxides mixed in the required proportions and exposing the charge to the microwaves. By making one or more of the constituent oxides slightly nonstoichiometric, enormous enhancement in reaction rates has been achieved, and single-phase PZT can be synthesized at temperatures as low as 600°C. Moreover, it has been shown that the combined use of nonstoichiometric precursors and microwave irradiation leads to different reaction pathways for the formation of PZT. Further, the microwave method diminishes PbO loss.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00816.x
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis of [NZP]-Structure-Type Materials by the Combustion Reaction Method (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: Ca0.5Sr0.5Zr4P6O24 and Ba1.25Zr4P5.5Si0.5O24 compositions, which belong to the [NZP] family of low-thermal-expansion materials, were synthesized by the combustion reaction method using urea as a fuel and NH4NO3 as an oxidizer. The combustion method is a highly exothermic reaction often referred to as self-propagating high-temperature synthesis. The raw materials used were metal zirconates and fine ZrO2 powders. An earlier-described combustion method using metal nitrates, zirconium oxynitrate, and ammonium dihydrophosphate to synthesize [NZP] compounds was modified in the present study by replacing these costly raw materials with less-expensive oxides. The reactivity of different combinations of raw materials also is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02541.x
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  • 6
    Electronic Resource
    Electronic Resource
    Development of Titanium Coatings on Particulate Diamond (2000)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), 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 performance of many wear-resistant materials can be improved further by incorporating diamond into the structure. Diamond that has been coated with titanium is known to adhere well to the matrix particles and also prevents reaction with H2, which often is used in the sintering atmosphere. Two coating methods of coating diamond with titanium have been explored in this study: a sputtering method and a procedure that involves heating the diamond in a mixture of salt and titanium. The latter, which uses a salt mix of NaCl, KCl, and CaCl2 and metallic titanium particles 3 μm in size, heated at a temperature of 750°C in an argon atmosphere, is determined to be the best method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01524.x
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis and Thermal Expansion Properties of the Ca(1+x)/2Sr(1+x)/2Zr4P6−2xSi2xO24 System (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: Ca(1+x)/2Sr(1+x)/2Zr4P6−2xSi2xO24(x≤ 0.37) compositions, which belong to the [NZP] family of low-thermal-expansion materials, were synthesized using the solid-state reaction method. The lattice thermal expansion of members of this system was determined up to 1000°C by high-temperature X-ray diffractometry. The bulk thermal expansion and the microcracking during cooling also were investigated. These properties depended on the composition, on the synthesis method, and on the sintering conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02428.x
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  • 8
    Electronic Resource
    Electronic Resource
    Decrystallizing Solid Crystalline Titania, Without Melting, Using Microwave Magnetic Fields (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: TiO2—a prototype ceramic—was decrystallized in a 2.45 GHz AC magnetic field in a single mode TE103 applicator. The titania powders were synthesized by a sol–gel process and pressed into circular pellets. The pellets were very slightly reduced at 1273 K in a reducing atmosphere. The reduced pellets were introduced into the single mode microwave cavity and placed at the magnetic field maximum node and exposed for 10–30 s in a forming gas atmosphere. The reacted samples were then characterized by XRD, SEM, Raman, and TEM. The data presented in this note demonstrate that a very short treatment in the AC magnetic field at 2.45 GHz can transform rutile structure oxides to a noncrystalline state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00261.x
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis and thermal expansion of Na3−x Ca x/2M2P3O12 (M = Fe, Cr) (1986)
    Springer
    Journal of materials science 5 (1986), S. 139-140 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01672025
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis of high-surface-area complex zirconium phosphates via mechanochemical activation route (1999)
    Springer
    Materials research innovations 2 (1999), S. 328-337 
    Details
    ISSN: 1433-075X
    Keywords: Key words Framework complex zirconium phosphates ; Metastable cubic phase ; Mechanochemical activation ; Hydrothermal synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  High-power ball mill activation of the mixture of hydrated zirconium and lanthanum salts (oxonitrates, oxochlorides) with ammonium phosphate followed by hydrothermal treatment at temperatures not exceeding 200°C and a nearly neutral pH was found to yield crystalline dispersed phase of a cubic NH4Zr2(PO4)3 type along with admixtures of disordered orthorhombic compounds of a zirconium orthophosphate type. In the same conditions and at the same Zr/P ratio, hydrothermal treatment of gels obtained by reacting mixed zirconium and lanthanum nitrates solutions with ammonium phosphates yields no crystalline products, and only treatment in acid media generates a phase of the α-ZrPO4(OH) type coexisting with the NH4Zr2(PO4)3 phase if polyethylene oxide is present. X-ray powder diffraction, transmission electron microscopy, 31MAS-NMR, FTIRS and thermal analysis were applied to elucidate factors affecting crystallization of complex zirconium phosphates in the hydrothermal conditions. The most essential factor appears to be generation of some nuclei of zirconium phosphates under high pressures developed in the course of mixed solids mechanical activation. These nuclei are embedded into matrix of such well-crystallized solid products as ammonium nitrate or chloride. Hence, metastable cubic or orthorhombic structure of the phases obtained via mechanical activation route can be assigned to the nuclei-matrix orientation relationship. Due to easily scaled-up synthesis procedure, these results appear to be very promising for manufacturing of dispersed framework zirconium phosphates as acid catalysts or fast proton conductors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100190050109
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