Mechanical properties of nanocrystalline materials

In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

저작근 근전도에 관한 정상교합자와 ii급 부정교합자의 비교 연구

The elastic properties, elastic models and elastic perspectives of metallic glasses

5.4. Miscellaneous Examples 2295 5.4.1. Couplings with Other Catalysts 2295 5.4.2. The Use of Other Boron Reagents 2295 5.4.3. Related Coupling Reactions 2296 5.5. Summary 2297 6. Sonogashira Coupling 2297 6.1. Couplings with Pd Particles 2297 6.2. Studies with Immobilized Palladium Complexes 2299 6.3. Miscellaneous Examples 2301 6.4. Carbonylative Sonogashira Couplings 2302 6.5. Summary 2302 7. Stille Couplings 2302 7.1. Stille Coupling 2302 7.2. Carbonylative Stille Coupling 2304 7.3. Summary 2304 8. Miscellaneous Cross-Coupling Reactions 2304 9. Allylations 2305 9.1. Tsuji-Trost Allylation 2305 9.2. Allylation of Boron Reagents 2306 10. Homocouplings 2307 10.1. Summary 2308 11. C-C Couplings in Continuous Systems 2308 12. Conclusions and Outlook 2311 Author Information 2314 Biography 2314 References 2314

Efficient, selective, and recyclable palladium catalysts in carbon-carbon coupling reactions.

α-Al2O3 nanopowders with mean particle sizes of 10, 15, 48, and 80 nm synthesized by the doped α-Al2O3 seed polyacrylamide gel method were used to sinter bulk Al2O3 nanoceramics. The relative density of the Al2O3 nanoceramics increases with increasing compaction pressure on the green compacts and decreasing mean particle size of the starting α-Al2O3 nanopowders. The densification and fast grain growth of the Al2O3 nanoceramics occur in different temperature ranges. The Al2O3 nanoceramics with an average grain size of 70 nm and a relative density of 95% were obtained by a two-step sintering method. The densification and the suppression of the grain growth are achieved by exploiting the difference in kinetics between grain-boundary diffusion and grain-boundary migration. The densification was realized by the slower grain-boundary diffusion without promoting grain growth in second-step sintering.

Densification and Grain Growth of Al2O3 Nanoceramics During Pressureless Sintering

Titania–nickel nanocomposite coatings consisting of a nanocrystalline nickel matrix (average grain size: 10 nm) and nanometer-sized titania particles dispersed in the nickel matrix on copper substrates were prepared by simultaneous electrodeposition of nickel and titania from a nickel electrolyte in which the titania particles were suspended. The nanocomposite coatings were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Vickers microhardness tests, and corrosion tests. The results indicate that the concentration of the titania particles in electrolytes affects the content of titania in the composite coatings. Vickers microhardness and corrosion resistance of the nanocomposite coatings increase with increasing content or decreasing grain size of titania particles in the composite coatings. The nanocomposite coatings containing anatase nanoparticles have a higher hardness and lower corrosion rate compared with those containing rutile microparticles.

Mechanical and corrosion-resistance performance of electrodeposited titania–nickel nanocomposite coatings

Influences of pH value on the microstructure and phase transformation of aluminum hydroxide

Crystal structure, electronic structure, and magnetic properties of bismuth-strontium ferrites

The Co nanoplatelets of 120 nm in diameter and 10 nm in thickness exist in both fcc and hcp crystal structures at room temperature. The saturation magnetization of the Co nanoplatelets is lower than that of the bulk Co because of the existence of the oxide layer. The coercivity is higher than that of the bulk Co. The equilibrium magnetic configuration of a single Co nanoplatelet without external magnetic field is a vortex structure, regardless of hcp or fee crystal structure. The Co nanoplatelets were coated by MnO2. The microwave properties of the MnO2-coated Co nanoplatelet composites and paraffin wax mixtures were measured in the 0.1-18 GHz frequency range. The complex permeability of the sample shows two broad resonance peaks and the complex permittivity of the sample shows one resonance peak in the frequency range of 0.1-18 GHz. The numerical simulations show that the reflection loss values of the MnO2-coated Co nanoplatelet composites and paraffin wax mixtures are less than - 12 dB in the 2-11.5 GHz frequency range. (C) 2007 Elsevier B.V. All rights reserved.

Jiangong Li

Papers

Densification and Grain Growth of Al2O3 Nanoceramics During Pressureless Sintering

Mechanical and corrosion-resistance performance of electrodeposited titania–nickel nanocomposite coatings

Influences of pH value on the microstructure and phase transformation of aluminum hydroxide

Crystal structure, electronic structure, and magnetic properties of bismuth-strontium ferrites

Magnetic and microwave properties of cobalt nanoplatelets