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

Nanodevices don't use much energy, and if the little they do need can be scavenged from vibrations associated with foot steps, heart beats, noises and air flow, a whole range of applications in personal electronics, sensing and defence technologies opens up. Energy gathering of that type requires a technology that works at low frequency range (below 10 Hz), ideally based on soft, flexible materials. A group working at Georgia Institute of Technology has now come up with a system that converts low-frequency vibration/friction energy into electricity using piezoelectric zinc oxide nanowires grown radially around textile fibres. By entangling two fibres and brushing their associated nanowires together, mechanical energy is converted into electricity via a coupled piezoelectric-semiconductor process. This work shows a potential method for creating fabrics which scavenge energy from light winds and body movement. A self-powering nanosystem that harvests its operating energy from the environment is an attractive proposition for sensing, personal electronics and defence technologies1. This is in principle feasible for nanodevices owing to their extremely low power consumption2,3,4,5. Solar, thermal and mechanical (wind, friction, body movement) energies are common and may be scavenged from the environment, but the type of energy source to be chosen has to be decided on the basis of specific applications. Military sensing/surveillance node placement, for example, may involve difficult-to-reach locations, may need to be hidden, and may be in environments that are dusty, rainy, dark and/or in deep forest. In a moving vehicle or aeroplane, harvesting energy from a rotating tyre or wind blowing on the body is a possible choice to power wireless devices implanted in the surface of the vehicle. Nanowire nanogenerators built on hard substrates were demonstrated for harvesting local mechanical energy produced by high-frequency ultrasonic waves6,7. To harvest the energy from vibration or disturbance originating from footsteps, heartbeats, ambient noise and air flow, it is important to explore innovative technologies that work at low frequencies (such as <10 Hz) and that are based on flexible soft materials. Here we present a simple, low-cost approach that converts low-frequency vibration/friction energy into electricity using piezoelectric zinc oxide nanowires grown radially around textile fibres. By entangling two fibres and brushing the nanowires rooted on them with respect to each other, mechanical energy is converted into electricity owing to a coupled piezoelectric–semiconductor process8,9. This work establishes a methodology for scavenging light-wind energy and body-movement energy using fabrics.

http://www.nanoscience.gatech.edu/zlwang/paper/2008/08_nat_1.pdf

Microfibre–nanowire hybrid structure for energy scavenging

We report a size dependence of Young's modulus in [0001] oriented ZnO nanowires (NWs) with diameters ranging from 17 to 550 nm for the first time. The measured modulus for NWs with diameters smaller than about 120 nm is increasing dramatically with the decreasing diameters, and is significantly higher than that of the larger ones whose modulus tends to that of bulk ZnO. A core-shell composite NW model in terms of the surface stiffening effect correlated with significant bond length contractions occurred near the {1010} free surfaces (which extend several layers deep into the bulk and fade off slowly) is proposed to explore the origin of the size dependence, and present experimental result is well explained. Furthermore, it is possible to estimate the size-related elastic properties of GaN nanotubes and relative nanostructures by using this model.

Size dependence of Young's modulus in ZnO nanowires.

I. Introduction A FUNCTIONAL relationship between cell growth and the initiation and progression of events associated with differentiation has been a fundamental question challenging developmental biologists for more than a century. In the case of bone, as observed with other cells and tissue, the relationship of growth and differentiation must be maintained and stringently regulated, both during development and throughout the life of the organism, to support tissue remodeling. For many years, bone was defined anatomically and examined largely in a descriptive manner by ultrastructural analysis and by biochemical and histochemical methods. These studies provided the basis for our understanding of bone tissue organization and orchestration of the progressive recruitment, proliferation, and differentiation of the various cellular components of bone tissue. Now, complemented by an increased knowledge of molecular mechanisms that are associated with and regulate expression of genes encoding phenotypic compone...

Molecular mechanism mediating proliferation, defferentiation interralationships during progressie development of the osteoblast phenotype

Giant and isotropic magnetoresistance as huge as −53% was observed in magnetic manganese oxide La0.72Ca0.25MnOz films with an intrinsic antiferromagnetic spin structure. We ascribe this magnetoresistance to spin‐dependent electron scattering due to spin canting of the manganese oxide.

31p-S-4 Giant Magnetoresistance in Magnetic Manganese Oxide with Intrinsic Antiferromagnetic Spin Structure

A simple steam-assisted solid phase synthesis method was developed for synthesis of boehmite nanowires in the presence of TEAOH surfactant The boehmite nanowires had uniform diameters (12-16 nm) and length up to 1-2 microm The morphology of the nanostructured wires was well preserved after being converted to pure gamma-Al2O3 by thermal treatment at 600 degrees C for 5 h The nanowires of Al2O3 exhibited excellent thermal stability by retarding the phase transformation and maintaining the wires-like nanostructure after being aged up to 1300 degrees C by preventing sintering between particles at high temperatures The surface areas of Al2O3 nanowires could be maintained as high as 68 m2/g at 1300 degrees C while the surface areas of Al2O3 micropowder shrank to 089 m2/g after same thermal treatment Both in-situ XRD and 27Al NMR results indicated that the crystal structure of gamma-Al2O3 nanowires was not transformed to alpha-Al2O3 at 1300 degrees C whereas micropowder Al2O3 was fully converted to alpha-Al2O3 at 1100 degrees C

Solid-phase low temperature steam-assisted synthesis of thermal stable alumina nanowires.

Dissolution resistance and adhesion strength are two main concerns for long-term stability of surface coated metal implants. In this study, fluorine ions are incorporated into magnesium-containing hydroxyapatite coatings (MgFyHA) via sol–gel method to improve the long-term stability of the implants. Surface and interface are studied in terms of phases, depth profiling and chemical bonds by grazing incidence X-ray diffraction, glow discharge optical emission spectroscopy and X-ray photoelectron spectroscopy. The long-term stability is evaluated by dissolution and pull-off test. The results show that fluorine promotes the incorporation of magnesium in HA lattice. The elemental interdiffusion and chemical bonding take place at the coating/substrate interface. Both the dissolution resistance and the adhesion strength are enhanced by fluorine incorporation, thus the long-term stability of the implant is improved.

Effect of fluorine incorporation on long-term stability of magnesium-containing hydroxyapatite coatings

Nickel induced lateral crystallization behavior of amorphous silicon films

Over the past several decades, producing materials from fossil-based sources has become a serious problem because such action continues to contribute to global warming and contamination of the ecosystem. Thus, it is highly desirable to address this issue through producing functional materials via green chemistry such as the use of renewable compounds. In this paper, the preparation of hydrophobic coatings based on isosorbide, a derivative of polysaccharides, is reported. The inherently hydrophilic thermoset derived from isosorbide was made hydrophobic through the use of the hydrophobic curing agent F8815. The influence of the F8815 concentration on the decomposition temperature, glass transition temperature and storage modulus of the biobased samples was explored using TGA, DSC and DMA, respectively. The results showed that, despite of its poor mechanical and thermal properties, incorporation of F8815 served to improve the thermal and mechanical properties of the isosorbide-based polymers. Deconvolution analysis of FTIR spectra and SEM images provided insightful information on the participation of F8815 in the polymer network.

Effect of a fluoroalkyl-functional curing agent on the wettability, thermal and mechanical properties of hydrophobic biobased epoxy coatings

Ti–Si–N–O nanocomposite coatings with different contents of oxygen were deposited by a combined dc/rf reactive unbalanced magnetron sputtering process in an Ar+N2+O2 mixture atmosphere. The composition, structure, mechanical, and tribological properties of the as-deposited coatings were analyzed by energy dispersive analysis of x-rays, x-ray diffraction (XRD), nanoindentation, and pin-on-disk tribometer experiments, respectively. It was found that in the range of lower oxygen content with atomic ratio of O∕N⩽0.72, the tribological properties of the Ti–Si–N–O coatings are evidently improved, in comparison with the coating without oxygen incorporation. At O∕N=0.72, the friction coefficient and wear rate of the as-deposited coatings are reduced to 20% and 45%, respectively. Meanwhile, however, their hardness was not reduced, but, on the contrary, slightly increased. With increasing oxygen content further to O∕N⩾0.72, coating hardness decreased significantly. The friction coefficient of the as-deposited coati...

Xianting Zeng

Papers

Solid-phase low temperature steam-assisted synthesis of thermal stable alumina nanowires.

Effect of fluorine incorporation on long-term stability of magnesium-containing hydroxyapatite coatings

Nickel induced lateral crystallization behavior of amorphous silicon films

Effect of a fluoroalkyl-functional curing agent on the wettability, thermal and mechanical properties of hydrophobic biobased epoxy coatings

Effect of oxygen incorporation on structural and properties of Ti–Si–N nanocomposite coatings deposited by reactive unbalanced magnetron sputtering