Hello everyone. In this lecture, we are going to talk about the 3-dimensional nanomaterials. The 3-dimensional nanomaterials are nanocomposites. So the composite consists of metrics and inclusions. The metrics is the continuous pieces. So the composite can be classified into three categories according to metrics material. So first type of composite is metal matrix composite and second type is the ceramic matrix composite, and third type is the polymer matrix composite. The properties of composite is a function of the properties of the constituent pieces. This is matrixes that their relative amount and the geometry of dispersed phase. This is the secondary phase. The particles, fibers, and any other morphological materials can be dispersed phases for composite. In material properties, the main purpose of metal matrix composite is to increase the yield stress, tensile strength, and creep resistance of metals. The main purpose for the ceramic matrix composite is to increase of fracture toughness of ceramic material. Then nanocomposite is multiphase solid material where one of the feces has one, two, three dimensions of less than 100 nanometer. Structures having nanoscale repeat distances. The nanocomposite is a solid combination of a bulk metrics and nano-dimensional phases as a secondary phases. The nanocomposites are building blocks within dimensions in the nanosize range. So we can design and create new material with unexpectedly high or low physical and chemical properties, including mechanical, electrical, thermal, optical, electrochemical, and catalytic properties. The interfaces between metrics and nano-inclusions has important to role in enhancing, limiting the overall properties of materials. For example, by incorporation of one-dimensional nanotube into polymer matrix, we can enhance the mechanical property of polymers significantly. For ceramic metrics nanocomposites. In this case, a metal can be incorporated into metrics as a secondary component. So optical, electrical, magnetic, tribological, corrosion-resistors of ceramic metrics can be enhanced. The important thing to fabricate the ceramic matrix nanocomposite is the control of chemical reaction between ceramic metrics and metal dispersion. So by incorporation of introduction of the metal nanoparticles we can enhance the fracture toughness and strength of ceramics and effectively prevent the degradation of mechanical property at higher temperatures and increase the registers to creep, fatigue and summer shock of ceramic materials. This like ceramic matrix nanocomposites have dispersed metallic secondary particles. So we can improve the several physical properties and this like nanocomposite can be fabricated by conventional powder methological methods such as solid state reaction where mechanical alloying and solution chemical process such as sol-gel and coprepicitation method and also sintering in reductive atmosphere. We can find a lot of nanocomposite with various functionality such as ferroelectric, piezoelectric, varistor, or ionic conducting behaviors. So actually we can enhance the strength, hardness, and toughness of ceramics. The important the ferroelectric barium titanate and semiconducting zinc oxide or the mechanical silicon oxide. Sometimes by dispersing conducting metallic nanoparticles into ceramic matrix, we can enhance the electrical properties but we should consider the population effect in this case. The bulk ceramic nanocomposites, there have been significant interest. This material shows the significantly enhanced the mechanical strings. So large improvement in the fracture toughness have been reported by publication of the ceramic nanocomposite bulk by material by embedding of nanoparticles the size of 20 to 300 nanometer. Let's think about the one example process of poor publicating the bulk ceramic nanocomposite. So firstly, we prepared the microsite particles of twophases, in this case, aluminum and silicon carbide. These materials are colloidally dispersed and consolidated to form uniform compact. So through this technology, we can obtain the green body of this material. Then silicon carbide phase particle oxidized to reduce them to nanometer cores. Interfacial reaction between the oxidized silicon carbide it is oxidized silicon and aluminum. So due to the reaction between silicon oxide and aluminum, the interface material, the new light three alumina and two silica can be generated. So actually this material have the aluminum matrix, and nanoscale silicon carbide is present, and also have interface reacted material of mullite. So through the processing technique, we can fabricate the bulk ceramic nanocomposite. Then let's think about the metal matrix nanocomposite. The metal matrix nanocomposite is reinforced metal matrix composites. So it is very important to realize the homogeneity of composite material. So by obtaining the homogeneity, we can enhance some mechanical properties of metals and sometimes by introduction of a carbon nanotube, we can enhance the tensiIe strength of metal material. Nanocomposites can also be classified based on the physical properties. This slide shows an example classification of nanocomposite according to their electrical conduction. So first type of nanocomposite is random nanocomposite including uniform doping, the material with incoherent inclusion and random boundaries and normal grains and spherical voids. So actually, in this figure, so you can see the semi-coherent includers. Whereas, in ordered nanocomposite you can find things like modulation doping, coherent inclusion and ordered boundaries and modified grains and columnar holes. So in detail. Ordered nanocomposites means the various well-organized nanostructures. So these can be obtained by the reconstruction of the lattice structure and this triggers the electronic transport in materials. The first one is modulation doping. As you know, modulation doping is the two-phase composite with heavily doped minor-phase provides the carrier and undoped matrix-phase as a high-speed transport channel. So in this modulation doped nanocomposite, we can realize high mobility and high carrier density simultaneously. So modulation doping approach is widely used to further the fabrication of the silicon-based the semiconductor. Second one is the coherent inclusion. Coherent means the well-matched lattice structure between metrics and inclusion. So this microstructure less deteriorate effect on the mobility than the incoherent inclusion useful to realize the superlattice or quantum well in three-dimensions. Ordered boundary ensure the reconstruction, the random boundary. So this triggers the electron transport. Modified grain, it makes the decouple the transport of phonons and electrons. Actually, do you know that there are important trade off relationship between phonon transport and electron transport? But by using modified grain, we can decouple the transport of phonons and electrons. The nanocomposite can be also classified at their morphological features. So figure A shows the micrograin composite material and figure B shows the nanograin composite material and figure C shows the nanoinclusion composite material and figure D is the broken material with modified grain boundaries and figure E is the schematic diagram for the hetero-nanograined composite materials. So for B, nanograin composite, if the phonon mean free path is similar with the grain size of this nanograin composite, we can minimize the lattice thermal conductivity of this material. Then in C, by incorporation of nanoinclusions, sometimes we can induce the enhanced electronic transport properties. For example, by introduction of some conducting nanoinclusion, we can induce the bending between the matrix and nanoinclusions, and that makes some difference in carrier relaxation time. Then that result in the enlarged density of states in this material. Sometimes nanoinclusion can act as phonon scattering center. So in nanoinclusion composite, we can also obtain the reuse lattice of conductivity. D shows the bulk materials with modified grain boundaries. So normally, the electrons carriers can be scattered at grain boundaries. But by modifying the interface structure, the grain boundary structure, some incoherent to semi-coherent or coherent, we can trigger the electron transport through the grain boundary. So in the nanocomposite structured material we can obtain the enhanced electrical conductivity and E is the hetero-nanograin structured composite. So in this composite material, the key feature is the large density of interface between material A and material B. The large density interface can sometimes reduce lattice semi-conductivity and sometimes enhance the carrier transport properties. In this module, we briefly review the definition and classification of ceramics and also discuss about the material science at the nanoscale. Because the nanostructuring is the one of the important operative to obtain the number and some new inorganic materials. Then we briefly review some several types of nanomaterials, including general demand, general nanoparticles, one-dimensional nanowires and two-dimensional [inaudible] and three-dimensional nanocomposite. So in the next module, we are talking about the defect engineering strategy. Since this approach is another important approach to develop new and noble inorganic materials. Thank you.
