Ceramic nanomultilayers are becoming hot research because of superhardness effect. Recent progresses and limitations in the research of these artificial hard materials is reviewed, and possible future work is highlighted. Over the past two decades, numerous experimental studies have been conducted leading to significant progress in the exploring of new superhard nanomultilayer systems and understanding of their microstructures. In the aspect of microstructure, it is now commonly accepted that the formation of coherent interface between modulation layers is a critical microstructure prerequisite for nanomultilayers to obtain superhardness. In the aspect of developing new nanomultilayer systems, owing to the template effect, coherent epitaxial growth can be easily realized between two modulation layers even if they naturally have different crystalline structures or one of them exists in amorphous, and material combination that is able to achieve superhardness are thus greatly expanded. On the other hand, in contrast to experimental studies, relatively slow progress has been achieved in theoretical studies aimed in explaining the hardening mechanism of these ceramic nanomultilayers. The mainstream theory currently employed is still the one that was proposed twenty years ago to explain the hardness anomaly enhancement in nanomultilayers formed by metal components, with emphasis on impediment to dislocation motion by interfaces. Therefore, future works should involve in building up new hardening mechanisms and design principles that can be applied to ceramic nanomultilayers, and exploring new multilayer material combinations such as carbides, borides, and even oxides.

One-dimensional magnesium hydroxide chloride hydrate (MHCH) with different structures and morphologies was prepared in CaO-MgCl₂-H₂O system via a hydrothermal method. The effects of MgCl₂ concentration, molar ratio of CaO to MgCl₂ (R), and hydrothermal conditions on the structure and morphology of MHCH were investigated. It was found that MHCH could be prepared when the concentration of MgCl₂ was greater than 3mol/L and R was less than 0.5. Both the diameter and radius length ratio of MHCH increased with the MgCl₂ concentration and R, and the optimum conditions of preparing MHCH were ［MgCl₂］=4mol/L and R=0.05. The phases of MHCH was strongly depended on the reaction temperature, where phase 3 (Mg₂(OH)₃Cl·4H₂O) was stable below 150℃ and phase 9 (Mg₁₀(OH)₁₈Cl₂·5H₂O) was formed above 150℃. In this reaction system at room temperature,Mg₃(OH)₅Cl·3H₂O and phase 5 (Mg₃(OH)₅Cl·4H₂O) appeared firstly, they were both transformed to phase 3 after aged for 1 d. Phase 3 could be converted to phase 9 during hydrothermal treatment at 160℃.

Single crystal dendritic and polycrystalline spherical PbS nanostructures were synthesized selectively with the assistance of surfactants sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) using Pb(Ac)2 as the plumbum source and TAA as the sulfur source. When the surfactant SDS is used only, the single crystal dendritic PbS nanostructure assembled by nanoparticles through the same crystallographic plane is synthesized. While the surfactants SDS and CTAB are used together, the polycrystalline spherical PbS nanostructure assembled by nanoparticles through the different crystallographic plane is fabricated. It is found that the size of the dendritic and spherical PbS nanostructures can be controlled by the concentration of reactants. Finally, The possible growth mechanism is discussed. It is found that the alkyl chain of SDS may work as a soft template to help the little PbS nanoparticles assemble into dendritic nanostructure while the surfactant SDS is used only. When another surfactant CTAB is added, the formed CTAB micelle in the solution will confine the growth of the dendritic nanostructure and the nanoparticles are obliged to assemble into spherical PbS nanostructure.

The effects of Zn-B glass additive on microstructure and electrical properties of low-voltage ZnO varistor were studied. The results show that ZnO varistor with x=0.1wt% obtains the optimal nonlinear electrical properties: E_1mA=36.7V/mm, α=30.4, I_L=0.1μA. The grain growth mechanism of low-voltage ZnO varistor doped with Zn-B glass is also investigated in terms of the phenomenological kinetic of crystalline grain growth. Based on the theory, the grain growth kinetic exponent n and apparent activation energy Q are calculated as 4.54 and 316.5kJ/mol for ZnO ceramics varistor sintered at the temperature below 1000℃. The grain growth mechanism is that non-melting Zn-B glass pins the ZnO grain boundaries, which inhibits the grain growth of ZnO varistor. However, n and Q value are 2.92 and 187kJ/mol at the temperature higher than 1000℃. It indicates that melting Zn-B glass wetting the ZnO grain boundaries creates a liquid phase sintering mechanism, which accelerates the grain growth of ZnO varistor.

Polystyrene (PS) microspheres with average diameter of 50nm and 450nm were prepared by step emulsion polymerization and emulsifier-free emulsion polymerization, respectively. On the basis of this, aluminosilicates with macro-meso-micropores were synthesized via insitu assembly of Y zeolite precursors by PS microspheres/P123 dual templates. The materials with macro-meso-micropores were characterized by means of XRD, SEM and TEM. The results showed that PS microspheres with the diameter of 50nm and 450nm can be obtained by step emulsion polymerization and emulsifier-free emulsion polymerization, respestively. Moreover, influence of various factors including diameters of PS microspheres, amount of templates, and amount of water on the synthesis of the macro-meso-microporous materials were systematically investigated. It was concluded that the composites synthesized by PS microspheres with the larger diameter contained more dispersed macropores. The optimum conditions for aluminosilicates preparation were found to be PS/precursors ratio of 1-0.5, water/precursors ratio of 7.5, and P123/precursors ratio of 0.1.

Silicon carbide (SiC) reticulated porous ceramics (RPCs) were fabricated by polymer sponge replicas method with PCS as sintering additive. Slurry with PCS as binder was recoated on the SiC reticulated porous performs by centrifuging process. The effects of sintering temperature and holding time on SiC RPCs microstructure and properties were investigated. On consideration of the strength and strut porosity of RPCs, the RPCs can be sintered at 1100℃ holding for 1h. With PCS slurry as recoating slurry, the strut thickness of SiC RPCs is very uniform. The optimal compressive strengths of the RPCs prepared by 10PPI sponge and 25PPI sponge are (1.08±0.21)MPa and (2.19±0.32)MPa, respectively. The refectory of them is as high as 1690℃. At the same time, the RPCs with PCS as sintering additive have good thermal shock resistance. After quenched at 1400℃, thermal shock resistance parameter of the RPCs prepared with 25PPI sponge is only 0.36.

The 2D C/C composites with different microstructures were fabricated by isothermal-isobaric chemical vapor infiltration (ICVI). The mechanical properties of the 2D C/C composites were investigated by 3-point bending tests. The microstructures of the pyrocarbon matrix were observed by polarized light microscope (PLM), scanning electron microscope (SEM), transmission electron microscope (TEM) combining selected area electron diffraction (SAED). The results show that 2D C/C composites with dominant layered-HT pyrocarbon matrix exhibit a pseudo-plastic failure behavior. The flake-like fragments MT and granular-like particles ISO are in favor of increasing the flexural strength of the materials. It exists a good interfacial bonding between the fiber and HT layer. The non-HT layer does not exist at the interface, but the orientation angle (OA) of the matrix slightly increases.

The source materials with different porosity were be prepared by different loading ways. Effects of the porosity (porosity: 50%,55%,60%) of the source materials on the crystal growth rate and the crystal quality in the initial stage of SiC crystal growth were investigated respectively. It is found that crystal growth rate rises and the crystal quality declines with the increase of the porosity of the source materials. The temperature distribution and mass transport in the source materials (porosity: 50%, 55%, 60%) as well as the growth rate in the initial growth stage are simulated by the finite element method. The heat transfer inside the source material under the typical growth temperature bases on thermal radiation between SiC granulas. The simulations indicate that it takes the least time to reach stationary heat transfer for the source materials with 60% porosity and its growth rate in the initial growth stage is the largest among them. Therefore, the simulations explain the results of the growth experiments very well.

Multi-walled carbon nanotubes as dielectric absorber and epoxy-silicone resin as matrix were used to fabricate multi-walled carbon nanotubes/epoxy-silicone resin coatings. The effects of multi-walled carbon nanotubes content and diameter on dielectric and microwave absorbing properties of the coatings were investigated in the frequency range from 2GHz to 18GHz. The results indicate that both of the real and imaginary part of the permittivity are enhanced with increasing multi-walled carbon nanotubes content and diameter. When the multi-walled carbon nanotubes content is 2wt%, the complex permittivity of the coatings keep almost constant in the frequency range from 2GHz to 18GHz, and are independent on the multi-walled carbon nanotubes diameter. As the multiwalled carbon nanotubes content increases to 5wt%, the complex permittivity of the coatings decreases with the increase of frequency, and also exhibits visible frequency-dependence dielectric response. The minimum reflection loss of the coatings shifts to the low frequency region (from 12.8GHz to 10.8GHz) as the multi-walled carbon nanotubes diameter increasing. The results of the microwave absorbing properties show that the good microwave absorption ability (below -10dB) can be obtained in a frequency range from 7GHz to 14GHz when the multi-walled carbon nanotubes content is 10wt% and the coating thickness is 2mm.

Three kinds of lutetium silicates powders were prepared by solgel method, marked by Lu₂O₃·SiO₂, Lu₂O₃·2SiO₂ and Lu₂O₃·2.26SiO₂, respectively. Their corrosion behavior in water vapor was investigated in 50%H₂O-50%O₂ steam environment with a total pressure of 1.01×10⁵Pa at 1400℃. The specific weight change as a function of corrosion time was recorded. The phase evolution of lutetium silicate at different corrosion stages was observed by X-ray diffraction. The bonds of samples after corroded for different times were characterized by fourier transform infrared spectroscope(FTIR). The composition of corroded samples was analyzed by EDS. The results show that the main crystal phases of the as-prepared samples are Lu₂SiO₅+Lu₂Si₂O₇, Lu₂Si₂O₇+SiO₂ and Lu₂Si₂O₇+SiO₂, respectively. Lu₂SiO₅, instead of Lu₂Si₂O₇, reacts with Al₂O₃ to form garnet phase (Lu₃Al₅O₁₂) in the water vapor environment. This indicates that Lu₂Si₂O₇ exhibits more excellent chemical stability than Lu₂SiO₅.

A series of （100-x）(0.85GeS₂-0.15Ga₂S₃)-xAgCl（x=0,5,10,15,20）glasses were prepared by conventional melt-quenching technique. The physical and optical properties, including densities, refractive indices, transition temperatures, crystallization temperatures, absorption spectra and transmission spectra, were determined. The allowed direct transition, indirect transition and Urbach energy of samples were calculated according to the classical Tauc equation. Z-scan technique was carried out to investigate the third-order nonlinear optical properties of the samples. The results show that these GeS₂-Ga₂S₃-AgCl glasses have a wide range of transmission approximately from 0.46μm to 11.5μm, and high refractive indices which are more than 2.2. With the AgCl content increasing, the refractive indices and the third-order nonlinearity increase, molar refraction, while metallization criterion and Urbach energy decrease. The effects of metallization criterion, optical band gap and Urbach energy on refractive indices of glass samples are also discussed.

The surface of P₂O₅-BaO-Al₂O₃-K₂O phosphate glass was modified by using both a chemical etching process and a subsequent high-temperature heat treatment, which can effectively remove the surface defects of phosphate glass and the surface contaminations caused by traditional polishing technology. The process of etching phosphate glass in hydrochloric acid was studied to investigate the etching mechanism and determine the etching optimum conditions. It is found that the etching reactions between hydrochloric acid and glass make the phosphate glass surface smooth while a crystal layer is formed on the glass surface. The optimum etching process is as follows, etching in a 9mol/L HCl solution for 30min. After further heating the glass at 550℃, the crystal layer can be removed as crystal particles on glass surface melt, which results in the increase of the transmittance of glass. The results show that a process combining chemical etching the phosphate glass with subsequent heating treatment is an effective method to improve the surface quality of the phosphate glass.

The composite TiO₂/SiO₂ hollow spheres (CHSs) were successfully prepared via sol-gel process using carboxyl-functionalized polystyrene spheres as templates. Then the titania layer was selectively modified with stearic acid and phosphate, forming hydrophobic and hydrophilic interior, respectively. Their hollow and porous structures were confirmed by scanning electron microscope (SEM) and N₂ sorption analysis. Fourier transform infrared (FT-IR) spectra indicate that the interaction between the modifiers and the surface of titania is not physical adsorption but chemical combination. Using ibuprofen (IBU) as a model drug, the investigation of drug loading amounts and release rates shows that they can be regulated by suitable modification. Compare with the unmodified system, the stearic acid modified CHSs exhibit higher drug loading amount and lower release rate due to the hydrophobic effect. The IBU loading amount reaches 189.8mg/g and only about 55% of IBU is released within 53h. However, the phosphate modified CHSs exhibit relatively low drug loading amount (153.0mg/g) and high release rate, probably associated to the hydrophilic shells and charge repulsion. Its release percentage reaches nearly 80% within 10h. Therefore, the produced CHSs have potential application in the sustained drug delivery.

During electrolytic deposition process of hydroxyapatite(HA) on Ti surface, 2.4mmol/L citrate is added into the electrolyte containing 0.6mmol/L Ca²⁺ ion and 0.36mmol/L H₂PO₄^- ion. The results show that the incubation period of the HA is prolonged significantly, and the HA crystals take the morphology of needlelike cone rather than the typical hexagonal prism. Through analyzing the deposition current, coating weight increment and crystal morphology changes, the whole deposition process is divided into 5 procedures: adsorption period, incubation period, eruptive growth period, extra-layer growth period and balanced growth period. Based on the further discussion of micro-mechanism of each period, the HA crystal growth model during electrolytic deposition process is proposed.

Foam SiC was prepared by macromolecule pyrogenation combined with reaction bonding method.The osteoblast-like cells MG63 were seeded and cultured in vitro on the foam SiC and observed under both SEM and TEM to further evaluate the cytocompatability of this novel material. The feasibility of the foam SiC as a bone replacement material for clinical treatment was also studied by establishing an animal model for repairing mandibular criticalsized defects in rabbits, and by using general observation, histological observation and bone histomorphometry.The results show that MG63 cells attach and grow well on the surface of the foam SiC, which indicates that the foam SiC is non-toxic and possesses good cytocompatibility. The 26 tested rabbits are all in healthy conditions and the wounds are healed completely. The different degree of osteogenesis is observed on both periphery and inner mesh of the foam SiC at each time point, and the foam SiC shows no adverse effect to the process of bone repair. It is found that both the rate of tetracycline fluorescence labeling and the new bone area on the foam SiC are lower than those of hydroxyapatite (HA) after 4w implantation, but there are no statistical differences after both 8w and 24w implantations, indicating that the foam SiC should be similar to HA in osteo-conduction ability judging from the long-term repair effect to mandibular defects.