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Lanthanum magnesium hexaaluminate (LaMgAl{sub 11}O{sub 19}) powders were synthesized successfully at 1300 {sup o}C for 4 h by solid-state reaction, and LaMgAl{sub 11}O{sub 19} ceramic was prepared at 1700 {sup o}C for 6 h by pressureless sintering. Phase composition, microstructure, mechanical and thermophysical properties of LaMgAl{sub 11}O{sub 19} ceramic were investigated. Results show that the flexural strength and fracture toughness of LaMgAl{sub 11}O{sub 19} ceramic are 353.3 {+-} 12.5 MPa and 4.60 {+-} 0.46 MPa m{sup 1/2}. Young's Modulus and Poisson ratio is 295 GPa and 0.23, respectively. The linear thermal expansion coefficient of LaMgAl{sub 11}O{sub 19} ceramic from 473 K to 1473 K is 9.17 x 10{sup -6}/K, and thermal conductivity at 1273 K is 2.55 W/m K.

The solid wastes fly ash and aluminum dross were used to prepare the low cost, high added-value product spinel-corundum-Sialon with anin situaluminothermic reduction-nitridation reaction. The effects of varying raw material components and heating temperatures on the phase compositions, microstructure, bulk density, apparent porosity, and bending strength of products were investigated. The presence of hazardous or impure elements in the products was also evaluated. The sintered materials mainly consisted of micro-/nanosized plate corundum, octahedral spinel, and hexagonal columnarβ-Sialon. The bulk density and bending strength of product samples initially increased and then decreased as Al content increased. Product samples with an Al content exceeding 10 mass% that were sintered at 1450°C exhibited the highest bending strength (288 MPa), the lowest apparent porosity (1.24%), and extremely low linear shrinkage (0.67%). The main impurity present was Fe5Si3with hazardous elements P, Cr, Mn, and Ni doping. This work could provide a new method to reduce environmental pollution and manufacture low cost high performance refractory materials using the abundant waste materials fly ash and aluminum dross.

Preparation of nanomaterials with various morphologies and exploiting their novel physical properties are of vital importance in nanoscientific field. Similarly to the III-N compound semiconductors, Si3N4 nanostructures also could be potentially used for making optoelectronic devices. In this paper, we report on an improved Fe-catalyzed chemical vapour deposition method for synthesizing ultra-long α-Si3N4 nanobelts along with a few nanowires and nanobranches on a carbon felt substrate. The ultra-long α-Si3N4 nanobelts grew via a combined VLS-base and nanobranches via a combined double-stage VLS-base and VS-tip mechanism, as well as nanowires via VLS-tip mechanism. The three individual nanostructures showed variant optical properties as revealed by a cathodoluminescence spectroscopy. A single α-Si3N4 nanobelt or nanobranch gave a strong UV-blue emission band as well as a broad red emission, whereas a single α-Si3N4 nanowire exhibited only a broad UV-blue emission. The results reported would be useful in developing new photoelectric nanodevices with tailorable or tunable properties.

Herein, ultralong silicon nitride nanowires were synthesized via a chemical vapor deposition method by using the low-cost quartz and silicon powder as raw materials. Simple processes were used for the fabrication of disordered and ordered nanowire membranes of pure silicon nitride nanowires. The nanowires in the disordered nanopapers are intertwined with each other to form a paper-like structure which exhibit excellent flame retardancy and mechanical properties. Fourier-transform infrared spectroscopy and thermal gravity analysis were employed to characterize the refractory performance of the disordered nanopapers. Highly ordered nanowire membranes were also assembled through a three-phase assembly approach which make the Si3N4 nanowires have potential use in textured ceramics and semiconductor field. Moreover, the surface nanowires can also be modified to be hydrophobic; this characteristic make the as-prepared nanowires have the potential to be assembled by the more effective Langmuir–Blodgett method and also make the disordered nanopapers possess a super-hydrophobic surface.

Well-aligned TiO2nanotube arrays were fabricated by anodizing Ti foil in viscous F−containing organic electrolytes, and the crystal structure and morphology of the TiO2nanotube array were characterized and analyzed by XRD, SEM, and TEM, respectively. The photocatalytic activity of the TiO2nanotube arrays was evaluated in the photocatalytic (PC) and photoelectrocatalytic (PEC) degradation of methylene blue (MB) dye in different supporting solutions. The excellent performance of ca. 97% for color removal was reached after 90 min in the PEC process compared to that of PC process which indicates that a certain external potential bias favors the promotion of the electrode reaction rate on TiO2nanotube array when it is under illumination. In addition, it is found that PEC process conducted in supporting solutions with low pH and containing Cl−is also beneficial to accelerate the degradation rate of MB.

Morphology control of one dimension (1D) nanomaterials is a pivotal issue in the field of nanoscience research to exploit their novel properties. Herein, we report the morphology controlled synthesis of 1D β-Sialon nanowires, nanobelts and hierarchical nanostructures via a thermal-chemical vapour deposition process using an appropriately selected catalyst and optimized temperature schedule. Vapour–solid (VS), a combination of vapour–liquid–solid (VLS)-based and VS-tip, and a combination of VS for one-generation nanowires with nucleation, growth and coalescence of two-generation nanobranches (NGCB) are used to explain the growth of β-Sialon nanowires, nanobelts and hierarchical nanostructures, respectively. Cathodoluminescence measurements show that the individual β-Sialon 1D nanostructures with different morphologies have different luminescent properties. All nanostructures exhibit two distinct emission peaks, the violet/blue emission centered at ∼390 nm (3.18 eV), attributable to the near band edge (NBE) emission, and the red emission centered at ∼728 nm (1.70 eV), assigned to the deep level (DL) emission. However, the DL emission is the ruling emission in the case of an individual β-Sialon nanowire, whereas the NBE emission becomes dominant in the case of an individual nanobelt as well as a hierarchical nanostructure due to the size and surface effects. The as-synthesized β-Sialon with controlled nanostructures and various morphologies can find potential applications in future nanodevices with tailorable or tunable photoelectric properties.

JEM-phase Sialon (LnSi6� zAl1+zOzN10� z) was revealed to have limited z values. To keep the structure stability, substitution of the Si- Nb ondby the Al-O bond isvery restricted and lanthanide-dependent (La /Sm). The z values of La-, Nd- and Sm-doped JEM-phase Sialons are � 1.0, � 0.6 and 0.4-0.2, respectively.

In this paper, a porous Sialon polytypoid material with multilayered structure was in situ synthesized at 1700 °C for 3 h in a nitrogen atmosphere via a nitriding process. The plate-like Sialon grains were observed using a scanning electron microscope (SEM), and the chemical composition, structure, chemical state and optical absorption of this material were characterized by energy dispersive X-ray spectroscopy (EDX), synchrotron X-ray diffraction (SXRD), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy (DRS). There are four layers with two ranges of grain sizes. The grains with sizes of 18–35 μm are in the inner layer (layer-4) and light-grey, while those grains with bigger sizes of 60–80 μm are present in the outer layers in green colour. These two types of grains have a slight difference in chemical composition, i.e. (La,Sm)0.1Si8Al14O5N21.1 and (La,Sm)0.33Si6Al12O1N21, respectively. They are polytypoids with different structures, which precipitated from the lanthanide-rich Sialon glass. The chemical states of the elements were different as indicated from XPS data. It is believed that the colour and size differences within layers resulted from the intrinsic differences of chemical composition, structure and chemical state of the two types of grains. This porous ceramic might be of potential applications in water treatment, building and automotive industries as a functionally gradient material (FGM) or ceramic filter.

Ultra-long single crystal α-Si3N4 nanobelts were prepared by thermal chemical vapour deposition (CVD) method. Silicon vapour from the original solid silicon raw material was allowed to react with flowing nitrogen at 1450 °C on the carbon felt deposited with Ni(NO3)2. The as-prepared α-Si3N4 nanobelts were 40–60 nm thick, 200–300 nm wide, and up to several millimetres long. Their growth process was governed by the VLS base-growth and the VS tip-growth mechanisms. The former was responsible for the initial nucleation and proto-nanobelt (template) formation of α-Si3N4 and the subsequent growth along the [101] or [100] direction, and the latter for the additional growth at the tips. The synergistic function from these two growth mechanisms resulted in the formation of a large quantity of ultra-long α-Si3N4 nanobelts. An intense violet–blue visible photoluminescence (PL) of the as-synthesized α-Si3N4 nanobelts was observed at room temperature, which could be highly valuable for the future potential applications in optoelectronic nanodevices.

Dielectric constant discrepancy of parallel and vertical to Z axis of tourmaline (Yunnan, China) can be ascribed to chemical composition, space-charge polarization, and crystal structure. Cations at Y sites of the crystal structure contribute most to dielectric properties. The variations in dielectric properties might be attributed to crystal orientation.

TiO2-based nanofibers were synthesized using a sol–gel method and electrospinning technique. The as-spun composite fibers were heat-treated at different temperatures (500°C, 550°C, 600°C, and 650°C) and atmospheres (ammonia and nitrogen) for 4 h. The fibers had diameters of 50 to 200 nm and mainly featured anatase and rutile phases. The anatase phase decreased and the rutile phase increased with increasing temperature. Different nitrogen conditions exerted minimal effects on the TiO2 crystalline phase. Different nitriding atmospheres during preservation heating yielded various effects on fibers. The effect of nitrogen in ammonia atmosphere is better than that in nitrogen atmosphere. The fibers heat-treated at 600°C and subjected to preservation heating in NH3 showed high photocatalytic activity.