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Ti3AlC2 bulk ceramics were prepared via aqueous gelcasting followed by C-rich and Al-rich pressureless sintering. The optimized pH value, zeta potential, dispersant content, and solid loading content were determined to be 10, 72.6 mV, 1.6 wt%, and 52 vol%, respectively. Impurities at ppm level containing in the flowing argon could cause severe decomposition of gelcasted bulk Ti3AlC2, forming whiskers of Al2OC and Al4O4C and floccule of AlN. C-rich pressureless sintering resulted in the delamination of a duplex layer of Ti(CO) and Ti3(AlO)Cx-Ti(O,C). The channels formed after debinding facilitated the outward diffusion of Al and the inward diffusion of O and C, and thereby promoting the decomposition of C-rich sintered Ti3AlC2. The combined effect of the unclosed channels and the porous reaction Ti3(AlO)Cx-Ti(O,C) layer brought a catastrophic reduction in the density and mechanical properties of the C-rich sintered Ti3AlC2 ceramic. While the Al-rich pressureless sintering system isolated C, CO and N2 and supplied a closed Al-rich atmosphere, thereby suppressing the decomposition reactions and promoting the sintering densification and ultimately leading to the superior in mechanical properties. The density, hardness, flexural strength and fracture toughness of the Al-rich sintered ceramic reaches 4.13 g/cm3, 4.36 GPa, 345 MPa, 4.79 MPa m1/2, respectively.

Using high-performance expanders is one of the keys to improve the efficiency of Organic Rankine Cycle (ORC). However, in large expansion ratio conditions, the performance deterioration caused by under-expansion seriously affects the performances of the ORC. For single-screw expanders, it is possible to utilize the kinetic energy of the screw groove exhaust to produce extra power. But there is still a lack of theoretical support for optimizing the exhaust kinetic energy utilization process of this new expander at present. Therefore, the energy conversion mechanism of Single Screw Expander with exhaust Kinetic energy Utilization (SSEKU) was investigated in this paper, and a mathematical model of SSEKU was developed to investigate the energy conversion mechanisms and predict the performances. The results show that introducing exhaust kinetic energy utilization process in single screw expander can reduce under-expansion losses effectively, and the effects in large size expanders were stronger than that in small scale machines. It was also found that the maximum increase in isentropic efficiency was 3.01, 5.47, and 9.38 percentage points for the expander with a screw diameter of 117 mm, 200 mm, and 350 mm, respectively.

Permeation behavior of deuterium (D) through various tungsten (W) materials, including rolled, annealed, recrystallized W and ZrC/La 2 O 3 -dispersion strengthened W, has been studied. Experiments were performed using a gas-driven permeation facility in the temperature range of 700–1000 K. The permeability of D was not sensitive to the dislocations/vacancies or ZrC/La 2 O 3 phases in W, and the measured permeation values are comparable to Frauenfelder and Zahkarov’s data. The diffusivity of D, however, is microstructure dependent. The higher the density of defects was, the lower the effective diffusivity was measured. These results imply that dislocations/vacancies or small amounts of ZrC/La 2 O 3 phases in W will not influence the hydrogen isotopes steady state permeation flux through the first wall.

A nanostructured surface layer was fabricated on commercial pure tungsten using the method of surface mechanical attrition treatment (SMAT). The microstructure evolution of the surface layer was characterized by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and its formation mechanism was discussed as well. Both refinement and elongation of the brittle W grains were confirmed. The elongated SMATed W was heavily strained, the maximum value of the strain at the grain boundaries reaches as high as 3–5%. Dislocation density in the SMATed W nanograins was found to be 5 × 1012 cm−2. The formation of the nanograins in the top surface layer of the W was ascribed to the extremely high strain and strain rate, as well as the multidirectional repetitive loading. Bending strength of commercial W could be improved from 825 MPa to 1850 MPa by SMAT process. Microhardness results indicated the strain range in SMATed W can reach up to 220 μm beneath the top surface. The notched Charpy testing results demonstrated that SMATed W possess higher ductility than that of commercial W. The top surface of the W plates with and without SMATe processing possesses residual compressive stress of about −881 MPa and −234 MPa in y direction, and −872 MPa and −879 MPa in x direction respectively. The improvement of toughness (DBTT shift) of SMATed W may be the synergistic effect of residual compressive stress, dislocation density improvement and microstructure refinement induced by SMAT processing. SMAT processing could be a complementary method to further decrease the DBTT value of tungsten based materials.

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A nanostructured laminar W-La2O3 alloy (WL10) with improved ductility was prepared using a surface mechanical attrition treatment (SMAT). φ1.5 mm ZrO2 WL10 balls subjected to SMAT (called φ1.5 mm ZrO2 ball SMATed WL10) samples possess the best surface profile and excellent integrated mechanical properties (the ductile-brittle transition temperature (DBTT) value decreases by approximately 200 °C, and the bending strength decreases by 100 Mpa). A highly dense group of laminates was detected near the surface of the φ1.5 mm ZrO2 ball SMATed WL10 sample. The SMATed WL10 laminates were composed of a micro-grain layer, an ultrafine-grain layer and a nanosized-grain layer. The nanostructured laminar surface layer of the φ1.5 mm ZrO2 ball SMATed WL10 sample is approximately 1–2 μm. The top surface of the WL10 plates with and without the SMAT process possesses residual compressive stress of approximately −883 MPa and −241 MPa, respectively, in the y direction and −859 MPa and −854 MPa, respectively, in the x direction. The SMAT process could be a complementary method to further improve the toughness of tungsten-based materials.

Gelcasting combined with pressureless sintering is a promising technological process to fabricate large scale or complex-shaped silicon carbide ceramics (SiC) products with excellent properties. To obtain high solid loading SiC slurry with low viscosity, two promising compact granulation and spray granulation methods were proposed to coarsen raw submicron SiC powders into a larger secondary granule. By compact and spray granulation processes, the average particle sizes were enlarged from 0.51 μm to 40.7 μm and 8.2 μm, respectively. The enlarged particles decreased the volume of structural water in the slurries remarkably, resulting in the decrease in the viscosity of slurry. The viscosities of slurry prepared from spray-granulated powders and compact-granulated powders were 1/2.5 and 1/3.5 to that from submicron powder at a shear rate of 100 s −1 , respectively. The lower viscosities benefited to the escaped air bubble in slurries, and leaded to a dense microstructure in green and sintered bodies. The bending strengths of green bodies and sintered bodies prepared from granulated powders were about 3 times and 2.2 times to that from submicron powders. It is worth to notice that even though the dried spray-granulated powders with sphere-like appearance displayed higher tap density and well fluidence, the slurry viscosity was 58 Pa s higher than that of compact-granulation powders due to the hollow particle structure. As a result, compact granulation powders showed desired slurry fluidity and dense green and sintered bodies, thus high bending strength.

Carbon nanotubes (CNTs) have the ideal structure to be used as templates for nanomaterials, especially for nanowires, and the tungsten nanowire is an important nanomaterial that is used as a strengthening phase. Therefore, we have proposed to apply mesoporous CNT (mCNT) as a template to prepare tungsten nanowires. However, the tungsten precursor should fill the hollow tube of mCNT firstly, and very few related studies have been reported. In this paper, we have systematically studied the filling process of ammonium metatungstate (AMT) aqueous solution. The results reveal that owing to the mesopores in the mCNT sidewall, the AMT can be encapsulated into the tube at room temperature (RT) and we can fully fill it without destroying the structure. In addition, vibration and solute concentration are also important factors. Besides, the mesoporous sidewall and hollow tubular core structure of mCNT are prerequisites to realize full filling. Furthermore, tungsten nanowires have been obtained after reduction of AMT in mCNTs.

In the present study, hydrothermal-hydrogen reduction process as a novel wet-chemical route was performed for the preparation of La2O3 doped ultra-fine W powders. WO3 precursor powders with nanorods were fabricated by the hydrothermal reaction of sodium tungstate, citric acid and sodium sulfate in aqueous solutions in autoclave, and then were reduced by high purity hydrogen to obtain doped tungsten powders. Reaction time and PH value of solution affected morphology of WO3 precursor powders and following doped tungsten powders. TEM results revealed that the obtained La2O3 doped W powders presented good sphericity with particle size of about 700 nm and narrow particle size distribution, which was determined mainly by the diameter of rod-like WO3 due to in-situ hydrogen reduction mechanism.

Well-dispersed titanium carbide/tungsten (TiC/W) core–shell nanoparticles with high-purity and uniform diameters were firstly synthesized by precipitate-coating process. The as-synthesized nanoparticles were characterized by X-ray diffraction (XRD), Filed-emission scanning electron microscope (FESEM), Transmission electron microscopy (TEM), energy dispersive spectrum (EDS). Results revealed that the as-synthesized nanoparticles possess uniform diameters about 100 nm, and high purity. TEM and the corresponding FFT images demonstrate that TiC nanoparticles were well-encapsulated by W shells. Such unique process suggests a new method for preparing X/W (X refers the water-insoluble nanoparticles) core–shell nanoparticles with different cores.

Composite powders containing silicon carbide (SiC) particles and silicon nitride nanowires (Si3N4-NWs) were synthesized by combustion synthesis, using elemental Si, carbon black, PTFE and small amount of metal powders as raw materials. The catalyst types and environmental gases and pressures have been altered to study their influence upon the crystal growth and the nature of the products. The products were characterized by X-ray diffraction, scanning and transmission electron microscopy. Results reveal that the metal/silicon liquid (e.g. Ni2Si and Fe3Si) formed during the combustion process is a key factor for the growth of Si3N4-NWs in nitrogen. For the process carried out in non-nitrogen gas (Ar, CO2 or mixed CO2/O2), pure SiC particles were obtained. The rise in nitrogen pressure can promote the growth of Si3N4-NWs as well as large SiC particles. The growth of Si3N4-NWs could be explained by the SLGS mechanism, and the growth of SiC particles was involved in the gas-phase and liquid-phase mechanisms.

The corrosion behaviors of CNS-I and modified CNS-II were evaluated by exposing to superciritical water (SCW) at 550 °C and 25 MPa with a dissolved oxygen concentration of 200 × 10−9 for up to 1000 h. Detailed corrosion results of these two alloys were provided, including the growth rate of the oxide scales, microstructure of the oxide scales, distribution of phases and alloying elements. The mass gains of CNS-I and modified CNS-II were 609.73 mg/dm2 and 459.42 mg/dm2, respectively, after exposing to SCW for 1000 h. A duplex oxide scale with an outer porous magnetite layer and an inner relatively dense magnetite/spinel-mixed layer was identified on CNS-I and modified CNS-II after the test. The oxide scales were rather porous at the beginning of the test but the porosity decreased with increase of the exposure duration. It was found that Fe was enriched in the outer oxide layer, Cr was enriched in the inner oxide layer and O existed at a very high concnetration in the whole oxide scale. Other alloying elements such as Mo, W, Mn were depleted from the outer oxide layer and showed slightly enrichment in the inner oxide layer. The distributution of Ni was different from other elements, it was enriched in the interface bewteen the base metal and the oxuJe scale and depleted in the outer and inner oxide layers.

Large quantities of Ti-catalyzed β-SiC nanowhiskers were efficiently prepared via a SHS process by pyrolysis of poly (tetrafluoroethylene) (PTFE). The as-synthesized β-SiC whiskers appear to be structurally uniform with width from 50 nm to 2 μm and length of up to several hundred microns, and they are single crystalline in nature. Results demonstrated that Ti particles could significantly accelerate the absorption and dissolving of Si- and C-related fragments. A Ti–Si–C alloy droplet was detected at the end of an individual β-SiC whisker, which indicated that β-SiC whiskers were grown via the vapor–liquid–solid (VLS) growth mechanism. The elastic bending modulus of individual whiskers was measured by an in-situ transmission electron microscopy (TEM) process; the average value of the elastic bending modulus of individual as-synthesized whiskers was 554 GPa.

Modified CNS-Ⅱ F/M steel was designed for in-core components of supercritical water cooled reactor. Study on the hot deformation behavior of modified CNS- Ⅱ F/M steel is of great importance for processing parameter planning and microstructure controlling during hot deformation. The hot deformation behavior of modified CNS-Ⅱ F/M steel was investigated through isothermal hot compression test at temperature ranging from 1 223 to 1 373 K and strain rate 0.01 to 10 s^-1. The true stress true strain data gained from compression tests were used to built constitu- tive equation of modified CNS-Ⅱ F/M steel. The influence of strain on the accuracy of constitutive analysis was in corporated, assuming strain has a influence on material constants. A 5th order polynominal equation with very good accuracy was used to represent the influence of strain on material constant. The flow stresses calculated from the constitutive equation were compared with test values in the whole experiment range and the absolute average error for the constitutive equation in predicting fl.ow stress is 4. 728 %. At last, the recrystallization behavior of modified CNS-Ⅱ F/M steel was investigated. The relationship of critical strain and peak strain with Zener-Hollomon parameter were given by an experimental equation.

Large-scale composite powders containing silicon carbide (SiC) particles and silicon nitride nanowires (Si 3 N 4 -NWs) were synthesized in situ by combustion synthesis (CS). In this process, a mixture of silicon, carbon black, polytetrafluoroethylene (PTFE) and a small amount of iron powders was used as the precursor. The products were characterized by XRD, SEM, EDS and TEM. The particles are equiaxed with diameters in the micron range, and the in situ formed nanowires are straight with uniform diameters of 20–350 nm and lengths of tens of microns. The Si 3 N 4 -NWs are characterized to be α-phase single crystals grown along the [1 0 1] or [1 0 0] direction. VLS and SLGS processes are proposed as the growth mechanisms of the nanowires. The as-synthesized powders have great potential for use in the preparation of high-performance SiC/Si 3 N 4 -NW composites.

Ferritic/martensitic (F/M) steels have been recommended as one of the candidate materials for supercritical water cooled reactor (SCWR) in-core components use for its high thermal conductivity, low thermal expansion coefficient and inherently good dimensional stability under irradiation condition in comparison to austenitic steel. CNS-II F/M steel which has good mechanical properties was one of the 9-12Cr F/M steels designed for SCWR in the previous work. In this study a modified CNS-II F/M steel was used and it's ultimate tensile strength was 925 MPa at room temperature and 483 MPa at 600 °C after optimizing heat treatment parameter. The ductile to brittle transition temperature of modified CNS-II F/M steel is −55 °C. Those are at the same level or even higher than that of CNS-II and some commercial F/M steels nominated for SCWR in-core component use. The transmission electron microscope (TEM) results showed that the mechanical properties of the tempered martensite was closely related to the decomposition stage of the martensite.

The synthesis of thermo-responsive hydrogels poly(N-isopropylacrylamide )(PNIPAm) by frontal polymerization (FP) was carried out in four mixed solvents, i.e. dimethylsulfoxide (DMSO) mixing with water, ethanol, tetrahydrofuran (THF) and acetone, respectively. The influences of mixed solvent on frontal parameters, pore morphologies, swelling behavior of PNIPAm hydrogels were investigated. The pore of PNIPAm hydrogel synthesized in THF/DMSO was observed a big honeycomb cells, others were channel-like cells. Furthermore, the sample obtained in THF/DMSO had higher swelling ratio as compared to others, and the one synthesized in Water/DMSO showed the lowest. Above results indicated that fine-tuned poly(N-isopropylacrylamide) hydrogels can be prepared in short time and with easy protocol by adjusting mixed solvents in frontal polymerization process.

The excavation and support problem of deep foundation pit is very interested by construction engineers with the development of the high buildings in cities and exploration utilization of the underground pace. Stability and economy are the most important problems in deep foundation pit support. This paper mainly studied on stability and economy of steel sheet pile support structure. The steel sheet pile support technique was fully introduced and analyzed here, using a combined method of theoretical guidance, calculation analysis, engineering application with finite element program simulation and market investigation.

Pile-soil stress ratio is defined as the average stress ratio of the head of pile to the soil around of piles, which is a very important indicator to reflect the level of the together-work of pile and the soil, also a major parameter of calculation of capacity of composite foundation and settlement. How to choose pile-soil stress ratio is still a problem unsolved. Bearing performance of the DJM pile composite foundation is studied by way of field static load tests and pile-soil stress ratio tests. This paper is to analyze the bearing performance of the DJM pile composite foundation in the Yellow River Delta region with the plane strain finite element method and gain the load-sharing ability of soil and regulations of pile-soil stress ratio with the changes of effecting factors.

Nuclear fusion is a promising source of environmental friendly energy for the future, and the ultra-fine grained Tungsten (W) is a hopeful candidate material to be used as plasma-facing materials (PFMs), which are the key materials in the International Thermonuclear Experimental Reactor (ITER), for its many useful advantages. While, due to its high melting point and high sintering temperature needed, the ultra-fine grain sized tungsten is not easy to be fabricated. In this paper, the method of explosive consolidation of powders as well as its mechanism and improvements are discussed, and finally the possibility of using this method to preparing of ultra-fine grained W plasma facing material are also introduced.

Jacket Offshore Platform is a complex statically indeterminate structure, reliability of which is impacted by many factors, and the earthquake is a main factor. This paper simplify the significant failure mode of Jacket Offshore Platform by standard. Calculate the reliability of Jacket Offshore Platform under the effect of earthquake with the Monte Carlo method based on ANSYS. The result can provide evidence for safety assessment of Jacket Offshore Platform.

In this article we present the testing, evaluation of infrared radiation properties of polycrystalline materials especially as cordierite-based glass-ceramics. Researches aim to make a comprehensive and systematic exposition of emissivity definition, test principles and test methods. And on the basis of measurement results of the infrared emissivity of cordierite-based glass-ceramics, the Infrared radiation property of this polycrystalline material was discussed. Research has a positive significance on the development of the infrared radiation heating and drying materials.

Based on finite element theory and finite element software ANSYS, this thesis establish three-dimensional pile-soil contact model pile to simulate the pile-soil interaction, analysis the bearing capacity particularity, analysis of different factors on the pile P-S curves. Using ANSYS optimization module Monte Carlo sampling method calculate pile capacity reliability, Simplify the cumbersome process of reliability analysis.

Offshore Jacket Platform is a very important infrastructure in the offshore oil exploration and exploitation. In order to make it more economical, designers should do Structural Optimization to it. This paper do Structural Optimization to Offshore Jacket Platform, and provide reference for the using of ANSYS in the Structural Optimization of Offshore Jacket Platform.

Ferritic/martensitic steels with Cr of 9% – 12% (in mass percent) are favourable candidates for fuel cladding tube and in-core components of supercritical water-cooled reactor. 9Cr-3WVTiTaN low activation ferritic/martensitic steel, designated as China Nuclear Steel- I (CNS- I), was patterned after T91 steel (modified 9Cr-1Mo) for the reactor. The idea of low activation material and microalloy technology was introduced into the design of the steel. The hardening, tempering and transformation behaviour of CNS- I steel was investigated. The steel has advantages in tensile properties at elevated temperature relative to zircaloy that has been widely used as cladding material for conventional light water reactors. CNS- I steel exhibits tensile properties and impact toughness comparable to T91 steel which exhibits availability in the present fission reactors and fast breeder reactor but includes undesired radioactive elements such as molybdenum and niobium.

A frontal polymerization method is used to produce highly porous polymer monoliths. The method is an approach to polymer synthesis that exploits the heat produced by the reaction itself. This heat triggers polymerization of neighboring monomer molecules, leading to a self-sustaining hot front, which propagates along the reacting vessel. Dissolved or microencapsulated foaming agents are decomposed only at the fronts, synchronizing the polymerization and the foaming. The ultimate pore structures appear to depend on the polymerization-front velocity and temperature. The resultant materials are porous, exhibiting tunable pore volume and a multimodal pore size distribution. No organic solvents or high-pressure equipment are used in the process, and no solvent residues are left in the resulting materials. Specifically, this route allows for the synthesis of large-scale samples with the additional advantages of high velocity, low energy cost, and the avoidance of multiple process steps. Substitution of hydrophilic acrylamide, N-isopropylacrylamide, with hydrophobic styrene and methyl methacrylate also leads to porous monolithic materials, suggesting that frontal polymerization represents a powerful and facile method for an exothermic polymerization reaction and the creation of porous polymers.

GdBaCuO bulk superconductors from precursors of Gd123 and ultrafine Gd211 powder have been fabricated by melt-textured-growth method in air. The ultrafine Gd211 powder was synthesized by an improved Pechini method. It was found that the lower temperature of synthesizing ultrafine Gd211 powder, the higher peritectic reaction temperature of GdBaCuO bulk superconductors. Jc reaches 4.7×104 A/cm2 at 77 K and self-field for ultrafine Gd211 starting particles with 0.2μm in diameter, and higher compared to larger Gd211 starting particles fabricated by solid state reaction. However, a large secondary peak effect did not appeared at Jc-B curves.

This paper describes the details on synthesizing nanocrystalline Gd2BaCuO5 (Gd211) using low-temperature combustion synthesis(LCS). The morphology and structure of the powders are characterized by field emission scanning electron microscopy (FESEM) and XRD. The size of obtained powders by this method calcined at 800 C is about 100nm, which is much smaller than the powders synthesizing by conventional solid state route. Besides, the Gd211 powders synthesizing by LCS have a low calcination temperature with a high-purity. The microstructure of melt-textured samples is also observed by FESEM, the result shows that the size of Gd211 particles trapped in GdBa2Cu3O7 (Gd123) matrix could be refined by using ultrafine Gd211 powder as a precursor. The refined Gd211 particles with a good distribution resulted in the improvement of Jc values in this system.

Ba3(Ca1.18Nb1.82)O9-d (BCN18) powder was synthesized using a wet chemical method from mixtures of all water-soluble compounds including Ba, Ca and Nb-citrate. It has been found that NH4NO3 in the initial solutions plays an important role in controlling the enthalpy of low temperature combustion process as well as the gel decomposition temperature. Further steps include evaporating, drying and calcinating. The obtained gels were characterized by TG-DSC, and the powder was characterized with XRD, TEM and BET. The experimental results have indicated that the heating temperature was only 800°C for synthesizing the powder and the average particle size was only about 40-50 nm. Furthermore it was found that a pure BCN18 phase with complexperovskite structure was formed at 800°C, which was about 800°C lower than that of the traditional solid-reaction method. So it is more practical and more superior to the traditional solid-reaction method and the present wet-chemical method in alcohol salt system reported in literature.

Non-agglomerated nano-sized BaTiO3 powders were prepared by a 3 step decomposition of barium titanyl citric acid chelate derived from Ba(NO3)2-TiO(NO3)2-citric acid-NH4NO3 based complex compound system. The 1st step was the thermal treatment of chelate wet gel at 150°C for 40min to remove water and non-bridging hydroxyl groups and to form expanded gel intermediate. The 2nd step was the decomposition of the organic fuel by igniting expanded gel intermediate at 300°C. The 3rd step was the formation of the high purity BaTiO3 by calcining the decomposed powders at 700°C for 2 hours. The most expanded gel intermediate was found to be a decisive factor for the elimination of hard agglomerate. In addition, the initial oxidant/fuel molar ratio was shown to strongly influence the characteristics of the powders thus obtained. The optimum oxidant/fuel value was 3 for obtaining non-agglomerated pure BaTiO3 powders with a particle size of 50 nm. The agglomerate degree of BaTiO3 powders was determined by particle morphology and uniformity of the green compact microstructure observed by field emission scanning electron microscopy and scanning electron microscope.

Polyacrylamide hydrogels with defined porous structure were synthesized through frontal polymerization (FP) in the presence of NaHCO3 as a foaming agent. Pore properties were analyzed using scanning electron microscopy and mercury intrusion porosimetry. The as-prepared hydrogels displayed a small cell diameter of ca 2 µm. The dissolved foaming agent dispersing at the level of molecules and the polymerization front propagating step by step should be responsible for the small uniform cell structure. The pore volume varied from 0.63 to 3.65 cm3 g−1 and the bulk density changed from 0.48 to 0.28 g cm−3 for a foaming agent content from 0 to 18%. The hydrogels synthesized by FP exhibited higher swelling rate and swelling ratio with respect to conventional batch polymerization. The highest swelling ratio and rate were obtained at a foaming agent concentration of 12% based on monomer. Copyright © 2007 Society of Chemical Industry

The frontal polymerization process was used to produce superab- sorbent hydrogels based on acrylic acid monomers grafted onto starch. Using a simple test tube which was nonadiabat- ic and permitted contact with air, the effects of initial temperature and tube size on the propagating front of graft- ing copolymerization and the proper- ties of hydrogels were explored. The unrestricted access of the reaction mix- ture to oxygen delayed the formation of self-propagating polymerization front. The ignition time was markedly lengthened with the increasing of tube size attributed to the formation of large amounts of peroxy radicals. The front velocity dependence on initial temperature could be fit to an Arrhe- nius function with the average appa- rent activation energy of 24 kJ mol � 1 , and on tube size to a function of higher order. The increase of the initial tem- perature increased the front tempera- ture, which lead to more soluble oligomers and higher degree of cross- linking. The interplay of two opposite effects of oligomer and crosslinking de- termined the sol and gel content. An increase in tube size had two effects on the propagating front. One was to reduce heat loss. The other effect was to increase the number of escaping gas bubbles. The combined action of the two effects resulted in a maximum value of front temperature, an increase in sol content and a reduction in gel content with tube size. The highest swelling capacity of hydrogels was ob- tained when the initial temperature or tube size favored a formation of porous microstructure of hydrogels.

The paper discusses the Y and Nd doped barium cerate perovskites prepared by a modified Pechini method. The series prepared is described by the formula BaCe 0.80 Y x Nd 0.2− x O 3− δ . The BaCeO 3 based powders, about 10–20 nm sized and uniformly shaped, were obtained through the calcination of the gel at 500 °C for 2 h. Their structures and ionic conductivities were characterized by X-ray diffraction and AC impedance spectroscopy. All the electrolytes were found to be barium cerate based solid solutions of perovskite type structures. Impedance spectra indicate that the grain boundary resistance of the specimen synthesized by this method is smaller than that of the samples prepared by a conventional solid-state method. The ionic conductivities of co-doped barium cerate were a factor of several times than that of the single-doped one at 673–1073 K. Among the electrolytes examined, the one co-doped with 5 mol% Nd and 15 mol% Y shows the best improvement in performance. These co-doped barium cerate are more ideal intermediate temperature (IT) electrolyte materials.

Anatase-type TiO2 (titania) doped with cerium up to 5 mol% was directly formed as nanometer-sized particles from TiO(NO3)2–Ce(NO3)2–NH4NO3–citric acid complex compound system by sol–gel auto-igniting synthesis process. The precursor gel was characterized by infrared spectroscopy and TG/DSC analysis. The XPS measurement showed that Ce(III) was easily oxidized to Ce(IV) at 550 °C and above. The XRD data, XPS spectra, and TEM selected-area diffraction patterns confirmed that cerium(IV) formed a solid solution in the anatase-type TiO2 powders. Doping of CeO2 into TiO2 shifted the phase transformation from anatase- to rutile-type structure to a high temperature. On the other hand, CeO2 was segregated on the surface of TiO2 and the rutile formation was accelerated during phase transformation from anatase to rutile at elevated temperature. When the cerium content was increased in the anatase phase, onset of optical absorption shifted to longer wavelengths, and absorption in the UV-light region and in the visible-light region over 400–500 nm clearly appeared in the diffuse reflectance spectra of the as-prepared Ce-doped TiO2.

Recently, a considerable amount of research has centered on uniquely structured polymers synthesized through self-propagating frontal polymerization. The obtained polymer materials have better features than those obtained by using the classical batch route. The additional advantages are short reaction times and low cost. This work describes the first frontal polymerization synthesis of a graft copolymer superabsorbent hydrogel of acrylic acid onto starch at high monomer and initiator concentration. The effects of varying the relative amounts of the reaction components on the most relevant parameters relating to frontal polymerization were explored. The front velocity dependence on initiator concentration could be fit to a power function. The temperature profiles were found to be very sharp with a maximum temperature below 150 degrees C, which was responsible for high monomer conversion. The ultimate properties of the product appear to depend on the polymerization front velocity and the temperature. The high-temperature and rapid temperature increase at the polymerization front led to products with interconnected porous structures caused by the evaporation of water. So, a fast-swelling, highly absorbing hydrogel with respect to batch polymerization was obtained.

Barium titanate powder has been prepared using sol-gel auto-ignition synthesis process and was compared with two commercial high purity BaTiO3 powders prepared by precipitation from oxalate precursor and by hydrothermal synthesis. Characterization by x-ray fluorescence, XRD, field emission scanning electron microscopy, SEM and BET revealed significant difference, particularly in particle size and agglomerate structure, resulting in different microstructure and dielectric property. The sol-gel auto-ignition synthesis process yielded weakly agglomerated powder with average particle size of 50 nm. This property is favorable for sintering and dielectric property.

Ba3(Ca1.18Nb1.82)O9-δ (BCN18) is a novel complex perovskite structure proton conductor. Nanocrystalline BCN18 was synthesized by means of sol-gel method. The solid oxide electrolyte was prepared by using this powder, and its sintering behavior was studied. SEM and XRD were performed to demonstrate its sintering properties. Its electrical conductivity was systematically investigated at intermediate temperature (400～600°C).

Large scale tungsten nanowires and tungsten nanodots are prepared in a controllable way. The preparation is based on mechanisms of chemical vapor transportation and phase transformation during the reduction of ammonium metatungstate (AMT) in H2. The AMT is first encapsulated into the hollow core of nanostructured carbon with hollow macroporous core/mesoporous shell (NC-HMC/MS) and forms nanorods, which are the precursors of both tungsten nanowires and tungsten nanodots. Just by controlling H2 flow rate and heating rate in the reduction process, the AMT nanorods could turn into nanowires (under low rate condition) or nanodots (under high rate condition). Besides, via heat treatment at 1200 °C, the as-obtained nano-sized tungsten could convert into W2C nanorods or WC nanodots respectively. Furthermore, the diameter of the as-obtained tungsten or tungsten carbide is confined within 50 nm by the NC-HMC/MS, and no agglomeration appears in the obtained nanomaterials.

In this article we present a new kind of large grain transparent glass-ceramics obtained by the method of crystal growth from a homogenous glass, the simultaneous variation of the glass matrix and crystalline compositions during the crystallization results in the high transparency of this kind of large grain, high crystalline volume glass-ceramics, which have suitable refractive indexes between respective phases. The nucleation and crystallization behaviors of this kind of glass-ceramics have been investigated. The optimum heat treatment schedule for the glass was determined by means of DSC, XRD and SEM. The desirable optical property, such as laser characteristics etc, of this new kind of glass-ceramics can be further developed by doping with transition metals or rare-earths.

SiC nanowires (NWs) are commonly prepared in a Si-C-N system, but its formation mechanism is not fully understood. High resolution transmission electron microscopy and electron energy loss spectroscopy observation recorded the growth process of how Si(3)N(4) NWs were transformed into SiC NWs, and demonstrated the validity of an intermediate template directed SiC NW growth via carbothermal reduction of intermediate Si(3)N(4) NWs in a Si-C-N system. Based on this discovery, an intermediate-template growth mechanism of SiC NWs was proposed.