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One of the critical issues in the application of supercritical water oxidation technology is to improve the corrosion resistance of reactor materials. Use of Al 2 O 3 coating is one of the most promising methods to address this issue. In this study, thick NiAl/Al 2 O 3 coatings on Inconel 625 substrates were prepared by a consecutive pack embedding and in-situ thermal oxidation process. The effect of aluminizing and oxidation temperature on phase structure and coating thickness is studied. Results show the diffusion of Al from the exterior to the interior of the alloy matrix to form intermetallic compounds between Al and metal elements in the matrix (Ni, Cr, Mo, etc.). Moreover, the coating thickness can reach above 300 μm at the aluminizing temperature of 950 °C. Increasing the aluminizing temperature above 950 °C will not increase the coating thickness further. After high temperature oxidation subsequently, only phases of NiAl and Al 2 O 3 were detected. The formation of Al 2 O 3 layer can be ascribed to the surface oxidization of Al. And the NiAl between the alloy substrate and Al 2 O 3 coating provides an interfacial layer that can alleviate the crack or exfoliation of ceramic coating due to the mismatching of thermal expand coefficient. The thick NiAl/Al 2 O 3 coatings prepared by aluminizing 950 °C and oxidizing at 1100 °C exhibit satisfied corrosion resistance after supercritical water test. This work would provide a significant method to develop advanced ceramics coating for the corrosion resistance of alloys. [ABSTRACT FROM AUTHOR]

Li 4 Si 1–x Ti x O 4 ceramic solid solution was considered as a promising tritium breeding material for fusion reactor blanket. In this work, the effects of the sintering atmosphere on the phase composition, microstructure, and mechanical properties of Li 4 Si 0.7 Ti 0.3 O 4 ceramic pebbles were investigated for the first time, aiming to explore the optimal sintering atmosphere for this solid solution. The results show that compared with air and argon atmosphere, the negative pressure of vacuum atmosphere was more favorable for Ti to enter the Li 4 SiO 4 crystal structure as a substitute for Si atom to form a solid solution. More importantly, sintering in argon-vacuum atmosphere can ensure the formation of solid solution while fully exerting the liquid phase sintering effect. The crushing load of the Li 4 Si 0.7 Ti 0.3 O 4 ceramic pebbles sintered at 800 °C in argon-vacuum atmosphere reaches 30.3 ± 3.2 N. In general, the appropriate sintering atmosphere was of great significance for obtaining Li 4 Si 0.7 Ti 0.3 O 4 solid solution to meet the performance requirements of tritium breeding blanket. [ABSTRACT FROM AUTHOR]

In this study, Li-rich 2Li 2 TiO 3 –Li 4 SiO 4 composite breeding ceramics were prepared for the first time through a two-step low-temperature sintering route to meet the increasingly stringent performance requirements of tritium breeding materials. The effects of excess Li addition and sintering atmosphere on the phase composition, mechanical properties, and microstructure of the composite breeding ceramics were systematically studied. A two-step low-temperature sintering method was proposed to integrate the advantages of different sintering environments. The results show that moderate Li addition can significantly enhance the crushing load of composite ceramics while maintaining the nanostructure. However, further increasing the amount of Li addition does not continue to increase the crushing load, and will even affect the structural uniformity of the composite breeding ceramics. Most importantly, the S2.5 (2Li 2.5 TiO 3 –Li 4 SiO 4 , molar ratio) composite breeding ceramics sintered at 750 °C in an air-vacuum environment exhibited a grain size of ∼86 nm and a crushing load of ∼66.9 N, which has not been achieved by previous studies. [ABSTRACT FROM AUTHOR]

In this study, AlON powders with different AlN contents were synthesized by the carbothermal reduction nitridation method and used to prepare transparent AlON ceramics. Lattice parameters of AlON powders were calculated from XRD patterns to evaluate the effects on microstructure. The influences of the AlN content on the properties of the resulting AlON ceramics was investigated in aspect of density, mechanical properties and optical properties. With an increase in the AlN content, the density of the AlON ceramics increased, the grain size decreased, and the hardness and fracture toughness increased. Transparent AlON ceramics were obtained at the AlN content of 21.6–29.7 mol%. The refractive index of the AlON ceramics increased from 1.688 to 1.702 at 4000 nm with an increase of AlN content. The correlation between the composition and properties of the AlON ceramics obtained in this study will provide both theoretical and experimental reference for industrial AlON ceramic manufacturing. [ABSTRACT FROM AUTHOR]

A novel mass production method of lithium titanite (Li 2 TiO 3) tritium breeder ceramic pebbles using polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) assisted granulation method (APG) was proposed. A binder solution of polyvinyl alcohol (PVA) was used to modify the Li 2 TiO 3 precursor powder. The powders with adhesive properties were prilled to form green pebbles (GPs) by spheronization at a low rotation speed and spraying with polyvinyl pyrrolidone (PVP), in several cycles. Then, the density and the crush load of the GPs were improved by high-speed rolling. Finally, the ceramic pebbles were produced by sintering. The phase, the microstructure, and the crush load of the ceramic pebbles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and with a universal tester, respectively. [ABSTRACT FROM AUTHOR]

Synthesis of fine Li 2 TiO 3 powders via low-temperature solid-state reaction (LTSSR) was studied. Solid Li 2 CO 3 and H 2 TiO 3 were blended by planetary ball mill with deionized water as medium. Calcination of the milled powder at low temperature of 500 °C resulted in the formation of pure Li 2 TiO 3 nanoparticles. Another Li 2 TiO 3 powder was also prepared by the conventional solid-state reaction (SSR) and a good comparison between different routes was realized. The results show that the particle size of LTSSR powder is significantly decreased to 19.6 nm while the one obtained by SSR is 146.6 nm. Low temperature calcined powders have less agglomeration and higher sinterability, which can be sintered at lower temperature. Pebbles sintered from the LTSSR powders at 750 °C exhibit small grain size (650 nm), high relative density (85.1%) and satisfactory crush load (42.8 N), whereas the SSR pebbles can only be sintered above 950 °C with the relative density close to 80%. Besides, the LTSSR samples also have a higher conductivity at room temperature, indicating the lower tritium diffusion barrier in ceramics. It is confirmed that H 2 TiO 3 rather than TiO 2 is more appropriate for the solid-state reaction to produce Li 2 TiO 3 powders with nano-size particles and favorable properties. [ABSTRACT FROM AUTHOR]

Lithium metatitanate (Li 2 TiO 3) ceramic pebbles were fabricated from the powder synthesised via low-temperature solid-state precursor method. Solid H 2 TiO 3 and LiOH·H 2 O react chemically during ball milling process to form a nano-sized precursor powder. Pure β-Li 2 TiO 3 powder can be obtained by calcining the precursor powder at 500 °C, which is half the temperature of conventional solid-state method. The synthesis process is simple and low-cost, which would be more available to achieve batch production among all feasible techniques. The low-temperature calcination will effectively avoid hard particle aggregates and poor sinterability caused by high-temperature heat treatment, which is conducive to prepare ceramics with good properties. The results show that the powder exhibits high sinterability with small particle size of 19 nm. The Li 2 TiO 3 ceramic pebbles sintered at 800 °C have small grain size (470 nm), high relative density (83%) and good crush load (45 N), which has great potential as tritium breeding materials for fusion reactors. [ABSTRACT FROM AUTHOR]

Abstract The influence of high B 4 C contents on the structural evolution of Al-B 4 C nanocomposite powders during high energy ball milling was investigated. Al-B 4 C nanocomposite powders with various weight percentages of B 4 C particles (10, 30 and 40 wt%) were prepared. The scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis were carried out for the evaluation of structural evolution in the matrix. Nanocrystalline Al-B 4 C composite powders were successfully synthesized after milling. The morphology of matrix transformed from flat elongated to more fragmented with partly equiaxed, and the size of matrix powders decreased as the B 4 C content increased. The XRD analysis shows that the average grain sizes of 48 nm, 46 nm, and 45 nm corresponded to B 4 C contents of 10, 30 and 40 wt% respectively after 60 h of milling, TEM observation (51, 41 and 42 nm, respectively) shows good conformance with XRD analytical results. It illustrated that the grain size of Al was decreased with the increase of B 4 C. However an inverse variation relationship of lattice strain, dislocation density is evident with the increase of B 4 C content. It indicated that Al-30% B 4 C and 40% B 4 C nanocomposite powders induced the finer grain size even with low lattice strain and dislocation density. It could be explained as the enhanced and prolonged effect of the grain size decreased rapidly in the early stage of ball milling, but the lattice strain and dislocation density are still lower than that in the later stage. The results revealed that grain refinement can enhance with high reinforcement content even at low lattice strain and dislocation density. Furthermore, the increase in the B 4 C content can also lead to the transformation from irregular or flat elongated grains to equiaxed nanograin morphology. [ABSTRACT FROM AUTHOR]

Lithium titanium oxide (Li 2 TiO 3) tritium breeder ceramic plates with nano- and coarse-grain size were fabricated. The preparation methods contained CTAB-modifying precursor, combining dry-pressing with isostatically cold-pressing, and calcinating at optimized sintering temperature in turn. Then their properties were characterized after radiation by 280 keV helium (He+) ion. Extensive characterization analyses were performed to reveal the changes in nano-grained and coarse-grained Li 2 TiO 3 after radiation. They contained glancing angle X-ray diffraction (GIXRD), atomic force microscopy (AFM), electron spin resonance (ESR), and scanning electron microscopy (SEM). The results showed as follows, GIXRD peak position of the nano-grained Li 2 TiO 3 was more stable than the coarse-grained Li 2 TiO 3 after radiation. Nano-grained Li 2 TiO 3 was less rough and swollen than the coarse-grained one after radiation. Nano-grained Li 2 TiO 3 had more excellent structural stability and less defect concentration of Eʹ-center after radiation. As a result, nano-grained Li 2 TiO 3 might have much better radiation tolerance than the coarse-grained one by comparing characterization results. [ABSTRACT FROM AUTHOR]

Alumina ceramics and graphene circuits-on-ceramics were 3D printed using inkjet technology. Water-based binders for ceramics and graphene oxide inks were prepared and jetted through thermal inkjet printhead. To increase the density of the 3D printed ceramics, two steps sintering and one step infiltration were performed. The sintering temperature dependent structure properties of the printed ceramics were systematically studied. The 3D printed α-Al 2 O 3 ceramic sintered at 1600 °C for 2 h has achieved maximum density of 95.2%, volume shrinkage rate of 32%, Vickers hardness of 291.6 Hv, surface roughness of 3.7 μm, and maximum compression strength and flexural strength of 89 MPa and 49.4 MPa, respectively. The average adhesion of reduced graphene oxide (rGO) to 3D printed α-Al 2 O 3 ceramic is 7.5 N/m. The printed graphene circuits-on-ceramics has achieved conductivity of 5.34 × 102 S m−1 after annealing at 600 °C in nitrogen atmosphere. [ABSTRACT FROM AUTHOR]

Li 4 TiO 4 is an attractive tritium breeding material due to its high lithium density for the application in fusion reactors. Diffusion in the crystal lattice is a vital step of the tritium release process. In this paper, we report the diffusion of a tritium interstitial in the Li 4 TiO 4 crystal from first-principles calculations. The tritium interstitial sites, diffusion paths and activation energies of diffusion are obtained. We find the most favorable tritium diffusion path is along <001> of the Li 4 TiO 4 crystal with an activation energy of 0.410 eV. The activation energy is 0.366 eV for tritium at 450 K after the vibrational correction is applied. The calculated activation energy is in good agreement with the experimental value of 0.370 eV. [ABSTRACT FROM AUTHOR]

The Li 4 TiO 4 ceramic is a promising solid-state tritium breeder material for the production of tritium fuel in the designs of fusion reactors. Tritium extraction efficiency is one of the key factors that determines the performance of the breeder material. Vacancies are known to trap tritium and adversely affect tritium extraction. Understandings of tritium-trapped defect configurations in Li 4 TiO 4 are limited so far. In this work, the oxygen/lithium vacancy (V O/Li) and the vacancy-tritium defect complex (V O/Li + T) in Li 4 TiO 4 are studied by first-principles density functional theory. The atomic configurations, formation energies and electronic structures of various charged defect species are obtained. We find that 2+ and 0 are the dominate charge states of V O , 1- is the dominate charge state of V Li , 1+ is the dominate charge state of the defect complex (V O + T), and 0 is the dominate charge state of (V Li + T). Tritium atoms trapped in V O are bonded to Ti atoms, and those trapped in V Li are bonded to O atoms. [ABSTRACT FROM AUTHOR]

ZnIn 2 S 4 /TiO 2 photocatalyst was obtained by a facile hydrothermal method. Various techniques were used to characterize the ZnIn 2 S 4 /TiO 2 , crystal structure and optical properties of ZnIn 2 S 4 /TiO 2. Cr (Ⅵ) as highly-toxic pollutant was used as the target reduction product to evaluate the catalytic performance of ZnIn 2 S 4 /TiO 2 under visible light irradiation. According to the experiment results, the reduction rate of Cr(VI) in the presence of ZnIn 2 S 4 /TiO 2 reaches 99% within 60 min, which is much better than ZnIn 2 S 4 and TiO 2 , respectively. At the same time, ZnIn 2 S 4 /TiO 2 also performs good stability for reduction rate hardly changes after 5 recycling experiments. [ABSTRACT FROM AUTHOR]

B 4 C ceramic pellets with diameter smaller than 0.7 mm have been simply fabricated via polyvinyl alcohol (PVA) assisted planet-type rotation method. Only commercial B 4 C powders and tiny amounts of PVA are needed in the experiment. The PVA solution is used to modify the commercial B 4 C powders. And the powders with adhesive properties are spheroidized to form green pellets during the rotation process. Results show that the green B 4 C pellets exhibit uniform size distribution and high sphericity. The appropriate diameter of 0.61 mm and high sphericity of 97.15% can be obtained by controlling the rotation time and the concentration of PVA solution. This fabrication method provides a low-cost and simple way to prepare B 4 C ceramic pellets with various diameters and high sphericity, and also sheds light on the mass production of other ceramic microspheres. [ABSTRACT FROM AUTHOR]

A comparative study between the microwave and conventional sintering of Li 2 TiO 3 –Li 4 SiO 4 biphasic ceramic pebbles was systematically performed. Comparing to samples sintered by conventional method, the microwave sintered samples exhibited homogeneous microstructure with uniform grain size distribution. In addition, the microwave sintered samples showed higher relative density (86.0% T.D.) and crush load (22.7 N). The results indicated that the microwave sintering process is a prospective method for fabricating Li 2 TiO 3 –Li 4 SiO 4 biphasic ceramic pebbles with excellent mechanical performance as tritium breeder materials. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a method combining hydrolysis of tetrabutyl orthotitanate (TBOT) and solvothermal reaction was first used to fabricate nanostructured Li 2 TiO 3 tritium breeder ceramic pebbles. Initially, superfine nanostructured Li 2 TiO 3 powders were synthesized with average particle size of about 10 nm, according to TEM. The surface area of precursor particles synthesized via this method was found to be 115.85 m2/g by BET analysis, which is much larger than that of the product obtained using traditional methods. The results showed that precursor particles had high sintering activity. XRD pattern revealed that the phase transition temperature for monoclinic phase Li 2 TiO 3 prepared by this method was nearly 450 °C, which was the lowest phase transition temperature reported among all wet chemical methods to date. Subsequently, investigation of ceramic sintering demonstrated that Li 2 TiO 3 ceramic pebbles with desired nano-crystalline sizes (27.98 ~ 55.03 nm) were obtained by sintering at 500 ~ 600 °C for 4 h. The possible mechanisms were proposed based on the reaction processes of TBOT hydrolysis, solvothermal reaction and sintering. [ABSTRACT FROM AUTHOR]