Preparation of Highly Crystalline TiO2 Nanostructures by Acid-assisted Hydrothermal Treatment of Hexagonal-structured Nanocrystalline Titania/Cetyltrimethyammonium Bromide Nanoskeleton

Highly crystalline TiO2 nanostructures were prepared through a facile inorganic acid-assisted hydrothermal treatment of hexagonal-structured assemblies of nanocrystalline titiania templated by cetyltrimethylammonium bromide (Hex-ncTiO2/CTAB Nanoskeleton) as starting materials. All samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The influence of hydrochloric acid concentration on the morphology, crystalline and the formation of the nanostructures were investigated. We found that the morphology and crystalline phase strongly depended on the hydrochloric acid concentrations. More importantly, crystalline phase was closely related to the morphology of TiO2 nanostructure. Nanoparticles were polycrystalline anatase phase, and aligned nanorods were single crystalline rutile phase. Possible formation mechanisms of TiO2 nanostructures with various crystalline phases and morphologies were proposed

Kinematics and Mechanical Properties of Knees following Patellar Replacing and Patellar Retaining Total Knee Arthroplasty

Knee injury is a common medical issue. A full understanding of the kinematics and mechanical properties of knees following total knee arthroplasty (TKA) repair utilizing patellar replacement (only the base of the patella is replaced) versus patellar retaining surgical techniques is still lacking. In the current paper, we investigated magnetic resonance (MR) imaging data from knees repaired by these two methods and evaluated total knee models created using imaging reconstruction technology that simulated gait conditions. Results revealed that patellar replacement had little influence on tibiofemoral kinematics, although the tibia-surface equivalent stress increased slightly. By contrast, patellar replacement had a significant influence on the patellofemoral joint; patellar internal rotation, external rotation, and medial-lateral translation were all increased. Moreover, the stress distribution on patellar prostheses was altered, resulting in an increased surface maximal equivalent stress on the corresponding area. Moreover, during the gait cycle, we found that the area with maximal equivalent stress shifted its position. Finally, the patellofemoral joint showed decreased motion stability. From the view of kinematics and mechanics, this paper suggests that patella should be retained during TKA if it is possible. The present study presented approaches and technologies for evaluating kinematics and mechanical properties of total knee joint after TKA under gait loads

Synthesis of nanostructured tungsten carbonitride (WNxCy) by carbothermal ammonia reduction on activated carbon and its application in hydrazine decomposition

A carbothermal NH3 reduction method was introduced for the synthesis of nanostructured tungsten carbonitride using support carbon and NH3 as carbon source and nitrogen source, respectively. A series of samples synthesized by this route from WO3/AC were characterized by X-ray diffraction, temperature-programmed surface reaction-mass spectroscopy, transmission electron microscopy, and microcalorimetry. The results demonstrated that a nanostructured tungsten carbonitride (WNxCy) was successfully synthesized on activated carbon at 800 degrees C and the resulting WNxCy was uniformly dispersed on the carbon support with particle size less than 2 nm. The WNxCy/AC prepared by the carbothermal NH3 process has stronger capability for CO adsorption and exhibited better catalytic performance for hydrazine decomposition than the WCx/AC-H catalyst prepared by the carbothermal H-2 reduction process. Further bench-scale tests indicated that it could be a promising substitute for the traditional Ir/Al2O3 catalyst in hydrazine decomposition technology. (C) 2016 Elsevier B.V. All rights reserved

Designing of highly selective and high-temperature endurable RWGS heterogeneous catalysts: recent advances and the future directions

Reverse water gas shift (RWGS) reaction can be served as a pivotal stage of transitioning the abundant CO2 resource into chemicals or hydrocarbon fuels, which is attractive for the CO2 utilization and of eventually significance in enabling a rebuilt ecological system for unconventional fuels. This concept is appealing when the process is considered as a solution for the storage of renewable energy, which may also find a variety of potential end uses for the outer space exploration. However, a big challenge to this issue is the rational design of high temperature endurable RWGS catalysts with desirable CO product selectivity. In this work, we present a comprehensive overview of recent publications on this research topic, mainly focusing on the catalytic performance of RWGS reaction over three major kinds of heterogeneous catalysts, including supported metal catalysts, mixed oxide catalysts and transition metal carbides. The reaction thermodynamic analysis, kinetics and mechanisms are also described in detail. The present review attempts to provide a general guideline about the construction of well-performed heterogeneous catalysts for the RWGS reaction, as well as discussing the challenges and further prospects of this process. (C) 2017 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved

A CFD model for predicting the heat transfer in the industrial scale packed bed

Compared to the traditional lumped-parameter model, computational fluid dynamics (CFD) attracted more attentions due to facilitating more accurate reactor design and optimization methods when analyzing the heat transfer in the industrial packed bed. Here, a model was developed based on the CFD theory, in which the heterogeneous fluid flow was resolved by considering the oscillatory behavior of voidage and the effective fluid viscosity. The energy transports in packed bed were calculated by the convection and diffusion incorporated with gaseous dispersion in fluid and the contacting thermal conductivity of packed particles in solids. The heat transfer coefficient between fluid and wall was evaluated by considering the turbulence due to the packed particles adjacent to the wall. Thus, the heat transfer in packed bed can be predicted without using any adjustable semi-empirical effective thermal conductivity coefficient. The experimental results from the literature were employed to validate this model. (C) 2017 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved

Supported Noble-Metal Single Atoms for Heterogeneous Catalysis

Single-atom catalysts (SACs), with atomically distributed active metal sites on supports, serve as a newly advanced material in catalysis, and open broad prospects for a wide variety of catalytic processes owing to their unique catalytic behaviors. To construct SACs with precise structures and high density of accessible single-atom sites, while preventing aggregation to large nanoparticles, various strategies for their chemical synthesis have been recently developed by improving the distribution and chemical bonding of active sites on supports, which results in excellent activity and selectivity in a variety of catalytic reactions. Noble-metal-based SACs are discussed, and their structural properties, chemical synthesis, and catalytic applications are highlighted. The structure-activity relationships and the underlying catalytic mechanisms are addressed, including the influences of surface species and reducibility of supports on the activity and stability, impact of the unique structural and electronic properties of single-atom centers modulated by metal/support interactions on catalytic activity and selectivity, and how the modified catalytic mechanism obtained by inhibiting the multiatoms involves catalytic pathways. Finally, the prospects and challenges for development in this field are highlighted