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Using microwave heating technology to assist concrete recycling have great potential for improve the quality of recycled concrete aggregate. Unfortunately, there are few studies explored on the properties of concrete incorporating microwave treated coarse aggregates. This study aims to investigate the performance of coarse aggregate after microwave treatment and to evaluate the properties of the resulting concrete incorporated microwave treatment aggregate. The water absorption and crushing value tests were carried out to study the effect of microwave heating treatment on the physical properties of coarse aggregates. Concrete incorporated aggregate with various microwave heating parameters was fabricated and tested. The results indicated that physical performance of microwave treated aggregate was within the range of specification requirement and water absorption and crushing value of coarse aggregate heated under low microwave power levels (2–3 kW) is very closed to the untreated samples, while coarse aggregates treated with high power levels showed a significant increase. It was also observed that concrete made out of low microwave power levels heated aggregates are able to achieve strength on par with natural coarse aggregate concrete. In addition, in case of similar strength, the elastic modulus of microwave treated aggregate concrete is similar to natural aggregate concrete. These results indicate that using low microwave power levels to assisted aggregates recycling can reduce the damage to coarse aggregates to some extent, which provide a further understanding for the application of microwave-assisted aggregates recycling.

Due to the potential for significant process benefit, microwave assisted concrete recycling is highlighted by many scholars and engineers over the world recently. In this paper, a multi-field model is established to simulate the microwave heating process of concrete specimen with single-particle aggregate by using of COMSOL Multiphysics. The validation of this model is verified by comparison with temperature from experiment. Mechanical properties of aggregate-mortar interface during microwave heating process was experimentally investigated. Electric, temperature, stress field evolution and moisture transformation during microwave heating process are discussed in detail. Temperature and stress gradient at mortar-aggregate interface influenced by microwave heating power, frequency and duration are analyzed and graphically presented, which are the dominant factors to achieve the interface debonding. Based on the comparison between concrete absorbed energy and temperature variation, energy efficiency for microwave heating concrete is also briefly discussed. Results of this investigation could provide a multi-field understanding for the microwave treatment on concrete.

Microwave processing is a useful technique for improving the mechanical breakage of rocks and rock minerals. The heating process of microwave absorption materials, transparency materials, and interface properties were investigated in this study. The crack propagation, interfacial debonding, and failure mode of materials under microwave heating were investigated experimentally. The cell model was then established to evaluate the effect of the heating process. In this model, pyrite was considered as a strong microwave absorber, and calcite was assumed to be a non-microwave response phase. The temperature field, stress gradient, and damage evolution of the materials under microwave irradiation were analyzed. Additionally, the effects of microwave power and irradiation time on the mechanical behavior were investigated. Furthermore, the effects of the volume content, particle size, and particle interaction on the heating results were simulated. Theoretical analysis was conducted to understand the related heating phenomenon. This study could enhance the comprehensive understanding of microwave-induced degradation of hard rocks.

Microwave heating is a novel and promising method to remove mortar that adheres to aggregates in recycled concrete. A systematic experiment was carried out to evaluate the heating results o...

Microwave assisted concrete recycling is highlighted by a large number of research groups all over the world due to its potential for significant process benefit. In this paper, systematic experiments are established to study the microwave heating and aggregate recycling of dried and saturated concrete, respectively, investigating the effect of moisture content on heating results. The heating characteristics, cracks propagation, concrete damage and micro-structure variations were demonstrated. The temperature was higher in dried concrete under microwave heating, while the concrete damage and mortar-aggregate interface debonding were firstly occurred in saturated concrete. Recycled aggregates could be obtained by the combinations of mechanical process and microwave treatment in dried sample. While in saturated concrete, aggregates could be easily separated under relatively sufficient microwave power input. The results show that water content has the vital influence on concrete heating and aggregate separation results. The properties of recycled aggregates were tested to evaluate its further applications. The experimental results can provide a new approach to improve the microwave-assisted concrete aggregate recycling efficiency through the increment of water content.

Development of highly active and durable non-precious metal bi-functional electrocatalyst for both oxygen reduction and evolution reaction (ORR and OER) remains a significant challenge. Herein, porous mixed spinel MnCoxO4 was loaded on the N-doped multi-walled carbon nanotubes (MnCoxO4/NCNT) through a facile one-pot hydrothermal method to work as a bi-functional oxygen electrocatalyst. Physical characterizations confirm that the MnCoxO4 nanoparticles are composed of mixed spinel-type Co2MnO4 and (Co, Mn)[Mn, Co]2O4 with a diameter of 5–10 nm, which are dispersed on NCNT with secondary aggregation and resultant porous structure. Electrochemical measurements show that the MnCoxO4/NCNT catalyst exhibits high ORR catalytic activity with a dominant four-electron ORR catalytic pathway, remarkable durability, excellent methanol-tolerance, as well as superior OER catalytic activity with significantly decreased overpotential of 0.479 V in alkaline media. The multiple valence states of Co and Mn ions in MnCoxO4 coupled with the enlarged specific surface area with the help of NCNT exert crucial roles for the superior catalytic performance for both ORR and OER. Such a bi-functional oxygen electrocatalyst based on mixed spinel MnCoxO4 provides a new direction for developing low-cost, highly efficient, and robust multiple valence states transition metal-based electrocatalysts for oxygen electrode.

Hyaluronic acid (HA) is applied in a number of medical applications and HA of different molecular weight (Mw) are used in different pharmaceutical preparations. In determination of Mw by muti-angle laser light-scattering (MALS), refractive index increment (dn/dc) is an important parameter for accuracy. Herein, the influence of dn/dc on the Mw of HA in stroke-physiological saline solution is investigated by MALS in this work. Additionally, the Mw variation of HA in the manufacturing process of preparations is measured. It is shown that each HA sample corresponds to a specific value of dn/dc, which is varied from 1.38 to 1.74 L/g with the Mw increasing from 13.5 to 2840 kDa in solution. It is indicated by the results from both MALS approach and viscometry that appropriate dn/dc should be selected for Mw determination. In steam sterilization process of preparations at 121 °C, the Mw and conformation of HA can be accurately and rapidly determined by MALS. This work provides a precise method to determine the Mw of HA in the medical applications and preparation industries.

Controllable growth of uniform nanoparticles with specific morphology to obtain high active electrocatalyst is a key common problem in developing efficient energy conversion and storage devices. In this work, a tangerine peel-derived carbon (TPC) supported mixed manganese oxides (MnOx/TPC) was synthesized for oxygen reduction reaction (ORR) through a facile pyrolysis procedure. By making full use of the confinement effect of tangerine peel cells, the MnOx nanoparticles of MnOx/TPC-800 are obtained with a components of Mn(II), Mn(III) and Mn(IV) with cubic morphology of about 15 nm and evenly dispersed on the TPC surface. Electrochemistry measurements show that MnOx/TPC-800 demonstrates excellent ORR performance with a comparable half-wave potential to commercial Pt/C and a high onset potential with a dominant 4e− catalytic process, superior stability, and remarkable immunity to methanol crossover effect in alkaline media. The synergy effect between multi-oxidation states MnOx and TPC of MnOx/TPC-800 is proved to play significant factor for its high ORR performance. This study provides a valuable and rational strategy to construct morphology-controlled metal nanoparticles with unique carbon materials in developing cost-effective catalysts for fuel cells and metal air batteries.

Exploring cost-effective, high-performance and durable non-precious metal catalysts is of great significance for the acceleration of sluggish oxygen reduction reaction (ORR). Here, we report an intriguing heteroatom-doped graphitized carbon encased Fe species composite by introducing N, S and B sequentially. The experimental approach was designed ingeniously for that the FeCl3·6H2O could catalyze thiourea to synthesize N, S co-doped carbon materials which would further react with H3BO3 and NH3 (emerged at the heat-treatment process) to prepare N, S and B co-doped carbon materials (Fe-N/S/B-C). The Fe-N/S/B-C exhibits an impressive ORR activity for its half-wave potential of −0.1 V, which is 36 mV or 19 mV higher than that of the corresponding single or dual doped counterparts (Fe-N-C or Fe-N/S-C) and 31 mV positive than that of Pt/C catalyst, respectively. Further chronoamperometric measurement and accelerated aging test confirm the excellent electrochemical durability of Fe-N/S/B-C with the stable core–shell structure. The remarkable ORR performance and facile preparation method enable Fe-N/S/B-C as a potential candidate in electrochemical energy devices.

Controlled synthesis of efficient core-shell non-precious metal catalysts for oxygen reduction reaction (ORR) is undoubtedly crucial but challenging for the extensive application of fuel cells and metal-air batteries. Herein, we prepared a core-shell structured Fe/FeCx nanoparticles and porous carbon composited catalyst (Fe/FeCx@NC) via a facile two-step heat treatment strategy. The Fe/FeCx@NC-800−0.5 prepared with secondary anneal at 800 °C for 0.5 h exhibits superior ORR performance to the commercial Pt/C in terms of comparable onset potential, higher half-wave potential, and outstanding long-term durability in alkaline media. Through combining the physical and electrochemical characterizations of Fe/FeCx@NC-T−t with different anneal temperature and precursors, the outstanding ORR performance of Fe/FeCx@NC-800−0.5 is caused by the synergistic effect between Fe/FeCx core and enriched pyridinic N- and graphitic N-doped carbon shell as well as porous carbon with large specific surface area. The structure-activity relationship of core-shell structured Fe–N–C catalysts for ORR provides directions for the development of advanced nonprecious metals catalysts.

Microwave assisted concrete recycling is highlighted by a large number of research groups all over the world due to its potential for significant process benefit. In this paper, systematic experiments are established to investigate the heating process of mortar-aggregate under microwave irradiation. Four different aggregate types are selected that widely used as aggregates in concrete to represent different kinds of aggregates. The temperature field of both mortar and aggregate under different heating time and microwave power input are obtained. The crack formation, propagation and material damage during the heating process are graphically presented. XRD tests and SEM analysis are carried out to clarify the chemical content and microstructure variation around the aggregate-mortar interface before and after microwave heating. The mechanical properties of recycled concrete are evaluated through the UCS tests. Energy consumptions are tested during the heating process. The applications of microwave recovering aggregates from standard concretes are conducted based on the results obtained in the simplified concrete. The research proves that microwave irradiation could weaken the bonding between mortar and aggregate effectively, which provide a contribution and reference for the further application of microwave-assisted aggregates recycling.

Microwave assisted concrete recycling is highlighted by a large number of research groups all over the world due to its potential for significant process benefit. In this paper, systematic experiments are established to investigate the heating outcomes of mortar-aggregate under microwave irradiation. Four different aggregates are selected that widely used as aggregates in concrete. The temperature variations of mortar and aggregate under different heating times and microwave power inputs are obtained. The crack formation, propagation and material damage during the heating process are illustrated. Push-out tests are conducted after microwave heating process to investigate the interface mechanical behavior of aggregate and mortar. The physical properties of recycled aggregate, including apparent density, porosity, water absorption, toughness and adhered mortar percentage after microwave treatment methods are evaluated. The research proves that microwave irradiation could weaken the bonding between mortar and aggregate effectively, which provide a contribution and reference for the further application of microwave-assisted aggregates recycling.

The purpose of this work was to develop a thermal oxidation technique to improve the wear resistance of titanium alloy for the application of biomedical field. It was found that rutile TiO 2 film was formed on the surface of titanium alloy after thermal oxidation at 700 °C in a gas mixture of nitrogen with 40% oxygen by volume ratio. The nanohardness of TiO 2 film was 21.11 GPa, 299.1% higher than that of titanium alloy. The biotribological test revealed that thermal oxidized titanium alloy exhibited low friction coefficient and high wear resistance, which indicated that the thermal oxidized titanium alloy could be a potential candidate for artificial joints.

Surface composition, the pore size and pore distribution of microporous titanium carbide were investigated to understand the potential use of titanium alloys in the field of artificial joints. The tribological behaviours of the ultra-high-molecular-weight polyethylene (UHMWPE) were investigated to evaluate the potential value of microporous titanium carbide coating on titanium alloys. The result showed that the uniform microporous titanium carbide coating was formed on the substrate of titanium alloys with a porosity of 24.4% after sequential carburization. It was found that the nanohardness values of the bottom and the edges of the pore were significantly increased and kept approximately the same value. Finally, the results also revealed that microporous titanium carbide could not only decrease the friction coefficient, but also decrease the wear rate of UHMWPE.

Enzyme-linked immunosorbent assays (ELISA) show extensive application in immunoassays, to detect and monitor protein biomarkers in clinical diagnosis. Nevertheless, the time required and its multiple steps limit its application. We take advantage of a polyethyleneimine (PEI) gold nanoparticle (GNP) coated microwell plate to perform blocking-free ELISA, in which no nonspecific protein adsorption appears on the GNP layer. If the PEI-GNP coated microwell plate and immobilization of captured antibodies on the plate are prepared in advance, such as using an ELISA kit, the whole ELISA process can be finished in less than 2 h. Meanwhile, we have ensured that the GNP layer can preserve the precision and good linearity of ELISA without causing negative effects on the plate.