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Biopolymer-based copper nanoparticles (CuNPs) have become an area of significant interest due to their wide-ranging applications in a variety of fields. However, there remains a challenge in tailoring their morphologies and improving their properties. In this study, CuNPs were synthesized via wet chemical reduction using sodium hypophosphite monohydrate (NaH 2 PO 2 ·H 2 O), l -ascorbic acid and chitosan. The effect of different synthesis conditions, including reaction pH, temperature, time, concentration of NaH 2 PO 2 ·H 2 O, l -ascorbic acid and chitosan, as well as the deacetylation degree (DD) of chitosan, on the synthesis of CuNPs was investigated. The synthesized CuNPs were characterized by various analytical techniques. The catalytic properties of synthesized CuNPs were investigated for the reduction of 4-nitrophenol (4-NP) in the presence of sodium borohydride. The synthesis-morphology-catalytic activity relationship of CuNPs was discussed. The results suggested that the morphology of CuNPs could be adjusted by controlling the synthesis conditions. Chitosan DD significantly impacts the morphology of the synthesized CuNPs. As the chitosan DD decreased from 91.8 % to 52.3 %, the average particle size of synthesized CuNPs decreased from 43.9 ± 10.6 to 17.7 ± 5.9 nm and the shape changed from anisotropy to near-sphere. CuNPs synthesized using low DD (53.2 %) chitosan (CuNPs-N3) demonstrated the highest 4-NP conversion rate of 99.1 % and reaction rate constant of 0.3540 min−1. CuNPs-N3 was thermodynamically and kinetically more feasible than CuNPs synthesized with high DD chitosan. These findings provide important insights for further designing and developing hierarchical nanostructured CuNPs catalysts for broader applications. [ABSTRACT FROM AUTHOR]

Calcite (CaCO3), one of the main impurities, has an uncertain effect on the volatilization behavior of tin oxide in the tin-bearing iron ore concentrates during the selective reduction volatilization process. In this study, natural calcite powders were added into the tin-bearing iron ore concentrates to investigate tin volatilization behavior affected by CaCO3under different roasting temperature, CO content, and roasting time. In addition, the effect of CaCO3on the phase transformation of SnO2was determined using XRD, SEM-EDS combined with thermodynamics calculation. The results indicated that CaCO3had a significantly adverse effect on the Sn volatilization ratio, because Ca2SnO4was easily formed under CO-CO2atmosphere. It was also found from the study that the generation of SnO(s)was the most critical intermediate for promoting the formation of Ca2SnO4. [ABSTRACT FROM AUTHOR]

A mild photo-assisted reduction method was developed to fabricate large-area, uniform reduced graphene oxide–TiO2films and micropatterns on various substrates in air at room temperature from a composite insulating film of graphene oxide sheets and TiO2nanoparticles, with a conductivity (0.5–2 Ω cm) comparable to chemically reduced graphene. [ABSTRACT FROM AUTHOR]

An investigation on the behavior of SnO 2 in the tin-bearing iron concentrates during the reduction sintering process (RSP) has been conducted by the authors' group. It was found that only about 30 wt.% of tin was removed under the optimal conditions. However, the underlying reason why it was so difficult to remove tin by the RSP was not understood. In this study, the phase evolution of tin oxide, iron oxide and calcium oxide under simulative sintering conditions was investigated by varying the gas compositions, sintering temperature and basicity (CaO/SiO 2 ). The results indicated that the Ca-Sn oxides were prior formed at 900 °C–1000 °C in the reduction atmosphere with CO / (CO + CO 2 ) = 10–40 vol.%, while the phases of Fe-Sn spinel (Fe 3 − x Sn x O 4 ) and Ca-Fe-Sn oxides were easily generated as the temperature increased to 1100 °C–1200 °C. The phases of Fe 2 − 4x/3 Sn x O 3 and Ca-Fe-Sn-Si oxides began to generate at 1100 °C in an oxidative atmosphere with O 2 /(O 2 + CO 2 ) = 25–100 vol.%. In addition, increasing alkalinity accelerated the formation of Ca-Sn oxides under reduction atmosphere, which brought about an adverse effect on the tin removal in the sintering process. [ABSTRACT FROM AUTHOR]

A selective reduction volatilization (SRV) process developed by the authors could remove excessive tin from the complex tin-bearing iron concentrates. But it was especially noteworthy that the volatilization ratio of Sn and the residual tin content were obviously influenced by the variation of roasting parameters during the SRV process. Hence, the existence form of residual tin in the roasted products and the possible reactions between SnO 2 and Fe 3 O 4 need to be further determined. In the present study, the effect of roasting parameters on the reduction of SnO 2 in the tin-bearing iron concentrates was first investigated. Then, samples with diverse cassiterite/magnetite (C/M) mass ratios were used to determine the effect of magnetite on phase transformation of SnO 2 by using XRD, SEM–EDS, etc. The results indicated that magnetite markedly affected the tin volatilization and phase transformation of SnO 2 under CO–CO 2 atmospheres. Fe–Sn spinel was easily formed during the reduction process, and higher roasting temperatures promoted the formation of Fe–Sn spinel, which had an adverse effect on the Sn volatilization ratio. [ABSTRACT FROM AUTHOR]

Quartz (SiO 2 ), one of the main gangue minerals in the tin-bearing iron concentrates, has an uncertain effect on the volatilization behavior of tin during the selective reduction volatilization (SRV) process. In this study, high purity quartz was added into the tin-bearing iron concentrates to investigate the tin volatilization behavior affected by SiO 2 under CO–CO 2 atmosphere of 10–70 vol.% CO at 900–1100 °C. In order to eliminate the interference of iron oxide in the iron concentrates, the reduction behavior of natural cassiterite and the mixture (20 wt.% cassiterite and 80 wt.% quartz) was also determined. Effect of SiO 2 on the phase transformation of SnO 2 was conducted using SEM–EDS, chemical phase analysis, etc. [ABSTRACT FROM AUTHOR]

Highlights: [•] High pressure study of graphene nanoplates is carried out by Raman spectroscopy. [•] The transition pressure for graphene nanoplates is found to be lower than that for graphite. [•] The reasons for the reduction of transition pressure for graphene nanoplates are discussed. [Copyright &y& Elsevier]