对9种不同掺量矿物掺合料条件下的不同配合比混凝土的耐久性能进行了研究。研究发现:随着矿物掺合料的掺入比例不断增加,由于混凝土内部孔结构和级配得到较为有效改善,混凝土的氯离子扩散系数不断减小,混凝土抵抗氯离子渗透能力逐渐增强...对9种不同掺量矿物掺合料条件下的不同配合比混凝土的耐久性能进行了研究。研究发现:随着矿物掺合料的掺入比例不断增加,由于混凝土内部孔结构和级配得到较为有效改善,混凝土的氯离子扩散系数不断减小,混凝土抵抗氯离子渗透能力逐渐增强,抗碳化能力不断降低,在混凝土的水胶比较大时效果明显。当水胶比为0.26,粉煤灰掺量为50%时,C70混凝土的氯离子扩散系数最小,达到0.403/(10-8 cm 2/s);粉煤灰掺量为40%时,C70混凝土的抗碳化性能最强,达到1.0 mm。展开更多
In this work, lemon and onion biomasses commonly found in street markets are for the first time used to develop a facile, fast and low-cost one-step microwave-assisted carbonization method for synthesis of highly fluo...In this work, lemon and onion biomasses commonly found in street markets are for the first time used to develop a facile, fast and low-cost one-step microwave-assisted carbonization method for synthesis of highly fluorescent carbon dots (CDs). The structure and optical properties of CDs were investigated by TEM, XRD, XRF, UV-Vis, FTIR, and fluorescence spectroscopy. CDs displayed satisfactory optical pro-prieties, a high quantum yield of 23.6%, and excellent water solubility, and the particle size was 4.23-8.22 nm with an average diameter of 6.15 nm. An efficient fluorescent resonance energy transfer (FRET) between the CDs and riboflavin was achieved with CDs acting as donor and riboflavin as acceptor. A linear relationship between FRET and the riboflavin concentration from 0.10 to 3.0 μg/mL was observed, allowing the development of an accurate and fast analytical method to determine this vitamin in multivitamin/mineral supplements. Despite the potential interferences in these supplements, CDs were selective for riboflavin under optimized conditions. A paired t-test at a 95% confidence level indicated no statistically significant difference between the proposed and the reference methods. Recovery test presented values ranged from 96.0% to 101.4%. The limit of detection and relative standard deviation were estimated at 1.0 ng/mL and <2.6% (n = 3), respectively. CDs were successfully synthesized in a domestic microwave oven (1450 W, 6 min), presenting satisfactory parameters when compared with results of other studies reported in the literature, suggesting that the proposed method is a potentially useful method for the synthesis of CDs and determination of riboflavin.展开更多
文摘对9种不同掺量矿物掺合料条件下的不同配合比混凝土的耐久性能进行了研究。研究发现:随着矿物掺合料的掺入比例不断增加,由于混凝土内部孔结构和级配得到较为有效改善,混凝土的氯离子扩散系数不断减小,混凝土抵抗氯离子渗透能力逐渐增强,抗碳化能力不断降低,在混凝土的水胶比较大时效果明显。当水胶比为0.26,粉煤灰掺量为50%时,C70混凝土的氯离子扩散系数最小,达到0.403/(10-8 cm 2/s);粉煤灰掺量为40%时,C70混凝土的抗碳化性能最强,达到1.0 mm。
文摘In this work, lemon and onion biomasses commonly found in street markets are for the first time used to develop a facile, fast and low-cost one-step microwave-assisted carbonization method for synthesis of highly fluorescent carbon dots (CDs). The structure and optical properties of CDs were investigated by TEM, XRD, XRF, UV-Vis, FTIR, and fluorescence spectroscopy. CDs displayed satisfactory optical pro-prieties, a high quantum yield of 23.6%, and excellent water solubility, and the particle size was 4.23-8.22 nm with an average diameter of 6.15 nm. An efficient fluorescent resonance energy transfer (FRET) between the CDs and riboflavin was achieved with CDs acting as donor and riboflavin as acceptor. A linear relationship between FRET and the riboflavin concentration from 0.10 to 3.0 μg/mL was observed, allowing the development of an accurate and fast analytical method to determine this vitamin in multivitamin/mineral supplements. Despite the potential interferences in these supplements, CDs were selective for riboflavin under optimized conditions. A paired t-test at a 95% confidence level indicated no statistically significant difference between the proposed and the reference methods. Recovery test presented values ranged from 96.0% to 101.4%. The limit of detection and relative standard deviation were estimated at 1.0 ng/mL and <2.6% (n = 3), respectively. CDs were successfully synthesized in a domestic microwave oven (1450 W, 6 min), presenting satisfactory parameters when compared with results of other studies reported in the literature, suggesting that the proposed method is a potentially useful method for the synthesis of CDs and determination of riboflavin.
