<div style="text-align:justify;"> Environmental barrier coatings (EBCs) play a critical role in mitigating the degradation of SiC<sub>f</sub>/SiC ceramic matrix composites (CMCs) in complex...<div style="text-align:justify;"> Environmental barrier coatings (EBCs) play a critical role in mitigating the degradation of SiC<sub>f</sub>/SiC ceramic matrix composites (CMCs) in complex combustion environment, and improve the service life of thermal engine components. In this paper, by adjusting the parameters of atmospheric plasma spraying (APS), the spraying process of ytterbium disilicate (Yb<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>) under a lower power has been optimized. A two-layer EBC system consisting of ytterbium disilicate and silicon is prepared on the SiC<sub>f</sub>/SiC composite substrate by using optimized technological parameters. The thermal resistance and water oxygen corrosion resistance of such two-layer EBC system are investigated. The results indicate that the current ytterbium disilicate/silicon EBC system exhibits good phase stability, excellent water vapor and oxygen corrosion resistance. However, the exposed silicon bonding layer tends to generate an excessive thermal growth oxide (TGO) layer known as SiO<sub>2</sub>, leading to an early spallation of the coating. </div>展开更多
This study compared the growth performance, nutrient utilization, and slaughter traits of Dorper crossbred male lambs fed as per the established nutrition recommendations for sheep, with an aim to verify the efficacy ...This study compared the growth performance, nutrient utilization, and slaughter traits of Dorper crossbred male lambs fed as per the established nutrition recommendations for sheep, with an aim to verify the efficacy of different feeding standards. A total of 576 lambs(4 months of age, 28.3 ± 0.86 kg BW) were randomly allotted to 3 treatments with 12 replicates per treatment(16 lambs per replicate).The lambs were fed diets formulated according to the following 3 nutritional systems: the nutrient requirements of Dorper crossbred lambs established by Chinese Academy of Agricultural Sciences(CAAS),NRC(National Research Council),(2007), and AFRC(Agricultural and Food Research Council)(1993). The experiment lasted for 81 d. Feed intake was recorded every 3 days, and lambs were weighed every 20 days. Digestibility trials were conducted with 6 lambs each group from d 42 to 53 and d 70 to 81. At the end of the experiment, 10 lambs randomly chosen from each group were sacrificed to determine the carcass traits and meat quality. The results indicated that the lambs in the NRC group had the highest dry matter intake(DMI), followed by those in the AFRC and CAAS groups(P < 0.05). The average daily gain,carcass weight, and dressing percentage were higher for lambs in the CAAS group than those in the NRC group(P < 0.05). The lambs in the CAAS group had the lowest feed conversion ratio, followed by those in the AFRC and NRC groups(P < 0.05). The apparent digestibility of DM was higher for the lambs in the CAAS group than those in the NRC group(P < 0.05). Water losing rate, as well as the lightness(L*),redness(a*), and yellowness(b*) values of the longissimus thoracis were not different among groups(P > 0.05). In conclusion, Dorper crossbred lambs fed diets formulated according to the CAAS recommendations exhibited superior growth performance than those fed diets formulated according to the American or British feeding standards.展开更多
文摘<div style="text-align:justify;"> Environmental barrier coatings (EBCs) play a critical role in mitigating the degradation of SiC<sub>f</sub>/SiC ceramic matrix composites (CMCs) in complex combustion environment, and improve the service life of thermal engine components. In this paper, by adjusting the parameters of atmospheric plasma spraying (APS), the spraying process of ytterbium disilicate (Yb<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>) under a lower power has been optimized. A two-layer EBC system consisting of ytterbium disilicate and silicon is prepared on the SiC<sub>f</sub>/SiC composite substrate by using optimized technological parameters. The thermal resistance and water oxygen corrosion resistance of such two-layer EBC system are investigated. The results indicate that the current ytterbium disilicate/silicon EBC system exhibits good phase stability, excellent water vapor and oxygen corrosion resistance. However, the exposed silicon bonding layer tends to generate an excessive thermal growth oxide (TGO) layer known as SiO<sub>2</sub>, leading to an early spallation of the coating. </div>
基金supported by the Inner Mongolia Science and Technology Key Project (201407011)Earmarked Fund for China Agriculture Research System (CAAS-38)the National Natural Science Foundation of China (Grant No: 41475126)
文摘This study compared the growth performance, nutrient utilization, and slaughter traits of Dorper crossbred male lambs fed as per the established nutrition recommendations for sheep, with an aim to verify the efficacy of different feeding standards. A total of 576 lambs(4 months of age, 28.3 ± 0.86 kg BW) were randomly allotted to 3 treatments with 12 replicates per treatment(16 lambs per replicate).The lambs were fed diets formulated according to the following 3 nutritional systems: the nutrient requirements of Dorper crossbred lambs established by Chinese Academy of Agricultural Sciences(CAAS),NRC(National Research Council),(2007), and AFRC(Agricultural and Food Research Council)(1993). The experiment lasted for 81 d. Feed intake was recorded every 3 days, and lambs were weighed every 20 days. Digestibility trials were conducted with 6 lambs each group from d 42 to 53 and d 70 to 81. At the end of the experiment, 10 lambs randomly chosen from each group were sacrificed to determine the carcass traits and meat quality. The results indicated that the lambs in the NRC group had the highest dry matter intake(DMI), followed by those in the AFRC and CAAS groups(P < 0.05). The average daily gain,carcass weight, and dressing percentage were higher for lambs in the CAAS group than those in the NRC group(P < 0.05). The lambs in the CAAS group had the lowest feed conversion ratio, followed by those in the AFRC and NRC groups(P < 0.05). The apparent digestibility of DM was higher for the lambs in the CAAS group than those in the NRC group(P < 0.05). Water losing rate, as well as the lightness(L*),redness(a*), and yellowness(b*) values of the longissimus thoracis were not different among groups(P > 0.05). In conclusion, Dorper crossbred lambs fed diets formulated according to the CAAS recommendations exhibited superior growth performance than those fed diets formulated according to the American or British feeding standards.
