光伏废料制备Si3N4-SiC材料的抗氧化性和抗侵蚀性

将光伏废料经酸洗除杂后,与硅粉按85∶15的质量比配料,以聚乙二醇做结合剂,成型为10 mm×10 mm×20 mm的生坯后,在1380℃保温2 h氮化制成Si3N4-SiC材料,然后研究了该Si3N4-SiC材料的抗氧化性和抗侵蚀性。结果表明:1)制备的Si3N4-SiC材料在空气气氛中抗氧化性较好,主要是由于其氧化产物Si2N2O和SiO2填充气孔,促进烧结,提高了试样的致密度。2)在静态熔盐(Na3AlF6)中的抗侵蚀性能较好,主要是由于Na3AlF6渗入气孔中,使其显气孔率降低。3)在动态熔盐中的抗侵蚀性相对变差,主要是由于CO2气体的搅拌和对Si3N4、SiC的氧化二者共同作用的结果。     

User idea implementation in open innovation communities: Evidence from a new product development crowdsourcing community

In collaborative crowdsourcing communities for open innovation, users generate and submit ideas as idea co‐creators. Firms then select and implement valuable ideas for new product development. Despite the popularity and success of these open innovation communities, relatively little is known about the factors that determine the implementation of the user‐generated ideas. Based on research on individual creativity, we propose a conceptual model integrating users' previous experience, idea presentation characteristics and feedback valence to explain the likelihood of idea implementation. We validate our research model with a panel data analysis of 43 550 ideas submitted by 16 360 users in the MIUI new product development community hosted by Xiaomi, a large electronics manufacturing company in China. We find an inverted U‐shaped relationship between users' past successful experience and idea implementation. Furthermore, the length of ideas is positively associated with the likelihood of idea implementation. There is also an inverted U‐shaped relationship between supporting evidence and idea implementation. Finally, we demonstrate the negative effect of positive feedback and the positive effect of negative feedback on idea implementation. These findings offer rich insights to understand the phenomenon of open innovation better. Theoretical and practical implications are discussed.     

On cutting temperatures in high and ultrahigh-speed machining

Since Dr. Carl Salomon proposed the well-known hypothesis on cutting temperatures in 1931, the debate on the hypothesis has never stopped. It shows that ev     

Protein quality and antioxidant properties of soymilk derived from black soybean after in vitro simulated gastrointestinal digestion

Protein quality and antioxidant properties of soymilk derived from black soybean (eight varieties) in China were analysed following in vitro simulated gastrointestinal digestion (including dialysis). Soymilk from black soybean possessed high okara weight but low yield, protein content and sensory scores. The in vitro digestibility of protein in all black soymilk samples was higher than 60%, and the Shenmu black soybean exhibited the highest digestibility. Non-digested milk from the black soybean exhibited significantly high total phenolic content (TPC) (127.15–173.04 mg/100 mL), ferric-reducing antioxidant power (FRAP) (272.18–366.27 μmol L⁻¹) and DPPH free radical-scavenging activity (61.20–83.81%). These parameters were significantly lower in the non-digested soymilk than those in soymilk after gastric digestion but higher than those of soymilk in the dialysed fraction. Gastric digestion significantly increased bioactive compound levels released from black soymilk, and the bioaccessibility of phenolic compounds was 24.37–36.05%. Hence, black soymilk was sufficiently available for human absorption.     

Effect of Temperature and Strain Rate on the Hot Deformation Behaviour of Ferritic Stainless Steel

Metals and Materials International - The flow behaviour and microstructure characteristics of a ferritic stainless steel were investigated using plain strain compression test on a Gleeble 3500...     

小方坯高拉速结晶器铜管温度的测量

阐明了小方坯结晶器铜管温度测量试验的方法与过程,通过在铜管内弧、外弧和侧面不同位置埋设的32支热电偶,对浇铸150 mm×150 mm过程中铜管温度进行在线检测,记录了不同工况下铜管温度随浇注时间的变化关系,分析了各种工艺参数对结晶器铜管温度分布的影响。结果表明,生产过程中结晶器铜管温度场是不稳定的,各点温度都在做非周期性、无规律的起伏变动;拉速越快,铜管四面的温度不均匀倾向越大;梅花型铜管各处温度要高于普通铜管,证明其换热效率更高,更适合高拉速的生产。     

Crystal structure,phase compositions,and microwave dielectric properties of malayaite-type Ca1−xSrxSnSiO5 ceramics

Low-permittivity Ca_1−xSr_xSnSiO₅ (0 ≤ x ≤ 0.45) microwave dielectric ceramics were prepared via traditional state-reaction at 1400°C-1450°C for 5 hours. Moreover the microwave dielectric properties of SnO₂ ceramic were obtained for the first time. SnO₂ ceramic was difficult to densify, and SnO₂ ceramic (ρ_rel = 65.1%) that was sintered at 1525°C exhibited the optimal microwave dielectric properties of ε_r = 5.27, Q × f = 89 300 GHz (at 14.5 GHz), and τ_f = −26.7 ppm/°C. For Ca_1−xSr_xSnSiO₅ (0 ≤ x ≤ 0.15) ceramics, Sr²⁺ could be dissolved in the Ca²⁺ site of Ca_1−xSr_xSnSiO₅ to form a single phase, and the partial substitution of Ca²⁺ by Sr²⁺ could improve the microwave dielectric properties of CaSnSiO₅ ceramic. Secondary phases (SnO₂ and SrSiO₃) appeared at 0.2 ≤ x ≤ 0.45 and could adjust the abnormally positive τ_f value of CaSnSiO₅ ceramic. The highest Q × f value (60 100 GHz at 10.4 GHz) and optimal microwave dielectric properties (ε_r = 9.42, Q × f = 47 500 GHz at 12.4 GHz, and τ_f = −1.2 ppm/°C) of Ca_1−xSr_xSnSiO₅ ceramics were obtained at x = 0.05 and 0.45, respectively.     

Neoteric Mn2+-activated Cs3Cu2I5 dazzling yellow-emitting phosphors for white-LED

Neoteric Mn²⁺-activated Cs₃Cu₂I₅ yellow-emitting halides were achieved by the simple solid-state reaction route. The near-ultraviolet light was the suitable excitation lighting source for the resultant halides. The resultant halides exhibited bright yellow emission under the excitation of 378 nm and the optimum dopant content was 11 mol%. The multipole-multipole interaction contributed to the concentration quenching mechanism and the critical distance was 28.65 Å. The thermal resistance of the prepared compounds was identified by the temperature-dependent emission spectra. Ultimately, the designed light-emitting diode showed bright white light with satisfied color rendering index, proper color coordinate, and suitable correlated color temperature. These results indicated that the prepared yellow-emitting halides were suitable for indoor illumination.     

整体壁板离散填料滚弯成形有限元模拟

具有一定曲率外形的铝合金整体壁板属于典型的多筋零部件,传统弯曲成形工艺成形困难,容易产生多种缺陷。提出了离散填料辅助滚弯成形整体2A12T4铝合金壁板滚弯工艺,并通过实验与整体填料滚变成形进行了对比,同时采用有限元模拟技术,探究了离散填料辅助整体壁板滚弯成形中的影响因素。研究结果表明:填料数量、上下垫板厚度等因素对成形性能影响较大,填料在3~6块时成形稳定,可以有效地避免筋条屈曲与失稳;随垫板厚度增加,壁板表面圆弧更加光滑、连续,但是回弹性增强;上下垫板分别在10~20 mm厚度时,综合性能较好。通过离散填料辅助滚弯技术可以成形出质量较高的整体壁板。