Effect of annealing atmosphere on the structure and dielectric properties of unfilled tungsten bronze ceramics Ba4PrFe0.5Nb9.5O30

Unfilled tungsten bronze ceramics with the nominal formula Ba₄PrFe_0.5Nb_9.5O₃₀ were synthesized via the standard solid-state sintering route, and the effects of oxygen vacancies on the dielectric and electrical properties were investigated in addition to the structure. Room-temperature X-ray diffraction showed that the N₂-annealed sample had the largest cell volume. Low-temperature spectrum showed that N₂ annealing rendered the dielectric constant and dielectric loss more frequency dispersive, whereas O₂ annealing inhibited the frequency dispersion. The dc conductivity of all the samples originated from the electrons produced in the second ionization of oxygen vacancies and was most likely controlled by a mixed conduction mechanism of the electron and oxygen-vacancy ions. The N₂-annealed sample has the highest dc conductivity owing to its high concentration of oxygen vacancies. The broadening of the Raman lines and the decrease of Raman intensity for the N₂-annealed sample originated from a significant structural disorder. X-ray photoelectron spectra demonstrated that the increased oxygen vacancies caused by the change of valences of Fe and Pr ions contributed to the structural disorder.     

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.     

Effects of W6+ substitution on crystal structure and microwave dielectric properties of Li3Mg2NbO6 ceramics

Li₃Mg₂(Nb_1-xW_x)O_6+x/2 (0 ≤ x ≤ 0.08) ceramics were synthesized by the solid-state reaction route. The effects of W⁶⁺ substitution on the phase composition, microstructure and microwave dielectric properties of Li₃Mg₂NbO₆ ceramics were investigated systematically. The XRD results showed that all the samples formed a pure solid solution in the whole doping range. The SEM iamges and relative density revealed the dense structure of Li₃Mg₂(Nb_1-xW_x)O_6+x/2 ceramics. The relationship between the crystal structure and dielectric properties of Li₃Mg₂(Nb_1-xW_x)O_6+x/2 ceramics was researched through polarizability, average bond valence, and bond energy. The substitution of W⁶⁺ for Nb⁵⁺ in Li₃Mg₂(Nb_1-xW_x)O_6+x/2 ceramics significantly promoted the Q × f values. In addition, the increase of W⁶⁺ content improved the thermal stability of the Li₃Mg₂(Nb_1-xW_x)O_6+x/2 ceramics. The Li₃Mg₂(Nb_0.94W_0.06)O_6.03 ceramics sintered at 1175 °C for 6h possessed excellent properties: ε_r ~ 15.82, Q × f ~ 124,187 GHz, τ_f ~ −18.28 ppm/°C.     

电子探针对磁铁矿中变价元素Fe的测试方法

充分利用岛津电子探针在硬件上的优势，采用全元素测试，即包括超轻元素氧在内的所有元素直接测试的思路对磁铁矿进行了测试，根据电价平衡原则计算出变价元素的含量，并使用状态分析的方法验证了FeO和Fe2O3含量的Lβ/Lα特点，得到了较为理想的测试结果。     

当33atomic％Ce替代Sm时(Sm1-yCey)2Fe17Nx的最大磁能积不下降

本文研究了完全氮化的(Sm1-yCey)2Fe17Nx（y = 0、0.20、0.33、0.40、0.45、0.50、0.67、0.80、1.00）粉末的磁性能和微观结构。当用33atomic％Ce代替Sm时，最大磁能积(BH)max从17.8 MGOe变为17.6 MGOe，几乎没有下降。相应的，性能/稀土价格比率提高了39.2％。 根据能量色散光谱（EDS）分析，Ce倾向于分布在REFe3 / REFe2晶界相中。XPS证实了(Sm1-yCey)2Fe17Nx中Ce离子的价态变化。     

Quick valence analysis method of vanadium toward accurate toxicity assessment of vanadium-containing hazardous wastes

In order to develop a quick, efficient and sensitive valence analysis method of vanadium(V), the high- performance liquid chromatography (HPLC) was utilized to separate and quantify EDTA-complexed V(III), V(IV) and V(V) ions. The influence of EDTA, TBAOH, solution pH and organic modifier on retention behavior of V−EDTA complexes was investigated. Complexed V(III), V(IV) and V(V) ions can be separated and quantified in 5 min, with detection limits of 0.04 mg/L V(III), 0.07 mg/L V(IV), and 0.06 mg/L V(V), respectively. The established method is applied to analyzing the hazardous waste of V−Cr-bearing reducing slag and results demonstrate 49.94% of its V element to be toxic V(V). This work opens a new avenue for quick and accurate toxicity assessment of hazardous wastes containing multivalent heavy metals.     

AI、Nb在Nd_2Fe_(14)B晶体中的价态及对其磁性的影响

本文研究了Al、Nb在Nd_2Fe_(14)B晶体中的价态及对其磁性的影响。结果表明:在Nd_2Fe_(14)B晶体中,具有较大结构体积的j_2晶位Fe原子[Fe(j_2)],由于受到近邻Nd的f电子的强烈作用,其d电子可以被“诱发”为磁电子,原子磁矩达3.4μ_B,比纯铁的2.4μ_B大得多;Nb原子在晶体中置换j_2、k_1、k_2晶位上Fe原子时,它的d电子也可能成为磁电子;Al和Nb原子在Nd_2Fe_(14)B晶体价电子结构中,以无晶格电子的价态置换有晶格电子的Fe原子价态,导致硬磁性相各向异性的增强;Nb的两个4d价电子参加晶体的键合,增强了材料的磁温度稳定性。     

BMA—IL型平板玻璃防霉液的研制

根据我们曾提出的玻璃表面的电势在水对玻璃侵蚀过程中可以有效屏蔽离子交换、降低离子交换速率的机理,用复合高价阳离子金属盐与弱酸混合制备了BMA-IL型玻璃防霉液.实验证明,该防霉液可以有效地延缓玻璃表面霉变,将有很大的应用前景.     

Al-Zn-Mg合金价电子理论研究

在电子结构上揭示Al-Zn-Mg合金时效强化机理,利用"固体与分子经验电子"理论中的键距差法,计算了Al-Zn-Mg合金中的过饱和固溶体,GP区,η相(MgZn2)以及T相(Al2Mg3Zn3)的电子结构,从而在价电子结构上解释Al-Zn-Mg合金在时效过程中GP区和η(MgZn2)稳定相对合金强化的原因,以及高温过时效时合金强度降低的原因。     

Ti-Nb-V钢中第二相粒子对焊接HAZ晶粒度及韧性影响的价电子结构分析

基于"固体与分子经验电子理论"(EET),利用合金相和相界面的价电子结构参数统计值n′A、E′A、Δρ′、σ分析第二相粒子和固溶Nb对焊接HAZ组织和韧性的影响。结果表明:Nb元素固溶时,因Δρ′/σ值大于其他合金元素而使Nb具有强烈阻碍奥氏体晶界迁移的作用;第二相粒子Ti(V、Nb)C(N)析出时,形成相界面的Δρ′/σ较大,因而更能有效地钉扎奥氏体晶界而使高温奥氏体晶粒显著细化;第二相粒子析出后,能够促进新相铁素体生成,改善焊接HAZ韧性的机理也可追溯到n′A、E′A及Δρ′。上述分析结果与实验结果符合很好。