High dielectric constant of NiFe2O4–LaFeO3 nanocomposite: Interfacial conduction and dielectric loss

Materials exhibiting colossal dielectric constant are the most sought-after materials due to their variety of applications in various electronics industries. NiFe₂O₄ and LaFeO₃ belonging to the spinel and perovskite structures, respectively, were coupled into a nanocomposite by adapting a one-pot sol-gel synthesis. The ratio of NiFe₂O₄:LaFeO₃ was varied and the synthesized materials were studied for their dielectric behaviors. Interestingly, among the samples studied, the nanocomposite with the ratio of 1:2 of NiFe₂O₄–LaFeO₃ exhibited a high dielectric constant value of 10390 at a frequency of 1 kHz with a several-fold increase in conductivity. The high conductivity resulted in a high dielectric loss. The origin of such a high dielectric constant and loss have been attributed to the Maxwell-Wagner type space charge polarization arising from the microstructure that consists of large and continuous grain boundaries, and the conducting phase at the interface, respectively.     

NaWuReT-Workshop: Forschung in der Reaktionstechnik für und mit der Gesellschaft

In this article, the results of the NaWuReT (Early Career Reaction Engineers) workshop on the topic “Are we doing relevant science?” are presented. The topics “(In)surmountable hurdles for Citizen Scientists in reaction engineering?” and “Circular Economy in reaction engineering with/for society?” were discussed. Therefrom, a variety of ideas and suggestions were extracted.     

3D CaP porous scaffolds with grooved surface topography obtained by the sol-gel method

The influence of surface topography on cellular behaviour and its importance for the development of three-dimensional scaffolds for bone tissue engineering are a topic of growing interest. To date, the introduction of topographical patterns into the surface of 3D porous ceramic scaffolds has proven difficult, due partly to the brittle nature of ceramic materials as well as the currently available fabrication technologies. In this study, a grooved pattern was introduced into the surface of 3D multilayer porous ceramic scaffolds by the chemical etching technique. The patterned scaffolds were characterised by X-Ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDX) and Digital Holographic Microscopy (DHM). Their bioactivity was also evaluated in vitro by immersion in simulated body fluid (SBF) for 12 h, 1, 7, 14 and 21 days. Scaffolds were constituted mainly with a mixture of the calcium pyrophosphate (Ca₂O₇P₂) and β-tricalcium phosphate (Ca?(PO?)?) phases. The pyrophosphate on the external layer was dissolved as a result of the etching process, leaving grooves on the surface. Ridges and grooves were nano-/micrometric, with dimensions of around 900 nm–1.5 μm in width and 200 nm–300 nm in depth. Moreover, the mechanical properties and bioactive capacity of the patterned scaffolds were not affected by chemical etching, making them suitable to be used in bone tissue engineering.     

Characteristics and gas sensor applications of ZnO-Perovskite heterostructure

In this study, zinc oxide (ZnO) nanofibers were prepared using the electrospinning method, and the effects of different spinning voltages and annealing temperatures on the fiber structure were tested. La_0.8Sr_0.2FeO₃ (LSFO) perovskite film was prepared by a sol-gel method. Then we dip LSFO on ZnO nanofiber and grow it on the interdigital gold electrode substrate for gas sensors. The results show that the ZnO/LSFO heterostructure gas sensor has a good sensing response to H₂S gas and exhibits good gas selectivity. The best gas response is 52.17% under 4 ppm H₂S and work temperature 200°C, which has good recovery and reproducibility.     

分布式遥感编队多星协同观测中的姿态控制

针对分布式遥感编队中的协同观测问题，本文开展了多星协同姿态控制研究。首先建立了参考航天器由对日定向到对目标凝视观测的期望姿态，设计了基于姿态、角速度偏差的比例-微分（PD）控制器，证明了闭环系统的李雅普诺夫稳定性。在此基础上，进一步建立了伴飞航天器的期望姿态，为使目标在不同航天器像平面上成像位置匹配，以伴飞航天器、参考航天器的姿态之差为基础设计了伴飞航天器的PD控制器，证明了系统的稳定性。最后，将理论结果进行了仿真验证，结果显示伴飞航天器、参考航天器姿态控制误差小于0.01°，精度满足分布式遥感多星协同观测的任务需求。     

2018 petroleum & chemical industry development report

In 2018, the petroleum and chemical industries of China achieved steady economic growth. The main business income of the entire industry was 12.4 trillion CNY, an increase of 13.6% over the previous year. The total profit was 83.93 billion CNY, an increase of 32.1% over the previous year. The total national oil and gas production reached 334 million tons of oil equivalent, increasing by 2.4% year-on-year. Among the total production, crude oil production was 189 million tons, decreased 1.2%, and natural gas production was 161.02 billion cubic meters, increased 7.5% year on year. Imported crude oil production was 462 million tons, an increase of 10.1% over the last year. Imported gas production was 125.72 billion cubic meters, increased 31.9%. The annual processing capacity of crude oil was 604 million tons, up by 6.8%. The refined oil production was 360 million tons, up by 3.6%. The industry structure was optimized for production growth in 2018, the transformation and upgrading of enterprises and products structure adjustment were sped up, energy efficiency was improved, and overall industrial benefit was rebounded. At present, the economic operation of the industry is still not very stable, and downward pressure is still great, mainly being reflected in the overcapacity of some industries, high cost operation of enterprises, increased tax burden, and weak investment. With the slow recovery of the global economy and the key support of high-quality development through technological innovation, it is expected that the petroleum and chemical industry of China will achieve the general objective of steady growth in 2019.     

Schnelle lokale Raman‐Messung zur Untersuchung von Konzentrationsprofilen bei Mischvorgängen in Mikrokanälen

For the evaluation of mixing processes in microreactors, it is necessary to be able to investigate them in detail. For this purpose, a novel optical measuring system is presented, which allows the visualization of mixing and diffusion‐limited processes as well as concentration differences in fluid films. It consists of focusing optics with a microscope objective. In combination with a Raman spectrometer, various processes such as diffusion in the microreactor can be measured and investigated non‐invasively.     

SiC/SiC mini-composites with multilayer ZrSiO4 interphase: Room-temperature properties and toughening mechanism

SiC/SiC mini-composites reinforced with SiC fibers coated with different numbers of ZrSiO₄ sublayers prepared via a non-hydrolytic sol-gel process were fabricated. The tensile strength and work of fracture of the prepared SiC/SiC mini-composites were determined, and the relationship between their mechanical properties and fracture morphologies was discussed. The toughening mechanism and the variation tendency of their mechanical properties were further elaborated by analyzing the interfacial debonding morphologies of the SiC/SiC mini-composites with 1 and 4 layers of ZrSiO₄ interphase as well as the results of prior studies. A relatively rare phenomenon—the delamination of the multilayer ZrSiO₄ interphase in the SiC/SiC mini-composites but not on the SiC fibers—was observed, which clearly demonstrated the weak bonding between the ZrSiO₄ sublayers in the SiC/SiC mini-composites. The ZrSiO₄ sublayer delamination mechanism was then explained based on the high-magnification morphologies found in and beside the ZrSiO₄ interphase.     

Challenges in supply chain redesign for the Circular Economy: a literature review and a multiple case study

Despite companies face several challenges when redesigning their supply chain for the Circular Economy, the literature lacks a systematisation of such challenges and of the ways to overcome them. Through a systematic literature review, this paper identifies and systematises 24 challenges that may hamper a supply chain redesign for the Circular Economy. Sixteen among these challenges are well known from research in related topics. On the contrary, the remaining eight are relatively new or take a different relevance within the Circular Economy context. A multiple case study in the household appliance supply chain is carried out, to explore how these challenges appear in practice and how companies may tackle them. The cases analysed involve actors at different supply chain levels, and findings suggest that a great degree of vertical integration by one actor in the supply chain is not a necessary condition for Circular Economy implementation. The empirical study, in conjunction with the literature analysis, leads to the development of a framework linking the challenges to specific levers that companies may pursue to overcome them. The framework can be seen as a reference for managers undertaking the path towards Circular Economy.