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Defects and defective technology are considered to be an efficient method for improving electromagnetic wave (EMW) absorption performance. In this study, W-type barium hexaferrite BaCo2Fe16O27 (BCFO) composites with Sm doping were synthesized by a simple ball milling and subsequent annealing process. The phase structure characteristics, magnetic properties, and microwave absorption performance of the BCFO composites were systematically investigated. Specifically, Sm-doped and annealed BCFO composites demonstrated outstanding microwave absorption characteristics because of the efficient interaction between ideal impedance matching and large dielectric loss, specifically, a minimum reflection loss (RL) value of −28.57 dB at 8.5 GHz with 3 mm thickness. Moreover, a broad effective absorption bandwidth reaches 11 GHz, covering the range of 7–18 GHz. It is believed that defects and vacancies induced by Sm doping or annealing in the Ar atmosphere may be an effective means for enhancing microwave absorption, and related mechanisms are discussed in detail. [ABSTRACT FROM AUTHOR]

The NiFe2O4 (NFO) assembly was synthesized via thermal decomposition in a gradient magnetic field, and its structure, composition, as well as magnetic and electromagnetic absorption properties were investigated. The applied magnetic field adjusts the size of nanoparticles, the magnetic properties change correspondingly. The saturation magnetic intensity increases from 54.21 emu/g to 61.67 emu/g, however, the coercivity changes less, and Hc is in the range of 32.75–34.01 Oe. Simultaneously, the XPS results suggest that an increase in oxygen vacancies with addition of magnetic field. With the magnetic field application, a higher complex permittivity and more excellent microwave absorption performance are achieved. With the application of magnetic field, the nanoparticles become smaller, and more interfaces are generated, the interfacial polarisation effect is strengthened. Simultaneously, the applied magnetic field also leads to an increase in oxygen vacancies. Therefore, dielectric loss values are enhanced. Moreover, the reflection loss was optimized to − 14.32 dB with a matching thickness of 5.5 mm when the sample prepared under magnetic field 0.32 T. The above results prove that the magnetic field can be used as an effective route to achieve excellent microwave performance for NFO. [ABSTRACT FROM AUTHOR]

Weak rigid parts are widely used in aerospace industry. These parts are characterized by thin walls. Most of these parts have the meter-level size and mesh surface, thus have a requirement for tool accessibility. Therefore, the end milling is an applicable process to reduce the thickness of these parts. Due to the weak rigidity of these parts in the normal direction, severe chatter will occur in the machining process, which will reduce the machining efficiency and spoil the machining surface, so the processing stability of the thin-walled part needs to be studied. In this paper, the dynamic model for end milling of thin-walled parts is presented. The regeneration effect in the surface normal direction is proposed, and the dynamic equation is constructed considering the vibration of the workpiece in the cutting tool axial direction. The stability lobe diagram is obtained by numerical method. It is found that the stability of weak rigid parts end milling is related to the cutting speed, the feed rate, and the width of cut, but not to the cutting axial depth. Finally, cutting experiments are conducted. The experimental result is coincident well with the prediction, thus verifying the proposed dynamic model and the stability analysis method. [ABSTRACT FROM AUTHOR]