Highly Symmetric and Extremely Compact Multiple Winding Microtubes by a Dry Rolling Mechanism

Rolled-up nanotechnology has received significant attention to self-assemble planar nanomembranes into 3D micro and nanotubular architectures. These tubular structures have been well recognized as novel building blocks in a variety of applications ranging from microelectronics and nanophotonics to microbatteries and microrobotics. However, fabrication of multiwinding microtubes with precise control over the winding interfaces, which is crucial for many complex applications, is not easy to achieve by existing materials and technologies. Here, a dry rolling approach is introduced to tackle this challenge and create tight windings in compact and highly symmetric cylindrical microstructures. This technique exploits hydrophobicity of fluorocarbon polymers and the thermal expansion mismatch of polymers and inorganic films upon thermal treatment. Quality parameters for rolled-up microtubes, against which different fabrication technologies can be benchmarked are defined. The technique offers to fabricate long freestanding multiwinding microtubes as well as hierarchical architectures incorporating rolled-up wrinkled nanomembranes. This work presents an important step forward toward the fabrication of more complex but well-controlled microtubes for advanced high-quality device architectures. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Additive manufacturing of powdery Ni-based superalloys Mar-M-247 and CM 247 LC in hybrid laser metal deposition

The present paper addresses the phenomena of hot cracking of nickel-based superalloys in the perspective of hybrid Laser Metal Deposition (combined application of induction and laser). This includes an extract of relevant theoretical considerations and the deduction of the tailored approach which interlinks material–scientific aspects with state-of-the-art manufacturing engineering. The experimental part reflects the entire process chain covering the manufacturing strategy, important process parameters, the profound analysis of the used materials, the gradual process development, and the corresponding hybrid manufacture of parts. Furthermore, hot isostatic pressing and thermal treatment are addressed as well as tensile testing at elevated temperatures. Further investigations include X-ray CT measurements, electron backscattered diffraction (EBSD), and scanning electron microscopy (SEM) as well as light optical microscope evaluation. The fundamental results prove the reliable processibility of the high-performance alloys Mar-M-247 and Alloy 247 LC and describe in detail the process inherent microstructure. This includes the grain size and orientation as well as the investigation of size, shape, and distribution of the γ′ precipitates and carbides. Based on these findings, the manufacturing of more complex demonstrator parts with representative dimensions is addressed as well. This includes the selection of a typical application, the transfer of the strategy, as well as the proof of concept

Sandwich-Stacked SnO₂/Cu Hybrid Nanosheets as Multichannel Anodes for Lithium Ion Batteries

We have introduced a facile strategy to fabricate sandwich-stacked SnO₂/Cu hybrid nanosheets as multichannel anodes for lithium-ion batteries applying rolled-up nanotechnology with the use of carbon black as intersheet spacer. By employing a direct self-rolling and compressing approach, a much higher effective volume efficiency is achieved as compared to rolled-up hollow tubes. Benefiting from the nanogaps formed between each neighboring sheet, electron transport and ion diffusion are facilitated and SnO₂/Cu nanosheet overlapping is prevented. As a result, the sandwich-stacked SnO₂/Cu hybrid nanosheets exhibit a high reversible capacity of 764 mAh g^–1 at 100 mA g^–1 and a stable cycling performance of ∼75% capacity retention at 200 mA g^–1 after 150 cycles, as well as a superior rate capability of ∼470 mAh g^–1 at 1 A g^–1. This synthesis approach presents a promising route to design multichannel anodes for high performance Li-ion batteries

Innovative Erstarrungs- und Mahltechnologie und deren Anwendung zur Herstellung von Solarsilizium : Abschlussbericht zum Verbundprojekt: SIMPUREM ; Berichtszeitraum: 01.06.2010 - 31.03.2013

[no abstract available