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The possibility of producing polymer-bonded magnets with the aid of additive processes, such as 3D printing, opens up a multitude of new areas of application. Almost any structures and prototypes can be produced cost-effectively in small quantities. Extending the 3D printing process allows the manufacturing of anisotropic magnetic structures by aligning the magnetic easy axis of ferromagnetic particles inside a paste-like compound material along an external magnetic field. This is achieved by two different approaches: First, the magnetic field for aligning the particles is provided by a permanent magnet. Secondly, the 3D printing process itselfs generates an anisotropic behavior of the structures. An inexpensive and customizable end-user fused filament fabrication 3D printer is used to print the magnetic samples. The magnetical properties of different magnetic anisotropic Sr ferrite and SmFeN materials are investigated and discussed.

In this publication, we describe the extrusion process and the properties of polymer-bonded anisotropic SrFe 12 O 19 filaments for fused filament fabrication (FFF). Highly filled polyamide 12 filaments with a filling fraction from 40 vol. % to 55 vol. % are mixed and extruded into filaments with a diameter of 1.75 mm. Such filaments are processable with a conventional FFF 3D printer. No modifications of the 3D printer are necessary. Detailed mechanical and magnetic investigations of printed samples are performed and discussed. In the presence of an external alignment field, the Sr ferrite particles inside the PA12 matrix can be aligned along an external magnetic field. The remanence can be increased by 40% by printing anisotropic structures. For the 55 vol. % filled filament, a remanence of 212.8 mT and a coercivity of 307.4 mT are measured. The capabilities of printing magnetic anisotropic structures in a complex external field are presented with a Halbach-array arrangement. With the aim of an inverse field model, based on a finite element method, the orientation of the particles and the quality of the print can be estimated by a nondestructive method.

The advancement of 3D-printing opens up a new way of constructing affordable custom terahertz (THz) components due to suitable printing resolution and THz transparency of polymer materials. We present a way of calculating, designing and fabricating a THz waveplate that phase-modulates an incident THz beam ({\lambda}=2.14 mm) in order to create a predefined intensity profile of the optical wavefront on a distant image plane. Our calculations were performed for two distinct target intensities with the use of a modified Gerchberg-Saxton algorithm. The resulting phase-modulating profiles were used to model the polyactide elements, which were printed out with a commercially available 3D-printer. The results were tested in an THz experimental setup equipped with a scanning option and they showed good agreement with theoretical predictions., Comment: 4 pages, 3 figures

A passive wireless radio frequency-identification (RFID) stress/strain sensor is presented. Stress is transformed into a change of magnetic field by utilizing an amorphous metal ribbon. This magnetic field change is measured by a giant magnetoresistance magnetic field sensor and converted into a digital value with a RFID chip for wireless access. Standard metal foil strain gauges have a gauge factor GF from around 2 to 5 and suffer from the disadvantage of a physically connected power supply and measurement equipment. For the presented sensor, a strain range of −10 μmm to 190 μmm results in a linear sensor response, a gauge factor of GF ≈ 245, and a detectivity of 4.10 nmm1Hz. The detectivity of the presented sensor is similar to the detectivity of a reference metal foil strain gauge. Due to low power consumption and easy signal analysis, this sensor is well suited for long term strain measurement inside closed spaces. RFID adds features like multiple tag detection, wireless passive operation and a user d...

Na 3 O has been generated by reacting preformed sodium clusters with O 2 and N 2 O in a crossed beam pickup arrangement. This “superalkali” species was probed by photodepletion spectroscopy coupled with one-photon ionizationmass spectroscopy to yield: (i) a first measure of visible/NIR region photodissociation cross sections showing several broad absorption features, (ii) a rough determination of the ground state dissociation energy (1.48±0.04 eV ), as well as (iii) a remeasurement of the ionization potential (3.69±0.15 eV ). The experimental investigations were supplemented by quantum chemical ab initio calculations employing coupled-cluster methods for ground and excited states of Na 3 O . Experiment and theory are in good agreement, allowing a tentative assignment of the Na 3 O depletion spectrum while providing further evidence for the computed D 3h ground state. Observed and calculated dipole-allowed electronic transitions are discussed in terms of the unusual electronic structure of this nominally one excess-electron species.

Contracted Gaussian basis sets of triple zeta valence (TZV) quality are presented for Li to Kr. The TZV bases are characterized by typically including a single contraction to describe inner shells and three basis functions for valence shells. All parameters—orbital exponents and contraction coefficients—have been determined by minimization of atomic self‐consistent field ground state energies. Advantages and necessary modifications of TZV basis sets are discussed for simple test calculations of molecular energies and nuclear magnetic resonance (NMR) chemical shieldings in treatments with and without inclusion of electron correlation.

Electroreflectance (ER) is a standard method to determine the band gap of semiconductor materials that has also been applied to thin-filmsolar cells (TFSCs). However, the lineshapes in typical ER spectra of TFSCs are significantly distorted compared to the model lineshapes, which are used for spectrum evaluation. These distortions are mainly due to thin-film interferences in the stratified system. In this letter, we demonstrate that these distortions are significantly suppressed in diffuse ER (D-ER) where the diffuse instead of the specular reflection of TFSCs is evaluated. The existence of an ER signal in the diffuse reflectance is shown by two-dimensional finite-difference time-domain simulations. Experimentally, the suppression of interference-related lineshape distortions is demonstrated on a series of Cu2ZnSnSe4solar cells with different layer thicknesses and therefore different optical path lengths for interference. The same working principle is demonstrated for a Cu(In,Ga)(S,Se)2solar cell as well. The resulting lineshapes in D-ER can then be interpreted using standard analysis methods such as Aspnes' Third-Derivative Functional Form.

In this response, we clarify some of the misconceptions that were brought up by Pal's Comments about our manuscript [S. A. Faroughi and C. Huber, J. Appl. Phys. 117, 055104 (2015)]. The main issue that was raised is that we account for the correction on the excluded volume (the net volume of the continuous phase in a finite composite decreases with increasing filler content) twice. We show here that this statement is incorrect and that our model is consistent with other models derived from a different standpoint. We also address the other comments raised by Pal.

In this study, we propose a theoretical model to compute the effective thermal conductivity of metal and dielectric spherical particle reinforced composites with interfacial thermal resistance. We consider a wide range of filler volume fraction with sizes ranging from nano- to macro-scale. The model, based on the differential effective medium theory, accounts for particle interactions through two sets of volume fraction corrections. The first correction accounts for a finite volume of composite and the second correction introduces a self-crowding factor that allows us to develop an accurate model for particle interaction even for high volume fraction of fillers. The model is examined to other published models, experiments, and numerical simulations for different types of composites. We observe an excellent agreement between the model and published datasets over a wide range of particle volume fractions and material properties of the composite constituents.

We report on order–disorder related band gap changes in Cu2ZnSn(S,Se)4 solar cells which are induced by post-annealing. The band gap changes of the absorber are detected utilizing electroreflectance and analyzed by comparison with predictions of the stochastic Vineyard model. This yields a critical temperature of TC=195 °C above which the Cu2ZnSn(S,Se)4 absorber layer is entirely disordered within the Cu–Zn layers of the kesterite unit cell. The temporal evolution of the band gap during annealing shows that the equilibrium value is reached on a timescale in the order of hours, depending on the annealing temperature. In contrast to other experimental techniques, electroreflectance precisely measures the band gap and is not influenced by defect-mediated radiative recombination.