Thermal Stability of Nitric Acid Solutions of Hydrazine Nitrate

Radiochemistry - Thermal stability of hydrazine nitrate (HN) in solutions in 4–12 M HNO3 in the temperature interval 70–150°C was studied. Exothermic reactions accompanied by gas...     

Natural-based polymers for antibacterial treatment of absorbent materials

In this study, polypropylene (PP) nonwoven fabric which can be used as topsheet layer of an absorbent hygienic product was modified by natural based antibacterial agents. Antibacterial herbal agents (cinnamaldehyde, geraniol, phenylethyl alcohol) were sprayed by ethanol or applied by means of polylactic acid (PLA) and polycyclohexene oxide (PCHO) based polymers prepared by three different chemical methods. Characterization of synthesized materials was conducted via thermogravimetric analysis (TGA), differential thermal analysis (DTA), and scanning electron microscopy–energy dispersive X–ray spectroscopy (SEM-EDX). Besides characterization, antibacterial and pH buffering performances of antibacterial polymers alone and on PP fabric were tested by antibacterial and pH tests. Effects of antibacterial treatments on air permeability and absorption period of nonwoven fabrics were also analyzed. According to the results, biopolymers changed the thermal stability of PP nonwoven fabric. Antibacterial performances can be ranked as cinnamaldehyde, geraniol, and phenylethyl alcohol from the best. Besides a slight decrease about liquid absorption performance, all of the treated topsheet fabrics are sufficient for an absorbent hygienic product. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48302.     

Production and Heat Treatment of Ti6–Al5.5–V–1.8Sn Powder Titanium Alloy

The mechanical properties of Ti6–Al5.5–V–1.8Sn powder titanium alloy are investigated as a function of its structure, which, in turn, depends on its production and heat treatment (quenching and aging).     

Corrections of magnification and focusing in a cathode lens-equipped scanning electron microscope

One of the well-proven and efficient methods of obtaining a very low-energy impact of primary electrons in the scanning electron microscope is to introduce a retarding field element below the pole piece of the objective lens (OL). It is advantageous to use the specimen alone as the negatively biased electrode (i.e., cathode of the cathode lens). The optical power of the cathode lens modifies some of the standard parameters of the image formation such as relation of working distance to OL excitation or magnification to the scanning coils current, the impact angle of primary electrons, and so forth. In computer-controlled electron microscopes these parameters, particularly with regard to focusing and magnification, can be corrected automatically. Derivation of algorithms for such corrections and their experimental verifications are presented in this paper. Furthermore, a more accurate analytical expression for the focal length of an aperture lens is derived.     

Influence of the orientation of the silicon substrate on the properties of avalanche Si:Er:O light-emitting structures

The influence of the orientation of silicon on the structural and luminescence properties of avalanche light-emitting diodes fabricated by the coimplantation of erbium and oxygen followed by solid-phase epitaxial (SPE) crystallization of the amorphized layer is considered. The luminescence properties are a consequence of the formation of various structural defects during the SPE crystallization: V-shaped dislocations and erbium precipitates form in (100) Si:Er:O layers, and larger structural defects, i.e, twins, are observed in (111) Si:Er:O layers along with an increase in the dislocation density by more than four orders of magnitude in comparison with the (100) orientation. The luminescence properties of avalanche and tunnel light-emitting diodes are also compared. In contrast to tunnel diodes, in avalanche diodes erbium ions are excited in the entire space-charge layer, and the effective excitation cross section of the Er³⁺ ions and their lifetime in the excited state are 3–4 times larger. Fiz. Tekh. Poluprovodn. 33, 660–663 (June 1999)     

Local spectroscopy of band gaps in ferroelectric photonic crystals

We have measured visible to near-UV reflection spectra of opal photonic crystals infiltrated with ferroelectrics: barium titanate, sodium nitrite, potassium iodate, and triglycine sulfate. An experimental procedure has been developed for the infiltration of various ferroelectrics into opal pores through laser ablation and laser implantation. Using a fiber-optic probe, we were able to analyze surface reflection spectra of photonic crystals with a 0.2-mm resolution. A deuterium lamp was used as a broadband UV source, which allowed us to observe both the first and second [111] photonic band gaps in the reflection spectrum of opal crystals.     

Fatigue crack initiation in Hastelloy X – the role of boundaries

In polycrystalline metals, microstructural features such as grain boundaries (GBs) influence fatigue crack initiation. Stress and strain heterogeneities, which arise in the vicinity of GBs, can promote the nucleation of fatigue cracks. Because of variations in grain size and GB types, and consequently variations in the local deformation response, scatter in fatigue life is expected. A deeper quantitative understanding of the early stages of fatigue crack nucleation and the scatter in life requires experimental and modelling work at appropriate length scales. In this work, experiments are conducted on Hastelloy X under fatigue conditions, and observations of fatigue damage are reported in conjunction with measurements of local strains using digital image correlation. We use a recent novel fatigue model based on persistent slip band–GB interaction to investigate the scatter in fatigue lives and shed light into the critical types of GBs that nucleate cracks. Experimental tools and methodologies, utilizing ex situ digital image correlation and electron backscatter diffraction, for high resolution deformation measurements at the grain level are also discussed in this paper and related to the simulations.