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Open access

Bożena Łowkis

Abstract

This paper presents three physical sources of the electric field in dielectrics: excess free volume charges with the distribution qv(x,y,z), free surface charges with the distribution qs(x,y,z) and frozen polarization state in the dielectric. They have a deciding influence on the parameters of the electret, in particular they determine the total lifetime of the electret and technical components made of it. The indeterminacy related to the mutual proportions of the spatial and surface charges was discussed: one can find an infinite number of distributions of surface qse(x,y,z) and spatial qve(x,y,z) charges leading to the same distribution of the electric field E(x,y,z). A general case of electret was considered, where a coexistence of relaxation decay of frozen polarization and Maxwellian relaxation dependent on volume conductivity of the dielectric is assumed. An attempt to interpret the charge lifetime in real electrets was made.

Open access

A. Zieliński, W. Serbiński, B. Majkowska, M. Jażdżewska and I. Skalski

Influence of laser remelting at cryogenic conditions on corrosion resistance of non-ferrous alloys

The main reason for laser remelting of the components made of aluminium, copper and titanium alloys is to obtain high hardness and corrosion resistance at the surface for longer lifetime as result of the rapid solidification. The final microstructure, phase composition and properties of aluminium, copper and titanium alloys depend on the laser process parameters and obviously on the nature of the equilibrium system.

The effect of laser surface remelting at cryogenic conditions on the microstructure and corrosion characteristics of the AlSi13Mg1CuNi, SUPERSTON and Ti-6Al-4V alloys are presented. The beneficial effects of laser treatment on the microstructure and corrosion behaviour of those alloys used for different products are observed.

Open access

E. Radziemska, T. Seramak and P. Ostrowski

Pure Silicon Recovering from Photovoltaic Modules

Photovoltaic technology is worldwide used to provide reliable and cost-effective electricity for industrial, commercial, residential and community applications. The average lifetime of PV modules can be expected to be more than 25 years. The disposal of PV systems will emerge as a problem, considering the still increasing production of PV modules. Recycling of such modules can be done at about the same cost level as its disposal. Recovering the pure silicon from damaged or end-of-life PV modules can lead to economical and environmental benefit. Chemical treatment conditions need to be precisely adjusted in order to achieve the required purity level of the recovered silicon. For crystalline silicon based PV systems, a series of etching processes has been carried out as follows: electric connectors (etching or removing), ARC and n-p junction etching. The chemistry of etching solutions was individually adjusted for the different silicon cell types. Efforts were taken in order to formulate a universal composition of etching solution.

Open access

A. Zieliński, S. Sobieszczyk, T. Seramak, W. Serbiński, B. Świeczko-Żurek and A. Ossowska

Biocompatibility and Bioactivity of Load-Bearing Metallic Implants

The main objective of here presented research is to develop the titanium (Ti) alloy base composite materials possessing better biocompatibility, longer lifetime and bioactivity behaviour for load-bearing implants, e.g. hip joint and knee joint endoprosthesis. The development of such materials is performed through: modeling the material behaviour in biological environment in long time and developing of new procedures for such evaluation; obtaining of a Ti alloy with designed porosity; developing of an oxidation technology resulting in high corrosion resistance and bioactivity; developing of technologies for hydroxyapatite (HA) deposition aimed at composite bioactive coatings; developing of technologies of precipitation of the biodegradable core material placed within the pores.

The examinations of degradation of Ti implants are carried out in order to recognize the sources of both early allergies and inflammation, and of long term degradation. The theoretical assessment of corrosion is made assuming three processes: electrochemical dissolution through imperfections of the anodic oxide layer, diffusion of metallic ions through the oxide layer, and dissolution of oxides themselves.

In order to increase the biocompatibility, the toxic elements, aluminium (Al) and vanadium (V) are eliminated. The experiments have shown that titanium - zirconium - niobium (Ti-Zr-Nb) alloy may be a such a material which can also be prepared by both powder metallurgy (P/M) technique and selective laser melting. The porous (scaffold) Ti-Zr-Nb alloy is now obtained by powder metallurgy, classical and with space holders used before melting and decomposed, or remained during melting and removed by subsequent water dissolution. The oxidation of porous materials is performed either by electrochemical technique in special electrolytes or by chemical and/or hydrothermal method in order to obtain the optimal oxide layer well adjacent to an interface, preventing the base metal against corrosion and bioactive because of its nanotubular structure, permitting injection of some species into the pores. The Ca, O and N ion implantation or deposition of zirconia sublayers may be used to increase the biocompatibility, bioactivity and corrosion resistance. The HA coating obtained by either electrophoretic, biomimetic or by sol-gel deposition should result in gradient structure similar to bone structure, possessing high adhesion strength. The core material of the porous material should result in a biodegradable material, allowing slower dissolution followed by stepwise growth of bone tissue and angiogenesis, preventing local inflammation processes, sustaining the mechanical strength close to that of non-porous material.

Open access

G. Golański, I. Pietryka, J. Jasak, J. Słania, P. Urbańczyk and P. Wieczorek

. Dobrzański J., Krztoń H., Zieliński A.: Development of the precipitation processes in low-alloy Cr-Mo type steel for evolution of the material state after exceeding the assessed lifetime, J. Achiev. Mater. Manufac. Eng., 2, 23, (2007), 19-22. 5. PN-75/H-84024 Steels for elevated temperatures service. Grades. 6. PN-EN ISO 643:2012 Steels - Micrographic determination of the apparent grain size. 7. Khan S. A., Islam M. A.: Influence of prior austenite grain size on the degree of temper embrittlement in Cr-Mo steel, J. Mater. Eng

Open access

D. Morozow, J. Narojczyk, M. Rucki and S. Lavrynenko

tribological performance. Surface and Coatings Technology, 206 (2011) 849-853. 12. Narojczyk J, Werner Z, Piekoszewski J., Szymczyk W., Effects of nitrogen implantation on lifetime of cutting tools made of SK5M tool steel. Vacuum, 78 (2005) 229-233. 13. Perry A.J., Treglio J.R., Bhat D.G., Boppana S.P., Kattamis T.Z., Schlichting G., Geist D.E., Effect of ion implantation on the residual stress, tribological and machining behavior of CVD and PVD TiN coated cemented carbide cutting tool inserts. Surface and Coatings Technology, 68-69 (1994) 294-300. 14

Open access

L. Łatka

barrier coatings - thermal and lifetime performance, Surface and Coatings Technology 268 (2015) 15-23. 76. Gupta M., Design of thermal barrier coatings, a modeling approach, Springer, London, 2015. 77. Fan W., Bai Y., Review of suspension and solution precursor plasma sprayed thermal barrier coatings, Ceramics International 42 (2016) 14299-14312. 78. Ma W., Jarligo M.O., Mack D.E., Pitzer D., Malzbender J., Vassen R., Stoever D., New generation perovskite thermal barrier coatings materials, Journal of Thermal Spray Technology 17 (2008) 831

Open access

Yi Sun, Tao Xu, Yuanjie Shu and Fachun Zhong

Abstract

HNS (2, 2′, 4, 4′, 6, 6′-hexanitrostillbene) is a heat-resistant photosensitive explosive widely used in the booster charge. Investigation of the photodecomposition mechanism may provide important information for controlling and enhancing the detonation performance, also for the lifetime prediction. The UV-induced photodecomposition of HNS has been subjected to experimental studies. The UV-Vis spectra, X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectra (EPR) demonstrate the formation of NO2 free radicals and nitroso derivatives of HNS upon UV irradiation, which proves well known facts that C-NO2 breaking and removal of oxygen from the nitro group take part in the photodecomposition of HNS.

Open access

Esra Yildiz

Abstract

Zr0.99Gd0.01O2, Zr0.98Gd0.01Dy0.01O2 and Zr0.98Gd0.01Yb0.1O2 phosphors were synthesized by Pechini method at 1200 °C for 12 h in air. The phosphors were characterized by using X-ray powder diffraction (XRD), differential thermal analysis/thermal gravimetry (DTA/TG), scanning electron microscopy (SEM) and photoluminescence spectrofluorometer (PL). X-ray powder diffraction studies showed that the phosphors were crystallized as monoclinic and tetragonal multiphases. The particle size of the phosphors after heat treatment at 1200 °C was found to be of 200 nm to 250 nm. Luminescence studies on these phosphors have been carried out on the emission and excitation, along with lifetime measurements. The results of emission analysis indicate that the phosphors are expected to find potential applications as new optical materials.

Open access

Tran Hoang Quang Minh, Nguyen Huu Khanh Nhan, Nguyen Doan Quoc Anh, Tran Thanh Nam and Hsiao-Yi Lee

Abstract

Based on some advantageous properties, such as fast response time, environment friendliness, small size, long lifetime, and high efficiency, white LEDs are increasingly used in common illumination applications. In this research, by co-doping of redemitting Sr2Si5N8:Eu2+ phosphor and adding SiO2 particles to yellow-emitting YAG:Ce phosphor compounds, a new approach for improving color uniformity and color rending index of remote-phosphor structure white LEDs is proposed and demonstrated. The obtained results clearly indicate that the color rendering index (CRI) and color uniformity (ΔCCT) significantly depend on Sr2Si5N8:Eu2+ concentration. The results provide a potential practical solution for manufacturing remote-phosphor white LEDs (RP-WLEDs) in the near future.