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Dettagli della rivista
Formato
Rivista
eISSN
2083-4799
Pubblicato per la prima volta
23 Sep 2008
Periodo di pubblicazione
4 volte all'anno
Lingue
Inglese

Cerca

Volume 17 (2017): Edizione 4 (December 2017)

Dettagli della rivista
Formato
Rivista
eISSN
2083-4799
Pubblicato per la prima volta
23 Sep 2008
Periodo di pubblicazione
4 volte all'anno
Lingue
Inglese

Cerca

5 Articoli
Accesso libero

Hydroxyapatite deposition on the laser modified Ti13Nb13Zr alloy

Pubblicato online: 11 Jan 2018
Pagine: 5 - 13

Astratto

Abstract

The Ti13Nb13Zr alloy was subjected to laser modification with the Nd:YAG laser provided that such treatment would increase the surface roughness followed improved adhesion of hydroxyapatite (HAp) coatings The hydroxyapatite was deposited by electrophoretic method in suspension of 0.5 g HA powder and 100 ml ethyl alcohol. The deposition was carried out for 10 min at 10 V voltage followed by drying at room temperature for 24 h and heating at 800°C for 1 h in vacuum. The thickness of the HAp coatings was found as of about 4.06 μm to 9.05 μm. The examinations of surfaces were carried out at each stage of the experiment with the ultra-high resolution scanning electron microscope. The measurements of surface roughness after laser treatment and after HAp deposition were performed with the Hommel Etamic Waveline profilograph.

Parole chiave

  • Ti13Nb13Zr alloy
  • laser treatment
  • hydroxyapatite
  • implants
Accesso libero

Energy storage: dielectrophores – molecules with non-linear polarizability

Pubblicato online: 11 Jan 2018
Pagine: 14 - 21

Astratto

Abstract

We examine the feasibility of film capacitors based on dielectrics with high non-linear polarizability as energy storage devices. Capacitors with increased energy density can be built by using composite materials with aromatic molecules (high polarizability) and envelope of alkyl tails (high resistivity). We determine the impact of the second order non-linearity onto energy density and translate high energy density requirements into molecular parameters necessary for high-performance capacitors. The relationship of permittivity and molecular polarizability is obtained by means of the non-linear Clausius–Mossotti equation. In order to demonstrate the the selection process for the molecular composition of dielectrophores, we compare several molecules, using quantum chemistry algorithms (Gaussian09). Starting from Langhals perylene (LP), we proceed with the nitrophenyl-perylene having one NH2 group (donor) and one NO2 group (acceptor). We show that, while their linear polarizabilities are comparable, the hyperpolarizabilities differ by several orders of the magnitudes. Two NH2 and NO2 groups can be attached to the nitro-naphthalene-perylene further increasing of the hyperpolarizability. Even larger polarization can be achieved by additional rylene groups increasing the polarizable electronic mass. We demonstrate that with such molecular engineering, capacitors can have the energy density which is attractive for practical applications.

Parole chiave

  • organic molecules
  • second-order permittivity
  • hyperpolarizability
  • stored energy density
Accesso libero

Bainitic reaction and microstructure evolution in two normalized and tempered steels designed for service at elevated temperatures

Pubblicato online: 11 Jan 2018
Pagine: 22 - 36

Astratto

Abstract

In the present work conventional heat treatment like normalizing (bainitic microstructure) and tempering of the alloys has been performed. The materials used in this study were two steels, one the laboratory prepared experimental low alloy Cr-Mo steel in comparison to typical commercial 10CrMo9-10 steel. The determined carbon concentrations of the residual austenite at the different temperatures of bainite transformation supports the hypothesis that the growth of bainitic ferrite occurs without any diffusion with carbon being partitioned subsequently into the residual austenite. It was found that bainitic reaction has stopped when average carbon concentration of the untransformed austenite is close to the T0 line and supports formation of bainitic ferrite by a shear mechanism, since diffusionless transformation is not possible beyond the T0 curve.

Normalized samples were air cooled down to room temperature before tempering at various temperatures in the range of 500-750°C. Samples have been austenitized at 980°C for 0.5 hour air cooled and tempered at 500, 550, 600, 650, 700 and 750°C for 1 hour. After heat treatment, the assessment in the microstructure and phase precipitation was made using the samples prepared for metallographic and transmission electron microscope (TEM) on thin foils analysis. Quantitative X-ray analysis was used to determine the retained austenite content after heat treatment like normalizing and tempering and the total volume fraction of the retained austenite was measured from the integral intensity of the (111)γ and (011)α peaks.

The changes observed in the microstructure of the steel tempered at the higher temperature, i.e. 750°C were more advanced than those observed at the temperature of 500°C. Performed microstructural investigations have shown that the degradation of the microstructure of the examined steel was mostly connected with the processes of recovery and polygonization of the matrix, disappearance of lath bainitic microstructure, the growth of the size of M23C6 carbides, and precipitation of the secondary M2C precipitates. The magnitude of these changes depended on the temperature of tempering.

Parole chiave

  • bainitic microstructure
  • normalizing
  • tempering
  • elevated temperatures
  • carbide precipitation
Accesso libero

Ultrasonic diagnostics of main pipelines

Pubblicato online: 11 Jan 2018
Pagine: 37 - 54

Astratto

Abstract

The main pipelines, like many engineering structures, are subject to high operational safety standards. The safety of their operation is supervised by various institutions from the operator, including supervisors such as the Office of Technical Inspection. Safe operation requires knowledge of their technical condition and trends. One of the important sources of information on the condition of pipelines is their periodic inspection carried out with so-called smart pigs. As a result of the inspection, the operator expects the following questions to be answered: what is the condition of the pipeline examined; where and what metal losses are occurring in its construction; what are the hazards causing these damages for the safety of the pipeline operation; what is the rate of increase in the size of metal losses in the pipeline wall. This article presents technical solutions and methodology to answer the above questions.

Parole chiave

  • operational safety
  • smart pigs
  • ultrasonic scanning
  • diagnosis
  • prognosis
Accesso libero

Fabrication and characterisation of porous, calcium enriched coatings on titanium after plasma electrolytic oxidation under DC regime

Pubblicato online: 11 Jan 2018
Pagine: 55 - 67

Astratto

Abstract

The purpose of this work is to produce and characterize (chemical composition and roughness parameters) porous coatings enriched in calcium and phosphorus on the titanium (CP Titanium Grade 2) by plasma electrolytic oxidation. As an electrolyte, a mixture of phosphoric acid H3PO4 and calcium nitrate Ca(NO3)2·4H2O was used. Based on obtained EDS and roughness results of PEO coatings, the effect of PEO voltages on the chemical composition and surface roughness of porous coatings was determined. With voltage increasing from 450 V to 650 V, the calcium in PEO coatings obtained in freshly prepared electrolyte was also found to increase. In addition, the Ca/P ratio increased linearly with voltage increasing according to the formula Ca/P = 0.035·U+0.176 (by wt%) and Ca/P = 0.03·U+0.13 (by at%). It was also noticed that the surface roughness increases with the voltage increasing, what is related to the change in coating porosity, i.e. the higher is the surface roughness, the bigger are pores sizes obtained.

Parole chiave

  • Plasma Electrolytic Oxidation PEO
  • Micro Arc Oxidation MAO
  • SEM
  • titanium
  • porous coatings
  • concentrated phosphoric acid HPO
  • calcium nitrate Ca(NO)·4HO
5 Articoli
Accesso libero

Hydroxyapatite deposition on the laser modified Ti13Nb13Zr alloy

Pubblicato online: 11 Jan 2018
Pagine: 5 - 13

Astratto

Abstract

The Ti13Nb13Zr alloy was subjected to laser modification with the Nd:YAG laser provided that such treatment would increase the surface roughness followed improved adhesion of hydroxyapatite (HAp) coatings The hydroxyapatite was deposited by electrophoretic method in suspension of 0.5 g HA powder and 100 ml ethyl alcohol. The deposition was carried out for 10 min at 10 V voltage followed by drying at room temperature for 24 h and heating at 800°C for 1 h in vacuum. The thickness of the HAp coatings was found as of about 4.06 μm to 9.05 μm. The examinations of surfaces were carried out at each stage of the experiment with the ultra-high resolution scanning electron microscope. The measurements of surface roughness after laser treatment and after HAp deposition were performed with the Hommel Etamic Waveline profilograph.

Parole chiave

  • Ti13Nb13Zr alloy
  • laser treatment
  • hydroxyapatite
  • implants
Accesso libero

Energy storage: dielectrophores – molecules with non-linear polarizability

Pubblicato online: 11 Jan 2018
Pagine: 14 - 21

Astratto

Abstract

We examine the feasibility of film capacitors based on dielectrics with high non-linear polarizability as energy storage devices. Capacitors with increased energy density can be built by using composite materials with aromatic molecules (high polarizability) and envelope of alkyl tails (high resistivity). We determine the impact of the second order non-linearity onto energy density and translate high energy density requirements into molecular parameters necessary for high-performance capacitors. The relationship of permittivity and molecular polarizability is obtained by means of the non-linear Clausius–Mossotti equation. In order to demonstrate the the selection process for the molecular composition of dielectrophores, we compare several molecules, using quantum chemistry algorithms (Gaussian09). Starting from Langhals perylene (LP), we proceed with the nitrophenyl-perylene having one NH2 group (donor) and one NO2 group (acceptor). We show that, while their linear polarizabilities are comparable, the hyperpolarizabilities differ by several orders of the magnitudes. Two NH2 and NO2 groups can be attached to the nitro-naphthalene-perylene further increasing of the hyperpolarizability. Even larger polarization can be achieved by additional rylene groups increasing the polarizable electronic mass. We demonstrate that with such molecular engineering, capacitors can have the energy density which is attractive for practical applications.

Parole chiave

  • organic molecules
  • second-order permittivity
  • hyperpolarizability
  • stored energy density
Accesso libero

Bainitic reaction and microstructure evolution in two normalized and tempered steels designed for service at elevated temperatures

Pubblicato online: 11 Jan 2018
Pagine: 22 - 36

Astratto

Abstract

In the present work conventional heat treatment like normalizing (bainitic microstructure) and tempering of the alloys has been performed. The materials used in this study were two steels, one the laboratory prepared experimental low alloy Cr-Mo steel in comparison to typical commercial 10CrMo9-10 steel. The determined carbon concentrations of the residual austenite at the different temperatures of bainite transformation supports the hypothesis that the growth of bainitic ferrite occurs without any diffusion with carbon being partitioned subsequently into the residual austenite. It was found that bainitic reaction has stopped when average carbon concentration of the untransformed austenite is close to the T0 line and supports formation of bainitic ferrite by a shear mechanism, since diffusionless transformation is not possible beyond the T0 curve.

Normalized samples were air cooled down to room temperature before tempering at various temperatures in the range of 500-750°C. Samples have been austenitized at 980°C for 0.5 hour air cooled and tempered at 500, 550, 600, 650, 700 and 750°C for 1 hour. After heat treatment, the assessment in the microstructure and phase precipitation was made using the samples prepared for metallographic and transmission electron microscope (TEM) on thin foils analysis. Quantitative X-ray analysis was used to determine the retained austenite content after heat treatment like normalizing and tempering and the total volume fraction of the retained austenite was measured from the integral intensity of the (111)γ and (011)α peaks.

The changes observed in the microstructure of the steel tempered at the higher temperature, i.e. 750°C were more advanced than those observed at the temperature of 500°C. Performed microstructural investigations have shown that the degradation of the microstructure of the examined steel was mostly connected with the processes of recovery and polygonization of the matrix, disappearance of lath bainitic microstructure, the growth of the size of M23C6 carbides, and precipitation of the secondary M2C precipitates. The magnitude of these changes depended on the temperature of tempering.

Parole chiave

  • bainitic microstructure
  • normalizing
  • tempering
  • elevated temperatures
  • carbide precipitation
Accesso libero

Ultrasonic diagnostics of main pipelines

Pubblicato online: 11 Jan 2018
Pagine: 37 - 54

Astratto

Abstract

The main pipelines, like many engineering structures, are subject to high operational safety standards. The safety of their operation is supervised by various institutions from the operator, including supervisors such as the Office of Technical Inspection. Safe operation requires knowledge of their technical condition and trends. One of the important sources of information on the condition of pipelines is their periodic inspection carried out with so-called smart pigs. As a result of the inspection, the operator expects the following questions to be answered: what is the condition of the pipeline examined; where and what metal losses are occurring in its construction; what are the hazards causing these damages for the safety of the pipeline operation; what is the rate of increase in the size of metal losses in the pipeline wall. This article presents technical solutions and methodology to answer the above questions.

Parole chiave

  • operational safety
  • smart pigs
  • ultrasonic scanning
  • diagnosis
  • prognosis
Accesso libero

Fabrication and characterisation of porous, calcium enriched coatings on titanium after plasma electrolytic oxidation under DC regime

Pubblicato online: 11 Jan 2018
Pagine: 55 - 67

Astratto

Abstract

The purpose of this work is to produce and characterize (chemical composition and roughness parameters) porous coatings enriched in calcium and phosphorus on the titanium (CP Titanium Grade 2) by plasma electrolytic oxidation. As an electrolyte, a mixture of phosphoric acid H3PO4 and calcium nitrate Ca(NO3)2·4H2O was used. Based on obtained EDS and roughness results of PEO coatings, the effect of PEO voltages on the chemical composition and surface roughness of porous coatings was determined. With voltage increasing from 450 V to 650 V, the calcium in PEO coatings obtained in freshly prepared electrolyte was also found to increase. In addition, the Ca/P ratio increased linearly with voltage increasing according to the formula Ca/P = 0.035·U+0.176 (by wt%) and Ca/P = 0.03·U+0.13 (by at%). It was also noticed that the surface roughness increases with the voltage increasing, what is related to the change in coating porosity, i.e. the higher is the surface roughness, the bigger are pores sizes obtained.

Parole chiave

  • Plasma Electrolytic Oxidation PEO
  • Micro Arc Oxidation MAO
  • SEM
  • titanium
  • porous coatings
  • concentrated phosphoric acid HPO
  • calcium nitrate Ca(NO)·4HO

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