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1 – 10 of over 6000B. Faridnia, M.M. Kashani Motlagh and A. Maghsoudipour
To evaluate the effect of flux, activator and co‐activator on solid state synthesis of SrAl2O4: Eu2 + , Dy3 + phosphor, where boric oxide, europium oxide and dispersium oxide…
Abstract
Purpose
To evaluate the effect of flux, activator and co‐activator on solid state synthesis of SrAl2O4: Eu2 + , Dy3 + phosphor, where boric oxide, europium oxide and dispersium oxide were used, respectively.
Design/methodology/approach
To optimise synthesis condition of long lasting phosphorescence SrAl2O4 phosphor, boric oxide was used as a flux. To improve relative intensity of SrAl2O4: Eu2 + phosphor, the critical concentration of Eu2 + was determined. The effect of various concentration of co‐activator on afterglow properties, the effect of Dy3 + ion on the emission and excitation spectra were examined.
Findings
The SrAl2O4: Eu2 + , Dy3 + phosphor powders have been synthesised by solid state reaction method. The result of XRD patterns indicated that, addition of 5 mol% B2O3 enhanced the formation of SrAl2O4 at 1,200°C. Investigation on the variation of emission intensity of different phosphors containing different amounts of Eu2 + revealed that after 6 mol% of Eu2 + concentration, quenching process occurred. Dy3 + formed trap levels and results demonstrated that increasing concentration of Dy3 + up to 5 mol% reduced the relative intensity and increased the decay time.
Originality/value
Using B2O3 as a flux and solid state reaction method for preparation of this phosphor is in good agreement with industrial production and make it economic, because of reduced sintering temperature.
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Aleksandr Viktorovich Zaichuk, Aleksandra Andreevna Amelina, Yurii Sergeevich Hordieiev, Liliya Frolova and Viktoriia Dmitrievna Ivchenko
The purpose of this paper is to conduct the directed synthesis of blue-colour aluminate spinel pigments based on spent aluminium–cobalt–molybdenum (ACM) catalyst and to study…
Abstract
Purpose
The purpose of this paper is to conduct the directed synthesis of blue-colour aluminate spinel pigments based on spent aluminium–cobalt–molybdenum (ACM) catalyst and to study peculiar features of mineral formation processes and changes in their colour indices depending on composition and firing temperature.
Design/methodology/approach
Aluminate spinel ceramic pigments with specified colour indices were synthesised by directed formation of their mineral composition and identification of the most rational technological parameters of production. Mineral composition of synthesised pigments was evaluated by X-ray phase analysis. The colour indices of pigments and pigment-containing glaze coatings were studied on the comparator colour. The chemical resistance of pigments was determined by loss of their weight loss after boiling in 1 N hydrochloric acid solution and 1 N sodium hydroxide solution.
Findings
Peculiar features of formation of the mineral composition of aluminate spinel pigments based on the ACM catalyst were studied. The expediency of using magnesium and zinc oxides in their composition has been proved. It is found that for the formation of stable pigments of intense blue colour, a concentration of cobalt (II) oxide in the amount of 0.5 mol is sufficient, which is 23.1 Wt.%. The colour of such pigments is determined by the ratios of cobalt, magnesium and zinc aluminates, which form a spinel solid solution.
Practical implications
The use of developed aluminate spinel pigments provides obtaining of high-quality glass coatings of blue colour, in particular, for ceramics.
Originality/value
Aluminium oxide in the spent ACM catalyst is predominantly in the active form (of amorphous aluminium hydroxide and y-Al2O3). This is a prerequisite for the use of this waste material as a complete substitute for chemically pure Al2O3 in the technology of aluminate spinel pigments and reduction of their firing temperature. Besides, spent ACM catalyst already contains 5 Wt.% of expensive cobalt (II) oxide in the form of stable colour-bearing phase CoAl2O4.
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Andrea Kalendova and Tereza Hájková
– This paper aims to synthesize anticorrosion pigments containing tungsten for paints intended for corrosion protection of metals.
Abstract
Purpose
This paper aims to synthesize anticorrosion pigments containing tungsten for paints intended for corrosion protection of metals.
Design/methodology/approach
The anticorrosion pigments were prepared by high-temperature, solid-state synthesis from the respective oxides, carbonates and calcium metasilicate. Stoichiometric tungstates and core-shell tungstates with a nonisometric particle shape containing Ca, Sr, Zn, Mg and Fe were synthesized. The pigments were examined by X-ray diffraction analysis and by scanning electron microscopy. Paints based on an epoxy resin and containing the substances at a pigment volume concentration (PVC) = 10 volume per cent were prepared. The paints were subjected to physico-mechanical tests and to tests in corrosion atmospheres. The corrosion test results were compared to those of the paint with a commercial pigment, which is used in many industrial applications.
Findings
The tungstate structure of each pigment was elucidated. The core-shell tungstates exhibit a nonisometric particle shape. The pigments prepared were found to impart a very good anticorrosion efficiency to the paints. A high efficiency was demonstrated for the stoichiometric tungstates containing Fe and Zn and for core-shell tungstates containing Mg and Zn.
Practical implications
The pigments can be used with advantage for the formulation of paints intended for corrosion protection of metals. The pigments also improve the paints’ physical properties.
Originality/value
The use of the pigments in anticorrosion paints for the protection of metals is new. The benefits include the use and the procedure of synthesis of anticorrosion pigments which are free from heavy metals and are acceptable from the environmental protection point of view. Moreover, the core-shell tungstates, whose high efficiency is comparable to that of the stoichiometric tungstates, have lower tungsten content.
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Beata Synkiewicz-Musialska, Dorota Szwagierczak, Jan Kulawik and Elżbieta Czerwińska
This paper aims to report on fabrication procedure and presents microstructure and dielectric behaviour of LiZn0.92Cu0.08PO4 ceramic material with Li2CO3 as a sintering aid.
Abstract
Purpose
This paper aims to report on fabrication procedure and presents microstructure and dielectric behaviour of LiZn0.92Cu0.08PO4 ceramic material with Li2CO3 as a sintering aid.
Design/methodology/approach
Substrates based on LiZn0.92Cu0.08PO4 with Li2CO3 addition were prepared via solid-state synthesis, doping, milling, pressing and sintering. Characterization of the composition, microstructure and dielectric properties was performed using X-ray diffractometry, energy dispersive spectroscopy, scanning electron microscopy, impedance spectroscopy in the 100 Hz to 2 MHz range and time-domain spectroscopy in the 0.1–3 THz range.
Findings
Doped LiZnPO4 ceramic, which exhibits a low dielectric constant of 5.9 at 1 THz and low sintering temperature of 800 °C, suitable for low temperature co-fired ceramics (LTCC) technology, was successfully prepared. However, further studies are needed to lower dielectric losses by optimising the doping level, synthesis and sintering conditions.
Originality/value
Search for new low dielectric constant materials applicable in LTCC technology and optimization of processing are essential tasks for developing modern microwave circuits. The dielectric characterization of doped LiZnPO4 ceramic in the terahertz range, which was performed for the first time, is crucial for potential millimetre-wave applications of this substrate material.
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Ibrahim A. Amar and Mohammed M. Ahwidi
This paper aims to investigate the electrocatalytic activity of CoFe1.9Mo0.1O4-Ce0.8Gd0.18Ca0.02O2-δ composite (CFMo-CGDC) for the direct synthesis of ammonia from H2O and N2…
Abstract
Purpose
This paper aims to investigate the electrocatalytic activity of CoFe1.9Mo0.1O4-Ce0.8Gd0.18Ca0.02O2-δ composite (CFMo-CGDC) for the direct synthesis of ammonia from H2O and N2 under atmospheric pressure.
Designs
CoFe1.9Mo0.1O4 nanoparticles (CFMo NPs) were synthesized via a sol-gel method. CFMo NPs were characterized using X-ray diffraction (XRD), Brunauer–Emmet–Teller (BET) specific surface area measurement and scanning electron microscope (SEM). Double-chamber reactor was used to synthesize ammonia using H2O and N2 as precursors. The factors affecting the ammonia formation rate (applied voltage and temperature) were studied.
Findings
CoFe1.9Mo0.1O4 nanoparticles (CFMo NPs) were synthesized via a sol-gel method. CFMo NPs were characterized using XRD, Brunauer–Emmet–Teller (BET) specific surface area measurement and SEM. Double-chamber reactor was used to synthesize ammonia using H2O and N2 as precursors. The factors affecting the ammonia formation rate (applied voltage and temperature) were studied.
Originality/value
The usage of CFMo-CGDC composite as an electrocatalyst for the synthesis of ammonia directly from H2O and N2.
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Tereza Hájková and Andrea Kalendova
– This paper aims to synthesise anticorrosion pigments containing molybdenum for paints intended for corrosion protection of metals.
Abstract
Purpose
This paper aims to synthesise anticorrosion pigments containing molybdenum for paints intended for corrosion protection of metals.
Design/methodology/approach
The anticorrosion pigments were prepared by high-temperature solid-state synthesis from the appropriate oxides, carbonates and calcium metasilicate. Stoichiometric molybdates and core-shell molybdates with a non-isometric particle shape containing Ca, Sr, Zn, Mg and Fe were synthesised. The pigments were examined by X-ray diffraction analysis and scanning electron microscopy. Paints based on an epoxy resin and containing the substances at a pigment volume concentration of 10 volume per cent were prepared. The paints were subjected to physico-mechanical tests and to tests in corrosion atmospheres. The corrosion test results were compared to those of the paint with a commercial pigment, which is used in many industrial applications.
Findings
The molybdate structure of each pigment prepared was elucidated. The core-shell molybdates exhibit a non-isometric particle shape. The pigments prepared were found to impart a very good anticorrosion efficiency to the paints. A high anticorrosion efficiency was found with the pigments Fe2(MoO4)3 and Fe2(MoO4)3/CaSiO3 and with Mg and Zn molybdates.
Practical implications
The pigments can be used for the formulation of paints intended for the corrosion protection of metals. The pigments also improve the paints’ physical properties.
Originality/value
The use of the pigments in anticorrosion paints for the protection of metals is new. The benefits include the use and the procedure of synthesis of the anticorrosion pigments which are free from heavy metals and are acceptable from the aspect of environmental protection. Moreover, the core-shell molybdates, whose high efficiency is comparable to that of the stoichiometric molybdates, have lower molybdenum contents.
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V. Rajasekharan and P. Manisankar
The purpose of this study is to introduce mechanochemically prepared polyaniline anticorrosive additives. In primer coating technology, there is an increasing interest in the…
Abstract
Purpose
The purpose of this study is to introduce mechanochemically prepared polyaniline anticorrosive additives. In primer coating technology, there is an increasing interest in the development of efficient anticorrosive additives which replace the conventional inorganic anticorrosive pigments like heavy metal chromates and phosphates normally added to primer paints for the coating on metals. Conducting polymers are found to be better alternatives.
Design/methodology/approach
Polyaniline phosphate is synthesized through solid-state conditions without using any solvent. The synthesized polyaniline phosphate is added in the primer formulation instead of zinc phosphate. Primers with different quantity of zinc phosphate are also formulated and studied for comparison. The comparison between their abilities to control corrosion of carbon steel were done with application of open-circuit potential monitoring, polarization and electrochemical impedance spectroscopy methods in 3.5 per cent NaCl solution.
Findings
Corrosion studies indicate that polyaniline phosphate can improve corrosion protection properties by taking part the passivation processes. The performance of polyaniline phosphate is better than zinc phosphate.
Originality/value
I certify that the results are from our original research and this paper is neither considered for publication elsewhere nor published previously.
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Kiranmai Uppuluri and Dorota Szwagierczak
The purpose of this work was to characterize NiMn2O4 spinel-based thermistor powder, to use it in screen printing technology to fabricate temperature sensors, to study their…
Abstract
Purpose
The purpose of this work was to characterize NiMn2O4 spinel-based thermistor powder, to use it in screen printing technology to fabricate temperature sensors, to study their performance for different sintering temperatures of thermistor layer, with and without insulative cover, as well as to investigate stability of the fabricated thermistors and their applicability in water quality monitoring.
Design/methodology/approach
After the characterization of starting NiMn2O4 spinel-based thermistor powder, it was converted to thick film paste which was screen printed on alumina substrate. Thermistor layers were sintered at four different sintering temperatures: 980°C, 1050°C, 1150°C and 1290°C. An interdigitated pattern of Ag-Pd conductive layer was used to reduce the resistance. Temperature-resistance characteristics were investigated in air and water, with and without insulative cover atop the thermistor layer. Stability of the fabricated thermistors after aging at 120°C for 300 h was also examined.
Findings
Thick film NiMn2O4 spinel thermistors, prepared by screen printing and sintering in the temperature range 980°C–1290°C, exhibited good negative temperature coefficient (NTC) characteristics in the temperature range −30°C to 145°C, including high temperature coefficient of resistance, good stability and applicability in water.
Originality/value
This study explores the range of sintering temperature that can be applied for NiMn2O4 thermistor thick films without compromising on the temperature sensing performance in air and water, as well as stability of the thermistors after aging at elevated temperatures.
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Mengistu Gelaw, Perumalla Janaki Ramulu, Dagmawi Hailu and Tariku Desta
The purpose of this paper is to manufacture an aluminium square cross-sectional bar by using conventional lathe machine from aluminium scraps through friction stir back extrusion…
Abstract
Purpose
The purpose of this paper is to manufacture an aluminium square cross-sectional bar by using conventional lathe machine from aluminium scraps through friction stir back extrusion (FSBE) process and study the viability of the process to produce the square bar.
Design/methodology/approach
The important tasks involved in this work are as follows: designing and manufacturing the chamber and plunger components used for experimental work, experimentally studying the thermo-mechanical progression of FSBE process on adapted conventional lathe machine and analyzing the relation between controlled parameter (like rotational speed and consolidation time) and response parameter (like extrusion time, extrusion rate, grain structure and hardness).
Findings
Preliminary results show that increasing or decreasing rotational speeds results in defects. Cold crack and twisting defect were shown on square bar fabricated using low rotational speed, and hot crack defects were observed on surface of the bars produced by higher rotational speed. The manufactured square bars were tested using optical microscope and Vickers hardness tester. Microstructural studies reveal that initial grains of aluminium wire undergo significant refinement and result in equiaxed and recrystallized grains in the square bar fabricated through FSBE method. The hardness tests show almost even distribution of hardness in the specimen, but hardness was lower than parent aluminium; in comparison, uneven distribution of hardness was seen in parent aluminium.
Originality/value
FSBE process is the new method to produce the bars and rods with better mechanical properties. The ambition of this work is to convert the existing scrap materials to useful products. Based on the literature review, the work has planned to perform extrusion process with the minimum effort and limited sources. In this manner, the work is highly original and under scientific mandate.
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Evgeny Morozov, Mikhail Novikov, Vyacheslav Bouznik and Gleb Yurkov
Active employment of additive manufacturing for scaffolds preparation requires the development of advanced methods which can accurately characterize the morphologic structure and…
Abstract
Purpose
Active employment of additive manufacturing for scaffolds preparation requires the development of advanced methods which can accurately characterize the morphologic structure and its changes during an interaction of the scaffolds with substrate and aqueous medium. This paper aims to use the method of nuclear magnetic resonance (NMR) imaging for preclinical characterization of 3D-printed scaffolds based on novel allyl chitosan biocompatible polymer matrices.
Design/methodology/approach
Biocompatible polymer scaffolds were fabricated via stereolithography method. Using NMR imaging the output quality control of the scaffolds was performed. Scaffolds stability, polymer matrix homogeneity, kinetic of swelling processes, water migration pathways within the 3D-printed parts, effect of post-print UV curing on overall scaffolds performance were studied in details.
Findings
NMR imaging visualization of water uptake and polymer swelling processes during the interaction of scaffolds with aqueous medium revealed the formation of the fronts within the polymer matrices those dynamics is governed by case I transport (Fickian diffusion) of the water into polymer network. No significant difference was observed in front propagation rates along the polymer layers and across the layers stack. After completing the swelling process, the polymer scaffolds retain their integrity and no internal defects were detected.
Research limitations/implications
NMR imaging revealed that post-print UV curing aimed to improve the overall performance of 3D-printed scaffolds might not provide a better quality of the finish product, as this procedure apparently yield strongly inhomogeneous distribution of polymer crosslink density which results in subsequent inhomogeneity of water ingress and swelling processes, accompanied by stress-related cracks formation inside the scaffolds.
Practical implications
This study introduces a method which can successfully complement the standard tests which now are widely used in either additive manufacturing or scaffolds engineering.
Social implications
This work can help to improve the overall performance of the polymer scaffolds used in tissue engineering.
Originality/value
The results of this study demonstrate feasibility of NMR imaging for preclinical characterization of 3D printed biocompatible polymer scaffolds. The results are believed to contribute to better understanding of the processes vital for improving the design of 3D-printed polymer scaffolds.
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