Synthesis and investigation of the properties of tungstate-based anticorrosion pigments in coatings

2015 ◽  
Vol 62 (5) ◽  
pp. 307-321 ◽  
Author(s):  
Andrea Kalendova ◽  
Tereza Hájková
Keyword(s):  
Corrosion Protection ◽  
Particle Shape ◽  
High Efficiency ◽  
Industrial Applications ◽  
Mechanical Tests ◽  
Core Shell ◽  
Pigment Volume Concentration ◽  
Content Type ◽  
The Core ◽  
Protection Of Metals

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.

scholarly journals Corrosion – inhibiting properties of molybdenum-containing pigments in coatings

2015 ◽  
Vol 63 (1) ◽  
pp. 14-28 ◽  
Author(s):  
Tereza Hájková ◽  
Andrea Kalendova
Keyword(s):  
Corrosion Protection ◽  
Particle Shape ◽  
High Efficiency ◽  
Industrial Applications ◽  
Core Shell ◽  
Pigment Volume Concentration ◽  
Content Type ◽  
The Core ◽  
Isometric Particle ◽  
Protection Of Metals

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.

Performance of coatings containing treated silica fume in the corrosion protection of reinforced concrete

2018 ◽  
Vol 47 (4) ◽  
pp. 350-359 ◽  
Author(s):  
Nivin M. Ahmed ◽  
Mostafa G. Mohamed ◽  
Reham H. Tammam ◽  
Mohamed R. Mabrouk
Keyword(s):  
Reinforced Concrete ◽  
Silica Fume ◽  
Corrosion Protection ◽  
Electrochemical Impedance ◽  
Electrochemical Techniques ◽  
Dual Function ◽  
Core Shell ◽  
Protection Efficiency ◽  
Content Type ◽  
Anticorrosive Pigments

Purpose This study aims to apply novel anticorrosive pigments containing silica fume-phosphates (Si-Ph), which were prepared using core-shell technique by covering 80-90 per cent silica fume (core) with 10-20 per cent phosphates (shell) previously, to play dual functions simultaneously as anticorrosive pigments in coating formulations and as an anticorrosive admixture in concrete even if it is not present in the concrete itself. Two comparisons were held out to show the results of coatings on rebars containing core-shell pigments in concrete, and concrete admixtured with silica fume can perform a dual function as anticorrosive pigment and concrete admixture. The evaluation of corrosion protection efficiency of coatings containing core-shell pigments and those containing phosphates was performed. Design/methodology/approach Simple chemical techniques were used to prepare core-shell pigments, and their characterization was carried out in a previous work. These pigments were incorporated in solvent-based paint formulations based on epoxy resin. Different electrochemical techniques such as open-circuit potential and electrochemical impedance spectroscopy were used to evaluate the anticorrosive efficiency of the new pigments. Findings The electrochemical measurements showed that concrete containing coated rebars with core-shell pigments exhibited almost similar results to that of concrete admixtured with silica fume. Also, the anticorrosive performance of coatings containing Si-Ph pigments offered protection efficiency almost similar to that of phosphates, proving that these new pigments can perform both roles as anticorrosive pigment and concrete admixture. Originality/value Although the new Si-Ph pigments contain more than 80 per cent waste material, its performance can be compared to original phosphate pigments in the reinforced concrete.

Ferromagnetic ZnO-TiO2 Core-Shell Nanowire PhotoCatalyst with High Efficiency and Recyclability

2011 ◽  
Vol 90-93 ◽  
pp. 1702-1705
Author(s):  
Xi Zhang ◽  
Gang Xiang
Keyword(s):  
High Efficiency ◽  
Hole Concentration ◽  
Band Gaps ◽  
The Other ◽  
Band Edge ◽  
Core Shell ◽  
Hole Density ◽  
The Core ◽  
Recyclable Photocatalyst ◽  
Shell Nanowires

We demonstrate the design of the recyclable photocatalyst based on ferromagnetic (FM) ZnO- TiO2 core-shell nanowires (NWs). Since the band gaps and band edge energies of bulk ZnO and anatase TiO2 are equal to each other within about 45mV, TiO2 and ZnO can form an p-p+ heterojunction free of band discontinuities and with a built-in potential. The resulting radial field will increase hole density in the TiO2 layer while reduce hole concentration at the interface between the core and the shell, which in turn will decrease the rate of recombination in the photocatalytic TiO2, and hence increase the efficiency of photocatalyst. On the other hand, the NWs with FM cores can be easily collected and refreshed using solenoid and suitable for the recyclable usage of the NW catalyst

Development and preparation of oxide mixture-based pigments for anticorrosion paints

2017 ◽  
Vol 46 (5) ◽  
pp. 342-355 ◽  
Author(s):  
Petr Benda ◽  
Andréa Kalendová
Keyword(s):  
Particle Size ◽  
Mechanical Tests ◽  
Particle Size Analysis ◽  
Size Analysis ◽  
Coating Materials ◽  
Pigment Volume Concentration ◽  
Oxide Mixture ◽  
Content Type ◽  
Steel Panels ◽  
Lamellar Zinc

Purpose The aim of the work is to develop an anticorrosion pigment based on an oxide mixture with lamellar particles. The pigments are prepared from lamellar zinc, zinc oxide and magnetite by calcination. An alkaline earth carbonate is added when embedding a third cation in the lattice of the ferrite that forms the envelope of the lamellar zinc. The properties of the pigments are tested both in the powdered state and when embedded in an epoxy-ester system using different pigment volume concentrations (PVC). Design/methodology/approach The properties of paints containing synthesised oxide mixture-based pigments at various volume concentrations and with the Q factor – Q = PVC/CPVC = 0.65 – were examined (where CPVC is critical pigment volume concentration). A series of isometric ferrite pigments were also synthesised for a comparison. Paints of both types with PVC = 10, 15 and 20 per cent were formulated. Steel panels coated with the paints were subjected to corrosion and mechanical tests. Findings The oxide mixtures with lamellar particles were subjected to particle size analysis and found to make up a broad distribution curve. Electron microscopy photographs confirmed that the oxide mixture pigments contained lamellar particles with a surface layer. A high anticorrosion effect was achieved owing to the combination of different oxide types. Research limitations/implications The properties of the oxide mixtures with lamellar particles are described. Their particle distribution curves can be obtained by particle size analysis methods with a view to obtaining additional information on the status and properties of the pigment particles that may be useful in the development of better paints/coating materials. Practical implications Oxide mixtures with lamellar particles can be used in paints protecting construction steel. Originality/value The composition of the prepared oxide mixture-based pigments is novel. Each oxide acts by its own anticorrosion mechanism and the final beneficial effect is due to their concerted action.

Stabilization of silica-coated silver iodide nanoparticles by ethanol-washing

2016 ◽  
Vol 45 (2) ◽  
pp. 99-105
Author(s):  
Yoshio Kobayashi ◽  
Tetsuya Ayame ◽  
Kyosuke Shibuya ◽  
Tomohiko Nakagawa ◽  
Yohsuke Kubota ◽  
...  
Keyword(s):  
Shell Structure ◽  
Silver Iodide ◽  
Colloid Solution ◽  
Core Shell ◽  
Simple Method ◽  
Content Type ◽  
X Ray ◽  
The Core ◽  
Core Shell Structure ◽  
Ethanol Washing

Purpose – This paper aims to propose a simple method for stabilizing silica-coated silver iodide (AgI/SiO2) core-shell particles, of which a colloid solution functions as an X-ray contrast agent. Design/methodology/approach – A colloid solution of AgI nanoparticles was prepared by mixing silver perchlorate and potassium iodide in water. The AgI/SiO2 nanoparticles were fabricated by a sol-gel method using NaOH, H2O and tetraethylorthosilicate in ethanol in the presence of AgI nanoparticles surface-modified with 3-mercaptopropyltrimethoxysilane. Findings – The silica shells of AgI/SiO2 particles were dissolved near the AgI nanoparticle surface, when they were washed by a process composed of centrifugation, removal of supernatant with decantation, addition of water as a washing solution and a shake with a vortex mixer. In contrast, the shells were not damaged by using ethanol as the washing solution, i.e. ethanol-washing. An X-ray photoelectron spectroscopy spectrum of the silica was changed after the ethanol-washing, which indicated that the ethanol-washing had an effect on the chemical bonds in silica. The effect also acted on the silica shells of AgI/SiO2 particles, which did not damage the core-shell structure, i.e. controlled the dissolution of shell. Originality/value – The paper demonstrates that the ethanol-washing is quite useful for stabilizing the core-shell structure composed of the silica shells.

Polyoxometalate-based metal–organic framework-derived bimetallic hybrid materials for upgraded electrochemical reduction of nitrogen

2020 ◽  
Vol 22 (18) ◽  
pp. 6157-6169 ◽  
Author(s):  
Xinming Wang ◽  
Zemin Feng ◽  
Boxin Xiao ◽  
Jingxiang Zhao ◽  
Huiyuan Ma ◽  
...  
Keyword(s):  
Hybrid Materials ◽  
Hybrid Material ◽  
Shell Structure ◽  
High Efficiency ◽  
Metal Organic Framework ◽  
Core Shell ◽  
Ambient Conditions ◽  
The Core ◽  
Metal Organic ◽  
Core Shell Structure

The core–shell structure of the Fe1.89Mo4.11O7/FeS2@C hybrid material exhibits high-efficiency electrocatalytic NRR activity and stability under ambient conditions.

scholarly journals Application of a novel a core-shell microstructured nanocomposites as a fire extinguishant using seawater

2021 ◽  
Vol 237 ◽  
pp. 01009
Author(s):  
Hao Liu ◽  
Tianwei Zhang ◽  
Cunwei Zhang ◽  
Lei Xiao ◽  
Qiang Liang
Keyword(s):  
High Speed ◽  
High Efficiency ◽  
Water Shortage ◽  
Core Shell ◽  
Dry Powders ◽  
The Core ◽  
Fire Extinguishing ◽  
External Shell ◽  
Treatment Technologies ◽  
In Fire

Water has unsurpassed capabilities in fire extinguishing. However, water scarcity is rapidly increasing in many regions and water shortage problems have led to find either new water resources or improve seawater treatment technologies. In this study, a new environment-friendly and high-efficiency powdered fire extinguishing agent with a core-shell structure is designed. The designed extinguishing agent is a colloidal powder with a 92% liquid content and is prepared through physical modification and high-speed shearing. Fumed silica is used for the external shell due to its chemical inertness, whereas seawater is used as the core due to its high extinguishing efficiency. Results show that the size of the prepared agent ranged between 100–200μm. The two fire extinguishing experiments of different scales demonstrate that the employing inorganic salts with seawater as the core can significantly increase the efficiency of the new powder in extinguishing gasoline and diesel fire compared with ultrafine and common ABC dry powders. The suppression mechanism of action is caused by the combined flame chemical and pyrolysis theories of the potassium compounds. This study would be of great theoretical significance and application value for improving the application scope of the seawater.

Robocasting of carbon-alumina core-shell composites using co-extrusion

2017 ◽  
Vol 23 (2) ◽  
pp. 423-433 ◽  
Author(s):  
Zongwen Fu ◽  
Matthias Freihart ◽  
Tobias Schlordt ◽  
Tobias Fey ◽  
Torsten Kraft ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Wall Thickness ◽  
Extrusion Process ◽  
Truss Structures ◽  
Core Shell ◽  
Lattice Structures ◽  
Content Type ◽  
The Core ◽  
Alumina Gels ◽  
Carbon Core

Purpose This study aims to achieve the fabrication of three-dimensional core-shell filament-based lattice structures by means of robocasting combined with co-extrusion. For core and shell materials, colloidal gels composed of submicron carbon and alumina powders were developed, respectively. Simultaneously, the co-extrusion process was also studied by numerical simulation to investigate the feed pressure-dependent wall thickness. Design/methodology/approach Significant differences in the rheological behavior of the carbon and alumina gels were observed because of differences of the particle morphology and surface chemistry of the carbon and alumina powders. Precise control over the cross-sectional diameter of the core and shell green state elements was achieved by alteration of the feed pressures used during co-extrusion. Findings After subsequent thermal treatment in an oxidizing atmosphere (e.g. air), in which the carbon core was oxidized and burned out, lattice structures formed of hollow filaments of predetermined wall thickness were manufactured; additionally, C-Al2O3 core-shell filament lattice structures could be derived after firing in an argon atmosphere. Originality/value Green lattice truss structures with carbon core and alumina shell filaments were successfully manufactured by robotically controlled co-extrusion. As feedstocks carbon and alumina gels with significantly different rheological properties were prepared. During co-extrusion, the core paste exhibited a much higher viscosity than the shell paste, which benefited the co-extrusion process. Simultaneously, the core and shell diameters were exactly controlled by core and shell feed pressures and studied by numerical simulation. The experimentally and numerically derived filament wall thickness showed qualitative agreement with each other; with decreasing core pressure during co-extrusion, the wall thickness increased.

scholarly journals Combining the core-shell construction with an alloying effect for high efficiency ethanol electrooxidation

2021 ◽  
pp. 100357
Author(s):  
Danye Liu ◽  
Qing Zeng ◽  
Hui Liu ◽  
Chaoquan Hu ◽  
Dong Chen ◽  
...  
Keyword(s):  
High Efficiency ◽  
Core Shell ◽  
Ethanol Electrooxidation ◽  
Alloying Effect ◽  
The Core

Thermal Conductivity of Core-Shell Nanostructures: From Nanowires to Nanocomposites

2005 ◽  
Author(s):  
Ronggui Yang ◽  
Gang Chen ◽  
Mildred S. Dresselhaus
Keyword(s):  
Thermal Conductivity ◽  
Silicon Nanowires ◽  
High Efficiency ◽  
Longitudinal Direction ◽  
Building Blocks ◽  
Phonon Transport ◽  
Generic Model ◽  
Core Shell ◽  
The Core ◽  
Shell Nanostructures

Core-shell heterostructures could potentially become the building blocks of nanotechnology for electronic and optoelectronic applications. The increased surface or interface area will decrease the thermal conductivity of such nanostructures and impose challenges for the thermal management such devices. In the mean time, the decreased thermal conductivity might benefit the thermoelectric conversion efficiency. In this paper, a generic model is established to study phonon transport in core-shell nanowire structures in the longitudinal direction using the phonon Boltzmann equation. The model can be used to simulate a variety of nanostructures, including nanowires and nanocomposites by changing some of the input parameters. We first report the dependence of the thermal conductivity on the surface conditions and the core-shell geometry for silicon core - germanium shell and tubular silicon nanowires. When the scattering at the outer shell surface in the generic model is assumed to be totally specular, the core-shell nanostructure resembles a simulation unit cell of periodic two-dimensional (2-D) nanocomposites. Thermal conductivity of nanowire composites and cylindrical nanoporous material in longitudinal direction is thus predicted as a function of the size of the nanowires and nanopores, and the volumetric fraction of the constituent materials. Results of this study can be used to direct the development of high efficiency thermoelectric materials.

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