Insulation Coatings Research Articles

Reduction of Shear Stresses in Friction Units with an Electrical Insulation Coating of the ITER Blanket Modules

During operation of the International Thermonuclear Experimental Reactor (ITER), its removable blanket modules undergo significant shock loads in the process of plasma disruption, which lead to the displacement of parts with a gas-thermal insulating coating on the mount points of the protective panels of the vacuum chamber. A high friction coefficient $$f~$$ ≥ 0.28 at maximum shear resistance provokes peeling, fracturing, and chipping of insulating coatings. Methods of reducing the friction coefficient of supporting surfaces coated with an electrical insulation coating (Al2O3, MgAl2O4) and mount points of the ITER blanket modules experiencing significant shear stresses are considered. The tribotechnical tests of electrical insulating coatings paired with the proposed modified zirconium alloy plates with an antifriction layer in the range of sliding speeds $${v}$$ = 10–5−10–2 m/s, loads $$N$$ = 100−600 N according to the pin-on-disk scheme at temperatures $$T$$ = 20°C, T = 250°C showed a change in the friction coefficient in the range $$f$$ = 0.08−0.23 and high wear resistance of ceramic coatings. The use of innovative intermediate plates with a modified layer (ZrO2−C) in blanket modules could be an alternative to low pressure plasma spraying of an antifriction MoS2 finish layer on electrical insulation coatings.

Enhanced thermal stability of the lepidocrocite‐type titanates by intercalation of large alkaline ions

AbstractLayered materials are promising candidates to serve for thermal insulation coatings because of their low out‐of‐plane thermal conductivity. The thin film preparation of the layered materials in layer‐by‐layer fashion can be realized by several solution processes. However, the layered materials suffer low thermal stability after the solution processes. Herein, we report a strategy to improve the thermal stability of the layered materials processed in solution. In this work, we studied the thermal stability of the lepidocrocite‐type titanate with various interlayer ions (Li+, Na+, K+, and Cs+) at elevated temperatures. We proved that the thermal stability of the titanate increased with the increase of the ionic radius. The Cs+ intercalated titanate can remain in its layered structure up to 1000°C, while the Li+ interacted titanate loses its structural stability at ~280°C. Our work suggests that increasing the size of the interlayer ions is an effective strategy to enhance the structural stability of layered titanates.

Changes in thermal conductivity and thermal shock resistance of YSZ-SiO2 suspension plasma spray coatings according to various raw material particle sizes

Recently, a technique for improving the thermal efficiency of automotive engines has received considerable attention, namely the application of thermal insulation coatings to automotive engine components to reduce heat loss. This study presents thermal shock resistance and related microstructural changes and thermal properties of 8 wt% yttria-stabilized zirconia (8YSZ)/SiO2 multi-compositional thermal insulation coatings with suspensions of various particle sizes, when subjected to suspension plasma spray. After 10,000 cycles of thermal shock testing of the coatings, it was found that different degradation behavior related to the different microstructure of the coatings was influenced by the particle sizes of the suspension. The thermal conductivity of the coatings was significantly reduced by increasing the distribution of the unmelted particles within the coating.

Preparation and Properties of Oriented Silicon Steel Insulation Coating with Repair Function

In order to improve the comprehensive performance of oriented silicon steel insulation coatings and repair surface defects, an insulating coating for oriented silicon steels with repair function was prepared. The repair function was investigated by a simulation experiment. Adhesion and magnetic characteristics were measured. Corrosion resistance was tested by neutral salt spray test. The structure of the insulating coating was characterized by infrared spectroscopy. Results exhibit that the coating has good performance and long service life. The surface is smooth, bright and even, the adhesion is A and the coating is able to embellish the defects of crystal exposing on the matrix layer. There is no corrosion occurred after 24h salt spray test; the magnetic induction intensity B800 is 1.81T, which meets the technical requirements of domestic steel mill products.

ВЛИЯНИЕ РАДИАЦИОННОГО ТЕПЛООБМЕНА НА ИНТЕНСИФИКАЦИЮ ТЕПЛОПЕРЕНОСА В ТОНКОПЛЕНОЧНОЙ ТЕПЛОВОЙ ИЗОЛЯЦИИ

Актуальность исследования обусловлена тем, что тепловая защита оборудования и трубопроводов играет важную роль при проведении энергосберегающих мероприятий на энергетических объектах различного назначения, а рост уровня потерь тепла или холода при транспортировке энергоносителей является причиной создания новых подходов к энергосберегающим мероприятиям при выполнении теплоизоляционных работ. Известно, что основным методом снижения потерь тепловой энергии при ее транспортировке и хранении является применение высокоэффективных теплоизоляционных материалов. Таким материалом является тонкопленочная тепловая изоляция. Уникальные теплофизические характеристики тонкопленочных теплоизоляционных покрытий позволяют использовать их в различных энергетических системах и оборудовании. Несмотря на это технологии применения тонкопленочных теплоизоляционных покрытий к настоящему моменту времени не получили развития. Это объясняется рядом причин, основными из которых являются: недостаток знаний о физических свойствах и механизмах процессов тепломассопереноса в тонкопленочных теплоизоляционных покрытиях. Цель: исследование кондуктивно-конвективно-радиационного теплопереноса в слое тонкопленочной тепловой изоляции с учетом разнородности свойств микросфер и связующих веществ. Объект: цилиндрический слой тонкопленочного теплоизоляционного покрытия. На внутренней и внешней поверхностях теплоизоляционного покрытия поддерживаются постоянные температуры. Геометрия тонкопленочного теплоизоляционного покрытия представляла собой связующее вещество и полые микросферы. Исследования проводились для слоя теплоизоляции толщиной 0,33 мм. Температура на внутренней и внешней поверхностях изоляции принималась в соответствии с экспериментальными данными. Предполагалось, что слой тонкопленочной теплоизоляции на 62 % состоит из микросфер диаметром 50 мкм и на 38 % из связующего вещества. Рассматривались два типа полых микросфер с толщинами стенок: 5 и 2 мкм. Методы. Решение поставленной задачи получено методом конечных элементов. Использовалась аппроксимация Галеркина, неравномерная конечно-элементная сетка. Параметры элементов сетки выбирались из условий сходимости решения. Увеличение числа элементов расчетной сетки проводилось с использованием метода Делоне. Результаты. Установлены величины тепловых потоков в слое тонкопленочной тепловой изоляции при наличии радиационного теплообмена. На основании сопоставления результатов численного моделирования теплопереноса в слое тонкопленочной тепловой изоляции, выполненного с использованием кондуктивно-конвективной модели теплопереноса, с результатами для кондуктивно-конвективно-радиационной модели установлено, что расхождение между ними не превышает 0,1 % и объясняется погрешностями численных расчетов. По этой причине в практических расчетах можно использовать более простую кондуктивную модель теплопереноса.

Hollow Silica Particles: Recent Progress and Future Perspectives.

Hollow silica particles (or mesoporous hollow silica particles) are sought after for applications across several fields, including drug delivery, battery anodes, catalysis, thermal insulation, and functional coatings. Significant progress has been made in hollow silica particle synthesis and several new methods are being explored to use these particles in real-world applications. This review article presents a brief and critical discussion of synthesis strategies, characterization techniques, and current and possible future applications of these particles.

Energy-efficient indicators of panel housing mass construction in the climatic conditions of central Russia

For the design of energy-efficient buildings, it is only necessary to ensure balanced energy consumption. The definition of energy efficiency is inextricably linked to compliance with requirements and economic costs. The concept of energy efficiency does not only apply to a new building. The new design used all the necessary elements. The use of single-layer prefabricated panels in new construction allows for external insulation taking into account the overlap of all monolithic joints. One of the potentially promising methods of thermal insulation of outdoor structures is the use of liquid-ceramic (thermal insulation) coatings. In the course of the study, it was concluded that the surface temperature of the reinforced concrete panel when using two different insulation options has similar indicators. But the difference in the values of the heat flux is 36.2%, i.e. when using liquid-ceramic insulation, the amount of heat transferred through the wall panel is more by 9.67 W / m2. Economic calculation shows that the use of liquid-ceramic insulation has a positive economic effect in comparison with the classical method of wall insulation by 19.56%.

A one-dimensional modeling study on the effect of advanced insulation coatings on internal combustion engine efficiency

This article presents a study of the impact on engine efficiency of the heat loss reduction due to in-cylinder coating insulation. A numerical methodology based on one-dimensional heat transfer model is developed. Since there is no analytic solution for engines, the one-dimensional model was validated with the results of a simple “equivalent” problem, and then applied to different engine boundary conditions. Later on, the analysis of the effect of different coating properties on the heat transfer using the simplified one-dimensional heat transfer model is performed. After that, the model is coupled with a complete virtual engine that includes both thermodynamic and thermal modeling. Next, the thermal flows across the cylinder parts coated with the insulation material (piston and cylinder head) are predicted and the effect of the coating on engine indicated efficiency is analyzed in detail. The results show the gain limits, in terms of engine efficiency, that may be obtained with advanced coating solutions.

Review on RTV Silicone Rubber Coatings Insulator for Transmission Lines

Nowadays, the usage of RTV Silicone Rubber as Insulator coatings are increased due to its advantages to avoid pollution flashover of contaminated insulator. Besides, the coatings can reduce the maintenance cost and scheduled routine. This paper had introduced the advantage of RTV Silicone Rubber coatings on insulator, such as good adhesion, nominal thickness range and good hydrophobicity. There are three method of coatings application, such as brushing, spraying and dipping. Suitable method is used to specific insulator application. Meanwhile, this paper also explained about installation of coated insulator in the field.

TiN-based organic-inorganic composite films with dual functions of solar control and low-emission for energy-saving coatings

With the fast development of modern intelligent buildings, the demand for a comfortable environment and ‘low carbon’ technologies, for example, energy-saving buildings, becomes more intense. Thermal insulation coatings as one of the most promising routes to alleviate the energy consumption of buildings attract extensive attention in recent years. In this work, titanium nitride-based organic-inorganic composite films (TiN O/I films) were introduced as the thermal insulation coatings to window glass via blade coating method. Additionally, two different synthesis methods were adopted to prepare the inorganic TiN nanoparticle and its effect on the optical property of the coatings was studied detailedly via the ultraviolet-visible-near-infrared (UV–vis-IR) spectrophotometer and Fourier transform infrared spectrometer characterizations. In addition, the thermal insulation properties of the films were characterized by a system that simulates the natural environment. Various characterizations show that the synthesized TiN O/I films can not only pass through the visible light but also has high reflectance at the mid-infrared range, that is with the functions of solar control and low emission, well satisfying the requirements of the energy-saving coatings for window glass. These results demonstrated the good feasibility of TiN O/I films in thermal insulation coatings, and also provide a direction for the development of more novel thermal insulation materials with large-scale.

Study on Corrosion Resistance and Thermal Insulation Properties of Graphene Oxide Modified Epoxy Thermal Insulation Coating

Study on Corrosion Resistance and Thermal Insulation Properties of Graphene Oxide Modified Epoxy Thermal Insulation Coating

Insulating polysiloxane coating forXLPE‐Si‐rubber interfaces with high long‐term stability

AbstractCable joints play an important role in the power supply systems, but at the same time, they greatly contribute to the majority of direct failures. Weak parts of the cable lines, especially for the solid‐solid interfaces in joints, attract much attention and are investigated by researchers worldwide. High‐voltage power transmission in electrical grids requires reliable and durable dielectric coatings for the interface insulation. The breakdown caused by local electric field enhancement is a gradual damaging process that leads to structural degradation and an increase of electrical conduction of dielectric materials, and ultimately, it results in catastrophic failure of the cable joints. Here, we demonstrate that the coating of silicone gel instead of silicone grease enables the improvements of tangential AC (alternating current) BDS (breakdown strength) and long‐term stability in the interfaces of joints. Under the pressure of Si‐rubber (silicone rubber) cold‐shrinkable cable accessories, the silicone gel almost did not lose, which improved the insulating stability of the interfaces. Our method allows us to fill the XLPE‐Si‐rubber (cross‐linked polyethylene and silicone rubber interfaces with silicone gel instead of silicone grease), which could reduce the risks of the power outage caused by cable joint faults.

Insulation Systems of Frameless Buildings

The article analyzes different ways of creating an insulating coating within the scope of frameless buildings. Among such constructions, the production halls, raw material and finished-products storages, agricultural storages, livestock housing, garages, covered parking, sports and cultural facilities are to be distinguished. Criteria that the heat-insulating materials should meet in the context of effective and durable insulation coatings are low thermal conductivity, vapor and water permeability, high operational durability and environmental friendliness as well. It is confirmed that products based on polyethylene foam, such as mats and rolls, fully meet the above-mentioned criteria. Furthermore, the possibility of obtaining a seamless joint during the installation process significantly increases the effectiveness of the insulating coating by means of minimizing cold bridges and eliminating leakages when connecting separate insulating elements. Polyethylene foam is an elastic and well stretching material. When fixing polyethylene foam rolls on the metal covering of the frameless construction, they will change their shape together with the metal due to the climatic temperature drops (stretch and constrict). The performed tests have revealed that the longitudinal tensile strength of the products with a metallized coating is 80–92 kPa, without a metallized coating - 80–87 kPa, and 29–32 kPa of the weld seam. The article includes information regarding the results of thermal imaging monitoring of frameless constructions with an insulating coating based on polyethylene foam. It is shown that hot-air welding (with the help of a hot air gun) allows minimizing heat losses both at the joints of the sheets and in the areas adjoining to the base and to the side walls of the buildings.

Research on Improving the Taper of Hole Processing by Insulation Coating of ECM Cathode

Electrochemical machining (ECM) is widely used in metal parts processing because of its high processing speed, good surface quality, no stress and deformation of the workpiece after processing, and no tool loss. However, when using electrochemical drilling, the taper of the hole is large due to the secondary electrolysis phenomenon. Therefore, this paper aims to reduce the taper of the anode workpiece hole by studying the degree of insulation of the cathode sidewall. The processing of the holes is performed by insulating coating the cathode structures to form different conductive radial heights h0. A multiphysics (electric field, flow field, temperature field and mathematical field) model for simulating ECM machining process using a moving cathode tool is proposed in different modes of conductive radial height h0. The mathematical relationship between the height h0 and the taper of the machined hole is established to obtain the optimum machining method.

КОНДУКТИВНО-КОНВЕКТИВНЫЙ ТЕПЛОПЕРЕНОС В ТОНКОПЛЕНОЧНОЙ ТЕПЛОВОЙ ИЗОЛЯЦИИ

Актуальность исследованияобусловлена тем, что тепловая защита оборудования и трубопроводов играет важную роль при проведении энергосберегающих мероприятий на объектах различного назначения, а рост уровня потерь теплоты или холода при транспортировке энергоносителей является причиной создания новых подходов к энергосберегающим мероприятиям при выполнении теплоизоляционных работ. Известно, что основным методом снижения потерь тепловой энергии при ее транспортировке и хранении является применение высокоэффективных теплоизоляционных материалов. Таким материалом является тонкопленочная тепловая изоляция. Уникальные теплофизические характеристики тонкопленочных теплоизоляционных покрытийпозволяют использовать их в различных энергетических системах и оборудовании. Несмотря на это технологии применения тонкопленочных теплоизоляционных покрытий к настоящему моменту времени не получили развития. Это объясняется рядом причин, основными из которых являются: недостаток знаний о физических свойствах и механизмах процессов тепломассопереноса в тонкопленочных теплоизоляционных покрытиях. Цель: исследование кондуктивно-конвективного теплопереноса в слое тонкопленочных теплоизоляционных покрытий с учетом разнородности свойств микросфер и связующих веществ. Объект: цилиндрическийслойтонкопленочных теплоизоляционных покрытий. На внутренней и внешней поверхностях тонкопленочных теплоизоляционных покрытий поддерживаются постоянные температуры. Геометриятонкопленочных теплоизоляционных покрытий представляла собой связующее вещество и полые микросферы. Исследования проводились для слоя тонкопленочных теплоизоляционных покрытий толщиной 0,33 мм. Температуры на внутренней и внешней поверхностях тонкопленочных теплоизоляционных покрытий принималась в соответствии с экспериментальными данными. Предполагалось, что слой тонкопленочных теплоизоляционных покрытий на 62 % состоит из микросфер диаметром 50 мкм и на 38 % из связующего вещества. Рассматривались два типа полых микросфер с толщинами стенок 5 и 2 мкм. Методы. Решение поставленной задачи получено методом конечных элементов. Использовалась аппроксимация Галеркина, неравномерная конечно-элементная сетка. Параметры элементов сетки выбирались из условий сходимости решения. Увеличение числа элементов расчетной сетки проводилось с использованием метода Делоне. Результаты.Выявлено влияние на тепловые потери вида связующего вещества и характеристик микросфер, толщины стенки микросферы и газовой фазы, содержащейся в полости микросферы. Для рассматриваемого случая отклонение от экспериментальных данных составило до 90 % в зависимости от состава тонкопленочных теплоизоляционных покрытий.Анализ результатов численного моделирования теплопереноса в слое тонкопленочных теплоизоляционных покрытий для кондуктивно-конвективной и кондуктивной моделей показал, что расхождение между ними не превышает 3 %и объясняется погрешностями численных расчетов. По этой причине в практических расчетах можно использовать более простую кондуктивную модель теплопереноса.

Mechanically Robust and Flame-Retardant Silicon Aerogel Elastomers for Thermal Insulation and Efficient Solar Steam Generation.

In this work, we report the synthesis of silicon aerogel elastomers (SAEs) by one-pot hydrolytic condensation of silanes, followed by drying at room temperature. The as-synthesized SAE features excellent flexibility and mechanical robustness, for example, a high compressive strength of up to 40 kPa at 75% strain was achieved. Combined with their thermal insulation properties (a low thermal conductivity of ca. 0.02 W m –1 K –1 in air), for the first time, such SAEs were used as a porous platform for both flame-retardant measurement and solar steam generation. By coating with Mg(OH)2 via a facile coprecipitation method, the treated SAEs show excellent flame retardancy with a peak heat release rate of 25.61 kW m–2, in addition to high fire resistance and excellent smoke suppression. When used as a solar steam generator, their evaporation efficiency was measured to be 82.7% (1 kW m–2), which could compete with that of other high-performance bilayered photothermal materials reported so far. Taking advantage of their simple and cost-efficient manufacture and superior mechanical robustness and flexibility, such SAEs with multifunctionalities may have great potential for a wide variety of energy-saving applications, for example, especially for thermal insulation coatings with better flame retardancy and efficient solar steam generation for desalination or freshwater production.

Silica Aerogel Thermal Insulation Coating as Commodity Usage

Silica aerogel-based thermal insulation coating (SA-coating) was prepared from a commercial acrylic binder. The purpose of this investigation is to determine the effectiveness of SA-coating with the application in energy-efficient home design for temperature insulation purposes. The weather acceleration test and thermal insulation property of SA-coating were investigated and compared to the original commercial binder. The weather acceleration test of SA-coating showed equivalent weathering stability and robustness compared to the original binder. The thermal insulation property was performed from an in-lab setup, called temperature difference (TD) measurement. In a closed chamber, without air circulation, the surface temperature with SA-coating was reduced by as much as 26 degrees from 90°C to ∼64°C. More so, if TD measurement was performed in a ventilated area, the temperature can be reduced from 50°C to 36°C (room temperature was 31 °C). The thermal conductivity of the coating at different temperatures was also measured. The water contact angle measurements and the scanning electron micrographs showed that SA-coating can be made hydrophilic to hydrophobic by simple abrasion.

Investigation on leakage current, erosion, and hydrophobic performance ofhigh-voltage insulator coatings of different thicknesses

Room-temperature vulcanizing (RTV) silicone rubber is used as a high-voltage insulator coating to enhance the pollution performance of conventional insulators, and the electrical performance of RTV coating depends on the several parameters. The present study shows the effects of the thickness on the leakage current, erosion, and hydrophobic performance of high-voltage insulator coating. Several different thicknesses of RTV silicone rubber were taken into consideration on porcelain substrates. Erosion and leakage current performances of the samples were evaluated by using inclined-plane tests (IPTs) based on the IEC 60587 standard. Eroded masses and fundamental and harmonic components of the leakage currents were investigated with respect to coating thicknesses. On the other hand, hydrophobic features of the samples were evaluated by using dynamic drop tests (DDTs) with regard to CIGRE TB442 documentation. Time to loss of hydrophobicity and the level of the leakage currents were investigated in DDTs considering the thicknesses.

Superhydrophobic nanostructured coatings for electrical insulators

AbstractControlling surface wettability of ceramic electrical insulators is one of the proposed alternatives to avoid undesired electrical events when these devices are installed in polluted environments. In this sense, the application of super‐hydrophobic nanostructured coatings has recently been proposed due to its high water repellency and possibility of surface self‐cleaning. In this present study, coatings based on polysiloxane, alumina trihydrate (ATH), and several types of silica (SiO2) were developed using a spray‐coating method. Contact angle (CA), sliding angle (SA), thermogravimetric analysis, transmission electron microscopy, scanning electron microscopy (SEM), atomic force microscopy, and inclined plane test (IPT) were applied to characterize fillers and coatings. The results showed that a high quantity of nanoparticles is necessary to achieve superhydrophobicity. The type of silica significantly affected the surface wettability leading to CA from 107 to 160° and SA from 3 to 90°. SEM analysis showed that coatings with hydrophilic silica present a more pronounced topography with microstructured aggregates. The resistance of superhydrophobic coatings to leakage current development was also dependent on type and amount of silica. The superhydrophobic coating with PDMS treated with silica had the best performance during the IPT showing fewer peaks and less accumulated electrical charge.

Experimental assessment of new insulation coatings for lean burn spark-ignited engines

Clean and highly efficient internal combustion engines will still be necessary in the future to meet the ambitious CO2 emissions reduction targets set for light-duty vehicles. The maximal efficiency of stoichiometric Spark-Ignited (SI) gasoline engines has been steadily increasing in recent years but remains limited by the important relative share of cooling losses. Low heat rejection engines using ceramic barrier coatings have been presented in the past but smart insulation coatings are gaining a renewed interest as a more promising way to further increase the engine maximal thermal efficiency. This article is highlighting some important effects of smart insulation coatings developed for lean-burn spark-ignited gasoline engines. Five different coatings with low heat conductivity and capacity are applied on aluminum engine parts with the atmospheric plasma spray technique and are tested with two different engines. The laser induced phosphorescence technique is firstly used in an optical single cylinder engine to quantify the thermal performance of these coatings in terms of temperature swing during combustion. A maximal increase in the piston surface temperature of around 100 °C is measured at low load, confirming thus the expected impact of the low heat conductivity and capacity, and suggesting thus a positive impact on fuel consumption. Thanks to the tests performed with a similar metal single cylinder engine, it is shown that the unburned hydrocarbon emissions can significantly increase by up to 25% if the open porosity on top of the coating is not properly sealed, while the surface roughness has no impact on these emissions. When applied on both the piston and the cylinder head, the optimized coating displays some distinct effects on the maximal heat release rate and NOx emissions, indicating that the thermal environment inside the combustion chamber is modified during combustion. Thanks to the temperature swing between cold and hot engine phases the volumetric efficiency can also be kept constant. However, no increase in efficiency can be measured with this optimized coating which suggests that the heat balance is not affected only by the reduction in the temperature differential between the walls and the gas.