Insulation Coatings Research Articles

Characterization of Rectangular Copper Wire Forming Properties and Derivation of Control Concepts for the Kinematic Bending of Hairpin Coils

As a result of the continuously growing demand for electric vehicles, innovative production technologies must be developed to fulfill the high automotive requirements for productivity and quality in the manufacturing of electric drives. By providing advantages regarding the degree of automation, the productivity as well as the attainable filling factors in comparison to established round wire winding technologies, the hairpin technology shows a high potential for meeting the requested specifications but also technological weaknesses, especially concerning the process reliability. The referring production process of stators is normally based on the spatial forming of open, hairpin-shaped coils of enameled flat copper wire as well as subsequent joining and contacting processes. Consequently, the hairpin coils represent the elementary components of the process chain and can be either shaped by robust tool-bound or flexible kinematic bending processes that enable the shaping of different contours at moderate tool costs. In this paper, the essential mechanical forming and product properties of flat copper wires with different dimensions and insulation coatings are characterized by means of uniaxial tensile tests as well as metallographic analyses of the material structure, at first. Subsequently, the identified forming properties are correlated to the applied manufacturing processes drawing, rolling as well as continuous extruding and considered as limits of possible material variations. To evaluate the effect of fluctuating wire qualities on the robustness of kinematic hairpin bending processes, the fabrication tolerances are analyzed by finite element simulations, using the example of elementary kinematic bending operations and modeled changes of the material properties. Based on the knowledge of material-based process tolerances, different control concepts for the kinematic bending of hairpin coils are derived and compared based on technical as well as economic aspects.

Development and performance of heat insulation coatings for hot rolling of titanium alloy and superalloy rings

In recent years, with the continuous development of the equipment manufacturing industry, the seamless rings made of high-performance titanium alloys and superalloys have been widely used. These seamless rings mainly include aeroengine casing rings, carrier rocket capsule rings, gas turbine rings, oil/gas pipeline rings and so on. The metal ring hot rolling technology has become an irreplaceable manufacturing technology with its characteristics of low material consumption, high efficiency and high performance [1,2].However due to the special features of titanium alloys and superalloys, they have poor thermal processing plasticity and high processing sensitivity, thus cracks occur easily during metal temperature drop in hot rolling process. At the same time, the metal surface oxidation in the heating process also affects the surface quality and rolled parts performance. Therefore, using heat insulation and protective coatings is the most effective and easiest solution for the problem.In view of the above problems, Beijing Tianlichuang Glass Technology Development Co., Ltd. has successfully developed the water-based heat insulation coatings for titanium alloy & superalloy hot rolling at different rolling processes (different temperatures and different holding times). The coatings are coated on the metal surface at room temperature and dried before the billets are sent to furnace for heating. During the heating process, the coatings can prevent metal oxidation at high temperature and preserve heat during the billet transfer & rolling process without generating lubrication effect. These heating preservation coatings use a variety of crystalline non-metallic oxides, minerals and non-crystalline glass powders as major solid base materials, and blended with additives, adhesives and water to create suspensions, then applied to metal surface via brushing or spraying before heating. When design coating formulas, in order to realize good compatibility with the metals and right high temperature viscosity & expansion coefficient so as to achieve perfect match with different hot rolling processes, we should consider specific hot rolling process of titanium alloy & superalloy rings, that is, heating temperature, holding time, furnace atmosphere, and hot rolling condition.The heat insulation coatings can solve the problem of billet heat preservation & protection in the titanium alloy / superalloy ring hot rolling process, meanwhile reduce the surface cracks after hot rolling, making the metal easier to obtain even and fine microstructures. Also, the coatings are easy to use, non-toxic and environment friendly.

Synthesis and characterization of hydrophobic nano-silica thin coatings for outdoor insulators

The hydrophobic characteristics of outdoor insulator surface have significant influence on the lifetime and performance of the power transmission lines. In this research, a textured silica layer was dip-coated on the surface using a tetraethyl-orthosilicate (TEOS) containing solution in order to create a hydrophobic surface. Subsequently, the created coating was modified by dipping it in an octadecyl-trichloro-silane/ethanol solution to decrease its surface energy. The coating was characterized by field emission scanning electron microscopy, X-ray diffraction method, Fourier-transform infrared spectroscopy and atomic force microscopy. The microstructural studies confirmed the formation of a uniform microstructure with the mean particle size of 19 nm and roughness of less than 80 nm. The results demonstrated that by creating the hydrophobic coating, the contact angle increased from 14 to 120?. The result of leakage current test at 10 kV showed that the leakage current of the coated insulator was about 24.4 ?A, while that of the non-coated one was about 32 ?A. The adhesion strength of the coating was 1.7MPa.

激光与等离子复合制备的隔热涂层微观特性与力学性能研究

激光与等离子复合制备的隔热涂层微观特性与力学性能研究

Microstructure and Property of Thermal Insulation Coating on the Carbon Fiber Reinforced Epoxy Resin Composites

Microstructure and Property of Thermal Insulation Coating on the Carbon Fiber Reinforced Epoxy Resin Composites

利用不同粒径玻璃微珠的复合构筑高效隔热反射真石漆

利用不同粒径玻璃微珠的复合构筑高效隔热反射真石漆

Experimental studies of the performance of the heat-shielding layer of composite pipelines during cooling with liquid hydrogen

The development of technology for aircraft and rocket engines more efficient and environmentally friendly cryogenic fuels in the form of liquefied gases: hydrogen (vinyl), oxygen (oxide), natural gas (methane), required the creation of pipelines from modern composite materials, as well as new thermal insulation coatings (TIC), providing reliable protection of these highways from external heat leakage. Fuel out-of-flight manifolds of reusable aircraft require a particularly reliable TIC, since during the operation of the product, their multi-cycle cooling down occurs when pouring cryogenic fuel into the pipelines and heating at the discharge. Thermally insulating coatings in the form of polyurethane foam (PUF), applied to the surface of the protected product, by spraying or pouring a mixture of the constituent components, which are widely used at the present time, are not fully suitable for cryogenic pipelines due to the deterioration of their heat insulating properties in the process of cyclic cooling. The aim of the work is to create a new design and technological solution that ensures the performance of the TIC in the conditions of high-cycle thermal loading. In connection with the prospect of using cryogenic fuels in an aviation (reusable) technology, ensuring the performance of a TIC in such conditions is relevant. For the developed technology, experimental determination of the main parameters of the TIC was carried out. Composite pipelines of curvilinear and rectilinear shape were used as objects of research. The pipeline design included a sealing film sheath, a power sheath made of a polymer composite material, a foam heat insulating coating and metal connecting flanges. On model composite samples of cryogenic pipelines, cyclic tests for cooling with liquid hydrogen (filling of fuel lines) and heating to ambient temperature (draining components) were carried out. During the tests, the pipeline was first cooled with hydrogen gas for one hour. Then, for one hour, liquid hydrogen was poured into the internal cavity, after which natural warming up to a normal temperature was carried out for an hour. The obtained results allowed to determine the dependence of temperature and heat flow of the shell with TIC on the number of cooling cycles, to propose a design and technological solution for a significant reduction of the cryopump at large temperature differences in the TIC, to show the effectiveness of cyclic cooling of foam porosity with closed porosity of the “Vikort-3M”

Possibility of using super-thin liquid thermal insulation for protection of steel beams embedded in brick wall exterior under building reconstruction

The article presents the results of calculations on changing the thermophysical properties of the connectivity node of the outer wall and the balcony plate resting on the cantilever fixed steel beams. A variant of insulation of steel beams with super-thin liquid insulation under the reconstruction of existing brick buildings with single-layer brick walls is proposed. The graphical analysis of the problem was carried out. The results of calculations of temperature with linear thermophysical properties show that the method of steel beams insulation within the conditions of reconstruction of residential buildings makes it possible to increase the building life. When using super-thin thermal insulation coatings, it is possible to reduce the local freezing of the balcony plate.

Research of Cracking Resistance of Thermal Insulation Coatings for Aerated Concrete

The high water demand of finishing compositions obtained using expanded perlite and vermiculite sand reduces the crack resistance of the resulting thermal insulation coatings. The use of microspheres as fillers should make it possible to increase the crack resistance of the resulting coatings. The crack resistance of lime heat-insulating coatings for the finishing of aerated concrete obtained using ash microspheres of aluminosilicate and expanded vermiculite sand has been determined. It is established, that coatings obtained using aluminosilicate ash microspheres, are characterized by good crack resistance due to low shrinkage deformations, high ultimate tensile properties and uniform distribution of moisture content in the process of moistening.

Thermal oxidation of TiN nanocylinder arrays: effects of insulator coatings by atomic layer deposition

Titanium nitride (TiN) is a plasmonic material, which efficiently absorbs the solar spectrum and is useful for light-to-heat conversion. Although TiN nanostructures have been developed for plasmonic applications including heat generators, TiN oxidizes to titanium dioxide (TiO2) at relatively low temperatures, as low as 350 °C in air, which limits the application of TiN. In this study, we protect TiN nanocylinder arrays with conformal coatings of insulator layers fabricated by atomic layer deposition. The coating increases the oxidation temperature of the TiN array in air up to 750 °C through suppression of oxygen diffusion by the insulator layer. We also demonstrate the benefit of the thermal oxidation of TiN as a route for nanofabrication of TiO2, a transparent high-refractive-index material. The TiN nanocylinders are converted to TiO2 nanocylinders without disturbing the periodic arrangement. The resultant TiO2 nanocylinder arrays act as two-dimensional (2D) photonic crystals.

Microelectrostatic simulation of insulated graphene–polymer nanocomposites using COMSOL Multiphysics

Graphene–polymer nanocomposites have shown promising potential as high dielectric constant and electrostatic energy storage materials. However, such nanocomposites often faced challenges of high energy dissipation and low voltage endurance due to direct contact of graphene nanosheets and localized electric field concentration. Various efforts have been made to address these shortcomings such as the insulative coating of graphene nanosheets in a polymer matrix. In this study, we simulated (using COMSOL Multiphysics) the effects of such insulative coatings on localized voltage concentration around graphene nanosheet in a polymer matrix. The simulation was done by consideration of various insulative materials with different dielectric constant and coating thickness on graphene nanosheets. It was noted that insulative coating can reduce localized voltage concentration around a graphene nanosheet in a polymer matrix, thereby improve the breakdown strength. Further increase in the coating thickness with low dielectric constant coating materials can further enhance breakdown strength. However, high coating thickness resulted in lowering the microcapacitance of the microcapacitor in the polymer matrix. Therefore, for the optimal energy density of such nanocomposites, a compromise dielectric constant of a coating material and coating thickness on graphene nanosheet must be reached. This study showcased the influence of insulative coatings on graphene nanosheets. It will be a guide for further studies on the selection of coating materials for graphene nanosheets for high breakdown strength nanocomposites.

Defects investigation in thermal insulation coatings with microwave imaging based on a 22 GHz holographic radar

The evaluation of microwave (MW) imaging radar capabilities in non-destructive tests to detect internal structures or defects in the inner volume of thermal insulation coating has been carried out. The MW imaging with high spatial resolution has been performed with holographic subsurface radar operated in the frequency range from 22.2 to 26.2 GHz. The investigation of this non-destructive testing (NDT) technology is important to evaluate the feasibility for quality check of assembled polyurethane sandwich parts for thermal insulation. The samples of polyurethane foam thermal insulation have been fabricated in collaboration with a manufacturing industry of household appliances to have a representative set of real defects. The images obtained are of high quality and easy to be interpreted as they reveal the shapes and plane positions of the defect into samples with thickness up to 90 mm.

Ceramic / inorganic-organic nano-hybrid composites for thermally stable insulation of electrical wires. Part I: Composition and synthetic parameters

Composite coatings comprising of particulate ceramic and silicon containing inorganic-organic nano-hybrids are synthesized and applied as high temperature capable coatings for electrical wire insulation. The nano-hybrids are synthesised from organosilanes bearing non-hydrolysable methyl, glycidyloxypropyl and phenyl groups. The molar ratios of organosilanes, acid catalysts and synthetic conditions are optimised to offer suitable mechanical and thermal performance to the composite coatings. Different particulate ceramics are tested in regard to their effects on mechanical stiffness of the resultant composite coatings. Vermiculite platelet is finally selected for its lower hardness. The mass ratio of nano-hybrids to platelets of 70:30 to 60:40 are found optimal for balanced performance in respect to thermal, mechanical and dielectric properties. Uniform composite coatings are produced on conductor wires using a reel-to-reel continuous coating process. Initial tests showed insulated wires have moderate mechanical flexibility, dielectric strength and excellent thermal stability, capable of withstanding over 1100V AC potential after 500°C heating.

Effect of Transition Metals Oxide Additives on the Properties of Mixed-Alkali Glass for Electric Insulating Coatings on Aluminum

In order to reduce the cost of the thick-film technology of microcircuits and heating elements, as well as to expand its areas of use, it became necessary to expand the range of materials that, along with ceramics and steel, can also be used as substrates for these products. One of these advanced materials is aluminum. Electrically insulated coatings on metals are subjected to repeated heating and cooling while their produce and use, which promotes the creation of temperature stresses in the coating and leads to their chipping. Therefore, in order to improve the water resistance and adhesion strength of electrical insulation coatings on aluminum, CuO, ZrO2 and Bi2O3 additives were examined. There was found an increase in water resistance with a simultaneous increase in the adhesion strength of the enamel coating with an aluminum substrate with the addition of not more than 3 pts. wt. of copper oxide (II), up to 1 pts. wt. of zirconium oxide (IV), and up to 4 pts. wt. of bismuth oxide (III) w.r.t. 100 pts. wt. of glass.

Thermal Conductivity of Silica Aerogel Thermal Insulation Coatings

In this study, silica aerogel microspheres were prepared through sol–gel method with tetraethyl orthosilicate as the silicon source. Thermal insulation coatings were prepared by mixing silica aerogel and acrylic emulsion. The relationships between the thermal conductivity and volume fractions, densities, sizes, and interfaces of silica aerogel microspheres were investigated through scanning electron microscopy and thermal conductivity analysis. The thermal insulation mechanism of composite coating was discussed in detail. Results showed that the aggregations prevented the decrease of thermal conductivity in the coating when the volume fraction of silica aerogel microspheres was lower than 30 %. However, the pores in the coating reduced the thermal conductivity when the volume fraction was higher than 30 %. The porosity of silica aerogel increased with the declining density, which improved the thermal insulation performance of silica aerogel and reduced the thermal conductivity of the coating. The thermal conductivity of the coating with large microspheres was lower than that with small microspheres at low volume fractions. However, the thermal conductivity of the coating with small silica aerogel microspheres was low because of their large interfacial thermal resistance at high volume fractions. Wetting agents were beneficial in improving the compatibility of hydrophobic aerogel microspheres and polymer, improving the volume fractions of silica aerogel microspheres in the coating, and reducing the thermal conductivity of the coating.

Research of conditions of supporting underground pipeline and loads on protective coating

During the construction and operation of underground pipelines, there is a need to develop projects for the engineering protection of insulation coatings from the mechanical effects of coarse soil. The task is most relevant with significant variability of the laying conditions along the length of the route. In particular, the difficult laying conditions include the passage of the route in the areas of distribution of rocky, gravelly and permafrost soils. The appropriateness of applying the methods of engineering protection of the insulation coating from mechanical stress should be justified both economically and in terms of technical and operational indicators. Therefore, the task of analyzing the conditions of support of the underground pipeline and the study of the created forces in the supporting part of the pipeline is very relevant and characterized by insufficient knowledge. The article analyzes the effect of bedding soil and backfill on the amount of force arising in the protective coating of the supporting part of the pipeline in the presence of unevenness of the base and its particle size distribution. The results of modeling the contact problem using models of a discrete (granular) medium at the base of the pipeline are presented. The wall thickness of the pipes affects the change in created force in the supporting part of the pipeline (for pipes are 1 420 mm the maximum difference is 22 %). In the presence of unevenness of the base, the force in the supporting part can increase by 3–5 times.

Preparation and Study of High Reflectance Color Solar Heat-reflective Insulation Coatings

Based on the existing preparation process of common thermal insulation coatings, a kind of high reflectance color solar heat-reflective insulation coatings was developed by improving the thermal insulation coatings. The effects of hollow glass beads, titanium dioxide and other factors on the properties of the coatings were discussed, and the thermal insulation properties of the coatings were characterized by solar reflectance ratio. The results show that the water-based color solar heat-reflective insulation coatings with high solar reflectance, high weathering resistance and high stain resistance can be prepared by using pure acrylic emulsion and silicone acrylic emulsion as the film-forming base material, using the rutile type titanium dioxide, calcined kaolin, precipitated barium sulphate and hollow glass beads as the insulated function pigments and fillers, and using the auxiliaries for coatings.

Research Progress and Application Status of Thermal Insulation Coatings

In this paper, the thermal insulation mechanism of thermal insulation coatings was outlined. The research progress of barrier, reflective, radiant and composite thermal insulation coatings was introduced at home and abroad. And the future research direction of thermal insulation coatings was prospected.

A Novel Fabrication of Spherical Fe50Ni50 Alloy Powders via in-Situ De-Wetting of Liquid Solid Interface

Spherical Fe50Ni50 alloy powders were fabricated via a novel route based on in-situ interface de-wetting between liquid Fe-Ni alloy and alumina. The obtained Fe50Ni50 alloy particles exhibit very good spherical shape according to SEM images. Furthermore, the cross-sectional SEM images show that there are no pores and bulk inclusions in the internal region of the spherical particles. The XRD results show a trace amount of the impurity alumina phase appearing in taenite phase. The size distribution agreed well with the SEM observation confirms that the alumina powders successfully segregated pre-alloy powders. As an incidental benefit, the surface alumina particles were treated as the electrical insulation coatings. The magnetic character shows that spherical Fe50Ni50 powders exhibit a good soft magnetic property even though with a slightly decreasing of saturation magnetization due to non-magnetic coatings. Our strategies provide a method to in-situ fabricate insulation coated Fe-Ni spherical alloy powders as magnetic powder core.

КОНДУКТИВНЫЙ ТЕПЛОПЕРЕНОС В СЛОЕ ТОНКОПЛЕНОЧНОЙ ТЕПЛОВОЙ ИЗОЛЯЦИИ

Актуальность исследования обусловлена необходимостью разработки новых энергосберегающих технологий для тепловой защиты элементов систем теплоснабжения и иного энергетического оборудования различного назначения. Высокий уровень тепловых потерь в системах теплоснабжения (например, тепловые сети, ТЭС, котельные) и энергетическом оборудовании различного назначения (химические производства, пищевая промышленность и т. д.) и неудовлетворительное состояние их тепловой изоляции обосновывают необходимость разработки новых технологий снижения уровня тепловых потерь в рассматриваемых системах. 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 обусловлено рядом причин, основными из которых являются: недостаток знаний о физических свойствах и механизмах процессов тепломассопереноса в тонкопленочных теплоизоляционных покрытиях. Цель: исследование кондуктивного теплопереноса в слое тонкопленочной тепловой изоляции с учетом разнородности свойств микросфер и связующих веществ. Объекты: цилиндрические слои тонкопленочного теплоизоляционного покрытия. На внутренней и внешней поверхностях теплоизоляционного покрытия поддерживаются постоянные температуры. Рассматривались два варианта геометрии тонкопленочного теплоизоляционного покрытия: «связующее вещество и полнотелые микросферы» и «связующее вещество и полые микросферы». Исследования проводились для слоя теплоизоляции толщиной 0,33 мм. Температуры 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. Экспериментальные исследования проводились с использованием оригинального лабораторного стенда. Решение поставленных задач 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. Установлено, что средний коэффициент теплопроводности тонкопленочного теплоизоляционного покрытия в диапазоне температур 50–90 °С составляет 0,0574 Вт/(м·К), что существенно отличается от заявленных фирмой-производителем значений. Выявлено влияние на тепловые потери вида связующего вещества и характеристик микросфер (полые или полнотелые), толщины стенки микросферы и газовой фазы, содержащейся в полости микросферы. Для рассматриваемого случая отклонение от экспериментальных данных составило от 9,36 до 91,12 % в зависимости от состава тонкопленочного теплоизоляционного покрытия. Такие отклонения обусловлены резким изменением эффективных теплофизических свойств тепловой изоляции при различных характеристиках компонентов тонкопленочной тепловой изоляции. Анализ результатов численного моделирования позволяет сделать вывод о том, что наиболее вероятный состав тонкопленочной теплоизоляции включает в себя полые микросферы и многокомпонентное связующее вещество.