Temperature Coefficient Of Linear Expansion Research Articles

ВЛИЯНИЕ НЕОКСИДНЫХ ДОБАВОК НА СВОЙСТВА СТЕКЛОКЕРАМИЧЕСКИХ ПОКРЫТИЙ ДЛЯ ДЕТАЛЕЙ ИЗ ЖАРОПРОЧНЫХ СПЛАВОВ (обзор)

A review of the scientific and technical literature is presented, which provides examples of improving glass-based coatings by introducing non-oxide modifying additives. The main groups of chemical compounds that are used to improve the properties of glass-ceramic coatings are considered. Such substances include compounds based on boron, silicon and rare earth metals. It is concluded that these additives have a positive effect on the following properties of coatings: heat resistance, heat resistance, mechanical strength, coating formation temperature, temperature coefficient of linear expansion and adhesion strength to the protected material.

ИССЛЕДОВАНИЕ ОСНОВНЫХ СВОЙСТВ СТЕКЛОТЕКСТОЛИТОВ ДЛЯ ПЕЧАТНЫХ ПЛАТ И ОЦЕНКА ВЛИЯНИЯ КЛИМАТИЧЕСКИХ ВОЗДЕЙСТВИЙ НА ПОКАЗАТЕЛИ ИХ ДИЭЛЕКТРИЧЕСКОЙ ПРОНИЦАЕМОСТИ

In this paper, the main properties of glass fiber laminates – dielectric composite materials for printed circuit boards are considered: glass transition temperature, temperature coefficient of linear expansion, ultimate strength in bending, water resistance. The influence of climatic influences (increased ambient temperature, low ambient temperature, increased air humidity, the effect of temperature changes, the effect of salt fog) on the dielectric constant of glass fiber laminates has been evaluated.

Calculation of thermal expansion, glass transition temperature and glass density in the system RO–Al2O3–B2O3–SiO2 (where RO=BaO, SrO, CaO, MgO, ZnO)

Glasses of the system RO–Al2O3–B2O3–SiO2 are used as a base for the fabrication of heat-resistant nonmetallic materials and general-purpose products. The purpose of this work is to develop mathematical models for calculating the temperature coefficient of linear expansion, glass transition temperature and density as a function of the composition of glass in the oxide system RO–Al2O3–B2O3–SiO2 where RO=BaO, SrO, CaO, MgO, ZnO. The disadvantage of the known models is that the range of their application is limited by the quantitative content of components in the glass. At the same time, an increase in the sample size of experimental compositions made it possible to obtain more accurate mathematical models for calculating these properties. The glasses included in the experimental sample are distinguished by a wide range of temperature coefficient of linear expansion (from 30 to 10510–7 К–1). The glass transition temperature of these glasses is within the range of 580–7100C, which allows a reasonable approach to the choice of temperature regime for the formation of the structure vitreous and glass-ceramic materials for different functional purposes. The mathematical models were developed with the use of the experimental and statistical method. The obtained mathematical models are adequate to the experimental data and allow calculating the thermal expansion, glass transition temperature and density of glasses; the mean-square deviations of temperature coefficient of linear expansion, glass transition temperature and density being 1.910–7 К–1, 16.00C and 0.06 g cm–3, respectively. Their accuracy is sufficient for the development of basic glass compositions for various functional purposes.

Constructive approach to reduce the influence of temperature on spring suspension eigenfrequencies

PurposeOne of the problems encountered by developers of inertial systems, such as gyroscopes and accelerometers, is the critical dependence of the eigenfrequencies of elastic suspensions (ES) on temperature when using substrates for sensors made of dielectric materials, such as borosilicate glass. The internal stresses arising in the ES caused by the difference in the temperature coefficients of linear expansion (TCLE) lead to deformation of the sensor and complication of the electronic part of the sensor. The purpose of this paper is to approach for in-plane and out-of-plane ES are considered that allow for minimization of the influence of internal stresses on eigenfrequencies.Design/methodology/approachAnalytical, finite element and experimental results are considered. The temperature coefficient of thermal expansion, the Young’s modulus and the Poisson ratio are given as a function of temperature. The shape of the spring elements (SEs) and the construction of the elastic suspension are the main topics of focus in this study. The authors’ out-of-plane ES based on a meander-like spring element implemented via finite element modeling show good agreement with the experimental results.FindingsMeander-like SEs have been developed that have lower temperature errors in comparison with traditional types of SEs. The main contribution to the change in the eigenfrequency from temperature is made by internal stresses that arose from the deformation of the bonded materials with different TCLE. The change of eigenfrequency from the temperatures that were calculated by finite element method did not exceed 0.15%, however, in practice, the scatter of the obtained characteristics for different samples showed a change of up to 0.3%.Originality/valueThis study shows a way to design and optimize the structure and theoretical background for the development of the microelectromechanical systems (MEMS) inertial module combining the functions of gyroscope and accelerometer. The obtained results will improve and expand the manufacturing technology of MEMS gyroscopes and accelerometers.

Deformation, heat treatment and properties of piston hypereutectic silumins

A series of piston hypereutectic silumins based on Al – (15 ÷ 20) % Si alloyed with copper, magnesium, nickel, and chromium was studied. The alloys were modified with phosphorus and hydrogen-containing reagents to increase the deformability and mechanical properties. The experimental ingots, cast in the steel mold, had dimensions: diameter 190 mm, height 500-550 mm, weight 32-40 kg. The mechanical properties and temperature coefficient of linear expansion (TCLE) of the experimental ingots and forgings made from them are determined. Temporary tensile strength and relative elongation of deformed ingots from hypereutectic silumins were 227-306 MPa and 5.7-7.5%, respectively. The optimal heat treatment of deformed silumins was determined: quenching with step heating and aging, which allows the strength of forgings to be increased up to 370-470 MPa. Moreover, the ductility indicators remain at a high level, and the average TCLE of the alloys is (18.0 ÷ 19.2) ·10−6 К−1 in the range of 50 ÷ 200 °C.

Spectroscopic ellipsometry investigation of electronic states and optical properties of thin films from Ge30AsxSe70-x system

This paper deals with the investigation of the optical properties of thin films from the Ge30AsxSe70-x system. The complex permittivity, ε^=ε1+iε2, and the optical band gap, Egopt, were determined by spectroscopic ellipsometry measurements. The spectra of ε2 in the ultraviolet spectral range were analysed on the base of the existing literature data for the valence band spectra obtained by X-ray photoelectron spectroscopy. It was found that the absorption in the spectral range 2.0–6.5 eV is related to the bonding and anti-bonding p-orbitals of Ge, Se and As atoms. The temperature coefficients of linear expansion, refractive index and the band gaps were determined. The evaluated values for the non-linear refractive index, γ, and the two-photon absorption coefficient, β, showed that the thin films exhibit a highly non-linear refractive index at the telecommunication wavelength.

СТВОРЕННЯ НАНОНАПОВНЕНИХ ЕПОКСИ-ПОЛІЕФІРНИХ КОМПОЗИТНИХ МАТЕРІАЛІВ ДЛЯ ЗАХИСТУ ЕЛЕМЕНТІВ СУДНОВИХ ТЕХНІЧНИХ ЗАСОБІВ

The influence of nanofillers on thermophysical properties of epoxy-polyester composites has been investigated in the work. The filler content (oxidized nanodisperse additive and pyrogenic silicon dioxide) has been varied within q = 0.02…1.0 pts.wt. per 100 pts.wt. of epoxy oligomer ED-20. It has been discovered that the introduction of the oxidized nanodisperse additive in the amount of q = 0.05…0.08 pts.wt. into the epoxy-polyester binder leads to an improvement in the thermophysical properties of the composite. Value of heat resistance (according to Martens) increased from Т = 335 К (for the epoxy-polyester matrix) to T = 346 K at the content of oxidized nanodisperse additive of q = 0.075 pts.wt. Introduction of q = 0.05 pts.wt. of oxidized nanodisperse additive allows to obtain improved values of the temperature coefficient of linear expansion in different temperature ranges: in the region ΔT = 303…323 K – α = 1.0 × 10-5 K-1, in the region ΔT = 303… 373 K - α = 1.9 × 10-5 K-1, in the region ΔT = 303… 423 K – α = 3.4 × 10-5 K-1. It has been determined that the composite material has also improved its heat resistance (according to Martens), which is T = 347 K and the minimum thermal coefficient of linear expansion at the content of q = 0.05 pts.wt. of pyrogenic silicon dioxide nanofiller. Values of the temperature coefficient of linear expansion were: α = 1.0 × 10-5 K-1 in the region (ΔT = 303… 323 K), α = 1.9 × 10-5 K-1 (in the region ΔT = 303… 373 K), Δα = 3.4 ×× 10-5 K-1 (in the region ΔT = 303… 423 K), α = 8.4 × 10-5 K-1 (in the region ΔT = 303… 473 K). It is recommended that in order to form a composite material with improved thermophysical properties to protect the elements of ship technical equipment, it is advisable to introduce the pyrogenic silicon dioxide nanofiller in the amount of q = 0.05 pts.wt. into the epoxy-polyester binder.

ИССЛЕДОВАНИЕ ВЛИЯНИЯ ВАКУУМНОЙ ТЕРМИЧЕСКОЙ ОБРАБОТКИ НА ТЕПЛОФИЗИЧЕСКИЕ СВОЙСТВА КОМПОЗИЦИОННОГО МАТЕРИАЛА СИСТЕМЫ Al–SiC С ВЫСОКИМ СОДЕРЖАНИЕМ АРМИРУЮЩЕЙ ФАЗЫ

The results of investigation of thermal treatment influence on thermophysical properties of metal composite material (MCM) based on aluminium casting alloy АК9ч (АЛ4) grade of Al–Si–Mg system reinforced with silicon carbide particles with content of reinforcing particles of 69±1% (volume) are given. MCM is made by solid-phase method followed by vacuum annealing. There are also presented studies of thermophysical characteristics of the material: thermal conductivity, temperature coefficient of linear expansion in the temperature range from 20 to 400 °C and density. It is shown that thermophysical characteristics depend on structural characteristics of the material.

Effect of Low-Temperature Treatment on the Structure and Physical Properties of Castable Carbon-Containing Invar Alloys

The effect of low-temperature thermocycling treatment of castable invar alloys on the microstructure and temperature coefficient of linear expansion (CLTE) is studied. The tooling used in the production of precision articles from carbon-filled plastic should possess a maximum CLTE, temperature stability of the structure, and invariability of the coefficient of thermal expansion under the impact of thermal cycles. It is shown that an optimum castable invar alloy with steadily low coefficient of thermal expansion should contain at least 32.7 wt.% nickel and about 0.8 wt.% additional carbon. The effect of the distribution of carbon in the alloy on its structural stability is discussed.

ВПЛИВ ХАРАКТЕРУ НАВАНТАЖЕННЯ НА НАПРУЖЕНИЙ СТАН З'ЄДНАНЬ З М'ЯКИМ ПРОШАРКОМ

In the work, the stress state (SS) was simulated by the finite element method using the ANSYS software package in cylindrical nodes with a soft interlayer having an elastic moduluslower than that of the base metal under conditions of power and thermal loading. The influence of the relative thickness of the interlayer on the formation of SS is studied. The fields and diagrams of the distribution of normal (radial, axial, circumferential), tangential and equivalent stresses, as well as the level of maximum and minimum stresses in various sections of the joint are analyzed. It was found that under joint loading by compression and lowering the temperature (during cooling), the level of equivalent stresses is higher in a material with a high temperature coefficient of linear expansion (TCLE), with increasing temperature - with a lower TCLE. In a small area of the base metal near the outer surface at the junction with the interlayer and in the interlayer itself, a complex SS with radial, axial, circumferential and tangential stresses arises. The radial stresses at the junction of the interlayer-material with a large TCLE are compressive, and at the junction of the interlayer-material with a lower TCLE, they are tensile. Axial stresses increase sharply in a material with a larger TCLE and a decrease in a material with a lower TCLE, which causes them to become tensile stresses. Circumferential and tangential stresses increase linearly from zero at the center of the joint to a maximum at the periphery. Equivalent stresses are distributed fairly evenly along almost the entire joint. The nature of the distribution depends little on the thickness of the interlayer, however, the level of stress changes with a decrease in the relative thickness of the interlayer. In the case of an increase in the relative thickness of the interlayer, the equivalent stresses in it increase, which contributes to the activation of the formation of a joint between materials with different thermal expansion rods during diffusion welding with a soft interlayer.

CALCULATION OF THE THERMODYNAMIC CHARACTERISTICS OF Fe – P SYSTEM BY METHOD OF MOLECULAR DYNAMICS

The problem of dephosphorization of iron-carbon alloys is relevant for the metallurgical industry, since a high concentration of phosphorus contributes to the appearance of a number of extremely undesirable phenomena. A lot of experimental work has been devoted to solving this problem, but it has still not been completely possible to cope with it. Any field experiments aimed at studying the process of phosphorus removal, require considerable material and time costs, but at the same time do not guarantee getting the desired result. Therefore, to search for new approaches to solving this problem, it is much more rational to use numerical simulation methods involving the computational capabilities of modern computers. At present, computer experiments are the same recognized research method as theoretical research and real experiment. To study the behavior of phosphorus atoms in iron using a numerical experiment, it is necessary to build a computational model and test it by calculating various characteristics whose values are known in advance. In this paper, the method of molecular dynamics was chosen as the method of computer simulation. Using this method, one can conduct experiments with given atomic velocities and describe dynamics of the studied processes. To describe the interparticle interaction, we used the potential calculated in the framework of the immersed atom method. The study was conducted on a computational cell simulating α-iron crystal with phosphorus substitution atoms. The constructed model demonstrated satisfactory results when calculating the known characteristics of the simulated system. Dependences of changes in such characteristics as temperature coefficient of linear expansion, melting point, latent heat of melting and heat capacity on the concentration of phosphorus atoms, as well as in some cases on magnitude of the applied external pressure were established. Calculations showed that, for example, the phosphorus concentration of 0.5 % leads to an increase in the average thermal coefficient of linear expansion by 9 %, a decrease in temperature and latent heat of fusion by 5 % and a heat capacity by 7 %.

Calculation of the Thermodynamic Characteristics of Fe–P System by the Molecular Dynamics Method

The problem of dephosphorization of iron-carbon alloys is relevant for the metallurgical industry, since a high concentration of phosphorus contributes to the appearance of a number of extremely undesirable phenomena. A lot of experimental work has been devoted to solving this problem, but it has still not been completely possible to cope with it. Any field experiments aimed at studying the process of phosphorus removal require considerable material and time costs, but at the same time do not guarantee getting the desired result. Therefore, to search for new approaches to solving this problem, it is much more rational to use numerical simulation methods involving the computational capabilities of modern computers. At present, computer experiments are the same recognized research method as theoretical research and real experiment. To study the behavior of phosphorus atoms in iron using a numerical experiment, it is necessary to build a computational model and test it by calculating various characteristics whose values are known in advance. In this paper, the method of molecular dynamics was chosen as the method of computer simulation. Using this method, one can conduct experiments with given atomic velocities and describe dynamics of the studied processes. To describe the interparticle interaction, we used the potential calculated in the framework of the immersed atom method. The study was conducted on a computational cell simulating α-iron crystal with phosphorus substitution atoms. The constructed model demonstrated satisfactory results when calculating the known characteristics of the simulated system. Dependencies of changes in such characteristics as temperature coefficient of linear expansion, melting point, latent heat of melting and heat capacity on the concentration of phosphorus atoms, as well as in some cases on magnitude of the applied external pressure, were established. Calculations showed that, for example, the phosphorus concentration of 0.5% leads to an increase in the average thermal coefficient of linear expansion by 9%, a decrease in temperature and latent heat of fusion by 5% and a heat capacity by 7%.

Development of engobe composition with the use of pharmaceutical glass waste for glazed ceramic granite

This paper reports results of research into the application of pharmaceutical glass waste, which is a mixture of medical ampoules, in the production of ceramic tiles. Disposal of such waste reduces the negative impact on the environment and contributes to saving mineral raw materials. At the same time, environmentally safe handling of ampoule forms of pharmaceutical glass waste at the disposal stage implies the removal of drugs’ residues from them. The appropriateness of using glass ampoules cleaned from drug residues as a fluxing component of engobe coatings for glazed ceramic granite is experimentally and theoretically substantiated. Comparative analysis of the charge composition of engobes of various manufacturers and of different chemical compositions of fluxing materials, which are components of these engobes, was carried out. The chemical composition of pharmaceutical glass waste was found to suggest the similarity of the basic properties of melts of these wastes and engobe glass frit. The paper considers the dependence of viscosity of the melts of engobe glass frits on the temperature. It was found that by the estimated values of viscosity of melts and experimentally determined characteristics of fusibility, glass waste can serve as substitutes for expensive engobe frits, when used with other traditional components of engobes. The chemical composition of the waste and of the basic engobe frit was determined by the method of X-ray spectrometry. Fusibility characteristics were explored using the thermoscope MISURA. Temperature coefficient of linear expansion of glass materials was determined with the use of the dilatometer LIL402PC. The research into the development of engobe coatings using pharmaceutical glass waste for the technology of glazed ceramic granite at firing temperature of 1185 °C was carried out. The rational charge composition of glazed engobe with a whiteness of 76 % was determined, which contains 30 % by weight of glass waste. The engobe tiles with water absorption of 0.3–0.4 % and the limit of flexural strength of 52–54 MPa were obtained

STUDY OF THE MICROSTRUCTURE OF MARTENSITE-BAINITE STEELS AND NICKEL ALLOYS WHEN MODELING HEAT TREATMENT MODES USING A DILATOMETRIC METHOD

We present the results obtained using the equipment available at the Center for collective use “Composition, structure, properties of structural and functional alloys” NRC “Kurchatov Institute” — CRISM “Prometey”: DIL 805A/D (TA Instruments) and DIL 402C (Netzsch) dilatometers. Dilatometric analysis which provides determination of the temperature coefficient of linear expansion and the temperature of phase transitions, as well as evaluation of the transformation kinetics, can also allow simulation of heat treatment modes to identify the size of the former austenitic grain using vacuum etching and conduct the research aimed at improving the technology of thermal and thermomechanical processing (TMO) of steels and alloys. The experiments were carried out both in vacuum and in dynamic helium atmosphere. The main methodological difficulties that we have faced with are described. For steels of martensite and martensite-bainite class (38KhMA, 38KhN3MFA, 20Kh3NMFA) conditions of vacuum etching in the chamber of the dilatometer are specified. The efficiency of the method for martensite-bainite steels in determination of the grain size compared to traditional methods of etching is deminstrated. The effect of thermodeformation parameters on the size of austenitic grain is estimated. When modeling the heat treatment modes by the dilatometric method, the microstructure of KhN55MVTs nickel alloy was also analyzed. Changes in the size and morphology of the grain structure at different stages of heat treatment are revealed. The obtained results were used to adjust the current modes of heat treatment and obtain a uniform fine-grained structure. The combined application of dilatometric and metallographic analyzes after vacuum etching of the material decreases the production costs attributed to obtaining the desired microstructure upon thermal and thermomechanical processing of the products and blanks.

Gray non-pigment glass coatings

Color is an important indicator of the aesthetic evaluation of the quality of materials and products for various purposes. The visual perception of the color by the human eye is subjective. For achromatic colors, the human eye responds better to a change in brightness (lightness) of dark colors than light ones, since the relative increment of lightness is higher in the first case than in the second. Gray is an achromatic color, which is the result of a mixture of classic colors — black and white. Depending on the lightness, the shade of gray changes from black (lightness 0%) to white (lightness 100%). In combination with other colors, it decorates any interior, emphasizes its dignity. Gray color is in great demand in the manufacture of steel enamelled household articles. To obtain a light gray color, the basic sodium borosilicate system (Na2O-B2O3-SiO2) was chosen. For the experimental enamels, physicochemical properties were determined, and for glass coatings – lightness and brilliance. In order to improve these properties, the components in the composition of enamels were varied. Leachability of the best enamel was 0.11 cm3/g, temperature coefficient of linear expansion – 94.2 · 10-7 degrees-1, spreadability – 24.3 mm, gloss of the glass layer – 76%, lightness – 57%, the coating withstood the effect of 4%th acetic acid for 5 minutes without losing gloss. On this enamel, the dependence of lightness and tint of the glass layer on the amount (0.067-0.6 parts by weight) of coloring oxides (CuO, NiO, CoO), which were injected in excess of 100.0% by weight, was studied. The optimum content of the coloring components was determined. Non-pigmented glass coatings of light gray color with a delicate blue tint and lightness (60-70%) have been developed, which can be used for enameling kitchen and tableware, as well as for other types of steel articles for household use.

On the defects of enamel coatings

The defects destroy the integrity of the enamel, and the paper examines the influence of the physical-mechanical and corrosion properties of frits and heat treatment on the defectiveness of the enamel coating. The surface defects were scanned by electron microscope. It has been established that the defectiveness of enamel coatings depends on the melting index, temperature coefficient of linear expansion, surface tension of the frits, and heat treatment conditions. When burning rate of the enamel coating decreases, the fine-meshed structure of the enamel changes, and the size of the defects decreases.

Determination of the temperature coefficient of linear expansion by processing of the interferograms

In this paper the theoretical and experimental justification of the simple high-precision method of determining the temperature coefficient of linear expansion of the holographic or digital speckle interferometry are presented. The interferogram is proposed to register under bending thermoelastic deformations of the sample caused by the temperature difference through thickness. The proposed method is contactless and does not impose special requirements to the surface material as in the case of classical interferometry. Is numerical modelling of thermoelastic deformations of the sample, confirming the correctness of the proposed method.

Дослідження термічних властивостей захисних літійалюмосилікатних склокерамічних матеріалів

Проаналізовано основні напрямки розробок літійалюмосилікатних склокерамічних матеріалів та встановлено перспективність впровадження у військовій галузі в якості захисних термостійких бронеелементів, які експлуатуються в умовах високошвидкісних механічних навантажень та дії високої температури. Метою даної науково-практичної роботи є дослідження термічних властивостей літійалюмосилікатних склокерамічних матеріалів. Досліджено вплив структури розроблених склокерамічних матеріалів на їх температурний коефіцієнт лінійного розширення та встановлено визначальний вплив фазового складу на термічні властивості. Розроблено модельні літійалюмосилікатні стекла та синтезовано склокерамічні матеріали на їх основі.
 Встановлено, що визначальним фактором при визначенні впливу фазового складу на температурний коефіцієнт лінійного розширення дослідних матеріалів є наявність та вміст β-сподумену у їх складі. Застосування як елементів індивідуального бронезахисту розроблених склокристалічних матеріалів дозволить знизити термоудар, який виникає при зіткненні снаряду з бронематеріалом, що дозволить їх застосовувати в якості матеріалів для бронеелементів.

Thermoelastic Martensite Transformations and the Properties of Ultrafine-Grained Ni54Mn20Fe1Ga25 Alloys Obtained by Melt Quenching

Studies of structural and phase transformations in the cast and melt-quenched ferromagnetic four-component alloy Ni54Mn20Fe1Ga25 were performed using transmission and scanning electron microscopy and X-ray diffraction, The obtained data have been compared with the results of studies of physical characteristics (electrical resistance, thermopower, magnetic susceptibility, magnetization, and temperature coefficients of linear expansion and relative elongation ΔL/L measured by the method of dilatometry) in the temperature range of 2–870 K. This work has established the effects of quenching on the microstructure, magnetic state, critical temperatures, and specific features of thermoelastic martensitic transformations in the alloy.

The use of secondary resource potential of pharmaceutical waste from glass in the pr duction of ceramic tiles

The article describes ecological aspects of pharmaceutical glass wastes. It is determined that the greatest negative impact on the environment components has wastes containing pharmaceutical residue. It was analyzed that pharmaceutical glass wastes mainly consist of used ampoules (UAs).The ecological necessity of taking away and disposing residues of pharmaceutical substances from UAs by their disposal is determined. The resource possibilities of using UAs as the secondary material in production of ceramic tiles is analyzed. Monitoring of the formation and accumulation of a mixture of ampoules in the therapeutic hospital department was carried out. The mixture consisted of ampoules containing remnants of solutions of various pharmaceuticals. To substantiate the ecological practicability and resource valuation of waste used in the process of ceramic tile production, the chemical composition and physicochemical characteristics of the mixture of UAs were experimentally determined. The chemical composition and physical and chemical characteristics of wastes are experimentally determined to justify ecological expediency and waste recoverability of UAs during ceramic tiles production. The experimentally determined values of the characteristic temperature parameters and the temperature coefficient of linear expansion of the ampoule glass mixture confirm this conclusion.