Papers by Keyword: Thermal Expansion

Abstract: The aim of this work was to determine thermal and physical properties of white-opaque sanitary glazes. Lampang pottery stone was used to replace silica (G2) and feldspar (G3) in the commercial sanitary glaze (G1). All formulations of glazes developed from Seger formula calculation and the glaze slurry was prepared by wet milling, green glazing on commercial ceramic body and firing at 1200^๐C with heating rate of 3^๐C/min by using electric kiln. Melting characteristics, specular gloss, lightness, color, and thermal expansion behavior of all sanitary glazes were investigated. As a result, the glaze G2 was a good reflecting surface with high lightness value. Linear thermal expansion difference at 500^๐C between the glaze G2 and the commercial ceramic body was-0.015%. This glaze-body fit was, therefore, under small compression and more compatible to ceramic sanitary products.

Abstract: Thermal expansion of anti-parallel beta pleated sheets with Bombyx mori silk nanostructures [Gly-Ser-Gly-Ala-Gly-Ala]_n and commonly used model of [Gly-Ala]_n have been investigated through molecular dynamics (MD) simulation calculations in conjunction with interatomic interactions modeled by CHARMM force field method between the temperature range of 300K-700K. Preliminary results indicate significant differences on thermal expansion of two structures that was observed on directions of chain and the direction perpendicular to plates.

Abstract: B₂O₃- or P₂O₅-doped Li₂O-MgO-Al₂O₃-SiO₂ (LMAS) glass-ceramics were prepared by solid state method using Li₂CO₃, MgO, Al₂O₃ and SiO₂ as the raw materials, B₂O₃ or P₂O₅ as the additives. The effects of adding B₂O₃ and P₂O₅ on the phase separation, crystallization and thermal expansion coefficient were investigated by means of X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM) and thermal dilatometer, respectively. The results showed that B₂O₃ or P₂O₅ addition could promoted phase separation of glass and increased the size of spherical phase separation droplet. With the addition of B₂O₃ or P₂O₅, the crystallization temperatures (Tc) of LMAS system decreased from 764 ^oC to 726 ^oC and 764 ^oC to 750 ^oC, respectively. However, the crystalline phase compositions did not changed, and β-quartz solid solution (s.s) (Li₂Al₂Si₃O₁₀) was still the main crystalline phase, and lithium silicate (Li₂SiO₃) and forsterite (Mg₂SiO₄) were the minor phases. The thermal expansion coefficient (α) of B₂O₃-doped and P₂O₅-doped LMAS glass-ceramics in the temperature range 20-600 ^oC were 5.215×10^-6/ ^oC and 5.008×10^-6/ ^oC, respectively, which were higher than that of LMAS glass-ceramics (α=3.790×10^-6/ ^oC).

Abstract: The ternary compound DyCo_0.67Ga_1.33 was synthesized and the thermal expansion of DyCo_0.67Ga_1.33 was studied in the temperature range of 309–608 K by high temperature powder X-ray diffraction technique. The volumetric coefficient of thermal expansion, , can be represented by . Its magnetic properties were measured between 30 and 300 K, and the magnetic susceptibility of DyCo_0.67Ga_1.33 was found to follow the Curie–Weiss law in the temperature range of 40–300 K. The effective magnetic moment and paramagnetic Curie temperature were estimated to be 9.86 μ_B and 40.4 K, respectively. Electrical resistivity of the compound DyCo_0.67Ga_1.33 was also measured between 5 and 300 K. Temperature variation of the electrical resistivity suggests the metallic character of the compound DyCo_0.67Ga_1.33 with an anomaly detected at 45 K. The residual resistivity ratio RRR of the compound is about 1.2.

Abstract: This article is focused on thermal expansion of cement-based composite. Studied materials are concrete containing alumina cement, silica aggregates and they are reinforced by basalt fibres. Three different concrete varying in fibres length were prepared and its basic physical properties and thermal expansion were measured. Fibres lengths were 6mm and 12mm. Total amount of fibres in mixtures were constant, whereas the ratio of the fibers were changed. Results were compared with reference concrete with no fibres. It was proved positive effect of fibres on thermal expansion, when the lowest values of thermal strain were shown by material with just longer fibres.

Abstract: FeMnO₃ powders were synthesized through a modified polyacrylamide gel route. The gel and the heat treated final powders have been characterized by X-ray diffractometry (XRD), differential scanning calorimetry and thermogravimetric analysis (TG/DSC) and field-emission scanning electron microscopy (SEM). Phase transformation sequence of dry gel during heating is (Mn⁺³,Fe⁺³)₂O₃→(α-Mn₂O₃)·(α-Fe₂O₃)→FeMnO₃. The thermal expansion properties of as-prepared sample were determined. From 100 to 700 °C, the average coefficient of expansion is 9.0139×10^-6 /K. The experimental results demonstrates that the FeMnO₃ sample exhibit a ferromagnetic transitions with T_N ≈ 40 K.

Abstract: Thermal expansion is an important material property. From change of this quantity phase transformations can be evaluated. Therefore dilatometry is a common tool for construction of transformation diagrams in steel and prediction of material structure according to the performed heat treatment. However there are some restrictions for quenching dilatometers, such as magnetic properties of the material or weldability of the controlling and measuring thermocouple. In this article the quenching dilatometry is proposed for evaluation of precipitation during continuous cooling from solution annealing temperature. Aluminium alloy EN AW 6082 was chosen as the experimental material. Due to poor weldability of the experimental material new sample geometry was introduced.

Abstract: An brief overview of the selected thermo-physical measurements realized in the VILA laboratories for the glass industry and for the fundamental research of glass is presented. Among the routine measurements realized for the glass industry the thermodilatometry for measuring the glass transition temperature, and linear thermal expansion coefficients of glass and metastable glassforming melt are described in detail. The fact that the glass transition temperature is not a single valued physical quantity is stressed in connection with the measurement time temperature schedule. The probably most important quantity related to the glass production technology is the viscosity. Its measurement in the range extending ten orders of magnitude is described. The combination of the falling ball method, the rotation viscosimetry and the thermomechanical analysis is needed to cover the above viscosity range. Among the methods used in the fundamental research of glass structure and properties the study of structural relaxation is overviewed. Here the own method of combined viscous flow and structure relaxation TMA measurement is described in detail.

Abstract: In this paper the results of storage modulus (E’), loss modulus (E’’) and damping parameter tan (δ)=E''/E' of epoxy resins Epidian 57 and L285 with curing agents Z1 and LH285, respectively are presented. In addition to this the stress-strain and thermal expansion characteristics of Epidian 53, 57 and L285 were obtained experimentally in order to compare Dynamic Mechanical Analysis (DMA) results. Temperature range of DMA investigations using Netzsch (Germany) DMA 242C analyzer was from-120 °C to +110 °C at the heating rate of 1 K/min with frequency of {0.1, 1, 10} Hz, respectively. Netzsch DIL 402C dilatometer was used to study the thermal expansion of the tested samples within temperature range from 30 °C to 80 °C at 1 K/min of heating and cooling rates, respectively and Huang TA computer servo control material testing machine HT-2402 was applied to determine the stress-strain characteristics. Measurements of sample elongation ΔL and physical α* were performed twice in heating and cooling cycles. The glass transition temperature T_g determined from maximum of tan (δ) curve at f = 1Hz was equal to 76.7 °C for E57 and 87.2 °C for L285. It has been observed durable deformed shape of L285 sample with deflection in the middle about 5 mm just after finishing the DMA first run of heating which significantly affected DMA results during the second run of heating

Abstract: Studies of the heat capacity temperature characteristics for microalloyed high strength steel S960QL is reported. The investigations were concentrated in the region of the second order phase transition. Experiments were carried out using the Differential Scanning Calorimeter DSC 404F1 Pegasus (Netzsch). As a tested material a sample from the high strength steel S960QL was used within temperature range of 50-1100 °C. In addition to this dilatometric investigations with the same temperature range as DSC ones were carried out using Netzsch dilatometer DIL 402C. Measurements of thermal characteristic, i.e. the heat capacity c_p(T) and thermal expansion α*(T) were performed several times in order to observe thermal processes taking place in microalloyed high strength steel. Previous investigations have revealed the thermal hysteresis of the linear expansion in the region of the second order magnetic phase transition in the S960QL steel.