501 超塑性変形したイットリア安定化ジルコニアの熱膨張率の評価

Thermal expansion is an important design parameter of materials, which should be taken into account when developing, producing and using products. To control this significant characteristic of new materials, it is necessary to develop equipment, methods and measurement procedures that take into account the novelty of the specific behavior of these materials. The production of specially shaped samples is the main limitation in thermal expansion measurements. This primarily applies to new materials (heterogeneous, composite, poorly processed) developed for special tasks. These factors necessitated the development of a method for measuring the temperature coefficient of linear expansion of products and materials with arbitrary sample shapes, which was not available in previous implementations of interferometric methods. An interference speckle dilatometer SD was developed for measuring samples with irregular shape in the temperature range from 200 to 400 K. When creating the speckle dilatometer SD, the speckle interferometry method was implemented to measure the elongation of samples with an irregular surface with nanometer sensitivity. Since this device has no analogues, a study was conducted on the uncertainty components arising when measuring the thermal coefficient of linear expansion of materials on this device. The analysis of the uncertainty components of the measurement of the thermal coefficient of linear expansion of materials on the speckle dilatometer SD was carried out. An experimental determination of the measurement uncertainty of the thermal coefficient of linear expansion of TCLE measures of arbitrary shaped samples was obtained using the SD speckle dilatometer. After research and initial certification, the developed measurement instrument was approved and included in the State Secondary Standard of the unit of thermal coefficient of linear expansion of solids in the range of values from 0.05 · 10–6 to 100.0 · 10–6 K–1 in the range of temperature values from 90 to 1,900 K.

Relevance. Coatings based on bioactive glass are widely used in maxillofacial and orthopedic implantology due to their ability to osseointegration, degradation control and bone compatibility. At the same time, when implants are operated in loaded areas, glass coatings experience mechanical loads, thermal fluctuations and the effects of an aggressive biological environment, which places high demands on their crack resistance, adhesion and thermo-mechanical stability. Objective. To carry out a comparative evaluation of the performance characteristics of the new bioactive coating for the dental implant FAR-5X and its analogue, aimed at identifying potential advantages in mechanical stability and compatibility with the titanium base. Materials and methods. This study presents a comparative analysis of the mechanical properties of two glass–ceramic composite coatings, FAR-5X and FAR-5.3/E, designed for application on titanium implants. The analysis focused on key mechanical parameters, including the coefficient of thermal linear expansion, Vickers microhardness, fracture toughness, Young’s modulus, and adhesion strength. All measurements were performed on seven samples of each coating type using standard micro-mechanical testing methods. Statistical processing was conducted using one-way ANOVA and Tukey's post-hoc test. Results. The developed glass composite coating FAR-5X demonstrates a set of high-performance characteristics due to its nanostructured morphology obtained through optimized thermal treatment. This approach promotes a homogeneous distribution of the crystalline phase within the amorphous matrix, enhancing the material’s mechanical integrity. The results revealed a statistically significant higher coefficient of thermal linear expansion value in the FAR-5X coating compared to FAR-5.3/E (p < 0.05), indicating improved thermomechanical compatibility with the titanium substrate. A statistically significant difference between the coatings was found only in the coefficient of linear thermal expansion, indicating better thermal compatibility of FAR-5X with the titanium base. No significant differences were observed in microhardness, fracture resistance, elastic modulus, or adhesion strength, confirming comparable mechanical integrity between the coatings. Conclusion. The findings suggest that the newly developed FAR-5X coating offers advantageous thermal expansion behavior while maintaining the necessary mechanical robustness, supporting its potential application as a bioactive coating in orthopedic and dental implant systems.

The corrugated layer structure bismuth has been successfully tailored into negative thermal expansion along c axis by size effect. Pair distribution function and extended X-ray absorption fine structure are combined to reveal the local structural distortion for nanosized bismuth. The comprehensive method to identify the local structure of nanomaterials can benefit the regulating and controlling of thermal expansion in nanodivices.

Effective thermal expansion of heterogeneous materials with application to low temperature environments

The mean coefficient of linear thermal expansion is used to define a new “instantaneous coefficient of linear thermal expansion” (ILTE) which is proved to be independent of reference temperatures required to define mean values. Hence it can be considered a true material property. The new ILTE provides a common reference to compare thermal expansion data of different materials. This instantaneous coefficient is different from the instantaneous value defined by ASTM standards. Values of the new coefficient are compared with the widely used mean coefficient values. Accuracy of calculations using the new ILTE is demonstrated using the mean coefficient data of two materials.

Three mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) were superplastically deformed under various conditions and microstructural evolution was characterized. Thermal expansion properties of the 3Y-TZP specimens were then measured by a push-rod type dilatometer in a temperature range from 300 K to 1473 K. Experimental results showed that the mean coefficient of linear thermal expansion, α, decreased with an increase in the volume fraction of cavities. The cavity dependence of α value was dependent on temperature and was weakened with an increase in temperature. Changes in the average grain size and grain aspect ratio due to the superplastic deformations were found to have little effect on the thermal expansion property within the present experimental range.

Influence of the structural state and crystallographic texture of Zr-2.5% Nb alloy samples on the anisotropy of their thermal expansion

Because of the lack of data on the thermal expansion of natural solid wood and many wood products, such as plywood, impreg, compreg, and many others, studies were conducted at the Forest Products Laboratory in an effort to obtain such data. The coefficients of linear thermal expansion, called α were measured on a wide variety of wood materials in three structural directions. General formulas were developed which permit calculation of the coefficients of linear thermal expansion in any grain direction of the specimen from the original and final specific gravities, the percentage by weight of resin and glue present, the percentage of cross-banding, and the slope of grain relative to any three axes of reference.

The results of dilatometric studies of thermal coefficient of linear expansion of dysprosium in the temperature range 110-1950 K are presented. The measurements were performed with an accuracy of (1.5-2.0)·10-7 K-1. The approximation dependences of thermal coefficient of linear expansion were obtained. The reference tables of dysprosium thermal properties for the range 110-1950 K of solid and liquid states were constructed using the previous results obtained by the gamma method. The character of thermal coefficient of linear expansion changes in the area of the Neel point has been established. Its critical exponents and the critical amplitudes have been determined. It is shown that both above and below the Neel temperature, the experimental data cannot be processed with a single scaling equation. A comparison with the published data has been performed.

A new technique for measuring Young's modulus of an ultra-thin film, with a thickness in the range of about 10 nm, was developed by combining an optical lever technique for measuring the residual stress and X-ray diffraction for measuring the strain in the film. The new technique was applied to analyze the mechanical properties of Ga-doped ZnO (GZO) films, that have become the focus of significant attention as a substitute material for indium-tin-oxide transparent electrodes. Young's modulus of the as-deposited GZO films decreased with thickness; the values for 30 nm and 500 nm thick films were 205 GPa and 117 GPa, respectively. The coefficient of linear thermal expansion of the GZO films was measured using the new technique in combination within-situresidual stress measurement during heat-cycle testing. GZO films with 30–100 nm thickness had a coefficient of linear thermal expansion in the range of 4.3 × 10−6– 5.6 × 10−6 °C−1.

The thermomechanical analyzer (TMA) is eminently suitable for the measurement of the thermal expansion coefficient of rubbers, provided the equipment is calibrated with materials of similar expansion coefficient. FKM or other thermally stable and amorphous polymers (of independently determined thermal expansion characteristics) can be used as calibration standards. The relative simplicity and precision of the TMA method for the determination of the coefficient of isotropic linear expansion, and hence, of volumetric expansion of rubbers, makes this important thermodynamic parameter easily accessible experimentally. Because of the frequently observed anisotropy of molded elastomeric compounds, measurements in all three dimensions are required to define linear, isotropic expansion and shrinkage which, to an excellent approximation, are represented by arithmetic averages of the three unidirectional values. Good agreement has been found between the average (isotropic) shrinkage determined experimentally and that calculated from the average (isotropic) coefficient of linear thermal expansion, α. The effect of fillers, such as carbon black, on α is additive. This makes it possible to predict α and shrinkage of all filled compounds from a single value of α of the unfilled rubber. The linear thermal expansion coefficients of the tested rubbers (FKM, NBR, EPDM) increase linearly with temperature, the increase being generally stronger for FKM than for the other elastomers. The appreciably higher mold shrinkage of FKM relative to NBR is directly due to the higher α of FKM for comparable levels of fillers. This must be kept in mind when expedience dictates the use of the same molds for FKM and NBR compounds.

High temperature thermal expansion of BaAl2Si2O8, CaAl2Si2O8, and Ca2Al2SiO7 studied by high-temperature X-ray diffraction (HT-XRD)

The linear thermal expansion coefficients(LTEC) of some different pieces of the grade GC-20SS of glassy carbon produced by Tokai Carbon Co. Ltd. Japan have been measured using both an interferometric dilatometer and a push-rod dilatometer in order to investigate the piece-to-piece and lot-to-lot consistency for thermal expansion. The results indicated that the differences in LTEC in the temperature range -50 to 220 °C for different pieces from the two glassy carbon lots are sufficiently small within ±4×10-8K-1, which is the same order of measurement uncertainty. Thus, no significant thermal expansion divergency exists among different pieces and lots of GC-20SS glassy carbon, this material seems to be a very promising candidate standard reference material for thermal expansion measurement.

Extrusion drawn amorphous and semicrystalline poly(ethylene terephthalate): 3. Linear thermal expansion analysis

Anisotropic thermal expansion of bio-based rigid low-density closed-cell polyurethane foams