Thermal Expansion Tests Research Articles

In-flight particle states and coating properties of air plasma sprayed ytterbium disilicates

The effects of processing parameters on the in-flight particle behavior, phase composition, and properties of air plasma sprayed ytterbium disilicate (Yb2Si2O7) coatings were investigated in this study. With the increase in plasma enthalpy, in-flight particle temperature increases. Higher particle temperature caused an increase in silica (SiO2) evaporation from the Yb2Si2O7 particles and, as a result, additional Yb2SiO5 phase appears in the Yb2Si2O7 coating. Thermal expansion tests showed the coating containing a higher volume of Yb2SiO5 phase has a larger coefficient of thermal expansion (CTE). Thermal cycling tests in a steam environment indicated that the Yb2SiO5 phase content in the APS Yb2Si2O7 coatings has a significant effect on the EBC's durability. Thermal cycling lives decrease with the increase of Yb2SiO5 phase content in APS Yb2Si2O7 coatings. Analysis of the failed coatings indicated that the predominant EBC failure mechanisms are due to growth of the thermally growth oxides (TGO) as well as the stresses induced by CTE mismatch. Furthermore, Calcium–magnesium–alumina-silicate (CMAS) corrosion tests showed that the recession rate decreases with the increase of Yb2SiO5 phase content in APS Yb2Si2O7 coatings.

Microstructure and mechanical property of sapphire joints reinforced byAl4B2O9 whiskers

Bismuth-borate glass, 40Bi2O3–60B2O3 (mol.%), was prepared and acted as a braze to join sapphire in air. Ahead of brazing, basic properties of glass were investigated, including structure and thermal parameters. The thermal expansion test showed that CTE of glass was 8.4 × 10−6/°C in period from 20 to 450 °C, suggesting a good thermal compatibility with sapphire. Bi45BO69 was the main crystalline phase in glass according to DSC analysis [BiO6], [BO3] and [BO4] were major units in 40Bi2O3–60B2O3 glass on the basis of FT-IR spectra analysis.In addition, the wetting behavior of the 40Bi2O3–60B2O3 glass on the sapphire substrate was favourable. Thereafter, sapphire plates were joined at 700 °C for 0 and 20 min, respectively. The results showed that Al4B2O9 whiskers grew in joint when holding for 20 min due to a reaction between 40Bi2O3–60B2O3 glass braze and sapphire. The shear strength was improved greatly as a result of Al4B2O9 whiskers’ appearance.

Toprak Alkali Kaynağı Hammaddelerin Vitrifiye Sırlarında Ergimeye Olan Etkisinin İncelenmesi

In this study, the effect of raw materials based of alkaline earth oxides used in ceramic sanitaryware glazes was investigated on the melting behavior of the glaze. For this purpose, new raw materials based of alkaline earth oxide were included in the Seger formulation and different glaze recipes were prepared. Prepared glaze compositions were applied on fine fire clay bodies with pistole and fired at 1200-1250°C in industrial firing regime. Melting behavior of glazes were investigated with physical flow test samples. The particle size analysis for glaze compositions, thermal expansion test, Harcourt test, L *- a *- b * color measurement and stain resistance tests were applied on all glazed samples. The results showed that the variation of raw material based of alkaline earth oxides has a significant influence on the physical flow lengths and thermal expansion coefficients of glazes without degrading surface quality.

High temperature behaviour of various natural building stones

The aim of this study is to investigate the effect of high temperature and identify important changes that occur when selected building stones (six french limestones and a sandstone) are laboratory-heated. Tests under high temperature such as thermogravimetric analysis, differential scanning calorimetry measurements but also thermal linear expansion tests were conducted in order to establish the thermo-chemical–mechanical behaviour of these materials when subjected to high temperature. Furthermore, these stones were exposed to four different heating–cooling cycles (200, 400, 600, 800 °C). Then, mechanical tests were performed to determine the evolution of compressive strength, tensile strength and dynamic elastic modulus.

Stereolithography additive manufacturing of multi-ceramic triangle structures with tunable thermal expansion

Ceramics and their structures with tunable thermal expansion are deemed necessary to develop. In this study, multi-ceramic structures with tunable thermal expansion, including negative thermal expansion (NTE), zero thermal expansion (ZTE), and positive thermal expansion (PTE), were developed for the first time. Firstly, multi-ceramic triangle structures with tunable thermal expansion were designed based on ZrO2 and Al2O3 ceramics. Then, multi-ceramic triangle structures were fabricated by using the stereolithography additive manufacturing technology. Functionally gradient ceramic (FGC) layers were applied for releasing the thermal mismatch stress among the structure. Finally, the thermal expansion behavior of the multi-ceramic triangle structures were characterized and analyzed by using a homemade thermal expansion testing system. The proposed design, fabrication and characterization methods of multi-ceramic structures with tunable thermal expansion are believed to promote the engineering application.

The origin of thermal expansion differences in various size fractions of silica sand

ABSTRACT In this study, thermophysical properties of a commonly used silica sand were investigated and their relation to its granulometric and chemical composition was studied. Thermal expansion and differential scanning calorimetry tests were performed on individual fractions of the silica sand together with X-ray fluorescence measurements to determine their constituents. It was found that the various size fractions of silica sand exhibit different levels of thermal expansion based on the differences in SiO2 content. The expansion behaviour of two additional silica samples and a recycled olivine sand was also investigated in relation to its grain size to justify the findings.

Effect of Annealing Temperature and External Tensile Stress on Negative Thermal Expansion to Cold Rolled Ti–23Nb–0.7Ta–2Zr Alloy

The effect of annealing temperature and external stress on the thermal expansion of a Ti–23Nb–0.7Ta–2Zr alloy were investigated by means of thermal expansion tests under constant load and X-ray diffraction (XRD). Negative thermal expansion (NTE), which is a shrinkage during heating, was observed in both a cold rolled and annealed specimens. The intensity of (200)β peak decreased while that of (211)β peak increased as the annealing temperature increased. The difference in expansion rate between 50 °C and 250 °C is found to decrease with an increasing annealing temperature from 600 °C to 800 °C, above which it kept almost constant. The expansion rate decreased as the applied stress increased.

Damping capacity of Al–12Si composites effected by negative thermal expansion of Y2W3O12 particle inclusions

Effects of Y2W3O12 particle inclusions and content on damping capacity of Al–12Si composites have been investigated. The Y2W3O12, which is a kind of negative thermal expansion material, can generate high local strain in the composites. Thermal expansion testing shows that the coefficient of thermal expansion (CTE) of Y2W3O12 has obvious changes between 100 and 200 °C The Y2W3O12/Al–12Si composites show damping peaks and display higher damping capacities than the pure Al–12Si alloy. The damping capacities of composites strongly depends on the content of Y2W3O12 inclusions. A thermal strain damping model is also established. Based on the model analysis results, there is a significant contribution of thermal strain to the damping capacity in the composites; the change in CTE of Y2W3O12 could cause the generation of damping peaks. Moreover, dislocation damping and interfacial damping are also main damping mechanisms in the investigated composites.

Non-contact method used to determine the swelling/shrinking coefficients under CO2 sorption/desorption on an HNBR O-ring - Study of coupling with temperature and pressure

To make use of an O-ring under different pressures and temperatures and to procedure predictive numerical simulations of its use, it becomes important to identify the O-ring behavior under coupled CO2 sorption (i.e. swelling) and desorption (i.e. shrinking) together with the effect of temperature. Therefore, the presented study deals with an experimental non-contact measurement technique to identify the swelling and shrinking coefficients during pressurization and depressurization under carbone dioxide (CO2) of an HNBR O-ring. In order to ensure the feasibility of CO2 sorption (or desorption) measurement from the non-contact method, a purely thermal expansion test permits to identify the thermal expansion coefficient of HNBR, which is well known by other methods including a standard. Numerical simulations complete this section. The simulations ensure that the chosen analysis methodology allows direct identification of swelling and shrinking coefficients and thus determine the seal volume change. CO2 pressurization and CO2 depressurization tests at pressures (2, 4 and 6 MPa) under isothermal conditions (60 and 130 °C) and a coupled temperature-pressure CO2 tests are conducted. The measurements made during these tests show that the CO2 swelling and shrinking coefficients are independent of pressure but temperature dependent. Besides, a good measurements reproducibility was observed and the order of magnitude of these coefficients leads to a strain in the same order as the thermal strain.

Characterizing the Performance of Ternary Concrete Mixtures Involving Slag and Metakaolin

Ternary blends of cementitious materials are investigated. A cement replacement level of 45% is used for all ternary mixtures consisting of 15% metakaolin and 30% slag replacements. Three metakaolin and two blast furnace slag, referred to as ‘slag’ for short, products commercially available are used to compare performance in ternary blends. A mixture with a 45% fly ash replacement is included to serve as a benchmark for performance. The control mixture contains 422 kg of cement per cubic meter of concrete, and a water-to-cementitious material ratio of 0.43 is used for all mixtures with varying dosages of superplasticizer to retain workability. Mixtures are tested for mechanical properties, durability, and volumetric stability. Mechanical properties include compression, split-cylinder tension, modulus of rupture, and dynamic Young’s modulus. Durability measures are comprised of rapid chloride-ion penetrability, sulfate resistance, and alkali–silica reactivity. Finally, the measure of dimensional stability is assessed by conducting drying shrinkage and coefficient of thermal expansion tests. Results indicate that ternary mixtures including metakaolin perform similarly to the control with respect to mechanical strength. It is concluded that ternary blends perform significantly better than both control and fly ash benchmark in tests measuring durability. Furthermore, shrinkage is reduced while the coefficients of thermal expansion are slightly higher than control and the benchmark.

Effect of aging heat treatment and uniaxial compression on thermal behavior of 7075 aluminum alloy

In the present work, thermal conductivity, coefficient of thermal expansion and hardness properties of aluminum alloy AA 7075 were analyzed by combined effect of aging heat treatment and uniaxial compression. Solution treatment was done at 480 °C for 90 min followed by rapid quenching into cold water. Artificial aging was done at 180 °C for 8 h. Uniaxial compression was performed on universal testing machine at varying percentage of compression at room temperature condition. Eight samples in addition to as-received sample were prepared along with the combination of above three processes. Optical microstructural, hardness measurements, X-ray diffraction, thermal conductivity test, coefficient of thermal expansion test were carried out. Improved thermal conductivity, coefficient of thermal expansion and hardness were observed in aging heat treatment and UAC has processed.

High-temperature martensitic transformation of CuNiHfTiZr high- entropy alloys

One of the major challenges of near-equiatomic NiTi shape memory alloys is their limitation for high-temperature applications. To overcome this barrier, researchers have tried to enhance the transformation temperatures by addition of alloying elements or even by introducing the concept of high-entropy alloys (HEAs). In this study, the CuNiHfTiZr HEAs were developed for high-temperature shape memory effect. Based on their solubility and electron configurations, the alloying elements are divided into two groups, (CuNi)50 and (HfTiZr)50. The content of Cu in (CuNi)50 is modulated to investigate the influences of Cu on martensitic transformation of the HEAs by studying structural evolution and transformation behavior. The results of x-ray diffraction and thermal expansion tests revealed that Cu15Ni35Hf16.67Ti16.67Zr16.67 possesses high transformation temperature, narrow hysteresis temperature loops, and good dimensional stability within this HEA system.

Effects of humidity and phosphor on silicone/phosphor composite in white light-emitting diode package

Silicone/phosphor composite, which serve as mechanical protection and light conversion material, is an integral part of white light-emitting diode (LED) package. In this paper, a comprehensive study is conducted to investigate the effect of humidity and phosphor on moisture absorption, hygroscopic swelling, mechanical behavior, as well as thermal properties of silicone/phosphor composite in comparison with the pure silicone. SEM/EDAX and FTIR were performed to identify the phosphor and silicone compositions. Through moisture sorption test, it has been observed that the addition of phosphor significantly lowers the capacity of moisture absorption, but accelerates the diffusivity of moisture absorption. The hygroscopic swelling test showed that the phosphor has little effect on the swelling compared to the pure silicone sample. Both moisture absorption/desorption and hygroscopic swelling/de-swelling are reversible. Strain ramp test revealed that the phosphor enhances the stiffness of the composite. The moisture absorption, however, has negligible impact on mechanical stiffness for both pure and composite samples. Finally, thermal expansion test showed that the coefficient of thermal expansion does not change with the addition of phosphor into pure silicone.

Microstructures and metal-ceramic bond properties of Co-Cr biomedical alloys fabricated by selective laser melting and casting

Selective laser melting (SLM) technique, based on a layer-by-layer production, was used to produce biomedical Co-Cr devices specifically developed for dental restoration applications. However, information on the metal-ceramic bond strength of SLM-manufactured parts was limited. In this study, SLM-fabricated Co-Cr alloy specimens were subjected to subsequent heat treatments (holding at 1150 °C for 1 h). The alloy microstructures were characterized by scanning electron microscopy (SEM) coupled with energy-dispersive x-ray spectroscopy (EDX), x-ray diffractometer (XRD), and transmission electron microscopy, whereas the bond properties were evaluated by 3-point bend tests and coefficient of thermal expansion (CTE) tests, as compared to casting (CAST) alloys. Results showed that SLM specimens exhibited fine grains and homogeneously dispersed intermetallic compounds, and the resultant XRD analysis revealed a predominated face-centered cubic γ-Co phase (72 %). Student's t-test demonstrated that bond strengths of SLM specimens (45.80 ± 1.91 MPa) were significantly lower than that of CAST specimens (54.05 ± 6.77 MPa) (P < 0.05), and SLM specimens with debonded surfaces analyzed via SEM/EDX analysis revealed a mixed fracture type of adhesive and cohesive fractures and lower area fractions of adherence porcelain. While porcelain firing, the microstructural evolution and thermal CTE matching seriously affected the metal-ceramic bond properties. SEM/EDX analysis of the metal-ceramic interface showed that reaction diffusion layers of CAST specimens were clearly thicker than that of SLM specimens, indicating that CAST specimens had a stronger chemical bonding force. Martensite transformation (γ →ε) occurred in the CAST metal matrix close to the interface, which was not found in the SLM specimens. Additionally, the dynamic thermal process revealed that CAST specimens exhibited superior CTE matching. Overall, Co-Cr alloy fabricated by SLM exhibited inferior metal-ceramic bond properties; however, it still meets the requirements for applications as dental prostheses (>25MPa specified in ISO9693).

Mechanical Properties of Al 25 wt.% Cu Functionally Graded Material

Abstract The present work refers to describe the effects of Al2Cu variations on various properties of thick-walled functionally graded (FG) cylindrical shell. Al-25 wt.% Cu hypo-eutectic alloy ingot is melted and centrifugally casted to obtain high entropy FG composite. A series of microstructure examinations such as FESEM and EDX analysis were carried out to determine the distributions of constituent phases and elements. It is revealed that the maximum volume fraction of Al2Cu particle is reached near the inner surface with 35.7 Vol.% and then reduces gradually to 32.5 Vol.% at the outer surface of FG cylindrical shell. The effects of the variations Al2Cu along radial direction of FG tube are discussed through Vickers hardness, wear rate, coefficient of thermal expansion and compressive test measurements. The experimental results show that the wear and hardness are varied in graded manner which the highest wear resistance with wear rate of 9.1×10−5 g/mm 2 and hardness with 153HV are found towards Al2Cu enriched zone or inner periphery. Moreover, the studied FG cylindrical shell shows drop 2.5% in yield stress and 4.5% in elastic modulus from intermediate to inner layers due to Al2Cu particles clustering in metal matrix.

Characterization of Zirconia- Hydroxyapatite Nanocomposites for Orthopedic and Dental Applications

Zirconium oxide ceramic was proposed for different biomedical applications. It is used in orthopedic as hip and knee prostheses and in dentistry due to the good mechanical, biological high corrosion and wear resistance properties, addition to the aesthetic property owing to tooth like color. Zirconia stabilized with Y2O3 has the best properties for these applications. The present work aims to study the effect of (5 and 10)Wt.% hydroxyapatite (HA) as additives to 3 mol% yttria stabilized zirconia (3YSZ) nano powder matrix. The green body samples were shaped by powder technology using cold pressing then sintering at (1300 and 1400)ᵒC. The 3YSZ/ HA nanocomposites samples were characterized by XRD to investigate phase stability with varying percent's of HA and different sintering temperatures, the mechanical properties (maximum bending strength and hardness) were investigated as a function of the HA content, the changes of the thermal expansion coefficient for composite samples were investigated using Dilatometer. The experimental results proved that additions of (5 and 10)Wt.% HA to 3YSZ matrix reduce both hardness and max. bending strength, while increasing sintering temperature from 1300ᵒC to 1400ᵒC leading to an increase in the hardness and bending strength for all composite samples. The results of thermal expansion test showed a reduction in the thermal expansion coefficient with presence of HA%, however the coefficient of 3YSZ/ 10%HA is closer to 3YSZ from 3YSZ/ 5%HA. EDS analysis shows improvement in the bioactivity of inert 3YSZ with HA% additions represented by increasing Ca and P ions on the composite samples after immersing in SBF for 6 days.

Phase equilibria in the Co-Mn-Ni system

Co-Mn-Ni alloys are promising shape memory alloys and functional materials. However, very limited information can be found regarding the phase transformations and magnetic properties in this ternary system. In this work, a series of 22 Co-Mn-Ni alloys with various compositions were selected and synthesized based on a computed phase diagram. Metallography, X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), differential scanning calorimetry (DSC), hardness and Gleeble tests were used for microstructural characterization and phase transformation investigations. The results indicate that all samples show a face-centered-cubic (FCC) structure after quenching from 1000 °C. Phase transformations and Curie temperatures of the samples were obtained through a combined method of analyzing the heat effects and thermogravimetric behavior of the alloys in the presence of a magnetic field during differential scanning calorimetry. Thermal expansion tests indicate that the FCC to BCC transformation is a thermoelastic transformation whereas the shape memory effect was not observed in the Co-Mn-Ni alloys tested.

Two-Way Shape Memory Effect Induced by Tensile Deformation in Columnar-Grained Cu71.7Al18.1Mn10.2 Alloy.

Columnar-grained Cu71.7Al18.1Mn10.2 shape memory alloy (SMA) was prepared by a directional solidification method and exhibited a high superelasticity of 8.18% and excellent ductility at room temperature, which provided the possibility of obtaining high shape memory. However, proper pre-deformation is an essential part of repeatedly obtaining large and stable shape change. In this paper, one-time uniaxial tensile pre-deformation was carried out at the temperature range −70–−80 °C. Then, the two-way shape memory effect (TWSME) of the alloy was evaluated by the martensitic transformation strain (εM) which was measured by a thermal expansion test to investigate the relationship between the pre-deformation strain (εT) and the TWSME. The results showed that εM of the columnar-grained Cu71.7Al18.1Mn10.2 alloy increased at first and then decreased with the increase of εT. The maximum value 2.91% of the εM could be reached when εT was 6%. The effects of the εT on transformation temperatures were also measured by differential scanning calorimetry. Based on the variations of transformation temperatures, the relationship between the internal stress induced by the pre-deformation process and the εM, and the influence mechanism of the pre-deformation strain on the TWSME in columnar-grained Cu71.7Al18.1Mn10.2 alloy, were discussed. The results obtained from this work may provide reference for potential applications of Cu-based SMAs, such as self-control components, fasteners, etc.

Properties of negative thermal expansion β-eucryptite ceramics prepared by spark plasma sintering**Project supported by the Programs for Tackling Key Problems in Science and Technology, Henan Province, China (Grant Nos. 172102210103, 182102310895, 182102210031, and 182102311079), the Doctoral Program of Henan Institute of Engineering, China (Grant Nos. D2016015 and D2016016), and the Nationallevel College Students Innovative Entrepreneurial Training Plan Program, China (Grant

β-eucryptite powders are prepared by the sol–gel method through using tetraethoxysilane lithium nitrate and aluminum isopropoxide as starting materials. β-eucryptite ceramics are prepared by spark plasma sintering. The effects of sintering temperature on the negative thermal expansion properties of the β-eucryptite are investigated by x-ray diffraction (XRD), scanning electron microscopy, and thermal expansion test. The XRD results exhibit no change in the crystal structure of the sample prepared by different sintering processes. The negative thermal expansion properties increase with the increase of the sintering temperature. The coefficient of thermal expansion of β-eucryptite ceramics sintered at 1100 °C is calculated to be −4.93 × 10−6 °C−1. Crystallization behaviors of the ceramics may play an important role in the increase of negative thermal expansion of β-eucryptite. High sintering temperature could improve the crystallization behaviors of the ceramics and reduce the residue glass phase, which can improve the negative thermal expansion properties of β-eucryptite ceramics.

Preparation and properties of W-SiC/Cu composites by tape casting and hot-pressing sintering

ABSTRACTIn this study, W-SiC/Cu composites were prepared by tape casting and vacuum hot-pressing sintering. The microstructures and properties of the composites were studied by means of X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, Vickers hardness test, bending strength test and coefficient of thermal expansion (CTE) test. The results showed that W2C, WC and WSi2 formed in the composites. The effects of SiC particle size on the relative densities, Vickers hardness, bending strength and CTE of composites were investigated. Vickers hardness, bending strength and CTE of the composite with SiC particle size of 6 µm reached the optimal values, which were 445.2 HV, 726.1 MPa, 9.24 ppm K−1.