Topic
Thermal expansion
About: Thermal expansion is a research topic. Over the lifetime, 21040 publications have been published within this topic receiving 349407 citations. The topic is also known as: heat expansion.
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TL;DR: The time-dependent rate of polymer flow from the pattern into the underlying layer, termed pattern "melting", is consistent with a model of elastic recovery from stresses induced by the molding process.
Abstract: The real-time shape evolution of nanoimprinted polymer patterns is measured as a function of annealing time and temperature using critical dimension small-angle X-ray scattering (CD-SAXS). Periodicity, line width, line height, and sidewall angle are reported with nanometer resolution for parallel line/space patterns in poly(methyl methacrylate) (PMMA) both below and above the bulk glass transition temperature (TG). Heating these patterns below TG does not produce significant thermal expansion, at least to within the resolution of the measurement. However, above TG the fast rate of loss in pattern size at early times transitions to a reduced rate in longer time regimes. The time-dependent rate of polymer flow from the pattern into the underlying layer, termed pattern “melting”, is consistent with a model of elastic recovery from stresses induced by the molding process.
78 citations
TL;DR: In this article, the anisotropic thermal expansion of α-titanium has been determined by the X-ray method, and it has been shown that αc (5.6 × 10−6.
Abstract: In order to resolve the discrepancy found in earlier work, the anisotropic thermal expansion of α-titanium has been determined by the X-ray method. If a small range of temperature is used the coefficient of expansion observed along the hexagonal axis (αc) is smaller than that in the basal plane (αa). The nature of the deviation of the α-titanium structure from ideal hexagonal close-packing and the room temperature elastic behaviour of the metal have been shown to be in agreement with the result that αc (5.6 × 10−6. °C−1) is smaller than αa (9.5 × 10−6. °C−1).
78 citations
TL;DR: In this paper, a modified indentation technique has been used to measure the interfacial shear stress in a number of ceramic matrices containing silicon carbide fibers, and it has been shown that the frictional component of interfacial stress was essentially zero when matrix thermal expansion was lower than that of the fiber and increased linearly with thermal expansion mismatch.
Abstract: A modified indentation technique has been used to measure the interfacial shear stress in a number of ceramic matrices containing silicon carbide fibers. It was shown that the frictional component of interfacial stress was essentially zero when matrix thermal expansion was lower than that of the fiber and increased linearly with thermal expansion mismatch when matrix thermal expansion was higher. The interfacial shear stress was lowered when the fibers were coated with BN. Lower matrix shear stresses resulted in a more extensive fiber pullout during the composite fracture.
78 citations
TL;DR: In this article, the volume of MgSiO3 perovskite has been precisely measured at pressures of 19 to 53 GPa and temperatures of 300 to 2300 K by means of in situ X-ray diffraction in a multi-anvil apparatus.
Abstract: [1] The volume of MgSiO3 perovskite has been precisely measured at pressures of 19 to 53 GPa and temperatures of 300 to 2300 K by means of in situ X-ray diffraction in a multi-anvil apparatus. The present results indicate the isothermal bulk modulus KT0 = 256(2) GPa and its pressure derivative K′T0 = 3.8(2). The fixed Debye temperature θ0 = 1030 K gives a Gruneisen parameter at ambient pressure γ0 = 2.6(1) and its logarithmic volume dependence q = 1.7(1). The pressure derivative of the isothermal bulk modulus, Anderson-Gruneisen parameter and thermal expansion coefficient at ambient pressure are found to be (∂KT/∂T)P = −0.035(2) GPa/K, δT = 6.5(5), α0 = 2.6(1) × 10−5 + 1.0(1) × 10−8 (T − 300)/K. Thus the thermal expansion coefficient largely becomes smaller with increasing pressure. The adiabatic geotherm would be fairly large, such as 0.41 K/km at a 660 km depth, and becoming smaller with increasing depth. The temperature and adiabatic geothermal gradient at the bottom of the D′ layer would be 2400 K and 0.14 K/km. The buoyancy-driven mantle convection could be very small in the lower part of the lower mantle.
78 citations
TL;DR: In this article, negative thermal expansion in the orthorhombic members of A2W3O12 tungstates is measured by high temperature X-ray diffraction.
Abstract: Negative thermal expansion in the orthorhombic members of A2W3O12 (A = Er, Yb, Y and Lu) tungstates is measured by high temperature X-ray diffraction. Two new compounds showing contraction in this iso-structural series, Yb2W3O12 and Er2W3O12 are identified. Axial thermal expansion coefficients of Y2W3O12, Er2W3O12, Yb2W3O12 and Lu2W3O12 calculated from high temperature X-ray diffraction (473–1073 K) shows rare earth size effect. The linear thermal expansion coefficient decreases as the ‘A’ cation size increases and the thermal contraction along the b-axis becomes more negative.
78 citations