Critical Temperature Of Order Research Articles

Potential of supercritical nitrogen to be used as cryogen for superconducting applications

Superconductors have been widely employed in the power applications and it has all potential to replace normal conductor. Superconductors are more efficient than conventional conductors and causing negligible losses. The only challenge with superconducting technology is to maintain working temperature below superconducting tape’s critical temperature in order to avoid thermal quench of the tape. The critical temperature for Hg-based superconducting tapes is near 134 K which is more the critical temperature (Tc) of nitrogen i.e. 126.19 K. In the present study, the potential of supercritical nitrogen for the cooling of such superconductors has been determined. In this manuscript, the density of supercritical nitrogen has been studied and it has been found that density of supercritical nitrogen is much larger than liquid nitrogen thus can be considered for cooling applications in future. An attempt has been made in order to correlate the density by using a temperature–pressure dependent correlation that can be implemented during numerical code generation in order to map point-to-point property variation effects. Error analysis has also been performed and it has been concluded that supercritical nitrogen has enough potential in cooling applications.

Modulation of VO2 metal-insulator transition by co-doping of hydrogen and oxygen vacancy

As a well-known thermochromic material, Vanadium dioxide (VO2) has drawn widespread interest due to its particular phase transition feature. Many endeavors have been implemented to decrease critical temperature in order to realize VO2-based smart window, while there is still much room to improve. Herein, we provide a facile way to control the critical temperature of VO2 by co-introducing of hydrogen and oxygen vacancy while without deteriorating its original metal-insulator transition behavior. SIMS was carried out to detect the depth profile of hydrogen element, and XPS was conducted to investigate the chemical state. Based on the first-principle calculation, it was found that the hydrogen played a crucial role on the structural evolution of VO2. For seldom hydrogen doping, rutile-like VO2 with metallic state was formed, in agreement with the XRD observation. Strikingly, it transformed into a more monoclinic structure as further introducing hydrogen atoms. In addition, the energy-efficient demonstration experiment exhibited a promising application for VO2 material in energy-saving field. The current findings offer a novel strategy to modulate the critical temperature of VO2, which will promote the development of VO2 in smart window and bring insight into comprehensive understanding the role of H in VO2 phase transition process.

Differences in induced thermotolerance among populations of Olympia oysters

An organism's ability to cope with thermal stress is an important predictor of survival in a changing climate. One way in which organisms may acclimatize to thermal stress in the short-term is through induced thermotolerance, whereby exposure to a sublethal heat shock enables the organism to subsequently survive what might otherwise be a lethal event. Whether induced thermotolerance is related to basal thermotolerance is not well understood for marine organisms. Furthermore, whether populations often differ in their capacity for induced thermotolerance is also unclear. Here, we tested for differences in basal thermotolerance and induced thermotolerance among six populations of Olympia oysters (Ostrea lurida) from three California estuaries. Oysters were raised under common-garden laboratory conditions for a generation and then exposed to two treatments (control or sublethal heat shock) followed by a spectrum of temperatures that bound the upper critical temperature in order to determine LT50 (temperature at which 50% of the population dies). All populations exhibited induced thermotolerance by increasing their LT50 to a similar maximum temperature when extreme thermal stress was preceded by a sublethal heat shock. However, populations differed in their basal thermotolerance and their plasticity in thermotolerance. Populations with the highest basal thermotolerance were least able to modify upper critical temperature, while the population with the lowest basal thermotolerance exhibited the greatest plasticity in the upper critical temperature. Our results highlight that populations with high basal thermotolerance may be most vulnerable to climate warming because they lack the plasticity required to adjust their upper thermal limits.

Prediction of true critical temperature of multi-component mixtures: An extension to Chueh and Prausnitz method

Chueh–Prausnitz method was proposed in 1967 for prediction of vapor–liquid critical temperature of multi-component mixtures. In order to calculate true critical temperature by this method, a binary interaction parameter (τij) is required for each binary set of components in the multi-component mixtures. τij for a binary set is evaluated by considering experimental data on critical temperature of the binary mixture. As the data used in the original paper were published earlier than 1967, it is necessary to add more recent experimental data on critical temperature in order to extend prediction capability of this method. In the present study, 4070 experimental data on vapor–liquid critical temperature for 529 different binary systems has been collected by a comprehensive literature review and a new interaction parameter (τij) is introduced for each binary system. Besides, a set of correlations has been developed in order to estimate τij for different systems containing different chemical families. Finally, the capability of the extended methods has been evaluated for prediction of critical temperature of 205 multi-component mixtures. The prediction results show average absolute relative deviation (AARD) of 1.5% from experimental values of critical temperature.

Dynamics of a wetting layer and Marangoni convection in microgravity

Near the liquid-vapor critical point in pure fluids, material and thermal properties vary considerably with temperature. In a series of microgravity experiments, sulfur hexafluoride (SF6) was heated ∼1 K above its critical temperature, then quenched below the critical temperature in order to form gas and liquid domains. We found a power law exponent of 0.389 ± 0.010 for the growth of the wetting layer thickness during the intermediate stage of phase separation. Full and microscopic view images of the sample cell unit were analyzed to determine the changes in the size distribution of liquid droplets inside the gas phase over time. We found that the distribution of diameters for liquid droplets always contains a fraction of very small droplets, presumably due to a continuous nucleation process. At the same time, the size distribution flattens over time and rapidly includes large-size droplets, presumably generated through a coalescence mechanism. By following both a large gas bubble over two hours of video recordings, we found periodic and synchronous motion of the gas bubble along both the x and y directions. By following a large liquid droplet embedded into the large gas bubble, we found periodic, out of phase motions, which we related to Marangoni convection. The experimentally measured velocity of the liquid droplet is in good agreement with the theoretical predicted velocity of ∼0.386 μm/s obtained from Young's thermocapillary effect.

Preparation and characterisation of zinc yellow pigment for low temperature ceramic glaze – Part II: the effects of reaction temperature and thermal treatment

PurposeTo investigate the effects of the temperature of synthesis and of the thermal treatment of zinc chromate on the properties of the zinc chromate pigments.Design/methodology/approachZinc chromate pigments was prepared using zinc salt solution, sodium hydroxide and potassium dichromate solutions. The reaction temperature was varied in order to evaluate the effect of the reaction temperature on the properties of the pigment synthesised. The pigment obtained was heated to 10°C above the critical temperature in order to investigate the effect of thermal treatment on the pigment properties. SEM, XRD, XFR and STA were employed for the characterisation of the pigments synthesised.FindingsReaction temperature had a significant effect on the properties of the resulting pigment. Thermal treatment of the pigment caused the decomposition of the zinc chromate phase to ZnO, ZnCr2O4 and K2CrO4 phases. The glaze containing zinc chromate had satisfactory colour characteristics.Research limitations/implicationsThe study focused on the preparation and evaluation of zinc chromate as a substitute for praseodymium zircon in glaze. The study could be extended to investigation of similar inorganic pigment for similar purposes.Practical implicationsThe information on the effects of the reaction temperature of pigment synthesis and of thermal treatment of the pigment is useful for industrial production of the pigment of satisfactory properties.Originality/valueNovel use of zinc chromate as a lower‐cost substitute for praseodymium zircon in glaze and understanding of the effects of the production conditions on the properties of the resulting pigment and the glaze.

Euclidean Group as a Dynamical Symmetry of Surface Fluctuations: The Planar Interface and Critical Behavior

The statistical mechanics of the interface between two discrete thermodynamic phases is studied in terms of a field $f$ which describes the deviation of the interface from planar. Exploiting the dynamical Euclidean invariance of the Hamiltonian of the field $f$, we construct $\ensuremath{\epsilon}$ expansions for Ising-like critical behavior in $1+\ensuremath{\epsilon}$ dimensions, with a critical temperature of order $\ensuremath{\epsilon}$, Scaling functions for the interface profile and width in a pinning potential are obtained.