Cooling Rate

Three kilns and a collection of baked bricks from Italian archaeological sites have been studied for archaeointensity determination using the Thellier method as modified by Coe. All sites are dated based on archaeological information and their ages range from 500 to 800 AD and 1500 to 1700 AD. Rock magnetic studies identify magnetite, Ti- magnetite and hematite as the main magnetic minerals, and magnetic susceptibility versus temperature shows a good thermal stability of the samples. The intensity results have been corrected for anisotropy of the thermoremanent magnetization and cooling rate effects. The new data together with 136 previously published results are used to estimate the variation of the Earth's magnetic field over the past three millennia. The time distribution of the Italian absolute intensity data is irregular with the majority of determinations concentrated during the last four centuries, while older periods are very poorly covered. Most of the data come from vo...

The NNE-SSW striking Giudicarie Fault System (composed of the Northern and Southern Giudicarie Fault and the Meran-Mauls Fault) represents a distinctive bend and offset in the Periadriatic Fault System (PFS). It terminates the E-W striking Tonale Fault Zone to the east, and the ESE-WNW striking Pustertal-Gailtal Fault to the west. Along the Giudicarie Fault System Oligocene tonalitic bodies occur, subsumed under the term 'Oligocene Tonalitic lamellae'. Along the southern part of the Northern Giudicarie Fault only a few < 50 m thick and 200 m long lenses crop out, often strongly affected by brittle deformation. So far no tonalitic bodies have been found between the locality Rumo (Val di Non) and Pawigl (south of Meran), i.e. for some 20 km. From Pawigl to the NE the lenses are more continuous, up to 150 m thick and less affected by brittle deformation. Fission Track analyses was carried out on samples from tonalitic lenses along the Northern Giudicarie Fault and the Meran ...

Thin films of CdS, deposited by chemical bath deposition (CBD) onto films of fluorine-doped tin oxide/glass (glass/FTO) substrates were prepared and investigated for photoelectrochemical conversion (PEC) of light into electricity. Knowing the hazardous nature of CdS, the focal theme of this work was to modify the electrodes by simple economic ways to maximize their conversion efficiency and minimize their degradation under PEC conditions. This was to avoid leaching out of hazardous Cd2+ ions. Different parameters have been investigated for this purpose. Multi-deposition preparation, redox couple, and electrode etching affected electrode PEC characteristics. Consistent with earlier literature, annealing the electrode enhanced its conversion efficiency and stability. On the other hand, effect of cooling rate of pre-annealed CdS electrodes, prepared by CBD, on their PEC characteristics has been investigated here for the first time. Controlling the cooling rate was one major factor that affected CdS surface morphology, conversion efficiency and stability under PEC conditions. The major recommendation coming out here is that PEC characteristics of CdS thin film electrodes can be significantly enhanced by pre-annealing the electrode at ∼250 °C followed by its slow cooling.

On two days during SUCCESS, the NASA DC-8 flew carefully designed flight tracks to sample wave clouds downstream of the Rocky mountains. Wave morphology was deduced by applying linear perturbation theory to in-situ measurements of the Meteorological Measurement System (MMS) and remotely sensed isentrope profiles of the Micro-wave Temperature Profiler (MTP). Vertical winds from the MMS were consistent with updraft velocities derived from air parcel displacements estimated from the MTP. Derived wave characteristics and cooling rates are useful inputs to cloud microphysics models.

Pre-print Manuscript available to download here -
Download published paper at: https://www.sciencedirect.com/science/article/pii/S2352152X19301355?via%3Dihub

Li-Ion batteries will play an important role in reaching emission targets by sustaining the further integration of renewable energy technologies and Electric Vehicles (EVs) in society. Their performance however is quite sensitive to temperature, leading to capacity fade, acceleration of ageing effect and possible thermal runaway. A Thermal Management System (TMS) should maintain a battery at an operating temperature within an optimal range and maximise temperature uniformity, i.e. approaching an isothermal condition. Many studies have experimentally investigated the electrical performance of Li-Ion batteries under controlled environmental temperatures. Notably however, these controlled conditions do not impose a uniform temperature or a controlled rate of cooling, as a TMS would. From a review of the relevant literature a ratio of the heat generation to the power production is proposed, i.e. quantifying an equivalent electro-chemical efficiency to advance research in this technological area and as additional TMS design metric. Overall, there is enough evidence that 25–30 °C is the best temperature range to minimise the ageing effect while 25–40 °C is typically reported as the general Li- Ion cells operating range. No specific temperature is identified to optimise the cycle electro-chemical efficiency and minimise the ageing effect. Therefore, a TMS should keep Li-Ion batteries within a specific temperature range according to the need for either higher electro-chemical efficiencies (i.e. higher powers and lower heat generation rates) or higher operating life. There are four main thermal management approaches of Li-Ion batteries: air-cooling, liquid-cooling, boiling and Phase Change Materials (PCM). Air cooling is preferred for safety reasons but is less efficient as the rate of heat transfer achievable is relatively low. Forced air cooling can effectively keep the temperature at a preferred level but fails to guarantee a uniform temperature. Liquid cooling is better in terms of heat transfer performance, but it is less safe and can still result in significant thermal gradients within the pack. Boiling effectively keeps Li-Ion cells temperature constant and uniform but can be quite complex to operate and control. Phase Change Materials (PCMs) as a passive cooling approach are proposed as an effective and low-cost isothermalisation technique. However, when Li-Ion batteries are operated under extreme conditions (high ambient temperature, high discharge rates), PCM are not able to recover all latent energy potential during solidification and this leads to possible thermal runaway. Overall, it is clear that no TMS alone is holistically better than others and the choice between air cooling, liquid cooling, boiling and latent heat PCM systems is entirely linked to the specific combination of temperatures, heat rates, cells capacity and geometry. Active PCM systems however, mainly a combination of liquid cooling and passive PCM, show promising results towards an ideal isothermal condition. Also, they introduce the potential to store the thermal energy and use it as needed, converting a Li-Ion cell from an Electrical Energy Storage System (EESS) to a Combined Heat and Power (CHP) system.

This study investigates the crystallization kinetics of palm stearin (PS), a palm oil fraction, in blends with sesame seed oil. The results indicate that the crystallization behavior of PS in sesame oil is mainly associated with the crystallization of tripalmitin. Therefore, crystallization of blends of 26, 42, 60, and 80% (wt/vol) PS in sesame oil was described by equations developed for simpler systems (e.g., Fisher and Turnbull equation). The isothermal crystallization, melting profile, and fitting of the kinetics of nucleation to the Fisher and Turnbull equation showed that the 26, 42, and 60% PS/sesame oil blends crystallized mainly in the β1′ polymorph state. In contrast, the 80% blend crystallized in two different polymorph states (i.e., β1′ at T⪯307.6 K and β1 at T≽308.2 K). The data indicated that, in spite of the higher concentration of PS in the 80% PS/sesame oil system, crystallization in the β1 state required more free energy for nucleation (δG c ) than β1′ crystallization in the 26, 42, and 60% PS/sesame oil. At the low cooling rate used (1 K/min) it was observed that, for a particular PS blend, the higher the effective supercooling the higher the viscosity of the oil phase and the smaller the induction time of crystallization (Ti). Additionally, the β1′ crystals from PS, developed at the highest effective supercooling investigated, were smaller than the β1 crystals obtained at lower effective supercooling.

Using differential scanning calorimetry, synchrotron time resolve X-ray diffraction and pulsed nuclear magnetic resonance, crystallisation mechanisms of milk fat were elucidated. Under the same crystallisation conditions, the microstructure of the milk fat was analysed with ...

The paper explores the structure and magnetic properties of multicomponent high-entropy Al-Cu-Fe-Ni-Si alloys in as-cast and splat-quenched state. This alloy system is characterized by the absence of expensive components, such as Co, V, Mo, Cr, usually used for the production of high-entropy alloys while its characteristics are not inferior to those of more expensive alloys. Components of the studied high-entropy alloys were selected taking into account both criteria for designing and estimating their phase composition, which are available in the literature and based on the calculations of the entropy and enthalpy of mixing, and the difference between atomic radii of components as well. The alloy films were fabricated by a known technique of splat-quenching. A cooling rate estimated by film thickness was ~ 106 K/s. Experimental results reveal that the studied alloys except the Al0.5CuFeNi one are multiphase, with the structure consisting of disordered BCC and FCC solid solutions. Th...

We have investigated the flash of light that accompanies laser damage using time-resolved spectroscopy. Damage events were initiated in the bulk of both fused silica and DKDP crystals with 355-nm 3-ns pulsed radiation. Spectra from the accompanying flash were recorded in the 200-500 nm wavelength range with 5-ns temporal resolution. Ten ns following damage initiation, the spectra were found to be roughly blackbody with temperatures on the order of 5000 K to 7000 K, depending on the material studied and excitation energy used. The observed temperatures and cooling rates can be related to the size and electron density of the plasma fireball that initiates the damage event.

The size and morphology of intermetallic compounds of Sn–Ag solder alloys can have a significant influence on the mechanical strength of solder joints. The aim of the present study is to characterize the as-cast microstructure of a Sn–2 wt.% Ag solder alloy, and to correlate the resulting scale of the dendritic matrix and the morphology of the Ag3Sn intermetallic compound (IMC) with the corresponding solidification cooling rate. Pre-heated low-carbon steel molds and a water-cooled solidification apparatus were used permitting a significant range of solidification cooling rates to be experimentally examined. It is shown that under very slow cooling conditions (0.02 °C/s) the microstructure of the sample is formed by a coarse dendritic matrix and a mixture of fiber and plate-like Ag3Sn IMC in the interdendritic region with the fibers located along the board line separating the matrix. For cooling rates from 0.15 to 1.15 °C/s a mixture of spheroid and fiber-like IMC and secondary dendrite arm spacings between 15 and 40 μm, with the spheroids located in the center of the interdendritic region. At higher cooling rates, of about 8 °C/s only Ag3Sn spheroids (of about 0.5 μm in diameter) prevail in the eutectic mixture.► 3D characterization of the morphology of Ag3Sn by an over-etching technique. ► Ag3Sn spheroids are associated with fine dendrite spacings, λ2, of Sn-rich phase. ► A mixture of Ag3Sn (spheroids + fiber-like) is associated with λ2 from 10 to 45 μm. ► A mixture of Ag3Sn (fibers + plate-like) is associated with λ2 of about 100 ± 15 μm. ► Pb-free solder manufacturers can control the microstructure by the cooling rate.