Different Tectonic Evolution of Fast Cooling Ophiolite Mantles Recorded by Olivine-Spinel Geothermometry: Case Studies from Iballe (Albania) and Nea Roda (Greece)

Mg-Fe2+ diffusion patterns in olivine and chromite are useful tools for the study of the thermal history of ultramafic massifs. In the present contribution, we applied the exponential modeling of diffusion patterns to geothermometry and geospeedometry of chromitite ores from two different ophiolite contexts. The Iballe ophiolite (Northern Albania) hosts several chromitite pods within dunites. Primary and re-equilibrated Mg#, estimated by using an exponential function, provided re-equilibration and primary temperatures ranging between 677 and 996 °C for chromitites and between 527 and 806 °C for dunites. Cooling rates for chromitites are higher than for dunites, suggesting a different genesis for the two lithologies, confirmed also by spinel mineral chemistry. Chromitites with MORB affinity formed in a SSZ setting at a proto-forearc early stage, explaining the higher cooling rates, while dunites, with boninitic affinity, were formed deeper in the mantle in a more mature subduction setting. At the Nea Roda ophiolite (Northern Greece) olivine in chromitites do not show Mg-Fe variations, and transformation into ferrian chromite produced “fake” diffusion patterns within chromite. The absence of diffusion patterns and the low estimated temperatures (550–656 °C) suggest that Nea Roda chromitites were completely re-equilibrated during an amphibolite-facies metamorphic event that obliterated all primary features.

Structural relaxation in Ag-Ni nanoparticles: Atomistic modeling away from equilibrium

The out-of-equilibrium structural relaxation of Ag-Ni nanoparticles containing about 1000--3000 atoms was investigated computationally by means of molecular dynamics trajectories in which the temperature is decreased gradually over hundreds of nanoseconds. At low silver concentration of 10--30\%, the evolution of chemical ordering in Ni$_{\rm core}$Ag$_{\rm shell}$ nanoparticles with different surface arrangements is found to proceed spontaneously and induce some rounding of the nickel core and its partial recristallization. Fast cooling of an initially hot metal vapor mixture was also considered, and it is shown to disfavor silver aggregation at the surface. Silver impurities are also occasionally produced but remain rare events under the conditions of our simulations.

Phase Evolution from Volborthite, Cu3(V2O7)(OH)2·2H2O, upon Heat Treatment

In the experiments on volborthite in situ and ex situ heating, analogues of all known natural anhydrous copper vanadates have been obtained: ziesite, pseudolyonsite, mcbirneyite, fingerite, stoiberite and blossite, with the exception of borisenkoite, which requires the presence of As in the V site. The evolution of Cu-V minerals during in situ heating is as follows: volborthite Cu3(V2O7)(OH)2·2H2O (30–230 °C) → X-ray amorphous phase (230–290 °C) → ziesite β-Cu2(V2O7) (290–430 °C) → ziesite + pseudolyonsite α-Cu3(VO4)2 + mcbirneyite β-Cu3(VO4)2 (430–510 °C) → mcbirneyite (510–750 °C). This trend of mineral evolution agrees with the thermal analytical data. These phases also dominate in all experiments with an ex situ annealing. However, the phase compositions of the samples annealed ex situ are more complex: fingerite Cu11(VO4)6O2 occurs in the samples annealed at ~250 and ~480 °C and quickly or slowly cooled to room temperature, and in the sample annealed at ~850 °C with fast cooling. At the same time, blossite and stoiberite have been found in the samples annealed at ~480–780 and ~780–850 °C, respectively, and slowly cooled to room temperature. There is a trend of decreasing crystal structure complexity in the raw phases obtained by the in situ heating with the increasing temperature: volborthite → ziesite → mcbirneyite (except of pseudolyonsite). Another tendency is that the longer the sample is cooled, the more complex the crystal structure that is formed, with the exception of blossite, most probably because blossite and ziesite are polymorphs with identical crystal structure complexities. The high complexity of fingerite and stoiberite, as well as their distinction by Cu:V ratio, may explain the uncertain conditions of their formation.

Production of Porous Agarose-Based Structures: Freeze-Drying vs. Supercritical CO2 Drying

In this work, the effect of two processes, i.e., freeze-drying and supercritical CO2 (SC-CO2) drying, on the final morphology of agarose-based porous structures, was investigated. The agarose concentration in water was varied from 1 wt% up to 8 wt%. Agarose cryogels were prepared by freeze-drying using two cooling rates: 2.5 °C/min and 0.1 °C/min. A more uniform macroporous structure and a decrease in average pore size were achieved when a fast cooling rate was adopted. When a slower cooling rate was performed instead, cryogels were characterized by a macroporous and heterogenous structure at all of the values of the biopolymer concentration investigated. SC-CO2 drying led to the production of aerogels characterized by a mesoporous structure, with a specific surface area up to 170 m2/g. Moreover, agarose-based aerogels were solvent-free, and no thermal changes were detected in the samples after processing.

Evaluation the Effect of different Cooling Cycles on the Hardness Surface of the Conventional Feldspathic Zirconia

Cooling rate is the main fact in success and life span of all ceramic restoration through its effect on mechanical properties and producing a residual tensile stress, crack propagation and failure restorations. The goals of this study is to assess the impact of diverse cooling cycles (slow cooling – fast cooling) on the surface hardness of the Zirconia (VM9). A total of 30 conventional Y-TZP Zirconia (Vita VM9) disks were fabricated according manufacturers recommendation. The samples were partition into three categories depending on the cooling system. Each group consisted of ten specimens in diameter (2mm×10mm). Control group: samples are unescorted by any change. Fast cooling group: these specimens were fast cooled after second firing (910C0 -600C0) with opening Oven muffle 25% withholding time for 5 minute and remove from the furnace to cool at room temperature. Slow cooling group: specimens were slow cooled after second firing (910C0 -400C0) with opening Oven muffle 25% withholding time for 5 minute and remove from the furnace to cool at room temperature. Each specimen was subjected to hardness test in load 9.8N at 15s using Digital microvickers Hardness tester, Scanning electron microscope. The statistical analysis revealed that, the highest vickers hardness mean value was for the control group (690.57 ± 69.9563) and for second group (618.12± 53.6164) and for third group (631.75±65.3858), The facts were statistically examined by applying ANOVA test (P- value) testes which revealed significant differences(p=0.038) (p<0.05) among groups. Conclusion: The impact of cooling cycle on the hardness surface measurements of the Zirconia (Vita VM9) between the three groups was significant. The slow cooling shows a higher value of (VH) Hardness and recommended for Zirconia than the fast cooling.

Using Atomic Force Microscopy to Evaluate Microstructure for Direct Metal Laser Melted Titanium

Additive Manufacturing (AM) is a relatively new technology that could potentially revolutionize industrial manufacturing. Currently, papers have studied the mechanical properties and microstructure of AM materials without the use of Atomic Force Microscopy (AFM). This paper utilizes AFM to analyze the Widmanstätten microstructure and porosity of Direct Metal Laser Melted (DMLM) titanium samples. The mechanical properties of the titanium samples were collected, and the samples exhibited favorable yield and tensile strengths, but suboptimal ductile properties. The DMLM titanium seemed to have an increase in yield and tensile strength while the ductility seemed to decrease as a result of the fast cooling rate utilized in the DMLM process. AFM was used when analyzing the Widmanstätten microstructure which had an average surface roughness of 142 nm and the pore depth of one sample was 3.3 μm. The substantial depth of the pores could potentially be related to the decrease in ductility and it could increase the potential of future premature fractures. AFM provided a lot of useful information for this study and could provide even more information within the metallurgical field when studying the microstructure and porosity of metals, especially for AM materials.

Study on Waste Heat-Driven Refrigeration System for Energy Saving and Fast Cooling of Dust Collector in Monocrystalline Silicon Manufacture

Single-crystal silicon is key raw material in photovoltaic industry. In its manufacture, silicon monoxide dust, a byproduct, is collected under vacuum environment. To clean the dust collector, air is recharged into the collector, reacting with the dust and causing very high temperature. Collector components may be damaged. It also takes several hours to cool down. In this paper, a cooling system based on ejection refrigeration cycle is proposed, which collects the reaction heat and simultaneously controls the collector temperature around 100°C. Then, it is driven by stored waste reaction heat and cools down the dust to a lower temperature. The designed cooling system, employing a 9.7972 m2 fin-tube heat exchanger, can simultaneously meet the cooling load of four dust collectors with 330L/S capacity. By a thermodynamic model established in this work, performance analysis is carried out. Generating temperature around 73°C and evaporating temperature around 6°C are recommended for system operation. Results also show the cooling system is able to provide 3270 kJ cooling energy that is needed by the collector, for fast cooling down the dust no longer than 620 s. It is about 92% shorter than the time of current collector, indicating the cooling system is effective and feasible.

Fast Drying Combined With Rapid Cooling Can Enhance The Survival of The Desiccation Sensitive Wheat Pollen After Ultra-Low Temperature Storage

Long-term storage of pollen is important for the fertilization of spatially or temporally isolated female parents, especially during hybrid breeding. Wheat pollen is dehydration-sensitive and rapidly loses viability after shedding. To preserve wheat pollen, we hypothesized that fast-(flash)-drying and fast cooling (150°C min-1) compared to slow-(air)-drying and slow cooling (1°C min-1) would increase the rate of intracellular water content (WC) removal, decrease intracellular ice crystal formation, and increase viability after exposure to ultra-low temperatures. High correlations were found between pollen WC and viability analyzed by impedance flow cytometry (IFC viability: r=0.92, P<0.001) and pollen germination (r=0.94, P<0.001). After 10 min of air-drying, 66% WC was lost and pollen germination was at 12.2±12.3%. After 10 min of flash-drying, WC of pollen reduced by 74%. IFC viability decreased from 90.2±6.7 to 39.4±17.9%, and pollen germination dropped from 33.7±16.9 to 1.9±3.9%. After 12 min of flash-drying, WCs decreased to <0.34 mg H2O mg-1 DW, ice crystal formation was completely prevented (ΔH=0 J mg-1 DW), and pollen germination reached 1.2±1.0%. After slow and fast cooling, flash-dried pollen (WC 0.91±0.11 mg H2O mg-1 DW) showed less ice crystal formation during cryomicroscopic-video-recordings and had IFC viability of 4.5±7.0% (slow) and 6.1±8.8% (fast), respectively, compared to air-dried pollen which lost all viability. Generally, fast-(flash)-drying and increased cooling rates may enable the survival of wheat pollen likely due to (1) a fast rate of intracellular WC loss that reduces deleterious biochemical changes associated with the drying process and (2) a delay and reduction in intracellular ice crystal formation.