Transient Study of Femtosecond Laser–Induced Ge2Sb2Te5 Phase Change Film Morphology

Femtosecond laser-induced crystallization and ablation of Ge2Sb2Te5 (GST) phase change film is investigated by reflectivity pump-probing technology. Below the ablation threshold, the face-centered cubic structure (FCC) state in the central area can be formed, and cylindrical rims are formed in the peripheral dewetting zone due to the solidification of transported matter. The time of surface temperature dropping to the crystallization point needs about 30 ps for 5.86 mJ/cm2 and 82 ps for 7.04 mJ/cm2, respectively. At higher laser fluence, crystallization GST island structures appear in the central ablation region due to the extremely short heating time (100 ps). Furthermore, crystallization rate is faster than the ablation rate of the GST film, which is caused by different reflectivity.

Study on Ultra-High Temperature Contact Solution Treatment of Al–Zn–Mg–Cu Alloys

Contact solution treatment (CST) of Al–Zn–Mg–Cu alloys can shorten solution time to within 40 s in comparison with 1800 s with traditional solution treatment using a heating furnace. Heating temperature is the key factor in solution treatment. Considering the short heating time of CST, the ultra-high solution temperature over 500 °C of Al–Zn–Mg–Cu alloys was studied in this work. The effects of solution temperatures on the microstructures and the mechanical properties were investigated. The evolution of the second phases was explored and the strengthening mechanisms were also quantitatively evaluated. The results showed that solution time could be reduced to 10 s with the solution temperature of 535 °C due to the increasing dissolution rate of the second phase and the tensile strength of the aged specimen could reach 545 MPa. Precipitation strengthening was the main strengthening mechanism, accounting for 75.4% of the total strength. Over-burning of grain boundaries occurred when the solution temperature increased to 555 °C, leading to the deterioration of the strength.

Advancement in the Pressureless Sintering of CP Titanium Using High-Frequency Induction Heating

High-frequency induction heating is applied as an alternative heating source for pressureless sintering of commercially pure Ti powders, aiming to intensify the sintering process. The effects of the process parameters on the properties of the sintered material are systematically studied. The initial powder compact density is the most influential parameter permitting sintered structures with highly porous to almost fully dense appearance. Short heating time combined with sintering to temperatures just above the β-transus resulted in a strong diffusion bonding between the Ti powder particles, and grain growth is observed at the former boundaries of the neighboring powder particles. The dimpled appearance of the fracture surface at those regions confirmed the strong metallic interparticle bonding. Tensile properties comparable to those of Ti-Grade 3 and Ti-Grade 4 are achieved, which also demonstrates the efficiency of the induction sintering process. A mechanism explaining the fast and efficient sintering is proposed. The process has the added advantage of minimizing the oxygen pickup.

The inactivation of Ascaris suum eggs by short exposure to high temperatures

Ascaris sp. is the most prominent and resilient helminth of human health importance found in faecal sludge, making Ascaris sp. an ideal index organism for inactivation testing. Heat treatment destroys helminths, allowing for safe handling and possible reuse of sludge. Technology development focuses on rapid heating to minimize equipment size and cost. This study evaluates Ascaris suum eggs' viability with short heating time. Ascaris eggs were placed in a water bath at temperatures from 60 to 80 °C for various exposure times (5 seconds to 4 minutes) and were immediately processed and analysed via light microscopy. For all samples within these temperature and time ranges, less than 10% viable eggs were recovered. For 70, 75 and 80 °C, complete inactivation was observed for exposure time of 5 seconds and above.

Effectiveness of Modified 1-Hour Air-Oven Moisture Methods for Determining Popcorn Moisture

Two of the most commonly used approved grain moisture air-oven reference methods for corn are the air oven method ASAE S352.2, which requires long heating time (72 h) at 103 ± 1°C for unground samples, and the AACC 44-15.02 air-oven method, which dries a ground sample for 1 h at 130 ± 1°C, but there is specific moisture measurement method for popcorn. The AACC 44-15.02 recommends a two-stage drying method for grain over 13%. But this involves more handling and drying time. The objective of this study was to develop an air-oven procedure for popcorn that requires short heating time (1h or less) based on existing reference method for ground corn (AACC 44-15.02). In the process of procedure development, two laboratory mills (Wiley Mini-Mill and Perten 3303 Mill) were optimized for mesh screen size and mill gap settings. The approved AACC method recommends using a 20-mesh screen fitted to the Wiley Mill, which failed, with wires breaking during the grinding process, possibly due to the hard nature of popcorn and/or clogging. It was replaced with the 10-mesh screen which produced larger particle size distribution with ~73% greater than 840 µm. The Perten Mill 3303 was set to gap No. 3 which produced ~68% particles that were greater than 840 µm. Additionally, this study evaluated the effectiveness of single-stage moisture measurement with the 14.5% and 16% moisture popcorn samples. Using the proposed procedure, four varieties of popcorn were tested at three different moisture contents (13%, 14.5%, and 16%). The method using the Wiley grinder and 60 min. heating time yielded oven moisture values which were statistically (p<0.05) similar to the approved ASAE S352.2 and AACC 44-15.02 (72-h, whole grain method). The moisture content of ground samples obtained from the Perten 3303 Mill had elevated moisture measurements and bias across the moisture levels when dried for 60 min. A reduction in heating time to 50 min. resulted in Perten mill samples yielding statistically (p<0.05) similar moisture measurements with the reference 72-h, whole grain method. Keywords: Air-oven, Drying, Popcorn.

Localized Laser Sintering of Metal Nanoparticle Inks Printed with Aerosol Jet® Technology for Flexible Electronics

Direct-write methods, such as the Aerosol Jet® technology, have enabled fabrication of flexible multifunctional 3-D devices by printing electronic circuits on thermoplastic and thermoset polymer materials. Conductive traces printed by additive manufacturing typically start in the form of liquid metal nanoparticle inks. To produce functional circuits, the printed metal nanoparticle ink material must be postprocessed to form conductive metal by sintering at elevated temperature. Metal nanoparticles are widely used in conductive inks because they can be sintered at relatively low temperatures compared with the melting temperature of bulk metal. This is desirable for fabricating circuits on low-cost plastic substrates. To minimize thermal damage to the plastics, while effectively sintering the metal nanoparticle inks, we describe a laser sintering process that generates a localized heat-affected zone (HAZ) when scanning over a printed feature. For sintering metal nanoparticles that are reactive to oxygen, an inert or reducing gas shroud is applied around the laser spot to shield the HAZ from ambient oxygen. With the shroud gas-shielded laser, oxygen-sensitive nanoparticles, such as those made of copper and nickel, can be successfully sintered in open air. With very short heating time and small HAZ, the localized peak sintering temperature can be substantially higher than that of damage threshold for the underlying substrate, for effective metallization of nanoparticle inks. Here, we demonstrate capabilities for producing conductive tracks of silver, copper, and copper–nickel alloys on flexible films as well as fabricating functional thermocouples and strain gauge sensors, with printed metal nanoparticle inks sintered by shroud-gas-shielded laser.

Significance of heat-moisture treatment conditions on the pasting and gelling behaviour of various starch-rich cereal and pseudocereal flours

The impact of heat-moisture treatment processing conditions (15%, 25%, and 35% moisture content; 1, 3, and 5 h heating time at 120 ℃) on the viscosity pasting and gelling profiles of different grain flours matrices (barley, buckwheat, sorghum, high β-glucan barley, and wheat) was investigated by applying successive cooking and cooling cycles to rapid visco analyser canisters with highly hydrated samples (3.5:25, w:w). At a milder heat-moisture treatment conditions (15% moisture content, 1 h heating time), except for sorghum, heat-moisture treatment flours reached much higher viscosity values during earlier pasting and subsequent gelling than the corresponding native counterparts. Besides heat-moisture treatment wheat flour, the described behaviour found also for non-wheat-treated flours has not been previously reported in the literature. An increased hydrophobicity of prolamins and glutelins in low moisture-short heating time heat-moisture treatment of non-wheat flours with high protein content (12.92%–19.95%) could explain the enhanced viscosity profile observed.

Stability of Capsaicinoid Content at Raised Temperatures

Capsaicinoids, found in the fruits of Capsicum species, contribute to the spiciness of foods. However, the fruits are often subjected to heat, particularly during food preparation and in other high temperature operations, and possible changes in the capsaicinoid content have not been systematically reported. Therefore, this investigation focused on the effects of initial concentration, temperature, time and pH on the final capsaicinoid content in a model system. With higher initial concentrations (200–1000 ppm) of capsaicinoids to start with, the reduction rates were slower as the heating time increased. Under a constant initial capsaicinoid concentration (200 ppm), neutral pH had a lower rate of change in capsaicinoid content than that of both alkaline and acidic conditions. Also, alkaline conditions were more stable than acidic. The rate of reduction was generally much faster at higher temperatures, no matter what the initial concentration. Apparently, to retain a high content of capsaicinoids at the end of heating at high temperature, a high initial concentration is necessary, as well as maintaining at neutral pH and having a short heating time.

Clay and pyrite transformations during ignition of pulverised coal

Clay minerals are the principal reactive, non-combustible, phases present in the pulverized coal burned in power station furnace units. Despite the short heating time involved, the clay mineral impurity is wholly transformed in the ignition.Illitic clays are partially melted, fluxed by water and potash, to produce an alumino-silicate melt phase. The melt is frothed by the synchronous production of carbon dioxide in an iron oxide catalysed oxidation of associated carbonaceous matter. This produces the hollow, gasfilled, glass-walled spheres (cenospheres) characteristic of pulverized fuel ash (PFA). Partial, primary devitrification crystallization of mullite and quartz from the high-alumina glass is general and the extent of devitrification may influence the pozzolanic efficiency of the PFA cenospheres.Without the advantage of potash fluxing, the kaolinite lattices are dehydrated and transformed, without melting, to amorphous aluminosilicate and crystalline mullite.Oxidation of pyrite leads to coating of cenospheres by condensed magnetite and the emission of sulphur dioxide in the flue gases.