Short Soaking Time Research Articles

Multi-Stage Heat Treatment of Second Generation TiAl Based Alloys

In this work the influence of the particular stages of a multi-stage heat treatment on microstructure and properties of the Ti-47Al-2W-0.5Si alloy was presented. The alloy was melted in a vacuum induction furnace at a special graphite crucible. The received alloy in form of cylindrical ingot with a diameter of 16 mm and a length of 120 mm was homogenized at 1400°C for 1 h with furnace cooling (Stage 1). The proposed further treatment consists of a cyclic heat treatment (Stage 2), under-annealing carried out in a two-phase α+γ area (Stage 3) and a short full annealing conducted in α-phase area (Stage 4). Selection of particular stage parameters including the upper cycle temperature, the soaking time at the upper cycle temperature, the cooling rate from the upper cycle temperature and number of cycles for the second stage and the temperature and time of annealing for the third and forth stage was presented. The purpose of the proposed treatment is microstructure refining. This refinement is associated with the massive transformation that occurs in the alloy after heating to a temperature of 1405°C, short soaking time and cooling in air. The effect of heat treatment parameters on the microstructure and hardness of the investigated alloy was characterized.

Characterization of ODS-tungsten microwave-sintered from sol–gel prepared nano-powders

Nano-sized W–1%La2O3 and W–1%Y2O3 powders were synthesized by sol–gel method followed by hydrogen reduction. The average particle size of the powders is smaller than 50nm. Microwave sintering method was used for the consolidation of tungsten samples, and a relatively low sintering temperature (1500°C) and short soaking time (30min) were used to reduce the grains growth. Nano-sized oxide particles with a size distribution of 10–50nm were homogeneously dispersed in the tungsten matrix. The relative density, average grain size and Vickers micro-hardness of the microwave-sintered W–1%La2O3 and W–1%Y2O3 samples are 92.4% and 93.6%, 1.1 and 0.7μm, 6.03 and 4.12GPa, respectively. The W–1%Y2O3 samples showed better sinterability, finer grains, and higher hardness than the W–1%La2O3 samples.

When a trap is not a trap: converging entry and exit rates and their effect on trap saturation of black sea bass (Centropristis striata)

AbstractBacheler, N. M., Schobernd, Z. H., Berrane, D. J., Schobernd, C. M., Mitchell, W. A., and Geraldi, N. R. 2013. When a trap is not a trap: converging entry and exit rates and their effect on trap saturation of black sea bass (Centropristis striata) – ICES Journal of Marine Science, 70: 873–882. Catch rates are often used to index the abundance of marine organisms, but catch saturation (i.e. declining catch rate as fishing time increases) can decouple catch and abundance. Researchers have struggled to account for saturation when using trap catch to infer population dynamics. We used the underwater video to document entries and exits of black sea bass (Centropristis striata) from chevron traps (n = 26) to quantify catch saturation. Black sea bass catch varied between 3 and 188 individuals for soak times of ∼90 min. Overall, 3564 black sea bass entered the traps and 1826 exited; therefore, over half (51%) of black sea bass entering traps exited before traps were retrieved. Black sea bass catch rates were non-linear and asymptotic for most (81%) trap samples, despite short soak times. Moreover, catch saturation occurred at 50 min, when the entry rate declined and the exit rate increased to a point where their confidence intervals overlapped. Several lines of evidence suggest that the level of black sea bass catch once saturation occurred may be positively related to true abundance, but additional research is needed to more fully test this hypothesis.

Histological Findings in a Failed Corneal Riboflavin–UVA Collagen Cross-linking Performed for Progressive Keratoconus

To report the histological and immunohistochemical findings in a cornea removed from a patient who had undergone collagen cross-linking (CXL) with riboflavin and ultraviolet-A for progressive keratoconus. CXL was performed following the Siena protocol. Two years post-CXL, a visual acuity impairment in the treated eye secondary to corneal stromal opacity had occurred, together with corneal thinning and flattening. The excised cornea was formalin-fixed, paraffin-embedded, and examined microscopically. Deparaffinized 4-μm sections were stained with hematoxylin-eosin and Masson trichrome. Further tissue sections were subjected to immunohistochemical evaluation of CD34 and Ki-67 antigens. Histologically, there was no scar tissue in the failed cornea. The biomicroscopic stromal opacity corresponded microscopically to an acellular area, devoid of keratocytes, and to compaction of the lamellar collagen. Amorphous, weakly eosinophilic interlamellar deposits, extending from the anterior to the posterior two thirds of the stroma, were noted. CXL is a promising procedure for the treatment of progressive keratoconus with minimal reported side effects. In the present case, we speculate that the short corneal soaking time (15 minutes according to the Siena protocol) may have resulted in inefficient ultraviolet-A blocking, thermal injury, and deeper keratocyte death. Inadequate keratocyte stem cells reservoir could also play a role in individual cases.

Novel pack cementations: direct current field assisted pack cementations

AbstractDirect current field (DCF) assisted pack cementation processes are designed to overcome the problems of higher processing temperature and longer time in conventional pack cementations (CPCs). Anode and specimen as cathode are parallel with each other, and are embedded in powder agents, all of which are sealed in a stainless steel box. Effects of DCF on pack cementations, including boriding, nitrocarburising, aluminising, siliconising and chromising, have been investigated by applying DCF between the electrodes during soaking. The results indicate that DCF can greatly enhance all these cementations. Effective pack cementations can be carried out at a lower temperature and/or by shorter soaking time with the help of DCF. Direct current field endows the treated specimen with properties being the same as or superior to that by CPC. It is proposed that DCF makes the concentrations of required element at and around the cathode specimen’s side facing the anode much higher than in any other positions in t...

Accidental Bait: Do Deceased Fish Increase Freshwater Turtle Bycatch in Commercial Fyke Nets?

Bycatch of turtles in passive inland fyke net fisheries has been poorly studied, yet bycatch is an important conservation issue given the decline in many freshwater turtle populations. Delayed maturity and low natural adult mortality make turtles particularly susceptible to population declines when faced with additional anthropogenic adult mortality such as bycatch. When turtles are captured in fyke nets, the prolonged submergence can lead to stress and subsequent drowning. Fish die within infrequently checked passive fishing nets and dead fish are a potential food source for many freshwater turtles. Dead fish could thus act as attractants and increase turtle captures in fishing nets. We investigated the attraction of turtles to decomposing fish within fyke nets in eastern Ontario. We set fyke nets with either 1 kg of one-day or five-day decomposed fish, or no decomposed fish in the cod-end of the net. Decomposing fish did not alter the capture rate of turtles or fish, nor did it alter the species composition of the catch. Thus, reducing fish mortality in nets using shorter soak times is unlikely to alter turtle bycatch rates since turtles were not attracted by the dead fish. Interestingly, turtle bycatch rates increased as water temperatures did. Water temperature also influences turtle mortality by affecting the duration turtles can remain submerged. We thus suggest that submerged nets to either not be set or have reduced soak times in warm water conditions (e.g., >20 °C) as turtles tend to be captured more frequently and cannot withstand prolonged submergence.

Effects of heat treatment on the physical properties of lightweight aggregate from water reservoir sediment

Lightweight aggregates (LWAs) were produced from water reservoir sediment with added calcium oxide by employing four heat treatments, respectively, at temperatures in the range of 1170–1230 °C. The results show that LWAs produced at temperatures above 1200 °C meet European Union regulation EN-13055-1, which states that the unit weight of LWAs should be lower than 2000 kg/m 3. The bulk density was easily lowered by extending the soaking time and increasing the heating rate. The ratio of strength to unit weight of the LWA produced at 1230 °C with a short soaking time and a fast heating rate was near that of a commercial product. The level of water adsorption was below 4%, which increased initially and then decreased due to pore connections and pore sealing. The formation of a glassy phase made the LWAs treated at higher temperature rough and sealed small pores (<0.1 mm) connected to the walls of large pores (>0.2 mm). The mineral phases of the LWAs were quartz, anorthite, and hematite.

Microwave sintering and grain growth behavior of nano-grained BaTiO 3 materials

In this paper, we investigated the effect of microwave sintering parameters on the development of the microstructure of nano-grained BaTiO 3 materials co-doped with Y and Mg species. It is observed that the materials can not only be sintered densely at a lower temperature (1150 °C) and a shorter soaking time (20 min), but also the grain growth can be suppressed by 2.45 GHz microwave heating process. However, the grain growth exhibits a unique tendency in some processing conditions such as microwave sintering for longer intervals (≧60 min) or at higher temperatures (1200 °C). The grain growth behavior after densification was investigated in terms of the phenomenological kinetics, and the activation energy for grain growth using microwave sintering (59.4 kJ/mol) is considerably less than that of the conventionally sintered ones (96.0 kJ/mol), which indicates that microwave sintering process can accelerate the densification rate of the BaTiO 3 materials comparing with the conventional sintering process.

The Effects of Fluxes on AlN:Eu2+Blue Phosphors Synthesized by a Carbothermal Reduction Method

Different fluxes had been used in the preparation of AlN:Eu2+blue phosphors by the carbothermal reduction method. The influence of these fluxes on the phase composition, crystallinity, particle size, and photoluminescence (PL) of the produced phosphors was investigated. X‐ray diffraction and microstructure characterizations showed that both CaF2and BaF2were excellent nitridation promoters for the synthesis of AlN:Eu2+phosphors, because pure and highly crystallized AlN was obtained with 3 wt% fluxes. The use of CaF2flux resulted in phosphors which featured a very weak blue shift emission due to lattice distortion and lattice imperfection caused by the incorporation of Ca into the AlN host, according to the results of IR spectra, decay curves, and the changes in lattice parameters. In comparison with phosphors produced without the use of fluxes, the use of BaF2flux resulted in phosphors with higher PL intensity by a factor of 2.4, which were produced at lower soaking temperature and shorter soaking time. Finally, a simple reaction mechanism for the nitridation process was also suggested.

Low‐Temperature Sintering and Properties of 0.98PZT–0.02SKN Ceramics with LiBiO2 and CuO Addition

The low‐temperature sintering behavior of Pb(Zr0.53, Ti0.47)O3–Sr(K0.25, Nb0.75)O3 (PZT–SKN) piezoelectric ceramics with LiBiO2 and CuO addition has been investigated. The addition of 6 wt% LiBiO2 or 1 wt% LiBiO2+1 wt% CuO promotes the sinterability of 0.98PZT–0.02SKN ceramics owing to the generation of a liquid phase, resulting in a reduction of sintering temperature by about 300°–350°C. The microstructure, dielectric, and piezoelectric properties of flux‐sintered ceramics were examined and compared with materials conventionally sintered at 1250°C. PZT–SKN ceramics with 1 wt% LiBiO2+1 wt% CuO addition were sintered to high density at 900°C for 1 h. The resulting samples exhibited a high‐field d33 piezoelectric coefficient of 415 pm/V with a Curie temperature Tc of around 351°C, dielectric constant ɛr of 1235, and planar coupling factor kp of 0.54. The reduced sintering temperature and short soaking time, together with the favorable dielectric and piezoelectric properties of the fluxed PZT–SKN ceramics, demonstrate the potential opportunity of integration with low‐temperature cofired ceramic materials and low‐fire electrode materials for the multilayer piezoelectric transducer application.

Effect of Soaking Time and Steeping Temperature on Biochemical Properties and γ-Aminobutyric Acid (GABA) Content of Germinated Wheat and Barley

The objective of this research was to investigate the effects of soaking time (6, 12 and 24 hr) and steeping temperature (25, 30 and 35℃) on germination time, germination percentage and weight loss of wheat and barley. Changes in chemical composition (such as protein, fat, and ash), reducing sugar content, enzyme activity and pasting profile and GABA (γ-animobutyric acid) content of germinated wheat and barley were also evaluated. The results clearly suggest that the short soaking time and lower steeping temperature significantly decreased germination time and weight loss, while germination percentage increased. Regarding the chemical composition, the protein content of wheat and barley was slightly increased after germination but there was no significant difference in content of crude fat and ash of both germinated cereals. The reducing sugar content of both germinated cereals decreased as the steeping temperature increased from 25℃ to 35℃. Increasing soaking time and steeping temperature led to increased amylase activity, and also corresponded to reduced paste viscosity. The highest GABA content that occurred with soaking times of 6 and 12 hr and a steeping temperature of 35℃ was 1,467.74 and 1,474.70 ㎍/g for germinated wheat and 2,108.13 and 1,691.85 ㎍/g for germinated barley. This study indicated that the optimum germination process for wheat and barley is a low steeping temperature and a short soaking time.

Utilization of partially ripe mangoes for freezing preservation by impregnation of mango juice and sugars

Frozen mango is texturally damaged due to formation of ice crystals during freezing preservation. The objective of this investigation was to use partially ripe mango as an alternative for ripe mango. Based on its stronger structure, partially ripe mango could better withstand texture damage by ice crystals. Its flavor and color could be enhanced by impregnation of mango juice and sugars (natural flavor) into the mango matrix. This investigation found that calcium carbide incubation for two days helped prepare the mango at a partially ripe state. Vacuum infusion was more effective than natural mass diffusion in incorporation of mango juice–sugar mixture (shorter soaking time (˜10 min at 74.66 kPa) and better mango quality (texture, solid content and color sensory scores ˜7–8 in a traditional 9-point hedonic scale). After freezing (air-blast, jet-impingement and cryogenic freezing) and thawing, the juice/sugar–infused mangoes were high in sensory scores (7–8) and low in drip loss (9–12 g/100g) values. They better tolerated freezing damage than did ripe mango. This proposed method can help reduce the post-harvest losses arising from the faster spoilage of more ripe mangoes. It enhances natural flavor and taste of the partially forced ripening mangoes which normally impart only color.

Low temperature sintering of Ba(Zr0.8 − xCexY0.2)O3 − δ using lithium fluoride additive

Lithium fluoride (LiF) was selected as a liquid phase sintering additive to lower the sintering temperature. The effects of LiF on the sinterability, microstructure, and electrochemical properties of Ba(Zr0.8−xCexY0.2)O3−δ (0≤x≤0.4) (BZCYs) ceramics were investigated. Using LiF as an additive, high density BZCYs ceramics can be obtained at sintering temperatures 200–300°C lower than the usual 1700°C with much shorter soaking time. Nuclear reaction investigations showed no lithium and a small amount of fluorine reside in the sample which indicates the non-concomitant evaporation of lithium and fluorine during the sintering process. Scanning electron microscopic investigations showed the bimodal structure of BZCYs ceramics and grain growth as Ce content increases. In a water saturated hydrogen containing atmosphere, BZCYs ceramics have higher conductivity when LiF is used in the sintering process. LiF-added BZCYs electrolyte-supported fuel cells with platinum electrodes were tested at temperatures from 500 to 850°C. Results show that LiF is an excellent sintering additive for lowering the sintering temperature of BZCYs.

Sensitisation Study of Normalized 316L Stainless Steel

Austenitic stainless steels with excellent corrosion resistance and good weldability have wide applications in industry. These iron-based alloys contain a high level of chromium which form protective oxide film on the surface hence resisting corrosion. The oxide film regenerates when damaged, making the steel 'stainless'. However, carbide precipitation due to a welding process or heat treatment can cause the occurrence of chromium-depleted zones at the boundaries, leading to a phenomenon known as sensitisation, in which the depleted zones become the focus of the intense corrosion. The present work was concerned with the study of the sensitization and desensitisation of 316L steel at the normalizing temperatures of 750- 950 0 C and soaking times of 0.5, 1, 2 and 8 hrs. 316L stainless steel was observed to be sensitized when heated to 750- 850 0 C and held for short soaking times of 0.5 – 2hrs before normalizing. Increasing soaking times at these temperatures to 8 hrs triggered the desensitization process which was fully accomplished at 750 0 C but ongoing at 800 and 850 0 C. At 900 0 C, sensitization did not occur at 30 mins soaking time but observed at soaking times of 1 and 2hrs. At a longer soaking time of 8 hrs, there was full desensitization. At 950 0 C, sensitization was already observed at 30 mins. Soaking time and desensitization was observed to be in progress at 1 and 2 hrs soaking time. By 8 hrs there was full desensitization. Thus it was observed that at 950 0 C, diffusion of Cr was thermally aided making desensitization fast. The hardness of normalized 316L stainless steel was also observed to decrease with soaking time and normalization temperature.

Developing almond shell-derived activated carbons as CO 2 adsorbents

Two series of carbon dioxide adsorbents were prepared from almond shells, by carbonisation followed either by activation with CO 2 or by heat treatment in the presence of ammonia gas (amination). Both procedures gave carbons with high CO 2 adsorption capacities in pure CO 2 as well as in a binary mixture of 15% CO 2 in N 2. Activation with carbon dioxide significantly developed porosity in the samples, mostly in the micropore domain, while amination at 800 °C moderately developed narrow microporosity in the char and incorporated stable nitrogen functionalities, which enhanced CO 2 selectivity. Amination showed two additional advantages over conventional activation with CO 2: a greater carbon yield and a shorter soaking time.

Piezoelectric, ferroelectric Pb(Mg1/3Nb2/3)O3–PbTiO3 thin films with compositions around the morphotropic phase boundary prepared by a sol-gel process of reduced thermal budget

Single perovskite polycrystalline Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) thin films with PMN to PT ratios around the morphotropic phase boundary composition (070PMN-0.30PT, 0.65PMN-0.35PT, and 0.60PMN-0.40PT) have been prepared by chemical solution deposition (CSD). Air-stable and precipitate-free PMN and PT precursor sols were separately synthesized, and PMN-PT sols were obtained by the simple mixture in air of the former. The PMN-PT sols were deposited onto Pt-coated Si substrates and dried on a hot-plate. Crystallization of the films was carried out by rapid thermal processing (RTP) in oxygen, using different temperatures, soaking times, and heating rates. Single perovskite PMN-PT thin films were obtained at low temperatures (650 °C) with short soaking times (6s) and rapid heating rates (200 °C/s). The films show a columnar growth and a uniform thickness. Both the evolution of the perovskite distortion and the electrical properties with the PMN to PT ratio indicate the correct formation of the solid solution. The temperature and frequency dependences of the permittivity and the ferroelectric loops also indicate an increase of the relaxor characteristic of the films as compared with bulk materials. Piezoelectric coefficients were measured across the ferroelectric loop by optical interferometry, and an enhancement of piezoelectricity at the MPB composition was found. A piezoelectric d33 coefficient of ∼55 pC/N was measured in ∼300-nm-thick films of this composition with a saturation polarisation of Ps ∼25 μC/cm2.

Demographic analyses of the dusky shark, Carcharhinus obscurus, in the Northwest Atlantic incorporating hooking mortality estimates and revised reproductive parameters

Demographic analyses were conducted for the dusky shark, Carcharhinus obscurus, in the Northwest Atlantic. Fishery-independent, fishery-dependent, and previously published data were used to estimate age specific by-catch mortality and reproductive cycle for incorporation into the analyses. Correspondence analyses were conducted for viability (dead or alive), shark length, month, soaktime, and region. Dead sharks were associated with small size, long soak times, and the spring season, while live sharks were associated with large size and shorter soak times. Data on reproduction suggested a 3-year reproductive cycle consisting of a 2-year gestation period and a 1-year resting period. Litter sizes ranged from 3–12 embryos. Decreasing age-specific fishing mortality and a 3-year reproductive cycle were used in age structured life tables which incorporated stochasticity in life history parameters through Monte Carlo simulation to estimate annual population growth. Demographic analyses showed that the dusky shark population would decline even at low levels of fishing mortality despite low natural mortality for neonates. The demographics of this species make it among the most vulnerable to excessive fishing mortality, and suggest stringent regulatory measures may be required to recover collapsed populations.

Influence of raw powder size, reaction temperature, and soaking time on synthesis of SiC/SiO2 coaxial nanowires via thermal evaporation

High-yield SiC/SiO2 core-shell nanowires were synthesized without adding metal catalysts from outside through a simple thermal evaporation of silicon powders during decomposition of methane gas. The influence of three parameters, size of Si raw powder (50 nm and 5 μm), reaction temperature (1573, 1623 and 1673 K), and soaking time (1, 3 and 6 h), was investigated. The typical synthesized nanowires from different conditions possess the diameter of no thicker than 100 nm with several tens micrometers in length. It was addressed that the condition using the smaller size Si powder, which contained the highest amount of oxygen, at higher temperature lead to more complete reaction to obtain a large quantity of nanowires. The synthesized nanowires at higher reaction temperature and longer soaking time possessed larger core than those nanowires prepared at lower reaction temperature and shorter soaking time. Oxidation of larger size Si powder improved yield of nanowires. Based on these results, it was suggested that the typical nanowires should be grown via the oxide-assisted growth mechanism.

Densification and Electrical Conductivity of Yttria-Stabilized Zirconia Containing NiO Additions

The role of NiO addition on sintering and electrical conductivity of 8YSZ was systematically studied in this work. Nickel carbonate was added to commercial 8YSZ to give 0.5, 1 and 5 mol% Ni. Sintering of powder compacts was carried out at several dwell temperatures and soaking times. Relative sintered density of Ni-doped pellets reached high values for short soaking times. For longer soaking times the densification of 8YSZ is higher than that of specimens containing the additive. Cubic NiO is the secondary phase formed when the additive exceeds the solubility limit, as determined by Raman spectroscopy. The grain conductivity does not change with additive up to 1 mol% independent on the soaking time. The grain boundary conductivity varies slightly in doped pellets and is lower in NiO-free samples.

Influence of Sintering on Electrical Properties and Phase Transition of La&lt;sub&gt;2&lt;/sub&gt;Mo&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;9&lt;/sub&gt;

High ionic conductivity ceramics have potential technological applications in chemical sensors, ceramic permeable membranes, oxygen pumps, and solid oxide fuel cells. Recently ionic conductivity values as high as those of doped zirconia solid solutions have been found in a lanthanum molybdate compound. The high ionic conductivity of this compound, La2Mo2O9, is obtained at temperatures above the structural phase transition temperature (~580 °C). In this work the La2Mo2O9 ceramic material was prepared by the polymeric precursor technique and sintered at several dwell temperatures and soaking times to study the effect of sintering conditions on phase transition. It was found that there is a strong dependence of phase transition on the sintering profile. At 950 °C the phase transition is suppressed for short soaking times, whereas it is observed to occur for longer times. Moreover, the relative magnitude of conductivity is also dependent on the sintering conditions. The main conclusion is that the phase transition in La2Mo2O9 is particle sizedependent.