Short Heating Time Research Articles

Early Stages of Microstructure and Texture Evolution during Beta Annealing of Ti-6Al-4V

The early stages of microstructure evolution during annealing of Ti-6Al-4V in the beta phase field were established. For this purpose, a series of short-time heat treatments was performed using sheet samples that had a noticeable degree of alpha-phase microtexture in the as-received condition. Reconstruction of the beta-grain structure from electron-backscatter-diffraction measurements of the room-temperature alpha-phase texture revealed that microstructure evolution at short times was controlled not by general grain growth, but rather by nucleation-and-growth events analogous to discontinuous recrystallization. The nuclei comprised a small subset of beta grains that were highly misoriented relative to those comprising the principal texture component of the beta matrix. From a quantitative standpoint, the transformation kinetics were characterized by an Avrami exponent of approximately unity, thus suggestive of metadynamic recrystallization. The recrystallization process led to the weakening and eventual elimination of the initial beta texture through the growth of a population of highly misoriented grains.

Nucleation behavior of ωo phase in TiAl alloys at different elevated temperatures

In this study, the location, morphology and composition of the ωo phase, which transformed from B2 phase in Ti–45Al–8.5Nb-(W, B, Y) (at.%) alloy, were investigated by short-time heat treatments in an intermediate temperature range. The results showed that the characteristics of B2 → ωo phase transformation differ with the reduction in temperature. Below the ωo solves, the B2 → ωo phase transformation will take place within B2 area. There are existing two stages in the phase transformations during cooling from 850 to 700 °C. When the temperature is high (850 °C), granular ωo populated along the dislocations existing in B2 phase and B2 grain boundaries, due to higher energy and the enrichment of Nb element at the B2/γ boundaries. It is worth noting that only two ωo variants nucleate at 850 °C. With the decrease in temperature, the nucleation sites of ωo phase would be migrated from the B2 boundaries to the inner area. At the temperature of 700 °C, four ωo variants with different orientations nucleate homogenously within B2 grain. The ordered ωo formation process of Ti–45Al–8.5Nb-(W, B, Y) alloy during cooling was postulated in this study.

Low-Temperature Sol-Gel Synthesis of Nitrogen-Doped Anatase/Brookite Biphasic Nanoparticles with High Surface Area and Visible-Light Performance

Nitrogen doping in combination with the brookite phase or a mixture of TiO2 polymorphs nanomaterials can enhance photocatalytic activity under visible light. Generally, nitrogen-dopedanatase/brookite mixed phases TiO2 nanoparticles obtained by hydrothermal or solvothermal method need to be at high temperature and with long time heating treatment. Furthermore, the surface areas of them are low (<125 m2/g). There is hardly a report on the simple and direct preparation of N-doped anatase/brookite mixed phase TiO2 nanostructures using sol-gel method at low heating temperature. In this paper, the nitrogen-doped anatase/brookite biphasic nanoparticles with large surface area (240 m2/g) were successfully prepared using sol-gel method at low temperature (165 °C), and with short heating time (4 h) under autogenous pressure. The obtained sample without subsequent annealing at elevated temperatures showed enhanced photocatalytic efficiency for the degradation of methyl orange (MO) with 4.2-, 9.6-, and 7.5-fold visible light activities compared to P25 and the amorphous samples heated in muffle furnace with air or in tube furnace with a flow of nitrogen at 165 °C, respectively. This result was attributed to the synergistic effects of nitrogen doping, mixed crystalline phases, and high surface area.

Temperature variation model of titanium alloy L-angle profile in hot stretch forming with resistance heating

Titanium alloy profiles are excellent candidates for lots of applications, especially in aerospace field. High temperature is needed in the hot stretch-forming process because of the low plasticity of titanium alloy at room temperature. Resistance heating, with the benefit of device simplification and energy saving, is one of the most commonly used heating methods. In this paper, temperature variation model was developed for titanium alloy profile during resistance heating. The results show that the equilibrium temperature rises as the heating power increases. The temperature variation curves show that the temperature increases rapidly firstly, then keep nearly constant. Shorter heating time is needed to achieve the equilibrium temperature when higher heating power is applied. The thermal variation shows promising agreement with the experimental data, which confirms the feasibility of the developed models.

Photovoltaic cell electrical heating system for removing snow on panel including verification.

Small photovoltaic plants in private ownership are typically rated at 5kW (peak). The panels are mounted on roofs at a decline angle of 20° to 45°. In winter time, a dense layer of snow at a width of e.g., 10cm keeps off solar radiation from the photovoltaic cells for weeks under continental climate conditions. Practically, no energy is produced over the time of snow coverage. Only until outside air temperature has risen high enough for a rather long-time interval to allow partial melting of snow; the snow layer rushes down in an avalanche. Following this proposal, snow removal can be arranged electrically at an extremely positive energy balance in a fast way. A photovoltaic cell is a large junction area diode inside with a threshold voltage of about 0.6 to 0.7V (depending on temperature). This forward voltage drop created by an externally driven current through the modules can be efficiently used to provide well-distributed heat dissipation at the cell and further on at the glass surface of the whole panel. The adhesion of snow on glass is widely reduced through this heating in case a thin water film can be produced by this external short time heating. Laboratory experiments provided a temperature increase through rated panel current of more than 10°C within about 10min. This heating can initiate the avalanche for snow removal on intention as described before provided the clamping effect on snow at the edge of the panel frame is overcome by an additional heating foil. Basics of internal cell heat production, heating thermal effects in time course, thermographic measurements on temperature distribution, power circuit opportunities including battery storage elements and snow-removal under practical conditions are described.

Clay mineral diagenesis and source rock assessment in the Bornu Basin, Nigeria: Implications for thermal maturity and source rock potential

An understanding of the mineral and organic matter modifications during burial are critical in assessments of potential source rocks in petroleum exploration studies. Here, we examined the relationships between clay mineral diagenesis and organic thermal indicators (vitrinite reflectance and Rock-Eval Tmax) to constrain the thermal maturity and hydrocarbon potential of source rocks in the Mbeji-1 well in the northeastern part of the Cretaceous/Tertiary Bornu Basin. X-ray diffraction mineralogical data show that the <2 μm clay-sized fraction consist of mixed layer illite/smectite (I/S), kaolinite, illite, and Fe-chlorite clay mineral assemblages. The major diagenetic changes in the clay mineral evolution are transformation of random (R0) to ordered (R1) illite/smectite (I/S) mixed layer between ∼2500 m and ∼3640 m depths, decrease in smectite in I/S with burial, and appearance of chlorite at ∼2500 m. Total organic carbon and Rock-Eval pyrolysis parameters (HI, S2, Tmax) indicate presence of lean shales consisting of gas prone to inert terrestrial organic matters. Source rocks at shallower depths below 2500 m are immature while those below this level within lower Fika Formation to upper Gongila formations are marginally matured with respect to hydrocarbon generation. The variation between I/S transformation and VR for the Mbeji-1 well shows a delay in illitization process compare to organic matter maturity. We considered that other than temperature, insufficient and variable potassium availability, and short-heating time resulted in retarding the smectite illitization reaction relative to the organic matter parameters (vitrinite reflectance and Tmax). These differences further demonstrates that organic matter responds quickly to increasing temperature than mineral reactions at short heating time in young sedimentary basins.

Synthesis, physical-chemical and biological properties of 7-benzyl-3-methyl-8-thioxanthine derivatives

Introduction . Interest to the problem of creating new effective antimicrobial agents among xanthine derivatives does not decrease. Primarily, this is due to the increasing of microbial resistance to conventional antimicrobial agents and the emergence of their new strains. In recent years interest to the therapeutic use of antioxidants in the treatment of diseases associated with oxidative stress has increased.The aim of this work is to elaborate simple laboratory methods of 7-benzyl-3-methyl-8-thioxanthine derivatives synthesis, unspecified in scientific papers earlier, and to study their physical, chemical and biological properties.Materials and methods. The melting point has been determined with the help of an open capillary method with PTP-M device. Elemental analysis has been performed with the help of the instrument Elementar Vario L cube, NMR-spectra have been taken on a spectrometer Bruker SF-400 (operating frequency of 400 MHz, solvent DMSO, internal standard – TMS). Study of antimicrobial and antifungal activity of synthesized compounds has been performed by two-fold serial dilution method. Standard test strains have been used for the study: Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, Candida albicans ATCC 885-653. Dimethylsulfoxide was used as the solvent of the compounds.Results. Under short-time heating up of the initial 7-benzyl-3-methyl-8-thioxanthine with alkyl, alkenyl, benzyl halides or heteroalkylchlorides in a water-propanol-2 mixture in the presence of an equimolar amount of sodium hydroxide leads to the formation of 8-S-substituted of 7-benzyl-3-methylxanthines. Structure of synthesized compounds was definitely proved by NMR-spectroscopy. We conducted primary screening research of antimicrobial activity of 7-benzyl-3-methyl-8-thioxanthine derivatives, which revealed moderate and weak activity in concentrations 50-100 mcg/ml. Most of the obtained compounds showed a pronounced antifungal effect. It was established that synthesized substances have weak antioxidant activity.Conclusions. Accessible laboratory methods have been elaborated for synthesis of 7-benzyl-3-methyl-8-thioxanthine derivatives. The NMR spectral characteristics of the synthesized compounds have been analyzed and interpreted. Antimicrobial, antifungal and antioxidant activities of the obtained compounds have been explored. Priorities for further research of biologically active compounds have been outlined.

High Temperature Dynamic Response of a Ti-6Al-4V Alloy: A Modified Constitutive Model for Gradual Phase Transformation

Dynamic deformation behavior of a commercial Ti-6Al-4V alloy is measured between room temperature and beyond the β-transus temperature with high thermal resolution using a rapid-heating Kolsky bar technique. The high thermal resolution allows for a thorough investigation of the dynamic thermal softening behavior of this alloy including effects related to the transformation from the initial hcp α/bcc β dual phase structure to a full β structure for improved modeling of high temperature dynamic manufacturing processes such as high-speed machining. Data are obtained at an average strain rate of 1800 s−1 from room temperature to 1177 °C, with total heating times limited to 3.5 s for all tests. Short heating times prevent thermal distortion of the Kolsky bar loading waves and can allow an investigation of non-equilibrium mechanical behavior, although no such behavior was identified in this study. Between 800 °C and 1000 °C, a progressive change in the thermal softening rate was observed that corresponded well with the equilibrium phase diagram for this alloy. The dynamic thermal softening behavior in the transformation region is incorporated via a new modification of the Johnson–Cook (J–C) viscoplastic constitutive equation. Rate sensitivity is determined at room temperature by combining Kolsky bar data with quasi-static measurements at strain rates from 7.5 × 10−5 s−1 to 0.16 s−1 and the data are fit using multi-parameter optimization to arrive at a full modified J–C model for Ti-6Al-4V to nearly 1200 °C. In its generic form, the modification factor we propose, G(T), is applicable to any material system undergoing gradual phase transformation over a range of temperatures.

Robust and elastic superhydrophobic breathable fibrous membrane with in situ grown hierarchical structures

A superhydrophobic fibrous membrane (FM), which consists of elastic polyurethane (PU) and chromatic polydiacetylenes (PDA), is fabricated using an electrospinning technique, followed by short-time UV irradiation and heating treatment. The FM with fine hierarchical roughness exhibits excellent superhydrophobicity and breathability under even 300% strain of biaxial stretching. It can effectively separate the oil–sea water mixture, solely using gravity, with fascinating permeate flux (6369.4 ± 37.7Lm−2h−1), high separation efficiency, excellent recyclability and stability against corrosive liquids. Furthermore, the FM shows good air permeability and mechanical properties. Our design starts from simple chemistry, and may offer a versatile and scalable approach to fabricate hierarchically structured superhydrophobic FMs for variously potential applications, including the cleanup of oil spills, waste water treatment, packaging of stretchable electronics and protective clothing.

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.

3D printing of hybrid biomaterials for bone tissue engineering: Calcium-polyphosphate microparticles encapsulated by polycaprolactone.

In present-day regenerative engineering efforts, biomaterial- and cell-based strategies are proposed that meet the required functional and spatial characteristics and variations, especially in the transition regions between soft (cartilage, tendon or ligament) and hard (bone) tissues. In a biomimetic approach we succeeded to fabricate amorphous Ca-polyP nanoparticles/microparticles which are highly biocompatible. Together with polycaprolactone (PCL), polyP can be bio-printed. This hybrid material attracts the cells, as documented optically as well as by a gene-expression studies. Since PCL is already a FDA-approved organic and inert polymer and polyP a physiological biologically active component this new bio-hybrid material has the potential to restore physiological functions, including bone remodelling and regeneration if used as implant.

Magnetic Properties of the Nanocrystalline Nd-Ho-Fe-Co-B Alloy at Low Temperatures: The Influence of Time and Annealing

A study is made of the effects of various factors such as time (7 years), temperature, high magnetic field up to 580 kOe and heat treatment (HT) on the morphological structure and magnetic hysteresis properties of a high-coercive nanocrystalline (Nd0.55Ho0.45)2.7(Fe0.8Co0.2)14B1.2 alloy with a low temperature coefficient of remanence. We find a rather weak time effect on (Nd0.55Ho0.45)2.7(Fe0.8Co0.2)14B1.2. After 7 years, the loss in the maximum magnetic energy product (BH)max is no more than 5%. Annealing of the sample at 250 °C for 30 min decreases the amount of amorphous phase from 7.2 to 1.7%, while the grains’ size of the 2-14-1 phase increases from 83 to 109 nm. For the HT alloy, a magnetization jump is observed at H ~500 kOe. It can be attributed to the first-order magnetization process or a spin-flip magnetic transition. Rectangularity of the hysteresis loop degrades after annealing. In case of the short-time heat treatment, losses in (BH)max are ~10%.

Thermal management system of lithium-ion battery module based on micro heat pipe array

Summary Temperature affects the performance of electric vehicle battery. To solve this problem, micro heat pipe arrays are utilized in a thermal management system that cools and heats battery modules. In the present study, the heat generation of a battery module during a charge-discharge cycle under a constant current of 36 A (2C) was computed. Then, the cooling area of the condenser was calculated and experimentally validated. At rates of 1C and 2C, the thermal management system effectively reduced the temperature of the module to less than 40°C, and the temperature difference was controlled less than 5°C between battery surfaces of the module. A heating plate with 30-W power effectively improved charge performance at low temperature within a short heating time and with uniform temperature distribution. Charge capacity obviously increased after heating when battery temperature was below 0°C. This study presents a new way to enhance the stability and safety of a battery module during the continuous charge-discharge cycle at high temperatures and low temperatures accordingly.

Influences of scanning speed and short-time heat treatment on fundamental properties of Ti-6Al-4V alloy produced by EBM method

This study was conducted to examine the influence of the scanning speed of an electron beam on the fundamental properties of Ti-6Al-4V alloy produced by EBM (electron beam melting) method. We further investigated the effect of short-time heat treatment on those properties. By increasing the scanning speed, the desired outer shape was more closely achieved. However, molding defects became larger and the density reduced. On balance, the appropriate range of scanning speed was between 1 and 2m/s. EBM materials had columnar microstructures elongated in the building direction. Although these characteristic microstructures were mainly composed of the stable α and β phases, the α' phase was partially generated at high scanning speed. By increasing the scanning speed, the amount of the α' phase increased and the hardness rose. The short-time heat treatment generated the fine α' and α phases in the prior β phase. This microstructural change markedly increased the hardness of EBM material.

Ohmic heating: A promising technology to reduce furan formation in sterilized vegetable and vegetable/meat baby foods

Abstract Occurrence of furan, classified as carcinogen 2B by the International Agency for Research on Cancer, in heat-processed foods, especially sterilized baby foods, is of a health concern. On this account, innovative processing practices ensuring microbial safety, acceptable sensorial features, and, at the same time, minimizing furan formation have to be searched. In this study, the potential of ohmic heating to mitigate furan formation was demonstrated. Compared to conventional retort sterilization, significant mitigation (70–90%) of furan was achieved, assumingly due to reduced degradation of furan precursor under faster terms heating conditions. In purees containing meat, approx. two times less furan was formed, regardless of the processing technology. In addition to furan, also other headspace volatiles were measured and statistically evaluated. Compounds originated through fatty acids oxidation and Maillard reaction products were more abundant in conventionally sterilized samples compared to those treated by ohmic heating. Industrial relevance Ohmic heating is an emerging technology being employed in the field of food processing which applies a direct electric current to food products, providing rapid and uniform heating throughout the product. Shorter heating times used in ohmic heating, as compared to conventional retort sterilization, reduce potential losses of valuable nutrients and as well as reduce the formation of undesirable processing contaminants, in particular furan. The presented work examines furan concentrations across various stages of baby food production, in order to compare ohmic heating and retort sterilization processes. Volatile compound fingerprints for baby food purees processed via both sterilization methods, both prior and post sterilization were assessed. The results presented in this work are of high potential interest to the baby food industry to reduce both heat induced chemical changes and exposure of infants and babies to hazardous processing contaminants such as furan.

Atom probe investigations on temper embrittlement and reversible temper embrittlement in S 690 steel weld metal

ABSTRACTSevere embrittlement was observed in weld material of a brand new penstock of a huge hydro power plant. Temper embrittlement (TE) was found as root case of embrittlement. Reversible temper embrittlement (RTE) treatment characterised by a short-time heating at about 600°C, by which the toughness of embrittled weld material can significantly be recovered, was qualified and successfully applied in the plant. Basic investigations were performed to explain the embrittlement as well as the de-embrittlement effect. By the application of high resolution analytics as Atom Probe Tomography (APT) applied on TE as well as on the RTE-treated material, revealed phosphorus segregation in the grain boundaries as root cause of embrittlement. By application of RTE treatment the APT results revealed, that the phosphorus segregation in the grain boundaries disappeared. The mechanism of this behaviour can be explained by referring the McLean [Grain boundaries in metals. Oxford: Clarendon Press; 1957] based grain boundary equilibrium segregation of phosphorous. During RTE treatment, which occur at higher temperatures (600°C) that segregation (which starts during cooling at about 550°C), desegregation occurs. During this higher temperature, the diffusion is much faster than segregation producing the fast recovery of toughness.

Mixed biopolymer nanocomplexes conferred physicochemical stability and sustained release behavior to introduced curcumin

Beta-lactoglobulin (BLG)-sodium alginate (ALG) electrostatic nanocomplexes were utilized to encapsulate and deliver curcumin in clear acidic media. Relative viscosity measurements confirmed that ALG wrapping around the globular BLG molecules occurred in the aqueous biopolymer mixture upon acidification. Curcumin was efficiently entrapped within developed green delivery systems. The encapsulation efficiency (EE) of curcumin was around 98%. The carriers were efficiently able to retain the curcumin inside over time. The physical stability of hydrophobic curcumin toward precipitation in aqueous solution was significantly improved after introduction into nanostructures. Moreover, nanocomplexes conferred considerable protection to curcumin against heat-induced degradation. At the end of 15-day storage at 45 °C, the amounts of curcumin loaded in nanocomplexes were significantly (p < 0.05) larger than those loaded in blank samples. Non-significant changes in the particle size after high temperature short time (HTST) heat treatment indicated that the presence of polysaccharide shell around the protein core increased the thermal stability of BLG at acidic conditions. No release occurred in simulated fasting and non-fasting gastric conditions. However, a sustained release behavior (78.5% during 12 h) was observed in simulated intestinal fluid.

Stable and self-healing superhydrophobic MnO2@fabrics: Applications in self-cleaning, oil/water separation and wear resistance

In this work, superhydrophobic fabrics were prepared through an in-situ growth method for fabricating hierarchical flower-like MnO2 nanoparticles on cotton fabric surface and subsequent STA modification, which exhibited multifunction for self-healing, self-cleaning, oil/water separation and wear resistance. After air-plasma treatment, the self-healing MnO2@fabric could restore superhydrophobicity by a short time heat treatment, and the water CA without obvious reduction after 8 cycles. Moreover, the MnO2@fabric could selectively filtrate oil from a mixture of oil and water repeatedly, and demonstrated high efficiency for oil/water separation capability and excellent self-cleaning property. Furthermore, the MnO2@fabric composite possessed high mechanical strength and good wear resistance, its wear rate could be reduced to 1.21×10−14m3 (Nm)−1. The MnO2@fabric still maintained superhydrophobicity even was seriously damaged after the friction test.

2009 개정 교육과정 초등과학에서 제시된 해륙풍 모형실험 분석 및 개선 방안

The purpose of this study is to analyze the problems of land and sea breeze model experiment that has presented in <TEX>$5^{th}$</TEX> grade curriculum in chapter "Weather and our lives" and makes better model simulation so that learners can have better and more effective way to study it. To survey the opinions from dedicated teachers about land and sea breeze model experiment, we produced the survey through interview with science exclusive teacher from M elementary school. An elementary science education expert, 3 men of science EdD modified and complemented survey and started Delphi survey to 12 science teachers who have career teaching more than 3 years. The problems found in this survey were 'one heat bulb, short heating time, small temperature difference of water and sand, lack of class time, empty space between sand and water, back of transparent boxes, little amount of scent and the location of the it' etc. But the most of all, it is hard to see the successful result of the experiment. Based on these kinds of investigations, and lots of trial and error, redesigned the new model experiment that has the most similarity to the real one and high probability of success. According to this, it was able to see the smoke forms horizontal movement along the sand and the smoke goes in one circulation cycle. through this experiment, we made a conclusion that although those scientific experiments in textbook were developed through lots of considerations of expert, to consider the aspect of consumer, it needs to reach the educational agreement about simulation experiment so that It can lead to successful experiment and high quality education.

Mechanism underlying the effect of conventional drying on the grinding characteristics of Ximeng lignite

Same amounts of moisture were removed from Ximeng lignite (XL) with different particle size ranges pretreated at different drying temperatures. The effect of conventional drying on the grindability of the XLs was investigated. Increasing the drying temperature improved the grindability of all the samples. The results of scanning electron microscopy and mercury intrusion porosimetry revealed that the dominant mechanism enhancing the grindability of XL with high moisture was the pore structure destruction induced by the steam jet flow generated with the removal of moisture. Especially, the development of large fractures had a strong connection with the change in the grindability. According to the pore size distribution, the internal structure of the 2.5-4.0mm coal samples did not develop well under high drying temperature because of the exceedingly short heating time. Therefore, coal particle size, drying temperature, and heating time must be coordinated well to achieve the enhanced drying effect. The grindability of XL had a negative linear correlation with the pore volume fractal dimension, revealing the possibility of fractal dimension for the analysis of lignite grindability.