Conventional Thermal Treatment Research Articles

Inverted-structure polymer solar cells fabricated by sequential spraying of electron-transport and photoactive layers

Inverted-structure polymer solar cells (I-PSCs) containing sequentially sprayed electron-transporting layers (ETLs) and photoactive layers were fabricated. Low-temperature sol–gel-derived ZnO thin films were used as the ETLs and films of a poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend were used as the photoactive layers. Nanoripples-containing ZnO ETLs could be successfully fabricated by controlling the spraying rate of the ZnO precursor solution and the subsequent annealing conditions. The P3HT/PCBM active layers sprayed on the ZnO ETLs were optimized using a unique solvent-assisted post-deposition treatment, namely, the sprayed solvent overlayer (SSO) treatment. The power conversion efficiency (PCE) of the I-PSCs based on the optimized ETLs and active layers was as high as 3.55%, which is comparable to that reported for I-PSCs fabricated using the conventional spin-coating method. The sprayed I-PSCs also exhibited high environmental stability, maintaining ∼80% of their PCE even after 40days of aging in air under ambient conditions without encapsulation. The I-PSCs based on the P3HT/PCBM photoactive layers optimized using the SSO treatment displayed much higher stability than those based on photoactive layers optimized using a conventional thermal annealing treatment. This result indicated that the SSO treatment is a suitable post-deposition treatment method for improving the morphological stability of P3HT/PCBM active layers. Further, the fabrication technique investigated in this study is a high-throughput low-temperature one and is suitable for fabricating high-stability PSCs.

Physicochemical properties and riboflavin encapsulation in double emulsions with different lipid sources

This paper examines the influence of the type of lipid source (chia oil, sunflower oil, olive oil or rendered pork backfat) on physicochemical properties and riboflavin encapsulation in food-grade W1/O/W2 double emulsions (DE) for use as functional healthier-fat food ingredients. DEs with encapsulated riboflavin were subjected to conventional thermal treatment (70 °C for 30 min) and storage at 4 °C for 8 days to determine their influence on oil droplet particle size characteristics, viscosity, dynamic rheological properties, physical stability and encapsulation efficiency. The thermal treatment caused minimal changes in these parameters. DEs containing rendered pork backfat (DEsRPF) collapsed after 3 days of storage at 4 °C, thus limiting their useful life. For that reason samples of this DEsRPF were stored at room temperature only and proved stable throughout storage in those conditions. Riboflavin was efficiently encapsulated, although the DEs containing chia oil (DEsCO) were the most efficient at the start. However, these DEs released riboflavin progressively during storage at 4 °C. After 8 days' storage at 4 °C, DEsRPF stored at room temperature had encapsulated riboflavin more efficiently than DEs containing oil sources. Overall, DEs were stable to environmental stresses typically occurring in the food industry.

The second-harmonic generation in chalcogenide glass-ceramic doped with CdS nanocrystals

An innovative way is proposed here to synthesize chalcogenide glass-ceramic by hot-pressing a combination of Ge20Sb12S68 glassy powder and non-linear CdS nano-particles. The cadmium sulfide nano-particles, which possess the second-harmonic generation property, were synthesized from basic cadmium solution strongly complexed by amine. The obtained glass-ceramics present homogeneous distribution of the crystals. The transmission reaches 30% at 5µm and up to 60% at 10.6µm. The second-harmonic generation at 0.9µm has been detected. This technique can overcome the uncontrollable hetero-crystallization which tends to occur in the glass-ceramics prepared by the conventional thermal treatment method.

Effects of sonication and ultraviolet-C treatment as a hurdle concept on quality attributes of Chokanan mango (Mangifera indica L.) juice.

The growing demand for fresh-like food products has encouraged the development of hurdle technology of non-thermal processing. In this study, freshly squeezed Chokanan mango juice was treated by paired combinations of sonication (for 15 and 30 min at 25 ℃, 40 kHz frequency) and UV-C treatment (for 15 and 30 min at 25 ℃). Selected physicochemical properties, antioxidant activities, microbial inactivation and other quality parameters of combined treated juice were compared to conventional thermal treatment (at 90 ℃ for 60 s). After thermal and combined treatment, no significant changes occurred in physicochemical properties. A significant increase in extractability of carotenoids (15%), polyphenols (37%), flavonoids (35%) and enhancement in antioxidant capacity was observed after combined treatment. Thermal and combined treatment exhibited significant reduction in microbial load. Results obtained support the use of sonication and UV-C in a hurdle technology to improve the quality of Chokanan mango juice along with safety standards.

Influence of high pressure and heating treatments on physical parameters of water-in-oil-in-water emulsions

The aim of this study was to evaluate the possibility of using food-grade W1/O/W2 double emulsions to develop novel functional foods. Two lipid sources (olive oil and pork lard) were used as the oil phase, and the resulting double emulsions were subjected to conventional thermal treatment (70 °C for 30 min), high pressure processing (non-pressurized, pressurized at 400 or 600 MPa for 5 min at 20 °C) and storage at chilling temperature (4 °C for 1, 6 and 10 days) to determine their influence on oil droplet particle size, physical stability, instrumental color and rheological properties. Results showed that the double emulsion containing olive oil was less stable to creaming. The thermal treatment did not affect oil droplet particle size, although it reduced stability. High pressure processing showed no effect on the studied parameters. The physical stability of the double emulsion was mainly affected by storage at chilling temperature. Overall, double emulsions are stable to environmental stresses typically occurring in the food industry. The preparation of double emulsions requires a relatively simple technology but also has a great potential for the development of healthier foods including functional foods. The reduction of fat (energy content), provide healthier fatty acid profiles, encapsulation of hydrophilic bioactive compounds and the reduction of sodium are some of the food-grade double emulsions applications. However, these emulsions are required to be stable to those treatments that typically occur in the food industry. In this frame, high pressure processing is an innovative non-thermal processing technique which is applicable for the processing and preservation of different foods. By combining these techniques it is, therefore, possible to produce healthier foods with minimal impact on their nutritional and sensory features.

Microwave-assisted crystallization into anatase of amorphous TiO2 nanotubes electrochemically grown on a Ti substrate

Hybrid thermal heating induced by a microwave oven was unprecedentedly used to successfully attain rapid and facile crystallization into the anatase phase of amorphous TiO2 nanotubes grown on a Ti substrate. Amorphous TiO2 nanotubes were obtained by anodic oxidation of a Ti foil either in aqueous or organic medium. Afterward, these TiO2 nanotubes were thermally treated by hybrid heating in a common commercial microwave oven. The as-grown amorphous nanotubes were characterized by SEM and XRD, whereas the evolution of the nanotubes crystallization with thermal treatment time was followed by XRD. The crystallization into the anatase phase of the amorphous TiO2 nanotubes occurred after only 2 or 3min of hybrid thermal treatment, which is very short and convenient as compared with several hours that are needed when conventional thermal treatment is used.

Remediation of hydrocarbon-contaminated soils by ex situ microwave treatment: technical, energy and economic considerations

In this study, the remediation of diesel-polluted soils was investigated by simulating an ex situ microwave (MW) heating treatment under different conditions, including soil moisture, operating power and heating duration. Based on experimental data, a technical, energy and economic assessment for the optimization of full-scale remediation activities was carried out. Main results show that the operating power applied significantly influences the contaminant removal kinetics and the moisture content in soil has a major effect on the final temperature reachable during MW heating. The first-order kinetic model showed an excellent correlation (r2 > 0.976) with the experimental data for residual concentration at all operating powers and for all soil moistures tested. Excellent contaminant removal values up to 94.8% were observed for wet soils at power higher than 600 W for heating duration longer than 30 min. The use of MW heating with respect to a conventional ex situ thermal desorption treatment could significantly decrease the energy consumption needed for the removal of hydrocarbon contaminants from soils. Therefore, the MW treatment could represent a suitable cost-effective alternative to the conventional thermal treatment for the remediation of hydrocarbon-polluted soil.

Efficiency Enhancement in ZnO:Al-Based Dye-Sensitized Solar Cells Structured with Sputtered TiO2Blocking Layers

We explored new strategies for efficiency enhancement in dye-sensitized solar cells (DSSCs) by combining dehydration–condensation reactions with sputtering deposition methods. The photoanodes were realized by means of low-temperature preparation of mesoporous TiO2 films on thin undoped TiO2 compact (blocking) layers on ZnO:Al (AZO) substrates and sensitization with ruthenium dye, N719. For photoanodes fabrication, an 8 μm thick mesoporous film of TiO2 and an under critical thermal budget, applied before dye loading (≤200 °C: i.e., 150 °C for the TiO2 mesoscopic layer and 200 °C for the TiO2 blocking/AZO bilayer), were employed, which renders the overall process competitive for the applications. The structural properties of the sputtered TiO2/AZO bilayer were optimized, and a cell efficiency as high as the 4.6%, above the current literature limit for AZO-based DSSC (3.8% for 10 μm thick mesoporous layers sintered at 450 °C and sensitized with N719), was achieved at T ≤ 200 °C. With the proposed scheme for the photoanode structure and using, instead, a conventional thermal treatment at 500 °C (30 s), the cell efficiencies were further raised up to 4.9%. It was thus evidenced that the use of optimized materials for the cell architecture makes the AZO-based DSSC nowadays rising devices.

Powder synthesis and densification of ultrafine B4C-ZrB2 composite by pulsed electrical current sintering

Abstract Submicrometer sized B 4 C-30 vol% ZrB 2 ceramic composites were made both by one-step in situ pulsed electric current sintering (PECS) of a B 4 C, ZrO 2 and carbon black powder mixture or by PECS of B 4 C-ZrB 2 powder mixtures synthesized by thermal treatment in vacuum at 1100–1400 °C for 2 h. The influence of the processing temperature on the phase evolution and chemical composition of the mixtures were investigated in detail by Rietveld XRD and SEM analysis. Conventional vacuum thermal treatments allowed to synthesize homogeneous and submicrometer sized B 4 C-ZrB 2 powder mixtures at 1300 and 1400 °C for 2 h, whereas 37 and 11 wt% (m + t)-ZrO 2 was present in the mixtures processed at 1100 and 1200 °C respectively. Subsequent PECS treatment at 2000 °C for 5 min allowed to obtain B 4 C-ZrB 2 composites from these thermally treated B 4 C + ZrO 2 + C powder mixtures. In the one-step in situ process, a PECS temperature of 1900 °C was necessary to complete the conversion of the in situ formed B 2 O 3 to B 4 C to form B 4 C-ZrB 2 composites. The composites prepared by both routes exhibited a Vickers hardness (HV 10 ) of 30–32 GPa, a modest fracture toughness of 2.4–2.9 MPa m 1/2 and a good flexural strength of 630–730 MPa.

Modification of the structural and rheological properties of whey protein/gelatin mixtures through high pressure processing

High pressure processing (HPP) can induce structure development in macromolecules which are distinct from those of conventional thermal treatments. Gelation properties of whey protein (5–20% w/w) upon 15min HPP at 600MPa and 5 or 30°C (initial sample temperatures) were examined in the presence and absence of 5% w/w gelatin. The values of storage modulus (G′) in pressure treated mixed gels were below those of their counterparts thermally treated at 80°C. Mixed systems subjected to HPP in the solution state possessed higher G′ than the mixed systems subjected to HPP in the form of gels. The cooling profile of G′ in pressurised mixed solutions was similar to that of the gelatin solution, which indicates that HPP resulted in a high degree of gelatin continuity. Confocal images confirmed that gelatin was the continuous phase whilst whey protein aggregated in discontinuous inclusions within the pressurised mixed systems.

Thermal and High-Pressure Inactivation Kinetics of Avidin

High-pressure (HP) inactivation of pure avidin as well as avidin in egg were evaluated and compared with conventional thermal inactivation kinetics. Test samples were treated at 500 to 700 MPa and 80 to100C for pure avidin and at 500 to 700 MPa and 30 to 50C for avidin present in egg white and whole liquid egg. Avidin inactivation was well described by the first-order kinetic model. Pure avidin was found to be relatively very resistant as compared with avidin in egg, and thermal inactivation was much slower than HP inactivation. Conventional thermal treatment at 100C gave a D value of 111 min while HP treatment (700 MPa) at the same temperature reduced the D value to 26 min for pure avidin. However, avidin naturally present in egg was sensitive to both thermal and pressure treatments. Avidin in egg had a D100C value of 10.0 to 10.9 min indicating greater heat sensitivity. Conventional thermal treatment at 50C had negligible effect on avidin inactivation in egg while HP treatment at 700 MPa almost completely inactivated it in 5–10 min (D value of 2.2 min). The pressure and temperature sensitivity parameters (z value) were also determined both as a function of pressure at different temperatures and as a function of temperature at different pressure levels. Practical Applications Avidin present in egg white possesses antinutritional properties as it can bind with biotin (vitamin B7) making it inaccessible to the body. Biotin is an important vitamin necessary for cell growth, metabolism of fats and amino acids in the human body. It has been shown that one molecule of avidin has the ability to bind four molecules of biotin. Since avidin is very stable, processing treatments aim at inactivating it so as to make biotin available for digestion and absorption by the body. Avidin is traditionally inactivated by thermal processing. HP processing is a nonthermal alternative to conventional thermal processing aimed at minimizing the thermal damage to quality factors. This research compares thermal and HP techniques for inactivating avidin. HP has been shown to accelerate the inactivation of avidin.

Impact of Nonthermal Pulsed Electric Field on Bioactive Compounds and Browning Activity in Emblica officinalis Juice

The effect of nonthermal pulsed electric field (PEF) and thermal treatment (90⁰C for 60s) was studied on quality parameters of Emblica officinalis juice for the period of 6 weeks at 4⁰C using monopolar rectangular pulse of 1µs width. The PEF treatment was given using static chamber at 24kV/cm for 500µs. The quality of Emblica officinalis juice was investigated in terms of non enzymatic browning index (NEBI), 5-hydroxymethyl-2-furfural (HMF), total polyphenol content and antioxidant capacity. ⁰Brix, pH and conductivity were evaluated as physical parameters. The aim of the work was to investigate the effect of PEF on the retention of bioactive compounds and retardation of browning activity. The results showed that conventional thermal treatment had led to a significant (p<0.05) decrease of 48.15% in polyphenol content (129.56 mg of GAE L-1), with higher NEBI and HMF formation (p < 0.05) whilst PEF suppressed NEBI and retained higher polyphenol compounds (168.59mg GAE L-1) with limiting the loss to 32.56% along maximum free radical scavenging activity (92.07%). However, pH, ⁰brix and electrical conductivity of treated juice samples remain unaffected. Therefore, PEF can be considered as an effective nonthermal treatment for retaining bioactive compounds along suppressing browning of emblica juice.

In situ synthesis-gelation at room temperature vs. heating–cooling procedure. Fine tuning of molecular gels derived from succinic acid and L-valine

HypothesisThe reaction between succinic anhydride and a diamine derived from L-valine should afford efficiently a molecular gelator. Based on this reaction, it should be feasible to prepare molecular gels at room temperature, avoiding the conventional thermal treatment required for the solubilization of the gelator, by in situ, simultaneous, synthesis and gelation. The gels prepared by in situ and conventional heating–cooling protocols could present important differences relevant for potential practical applications of these materials. ExperimentalThe gelator was synthesized by reaction of succinic anhydride and a diamine derived from L-valine, affording two new amide bonds. The molecular gels were studied by IR, NMR, electron microscopy, X-ray diffraction and DSC. FindingsThe results indicate that different polymorphic fibrillar networks are formed depending on the gel preparation method, highlighting how the properties of molecular gels can be tuned in this way. Significant differences between thermal and in situ gels were found in properties such as thermal stability, thixotropic behavior or release of an entrapped dye. In situ synthesis-gelation has also been shown to provide gels in media such as oleic acid which cannot be jellified by conventional heating–cooling procedures.

Dimensional Stability Analysis of Unconventional Treated Steel Bearings

One of the most important characteristics of the element bearings behaviour evaluation is the dimensional stability in time. The structures resulting in conventional thermal treatments are characterized by a major instability along time. Structural changes cause dimensional changes for both austenite and martensite transformations. Residual austenite transformation generates an increase in volume while the martensite transformation decomposes when volume decreases. Research has shown that cryogenic treatment and steel tempering in ultrasonic field applied to bearing steels have a positive influence on the dimensional stability. In what the dimensional stability concerns, the heat treatment below 0°C acts specifically on those sources of strain that have a maximum contribution to further parts dimension modification, especially on the transformation of austenite into martensite. It would have been better if the amount of austenite that remained after quenching at room temperature had been higher and the steel contained more carbon and alloying elements [.

Chemical durability of hierarchically porous silicalite-I membrane substrates in aqueous media

Abstract

Microwave heating remediation of soils contaminated with diesel fuel

Diesel fuel represents a permanent source of soil pollution, and its removal is a key factor for human health. To address the limitations of conventional remediation techniques, microwave (MW) heating could be employed due to its great potentiality. This work presents the lab-scale experiments performed to study the potential of MW processing for diesel-polluted soils treatment and related modeling for the optimization of MW systems operating conditions. A sandy soil was artificially contaminated with diesel fuel, moisturized with different amounts of water content, and thermally treated by MW radiation using a lab-scale apparatus to investigate the effect of soil moisture on soil temperature profiles and contaminant removal kinetics. An operating power, ranging from 100 to 1,000 W, and treatment times of 5, 10, 18, 30, and 60 min were investigated. Contaminant residual concentration values were fitted using the first order kinetic model, and desorption parameters were calculated for each soil at different operating powers. Main results show that the operating power applied significantly influences the contaminant removal kinetics, and the moisture content in soil has a major effect on the final temperature reachable during MW heating. Minimal contaminant concentrations were achievable by applying powers higher than 600 W for a treatment time longer than 60 min. For remediation times shorter than 10 min, which result in a soil temperature of about 100 °C, the effect of the distillation process increases the contaminant removal, whereas for longer times, soil temperature is the main key factor in the remedial treatment. MW thermal desorption of diesel-polluted soil was shown to be governed by pseudo-first-order kinetics, and it could be a better choice for remediation of diesel-polluted soils, compared to several biological, chemical–physical, or conventional thermal treatments, due to its excellent removal efficiency. The results obtained are of scientific and practical interest and represent a suitable tool to optimize the treatment operating conditions and to guide the design and the scale-up of MW treatments for full-scale remediation activities of diesel-polluted soils.

Nonthermal Pasteurization of Takju using Batch High Voltage Pulsed Electric Fields with Exponential Decay Pulse

Makgeolli, a traditional Korean turbid rice wine, was treated with pulsed electric fields (PEF) for the purpose of a development of a new cold pasteurization processes. Inactivation of yeast in the makgeolli increased with increase in intensity of the electric field strength and treatment time. The initial yeast count of the makgeolli was 2×10 cfu/ ml. A reduction of 2D was obtained at 30 kV/cm and 256 exponential decay pulses at room temperature. The combination of PEF and conventional thermal treatment inactivated the yeast more effectively. Reductions of up to 8D were observed when the makgeolli was treated with PEF of 20 kV/cm and 256 pulses at 50C. The inactivation of the yeast in makgeolli increased with an increase in alcohol content. When the alcohol content of the makgeolli increased to 12%, PEF treatment with 30 kV/cm and 256 pulses resulted in a 4.8D reduction of yeast. No changes in pH, acidity, or the growth of yeast were observed in the PEF treated makgeolli during storage at 4C for 4 weeks.

Comparison of microwaves and conventional thermal treatment on enzymes activity and antioxidant capacity of kiwifruit puree

Enzymes are naturally present in food and can cause product deterioration. For this reason, most food-processing steps try to reduce the enzymatic activity. The aim of this work was to compare, in terms of both the inactivation of kiwifruit puree peroxidase, polyphenoloxidase and pectinmethylesterase and also the maintenance of the antioxidant capacity of the product, the effect of a microwave treatment with a conventional thermal treatment designed to cause the same level of peroxidase inactivation (90%). The microwave power and process time that best permitted the maximisation of both the enzyme inactivation and the antioxidant capacity of the product, were selected by means of the Response Surface Methodology. The results obtained point to microwave heating as an appropriate technology with which to produce a stable kiwifruit puree, since these treatments were more effective at enzyme inactivation and antioxidant capacity retention than the conventional thermal treatment. Food industry is currently focused on the development of novel and minimally processed products with improved quality. Traditional thermal processing has been assumed to require the use of high temperatures and long times to stabilise food products, which lead to dramatic losses of products' quality. Thus, a variety of different processing technologies are being explored as alternative to traditional thermal processing. The results of this study point out that more than conventional heating, microwave technology can be an appropriate means of achieving the required level of enzyme inactivation at which to obtain a stable kiwifruit puree with an improved antioxidant capacity.

Laser-induced metal organic decomposition for Ce0.9Zr0.1O2−y epitaxial thin film growth

Cerium–zirconium propionates precursor layers were decomposed by pulsed laser radiation for the development of epitaxial Ce0.9Zr0.1O2−y (CZO) thin-films on yttria-stabilized zirconia (YSZ) (001) single crystal substrates. The laser treatments were performed by means of a Nd:YAG laser system (λ=266nm, τ=3ns, ν=10Hz). The influence of processing parameters such as the laser fluence, number of pulses and substrate temperature on the morphology, surface roughness and composition of the irradiated material was studied and correlated with the optical properties and thermochemical characteristics of the propionate precursors. We conclude that the metal organic decomposition proceeds both from direct optical absorption of the precursor film and from the heating effect associated to the optical absorption of the YSZ substrate. FTIR spectra allow us to define the laser irradiation conditions where a full elimination of the organic precursors is achieved. After the metal organic precursor decomposition, we investigated the thin films crystallization process through furnace annealing. Our analyses demonstrate that through an optimized laser treatment and a furnace heating process it is possible to create epitaxial 20nm-thick CZO films, with similar nanostructure and surface flatness than in conventional thermal treatments but with an important saving of processing time and an enhanced versatility to define micrometric patterns.

Methane conversion under cold plasma over Pd-containing ionic liquids immobilized on γ-Al2O3

Pd-containing ionic liquid (IL) l-hexyl-3-methylimidazolium tetrafluoroborate (C6MIMBF4) immobilized on γ-Al2O3 (Pd-IL/γ-Al2O3) was prepared and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis. The influences of C6MIMBF4 loading and Pd on methane conversion to C2 hydrocarbons under cold plasma were investigated. FTIR and SEM analyses indicated that C6MIMBF4 had been successfully immobilized on γ-Al2O3 and the C6MIMBF4 showed excellent stability under cold plasma. The results of BET and methane conversion showed that with the increase in immobilization amount of C6MIMBF4 onto γ-Al2O3, the specific surface area and pore volume of IL/γ-Al2O3 decreased, while the selectivity and yield of C2 hydrocarbons increased. The selectivity of C2 hydrocarbons was 94.6% when the loading of C6MIMBF4 was 40%, and the percentage of C2H4 in C2 hydrocarbons was as high as 64% when using Pd-IL/γ-Al2O3 as a catalyst with no conventional thermal reduction treatment. Optical emission spectra (OES) from the cold plasma reactor during methane conversion were also studied. The results indicated that the intensity of the C2, CH, H, and C active species from methane and hydrogen decomposition increased when IL/γ-Al2O3 or Pd-IL/γ-Al2O3 was introduced into the plasma system. Based on the analyses of the gas product and OES spectra, it can be concluded that the surface catalyzed reactions between plasma and ionic liquid were very important for the reduction of Pd2+ and the formation of C2H4