Conventional Thermal Treatment Research Articles

From natural aluminosilicate minerals to hierarchical ZSM-5 zeolites: A nanoscale depolymerization–reorganization approach

In this article, we describe a novel strategy for synthesizing hierarchical ZSM-5 zeolites via the nanoscale depolymerization–reorganization of natural aluminosilicate minerals. This strategy involves two important steps: the first is the top-down depolymerization of one aluminum-rich aluminosilicate mineral via a novel submolten salt system and one silicon-rich aluminosilicate mineral via conventional thermal treatment into nanoscale building blocks, and the second is the bottom-up rearrangement and reorganization of nanoscale building blocks in the synthesis system into hierarchical ZSM-5 zeolites. When used as a fluid catalytic cracking catalyst additive, the resulting ZSM-5 zeolite with hierarchical micro–mesoporous structure exhibited high activity and selectivity for valuable products in preliminary oil refining tests. The salient features of the strategy lie in that it neither involves any inorganic aluminum and silicon salts as precursors nor uses any secondary mesoscale template and post-treatment to create mesopores, thus demonstrating itself to be a green route to synthesizing hierarchical zeolites.

Structural properties of condensed ovalbumin systems following application of high pressure

The effect of high pressure on thermomechanical and physicochemical properties of ovalbumin samples up to 80% (w/w) solids is presented and compared to conventional thermal treatment. Results from small deformation dynamic oscillation in shear, modulated differential scanning calorimetry (MDSC) and Fourier transform infrared spectroscopy (FTIR) revealed that pressure-treated ovalbumin maintains its native conformation in condensed systems of 80% (w/w) solids, whereas its structure has been irreversibly changed in the aqueous environment of 20% (w/w) solids, and partially altered at intermediate levels of solids (30–60%, w/w). That was rationalized on the basis of specific rearrangements between sulfhydryl and disulphide bonds following application of high pressure and the high hydrophobicity of the ovalbumin molecule. Cooling to subzero temperatures results in vitrification and the formation of a matrix with glassy consistency for both atmospheric and pressurised materials. Application of the method of reduced variables and the combined WLF/free volume theoretical framework are able to predict the glass transition temperature of condensed ovalbumin preparations.

UV-assisted rapid thermal annealing for solution-processed zinc oxide thin-film transistors

An ultraviolet (UV)-assisted thermal annealing (TA) method is proposed for the rapid fabrication of solution-processed zinc oxide (ZnO) thin-film transistors (TFTs). Conventional thermal treatment of zinc hydroxide solution, which was carried out at 150 °C for 60 min in air, produced ZnO materials. Electrical properties of the TFTs employing thermally-annealed ZnO films were reproduced in the transistors fabricated using a simultaneous thermal treatment combined with UV irradiation at 150 °C for 3 min in air. These results demonstrate that the UV-assisted TA method can expedite the decomposition of precursor materials, contributing to rapid crystallization into thin films.

Structural modification in condensed soy glycinin systems following application of high pressure

The structural behaviour of soy glycinin systems following application of industrially relevant high hydrostatic pressure (600 MPa for 15 min at ambient temperature) was investigated throughout the experimental range up to 80% (w/w) solids content, and results were compared to conventional thermal treatment. Using small-deformation dynamic oscillation in shear, modulated differential scanning calorimetry, infrared spectroscopy and X-ray scattering, it was demonstrated that soy glycinin with twelve disulphide linkages displays extensive unfolding at low to intermediate solid levels (30–60%, w/w). In contrast, it largely maintains native conformation at 70 and 80% (w/w) solids showing about 20% denaturation, as compared to the thermal transition of native counterparts. Experimental data from infrared spectroscopy also argue for retention of the native conformation in condensed soy glycinin systems comprising mainly beta sheets in the secondary structure. At subzero temperatures, condensed glycinin at atmospheric and pressurised conditions undergoes vitrification phenomena recording experimental glass transition temperatures. Experimental data were successfully modelled using theoretical frameworks for mechanical studies on amorphous synthetic polymers.

Dual-stage forward osmosis/pressure retarded osmosis process for hypersaline solutions and fracking wastewater treatment

Hypersaline solution with high TDS is not suitable for direct treatment by the conventional membrane and thermal processes. The current study proposes a dual-stage FO/PRO process for hypersaline solution treatment and power generation. The treatment process reduces the concentration of saline wastewater and hence renders it suitable for disposal directly to sea or treatment by the conventional membrane and thermal processes. The draw and feed solutions in the FO process were the hypersaline solutions and wastewater effluent, respectively. Five concentrations were evaluated for the process treatment with different concentrations ranging from 53g/L to 157g/L. The performance of FO membrane was estimated using pre-developed computer software. The results showed that a higher power can be generated from the PRO-FO system than from the FO-PRO system without compromising the concentration of hypersaline solution after dilution. The study also showed that although increasing the flow rate of draw solution resulted in an increase in the permeate flow rate, it caused a reduction in the dilution of draw solution. On the other hand, the study showed a negligible improvement in the performance of FO membrane upon increasing the feed solution flow rate. Finally, the simulation results showed that the concentration of diluted draw solution was suitable for the conventional membrane and thermal treatments or discharge to seawater after the dual-stage FO membrane treatment.

Nonvolatile transparent manganese oxide thin film resistance random access memory devices

In this study, the electrical conduction and bipolar switching properties in transparent manganese oxide thin films were investigated and discussed. The as-deposited manganese oxide thin films were prepared by the rf magnetron sputtering method with the rf power of 130 W, chamber pressure of 10 mTorr, substrate temperature of 550 °C, and different oxygen concentrations. To discuss the resistive switching properties of the manganese oxide thin films, the conventional thermal annealing treatment of the manganese oxide thin film resistive random access memory (RRAM) devices were investigated. Finally, the current–voltage characteristics were determined by the ohmic contact and the Poole–Frankel emission conduction method in low/high-voltage regions, respectively.

Enhanced recovery and recrystallization of metals due to an applied current

The influence of an applied current on the recovery and recrystallization of pure Cu has been investigated. By comparing samples heated by the Joule effect with those heated in a salt bath, it is shown than recovery and recrystallization are greatly accelerated by the current. At low temperatures, where only recovery occurs during conventional thermal treatments, fully recrystallized microstructures are obtained when the heating is applied through the Joule effect.

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.