Influence of pulsed electric field and heat treatment on Emblica officinalis juice inoculated with Zygosaccharomyces bailii

The effects of pulsed electric field (PEF) applying 26 kV cm⁻¹ with 1 μs monopolar pulses (for 500 μs) on inactivation of Zygosaccharomyces bailii and the stability for the key quality characteristics (vitamin C, phenolic content, antioxidant capacity, nonenzymatic index, 5-hydroxymethyl-2-furfural (HMF), °brix, and pH) in Emblica officinalis juice were studied. These results were then compared to those of heat treatment (90 °C for 60 s) up to 40 days on storing at 4 °C. PEF treatment reduced 5.1 log cycles of Z. bailii with decreases in HMF concentration and browning index relative to heat treated juice. Simultaneously, PEF treated juice retained 63% of vitamin C and 88.9% of antioxidant capacity (p < 0.05). However, heat treated juice lowered 4.9 log cycles of Z. bailii and exhibited significant degradation of vitamin C and antioxidant capacity (p < 0.01). After all, both treatments did not induce any major changes in pH and °brix levels of emblica juice. Electron microscopy was used as a tool to find Z. bailii damage induced. Investigation of their morphology showed a leakage of cellular debris owing to the rupture of cell membrane of PEF treated Z. bailii. Thus, PEF treatment on emblica juice may offer an enormous potential for upgrading its quality than the heat processing method.     

Synthesis of Mg0.48Cu0.12Zn0.40Fe2O4 ferrite and its aptness for multilayer chip component application

Here we reported the synthesis of MgCuZn ferrite (Mg_0.48Cu_0.12Zn_0.40Fe₂O₄) by ceramic and self-sustaining auto-combustion (sucrose) methods. Required oxides in powder form were processed (hand mill=3 h, pre-sinter=600 °C for 180 min and final sinter=910 °C for 9 h) to obtain the ferrite sample through the ceramic methods. Whereas, aqueous metal nitrates along with the sucrose as fuel were processed (at 200 °C, final sinter=600 °C for 180 min) to obtain ferrite product via the auto-combustion route. As-synthesized ferrite samples were then subjected to crystallographic, structural and magnetic investigations by techniques viz. X-ray diffraction, IR spectroscopy and B–H measurements. Purity and phase formation were confirmed by XRD examinations. Cation redistribution was also suggested by XRD analyses which supplement the variation of magnetic properties. IR absorption bands were found to be in the expected high frequency range (574.95 cm^?1 and 582.39 cm^?1) and low frequency range (≈431 cm^?1) which fortifies the spinel phase formation. Boost in magnetic performance of sucrose methods' yield was observed owing to reduced porosity and increased surface area. Thus, MgCuZn ferrite prepared via the self-sustaining auto-combustion route has superior magnetic properties at relatively low sintering temperature and can be employed in multi-layer chip application readily.     

Preparation and characterization of mesoporous silicon oxycarbide ceramics without free carbon from polysiloxane

Mesoporous silicon oxycarbide ceramics without free carbon were prepared by pyrolysis of cross-linked polysiloxane at different temperatures (1300–1450 °C) followed by post treatments. The post treatments comprised two steps (HF etching and oxidation at 650 °C in air). The sample pyrolyzed at 1300 °C after post treatments exhibits the largest specific surface area (SSA) reaching up to 204 m²/g and the biggest total pore volume (0.58 cm³/g) with an average pore size of 11.4 nm. Increasing pyrolysis temperature will lead a quick decline of SSA and total pore volume. The thermal stability of pore structure of the sample pyrolyzed at 1300 °C with post treatments was investigated in air. The SSA and total pore volume almost keeps the same up to 750 °C, and subsequently decreases with a high speed. The most possible reason is the pores are severely closed by viscous flow of SiO₂ produced from SiC nanocrystallites.     

Oxidation behavior of SiC ceramics synthesized from processed cellulosic bio-precursor

Oxidation behavior of Si/SiC ceramic composite synthesized from processed cellulosic bio-precursor was studied in dry air over the temperature range 1200–1350 °C. The material was synthesized from processed bio-precursors (bleached bamboo kraft pulp in the form of flat board of bulk density 0.58 g cm^?3) and had a bulk density of 2.66 g cm^?3, porosity of 0.6 vol% and contents of Si and SiC phases of 39.1% and 60.3% (v/v) respectively. The process of oxidation could be described closely by a parabolic oxidation equation. An activation energy of 141.4 kJ/mol was obtained. Both the SiC and Si phases oxidized and the oxidation was mainly controlled by the transport of molecular oxygen through the growing oxide layer. Pre-oxidation at 1300 °C for 24 h in ambient air increased the strength of Si/SiC ceramics by around 46% because of the healing of the surface defects created during surface preparation by the oxide layer.     

Ce0.9Gd0.1O1.95 supported La0.6Sr0.4Co0.2Fe0.8O3−δ cathodes for solid oxide fuel cells

Lanthanum-based iron- and cobalt-containing perovskite has a high potential as a cathode material because of its high electro-catalytic activity at a relatively low operating temperature in solid oxide fuel cells (SOFCs) (600–800). To enhance the electro-catalytic reduction of oxidants on La_0.6Sr_0.4Co_0.2Fe_0.8O_3?δ (LSCF), Ga doped ceria (Ce_0.9Gd_0.1O_1.95, GDC) supported LSCF (15LSCF/GDC) is successfully fabricated using an impregnation method with a ratio of 15 wt% LSCF and 85 wt% GDC. The cathodic polarization resistances of 15LSCF/GDC are 0.015 Ω cm², 0.03 Ω cm², 0.11 Ω cm², and 0.37 Ω cm² at 800 °C, 750 °C, 700 °C, and 650 °C, respectively. The simply mixed composite cathode with LSCF and GDC of the same compositions shows 0.05 Ω cm², 0.2 Ω cm², 0.56 Ω cm², and 1.20 Ω cm² at 800 °C, 750 °C, 700 °C, and 650 °C, respectively. The fuel cell performance of the SOFC with 15LSCF/GDC shows maximum power densities of 1.45 W cm^?2, 1.2 W cm^?2, and 0.8 W cm^?2 at 780 °C, 730 °C, and 680 °C, respectively. GDC supported LSCF (15LSCF/GDC) shows a higher fuel cell performance with small compositions of LSCF due to the extension of triple phase boundaries and effective building of an electronic path.     

Electrochemical and microstructural characteristics of nanoperovskite oxides Ba0.2Sr0.8Co0.8Fe0.2O3−δ (BSCF) for solid oxide fuel cells

Nanoperovskite oxides, Ba_0.2Sr_0.8Co_0.8Fe_0.2O_3?δ (BSCF), were synthesized via the co-precipitation method using Ba, Sr, Co, and Fe nitrates as precursors. Next, half cells were fabricated by painting BSCF thin film on Sm_0.2Ce_0.8O_x (samarium doped ceria, SDC) electrolyte pellets. X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical impedance spectroscopy (EIS) measurements were carried out on the BSCF powders and pellets obtained after sintering at 900 °C. Investigations revealed that single-phase perovskites with cubic structure was obtained in this study. The impedance spectra for BSCF/SDC/BSCF cells were measured to obtain the interfacial area specific resistances (ASR) at several operating temperatures. The lowest values of ASR were found to be 0.19 Ω cm², 0.14 Ω cm² 0.10 cm², 0.09 Ω cm² and 0.07 Ω cm² at operating temperatures of 600 °C, 650 °C, 700 °C, 750 °C and 800 °C, respectively. The highest conductivity was found for cells sintered at 900 °C with an electrical conductivity of 153 S cm^?1 in air at operating temperature of 700 °C.     

Ion implantation and anneal to produce low resistance metal–diamond contacts

Contacts to boron-doped, (100)-oriented diamond implanted with Si or with Si and B were formed and the effects of dose, implantation energy and anneal treatment on the specific contact resistance were examined. Ti/Au contacts on heavily implanted diamond (10¹⁶ Si ions cm⁻², E_i=30 keV or 10¹⁷ Si and B ions cm⁻², E_i=15 keV (Si) and E_i=10 keV (B)) had a specific contact resistance lower than the best contacts produced on unimplanted diamond. A specific contact resistance of (1.4±6.4)×10⁻⁷ Ω cm⁻² was achieved following a 450°C anneal. The results were consistent with a reduction in barrier height brought about by silicide formation. Light silicon implantation (10¹³ ions cm⁻²) or relatively light dual implantation (B, Si<10¹⁶ ions cm⁻²) did not reduce the specific contact resistance. Increasing the diamond conductivity by 4×10⁴ decreased the specific contact resistance by over three orders of magnitude, in agreement with the trend observed by Prins (J.F. Prins, J. Phys. D 22 (1989) 1562).     

Reprint of "Palladium Ohmic contact on hydrogen-terminated single crystal diamond film"

Contact properties of Palladium (Pd) on the surface of hydrogen-terminated single crystal diamond were investigated with several treatment conditions. 150 nm Pd pad was deposited on diamond surface by thermal evaporation technique, which shows good Ohmic properties with the specific contact resistivity (ρ_c) of 1.8 × 10^− 6 Ω cm² evaluated by Transmission Line Model. To identify the thermal stability, the sample was annealed in Ar ambient from 300 to 700 °C for 3 min at each temperature. As the temperature increased, ρ_c firstly decreased to 4.93 × 10⁻⁷ Ω cm² at 400 °C and then increased. The barrier height was evaluated to be − 0.15 eV and − 0.03 eV for as-deposited and 700 °C annealed sample by X-ray photoelectron spectroscopy analysis. Several surface treatments were also carried out to determine their effect on ρ_c, among which HNO₃ vapor treated sample indicates a lower value of 5.32 × 10⁻⁶ Ω cm².     

Effects of electrical pre-treatment and alternative heat treatment applications on orange juice production and storage

Electroplasmolysis (EP) as a pre-treatment and microwave (MW) and ohmic heating (OH) as an alternative to traditional heating were used in orange juice production, and the effects of these electrical methods on juice quality were investigated. Trials were done in six application groups with single electrical treatment and combinations. Orange juices were stored for six months at +4 °C and the analyses were performed in a two-month period. As a result of the electroplasmolysis application, more than an 8% increase in yield was determined. In addition, more than 95% PME inactivation was found in moderate (69–75 °C) temperature conditions for MW and OH applications. The results showed that the highest quality values, such as total pectin and ascorbic acid were determined on combined applications of electrical methods. The results suggested that juice yield and functional properties were increased by electroplasmolysis applications; electroplasmolysis and electrical heating applications gave better quality results comparing the conventional thermal heating (CH) in orange juice production. Quality characteristics of the juices can be preserved better and longer in the juices that are processed with electrical methods than the conventional methods.     

A storage study of encapsulated gac (Momordica cochinchinensis) oil powder and its fortification into foods

This study investigated the effects of different storage conditions, temperatures of −20, 10, room temperature (RT), 40 and 63 °C for up to 12 months in the presence or absence of air and light, on the stability of an encapsulated gac (Momordica cochinchinensis) oil powder. A stability trial of the encapsulated oil powder incorporated into yoghurt, pasteurised milk and cake mix stored at 4 ± 0.5 °C and RT for different storage times was also carried out. The results showed that a progressive degradation of colour, β-carotene and lycopene, and a progressive increase in surface oil content and peroxide value (PV) occurred in the encapsulated powders with increasing storage temperatures and storage times. However, the degradation was much less when the encapsulated powder was stored at low temperature in the absence of air and light. The degradation of β-carotene and lycopene in all samples during storage fitted a first-order reaction. The sorption curves of the encapsulated powders at 10, 30 and 40 °C were fitted with BET and GAB models. The results also showed that the encapsulated gac oil powder could be successfully incorporated into food products in terms of retention of colour, β-carotene and lycopene, and low PV.     

Synthesis of cordieritic materials using raw kaolin,bauxite, serpentinite/olivinite and magnesite

In this work it was investigated whether it is attainable to create cordieritic materials for possible uses in ceramic applications using combinations of bauxite, kaolin, serpentinite/olivinite and magnesite. For this reason various mixtures of selected samples for the synthesis of ceramic materials consisting mainly of cordierite, among other phases, were used. After appropriate processing, specimens prepared from the mixtures were fired at various temperatures up to 1350 °C. The ceramic materials resulted after firing, were investigated regarding their phases composition and physical properties of technological interest. On this way the creation of materials having interesting combinations of properties such as shrinkage (varied from 0.11% to 9.87%), porosity (varied from 0.6% to 38.5%), density (varied from 1.43 to 2.59 g/cm³), sufficient compressive strength (range of 13.1–31.0 MPa) and low coefficient of expansion (varied from 2.2 to 4.5⁎10⁻⁶/C) at high temperatures is achieved.     

Power high-voltage and fast response Schottky barrier diamond diodes

We developed and investigated a set of packaged vertical diamond Schottky barrier diodes (SBDs) with a large crystal area of up to 25 mm². All devices show forward current above 5 A and the blocking voltage over 1000 V in the temperature range from 20 °C to 250 °C. Due to the large crystal area and finite thermal resistance of the crystal-case interface the forward current self-heating effect results in a good diamond SBDs performance not only at elevated temperatures but also at normal conditions. As a result we measured about 4 V forward voltage drop, 35 mΩ × cm² specific on-resistance and 100 nA/cm² leakage current for the diode case at room temperature. At a case temperature of 250 °C the forward voltage drop was less than 2.5 V, the specific on-resistance about 40 mΩ × cm² and the leakage current about 100 μA/cm². The Baliga's figure of merit was 25–30 MW/cm² in the temperature range of 20-250 °C. The typical value of the reverse recovery time less than 10 ns while switching from 2 A forward current to 100 V blocking voltage meets the requirements for practical use of diamond SBDs in effective switch-mode power converters operating at frequencies higher than 1 MHz. Further device design optimization and the diamond epitaxial layer quality improvement will help to reduce the power losses in on-state and make diamond SBDs competitive with SiC diodes even at room temperature.     

Synthesis of SiC ceramics from processed cellulosic bio-precursor

Synthesis of SiC ceramic from processed cellulosic bio-precursor was investigated. Bamboo (Bambusa tulda Roxb.) plants abundantly available in the Jorhat district of Assam, India, were selected for extraction of fibers following Kraft pulping method and bleached bamboo pulp fibers were suitably cast in the form of rectangular boards. Coir fibers available in the Alleppy district of Kerala, India, were initially digested with dilute alkali, mixed with cellulose acetate solution, air dried and then hot-pressed at 140 ± 5 °C under 2.0–2.5 MPa pressure to make rectangular boards. Well-characterized processed bio-precursors were pyrolysed at ～800 °C under flowing N₂ atmosphere to prepare the bio-carbonaceous preforms (carbon templates) which showed nearly uniform shrinkages in all directions. Coir fiber composite board carbon showed lower pyrolytic weight loss (～66%), higher density (0.49 g cm^?3), lower porosity (～58%) and narrower pore diameter (10 μm) compared to the cast bamboo pulp fiber board carbon. The carbon samples showed perfect retention of fibrous morphological features of hierarchically grown bio-structures. Ceramization of carbon templates could be done by reactive melt silicon infiltration into porous channels at ～1600 °C under vacuum. The final ceramics were adequately dense (%theoretical density > 99%), showed negligible linear dimensional changes (indicating net-dimension formation capability), presence of crystalline Si and SiC phases and duplex microstructure with complete preservation of fibrous architecture of plant bio-structure. The Si/SiC ceramic composite synthesized from coir fiber board gave room temperature 3-point flexural strength and Young's modulus values of 121 MPa and 276 GPa, respectively. Both the ceramic composites showed adequate oxidation resistance during heating at 1300 °C for 7 h in air.     

Impact of pulsed electric field on cell disintegration and mass transfer in sugar beet

This study investigated the effects of pulsed electric field (PEF) treatments on sugar beet tissues. A PEF system was used to vary field strength, pulse number and capacitance in respective range of 0.5–6 kV cm^?1; 1–100 pulses; 0.5–32 μF. It was observed that tissue damage in sugar beet was most influenced by total energy input and electric field strength. Furthermore, the energy consumption for cell disintegration by PEF treatment was significantly lower compared to thermal treatment indicating average values of about 8 kJ kg^?1 and 156 kJ kg^?1 respectively. The transfer of solids at room temperature from PEF pretreated sugar beet (1 or 2 kV cm^?1, 8 μF, and 20 pulses) was higher than the untreated and thermal treated samples at 75 °C. The overall results showed that the optimization of PEF treatment conditions is very important to achieve high cell disintegration and sugar beet yield.     

Enrichment of diterpenes in green coffee oil using supercritical fluid extraction – Characterization and comparison with green coffee oil from pressing

Supercritical fluid extraction (SFE) was used to obtain green coffee oil (Coffea arabica, cv. Yellow Catuaí) enriched in the diterpenes, cafestol and kahweol. To obtain diterpenes-enriched green coffee oil relevant for pharmaceuticals, a central composite rotational design (CCRD) was used to optimize the extraction process. In this study, pressure and temperature did not have influences on cafestol and kahweol concentrations, but did affect the total phenolic content (TPC), which ranged from 0.62 to 2.62 mg GAE/g of the oil. The analysis and quantification of diterpenes according to gas chromatography indicated that green coffee oil from SFE presented a cafestol content of 50.2 and a kahweol content of 63.8 g/kg green coffee oil under optimal conditions. The green coffee oil produced from conventional pressing methods presented lower diterpenes content of 7.5 and 12.8 g/kg green coffee oil for cafestol and kahweol, respectively. When SFE was used, the content of the diterpenes in the same green coffee beans was relatively higher, approximately 85% for cafestol and 80% for kahweol. Green coffee oil from SFE also presented fatty acids, such as palmitic acid (9.3 mg MAE/g green coffee oil), the polyunsaturated linoleic acid (ω-6; 11 mg MAE/g green coffee oil) and oleic acid (ω-9; 3.8 mg MAE/g green coffee oil). The physical properties for green coffee oil produced from SFE and conventional pressings showed that densities and viscosities decreased with temperature. For oils produced from both extractions, the density behaviors were similar with values ranging from 0.9419 g/cm³ (25 °C) to 0.9214 g/cm³ (55 °C) from pressings and 0.9365 g/cm³ (25 °C) to 0.9157 g/cm³ (55 °C) for the oil obtained by the SFE. The dynamic viscosity for the pressed oil ranged from 127.8798 mPa × s (25 °C) to 35.0510 mPa × s (55 °C); for the oil from SFE, these lower values ranged from 84.0411 mPa × s (25 °C) and 24.2555 mPa × s (55 °C).     

Thermal cycling induced capacity enhancement of graphite anodes in lithium-ion cells

Graphite electrodes were electrochemically cycled in Li-ion cells at 50 and 60 °C in order to determine the changes in their surface properties in comparison to the electrodes tested at 25 °C. A 17% drop in planar capacity occurred during the first cycle at 60 °C compared to a 40% at 25 °C and reduced the amount of damage that occurred to graphite due to a rapidly formed solid electrolyte interphase (SEI). During the following cycles, a planar capacity of 3.11 ± 0.12 mAh cm⁻² was attained at 60 °C rather than 0.53 ± 0.03 mAh cm⁻² at 25 °C. The SEI layer formed at 60 °C predominantly consisted of Li₂CO₃ and was devoid of residual LiClO₄ detected at 25 °C. At 25 °C, the diffusion coefficient of Li⁺ (D_Li⁺) was calculated as 1.07 × 10⁻⁸ cm² s⁻¹, whereas at 60 °C, D_Li⁺ increased to 3.25 × 10⁻⁸ cm² s⁻¹. A pre-treatment conducted at 60 °C enhanced the cyclic performance of graphite subsequently cycled at 25 °C; a Li₂CO₃-enriched SEI, generated during the 60 °C pre-treatment, covered the graphite surface uniformly and resulted in a 28% increase in battery capacity at 25 °C.     

Silicon carbide films from polycarbosilane and their usage as buffer layers for diamond deposition

Thin films of polycarbosilane (PCS) were coated on a Si (100) wafer and converted to silicon carbide (SiC) by pyrolyzing them between 800 and 1150 °C. Granular SiC films were derived between 900 and 1100 °C whereas smooth SiC films were developed at 800 and 1150 °C. Enhancement of diamond nucleation was exhibited on the Si (100) wafer with the smooth SiC layer generated at 1150 °C, and a nucleation density of 2 × 10¹¹ cm^− 2 was obtained. Nucleation density reduced to 3 × 10¹⁰ cm^− 2 when a bias voltage of − 100 V was applied on the SiC-coated Si substrate. A uniform diamond film with random orientations was deposited to the PCS-derived SiC layer. Selective growth of diamond film on top of the SiC buffer layer was demonstrated.     

Hydration kinetics modeling of the effect of curing temperature and pressure on the heat evolution of oil well cement

The heat evolution of Class G and Class H oil well cements cured under different temperatures (25 °C to 60 °C) and pressures (2 MPa to 45 MPa) was examined by isothermal calorimetry. Curing pressure was found to have a similar effect on cement hydration kinetics as curing temperature. Under isothermal and isobaric conditions, the dependency of cement hydration kinetics on curing temperature and pressure can be modeled by a scale factor which is related to the activation energy and the activation volume of the cement. The estimated apparent activation energy of the different cements at 2 MPa varies from 38.7 kJ/mol to 41.4 kJ/mol for the temperature range of 25 °C to 40 °C, which decreases slightly with increasing curing temperature and pressure. The estimated apparent activation volume of the cements at 25 °C varies from − 23.1 cm³/mol to − 25.9 cm³/mol for the pressure range studied here, which also decreases slightly in magnitude with increasing curing temperature.     

Development of PLZT dielectrics on base metal foils for embedded capacitors

We have deposited Pb_0.92La_0.08Zr_0.52Ti_0.48O₃ (PLZT) films on nickel and copper substrates to create film-on-foil capacitors that exhibit excellent dielectric properties and superior breakdown strength. Measurements with PLZT films on LaNiO₃-buffered Ni foils yielded the following: relative permittivity of 1300 (at 25 °C) and 1800 (at 150 °C), leakage current density of 6.6 × 10^?9 A/cm² (at 25 °C) and 1.4 × 10^?8 A/cm² (at 150 °C), and mean breakdown field strength ≈2.5 MV/cm. With PLZT deposited directly on Cu foils, we observed dielectric constant ≈1100, dielectric loss (tan δ) ≈0.06, and leakage current density of 7.3 × 10^?9 A/cm² when measured at room temperature.     

Signature of multiferroicity and pyroelectricity close to room temperature in BaFe12O19 hexaferrite

In this paper, we have reported the signature of multiferroicity and pyroelectricity in BaFe₁₂O₁₉ hexaferrite close to room temperature. The BaFe₁₂O₁₉ hexaferrite samples are synthesized by co-precipitation method at different sintering temperature ranging from 800 to 1200 °C and study their structural, ferroelectric, magnetic, magnetoelectric and pyroelectric properties. X-ray Diffraction patterns show the pure phase formation for all samples. Morphological changes are examined through the scanning electron microscope. The maximum ferroelectric polarization (0.66 μC/cm²) is observed for the sample sintered at 1200 °C, however maximum magnetic polarization 74 emu/g is observed for sample sintered at 1000 °C. Magneto-electric coupling measurements are also performed through dynamic method and average magneto-electric coupling coefficient (~ 7.05 × 10⁻⁷ mV/cm Oe²) is observed at room temperature for the sample sintered at 1200 °C. Furthermore, maximum pyroelectric constant (147 × 10⁻¹³C/cm² °C) is observed at 75 °C for BaFe₁₂O₁₉ samples sintered at 1200 °C. The observation of both multiferroicity and pyroelectricity close to room temperature in BaFe₁₂O₁₉ hexaferrite is interesting and useful for multifunctional devices.