Further Rise In Temperature Research Articles

Long-term response of rainfed sorghum to diverse growing environments and optimal sowing window at Coimbatore

Rainfed sorghum production is profoundly vulnerable to climate variability. Sowing the crop at an appropriate time could be one of the most crucial climate-resilient options to improve the yield. The well-calibrated and validated CERES-Sorghum model was employed to study the rainfed sorghum response to varied environments over the long term (1983–2021) and to determine the optimum sowing window at Coimbatore, Tamil Nadu. The CERES-Sorghum model was used for automatic-planting with a different minimum threshold of 50,60,70 and 80 percent soil water content at 15 cm soil depth under various sowing windows from 1stSeptember to 13th October at a 7-day interval. The model results of automatic planting event indicated the best performance of 1st September sowing window at 50 percent soil water content over 39 years under semi-arid environment. The temperature rise of 1˚C exhibited no significant influence on sorghum grain yields at all sowing windows and a slight reduction in yield was observed at an elevated 2˚C temperature. A further rise in temperature reduced the yield drastically on September month sowings. Across the sowing window, first week sowing window (1st to 7th September) yield was higher under current climatic conditions. The yield of 1st September sowing window remained higher in the elevated temperature conditions as well as in both deficit and excess rainfall conditions than other sowings. In current and future climatic conditions, 1st September sowing window would be the best sowing time to mitigate climate risk in rainfed sorghum.

Production of Biodiesel from Jatropha Curcas by using Heterogenous Dopped Zinc Oxide

Heterogenous copper based nano catalyst was synthesized by Co-precipitation method. The effect of nano catalyst particle size from 0.5 to 52 nm was investigated. The Cupper dopped zinc oxide the nano particle size was used from 0.5 to 52 nm, and Transesterification method was used to produce the biodiesel. The optimum yield of bio-biodiesel was obtained 92% from Jatropha Curcas seed oil. SEM shows the surface morphology, topography, composition, crystallographic and structural shape of synthesized Cu-ZnO nano catalyst. XRD and EDX results depicted good morphology of prepared catalyst. XRD and EDX also displays the pattern of a model Cu-ZnO. FTIR results showed the major functional groups identified were alkanes , aromatics and carboxylic acid . Among these functional groups, alkanes were qualitatively noted to be the main constituents which indicate the good catalytic cracking activity of the catalyst.The UV, absorbance peak indicated the presence of ZnO nanoparticles, which is in accordance of UV absorbance result shown by previous studies. The effect of temperature on biodiesel yield showed from higher yield with 45 o C from 64.33 to 80 ml of ethanol concentration at 45 o C. On further rise in temperature resulted 92% product yield. Furthermore, effect of methanol on bio- diesel yield showed that, as the methanol ratio subsequently increased from 1: 05 to 1: 12increased the product yield. Besides this, the heterogeneous nano catalyst showed good catalytic activity in transforming Jatropha seed oil up to 92% of biodiesel yield.

Green synthesis, characterization of SnO2 3D microbars with surface 2D nanostructures and evaluation of electrical properties of PMMA-SnO2 hybrid nanocomposites

SnO2 3D microbars (L ∼ 10 µm × B ∼ 1 µm x T ∼ 1 µm) distributed with 2D nanostructures (D ∼ 20 - 50 nm x l ∼ few nm) were synthesized by green approach using Plectranthus amboinicus plant extract. Effect of calcination treatments on the morphological changes of both primary microbars and secondary nanostructures were investigated. Dense corrugated networks of secondary particles were observed in the freshly synthesized material. When subjected to a temperature of 200 °C the densely covered particles on the surface, separate to distinct nanostructures. On further rise of temperature up to 400 °C, nanostructure networks break to complete individual nanoparticles, along with mild fragmental damage of particles. Presence of functional groups and bandgap energy levels of 3D/2D SnO2 material was studied using Fourier Transform Infra-Red (FTIR) and UV-Visible (UV-Vis) spectroscopy, respectively. Bandgap energy level of 3.05 eV was observed at 400 °C and 3.06 eV was observed at other two conditions. Structural, morphological and elemental characterization of the material was studied by X-ray diffraction (XRD), Field Emission-Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-ray Analysis (EDAX) spectroscopy. Using Polymethyl methacrylate (PMMA) as matrix and 3D/2D SnO2 as the dispersed filler phase nanocomposite films were prepared. Effect of 3D/2D SnO2 loading on the alternating current (AC) conductivity of the nanocomposite films was investigated. Effect of frequency on AC conductivity, permittivity and loss factor of the composites were reported. The composites exhibited frequency dependent conductivity at lower frequencies and frequency independent conductivity at higher frequencies.

Analytical models for predicting the behavior of the Fukushima fuel debris during laboratory tests and long-term storage

The results of the laboratory-based aging experiments with synthesized fuel debris (simulated corium–concrete compound) are discussed. The tests included dynamic (i.e. with periodic solution renewal) experiments with monoliths of the synthesized fuel debris. At the time scale of the experiments, at a temperature of 25 °C, no evolution in the composition of the leachate debris was observed. At the elevated temperature regime, T = 50, 90 and 120 °C and pH ranges from acid to alkaline condition (pH=4, pH=7, and pH=9), the major chemistry changes that occurs during the leaching were the increase of Si, Al and Ca, as structural elements of the concrete fraction of the debris, while the major elements of the melted fuel matrix, U and Zr, were found in the leachate in trace quantities. The release of Si, Al and Ca, was proved to be non-congruent (Ca and Al releases much faster compared to Si) that corresponds to the basic concept of multioxide silicate dissolution. Such system behavior as well as a number of the chemical interactions between the elements limits the classical chemical thermodynamic and kinetic methods and forced us to use a simplified, semi-empirical, effective approach. The component release rates measured in batch tests were fitted to a proposed diffusion and kinetics model which accounts also for the various pH and temperature conditions. Long-term prediction of the glassy phase dissolution and surface enrichment with a poorly dissolved fuel fraction, (U, Zr)O2, is based on a first-order kinetic model inherited the significant properties of the more detailed lab-scale model. To evaluate the growth kinetics of (U, Zr)O2 layer on debris surface, dissolution rate coefficients from the aging laboratory experiments were used. These coefficients calculated for high-temperature (T = 50 and 90 °C) surface reactions, were extrapolated to low-temperature debris storage conditions via the Arrhenius equation. It was shown, that the aging of debris in a water environment at room temperature and neutral pH under no-flow storage conditions results in the density accumulation of the (U, Zr)O2 product up to several g/m2. At the alkaline condition (pH=9) these values increase about five times. The further rise in temperature results in further intensification of the silica leaching process that may dramatically increase the accumulation amount of (U, Zr)O2.

Electrochemical corrosion of FV520B stainless steel in solutions bearing hydrogen bromide and acetic acid at high temperature from 130 to 200 °C

ABSTRACT FV520B stainless steel is an important material for compression turbine impellers. Its corrosion resistance at high temperatures is critical for the manufacturing and service reliability management of impellers. Therefore, this study investigated the electrochemical corrosion of FV520B stainless steel in an acetic acid solution bearing hydrogen bromine from 130 to 200 °C by potentiodynamic polarisation, electrochemical impedance and corrosion morphology observation. Active corrosion peaks were evident, and the corrosion current densities increased with the increase of the concentration of hydrogen bromine and temperature. However, the breakdown potential first shifted into noble value and then decreased with the further rise in temperature, where the maximum value was at 175 °C. EIS analysis and corrosion morphology revealed that the presence of pitting potential peak is possibly attributed to the competition between the attack of bromine ion and the growth of a surface oxide film under high-temperature water.

Physical and mechanical properties of porcelain tiles made from raw materials in Uganda

This study was intended to determine the physicomechanical properties of porcelain tiles made from raw materials in Uganda, hitherto not used for the same. The raw materials were mixed in proportions of 40–60% clays, 30–40% feldspar and 10–30% sand, the goal was to identify a mixture with properties that meet the ISO 13006 standards after firing. Test tile samples were formulated at a pressure of 40 MPa and fired from 1050 to 1250 °C in steps of 50 °C. A firing rate of 40 °C per minute and a dwell time of 2 h were applied. The microstructures and phase analysis of the fired samples were studied using a scanning electron microscope (SEM) and X-ray diffractometer (XRD), respectively. The XRD analysis revealed mullite and quartz as crystalline phases present in the fired bodies. At 1150 °C, the SEM micrograph depicted few, short and thick mullite fibers. At 1200 °C, the mullite population increased. The nature of the fibers (long, fine and more interlocking) resulted in an increase in flexural strength. A further rise in temperature had no significant change on the nature of the fibers and flexural strength of the samples. The best properties; flexural strength (33 MPa) and water absorption (0.08%) were exhibited at 1200 °C by samples with 30–40% kaolin, 30–40% feldspar, 20% ball clay and 10% sand. The results indicate that these samples are comparable to the ISO 13006 standards for porcelain tiles which are ≥ 35±2 MPa flexural strength and <0.5% water absorption. The other mix proportions did not meet these standards, specifically in terms of flexural strength (<25 MPa).

Comparative studies on strength properties of flyash based geopolymer concrete incorporating ggbs and alccofine subjected to elevated temperature

Geopolymer concrete is a novel material trying to be implemented in the construction field. Efforts being made by the researchers to unfurl the advantages and application of Geopolymer concrete in engineering fields. Geopolymer concrete does not require cement in making and utilizes industrial waste products. Hence replacing the OPC concrete by GPC, we not only reduce the pollution caused by manufacturing cement, but also use calcium, silica and alumina rich industrial waste. It is important to study the performance of GPC subjected to elevated temperature before considering it for structures like industrial buildings, complexes which are vulnerable to fire accidents. Present study investigates the properties like compressive strength, weight loss/gain, and Thermal energy absorption for GPC subjected to elevated temperature from 1000C, 2000C, 4000C, 6000C and 8000C for exposure time of 1hour and 2hours. We compare these properties of GPCs, one made using Flyash and GGBS as binders named FGGPC and the other using Flyash and Alccofine 1203 named FAGPC. From the results we found that strength of GPC increases with the rise in temperature up to 2000C and then rapidly decreases with further rise in temperature. Use of FAGPC is advantageous than using FGGPC on field vulnerable to fire.

Investigation of tribological and functional properties of Cr,Mo-(Cr,Mo)N-(Cr,Mo,Al)N multilayer composite coating

The article describes the investigation of the properties of the Cr,Mo-(Cr,Mo)N-(Cr,Mo,Al)N multilayer composite coating. For the coated sample, the adhesion component fadh of the coefficient of friction increases almost linearly with an increase in temperature from 500 to 700 °C. Then, with a further rise in temperature up to 800 °C, the growth of fadh slows down significantly, and when the temperature rises from 800 to 1000 °C, fadh begins to decrease noticeably. The studies deal with the cutting properties of carbide tools with the coating under study during the cutting of corrosion-resistant AISI 321 at various cutting speeds. The wear pattern on the coating during the cutting was considered. An diffusion layer with the thickness of 20–40 nm was detected during the studies of the elemental and phase compositions in the region of the “tool material–coating” interface. In this layer, the studies revealed the active diffusion of Fe and other steel components into the coating, as well as the diffusion of Mo from the coating into the material being machined in combination with oxidation processes. It was found that during the cutting with the coated tool, the thickness of the diffusion layer was 10–15 times lower compared to that in the uncoated tool. While a certain content of oxygen is detected in the layers on the coating surface, no active formation of the oxides of Al2O3, MoO3, and Cr2O3 was revealed, and the formation of a noticeable amount of Fe2O3 was found in the layers of the material being machined adjacent to the coating surface.

Effect of temperature on equilibria for physical and reactive extraction of protocatechuic acid

Owing to its biological and chemical applications, the separation of protocatechuic acid, a polyphenol compound, is of interest to researchers. Extraction studies with initial acid concentration (0.001–0.01 kmol m−3) using aminic extractant tri-n-octyl amine (TOA) (0.2287 kmol m−3 -1.1436 kmol m−3) in diluent octanol at diverse temperature ranges from 288 K - 313 K was done. Parameters like loading ratio, distribution coefficient, equilibrium complexation constant, diffusion coefficient, number of stages necessary for protocatechuic acid counter-current extraction were obtained; this information is useful in designing a process for the in situ separation of the acid from the fermentation broth as well as from the waste streams. The increase in temperature distribution coefficient was found to increase up to the temperature of 303 K and was found to decrease with a further rise in temperature. The entropy and enthalpy values for the reaction at different temperatures were obtained. The highest extraction of 91.1 % and distribution coefficient of 1.14 were obtained at 313 K for an acid concentration of 0.01 kmol m−3, and TOA concentration of 1.1436 kmol m−3 and 4 stages are required for counter-current extraction process for acquiring the required separation efficiency. Development of 1:1 complex of protocatechuic acid and TOA take place as concluded from the values of the loading ratio.

Effect of sintering parameters on the microstructure and compressive mechanical properties of porous Fe scaffold fabricated using 3D printing and pressure less microwave sintering

The demand for the porous scaffold has been increasing globally in the biomedical field due to numerous advantages over dense structures like high damping capacity, high specific strength, and improved cell integration growth. In the present study, porous iron scaffolds were fabricated using micro-extrusion-based three-dimensional printing and pressureless microwave sintering. For the preparation of samples, metal-based polymeric ink was developed. Thereafter, cylindrical samples were printed and then sintered in a microwave sintering furnace. The experimental investigations were performed to estimate the effect of sintering parameters such as sintering temperature, heating rate and soaking time on the compressive and microstructural property of the fabricated samples. Microstructural characterization was done using the electron backscatter diffraction technique. The experimental observations deduced that the compressive yield strength and apparent density of the sintered sample increased with the increase in sintering temperature and decreased with a further rise in temperature. Moreover, the electron backscatter diffraction analysis unveiled that the high heating rate resulted in the reduction of compressive yield strength due to rapid grain growth. Additionally, the significant effect of soaking time on the compressive mechanical properties was also noticed due to the increase in the grain size diameter. From the X-ray diffraction plot, it was found that there was no contamination present in the fabricated scaffold. In order to evaluate the process capability, a case study was performed wherein the topologically ordered porous structure of iron was fabricated at optimum sintering parameters.

Respiratory Activity of Some Lichen Species–Representatives of Antarctic Flora

Data on the respiratory activity of 12 species of Antarctic lichens are presented. It is found that the respiration of foliose lichens is more intensive than the respiration of fruticose lichens. The O2 uptake rate correlates positively with the nitrogen content in the biomass of thalli and depends on temperature. The thalli O2 uptake rate increased 2.2–2.4 times with a temperature increase from 5 to 15°C. The reaction of respiration upon a further rise in temperature is species-specific. The decrease in the temperature coefficient of respiration (Q10) with a temperature increase to 35°C is most pronounced in the endemic species Usnea aurantiaco-atra, which is well-adapted to Antarctic conditions. The calculations show that, in summer, lichens are able to lose an amount of substrate equivalent to 0.8–1.4% of the thallus dry biomass in respiration daily. The total respiration cost of the lichen maintenance under snow during the winter can reach of 30–35% from their biomass. These results extend our knowledge on Antarctic lichens, and prediction their response to climatic change.

Improving Potato Stress Tolerance and Tuber Yield Under a Climate Change Scenario - A Current Overview.

Global climate change in the form of extreme heat and drought poses a major challenge to sustainable crop production by negatively affecting plant performance and crop yield. Such negative impact on crop yield is likely to be aggravated in future because continued greenhouse gas emissions will cause further rise in temperature leading to increased evapo-transpiration and drought severity, soil salinity as well as insect and disease threats. This has raised a major challenge for plant scientists on securing global food demand, which urges an immediate need to enhance the current yield of major food crops by two-fold to feed the increasing population. As a fourth major food crop, enhancing potato productivity is important for food security of an increasing population. However, potato plant is highly prone to high temperature, drought, soil salinity, as well as insect and diseases. In order to maintain a sustainable potato production, we must adapt our cultivation practices and develop stress tolerant potato cultivars that are appropriately engineered for changing environment. Yet the lack of data on the underlying mechanisms of potato plant resistance to abiotic and biotic stress and the ability to predict future outcomes constitutes a major knowledge gap. It is a challenge for plant scientists to pinpoint means of improving tuber yield under increasing CO2, high temperature and drought stress including the changing patterns of pest and pathogen infestations. Understanding stress-related physiological, biochemical and molecular processes is crucial to develop screening procedures for selecting crop cultivars that can better adapt to changing growth conditions. Elucidation of such mechanism may offer new insights into the identification of specific characteristics that may be useful in breeding new cultivars aimed at maintaining or even enhancing potato yield under changing climate. This paper discusses the recent progress on the mechanism by which potato plants initially sense the changes in their surrounding CO2, temperature, water status, soil salinity and consequently respond to these changes at the molecular, biochemical and physiological levels. We suggest that future research needs to be concentrated on the identification and characterization of signaling molecules and target genes regulating stress tolerance and crop yield potential.

Occurrence and Behavior of Phosphorus‐Bearing Minerals in Metallurgical Coke

The behavior of phosphorus‐bearing minerals is characterized from coking coals to the feed coke and the blast furnace (BF) coke using scanning electron microscope and thermodynamic calculations. In coals, they are represented mostly by apatite (major phase, used for thermodynamic calculations), crandallite, gorceixite, goyazite, monazite and xenotime. Apatite fully transforms to Ca4P2O9 and Ca3P2O8 at coking temperatures. In the samples of BF coke, phosphorus‐bearing phases are 5–30 μm in size. In the case of a closed system (inside pieces of coke, no gas), phosphorus is presented in the BF in the form of Ca4P2O9 and Ca3P2O8 up to 1250 °C. Above this temperature, it is transformed to Fe3P (stable until 1495 °C). A further rise in temperature leads to the transformation of Fe3P to Fe2P (stable up to 1930 °C − tuyere level of the BF). In the case of an open system with intensive flow of BF gas, the formation of Fe3P from Ca4P2O9 and Ca3P2O8 starts at 1178 °C. The Fe2P appears near 1494–1495 °C, and after that it goes to a molten state.

Interface intermixing and interdiffusion characteristics in MOVPE grown spontaneous AlxGa1-xAs/GaAs (100) superlattice structures using high resolution X-ray diffraction

Thermal diffusion characteristics in naturally grown ultra-nanoscale superlattice structures have been studied. In absence of any suitable direct experimental tool due to the physical resolution limit, here we rely on the theoretical analysis of x-ray rocking curve simulations coupled with the diffusion equation to arrive at the diffusion characteristics across the interfaces of spontaneously grown AlxGa1-xAs/AlyGa1-yAs superlattice structures. The simulation approach presented here is a combination of a virtual interdiffusion code and a code on x-ray diffraction. We have obtained the variation in the actual diffusion coefficient as a function of time at different temperatures from the decay rates of the integrated satellite peak intensities. We have also found the diffusion coefficient to be highly nonlinear across the interface with time. The satellite decay equation could fit the experimental data taking the maximum Al composition alone at each time step. The pre exponential factor and the activation enthalpy values for interdiffusion are found out to be 0.17–0.25 cm2/s and 0.5–0.6 eV for Al diffusion whereas 0.01–0.11 cm2/s and 3.45–3.5 eV for Ga diffusion, respectively in the studied temperature range of 500 °C–700 °C. The interdiffusivity increases with temperature from 500 °C to 625 °C and decreases for further rise in temperature as the compositional contrast between the two layers decreases significantly at higher temperatures.

Structural and Thermoelectric Properties of Optically Transparent Thin Films Based on Single-Walled Carbon Nanotubes

Thin films have been produced via a spray method from commercially available single-walled carbon nanotubes (SWCNTs). A SWCNT film thickness has ranged from ~10 to ~80 nm. The SWCNT diameter has accepted values of 1.6–1.8 nm. The existence of SWCNTs longer than 10 μm is established. The optimal thickness of a SWCNT thin film is found to be ~15 nm at which the transmittance exceeds 85%. The specific resistance of SWCNT thin films goes from ~1.5 × 10–3 to ~3 × 10–3 Ohm cm at room temperature. The pioneering study of the temperature dependences of the Seebeck coefficient and surface resistance is performed for this type of SWCNT. A surface resistance is found to increase with rising temperature. Furthermore, the Seebeck coefficient of SWCNT thin films weakly depends on temperature. Its value for all samples is evaluated to be ~40 μV/K. According to the sign of the Seebeck coefficient, thin films exhibit hole-type conductivity. Moreover, the power factor of a 15-nm thin SWCNT-film decreases with a temperature increase to 140◦C from the value of approximately ~120 to ~60 μW m–1 K–2. A further rise in temperature has led to a gain in the power factor.

Thermally induced plasmonic resonance of Cu nanoparticles in fullerene C70 matrix

Nanocomposite of fullerene C70 embedded with Cu nanoparticles is synthesized using thermal co-deposition method. The temperature dependency of SPR and size of Cu nanoparticles are assessed by thermal annealing in inert atmosphere up to a temperature of 350 °C. Rutherford backscattering spectroscopy is performed to assess the thickness of the film and the atomic fraction of Cu metal. The UV-visible absorption spectra on as-deposited and annealed samples reveal that the SPR peak of Cu nanoparticles appears at 300 °C and its evolution with further rise in temperature takes place with a red shift and broadening of the peak at 350 °C. The thermal induced growth of Cu nanoparticles at higher temperature is responsible for the red shift. Raman spectra show the decrease in the intensity of vibrational modes of fullerene C70 with temperature due to breaking of bonds among carbon atoms in fullerene molecules. Transmission electron microscopy confirms the evolution of Cu nanoparticles with bi-modal distribution at 350 °C. Atomic force microscopy is performed to observe the variation in the morphology and roughness of nanocomposite film with temperature. The evolution of Cu nanoparticles and excitation of SPR with temperature makes it an interesting nanocomposite for SPR sensing applications.

Characteristics of acoustic phonon transport and thermal conductance in multi-frame graphene nanoribbons

Using non-equilibrium Green’s function method and maintaining the zigzag carbon chains unchanged, we investigate the transmission rate of acoustic phonon and the reduced thermal conductance through multi-frame graphene nanoribbons (GNRs). The results show that the reduced thermal conductance approaches [Formula: see text] in the limit [Formula: see text]. Due to the fact that only long wavelength acoustic phonons with zero cutoff frequency are excited at such low temperatures, the scattering influence on the long wavelength acoustic phonons by the multi-frame in GNRs can be ignored and these phonons can go through the scattering region perfectly. As the temperature goes up, the reduced thermal conductance decreases. This is because the high-frequency phonons are excited and these high-frequency phonons are scattered easily by the scattering structures. With the further rise in temperature, acoustic phonon modes with the cutoff frequency greater than zero are excited, which leads to a rapid increase of the reduced thermal conductance. This study shows that changing the frame structure by a small length can lead to a significant change of transmission probability. In the higher frequency region, the transmission spectra display complex peak-dip structures, which results from the fact that in higher frequency region more phonon modes are excited and scattered in the middle scattering region with multi-frames, and the scattering phonons are coupled with the incident phonons, with the increase of the length of frame structure, the scattering of the phonon is also enhanced, which leads to the decrease in the phonon transmission; by changing the frame structure, the parameters can effectively adjust the position of low-frequency phonon transmission valley. The frame structure can induce high-frequency phonon blocking effect and the blocking effect depending on the structure parameter of the frame. When the single frame and double frame GNRs are narrowest, the scattering from low-frequency phonons by the scattering structure is largest, which leads to the fact that the reduced thermal conductance is smallest at low temperatures; however, at high temperature, the reduced thermal conductance is biggest when the single frame and double frame GNRs are narrowest. This is because the scattering from high-frequency phonons by the scattering structure is the smallest. When the length of the frame structure is unchanged, a graphite chain is inserted in which the reduced thermal conductance is always reduced. These results provide an effective theoretical basis for designing the thermal transport quantum devices based on GNRs.

Rapid manufacturing of biodegradable pure iron scaffold using amalgamation of three-dimensional printing and pressureless microwave sintering

In the present work, a rapid tooling process using three-dimensional printing and pressureless microwave sintering has been developed for the fabrication of biodegradable pure iron. Carbonyl iron particles were used for sample preparation and phosphate-based investment material was used for mould fabrication. Cylindrical samples were fabricated successfully using the developed rapid tooling process. The fabrication experiments were planned based on response surface methodology to evaluate the effect of microwave sintering parameters, namely sintering temperature, heating rate and soaking time on sintered density, shrinkage and compressive yield strength. The results showed that sintered density and compressive yield strength increased with the rise in sintering temperature from α to γ iron transformation temperature and were found to decrease with further rise in temperature. The shrinkage was found to increase with the increase in sintering temperature. Moreover, with the increase in soaking time and decrease in heating rate, sintered density, shrinkage and compressive yield strength were found to increase. Scanning electron microscopy and the X-ray diffraction plot of the fabricated iron samples showed that even without the application of pressure proper bonding of carbonyl iron particles was achieved. Mould material contamination or oxidation was not evidenced in the experiments. A multi-objective optimization using genetic algorithm was performed to obtain optimum microwave sintering parameters for maximum sintered density as well as compressive strength and minimum shrinkage. A case study on the fabrication of scaffold for human skull was performed to test the efficacy of the developed rapid tooling process.

Thermally enhanced photoluminescence for energy harvesting: from fundamentals to engineering optimization

The radiance of thermal emission, as described by Planck’s law, depends only on the emissivity and temperature of a body, and increases monotonically with the temperature rise at any emitted wavelength. Non-thermal radiation, such as photoluminescence (PL), is a fundamental light–matter interaction that conventionally involves the absorption of an energetic photon, thermalization, and the emission of a redshifted photon. Such a quantum process is governed by rate conservation, which is contingent on the quantum efficiency. In the past, the role of rate conservation for significant thermal excitation had not been studied. Recently, we presented the theory and an experimental demonstration that showed, in contrast to thermal emission, that the PL rate is conserved when the temperature increases while each photon is blueshifted. A further rise in temperature leads to an abrupt transition to thermal emission where the photon rate increases sharply. We also demonstrated how such thermally enhanced PL (TEPL) generates orders of magnitude more energetic photons than thermal emission at similar temperatures. These findings show that TEPL is an ideal optical heat pump that can harvest thermal losses in photovoltaics with a maximal theoretical efficiency of 70%, and practical concepts potentially reaching 45% efficiency. Here we move the TEPL concept onto the engineering level and present Cr:Nd:YAG as device grade PL material, absorbing solar radiation up to 1 μm wavelength and heated by thermalization of energetic photons. Its blueshifted emission, which can match GaAs cells, is 20% of the absorbed power. Based on a detailed balance simulation, such a material coupled with proper photonic management can reach 34% power conversion efficiency. These results raise confidence in the potential of TEPL becoming a disruptive technology in photovoltaics.

Flavour-active compounds in thermally treated yeast extracts.

Aroma-active compounds and non-volatile substances determine the characteristic aroma and taste of yeast extract (YE). Changes in the characteristic aroma and taste of YE due to thermal reaction are rarely studied, and the relationship between aroma-active compounds and non-volatile compounds is not yet clear. Non-volatile compounds identified by HPLC and LC/MS/MS were reduced by a rise in temperature, except for some amino acids. Peptides underwent degradation. In addition, a further rise in temperature above 120 °C resulted in a bitter and sour taste. Furans, pyrazines, thiophenes, thiazoles and some branched chain sulfur compounds were derived from GC/O/MS (SPME and SAFE). Sensory results revealed that the concentration of volatile compounds increased with an increase in temperature. The overall aroma profiles of YE at 25, 100 and 110 °C were buttery, green, nutty and meaty, while YE at 140 °C had a strong sour and sulfur odour. The non-volatile compounds of YE were reduced and different volatile compounds were produced under different thermal treatments. There was a negative correlation between these two types of compounds. The different taste sensors and all precursors were correlated with each other. There are significant relationships between different odorants and aroma-active compounds of YE after thermal treatment. © 2018 Society of Chemical Industry.