Moderate Temperature Range Research Articles

High-performance eco-friendly MnTe thermoelectrics through introducing SnTe nanocrystals and manipulating band structure

Abstract MnTe, which is comprised of earth-abundant and environmentally friendly elements, shows great potential for waste heat recovery in the moderate temperature range. However, its low carrier concentration limits its thermoelectric performance. Here, we achieved ultrahigh thermoelectric performance of MnTe by manipulating band structure and introducing SnTe nanocrystals. We found that incorporation of SnTe exerts a high band convergence in the electronic structure of MnTe, leading to remarkable enhancement of Seebeck coefficient. The Seebeck coefficient was greatly enhanced compared with previously reported doped MnTe. Furthermore, the carrier concentration can be optimized simultaneously by introducing SnTe. The large Seebeck coefficient combined with increased electrical conductivity give rise to high power factor ~1230 μWm−1 K−2. Meanwhile, SnTe nanocrystals help to achieve highly effective phonon scattering leading to markedly reduced lattice thermal conductivity. The proposed novel strategy decouples electron and phonon transport of MnTe, contributing to a record high ZT of ~1.4 at 873 K for the Mn1.06Te-2% SnTe material. Our finding promotes MnTe-based materials as a robust candidate for waste heat recovery at medium temperature.

ZAPP TiAl6V4

Abstract Zapp TiAl6V4 is an alpha-beta titanium alloy that is used in the annealed or solution heat treated and aged condition for applications requiring high strength, relatively low weight, and excellent corrosion resistance. It is typically used in the low to moderate temperature range (up to about 400 °C, or 750 °F). Ti-6Al-4V is the most widely used titanium alloy, accounting for more than 50% of the total titanium used. The aerospace industry accounts for more than 80% of this usage. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Ti-173. Producer or source: Zapp AG.

Impact of Extreme Temperatures on Ambulance Dispatches Due to Cardiovascular Causes in North-West Spain.

Introduction and objectives. The increase in mortality and hospital admissions associated with high and low temperatures is well established. However, less is known about the influence of extreme ambient temperature conditions on cardiovascular ambulance dispatches. This study seeks to evaluate the effects of minimum and maximum daily temperatures on cardiovascular morbidity in the cities of Vigo and A Coruña in North-West Spain, using emergency medical calls during the period 2005–2017. Methods. For the purposes of analysis, we employed a quasi-Poisson time series regression model, within a distributed non-linear lag model by exposure variable and city. The relative risks of cold- and heat-related calls were estimated for each city and temperature model. Results. A total of 70,537 calls were evaluated, most of which were associated with low maximum and minimum temperatures on cold days in both cities. At maximum temperatures, significant cold-related effects were observed at lags of 3–6 days in Vigo and 5–11 days in A Coruña. At minimum temperatures, cold-related effects registered a similar pattern in both cities, with significant relative risks at lags of 4 to 12 days in A Coruña. Heat-related effects did not display a clearly significant pattern. Conclusions. An increase in cardiovascular morbidity is observed with moderately low temperatures without extremes being required to establish an effect. Public health prevention plans and warning systems should consider including moderate temperature range in the prevention of cardiovascular morbidity.

Spatially resolving heterogeneous thermal conductivity of BiCuSeO based thermoelectric nanostructures via scanning thermal microscopy

Oxyselenide BiCuSeO is a promising thermoelectric material in the moderate temperature range, and nanostructuring is often adopted to enhance its thermoelectric properties. In these processes, secondary phases can be either induced inadvertently via doping or intentionally processed through nanocomposites, and their effects on local thermal transport remain unresolved from the experimental point of view. In this Letter, we take Pb-doped BiCuSeO and BiCuSeO embedded with rGO (BiCuSeO-rGO) as examples, and we reveal the effect of the secondary phase on local thermal conduction via quantitative scanning thermal microscopy in combination with finite element simulation. It is found that Pb-doping effectively reduces the thermal conductivity of BiCuSeO, while the rGO secondary phase slightly increases its thermal conductivity. Good quantitative agreement is observed between our nanoscale measurement and bulk values reported in the literature. Our work thus not only offers guidance for tuning the thermal transport properties of BiCuSeO but also provides an effective method to spatially resolve heterogenous thermal conductivity at the nanoscale.

Surface-Bound and Volatile Mo Oxides Produced During Oxidation of Single MoS2 Crystals in Air and High Relative Humidity.

We report on the MoO3 oxides and their derivatives on microscopic 2H MoS2 flakes oxidized in air and high relative humidity at a moderate temperature range below 410 °C. We combine XPS and AFM measurements such as topography, friction, creation of nanoscale ripples and scratches on the MoS2 flakes deposited on Si substrates. We detect MoO3 oxides mostly by measuring selected nanomechanical properties of the MoO3 layer, such as its compressive mechanical stress at the plastic yield. We discuss basal surface coverage of the single MoS2 flakes by the MoO3 oxides. We discuss conditions for appearance of all possible MoO3 oxide derivatives, such as molybdenum(VI) hydroxyoxides and MoO3 hydrates. Our findings agree with an expected mechanistic switch in thermal oxidation in water vapors vs. air.

Probing an intermediate state by X-ray absorption near-edge structure in nickel-doped 2LiBH4–MgH2 reactive hydride composite at moderate temperature

Transition metal nickel (Ni) efficiently provokes an enhanced hydrogen desorption kinetics of the 2LiBH4–MgH2 reactive hydride composite (RHC) system by in-situ formed MgNi3B2. However, the detailed information about the complete evolution process of Ni in the 2LiBH4–MgH2 system is still insufficient and deserves further research. Herein, an interesting phenomenon that inconspicuous exothermic process coupled with unimpressive hydrogen-releasing behavior at a relatively moderate temperature range (150–300 °C) was found in the typical 2LiBH4–MgH2 RHC system when doped with nanosized Ni/C derived from the pyrolysis of MOFs-74-Ni. The X-ray absorption near-edge structure spectra of 2LiBH4–MgH2–15%Ni/C sample under various temperatures confirm that chemical valence of Ni presents a distinct intermediate state. After that, phase analysis indicates that Ni most likely reacts with LiBH4 to form a temporary Ni4B3, and a series of meticulous supplementary data were calculated to identify the authenticity of the proposed assumption. More precisely, the experimental calorific value (15.43 mJ) and hydrogen release capacity (0.47 wt%) are highly consistent with the theoretical calculation value (15.66–15.99 mJ and 0.48 wt%) of the proposed reaction. It is revealed that the Ni4B3 intermediate phase will further transform into catalytic active MgNi3B2 species, which provokes a significantly enhanced kinetic behavior and also high hydrogen storage capacity (above 9.0 wt%) of the 2LiBH4–MgH2 RHC system. Finally, the heterogeneous nucleation mechanism of the MgNi3B2 catalytic active substance is also collaboratively verified through careful scanning electron microscope and high-resolution transmission electron microscopy observations. This work ideally reveals the complete evolution process of Ni in the 2LiBH4–MgH2 RHC system by the detection of a nanosized intermediate state. More importantly, it provides ideas and inspirations for the other nanosized catalytic complex hydride systems.

Temperature and solvent facilitated extrusion based 3D printing for pharmaceuticals

On demand manufacturing of patient-specific oral doses provides significant advantages to patients and healthcare staff. Several 3D printing (3DP) technologies have been proposed as a potential digital alternative to conventional manufacturing of oral tablets. For an additive manufacturing approach to be successful for on-demand preparation, a facile process with minimal preparation steps and training requirements is needed. A novel hybrid approach to the 3D printing process is demonstrated here based on combining both a solvent and heating to facilitate extrusion. The system employed a moderate elevated temperature range (65-100 °C), a brief drying period, and a simple set-up. In this approach, a compact material cylinder is used as a pharmaceutical ink to be extruded in a temperature-controlled metal syringe. The process proved compatible with hygroscopic polymers [Poly(vinyl alcohol (PVA) and polyvinylpyrrolidone (PVP)] and a number of pharmaceutical fillers (lactose, sorbitol and D-mannitol). The fabricated tablets demonstrated acceptable compendial weight and content uniformity as well as mechanical resistance. In vitro drug release of theophylline from 3D printed tablets was dependent on the nature of the polymer and its molecular weight. This reported approach offers significant advantages compared to other 3DP technologies: simplification of pre-product, the use of a moderate temperature range, a minimal drying period, and avoiding the use of mechanically complicated machinery. In the future, we envisage the use of this low-cost and facile approach to fabricate small batches of bespoke tablets.

Evaluation of Mechanical Properties of Titanium Alloy after Thermal Oxidation Process

The presented research work exhibited the experimental outcomes of the thermal oxidation process adopted for the surface modification of titanium alloy grade 2. It revealed the oxidation process kinetics of the titanium substrate within a specified temperature range of 600–800 °C, over time duration of 1/3 h to 72 h. An incremental change in mass of the specimen (titanium grade 2) was observed over an oxidizing temperature of 800 °C. Surface morphology as well as topography of the oxidized surface was investigated gently. Oxide film deposited over titanium substrate was observed to be comparatively larger at 600 °C as compared to 700 °C and 800 °C. Very fine and homogenized oxide particle deposition was observed at comparatively higher temperature. XRD analysis revealed that titanium oxide (TiO2) presented in its crystallized form (rutile) and Ti3O was the prevalent form of oxide at moderate temperature range (600–700 °C), whereas at higher temperature of 800 °C, only rutile form of titanium oxide (TiO2) was observed. After thermal oxidation of titanium alloy, tribological test was performed and it was observed that oxidized surface offered anti-wear strength to the titanium alloy, especially in case of abrasive wear. Volumetric wear reduction from 48% to more than 60% was evaluated for oxidized surface at temperature of 600 °C and 700 °C, respectively.

Vacancy effect of antimony on shear deformation mechanisms of CoSb3 thermoelectric material

Skutterudite CoSb3 is one of the most extensively studied thermoelectric materials in the moderate temperature range, but the easily volatilization of element Sb leads to the vacancy defect as well as the poor mechanical properties of CoSb3. To examine the effect of Sb vacancy on its failure mechanisms, we applied shear loads on defective CoSb3 along (0 0 1)/〈1 0 0〉 slip system by using both density functional theory (DFT) and molecular dynamics (MD) simulations. Both DFT and MD simulation results showed that Sb vacancies can remarkably reduce the mechanical strength of CoSb3. When the Sb vacancy fraction is 4%, the mechanical strength decreases 36% compared with that (7.17 GPa) in flawless CoSb3. Sb vacancies lead to incomplete Sb4-rings and Co-Sb frameworks. This would weaken the local rigidity of the structure, accelerating the breakage of Sb4-rings as well as the slippage of the Co-Sb frameworks. The results provide a perspective for better understanding the vacancy effect on the failure mechanisms of skutterudite CoSb3.

Plant proteases from Carica papaya and Vasconcellea quercifolia with potential application for a cleaner processing in tanneries

In the leather industry, proteases can be used as tools to achieve cleaner technology. In the present study, proteolytic preparations obtained from the latex of Carica papaya (Cp) and Vasconcellea quercifolia (Vq) were assayed as dehairing agents for leather processing. Both Cp and Vq showed activity against substrates representative of collagen, keratin, elastin, and epidermis in a range of moderate temperatures (25 to 55 °C). When comparing with a commercial dehairing enzyme, the activity of Cp and Vq on the substrates representative of epidermis and collagen was of around 70% and 100% of the commercial one, respectively, with that of Cp being more keratinolytic. Both Cp and Vq were able to dehair cowhides at 25 °C for 24 h without adding Ca(OH)2 or Na2S, two harmful pollutants used in conventional dehairing, Cp being more effective than Vq. Scanning electron microscopy microphotographs showed epidermis and hair-free hides with clean pores and without significant damage on the grain surface. Further, no damage was detected in collagen fibres and both Cp and Vq showed a slight opening of collagen fibres. We concluded that both Cp and Vq could be used as tools for a cleaner technology in tanneries, either for lime- and sulphide-free dehairing or for the treatment and valorisation of protein waste.

Infrared optical and thermal properties of microstructures in butterfly wings

While surface microstructures of butterfly wings have been extensively studied for their structural coloration or optical properties within the visible spectrum, their properties in infrared wavelengths with potential ties to thermoregulation are relatively unknown. The midinfrared wavelengths of 7.5 to 14 µm are particularly important for radiative heat transfer in the ambient environment, because of the overlap with the atmospheric transmission window. For instance, a high midinfrared emissivity can facilitate surface cooling, whereas a low midinfrared emissivity can minimize heat loss to surroundings. Here we find that the midinfrared emissivity of butterfly wings from warmer climates such as Archaeoprepona demophoon (Oaxaca, Mexico) and Heliconius sara (Pichincha, Ecuador) is up to 2 times higher than that of butterfly wings from cooler climates such as Celastrina echo (Colorado) and Limenitis arthemis (Florida), using Fourier-transform infrared (FTIR) spectroscopy and infrared thermography. Our optical computations using a unit cell approach reproduce the spectroscopy data and explain how periodic microstructures play a critical role in the midinfrared. The emissivity spectrum governs the temperature of butterfly wings, and we demonstrate that C. echo wings heat up to 8 °C more than A. demophoon wings under the same sunlight in the clear sky of Irvine, CA. Furthermore, our thermal computations show that butterfly wings in their respective habitats can maintain a moderate temperature range through a balance of solar absorption and infrared emission. These findings suggest that the surface microstructures of butterfly wings potentially contribute to thermoregulation and provide an insight into butterflies' survival.

First insights for hydrogen production using an alkaline ceramic through the water-gas shift reaction

• Li 2 CuO 2 was analyzed as multifunctional material in the WGSR. • In the C-WGSR, H 2 production was obtained in a short time range. • The best H 2 production was obtained between 200 and 250 °C in the S-WGSR. • Li 2 CuO 2 acts as hydroxide source, catalyst and/or CO 2 captor. • A high Li 2 CuO 2 regeneration was obtained under O 2 at 700 °C. Hydrogen production was successfully obtained and enriched using lithium cuprate (Li 2 CuO 2 ) as a multifunctional material during the water-gas shift reaction (WGSR). For this propose, water vapor and carbon monoxide reacted consecutively (C-WGSR) or simultaneously (S-WGSR) over the Li 2 CuO 2 particle surface. In both cases, Li 2 CuO 2 functioned as a catalyst, producing H 2 and CO 2 in a moderate temperature range (250–450 °C). In addition, lithium cuprate was able to capture the CO 2 produced in WGSR, enhancing the H 2 purity in the final gas flow. When the consecutive procedure (C-WGSR, first water vapor and then CO) was employee, the best H 2 formation (75%) was obtained at around 250 °C. However, it was limited by the amount of H 2 O previously sorbed on Li 2 CuO 2 surface, proceeding the reaction only in a short period of time (t < 1 min). In the second case S-WGSR, H 2 O vapor and CO were flowed simultaneously at 300 °C, resulting in lower amounts of H 2 (between 30 and 50 %) than in C-WGSR. However, hydrogen production was maintained for longer times (0 < t < 120 min), presenting an important advantage over the consecutive procedure. It must be mentioned that in S-WGSR, the CO 2 chemisorption on the ceramic tended to diminish the H 2 production as Li 2 CO 3 produced through the capture process blocking the H 2 O sorption sites, although the CO continued being totally converted. Further cyclic experiments showed that it was possible to maintain H 2 formation during several consecutive cycles when lithium cuprate regeneration was performed under an oxygen flow at 700 °C. Finally, this work is the first experimental evidence that an alkaline ceramic can act as a functional material to produce a clean energy source, such as hydrogen through the WGSR process at low and moderate temperatures.

Vacancy doping and charge transport in Bi2S3 nanoparticle films for photovoltaic applications

Native point defect doping via thermal treatment is an easy and promising method to tune the electrical transport properties of semiconductors made for renewable-energy conversion. In this study, we investigate the vacancy doping of the lowly toxic semiconductor $\mathrm{B}{\mathrm{i}}_{2}{\mathrm{S}}_{3}$ using electrical conductivity as well as thermoelectric power measurements. We enhance the electrical conductivity of bismuth sulfide nanoparticle layers by more than four orders of magnitude by a stepwise thermal treatment in a moderate temperature range (300--480 K). Via thermoelectric power measurements we attribute this enhancement to an increase in charge-carrier mobility by two orders of magnitude and to an increase in charge-carrier density by more than two orders of magnitude. We find that the energetic position of the electron-doping sulfur vacancies of bismuth sulfide nanoparticles is significantly shallower than previously reported for bulk material. Subsequently, we implement $\mathrm{B}{\mathrm{i}}_{2}{\mathrm{S}}_{3}$ nanoparticles doped with sulfur vacancies by thermal annealing in photovoltaic devices using P3HT as an electron donor molecule. We find that annealing up to 383 K yields the best compromise between improving charge-carrier transport and increasing defect densities.

Oxidation behaviour of a Ge-modified silicide coating on an Nb-Si based alloy in the moderate temperature range

The oxidation characteristics of Ge-modified silicide coating on the Nb-Si based alloy within the moderate temperatures were investigated. Results show that the mass gains of the coated alloys are 0.41, 0.58 and 0.37 mg/cm2 after oxidation at 700 °C, 750 °C and 800 °C for 100 h. There is no pest phenomenon at the test temperatures. The oxide scale is composed of amorphous aluminosilica and SiO2-GeO2 with TiO2 dispersed in some of SiO2-GeO2. The good oxidation resistance of the Ge-modified silicide coating at moderate temperatures is attributed to the selective oxidation of Ti and Si, as well as the formation of glassy SiO2-GeO2.

High-Level Heterologous Expression of Endo-1,4-β-Xylanase from Penicillium citrinum in Pichia pastoris X-33 Directed through Codon Optimization and Optimized Expression.

Most common industrial xylanases are produced from filamentous fungi. In this study, the codon-optimized xynA gene encoding xylanase A from the fungus Penicilium citrinum was successfully synthesized and expressed in the yeast Pichia pastoris. The levels of secreted enzyme activity under the control of glyceraldehyde-3-phosphate dehydrogenase (PGAP) and alcohol oxidase 1 (PAOX1) promoters were compared. The Pc Xyn11A was produced as a soluble protein and the total xylanase activity under the control of PGAP and PAOX1 was 34- and 193-fold, respectively, higher than that produced by the native strain of P. citrinum. The Pc Xyn11A produced under the control of the PAOX1 reached a maximum activity of 676 U/mL when induced with 1% (v/v) methanol every 24 h for 5 days. The xylanase was purified by ion exchange chromatography and then characterized. The enzyme was optimally active at 55 °C and pH 5.0 but stable over a broad pH range (3.0–9.0), retaining more than 80% of the original activity after 24 h or after pre-incubation at 40 °C for 1 h. With birchwood xylan as a substrate, Pc Xyn11A showed a Km(app) of 2.8 mg/mL, and a kcat of 243 s−1. The high level of secretion of Pc Xyn11A and its stability over a wide range of pH and moderate temperatures could make it useful for a variety of biotechnological applications.

Influence of Humidity on NO2-Sensing and Selectivity of Spray-CVD Grown ZnO Thin Film above 400 °C

Thin films are being used more and more in gas sensing applications, relying on their high surface area to volume ratio. In this study, ZnO thin film was produced through a thermal aerosol spraying and chemical vapor deposition (spray-CVD) process at 500 °C using zinc acetate as a precursor. The phase identification and the morphologies of the film were investigated by XRD and SEM, respectively. Gas-sensing properties of the ZnO thin film were evaluated toward NO2, CO, and NO at a moderate temperature range (400–500 °C) in dry and humid air (relative humidity = 2.5, 5, 7.5, and 10% RH). The obtained results show good sensor signal for both NO2 (ΔR/R0 = 94%) and CO (92%) and poor sensor signal to NO (52%) at an optimum temperature of 450 °C in dry air. The response and recovery times decrease with the increase of NO2 concentration. In the presence of humidity (10% of RH), the sensor is more than twice as sensitive to NO2 (70%) as CO (29%), and accordingly, exhibits good selectivity toward NO2. As the amount of humidity increases from 2.5 to 10% RH, the selectivity ratio of ZnO thin film to NO2 against CO increases from 1 to 2.4. It was also observed that the response and the recovery rates decrease with the increase of relative humidity. The significant enhancement of the selectivity of ZnO thin film toward NO2 in the presence of humidity was attributed to the strong affinity of OH species with NO2.

Particle current rectification in a quasi-periodic double-stranded ladder

We report transport properties and particle current rectification operation in a double-stranded tight-binding ladder network within non-equilibrium Green’s function formalism that can easily be generalized in multi-stranded systems. First, we explore the rectification operation considering the model of an artificial double-stranded DNA molecular system with Fibonacci type substitutional sequence. Substitutional sequences form quasi-periodic potentials. This analysis may shed new light in designing efficient nanoscale rectifier. It can also be directly implemented to different biomolecular systems like nucleic acids and most proteins as they follow quasi-periodic orders. Motivated with this fact, we consider different configurations depending on the choices of on-site energies and/or inter or intra strand nearest-neighbor hopping integrals in the form of Aubry–André–Harper (AAH) model (that also obeys quasi-periodic order), and in all the cases we find almost current rectification even at very low bias region. Along with this, we observe that the phase (positive or negative) of rectification can suitably be engineered by tuning the Fermi energy and AAH phase. The effects of electron–electron (e–e) interaction and temperature are also studied, which show that a reasonably large rectification can be observed even for moderate temperature range and e–e interaction strength.

Chlorine removal from MSWI fly ash by thermal treatment: Effects of iron/aluminum additives

The high content of alkali chlorides in municipal solid waste incineration (MSWI) fly ash limit its resource reuse due to the potential environmental risks. In this paper, with superheated steam as the gasifying agent and inducer, chlorides in fly ash were removed by thermal treatment within a moderate temperature range. Thermal treatment experiments were performed under different conditions: temperature (500–800°C), steam addition (mass ratio of steam to fly ash = 0.25–1) and residence time (0.5–3 hr). Iron and aluminum powders were added to fly ash to improve the chlorine removal efficiency. Water-soluble chlorides included NaCl and KCl, and insoluble chlorides mainly included Ca(OH)Cl. The heating process with the addition of water steam was more efficient than that without steam in terms of the removal performance of water-soluble chlorides. The removal efficiency of soluble chlorides reached 75.25% for a mass ratio of 1:1 after 1-hr thermal treatment at 700°C. When the residence time was increased above 1 hr, the total dechlorination efficiency was not increased dramatically. Moreover, adding iron and aluminum powder into the fly ash improved the removal of water-insoluble chlorides, and the total dechlorination efficiency was increased by 11.41%–16.64%.

Advanced photovoltaic thermal collectors

The solar irradiance received by the solar cell is partially lost as heat, which carries negative effect on its voltage and in turn, its generated power. This trapped heat within the photovoltaic module is considered waste energy. Hence, techniques to extract this heat to utilize it for thermal loads, such as water heating or drying, are presented throughout the literature. Most prominent technique is the hybrid photovoltaic thermal collector. This device will serve in cooling the solar cell and hence improving its efficiency during operation. Meanwhile, it will absorb the heat and transfer it into a working fluid. The fluid could be utilized directly or indirectly for thermal loads in moderate and low temperature range applications. The type of working fluid highly affects the photovoltaic thermal performance and its physical design. This paper tracks the development of working fluids and analyzes highly efficient photovoltaic thermals from the literature. Moreover, a lengthy discussion on state-of-the-art photovoltaic thermal systems is presented and recommendations for future works are listed as well.

The enhancement of thermoelectric performance of p-type Li doped Mg2Ge0.4Sn0.6 by Si addition

Mg2(Ge, Sn) solid solutions are eco-friendly thermoelectric materials in moderate temperature (500–800 K) range. However, p-type Mg2(Ge, Sn) solid solutions show poor thermoelectric performance compared to the n-type counterpart. In this work, the filtering of low energy holes and the blocking of thermal excited electrons in Mg1.92Li0.08 Ge0.4Sn0.6 by Si addition are demonstrated, which optimize the power factor by interface barrier and reduce the lattice thermal conductivity by nanoscale composition fluctuation. Finally, the power factor of ~1.85 × 10−3 Wm−1 K−2 and the dimensionless figure of merit ZT ~0.75 are achieved in Li doped Mg2Ge0.4Sn0.6 with Si addition at 723 K.