A detailed comparative study on the main electrical parameters of Au/n-Si and Au/PVA:Zn/n-Si Schottky barrier diodes

We have fabricated Au/n-Si and Au/PVA:Zn/n-Si Schottky barrier diodes (SBDs) to investigate the effect of organic interfacial layer on the main electrical characteristics. Zn doped poly(vinyl alcohol) (PVA:Zn) was successfully deposited on n-Si substrate by using the electrospinning system and surface morphology of PVA:Zn was presented by SEM images. The current–voltage (I–V) characteristics of these SBDs have been investigated at room temperature. The experimental results show that interfacial layer enhances the device performance in terms of ideality factor (n), zero-bias barrier height (Φ_B0), series resistance (R_s), and shunt resistance (R_sh) with values of 1.38, 0.75 eV, 97.64 Ω, and 203 MΩ whereas those of Au/n-Si SBD are found as 1.65, 0.62 eV, 164.15 Ω and 0.597 MΩ, respectively. Also, this interfacial layer at metal/semiconductor (M/S) interface leads to a decrease in the magnitude of leakage current and density of interface states (N_ss). The values of N_ss range from 1.36×10¹² at E_c—0.569 eV to 1.35×10¹³ eV^?1 cm^?2 at E_c—0.387 eV for Au/PVA:Zn/n-Si SBD and 3.34×10¹² at E_c—0.560 eV to 1.35×10¹³ eV^?1 cm^?2 at E_c—0.424 eV for Au/n-Si SBD. The analysis of experimental results reveals that the existence of PVA:Zn interfacial layer improves the performance of such devices.     

Achieving zT > 1 in Inexpensive Zintl Phase Ca9Zn4+xSb9 by Phase Boundary Mapping

Complex multinary compounds (ternary, quaternary, and higher) offer countless opportunities for discovering new semiconductors for applications such as photovoltaics and thermoelectrics. However, controlling doping has been a major challenge in complex semiconductors as there are many possibilities for charged intrinsic defects (e.g., vacancies, interstitials, antisite defects) whose energy depends on competing impurity phases. Even in compounds with no apparent deviation from a stoichiometric nominal composition, such defects commonly lead to free carrier concentrations in excess of 10²⁰ cm^?3. Nevertheless, by slightly altering the nominal composition, these defect concentrations can be tuned with small variation of the chemical potentials (composition) of each element. While the variation of chemical composition is undetectable, it is shown that the changes can be inferred by mapping (in nominal composition space) the boundaries where different competing impurity phases form. In the inexpensive Zintl compound Ca₉Zn_4+x Sb₉, the carrier concentrations can be finely tuned within three different three‐phase regions by altering the nominal composition (x = 0.2–0.8), enabling the doubling of thermoelectric performance (zT). Because of the low thermal conductivity, the zT can reach as high as 1.1 at 875 K, which is one of the highest among the earth abundant p‐type thermoelectrics with no ion conducting.     

A Hybrid Solar Absorber–Electrocatalytic N‐Doped Carbon/Alloy/Semiconductor Electrode for Localized Photothermic Electrocatalysis

Converting and storing intermittent solar energy into stable chemical fuels of high efficiency depend crucially on harvesting excess energy beyond the conventional ultraviolet light spectrum. The means of applying highly efficient solar–thermal conversion on practical electricity‐driven water splitting could be a significant stride toward this goal, while some bottlenecks remain unresolved. Herein, photothermic electrocatalytic oxygen and hydrogen evolution reactions are proposed, which bestow a distinctive exothermic activation and electrochemical reactivity in a reconstructed electrolyzer system, and which are poised for efficient renewable energy production. Attributed to the synergistic in situ coupling of the N‐doped carbon, metallic alloy and oxides, in view of their broadband light absorption, high electrochemical surface area, and efficient charge transfer attributes, the hybrid photothermal electrocatalytic electrode simultaneously satisfies efficient photon‐to‐heat conversion and augmented electrochemical catalytic activity. Finally, a system level design of an appropriate photothermally mediated electrolytic cell with close‐proximity light‐illumination window along with a low‐thermal‐emittance electrolyte separator that preserve an overall large localized thermal gradient and efficient mass transport is devised. Such a photothermally mediated electrocatalytic system presented here may open up new avenues for the development of solar–thermal energy utilization in other forms.     

Alkyd resins based on waste PET for water-reducible coating applications

Simultaneous glycolysis and neutral hydrolysis of waste PET flakes obtained from grinding post-consumer bottles was carried out in the presence of xylene and an emulsifier at 170 °C. The product was separated from ethylene glycol (EG), water, and xylene by filtration, and was extracted by water at boiling point thrice. The remaining solid was named water insoluble fraction (WIF). The filtrate was cooled to 4 °C, and the crystallized solid obtained by filtration was named water soluble crystallizable fraction (WSCF). These fractions were characterized by acid value (AV) and hydroxyl value (HV) determinations. WSCF and WIF were used for preparation of the water-reducible alkyd resins. Three long oil alkyd resins were prepared from phthalic anhydride (PA; reference alkyd resin) or depolymerization product of the waste PET (PET-based alkyd resin), glycerin (G), fatty acids (FA), and glycol (EG; reference alkyd resin) or depolymerization product of the waste PET (PET-based alkyd resin). Film properties and thermal degradation stabilities of these alkyd resins were investigated. Physical properties (drying times and hardness) and thermal degradation stabilities of the PET-based alkyd resin is better than these properties of the reference alkyd resin.     

Comparison of the mechanical,thermomechanical, thermal,and morphological properties of pumice and calcium carbonate‐filled poly(phenylene sulfide) composites

In this study, it was aimed to investigate the mechanical, thermal, thermomechanical, and morphological properties of pumice and calcium carbonate (CaCO₃)‐filled poly(phenylene sulfide) (PPS) composites and compare the effect of these filler materials on the properties of composites. Mechanical test results indicate that %1 pumice and CaCO₃ addition increased the tensile strength value of PPS. With the %1 loading level of pumice, tensile strain of composites remained unchanged, but for other loading levels of both fillers, tensile strain of composites decreased. Hardness of composites increased with the addition of pumice to PPS matrix for all loading levels of pumice. The lowest damping factor peak intensity was observed for %1 pumice included composites. Morphological analyses results revealed that pumice particles are clearly embedded in the PPS matrix and covered with matrix. On the other hand, there are a number of microvioids that can be observed in the tensile fracture surfaces of CaCO₃‐filled composites. POLYM. COMPOS., 37:3160–3166, 2016. © 2015 Society of Plastics Engineers     

The effect of the wrapped carbon fiber reinforced polymer material on fir and pine woods

The aim of this study is to observe the strength changes of the wood material. The compression and bending strength of the specially wrapped wood materials were investigated. Carbon fiber reinforced polymer (CFRP) material was wrapped onto the wood surface by using a polymer-based glue. The strength ratio of the wrapped and non-wrapped materials was investigated. The specimens were prepared from fir and pine woods that are used widely in buildings. At the same time, two types of woods were compared in terms of strength ratios. As a result of this study, the increase of the compression and three-point bending strength was determined for wrapped CFRP wood materials.     

Pre‐college Electrical Engineering Instruction: The Impact of Abstract vs. Contextualized Representation and Practice on Learning

Background While engineering instructional materials and practice problems for pre‐college students are often presented in the context of real‐life situations, college‐level texts are typically written in abstract form. Purpose (Hypothesis ) The goal of this study was to jointly examine the impact of contextualizing engineering instruction and varying the number of practice opportunities on pre‐college students' learning and learning perceptions. Design/ Method Using a 3 × 2 factorial design, students were randomly assigned to learn about electrical circuit analysis with an instructional program that represented problems in abstract, contextualized, or both forms, either with two practice problems or four practice problems. The abstract problems were devoid of any real‐life context and represented with standard abstract electrical circuit diagrams. The contextualized problems were anchored around real‐life scenarios and represented with life‐like images. The combined contextualized‐abstract condition added abstract circuit diagrams to the contextualized representation. To measure learning, students were given a problem‐solving near‐transfer post‐test. Learning perceptions were measured using a program‐rating survey where students had to rate the instructional program's diagrams, helpfulness, and difficulty. Results Students in the combined contextualized‐abstract condition scored higher on the post‐test, produced better problem representations, and rated the program's diagrams and helpfulness higher than their counterparts. Students who were given two practice problems gave higher program diagram and helpfulness ratings than those given four practice problems. Conclusions These findings suggest that pre‐college engineering instruction should consider anchoring learning in real‐life contexts and providing students with abstract problem representations that can be transferred to a variety of problems.     

Control freaks [induction furnace logic controller]

The induction furnace has been used in a massive range of applications from heating, melting and welding to shrink-fitting, forming, soldering and even plasma physics. Furnaces operate at frequencies between 10 Hz to 60 MHz, and as a result, different power supplies - operating at different frequencies - have also been developed. Induction steel heating furnaces (ISHF) have several advantages in practical applications. However, when a material is heated within an ISHF, its resistivity and magnetic permeability fluctuate, which proves detrimental to the control of power within the furnace. One way to improve power control within an ISHF is to use a programmable logic controller (PLC). Indeed, modern PLCs are modular, affordable, have large memory capacities, and also have special functions such as pulse wave modulation (PWM) and data communication. Using a PLC not only eases position, temperature and pressure control within the ISHF, but also provides overvoltage and overcurrent protection. A new PLC control system design allows heating to take place at constant power while maintaining a steady resonance frequency. The article introduces the system.     

Flame-retardant effects of cyclic phosphonate with HALS and fumed silica in polypropylene

In this study, an N-alkoxy-hindered amine-based UV stabilizing agent (NOR-116) and nanosized silica particles (Aerosil R-972) were combined with a cyclic phosphonate based-flame retardant (FR; PCO-900) and incorporated into polypropylene via melt extrusion in a microcompounder. In order to stimulate the conditions in the favor of further processing such as fiber spinning, the content of additives in polypropylene was kept low (up to 6.5 wt %). The effects of the PCO-900, alone and in combination with NOR-116 and Aerosil-R972, on the flammability and thermal stability of polypropylene were evaluated by limit oxygen index (LOI) tests, cone calorimetry, and thermogravimetric analysis. The proposed system with 3.5 wt % PCO-900/1.5 wt % NOR-116/1 wt % Aerosil-R972 decreased the heat release, increased the LOI and thermo-oxidative stability, and, thus, improved the fire resistance of polypropylene. The possible mode of FR activity was also discussed based on the analysis. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48308.