Organic π-type thermoelectric module supported by photolithographic mold: a working hypothesis of sticky thermoelectric materials

To examine the potential of organic thermoelectrics (TEs) for energy harvesting, we fabricated an organic TE module to achieve 250 mV in the open-circuit voltage which is sufficient to drive a commercially available booster circuit designed for energy harvesting usage. We chose the π-type module structure to maintain the temperature differences in organic TE legs, and then optimized the p- and n-type TE materials’ properties. After injecting the p- and n-type TE materials into photolithographic mold, we eventually achieved 250 mV in the open-circuit voltage by a method to form the upper electrodes. However, we faced a difficulty to reduce the contact resistance in this material system. We conclude that TE materials must be inversely designed from the viewpoints of the expected module structures and mass-production processes, especially for the purpose of energy harvesting.     

Preparation of β-FeSi2 thermoelectric material by laser sintering

Laser sintering has been applied for preparing β-FeSi₂ based thermoelectric alloy for the first time. Effects of laser sintering time on alloying, phase transformation and microstructure of FeSi₂ were investigated by X-ray diffraction (XRD) analysis and scanning electron microscope (SEM). Effects of annealing temperature and time on phase transformation were also studied through Seebeck coefficients. The results show that for 90 s laser-sintered samples, it takes only 15 h to obtain β phase under Ar atmosphere followed by an annealing at 1073 K. These samples exhibit homogeneous microstructure with average grain size of less than 5 μm. A maximum Seebeck coefficient at room temperature could reach 115 μV/K. It indicates that laser sintering could be an alternate faster preparation method to generate high quality β-FeSi₂ thermoelectric material with little contamination due to its advantages of rapid heating rate, high cooling rate and rapid solidification.     

Optimization of the thermoelectric performance of α-MgAgSb-based materials by Zn-doping

Journal of Materials Science - Recently, α-MgAgSb-based materials have proved to be a kind of potential thermoelectric materials around room temperature. Here, a series of Zn-doped...     

Synthesis and characterization of an electro-deposited polyaniline-bismuth telluride nanocomposite — A novel thermoelectric material

The present work consists of synthesis and characterization of a novel thermoelectric material polyaniline (PANI)-bismuth telluride (Bi₂Te₃) nanocomposite using simultaneous electrochemical reactions and deposition method. The inorganic bismuth nitrate has been used as a dopant for polyaniline to achieve high electrical conductivity. A semi-batch mode of operation has been employed to control the rate of deposition of an individual component and thus the molecular architecture of the composite. The electro-deposited composite film on ITO coated glass substrate has been characterized by X-ray diffraction analysis (XRD), FTIR analysis, scanning electron microscope (SEM), and transmission electron microscope (TEM). The microscopic analysis reveals the formation of rod-like nanostructures of diameter less than 100 nm. It has been found that smaller molecules of Bi₂Te₃ are dispersed in the macromolecules of PANI. The nanocomposite has been characterized by thermoelectric power.     

Enhanced thermoelectric properties of Bi₀.₅Sb₁.₅Te₃ films by chemical vapor transport process

Bi?.?Sb?.?Te? films were prepared by a novel chemical vapor transport process through delicate controlling the temperature of the substrate and vapor source. The power factor reaches 30 μW cm?1 K?1 at room temperature, which is much higher than the value of the Bi?.?Sb?.?Te? films prepared by other techniques. The enhancement of thermoelectric properties might be attributed to the higher carrier mobility (252 cm2 V?1 s?1), coming from the effective interparticle contiguity of (00L) oriented nanoplates embedded in the present Bi?.?Sb?.?Te? films.     

Enhanced thermoelectric properties in Co4Sb12 − xTex alloys prepared by HPHT

Skutterudite compounds Co₄Sb_12 ? xTe_x with bcc crystal structure were prepared by high pressure and high temperature (HTHP) method. The study explored chemical doping with Te at the Sb site in an attempt to optimize the thermoelectric figure of merit ZT in the system Co₄Sb_12 ? xTe_x. The electrical resistivities, Seebeck coefficients and thermal conductivities of the samples were measured in the temperature range of 300–710 K. We found that the presence of Te substantially decreased the electrical resistivity without any detrimental effect on the Seebeck coefficients, which improved the power factor. Among all the samples, Co₄Sb_11.5Te_0.5 shows the highest power factor of 35.3 µw/(cmK²) at 710 K, and the maximum ZT value reaches 0.67 at 710 K.     

A Method of Observing Fatigue Crack Growth by SEM

This paper introduces a modified control cir-cuit of static tensile stage of Cambridge S-200SEM.The function of the stage is extended to thatof a tensile/compressive dynamic fatigue testingstage.It can be used for studying fatigue microcharacteristic and crack growth.Direct observa-tions of small crack growth behaviour were carriedout under the SEM with modified stage.Resultsshowed the various stages in the development of acrack.     

A review—Pitting corrosion initiation investigated by TEM

Passive metals have superior resistance to general corrosion but are susceptible to pitting attack in certain aggressive media, leading to material failure with pronounced adverse economic and safety consequences. Over the past decades, the mechanism of pitting corrosion has attracted corrosion community striving to study. However, the mechanism at the pitting initiation stage is still controversy, due to the difficulty encountered in obtaining precise experimental information with enough spatial resolution. Tracking the accurate sites where initial dissolution occurs as well as the propagation of the dissolution by means of multi-scale characterization is key to deciphering the link between microstructure and corrosion at the atomic scale and clarifying the pitting initiation mechanism. Here, we review our recent progresses in this issue by summarizing the results in three representative materials of 316F, and Super 304H stainless steel as well as 2024-Al alloy, using in situ ex-environmental TEM technique.     

Is speeding a "real" antisocial behavior? A comparison with other antisocial behaviors

The relationship between speed and crashes has been well established in the literature, with the consequence that speed reduction through enforced or other means should lead to a reduction in crashes. The extent to which the public regard speeding as a problem that requires enforcement is less clear. Analysis was conducted on public perceptions of antisocial behaviors including speeding traffic. The data was collected as part of the British Crime Survey, a face-to-face interview with UK residents on issues relating to crime. The antisocial behavior section required participants to state the degree to which they perceived 16 antisocial behaviors to be a problem in their area. Results revealed that speeding traffic was perceived as the greatest problem in local communities, regardless of whether respondents were male or female, young, middle aged, or old. The rating of speeding traffic as the greatest problem in the community was replicated in a second, smaller postal survey, where respondents also provided strong support for enforcement on residential roads, and indicated that traveling immediately above the speed limit on residential roads was unacceptable. Results are discussed in relation to practical implications for speed enforcement, and the prioritization of limited police resources.     

Synthesis and thermoelectric properties of filled skutterudite compounds CeyFexCo4?xSb12 by solid state reaction

Filled skutterudite compounds, Ce _y Fe _x Co_4–x Sb₁₂(x= 0–1.0, y= 0–0.15), were synthesized by solid state reaction using Co, Fe, Sb and CeCl₃· nH₂O powders as source materials. The lattice constants of Ce _y Fe _x Co_4–x Sb₁₂increased with increasing substitution of Fe at Co sites and with increasing Ce filling fraction in the Sb-icosahedron voids. All specimens showed p-type conduction. Carrier concentration (p) and electrical conductivity () increased with increasing substitution of Fe at Co sites and decreased with increasing Ce filling fraction. The Seebeck coefficient () decreased with increasing Fe content and increased with increasing Ce filling fraction. Thermal conductivity () decreased with increasing substitution of Fe at Co sites and with increasing Ce filling fraction. A maximum ZTvalue of 0.8 was obtained for Ce_0.12Fe_0.71Co_3.29Sb₁₂at 750 K.     

A Study of AlN Films Prepared by Arc Ion Plating

Hexagonal AlN films have been obtained by arc ion plating at different negative biases ,X-ray diffraction and scanning electron microscopy results show that AlN films with smooth surfaces and (002) preferred orientation are obtained at low biases ,whereas those with coarse surfaces and (100) preferred orientation are obtained at high biases,The formation mechanism of AlN is analyzed and the experiment results are discussed,The effect of bias on adhesion strength has also been examined.     

The heating of polymer composites by electromagnetic induction – A review

Since the late 1980s a small number of research groups have been attracted with the idea of using induction heating technology for the processing of fibre reinforced polymer composites. Induction technology is suitable for the processing of thermoplastic and thermoset polymer materials but requires special susceptor additives (conductive materials) either in the form of structured fibres and fabric or particulate that can transform the electromagnetic energy into heat. This paper aims to summarize the principles of induction heating with respect to polymer composites processing taking a look first at material and equipment based process influences. State of the art applications and research activities are then reviewed, from thermoplastic composite welding, thermoset curing, selective material heating and fast mould heating technologies. Current simulation possibilities and available software tools have also been covered. Finally, some new ideas and possibilities for future developments in the field of polymer composites processing have been discussed.     

The semi-elliptical surface crack—A solution by the alternating method

A numerical solution to the three-dimensional equations of elasticity is presented for the problem of a semi-elliptical surface crack in the surface of a finite thickness solid. The alternating method is used to develop the numerical results which incorporate the effects on the stress intensity factor due to the presence of both the front and the back surfaces. The stress intensity factor is presented as a function of position along the crack border for a variety of crack shapes and crack depths. A comparison of the results of this study is made with previous theoretical and experimental work.

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Résumé Une solution numérique à équations tridimensionnelles d'élasticité est présentée pour le problème de la fissure de surface semi-elliptique située en surface ou en solide d'épaisseurs finies.La méthode proposée est utilisée pour développer des résultats numériques qui incorporent les effets des facteurs d'intensité des contraintes associée à la fois des surfaces recto et verso du solide. Le facteur d'intensité des contraintes est décrit pour diverses positions de la fissure et ce dans divers cas de formes et de profondeurs de fissuration. Une comparaison est faite entre les résultats de cette étude et des travaux théoriques et expérimentaux antérieurs.

     

A microstructural examination of apatite induced by Bioglass® in vitro

Bioglass®, a clinically used bone graft material, has been tested in vitro in a simulated body fluid (SBF) up to four weeks. Apatite crystals were not only found to form on its surface but also in the reaction solutions. The apatite crystals have been examined by high-resolution transmission electron microscopy (TEM). The crystals formed in the solutions appear identical in morphology and structure with those formed on the Bioglass® surface. It may be that the soluble Si in the solution serves as the nucleating site for the apatite crystal or that apatite nuclei are released from the Bioglass® surface to the solution resulting in crystal growth.