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By Sung Wng Kim

The binary antimonide compounds with the skutterudite structure have a potential for thermoelectric applications because of the high carrier mobility, high thermoelectric power, and relatively low thermal conductivity due to the complex crystal structure. However, the room temperature thermal conductivity of these skutterudite materials is as high as about IOW/mK with an estimated 80-90% contribution from the lattice thermal conductivity. Because the lattice thermal conductivity of related ternary skutterudite compounds can be substantially reduced due to the additional phonon scattering, a study of thermoelectric properties of these compounds is of interest. The binary IrSb3, ternary Ir1.xRuxSb3 and Ir(MxSb1.x)3(M=Ge, Sn) compounds were prepared by hot pressing of pre-reacted powders. We have measured the electrical resistivity, thermoelectric power, and thermal conductivity, in a temperature range from room temperature to 973K. The binary IrSb3 compound is found to have P-type electrical properties exhibiting a good Seebeck coefficient (up to 225µV/K around 773K), electrical resistivity(5x10-5Ohm M around 933K), and relatively low thermal conductivity(6W/mK around 950K). The lattice thermal conductivity, K[2] was calculated from the Wiedemann-Franz relationship.

Jan 1, 2002

By Paul Foote

SEEBECK discovered, in 1821, that if, in a closed circuit of two metals the two junctions are at different temperatures, an electric current will flow in the circuit. In the case of an iron and a copper wire, for example, current will flow from copper to iron at the hot junction, or from iron to copper at the cold junction. Two factors combine to cause the current. An electromotive force exists between the two metals, the magnitude of which, depends upon the temperature and upon the metals; this is called the Peltier e.m.f. If a single wire of homogeneous material is heated at one end, an electromotive force is developed between the ends of the wire, the magnitude of which depends upon the metal and upon the difference in temperature; this is known as the Thomson e.m.f: The total e.m.f. acting in the circuit is the sum of the Peltier e.m.f. at the two junctions and the Thomson e.m.f. in each wire, consideration being given, of course, to the algebraic signs of the four e.m.f.'s. The total electromotive force thus depends upon the difference in temperature of the two

Jan 9, 1919

J. T. LITTLETON, JR., ? Corning, N. Y. (written discussion?).-This. discussion will add little that has not been brought out but will show how the problems encountered in the Corning Glass Works were overcome. The chief points of consideration in any equipment are, first, the work the equipment is called upon to do; second, the installation; and, third, the man who will use it. These three points should determine the type of apparatus adopted. If only rough measurements, merely a little better than the eye, are desired, the cost of the instruments should be considered; but if accurate temperature control is necessary, the cost of the equipment deserves only small consideration. There is no question that the real problem for any factory is the installation, making sure that the elements really give the temperatures desired; also, the instruments must be so designed that any man can use them.

Jan 12, 1919

C. H. WILSON,* New York, N. Y. (written discussion?).-On page 2680, under the heading Junction Box and Zone Box, the authors say, with reference to the zone-box principle of connections between primary couple, compensator couple, and copper leads, which method in its appli-cation to a single couple is shown in Fig. 34, that if this principle is adopted for a multiple installation, so as to save compensating leads; a selective switch may be (and the inference is that it must be) inserted between the zone box and the different couples, putting the switch at an inconvenient point, or putting up with some complicated interlacing of connections.. Wilson-Maeulen Co. has employed the zone-box method extensively for several years and in none of the many multiple installa-tions has either of those alternatives been resorted to. Instead there has been used a method of wiring with the switch at the indicator and involv-ing no more complications than the junction-box method shown III

Jan 11, 1919

By Douglas M. Matson, Rongbiao Gu, Christopher San Marchi, Anil Saigal

"Hydrogen embrittles most structural metals, although the form and magnitude of embrittlement depends on the source of the hydrogen as well as the stress in the metal. Hydrogen fuel cell systems typically store gaseous hydrogen fuel at high-pressure, which provides both a source of hydrogen and high stresses in the containment materials. Understanding and measuring the effects of hydrogen on the mechanical properties of common structural metals, especially fatigue properties, is important for safe, long-term operation of such systems. This work explores the use of thermography to efficiently and quantitatively evaluate hydrogen-assisted fatigue of type 304 austenitic stainless steel. In particular, thermographic analysis was used with rotating-beam fatigue testing and shown to provide repeatable results which are in general independent of test cycle frequency while reducing test times by several orders of magnitude. The effects of hydrogen were studied by thermally precharging fatigue test specimens in gaseous hydrogen prior to thermography-assisted fatigue testing and then compared to testing of non-charged specimens. Hydrogen-precharging increased the strength of this type 304 austenitic stainless steel and increased the fatigue life by a factor of about 50-100.IntroductionThe world is facing a severe energy and environmental challenge: how to provide competitive and clean energy for its citizens in light of an escalating global energy demand and concerns over energy supply security, climate change and local air pollution. As a carbon-free energy carrier, hydrogen provides a promising vector for storing and distributing renewable energy. Hydrogen is an important industrial gas that is used extensively in many industries. However, with growing demand for clean energy, hydrogen fuel cell systems are being developed for use in consumer products, such as fuel cell vehicles, which changes the landscape for safe design of high-pressure gaseous hydrogen systems."

Jan 1, 2012

By Qingyun Huang, Wei Lv, Junyi Xiang, Xuewei Lv, Chenguang Bai

The roasting is the key step for the extraction of vanadium from vanadium slag by calcification roasting–acid leaching process. In this study, thermogravimetric analysis and kinetic study of vanadium slag in the presence of calcium oxide was investigated. The maximum oxidation degree was slightly increased by increasing temperature from 700 to 900 °C then almost unchanged further increasing temperature to 1000 °C. The reaction mechanism was analyzed through both Sharp method and ln-ln method. Results showed that the mechanism the reaction in the a range of 0.1–0.8 corresponded to the random nucleation and subsequent growth, as represented as (G( a)=[ −ln(1−a)] 1/3 = kt. The apparent activation energy was calculated to be 3.5 kJ/mol according to Arrhenius equation.

Mar 1, 2018

By Qiang Zhong, Qian Li, Yongbin Yang, Tao Jiang

Thermogravimetric analysis (TGA) has been used to research the pyrolysis and combustion processes of coal used in rotary kiln of iron ore oxide pellet. Furthermore, the effects of air flow and oxygen concentration on the combustion behavior of coal were examined with TGA. The results showed that two individual stages can be distinguished for the pyrolysis of coal, the water evaporation stage and the de-volatilization stage. And the information on ignition and burnout characteristics can be obtained from the combustion process analyzed by TGA. Large air flow almost has no effect to the combustion process except that it enhances combustion intensity. However, the combustion process is further accelerated under oxygen-enriched conditions. With all experimental results, it could provide an attractive approach of analyzing coal for the rotary kiln process.

Jan 1, 2016

By Chengyi Ding, Yangyang Xie, Xuewei Lv, Senwei Xuan, Chenguang Bai, Kai Tang, Gang Li

Dicalcium ferrite (2CaOFe2O3, C2F) is one of the most significant bonding phase of fluxed sinters. Reduction of C2F was investigated via thermal kinetics analysis. The isothermal reduction behavior of C2F by 30% H2 and 70% N2 at 1123 K (850 °C), 1173 K (900 °C), and 1223 K (950 °C) were discussed by thermogravimetric analysis in this paper. The results revealed that the C2F reduction was typical one-step reaction. The apparent activation energy of the C2F reduction was 27.40 kJ/mol. The rate-determining steps of the C2F reduction were the first inner gas diffusion, then the inner gas diffusion and interface chemical reaction mixed controlling. The ln-ln analysis implied that the C2F reduction was described by the Avrami–Erofeev (A-E) equation, thus appeared as a 2D A-E equation kinetics reaction.

Mar 1, 2018

By M. J. Makhula, R. M. S. Falcon, S. O. Bada, L. M. Falcon

"SynopsisThe combustion and co-combustion behaviour of macadamia nut shell, high-ash coal, and anthracite, along with their blends was studied using thermogravimetry. The reactivities of all samples were analysed in air, oxygen, and CO2 atmospheres and at different heating rates from 10 to 40°C/min. Macadamia shell was found to have a lower ash content, 0.36%, than coal with 27.49% ash. The calorific values were similar, 19.64 MJ/kg and 19.44 MJ/kg respectively. The differential thermogravimetric results indicate that as the heating rates increase the ignition, peak, and burnout temperatures increase significantly, leading to high combustion rates. The interaction between the fuels was evaluated using the weighted average model, and the results indicated that there is more synergetic interaction between 20% macadamia plus 80% coal under oxygen than in air and CO2 atmospheres. The results of the investigation provide the combustion and co-combustion characteristics of various samples and their blends and indicate their combustion compatibilities. IntroductionThe global macadamia nut industry is developing at a very rapid rate. South Africa is currently the world’s third largest producer, with a production of about 35 000 t as of 2012 (Department of Agriculture, Forestry and Fisheries, 2013), compared to 840 t produced in 1996. The greatest numbers of the macadamia nut farms in South Africa can be found in Mpumalanga, Limpopo, and KwaZulu-Natal provinces, with Mpumalanga as the largest producing area. There are many factors influencing the increased demand for macadamia nuts, the most important factor perhaps being their nutritional value (California Dried Fruit and Nuts, 2011; MPC, 2014) and their suitability as a feedstock for manufacturing cosmetics, bakery products, nut paste, chocolates, sauces, and ice-cream. As a fuel, macadamia shell has a high heating value ‘as-fired’ of about 20.71 MJ/kg (Vhathvarothai et al., 2013), which could in turn be used in drying the nust, and the shell could also be milled and applied as a fertilizer."

Jan 1, 2015

By I. Iwasaki, R. Titi-Manyaka

Thermogravimetric analyses were used to formulate the chlorination and chloridization behaviors of such metals as iron, manganese, copper, tin, nickel, and zinc and their oxides; of lime and magnesia; and of such minerals as calcite, siderite, rhodochrosite, rhodonite, and apatite- all commonly encountered in ironmaking raw materials. Complexities of the reaction steps involved were indicated by plotting thermogravimetric analysis curves and the possible mechanisms were discussed based on the theoretical weight changes and thermodynamic considerations. The relative effectiveness of chlorine and hydrogen chloride as chloridizing agents was considered in the light of the experimental results.

Jan 1, 1973

By I. Iwasaki, K. Adam

The oxidation behaviors of simple and complex chloride systems of copper, iron, nickel, cobalt, and manganese in a stream of oxygen were investigated using a thermogravimetric analysis technique. Their reaction mechanisms are discussed from stoichiometry, thermodynamic feasibility, and X-ray diffraction analysis of reaction products. The results are used to determine an optimum operating temperature of the selective oxidation step in a chlorination process for producing nonferrous metal chlorides, elemental sulfur, and ferric oxide from copper-nickel sulfide flotation concentrates.

Jan 1, 1985

By T. Yegulalp, R. Farrauto, A. Belova, M. Castaldi

Calcium oxide, with its ability to capture and store carbon dioxide, is emerging to become an important tool in carbon management. Calcium oxide can be used reversibly to capture carbon dioxide in situ and then be regenerated to produce a pure stream of carbon dioxide ready for sequestration; the Zero Emission Coal Alliance technology utilizes this property of calcium oxide to generate emissions-free electric power from coal. The reaction of calcium oxide with carbon dioxide resulting in thermodynamically stable carbonate is well understood; however, the efficiency of this reaction is limited by the diffusion of gases through bulk calcium oxide and through a layer of carbonate formed on the surface. In addition, the regeneration of calcium oxide is an endothermic reaction and is favored at high temperatures. The purpose of this paper is twofold: first, to address the diffusion limitation, a thin layer of calcium oxide, supported on a high surface area material, is studied thermogravimetrically to demonstrate the physical adsorption of carbon dioxide on calcium oxide. The adsorption is to take place at temperatures lower than required to form calcium carbonate.

Jan 1, 2007

By Jhon Cuya

Titanium dioxide is the well-known catalyst for the photodecomposition of water in UV region and its nanoparticles show better performance than its bulk materials. Furthermore, partially sulfurized TiO2 is expected to be chemically stable and have an enhanced photocatalytic activity compared with TiO2. For this purpose, the sulfurization behavior of TiO2 nanoparticles was thermogravimetically (TG) studied by a thermo-balance with a quartz spring using CS2. From the TG curve of TiO2 nanoparticles, first, the weight decrease appeared down to around 8 wt% and then sulfurization reaction started at around 500 °C at heating rate of 1O 'Cumin. The weight increase curve showed a maximum of ca 30 wt% at around 750 T and then gradually decreased to ca 12w% at 1000OC. This would be caused by the formation of TiS2 followed by the decomposition of TiS2 to lower sulfides, such as Til.08S2 and Ti3S4. From the comparison of the sulfurization of TiO2 nanpparticles with that of anatase, rutile and Ti(OH)4, it was found that TiO2 nanoparticles showed a similar behavior to that of Ti(OH)4.

Jan 1, 2003

By Jhon Cuya

Titanium dioxide is the well-known catalyst for the photodecomposition of water in UV region and its nanoparticles show better performance than its bulk materials. Furthermore, partially sulfurized TiO2 is expected to be chemically stable and have an enhanced photocatalytic activity compared with TiO2. For this purpose, the sulfurization behavior ofTiO2 nanopartic1es was thermogravimetrically (TG) studied by a thermo-balance with a quartz spring using CS2. From the TG curve of TiO2 nanopartic1es, first, the weight decrease appeared down to around 8 wt% and then sulfurization reaction started at around 500°C at a heating rate of 1 C°/min. The weight increase curve showed a maximum of ca 30 wt% at around 750°?C and then gradually decreased to ca 12 wt% at 1000°C. This would be caused by the formation of TiS2 followed by the decomposition ofTiS2 to lower sulfides, such as Tit.0.8S2 and Ti3S4. From the comparison of the sulfurization of TiO2 nanoparticles with that of anatase, rutile and Ti(OH)4, it was found that TiO2 nanoparticles showed a similar behavior to that of Ti(OH)4.

Jan 1, 2003

By J. F. Elliott

The thermodynamic behavior of sulfur and oxygen in copper matte has been measured by equilibration of the melt 00 a gas consisting of CO, SO2 and Ar. The oxygen potential ranges from 10-9 to 10-7 and that for sulfur from 10-4 to 10-2 atm. The work is a continuation of the earlier study by Luraschi and Elliott in our laboratory. A model has been developed that permits extra-polation of the results to ascertain compositions of the matte that are saturated with various oxides of iron.

Jan 1, 1983

By Ypma PJM

The Westmoreland uranium deposits occur on the northern flank of the Murphy Tectonic Ridge in the upper member of the Westmoreland Conglom- erate. Uranium mineralization is spatially associated with the contact of the overlying basaltic Siegal Volcanics and the margins of in- trusive dolerite dykes which are geochemically similar to the Siegal Volcanics. Thermoluminescence (TL) measurements on 800 samples from within the orebodies and surr- ounding host rock (up to 8 kilometres away from the deposits) have indicated that all of the Westmoreland Conglomerate has suffered major radiation damagg attributable to at least 10 ppm uranium over 10 years. The underlying rhyolitic Mid Proterozoic Cliffdale Volcanics have distinctive TL glow curves indicative of radiation sensitization caused by high uranium contents. These vol- canics are part of the Mid Proterozoic volcanic event known to be enriched in uranium. The Westmoreland Conglomerate has been derived by erosion of the uranium-rich Cliffdale Volcanics and associated Nicholson Granite Complex which makes it likely that the Westmoreland Conglom- erate had a high inherent uranium content.

Jan 1, 1984

By D J. McDougall

Due to changes in the solid-state conditions of minerals in the rocks surrounding hydrothermal, contact meta-somatic or metamorphosed ore deposits, positive or negative thermoluminescent anomalies may be found in their vicinity. Several types of equipment which can be used for both quantitative and semi-quantitative measurements of the emission are discussed and compared. Methods of selecting, preparing and testing samples to ensure reproducible results are outlined, along with the kind of data which can be obtained from different types of equipment. The normal thermoluminescence of rock-forming min~ erals in the common rock types is noted, and variations in the solid-state conditions in the wall rocks which will cause marked increases or decreases of true thermoluminescence are outlined, as well as the thermolum-nescence-like emissions which are present in the vicinity of ore deposits. Introduction T HERMOLUMINESCENCE occurs when certain crystalline materials are heated to temperatures ranging between 180' and 400°C. The light emission can be ascribed to the release of electrons metastably trapped within the crystal lattice, with peak emissions taking place at temperatures which are more or less specific for a particular set of traps; the area under

Jan 1, 1965

By Charles A. Schacht

"Relining, lining maintenance, and ladle repair can represent a significant cost in steelmaking. Therefore, the objective of all steelmaking shops is to minimize this cost and to maximize the lining life. However, the thermomechanical behaviour of the ladle lining is highly complicated and sometimes misunderstood. The ladle design also has a significant influence on lining life. Other factors which have a direct influence on lining life are the shop lining installation practices and manner in which the ladle is used. The objective of this paper is to provide an understanding of the impact of these factors as related to improving the integrity of the lining and increasing lining life.Fundamentals of Steelmaking Ladle Lining Expansion ForcesNumerous studies have been conducted by the author on steelmaking ladles with molten metal capacities ranging from 110 ton s to 350 tons. The steelmaking ladle typically has a sidewall plate with a slight taper and for analytical purposes can be classified as a cylindrical vessel.A typical ladle is described in Figure I. The ladle sidewall lining usually consists of a working lining and a safety lining. Although the type of refractory used in the working lining varies based on the type of steel produced and other metallurgical requirements, the refractories typically used are: 70% alumina brick; direct bond mag-chrome brick; resin bond dolomite brick; and direct bond dolomite brick. Fireclay brick, high alumina brick, or a similar strength brick is used as the safety lining.Normally, the ladle lining is exposed to a through-thickness temperature gradient and restrained by the ladle sidewall plate, is described in Figure 2. The hot face side of the refractory lining develops a compressive thermal force and the ladle sidewall plate develops an equilibrating tensile force. The radial joints open on the cold side of the working lining as the lining joints have little or no tensile strength. A radial compressive load (P) develops between the working lining and the vessel shell due to the thermal restraint imposed on the lining by the shell. The radial compressive load is transferred from the working lining through the safety lining onto the ladle sidewall. Therefore, the safety lining must have the strength to accommodate the radial compressive load (P)."

Jan 1, 1991

By Paul F. Gnirk, Ralph A. Wagner, Joe L. Ratigan

This thermomechanical analysis used the finite element method to investigate the behavior of crushed salt backfill in a waste disposal room situated in a salt dome repository. The first of two objectives was to determine the transient temperature rise and degree of thermomechanical consolidation that occur in the backfill as a function of drillhole depths. The second objective involved the evaluation of closure due to salt creep of unlined emplacement drillholes and the determination of pressure on steel sleeve liners in the drillholes should liners become necessary for canister retrieval. The retrievability period was considered to extend for 25 years after waste emplacement. The canisters were assumed to contain ten-year old high level waste with a thermal output of 4.3 kW at the time of emplacement.

Jan 1, 1981

By M. Boussuge

Ceramics and refractories have many common constituents and consecutively exhibit several analogous properties. For example, concerning the thermomechanical properties this paper will focus on, the type of creep that can be observed in both materials is often the same (kinematic hardening). Changes in microstructure (phase transformation, dehydration, sintering, crystallisation,...), induced by heating and/or cooling, can also drastically modify the mechanical behaviour of ceramics and refractories. But the coarse granulates, the porosity and the impurities contained in industrial refractories may lead to specific responses of this material to thermal and/or mechanical loadings. In particular, some differences can be observed with technical ceramics in the main type of damage observed in service : diffuse damage in refractories (microcracking) and localised damage in ceramics (macrocracking). In this paper, the possibilities of transferring a part of knowledge from ceramics to refractories will be discussed, in the field of thermomechanical properties : experimental characterization techniques, mechanical behaviour models. Finally, some problems caused by scale effects and by the integration of thermomechanical properties of refractories in the numerical simulation of industrial structures will be evoked.

Jan 1, 2004