Radon exhalation rate measurement in the environment of Hassan district of southern India

The radon exhalation rate from soil and building materials collected from the Hassan district of southern India was studied by the sealed can technique. The surface exhalation rates of the building materials were found to vary from 13.07 ± 0.19 to 430 ± 9 mBq m^–2 h^–1 with a mean value of 141 ± 4 mBq m^–2 h^–1. The surface exhalation rates of the soil samples were found to vary from 36.5 ± 0.8 mBq m^–2 h^–1 to 376 ± 7 mBq m^–2 h^–1 with a mean value of 140 ± 4 mBq m^–2 h^–1. Good positive correlation was observed between the effective radium content and radon exhalation rate for both soil and building materials. Annual effective dose and α-index have also been estimated for the population of the region.     

Effect of moisture on the radon exhalation rate from soil, sand and brick samples collected from NWFP and FATA, Pakistan

A series of experiments were carried out to study the effectof the moisture content on the radon exhalation rate from soil,sand and brick samples that were collected from the North WestFrontier Province and Federally Administered Tribal Areas ofPakistan, using CR-39-based radon dosimeters. After processing,samples were prepared by adding 15, 30 and 45% moisture contents(by weight) and were placed in plastic containers. The dosimeterswere installed in it at heights of 25 cm above the surface ofthe samples. These containers were then hermetically sealedand the dosimeters were exposed to radon for 60 to 65 days.After exposure, CR-39 detectors were etched in 25% NaOH at 80°Cfor 16 h, and track densities were counted. From the measuredtrack densities, exhalation rate was determined using two differentapproaches. Maximum average radon exhalation rates of 385 ±86, 393 ± 31 and 362 ± 36 mBq m^–2 h^–1were observed at 30% moisture content from soil, sand and bricksamples, respectively. A slight decrease in exhalation ratewas observed in all samples at moisture content of 45%. Accordingto the t-test, change in the exhalation rate as a function ofhumidity is significant at 95% confidence level.     

Time-dependent mechanical properties of high-strength cements

A high-strength cement paste based on aluminous cement with the addition of water-soluble polymer was found to have a flexural strength which increased at about 12 MPa per decade increase in strain rate over the range 10⁻⁶ to 10⁻² sec⁻¹. The effect of soaking in water was to markedly reduce the strength. Swelling occurred on soaking in water for both Portland and aluminous cement-based pastes but was more gradual for the latter. Wetting swelling and drying shrinkage increased with polymer content for Portland-based pastes. Creep and stress relaxation in one type of Portland cement-based paste and in aluminous cement-based paste were markedly increased by soaking, but in a second type of Portland-based paste there was little effect. These effects are attributed to the polymer content of the pastes and its distribution in the pastes.     

Hot deformation behavior of Ti-15-3 titanium alloy: a study using processing maps,activation energy map,and Zener–Hollomon parameter map

The hot deformation behavior of Ti-15-3 titanium alloy was investigated by hot compression tests conducted in the temperature range 850–1150 °C and strain rate range 0.001–10 s⁻¹. Using the flow stress data corrected for deformation heating, the activation energy map, processing maps and Zener–Hollomon parameter map were developed to determine the optimum hot-working parameters and to investigate the effects of strain rate and temperature on microstructural evolution of this material. The results show that the safe region for hot deformation occurs in the strain rate range 0.001–0.1 s⁻¹ over the entire temperature range investigated. In this region, the activation energy is ~240 ± 5 kJ/mol and the ln Z values vary in range of 13.9–21 s⁻¹. Stable flow is associated with dynamic recovery and dynamic recrystallization. Also, flow instabilities are observed in the form of localized slip bands and flow localization at strain rates higher than 0.1 s⁻¹ over a wide temperature range. The corresponding ln Z values are larger than 21 s⁻¹. The hot deformation characteristic of Ti-15-3 alloy predicted from the processing maps, activation energy map, and Zener–Hollomon parameter map agrees well with the results of microstructural observations.     

Interfacial interaction of solid cobalt with liquid Pb-free Sn–Bi–In–Zn–Sb soldering alloys

Dissolution kinetics of cobalt in liquid 87.5%Sn–7.5%Bi–3%In–1%Zn–1%Sb and 80%Sn–15%Bi–3%In–1%Zn–1%Sb soldering alloys and phase formation at the cobalt–solder interface have been investigated in the temperature range of 250–450 °C. The temperature dependence of the cobalt solubility in soldering alloys was found to obey a relation of the Arrhenius type c _s = 4.06 × 10² exp (−46300/RT) mass% for the former alloy and c _s = 5.46 × 10² exp (−49200/RT) mass% for the latter, where R is in J mol⁻¹ K⁻¹ and T in K. For tin, the appropriate equation is c _s = 4.08 × 10² exp (−45200/RT) mass%. The dissolution rate constants are rather close for these soldering alloys and vary in the range (1–9) × 10⁻⁵ m s⁻¹ at disc rotational speeds of 6.45–82.4 rad s⁻¹. For both alloys, the CoSn₃ intermetallic layer is formed at the interface of cobalt and the saturated or undersaturated solder melt at 250 °C and dipping times up to 1800 s, whereas the CoSn₂ intermetallic layer occurs at higher temperatures of 300–450 °C. Formation of an additional intermetallic layer (around 1.5 μm thick) of the CoSn compound was only observed at 450 °C and a dipping time of 1800 s. A simple mathematical equation is proposed to evaluate the intermetallic-layer thickness in the case of undersaturated melts. The tensile strength of the cobalt-to-solder joints is 95–107 MPa, with the relative elongation being 2.0–2.6%.     

Creep behavior of AZ31 magnesium alloy in low temperature range between 423 K and 473 K

The deformation behavior of coarse-grained AZ31 magnesium alloy was examined in creep at low temperatures below 0.5 T _m and low strain rates below 5 × 10⁻⁴ s⁻¹. The creep test was conducted in the temperature range between 423 and 473 K (0.46–0.51 T _m) under various constant stresses covering the strain rate range 5 × 10⁻⁸ s⁻¹–5 × 10⁻⁴ s⁻¹. All of the creep curves exhibited two types depending on stress level. At low stress (σ/G < 4 × 10³), the creep curve was typical of class I behavior. However, at high stresses (σ/G > 4 × 10³), the creep curve was typical of class II. At the low stress level, deformation could be well described by solute drag creep whereas at the high stress level, deformation could be well described by dislocation climb creep associated with pipe diffusion or lattice diffusion. The transition of deformation mechanism from solute drag creep to dislocation climb creep, on the other hand, could be explained in terms of solute-atmosphere-breakaway concept.     

Effects of dynamic strain aging on mechanical properties of SA508 class 3 reactor pressure vessel steel

An as-received reactor pressure vessel (RPV) steel SA508 class 3 (SA508 Cl.3) has been subjected to uniaxial tension tests in the strain-rate range of 6.67 × 10⁻⁵ s⁻¹ to 1.2 × 10⁻² s⁻¹ and the temperature range of 298 K to 673 K to investigate the effects of temperature and strain rate on its mechanical properties. It was found that the region of dynamic strain aging (DSA) was in the temperature range of 523–623 K at a strain rate of 1.2 × 10⁻³ s⁻¹, 473–573 K at 1.2 × 10⁻⁴ s⁻¹, and 473–573 K at 6.67 × 10⁻⁵ s⁻¹, respectively. Serrated stress–strain behaviors, predominately consisting of type A, B, and C, have been observed in these temperatures and strain-rate ranges. The solutes responsible for DSA have been identified to be carbon and nitrogen, and nitrogen atoms play a more important role. The relative DSA mechanisms for this RPV steel are discussed.     

Microstructure and elevated temperature properties of a refractory TaNbHfZrTi alloy

Compression properties of a refractory multi-component alloy, Ta₂₀Nb₂₀Hf₂₀Zr₂₀Ti₂₀, were determined in the temperature range of 296–1473 K and strain rate range of 10⁻¹–10⁻⁵ s⁻¹. The properties were correlated with the microstructure developed during compression testing. The alloy was produced by vacuum arc melting, and it was hot isostatically pressed (HIPd) and homogenized at 1473 K for 24 h prior to testing. It had a single-phase body-centered cubic structure with the lattice parameter a = 340.4 pm. The grain size was in the range of 100–200 μm. During compression at a strain rate of έ = 10⁻³ s⁻¹, the alloy had the yield strength of 929 MPa at 296 K, 790 MPa at 673 K, 675 MPa at 873 K, 535 MPa at 1073 K, 295 MPa at 1273 K and 92 MPa at 1473 K. Continuous strain hardening and good ductility (ε ≥ 50%) were observed in the temperature range from 296 to 873 K. Deformation at T = 1073 K and έ ≥ 10⁻³ s⁻¹ was accompanied by intergranular cracking and cavitation, which was explained by insufficient dislocation and diffusion mobility to accommodate grain boundary sliding activated at this temperature. The intergranular cracking and cavitation disappeared with an increase in the deformation temperature to 1273 and 1473 K or a decrease in the strain rate to ~10⁻⁵ s⁻¹. At these high temperatures and/or low-strain rates the alloy deformed homogeneously and showed steady-state flow at a nearly constant flow stress. Partial dynamic recrystallization, leading to formation of fine equiaxed grains near grain boundaries, was observed in the specimens deformed at 1073 and 1273 K and completed dynamic recrystallization was observed at 1473 K.     

Investigation of the quasi-ternary system LaMnO3–LaCoO3–“LaCuO3”. II: The series LaMn0.25?xCo0.75?xCu2xO3?δ and LaMn0.75?xCo0.25?xCu2xO3?δ

This paper investigates the crystal structure, thermal expansion, and electrical conductivity of two series of perovskites (LaMn_0.25−x Co_0.75−x Cu_2x O_3−δ and LaMn_0.75−x Co_0.25−x Cu_2x O_3−δ with x = 0, 0.025, 0.05, 0.1, 0.15, 0.2, and 0.25) in the quasi-ternary system LaMnO₃–LaCoO₃–“LaCuO₃”. The Mn/Co ratio was found to have a stronger influence on these properties than the Cu content. In comparison to the Co-rich series (LaMn_0.25−x Co_0.75−x Cu_2x O_3−δ), the Mn-rich series (LaMn_0.75−x Co_0.25−x Cu_2x O_3−δ) showed a much higher Cu solubility. All compositions in this series were single-phase materials after calcination at 1100 °C. The Co-rich series showed higher thermal expansion coefficients (α_max = 19.6 × 10⁻⁶ K⁻¹) and electrical conductivity (σ_max = 730 S/cm at 800 °C) than the Mn-rich series (α_max = 10.6 × 10⁻⁶ K⁻¹, σ_max = 94 S/cm at 800 °C). Irregularities in the thermal expansion curves indicated phase transitions at 150–350 °C for the Mn-rich series, while partial melting occurred at 980–1000 °C for the Co-rich series with x > 0.15. I. Arul Raj—on leave from Central Electrochemical Research Institute, Karaikudi, 630006 India.     

Structural, optical, magnetic and electrical properties of Zn1−x Co x O thin films

Despite a considerable effort aiming at elucidating the nature of ferromagnetism in ZnO-based magnetic semiconductor, its origin still remains debatable. Although the observation of above room temperature ferromagnetism has been reported frequently in the literature by magnetometry measurement, so far there has been no report on correlated ferromagnetism in magnetic, optical and electrical measurements. In this paper, we investigate systematically the structural, optical, magnetic and electrical properties of Zn_1−x Co _x O:Al thin films prepared by sputtering with x ranging from 0 to 0.33. We show that correlated ferromagnetism is present only in samples with x > 0.25. In contrast, samples with x < 0.2 exhibit weak ferromagnetism only in magnetometry measurement which is absent in optical and electrical measurements. We demonstrate, by systematic electrical transport studies that carrier localization indeed occurs below 20–50 K for samples with x < 0.2; however, this does not lead to the formation of ferromagnetic phase in these samples with an electron concentration in the range of 6 × 10¹⁹ cm⁻³ ∼1 × 10²⁰ cm⁻³. Detailed structural and optical transmission spectroscopy analyses revealed that the anomalous Hall effect observed in samples with x > 0.25 is due to the formation of secondary phases and Co clusters.     

Compressive deformation behavior of Al 2024 alloy using 2D and 4D processing maps

The hot deformation behavior of Al 2024 was studied by isothermal hot compression tests in the temperature range of 250–500 °C and strain rate range of 10⁻³ to 10² s⁻¹ in a computer-controlled 50 kN servo-hydraulic universal testing machine (UTM). The results show that the flow stress of Al 2024 alloy increases with strain rate and decreases after a peak value, indicating dynamic recovery and recrystallization. The processing map exhibits two domains of optimum efficiency for hot deformation at different strains, including the low strain rate domain at 500 °C and between 10⁻² and 10⁻¹ s⁻¹ and the high strain rate domain in 250 and 300 °C in the strain rate range of 10¹ to 10² s⁻¹. An attempt has been made in this article to generate a new hybrid 4D process map which illustrates contours of power dissipation and instability in the 3D space of strain rate, temperature, and strain.     

Supercapacitive performance of hydrous ruthenium oxide (RuO<Subscript>2</Subscript>·<Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O) thin films deposited by SILAR method

The amorphous hydrous ruthenium oxide (RuO₂·nH₂O) thin films were deposited by a simple and inexpensive successive ionic layer adsorption and reaction (SILAR) method. These films were characterized for their structural, surface morphological, and compositional study by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDAX) techniques. The wettability test was carried out by measuring the water contact angle. The scanning electron microscopy study showed small RuO₂ particles are grouped together to form porous agglomerates. The FT-IR study confirmed the formation of hydrous ruthenium oxide films. The hydrophilic nature of ruthenium oxide (RuO₂·nH₂O) thin films was observed from water contact angle measurement. The presence of Ru and O in the film was confirmed by EDAX analysis. The supercapacitor behavior of these films studied in 0.5 M H₂SO₄ electrolyte showed maximum specific capacitance of 162 F g⁻¹ at 10 mV s⁻¹ scan rate. These films exhibit 80% cycling performance after 2,000 cycles. The charge–discharge studies carried at 1 mA cm⁻² current density revealed the specific power of 3.5 KW kg⁻¹ and specific energy of 29.7 W Kg⁻¹ with 93% coulombic efficiency.     

Unloading‐Based Stiffness Characterisation of Cement Pastes During the Second,Third and Fourth Day After Production

The stiffness evolution of binder ‘cement paste’ is triggering the stiffness of concrete. In the engineering practice, concrete formworks are typically removed 24 h after production. This underlines that knowledge on mechanical properties of cementitious materials during the second, third and fourth day after production is of high relevance for the ongoing construction process. This provides the motivation to perform early‐age stiffness characterisation on hydrating cement pastes, by means of the following three test methods. Unloading modulus is determined using a novel setup for non‐destructive uniaxial compression testing including overdetermined deformation measurements. Dynamic Young's moduli are obtained from ultrasonics experiments. Isothermal differential calorimetry allows for linking the observed temporal evolution of early‐age stiffness to the hydration degree of cement. Pastes with three different compositions are investigated, defined in terms of the initial water‐to‐cement mass ratio w/c and the initial water‐to‐solid (binder) mass ratio w/s. Pure cement pastes exhibit w/c = w/s = 0.50 and w/c = w/s = 0.42, respectively. A fly ash‐blended cement paste refers to a cement mass replacement level of 16%, and this is related to w/c = 0.50 and w/s = 0.42. Both unloading moduli and dynamic Young's moduli of all three materials increase practically linearly with increasing hydration degree, in the investigated regime of hydration degrees ranging from 40 to 60%. Fly ash does not contribute significantly to the early‐age hydration of the material, i.e. it represents a quasi‐inert part of the material's microstructure, exhibiting a significant stiffening effect.     

Fabrication of dense β-calcium orthophosphate with submicrometer-sized grains and its high-temperature superplastic deformation

High-density β-calcium orthophosphate (β-Ca₃(PO₄)₂, also called β-tricalcium phosphate: β-TCP) ceramics with submicrometer-sized grains were fabricated using a pulse-current pressure firing route. The maximum relative density of the β-TCP compacts was 98.7% at 1050 °C and this was accompanied by a translucent appearance. The mean grain size of the β-TCP compacts increased slightly with temperature to reach 0.78 μm at 1000 °C. However, upon further increasing the firing temperature to 1050 °C the mean grain size increased significantly to 1.6 μm. The extent of plastic deformation during tensile testing was examined at temperatures between 900 and 1100 °C using a strain rate in the range 9.26 × 10⁻⁵ to 4.44 × 10⁻⁴ s⁻¹. The maximum tensile strain achieved was 145% for a test temperature of 1000 °C and strain rate of 1.48 × 10⁻⁴ s⁻¹ and this was attributed to the relatively high density and small grain size.     

Compressive deformation behavior of ternary compound Cr<Subscript>2</Subscript>AlC

The compressive properties of ternary compound Cr₂AlC at different temperatures and strain rates were studied. When tested at a strain rate of 5.6 × 10⁻⁴ s⁻¹, the compressive strength decreases continuously from 997 ± 29 MPa at room temperature to 523 ± 7 MPa at 900 °C. The ductile-to-brittle transition temperature is measured to be in the range of 700 to 800 °C. When tested in the strain rate range of 5.6 × 10⁻⁵ to 5.6 × 10⁻³ s⁻¹, Cr₂AlC fails in a brittle mode at room temperature, whereas the deformation mode changes from a brittle to a ductile as the strain rate is lower than 5.6 × 10⁻⁴ s⁻¹ when compressed at 800 °C. The compressive strength increases slightly with increasing strain rate at room temperature and it is less dependent on strain rate when tested at 800 °C. The plastic deformation mechanism of Cr₂AlC was discussed in terms of dislocation-related activities, such as kink band formation, delamination, decohesion of grain boundary, and microcrack formation.     

Preparation, proton conduction, and application in ammonia synthesis at atmospheric pressure of La0.9Ba0.1Ga1– x Mg x O3–α

La_0.9Ba_0.1Ga_1–x Mg _x O_3–α (0 ≤ x ≤ 0.25) was prepared by the microemulsion method. A single phase of LaGaO₃ perovskite structure was formed when x was ≥0.15. Electrochemical hydrogen permeation (hydrogen pumping) proved that La_0.9Ba_0.1Ga_1–x Mg _x O_3–α had proton conduction, and the proton conduction was measured by AC impedance spectroscopy method from 400 to 800 °C in hydrogen atmospheres. Among these samples, La_0.9Ba_0.1Ga_0.8Mg_0.2O_3–α has the highest proton conductivity with the values of 9.51 × 10⁻⁴ to 4.68 × 10⁻² S cm⁻¹ at 400–800 °C. Ammonia was synthesized from nitrogen and hydrogen at atmospheric pressure in an electrolytic cell using La_0.9Ba_0.1Ga_0.8Mg_0.2O_3–α as electrolyte. The rate of NH₃ formation was 1.89 × 10⁻⁹ mol s⁻¹ cm⁻² at 520 °C upon imposing a current of 1 mA through the cell.     

Hot deformation behavior of an 8% Cr cold roller steel

An 8% Cr cold roller steel was compressed in the temperature range 900–1200 °C and strain rate range 0.01–10 s⁻¹. The mechanical behavior has been characterized using stress–strain curve analysis, kinetic analysis, processing maps, etc. Metallographic investigation was performed to evaluate the microstructure evolution and the mechanism of flow instability. It was found that the work hardening rate and flow stress decreased with increasing deformation temperature and decreasing strain rate in 8% Cr steel; the efficiency of power dissipation decreased with increasing Z value; flow instability was observed at higher Z-value conditions and manifested as flow localization near the grain boundary. The hot deformation equation and the dependences of critical stress for dynamic recrystallization and dynamic recrystallization grain size on Z value were obtained. The suggested processing window is in the temperature range 1050–1200 °C and strain rate range 0.1–1 s⁻¹ in the hot processing of 8% Cr steel.     

Thermal Diffusivity and Heat of Formation of Harzburgite and Its Major Constituent Minerals

The thermal diffusivity, D, and its temperature dependence of Oman harzburgite rock and its major mineral olivine have been evaluated from the basic properties such as seismic velocities, density, and Debye temperature. The Arrhenius-type temperature dependence of the diffusivity was utilized to evaluate the heat of formation, ΔH _D. The diffusivity values, 1.80mm² · s⁻¹ and 2.1mm² · s⁻¹ obtained at room temperature for harzburgite and olivine, respectively, are consistent with available data. The diffusivity values for Oman harzburgite are overestimated by an amount of 0.27mm² · s⁻¹ relative to those of PNG harzburgite. The ΔH _D value (−2.40 kJ · mol⁻¹) for harzburgite rock of the Oman ophiolite suite is comparable with that (−2.90 kJ · mol⁻¹) of the harzburgite rock of Papua New Guinea. The disagreements in the thermal diffusivity and heat of formation values may be partly due to ignoring the effect of pyroxene in Oman harzburgite.     

Immobilization of tritium-containing oil wastes by their incorporation in a cement matrix

Tritium leaching from cement-based composites incorporating spent tritium-containing oil sorbed on zeolites, active alumina, or activated carbon was studied. Activated carbon is a preferable sorbent compared to the other examined materials, and with this sorbent the rate and degree of tritium leaching were the lowest. The leaching is due to diffusion mobility of water in the cement matrix. The tritium diffusion coefficient in the system is D = (4.7 ± 0.3) × 10⁻¹¹ m² s⁻¹.     

Synthesis, crystal stability, and electrical behaviors of La0.7Sr0.3Cr0.4Mn0.6O3?δ–XCu0.75Ni0.25 for its possible application as SOFC anode

La_0.7Sr_0.3Cr_0.4Mn_0.6O_3−δ (perovskite-type) nanocomposites impregnated with XCu_0.75Ni_0.25 have been synthesized by sol–gel method. Crystal structure of LSCM–Cu_0.75Ni_0.25 composites were refined by the Rietveld method. Crystal symmetry of CuO and NiO nanoparticles have monoclinic and cubic symmetry, respectively, but after sintering at 1,200 °C and reducing the temperature to 600 °C, it’s transformed into a new Cu_0.75Ni_0.25 intermetallic solid solution without secondary phase. We have detected a cationic inter-diffusion in Cu ↔ Ni interphase crystals during this reduction process; however, when sintering time exceeds 2 h at 1,200 °C this reaction mechanism is interrupted by a sublimation phenomenon; which causes Cu₂O cubic structure segregation from monoclinic CuO structure. This leads to Cu precipitation from the Cu_1−x Ni _x solid solution. Cu_0.75Ni_0.25 inhibits the LSCM perovskite-type grain growth (t ≈ 220 nm). Electrical conductivity indicates the presence of semiconductor and metallic-type behaviors with a maximum electrical conductivity (800 °C) >4.5 (log σ, Sm cm⁻¹). When Cu_0.75Ni_0.25 concentration was 25 and 35 %, semiconductor behavior were dominated. Thermal expansion coefficients showed a linear dependence inversely proportional to Cu_0.75Ni_0.25 concentration. Electrical conductivity, Rietveld analysis, Porosity, TEC, and E _a behaviors lead to the conclusion that the anodes between 25 and 35 % (Cu_0.75Ni_0.25) are closer to applications at SOFC.