Composition Of Initial Material Research Articles

Correlation Analysis of Linear Viscoelastic (LVE) Properties, Damage Resistance and Microstructure of Unmodified Asphalt Binders with the Same Penetration Grade.

The penetration grade system is still widely adopted for selecting asphalt binder with desired paving performance. However, the initial material compositions of asphalt binder with the same penetration level are still different, and vary with the crude oil source and essentially result in different rheological performance. This study aimed to assess the linear viscoelastic (LVE) properties, and high- and intermediate-temperature and microscale characteristics of seven unmodified asphalt binders from different sources and countries with the same penetration level of 70. The LVE parameters were firstly evaluated followed by comparisons to various damage-based indexes. The microstructure of asphalt binders was further investigated followed by correlations between morphology and performance parameters. Experimental results indicate the |G*|/sin δ is well related to the MSCR-based non-recoverable creep compliance; furthermore, the R and |G*|·sin δ can generally represent the LAS-based failure strain and fatigue life, respectively. The viscoelastic nature of tested binders was clearly distinguished and related to rheological performance by atomic force microscopy (AFM). The roughness parameters and the phases' content derived from AFM images showed significant correlations with LVE characteristics and fatigue resistance nature, respectively. This research provides theoretical foundations for further investigating the rheological performance and microstructure characteristics, and their correlations with asphalt binders.

Peculiarities of Dynamics of Hypergenic Mineral Transformation of Nickel Weathering Crusts of Ultramafic Rocks of the Kempirsay Group of Deposits in Western Kazakhstan

Nickel weathering ores are used to produce metallic nickel, stainless steels, and nickel sulfate, the main component of batteries. The global production of nickel from weathering ores is increasing and has surpassed production from sulfide magmatic deposits. The efficiency of the mining and processing of nickel ores from weathering rocks is determined by their mineralogical composition. The weathering crust profile of the Kempirsay ultramafite massif is divided into three zones—leached (kerolitized) serpentinites, nontronites, and final hydrolysis minerals (later referred to as “ochers”). The kerolitized zone consists of a mixture of Ni-bearing talc and saponites (later referred to as “kerolite”). During the geological mapping of the Donskoye, Buranovskoye, and Shelektinskoye deposits, the products of ultramafite hypergenic transformation into disintegrated and leached serpentinites, kerolites, nontronites, and ochers were selected and studied. For this purpose, 44 rock samples were studied via X-ray diffractometric and thermal analyses, supplemented with data from chemical, microscopic, and granulometric determinations. Based on the obtained numerical parameters of the crystalline structure of the weathering products, the thermochemical values were obtained. The hypergenic transformation of the initial minerals and their subsequent transformation were traced. The trace element distribution along the profile of the serpentinite weathering ores is related to the initial material composition of the ultramafites. The accumulation of nickel in industrial concentrations is associated with the nontronite–kerolite zone. X-ray diffractometric analysis can be used as a fast and reliable method for controlling the nickel content of ores and monitoring their mineralogical composition.

Influence of operating conditions on cermet inert anode corrosion in cryolite for aluminium production

A (NixFeyO4–Ni1−x′Fex’O)/(Cux′’Niy’’) cermet candidate as inert anode was investigated in cryolite at 960 °C. Immersion tests were performed and different conditions tested: cryolite ratio, alumina content, electrolyte quality, metallic aluminium content and atmosphere. Then, electrolysis was realised at 0.8 A cm-2 for 4 h in industrial conditions: industrial grade electrolyte, CR 2.2, saturated Al2O3, 960 °C and presence of metallic Al. The initial material composition was still present in the bulk and the phases compositions in the oxidised zone are Ni0.90Fe2.10O4 and Ni0.90Fe0.10O, as observed during immersion tests. The metallic phase is partly oxidised, leading to porosity in the cermet.

Effect of debris material composition on post accidental heat removal in a sodium cooled fast reactor

Following a core meltdown accident in a pool type sodium cooled fast breeder reactor (SFR), a debris bed is formed over the core catcher. The influence of initial material composition of the debris bed (consisting of fuel and steel) on the post accidental heat removal processes has been investigated in view of reactor safety. A one dimensional transient multiphase thermal model has been developed and employed for this purpose. The model includes sodium boiling, steel melting, fuel melting, slumping of molten particles and formation of molten pool. The overall steel fraction in the debris bed, the extent of steel stratification in the bed due to density difference between the debris particles and the overall porosity of the debris bed are considered as main parameters. It is seen that the assumption of a homogeneous initial mixture of fuel and steel in the debris bed yields a low core catcher plate (CCP) temperature compared to stratified debris beds where steel fraction increases with debris height. In a debris mixture with a low steel content (20% steel and 40% fuel), the peak temperature experienced by the CCP increases only marginally, from 872 K for homogeneous mixture to 900 K for a highly stratified mixture. But, in a debris mixture rich in steel content (30% steel and 30% fuel) the corresponding peak temperatures experienced by CCP are 886 K and 932 K respectively, suggesting that material stratification has significant effect in steel-rich debris mixture. For identical steel stratification profiles, the peak CCP temperature in a steel lean debris mixture is lower than that in a steel rich debris mixture. For 20% overall steel fraction, the peak temperature experienced by CCP is less than the creep limit of 923 K even for the worst stratification. But for 30% overall steel fraction, increasing the extent of steel stratification above a specific value results in CCP peak temperature exceeding the safe limit based on creep failure. Thus, the thermal load on the CCP increases with steel content though the thermal conductivity of steel is much higher than that of the fuel.

Channel flow simulation of a mixture with a full-dimensional generalized quasi two-phase model

We consider a newly constructed, mechanics-based, non-linear generalized quasi two-phase model [55] for a rapid flow of mixture of viscous fluid and solid particles down a channel. Based on the underlying physics and simulation results, we present new non-linear phenomena and mechanical insights of the model. We also present a full discretization of the model for the generalized mixture viscosity, velocity, pressure and effective bulk friction with higher order central differences and donor-cell method. This suitably tackles the complexities. Fundamentally new results are presented for the generalized mixture viscosity, velocity, pressure and effective bulk friction. Detailed analyses are performed for the full dimensional evolution of mixture velocities, dynamic pressure and effective viscosity. Our analysis reveals several mechanically very important novel non-linear features associated with the model under consideration, but often ignored in mass flow simulations, including: (i) The non-linear dynamics; as characterized by the flow mobility, kinetic energy, and the flow evolution are strongly controlled by the initial material composition. (ii) The flow becomes thicker as solid fraction increases, the front head develops into bulking, and the main body shows depletion. (iii) A strong velocity shearing develops through the flow depth. (iv) The full dynamic pressure exhibits strongly non-linear structures. (v) It appears that the hydrostatic pressure may significantly underestimate the full dynamic pressure. (vi) Mixture viscosity increases in different rates (slowly and rapidly) in different regimes of solid volume fractions which is justified by mechanical perspective of the mixture flow. (vii) The proper understanding of the incipient flow behavior is important, and shows that the process of flow release must be described by the full dimensional models. These features highlight the application potential of our new mixture mass flow model and simulation strategy for the hazard mitigation and planning.

Evaluation of Fuel Burn-up and Radioactivity Inventory in the 2 MW TRIGA-Plate Bandung Research Reactor

Currently plate-type fuels are planned to use in the research reactor TRIGA-2000 Bandung, Indonesia (further called as TRIGA-Plate reactor). Plate type fuel consists of enriched uranium sandwiched between metal cladding. Plate-type fuel is used in some research reactors to obtain high neutron flux and is used to study material irradiation or isotope production. For the purpose of Safety Analysis Report (SAR) on the fuel-type modification plan of TRIGA-2000 Bandung, it is necessary to calculate radioactivity inventory from the reactor core under operating conditions. The radioactivity inventory of materials irradiated in a reactor depends on the initial material composition at the BOC, burn-up history from BOC to EOC and the power peaking factor. The purpose of the present work is to evaluate the fuel burn-up and radioactivity inventory in fuel materials of TRIGA-Plate research reactor. The mass of U-235 consumed and the mass of Pu-239 and Th-232 produced are also evaluated. The calculation results obtained using ORIGEN2 code are: the mass of U-235 consumed is 1.40E+02 gram; while the mass of Pu-239 produced is 1.36E+00 gram and Th-232 produced is 1.03E-06 gram. The largest radioactivity inventories of the reactor at the EOC sequentially are: Kr group is about 2.29E+02 Ci; for group I is 7.77E+03 Ci and for groups Cs is 1.92E+02Ci.

Some Simulation Results and Parameter Analyses of a Generalized Quasi Two-Phase Bulk Mixture Model

Here, we consider a newly constructed generalized quasi two-phase bulk model for a rapid flow of a debris mixture consisting of viscous fluid and solid particles down a channel. The model is a set of coupled partial differential equations with new mechanical description of generalized bulk and shear viscosities, pressure, velocities and effective friction. The dynamical variables, physical parameters, inertial and dynamical coeffcients and drift factors involved in the equations contain certain important physics of mixture flow. So, we analyze the behaviour of some inertial and dynamical coeffcients involved in the model. These coeffcients strongly depend upon the initial material composition. We also simulate the evolution of the dynamical variables so as to reveal their strong non-linear behaviours. Through simulations, we also analyze the front position of the debris material, bottom-slip velocity and maximum velocity, which show fundamentally different dynamics for varied material compositions, from dilute to dense flows. Generalized mixture viscosity decreases as the ow moves downslope, and the rate at which it decreases depends upon the initial solid-volume fraction. We also compare the effective viscosity and the bulk mixture viscosity with respect to the norm of the strain rate tensors to reveal different non-linear behaviours.

The use of mechanochemical activation for the synthesis of garnet-based pigments

Green pigments based on uvarovite Ca3Cr2[SiO4]3 were obtained from cheap silica-containing materials of the Siberian region by high-temperature solid-phase synthesis with the use of mechanical activation of an initial mixture. The chemical composition of quartz sand and marshallit, the main initial components of pigments, is determined using an optical emission spectrometer with inductively coupled plasma (iCAP 6300 Duo, Thermo Scienfitic). The structure and phase composition of initial materials and reaction products were analyzed by X-ray diffraction (DRON-UM1 diffractometer, filtered CuKa-radiation), IR spectroscopy (Nicolet 5700 FTIR spectrometer), and scanning electron microscopy (Philips SEM 515). Calcium carbonate is shown to decompose during mechanochemical activation. The reactions occurring during the synthesis of pigments were studied using a thermal analyzer (SDT Q600) in the temperature range of 25-1200°C at a heating rate of 20 deg/min. Mechanical activation of initial components in a planetary mill M3 with an acceleration of 45 g for 300 s leads to a decrease in the synthesis temperature by 200°C and increases the degree of conversion of the final products.

Composition optimization strategy based on multiple radiological responses for materials in spatially and temporally varying neutron fields

Structural materials present in and around any fusion device will face stringent conditions due to the high-energy and high-flux neutrons emitted from the fusion plasma. These neutrons can cause induced radioactivity, gas production, energetic knock out atoms, atomic displacement and decay heat in these materials. This would have a significant life-limiting impact on the materials and would also cause biological hazards and radioactive waste. Hence designing low activation materials for fusion devices is warranted. This paper presents a novel tool for quantification of radiological responses in terms of the elements present in the initial material composition. Such a framework would help in the identification and optimization of the fraction of most dangerous elements/isotopes from the material composition. In practical scenarios, the material encounters a large spatial and temporal variation of neutron fluxes. This problem has been effectively treated in the present work using a multi-parameter optimization scheme. The scheme optimizes the material composition (elemental or isotopic) based on various nuclear responses and there spatial and temporal variations within the user-defined constraints. This scheme is further included in the multi-point activation code ACTYS-1-GO. The tool provides a comprehensive picture of the material response during neutron irradiation and after shutdown, enabling the assessment of structural integrity of components in a fusion device. As an aide to the material optimization process, this paper also introduces a visual representation of the evaluated information like quantification of radiological responses produced by the parent elements/isotopes in a material. This has been implemented through a series of spectrum independent and spectrum-dependent diagrams called the radiation response diagrams. These diagrams show the variation of contributing parents toward the radiological responses as a function of cooling time. Such a graph could be very useful as a first approximation for material design.

Estimation of the radionuclide inventory in LWR spent fuel assembly structural materials for long-term safety analysis

The radionuclide inventory of materials irradiated in a reactor depends on the initial material composition, irradiation history and on the magnitude and spectrum of the neutron flux. The material composition of a fuel assembly structure includes various alloys of Zircaloy, Inconel and stainless steel. The existing impurities in these materials are very important for accurate determination of the activation of all nuclides with a view to assessing the radiological consequences of their geological disposal. In fact, the safety assessments of geological repositories require the average and maximum (in the sense of very conservative) inventories of the very long-lived nuclides as input. The purpose of the present work is to describe the methodology applied for determining the activation of these nuclides in fuel assembly structural materials by means of coupled depletion/activation calculations and also to crosscheck the results obtained from two approaches. UO2 and MOX PWR fuels have been simulated using SCALE/TRITON, simultaneously irradiating the fuel region in POWER mode and the cladding region in FLUX mode and aiming to produce binary macro cross-section libraries by applying accurate local neutron spectra in the cladding region as a function of irradiation history that are suitable for activation calculations. The developed activation libraries have been re-employed in a second run using the ORIGEN-S program for a dedicated activation calculation. The axial variation of the neutron flux along the fuel assembly length has also been considered. The SCALE calculations were performed using a 238-group cross-section library, according to the ENDF/B-VII. The results obtained with the ORIGEN-S activation calculations are compared with the results obtained from TRITON via direct irradiation of the cladding, as allowed by the FLUX mode. It is shown that an agreement on the total calculated activities can be found within 55% for MOX and within 22% for UO2 , whereas the latter is reduced to 9% when more accurate irradiation data are used (core-follow flux data instead of life-average flux data).

Technology obtaining of nitrogen fertilizer from the calcium is containing waste of production of calcium saltpetre

The new technology of obtaining nitrogen fertilizer from calcium-containing sludge of calcium saltpeter production is considered in the paper. The main objective of the research is the development of processing technology of sludge of calcium saltpeter production into alkaline nitrogen fertilizer, analysis of the composition of initial material and finished product, testing of fertilizer by means of vegeta­tive studies and determination of expenditure of drying agent that is exhaust gases of the nitrate acid production unit after recuperation turbine. The main properties of initial sludge and finished product were studied, their composition was determined using the method of atom-absorption spectral analysis. It is shown that the obtained fertil­izer contains bound nitrogen and other nutrient elements (Na, K, Ca, Mg, P), and the content of water-insoluble residue is the precondition for the prolonged effect of fertilizer. The technology of obtaining cheap nitrogen fertilizer on the basis of sludge of calcium saltpeter produc­tion - calcium-containing sludge, which includes extrusion of initial sludge and two-phase drying, using exhaust gasses of the nitrate acid production unit after recuperation turbine as drying agent, was devel­oped. The efficiency of the obtained fertilizer was proved by vegetative tests, carried out in laboratory conditions on the example of wheat.

Experimental and modelling research of the accelerated calcium leaching of cement paste in ammonium nitrate solution

Calcium leaching of cement-based materials is of concern for scientific and application significance. Considering the altered solid–liquid equilibrium curve, an accelerated calcium leaching model of pure cement paste in 6mol/L ammonium nitrate leaching solution was built up in this research. The model was numerically solved using finite difference method, and the influences of w/c ratio and initial cement composition on leaching were addressed. The accelerated model was further verified using elemental distributions and leaching fronts. Besides, through comparing the accelerated model in 6mol/L ammonium nitrate solution and the un-accelerated model in deionized water, an accelerated factor of about 130 was found, which was slightly influenced by the initial material compositions.

Al-Zn-Mg-Cu 合金単結晶の硬さと応力-ひずみ曲線

The present paper describes the variations in mechanical properties of Al-Zn-Mg-Cu alloy single crystals with various aging times. The cylindrical single crystals of 7475 aluminum alloys were produced at 1033 K by the Bridgman method, where the composition of initial material and the shape of carbon mold were modified for the growth of quaternary crystals. Specimens appropriate for tensile and hardness testing were obtained from the single crystal rod homogenized at 823 K for 900 ks using a spark-cutting method. Subsequently, they were aged at 393 K for 3.6, 86.4, 900 and 2880 ks after quenching in ice water from 773 K. In the stress-strain curves of the alloy single crystals, the yield stress increased remarkably with the increase of aging time. Also, a decrease of elongation for the aged specimens was seen accompanying a decrease in the rate of work hardening after yielding. Moreover, some serrations occurred particularly in the final plastic stage on the curves. Hardness of the alloy single crystals agreed with those of polycrystals due to the occurrence of multiple slips during loading. However, the alloy single crystals exhibited a marked decrease in yield strength in comparison to the polycrystals. In single crystals, a single glide was found to occur. If we compare the increase of critical resolved shear stress (CRSS) derived from two different theories of precipitation hardening with the experimental value, the present results were roughly in agreement with the theoretical values except for the specimen aged for 3.6 ks. This fact indicated that the maximum strength of Al-Zn-Mg-Cu alloy single crystals was achieved in the transition from the mechanism in which dislocations cut through the precipitated particles to the bypass mechanism of Orowan with the growth in particle size.

Hardness and Stress-Strain Curves of Al-Zn-Mg-Cu Alloy Single Crystals

The present paper describes the variations of the mechanical properties of Al-Zn-Mg-Cu alloy single crystals with various aging times. The cylindrical single crystals of 7475 aluminum alloys were produced at 1033 K by the Bridgeman method, where the composition of initial material and the shape of carbon mold were modified for the growth of quaternary crystals. The specimens proper for tensile and hardness testing were obtained from the single crystal rod homogenized at 823 K for 900 ks using spark-cutting method. Subsequently, they were aged at 393 K for 3.6, 86.4, 900 and 2880 ks after quenching in ice water from 773 K. In the stress-strain curves of the alloy single crystals, the increase of yield stress and the decrease of elongation with an increase of aging time are seen together with a decrease in the rate of work hardening. Moreover, some serrations occur especially in the final plastic stage on the curves. Hardness of the alloy single crystals agrees with those of polycrystals due to the occurrence of multiple slips during loading. However, the alloy single crystals exhibit a marked decrease of yield strength in comparison with the polycrystals, which results from a single glide occurring in the single crystals. If we compare the increase of critical resolved shear stress (CRSS) derived from two kinds of theories of precipitation with the experimental value, both of them are roughly in agreement except for the specimen aged for 3.6 ks. The obtained results indicate that the maximum strength of Al-Zn-Mg-Cu alloy single crystals is achieved in the transitional process between the mechanism of particle cutting and the Orowan mechanism. [doi:10.2320/matertrans.MER2008178]

Effect of the composition of initial materials on the formation and properties of spot welded joints between titanium alloys and steel and nickel

(1990). Effect of the composition of initial materials on the formation and properties of spot welded joints between titanium alloys and steel and nickel. Welding International: Vol. 4, No. 4, pp. 300-302.