Selective and in-situ determination of carbonate and oxide particles in aqueous solution using laser-induced breakdown spectroscopy (LIBS) for wearable information equipment

Laser-induced breakdown spectroscopy (LIBS) has been applied for quantitative analysis of Al₂O₃, CaCO₃ and MgO particles suspended in water. In the single elemental system, the plasma emission intensities of Al, Ca and Mg were linearly increased with concentration of elements in the range of 1.0×10^?5–1.0×10^?3  M, 1.0×10^?4–2.0×10^?3 M and 8.0×10^?5 –4.0×10^?3 M, respectively. We also investigated the concentration dependence of breakdown spectra for suspended mixtures of Al₂O₃, CaCO₃ and MgO particles. The emission lines, such as Al I, Ca I, Ca II and Mg I, were appeared in the LIBS spectrum simultaneously, and each emission peak could be deconvoluted. The plasma emission intensities of Al, Ca and Mg in the multielemental system were also linearly increased with their concentrations in the range of 1.0×10^?5–1.0×10^?3 M, 1.0×10^?4–2.0×10^?3 M and 4.0×10^?4–2.0×10^?3 M, respectively. LIBS was found to be available for quantitative and qualitative measurement of the concentrations of Al₂O₃, CaCO₃ and MgO particles suspended in water. The present results suggest that LIBS is a potentially useful tool for in-situ analysis on particles composition and concentrations for environmental monitoring by the wearable information equipments.     

Phase equilibria of the Al2O3–CaO–SiO2-(0%, 5%, 10%) MgO slag system for non-metallic inclusions control

Al₂O₃–CaO-(MgO–SiO₂) inclusions are one of the dominant inclusions in Al-deoxidized spring steel, the compositions changes of which are closely related to refining slags and deoxidization process. The Al₂O₃–CaO–SiO₂–MgO system can represent the primary ingredients of the Al₂O₃–CaO inclusions. According to analyzed compositions and predicted liquidus temperature ranges of inclusions and refining slag, equilibra experiments under high temperature, water quenching technique and subsquent electron probe X-ray microanalysis (EPMA) has been conducted to ascertain detailed thermodynamic database for inclusions control. Liquidus temperatures within the dominant phase fields of Ca₃SiO₅, Ca₂SiO₄, CaAl₂O₄, Ca₃Al₄O₉, spinel and MgO with the intervals of 20 °C from 1350 to 1560°C were identified. To further promote inclusions control, the influences of mass ratios of Mass(Al2O3)Mass(Al2O3+SiO2+CaO) and MgO contents on equilibrated phases and liquidus temperature changes have been explored. To further enhance modification levels of Al₂O₃–CaO-(MgO–SiO₂) system inclusions, it is suggested that refining time could be suitably prolonged.     

Application of phase equilibrium studies of CaO–SiO2–Al2O3–MgO system for oxide inclusions in Si-deoxidized steels

In the steelmaking process, the compositions of the oxide inclusions could be modified by refining slags to a large extent. The chemistries of the oxide inclusions and refining slags can be described by the system CaO–SiO₂–Al₂O₃–MgO. Phase equilibria and liquidus temperatures in this system have been experimentally investigated in the composition and temperature ranges related to the oxide inclusions and refining slags by means of high-temperature equilibration, quenching and electron probe X-ray microanalysis. Isotherms in the interval of 20 °C between 1260 and 1560 °C were determined in the primary phase fields of wollastonite, anorthite, spinel, and melilite. Effects of the mass ratio of (Al₂O₃+SiO₂)/((Al₂O₃+SiO₂)+(CaO + SiO₂)) and MgO content on the liquidus temperatures have been discussed to assist inclusion control. To obtain the lowest liquidus temperature of Al₂O₃–SiO₂–CaO–MgO system inclusions, refining time ought to be properly controlled.     

Calculation of quasibinary and quasiternary oxide systems — I

A data base is being developed for calculation of quasi-binary and quasi-ternary phase diagrams of ceramic systems. The initial segment of this base covers combinations of Cr₂O₃, MgO, Al₂O₃, Fe₂O₃, Fe₃O₄and “FeO”. Lattice Stability, Solution and Compound Phase Parameters are presented covering the liquid, spinel, periclase and corundum phases in systems composed of these oxides. These parameters permit calculation of the thermochemical properties and phase diagrams of combinations of these oxides in good agreement with limited experimental data. Twelve calculated quasi-binary phase diagrams and three calculated quasi-ternary phase diagrams are presented illustrating the applicability of the data base.     

Stability effect of some organic and inorganic additions in the EMITFSI–LiTFSI nanocomposite electrolytes for lithium-air batteries

Since the EMITFSI/LiTFSI electrolyte possess low viscosity, high ionic conductivity and thermal stability properties, in this study, 1M 1-ethyl-3-methyl-imidazoliumbis (trifluoromethanesulfonyl) imide (EMITFSI)/Lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) based electrolytes were studied for Li-air battery cells. A series of electrolytes was studied with organic compound additions of Poly(ethylene oxide) (PEO) and polyvinylidene fluoride (PVDF). Nano Al₂O₃ particles with 50 nm in size were also used in 1.0 wt% as inorganic additive to provide stability of the polymer added electrolytes. The nanocomposite electrolytes were prepared in a glove box under dry argon atmosphere. Porous electrode, Gas Diffusion Layer (GDL), was used as cathode, a lithium disk was used as anode while glass fiber was used as the separator in ECC-air test cell. The cells were cyclically tested using 0.1 mA/cm² current density over a voltage range of 1.5–4.5 V. Electrochemical impedance spectroscopy measurements was applied to investigate the effect of the PVDF/Al₂O₃ and PEO/Al₂O₃ nano additives on the resistivity of the electrolyte. After the electrochemical cycling test, the morphologies of the cathodes (GDL) were analyzed using scanning electron microscopy, X-ray diffraction analysis to determine reaction products and lithium compounds during cycling test.     

High temperature stability of electrically conductive Pt–Rh/ZrO2 and Pt–Rh/HfO2 nanocomposite thin film electrodes

Nanocomposite films made up of either Pt–Rh/ZrO₂ or Pt–Rh/HfO₂ materials were co-deposited using multiple e-beam evaporation sources onto langasite (La₃Ga₅SiO₁₄) substrates, both as blanket films and as patterned interdigital transducer electrodes for surface acoustic wave sensor devices. The films and devices were tested after different thermal treatments in a tube furnace up to 1,200 °C. X-ray diffraction and electron microscopy results indicate that Pt–Rh/HfO₂ films are stabilized by the formation of monoclinic HfO₂ precipitates after high temperature exposure, which act as pinning sites to retard grain growth and prevent agglomeration of the conductive cubic Pt–Rh phase. The Pt–Rh/ZrO₂ films were found to be slightly less stable, and contain both tetragonal and monoclinic ZrO₂ precipitates that also helps prevent Pt–Rh agglomeration. Film conductivities were measured versus temperature for Pt–Rh/HfO₂ films on a variety of substrates, and it was concluded that La and/or Ga diffusion from the langasite substrate into the nanocomposite films is detrimental to film stability. An Al₂O₃ diffusion barrier grown on langasite using atomic layer deposition was found to be more effective than a SiAlON barrier layer in minimizing interdiffusion between the nanocomposite film and the langasite crystal at temperatures above 1,000 °C.     

Driving characteristics of the electrowetting-on-dielectric device using atomic-layer-deposited aluminum oxide as the dielectric

Electrowetting on dielectric (EWOD) is useful in manipulating droplets for digital (droplet-based) microfluidics, but its high driving voltage over several tens of volts has been a barrier to overcome. This article presents the characteristics of EWOD device with aluminum oxide (Al₂O₃, ε _r  ≈ 10) deposited by atomic layer deposition (ALD), for the first time as the high-k dielectric for lowering the EWOD driving voltage substantially. The EWOD device of the single-plate configuration was fabricated by several steps for the control electrode array of 1 mm × 1 mm squares with 50 μm space, the dielectric layer of 1,270 Å thick ALD Al₂O₃, the reference electrode of 20 μm wide line electrode, and the hydrophobic surface treatment by Teflon-AF coating, respectively. We observed the movement of a 2 μl water droplet in an air environment, applying a voltage between one of the control electrodes and the reference electrode in contact with the droplet. The droplet velocity exponentially depending on the applied voltage below 15 V was obtained. The measured threshold voltage to move the droplet was as low as 3 V which is the lowest voltage reported so far in the EWOD researches. This result opens a possibility of manipulating droplets, without any surfactant or oil treatment, at only a few volts by EWOD using ALD Al₂O₃ as the dielectric.     

Sedimentation and precipitation of nanoparticles in power-law fluids

Our experiment reported here adopts water, alcohol (100 %), carboxymethyl cellulose (CMC) aqueous solution with different concentrations as the base-fluid of nano-fluids. We show diffusion, aggregation and precipitation of nano-size particles in the optical quartz glass Petri dishes filled with nano-fluids flat with the help of a rotating cone. The experimental results illustrate that nanoparticles are preferably suspended in CMC aqueous solution than in water or alcohol, which means the effective Hamaker constant of water- or alcohol-particle suspensions is bigger than that of CMC-particle suspension. In the experiment with CMC as the base solution, increasing the viscosity of the solution can alleviate the settling velocity of particles and make the suspension better. The experiment also discovers that in static condition, the mutual attractive force between nanoparticles plays an important role in the suspension; however, if external forces, which are higher than the attraction, exist, they are decisive parts. In addition, Al₂O₃ solution is much more sensitive than the Cu solution with the varying concentration and status in the experiment because the density of Al₂O₃ particles is smaller than that of Cu-nanoparticles.     

Heat capacities and standard entropies and enthalpies of some compounds essential for steelmaking and refractory design approximated by Debye-Einstein integrals

Heat capacity data for compounds located in the binary CaO–SiO₂, CaO–Al₂O₃ and MgO–Al₂O₃ systems are fitted by Debye-Einstein integrals. Starting from the fitted heat capacities, the standard values of the thermodynamic functions of these compounds are calculated. In almost all cases investigated, the derived standard entropies are within the uncertainties of the values provided in literature. The Debye-Einstein coefficients obtained in this thermodynamic assessment can be used to approximate the heat capacities, enthalpies and entropies of these compounds in the temperature range from 0 to 298.15 K.     

Investigation on the structural and spectral characteristics of deposited FBG stacks at elevated temperature

A composite nano-crystalline structured thin film was realized by depositing mixed Al₂O₃ and MgO coating material using physical vapor deposition approach and then annealing at high temperature. The film thus fabricated retains a high transmission even after annealing at 1500 °C. The grain size of less than 100 nm was measured by atomic force microscopy and the composite nano-crystalline structure of spinel and corundum was confirmed by the X-ray diffraction pattern analysis. Based on this, Bragg grating stacks were fabricated by depositing alternating quarter-wave layers of Al₂O₃ and Al₂O₃/MgO at the end of a sapphire crystal fiber at first and then the layers of NiO and Al₂O₃/MgO on the surface of a sapphire slice. The performance of the grating stacks at high temperature or after high temperature annealing was measured. It was found that the reflection peak measured from the grating stacks can survive a high temperature up to 1050 °C but will disappear after annealing at temperature of 1100 °C or above. A conclusion of inter-diffusion between layers of stack was obtained to explain the phenomenon of reflection peak disappearing after annealing at high temperature.     

Modeling the viscosity of silicate melts containing Fe oxide: Fe saturation condition

Our recently developed model for the viscosity of silicate melts is applied to describe and predict the viscosities of oxide melts containing iron oxide. In the present study, the viscosity experimental data under the reduced atmosphere, which is Fe saturation condition were critically reviewed and three pairs of adjustable model parameters related to ‘FeO’ were optimized to best reproduce all experimental data in the FeO–SiO₂–Al₂O₃–CaO–MgO–Na₂O–MnO–Ti₂O₃–TiO₂ system. The viscosities of a wide compositional and temperature range of binary, ternary and multicomponent melts were well reproduced by the present model within the scatter of experimental data.     

Metal-ceramic-composite casting of complex micro components

Metal-ceramic-composite casting has a huge potential as a new manufacturing method for the production of complex-shaped micro sized parts or microsystems consisting of different metals and ceramics. The fundamental advantage of this method is the capability of multi-component part fabrication in one step avoiding first time consuming joining or assembling techniques; second the used material combinations can fulfill complex functionalities and enhanced mechanical properties. One of the most challenging factors in micro composite casting is a stable mechanical bonding between the used individual materials. But under consideration of the different physical properties like thermal expansion coefficient as well as of the wettability of the ceramic inserts and of the applied metal casting material it is possible to manufacture form and force fitting microsystems. Within the framework of this feasibility study complex metal-ceramic micro composites have been realized successfully using the lost-wax casting process. Casting experiments were performed at different muffle preheating temperatures with Al-bronze of the type CuAl10Ni5Fe4 as casting material. The ceramic parts, respectively inserts cast around by metal are micro gear wheels (2.5 mm diameter) consisting of ZrO₂ and Al₂O₃.     

Erosion–corrosion synergism in an alumina/sea water nanofluid

Since nanofluids increase the thermal conductivity of a fluid mixture compared with the base fluid, it is important to investigate any damaging effects caused by the presence of the solid particles. Thus, this paper explores the nanofluid synergistic effects produced by the addition of 1 g dm^?3 Al₂O₃ nanoparticles to sea water and compares the performance with the base fluid without nanoparticles. Studies are conducted on carbon steel, using a hydrodynamically smooth-rotating cylinder electrode in turbulent flow at 298 K. The pure corrosion rate and erosion rate of carbon steel in the fluids free of nanoparticles are, respectively, higher (up to 82 %) and lower (ca. 11 %) than in the nanofluids. The synergistic effect of erosion and corrosion in a nanofluid is much higher (up to 237 %) than in the base fluid. These results indicate that the presence of nanoparticles in a flowing fluid could lead to considerable rates of material loss.     

Experimental determination of the liquidus in the high basicity region in the Al2O3(30 mass%) - CaO - MgO - SiO2 system

The liquidus in the high basicity region in the Al₂O₃(30 mass%)-CaO-MgO-SiO₂ system were determined experimentally at 1773 and 1873 K using the quench technique followed by EPMA analysis. Based on the experimental data, a phase diagram of the Al₂O₃(30 mass%)-CaO-MgO-SiO₂(<20 mass%) section was constructed for 1773 and 1873 K. The solubilities of 2CaO.SiO₂ and 3CaO.SiO₂ at 1773 K were found to be considerably higher in comparison with the existing phase diagram. Even the solubility of MgO at 1873 K was found to be somewhat higher. In addition, the activities of MgO, CaO and Al₂O₃ at 1773 K were estimated using the phase diagram information.     

Effects of Al2O3 and “Cr2O3” on phase equilibria of the system “FeO”−MgO−SiO2 at iron saturation

“FeO”, MgO and SiO₂ are the major components of the nickel laterite smelting slags. Significant amounts of Al₂O₃ and “Cr₂O₃” may be present in the slag that come from laterite, coal ash and refractory. Effects of Al₂O₃ and “Cr₂O₃” on liquidus temperatures and solid solutions have been determined in the olivine and spinel primary phase fields in equilibrium with metallic iron. The results are presented in the form of MgO−‘‘FeO’’−SiO₂ pseudo-ternary section at fixed 7 wt% Al₂O₃ and 2 wt% “Cr₂O₃”. A series of pseudo-binary phase diagrams have been constructed to demonstrate the application of phase diagram on smelting reduction of laterite. The liquidus temperatures and the compositions of solid solutions are compared between experimental data and FactSage thermodynamic modelling. The possible reasons for the different results have been discussed which will help FactSage to optimize the relevant databases.     

Modeling the viscosity of silicate melts containing Fe oxide: FeO/Fe2O3 containing system

In the present study, the viscosity experimental data for the Fe_tO-containing silicate melts under oxidation atmosphere, which Fe³⁺ and Fe²⁺ co-exist were critically evaluated and model parameters related to Fe₂O₃ were optimized to best reproduce all reliable experimental viscosity data. The charge compensation effect on the viscosity for the systems containing Fe₂O₃ was modeled with the Gibbs energies for LiFe, NaFe, KFe and CaFe₂ “associate species” formation. The viscosities of a wide compositional and temperature range of binary, ternary and multicomponent melts containing Fe₂O₃–FeO–SiO₂–Al₂O₃–CaO–MgO–Li₂O–Na₂O–K₂O–MnO–Ti₂O₃–TiO₂ were well reproduced by the present model within the scatter of experimental data.     

Phase Equilibrium studies in the system “FeO”–SiO2–Al2O3–CaO–MgO at 1200 °C and Po2 10-8atm

Iron oxides and silica are the major components of copper smelting slag. The oxides of aluminum, calcium and magnesium are also present in the slag that is introduced through copper concentrate, flux and refractories. Liquidus temperatures of the copper smelting slags are usually controlled by Fe/SiO₂. The concentrations of Al₂O₃, CaO and MgO, and FeO/Fe₂O₃ in the slag can also affect the liquidus temperatures where FeO/Fe₂O₃ is a function of oxygen partial pressure. High temperature equilibration under controlled oxygen partial pressure followed by quenching and electron probe microanalysis were used to determine the compositions of the liquid and solid phases at 1200 °C and Po₂ 10^-8 atm. The experimental results are presented in the forms of pseudo-ternary sections “FeO”-CaO-SiO₂ at fixed 2, 4 and 6 wt pct MgO, and 2 + 2, 4 + 4 and 6 + 6 wt pct MgO + Al₂O₃. Spinel and tridymite are the major primary phases in the composition range investigated. In addition, CaSiO₃, pyroxene, olivine, and melilite are also present. The isotherms in the spinel and tridymite primary phase fields move towards higher SiO₂ concentration directions with increasing CaO, Al₂O₃, and MgO concentrations. The experimentally determined results are compared with the FactSage calculations.     

Investigations on electrical conductivity of stabilized water based Al2O3 nanofluids

The electrical conductivity is an important property of nanofluids that has not been widely studied. To study both the effects of temperature and concentration, the electrical conductivity of water-based Al₂O₃ nanofluids with 12?nm diameter particles is measured. Conventional models, such as the Maxwell model and Bruggemann correlation, were considered for comparison and disagreement were noticed. Experimental results showed the Al₂O₃ nanofluids increased their electrical conductivity with increasing volume fraction as compared to that of the base fluid, as well as with temperature increasing. A stronger influence on volume fraction was noticed. Electrical conductivity measurements for these nanofluids indicate an enormous enhancement (390.11?%) at 60?°C for a volume fraction of 4?%in distilled water. Furthermore, at higher volume fractions, the electrical conductivity enhancement begins to level off, which is attributed to ion condensation effects in the high-surface charge regime. A 3D statistical analysis was also considered to obtain an empirical correlation.