Controlled Gas Atmospheres Research Articles

Experimental investigation of gas/slag/matte/tridymite equilibria in the Cu–Fe–O–S–Si system in controlled gas atmosphere at T = 1 200 °C and P(SO2) = 0.1 atm

AbstractThe effects of partial pressure of sulphur dioxide on the gas/slag/matte/tridymite equilibria in the Cu–Fe–O–S–Si system at 1 200 °C have been experimentally investigated and compared with the previous studies at various P(SO2). The experimental procedure includes equilibration of the sample and silica substrate at high temperature for the designated time, rapid quenching to preserve the equilibrium phases, followed by measuring the composition of the condensed phases with electron probe X-ray microanalysis. A set of graphs were constructed to present the compositions of slag and matte as a function of copper concentration in matte. The present study confirmed that the chemically dissolved copper and sulphur for the given Cu in matte are independent of the partial pressure of SO2. However, the experimentally measured liquidus (Fe/SiO2) are different for various P(SO2). The new data provide an important, accurate and reliable quantitative foundation for improvement of the thermodynamic databases for the chemical systems containing copper matte and slag. The present study is a part of a broader overall research program on the characterisation of the multi component (Cu–Fe–O–S–Si–Al–Ca–Mg), multi-phase (gas/slag/matte/metal/solids) systems with minor elements.

Nanoclustered Pd decorated nanocrystalline Zn doped SnO2 for ppb NO2 detection at low temperature

Nanoclustered Pd (2 mol%) was used to decorate Zn doped SnO2 (10 mol% Zn) in order to increase its sensing performances. Zn doped SnO2 built from nanoparticles was prepared by a hydrothermal method using a non-ionic surfactant - Brij52 and Tripropylamine (TPA) as co-templates. The presence of well-dispersed Zn2+ ions in the SnO2 matrix leads to a nonstoichiometric surface. Pd was deposited by subsequent wet impregnation using hydrazine as reducing agent. The as obtained powders were deposited as thick layers onto commercial substrates, in order to obtain the sensitive structures. The coexistence of a mixture of valence states (Pd0, Pd2+ and Pd4+) was highlighted on the surface of the as prepared layers. Several aspects have been followed regarding the Zn and Pd dispersion into the SnO2 matrix: the large scale and low scale morphology (SEM and TEM/HRTEM) in relation with the synthesis route, the obtained crystallographic phases (XRD, SAED) and the way in which the Zn2+ ions are inserted into the SnO2 structure (XRD, XPS, EPR), the spatial distribution of the added chemical elements, Zn and Pd (SEM, STEM, EDS). All these morphological and structural aspects, as well as the Pd surface chemistry, have been correlated with the sensing properties of the nanostructured materials under controlled gas atmosphere. Through this study, we could harvest the specific role of the aforementioned loadings towards selective detection of low NO2 concentrations, between 350 ppb to 5 ppm, at low operating temperature of 100 °C, for infield conditions.

Experimental investigation of gas/matte/spinel equilibria in the Cu–Fe–O–S system at 1250°C and P(SO2) = 0.25 atm

Abstract Experimental investigation of the gas/matte/spinel equilibria in the Cu–Fe–O–S system was undertaken at 1250°C, P(SO2) = 0.25 atm, and a range of oxygen partial pressures. The experimental methodology involved high temperature equilibration using spinel substrates in controlled gas atmospheres (CO/CO2/SO2/Ar), rapid quenching of the equilibrated phases, followed by direct measurement of phase compositions using electron probe X-ray microanalysis technique. The influence of temperature on the gas/matte/spinel equilibria and comparison with previous studies are provided. The new data obtained in the present study can be used for revision of the existing thermodynamic database for the copper-containing systems.

Distributions of Ag, Bi, and Sb as Minor Elements between Iron-Silicate Slag and Copper in Equilibrium with Tridymite in the Cu-Fe-O-Si System at T = 1250 °C and 1300 °C (1523 K and 1573 K)

New experimental data on the distributions of silver (Ag), bismuth (Bi), and antimony (Sb) between liquid iron-silicate slag and liquid copper metal in equilibrium with tridymite in the Cu-Fe-O-Si system at T = 1250 °C and 1300 °C (1523 K and 1573 K) have been obtained. The experimental methodology involved high-temperature equilibration, rapid quenching of the equilibrated phases, followed by direct measurement of the equilibrium phases with electron probe X-ray microanalysis (EPMA) for measurement of major element concentrations and laser ablation inductively coupled plasma mass spectrometry (LAICPMS) for the measurement of minor element concentrations. The 4-point test approach was employed to confirm the achievement of chemical equilibrium in the current study. Open-system equilibration on quartz substrates in controlled gas atmospheres (CO/CO2/Ar) and closed-system equilibration in sealed quartz ampoules were used. The new experimental data resolve significant discrepancies found in previous studies and can be used as input for the development of thermodynamic databases for copper-making processes.

Coupled Inductive Annealing‐Electrochemical Setup for Controlled Preparation and Characterization of Alloy Crystal Surface Electrodes

AbstractThe present versatile multifunctional electrochemical crystal preparation‐test station features capabilities for controlled thermal annealing of any type of (binary) metallic or oxidic catalyst or support crystal surfaces, in particular single crystals. The setup enables rapid inductive heating of the electrodes to temperatures up to 1900 °C under precise infrared temperature control in controlled gas atmospheres. The constant overpressure inside the cell prevents the ambient atmosphere to permeate and contaminate the process. Finely adjusted sensors afford accurate and instant information on the electrodes' surface temperature. The subsequent cooling process in argon atmosphere proceeds without any treatment in water. After annealing, the crystals inside the chamber can immediately be subjected to any type of electrochemical deposition, modification, or characterization in two distinct three‐electrode chambers, again without any exposure to air. Both chambers feature pump‐controlled supply and withdrawal of liquid electrolyte. A special characteristic is the inert‐gas flow inversion capability to transfer electrodes into separate portable inert‐gas chambers. Design details are presented and their functionality during thermal preparation and electrochemical voltammetry of Ir(111) catalysts for the oxygen evolution reaction are demonstrated. The station provides a crystal handling environment superior to the classic flame annealing approaches, yet to constitute a cost‐effective alternative to vacuum chambers.

Titanium nitride formation by a dual-stage femtosecond laser process

Formation of TiN by femtosecond laser processing in controlled gas atmosphere is reported. A dual-stage process was designed and aimed to first remove and restructure the native oxide layer of titanium surface through laser irradiation under an argon-controlled atmosphere, and then to maximize titanium nitride formation through an irradiation under a nitrogen reactive environment. An extensive XPS study was performed to identify and quantify laser-induced titanium surface chemistry modifications after a single-stage laser process (Ar and N2 individually), and a dual-stage laser process. The importance of each step that composes the dual-stage laser process was demonstrated and leads to the dual-stage laser process for the formation of TiO, Ti2O3 and TiN. In this study, the largest nitride formation occurs for the dual stage process with laser conditions at 4 W/1.3 J cm−2 under argon and 5 W/1.6 J cm−2 under nitrogen, yielding a total TiN composition of 8.9%. Characterization of both single-stage and dual-stage laser process-induced surface morphologies has been performed as well, leading to the observation of a wide range of hierarchical surface structures such as high-frequency ripples, grooves, protuberances and pillow-like patterns. Finally, water wettability was assessed by means of contact angle measurements on untreated titanium surface, and titanium surfaces resulting from either single-stage laser process or dual-stage laser process. Dual-stage laser process allows a transition of titanium surface, from phobic (93°) to philic (35°), making accessible both hydrophilic and chemically functionalized hierarchical surfaces.

Experimental Investigation of Gas/Slag/Matte/Tridymite Equilibria in the Cu-Fe-O-S-Si System in Controlled Gas Atmosphere: Experimental Results at 1523 K (1250 °C) and P(SO2) = 0.25 atm

To assist in the optimization of copper smelting and converting processes, accurate new measurements of the phase equilibria of the Cu-Fe-O-S-Si system have been undertaken. The experimental investigation was focused on the characterization of gas/slag/matte/tridymite equilibria in the Cu-Fe-O-S-Si system at 1523 K (1250 °C), P(SO2) = 0.25 atm, and a range of P(O2)s. The experimental methodology, developed in PYROSEARCH, includes high-temperature equilibration of samples on substrate made from the silica primary phase in controlled gas atmospheres (CO/CO2/SO2/Ar) followed by rapid quenching of the equilibrium condensed phases and direct measurement of the phase compositions with electron-probe X-ray microanalysis (EPMA). The data provided in the present study at 1523 K (1250 °C) and the previous study by the authors at 1473 K (1200 °C) has enabled the determination of the effects of temperature on the phase equilibria of the multicomponent multiphase system, including such characteristics as the chemically dissolved copper in slag and Fe/SiO2 ratio at silica saturation as a function of copper concentration in matte. The new data will be used in the optimization of the thermodynamic database for the copper-containing systems.

Catalysis by Metal Nanoparticles in a Plug-In Optofluidic Platform: Redox Reactions of p-Nitrobenzenethiol and p-Aminothiophenol

The spectroscopic characterization by surface-enhanced Raman scattering (SERS) has shown great potential in studies of heterogeneous catalysis. We describe a plug-in multifunctional optofluidic platform that can be tailored to serve both as a variable catalyst material and for sensitive optical characterization of the respective reactions using SERS in microfluidic systems. The platform enables the characterization of reactions under a controlled gas atmosphere and does not present with limitations due to nanoparticle adsorption or memory effects. Spectra of the gold-catalyzed reduction of p-nitrothiophenol by sodium borohydride using the plug-in probe provide evidence that the borohydride is the direct source of hydrogen on the gold surface, and that a radical anion is formed as an intermediate. The in situ monitoring of the photoinduced dimerization of p-aminothiophenol indicates that the activation of oxygen is essential for the plasmon-catalyzed oxidation on gold nanoparticles and strongly supports th...

Experimental Investigation of Gas/Matte/Spinel Equilibria in the Cu-Fe-O-S System at 1473 K (1200 °C) and P(SO2) = 0.25 atm

The Cu-Fe-O-S system is the key system for the characterisation of the phase chemistry in high-temperature copper making processes. An experimental study was undertaken to investigate the gas/matte/spinel equilibria in the Cu-Fe-O-S system at 1473 K (1200 A degrees C), P(SO2) = 0.25 atm, and a range of oxygen partial pressures. The experimental methodology involved high temperature equilibration using a primary phase substrate technique in controlled gas atmospheres (CO/CO2/SO2/Ar), rapid quenching of the equilibrated phases, followed by direct measurement of phase compositions using electron probe x-ray microanalysis. Particular attention was given to the analysis of reactions during equilibration and confirmation of the achievement of equilibrium in the present study. The new data provide important information for understanding of the gas/matte/spinel interactions at high temperature and provide an essential foundation for the development of the multicomponent thermodynamic database for copper-containing systems.

Iron Precursor Decomposition in the Magnesium Combustion Flame: A New Approach for the Synthesis of Particulate Metal Oxide Nanocomposites

AbstractPowders of Fe–Mg–O nanocomposite particles have been grown using a novel chemical vapor synthesis approach that employs the decomposition of a metalorganic precursor inside the metal combustion flame. After annealing in controlled gas atmospheres composition distribution functions, structure and phase stability of the obtained magnesiowüstite nanoparticles are measured with a combination of techniques such as inductively coupled plasma‐optical emission spectroscopy, energy dispersive X‐ray spectroscopy, X‐ray diffraction, and scanning and transmission electron microscopy. Complementary Mössbauer spectroscopy measurements reveal that depending on Fe loading and temperature of annealing either metastable and superparamagnetic solid solutions of Fe3+ ions in periclase (MgO) or phase separated mixtures of MgO and ferrimagnetic magnesioferrite (MgFe2O4) nanoparticles can be obtained. The described combustion technique represents a novel concept for the production of mixed metal oxide nanoparticles. Adressing the impact of selected annealing protocols, this study underlines the great potential of vapor phase grown non‐equilibrium solids, where thermal processing provides means to trigger phase separation and, concomitantly, the emergence of new magnetic properties.

Oxidation of Zircaloy-4 in steam-nitrogen mixtures at 600–1200 °C

High-temperature oxidation of zirconium alloys in steam-nitrogen atmospheres may be relevant during various nuclear accident scenarios. Therefore, isothermal oxidation tests with Zircaloy-4 in steam-nitrogen mixtures have been performed at 600, 800, 1000, and 1200 °C using thermogravimetry. The gas compositions were varied between 0 and 100 vol% nitrogen including 0.1 and 90 vol%. The strong effect of nitrogen on the oxidation kinetics of zirconium alloys was confirmed in these tests in mixed steam-nitrogen atmospheres. Even very low concentrations of nitrogen (starting from less than 1 vol%) strongly increase reaction kinetics. Nitrogen reduces transition time from protective to non-protective oxide scale (breakaway). The formation of zirconium nitride, ZrN, and its re-oxidation is the main reason for the highly porous oxide scales after transition. The results of this study have shown the safety relevant role of nitrogen during severe accidents and, more generally, suggest the need of using well controlled gas atmospheres for experiments on oxidation of zirconium alloys.

Thermodynamic and Experimental Investigations of High-Temperature Refractory Corrosion by Molten Slags

Corrosion mechanisms between MgO refractory substrates and FeNi slags were investigated. The FeNi slags taken into consideration represent a simple synthetically mixed slag with specific oxides and a real slag from a ferroalloy producer. The MgO refractory substrates with the specimens of FeNi slag were heated in a hot-stage microscope at 10 K/min from room temperature to three different temperatures 1573 K, 1723 K, and 1923 K (1300 °C, 1450 °C, and 1650 °C). The experiments were carried out under a controlled gas atmosphere that simulates the relevant process conditions. The corrosion mechanisms of each system were followed by scanning electron microscope analyses. The results obtained showed that slag corrosion dominates, with a pronounced partial dissolution of refractory fines forming Mg-silicates of type forsterite. It was also observed that iron oxide present in the slag diffused into the coarse refractory grains forming magnesiowustite. Finally, the results obtained were compared with those predicted by FACTSAGE software to understand the corrosion mechanisms and draw implications for improving the refractory performance and lifetime.

Slag density and surface tension measurements by the constrained sessile drop method

Density and surface tension of slag are important properties for mineral processing, metal processing, slagging combustion and slagging gasification. In the case of slagging gasification, slag properties will impact the efficiency, reliability, maintenance cost and environmental performance of the process. There are several methods to determine the density and surface tension of slags. A commonly used technique is the sessile drop technique since it allows determination of both the density and surface tension, and can be performed at high temperatures in controlled gas atmospheres. This technique usually requires substrates that provide high contact angles with the samples for accurate results. To circumvent this issue, constrained sessile drops can be used. The limitations and accuracy of the constrained sessile drop technique for slag density and surface tension measurements were evaluated by a series of tests and phase equilibria predictions. Although molybdenum and alumina substrates provide lower contact angles than graphite substrates with the synthetic coal and petroleum coke slags tested, they interact less with the slags and alumina allows for measurements in both oxidizing and reducing conditions. Use of constraining 8mm diameter molybdenum and alumina substrates resulted in greater precision than use of larger constraining and non-constraining substrates. The density of the synthetic coal slag studied is in the range of ∼2.4g/cm3 for the temperature range of 1200–1600°C, in both oxidizing and reducing conditions. Based on measurements with a molybdenum substrate, its surface tension is ∼420mJ/m2 for the same temperature range. Measurements with alumina substrates, in both oxidizing and reducing conditions, yielded similar results above 1450°C, but higher surface tension was observed at lower temperatures. Measurements with real coal slag provided similar results to measurements with synthetic coal slag. In the temperature range of 1530–1630°C, the synthetic petroleum coke slag has a density of ∼2.4g/cm3. Its surface tension is ∼360mJ/m2 in oxidizing conditions and ∼460mJ/m2 in reducing conditions. The surface tension difference is likely due to different phase equilibria with oxidizing and reducing environments, and may be impacted by the presence of solids in reducing conditions.

Correlating the Onset of Coking with Electrode Surface Chemistry during CO2 Electrolysis with Near Ambient Pressure X-Ray Photoelectron Spectroscopy

Recycling carbon dioxide into carbon monoxide as a feedstock for industry and transportation has become of great interest as a means to reduce the impact of humanity on the environment. Due to the high thermodynamic efficiency inherent in electrochemical reduction of CO2 at high temperatures (~800 oC), solid oxide electrolysis is an attractive method for CO production. Furthermore, in steam and CO2 co-electrolysis (SOE), the hydrogen and CO products constitute syngas, of significant importance to industry. Additionally, SOE of CO2 is actively being explored by the National Aeronautics and Space Administration (NASA) to generate O2 for rocket propellant and life support for future missions to Mars. Mitigating degradation of SOE cell performance over time remains a key challenge of the technology. For example, carbon accumulation (coking) on the cathode electrode during reduction of CO2, particularly problematic in dry conditions, leads to mechanical and electrochemical degradation of the cell. Other degradation modes, well known in the solid oxide fuel cell community, such as large electrode volume changes during redox (i.e., chemical expansion) with subsequent mechanical failure are also of concern. As a result, electrodes have been developed to counter these degradation modes in electrolysis and fuel cell operation. The majority of studies have largely been guided by empirical evidence indicating coke tolerant electrodes. In this presentation, we describe an investigation into the relationship between gas/solid interface compositional and operational factors that lead to the onset of coking. We take advantage of surface sensitive spectroscopy performed in situ in controlled gas atmosphere and temperature, known as near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS). NAP-XPS was used to evaluate conditions leading to coking using CO/CO2 mixtures at approx. 200 mTorr total pressure at 450 oC. Electrical bias was applied to ceria based films, deposited using pulsed laser deposition on “buried” Pt electrodes, supported on ionic conducting substrates of yttria stabilized zirconia to in situ drive the CO2 reduction reaction. Two different Gd doped ceria based films were studied, one with Zr doping (suggested to exhibit greater coke tolerance) and one without. The surface spectroscopy analysis yields information about the relationship between onset of coking, surface defect concentration (e.g., oxygen vacancies), surface composition (e.g., relative cation and impurity), and area specific resistance. In this presentation, we will discuss the relationship between these factors, as well as the role of gas composition (CO/CO2).

Mixed Proton/Electron Conductivity in Nano-Grained Bulk Body of TiO2

Background Proton-conducting solid electrolytes are paid much attention from various applications such as SOFC and electrochemical catalyst. As a new class of materials other than bulk conductors, low temperature proton conductivity on the surface of nano-grained oxides like YSZ [1] and CeO2 is studied by many researchers in these days. The previous study by the authors has suggested that the dominant mechanism for proton conduction depends on the temperature, and three types of mechanism are suggested for corresponding temperature ranges; a proton hopping via hydroxyl(M-OH−) on the surface of metal oxide at the highest temperature range above 250, that via hydrogen-bonded H2O molecules by the Grotthuss mechanism at temperatures between 60 ºC and 250 ºC, and the Vehicle mechanism, using H3O+s as a vehicle. H3O+s are delocalized from the surface to diffuse into the hydrated multilayer above the surface below 60 ºC. Possible and unique applications of this surface proton conductivity are electrochemical catalysts and reactors by combining surface proton conductivity with variety of bulk functionalities like electronic conductivity and photocatalytic activity. To promote the catalytic reaction, i.e.COOH+3H++3e-→CH3OH+1/2O2, both protons and electrons are to be migrated to the active sites for anodic and cathodic reactions. As TiO2 in anatase form is a bulk n-type semiconductor, nano-grain anatase is a candidate to achieve both proton and electron conduction simultaneously. In this research, electrical conductivity of nano-grained TiO2 is analyzed to examine a possible application of TiO2 for such an electrochemical and photochemical catalysts. Method TiO2 nanoparticle in anatase form was obtained by hydrolysis of alkoxide (Ti(OC4H9)4). The obtained nano-grained powder with its grain size about ~20nm, estimated from XRD and SEM images, was pressed at room temperature (RT), using cubic anvil at 4GPa with pyrophylite as a pressure media, resulting in a compact body of anatase. After shaping into rectangular plate, Au electrodes on both sides of rectangular face ware fabricated, and the sample was subjected to subsequent electrical conductivity measurement. Two-probe ac impedance measurements ware conducted under controlled temperature and gas atmospheres. The gas mixtures employed are categorized as reducing (1%H2-99%Ar) and oxidizing atmosphere (100%O2) with and without CO2. All the gas mixtures are humidified by either H2O or D2O, to examine isotope effect. The measurements were made from RT to 400 ºC FT-IR is used to characterize surface adsorbates at the same atmosphere and temperatures with electrical measurements. Result Figure1 shows the electrical conductivity under oxidizing and reducing conditions with and without CO2. In oxidized atmosphere, the measured conductivity above 250 ºC increases with the increase of temperature, while the conductivity increases with the decrease of temperature below 250 ºC which is typical behavior of surface proton conductivity of nano-grained oxide materials. In addition, H-D isotope effect on the conductivity is observed in entire temperature range measured, suggesting the predominant proton conductivity. An inversion of the temperature dependence of the electrical conductivity around 250 ºC suggests the presence of two different proton conductivity mechanisms in the nano-grained TiO2 system. In reducing atmosphere (1%H2−99%Ar), the conductivities above 150 ºC are higher than those in oxidized atmosphere by several orders of magnitude, in contrast to the similar values between oxidizing and reducing atmosphere below 150 ºC In addition, the conductivity is approximately proportional to one half power of P H2(partial pressure of H2 gas). This dependency can be explained by the following formation reaction of interstitial Ti3+, which is considered to be the dominant defect in bulk TiO2. TiTi x+2OO x+2H2→Tii •••+3e’+2H2O This consistency with the bulk defect chemical reaction suggests that the electronic conduction in bulk is dominant in reduced atmosphere above 150 ºC The influence of the CO2 adsorption is limited to the low temperature range below 175 ºC, probably because of desorption of CO2 above this temperature. The decrease of conductivity by CO2 adsorption observed agrees with the decrease observed in nano-grained YSZs reported earlier, suggesting similar mechanism is seemingly working behind. In summary, we could successfully observe both electronic and ionic conductivities for nano-grained TiO2 bulk body fabricated by ultra-high pressure pressing at room temperature. Reference [1] S. Miyoshi et al. Chem. Mater., 26 (2014) 5194.[2] R. Sato et al. J. Phys. Chem. C, 119 (2015) 28925. Figure 1

Implementation of diverse non-centrosymmetric layer concepts for tuning the interface activity of a magnesium alloy

Magnesium and its alloys are the lightest metallic materials used for structural applications. Tuning the surface functionalization of magnesium alloys may contribute to increasing their durability. Dry or wet processes may be effective for the modification of magnesium alloy surfaces. The resulting layers may cover surface inhomogeneities and separate the substrate surface from molecular films. This work demonstrates the feasibility and effectiveness of the concepts and techniques comprising laser or plasma based pretreatment processes or dipping procedures that involve synthetic amphiphilic polymers or biopolymers. In detail, the effects of barrier layers that have been applied by the deposition of siliceous polymer coatings in low pressure plasma processes, by laser surface treatments in controlled gas atmospheres or by dipping in liquid formulations containing a recently developed polymeric inhibitor or a mixture of the enzyme laccase and the polysaccharide maltodextrin are monitored. In this respect, a time-resolved hydrogen bubble formation test is performed, revealing interactions between water films and the modified surfaces. The surface modification is shown with X-ray photoelectron spectroscopy investigations and, in addition, the alloy surface and grain structure is characterized using energy dispersive X-ray analysis, scanning electron microscopy and scanning force microscopy. These investigations reveal that the thus established layer/substrate and layer/environment interphases differ in their composition as a result of the non-centrosymmetric layer concepts for surface functionalization applied here.

A simple and inexpensive method to control oxygen concentrations within physiological and neoplastic ranges

Traditional methods for regulating oxygen concentration ([O2]) in in vitro experiments over the range found in normal and tumor tissues require the use of expensive equipment to generate controlled gas atmospheres or the purchase of a range of gas cylinders with certified O2 percentages. Here we describe a simple and inexpensive enzymatic method for generating low, precise steady-state [O2] levels that are stable for several hours. This method is particularly applicable to the in vitro study of some classes of hypoxia-targeted antitumor prodrugs and bioreductively activated agents.

Local measurement of mass transfer in a reactive spray for CO2 capture

CO2 capture is still a major challenge for the environment and decarbonization of gas streams. It has been industrially feasible for several decades using chemical absorption by alkanolamine solvents. The purpose of this work is to characterize the mass transfer in a spray contactor during CO2 absorption using monoethanolamine as a solvent. A new, effective way to investigate mass transfer is to measure the refractive index during the reactive absorption. Indeed, the concentration and temperature evolution inside the droplet during absorption induces a modification of the refractive index. By using rainbow refractometry technique (GRT), the liquid side mass transfer coefficient was measured in a controlled gas atmosphere during a transfer process in aqueous 30 % (w/w) monoethanolamine and compared to the literature.

135 EFFECT OF L-ERGOTHIONEINE SUPPLEMENTATION DURING CULTURE ON IN VITRO EMBRYO DEVELOPMENT IN BUFFALO (BUBALUS BUBALIS)

It is known that in vitro mammalian embryo development is negatively affected by the increased oxidative stress occurring under culture conditions. The oxidative damage of cell components via reactive oxygen species interferes with proper cell function. Buffalo embryos are particularly sensitive to oxidative stress because of their high lipid content (Boni et al. 1992 Acta Med. Vet. 38, 153–161). l-Ergothioneine (LE) is a powerful scavenger of hydroxyl radicals (OH) and an inhibitor of iron or copper ion-dependent generation of OH from hydrogen peroxide (H2O2). The aim of this study was to evaluate whether enriching the in vitro-culture medium with LE improves in vitro embryo production efficiency in buffalo. Abattoir-derived buffalo oocytes (n = 854, over 6 replicates) were in vitro matured and fertilized according to standard procedures (Gasparrini et al. 2006 Theriogenology 65, 275–287). Twenty hours after IVF presumptive zygotes were cultured in SOFaa supplemented by 8 mg mL–1 BSA in a controlled gas atmosphere consisting of 5% CO2, 7% O2, 88% N2, in humidified air, at 38.5°C with 0 (control; n = 214), 0.05 mM LE (n = 217), 0.1 mM LE (n = 204), and 1 mM LE (n = 219). Cleavage rate was assessed at the time of change of culture (Day 5) and the cleaved elements were cultured for a further 2 days. The embryos obtained by the end of culture, i.e. on Day 7 post-IVF, were scored for quality, based on morphological criteria, and for developmental stage, as previously described (Robertson, Nelson 2010 Manual of the International Embryo Transfer Society 86–105). The percentages of total transferable embryos and Grade 1 and 2 blastocysts in relation to cleaved oocytes were recorded. Because the chronology of development is known to be one of the most reliable parameters for assessing quality, the percentage of fast-developing embryos, i.e. hatched and expanded blastocysts, was also recorded. Data were analysed by Chi-squared test. Cleavage rate was not affected by the treatment (71.4, 66.8, 68.7, and 63.0%, respectively, with 0, 0.05, 0.1, and 1 mM LE). The total embryo output increased in groups supplemented with 0.05 and 0.1 mM LE (31.3, 42.2, 43.8, and 21.7%, respectively, with 0, 0.05, 0.1, and 1 mM LE; P < 0.05). However, the enrichment of in vitro culture with 0.1 mM LE also increased the percentage of Grade 1 and 2 blastocysts compared with the control and to 1 mM LE (21.6, 30.9, 33.9, and 21.7%, respectively, with 0, 0.05, 0.1, and 1 mM LE; P < 0.05). Likewise, 0.1 mM LE gave higher percentages of fast developing embryos than the control and 1 mM LE groups. In conclusion, these results demonstrated a beneficial effect of LE during culture on buffalo in vitro embryo development. The dose response trial indicated that the optimal concentration is 0.1 mM that also influenced the chronology of development and hence embryo viability.

Improvement of oxidation resistance of TiCN films prepared by laser alloying

In this paper, we report the structural and electronic properties of TiCxNy films prepared by laser treatment under controlled gas atmosphere. X-ray diffraction shows the formation of TiCxNy along with the solid solutions of Ti(CN). The TiCxNy phases have been formed and are stable up to 650 °C. Subsequent laser irradiation at different laser energy densities in Ar-atmosphere modifies the microstructure and becomes oxidation resistant. Due to the formation of nano-crystalline TiCxNy, the affinity of Ti toward oxygen has been reduced remarkably after the Ar-treatments. Surface structure analysis by valence band spectroscopy reveals that the hybridization between Ti 3d and C 2p is increasing after the subsequent Ar-treatment at the cost of Ti 3d and N 2p hybridization.