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At least 1,495 records · Page 83
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Biosynthesis, Microstructural Characterisations and Investigation of In-Vitro Mutagenic and Eco-Toxicological Response of a Novel Microbial Exopolysaccharide Based Biopolymer

A modified microbial polysaccharide based biopolymer has been investigated as a potential candidate towards development of sustainable biomaterials and bioplastics. An in-depth study was carried out to biosynthesize, characterize and assess any possible mutagenic potential and ecotoxicity of the microbial polysaccharide biopolymer. Microstructural investigations using confocal microscopy, Fourier transform (FT)-Raman depth profile mapping and scanning electron microscopy (SEM) of the biosynthetically modified polysaccharide revealed internal structural perturbations, as well as occlusion of granular pores by extraneous materials. The Raman 3D mapping depth profile along with time-of-flight (MALDI-TOF) mass spectrometry also indicated important structural and surface modifications, which could be correlated to the production of microbial exopolysaccharides and secondary metabolites. The study then looked into any possible genetic mutation and ecological risks associated with the biosynthetically modified polysaccharide through the investigation of genotoxicity and ecotoxicity. The genotoxicity study was carried out through bacterial reverse gene mutation (Ames) test by using two different strains (TA98 and TA100) of bacteria. The results did not indicate any mutagenic effect against either of the strains used for the biopolymer samples and was found to be genotoxically safe. Ecotoxicity tests, carried out using bioluminescent bacteria Vibrio fisheri further indicated no ecotoxicity within the given experimental conditions. The study measured the half maximal effective concentration (EC50) to cause a 50% decrease in the light output of the bacteria, a measure of ecotoxicological response of the biopolymer. Overall, results from this study indicated that the novel biopolymer was genotoxically and ecotoxically safe, which offers immense potential for future use of this biopolymer.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Flow Behaviour and Microstructure of a β-Glucan Concentrate

The extensional viscosity is an important rheological characteristic of polymer melts. It is however not as frequently reported on as the shear viscosity. The extensional viscosity is of special interest when considering polymeric materials for foaming and film blowing processes. Here, the extensional (and shear) viscosity along with the melt strength and the tensile properties of the corresponding solid film of a β-glucan concentrate are reported on. A capillary viscometer equipped with a hyperbolic die, yielding a contraction flow, was used to assess the extensional viscosity of the aqueous β-glucan compound at room temperature and at elevated temperatures (110 and 130 °C). In general, the extensional viscosity as well as the shear viscosity decreased with increasing deformation rate. The influence of two different amounts of added water (40 and 50%) was also examined. As expected, both types of viscosities decreased with increasing temperature. It is suggested that gelatinization of the starch fraction in the concentrate at 110 and 130 °C contributes to temperature dependence of the viscosity. To some extent, this is supported by light microscopy and confocal scanning laser microscopy studies of the microstructure of the materials. The results reported here indicate that the β-glucan concentrate might, after some modifications, be used as a complement to fossil-based polymers and processed by conventional manufacturing techniques.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Influence of Iron Content on Microstructure and Magnetic Properties of Sr{sub 0.3}La{sub 0.4}Ca{sub 0.3}n(Fe{sub 2}O{sub 3})Co{sub 0.4}

In this work, the hexagonal ferrite Sr{sub 0.3}La{sub 0.4}Ca{sub 0.3}n (Fe{sub 2}O{sub 3})Co{sub 0.4}, where n ranging from 5.5 to 6.0 with a step of 0.1, and magnetic powders and magnets were synthesized by solid-states reaction. The microstructure of the magnetic powders was investigated by X-ray diffraction (XRD). And then we can found that a single magnetoplumbite phase is obtained for magnetic powders as a result when 5.6 ≤ n ≤ 5.8. When the iron content in the magnetic powders increased continuously, the diffraction peaks of α-Fe{sub 2}O{sub 3} were observed. Scanning electron microcopy (SEM) was used to explore the micrographs of the magnets and the hexagonal-shaped crystals were found obviously. The magnetic properties of the M-type hexagonal ferrites Sr{sub 0.3}La{sub 0.4}Ca{sub 0.3}n(Fe{sub 2}O{sub 3})Co{sub 0.4} were studied by using vibrating sample magnetometry. The saturation magnetization (M{sub s}) first increased and then began to decrease with the n increasing. While the coercivity first decreased with the n from 5.5 to 5.9 and then increased when n ≥5.9. The coercivity (H{sub c}) of the hexagonal ferrite Sr{sub 0.3}La{sub 0.4}Ca{sub 0.3}n(Fe{sub 2}O{sub 3})Co{sub 0.4} reaches the maximum value (H{sub c} = 1130 Oe) when the iron content (n = 5.5).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Synthesis and Microstructural Analysis of Magnetic CaFe{sub 0.5}Co{sub 0.5}O{sub 3−δ} Using Rietveld Method

Perovskite cobaltates are widely recognized as potential candidates for their applications in magnetic and magnetoresistive applications. In this report, pseudo-magnetic CaFe{sub 0.5}Co{sub 0.5}O{sub 3−δ} was synthesized at ambient pressure. Various calcinations, heating times, and sintering temperatures were applied in order to achieve the optimized conditions. The optimal sintering temperature with excellent phase and microstructure was found at ∼1050 °C using CaCO{sub 3} as precursor. Rietveld analysis was carried out to solve and refine the XRD pattern of the final specimens. The sample with excellent refined values was solved in orthorhombic phase and pbcm space group. From the SEM and EDS analysis, the excellent grain growth with high densification and ABO{sub 3} structure was confirmed respectively.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of the Ce Content on the Magnetic Properties and Microstructure of CeCo{sub 5}-based Sintered Bulk Magnets

CeCo{sub 5}-based magnets have recently attracted much attention due to their moderate magnetic performance and low cost. Nevertheless, there have been few studies on the effects of Ce content on the magnetic properties and microstructures of CeCo{sub 5}-based magnets. In response to this, the magnetic properties of sintered bulk magnets with nominal compositions of Ce(Co{sub 0.73}Cu{sub 0.135}Fe{sub 0.135}){sub z} (z = 4.95, 5.15, 5.35, and 5.55), prepared by the conventional powder metallurgy method, were investigated here. Based on experimental findings, it was shown that Ce(Co{sub 0.73}Cu{sub 0.135}Fe{sub 0.135}){sub 5.15} sintered bulk magnets had comprehensive magnetic properties—maximum energy product of 80 kJ m{sup − 3} (10 MGOe) and intrinsic coercivity (H{sub cj}) of 452 kA m{sup − 1} (5.69 kOe)—superior to those previously reported by us. For z = 5.35 and 5.55, due to the presence of the minor Ce{sub 2}Co{sub 17} phase (which has a Curie temperature (T{sub c}) < 20 °C), magnets had low H{sub cj} values. Based on x-ray diffraction and scanning electron microscopy observations, it was suggested that the volume fraction of the 1:5 matrix phase was the main factor determining the H{sub cj} of CeCo{sub 5}-based sintered bulk magnets obtained with different Ce contents. Furthermore, the importance of the dispersion characteristics of the Ce{sub 2}O{sub 3} phase within the matrix was emphasized. Uniform dispersion of the Ce{sub 2}O{sub 3} phase can significantly improve the overall magnetic performance of CeCo{sub 5}-based magnets.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Ti Capping Layer Effects in Microstructure and Magnetic Properties of Sputter-Deposited FePt Thin Film

Ti/FePt/Fe nano-thin films were fabricated by a DC facing-target magnetron sputtering method onto glass substrates at room temperature and were subsequently annealed in situ in vacuum. The impacts of the Ti capping layer on microstructural and magnetic properties of the FePt films were investigated in detail. X-ray diffraction (XRD) patterns demonstrate that the film is deposited onto glass substrates and the addition of a Ti layer forms ternary TiFePt, and binary PtTi and FeTi alloys. The results reveal refined granularity, decreased roughness, and enhanced coercivity and degree of squareness after the introduction of a Ti capping layer.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of Fe Substitution on Microstructure and Magnetic Properties of Ni{sub 1−x}Fe{sub x}O{sub 2} Nanoparticles

Fe-substituted NiO nanoparticles (Ni{sub 1−x}Fe{sub x}O{sub 2}) (x= 0.00, 0.03, 0.05, 0.07, and 0.09) were synthesised using ball-milling method followed by vacuum sintering and studied for their microstructural and magnetic properties. All the samples show a cubic structure with a crystallite size of 17–26 nm. Secondary phases related to Fe{sub 2}O{sub 3} were identified from XRD, indicating that the observed ferromagnetism may be due to the dopants. The doping of Fe ions does not cause any significant variation in the crystal structure. The pure NiO nanoparticles were weak ferromagnetic in nature, and Fe-doped NiO nanoparticles exhibit room temperature ferromagnetism. The strength of magnetization increased from 0.57 to 0.94 emu/g with an increase of Fe concentration from 3 to 7 at.%, respectively. A high coercive field of 173 Oe was observed for the Ni{sub 1−x}Fe{sub x}O{sub 2} nanoparticles at x= 0.09. The results and the process of development of ferromagnetism at room temperature in the Ni{sub 1−x}Fe{sub x}O{sub 2} nanoparticles were presented and discussed in detail.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of Yb Substitution on Microstructure and Superconducting Properties of Y{sub 1−x}Yb{sub x}Ba{sub 2}Cu{sub 3}O{sub 7−δ} Films

The purpose of this study was to improve the critical current density (J{sub c}) of YBa{sub 2}Cu{sub 3}O{sub 7−δ} (YBCO) superconducting films at high magnetic fields. Thin Y{sub 1−x}Yb{sub x}Ba{sub 2}Cu{sub 3}O{sub 7−δ} (Y{sub 1−x}Yb{sub x}BCO) superconducting films on LaAlO{sub 3} substrates were prepared by modified low-fluorine metal organic deposition method (LF-MOD) in order to investigate the effect of Yb substitution on the microstructure and superconducting properties of a YBCO-coated conductor. In this study, single-phased, c-axial-aligned Y{sub 1−x}Yb{sub x}BCO films were obtained. Yb doping had a little effect on the critical temperature (T{sub c}) and transition width (ΔT) values of Y{sub 1−x}Yb{sub x}BCO films. An abnormal phenomenon was observed that the J{sub c} of Y{sub 1−x}Yb{sub x}BCO films at low field was smaller than that of the pure YBCO film, but the J{sub c} of Y{sub 1−x}Yb{sub x}BCO films at high field was much greater than that of the undoped YBCO film. Compared to pure YBCO film, the J{sub c} values of Y{sub 0.75}Yb{sub 0.25}BCO and Y{sub 0.25}Yb{sub 0.75}BCO films were enhanced by a factor of 8 at 8 T, 65 K, which meant that chemical substitution of Yb into the Y site could improve flux pinning significantly under the high magnetic field in Y{sub 1−x}Yb{sub x}BCO coated conductors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Structural, Microstructural, Magnetic, and Ferroelectric Properties of Ba{sup 2+}-Doped BiFeO{sub 3} Nanocrystalline Multifferroic Material

Multiferroic barium-substituted nanocrystalline samples having the general formula Bi{sub 1−x}Ba{sub x}FeO{sub 3} (where x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25) were prepared by cost-effective sol–gel method using metal nitrates as oxidants. The prepared samples were annealed at 650 {sup ∘}C for 4 h using a muffle furnace. The influence of Ba{sup 2+} doping on the structural, microstructural, magnetic, and ferroelectric properties of bismuth ferrite (BFO) was studied systematically by standard techniques. All the samples were characterized by X-ray diffraction (XRD) technique, and the average crystallite size was calculated using Scherrer’s formula. The surface morphology of the prepared nanocrystalline samples was studied using field emission scanning electron microscopy (FE-SEM) technique. FTIR spectra were obtained to confirm the formation of the perovskite structures. The elemental compositional details obtained were confirmed by energy dispersive spectrum (EDS) analysis. Room temperature magnetic measurements were carried out up to a field of 15 kOe, and the parent sample (BFO) shows weak ferromagnetism. Further on, Ba{sup 2+} substitution in BFO shows an increase in magnetization. P–E loops were obtained to study the ferroelectric properties of all the samples. Obtained enhancement in magnetic and ferroelectric properties at room temperature is of great interest within the research community due to its wide range of applications in memory storage, spintronics, sensors, and multi-functional devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Superconducting Performance, Structure, Microstructure, and Trapped Field of Top-Seeded Melt-Processed Bulk Y{sub 3}Ba{sub 5}Cu{sub 8}O{sub x}

The sintering temperature for the production of Y{sub 3}Ba{sub 5}Cu{sub 8}O{sub 18} (Y-358) preform powders synthesized in sol-gel spontaneous combustion technique was optimized. A large single-grain bulk Y-358 crystal was fabricated employing a top-seeded melt-growth technique utilizing the optimally sintered preform powders (i.e., at 900 {sup ∘}C for 12 h). Structural, microstructural, elemental, and magnetic properties were investigated by means of X-ray diffraction, scanning electron microscopy, and SQUID, respectively. The structural characterization indicated that the sample is highly textured in (00l) direction. The Y-358 phase fractions were estimated in both preform powders and bulk sample using Rietveld refinement. The onset of superconducting transition is observed at 92.5 K, and the curve is very sharp indicative of the high quality of the produced bulk sample. The field dependence of critical current density (J{sub c}) was determined at 77 K, and the self-field J{sub c} was found to be ∼26 kA/cm{sup 2}. A magnetic field of 0.27 T was trapped by the sample at 77 K.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of the Laser Scan Rate on the Microstructure, Magnetic Properties, and Microhardness of Selective Laser-Melted FeSiB

FeSiB alloys have been fabricated by selective laser melting (SLM) using a laser scan rate of 0.1–1.5 m/s, laser power of 90 W, scan line spacing of 40 μ m, and layer thickness of 50 μ m. X-ray diffraction, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, atomic force microscopy, profilometer, microdurometer, and vibrating sample magnetometer have been used to investigate the structural, microstructural, roughness, microhardness, and magnetic property changes during the laser melting process. The produced samples exhibit a nanocomposite structure consisting of nanocrystalline α-Fe{sub 0.95}Si{sub 0.05} and Fe{sub 2}B phases embedded into an amorphous ε-FeSi-type matrix. The selective laser-melted samples show high density, low surface roughness, higher microhardness values (1654–2273 Hv), and soft magnetic properties (M{sub s} = 188.6–199 emu/g and H{sub c} = 43.8–73 Oe).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Effects on Glass Forming Ability, Microstructure, Crystallization Behaviors, and Magnetic Properties of Si Substituting for P in Fe-Rich Fe{sub 86}B{sub 13−x}Si{sub x}P{sub 1}Cu{sub 0.6}Hf{sub 0.4} Alloys

In the paper, we have studied the effects on glass forming ability (GFA), microstructure, crystallization behaviors, and saturation magnetization (M{sub s}) of Si substitution for P in Fe-rich Fe{sub 86}B{sub 12}Si{sub x}P{sub 1−x}Cu{sub 0.4}Hf{sub 0.6} alloys. The amorphous structure is identified by X-ray diffraction first, and the patterns with Si addition less than x = 0.75 only show one halo scattering peak at 2θ = 45°; further, the ribbons with entirely amorphous structure have been fabricated successfully and the alloys have a good GFA. Then, by differential scanning calorimetry testing, the curves show two separated exothermic peaks and the ribbons will go through a two-step crystallization before reaching stable state; further, the first peak is ensured by the crystallization of a-Fe phase while the second peak is ensured by the precipitation of FeB or Fe(BP) compounds. As Si was added, the apparent activation energy of the first crystallization (E{sub a1}) and the second crystallization (E{sub a2}) shows an increased tendency first and then decreases slightly. By comparison, as x = 0, x = 0.25, and x = 0.5, the ribbons easily form Hf{sub 3}P{sub 2} compounds during the first crystallization process simultaneously, where the ribbons of x = 0.75 and x = 1.0 are easier to finish the first crystallization for forming the uniform a-Fe phase entirely. By vibrating sample magnetometer testing, with the addition of Si, M{sub s} value shows an increased trend and reaches to the maximum about 177.5 emu/g (x = 1.0), and which shows an increased trend in the subsequent annealing process and reaches to the maximum 206.3 emu/g (x = 0), 212.3 emu/g (x = 0.25), 214.2 emu/g (x = 0.5), 214.9 emu/g (x = 0.75), and 208.3 emu/g (x = 1.0) as the annealing temperature higher than T{sub p1} but less than T{sub x2}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Influence of Packing Atmosphere on the Microstructures and Transport Properties of Bi-2223/AgAu Tapes

Oxygen partial pressure was the key factor to tune the phase evolution mechanism of Bi-2223 system. In order to investigate the influence of packing atmosphere on the phase formation rate of Bi-2223, microstructures‚ and the current capacity of final tapes‚ 37-filamentary Bi-2223/AgAu tapes were fabricated by powder-in-tube (PIT) process, and the powder packing process operated in the glove box under different atmosphere of pure O{sub 2}‚ air, and N{sub 2}–7.5%O{sub 2}, with the oxygen partial pressure of 100%‚ 25%, and 7.5%, respectively. With different packing atmosphere, the phase formation rate of Bi-2223 increased obviously during the first heat treatment process (HT1). While, based on the same HT1 process, the maximum Bi-2223 phase content was obtained in the tapes with packing atmosphere of N{sub 2}–7.5%O{sub 2}‚ which should be attributed to the suitable Bi-2223 content and distribution. Due to the improvement of superconducting phase content and better texture structure, the critical current density increased with decreasing oxygen partial pressure of packing atmosphere and the maximum value of 19.9 kA/cm{sup 2} was reached. Moreover‚ the in-field current capacities of these Bi-2223/AgAu tapes have also been enhanced with low oxygen partial pressure in packing atmosphere, attributed to the improvements of intergrain connectivity.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Influence of Annealing on Microstructure, Electrochemical, and Magnetic Properties of Co-Doped SrTiO{sub 3} Nanocubes

Effect of annealing on microstructure, electrochemical, and magnetic properties of Co-doped SrTiO{sub 3} nanocubes obtained by the hydrothermal method was studied. X-ray diffraction (XRD) results of all as-prepared and annealed Co-doped SrTiO{sub 3} samples revealed a cubic perovskite structure with the second phases of SrCO{sub 3} and Co{sub 3}O{sub 4}in as-prepared and annealed SrTi{sub 0.90}Co{sub 0.10}O{sub 3} samples, respectively. Agglomerated nanocubes could be clearly observed in all as-prepared and annealed Co-doped samples by scanning electron microscope (SEM) and transmission electron microscope (TEM). X-ray absorption near edge spectroscopy (XANES) results suggested the presence of Co{sup 2+} cations in as-prepared Co-doped SrTiO{sub 3} samples, while both of Co{sup 2+} and Co{sup 3+} cations were found in annealed Co-doped SrTiO{sub 3} samples. The cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) results of as-prepared and annealed SrTi{sub 1-x}Co{sub x}O{sub 3} (x = 0.05, 0.075 and 0.10) electrodes revealed pseudocapacitor behavior of the Faradaic redox reaction type. The specific capacitance (Csc) was affected by the increase of Co content in all as-prepared and annealed Co-doped SrTiO{sub 3} samples with an excellent cycling stability after 200 cycle test of 97.24% and the highest value of 75.28 F g{sup −1} at 1 A g{sup −1} in an annealed SrTi{sub 0.925}Co{sub 0.075}O{sub 3} electrode. Magnetization measurements at room temperature using vibrating sample magnetometer (VSM) revealed diamagnetic behavior of as-prepared SrTiO{sub 3} sample, whereas paramagnetic behavior was observed in all as-prepared Co-doped SrTiO{sub 3} samples. After annealing, undoped sample exhibited paramagnetic behavior, whereas ferromagnetic behavior was observed in all Co-doped SrTiO{sub 3} samples with the increase of saturation magnetization (M{sub s}) at 10 kOe from 0.58 to 1.63 emu/g and the coercive field (H{sub c}) from 43.71 to 123.87 Oe, suggested to originate from the face-center exchange (FCE) mechanism.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Implications of theoretical analysis to explore the functional core dimension in one-rod core microstructured optical fibers

A new development in optical fiber technology that has attracted interest for multitude of novel and potential applications is an all-in-silica microstructured optical fibre (MOF) with one-rod core. We aim to estimate the functional core dimension for one-rod core triangular MOF (T-MOF) from its geometrical characteristics by using an alternative analytical field model. Moreover, to scrutinize the validity of the choice of effective core dimension (by adapting V-parameter, i.e., the normalized frequency) for T-MOF, we have explored the rudimentary propagation characteristics of the T-MOF in single mode guidance realm. We made comparisons with those which are based on the experimental and numerical studies. Relative errors are also reported.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

The Influence of Microstructure on Oxidation Rate Of V–Cr–Ta–Zr Alloy During Its Chemical-Heat Treatment

Using the methods of scanning (electron backscatter diffraction) and transmission electron microscopy, an investigation of the influence of microstructure of a V–Cr–Ta–Zr alloy on the rate of surface oxide scale formation in the course of its chemical-heat treatment using oxidation in air is performed. It is shown that a preliminary plastic deformation, ensuring a multiple increase in the density of dislocations and misorientation boundaries, results in a 10% thicker surface oxide layer and a respective increase in the concentration of oxygen in the alloy during the final stage of its chemical-heat treatment. The role of this factor in developing the chemical-heat treatment regimes is discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Special Aspects of Microstructure, Deformation and Fracture of Bioinert Zirconium and Titanium-Niobium Alloys in Different Structural States

The characteristics of microstructure, deformation and fracture of Zr – 1 wt% Nb and Ti – 45 wt% Nb bioinert alloys in the coarse- and ultrafine-grained states are investigated. It is shown that the ultrafine-grained structure formed in them ensures excellent mechanical properties of the alloys and affects the stages of the stress-strain curves and the behavior of the maximum temperature vs. deformation time plot. The formation of an α-phase in the Ti – 45 wt% Nb ultrafine-grained alloy suppresses the linear stage VI characterized by a constant strain hardening coefficient. In stage VII, the strain hardening coefficient rapidly becomes negative, which indicates the material softening prior to its failure.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Microstructural Changes and Kinetics of Reduction of Hematite to Magnetite in CO/CO{sub 2} Gas Atmospheres

The microstructures of porous magnetite formed on gaseous reduction of dense hematite have been examined using high-resolution scanning electron microscopy. It has been shown that cellular pores are formed on reduction in the temperature range 573 K to 973 K (300 °C to 700 °C). Dendritic shaped gas pores are formed on reduction at temperatures between 1073 K and 1273 K (800 °C and 1000 °C). The apparent chemical reaction rate constant for the reduction of hematite to magnetite in CO/CO{sub 2} gas mixtures has been derived from measurements of product thickness against reaction time; the rate constant is described by the relation φ{sub CO} = 0.232exp(76,000/RT) µm s{sup −1} atm{sup −1}.

36 MATERIALS SCIENCE↗