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Growth kinetics of ? particles in ?-Ti matrix studied by in-situ small-angle x-ray scattering.

ABSTRACT: Nucleation and growth kinetics of nanoparticles of hexagonal ? phase in a body-centered cubic ? titanium matrix in single crystals of ?-Ti alloys were investigated by small-angle x-ray scattering measured in-situ during ageing at various temperatures up to 450 °C. The experimental data were compared with numerical simulations based on a three-dimensional short-range order model of nanoparticle self-ordering. The x-ray contrast of the particles is caused by an inhomogeneous distribution of impurity atoms (Mo, Fe and Al), whose density profile around growing nanoparticles was simulated by solving the corresponding diffusion equation with moving boundary conditions. From the analysis of the experimental data we determined the mean distance and size of the nanoparticles and confirmed the validity of the ? t1/3 growth law following from the Lifshitz-Slyozov-Wagner theory. From a detailed comparison of the experimental data with simulations we also assessed the diffusion coefficient of the impurity atoms and its activation energy.

SUBMITTER: Smilauerova J

PROVIDER: S-EPMC5701744 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

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Growth kinetics of ω particles in β-Ti matrix studied by in-situ small-angle x-ray scattering.

Šmilauerová J J Harcuba P P Kriegner D D Janeček M M Holý V V

Acta materialia 20150830

Nucleation and growth kinetics of nanoparticles of hexagonal ω phase in a body-centered cubic β titanium matrix in single crystals of β-Ti alloys were investigated by small-angle x-ray scattering measured in-situ during ageing at various temperatures up to 450 °C. The experimental data were compared with numerical simulations based on a three-dimensional short-range order model of nanoparticle self-ordering. The x-ray contrast of the particles is caused by an inhomoge ...[more]

PMID: 29176930

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Project description:Small-angle x-ray scattering (SAXS) was used to study the behavior of equine metmyoglobin (Mb) and bovine pancreatic trypsin inhibitor (BPTI) at concentrations up to 0.4 and 0.15 g/mL, respectively, in solutions also containing 50% D2O and 1 M urea. For both proteins, significant effects because of interference between x-rays scattered by different molecules (interparticle interference) were observed, indicating nonideal behavior at high concentrations. The experimental data were analyzed by comparison of the observed scattering profiles with those predicted by crystal structures of the proteins and a hard-sphere fluid model used to represent steric exclusion effects. The Mb scattering data were well fit by the hard-sphere model using a sphere radius of 18 Å, only slightly smaller than that estimated from the three-dimensional structure (20 Å). In contrast, the scattering profiles for BPTI in phosphate buffer displayed substantially less pronounced interparticle interference than predicted by the hard-sphere model and the radius estimated from the known structure of the protein (15 Å). Replacing the phosphate buffer with 3-(N-morpolino)propane sulfonic acid (MOPS) led to increased interparticle interference, consistent with a larger effective radius and suggesting that phosphate ions may mediate attractive intermolecular interactions, as observed in some BPTI crystal structures, without the formation of stable oligomers. The scattering data were also used to estimate second virial coefficients for the two proteins: 2.0 ×10(-4) cm(3)mol/g(2) for Mb in phosphate buffer, 1.6 ×10(-4) cm(3)mol/g(2) for BPTI in phosphate buffer and 9.2 ×10(-4) cm(3)mol/g(2) for BPTI in MOPS. The results indicate that the behavior of Mb, which is nearly isoelectric under the conditions used, is well described by the hard-sphere model, but that of BPTI is considerably more complex and is likely influenced by both repulsive and attractive electrostatic interactions. The hard-sphere model may be a generally useful tool for the analysis of small-angle scattering data from concentrated macromolecular solutions.

Dataset Information

Growth kinetics of ? particles in ?-Ti matrix studied by in-situ small-angle x-ray scattering.

Publications

Growth kinetics of <i>ω</i> particles in <i>β</i>-Ti matrix studied by in-situ small-angle x-ray scattering.

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