Person:
KAYMAKSÜT, Hande Öztürk

First Name

Hande Öztürk

Last Name

KAYMAKSÜT

Organizational Unit

Mechanical Engineering

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Publication Search Results

Now showing 1 - 10 of 11

Metadata only
Combining tensile test results with atomistic predictions of elastic modulus of graphene/polyamide-6,6 nanocomposites
(Elsevier, 2023-06) Batyrov, Merdan; Dericiler, K.; Palabıyık, Büşra Akkoca; Okan, B. S.; Öztürk, Hande; Fındıkçı, İlknur Eruçar; Mechanical Engineering; KAYMAKSÜT, Hande Öztürk; FINDIKÇI, Ilknur Eruçar; Batyrov, Merdan; Palabıyık, Büşra Akkoca
In this work, we combined tensile test results with atomistic simulations to investigate the effect of filler parameters including distribution, stacking, loading and lateral graphene size on elastic moduli of graphene/PA-6,6 nanocomposites. Stacked and randomly distributed atomistic models were adapted in Molecular Dynamics (MD) simulations to establish the limits of stiffness enhancement in graphene reinforced PA-6,6 nanocomposites with loading ratios changing from 0 to 1 wt%. Experimental results showed that incorporating of 0.3–0.4 wt% graphene loading improved the elastic modulus of the neat polymer by 41.7%−43.5%. While the test sample behaved close to the computational results of the stacked atomistic model at low graphene loadings up to 0.4 wt%, it overshot the predictions of the randomly distributed model at all considered loadings up to 1 wt%. Elastic moduli of graphene-based PA-6,6 nanocomposites increased linearly with graphene loading in the stacked model, however, no such relation was detected in the randomly distributed model. The lower stiffness enhancement provided by the randomly distributed model compared to the stacked model was revealed as the small lateral size of graphene plates in PA-6,6 matrix. As the graphene size increased, the elastic modulus of the graphene dramatically increased, directly improving the elastic modulus of the nanocomposite. The developed computational approach is highly useful to estimate the boundaries of stiffness enhancement provided by graphene dispersions in macroscale nanocomposite samples.
Open Access
Investigation of pair distribution function method on structural analysis of nanocrystalline powders
(Int Union Crystallography, 2022-08) Baloochiyan, Abolfazl; Öztürk, Hande; Mechanical Engineering; KAYMAKSÜT, Hande Öztürk; Baloochiyan, Abolfazl
N/A
Open Access
Accuracy limits of pair distribution function analysis in structural characterization of nanocrystalline powders by X-ray diffraction
(Turkish Chemical Society, 2022) Baloochiyan, Abolfazl; Batyrow, Merdan; Öztürk, Hande; Mechanical Engineering; KAYMAKSÜT, Hande Öztürk; Baloochiyan, Abolfazl; Batyrow, Merdan
We report the minimum errors of structural parameters, namely lattice parameter, crystallite size, and atomic displacement parameters, expected from Pair Distribution Function (PDF) analysis of nanocrystalline gold powders for the first time by a self-consistent computational methodology. Although PDF analysis has been increasingly used to characterize nanocrystalline powders by X-rays, the current literature includes no established error bounds to be expected from the resulting structural parameters. For accurate interpretation of X-ray diffraction data, these error bounds must be determined, and the obtained structural parameters must be cleared from them. Our novel methodology includes: 1) simulation of ideal powder diffraction experiments with the use of the Debye scattering equation, 2) pair distribution function analysis of the diffraction data with the Diffpy-CMI analysis software, and 3) determination of the errors from PDF analysis of the simulated diffraction data by comparing them with real-space analysis of spherical gold nanocrystals that are 30 nm size and smaller. Our results show that except for the lattice parameters and even with an ideal crystalline powder sample and ideal diffraction data, the extracted structural parameters from PDF analysis diverge from their true values for the studied nanopowder. These deviations are dependent on the average size of the nanocrystals and the energy of the X-rays selected for the diffraction experiments, where lower X-ray energies and small-sized nanocrystalline powders lead to greater errors.
Open Access
Resolving 500 nm axial separation by multi-slice X-ray ptychography
(International Union of Crystallography, 2019-03) Huang, X.; Yan, H.; Ge, M.; Öztürk, Hande; Fang, Y.-L. L.; Ha, S.; Lin, M.; Lu, M.; Nazaretski, E.; Robinson, I. K.; Chu, Y. S.; Mechanical Engineering; KAYMAKSÜT, Hande Öztürk
Multi-slice X-ray ptychography offers an approach to achieve images with a nanometre-scale resolution from samples with thicknesses larger than the depth of field of the imaging system by modeling a thick sample as a set of thin slices and accounting for the wavefront propagation effects within the specimen. Here, we present an experimental demonstration that resolves two layers of nanostructures separated by 500 nm along the axial direction, with sub-10 nm and sub-20 nm resolutions on two layers, respectively. Fluorescence maps are simultaneously measured in the multi-modality imaging scheme to assist in decoupling the mixture of low-spatial-frequency features across different slices. The enhanced axial sectioning capability using correlative signals obtained from multi-modality measurements demonstrates the great potential of the multi-slice ptychography method for investigating specimens with extended dimensions in 3D with high resolution.
Open Access
Colloidal aluminum antimonide quantum dots
(American Chemical Society, 2019-07-09) Jalali, H. B.; Sadeghi, S.; Şahin, M.; Öztürk, Hande; Ow-Yang, C. W.; Nizamoglu, S.; Mechanical Engineering; KAYMAKSÜT, Hande Öztürk
AlSb is a less studied member of the III–V semiconductor family, and herein, we report the colloidal synthesis of AlSb quantum dots (QDs) for the first time. Different sizes of colloidal AlSb QDs (5 to 9 nm) were produced by the controlled reaction of AlCl3 and Sb[N(Si(Me)3)2]3 in the presence of superhydride. These colloidal AlSb quantum dots showed excitonic transitions in the UV-A region and a tunable band-edge emission (quantum yield of up to 18%) in the blue spectral range. Among all III–V quantum dots, these quantum dots show the brightest core emission in the blue spectral region.
Open Access
Lower uncertainty bounds of diffraction-based nanoparticle sizes
(Wiley, 2022-06) Noyan, İ. C.; Öztürk, Hande; Mechanical Engineering; KAYMAKSÜT, Hande Öztürk
A self-consistent analysis is reported of traditional diffraction-based particle size determination techniques applied to synthetic diffraction profiles generated with the Patterson approach. The results show that dimensions obtained from traditional techniques utilizing peak fitting or Fourier analysis for single-crystal nanoparticles have best-case error bounds of around 5%. For arbitrarily shaped particles, lower error magnitudes are possible only if the zeroes of the thickness fringes are used. The errors for sizes obtained by integral-breadth-And Fourier-decomposition-based techniques depend on the shape of the diffracting domains. In the case of integral-breadth analysis, crystal shapes which scatter more intensity into the central peak of the rocking curve have lower size errors. For Fourier-decomposition analysis, crystals which have non-uniform distributions of chord lengths exhibit nonlinearities in the initial ranges of the normalized Fourier cosine coefficient versus column length (|A L | versus L) plots, even when the entire rocking curve is used in the decomposition. It is recommended that, in routine analysis, all domain size determination techniques should be applied to all reflections in a diffraction pattern. If there is significant divergence among these results, the 'average particle size(s)' obtained might not be reliable.
Open Access
First-principle diffraction simulations as a tool to solve the nanodiffraction problem
(International Union of Crystallography, 2021-08) Öztürk, Hande; Noyan, I. C.; Mechanical Engineering; KAYMAKSÜT, Hande Öztürk
N/A
Metadata only
Size dependent change of mean square displacement in gold nanocrystals: A molecular dynamics simulation
(Wiley, 2023-11-01) Batyrow, Merdan; Fındıkçı, İlknur Eruçar; Öztürk, Hande; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar; KAYMAKSÜT, Hande Öztürk; Batyrow, Merdan
Thermally activated atomic vibrations significantly decrease the x-ray diffraction intensities of nanocrystalline powders. Hence their quantification is critical for accurate structural characterization of small nanocrystals by x-ray diffraction. In this study, atomic vibrations in the form of mean square displacements (MSDs) in 5, 10, 15, 20, and 30 nm diameter spherical gold nanocrystals were computed by molecular dynamics (MD) simulations at room temperature and below. A strong size and temperature dependency of MSD was observed from spherical gold nanocrystals. Moreover, these displacements increased radially from the center of the nanocrystals and reached a maximum at the surface layers due to the presence of undercoordinated surface atoms and their relatively unrestricted motions. High temperature simulations were performed to investigate the evolution of structural stability of nanoparticles with increasing temperature. Surface melting was observed before complete melting of nanocrystals. Results of this work will be useful to understand the effect of nanocrystal size on the amplitude of thermally activated atomic vibrations and their quantification in measured intensities by x-ray diffraction experiments.
Metadata only
Microstructural examination of black seawater mixed sulfate-resistant cement concrete
(ASCE, 2024-01-01) Aydoǧan, O. G.; Akca, A. H.; Bilici, S.; Öztürk, Hande; Dilber, A. A.; Özyurt, N.; Mechanical Engineering; KAYMAKSÜT, Hande Öztürk
The use of seawater as the mix water has been thought to be inevitable for the near future as a result of increasing water scarcity. Hundreds of papers related to seawater mixed cement-based materials were published in recent years. Even though sulfate-resistant cement can be beneficial for internal sulfate attack and binding chloride ions, there is no related study on the sulfate-resistant cement together with seawater. In this study, the microstructure of seawater mixed sulfate-resistant pozzolanic cement was studied for the first time to understand possible reactions. Tap water and seawater mixes were designed by using Portland cement and sulfate-resistant cement with and without fibers. To examine the effect of seawater as the mix water on the microstructure quantitatively and to construct bridge between mechanical properties and microstructure, Rietveld refinements were performed on the obtained X-ray diffraction patterns. Thermogravimetric analyses were also carried out to correctly interpret and verify X-ray diffraction data. The possibility of internal sulfate attack, possible reactions and resulting hydration products were discussed. The results showed that internal sulfate attack is not a threat for seawater mixed concrete and sulfate-resistant cement can be a better alternative than portland cement owing to more chloride binding ability for seawater-mixed concretes.
Open Access
Evaluating the accuracy of rietveld analysis for diffraction data from nanocrystalline powders
(International Union of Crystallography, 2022-08) Hekmatjou, Hamidreza; Öztürk, Hande; Mechanical Engineering; KAYMAKSÜT, Hande Öztürk; Hekmatjou, Hamidreza
N/A