https://hdl.handle.net/20.500.11857/550 2026-06-02T19:45:24Z 2026-06-02T19:45:24Z Yeşiltaş, Mehmet Kaya, M. Glotch, T. D. Brunetto, R. Maturilli, A. Helbert, J. Ozel, M. E. https://hdl.handle.net/20.500.11857/3706 2023-01-28T12:23:31Z 2020-01-01T00:00:00Z

Biconical reflectance, micro-Raman, and nano-FTIR spectroscopy of the Didim (H3-5) meteorite: Chemical content and molecular variations Yeşiltaş, Mehmet; Kaya, M.; Glotch, T. D.; Brunetto, R.; Maturilli, A.; Helbert, J.; Ozel, M. E. The Didim meteorite contains multiple lithologies and clasts of different petrologic types in a single stone. A mixture of H5 clasts in an unequilibrated H3 host was previously observed in Didim, according to the initial characterization reported in the Meteoritical Bulletin Database, providing an opportunity to investigate molecular composition that contains varying degree of equilibrium with varying mineralogy. We have taken a from large scale to small scale approach to spectroscopically investigate the chemical content of Didim. Centimeter-scale biconical reflectance spectra show that Didim contains abundant olivine, pyroxene, and other optically active minerals, evident from a strong Band I near 0.93 mu m and a weak Band II near 1.75 mu m. Micrometer-scale Raman spectroscopic investigations reveal the presence of carbonaceous material in addition to forsteritic olivine, pyroxene (augite and enstatite), feldspars, and opaque phases such as chromite and hematite. 3-D Raman tomographic imaging shows that the carbonaceous material near chondrules extends underneath a large olivine grain, going further down toward the interior, indicating that the observed carbonaceous matter is likely indigenous. Nano-scale infrared measurements reveal that the observed chemical materials in Didim contain spectral, and therefore, molecular, variations at the similar to 20 nm spatial scale. These chemical variations are normally not accessible via conventional infrared techniques, and indicate the presence of different cations in the molecular composition of observed minerals. By taking the large scale to small scale approach, we show that these compositional variations can be captured and investigated nondestructively in meteorites to understand formation/evolution of chemical components in the parent body.

2020-01-01T00:00:00Z Yeşiltaş, Mehmet Glotch, Timothy D. Jaret, Steven Verchovsky, Alexander B. Greenwood, Richard C. https://hdl.handle.net/20.500.11857/3671 2023-01-28T12:17:25Z 2019-01-01T00:00:00Z

Carbonaceous matter in the Saricicek meteorite Yeşiltaş, Mehmet; Glotch, Timothy D.; Jaret, Steven; Verchovsky, Alexander B.; Greenwood, Richard C. As of today, the Saricicek (SC) meteorite is the newest howardite and the only confirmed fall among the 17 known howardites. In this study, we present isotopic, infrared, and Raman data on three distinct pieces of the SC meteorite. Our oxygen isotopic measurements show that Delta O-17 values of the pieces are close to each other, and are in good agreement with other howardites, eucrites, and diogenites. The carbon isotopic measurements, which were conducted by combusting terrestrial contamination selectively at temperatures lower than 500-600 degrees C, show the presence of indigenous carbon in the SC specimens. The matrix of these specimens, investigated via infrared microspectroscopy, appears to be dominated by clinopyroxene/orthopyroxene, forsterite, and fayalite, with minor contributions from ilmenite, plagioclase, and enstatite. Carbon-rich regions were mapped and studied via Raman imaging microspectroscopy, which reveals that both amorphous and graphitic carbon exist in these samples. Synchrotron-based infrared microspectroscopy data show the presence of very little aliphatic and aromatic hydrocarbons. The SC meteorite is suggested to be originating from the Antonia impact crater in the Rheasilvia impact basin on 4 Vesta (Unsalan etal. 2019). If this is in fact the case, then the carbon phases present in the SC samples might provide clues regarding the impactor material (e.g., carbonaceous chondrites).

2019-01-01T00:00:00Z Yeşiltaş, Mehmet Glotch, Timothy D. Sava, Boğdan https://hdl.handle.net/20.500.11857/3660 2023-01-28T12:23:28Z 2021-01-01T00:00:00Z

Nano-FTIR spectroscopic identification of prebiotic carbonyl compounds in Dominion Range 08006 carbonaceous chondrite Yeşiltaş, Mehmet; Glotch, Timothy D.; Sava, Boğdan Meteorites contain organic matter that may have contributed to the origin of life on Earth. Carbonyl compounds such as aldehydes and carboxylic acids, which occur in meteorites, may be precursors of biologically necessary organic materials in the solar system. Therefore, such organic matter is of astrobiological importance and their detection and characterization can contribute to the understanding of the early solar system as well as the origin of life. Most organic matter is typically sub-micrometer in size, and organic nanoglobules are even smaller (50-300 nm). Novel analytical techniques with nanoscale spatial resolution are required to detect and characterize organic matter within extraterrestrial materials. Most techniques require powdered samples, consume the material, and lose petrographic context of organics. Here, we report the detection of nanoglobular aldehyde and carboxylic acids in a highly primitive carbonaceous chondrite (DOM 08006) with similar to 20 nm spatial resolution using nano-FTIR spectroscopy. Such organic matter is found within the matrix of DOM 08006 and is typically 50-300 nm in size. We also show petrographic context and nanoscale morphologic/topographic features of the organic matter. Our results indicate that prebiotic carbonyl nanoglobules can form in a less aqueous and relatively elevated temperature-environment (220-230 degrees C) in a carbonaceous parent body.

2021-01-01T00:00:00Z Kısasöz, Alptekin Tumer, Mustafa Karaaslan, Ahmet https://hdl.handle.net/20.500.11857/3500 2023-01-28T12:11:27Z 2021-01-01T00:00:00Z

Microstructure, Mechanical and Corrosion Properties of UNS 32205 Duplex Stainless Steel Weldment Joints by Multipass FCAW Kısasöz, Alptekin; Tumer, Mustafa; Karaaslan, Ahmet In this study, the effect of multipass welding on the microstructure, mechanical and corrosion properties of the UNS 32205 duplex stainless steels (DSS) is investigated. The UNS 32205 DSS is welded in 3 or 7 passes by flux-cored arc welding (FCAW) using E2209 T1-1/4 flux cored wire. The weldments are characterized by light optical microscopy (LOM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Feritscope analysis, Charpy impact tests and electrochemical corrosion tests. The results suggest that the multipass FCAW process induces the formation of gamma(2 )in the weld seam. The mechanical and the corrosion properties of the weld joints are affected by the heat input variation and the phase transformations. Especially, the formation of the gamma(2) in the weld seam results in a decrease in the corrosion resistance of the joint samples.

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