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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only Surface hardening of Ti-AL-V superalloy spinal implant by using the boronization method(IOS Press, 2024) Hekimoğlu, Mehdi; Özer, Hidir; Onursal, Ceylan; Department of Chemistry; Kiraz, Kamil; Özer, Ali Fahir; Department of Chemistry; College of Sciences; School of MedicineBackground: We compared the raw Ti-Al-V super alloy transpedicular implant screws with boronized and surfacehardened transpedicular implant screws. OBJECTIVE: To improve patients' postoperative prognosis with the production of harder and less fragile screws. METHODS: Surface hardening was achieved by applying green-body encapsulation of the specimen with elemental boron paste which is sintered at elevated temperatures to ensure the boron-metal diffusion. Boron transported into the Ti-Al-V super alloy matrix gradually while suppressing aluminum and a homogeneously boronized surface with a thickness of similar to 15 microns was obtained. The uniform external shell was enriched with TiB2, which is one of the hardest ceramics. The Ti-Al-V core material, where boron penetration diminishes, shows cohesive transition and ensures intact core-surface structure. RESULTS: Scanning electron microscope images confirmed a complete homogeneous, uniform and non-laminating surface formation. Energy-dispersive X-ray monitored the elemental structural mapping and proved the replacement of the aluminum sites on the surface with boron ending up the TiB2. The procedure was 8.6 fold improved the hardness and the mechanical resistance of the tools. CONCLUSIONS: Surface-hardened, boronized pedicular screws can positively affect the prognosis. In vivo studies are needed to prove the safety of use.Publication Metadata only Structures and properties of NbOF3 and TaOF3 - with a remark to the O/F ordering in the SnF4 type structure(Wiley-V C H Verlag Gmbh, 2002) Köhler, J; Simon, A; van Wullen, L; Cordier, S; Roisnel, T; Poulain, M; Department of Chemistry; Somer, Mehmet Suat; Faculty Member; Department of Chemistry; College of Sciences; 178882Powder samples of NbOF3 und TaOF3 were prepared by heating mixtures of NbO2F and NbF5 or TaO2F and TaF5, respectively, in the corresponding stoichiometric ratio in platinum crucibles under argon atmosphere (180-220degreesC). Both oxide fluorides are coulourless with a slight greyish tinge. They are sensitive to moisture and decompose in air at room temperature within hours. Both, NbOF3 and TaOF3 crystallize as a variant of the SnF4 type structure, space group 14/mmm. The structures have been refined from X-ray powder diffraction data using the Rietveld method (a = 3.9675(1) Angstrom, c = 8.4033(1) Angstrom, R-B = 3.60%, R-p = 4.58% for NbOF3 and a = 3.9448(1) Angstrom, c = 8.4860(1) Angstrom, R-a = 2.07%, R-p = 2.44% for TaOF3). Characteristic building units are sheets of corner sharing MX6 octahedra which are stacked via van der Waals interactions to a three dimensional framework. The occupancy of the two crystallographic sites for the anions by O and F is discussed on the basis of structure refinements, bond order summations, IR and NMR data and calculations of the Madelung parts of the lattice energy.Publication Metadata only Nanoparticle silicalite-1 crystallization from clear solutions: nucleation(Elsevier Science Bv, 2009) Tokay, Begüm; Erdem-Şenatalar, Ayşe; Schueth, Ferdi; Thompson, Robert W.; Department of Chemistry; Somer, Mehmet Suat; Faculty Member; Department of Chemistry; College of Sciences; 178882Despite much effort spent by various research groups, there remain many aspects of nanoparticle silicalite-1 crystallization from clear solutions which require further investigation. In order to shed light, especially on the nucleation of silicalite-1, particle growth at 100 degrees C from several starting compositions known to yield colloidal silicalite-1, which have been studied previously by other researchers using various techniques, was followed in this study by laser light scattering using scattering angles of 90 degrees and 173 degrees, and zeta potential and pH measurements. Crystallinity was monitored by X-ray diffraction, Fourier transform infrared analysis and transmission electron microscopy. Thermogravimetric analyses and density measurements were also used to characterize the products obtained at various times during the syntheses. The results demonstrate that the distinct time of sudden jump in the effective diameter of the nanoparticles in solution, as observed more clearly by using the back-scattering device, and which marks the beginning of the constant linear growth rate of the particles, corresponds to the nucleation of the silicalite-1 crystal structure. This time was also shown to coincide with the exo-endo thermal switch time of the reaction mechanism, which has been observed previously by another research group. Nucleation was accompanied by an aggregation of a population of smaller particles, as indicated by the broadening of the particle size distribution, and the variation of the pH and zeta potential values during synthesis.Publication Metadata only Crystallization of poly(ethylene oxide) in thin films(Taylor & Francis Inc, 2003) N/A; Department of Chemistry; Department of Chemistry; Ok, Salim; Demirel, Adem Levent; Undergraduate Student; Faculty Member; Department of Chemistry; College of Sciences; College of Sciences; N/A; 6568Crystallization of poly(ethylene oxide) (PEO) in thin films was studied using hot-stage polarized optical microscopy. Isothermal linear crystal growth rates were measured for various film thicknesses at various degrees of undercooling. At a given crystallization temperature, the linear crystal growth rate decreased exponentially with decreasing film thickness below a film thickness of 80 nm. Films showed similar spherulitic morphology down to a film thickness of 30 nm. Control experiments on hydrophilic and hydrophobic surfaces showed that surface chemistry affects stability of the polymer films and causes a competition between crystallization and dewetting.Publication Metadata only The effect of nanoparticles on the surface hydrophobicity of polystyrene(Springer, 2008) N/A; Department of Chemistry; Yüce, Mehdi Yavuz; Demirel, Adem Levent; PhD Student; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; N/A; 6568The surface hydrophobicity of polystyrene-nanoparticle nanocomposites has been investigated as a function of the nanoparticle content. The addition of hydrophobically coated nanoparticles in polystyrene increased the contact angle θ of a water drop with respect to that on polystyrene surface due to change of surface composition and/or surface roughness. When the nanoparticles dispersed well in the polymer, cos θ decreased linearly with increasing amount of nanoparticles indicating a composite surface consisting of smooth polystyrene regions and rough nanoparticle regions. In case of formation of nanoparticle aggregates in polystyrene, cos θ decreased sharply at a critical concentration of nanoparticles. The observed behaviour was modeled in terms of a transition from Wenzel regime to Cassie-Baxter regime at a critical roughness length scale below which the Laplace pressure prevented the penetration of the water drop into the surface undulations. We argue that multiple length scales are needed below the critical roughness length scale to increase the contact angle further by decreasing the fraction of surface area of solid material (increasing the fraction of surface area of air) underlying the water drop.Publication Metadata only Crystal structure of bis[µ2-(3-benzimidazol-2-yl)-2-ethanethiolato-N,S,S)- chloro-palladium(II)], [(C6H4N2HCCH2CH2S)PdCl]2 C2H5OH(Walter de Gruyter GmbH, 2005) Agh-Atabay, N.M.; Borrmann, H.; Department of Chemistry; Department of Chemistry; Somer, Mehmet Suat; Haciu, Durata; Faculty Member; Teaching Faculty; Department of Chemistry; College of Sciences; College of Sciences; 178882; N/AC20H24Cl2N4OPd2S2, triclinic, P1 (no. 2), a = 8,796(1) Å, b = 9.844(1) Å, c = 14.718(2) A, α = 94.330(6)°, β = 98.546(6)°,γ = 99.258(7)°, V= 1237.3 Å3, Z= 2, Rgt(F) = 0.068, wRref(F2)= 0.142, T= 295 K.Publication Metadata only Crystal structure of mono(silver, gallium) trimagnesium, Ag 0.55Ga0.45Mg3(Walter de Gruyter GmbH, 2005) Kudla, C.; Prots, Yu.; Kleiner, G.; Department of Chemistry; Oruçoğlu, Egemen; Undergraduate Student; Department of Chemistry; College of Sciences; N/AAg0.55Ga0.45Mg3, trigonal, R3̄ (no. 148), a = 8.248(1) Å, c = 25.658(4) Å, V = 1511.8 Å3, Z = 18, Rgt(F) = 0.031, wRref(F 2) = 0.060, T = 293 K.Publication Metadata only Novel barium beryllates Ba[Be2N2] and Ba-3[Be5O8]: syntheses, crystal structures and bonding properties(Wiley-V C H Verlag Gmbh, 2005) Leoni, Stefano; Niewa, Rainer; Akselrud, Lev; Prots, Yurii; Schnelle, Walter; Kniep, Rüdiger; Department of Chemistry; Department of Chemistry; Department of Chemistry; Göksu, Tahsin; Çetinkol, Mehmet; Somer, Mehmet Suat; Undergraduate Student; Undergraduate Student; Faculty Member; Department of Chemistry; College of Sciences; College of Sciences; College of Sciences; N/A; N/A; 178882Ba[Be2N2] was prepared as a yellow-green microcrystalline powder by reaction of Ba2N with Be3N2 under nitrogen atmosphere. The crystal structure Rietfeld refinements (space group I4/mcm, a = 566.46(5) pm, c = 839.42(9) pm, R-int = 4.73 %, R-prof = 9.16 %) reveal the compound to crystallize as an isotype of the nitridoberyllates A[Be2N2] (A = Ca, Sr) consisting of planar 4.8(2) nets (2)(infinity)[(Be2N2)(2-)] of mutually trigonal planar coordinated Be and N species. Averaged magnetic susceptibility values for the anion [(Be2N2)(2-)] determined from measurements on A[Be2N2] with A = Mg, Ca, Ba allow to derive a diamagnetic increment for N3- chi(dia) = (-13 +/- 1stat.) (.) 10(-6)emu mol(-1). Colorless Ba-3[Be5O8] was first obtained as an oxidation product of Ba[Be2N2] in air. The crystal structure was solved and refined from single crystal X-ray diffaction data (space group Pnma, a = 942.9(1) pm, b = 1163.47(7) pm, c = 742.1(1) pm, R1 = 2.99 %, wR2 = 7.15 %) and contains infinite rods of Be in trigonal planar, tetrahedral and 3 + 1 coordination by O. The crystal structure is discussed in context with other known oxoberyllates. Electronic structure calculations and electron localization function diagrams for both compounds support the classification as nitrido- and oxoberyllate, respectively.Publication Metadata only Crystal structures of strontium octabarium hexakis(dinitridoborate) and europium octabarium hexakis(dinitridoborate), M Ba8[BN 2]6 (M = Sr, Eu)(Walter de Gruyter GmbH, 2005) N/A; N/A; Department of Chemistry; Department of Chemistry; Öztürk, Sinan S.; Kokal, İlkin; Somer, Mehmet Suat; Master Student; Master Student; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; 178882B6Ba8N12Sr, cubic, In3̄m (no. 229), a = 7.913(1) Å, V = 495.6 Å3, Z = 1, Rgt(F) = 0.031, wRref(F2) = 0.098, T = 293 K. B6Ba 8EuN12, cubic, Im3̄m (no. 229), a = 7.839(1) Å, V = 481.8 Å3, Z = 1, Rgt(F) = 0.014, wR ref(F2) = 0.056, T = 293 K.Publication Metadata only Crystal structure of pentastrontium bis(dinitridocobaltate(I)), Sr5[CoN2]2, Co2N4Sr5(Walter De Gruyter Gmbh, 2015) Ovchinnikov, Alexander; Hoehn, Peter; Borrmann, Horst; Kniep, Ruediger; Department of Chemistry; Kazancıoğlu, Monika; Undergraduate Student; Department of Chemistry; College of Sciences; N/ACO2N4Sr5, tetragonal, P4/ncc (no. 130), a = 8.6730(5) angstrom, c = 12.443(1) angstrom, V = 936.0 angstrom(3), Z = 4, R-gt(F) = 0.0293, wR(ref)(F-2) = 0.0684, T = 295 K.