Tuning the Frictional Properties of Carbon Fabrics Using Boron Carbide Particles

Selim Gürgen,Abhijit Majumdar 한국섬유공학회 2019 Fibers and polymers Vol.20 No.4

In recent years, researches have made many efforts to improve the frictional properties of high performance fabricsby using different methods such as applying natural rubber latex, developing metal oxide nano-rods and treating with shearthickening fluids. Even though these methods have provided beneficial results for enhanced frictional behavior, they exhibitsome drawbacks in terms of flexibility, stability and ease of application. For this reason, an attempt has been made in thisresearch to tune the frictional properties of carbon fabric through a simple process such as coating the fabric with boroncarbide particles in polyethylene glycol medium. The surface friction as well as yarn-to-yarn friction were evaluated and itwas found that the presence of only polyethylene glycol (PEG) or the mixture of PEG/boron carbide enhances the surfacefriction and yarn-to-yarn friction in the fabric. In addition, the role of boron carbide concentration used in the treatmentprocess was investigated. It was found that the friction in carbon fabric can be controlled by altering the amount of boroncarbide particles used in the treatment process.

Oxidation and thermal shock behavior of thermal barrier coated 18/10CrNi alloy with coating modifications

Selim Gürgen,Seyid Fehmi Diltemiz,Melih Cemal Kuşhan 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.1

In this study, substrates of 18/10CrNi alloy plates were initially sprayed with a Ni-21Cr-10Al-1Y bond coat and then with an yttria stabilized zirconia top coat by plasma spraying. Subsequently, plasma-sprayed Thermal barrier coatings (TBCs) were treated with two different modification methods, namely, vacuum heat treatment and laser glazing. The effects of modifications on the oxidation and thermal shock behavior of the coatings were evaluated. The effect of coat thickness on the bond strength of the coats was also investigated. Results showed enhancement of the oxidation resistance and thermal shock resistance of TBCs following modifications. Although vacuum heat treatment and laser glazing exhibited comparable results as per oxidation resistance, the former generated the best improvement in the thermal shock resistance of the TBCs. Bond strength also decreased as coat thickness increased.

Functionalization of Ti-40Nb implant material with strontium by reactive sputtering

Markus Göttlicher,Marcus Rohnke,Yannik Moryson,Jürgen Thomas,Joachim Sann,Anja Lode,Matthias Schumacher,Romy Schmidt,Stefan Pilz,Annett Gebert,Thomas Gemming,Jürgen Janek 한국생체재료학회 2017 생체재료학회지 Vol.21 No.4

Background: Surface functionalization of orthopedic implants with pharmaceutically active agents is a modern approach to enhance osseointegration in systemically altered bone. A local release of strontium, a verified bone building therapeutic agent, at the fracture site would diminish side effects, which could occur otherwise by oral administration. Strontium surface functionalization of specially designed titanium-niobium (Ti-40Nb) implant alloy would provide an advanced implant system that is mechanically adapted to altered bone with the ability to stimulate bone formation. Methods: Strontium-containing coatings were prepared by reactive sputtering of strontium chloride (SrCl2) in a self-constructed capacitively coupled radio frequency (RF) plasma reactor. Film morphology, structure and composition were investigated by scanning electron microscopy (SEM), time of flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). High-resolution transmission electron microscopy (HR-TEM) was used for the investigation of thickness and growth direction of the product layer. TEM lamellae were prepared using the focused ion beam (FIB) technique. Bioactivity of the surface coatings was tested by cultivation of primary human osteoblasts and subsequent analysis of cell morphology, viability, proliferation and differentiation. The results are correlated with the amount of strontium that is released from the coating in biomedical buffer solution, quantified by inductively coupled plasma mass spectrometry (ICP-MS). Results: Dense coatings, consisting of SrOxCly, of more than 100 nm thickness and columnar structure, were prepared. TEM images of cross sections clearly show an incoherent but well-structured interface between coating and substrate without any cracks. Sr2+ is released from the SrOxCly coating into physiological solution as proven by ICP-MS analysis. Cell culture studies showed excellent biocompatibility of the functionalized alloy. Conclusions: Ti-40Nb alloy, a potential orthopedic implant material for osteoporosis patients, could be successfully plasma coated with a dense SrOxCly film. The material performed well in in vitro tests. Nevertheless, the Sr2+ release must be optimized in future work to meet the requirements of an effective drug delivery system.

The effect of carbide particle additives on rheology of shear thickening fluids

Selim Gürgen,Melih Cemal Kuşhan,Weihua Li 한국유변학회 2016 Korea-Australia rheology journal Vol.28 No.2

In this paper, shear thickening fluids (STFs) including silicon carbide particles are presented. We fabricated a kind of STF based on nanosize fumed silica suspended in a liquid medium, polyethylene glycol, at a constant concentration of 20 wt.%. Then, different particle size silicon carbide (SiC) particles were added to the STF with various amounts. Their rheological properties under various temperatures were tested by using a rheometer. The suspension exhibits different systematic variations with respect to the varied parameters.

Effect of heat treatment on the bending behavior of aluminum alloy tubes

Abdullah Sert,Selim Gürgen,Osman Nuri Çelik,Melih Cemal Kuşhan 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.11

Quasistatic experiments and numerical simulations were performed to investigate the three-point bending behavior of different temper AA6082 tubes in this study. The effect of heat treatment on the samples was investigated by microstructural analyses. Temper designations of T6, T4 and O were applied to the samples to study the load-carrying capacity and bendability of AA6082 tubes. The samples with T4 and O tempers show appropriate bendability of up to the punch travel distance of 60 mm under low-punch forces. However, the samples with T6 temper require three times more punch force than the other temper samples. Furthermore, the T6 temper samples cannot hold their structural integrity. Therefore, crack formation occurred at the enhanced bending angle stages. Experimental results were compared with the numerical simulation outputs, and the deformation mechanism was observed with finite element method. In addition, various element formulations in the numerical simulations were compared in terms of bending force and computational time. Based on the numerical results, element formulations exhibit different performances with respect to temper conditions.

Single Crystals of C12A7 (Ca₁₂Al₁₄O₃₃) Substituted with 1 mol % Iron

Ebbinghaus, Stefan G.,Krause, Holger,Lee, Doh-Kwon,Janek, Jü,rgen American Chemical Society 2014 Crystal Growth & Design Vol.14 No.5

<P>Single crystals of Ca<SUB>12</SUB>Al<SUB>14</SUB>O<SUB>33</SUB> (C12A7, mayenite) substituted with 1 mol % Fe were grown by the floating zone technique in an atmosphere of 2% O<SUB>2</SUB>/98% N<SUB>2</SUB>. The iron substitution leads to an increase of the unit cell parameter by roughly 0.002 Å. Optical spectroscopy reveals an additional broad absorption band at 310 nm for the iron-substituted sample reflecting the yellow color of the crystals. XANES measurements at the Fe–K absorption edge prove the incorporation of Fe<SUP>3+</SUP> on the aluminum sites. Measurements of the magnetic susceptibility resulted in a value of 5.8 μ<SUB>B</SUB> per iron ion as expected for high-spin Fe<SUP>3+</SUP>. C12A7 is known to be a very good oxygen ion conductor at high temperatures. In pure oxygen, the iron substitution leads to a slightly reduced conductivity between approximately 500 and 800 °C, while at higher temperatures, the conductivity is very similar to the pristine material. Under reducing conditions, the slope of log(σ) vs log(<I>p</I>(O<SUB>2</SUB>)) of the iron-substituted sample was found to be steeper than that for pure C12A7.</P><P>Yellow-colored single crystals of iron-substituted Ca<SUB>12</SUB>Al<SUB>14</SUB>O<SUB>33</SUB> were grown by the floating zone technique. Fe−K XANES, optical spectroscopy, and magnetic measurements prove the incorporation of 1 mol % Fe<SUP>3+</SUP> on the aluminum sites. Compared with pristine C12A7, a slightly enhanced activation energy for the oxide ion conductivity was found. At high temperatures and under reducing atmosphere, the conductivity of C12A7:Fe strongly increases.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cgdefu/2014/cgdefu.2014.14.issue-5/cg401823k/production/images/medium/cg-2013-01823k_0007.gif'></P>

Room Temperature in Situ Growth of B/BO_<i>x</i> Nanowires and BO_<i>x</i> Nanotubes

Gonzalez-Martinez, Ignacio G.,Gorantla, Sandeep M.,Bachmatiuk, Alicja,Bezugly, Viktor,Zhao, Jiong,Gemming, Thomas,Kunstmann, Jens,Eckert, Jü,rgen,Cuniberti, Gianaurelio,Rü,mmeli, Mark H. American Chemical Society 2014 NANO LETTERS Vol.14 No.2

<P>Despite significant advances in the synthesis of nanostructures, our understanding of the growth mechanisms of nanowires and nanotubes grown from catalyst particles remains limited. In this study we demonstrate a straightforward route to grow coaxial amorphous B/BO<SUB><I>x</I></SUB> nanowires and BO<SUB><I>x</I></SUB> nanotubes using gold catalyst particles inside a transmission electron microscope at room temperature without the need of any specialized or expensive accessories. Exceedingly high growth rates (over 7 μm/min) are found for the coaxial nanowires, and this is attributed to the highly efficient diffusion of B species along the surface of a nanowire by electrostatic repulsion. On the other hand the O species are shown to be relevant to activate the gold catalysts, and this can occur through volatile O species. The technique could be further developed to study the growth of other nanostructures and holds promise for the room temperature growth of nanostructures as a whole.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2014/nalefd.2014.14.issue-2/nl404147r/production/images/medium/nl-2013-04147r_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl404147r'>ACS Electronic Supporting Info</A></P>

Few-Layer Graphene Shells and Nonmagnetic Encapsulates: A Versatile and Nontoxic Carbon Nanomaterial

Bachmatiuk, Alicja,Mendes, Rafael G.,Hirsch, Cordula,Jä,hne, Carsten,Lohe, Martin R.,Grothe, Julia,Kaskel, Stefan,Fu, Lei,Klingeler, Rü,diger,Eckert, Jü,rgen,Wick, Peter,Rü,mme American Chemical Society 2013 ACS NANO Vol.7 No.12

<P>In this work a simple and scalable approach to coat nonmagnetic nanoparticles with few-layer graphene is presented. In addition, the easy processing of such nanoparticles to remove their core, leaving only the 3D graphene nanoshell, is demonstrated. The samples are comprehensively characterized, as are their versatility in terms of functionalization and as a material for electrochemical storage. Indeed, these 3D graphene nanostructures are easily functionalized much as is found with carbon nanotubes and planar graphene. Electrochemical investigations indicate these nanostructures are promising for stable long-life battery applications. Finally, initial toxicological investigations suggest no acute health risk from these 3D graphene nanostructures.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2013/ancac3.2013.7.issue-12/nn4051562/production/images/medium/nn-2013-051562_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn4051562'>ACS Electronic Supporting Info</A></P>

Local structure change evidenced by temperature-dependent elastic measurements: Case study on Bi_1/2Na_1/2TiO₃-based lead-free relaxor piezoceramics

Dittmer, Robert,Jo, Wook,Webber, Kyle G.,Jones, Jacob L.,Rö,del, Jü,rgen American Institute of Physics 2014 JOURNAL OF APPLIED PHYSICS - Vol.115 No.8

Increased detection of invasive enteropathogenic bacteria in pre-incubated blood culture materials by real-time PCR in comparison with automated incubation in Sub-Saharan Africa

Frickmann, Hagen,Dekker, Denise,Boahen, Kennedy,Acquah, Samuel,Sarpong, Nimako,Adu-Sarkodie, Yaw,Schwarz, Norbert G.,May, Jü,rgen,Marks, Florian,Poppert, Sven,Wiemer, Dorothea F.,Hagen, Ralf M. Informa Healthcare 2013 Scandinavian journal of infectious diseases Vol.45 No.8

<P><I>Background:</I> Invasive enteropathogenic bacteria can cause systemic infections. Data from studies with PCR detection suggest, at least for Salmonella enterica, that blood culture may lead to underestimation in the tropics. Corresponding data are lacking for other invasive enteropathogenic bacteria. We compared classical blood culture and molecular methods for the diagnosis of blood infections. <I>Methods:</I> A real-time multiplex PCR for Salmonella spp., Shigella spp./entero- invasive Escherichia coli (EIEC), Yersinia spp., and Campylobacter jejuni was applied to 2321 retained blood culture samples from Ghanaian patients, after enrichment by automated culture. <I>Results:</I> PCR detected Salmonella DNA in 56 out of 58 pre-incubated Ghanaian blood cultures with growth of S. enterica. In 2 samples molecular diagnosis was only possible after 1:10 dilution. Twenty-two samples negative by blood culture and 1 positive with Micrococcus spp. were PCR-positive for Salmonella spp. In addition, 3 Shigella spp./EIEC, 2 Yersinia spp., and 1 C. jejuni were detected by PCR but not by culture growth. <I>Conclusions:</I> Real-time PCR was more sensitive in identifying invasive enteropathogenic bacteria than automated blood culture, which is hampered by a lack of evidence-based standardization of pre-analytic conditions in the tropics. Primary agar culture and Gram-staining prior to automated blood culture is advisable in cases where transportation times are long.</P>