Texture development in Fe-doped alumina ceramics via templated grain growth and their application to carbon nanotube growth

Fe-doped alumina (Fe-Al2O3) materials with a controlled microstructure could be designed for some special uses such as a substrate for carbon nanotube growth. In this study, Fe-doped Al2O3 ceramics with varying degrees of texture were prepared via Templated Grain Growth method and utilized for carbon nanotube synthesis by Catalytic Chemical Vapor Deposition in order to investigate how alpha-Al2O3 crystal orientation affects carbon nanotube growth in polycrystalline ceramics. The degree of texture increased with the Fe content in the presence of liquid phase. Three kinds of carbon filaments (few-wall carbon nanotubes bundles, individual multi-wall nanotubes and carbon nanofibres) were observed over Fe-doped Al2O3 ceramics with varying degrees of texture depending on the surface roughness, crystallographic orientation and the size of the catalyst nanoparticles. While well-textured substrates with a rough surface led to a small amount of randomly oriented carbon nanotube bundles, perpendicularly oriented individual multi-wall nanotubes were obtained over relatively smooth single crystal alpha-Al2O3 platelet surfaces (basal planes) which remained in the matrix without growing

Organized growth of carbon nanotubes on Fe-doped alumina ceramic substrates

Polycrystalline Fe-doped alumina (Al2O3) ceramics have been produced and used as a substrate for organized carbon nanotubes (CNTs) growth by catalytic chemical vapor deposition (CCVD). In these substrates, Fe3+ cations, which are the catalyst source, are initially substituted to Al3+ in a-Al2O3, instead of being simply deposited as a thin Fe layer on the surface of the substrate. The selective reduction of these substrates resulted in in situ formation of homogeneously distributed Fe nanoparticles forming patterns at nanometerscale steps and kinks. These nanoparticles then catalyzed the growth of high quality CNTs, with some degree of organization thanks to their interaction with the topography of the substrate

A comparative study on few-layer graphene production by exfoliation of different starting materials in a low boiling point solvent

Three different graphite-based powders (expandable graphite and two different nano-graphite powders) were investigated as starting materials for an effective liquid phase exfoliation process in isopropyl alcohol (IPA). The prepared dispersions were analyzed and compared in terms of their graphene concentration, stability, number of graphene layers and quality, as well as the electrical conductivity of the prepared graphene-based materials. Good quality graphene dispersions (ID/IG < 0.3) with a relatively high concentration (∼1.1 mg/ml) were prepared in IPA within 90 min sonication time by utilizing a high specific surface area (∼175 m2/g) nano-graphite powder derived from natural graphite. Transmission electron microscope analyses of this sample revealed mostly folded and scrolled few layer graphene (FLG) sheets (<5 layers) entangled each other. The electrical conductivity of the thin film prepared from this dispersion was ∼15 and 86 S/m, before and after annealing, respectively. FLG prepared from expanded graphite, obtained by thermal treatment of expandable graphite, exhibited both much higher quality (ID/IG < 0.09) and electrical conductivity (∼2104 and 19,200 S/m before and after annealing, respectively) when dispersed in IPA for 90 min. However, the graphene-based material concentration of the prepared dispersion was relatively low (∼0.06 mg/ml)

Relationship between heating atmosphere and copper foil impurities during graphene growth via low pressure chemical vapor deposition

Low-pressure chemical vapor deposition synthesis of graphene films on two different Cu foils, with different surface oxygen and carbon contents, was performed by controlling H2 and/or Ar flow rates during heating. The influences of heating atmosphere on the final impurity level, quality of the synthesized graphene films and thickness uniformity were investigated depending on Cu foil impurities. Heating of carbon-rich, but oxygen-poor Cu foil in H2 environment resulted in covering the foil surface by residual carbon which then acted as active sites for multilayer graphene growth. Ar-only flow was required during heating to promote high quality graphene growth on this foil. On carbon-poor, but oxygen-rich Cu foil high quality graphene growth was promoted when the heating was carried out under Ar/H2 environment. Almost no carbon residues were observed on this foil even under H2 only flow during heating. The heating atmosphere affected not only graphene growth, but also the type and amount of impurities formed on the surface. H2 and Ar/H2 heating resulted in the formation of spherical nanometer-sized impurities, while irregular-shaped, large (a few mm) SiO2 impurities were observed when Ar alone was used during heating. Quality of the grown films was tested by Quantum Hall Effect measurements

Anisotropic mechanical and functional properties of graphene-based alumina matrix nanocomposites

Graphene platelets (GPLs) containing Al2O3 nanocomposites, which exhibit anisotropic microstructure,have been prepared by spark plasma sintering (SPS), and effects of this anisotropy on mechanical, elec-trical and thermal properties of the nanocomposites have been investigated. 3 vol.% GPLs addition intomonolithic Al2O3caused fracture toughness (Kıc) to increase by 26.7% in the in-plane direction and todecrease by 17.2% in the through thickness direction. Kıcstarted to decrease in the in-plane direction andto increase in the through-thickness direction with further increase in the GPLs amount. The electricalconductivity of the nanocomposites exhibited a slight anisotropy with a lower resistivity in the in-planedirection. Oriented GPLs also led to a less resistive heat conduction path in the in-plane direction. ∼44%increase in the in-plane thermal conductivity was achieved at 600◦C with 15 vol.% GPLs addition into themonolithic Al2O3and this resulted in ∼52% increase in the kin-plane/kthrough-thicknessratio

COMMON CAUSES OF CHANGE OF THE GORDES CARPETS

Manisa İline bağlı Gördes İlçesi Türk dokuma kültürünün şekillendiği ve devam ettirildiği önemli merkezlerden birisidir. Kendine özgü renk, motif ve desen özellikleriyle Türk Halı Sanatı içerisinde farklı bir yeri olan Gördes halılarının 17. yüzyıldan itibaren dokunmaya başlandığı bilinmektedir. Gördes ve çevresi zaman içerisinde Anadolu’nun önemli halı merkezlerinden birisi haline gelmiştir. Ancak son zamanlarda geleneksel dokumacılığımızın yaşadığı değişim Gördes halılarında da kendisini hissettirmektedir. En yaygın sebep olarak bilinen ticari kaygıların sonucunda ortaya çıkan bu değişim, yöre halılarında renk, motif ve desen özeliklerinin değişmesi ile kendisini belli etmektedir. Bu çalışmada da Gördes halılarının renk, motif ve desen özelliklerinde görülen bu değişimin belirlenmesi ve belgelenmesi amaçlanmıştır. Yapılan araştırma sonucunda yörede dokumada kullanılan ipliklerin bitkisel boyalarla boyanmasının giderek azalması ve yapay boyaların bu amaçla kullanımın yaygınlaşması sonucunda renklerde önemli bir değişim yaşandığı gözlenmiştir. Bununla birlikte Gördes halısı dokumacılığının azaldığı, bu geleneksel halıların yerini de daha çok ticari amaçlı dokunan ve desen adı olarak “Kırkyama” ile “Şal” olarak isimlendirilen halıların aldığı tespit edilmiştir.Gordes District of Manisa Province is one of the major center which Turkish culture has shaped and continue weaving. From the 17th century is known as Gordes carpets began to weave with its unique color, pattern and texture features. Gordes and the environment has become one of the Anatolia\'s most important centers of carpet over time. However, the changes recently experienced by traditional weaving is reflected also in Gordes carpets. Known as the most common cause of this change occurring as a result of commercial considerations, local carpets colors, designs and patterns with changes. In this study, the color of Gordes carpets, motifs and patterns identified and documented these changes in properties were investigated. As a result of in this study, weaving yarns which are dyed by herbal pigment, decreased in time step by step and the colors changed significantly due to the expansion of artificial dyes is being observed. Moreover, weaving Gordes carpet decreased and commercial products, called “patchwork” and “throw” become widespread instead of traditional Gordes carpet at the same time

Carbon : nickel nanocomposite templates – predefined stable catalysts for diameter-controlled growth of single-walled carbon nanotubes

Carbon : nickel (C : Ni) nanocomposite templates (NCTs) were used as catalyst precursors for diameter-controlled growth of single-walled carbon nanotubes (SWCNTs) by chemical vapor deposition (CVD). Two NCT types of 2 nm thickness were prepared by ion beam co-sputtering without (type I) or with assisting Ar+ ion irradiation (type II). NCT type I comprised Ni-rich nanoparticles (NPs) with defined diameter in an amorphous carbon matrix, while NCT type II was a homogenous C : Ni film. Based on the Raman spectra of more than 600 individual SWCNTs, the diameter distribution obtained from both types of NCT was determined. SWCNTs with a selective, monomodal diameter distribution are obtained from NCT type I. About 50% of the SWCNTs have a diameter of (1.36 ± 0.10) nm. In contrast to NCT type I, SWCNTs with a non-selective, relatively homogeneous diameter distribution from 0.80 to 1.40 nm covering 88% of all SWCNTs are obtained from NCT type II. From both catalyst templates predominantly separated as-grown SWCNTs are obtained. They are free of solvents or surfactants, exhibit a low degree of bundling and contain negligible amounts of MWCNTs. The study demonstrates the advantage of predefined catalysts for diameter-controlled SWCNT synthesis in comparison to in situ formed catalysts.ISSN:2040-3364ISSN:2040-337