Tribological and corrosion behaviour of electroless Ni-B coating possessing a blackberry like structure

This study aims to evaluate the tribological and corrosion properties of the electroless Ni-B coating deposited on AISI 304 stainless steels. The microstructure of the coating was characterized using x-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectrometry (SEM-EDS). XRD analysis revealed that the prepared coating possessed an amorphous character. SEM-EDS investigation also indicated that a non-stoichiometric Ni-B coating was deposited with a columnar growth mechanism on the stainless steel substrate and the morphology of the growth surface was blackberry-like. The hardness and tribological properties were characterized by microhardness and a pin-on-disc wear test. The electroless Ni-B coated sample had a higher degree of hardness, a lower friction coefficient and a lower wear rate than the uncoated substrate. The electrochemical potentiodynamic polarization method was used to evaluate the corrosion resistance of the coating. The electroless Ni-B coating offered cathodic protection on the substrate by acting as a sacrificial anode although it was electrochemically more reactive than the stainless steel substrate.     

The effect of aggregation on the nonlinear optical absorption performance of indium and gallium phthalocyanines in a solution and co-polymer host

The nonlinear optical properties (NLO) of Pcs can be modified by substituting different metal atoms into the ring or altering peripheral and axial functionalities. In this study, nonlinear optical absorption properties of tetra-substituted gallium and indium phthalocyanine complexes both in solution and polymeric film have been investigated by open aperture Z-scan measurements with nanosecond pulses at 532 nm. All investigated compounds exhibited reverse saturable absorption for both solution and film experiments. The investigated compounds in the solution showed better nonlinear optical absorption properties than polymeric films. The observed nonlinear optical absorption differences depending on the aggregation are discussed using the ultrafast dynamics and decay processes of excited states found from femtosecond pump-probe spectroscopy with white light continuum experiments.     

The effect of oxygen content on the temperature dependent tribological behavior of Cr-O-N coatings

CrN, Cr-O-N and Cr-O coatings with different oxygen contents were produced with reactive cathodic arc physical vapor deposition on high speed steel substrates. The temperature dependent friction and wear behaviours of these coatings were investigated within the temperature range of 25-100 °C. The results of the study showed that it is possible to produce CrN coatings with temperature independent, low coefficient of friction (CoF) and wear behavior by introducing oxygen into them. The amount of oxygen in the coating played a critical role on the tribological behavior. Only, in the coatings produced with oxygen content higher than 46%, a temperature independent wear behavior was observed. The structure and chemistry of the coatings and wear tracks were investigated with XRD and micro Raman spectroscopy. The coatings, with an oxygen content higher than 46%, consisted of Cr₂O₃ and other compounds that are giving broad Raman shifts between 675-834 cm^− 1. With the presence of compounds giving Raman shifts at 675-834 cm^− 1, in the film and/or in the wear track, it became possible to achieve films with temperature independent, low CoF and wear behavior.     

Chemical composition of building materials used in Turkey

The main goal of this work was to determine the chemical composition of building materials used in Turkey by utilizing energy dispersive X-ray fluorescence (EDXRF) spectrometry. Gas concrete, cement, sand, bricks, roofing tiles, marble, lime and gypsum materials were selected as building materials for this research. The chemical contents and their trace concentrations of the selected samples were determined. The most abundant oxides measured were generally SiO₂, Al₂O₃, CaO, MgO, Fe₂O₃, K₂O and SO₃ for all samples. While the main chemical component of gas concrete, cement, sand and marble samples were SiO₂ and CaO, brick and roofing tile mainly consisted of SiO₂ and Al₂O₃. CaO and SO₃ were major component of lime and gypsum samples, respectively. For U and Th concentrations in the samples, activities of ²²⁶Ra and ²³²Th were measured by utilizing gamma spectrometry. ANOVA and Pearson correlation analyses were performed on the studied data for statistical analysis.     

Effect of Cement on Emulsified Asphalt Mixtures

Emulsified asphalt mixtures have environmental, economical, and logistical advantages over hot mixtures. However, they have attracted little attention as structural layers due to their inadequate performance and susceptibility to early life damage by rainfall. The objective of this article is to provide an improved insight into how the mechanical properties of emulsion mixtures may be improved and to determine the influence of cement on emulsified asphalt mixtures. Laboratory tests on strength, temperature susceptibility, water damage, creep and permanent deformation were implemented to evaluate the mechanical properties of emulsified asphalt mixtures. The test results showed that mechanical properties of emulsified asphalt mixtures have significantly improved with Portland cement addition. This experimental study suggested that cement modified asphalt emulsion mixtures might be an alternate way of a structural layer material in pavement.     

The synthesis and characterization of Cu(II) phthalocyanine bearing peripheral monoazacrown ethers and a spectral investigation of its film forming character

The synthesis, liquid crystalline behavior and self-organizing properties of Cu(II)Pc bearing monoazacrown ether moieties that contain long alkyloxyphenyl N-pivotal groups are described. The Cu(II) phthalocyanine derivative has a hexagonal, columnar structure; optical absorption and vibrational spectroscopy revealed a predominantly co-facial interaction between the chromophores and their orientation parallel to a NaCl surface. It is proposed that such homeotropic alignment is attributable to the ability of the pendant monoazacrown ether groups to coordinate the Na⁺ ions within the NaCl surface.     

Synthesis,characterization, mesomorphic and electrical properties of tetrakis(alkylthio)-substituted lutetium(III) bisphthalocyanines

The synthesis of new lutetium(III) bisphthalocyanines substituted with alkylthio groups (1–5) is described. These compounds (Pc₂Lu) are soluble in most common organic solvents and have been fully characterized (elemental analysis, FT-IR, UV–Vis spectroscopy, mass spectrometry). The thermal stabilities of the Pc compounds were determined by thermogravimetric analysis (TGA). The mesogenic properties of these new materials forming columnar-hexagonal (Col_h) mesophases were studied by differential scanning calorimetry (DSC), optical microscopy and X-ray diffraction. The compounds 2–5 exhibit a double clearing point. DC electrical properties of these compounds in different phases were determined by measuring I–V characteristics and dark current of their thin films on interdigital electrodes. The measurements were carried out in ambient air, in vacuum and in high purity nitrogen (N₂) flow in the temperature range between 300 and 420 K. Dark current measurements obtained in the crystal, liquid crystal (LC) and isotropic liquid phases were in agreement with the phase transitions of these compounds obtained by DSC and optical microscopy results. The relation between the phase transition and conductivity of the Pc₂Lu derivatives were investigated. Also, the influence of the nature of the substituted group (alkylthia and alkoxy) upon the DC electrical properties of the Pc₂Lu derivatives was investigated. The DC conductivities and the thermal activation energies depending on alkyl chain lengths of these compounds were found to be in the range of 10^?8 to 10^?5 S/cm and 0.12–0.38 eV in solid phase.     

Oxidizing gas sensing properties of mesogenic copper octakisalkylthiophthalocyanine chemoresistive sensors

In this study, the effect of oxidizing gases, such as oxygen (O₂), nitrogen dioxide (NO₂), and ozone (O₃), on a liquid-crystalline copper octakisalkylthiophthalocyanine[(C₆S)₈PcCu] thin film was investigated in the temperature range of 25-150 °C. Starting from a chloroform solution of (C₆S)₈PcCu, a jet-spray technique in an inert ambient atmosphere was used to coat the thin film of the compound on to an Interdigital Transducer (IDT) with gold electrodes. The concentration ranges for NO₂ and O₃ exposed to the (C₆S)₈PcCu thin film were 1-10 ppm and 50 ppb-50 ppm, respectively. The response time in NO₂ measurements was observed to be approximately 1 min at room temperature, and it decreased to a few seconds with increasing temperature. A good sensor response of 2000% ppm^− 1 was observed when the sensor was exposed to 1 ppm NO₂ at room temperature. The oxidizing gases were found to be desorbed by annealing the thin film.     

Performance of AC overlays using geogrids on PCC contraction joints

It is widely known that vertical displacements and strains occur on the joints and these cause defects on the asphalt concrete (AC) overlays on existing Portland cement concrete (PCC) pavements. Various approaches were introduced to minimize these defects. In this study, the effect of joint support formed using the geogrid material with grout mortar on the vertical displacement of PCC and the strain at the bottom of the AC layer. Produced layers were exposed to 1,186,000 Equivalent Single Axle Load (ESAL) in an APT (Accelerated Pavement Test) facility and the results were monitored. According to the obtained results, the use of AC overlay reduces vertical displacement in the PCC by 75%. When geogrid reinforced AC overlay was used, an additional reduction in displacement by 41.2% was achieved. Geogrid reinforcement reduced strain values formed at the bottom of the AC layer from 29.5% to 92.5%. The use of geogrid at joints instead of increasing the thickness of the AC layer from 50 to 80 mm resulted a more significant reduction in both strain and displacement. Besides, the usage of a geogrid interlayer instead of increasing the thickness of the AC layer also provided a significant cost reduction of 57.9% in overall cost.     

Silver and proton driven fluorescent multiple-mode molecular logic gates employing phthalocyanines

Spectral properties and switch behavior of two alkyl thia units bearing Zn (II) phthalocyanine derivatives (Pc-A and Pc-B) were investigated in solvents and in solid matrix of ethyl cellulose by means of absorption and emission spectroscopy. Fluorescence lifetime and fluorescence quantum yield values of the Zn (II) phthalocyanines were calculated. The employed phthalocyanines demonstrated multiple molecular logic gate functions operated by H⁺ and Ag⁺ ions as chemical inputs. The silver driven fluorescence modulation of the Pc-A arises from reversible variations in emission signal intensity at 717 nm. The Pc-B exhibited a similar decreasing emission response to proton and silver ions and an accompanying increasing peak yielding an isobestic point at 746 nm upon protonation. The phthalocyanine doped thin films selectively responded to silver ions in sub-nano and/or pico molar levels. Observed detection limits were 7.6 × 10⁻¹² and 2.3 × 10⁻¹¹ M for Pc-A and Pc-B, respectively. In immobilized phases the attained reversible relative signal changes of Pc-A and Pc-B were 82 and 90%, respectively.