Electrorheological properties and creep behavior of polyindole/poly(vinyl acetate) composite suspensions

In this study, electrorheological (ER) properties of polyindole (PIN) and polyindole/poly (vinyl acetate), (PIN/PVAc) conducting composites having different compositions were investigated. Conductivities and dielectric properties of these composites were determined. The particle sizes of the composites were determined by dynamic light scattering method. Suspensions of PIN and PIN/PVAc composites were prepared in silicone oil, at several concentrations (c = 5–25%, m/m) and their sedimentation stabilities were determined. Then the effects of dispersed particle concentration, shear rate, electric field strength, frequency, and temperature onto ER activities of suspensions were investigated. The flow times of these suspensions at various dc electric field strengths were measured. Further, creep tests were applied to the composite suspensions and a reversible viscoelastic deformation was observed.     

Synthesis and characterization of novel poly(dimethylsiloxane)/polyindole composites

A series of composites of polyindole (PIN) and poly(dimethylsiloxane) (PDMS) were synthesized chemically using FeCl₃ as an oxidant agent in anhydrous media. The composites were characterized by FTIR and UV‐visible spectroscopies, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X‐ray diffraction (XRD), elemental analysis, inductively coupled plasma‐optic emission spectroscopy (ICP‐OES), magnetic susceptibility, stress–strain experiments, and conductivity measurements. The conductivities of PIN at different temperatures were also measured and it was revealed that their conductivities were slightly increased with increasing temperature. Moreover, the freestanding films of PDMS/PIN composites were prepared by casting on glass Petri dishes to examine their stress–strain properties. From thermogravimetric analysis results it was found that PDMS/PIN composites were thermally more stable than PIN. Thermal stabilities of PDMS/PIN composites increased with increasing PIN content. It was found that the conductivities of PDMS/PIN composites depend on the indole content in the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Electrical and dielectric characteristics of Al/polyindole Schottky barrier diodes. II. Frequency dependence

The dielectric properties and ac electrical conductivity of Al/polyindole (Al/PIN) Schottky barrier diodes (SBDs) were investigated by using admittance spectroscopy (capacitance–voltage [C‐V] and conductance–voltage [G/ω‐V]) method. These C‐V and G/ω‐V characterizations were performed in the frequency range of 1 kHz to 10 MHz by applying a small ac signal of 40 mV amplitude from the external pulse generator, whereas the dc bias voltage was swept from (−10 V) to (+10 V) at room temperature. The values of dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tanδ), real and imaginary part of electrical modulus (M′ and M″), ac electrical conductivity (σ_ac), and series resistance (R_s) of the Al/PIN SBDs were found to be quite sensitive to frequency and applied bias voltage at relatively low frequencies. Although the values of the ε′, ε″, tanδ, and R_s of the device were observed to decrease with increasing frequencies, the electric modulus and σ_ac increased with increasing frequency for the high forward bias voltages. These results revealed that the interfacial polarization can more easily occur at low frequencies and that the majority of interface states (N_ss) between Al and PIN, consequently, contribute to deviation of dielectric properties of the Al/PIN SBDs. Furthermore, the voltage‐dependent profile of both R_s and N_ss were obtained from the C‐V and G/ω‐V characteristics of the Al/PIN SBDs at room temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Bond strength of polymer lightweight aggregate concrete

Bond strength, physical, and mechanical properties of lightweight PC were investigated with inclusion of pumice lightweight aggregate in maximum size of 12 mm. As binder material, epoxy resin‐based polymer was used with its hardener. The binder to aggregate ratio was 30% by weight. In addition, steel fibers were added to lightweight PC mixtures in ratio of 0, 0.5, and 1%. After lightweight PC mixture was prepared, it was poured in the molds with different type of steel‐bars in size of 100 × 100 × 100 mm³. The steel‐bars centered in the cubic molds, and they were in size of Ø12, Ø14, and Ø16. The specimens were cured at 60°C for 2 h. On the hardened polymer lightweight concrete (PLC), pull‐out test for bond strength and compressive strength tests were performed. Moreover, ultrasonic pulse velocity, water absorption by weight, specific porosity, and density experiments were carried out. The relation between physical and mechanical properties showed that PLCs become more durable when using ratio of steel fibers. POLYM. COMPOS., 34:2125–2132, 2013. © 2013 Society of Plastics Engineers     

Measurement of cloth fell position using image analysis

In this paper, a computer‐aided image‐analyzing method for measuring cloth fell position directly in a non‐contact manner is introduced. The method measures the cloth fell position from an image taken by means of a camera which is mounted over the woven fabric and warp region including cloth fell on a weaving loom. Laser light lines are used as reference lines. The image containing the reference lines, the fabric and warp system is decomposed using wavelet transforms. Horizontal detail coefficient matrix is filtered with local standard deviation of a kernel for textural feature extraction and grouping achieved by means of k‐means clustering in order to determine the cloth fell position. Due to the fact that reference line positions remain the same on the fabric, cloth fell position alterations can be calculated by measuring the distance between the reference line and the cloth fell. The conversion of the distance between the cloth fell position and the reference line, measured by the number of pixels, can be accomplished by using the known distance between reference lines as a means of calibration.     

Investigation of tribological properties of boronized Fe-based SAE 1020 and TS-DDK 40 journal bearings at high loads

In practice, ferrous based materials are not used because they show similar properties to shaft material and are known to cause adhesive wear in journal bearings. With boronizing process, adhesive wear can significantly be decreased. In this study, boronizing has been applied to some ferrous based (SAE 1020, TS-DDK 40) journal bearings. Wear experiments were done on SAE 1050 steel shaft as counter abrader with 100 N loads, and 1500 rpm for 5 h by using a radial journal bearing test rig. Boronizing treatment increased wear resistance of SAE 1020, TS-DDK 40 about 10–25, and 5–7 times respectively.     

Experimental investigation of drying shrinkage cracking of composite mortars incorporating crushed tile fine aggregate

Drying shrinkage is generally classified as an important hardened concrete property. It expresses the strain occurring in hardened concrete due to the loss of water. During the drying process, free and absorbed water is lost from the concrete. When the drying shrinkage is restrained, cracks can occur, depending on the internal stresses in the concrete. The ingress of deleterious materials through these cracks can cause decrease in the compressive strength and the durability of concrete. In this study, being as a fine aggregate in mortars, crushed tile (CT) effect on drying shrinkage and drying shrinkage cracking is investigated. Thus, compressive and flexural strength, modulus of elasticity, and free and restrained drying shrinkage tests are conducted on mortar specimens produced with and without crushed tile fine aggregate. The ring test has been used in order to investigate the cracks induced by restrained drying shrinkage. In this way, free drying shrinkage strain, along with the number and development of drying shrinkage cracks, of the crushed tile fine aggregate mortar composites are quantified and observed.     

Effect of Porosity on the Mechanical Properties and Wear Performance of 2% Copper Reinforced Sintered Steel Used in Shock Absorber Piston Production

Powder metallurgy(P/M)method has mainly been used to produce automobile parts such as self-lubrication beds,shock absorber parts,and gear wheels.In order to investigate the effect of porosity on the mechanical and tribological properties in sintered steel,specimens with 10%,15%,and 20%porosity were produced in a 10 mm×10 mm×55 mm prismatic shape by pre-alloying powders of the MPIF Fe-C-0.205 alloy used in the production of shock absorber pistons.Sintering was carried out at 900-C for 45 min in an argon atmo...     

A new metal chelate sorbent for glucose oxidase: Cu(II)- and Co(II)-chelated poly(N-vinylimidazole) gels

Poly(N-vinylimidazole) (PVIm) gels were prepared by irradiating a binary mixture of N-vinylimidazole (VIm)–water in a ⁶⁰Co-γ source having 4.5 kGy/h dose rate. In the glucose oxidase (GOx) adsorption studies, affinity gels with a swelling ratio of 1100% for PVIm and 40 and 55% for Cu(II)- and Co(II)-chelated PVIm gels, respectively, at pH 6.5 in phosphate buffer were used. FTIR spectra were taken for PVIm and Cu(II)- and Co(II)-chelated PVIm, and glucose oxidase adsorption on these gels, to characterize the nature of the interactions in each species. The results show that PVIm–glucose oxidase interaction is mainly electrostatic and metal ion–chelated PVIm gel–glucose oxidase interaction is of coordinate covalent nature. Cu(II) and Co(II) ions were chelated within the gels via amine groups on the imidazole ring of the gel. Different amounts of Cu(II) and Co(II) ions [maximum 3.64 mmol/g dry gel for Cu(II) and 1.72 mmol/g dry gel for Co(II)] were loaded on the gels by changing the initial concentration of Cu(II) and Co(II) ions at pH 7.0. GOx adsorption on these gels from aqueous solutions containing different amounts of GOx at different pH was investigated in batch reactors. GOx adsorption capacity was further increased when Cu(II) and Co(II) ions were attached [up to 0.53 g GOx/g dry Co(II)-chelated PVIm gels]. More than 90% of the adsorbed GOx was desorbed in 5 h in desorption medium containing 1.0M KSCN at pH 7.0 for plain gel and 0.05M EDTA at pH 4.9 for metal-chelated gel. Nonspecific glucose oxidase adsorption on/in the metal ion–chelated PVIm gel was investigated using 0.02M of phosphate buffer solution. The nonspecific GOx adsorption was determined to be about 18% for PVIm and 8% for the metal ion–chelated PVIm gels. The ionic strength effect was investigated both on PVIm and on the metal ion–chelated PVIm gels for the glucose oxidase adsorption. It was found that ionic strength was more effective on the PVIm gel because of the electrostatic interaction between protonated gel and the deprotonated glucose oxidase side chain. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 446–453, 2001     

Why environmental dust influences solar energy harvesting

In order to minimize dust effects on optical surfaces related to the solar energy harvesting, adhesion between the active surface of energy harvesting device and the dust particles needs to be lowered. Consequently, the pinning force for the dust particles reduces, and the dust particles can be removed via creating the self‐cleaning effect. The wetting state of the active surface becomes critical towards reducing the pinning force. In this case, hydrophobic surfaces remain favorable reducing the dust adhesion on the surfaces. In the present perspective, characteristics of the environmental dust particles and their effects in humid air ambient are presented. The methods for dust removal from the surfaces and the optical transmittance reduction by the dust particles are discussed. The challenges and future perspectives of surface texturing towards achieving hydrophobicity and optical transmittance are also introduced.