The Optical and Structural Properties of Undoped ZnO and Co-doped ZnO:Alx:Cdy x = 1 at %, y = 1, 2, 3, 5 at % Thin Films,and Their Electrical Characteristics as Photodiode

Protection of Metals and Physical Chemistry of Surfaces - ZnO semiconductor thin films with and without Al/Cd additives were produced with sol–gel spin coating technique. Also, photodiodes...     

The effects of surface roughness on varnish adhesion strength of wood materials

In this study, the effects of surface roughness of wood material on the adhesion strength of varnish layers have been tested. For this purpose, test samples of beech (Fagus orientalis L.), Scots pine (Pinus sylvestris L.), and cherry (Prunus cerasus) wood species were prepared and sanded with 80, 120, and 180 grit abrasives. The surface roughness values of specimens were determined using a stylus-type profilometer TIME TR 200 according to the ISO 4287 standards. Then, water-based, polyurethane, and acrylic varnish were applied to the surfaces of the samples in accordance with ASTM-D 3023. Layer adhesion strength was determined to the TS EN ISO 4624 standards. As a result, the highest adhesion strength value (2.52 N/mm²) was found in cherry, while the Scots pine had the lowest value (2.32 N/mm²). For the varnish types, polyurethane varnish types gave the highest value (3.15 N/mm²), while the lowest value was obtained from the water-based varnish. Looking at interactions between adhesion strength and surface roughness, the water-based varnish had the strongest correlation with adhesion strength (69%) and acrylic varnish also had a similar result (67%), while polyurethane varnish had the weakest result (33%) in this interaction.     

A comparison of basic dye adsorption onto zeolitic materials synthesized from fly ash

This investigation reveals the adsorption characteristics of two basic dyes, thionine (TH) and safranine T (ST), onto fly ash (FA) and its three zeolitized products prepared at different hydrothermal conditions. Typical two-step isotherms were observed for TH adsorption onto four adsorbents, whereas the isotherms of the larger ST molecules were S-shaped. The adsorption capacities of the zeolitized fly ash (ZFA) estimated from the first plateau region of the TH isotherms was nearly twice the FA capacity. The capacities increased by up to five times in the second plateau region. The adsorption capacity of FA for ST is equivalent that of TH, whereas the capacities of ZFA are lower than those found for TH. The equilibrium results were well-described by the Freundlich isotherm model. The kinetic data obtained in the temperature range of 298-318 K was analyzed using Paterson's and Nernst Plank's approximations based on the homogeneous surface diffusion model (HSDM). The thermodynamic functions for the transition state were evaluated from the temperature-dependence of the surface diffusion coefficients by applying the Eyring model.     

Optical dispersion and dielectric properties of rubrene organic semiconductor thin film

Rubrene thin film has been fabricated on a glass substrate by spin-coating at 300 K. The optical dispersion and dielectric properties of the film have been determined from the analysis of transmittance and reflectance measurements at normal incident of light between 200 and 700 nm. The optical transmittance of the film was estimated as of 80–85 % in the visible range. Optical absorption characteristics show that the absorption mechanism is due to the indirect transition. The transport and onset optical energy gaps were determined as 2.93 and 2.31 eV, respectively. Single term Sellmeier dispersion relation and Wemple–DiDomenico single oscillator model were used to determine the optical dispersion parameters. Several dispersion parameters such as lattice dielectric constant, optical dielectric constant at higher frequency, dispersion energy, oscillator energy, the ratio of carrier concentration to the effective mass, the average oscillator wavelength, and average oscillator strength were determined by analysis of refractive index dispersion. The loss factor, the electric modulus, the optical conductivity, the volume and surface energy loss functions, and the relaxation time were also evaluated from the optical dielectric constants analysis.     

Analyzing the effect of the elastane-containing dual-core weft yarn density on the denim fabric performance properties

Denim fabrics form today’s mostly utilized fabric type. As is the case with the other textile products, there are many factors affecting the properties and the performance of the denim products. Within the scope of this study, we have evaluated the effect of the density changes in the use of the dual-core threads – used in an ever-increasing fashion in the textile industry – in weft have on the fabric properties. We have analyzed the extent to which the weight, size, elasticity, tensile strength, and cost properties of the denim fabrics woven with the dual-core weft thread in various densities are affected by the changes in the number of dual-core weft threads per unit length. In conclusion, we have come to such striking remarks as that the construction has a much more impact on the fabric width and thus on the unit weight than the elasticity ratio, and that density changes in the elastane-containing threads cause serious differences on the fabric’s color values.     

Use of nanoclay as an environmentally friendly flame retardant synergist in polyamide-6

Due to their very high levels of flame retardancy, chlorinated and brominated flame retardants had been the most widely used flame retardant additives in plastics industry. However, these flame retardants lead to formation of very toxic volatiles and by-products during fire. Therefore, the recent trend is to replace all of them with non-halogenated flame retardants. In this respect, the use of nanoclays as a synergist flame retardant is becoming more and more important. Thus, the main aim of this work was to investigate the synergistic flame retardant effect of nanoclays with phosphorous compounds in polyamide-6 composites. For this purpose, exfoliated clay nanocomposites of flame retarded/glass fiber reinforced polyamide-6 were prepared by melt compounding. A flame retardant based on phosphorus compounds was used at various levels in glass fiber reinforced polyamide-6 and nanocomposites. Flammability and fire behaviors were evaluated by limiting oxygen index, UL94 and cone calorimeter tests. Substitution of a certain fraction of the flame retardant with nanoclays was found to significantly reduce the peak heat release rate and delay the ignition in cone calorimeter. Moreover, remarkable improvements were obtained in limiting oxygen index along with maintained UL94 ratings.     

Quenched bond randomness: Superfluidity in porous media and the strong violation of universality

The effects of quenched bond randomness are most readily studied with superfluidity immersed in a porous medium. A lattice model for³He-⁴He mixtures and incomplete⁴He fillings in aerogel yields the signature effect of bond randomness, namely the conversion of symmetry-breaking first-order phase transitions into second-order phase transitions, the λ-line reaching zero temperature, and the elimination of non-symmetry-breaking first-order phase transitions. The model recognizes the importance of the connected nature of aerogel randomness and thereby yields superfluidity at very low⁴He concentrations, a phase separation entirely within the superfluid phase, and the order-parameter contrast between mixtures and incomplete fillings, all in agreement with experiments. The special properties of the helium mixture/aerogel system are distinctly linked to the aerogel properties of connectivity, randomness, and tenuousness, via the additional study of a regularized “jungle-gym” aerogel. Renormalization-group calculations indicate that a strong violation of the empirical universality principle of critical phenomena occurs under quenched bond randomness. It is argued that helium/aerogel critical properties reflect this violation and further experiments are suggested. Renormalization-group analysis also shows that, adjoiningly to the strong universality violation (which hinges on the occurrence or non-occurrence of asymptotic strong coupling—strong randomness under rescaling), there is a new “hyperuniversality” at phase transitions with asymptotic strong coupling—strong randomness behavior, for example assigning the same critical exponents to random-bond tricriticality and random-field criticality.     

Remote control of an ultrasonic motor by using a GSM mobile phone

In this study, remote control of an ultrasonic motor has been implemented by using a standard GSM mobile phone. To drive the ultrasonic motor a digitally controlled drive system has been designed. Then a tone decoder circuit and microcontroller have been added between output of a mobile phone and the drive system of the motor. This system is flexible to be controlled with both GSM and DTMF based phones. With the developed drive and control system the overall control of the ultrasonic motor has been achieved. The system has been tested for different speed, position and direction conditions successfully. The experimental results verify that the GSM controlled drive system is highly effective, reliable, proper and applicable to achieve remote control of the ultrasonic motor. This study gets novel and important point of view for GSM based remote control applications addition to the control of ultrasonic motors.