Influence of crystallographic orientation on hydration of MgO single crystals

This study has been performed in order to find out the influence of crystallographic orientation on hydration of MgO single crystal substrates with (1 0 0)-, (1 1 0)-, and (1 1 1)-orientations. The samples were left in a hydration chamber with an 88% relative humidity for 18 h at room temperature. The effect of humidity on the samples was examined by scanning probe microscope (SPM) and scanning electron microscope (SEM) which showed that the degree of hydration was noticeably influenced by the crystallographic orientation. It was found that the MgO with (1 1 1)-orientation has the highest tendency to hydrate than the other orientations. Second most affected sample was (1 1 0) crystal. Loss of MgO on the surface by hydration is most severe when the crystal is oriented in (1 1 1) plane with the maximum hydrate layer thickness of 174 nm after 18 h of exposure

A microstructural study of surface hydration on a magnesia refractory

Hydration of the surface of a periclase refractory was studied in a controlled humidity atmosphere (92% relative humidity) at 26 °C for up to 92 h. The effect of humidity on the specimens was examined using a scanning probe microscope (SPM) and a scanning electron microscope (SEM), which showed that the degree of hydration was noticeably less in the intergranular bond phase compared to the periclase crystallites. The SPM study indicated significant growth of hydrates on the refractory grain surface. Growth rate of the hydrate layer was least on (0 0 1) orientation, higher for the (1 0 3) orientation, and highest for the (1 0 1) oriented grain. The rate of loss of refractory phases by hydration on a (1 0 1) oriented grain was 4.53 nm/h. This material loss may be insignificant for a bulk brick, but is a serious threat for a magnesia castable consisting of fine magnesia powder due to large surface area exposed to humidity or water itself. © 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved

Odor adsorption kinetics on modified textile materials using quartz microbalance technique

1st International Congress on Advances in Applied Physics and Materials Science (APMAS), Ankara, Turkey, 12-15 May, 2011In this study, a functional product with aromatic oil and vitamins for use at aromatherapy and spa centers or personal care has been designed to improve life quality of users by using multifunctional products with good odor, moisturizing, relaxation, anti-aging effects. For this purpose, commercial berry berry oil was capsulated in β-cyclodextrin, and then applied to 100% cotton towel fabric. Quartz crystal microbalance sensors were used to investigate odor adsorption kinetics on modified textile materials for the first time. The frequency responses vs. time plot shows clear linear step responses to the change in the concentration of odor molecules coming from the container filled with berry berry applied textile. The results also reveal that TiO 2 coated quartz crystal microbalance sensors can be used as e-nose to sense odor from textile coated with berry berry oil containing β-cyclodextrin capsules.This research was supported by TÜBİTAK under project numbers TBAG 109T240 and 110M349 and IYTE research project number 2010IYTE25

A MOF-based electronic nose for carbon dioxide sensing with enhanced affinity and selectivity by ionic-liquid embedment

The unequivocal detection of CO$_2$ is important in many situations, like in the living environment, plant cultivation and the conservation of cultural relics and archives. Due to their large specific surface areas and highly ordered and tunable structures, metal–organic frameworks (MOFs) have the potential to improve CO$_2$ sensing, however, they often suffer from low CO$_2$ affinity and selectivity. Ionic liquids (ILs) have high CO$_2$ affinity, but their performance in sensors is hampered by their nonporous, liquid form. Here, we present a low-cost and portable CO$_2$ sensor system based on an array of gravimetric sensors made of MOF films with embedded ILs in the pores. The array is composed of MOF films of two different structures, which are HKUST-1 and UiO-66, filled with 3 different types of ILs and 2 different pore-filling levels, resulting in an array of up to 14 different sensors. We show that the different combinations of IL and MOF result in different affinities for CO$_2$ and other analytes. With the help of machine learning using a neural network, the sensor array was used to quantify the CO$_2$ concentration as well as to distinguish CO$_2$ from other gases and vapors, like nitrogen, ethanol, methanol and water, and to distinguish certain binary mixtures. While the MOF-sensor array without IL achieves only a small accuracy for determining the CO$_2$ concentration, the IL@MOF sensor array can accurately classify the gas types (98% accuracy) in mixed gas atmospheres of unknown composition and concentration as well as can determine the CO$_2$ gas concentration with an average error of only 2.7%. Using only MOFs with a pronounced chemical stability (like UiO-66) in the sensor array also allows the detection and identification of CO$_2$ in a humid atmosphere. Moreover, the presented sensor system has very high sensitivity with a CO$_2$ limit of detection below 100 ppm, which is four times smaller than the CO$_2$ concentration in air. This work shows the unprecedented performance of the sensor arrays of MOFs with embedded ILs, referred to as IL@MOF-electronic nose (IL@MOF-e-nose), for sensing the composition and concentration of CO$_2$ gas mixtures

The effect of annealing temperature on the optical properties of a ruthenium complex thin film

The stability of the optical parameters of a ruthenium polypyridyl complex (Ru-PC K314) film under varying annealing temperatures between 278 K and 673 K was investigated. The ruthenium polypyridyl complex thin film was prepared on a quartz substrate by drop casting technique. The transmission of the film was recorded by using Ultraviolet/Visible/Near Infrared spectrophotometer and the optical band gap energy of the as-deposited film was determined around 2.20 eV. The optical parameters such as refractive index, extinction coefficient, and dielectric constant of the film were determined and the annealing effect on these parameters was investigated. The results show that Ru PC K314 film is quite stable up to 595 K, and the rate of the optical band gap energy change was found to be 5.23 × 10- 5 eV/K. Furthermore, the thermal analysis studies were carried out in the range 298-673 K. The Differential Thermal Analysis/Thermal Gravimmetry/Differantial Thermal Gravimmetry curves show that the decomposition is incomplete in the temperature range 298-673 K. Ru-PC K314 is thermally stable up to 387 K. The decomposition starts at 387 K with elimination of functional groups such as CO2, CO molecules and SO3H group was eliminated between 614 K and 666 K.State Planning Organization of Turkey (DPT2003K120390); Scientific and Technological Research Council of Turkey (TBAG-109T240

Microstructural and electrical characterization of Ti and Mg doped Cu-clad MgB2 superconducting wires

The recent studies on Ti doping effect on the critical current density (Jc) of MgB2 composite superconductors prepared under ambient pressure has shown an important enhancement at 20 K. In the present work, we have fabricated Ti and Mg doped superconducting MgB2 wires by packing reacted MgB2 and Ti or Mg powders together inside Cu tubes with a diameter of 6 mm. The tubes were then cold worked by rolling or drawing to smaller diameters. The prepared Cu-clad Ti and Mg added MgB 2 superconducting wires were annealed at various temperatures to enhance the grain connectivity of the MgB2 bulk materials. The effect of the sintering time has been investigated for high performance characteristics of superconducting Cu-clad Ti and Mg added MgB2 wires. The microstructural evaluation of the superconducting wires has been carried out using XRD and SEM equipped with EDX analysis system. The interfacial properties between Cu sheath and superconducting core was characterized using SEM-EDX. Furthermore, the influence of the presence of Ti and Mg on Tc has been investigated to understand the structural and electronic properties of superconducting Ti and Mg doped MgB2 wires

Gas sensing properties of carbon nanotubes modified with calixarene molecules measured by QCM techniques

1st International Congress on Advances in Applied Physics and Materials Science (APMAS), Antalya, Turkey, 12-15 May, 2011This study focuses on the characterization and optimization of calixarene modified carbon nanotube thin films for gas detection. Calixarene molecules were synthesized individually by considering their functional groups to attract the gas. Calixarene modified carbon nanotube based sensors were fabricated using drop-casting method on a quartz crystal microbalance gold electrode. Carbon monoxide, carbondioxide, oxygen and dry air were used as active gases for adsorption process, while high-purity nitrogen gas was used for desorption process. The selectivity and sensitivity of calixarene modified carbon nanotube are investigated in detail. Our experimental results show that functional calixarene modified carbon nanotube coated quartz crystal microbalance sensors are very sensitive and selective to gas of CO 2 at room temperature operation.This research was supported by TÜBİTAK under project numbers TBAG 109 T240 and 110 M349 and IYTE research project number 2010IYTE2

Instability phenomena in microcrystalline silicon films

Microcrystalline silicon (μc-Si:H) for solar cell applications is investigated with respect to the material stability upon treatment of the material in various environments, followed by annealing. The material can be separated into two groups: (i) material with high crystalline volume fractions and pronounced porosity which is susceptible to in-diffusion of atmospheric gases, which, through adsorption or oxidation affect the electronic properties and (ii) compact material with high or low crystalline volume fractions which show considerably less or no influence of treatment in atmospheric gases. We report the investigation of such effects on the stability of μc-Si:H films prepared by plasma enhanced chemical vapour deposition and hot wire chemical vapour deposition

Low-field behavior of Ti-added MgB2/Cu superconducting wires

We report on low-field magnetic properties of Ti-added (0-20 wt.% of Ti) Cu-clad MgB2 superconducting wires. Wires were produced by mixing appropriate amount of Ti and reacted MgB2 powder which was then placed inside Cu tubes with a diameter of 6 mm. The tubes were then cold worked by rolling or drawing to smaller diameters and then annealed at various temperatures to enhance the grain connectivity. XRD studies show that Ti addition results in new but minor phases. We have then measured ac susceptibilities in the temperature range between 20 K and 40 K in ac fields of 20-1600 A/m. The data show that an additional loss mechanism is established with Ti-addition. The calculated ac losses are increasing with increasing Ti-content in the main superconducting matrix

The Role of Hydrophobicity in the Development of Aluminum and Copper Alloys for Industrial Applications

Improvement of corrosion resistance is a main challenge in surface and corrosion engineering. Water is a main part of corrosion mechanism, and the omission of this part will be helpful. By mimicking from nature, superhydrophobicity is a helpful method to decrease corrosion and water presence on the surface. Superhydrophobic surface and coating is a new type of coating that extension in recent decade and increase application of this area every day. These type of coatings are using on widespread of applications such as solar panels, displays, windows, paints and fabrics to obtain water-proof, anticorrosive, self-cleaning and stain-resistant surfaces. Many different studies have been reported to produce superhydrophobic surfaces from many diverse materials (polymers, metals and other inorganic materials, composites, textiles, paper). In this chapter, recent developments in the application of superhydrophobic coatings for corrosion protection of aluminum and copper alloys will be discussed. This chapter includes new production methods, theoretical works, and the limitations of superhydrophobic coatings