Prediction of the resource-efficient potential of Turkish manufacturing industry: a country-based study

Clean Technologies and Environmental Policy - As an emerging country, there is a rapid industrial development and associated excessive resource consumption in Turkey. In this case, the...     

A Facile Technique to Produce Open Cell Titanium Foams

Nature prefers open cell order in most structures such as trees and skeletons. Engineers have been imitating the nature, to obtain high specific strength, to transfer heat, energy absorbance and filtering for various applications such as filters, heat exchangers, impact absorbers, bone implants. Although ceramic foams have been produced and used as heat shields and filters, recently a great effort has been put on metallic foams produced from aluminium, copper, iron, stainless steel, nickel and titanium. Studies on open cell structured titanium foams are steps forward among these materials due its good biocompatibility and high specific strength. In this study, open cell titanium foams are produced utilizing polymer impregnation process accompanied by a facile sintering method. In traditional foam making, long sintering durations reduce the efficiency as far as cost and delivery time for producers. In order to overcome these problems, an alternative solution is made in the production of open cell titanium foams. A facile method is designed to sinter the impregnated polymers by using induction heating. Titanium foams with open cell structures are successfully produced. SEM, XRD, metallographic characterizations are performed. Average hardness value is calculated as 815.093 ± 6.59 Hv0.1.     

Synthesis of UV-curable tung oil and UV-curable tung oil based alkyd

Two UV-curable tung oil-based resins were synthesized via a Diels–Alder cycloaddition. An UV-curable tung oil (UVTO) was prepared from bodied tung oil and trimethylolpropane trimethacrylate (TMPTMA). An inhibitor, phenothiazine, was added to avoid homopolymerization of TMPTMA. The UV-curable tung oil alkyd (UVTA) was prepared from the monoglyceride process and then reacted with TMPTMA via the Diels–Alder reaction similar to the UVTO. The UVTO and UVTA were characterized by ¹H NMR, ¹³C NMR, and MALDI-TOF mass spectroscopy. The UVTO and UVTA were formulated with a free radical reactive diluent, tripropylene glycol diacrylate (TPGDA) and photoinitiator Irgacure 2100. Photo differential scanning calorimeter (Photo-DSC) was used to investigate curing kinetics of the UVTO and the UVTA. Both the UVTO and UVTA were photocurable with the UVTA formula exhibiting a faster curing speed than the UVTO.     

How does antiseptic mouthwashes against SARS-COV-2 affect the bond strength of universal adhesive to enamel?

This study compares the effect of different mouthwashes that have been recommended during the Coronavirus disease 2019 (COVID-19) pandemic on shear bond strength (SBS) of universal adhesive to enamel in regards to self-etch (SE) and etch-and-rinse (ER) modes. Flat enamel surfaces were obtained from 100 sound human maxillary central incisors. They were randomly allocated to five groups according to the different mouthwashes (no mouthwash/control [Ctrl], 0.2% chlorhexidine 1.5% hydrogen peroxide [H₂O₂], 0.2% povidone-iodine [PVP-I], Listerine [L]), and adhesive application modes (ER and SE) (n = 10). After the application of a universal adhesive (single bond universal), composite resin (Filtek Z250) was bonded by a cylinder-shaped mold (height: 2 mm, diameter: 2.4 mm). They were subjected to SBS test using a universal testing machine (AGS-X, Shimadzu Corp.) (crosshead speed: 1 mm/min). The resin–enamel interfaces were observed with a scanning electron microscope (SEM). The semiquantitative chemical microanalyses were performed with energy-dispersive spectroscopy (EDS). The data were statistically analyzed by two-way analysis of variance and Bonferroni test (p < .05). In SE mode, Group Ctrl revealed significantly higher SBS than all mouthwash groups (p < .05). In ER mode, Group Ctrl showed significantly higher SBS than H₂O₂ and PVP-I groups (p < .05). ER mode caused significantly higher SBS than SE mode in all mouthwash groups (p < .05). The SEM observations highlighted that Group Ctrl had a regular and intact hybrid layer with resin tag formation while the H₂O₂ and PVP-I groups exhibited a thin hybrid layer in both modes. EDS analysis indicated that in SE mode, all mouthwash groups presented increased O content compared to Group Ctrl. H₂O₂ and PVP-I that were suggested for preprocedural use during the COVID-19 pandemic, reduced the enamel bond strength of the universal adhesive in ER mode.     

Application of nanoporous silicon for a metal-semiconductor-metal visible light photodetector

In this paper we present a study on the application of nanoporous silicon to an optoelectronic device called a nanoporous silicon metal-semiconductor-metal (MSM) visible light photodetector. This device was fabricated on a nanoporous silicon layer which was formed by electrochemical etching of a silicon wafer in a hydrofluoric acid solution under various anodization conditions such as the resistivity of the silicon wafer, current density, concentration of the hydrofluoric acid solution and anodization time. The structure of this device has two square Al/nanoporous silicon Schottky-barrier junctions on the silicon substrate and the electrode spacing is 500 microm. The experiment will study photoresponse and the response time of a nanoporous silicon MSM photodetector which was fabricated on the various porosity of a nanoporous silicon layer. It is found that when devices are fabricated on a higher porosity nanoporous silicon layer, the photoresponse of the device will expand toward the short-wavelength and the bandwidth of the spectrum response will cover visible light. In addition, it is found that the response time of the device decreases.     

Nematic phase formation of Boehmite in polyamide-6 nanocomposites

Nematic phase behavior of titanate-treated Boehmite rods in a polyamide-6 matrix is reported. Optical polarization microscopy (OPM) and wide-angle X-ray scattering (WAXS) performed during heating and cooling cycles, are used to provide information on the level of orientation of Boehmite rods and polyamide-6 crystallites. The nematic orientation of Boehmite is clearly indicated by the permanent birefringence in OPM, which persists above the melting point of the polymer. The WAXS data show that the projection of Boehmite peaks on the 2D detector transform from isotropic to anisotropic as the Ti-Boehmite concentration is increased, regardless of temperature or the physical state of the polymer. Nematic order parameters are obtained by fitting a Maier-Saupe type function into the WAXS intensity curves. According to that, nematic order of the Boehmite peak increases gradually with the Ti-Boehmite content and it is unaffected by the heating-cooling cycles. As for the polyamide-6, nematic order of the γ-phase and one of the α-phase peaks decrease while that of the other α-phase peak increases with the number of cycles. Based on these observations, a structure for the colloidal liquid crystalline nanocomposite samples is proposed.     

Trace elements in Turkish biomass fuels: Ashes of wheat straw, olive bagasse and hazelnut shell

Ash contents of wheat straw, olive bagasse and hazelnut shells were 7.9%, 3.9%, 1.2%, respectively, which seemed to be within the average values of ash of biomass. The microstructure of ashes included smooth, polygonal, granular and molten drop structures. A large percentage of particles present in ashes are commonly ∼1-20 μm in size. SEM/EDS analyses performed on the major ash forming elements in different ashes indicated that Si, Ca, K and Mg and P were generally the most abundant species. Trace element levels in ash samples of various biomass types such as hazelnut shell, wheat straw, olive bagasse were analysed using ICP spectroscopy. The elements determined were some of those considered being of great environmental concern such as, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pb. In all of the ashes studied Fe had the highest concentration among other trace elements, Mn was the second element that exhibited higher concentrations. The order of concentration of elements in the ashes from the highest to the lowest values was as follows: Fe > Mn > Zn > Cu > Ni > Cr > Pb > Co.