Murat Bengisu

Gelcasting of alumina and zirconia using chitosan gels

Abstract A new gelcasting system has been analysed. The gel forming system is based on a solution of 1% chitosan in diluted acetic acid and reaction with glutaraldehyde. An Al 2 O 3 powder-loading rate of 50 vol.% was achieved under optimised conditions. Advantages of this new system include the use of a biopolymer (chitosan), possibility of air drying of green parts, possibility of gelcasting at ambient temperature, and versatility of the process by changing process parameters leading to well specified reaction times. The effect of process parameters on reaction time, slurry properties, and green part properties are presented. Slurries prepared from ZrO 2 powders were not fluid. However, dense green parts could still be obtained by transferring these slurries to a mould and drying.

Oxidation and pyrolysis of chitosan as a route for carbon fiber derivation

The oxidation and pyrolysis of chitosan were studied with the aim of obtaining carbon fibers from chitosan fibers. The effect of heat treatment temperature and time as well as pretreatment with ammonium chloride on the conversion process was analyzed. The mechanism for the conversion of chitosan to carbon during oxidation, suggested by FTIR analysis, is one where degradation takes place together with decomposition of the pyranose ring with partial dehydration and deamination. Pretreatment of chitosan improved the carbon yield significantly in the end product. Improved tensile strengths were observed upon pyrolysis. Although the heat treatment temperatures were considerably low, a higher C yield was obtained with chitosan fibers compared to rayon fibers (>20 vs. 15%, respectively). It is concluded that pyrolysis of chitosan fibers in an inert atmosphere can be an alternative method for the production of carbon fibers with regard to pyrolysis of cellulose (rayon) fibers.

On whisker toughening in ceramic materials

Abstract Toughening achieved by incorporation of whiskers to ceramic matrices was calculated based on an approach that combines individual contributions from effective toughening mechanisms. The relative importance of each mechanism, among others, was found to substantially vary depending on the selection of whisker and composite parameters. Analysis of the effect of various parameters showed that whisker strength, pullout length, debond length, and volume fraction of whiskers are the most important parameters in whisker toughening. Very good agreement was found between predictions made by the combinatory approach and experimental toughness values of Al2O3/SiCw composites.

Preparation and characterization of physical gels and beads from chitin solutions

Abstract A detailed account of physical bulk gel and bead formation from various chitin solutions and nonsolvents is given. Instant gel formation occurs upon contact of chitin solutions in dimethylacetamide (DMAc)/lithium chloride (LiCl) or N -methyl-pyrrolidinone (NMP)/LiCl solvents and nonsolvents such as water, ethanol, or acetone. Ethanol was found to be the optimal nonsolvent for homogeneous spherical bead formation from chitin solutions. Similarly, DMAc-based chitin solutions proved to yield higher quality beads compared to NMP-based solutions. The differences in bead morphology, crystallinity, and thermal degradation are explained in light of the attainment of a balance between attractive hydrogen bonding in the chitin gel network and segment–nonsolvent interactions. The dependence of swelling of chitin gels on pH indicated a maximum of swelling ratio value of 4.3 at pH 11 in aqueous solutions while the equilibrium swelling ratio value of chitin beads formed with ethanol reached a maximum of 2.4. Bulk gels formed under favorable conditions were demonstrated to be recyclable after solvent separation and drying.

Employment of the workforce with disabilities in the hospitality industry

A three-stage Delphi study was conducted with experts and professionals working in the fields of disability and hospitality in order to identify some basic principles with respect to employment of people with disabilities (PWD). The potential effects of employing PWD on safety, cost, efficiency, service quality and management were investigated. Potentials and limitations of people with different types and degrees of disabilities with regard to jobs in the hospitality industry were also questioned. A notable guiding principle emanating from this study is that hiring of employees should be based on merit, suitability and capability of the candidate, regardless of the presence or degree of disability. Another important outcome is that the job or task appointed to PWD should not deteriorate the disability. A common guideline expressed by the participants was that jobs which critically require a certain sense or ability are not suitable for PWD who do not possess this sense or ability even with the aid of technology or by other means. However, apart from such extreme and obvious cases, experts mostly agree that PWD can fulfill any task in the hospitality industry as long as their professional knowledge and skills fit those tasks.

Critical and emerging technologies in Materials, Manufacturing, and Industrial Engineering: A study for priority setting

Technologies that were assumed to be critical or emerging in Materials, Manufacturing, and Industrial Engineering were combined from different sources. These were compared to recent data and trends based on publications as well as patents in these fields. Some of these technologies were found to be non-critical or non-emergent. Top-ten lists of critical and emerging technologies were derived using simple statistical tools and easily accessible databases. The present methodology is proposed as an effective procedure for priority setting in science and technology policy making.

Borate glasses for scientific and industrial applications: a review

Research in borate glasses has started as a scientific curiosity and as an aid to explain the structure of oxide glasses in general. This effort led to a better understanding of the structure and unique properties of borate glasses. Although silicate and borosilicate glasses satisfy the vast majority of scientific and industrial needs, there are certain circumstances where they are not satisfactory. Furthermore, borate glasses offer certain advantages over silicate glasses which are not well known, neither well explored. However, certain characteristics of borate glasses such as their affinity to water requires that they are well selected, designed, or developed to satisfy the specifications of a given application. This review aims to explore and report some of the key properties of binary borate glasses. It also provides certain guidelines for several applications where the scientific literature is discussed in connection with industrial experience and technological needs.

Synthesis and Characterization of Aliphatic Tri-functional Oligomeric Urethane Methacrylate used for UV-Curable Aluminum Pigmented Coatings

A new UV-curable coating with aluminum pigments was developed as part of an effort to replace chromium coatings, which raise health and environmental concerns. For achieving this, aliphatic tri-functional oligomeric urethane methacrylate (ATOUA) was synthesized using trimethylol propane (TMP), isophorone diisocyanate (IPDI), hydroxyethyl methacrylate (HEMA) and dibutyltin dilaurate (DBTDL) as a catalyst. In order to obtain a metallic shine effect, leafing and non-leafing aluminum pigments were formulated with ATOUA to obtain a series of coatings. The UV-curable aluminum pigmented coatings were prepared by blending ATOUA, 1,6-hexanediol diacrylate (HDDA) and trimethylol propane triacrylate (TMPTA) as reactive diluents, benzophenone as photoinitiator, N-methyl diethanolamine as co-initiator, aluminum pigments, and wetting and dispersing agent (OA 10EO). Surface morphology of the coatings was investigated through SEM. FTIR; 1H-NMR and 13C-NMR spectroscopes were used to characterize composition of the synthesized oligomer. Physical, chemical and mechanical properties of surface coatings have been determined using König hardness, cross cut, impact, gloss, mandrel, cupping and salt spray test. Thermal properties of the cured coating were also investigated by means of DSC and TGA.

Assistive Technologies for Visually Impaired Individuals in Turkey

ABSTRACT A phone survey was conducted with 80 visually impaired people in Turkey to understand what types of assistive products are used and to what extent. The perceived utility of selected products and reasons for nonuse were investigated. Descriptions of products that would be useful for the participants but may not be available on the market were also obtained. The three most used assistive products were found to be computer screen readers (46%), talking watches (26%), and screen readers for cellular phones (21%). Cellular phones with screen reading capability are the most desired assistive products among the visually impaired community, but their high cost is a major barrier. Most of the relevant technologies are available but some product development, such as adaptation to the Turkish language, is necessary. The three products most frequently requested are bus station/destination announcement systems, devices that warn the person about barriers, and devices that read printed documents and signs.

Materials that Change Color

This chapter introduces materials that change color with scientific definitions and explanations of different categories such as photochromic, thermochromic, and electrochromic materials. The behaviors in relation to the stimuli to which they react is presented and a general picture of the potential of these materials are given with some examples/applications of the most commonly used types. This information will help to understand how materials that change color work, how they are applied to products and systems, and how their multi-faceted nature was put to use until today.