ICMCTF2014 Session TSP: Symposium TS Poster Session

Dye-sensitized solar cells have been intensively studied since the discovery of them in 1991. however, a number of problems remain to be solved in order to enhance their efficiency. In particular, one of the main limiting factors is the electron recombination that occurs due to contact between the transparent conductive oxide and the redox electrolyte.

In this work, we report an improvement in the photovoltaic characteristics of dye-sensitized solar cells by using a TiCl₄ and ZnO treated TiO₂ Nanotube. The introduction of one-dimensional structure with TiO₂ nanotube, with a much more open structure, allows the polymer electrolyte to penetrate easily inside the film, increasing the interfacial contact between the nanotube/dye and the electrolyte.

In addition, a suitable amount of TiCl₄ and ZnO in the film could provide a large surface area for dye adsorption. Therefore, It is well known that the photocurrent of DSSC is correlated directly with the number of dye molecules, with more dye molecules adsorbed leading to more incident light being harvested, as well as a larger photocurrent. It is expected that the photoelectrical performance of the DSSC can be improved.

Aluminum nitride is an important material for various applications due to its specific properties. Whereas the stable wurtzite structure is well characterized, only little is known for the metastable high-pressure phase face centered cubic (B1, rock-salt type) AlN. By coherency strains to lattice matched materials, like B1-CrN, AlN can be stabilized in the metastable B1 crystal structure even under ambient conditions. However, the maximum thickness of fully stabilized B1-AlN is limited to a few nm because the high chemical driving force for transformation into its stable wurtzite allotrope prevents the existence of bulk free-standing pieces of this phase.

The experimental characterization of phases in such small dimensions is a challenging task. Here, an approach is proposed that combines in-situ wafer curvature experiments with continuum mechanics modeling to determine the in-plane coefficient of thermal expansion (CTE) and elastic properties of B1-AlN. In the experiments CrN/AlN superlattice films on Si (100) are investigated with 1 nm thick AlN layers stabilized in the B1 structure as confirmed by high-resolution transmission electron microscopy. The continuum mechanics approach is formulated as inverse problem solved by means of finite element methods.

To cross-validate the results, the temperature dependent CTE is calculated using ab initio methods. The elastic properties of B1-AlN are reproduced from previous studies, emphasizing the significant difference of B1-AlN compared to other nitride materials used as hard protective coating materials.

For the application of direct liquid fuel cell (DLFC), the Ag/Pt bimetallic nanoparticles were synthesized using an electrical discharge process in a liquid environment, namely solution plasma process (SPP). A SPP facilitated the concurrent synthesis of Ag/Pt bimetallic nanoparticles supported on carbon via the reduction of AgNO₃ and Pt (II) acetylacetonate, and the decomposition of ethylene glycol for carbon formation. It is shown from transmission electron microscopy (TEM) that the structure of Ag/Pt bimetallic nanoparticles exhibited dendritic nanocomposites consisting of faceted Pt nanocrystals on Ag branches. The activities of Ag/Pt bimetallic nanoparticles supported on carbon for the electrochemical oxidation of methanol were compared with Pt nanoparticles supported on carbon in acid solution by cyclic voltammetry. The Ag/Pt bimetallic nanoparticles supported on carbons exhibits much better methanol oxidation activity than the Pt nanoparticles supported carbons. This significant improvement in catalytic performance may be attributed to inhibition of CO oxidation. Detailed experimental results will be presented.

Acknowledgement

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2013M2A8A1042684).

Roughness plays an important role in scratch testing. This is not only due to the fact that roughness influences the friction conditions and splits the otherwise single global contact into a jumble of smaller contacts, but simply also leads to a great variety of loads and moments contributing to the final displacement field. So, apart from the external normal and lateral (scratch) load one locally has to deal with lateral loads in the direction perpendicular to the scratch axis plus tilting and twisting moments only being caused by the surface topography or roughness.

This work will show which additional information are needed for this new approach and how the scratch measurements have to be performed. Examples will be used to show the differences between a corrected scratch test with complete topography information and a standard analysis using only the measured forces and pre scan information in scratch direction.

The worldwide need to obtain new sources of energy has motivated many types of research to supply the imminent scarcity of fossil fuels, with this promising scenario lignocellulosic materials such as bagasse and sugarcane are showing great potential, because from them is possible to obtain the second generation ethanol.

However, a major difficulty to obtain an efficient production of second generation ethanol is the pretreatment of biomass, which should at the same time, extract elements that hinder sugars conversion to ethanol and still keep them intact for subsequent process of fermentation and ethanol production.

Due to it, this paper present the results of the use of a new technology for pretreatment of lignocellulosic biomass, held by a plasma reactor with discharge by dielectric barrier, discharge which occur in the surface of the liquid, that different of conventional plasma technique explored in the literature, allows treat whole biomass and not just its surface. This modification in the process makes the pretreated biomass become more susceptible to next step of process, which is the enzymatic hydrolysis. From the pre-treatment used was possible to achieve a high degree of lignin extraction, which is a major inhibitor sugar extraction during the enzymatic hydrolysis with a lower concentration of lignin in the biomass is possible to achieve a higher yield enzyme, which lowers production costs and increases ethanol yield of the process.

Silicon oxide (SiO₂) thin films were deposited as anti-corrosion layers on AZ31 magnesium alloy substrates by atmospheric pressure plasma jet (APPJ) from tetraethoxysilane (TEOS) as the precursor. The effect of varying carrier gas flow rates resulted in control of surface morphology, microstructure, and chemical composition has been investigated and characterized by contact angle goniometer, XRD, FE-SEM, FTIR, and XPS, respectively. The corrosion resistance of SiO_x film evaluated using potentiodynamic polarization measurements in 3.5 wt% NaCl solutions confirmed that the anticorrosion behavior of 50nm-thick SiO₂ films deposited at the O₂ flow rate of 1800 sccm on AZ31 reveals a higher anticorrosion resistance with a corrosion potential (E_corr = -1.39 V) and a corrosion current (I_corr.= 5.3×10^-4 mA cm^-2) as compared to raw AZ31 materials (E_corr = -1.46 mV；I_{corr .}= 2.4×10^-1 mA cm^-2).

Graphene, a planar monolayer of carbon atoms that are densely packed into a 2D honeycomb lattice, has become one of the most intensively explored carbon allotropes in materials science due to its reported unique electronic and mechanical properties. One area that graphene has significantly impacted is in the field of electrochemistry where it is potentially the world’s thinnest electrode material and has been applied in many areas, such as in sensing and energy storage/conversion.

We report the electrochemical properties of pristine monolayer, double layer and few-layer (termed quasi-) graphene grown via CVD and transferred using PMMA onto an insulating substrate (silicon dioxide wafers). The graphene response is compared to other available graphitic electrodes, namely that of basal- and edge- plane pyrolytic graphite electrodes constructed from Highly Ordered Pyrolytic Graphite (HOPG) and information on the respective heterogeneous electron transfer rate constant (k^o) is obtained. We observe, for the first time, a correlation in the structure of graphene, in terms of its ‘number of layers’ directly upon its macroscopic electrochemical performance, which in turn corresponds to the density of edge plane like-site/defects comprising its structure. Given that pristine monolayer graphene has a low degree of edge plane coverage compared to the multi-layered structures of quasi-graphene and HOPG, in comparison it possesses slow electrochemical properties and thus in scenarios when a large/favourable k^o is required, recourse to quasi-graphene and edge plane of HOPG is suggested.

It is evident that manipulation of the graphene structure, in terms of orientation (such as exposing more edge) or through the introduction of surface edge plane like-sites/defects, will result in beneficial alterations in the observed electrochemical properties, with the development of scalable production techniques also likely to further encourage graphene exploitation.

A membrane-capacitive deionization (CDI), consisting of a fixed carbon electrode and membrane, has been applied to seawater desalination equipment because of the relatively low energy consumption compared with the reverse osmosis method. However, ion absorbability gradually decreases b ecause ion absorption mainly takes place at the interface area in contact with solution, reducing the absorption–adsorption efficiency of the electrode. Therefore, a fluidized bed electrode is applied to seawater desalination to overcome the limited absorbability of the fixed bed electrode and eliminate the recycle process. In this work, active carbon particles were coated with a cation-exchanged polymer for preparing the core–shell particles having a simultaneous absorption–desorption property, to be used as a fluidized bed electrode in seawater desalination. To adequately utilize the features of the core–shell particles, the polymer should be uniformly coated on the surface of independent active carbon particles. To do that, the active carbon particles prior to the polymer coating were modified with an acid for individual separation without agglomeration between particles, producing a more effective coating of polymer on the carbon particles. The modified carbon particles were well dispersed in an aqueous solution by the hydrophilic group in the cation-exchanged polymer, resulting in the homogeneous coating of polymer on the surface of individual carbon particles. This means that the core–shell particles prepared with heterogeneous materials could be applicable to a fluidized bed electrode in seawater desalination.

Aluminum (Al) precursor was coated onto the surface of carbon to improve the oxidation resistance in a magnesium carbon (MgO-C) refractory, and its effects on the fracture strength by controlling the amount of antioxidant and the coating thickness. To enhance the coating efficiency, the surface of graphite employed as a carbon source was treated by an acid. The Al-coated graphite showed a less weight loss than the pristine graphite in oxidation tests. The MgO-C refractory with the Al-coated graphite showed the similar fracture strength than that with the pristine refractory, even though the amount of antioxidant was reduced. The highest fracture strength was about 17 MPa, which was shown in the MgO-C refractory with the Al-coated graphite. The increase of fracture strength in the modified MgO-refractory was due to the homogeneous coating of Al precursor, showing the thickness of about 400 nm. The relationship between fracture strength and process parameters was discussed, based on the properties observed.