Qatar Foundation Annual Research Conference Proceedings Volume 2014 Issue 1

The main two challenges hindering the deployment of solar cells in large scale are the high cost and low efficiency. One of the strategies to reduce the cost is by using thin film materials with enhanced solar cell conversion efficiency. However, thin film materials suffer from weak absorption and the presence of defects, which act as recombination canters for charge carriers. Various studies were conducted to improve absorption in thin film solar cells. However, those approaches are not optimized yet for high efficiency solar cells. In this study, we focus on enhancing light absorption of thin film silicon solar cells by using Zinc Oxide (ZnO) nanostructures.

BACKGROUND & OBJECTIVES: Improving materials properties is one of the biggest scientific issues of all the times. When it becomes impossible to further manipulate the raw material, one feasible way to push its properties beyond the theoretical limits is to modify the properties of the surface. That is where advanced surface coatings come in. From a manufacturing point of view, tools for machining are of particular interest. These tools are usually made of hard steels and cemented carbide (WC-Co). For specialized applications, such as aluminium machining, diamond or polycrystalline cubic boron nitride are also used. The main problem with steel, is that it exhibits a relatively low hardness (below 10 GPa) which strongly decreases upon annealing above about 600 K. Thus, the majority of modern tools are nowadays coated with hard coatings, in order to: (i) increase the hardness, (ii) decrease the coefficient of friction, and (iii) protect the tools against oxidation. A similar approach has been recently used to obtain a longer duration of the dies for aluminium die-casting. Multi-component and nanostructured materials represent a promising class of protective hard coatings due to their enhanced mechanical and thermal oxidation properties. METHODS: Three different thin hard nitrogen-rich coatings were mechanically, microstructurally, and thermally characterized: (i) a 2.5 micron-thick nano-layered CrN-NbN, (ii) a 11.7 micron-thick monolayer TiAlN, and (iii) a 2.92 micron-thick multilayer AlTiCrxNy. The main feature of the CrN-NbN coating is the fabrication by the alternate deposition of 4 nm thick-nanolayer of NewChrome (new type of CrN, with strong adhesion and low coating temperature). All the three coatings can reach values of hardness and elastic modulus exceeding 20 and 250 GPa, respectively. Their main applications include stainless steel drawing, plastic materials forming and extrusion, and aluminum alloys die-casting. The here studied TiAlN (SBN, super booster nitride) is one of the latest evolution of TiAlN coatings for cutting applications, where maximum resistance to wear and oxidation are required. The AlTiCrxNy combines the very high wear resistance of the Cr-coatings with peculiarities of the Al-containing coatings, such as high thermal stability and high-temperature hardness. All the coatings were deposited on a S600 tool steel. The coatings were subjected to two different thermal cycling tests: (i) 100 thermal cycles consisting of 60 s dwelling time, respectively at the high- (573 to 1173 K) and at the room-temperature, and (ii) 100 thermal cycles consisting of 115 s dwelling time, at same temperatures of the first test, followed by 5 s dwelling at room-temperature. The temperature induced hardness and elastic modulus coating variations were measured by nanoindentation. RESULTS: During thermal cycling, the TiAlN monolayer coating and the AlTiCrxNy multilayer coating showed a high oxidation resistance even at high temperature, while the CrN-NbN nano-layer coating undergoes a oxidation phenomena, for temperatures above 873 K. CONCLUSIONS: The investigated coatings showed a sufficient-to-optimal thermal response either in terms of mechanical stability, such hardness and elastic modulus, and in terms of oxidation degradation.

The development of artificial photosynthesis is one of the greatest scientific challenges of our times, not only to protect the environment but also to ensure global economic security. To mimic the natural photosynthesis process, a complete understanding of the natural photosynthesis process at the molecular level is essential to enable the production of inexpensive, lightweight, and high-energy-density fuels. Artificial photosynthesis may involve photo/electrocatalytic H2 generation by water splitting or the use of H2 in combination with atmospheric/industrially sourced CO2 conversion products to provide a continuous supply of high-energy carrier fuels at small/medium scales. Recently, Cu2O has received considerable attention in various energy-conversion applications, including photo/electrochemical hydrogen production and the photo/electrochemical conversion of carbon dioxide (CO2) to energy-carrier fuels. The Cu(I) state, with its d10 electronic configuration, is required for cuprous oxides to exhibit photo/electrochemical and chemical catalytic activity. For electrochemical CO2 reduction, Cu(I) sites are proposed to stabilize reaction intermediates such as CO, carbonates (CO23−), formates (HCOO−), and methoxy (H3CO−) adsorbates, as expected from their high heats of adsorption. Although the Cu(I) state makes these materials attractive, the stability of Cu(I) species toward redox reactions remains an issue to be solved. In this study, we report the novel design of multi-metal based electrocatalysts which may introduce different (other than Cu) active species due to effect of the hetro-atoms on the Cu surface. As a result the reaction intermediates on the surface may be stabilized generating CO exclusively as a reaction product of electrochemical reduction of aqueous CO2 while suppressing the competitive H2 generation. The higher selectivity towards CO generation may be attributed to perturbing the d-band metal center or the geometric effects caused by the second metal center around Cu.

Disinfection of drinking water is one of the extreme public health activities in Qatar. Chlorination, ozonation, ultra-violet, chloramination, and others are the most important treatment processes used and they can cause the formation of toxic by-products. The existence of bromide (Br-), for example, in water sources might cause in formation of brominated toxic by-products. Up-to-date drinking water treatment methodologies are challenged to successfully eliminate Br- before final consumption. Remediation onto activated carbons has a number of restrictions. Date pits are suitable as raw remediating adsorbent for preparing various modified adsorbents, because particular surface functional groups and the micro-pore structures can be attained by active modifications. The overall objective of this study was to develop an economical and environmentally acceptable process to safely eliminate the levels of Br- from desalinated water. Roasted date pits (RODPs) and activated charcoal (AC) (used as a control) were crushed and sieved with four different particles size ranges. The percentage of Br- removal was also studied under different experimental conditions such as pH, sorbent mass and initial concentration. In addition, surface characterization was also investigated. Experimental date analyses were investigated using different isotherm and kinetic sorption models. The modification of the date pits surface enhanced the Br- removal capacity at high initial concentration of bromide (200 ppm) by 27%. Using scanning electron microscope (SEM), the date pits surface images showed a different in pore sizes upon modification. Removal capacity of RODPs reached 39% at pH 4. In this study the heterogeneity of adsorbing mechanisms and the fitting with pseudo second order model and inter particulate diffusion models were concluded, and more than 35% of Br- removal efficiency was achieved within the RODPs at the first hour of contact time. The adsorption Br- onto RODPs was not fitted well with the pseudo-first order model. It was found that the kinetics of Br- adsorption was followed the pseudo-second order. It was also observed fluctuations in the removal efficiency for smaller particle sizes; indicating heterogeneity of adsorption/desorption and potential chemical bindings, this particular behaviour was not observed and investigated elsewhere in the literature (Figure below). The surface of RODPs contains oxygen functional groups such hydroxyl; hence the presence of such functional groups on the surface of date pits considerably influences on the adsorption mechanism of organic and inorganic compounds on the RODP. Economically RODPs are successfully used to remove Br-, comparing to AC. However, both adsorbents have nearly the same removal efficiency after one hour contact time. Apparently, the removal efficiency of both systems was quite significant. This may cover the way for the cheap and widely available date pits to be used as an adsorbent in water purification process.

Many hydrocarbon reservoirs - in Qatar and worldwide - are constituted of dolomite. For this reason, the origin of this Ca-Mg carbonate mineral has been extensively studied by generations of geologists, with the goal of exploiting gas and oil from rock reservoirs in the most efficient way. However, despite more than two centuries of research, several fundamental questions regarding the origin of sedimentary dolomite remain without a convincing answer. Recent research conducted in the field of geobiology suggests that dolomite formation may be the result of a microbial process, that is, organic molecules that in natural environments are produced by microorganisms seem to play a key role for dolomite nucleation at low temperatures in many geological settings. However, this innovative hypothesis is far from being unanimously accepted by the scientific community, and many details on the exact mechanism through which microorganisms mediate dolomite formation are still to be fully understood. The aim of this contribution is to summarize the most recent scientific studies that support the microbial model for dolomite formation, providing examples from culture experiments conducted in the laboratory using artificial growth solutions and from modern dolomite forming environments, such as the hypersaline lagoons located in the State of Rio de Janeiro (Brazil), the sabkhas of Abu Dhabi (UAE), and the sabkhas of Dohat Faishakh and Khor Al-Adaid (Qatar). Furthermore, we will elaborate on why we consider the coastal sabkhas of Qatar to be among the most ideal places on Earth where it is possible to study microbe-mineral interactions in evaporitic environments. In fact, thanks to the distinctive geology that characterizes this region, it is possible to obtain samples documenting the progressive transformation of the living microbial mats that mediate dolomite formation and other authigenic minerals into a fully lithified sediment, which is analogous to dolomite formations constituting economically important gas/oil reservoir rocks. This approach will provide key insights to test whether dolomite present in ancient evaporitic sequences can be interpreted as a fully biological product associated with early diagenesis or whether most of the dolomite forms during later stage metamorphic/replacement events that are controlled by purely abiotic processes. Finally, considering not only the scientific importance but also the aesthetic beauty of the Qatari evaporitic environments, we will discuss the idea and the challenges of transforming selected areas of the modern sabkhas into geoparks - protected natural reserves that would be of interest for the local Qatari population, as well as for tourists visiting Qatar.

Management of production from gas reservoirs can be a challenging process. The challenge gets bigger when the reservoir is characterized by having a small pore size, such as the tight carbonate reservoirs which are prominent in this part of the world. In such conditions, condensate blockage becomes a real threat to productivity. Carbon dioxide can be injected into the reservoir to combat this threat. We built a reservoir model to conduct a simulation study with the goal of finding the most feasible method for overcoming the negative impact of condensate formation. We have attempted to simulate huff-n-puff enhanced gas recovery in the same reservoir model, but this method did not achieve much success in alleviating the damage caused by condensate blockage. As a result, according to the model and data we collected, using huff-n-puff is not efficient since it failed to maintain the average reservoir pressure as well as CO2 did, therefore peripheral CO2 injection have been tested. The minimum requirement again is to achieve gas plateau production, while also maximizing the condensate recovery and minimizing the CO2 breakthrough into the wells. It was decided that seven CO2 injector wells were to be placed at strategic locations (injectors have been planned to be drilled away from the reservoir and producing wells) across the field in order to enhance the sweeping of condensate as well as minimize CO2 breakthrough. In other words, the injectors had to be at a distance where it can achieve all our simulation objectives. We ended up understanding the effect of the CO2 injection on condensate formation. As a result, it could be notice how the saturation of oil is high near the producing end of the core, this kind of saturation can completely nullify the relative permeability of gas, whereas after using CO2 flooding, the saturation is decreased significantly and the amount of condensate throughout the core is also much less.

Qatar and the region are experiencing transformative growth over relatively very short periods of time, due primarily to hydrocarbon based energy resources. As the country pushes to meet growing global demand for its finite fossil fuel reserves, it is looking also to capitalize on renewable energy sources including solar power generation. However, the high ambient humidity, high annual average surface temperature, high atmospheric aerosols including haze, secondary organic aerosols and dust particulates, all negatively impact the efficiency of solar power generation technology. We will present over ten years of Aerosol Optical Thickness (AOT) measurements from both ground and satellite based remote sensing data from NASA's Aerosol Robotic Network (AERONET) and Multi-angle Imaging SpectroRadiometer (MISR) instrument onboard the TERRA satellite. AOT is a measure of the atmosphere's ability to attenuate incoming solar radiation. As AOT increases, surface insolation decreases which in-turn decreases the theoretical limit for solar power generation. The data shows a net positive trend in AOT of >1% per annum over most of the Arabian Peninsula, including Qatar. The positive trend is associated with increased intensity of dust events, but not necessarily in the frequency of the events. The trend is observed over the operational spectral range of Photovoltaic (PV) cells (340-1020 nm.) The AOT trend is positive for all months of the year, except November, but exhibits a strong seasonal signature that indicates the dusty months are becoming dustier (March through July) and less productive for solar power generation. Trends in the angstrom parameter, an indicator of the size of the atmospheric aerosols, during the less dusty winter months, indicate an increase in the average size of the atmospheric aerosols, i.e. the winter months too are becoming dustier. Work continues on quantifying the net impact of the observed trend on solar power generation.

Power monitoring is needed in most electrical systems, and is crucial for ensuring reliability in everything from industrial and telecom applications, to automotive and consumer electronics. Power monitoring of integrated circuits (ICs) is also essential, as today ICs exist in most electrical and electronic systems, in a vast range of applications. Many ICs have functional blocks across the chip that are used for different purposes. Power ICs also have multiple circuit blocks, each performing their own function. Measuring circuit block currents in both analog and digital ICs is important in a wide range of applications, including power management as well as IC testing and fault detection and analysis. For example, the presence of different kinds of faults in IC circuit blocks during IC fabrication causes the currents flowing through these circuit blocks to change from the expected values. There has been general interest in monitoring currents through different circuit blocks in an attempt to identify the location and type of the faults. Previous works on nonintrusive load monitoring as well as on power-line communications (PLCs) provide motivation for the work presented here. The techniques are extended and used to develop a new method for power monitoring in ICs. Most solutions to the challenge of measuring currents in different circuit blocks of the IC involve adding circuitry that is both costly and power consuming. In this work, a new method is proposed to enable individual measurement of current consumed in each circuit block within an IC while adding negligible area and power overhead. This method works by encoding the individual current signatures in the main supply current of the IC, which can then be sensed and sampled off-chip, and then disaggregated through signal processing. A demonstration of this power monitoring scheme is given on a modular discrete platform that is implemented based on the UC3842 current-mode controller IC, which can also be used for educational purposes.

Solution combustion synthesis (SCS) is a widely used technique for synthesizing variety of high purity oxide nanoparticles. Two basic modes for combustion synthesis are the self-propagating high temperature synthesis (SHS) and Volume Combustion Synthesis (VCS). The first method is based on the reaction that is locally ignited by an external source (laser, tungsten coil etc) which ends up with an exothermic redox reaction in a self-sustained manner without requiring any further energy for the combustion. Second method is the uniform heating of the entire sample in a controlled manner using a constant heat until the reaction occurs simultaneously throughout the volume. SCS typically involved a self-sustained reaction in a homogeneous solution of oxidizer (metal precursor) and oxygen containing fuels (urea, glycine, hydrazine etc). The selection of fuel is based on the reactive groups such as amino, hydroxyl and carboxyl bonded to a hydrocarbon chain. In our total work, we used two modes of synthesis: VCS and ILCS (impregnated layer combustion synthesis) to synthesize transition metal nanoparticles. The precursors used in this work were Nickel nitrate hexahydrate, Ni(NO3)2.6H2O, Copper nitrate hexahydrate, Cu(NO3)23H2O, Cobalt nitrate hexahydrate, Co(NO3)2. 6H2O and Glycine CH2NH2COOH. The ratio of metal nitrates and glycine were optimized to give pure metals of high surface area. The precursors were thermally analyzed using TGA/DTA to understand the metal phase development with increasing temperature. Phase Composition and average particle size were analyzed using XRD and the specific surface area of the synthesized particle was calculated using BET method, while its morphology was analyzed by SEM. The objective of our work is to synthesize nanoparticle with high surface area, selectivity and reactivity, which will be more suitable to be act as catalysts for electrochemical reaction in the conversion of CO2 to valuable products The XRD calculations indicated crystallite size to be in the range of 8nm - 15 nm indicating small nanoparticles with high surface area suitable of catalytic applications. The XRD profile of Copper-Nickel in glycine for different stiochiometric ratios shows the presence of pure alloy of Copper Nickel at its higher value of ?, say it as 1.75. The multiple peaks in XRD for its lower stiochiometric ratio indicates the presence of oxide. The objective of our work is to synthesize nanoparticle with high surface area, selectivity and reactivity, which will be more suitable to be act as catalysts for electrochemical reaction in the conversion of CO2 to valuable products The large surface area for Copper Nanoparticles were synthesized first which having large surface active sites, they become excellent catalysts in metallurgical and petrochemical Investigation has been done based on the basic mechanism to describe the phase transformation in the combustion front. The SEM analysis pointed a remarkable change in the particle distribution, grain size, porosity and its microstructure by changing the oxidizer/ fuel ratio These nanoparticles are currently being investigated for catalytic reduction of CO2 to valuable chemicals.

Spent Pot Lining (SPL) is produced in thousands of tons annually as a waste from the aluminum industry. SPL is classified into two types, 1st and 2nd Cut SPL. The 1st cut, which is the material under investigation in this study, is a contaminated graphite/ceramics material (50 - 60% of graphite) that is used in lining the electrolytic cell within which aluminum is produced by the reduction of molten Al2O3. 1st Cut SPL is considered as a hazardous material since it contains many other contaminants such as fluorides, cyanides, lead and chromium in addition to its production of flammable gases when it comes in contact with water e.g. ammonia, phosphine, hydrogen and methane. The aim of this study is threefold: (i) fully characterize the 1st Cut SPL produced by Qatalum in Qatar to help in creating the materials safety data sheet (MSDS), (ii) chemically treat this 1st Cut SPL in order to extract the graphite component to use it in other applications in addition to the Cryolite and finally (iii) use the extracted graphite in removing heavy metal ions from aqueous solutions. In this work, the first treatment for 1st Cut SPL was washing it with deionized water. The produced gases were collected in gas bags and characterized using GC-MS which confirmed the evolution of H2 gas when the 1st Cut SPL comes in contact of water. The second step was washing the 1st Cut SPL powder several times with organic solvents to dissolve the existing organic compounds and characterize the eluent using HPLC-MS technique to identify the dissolved organics. A thermal treatment to get rid of the undissolved organic materials was done. Next, surface characterization was carried out for the dried powder which confirmed the absence of any organic materials. Later, the powder was treated with cycles of different concentrations of NaOH, HNO3 and deionized water to remove the remaining inorganic contaminants. The eluents, resulted from the chemical treatment and washing processes, were collected and analyzed using HPLC-MS and ICP. The purity of the produced graphite powder was characterized using XRD to check its purity. The produced graphite powder was functionalized through boiling in 1:1 of H2SO4 : HNO3, washing with deionized water, hot NaOH and finally with deionized water to increase the carboxylate groups on the graphite surface which increases the negative charge on the graphite's surface once mixed with water. The functionalized graphite was proved to Cu ions from aqueous solutions at different pH values with efficiency close to 100 % at pH 10.