Qatar Foundation Annual Research Conference Proceedings Volume 2016 Issue 1

The State of Qatar wants to generate 20% of its electricity requirement from solar power by 2020. This policy aims to meet the increasing electricity demand induced by increasing population and the associated urbanization with its energy-hungry life-style while adopting at the same time environmental-friendly renewable energy. Qatar's population has increased almost five times from 0.37 million to 1.74 million between 1986 and 2010, and six times between 1986 and 2014.

The electricity and water company in Qatar KAHRAMAA has reported an increase in the maximum network load from 941 MW in 1988 to 3,990 MW in 2008 and reached 6255 MW in 2012. The number of customers increased from 132,429 in 1998 to 293,604 in 2013.

This increase in demand is triggered also by changes in life-style, indicated by electricity per capita consumption figures. The per capita consumption grew from 12.963 KW to 17.774 KW in 2007.

To meet this increasing demand for electricity, and as a dry country with no hydro-power resources, Qatar has increased the number of gas-generated electricity plants in the 2000s from 3 to 8 plants. Gas energy is used to generate electricity in these plants.

Qatar is ranked as having the second-highest per capita ecological footprint among 150 countries, down from being the highest in 2012, according to the WWF's Living Planet Report. This report is published every two years. With these environmental concerns and the unstable oil prices in mind Qatar has decided to introduce clean renewable energy to produce electricity as opposed to non-renewable environmentally un-friendly natural gas.

Solar energy is arguably the most effective way to meet the increasing energy demand of Qatar and the region, for the following reasons: firstly, solar energy is renewable as opposed to the non-renewable gas and oil which are finite resources. Secondly, solar energy is clean and limits the emissions of Greenhouse Gases. Thirdly, using solar energy lengthens the life of oil and natural gas resources, and reserves them for future generations.

A preliminary analysis of solar energy potentials carried out by QF-QEERI using historical data collected by Qatar Meteorological Department (QMD), reveals that there is a high potential of solar energy in Qatar. The ground-measured yearly average Global Horizontal Irradiation (GHI) for Qatar is 2113 kWh/m²/year. GHI is suitable for the Photovoltaic (PV) method of converting solar energy into direct current electricity.

The selection of optimum sites for Photovoltaic (PV) solar energy production facilities has been one of the single most sought after objectives by solar scientists, and decision makers, as it can determine the success or the failure of solar projects with big budgets.

In the State of Qatar one of the main issues that faces large scale implementation of solar Photovoltaic (PV) energy production is the availability of land. With an area of 11,500 km², including growing urban centers, agricultural farms, industrial cities, and with most of the desert areas are environmentally protected land, or used as utility corridors such as oil and gas pipes, or reserved for future plans, finding large tracks of land for solar farms is not an easy task/exercise.

Multi-criteria analysis is carried out in this study using ESRI ArcGis to identify the optimum sites for solar energy farms in the country. Criteria for land suitability for solar farms has been identified and used in the GIS analysis and model building, these are: land slope, aspects, proximity to coast-line, proximity to roads (i.e. accessibility), proximity to electric grid, restricted areas, urban areas, environmentally protected areas, and water ponds. These criteria are then used as a base for assigning suitable weights in the model building in MODEL BUILDER of ArcGis software. Different geospatial analysis techniques were included in the model such as, buffering, surface analysis and weighed overlaying of datasets.

The main result obtained in this study is the model itself, as it can be run with different sets of scenarios according to the requirements of the scientists and decision makers. The model produces maps showing the optimum sites for PV solar energy production in Qatar.

GIS is proved to be very efficient (time and cost effective) tool in finding solutions to such cumbersome problem, where many factors need to be taken into account. The project demonstrates a real application of GIS where it is used as a decision making tool at a national level projects.

Date palm (Phoenix dactylifera) is one of the most important crops in many arid land cultures. The date fruits are rich in essential nutrients, minerals, vitamins and fiber, making them a critical food source linked to the history of the Arab world. The most frequent method of propagation is by offshoots, which guarantees that the characteristics and quality of the fruit are maintained; however, it significantly reduces the genetic variability of the date palm plantations, making them extremely vulnerable to pests and diseases. During the past few years, advances on date palm research have provided some information about the molecular markers associated with different desirable agronomical traits, including gender and fruit color.

We recently showed that P. dactylifera employs and XY sex-chromosome system, and generated a genetic map that localized this gender determination locus to the lower arm of linkage group 12. Based on this initial information, we designed markers to screen a Bacterial Artificial Chromosome (BAC) library of a male P. dactylifera to sequence the X and Y alleles in date palm. A combination of approaches that include next-generation (Illumina) and Single Molecule, Real-Time (SMRT) Sequencing (PacBio) of more than one hundred BAC clones, have allowed us to map eighty markers to eleven larger DNA contigs, containing the corresponding female and male specific regions, spanning approximately 4Mb. However, multiple sequence gaps still exist within and between the sequenced region, and further analysis have indicated that the borders of most assembled contigs correspond to repetitive elements, which likely constitute a big portion of the unassembled DNA sequences. Non-recombining regions of sex chromosomes, particularly the Y chromosome, are highly repetitive due to degeneration, making it more challenging to design markers and extend the assembled sequences by chromosome walking.

These observations, led us to propose a parallel approach to complement and advance on the initial sequencing strategy. Date palm, and all other thirteen members of the genus Phoenix, are dioecious, with roughly half of the individuals planted from seed expected to be fruit-bearing female trees. The conservation of dioecy in this entire clade in the Palm family (Arecaceae) suggests that in the genus Phoenix, dioecy evolved before speciation. Therefore, we recently started using comparative genomics to analyze male and female individuals from the remaining thirteen Phoenix species, which has allowed us to narrow down the Y-specific region to a very small portion of the genome, containing only a few genes. Our latest findings are providing a new insight into the evolution of plant sex chromosomes and sex determination in date palm. Standardization and validation of new methodologies that allow for large-scale sequencing and analysis of polymorphisms in date palm, will provide valuable tools for the development of marker-assisted selection programs, for the improvement of date palm production. This will allow Qatar to diversify the varieties of dates it grows, and in the near future will allow us to test for the most desirable agricultural traits, which will significantly improve the quality of the fruit, making Qatar a more competitive date producer in the region.

Carburization of metal is a catalytic reaction that occurs on metal surfaces exposed to hydrocarbon atmosphere at high temperatures. This reaction is a form of the well-known Fischer-Tropsch synthesis and is immensely important to various industrial aspects, most notably metal dusting corrosion (MDC) [1] and catalytic conversions [2]. On Fe surfaces, carburization occurs at high temperature, initiated by adsorption of gaseous hydrocarbons and is responsible for triggering both MDC, a catastrophic failure of the structural integrity of metals and alloys and a severe threat to the petrochemical industries, and a central reaction in catalytic converters, that are purposefully designed to produce a high yield of carburization to reduce the emission of toxic gasses. One of the most abundant and widely-studied carburizing gas is carbon monoxide (CO) that has been observed to react with Fe surface and dissociate at temperatures 600–900 K. In a hydrocarbon environment, the reaction is given by,

CO+H_(2) ( → ⊥ 800K)[C^^* + H]_2|O

Where C* is adsorbed on the Fe surface. The reaction is sustainable without the presence of hydrogen [3]. Gaseous hydrogen reacts with O atoms deposited on the surface from the dissociation of CO and removes the O atoms as steam [4].

From atomic to continuum scale, the reaction characteristics have been studied widely using computer simulations of various approaches and have produced reliable results and predictions in agreement with relevant experiment results [5–9].

From an atomistic modelling perspective, the reaction between CO and Fe surface can be broken into two consecutive processes, adsorption and dissociation. Adsorption describes the process of a CO molecule getting attached to the Fe surface. During dissociation, this molecule decomposes into C and O adatoms directly at the surface, with the two atoms moving into their most stable adatom site. Adsorption of CO is a barrier-less exothermic process. Dissociation, on the other hand, is an endothermic process that requires breaking a C-O triple bond, displaying an 11.2 eV/molecule average dissociation energy in vacuum [10]. The catalytic effect of the metal surface plays therefore a crucial role for breaking this bond at a much lower energy [4]. Earlier density functional studies show that on Fe-110 surface, the CO dissociation barrier is close to 1.5 eV [8]. However, this energy is still high in order to achieve from thermal activation only. A number of experiments suggest that the temperature threshold for CO dissociation can be as low as 380 K [11]. Therefore, it can be assumed that in practice, the reaction pathway is more complex than it has been modelled in previous works [7, 8] and one has to take into account that the metal surface contains impurities and defects that could assist the dissociation process [12]. Furthermore, the interactions originating from the periodic boundary condition of the simulations must be evaluated and dealt with accordingly. Commonly, an unwanted interaction from periodic boundary condition can be minimized by choosing a large simulation box. However, large simulations are computationally expensive and therefore an efficient method should be developed that can describe the CO-Fe surface reaction accurately yet is sustainable regarding computational resources.

In this work, these challenges are addressed with a systematic study of the adsorption and dissociation of CO molecule on Fe surface, following further diffusion of C atom to subsurface and bulk using a multiscale technique combining atomistic density functional theory and empirical potential (EP) method. For atomistic scale study, we used density functional theory (DFT) with PBE-GGA pseudopotential technique implemented on the VASP code. Preliminary investigations on different low-index Fe surfaces confirm that the 110 surface is the most densely-packed surface and has the minimum structural reconstruction and minimum surface energy and is chosen as standard for our work. Hence we successfully reproduced CO adsorption energies, energy profiles for dissociation and subsurface diffusion of the C, in good agreement with results computed in earlier works [7, 8, 13, 14]. However, we have noticed that the periodic boundary condition applied to these simulation, which is also used to control the concentration of CO on the surface (coverage), has a significant effect on the energetics of these processes. The CO molecule has a strong dipole moment and it leads to van der Waals interaction between the molecules [15] adsorbed on the surface. Taking van der Waals interaction into consideration, adsorption energy studies on surfaces with CO fractional coverages of 0.25 and 0.0625 monolayers (ML) reveal that adsorption CO on 110 surface is energetically more favourable at dilute coverages. Most importantly we demonstrate here that the dissociation of CO also is energetically favourable in dilute surface as the energy barrier is reduced to half when the CO-coverage is reduced from 0.25 to 0.0625 ML [16].

Since one expects surface defects to be present on Fe surfaces and to act as corrosion initiator, here we show computationally using accurate electronic structure calculations that the single vacancy defects on the surface are energetically inexpensive and therefore prone to be naturally abundant. In fact, we find that vacancy defects lower the adsorption energy for CO molecules adsorbed next to a vacancy and allows the C atoms to diffuse to the subsurface layers through the cavity. As a result, the reaction path becomes more complex and in order to examine the role of defect in the carburization process, one must compare the pathway with the combined pathway of dissociation of CO on clean surface, and subsequent surface to subsurface diffusion of C. It is worth noting that in the previously published works on surface to subsurface diffusion of C, the O adatom, as a by-product of the dissociation reaction, is ignored and its effects not taken into account. We take the O adatom adsorbed on the surface into consideration in this work and we carried out electronic structure and charge density analysis. It is demonstrated here that the influence of the O adatom is quite significant: 1. The O atom does not directly bond with the Fe surface but due to its high electron affinity, electronic charge is transferred from the surface to the O atom via the Fe-C bond in order to facilitate the breaking of C-O bond. 2. A surface vacancy defect creates an electron deficit that restricts the C atom from forming strong covalent bonds with Fe atoms. Interestingly, even after the C-O bond is completely dissociated, the O atom influences the surface-to-subsurface diffusion of C. Calculation of surface-to subsurface diffusion paths with and without O adatom on the surface shows that in presence of O, the diffusion barrier is higher and the C penetration depth into Fe is lowered.

The dissociation and diffusion pathways discussed above were estimated using the nudged elastic band (NEB) method [18]. In order to find a transition state, the end-point (initial and final) configurations for the reaction are first fully relaxed with high precision. NEB uses an interpolated chain of intermediate configurations between the two end point configurations, connected by springs. The whole chain is then relaxed simultaneously with a fixed spring constant until the total average force minimizes under the tolerance limit of 0.01eV/Å. In this work, 8–16 intermediate configurations or images are considered, depending on the length of the path. It is evident that these calculations with DFT are extremely demanding regarding computational resource and therefore we need to anticipate the best possible dissociation/diffusion path with to minimize computation time. This issue is addressed by employing a combined empirical potentials (EP) – DFT technique where we employ the LAMMPS code, to pre-estimate possible minimum energy paths for dissociation and diffusion using NEB and from empirical Molecular dynamics simulations that are able to easily treat thousands of atoms thus increasing the length scales.

Starting with the converged set of configurations from this pre-estimated transition pathways using EP, DFT is used to obtain more precise results. With the use of a potential that has been extensively tested to yield results in agreement with DFT [17], the pre-estimate shortens the computational time significantly. For the calculation of the surface-to-subsurface diffusion path of C, this process has reduced the computation real-time from 33792 to 18464 CPU-hours, which is a 45% drop, still producing identical results within the tolerance of 0.01 eV. However, in order to predict a reliable pre-estimate the potential needs to be tested with DFT. The embedded atom method (EAM) potential used in this work by Becquart et al [18] is rigorously calibrated with several DFT-estimated parameters. Unfortunately, this potential represents only Fe-C systems and for surface calculation with CO, we must consider a potential representing a Fe-C-O system. For this purpose, we have also been characterizing a reactive force-field potential designed by van Duin et al [19], specifically for catalytic reaction on Fe. This potential is anticipated to be used in near future to provide a complete atomistic description of this reaction mechanism. Which efficient multiscale technique are you referring to?

In summary, the computational understanding gained in this study on the role of vacancy defects on dissociation of CO molecule, followed by subsurface diffusion of C, is beneficial for predicting the nature of the CO-Fe reaction for a practical scenario such as presence of larger vacancy defects on the surface and whether they act as dusting corrosion initiators. Simulation at different length and time scale are underway towards modelling physical and chemical phenomena governing the carburization of steel. Acknowledgement: The advanced computing facility of Texas A&M University at Qatar is used for all calculations. This work is supported by the Qatar National Research Fund (QNRF) through the National Priorities Research Program (NPRP 6-863-2-355).

References

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Organic pollutants dyes are the highly toxic major waste products causing severe harmful environmental pollution. From the viewpoint of environmental issues, the removal of harmful organic dye compounds is of great interest and importance1. Traditionally physical and biological methods are generally used to decompose many organic pollutants. However, these methods suffers from certain disadvantages and are time-consuming process. 2,3 Visible-light photocatalysis has been renewable “green” technologies which can harvest solar energy in the environmental remediation capable of removing harmful heavy organic contaminations4. This presentation is focused on the design of a novel kind of photocatalyst that cover entire solar spectrum i.e. from ultraviolet to infrared (IR) regions to decolorize and degrade the organic dye such as rhodamine 6G in an effective way.

Now a days, the use of layered double hydroxides (LDHs) as active photo-catalysts has been receiving considerable attention over the layered metal oxides. A number of photocatalysts have been reported for the photocatalytic degradation of organic pollutants. Among the new generation photocatalyst, LDH was very much promising material for pollutant degradation5. However, designing novel visible light active LDH catalysts to meet present technical requirements is a great challenge. Intercalation of different polyoxometalic anionic species into inorganic layered materials like layered double hydroxide (LDH) offers a technique in which altering the properties of the two components are combined into a single modified material. By intercalating different anions, the characteristics of the layered double hydroxide (LDH) can be improved. Layered double hydroxide basically called Hydrotalcite consist of a cationic brucite like sheets with anionic moieties in the interlayer through electrostatic interaction. The unique structure, surface hydroxyl groups, interlayer spaces with intercalated anions, swelling properties, oxo-bridged linkage and high chemical stability are some of the added advantages of this group of materials. To harvest solar energy efficiently a series of Mg/Fe Layered double hydroxide materials has been synthesized by hydrothermal method and modified by intercalating molybdate anion by ion exchange. These materials have been characterized by various techniques and tested for their photocatalytic activity for the pollutant removal.

The broad absorption band in case of Mg/Fe LDH was found due to the metal ligand charge transfer band of O2p →Fe³⁺ and the metal-metal-charge-transfer spectra of Mg²⁺-O-Fe³⁺. The metal to metal charge transfer (MMCT) for an oxo-bridged bimetallic system with different oxidation states was defined to be an excitation transition of an electron from one metal to the other, which is known to absorb visible light and even near-IR light. 6,7 In the case of Mg/Fe/Mo LDH, the absorption edge shifted towards near IR is due to the HOMO-LUMO OMCT of Interlayer Molybdate where the HOMO is mainly derived from the O 2p orbitals and the LUMO is from the Mo 4d orbitals. These materials show enhanced photoactivity for the degradation of organic dyes such as rhodamine 6G. The enhanced photoactivity is due to edge shared metal oxygen octahedron of (MO6) of brucite sheet, visible light absorbing species, low recombination of charge carriers’, metal-metal charge transfer spectra (MMCT) of the oxo-bridged bimetallic Mg²⁺-O-Fe³⁺ system, long life time of photogenerated charge carriers and HOMO–LUMO oxygen metal charge transfer spectra of intercalated Molybdate anions. These modified photo catalysts can be reused easily with several times without substantial loss of catalytic activity, which is green alternative material for practical applications for degradation of organic dyes like rhodamine 6G.

References

1. Yanlan Liu, Kelong Ai, and Lehui Lu, Chem. Rev., 2014, 114, 5057–5115.

2. Ana Ballesteros-Gómez, Soledad Rubio, Anal. Chem., 2011, 83, 4579–4613.

3. Ian L. Gunsolus and Christy L. Haynes, DOI: 10.1021/acs.analchem.5b04221.

4. Y. Takahashi, S. Kubuki, and T. Nishida, Green Catalysts for Energy Transformation and Emission Control, Chapter 4, 2014, 71–84.

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Pipelines are used to transport natural gas and oil. The common way to join the pipes together is welding. Welded areas and heat affected zones have proven to be the weakest part of the pipeline, these areas are often exposed to the environment and as a consequence exhibit more cracks and failures than the rest of the pipe. Such failures lead to leaks of gases, oil, and process fluids that are harmful to the environment. In addition, leaks cause a production loss which is very costly. In the past decades, there have been various leaks that lead to fatalities and that resulted in major environmental impacts.

Shape memory alloys (SMAs), also known as smart alloys, are engineering materials that gained their name due to their unique capability of remembering the shape they had before deformation and returning to it. They undergo reversible solid-to-solid phase transformation (martensitic transformation) when a load, temperature or magnetic field is applied to them, and can recover their original shape if the external stimulus is removed. The most commercially available SMAs are nickel–titanium (Ni-Ti or Nitinol) alloys, which are used mostly in orthodontic and medical applications. These alloys are expensive, have limited temperature range of application, and are difficult to process for large scale applications. Due to these limitations, the current research interest has shifted towards developing new SMAs that are cheaper, exhibit a similar shape memory effect, and that are corrosion resistance.

Among the new SMAs competing with Ni-Ti smart alloys are iron-based SMAs (Fe-based SMAs). Since the discovery of the shape memory effect in Fe-30Mn-1Si in early 1980s, the Fe-based SMAs alloys have attracted the researcher's attention due to their low cost, good mechanical properties, high temperature range of application, workability and weldability. However, they exhibited relatively poor shape recovery which made it necessary to treat them using cycles of thermomechanical treatment known as ‘training’ to enhance their shape memory effect.

The Fe-based SMAs have shown a promising potential to be used as pipe couplers in oil and gas applications. Pipe couplers made from SMAs can be installed easily, and can be a good replacement for welding in pipes. Welding involves heat that affects the structure of the piping metal and the resulted heat affected zone usually possess a favorable location for failure and cracking. This has made Fe- based SMAs pipe couplers a better option due to their low cost and long-term reliability. The use of these alloys to join pipes is aimed to replace the welding process. The SMAs pipe couplers use the shape memory effect to apply a contact pressure onto the surface of the pipes to be coupled. Compared to currently available couplers that work by brazing, smart alloy couplers are easier to install, require lower installation temperatures, and have similar coupling capabilities. The seal is more temperature resistant than that provided by brazed couplers.

In this research, the corrosion resistance of the Novel FeNiCoAlTa (Fe-28%Ni-17%Co-11.5%Al-2.5%Ta) SMA that was developed by the National Aeronautics and Space Administration (NASA) was investigated for using as a pipe coupler. The effect of two different cycles of treatment on the alloy was investigated. In addition, the alloy's corrosion resistance was compared to the resistance of the most common SMA (Ni-Ti or Nitinol). The corrosion potential, polarization resistance and potentiodynamic polarization of the alloys were compared at different temperatures and different PHs. Moreover, the corrosion resistance of the alloy was compared to the resistance of different carbon steel, and stainless steels that are commonly used in oil and gas applications, when electrochemically tested in 3% NaCL solution. The research also investigated the galvanic corrosion of FeNiCoAlTa SMA when coupled to carbon steel and different types of stainless steels. It was found that even though increasing the treatment cycles improved the shape memory effect of the alloy, it reduced its corrosion resistance. One has to decide on whither to enhance the shape memory effect of a pipe coupler or to improve its corrosion resistance. Nevertheless, the alloy exhibited good corrosion resistance, even after increasing the cycles of the treatment showing that it could be a potential replacement to pipe welding.

Very few oil & gas installation locations around the world experience sustained high humidity and high temperature for long periods of the year as what is experienced in Qatar. For example, the humidity in Qatar readily reaches 90% and the summer temperature, measured on metal surfaces, can reach 80 °C. The severe temperature fluctuations causes seawater to evaporate, then condense, and then dry on hot metal surfaces, thereby enhancing local build-up of aggressive species such as chloride on the metal surfaces. In some situations, this is complicated by sand storms which leave contaminating sand particles on exposed surfaces in this environment.

Qatar has many oil and gas (upstream), petrochemical and chemical plants (downstream) in both offshore and onshore marine locations. For chloride stress corrosion cracking to take place, three important ingredients have to exist: (i) a critical environment, (ii) a susceptible material and (iii) tensile stress. All these three ingredients exist in Qatar onshore and offshore sites. The presence of residual tensile stresses due to welding or other forming process or fit up stresses from assembly increases the susceptibility of the component to CSCC. Chloride stress corrosion cracking can occur fast when evaporation exists even at room temperature. A number of catastrophic CSCC failures of stainless steels roof construction in swimming pool environments has resulted in human causalities over the past decades. Due to the nature of the local environment and the abundance of stainless steel used in Qatari installations the investigation of chloride stress corrosion cracking (CSCC) of stainless steel alloys is very much warranted.

The critical temperature for application of protective coating to prevent CSCC is still to be identified with any certainty. According to NORSOK standard M-001 recommendations, the maximum operating temperature for 316 stainless steel is 60 °C, and for duplex stainless steels is 100 °C, above which, protective coating has to be applied to prevent CSCC. These temperature limits are being questioned and there are concerns being raised about their accuracy when field evidence shows that cracking is occurring at temperatures below these limits. CSCC can lead to oil and gas leaks that have a major impact on the environment and on public safety as well as production loss.

In this research, a modified ISO drop evaporation test was developed to identify the threshold temperature for cracking for three different austenitic stainless steels, mainly 316, 304 and 904L stainless steels. The samples are prone to load and heat, while Qatar specific seawater is dripped on them, the samples are heated using electrical resistant heating. The test is conducted at four different temperatures (room temperature, 40 °C, 50 °C and 60 °C) and under three different loads (70% σ = < /AσΣETHιγηλιγητ>0.2, 80% σ = < /AσΣETHιγηλιγητ>0.2 and 90% σ = < /AσΣETHιγηλιγητ>0.2). The temperature and load are continuously monitored and adjusted when deviated. The lab-built test setup enabled the testing of sixteen parallel fixtures concurrently. The threshold temperature for cracking for the tested material was recorded at each applied load. Severe pitting was observed underneath the salt layer, and was dependent on the applied load. A new threshold temperature for cracking was recorded and a recommendation to the local industry to revise the threshold temperature for chloride stress corrosion cracking is to be issued.

The development of nano-composite materials is making a significant impact on modern technology due to their wide range of applications and their superior properties1. Several methods have been proposed and developed to prepare polymer nano-composites. Graphene nano-composites, in particular, have attracted the interest of researchers because of their excellent properties, such as high electrical conductivity, high thermal stability and excellent mechanical strength 2–3. Graphene, a two-dimensional carbon atoms structure, exhibits exceptional properties4–5. Incorporating these nano-fillers with high performance polymers results in a unique combinations of properties.

This paper reports on the synthesis and characterization of graphene and LLDPE (Linear Low Density Polyethylene)/graphene nano-composites with different weight ratios of graphene. Graphene was synthesized from graphene oxide, which was prepared by using modified hammers method. The obtained few layers of graphene were confirmed by different characterization methods such as FTIR, XRD, Raman spectroscopy and SEM. LLDPE/Graphene composites at different weight ratios of graphene, i.e. 1, 4, and 8 wt% were compounded in twin screw extruder. Extruded granules of LLDPE/Graphene materials were used in the preparation of nano-composites by compression molding. In this research, we used the LLDPE as the polymer matrix, because PE (polyethylene) is one of the most common plastic resins in the world and it is produced on a large scale in the State of Qatar by Qatar Petrochemical Company (QAPCO). LLDPE has grown most rapidly within the PE family due to its good balance of mechanical properties and process-ability compared to other types of PE. The effect of graphene ratio on the mechanical, thermal and electrical properties were investigated. LLDPE/Graphene composites with 4% graphene showed higher tensile strength and tensile modulus than the other graphene loading composites. Agglomeration was a problem in the composites with high wt% of the graphene which caused the reduction in tensile properties. Graphene marginally increased the melting temperature of the nano-composites whereas crystallization temperature, thermal stability and electrical conductivity were increased with increase of graphene loading. The results obtained showed that the graphene can increase the thermal stability of the polymer mixture. Increment of thermal stability is due to the high thermal stability of the graphene and the formation of phonon and charge carrier networks in the matrix. The electrical conductivity of LLDPE is 4.28 × 10^− 11 and for nano composites is 9.2 × 10^− 05. The high electrical conductivity of the graphene converts the LLDPE polymer insulator to an electrical conductor. Electrically conductive PE based composite materials can be used as electron magnetic-reflective materials, as well as in high voltage cables. The enhancement in mechanical, thermal and electrical properties of LLDPE/Graphene nano-composites achieved by melt mixing of graphene into the polymer can enable mass production of new and low cost novel materials with superior tensile strength, thermal stability and electrical conductivity.

References

1. Gossard Didier, Karkri Mustapha, Mariam A. AlMaadeed, Igor Krupa A new experimental device and inverse method to characterize thermal properties of composite phase change materials. Compos. Struct. 2015,133(1), 1149–1159.

2. X. Huang, Z. Yin, S. Wu, X. Qi, Q. He, Q. Zhang, Q. Yan, F. Boey, H. Zhang. Graphene based materials: synthesis, characterization, properties and application. Smal. 2011, 18, 1876–1902.

3. J.R. Potts, D.R. Dreyer, C.W. Bielawski, R.S. Ruoff. Graphene based polymer nanocomposites. Polymer 2011, 52, 5–25.

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Understanding the features of weather system around and over the Arabian Gulf is a prerequisite for setting up of a numerical weather forecasting system. The reanalysis, ERA-Interim data with a spatial resolution of ∼80 km has been utilized for analyzing the wind climatology for a period of 35 year. It is found that in the Arabian Gulf, throughout the year, the predominant wind is from north-west and the average wind speed is high in the summer between June and August. The high wind speed systems in summer are known as summer Shamals and have a typical duration of one week. Often, the high speed and long duration of the Summer Shamals makes it a good carrier of sand/dust. The winter season is dominated by south-east passage of frontal systems. The presence of land-sea contrast can cause mesoscale wind systems such as land-sea breeze. Qatar being a narrow peninsular region with width less than 100 km, the setting up of these land-sea breeze systems can be from either of the sides. This can lead to the interaction of two sea breezes from opposite sides, which may lead to the development of a convergence zone. This complex systems can affect the local weather and air-quality of coastal areas. These mesoscale phenomena and complexities are not well represented through a global model. Though the low resolution (80 km) data (ERA-interim) shows the presence of Shamal winds, the data misses the detail structure and their spatial variability. This necessitates for setting up of a high resolution mesoscale simulation approach.

A non-hydrostatic mesoscale model, Weather Research and Forecast (WRF) developed by NCAR (Skamarok et al 2008) is used here for simulating and forecasting the wind systems associated with the Arabian Gulf. The model is run on an operational basis to forecast the wind fields, for a 48 hr. The modeling suite consists of a preprocessor, WPS, the model, WRF and a post processor, ARWpsot. The total suite has been compiled and installed successfully using FORTRAN and C compilers. A two way nested WRF domains with a grid size ratio of 1:3 is configured. The resolutions for the outer domain and inner domain are set to 9 km, and 3 km respectively. Various physical parametrization schemes are available within WRF modelling system. The physical parameterization schemes used in the current configuration includes MYJ boundary layer parametrization, Janjic Eta Monin–Obukhov surface layer scheme, Dudhia shortwave radiation, Rapid Radiative Transfer Model (RRTM) long wave radiation, WRF Single-Moment 6-Class (WSM6) microphysics, and the NOAH land surface scheme. Cumulus scheme, Grell is used only for the outer domain. Both of the model domains have a total of 39 vertical levels, with the topmost level at 50 hPa and lowermost level at approximately 30 m above the ground level. The initial and boundary conditions are obtained from the National Centers for Environmental Prediction's (NCEP) Global forecast System (GFS) available at resolution 0.50 (∼50 km), and the boundary conditions are updated at 6 hr interval. The entire process is automatized and run on RAAD Linux HPC cluster computing system.

A two day simulation of WRF is analyzed and the sea breeze system of Qatar peninsula is examined and compared with the automatic weather station (AWS) data of Qatar Meteorological Department. The time of onset and duration of sea breeze are identified. The simulation of WRF clearly shows the development of a thermal internal boundary layer over the coastal city Doha. The existence of a convergence zone with high vertical updraft was also found. This may be due to the interaction of sea breezes coming from opposite sides of Qatar peninsula. Understanding the system of sea breeze would benefit the overall understanding pollutant transport and the dispersion mechanisms.

The sabkhas (i.e., salt flats) of Qatar are among the rare places on Earth where carbonate and sulfate minerals similar to those constituting economically important hydrocarbon reservoirs are still forming today, under the arid conditions that characterize the coastline of the country. Since the 1960’s, the sabkhas of Qatar have been studied with great interest as a modern analogue for ancient sedimentary sequences (e.g., Wells, 1962; Illing & Taylor, 1995; Alsharhan & Kendall, 2003). The results of these studies provided important insights for formulating stratigraphic models of subsurface hydrocarbon reservoirs. Notable examples of gas and oil reservoirs that formed in arid, evaporitic environments include the Permo-Triassic Khuff (which is estimated to contain about 15–20% of the world's gas reserves and is of fundamental importance for the economy of Qatar), the Jurassic Arab formations, and the Triassic Kurra Chine, all of the Middle East, and the Permian Zechstein of Northern Europe. Although extremely valuable, most of these early studies were based on purely physical and chemical approaches, which may have not fully captured the complexity of the mineralization processes occurring in the sabkha environment. Indeed, research conducted in more recent years has shown that microorganisms play an important and, as yet, poorly understood role for the mineralization processes occurring in these evaporitic environments (Bontognali et al., 2010; Bontognali et al., 2012; Bontognali et al., 2014; Brauchli et al., 2015; Paulo & Dittrich, 2013; Strohmenger et al., 2011).

Here we present the results of a field campaign conducted in the Khor Al-Adaid sabkha, which is located in the southeast of Qatar, in a large tidal embayment composed of two shallow inland lagoons. The main goal of the field campaign was to identify regions of the intertidal zone that are particularly rich in microbial mats, and that represent ideal sites at which to study microbe-mineral interactions. Three sites of interest have been defined.

Site 1 is characterized by the presence of microbial mats that develop in a restricted pond where abundant precipitation of gypsum takes place. This site is an ideal place to look for geochemical or mineralogical signatures of microbes in the gypsum crystals. This, in turn, may allow for the definition of new proxies for identification of microbially-mediated gypsum in ancient sedimentary sequences. Because gypsum and anhydrite are common seals of hydrocarbon reservoirs, a broad understanding of the mechanism of their formation is of unquestioned interest in the field of hydrocarbon exploration.

Site 2 is characterized by the presence of thick (more than 5 cm) microbial mats. Spherical authigenic carbonate minerals are visibly forming in association with the extracellular polymeric substances constituting these mats. X-ray diffraction analyses revealed that dolomite is among the carbonate minerals forming at this site. Thus, the mats will be studied with the goal of providing new insights helpful in solving the long-standing enigma surrounding the origin of sedimentary dolomite. Dolomite is a common mineral in ancient sedimentary sequences (including many hydrocarbon reservoirs) but historically it has been very difficult to form in laboratory experiments that simulate Earth's surface conditions. For this reason, the mechanism of its formation remains highly debated. It has been proposed that microorganisms play a key role for overcoming the kinetic barriers that prevent dolomite formation at low temperature (Vasconcelos et al., 1995). Because this “microbial hypothesis” is not unanimously accepted, the mats present at site 2 represent an ideal material to study for better understanding and further demonstration of the existence of this biomineralization process.

Site 3 is characterized by the presence of well-layered, domical microbial mats. Gas is produced in abundance within the mats, which likely influences pore-water chemistry and might, in turn, influence the rate and the type of mineral precipitation.

Work is currently in progress to characterize the microbial diversity of the three sites through “next generation sequencing” methods, as well as characterization of the mineralogy and the isotopic composition of the carbonate and gypsum forming within the microbial mats. The ultimate goal is the better understanding of what role microbes play in the formation of ancient evaporitic sequences.

References

Alsharhan, A. S., and Kendall, C. G. S. C., 2003, Holocene coastal carbonates and evaporites of the southern Arabian Gulf and their ancient analogues: Earth-Science Reviews, v. 61, no. 3–4, p. 191–243.

Brauchli, M., McKenzie, J.A., Strohmenger, C.J., Sadooni, F., Vasconcelos, C., Bontognali, T.R.R., 2015. The importance of microbial mats for dolomite formation in the Dohat Faishakh sabkha, Qatar. Carbonates and Evaporates, p. 1–7.

Bontognali, T. R. R., Vasconcelos, C., Warthmann, R. J., Bernasconi, S. M., Dupraz, C., Strohmenger, C. J., and McKenzie, J. A., 2010, Dolomite formation within microbial mats in the coastal sabkha of Abu Dhabi (United Arab Emirates): Sedimentology, v. 57, no. 3, p. 824–844.

Bontognali, T. R. R., Vasconcelos, C., Warthmann, R.J., Lundberg, R., McKenzie, J.A., 2012. Dolomite-mediating bacterium isolated from the sabkha of Abu Dhabi (UAE). Terra Nova 24, 248–254.

Bontognali, T. R. R., McKenzie, J. A., Warthmann, R. J., and Vasconcelos, C., 2013, Microbially influenced formation of Mg-calcite and Ca-dolomite in the presence of exopolymeric substances produced by sulfate-reducing bacteria: Terra Nova, p. 1–6.

Illing, L. V., and Taylor, J. C. M., 1993, Penecontemporaneous dolomitization in Sabkha Faishakh, Qatar; evidence from changes in the chemistry of the interstitial brines: Journal of Sedimentray Research, v. 63, no. 6, p. 1042–1048.

Paulo, C., and Dittrich, M., 2013, 2D Raman spectroscopy study of dolomite and cyanobacterial extracellular polymeric substances from Khor Al-Adaid sabkha (Qatar): Journal of Raman Spectroscopy, v. 44, no. 11, p. 1563–1569.

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Vasconcelos, C., McKenzie, J. A., Bernasconi, S., Grujic, D., and Tiens, A. J., 1995, Microbial mediation as a possible mechanism for natural dolomite formation at low temperatures: Nature, v. 377, no. 6546, p. 220–222.

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