In this work, pure BiFeO3 and samples doped with different concentrations of chromium were synthesized to improve the optical properties and efficiency of solar cells based on BiFeO3. The sol-gel method was used for synthesis due to its ability to produce nanostructured materials with high purity and good homogeneity, as well as the possibility of controlling the size and shape of the resulting particles. The samples were characterized by different analytical techniques. Thermal analysis results indicate that the dopant increases the weight loss of the sample from 61 to 81%, with an increase in the exothermal in the nucleation and crystallization temperature range. The X-ray diffraction patterns and UV-visible spectra show a dependence of the crystallite size and bandgap with respect to the amount of Cr dopant, decreasing from 168 to 73 nm and from 2.14 to 1.92 eV, respectively. Scanning electron microscopy images display a decreasing grain size as a result of an increasing amount of dopant. The I-V analysis results show a 1% Cr-doped BiFeO3 photovoltaic device exhibits enhanced photovoltaic performance with higher photocurrent and 4.17 times greater energy conversion efficiency compared with a pure BiFeO3 photovoltaic device. For their behavior, Cr-doped BiFeO3-based photoelectrodes are very promising materials for photovoltaic devices.
Pure and Fe-doped TiO2 nanoparticles were synthesized by the sol–gel method. The samples were characterized by X-ray diffraction, Raman spectroscopy, BET, UV-vis diffuse reflectance spectroscopy, and scanning electron microscopy. The results show a dependence between the crystallite size and the amount of dopant, which decreases from 13.02 to 12.81 nm. The same behavior was observed in the optical properties, where the band gap decreased from 3.2 to 2.86 eV. The arsenic (V) adsorption was tested in aqueous solution containing 5 mg/L of arsenic and 0.5 g/L of adsorbent at pH 7 and in dark conditions. The results indicate that the TiO2-B sample shows a higher arsenic removal, reaching 88% arsenic removal from the water at pH 7. Thus, it is also shown that the best performance occurs at pH 5, where it reaches an arsenic removal of 94%. Ion competition studies show that arsenic removal capacity is slightly affected by chloride, carbonate, nitrate, and sulfate ions. According to the results, the synthesized samples are a promising material for treating arsenic-contaminated water.
Over the last 12 years, technology in the drilling and completions space has reduced cycle time and dramatically lowered costs for operators. With the adoption of re-stimulations, additional production is being gained from existing wells at a cost that is less than the cost of drilling new wells. However, there has been limited development of low-cost intervention techniques to restore lost production or to extend the life of existing wells.
To address this relatively untapped area of intervention, new tools and techniques are needed to revitalize older wells in unconventional reservoirs that are more cost effective than traditional intervention techniques.
The economics of a workover are challenged by the uncertainties of successfully removing the existing production tubing and replacing it with a newly designed completion. In response a tool and cleanout technique has been developed that improves the ability of 1.25 in. coiled tubing to clean out the 5.5 in. casing through the 2.375 in. tubing string, thereby eliminating the need to pull and replace the upper completion.
A recent application of this new technique in an unconventional well demonstrated that a modified jetting tool (Reverse Nozzle Bit Sub or RNBS), along with a regimented cleanout schedule, can clean out most of the lateral length and restore lost production at a greatly reduced time and cost compared to jointed pipe workovers. Additionally, using coiled tubing to spot acid along the length of the lateral in a uniform matter can remove scale buildup and clean up perforations for improved performance.
This paper will review the design, testing and field application of the new tool and technique as well as show early results.
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