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Effects of electrochemical synthetic conditions on surface property and photocatalytic performance of copper and iron-mixed p-type oxide electrodes

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Journal of materials Science & Technology 2018年第9期34卷 1503-1510页

作者： Sun Hee Yoon Dong Suk Han Unseock Kang Seung Yo Choi Wubulikasimu Yiming Ahmed Abdel-Wahab Hyunwoong Park Chemical Engineering Program Texas A&M University at Qatar School of Energy Engineering Kyungpook National University Department of mechanical Engineering Texas A&M University at Qatar

Earth-abundant copper and iron-mixed oxide（CuO/CuFeO_2; CFO） film electrodes are synthesized using an electrochemical deposition（ED） technique at two different ED potentials（-0.36 and-0.66 V vs saturated calomel electrode（SCE）; denoted as ED-1 and ED-2, respectively）. Then, their surface morphologies are compared, and the photo（electro）catalytic activities for the reduction of Cr（VI） are examined in aqueous solutions at pH 7 under simulated sunlight（Am 1.5 G; 100 mW cm（-2））. The degree of the electrical potential applied to the ED process significantly affects the thickness of the synthesized electrode film and the intensity ratio of the diffraction peaks of CuO（111） and CuFeO_2（012）. A 200 μm thick ED-2 sample with a distinct stacking of CuO on CuFeO_2 exhibits a larger broadband absorption spectrum than the 50-μm thick ED-1 with less separate stacking. Furthermore, the ED-2 sample has a higher intensity ratio of the diffraction peaks of CuO（111） and CuFe02（012） than ED-1. As-synthesized ED-2 samples produce larger photocurrents, leading to faster Cr（VI） reduction on the surface under given potential bias（-0.5 V vs SCE）or bias-free conditions. The energy levels（i.e., flatband potential） for the two samples are almost the same（only 10 mV difference）, presumably supposing that the enhanced photoactivity of the ED-2 sample for Cr（VI） reduction is due to the facilitated charge transfer. The time-resolved photoluminescence emission spectra analysis reveal that the lifetime（r） of the charge carriers in the ED-1 sample is 0.103 ns, which decreases to 0.0876 ns in the ED-2. The ED-2 sample synthesized at a high negative potential is expected to contribute greatly to the application of other solar-to-fuel energy conversion fields as a highly efficient electrode material.

关键词： Artificial photosynthesis Solar fuel Delafossites morphology Charge transfer

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Evaluation of the viability of nanoparticles in drilling fluids as additive for fluid loss and wellbore stability

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Petroleum 2023年第3期9卷 342-351页

作者： Albertus Retnanto Rommel Yrac Abdullah Shaat Adhika Retnanto Laith Abughaush maha Al Sulaiti Najla Badar texas a&m university at qatar Qatar Georgia Institute of Technology USA

Wellbore instability is an issue that,if left untreated,can cause wells to collapse,resulting in human,environmental,equipment,and revenue *** fluids have been used to enhance the drilling process by lubricating and cooling the drill bit,eliminating cuttings,and most importantly,by improving the stability of the well by preventing fluid ***,there has been an increase in operational demands and challenges that call for drilling fluids to be more effective,economical,sustainable,and environmentally *** shales that have infinitesimally small pores,nanoparticle additives in drilling fluids can be crucial in providing the properties that are necessary to prevent fluid loss and provide wellbore stability while meeting the operational demands of the present ***,this paper examines the use of nanoparticle additives including copper(Ⅱ)oxide(CuO),magnesium oxide(mgO),and aluminum oxide(Al_(2)O_(3))where they are tested under three conditions using the permeable plugging tester(PPT),high-temperature high-pressure(HTHP)fluid loss apparatus,and API low-temperature e low-pressure(LTLP)fluid loss apparatus under concentrations of 0.03%and 0.10%.Finally,based on the results,each nanoparticle sample(particle sizes between one and 100 nm)performed well in contributing to the aim of this *** is the most effective inhibitor across all concentrations and under the three different *** contributed to reducing the fluid loss from 37.6 mL to 18.2 and 13.2 mL,which is between 52%and 65%of fluid *** mgO,it contributed to fluid loss reduction to 23.8 mL and 15 mL,which translated to 37%e60%of fluid loss *** use of Al_(2)O_(3) nanoparticles resulted in a fluid loss reduction to 33.6 mL and 17.8 mL,reducing the fluid loss up to 11%,at HTHP and up to 53%at *** CuO and mgO,Al_(2)O_(3) was less effective under HTHP conditions when compared to LTLP ***_(2)O_(3) did not suffer as a significant diminishing

关键词： Nanoparticles Drilling fluids Additives Fluid loss High-temperature and high-pressure

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Removal of arsenite by reductive precipitation in dithionite solution activated by UV light

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Journal of Environmental Sciences 2018年第12期30卷 168-176页

作者： Bahngmi Jung Aya Safan Yuhang Duan Vishakha Kaushik Bill Batchelor Ahmed Abdel-Wahab Chemical Engineering Program Texas A&M University at Qatar Education City Zachry Department of Civil Engineering Texas A&M University College Station

This study investigates the removal of arsenite（As（III）） from water using dithionite activated by UV light. This work evaluated the removal kinetics of As（III） under UV light irradiation as affected by dithionite dose and light intensity, and characterized the nature of the precipitated solids using XPS and SEm-EDS. Photolysis of dithionite was observed by measuring dithionite concentration using UV absorbance at 315 nm. This study also investigated the effect of UV light path length on soluble As concentrations to understand resolubilization mechanisms. Total soluble As concentrations were observed to decrease with reaction time due to reduction of arsenite to form solids having a yellow-orange *** removal mechanism was found to be reductive precipitation that formed solids of elemental arsenic or arsenic sulfide. However, these solids were observed to resolubilize at later times after dithionite had been consumed. Resolubilization of As was prevented and additional As removal was obtained by frequent dosing of dithionite throughout the experiment. As（III） removal is attributed to photolysis of dithionite by UV light and production of reactive radicals that reduce As（III） and convert it to solid forms.

关键词： Arsenite Sodium dithionite Reductive precipitation and Ultraviolet light

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Post processing of additive manufactured mg alloys:Current status,challenges,and opportunities

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Journal of magnesium and Alloys 2024年第4期12卷 1283-1310页

作者： Nooruddin Ansari Fatima Ghassan Alabtah mohammad I.Albakri marwan Khraisheh mechanical Engineering Program Texas A&M University at QatarP.O.Box 23874DohaQatar

magnesium(mg)and its alloys are emerging as a structural material for the aerospace,automobile,and electronics industries,driven by the imperative of weight *** are also drawing notable attention in the medical industries owing to their biodegradability and a lower elastic modulus comparable to *** ability to manufacture near-net shape products featuring intricate geometries has sparked huge interest in additive manufacturing(Am)of mg alloys,reflecting a transformation in the manufacturing ***,Am of mg alloys presents more formidable challenges due to inherent properties,particularly susceptibility to oxidation,gas trapping,high thermal expansion coefficient,and low solidification *** leads to defects such as porosity,lack of fusion,cracking,delamination,residual stresses,and inhomogeneity,ultimately influencing the mechanical,corrosion,and surface properties of Am mg *** address these issues,post-processing of Am mg alloys are often needed to make them suitable for *** present article reviews all post-processing techniques adapted for Am mg alloys to date,including heat treatment,hot isostatic pressing,friction stir processing,and surface *** utilization of these methods within the hybrid Am process,employing interlayer post-processing,is also *** post-processing conditions are reported,and their influence on the microstructure,mechanical,and corrosion properties are ***,future prospects and research directions are proposed.

关键词： magnesium alloy Additive manufacturing Post-processing Heat treatment HIP

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Bivariate Gonarov polynomials and integer sequences

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Science China mathematics 2014年第8期57卷 1561-1578页

作者： KHARE Niraj LORENTZ Rudolph YAN Catherine Huafei Department of mathematics Texas A&M University at Qatar Department of mathematics Texas A&M University College Station

Univariate Gonarov polynomials arose from the Goncarov interpolation problem in numerical *** provide a natural basis of polynomials for working with u-parking functions,which are integer sequences whose order statistics are bounded by a given sequence *** this paper,we study multivariate Goncarov polynomials,which form a basis of solutions for multivariate Goncarov interpolation *** present algebraic and analytic properties of multivariate Gonarov polynomials and establish a combinatorial relation with integer ***,we prove that multivariate Goncarov polynomials enumerate k-tuples of integers sequences whose order statistics are bounded by certain weights along lattice paths in *** leads to a higher-dimensional generalization of parking functions,for which many enumerative results can be derived from the theory of multivariate Goncarov polynomials.

关键词： Goncarov polynomials interpolation parking functions order statistics

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Nonlinear wave dispersion in monoatomic chains with lumped and distributed masses:discrete and continuum models

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Applied mathematics and mechanics(English Edition) 2024年第4期45卷 633-648页

作者： E.GHAVANLOO S.EL-BORGI School of mechanical Engineering Shiraz UniversityShiraz 71963-16548Iran mechanical Engineering Program Texas A&M University at QatarDoha 23874Qatar

The main objective of this paper is to investigate the influence of inertia of nonlinear springs on the dispersion behavior of discrete monoatomic chains with lumped and distributed *** developed model can represent the wave propagation problem in a non-homogeneous material consisting of heavy inclusions embedded in a *** inclusions are idealized by lumped masses,and the matrix between adjacent inclusions is modeled by a nonlinear spring with distributed ***,the model is capable of depicting the wave propagation in bi-material bars,wherein the first material is represented by a rigid particle and the second one is represented by a nonlinear spring with distributed *** discrete model of the nonlinear monoatomic chain with lumped and distributed masses is first considered,and a closed-form expression of the dispersion relation is obtained by the second-order Lindstedt-Poincare method(LPm).Next,a continuum model for the nonlinear monoatomic chain is derived directly from its discrete lattice model by a suitable continualization *** subsequent use of the second-order method of multiple scales(mmS)facilitates the derivation of the corresponding nonlinear dispersion relation in a closed *** novelties of the present study consist of(i)considering the inertia of nonlinear springs on the dispersion behavior of the discrete mass-spring chains;(ii)developing the second-order LPm for the wave propagation in the discrete chains;and(iii)deriving a continuum model for the nonlinear monoatomic chains with lumped and distributed ***,a parametric study is conducted to examine the effects of the design parameters and the distributed spring mass on the nonlinear dispersion relations and phase velocities obtained from both the discrete and continuum *** parameters include the ratio of the spring mass to the lumped mass,the nonlinear stiffness coefficient of the spring,and the wave amplitude.

关键词： nonlinear mass-spring chain discrete model continuum model LindstedtPoincare method(LPm) method of multiple scales(mmS) dispersion phase velocity

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Investigation of a solid particle deposition velocity in drag reducing fluids with salinity

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Petroleum Research 2024年第3期9卷 347-358页

作者： Chinemerem Obi mohammad Azizur Rahman Ibrahim Hassan Rashid Hasan texas a&muniversity Qatar texas a&m university CsCollege StationUSA

Optimal and cost-effective drilling operations in extended-reach horizontal wells depend on efficient solid cuttings removal from the *** solids-suspended multiphase processes such as crude petroleum transportation,separation,and processing of oil and gas streams also require the efficient removal of these *** terminal settling velocity(Vts)of the solid particle is a vital parameter that controls the removal efficiency of these *** a drilling scenario when there is a hold on fluid cir-culation such as connection time,the accurate estimation of Vs provides the driller with time available to prevent solid *** severe conditions,this can result in a stuck pipe,especially for extended-reach horizontal *** this work,both spherical and non-spherical particle deposition were experi-mentally investigated in several fluid rheology and *** concentrations(0.1 vol%and 0.05 vol%.)of partially-hydrolyzed polyacrylamide(PHPA)were used as a drag-reducing additive for water-based drilling *** PHPA drag-reducing fluid(reduced pressure loss)acts as a turbulence *** PHPA polymer chain suppresses any turbulence in the flow,reducing the turbulent eddy *** effects of salinity(3 wt.%Nacl and 3 wt.%CaCl_(2) contamination)on solid particle settling velocity(Vs)in drag-reducing fluids were also *** velocity was achieved for all experiments and seemed to increase with increased diameter/***,cases when this trend was not consistent were observed and therefore a new parameter of@(sphericity index×diameter)was pro-posed.V,increases with Q value for all *** drilling,PHPA also aids in sealing the fracture in the *** and without salt in the fluid,how lowering drag affected the settling velocity of solid particles(drill cuttings)could be *** settling velocity tests will be improved in drag-reducing PHPA solutions with the knowledge from this study.

关键词： Deposition velocity Drag reducingfluids Salinity Visualization Drilling

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Corrosion behavior of mg-Zn-Zr-RE alloys under physiological environment-Impact on mechanical integrity and biocompatibility

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Journal of magnesium and Alloys 2022年第6期10卷 1542-1572页

作者： marwa AbdelGawad Chaudhry A.Usman Vasanth C.Shunmugasamy Ibrahim Karaman Bilal mansoor mechanical Engineering Program Texas A&M University at QatarEducation CityDoh1Qatar Department of mechanical Engineering Texas A&M University3123 TAMUCollege StationTX 77843United States of America Department of materials Science and Engineering Texas A&M University3003 TAMUCollege StationTX 77843United States of America

Benefits of RE addition on mg alloys strength and corrosion resistance are widely reported but their effects on biodegradability and biocompatibility are still of *** paper investigates the effect of RE additions on biodegradability of mg-Zn alloys under simulated physiological *** this context,two commercial mg-Zn-Zr-RE alloys,namely ZE41 and EZ33,with same RE addition but different concentrations are studied in Hank’s Balanced Salt Solution(HBSS)at 37℃and with pH of ***-loss,hydrogen evolution,real-time insitu drop test,electrochemical impedance spectroscopy(EIS)and potentiodynamic polarization are deployed to study corrosion *** mechanical integrity of both alloys is assessed by mechanical testing post ***,in vitro biocompatibility is evaluated by indirect cytotoxicity tests using NIH3T3 *** reveal that although both alloys showed similar microstructure,size and distribution of precipitates played a significant role on its corrosion *** and open circuit potential results show stable film formation on EZ33,while ZE41 showed passive layer formation followed by its deterioration,over the analyzed time *** real-time drop test,it was shown in ZE41 alloy that both T-phase and Zr-rich precipitates acted as micro cathodes,resulting in an unstable surface *** EZ33,Zr-rich regions did not influence corrosion response,resulting in better corrosion resistance that was corroborated by post-immersion surface morphology *** higher degradation observed in ZE41 alloy resulted in higher drop in flexural and tensile strength compared to EZ33 *** addition,cytotoxicity tests on NIH3T3 cells revealed that cell viability of EZ33 increased with increasing incubation time,contrary to ZE41,owing to its lower biodegradation behavior and despite higher concentrations of *** results show that an increase in RE concentration in EZ33,relative to ZE41,had a positive effect on

关键词： magnesium alloy Corrosion EIS mechanical integrity Cytotoxicity

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In vitro and in vivo study on fine-grained mg-Zn-RE-Zr alloy as a biodegradeable orthopedic implant produced by friction stir processing

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Bioactive materials 2023年第10期28卷 448-466页

作者： Vasanth C.Shunmugasamy marwa AbdelGawad muhammad Umar Sohail Talal Ibrahim Talha Khan Thomas Daniel Seers Bilal mansoor mechanical Engineering Program Texas A&M University at QatarEducation CityDohaQatar Department of mechanical Engineering Texas A&M University3123 TAMUCollege StationTX 77843USA Proteomics Core Weill Cornell MedicineEducation CityDohaQatar Department of Surgery Division of Orthopedic SurgerySidra MedicineDohaQatar Clinical Orthopedic Surgery Weill Cornell MedicineEducation CityDohaQatar Petroleum Engineering Program Texas A&M University at QatarEducation CityDohaQatar Department of materials Science and Engineering Texas A&M University3003 TAMUCollege StationTX 77843USA

magnesium alloys containing biocompatible components show tremendous promise for applications as temporary biomedical devices. However, to ensure their safe use as biodegradeable implants, it is essential to control their corrosion rates. In concentrated mg alloys, a microgalvanic coupling between the α-mg matrix and secondary precipitates exists which results in increased corrosion rate. To address this challenge, we engineered the microstructure of a biodegradable mg-Zn-RE-Zr alloy by friction stir processing (FSP), improving its corrosion resistance and mechanical properties simultaneously. The FS processed alloy with refined grains and broken and uniformly distributed secondary precipitates showed a relatively uniform corrosion morphology accompanied with the formation of a stable passive layer on the alloy surface. In vivo corrosion evaluation of the processed alloy in a small animal model showed that the material was well-tolerated with no signs of inflammation or harmful by-products. Remarkably, the processed alloy supported bone until it healed till eight weeks with a low in vivo corrosion rate of 0.7 mm/year. moreover, we analyzed blood and histology of the critical organs such as liver and kidney, which showed normal functionality and consistent ion and enzyme levels, throughout the 12- week study period. These results demonstrate that the processed mg-Zn-RE-Zr alloy offers promising potential for osseointegration in bone tissue healing while also exhibiting controlled biodegradability due to its engineered microstructure. The results from the present study will have profound benefit for bone fracture management, particularly in pediatric and elderly patients.

关键词： Biodegradable magnesium Bone healing Friction stir processing microstructure Corrosion resistance

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Implications of regional identity for neural stem and progenitor cell transplantation in the injured or diseased nervous system

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Neural Regeneration Research 2024年第4期19卷 715-716页

作者： Prakruthi Amar Kumar Jennifer N.Dulin Department of Biology Texas A&M UniversityCollege Station texas a&m Institute for Neuroscience Texas A&M UniversityCollege Station

Neural stem and progenitor cell(NSPC)transpla ntation has emerged as a promising therapeutic strategy for replacing lost neuronal populations and repairing damaged neural circuits following nervous system injury and disease.A great deal of experimental work has investigated the biology of NSPC grafting in preclinical animal models;more recently.

关键词： neural system injured

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