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Adhesion Studies of Diamond-Like Carbon Films Deposited on Ti6al4V alloy after Carbonitriding

Open Journal of Metal 2012年第1期2卷 1-7页

作者： Deiler Antonio Lima-Oliveira Romina Paula Castro Costa Gislene Valdete martins Evaldo joséCorat Vladimir Jesus Trava-Airoldi Anderson Oliveira Lobo Fernanda Roberta marciano Instituto Nacional de Pesquisas Espaciais Sao Josédos CamposSão PauloBrazil Faculdade de Ciencia e Tecnologia da Universidade de Coimbra CoimbraPortugal Clorovale Diamantes Indústria e Comércio S.A. Sao Josédos CamposSao PauloBrazil Universidade do Vale do Paraíba Sao Josédos CamposSao PauloBrazil

Diamond-like Carbon (DLC) coatings have attracted significant attention due to their low friction coefficient, high degree of hardness, chemical inertness, and high wear resistance as well as and their many possible uses in metallurgical, aeronautical, and biomedical applications. However, DLC has low adhesion strength to metallic substrates. Carbonitriding was performed before DLC deposition to improve this adherence. Different concentration of nitrogen in the gas mixture was used during the carbonitriding of Ti6al4V alloy. DLC films were subsequently grown from methane using plasma enhanced chemical vapor deposition. The samples were characterized with Raman scattering spectroscopy, nanoindentation, and tribological tests. Films from 80.0% N2 had the best friction coefficient (0.07) and a critical load of ~22 N. In the scratching test, these films had adhesive failure and they completely detached from the substrate only in the end of the tests. SEM images show carbonitring promoted a significant increase in the surface defects (homogeneously distributed) but without the presence of microcracks. EDX analysis indicated that nitrogen element was diffused throughout the thickness of the samples. Hydrogen and carbon atoms from carbonitriding formed a diffusion-barrier layer that can be used as the first step for DLC deposition. This carbonitriding can also provide a carbide layer, which serves as the precursor for the nucleation and growth of DLC films.

关键词： Diamond-Like Carbon Carbonitriding Ti6al4V alloy

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An Assessment of Rare Earth aluminates as Possible Radiation Shields for Artificial Satellites in Low Earth Orbit

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Materials Sciences and Applications 2018年第4期9卷 430-439页

作者： Ernesto Ortiz josé Francisco Valdés-Galicia Rocío García Lorenzo M. martínez de la Escalera marcos Anzorena Lorenzo martínez-Gómez Instituto de Ciencias Físicas Universidad Nacional Autónoma de México Cuernavaca Mexico Instituto de Geofísica Universidad Nacional Autónoma de México Ciudad de México Mexico Corrosión y Protección (CyP) Ciudad de México Mexico

Charged particles injected into dielectric material of artificial satellites may cause data flipping, command errors and charges in dielectric material properties. In this work we report the results of an evaluation of rare earth aluminates as possible radiation shields for its application in Low Earth Orbit (LEO) satellite construction. With help of Geant4 software, we calculated the radiation dose that a target receives at a typical LEO (685 km) as a function of the shield thickness. The target used was a silicon plate, the shields used were hollow cubes of rare earth aluminate walls (YalO3, LaalO3, NdalO3 and GdalO3), and we also used aluminium oxide (al2O3). The radiation source was the measured fluxes of electron and proton with a spectrum corresponding to a LEO. We found that of the total radiation dose received by the target without shield is 5847 microGy/hour, of which, the electrons contribute with 94.9% and the protons with 5.1%. The rare earth aluminates are a better shield than the al2O3 to protect a target against the radiation that permeates a LEO near to equator.

关键词： Rare Earth aluminates Cosmic Radiation Artificial Satellites

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al-Doping Effect on the Surface Morphology of ZnO Films Grown by Reactive RF Magnetron Sputtering

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Materials Sciences and Applications 2013年第12期4卷 761-767页

作者： Erica Pereira da Silva Michel Chaves Gilvan Junior da Silva Larissa Baldo de Arruda Paulo Noronha Lisboa-Filho Steven Frederick Durrant josé Roberto Ribeiro Bortoleto Technological Plasmas Laboratory Sao Paulo State University-UNESPSorocabaBrazil Group of Advanced Materials Sao Paulo State University-UNESPBauruBrazil

Zinc oxide (ZnO) and aluminum-doped zinc oxide (ZnO:al) thin films were deposited onto glass and silicon substrates by RF magnetron sputtering using a zinc-aluminum target. Both films were deposited at a growth rate of 12.5 nm/min to a thickness of around 750 nm. In the visible region, the films exhibit optical transmittances which are greater than 80%. The optical energy gap of ZnO films increased from 3.28 eV to 3.36 eV upon doping with al. This increase is related to the increase in carrier density from 5.9 × 1018 cm-3 to 2.6 × 1019 cm-3. The RMS surface roughness of ZnO films grown on glass increased from 14 to 28 nm even with only 0.9% at al content. XRD analysis revealed that the ZnO films are polycrystalline with preferential growth parallel to the (002) plane, which corresponds to the wurtzite structure of ZnO.

关键词： ZnO Thin Films Surface Morphology RF Magnetron Sputtering

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Microstructural evolution and microsegregation in directional solidification of hypoeutectic al−Cu alloy:A comparison between experimental data and numerical results obtained via phase-field model

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Transactions of Nonferrous Metals Society of China 2021年第7期31卷 1853-1867页

作者： alexandre F.FERREIRA Ivaldo L.FERREIRA Rangel P.alMEIDA jose A.CASTRO Roberto C.SalES Zilmar A.JUNIOR Graduate Program on Metallurgical Engineering Federal Fluminense University27255-125Volta RedondaRJBrazil Federal University of Para College of Mechanical Engineering66075-110BelemPABrazil

The objective of the work is focused on predictions of microsegregation,solidification speed,dendritic arm spacings and dendrite morphology by phase-field *** numerical results were compared with experimental *** experimental values for cooling rates and effective partition coefficient were adopted during *** results of microsegregation through phase-field model show excellent agreement with the experimental *** excellent agreement is because cooling rates,effective partition coefficient and back-diffusion of solute are considered in the *** solidification speed,the calculation results show good agreement with the experimental *** dendritic arm spacing calculated with phase-field model is compared with experimental *** results show good agreement between *** dendrite arm spacing varies with position because high cooling rates are responsible for the refinement effect on ***,two-dimensional simulation produced a dendrite that is similar to that found in the experiment.

关键词： hypoeutectic al−Cu alloy effective partition coefficient dendritic arm spacing microsegregation phase-field model

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Natural ECM-Bacterial Cellulose Wound Healing—Dubai Study

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Journal of Biomaterials and Nanobiotechnology 2015年第4期6卷 237-246页

作者： Safwat Mohd. El-Hoseny Pierre Basmaji Gabriel Molina de Olyveira Ligia maria Manzine Costa Abdulwahid M. alwahedi josé Domingos da Costa Oliveira Gino Bruno Francozo al Qassimi Hospital Sharjah United Arab Emirates Innovatec’s-Biotechnology Research and Development S&atildeo Carlos Brazil Department of Physical Chemistry UNESP Araraquara Brazil Department of Chemistry USP FFCLRP Ribeir&atildeo Preto Brazil

Bacterial cellulose (BC) can be used in wide area of applied scientific, especially for tissue regeneration and regenerative medicine, lately, bacterial cellulose mats are used in the treatment of skin conditions such as burns and ulcers, because of the morphology of fibrous biopolymers serving as a support for cell proliferation, its pores allow gas exchange between the organism and the environment. Moreover, the nanostructure and morphological similarities with collagen make BC attractive for cell immobilization, cell support and Natural Extracellular Matrix (ECM) Scaffolds. In this scope, Natural ECM is the ideal biological scaffold since it contains all the components of the tissue. The development of mimicking biomaterials and hybrid biomaterial can further advance directed cellular differentiation without specific induction. The extracellular matrix (ECM) contains several signals that are received by cell surface receptors and contribute to cell adhesion and cell fate which control cellular activities such as proliferation, migration and differentiation. As such, regenerative medicine studies often rely on mimicking the natural ECM to promote the formation of new tissue by host cells, and characterization of natural ECM components is vital for the development of new biomimetic approaches. In this work, the bacterial cellulose fermentation process is modified by the addition of vegetal stem cell to the culture medium and natural materials before the bacteria are inoculated. In vivo behavior using natural ECM for regenerative medicine is presented.

关键词： Bacterial Cellulose (Nanoskin) Natural Nanocomposites Regenerative Medicine Stem Cells

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Electrochemical Corrosion Study in H₂SO₄ of Nial with Cu Additions, Microstructure and Micro-Hardness at Room Temperature

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Journal of Minerals and Materials Characterization and Engineering 2022年第3期10卷 225-241页

作者： Jesús M. Colín de la Cruz Sergio A. Serna Barquera alvaro Torres-Islas Arturo Molina-Ocampo Edgar Valenzuela josé G. González Rodríguez Universidad Autónoma del Estado de Morelos Facultad de Ciencias Químicas e Ingeniería UAEM-FCQeI. Av. Universidad 1001Colonia Chamilpa Cuernavaca Morelos México Universidad Autónoma del Estado de Morelos Centro de Investigación en Ingeniería y Ciencias Aplicadas UAEM-CIICAp Cuernavaca Morelos México UABC Baja California Sur México

For many years, intermetallic materials promise applications in a wide variety of technology areas. Nial intermetallic compound is material that exhibits important characteristics such as high corrosion resistance and low density besides its ability to retain strength and stiffness at elevated temperatures. However Nial intermetallic is too hard, brittle and exhibits very low ductility at room temperature being the reason because this material is not yet available for structural applications. In order to increase the ductility of the Nial intermetallic compound, the addition of a third alloying element has been proved, nevertheless it is important to determine if such additions decrease or increase the hardness and the corrosion resistance of the alloy. So, the present investigation reports the corrosion performance of the Nial intermetallic compound modified with Cu, emphasizing the EIS analysis and the relation between physical parameters and the modelling equations used in the Equivalent Electric Circuit. It was found that the addition of Cu promotes the formation of the γ’-Ni3al phase in Cu contents greater than 15 at. %, in addition to a decrease in micro hardness and an increment in the Icorr values. In this way, the electrochemical characterization evidenced a high corrosion resistance of these intermetallic alloys.

关键词： Nial-Cu Corrosion Behavior Electrochemical Impedance Spectrum Vickers Micro Hardness Microstructure

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Influence of Ni and Cr Content on Corrosion Resistance of Ni-Cr-Mo alloys for Fixed Dental Prostheses in 0.05% NaF Aqueous Solution

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Materials Sciences and Applications 2010年第6期1卷 369-372页

作者： Nilo A. S. Sampaio josé W. J. Silva Heloisa A. Acciari Roberto Z. Nakazato Eduardo N. Codaro Hamilton de Felipe 不详

The Ni-Cr-Mo alloys have been used as dental prostheses because they own a good mechanical strength, high corrosion resistance and even to be economically viable. These alloys corrosion protection against in salt solutions typical of physiological media is due to passivation phenomenon with an oxide surface layer formation, mainly chromium oxides. This protective film, subjected to a mechanical stress in a corrosive environment, can partially dissolve by releasing ions, which have deleterious effects in a human body. Fluoride ions, existing in hygiene products, change the buccal environment and their presence may enable a localized corrosion process initiation. The aim of this work has been to investigate the chemical composition influence of three alloys in corrosion resistance to: A (Ni-73% Cr-14% Mo-8.5% Be-1.8% al-1.8%), B (Ni-61% Cr-25% Mo-10.5% Si-1.5%) and C (Ni-65% Cr-22.5% Mo-9.5%) in media containing fluorides that simulate mouthwashes solution. The study has been done in a 0.05% NaF solution, pH 6, at 37°C using electrochemical techniques. The alloy with the highest nickel and the lowest chromium content is not passive in the middle studied, showing a continuous increase in current density with the potential increasing, while the other alloys show passivation range of 600 mV and passive current density of about 10-6 A/cm2.

关键词： Ni-Cr-Mo alloys Dental Prostheses Corrosion

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Correspondence

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World Journal of Pediatrics 2014年第2期 186-186页

作者： joséG.Dórea Faculty of Health Sciences Universidade de Brasilia 70919-970 BrasiliaDFC.P.04322Brazil

Health professionals in pediatrics,especially in neonatology,welcome the timely work of Chen et al.[1]Despite the widespread use of Thimerosal-containing vaccines(TCVs)in premature newborns,this is the first attempt to model exposure to thimerosal and neurodevelopment;that is why this study is both interesting and *** the special circumstances of the immature neurologic and immunologic systems of the premature-newborn,it is worth raising additional relevant issues to this revealing paper.

关键词： revealing spite welcome

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Musical and Photographic Stimulations on the Symptomatology of alzheimer’s Disease in Elderly

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World Journal of Neuroscience 2020年第4期10卷 155-165页

作者： Jamylly Ferreira Targino Silva Mayara Leite alves da Silva Maykon Wanderley Leite alves-da-Silva Douglas Nijenhuis de Castro Euclides Maurício Trindade Filho Janise Dal Pai Lysien Ivania Zambrano Valtuir Barbosa Felix Elionai Dias Soares Camila Conceição Luz Soares albérico josé de Moura Saldanha Filho Magnúcia de Lima Leite Emanuel Guilherme de almeida Carvalho Matheus Santos Freitas josé Claudio da Silva State University of Health Sciences of alagoas (UNCISal) Maceió Brazil CESMAC University Center Maceió Brazil Federal University of São Paulo (UNIFESP) S&#227o Paulo Brazil Facultad de Ciencias Medicas Universidad Nacional Autónoma de Honduras Tegucigalpa Honduras Division of Therapeutic Support and Diagnosis of HUPAA/UFal/EBSERH Maceió Brazil Tiradentes University Center (UNIT-al) Maceió Brazil Faculdade Tiradentes (FITS) Recife Brazil

Background: alzheimer’s disease is a progressive and neurodegenerative disorder characterized by deterioration of brain functions. Psychosocial interventions such as music and photographic stimuli may contribute to c... 详细信息

Background: Alzheimer’s disease is a progressive and neurodegenerative disorder characterized by deterioration of brain functions. Psychosocial interventions such as music and photographic stimuli may contribute to cognitive and sensory exercise or rehabilitation. Objective: Evaluate musical and photographic stimuli in elderly people with Alzheimer’s disease. Methods: It is an uncontrolled clinical trial, before-after type, eleven subjects composing the sample. Participants were submitted to Katz Index, Autobiographical Memory Test, GDS-15, Mini-Mental State Examination. The collection instruments were used on the first and last day of intervention, individually. There were 2 sessions in the week with duration of 50 minutes totaling 20 sessions. Data were analyzed by descriptive and inferential statistics and as variables expressed as mean standard deviation. Results: There was a significant effect of cognitive activity (P , it was observed that a small advance (P = 0.05) of the daily life activities. With the analysis of GDS-15, it is verified that they are more effective for the increase of the previous self-estimation of the therapy (P = 0.94). In the application of the AMT, it is observed that there was a better recruitment of the memory for the neutral words. Conclusion: Musical and photographic stimuli had a positive effect on the cognitive level, daily life activities and autobiographical memory in seniors with alzheimer’s disease.

关键词： alzheimer’s Disease Health of the Elderly Depression Memory

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Synthesis of aluminum-doped Zinc Oxide Nanowires Hydrothermally Grown on Plastic Substrate

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Advances in Materials Physics and Chemistry 2012年第4期2卷 56-59页

作者： Concepción Mejía García Elvia Díaz Valdés Ana Ma. Paniagua Mercado Arturo F. Méndez Sánchez josé A. Andraca Adame Velumani Subramaniam josué Romero Ibarra Centro de Nanociencias y Micro y Nanotecnologías del IPN UPalM Luis Enrique Erro S/N México 07738 México Departamento de Física Escuela Superior de Física y Matemáticas – IPN Edif. 9 UPALM Col. San Pedro Zacatenco Deleg. GAM México 07738 México Depto. de Ing. Eléctrica Sección de Estado Sólido Av. IPN No. 2508 Col. San Pedro Zacatenco México 07360 México

We report the synthesis of undoped ZnO and al-doped ZnO (ZnO:al) nanowires grown using a two-step process: (a) preparation of the seed layer, and (b) growth of the nanostructures. In the first step,? 10 mM solutions of zinc acetate dihydrate and 1-propanol were spin coated on polyethylene terephthalate? (PET) substrate at 2000 rpm by 30 s. Vertical nanowires were then grown by dipping the substrates in an equimolar solution of zinc nitrate hexahydrate and hexamethylenetetramine. As doping source, aluminum nitrate nonahydrate powders were added in the solution. In the solutions, al doping concentrations were established as 0.5 At %, 1.0 At %, 2.0 At % and 3.0 At %, respectively. The hydrothermal process were carried out with a commercially microwave at 140 W power setting. The nanowires were characterized optically and morphologically. XRD patterns show the presence of ZnO, Zn(OH)2 and Zn6al2O9. Scanning electron microscopy analysis showed that the size of ZnO nanowires was 50 nm in diameter. The undoped ZnO and ZnO:al nanowires bandgap energy was obtained from optical transmission spectra.

关键词： Nanowires ZnO ZnO:al Nanowires Spin Coating Hydrothermal Process

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