Navegando por Autor "Sousa, R. R. M."

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Novel antibacterial silver coating on PET fabric assisted with hollow-cathode glow discharge
(Wiley, 2020-07-30) Nascimento, Rubens Maribondo do; Naeem, Muhammad; Felipe, M. B. M. C.; Medeiros, Silvia Regina Batistuzzo de; Costa, Thércio Henrique de Carvalho; Libório, Maxwell Santana; Alves Júnior, Clodomiro; Nascimento, Igor Oliveira; Sousa, R. R. M.; Feitor, Michelle Cequeira
The silver-coated fabrics are of much importance because of their outstanding antibacterial features and are useable in several medical and hygienic applications. The silver deposition on fabrics by conventional techniques is not feasible because of their high processing cost, long processing duration, complex equipment, and multiple steps processing (nanoparticle synthesis and subsequent deposition on fabrics). In this novel study, the antibacterial silver coating is deposited by using a hollow cathode discharge (HCD) capable of generating high-density plasma, and thus it exhibits high-efficiency processing. The silver is deposited on woven and non-woven PET fabrics for various treatment times (10-60 minutes), and their antibacterial performance against E. coli and S. aureus bacterial is tested. The XRD results verified the deposition of silver with (111) preferred orientation, while SEM analysis depicted the uniform/ homogeneous deposition of silver particles. The interfacial free energy of adhesion depicts that after the silver deposition on both fabrics, the surface is actively unfavorable for bacterial adhesion. The antibacterial test revealed that the silver-coated woven and non-woven PET fabrics exhibit exceptional antibacterial activity against E. coli and S. aureus bacteria. As the HCD technique is relatively cost-effective, no need for specific sputtering targets, eco-friendly, and require single-step processing for silver deposition. Thus the results are expected to be of remarkable importance to prepare silver-coated antibacterial fabrics useable in hospitals and other appropriate applications
Surface modification of M2 steel by combination of cathodic cage plasma deposition and magnetron sputtered MoS2-TiN multilayer coatings
(Elsevier, 2020-02) Alves, Salete Martins; Libório, Maxwell Santana; Praxedes, G. B.; Lima, L. L. F.; Nascimento, Igor Oliveira; Sousa, R. R. M.; Naeem, Muhammad Salman; Costa, Thércio Henrique de Carvalho; Iqbal, Javed
Titanium nitride (TiN) is a good choice for the improvement in surface hardness of high-speed steel. Unfortunately, it has low adhesion with substrate and exhibits high friction coefficient; as a result it does not provide sufficient protection against sliding wear in metal-to-metal contact. The adhesion problem can be removed by nitriding process, whereas friction coefficient can be reduced by solid lubrication coating. In this study, an attempt is made to synthesize TiN hard coating as well as solid lubrication coating of molybdenum disulfide (MoS2) using magnetron sputtering, along with substrate pre-treatment by cathodic cage plasma de- position using titanium cathodic cage. The cathodic cage plasma nitrided sample exhibits significantly higher surface hardness, which reduced by solid lubrication coating. The nitrided sample depicts the presence of ironnitrides, TiN and nitrogen diffused martensite phases, whereas coated samples shows the presence of MoS2 and TiN phases. The friction coefficient and machining temperature are dramatically reduced by lubrication coating. This study recommends that the use of cathodic cage plasma nitriding using titanium cathodic cage is beneficial for improved surface hardness, and addition of solid lubrication coating is beneficial for reducing the coefficient of friction and machining temperature by scarifying hardness. As, both the systems are already proven to be appropriate for industrial-scale uses, thus results from this study can be applied for industrial-scale application
Surface modification of tool steel by cathodic cage TiN deposition
(Taylor and Francis, 2019-09-11) Feitor, Michelle Cequeira; Barbosa, M. G. C.; Viana, Bartolomeu C.; Santos, F. E. P.; Fernandes, Fernanda de Melo; Costa, Thércio Henrique de Carvalho; Naeem, Muhammad Salman; Sousa, R. R. M.
The aim of this work is to investigate the effect of titanium nitride coating for various treatment times (0.5–4 h) by cathodic cage plasma deposition (CCPD) on surface properties of AISI D6 tool steel. The obtained results depict micrometric-sized TiN film deposition under all processing condition with improved surface hardness and corrosion resistance. Raman and EDS analysis are used to calculate N/Ti ratios for stoichiometric calculations of samples. This study depicts that the surface properties of tool steel can be effectively improved by TiN film deposition using CCPD, with low processing time, low processing temperature and better uniformity, as compared to conventional techniques. Additionally, the problems associated with the conventional TiN films such as pores and voids are eliminated. This technique is compatible with industrial-scale applications, and thus results from this study are expected to be beneficial for the surface engineering industry
Synthesis and characterization of ZnO/ZnAl2O4/ Zn2TiO4 composite films by AreO2 mixture hollow cathode glow discharge
(Elsevier, 2021) Feitor, Michelle Cequeira; Queiroz, José César Augusto de; Naeem, Muhammad; Azevedo Filho, João Batista; Libório, Maxwell Santana; Queiroz, M. G. O.; Sousa, R. R. M.; Melo, E. B.; Costa, Thércio Henrique de Carvalho
In this study, ZnO/ZnAl2O4/Zn2TiO4 composite nanostructured thin films are deposited assisted with hollow-cathode glow discharge (HCD). The films are deposited using various argon-oxygen gases mixture (0e50% O2), and its effect on film quality, optical and electrical properties is examined. Remarkably, instead of metallic targets, ZnO, TiO2, and Al2O3 powders filled in hollow-cathode are used for deposition, and thus no specific metallic targets are required in this technique. The deposited films consist of hexagonal wurtzite ZnO structure, ZnAl2O4, and Zn2TiO4 phases, and the crystalline size of films increases for higher oxygen contents. The thickness of films reduced by increasing oxygen contents, and all deposited films exhibit transmittance higher than 82%. The carrier concentration and mobility increase, whereas resistivity decreases when a higher amount of oxygen is added. This study shows that HCD can effectively synthesize the composite film with good optical and electrical properties. Additionally, the film’s properties and elemental composition can be tuned by changing the gas composition, and thus, no separate target metallic materials with the specific composition are required
Synthesis of Al-Doped ZnO films assisted with hollow-cathode glow discharge and their characterization
(Journal of Electronic Materials, 2021-02-19) Feitor, Michelle Cequeira; Queiroz, José César Augusto de; Naeem, Muhammad; Azevedo Filho, João Batista; Liborio, Maxwell Santana; Santos, E. J. C.; Sousa, R. R. M.; Costa, Thércio Henrique de Carvalho; Khan, Naveed H.
Transparent conductive oxides, such as aluminum-doped zinc oxide (AZO), are of substantial importance for use in a broad range of applications because of their excellent optical and electrical properties. AZO film can be deposited by using several conventional techniques, although they suffer from limitations such as long deposition time, high cost, and the requirement for complex deposition equipment. Here, we used hollow-cathode glow discharge, which produces a high-density plasma and achieves high deposition efficiency. Remarkably, instead of metallic target materials, we used Al2O3 and ZnO powders filled in the hollow cathode as a target, thus avoiding the need for specifically designed targets in this technique. The films were deposited using mixtures of argon and oxygen at various ratios (0% to 50% oxygen), to improve the film characteristics. The films deposited under all conditions exhibited hexagonal wurtzite ZnO structure, while the grain size increased with increasing oxygen content. The film was thick and porous when using low oxygen content, but became thin and dense with increasing oxygen content. The optical transmittance was found to be strongly dependent on the processing gases used, with the highest transmittance of 84% being attained when using 25% oxygen gas. The bandgap of the films lay between 3.27 eV and 3.33 eV. The highest carrier concentration and mobility were attained when using 25% oxygen, and the Hall resistivity decreased with increasing oxygen content. Besides the excellent transmittance and electrical properties of the deposited films, it is expected that the results of this study will be useful for solar cells and optoelectronic applications due to the relatively low cost of this technique and the lack of specific target requirements

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Navegando por Autor "Sousa, R. R. M."