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The mechanical behavior and wear of the different hardened phases with bore-induced changes in AISI 4340 and AISI D2 steels were investigated. The hardness and modulus of elasticity were measured by nanoindentation and the values obtained for the layers in AISI D2 steel were 18 GPa and 325 GPa in the Fe2B boride phase, and 20 GPa and 360 GPa in the FeB boride phase, respectively. The AISI 4340 steel presented mainly the Fe2B phase. It was then possible to analyze the coefficient of friction obtained in the Fe2B phase of the steel AISI 4340 presented a range of 0.04 to 0.06. The AISI D2 steel presents two different phases in the boride layer being the coefficient of friction higher for the test in the FeB phase than for Fe2B, and the values vary from 0.065 to 0.075. These parameters were obtained with micro-wear tests. No adhesion failures were observed after the sliding tests in the interface of the two different boride layers. Cracks in the FeB phase after the sliding test were much more frequent.

Plasma immersion ion implantation (PIII) was conducted in a large volume chamber with a current-controlled high-voltage pulser, to test the vacuum, plasma, and PIII conditions, in a preparation for the treatments of large workpieces or the batch-processing mode. For that purpose, a rugged high-power pulser (10 kW average) based on solid-state moderate voltage pulse system (1 kV) was coupled to a high-voltage transformer (1:22) to feed different loaded sample supports placed in different positions inside the chamber. It was found that the plasma, when produced by a hot filament enhanced glow discharge source, is not uniformly distributed in the chamber but despite that, implantation doses are locally uniform within 10% for 10–15-cm distances, along with the supports. Stainless steel 304 (SS304) -type samples were successfully treated with nitrogen PIII and different tests showed improvements on their mechanical and tribological properties.

By altering some synthesis variables, the morphology and structural properties of anodic TiO2nanotube arrays (TiO2NTs) can be tailored to a specific application. This study aims to investigate the effect of electrolyte-containing ions from human plasma and annealing temperature on structural, morphological, and mechanical parameters of TiO2NTs films, targeting its potential biomedical applications. Bio-inspired TiO2NTs were grown from Ticpand its Ti6Al4V alloy by potentiostatic anodization in the recently developed SBF-based electrolyte, maintained at 10 °C and 40 °C. The thermal investigation was performed by TGA/DSC and used to define the phase transition temperatures used for annealing (450 °C and 650 °C). Morphological and structural parameters were evaluated by FE-SEM, XRD, contact angle measurements, and nanoindentation. Results show that self-organized as-formed TiO2NTs were grown under all synthesis conditions with different wettability profiles for each substrate group. At 450 °C annealing temperature, the beginning of nanostructures collapse starts, becoming evident at 650 °C. The nanoindentation characterization reveals that both electrolyte and thermal annealing exhibited low effects on the hardness and Young's modulus. The tailoring of specific properties by different synthesis conditions could allow the individualization of treatments and better performancein vivo.

Made available in DSpace on 2019-10-04T12:34:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-03-30 Fundacao Araucaria Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) A number of researches have been concerned about the development of beta-type titanium alloys because they can present good biocompatibility, non-cytotoxicity, suitable mechanical and corrosion resistance behavior. However, due to their chemical inertness property, the surfaces of the novel Ti alloys must be modified by different methods to improve their bioactivity. This work is focused on the electrochemical surface modification of Ti-10Nb and Ti-20Nb alloys by Plasma Electrolytic Oxidation (PEO) method in 1.0 M H3PO4 electrolyte at 250 V. X-Ray diffraction showed that both binary Ti-Nb alloys are mainly composed of (alpha+beta) phase. The PEO treatment led to producing rough and thick titanium and niobium oxides films on the Ti-Nb alloys. The oxide films produced on the Ti-10Nb alloys have the anatase structure, whereas those formed on the Ti-20Nb alloy have an amorphous structure observed by Raman Spectroscopy. Hardness and elastic modulus were measured by instrumented indentation. Both oxide films are harder than their substrates (4.0-6.0 GPa) and have reduced elastic modulus values (100-110 GPa) compared to cp-Ti (reference). Linear reciprocating tests were employed to study the surface wear resistance of the samples. Among the non-treated samples, the Ti-10Nb alloy presented a better wear performance. In addition, the titanium and niobium oxides films formed on the Ti-10Nb alloy presented the most resistant surfaces. In relation to the cellular viability evaluation, the oxide films produced on both Ti-Nb alloys did not show any sign of cytotoxicity. Indeed, the porosity, roughness and chemical composition of the resulting titanium and niobium oxides films were able to promote osteoblast cells attachment and proliferation on their surfaces. Based on these findings, the PEO electrochemical treatment on Ti-10Nb alloy can form porous oxides coating and could be used as a reference line for manufacturing more wear resistant and non-cytotoxic surfaces to biomedical applications. (C) 2018 Elsevier B.V. All rights reserved. Univ Fed Parana, Programa Posgrad Engn Ciencia Mat PIPE, Curitiba, Parana, Brazil Athlone Inst Technol, Mat Res Inst, Athlone, Ireland Ctr Univ Volta Redonda UniFOA, Volta Redonda, RJ, Brazil Univ Fed Parana, Programa Posgrad Engn Mecan, BR-81531990 Curitiba, Parana, Brazil Univ Tecnol Fed Parana, Programa Posgrad Engn Mecan & Mat, Curitiba, Parana, Brazil Univ Fed Campina Grande, Dept Engn Mat, Campina Grande, PB, Brazil Pontificia Univ Catolica Parana, Escola Politen, Dept Engn Mecan, Curitiba, Parana, Brazil Univ Estadual Paulista, Dept Fis, Campus Bauru, BR-17033360 Bauru, SP, Brazil Univ Estadual Paulista, Dept Fis, Campus Bauru, BR-17033360 Bauru, SP, Brazil Fundacao Araucaria: 685/2014 Fundacao Araucaria: 42466 CNPq: 307037/2014-2 CAPES: 1522225

Among titanium alloys with non-toxic elements, the Ti-25Nb-25Ta alloy has good elastic behavior for applications in osseous implants, biocompatibility, and excellent corrosion resistance. The present study aimed to better the biocompatibility characteristics of Ti-25Nb-25Ta alloy modifying its surface through Plasma Electrolytic Oxidation (PEO) treatment. The formed oxide coating is amorphous and composed of two distinct porous formations: smaller hole-shaped pores and larger volcano-like pores. The regions with the formation of smaller pores and in the hole shaped presented the highest atomic percentage of the chemical element phosphorus. Nanoindentation tests have shown that the hardness of the Ti-25Nb-25Ta alloy is slightly lower than the commercially pure grade 2 titanium (a material used as reference), while elastic modulus measurements of Ti-25Nb-25Ta presented more suitable values for implant application (lower values when compared with titanium reference). After PEO treatment there were significant mechanical surface improvements (increased fairly surface hardness and decreased elastic modulus) for application in osseous tissue. Despite the Ti-25Nb-25Ta alloy presented excellent characteristics for applications in hard biological tissues, the PEO treatment better its features. Keywords: Titanium alloy, Ti-25Nb-25Ta, nanoindentation, mechanical properties, Plasma Electrolytic Oxidation.

Nanotubes grown on titanium and its alloys can improve biocompatibility, surface wettability and corrosion resistance when compared to untreated materials. However, the tribological properties of these films are scarcely investigated. In this study, hardness and elastic modulus pure titanium and Ti-35Nb alloy were analyzed, while tribological properties of these materials were compared with those of nanotube films grown on Ti-35Nb alloy. The Ti-35Nb alloy, composed of alpha and beta phases, presented the higher hardness (3.7 GPa) and the lower elastic modulus (96 GPa) than the pure alpha‑titanium (2.3 GPa and 145 GPa, respectively). The coefficient of friction of the alloy was approximately 1.3, which was higher than that of titanium (~1.05). Analyses of the worn tracks revealed abrasive and adhesive wear mechanisms occurring in both titanium and Ti-35Nb alloy. However, the presence of beta phase was responsible for the strongest adhesion wear and the highest wear rate of the Ti-35Nb alloy. The nanotube films with approximately 1.0 μm thick were produced through controlled anodization. The tubes diameters were random; their composition was a TiO2 and Nb2O5 crystalline phases mixture. In reciprocating sliding tests, nanotubes were compacted on the surface, being damaged on the outer part of the film. However, the wear rate of surfaces with nanotube films was only 42% [(0.055 ± 0.012)·10−3 mm3/Nm] the value measured for the Ti-35Nb substrate [(1.661 ± 0.129)·10−3 mm3/Nm]. To summarize, the Ti35Nb alloy were more suitable than titanium, regarding mechanical properties, for use in bone implants; moreover, its tribological performance was enhanced through a lubricating effect provided by oxide nanotube films grown on it.

Made available in DSpace on 2018-11-26T17:51:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-08-01 Fundacao Araucaria Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Nanotubes grown on Ti and its alloys have been extensively investigated for the biomaterials applications, since these structures improve the surface biocompatibility and the corrosion resistance due to oxide formation. Some researchers showed that the microstructure of the pure Ti affect the morphology of nanotubes grown by anodic process. However, this subject is rarely investigated for nanotubes grown on Ti alloys. In the same way, nanostructured films formed by concomitant regions of tubes and lamellar structures hardly ever were reported. Investigations concerning these topics are required once beta titanium alloys are suitable candidates to replace the pure Ti and Ti-Al-V alloys for biomedical applications. Beta alloys composed of non-toxic elements (Nb, Ta, Mo) are biocompatible and have an excellent mechanical properties and corrosion resistance. The present work investigated questions regarding to the effect of microstructure of Ti-10Nb alloy on morphology of nanostructured film growth by anodization. The morphology, thickness, composition and atomic arrangement (amorphous/crystalline) of formed oxides, and the contact angle of anodic film were investigated. The X-ray diffraction patterns and SEM image show that the Ti-10Nb alloy is composed by alpha (hcp) and beta (bcc) phases. SEM and TEM techniques revel that self-organized nanotubes grew on alpha phase, whereas a lamellar structure with transversal holes grew on beta-phase. Crystalline oxides are formed at oxide-metal interface, as indicated by X-ray diffraction patterns. However, the tubes and lamellas grown over the compact oxide are amorphous, as-prepared and annealed at 230 degrees C for 3 h, as showed by SAED patterns. The nanostructured films annealed at 430 degrees C and at 530 degrees C were damaged. A few changes were observed in XRD patterns of film annealed at 230 degrees C while the morphology held similar as the unannealed film. Finally, the presence of phosphorus ions incorporated into the anodic layer makes the surface hydrophilic, since a similar nanostructured film without phosphorous incorporation results hydrophobic. (C) 2018 Elsevier B.V. All rights reserved. Univ Fed Parana, Programa Posgrad Engn & Ciencia Mat PIPE, BR-81531990 Curitiba, Parana, Brazil Pontificia Univ Catolica Parana, Escola Politecn, Dept Engn Mecan, BR-80215901 Curitiba, Parana, Brazil Univ Tecnol Fed Parana, Programa Posgrad Engn Mecan & Mat, BR-81280340 Curitiba, Parana, Brazil Univ Estadual Paulista, Lab Anelasticidade & Biomat, Dept Fis, BR-17033360 Bauru, SP, Brazil Univ Fed Parana, Dept Fis, BR-81531990 Curitiba, Parana, Brazil Univ Estadual Paulista, Lab Anelasticidade & Biomat, Dept Fis, BR-17033360 Bauru, SP, Brazil Fundacao Araucaria: 685/2014 Fundacao Araucaria: 42466

The aim of this paper is to report the use of the anodic bonding technique to bond titanium alloy and two different bioactive glasses aiming the medical application of these biomaterials. Ti alloy and bioactive glasses 52S4.6 and 45S5 were successfully bonded using anodic bonding technique for range of temperature and applied potential. The effects of anodic bonding parameters over the total charge transferred and the bonding time were evaluated. The adhesion of Ti alloy and bioactive glasses was measured by shear test. Due to polishing process, titanium alloy samples shown a slightly rounding and consequently the bonding area was limited to part of the sample area. It was found the temperature and potential have effect with statistical significance over the total transferred charge and the bonding time. The results herein discussed suggest the viability of anodic bonding added to process versatility and material compatibility for the use of bioglass and Ti alloy bonded together on medical application.

This work aims to investigate the role of epoxy addition in high density polyethylene (HDPE) matrix. The block copolymer polyethylene-b-poly (ethylene glycol) (PEG-co-PE) was used as a compatibilizer. The samples were obtained by melt mixing using a torque rheometer. Instrumental nanoindentation was used to determine Young's modulus and nanohardness, thermal properties were analyzed by differential scanning calorimetry (DSC) and phase morphology was investigated through transmission and scanning electronic microscopy. The epoxy addition increased HDPE crystallinity by 13% and Young's modulus by 8%. The addition of PEG-co-PE decreased the size of dispersed phase by approximately 50% and improved phase adhesion and homogeneity compared to the blends without block copolymer. The experimental results were compared to numerical results obtained from the use of the homogenization by asymptotic expansion approach. The numerical results presented a fair agreement to the experimental values.

Made available in DSpace on 2020-12-10T19:47:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-25 LORXI at UFPR, Brazil Hydroxyapatite (HA) is a bioactive calcium phosphate capable of enhancing the implant/bone connection improving osteoconductivity and osseointegration process. However, the HA presents mechanical properties limiting its application. A good way to resolve this limitation is to combine the excellent biological properties of HA with materials with suitable mechanical behavior, like Ti-25Nb-25Ta alloy. The Ti-25Nb-25Ta alloy is cornposted by non-toxic and corrosion-resistant elements, presenting good biological compatibility. In this work, Plasma Electrolytic Oxidation (PEO) (using direct current-DC) was applied in conventional mode and Two-Step PEO aiming to produce a porous coating containing HA. It was not possible to produce a satisfactory coating applying conventional PEO due to successive spalling during the oxidation process. Adding a pretreatment to the conventional PEO changed the process to Two -Step PEO allowing to form a porous coating containing HA. The pretreatment was made by PEO using phosphoric electrolyte to produce a pre-coating. After that, the pre-coating was re-oxidized with calcium/phosphorus electrolyte. The Two -Step oxidized surface presented well-known good characteristics to applications in osseous implant devices such as porous formation, roughness in the micrometrical range, surface containing calcium and phosphorus, bioactive crystalline titanium oxide, and well adhered HA formation. However, the coating morphology and chemical composition of pre-coating and Two Step oxidized surfaces were not uniform. The non-uniformity of the Two -Step oxidized surface follows a similar non-uniformity pattern of the pre-coating surface. Two distinct morphologies were identified on the Two-Step oxidized surface: a velvety morphology with HA formation and a highly porous morphology. Regarding the Ti-25Nb-25Ta alloy, the Two-Step oxidation produced an adhered coating with porous apatite distribution interspersed with calcium-rich porous oxide. Univ Fed Parana, Postgrad Program Mat Engn & Sci PIPE, Curitiba, Parana, Brazil Athlone Inst Technol, MRI, Athlone, Ireland Univ Tecnol Fed Parana, Dept Mech Engn Curitiba, Curitiba, Parana, Brazil Univ Fed Parana, Dept Phys, Curitiba, PR, Brazil Univ Estadual Paulista, Dept Mat & Technol, Guaratingueta, SP, Brazil Univ Estadual Paulista, Dept Mat & Technol, Guaratingueta, SP, Brazil LORXI at UFPR, Brazil: FINEP CT-INFRA 793/2004 LORXI at UFPR, Brazil: 3080/2011

Made available in DSpace on 2021-06-25T11:08:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01. Added 1 bitstream(s) on 2021-07-15T15:05:35Z : No. of bitstreams: 1 S1516-14392020000600217.pdf: 1821129 bytes, checksum: 9bd546707a67f99a16bad21d1d91ef3c (MD5) Universidade Federal do Paraná The present study produced binary titanium-niobium alloys Ti-xNb with high niobium percentage (x = 50, 80 e 90 wt.%) aiming to apply it as a base material in osseous implant devices. The produced TiNb alloys presented a cubic crystalline phase, lower corrosion rate than titanium, lower elastic modulus values, and superior cellular viability than titanium and niobium. The Ti50Nb alloy among all analyzed metallic substrates showed the best values of elastic modulus, corrosion properties, wettability, and cellular viability. Thus, this work suggests a Ti/Nb ratio close to 1 (Ti50Nb) displays optimum characteristics to apply in orthopedic devices. Universidade Federal do Paraná Programa de Pós-Graduação em Engenharia e Ciência dos Materiais (PIPE) Universidade Federal do Paraná Departamento de Física Athlone Institute of Technology Universidade Tecnológica Federal do Paraná Departamento de Engenharia Mecânica Pontifícia Universidade Católica do Paraná Departamento de Engenharia Mecânica Universidade Estadual Paulista (UNESP) Laboratório de Anelasticidade e Biomateriais Colorado State University Department of Mechanical Engineering Universidade Estadual Paulista (UNESP) Laboratório de Anelasticidade e Biomateriais

The UNS S32750 super duplex stainless steel (SDSS) was low temperature plasma nitrided at 350 °C and 400 °C for 4 h. Pitting and crevice corrosion resistance was evaluated using electrochemical techniques in a NaCl neutral solution. Nitriding treatments resulted in increased in hardness, general corrosion resistance and in the passive layer breakdown potential. Regarding crevice corrosion tests, the nitrided surfaces showed lower current densities during the potentiostatic polarization and lower corrosion depths when compared to the untreated surface. The nitrogen played a fundamental role in the passivation behavior and in the susceptibility to repassivation of localized corrosion.

Well-adhered nanotube arrays were produced through the anodizing technique on a Ti-25Nb-25Ta alloy and tribo-mechanically evaluated by nanoindentation and nanoscratch tests. Disregarding substrate effects, the hardness of the nanotube arrays layer was 0.7 ± 0.1 GPa and elastic modulus was

Poly(4,4′-oxydiphenylene-oxydiphthalimide) (POO) was thermally treated at 773 K for 1, 15 and 60 min under argon atmosphere resulting in free-standing films with intermingled characteristics between polymer and carbon-rich derivatives. Degradative thermal analysis performed by pyrolysis-gas chromatography/mass spectroscopy (Py-GC/MS) revealed CO2 among the major products of thermal decomposition which according to electron paramagnetic resonance (EPR) passed through a radical process. X-ray diffraction (XRD) revealed thermal treated samples with semicrystalline organization that was attributed to the development of lamellae structure. Moreover, Atomic force microscopy (AFM) showed an increase in the roughness of the samples that acquired pronounced roughcast-like surface. Hence, there was an enhancement of mechanical strength and dielectric permittivity. From the data collected a mechanism of thermal decomposition was proposed.

The following chapter gives an overview of the anodic layers and nanotubes produced with plasma electrolytic oxidation. An introduction into the mechanisms involved in producing these nanofilms, such as the required processing parameters including voltage, current, and time, are discussed. In addition to an examination into the relation and the requirements for a good interface between the implant using these nanofilms and the bone, we also investigate and discuss the available commercial implants employing nanofilms. Commercial applications have enormous potential and are an area of interest for future work. Finally, we discuss the mechanical properties and the improvements obtained on these nanofilms by the scientific community.

Made available in DSpace on 2018-11-26T15:28:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) A simple and versatile route for the preparation of self-adhesive, corrosion-resistant and photochromic hybrid coatings is presented in this paper. The coatings are based on aliphatic poly(dimethylsiloxane)-derived hydroxyurethanes (PDMSUr), produced by the isocyanate-free route for inorganic substrates such as glass and metal alloys. This route involves the ring opening polymerization of a PDMS-derived bis(cyclic carbonate) (CCPDMS) with diamines and aminosilane. The cyclic carbonate was synthesized by cycloaddition of CO2 into a PDMS diglycidyl ether. The use of aminosilanes with CCPDMS enables hybrid organic-inorganic urethanic coatings to be obtained by the sol-gel process. The crystallinity of the coating can be easily controlled through the interplay of the ratio of monoamines and diamines in the formulation. The hybrid PDMSUr materials were tested as an adhesive/coating for metallic and glazed surfaces, presenting adhesion strengths of up to 7 MPa and a maximum usage temperature of 160 degrees C. The incorporation of phosphotungstic acid (PWA) produced a hard material (20-60 MPa) and the elastic modulus rose by more than a hundred times as the PWA content increased. The hybrid PDMSUr 2_35% PWA presented photochromic properties and is suitable as an adhesive and impact damping layer for laminated glass used for smart window production. Furthermore, these coatings are suitable for the protection of metallic substrates against corrosion in acidic, basic and seawater media. Univ Sao Paulo, Inst Chem Sao Carlos, BR-13563120 Sao Carlos, SP, Brazil Univ Fed Parana, Dept Phys, BR-81531980 Curitiba, PR, Brazil Univ Sao Paulo, Inst Phys Sao Carlos, BR-13566590 Sao Carlos, SP, Brazil State Univ Julio de Mesquita Filho, Engn Fac, Ilha Solteira, SP, Brazil Fraunhofer Inst Mfg Technol & Adv Mat IFAM, D-28359 Bremen, Germany State Univ Julio de Mesquita Filho, Engn Fac, Ilha Solteira, SP, Brazil FAPESP: 2011/06019-0 FAPESP: 2013/05279-3 FAPESP: 2011/08120-0 CAPES: 57060300

Objective :This study evaluated the hardness and modulus of elasticity of the dentin bond interface using total-etch (Single Bond /SB) and self-etch (Clearfil SE Bond/CSEB) adhesives associated with Nd:YAG Laser irradiation through the unpolymerized adhesives. Material and Methods : The occlusal surfaces of 12 human third molars were ground until superficial dentin was exposed. A standardized circular cavity was performed on the occlusal surface. Specimens were sectioned in the mesio-distal direction, and the 24 hemi-crowns were divided into four groups: Group SB/Control - SB + polymerization; Group SB/Laser - SB + Nd:YAG laser ( 174.16J/cm 2 /60s/non-contact) + polymerization; Group CSEB/ Control – CSEB + polymerization; Group CSEB /Laser - CSEB + Nd:YAG laser ( 174.16J/cm 2 /cm 2 /60s/non-contact) + polymerization. Composite were placed in the cavities and polymerized. The specimens were immersed in distilled water and stored in an oven at 37oC for 24h and then submitted to nanoindentation in a Nano Indenter® XP appliance. Results : The results were submitted to ANOVA, Tukey’s test and Student's- t test (p < 0.05). Conclusao: It was concluded that the application of the Nd:YAG laser in both adhesive systems did not changed the hybrid layer hardness; however, it increases the modulus of elasticity in the hybrid layer for both adhesives tested and it maybe preserves the integrity of the adhesive interface and its durability. Clinical relevance: The application of Nd:YAG laser prior to photopolymerization of adhesive systems can increase the modulus of elasticity in the hybrid layer and may contribute to stress distribution in the adhesive interface during the polymerization preserving the integrity of the adhesive interface and its durability.

Tubes of stainless steel (SS) embedded in external magnetic field were used to study the effects of plasma immersion ion implantation (PIII) as a function of their diameter. The study was complemented with and without a grounded auxiliary electrode (AE) placed at the axis of the tube. During the discharge tests in tubes of larger diameter (D = 11 cm), with and without AE, nitrogen gas breakdown was established inside the tube at pressures near 2.0 × 10−2 mbar. Under the same operation conditions, stable plasmas with similar PIII current densities were obtained for both arrangements. Reducing the diameter of the tube (D = 1.5 cm) turned the plasma unstable and made it inappropriate for ion implantation. This situation was solved by supplying gas at higher pressure or using higher magnetic field, without the presence of an AE. Under these conditions, nitrogen PIII treatments of these small diameter tubes were performed but gave not the best implantation results yet. Our results have also shown higher ion implantation current density (16 mA/cm2) in tube of intermediate diameter (D = 4 cm) using AE, compared to largest diameter tube used. In this case, a thick nitrogen layer of about 9 μm was obtained in the SS sample placed inside the tube. As a consequence of this, its structural and mechanical properties were enhanced. These results are attributed to the thermal diffusion promoted by ions hitting the inner wall in a large number due to the presence of the AE and the magnetic field.

The addition of nanoparticles has been reported as an option to increase the fracture toughness of thermosetting polymers without compromising the stiffness. In this paper, alumina or carbon nanotubes (CNTs), in three different concentrations, were dispersed in an epoxy resin. Mechanical properties were measured through tensile test and the results indicate increases for all nanocomposites, with a maximum for the addition of 0.5% of CNTs (17% in elastic modulus and 22% in ultimate stress). Using TEM images, it was possible to identify the nanostructures and mechanisms that lead to improved stiffness. Fracture toughness tests and SEM images showed that cavitation – shear yielding (for epoxy/alumina nanocomposites) and crack bridging – pull-out (for epoxy/CNTs nanocomposites) are the predominant mechanisms.

In this paper, nanocomposites with multiwalled carbon nanotubes (MWCNT) or graphene nanosheets were prepared using a high density polyethylene (HDPE) matrix. Two different processes were employed: a solution method and a melt mixing method. The crystallinity index of the HDPE showed similar levels in nanocomposites after the addition of carbon nanotubes. It can be seen that the preparation process modified the degree of crystallinity of the HDPE matrix with graphene nanosheets. Nanocomposites prepared by the solution method showed a decrease in the crystallinity index. The addition of carbon nanotubes led to an increase of Young´s Modulus with an increase in the MWCNT quantity, regardless of the preparation process used, with a 22.8 % increase for composites with 0.5 wt% of CNTs. The nanocomposites with graphene nanosheets exhibited a different behavior with each mixing method. Nanocomposites prepared by the solution method showed a higher Young´s Modulus than those prepared by melt mixing. Results of transmission electronic microscopy and field emission scanning electronic microscopy indicated homogeneous dispersion for carbon nanotubes in melt mixing. Graphene nanocomposites showed some agglomerates, with smaller platelets in the nanocomposites prepared by solution mixing compared to that prepared by the melt mixing. Keywords: nanocomposites, high density polyethylene, graphene, carbon nanotube, mixing methods

Niobium plates were electrochemically treated by Plasma Electrolytic Oxidation (PEO) with electrolytes containing phosphorous and/or calcium. Three different electrolyte and experimental parameters were used forming three different surfaces. Film morphology, thickness, and chemical composition were analyzed by scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). A profilometer and the sessile drop technique measured the average surfaces roughness (Ra) and contact angles respectively. X-ray diffraction technique (XRD) analyzed the oxide crystallinity, and scratch tests evaluated the film adhesion. All oxidized surfaces presented pores, without observed cracks. Comparing the different experimental conditions, films obtained with phosphoric acid (P100) show superficial pores, phosphorus incorporation, high hydrophilicity, non-crystalline oxide formation, and good scratch resistance. Films treated with calcium acetate electrolyte (Ca100), compared to P100 exhibit smaller size pores and film thickness, smaller hydrophilicity, and lower scratch resistance. They also demonstrated higher oxide crystallinity, calcium incorporation, and pores interconnections. When the PEO was executed with a blended electrolyte containing calcium acetate and phosphoric acid (Ca50P50) the formed films presented the highest thickness, high phosphorus incorporation, and the lowest contact angle compared with other films. In addition, the pores size, the scratch resistance, calcium incorporation, and oxide crystallinity present intermediate values compared to P100 and Ca100 films. Film crystallinity seems to be influenced by calcium incorporation, whereas, hydrophilicity is phosphorus amount dependent. The pores amount and their interconnections reduced the scratch resistance. Surface features obtained in this work are largely mentioned as positive characteristics for osseointegration processes.

In this work, nanocomposites with simultaneous dispersion of carbon nanotubes and clays in a high density polyethylene (HDPE) matrix were prepared. Two different processes of preparation were employed: solution or melt intercalation. Two different montmorillonite clays were used separately: a natural (MMT-Na) or an organoclay (MMT-30B) and it was used multiwalled carbon nanotubes (MWCNT). Thermal properties were evaluated by DSC and TGA, mechanical properties were evaluated by nanoindentetion and morphology was investigated by transmission electronic microscopy (TEM). Alterations of 20% in crystallinity were detected, increases in Young´s modulus up to 12% were observed and up to 20% of increase was observed in Oliver-Pharr hardness. It is possible to explain part of those results based on the state of dispersion observed in our TEM results.

The objective of this study was to assess the in vitro effect of a quaternary ammonium methacrylate polymer (QAMP) incorporated into a self-etching adhesive system on inhibiting caries by evaluating the mechanical properties of the adhesive interface. Twenty-four human third molars were distributed into: Clearfil™ SE Bond containing 5% QAMP (experimental group), Clearfil™ Protect Bond (positive control), and Clearfil™ SE Bond (negative control). Teeth of each group were divided according to the method for producing artificial caries lesions: pH-cycling or microbiological assay. All samples were sectioned and polished in order to obtain hardness (H) and Young's modulus (E) values by nanoindentation test in the hybrid layer and dentin. Data were analyzed by ANOVA and Games Howell's post hoc test (α = 0.05). Regarding the hybrid layer, Clearfil™ SE Bond containing QAMP demonstrated H and E values statistically higher than Clearfil™ SE Bond in both pH-cycling and microbiological experiments. Considering denti...

Bioactive layers produced on titanium to induce osseointegration may not be mechanically stable and/or attend to the requirement for the bone-matching elastic modulus. The previous surface modification by ion nitriding can eventually improve adhesion and mechanical properties of such bioactive coatings. Titanium samples were DC plasma nitrided in low conditions of temperature (673 K and 873 K) and time (1 h and 3 h). The surfaces were studied by grazing-incidence X-ray diffraction, micro-Raman spectroscopy, atomic force microscopy, scanning electron microscopy, instrumented indentation and nanoscratch tests. The treatments at 873 K produced a stratified surface containing δ-TiN, e-Ti2N and N-solid solution Ti(N), whereas the 673 K samples presented Ti(N) and evidence of nitride precipitates at a very shallow depth, as suggested by micro-Raman (depth of analysis ≤ 25 nm). The asperity degree and distribution increased with the treatment temperature and time, whose effects on hardness and elastic modulus were corrected by the contact stiffness analysis. The most significant changes in the near surface hardness (5 to 15 GPa) and elastic modulus (170 to 200 GPa) profiles in respect to the pristine Ti were observed for 873 K treatments. However, the 673 K – 3 h sample presented scratch hardness twice as high as the substrate value, even if the ductile-like tribological response was preserved. Afterwards, Ca–P containing titania coatings were produced by anodic oxidation on selected samples. The layers presented reduced brittleness under normal loading if grown on the previously nitrided surfaces, whereas elastic modulus profiles (75–90 GPa) were kept lower than bulk Ti. We conclude that Ti surfaces can be tailored by plasma nitriding to improve their load bearing capacity for deposition of bioactive layers.

Al oxide thin films were deposited on 304L stainless steel substrates to investigate their potential as protective coatings in metal dusting environments. Deposition of the films was carried out by d.c. reactive magnetron sputtering varying feeding mode of O2 flow and application of a Cr interlayer. The response to metal dusting of coated and uncoated substrates was evaluated by thermogravimetry in an atmosphere of CH4+H2+residual oxygen at 1073 K for 20 h. The results indicated that these types of coatings can effectively protect the 304L steel in these conditions. The protection was associated to good adhesion provided by the Cr interlayer and the role of the Al oxide as a barrier for diffusion. Improvement of the present coatings can be achieved within magnetron sputtering deposition techniques.

The effect of magnetic field enhanced plasma immersion ion implantation (PIII) on SS304 austenitic stainless steel samples has been investigated. Application of magnetic field in PIII process leads to the formation of the crossed E × B field configuration, promoting the increase of the plasma density by electron-neutrals collision. As a result, a high nitrogen ion flux on SS304 sample was achieved. In this experiment, a moderate temperature of about 350 °C was measured after two hour of treatment, discarding the possibility of the formation of chromium nitride. Measurements performed by Auger electron spectroscopy (AES) showed the formation of a nitrogen implanted layer which was much greater than the one obtained by standard PIII (at the same pulsing conditions). Due to that, new peaks in the characteristic profile of X-ray diffraction were observed as consequence of the formation of a new phase (γ N phase). It has caused as twice as high improvement in the surface hardness compared to the conventional PIII. Consequently, a substantial reduction in the wear rate was obtained.

The use of titania (TiO2) nanotubes is becoming one of the most attractive techniques as surface treatment for implants due its combination of morphology (that accelerates osteoblast adhesion and proliferation), bioactivity and possibility of being use as a drug vehicle. Anodic oxidation is one of the cheapest and simplest approaches to obtain highly ordered nanotubes. Parameters such as applied potential, reaction time and fluoride containing in the electrolyte define the nanotubes morphology. However, the mechanical properties of the nanotubes layer do not have been completely elucidated and they play a crucial role in the implant long term stability. The objective of this research was to obtain TiO2nanotubes using anodic oxidation and to determine their elastic modulus and hardness. The TiO2nanotubes layer was obtained in a fluoride containing electrolyte for 1 hour, one group at 15 V and another one at 25 V. The TiO2nanotubes morphology was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The elastic modulus and hardness were evaluated by nanoindentation experiments using a spherical tip. SEM images showed highly ordered nanotubes on all titanium surfaces and it was observed that the nanotubes diameters are directly related with the applied potential. Nanotubes diameters are 66 ± 9 nm and 131 ± 22 nm for nanotubes obtained at 15 V and 25 V, respectively. Nanoindentation test results showed a decrease in the elastic modulus comparing with titanium reference and these values approach to cortical bone elastic modulus. These results demonstrate that it was possible to obtain a homogeneous TiO2nanotubes layer that has mechanical properties adequate to improve implant long-term stability.

Modified titanium nanotubes (TiO2NTs) coatings are grown in simulated body fluid (SBF) from Ticp and Ti6Al4V. The addition of 1% v/v of SBF to the electrolyte neither modifies film morphology nor the structural oxide characteristics for both metal substrates. However, an improvement in mechanical properties (hardness and elasticity model) and wettability is observed. From bioactive assay, a higher amount of fl yes

The present work reports increase of the cavitation erosion resistance for low-temperature plasma nitrided CA-6NM martensitic stainless steel, which was investigated by means of a 20 kHz ultrasonic vibrator at peak-to-peak amplitude of 50 μm. The study was emphasized for the three first cavitation stages, usually presented at the cumulative material mass loss–time curve, for surfaces treated in dc pulsed plasma at 350 °C, in 5% N2+95% H2 gas mixture, for different nitriding times of 6, 12, and 24 h. The changes on nitrided surfaces were evaluated by XRD and nanoindentation technique. The modification of the treated surface morphology as a function of the testing time in the incubation, acceleration, and maximum erosion rate stages was also verified by SEM analysis. The improvement of the cavitation erosion resistance for nitrided surfaces is believed to be due to the nitrogen-expanded austenite (γN-Fe) formation from a tempered martensite matrix.

The response to metal dusting of Cr/Cr 2 O 3 thin films deposited on 304L stainless steel substrates by reactive magnetron sputtering (RMS) under various deposition conditions was investigated. Selected coated samples and bare substrates were exposed to an atmosphere of CH 4 + H 2 + residual oxygen at 800 °C for up to 20 h via thermogravimetric analysis (TGA). The results indicate that the presence of the Cr/Cr oxide film resulted in a clear improvement in resistance against metal dusting of the 304L steel. The protective behavior of the Cr/Cr oxide coatings arises from several effects: decrease of catalytic deposition of carbon on the Cr oxide surface (and expected prevention of inward diffusion of carbon through the Cr oxide), and hindrance of outward Cr and Fe diffusion which were identified as important events in the metal dusting of the bare 304L steel. The structural differences among the various Cr/Cr oxide films prepared in the present conditions played a lesser role in their protective behavior than the presence of the outer Cr oxide layer.

Plasma nitriding using high H 2 content gas mixtures in CA-6NM martensitic stainless steel was studied in the present work. Nitriding was performed in H 2 + N 2 gas mixtures for 5, 10 and 20% N 2 , in volume, at 773 K (500 °C), during 2 h. Changes in the surface morphology and nitrided layer constitution were characterized by SEM, XRD, roughness analysis, and nanoindentation technique. Cavitation erosion behavior of the nitrided samples was also investigated by means of a 20 kHz ultrasonic vibrator. The study was emphasized for the three first cavitation stages (incubation, acceleration, and maximum erosion rate stage) of the cumulative erosion–time curve. Results indicate that the gas mixture nitrogen content strongly influences the phases’ formation and its distribution on the nitrided layer. Better cavitation erosion resistance which was attributed to the finer and more homogeneous distribution of the nitrided layer phases was verified for samples treated at 5% N 2 . Otherwise, worse cavitation erosion behavior for samples nitrided at 20% N 2 is supposed to be due to the formation of multiphase compound layer constituted by Fe 4 N + Fe 2–3 N + CrN, which can infer residual stress in treated surface.

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A natural mixture of heavy rare earths oxides extracted from xenotime mineral have been used to prepare large single crystals of high-temperature REBa2Cu3O(7-\delta) superconductor grown using the CuO-BaO self-flux method. Its mechanical properties along the ab-plane were characterized using instrumented indentation. Hardness and elastic modulus were obtained by the Oliver and Pharr method and corresponds to 7.4 \pm 0.2 GPa and in range 135-175 GPa at small depths, respectively. Increasing the load promotes the nucleation of lateral cracks that causes a decrease in hardness and the measured elastic modulus by instrumented indentation at higher loads. The indentation fracture toughness was estimated by measuring the radial crack length from cube-corner indentations at various loads and was 0.8 \pm 0.2 MPa.m1/2. The observed slip systems of REBa2Cu3O(7-\delta) single crystals were [100](001) and [010](001), the same as for YBa2Cu3O(7-\delta) single crystals. The initial stages of deformation and fracture in the indentation process were investigated. The hardness and elastic modulus were not strongly modified by the crystallographic orientation in the ab-plane. This was interpreted in terms of the resolved shear stresses in the active slip systems. Evidence of cracking along the {100} and {110} planes on the ab-plane was observed. As a conclusion, the mechanical properties of REBa2Cu3O(7-\delta) single crystals prepared from xenotime are equivalent to those of YBa2Cu3O(7-\delta) single crystals produced by conventional rare earths oxides., Comment: The paper will appear in Volume 42 (2012) of the Brazilian Journal of Physics

The evolution of the structure and properties of Cr/Cr oxide thin films deposited on HK40 steel substrates by reactive magnetron sputtering (RMS) was investigated and linked to their potential protective behavior against metal dusting. Deposition time, mode of oxygen feeding, and application of bias voltage were varied to assess their effect on the density, adhesion, and integrity of the films. All the films showed a very fine columnar microstructure and the presence of amorphous Cr oxide. Both, an increasing time and a constant oxygen flow during deposition led to the development of relatively low density films and mud-like cracking patterns. A graded oxygen flow resulted in films with fewer cracks, but a careful control of the oxygen flow is required to obtain films with a truly graded structure. The effect of the bias voltage was much more significant and beneficial. An increasing negative bias voltage resulted in the development of denser films with a transition to an almost crack-free structure and better adhesion. The amorphous oxide resulted in low values of hardness and Young's modulus.

The influence of hydrogen loading temperature on the mechanical strength of optical fibers is investigated. Fibers subjected to high-pressure hydrogen loading at different temperatures were submitted to bend tests, and the results compared with those for pristine fibers. The Weibull probability distribution function was used to analyze the data of the mechanical bending strength of the fibers. Fiber strength is reduced by the presence of hydrogen, and this decrease is greater for higher hydrogen loading temperatures. The mechanical properties of the polymers used to coat fibers are affected by the hydrogen loading process and also by the increase in temperature. However, there is no evidence of cracks formation that might allow water to penetrate to the surface of the glass. Observation using scanning electron microscopy revealed that the morphology of fractures in nonhydrogen-loaded fibers have distinct fracture characteristics to that of fibers that are hydrogen loaded at 90°C and 120°C.

In this work, thermal and mechanical behaviors of nanocomposites of a photocurable epoxyacrylate resin and multiwalled carbon nanotubes (MWCNT) were investigated. A combination of sonication, and mechanical and magnetic stirring was used to disperse 0.25 wt% and 0.75 wt% of MWCNTs into the resin. Two photocuring cycles using 12 and 24 h UV-A radiation were studied. Nanoindentation was the chosen technique for characterizing the modulus of elasticity and hardness of samples. The curing degree and glass transition temperature of the epoxyacrylate matrix and the nanocomposites were determined by Differential Scanning Calorimetry (DSC). In addition, the Vickers microhardness and nanocomposite morphology were also investigated by Scanning Electronic Microscopy (SEM) and Transmission Electronic Microscopy (TEM). The results indicate an increase in the stiffness and hardness of the material, and a shift in the glass transition temperature. The increase in the elastic modulus is in concordance with the predictions made by two simple models: rule of mixture and Halpin–Tsai equation. A fair agreement between nanoindentation and microhardness measurements is also found. Finally, the importance of curing degree in some of the properties investigated in this study is also discussed.

Lithium disilicate glass has been submitted to a high pressure treatment associated to a heat treatment, and the effects of densification and crystallization at high pressure on the mechanical properties were evaluated. The hardness and elastic modulus were examined by instrumented indentation using a Berkovich tip. The crack pattern morphology after indentation with a cube corner indenter was also investigated. The hardness and elastic modulus of the samples submitted to high pressure at room temperature decreased with increasing pressure. The hardness and elastic modulus of the samples submitted simultaneously to high pressure (up to 7.7 GPa) and high temperature increased noticeably. The amount, length and type of cracks induced by the cube corner tip changed with increasing pressure. These results indicate that the high temperature treatment under high pressure improved the mechanical properties of LS 2 .