Academics and industry have sought after combining the exceptional properties of diamonds with th... more Academics and industry have sought after combining the exceptional properties of diamonds with the toughness of steel. Since the early 1990s several partial solutions have been found but chemical vapor deposition (CVD) diamond deposition on steel substrate continues to be a persistent problem. The main drawbacks are the high carbon diffusion from gas phase into substrate, the transition metals on the material surface that catalyze sp 2 bond formation, instead of sp 3 bonds, and the high thermal expansion coefficient (TEC) mismatch between diamond and steels. An intermediate layer has been found necessary to increase diamond adhesion. Literature has proposed many efficient intermediate layers as a diffusion barrier for both, carbon and iron, but most intermediate layers shown have not solved TEC mismatch. In this review, we briefly discuss the solutions that exclusively work as diffusion barrier and discuss in a broader way the ones that also solve, or may potentially solve, the TEC mismatch problem. We examine some multilayers, the iron borides, the chromium carbides, and vanadium carbides. We go through the most relevant results of the last two and a half decades, including recent advances in our group. Vanadium carbide looks promising since it has shown excellent diffusion barrier properties, its TEC is intermediary between diamond and steel and, it has been thickened to manage thermal stress relief. We also review a new deposition technique to set up intermediate layers: laser cladding. It is promising because of its versatility in mixing different materials and fusing and/or sintering them on a steel surface. We conclude by remarking on new perspectives.
A tecnologia de crescimento de filmes de diamante CVD tem sido usada para a fabricação de ferrame... more A tecnologia de crescimento de filmes de diamante CVD tem sido usada para a fabricação de ferramentas de corte especiais, aplicadas para usinagem de materiais difíceis, como o vidro borossilicato. A broca anelar de diamante CVD é um exemplo desse tipo de ferramenta. Essa ferramenta é composta por um anel de molibdênio recoberto com diamante CVD, crescido através da técnica, assistido por filamento quente. Experimentos mostraram que as brocas anelares de diamante CVD possuem melhores resultados técnicos de operação, quando comparadas com as brocas anelares comerciais, fabricadas com o diamante HPHT, como menor ruído operacional e furos obtidos sem defeitos em suas bordas. Palavras-Chave: Diamante CVD; Ferramentas de corte; Usinagem de vidro; Brocas anelares. CVD-diamond ring core bit-Application for holing boron-silicate glass Abstract The technology for growing CVD-diamond layers has been used for fabrication of special cutting tools, applied for machining difficult materials, as boron-silicate-glass. The CVD-diamond ring core bit is an example. This tool is composed for a molybdenum ring, covered with CVD-diamond, growth through hot filament assistance technique. Experiments show that the CVD ring core bit possess better technique results, when compared with the commercial HPHT diamond ring core bit, as a minor operational noise and holes machined without defects around its edges.
... [! ! ] NG Ferreira, EJ Corat, VJ TravaAiroidi, NF Leite, E. Del Bosco, Diamond Relat. Mater. ... more ... [! ! ] NG Ferreira, EJ Corat, VJ TravaAiroidi, NF Leite, E. Del Bosco, Diamond Relat. Mater. submitted. [12] M. Allan, SF Wong, J. Chem. ... [11]. NG Ferreira, EJ Corat, VJ Trava-Airoldi, NF Leite, E. Del Bosco, Diamond Relat. Mater. submitted. [12]. M. Allan and SF Wong. J. Chem. ...
Nanohydroxyapatite (nHAp) is an emergent bioceramic that shows similar chemical and crystallograp... more Nanohydroxyapatite (nHAp) is an emergent bioceramic that shows similar chemical and crystallographic properties as the mineral phase present in bone. However, nHAp presents low fracture toughness and tensile strength, limiting its application in bone tissue engineering. Conversely, multi-walled carbon nanotubes (MWCNTs) have been widely used for composite applications due to their excellent mechanical and physicochemical properties, although their hydrophobicity usually impairs some applications. To improve MWCNT wettability, oxygen plasma etching has been applied to promote MWCNT exfoliation and oxidation and to produce graphene oxide (GO) at the end of the tips. Here, we prepared a series of nHAp/ MWCNT-GO nanocomposites aimed at producing materials that combine similar bone characteristics (nHAp) with high mechanical strength (MWCNT-GO). After MWCNT production and functionalization to produce MWCNT-GO, ultrasonic irradiation was employed to precipitate nHAp onto the MWCNT-GO scaffolds (at 1-3 wt%). We employed various techniques to characterize the nanocomposites, including transmission electron microscopy (TEM), Raman spectroscopy, thermogravimetry, and gas adsorption (the Brunauer-Emmett-Teller method). We used simulated body fluid to evaluate their bioactivity and human osteoblasts (boneforming cells) to evaluate cytocompatibility. We also investigated their bactericidal effect against Staphylococcus aureus and Escherichia coli. TEM analysis revealed homogeneous distributions of nHAp crystal grains along the MWCNT-GO surfaces. All nanocomposites were proved to be bioactive, since carbonated nHAp was found after 21 days in simulated body fluid. All nanocomposites showed potential for biomedical applications with no cytotoxicity toward osteoblasts and impressively demonstrated a bactericidal effect without the use of antibiotics. All of the aforementioned properties make these materials very attractive for bone tissue engineering applications, either as a matrix or as a reinforcement material for numerous polymeric nanocomposites.
Diamond with different grain sizes and nanographite films were grown on silicon and diamond subst... more Diamond with different grain sizes and nanographite films were grown on silicon and diamond substrate using 90vol.% argon in hydrogen and methane gas mixtures by hot filament chemical vapor deposition method (HFCVD). In current study, the methane volume concentration was varied from 0.125 to 2vol. % in order to estimate its effect on film morphology. The substrate temperature was varied
The martensitic stainless steel X45CrSi93 is widely used in the automotive industry. One way to i... more The martensitic stainless steel X45CrSi93 is widely used in the automotive industry. One way to improve its properties is the deposition of high adhesiveness DLC films, which are well known for their excellent properties such as high hardness, low friction coefficient, chemical inertness, biocompatibility and excellent wear resistance. In this work, the adhesion between substrate and film was studied, by growing silicon interfaces with different deposition parameters. The technique used for growing these films was PECVD pulsed-DC. In order to obtain information of the silicon interface formation, ionic sub-implantation simulations were performed, by the software SRIM/TRIM. Raman spectroscopy was used to verify the atomic structure of the films. Scratch tribological test was performed to study adhesion. It was observed that the mechanical and tribological properties were greatly improved with the deposition of DLC films on the silicon interface. A correlation between the residual stress and adhesion of DLC films was found.
... ELSEVIER Surface and Coatings Technology 76-77 (1995) 797-802 S#HMCE COATINGS H6MOLO6Y Hot fi... more ... ELSEVIER Surface and Coatings Technology 76-77 (1995) 797-802 S#HMCE COATINGS H6MOLO6Y Hot filament scaling-up for CVD diamond burr manufacturing Vladimir Jesus Trava-Airoldi, Evaldo Jos6 Corat, Edson Del ... 12 ] KR Walton, JP Dismukes, RA Krueger, FR Field ...
Academics and industry have sought after combining the exceptional properties of diamonds with th... more Academics and industry have sought after combining the exceptional properties of diamonds with the toughness of steel. Since the early 1990s several partial solutions have been found but chemical vapor deposition (CVD) diamond deposition on steel substrate continues to be a persistent problem. The main drawbacks are the high carbon diffusion from gas phase into substrate, the transition metals on the material surface that catalyze sp 2 bond formation, instead of sp 3 bonds, and the high thermal expansion coefficient (TEC) mismatch between diamond and steels. An intermediate layer has been found necessary to increase diamond adhesion. Literature has proposed many efficient intermediate layers as a diffusion barrier for both, carbon and iron, but most intermediate layers shown have not solved TEC mismatch. In this review, we briefly discuss the solutions that exclusively work as diffusion barrier and discuss in a broader way the ones that also solve, or may potentially solve, the TEC mismatch problem. We examine some multilayers, the iron borides, the chromium carbides, and vanadium carbides. We go through the most relevant results of the last two and a half decades, including recent advances in our group. Vanadium carbide looks promising since it has shown excellent diffusion barrier properties, its TEC is intermediary between diamond and steel and, it has been thickened to manage thermal stress relief. We also review a new deposition technique to set up intermediate layers: laser cladding. It is promising because of its versatility in mixing different materials and fusing and/or sintering them on a steel surface. We conclude by remarking on new perspectives.
A tecnologia de crescimento de filmes de diamante CVD tem sido usada para a fabricação de ferrame... more A tecnologia de crescimento de filmes de diamante CVD tem sido usada para a fabricação de ferramentas de corte especiais, aplicadas para usinagem de materiais difíceis, como o vidro borossilicato. A broca anelar de diamante CVD é um exemplo desse tipo de ferramenta. Essa ferramenta é composta por um anel de molibdênio recoberto com diamante CVD, crescido através da técnica, assistido por filamento quente. Experimentos mostraram que as brocas anelares de diamante CVD possuem melhores resultados técnicos de operação, quando comparadas com as brocas anelares comerciais, fabricadas com o diamante HPHT, como menor ruído operacional e furos obtidos sem defeitos em suas bordas. Palavras-Chave: Diamante CVD; Ferramentas de corte; Usinagem de vidro; Brocas anelares. CVD-diamond ring core bit-Application for holing boron-silicate glass Abstract The technology for growing CVD-diamond layers has been used for fabrication of special cutting tools, applied for machining difficult materials, as boron-silicate-glass. The CVD-diamond ring core bit is an example. This tool is composed for a molybdenum ring, covered with CVD-diamond, growth through hot filament assistance technique. Experiments show that the CVD ring core bit possess better technique results, when compared with the commercial HPHT diamond ring core bit, as a minor operational noise and holes machined without defects around its edges.
... [! ! ] NG Ferreira, EJ Corat, VJ TravaAiroidi, NF Leite, E. Del Bosco, Diamond Relat. Mater. ... more ... [! ! ] NG Ferreira, EJ Corat, VJ TravaAiroidi, NF Leite, E. Del Bosco, Diamond Relat. Mater. submitted. [12] M. Allan, SF Wong, J. Chem. ... [11]. NG Ferreira, EJ Corat, VJ Trava-Airoldi, NF Leite, E. Del Bosco, Diamond Relat. Mater. submitted. [12]. M. Allan and SF Wong. J. Chem. ...
Nanohydroxyapatite (nHAp) is an emergent bioceramic that shows similar chemical and crystallograp... more Nanohydroxyapatite (nHAp) is an emergent bioceramic that shows similar chemical and crystallographic properties as the mineral phase present in bone. However, nHAp presents low fracture toughness and tensile strength, limiting its application in bone tissue engineering. Conversely, multi-walled carbon nanotubes (MWCNTs) have been widely used for composite applications due to their excellent mechanical and physicochemical properties, although their hydrophobicity usually impairs some applications. To improve MWCNT wettability, oxygen plasma etching has been applied to promote MWCNT exfoliation and oxidation and to produce graphene oxide (GO) at the end of the tips. Here, we prepared a series of nHAp/ MWCNT-GO nanocomposites aimed at producing materials that combine similar bone characteristics (nHAp) with high mechanical strength (MWCNT-GO). After MWCNT production and functionalization to produce MWCNT-GO, ultrasonic irradiation was employed to precipitate nHAp onto the MWCNT-GO scaffolds (at 1-3 wt%). We employed various techniques to characterize the nanocomposites, including transmission electron microscopy (TEM), Raman spectroscopy, thermogravimetry, and gas adsorption (the Brunauer-Emmett-Teller method). We used simulated body fluid to evaluate their bioactivity and human osteoblasts (boneforming cells) to evaluate cytocompatibility. We also investigated their bactericidal effect against Staphylococcus aureus and Escherichia coli. TEM analysis revealed homogeneous distributions of nHAp crystal grains along the MWCNT-GO surfaces. All nanocomposites were proved to be bioactive, since carbonated nHAp was found after 21 days in simulated body fluid. All nanocomposites showed potential for biomedical applications with no cytotoxicity toward osteoblasts and impressively demonstrated a bactericidal effect without the use of antibiotics. All of the aforementioned properties make these materials very attractive for bone tissue engineering applications, either as a matrix or as a reinforcement material for numerous polymeric nanocomposites.
Diamond with different grain sizes and nanographite films were grown on silicon and diamond subst... more Diamond with different grain sizes and nanographite films were grown on silicon and diamond substrate using 90vol.% argon in hydrogen and methane gas mixtures by hot filament chemical vapor deposition method (HFCVD). In current study, the methane volume concentration was varied from 0.125 to 2vol. % in order to estimate its effect on film morphology. The substrate temperature was varied
The martensitic stainless steel X45CrSi93 is widely used in the automotive industry. One way to i... more The martensitic stainless steel X45CrSi93 is widely used in the automotive industry. One way to improve its properties is the deposition of high adhesiveness DLC films, which are well known for their excellent properties such as high hardness, low friction coefficient, chemical inertness, biocompatibility and excellent wear resistance. In this work, the adhesion between substrate and film was studied, by growing silicon interfaces with different deposition parameters. The technique used for growing these films was PECVD pulsed-DC. In order to obtain information of the silicon interface formation, ionic sub-implantation simulations were performed, by the software SRIM/TRIM. Raman spectroscopy was used to verify the atomic structure of the films. Scratch tribological test was performed to study adhesion. It was observed that the mechanical and tribological properties were greatly improved with the deposition of DLC films on the silicon interface. A correlation between the residual stress and adhesion of DLC films was found.
... ELSEVIER Surface and Coatings Technology 76-77 (1995) 797-802 S#HMCE COATINGS H6MOLO6Y Hot fi... more ... ELSEVIER Surface and Coatings Technology 76-77 (1995) 797-802 S#HMCE COATINGS H6MOLO6Y Hot filament scaling-up for CVD diamond burr manufacturing Vladimir Jesus Trava-Airoldi, Evaldo Jos6 Corat, Edson Del ... 12 ] KR Walton, JP Dismukes, RA Krueger, FR Field ...
Uploads
Papers by Evaldo Corat