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This thesis concerns the synthesis of cadmium based nanoparticles that emitted from 400 to the near infrared (NIR) region. Once synthesised they can be possibly used as biomarkers once encapsulated in microspheres. A brief introduction to the area of nanomaterials is also provided. The focus of this thesis is split into three main categories. Firstly core/shell nanoparticles were synthesised due to their ability to emit over a large range of wavelengths. Alloyed nanoparticles were then synthesised due to their ability of being very good photoemitters. Finally core/shell/shell nanoparticles were synthesised as they had the ability of emitting in the NIR region. This thesis is split into five main chapters. The first chapter is a brief introduction to the field of nanomaterials, analysis techniques and current and possible future applications. Chapters 2, 3, and 4 contain the main research carried out with brief synthetic methods and detailed analysis and characterization. Chapter 5 contains detailed synthetic methods with experimental conditions and specific equipment used for this research.

The quest for efficient and cost-effective thin-film photovoltaic (PV) materials has recently zeroed in on hybrid lead halide perovskites, owing to their low cost, ease of processing, and exceptional efficiency metrics—peaking at 33.9% when combined with silicon in tandem devices. Nevertheless, there are substantial concerns about the stability, toxicity, and consequential environmental footprint of lead-based perovskites, thereby necessitating rigorous research to identify and develop alternative materials with superior stability profiles and diminished toxicity. Amongst the myriad candidates, chalcogenide perovskites and their related structures, represented by the empirical formula ABQ3 (with A = Ca, Ba, Sr; B = Zr, Hf, Ti; Q = S, Se), have emerged as particularly promising contenders. These materials are distinguished by their optimal optoelectronic properties and robust stability. Notably, barium zirconium sulfide, BaZrS3, has garnered significant attention in the scientific community due to its distinctive perovskite structure and several unique optoelectronic properties, making it a frontrunner in this domain of PV materials research. However, synthetic routes to these materials, especially as colloidal nanomaterials, remain limited, due in part to their high crystallization energy and oxophilicity. In this thesis, we have successfully devised solution-based approaches to synthesize colloidal nanomaterials of BaTiS3 and BaZrS3, including its titanium- and selenium alloyed phases. Our methodology involves utilizing reactive metal amide precursors in oleylamine, with diethylthiourea and trioctylphosphine selenide serving as sources for sulfur and selenium, respectively. Chapter I discusses the general background of current and emerging PV materials. Chapter II delves into various synthetic routes reported for inorganic ternary and binary sulfide and selenide nanomaterials, incorporating transition metals from groups 3, 4, and 5. This section also encompasses our synthetic methods for BaZrS3 and BaTiS3 colloidal nanomaterials. Chapter III provides an in-depth discussion of our developed techniques for producing nanorods and nanoparticles of barium titanium sulfide. In Chapter IV, our focus shifts to the synthesis of colloidal nanoparticles of barium zirconium sulfide perovskites. Additionally, Chapter V explores the synthesis of titanium and selenium alloyed barium zirconium sulfide. Finally, the synthesis of mixed halide lead perovskite nanocrystals, achieved through a postsynthetic anion-exchange method, is discussed in Appendix E.

Submitted by WILLIAN ROBERTO VALICELLI SANITÁ null (willian.r.sanita@gmail.com) on 2017-03-17T01:27:33Z No. of bitstreams: 1 API 5L X-70 NdYAG - REV-00.pdf: 14588761 bytes, checksum: 027f498ff74dcf88e5b24148813899ae (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2017-03-21T18:52:02Z (GMT) No. of bitstreams: 1 sanita_wrv_me_ilha.pdf: 14588761 bytes, checksum: 027f498ff74dcf88e5b24148813899ae (MD5) / Made available in DSpace on 2017-03-21T18:52:02Z (GMT). No. of bitstreams: 1 sanita_wrv_me_ilha.pdf: 14588761 bytes, checksum: 027f498ff74dcf88e5b24148813899ae (MD5) Previous issue date: 2017-02-17 / Conduziu-se um estudo da soldagem laser na condição “bead on plate” no aço microligado ARBL API 5L Gr. X70 na forma de chapas com 1,0 x 20 x 120 mm (A x L x P). Realizou-se 12 soldas em atmosfera de gás argônio com fluxo de gás de 15 l/min, diâmetro de feixe de 0,2 mm, ângulo de 90º, taxa de repetição de 9, 8, 7, 6, 5 Hz, velocidade de soldagem de 1 mm/s, profundidades de foco iguais a 0,57 mm abaixo da superfície da peça e energia do pulso (Ep) fixada em 10,0 J. A largura temporal (Lt) foi mantida em 10 ms. O aporte térmico foi variado em 90, 80, 70, 60 e 50 J/ mm. Os resultados foram analisados com base na relação entre potência, geometria do cordão de solda, corrosão, dureza Vickers e microestrutura. Para revelação dos metais de solda utilizou-se reagente Nital 5%. As medidas de geometria (largura e profundidade) dos cordões de solda foram realizadas através de imagens obtidas em câmera digital em um microscópio óptico comum. Foram realizados ensaios de microscopia em microscópio eletrônico de varredura em detector retroespalhado (BSD), afim de verificar com maior clareza as microestruturas das amostras. Para verificação da resistência mecânica foi ensaio de tração nas amostras e no metal de base sem a inserção de entalhe. Para verificação de dureza foram analisados quatro parâmetros sendo eles três linhas horizontais e uma linha vertical no centro do cordão de solda. Para verificação da corrosão foi conduzido ensaio em um potenciostato para ensaio de polarização potenciodinâmica onde foram analisadas as curvas de polarização. Os maiores valores de largura profundidade foram encontrados em maiores valores de potência e largura temporal. As microestruturas das amostras apresentaram formações de ferrita acicular, ferrita alotriomórfica e possíveis elevados teores de martensita no caso das amostras de menor aporte térmico (60 e 50 J/ mm). Todas as amostras apresentaram maior resistência mecânica do que o metal de base, visto que todas romperam no metal de base. Os coeficientes de dureza se mostraram mais elevados para amostras de menor aporte térmico. As resistência de corrosão se mantiveram próximas ao metal base e alguns casos superiores (Ap 70 J/ mm) , visto que provavelmente tenha se formado um filme passivo de óxido após processo de soldagem, resultando em maior resistência. / We carried out a study of laser welding provided "bead on plate" in micro-alloyed steel ARBL API 5L Gr. X70 in the form of plates with 1,0 x 20 x 120 mm (H x W x D). 12 welds was performed in argonic gas flow of 15 l/min, beam diameter 0,2 mm, angle of 90°, repetition rate of 9, 8, 7, 6 and 5 Hz, welding speed of 1 mm/s, gas depths focus equal to 0,57 mm below the surface of the workpiece and the pulse energy (Ep) set at 10,0 J. The time width (Lt) set at 10 ms. The heat input was varied at 90, 80, 70, 60 and 50 J/mm. The results were analyzed based on the relationship between power, weld bead geometry, corrosion, Vickers hardness, chemical analysis and microstructure. For structure revelation of the weld metals used both Nital 5%. Measures of geometry (width and depth) of the weld beads were made using images taken by digital camera on an ordinary optical microscope. Microscopy tests were carried out using a scanning electron microscope in a backscattered detector (BSD), in order to verify with greater clarity the microstructures of the samples. For verification of mechanical strength was tensile test on samples and base metal without notch insertion. For verification of hardness were analyzed four parameters being three horizontal lines and a vertical line in the center of the weld bead. To verify the corrosion, a potentiostat test was conducted for potentiodynamic polarization test where the polarization curves were analyzed. The greatest values of depth width were found in higher values of power and temporal width. The microstructures of the samples showed formations of acicular ferrite, allotriomorphic ferrite and possible high martensite contents in the case of samples with lower heat input (60 and 50 J / mm). All samples showed higher mechanical strength than the base metal, since all of them broke in the base metal. The coefficients of hardness were higher for samples with lower thermal input. The corrosion resistance remained close to the base metal and some higher cases (Ap 70 J / mm), since a passive oxide film probably formed after welding, resulting in higher strength.

This thesis focuses on development of novel nanomaterials, including semiconductor quantum dots (QDs) and gold nanoparticles (AuNPs), for fabricating white-light emitting devices and assaying thiols in biological and environmental samples. The thesis mainly contains two divisions. One demonstrates synthesis, optical properties and white-light emissions of alloyed quantum dots and their application to light-emitting devices. The other describes to combine functionalized gold nanoparticles with capillary electrophoresis and accomplish high selectivity and ultrasensitive detection for thiols. First, through one-step aqueous synthesis, alloyed ZnxCd1¡VxSe QDs have been successfully prepared at low temperatures by reacting a mixture of Cd(ClO4)2 and Zn(ClO4)2 with NaHSe using 3-mercaptopropionic acid as a surface-stabilizing agent. The optical properties and composition of the alloyed QDs were highly dependent on the molar ratio of Zn2+ to Cd2+. With the increase in Zn content, a systematic blue shift occurred in the first exciton absorption and band edge emission. Moreover, X-ray diffraction peaks of the alloyed QDs systematically shifted to larger angles simultaneously. These systematic shifts indicated the formation of the alloyed QDs. Interestingly, among these alloyed QDs, Zn0.93Cd0.07Se QDs exhibited white-light emission with quantum yields of 12%. In addition, we discovered that we could adjust the relative strength of the band edge and trap state emissions by controlling the reaction time, thereby attain white-light-emitting QDs. Finally, we blended alloyed QDs with ultraviolet-transparent polydimethylsiloxane (PDMS) to develop a white-light, solid-state lighting device by using a 365-nm UV lamp as the pump source. In the other part of this thesis, we proposed a method for selective enrichment of thiols using Tween 20-capped gold nanoparticles (AuNPs) prior to capillary electrophoresis coupled with laser-induced fluorescence (CE-LIF). By forming Au-S bonds, Tween 20-AuNPs can selectively extract thiols from a complicated matrix. A Tween 20 capping layer not only suppresses nonspecific adsorption, but also enables NPs to disperse in a highly-salinity solution. For analyses of aminothiols, after extraction and centrifugation, thioglycollic acid was utilized to remove aminothiols that attached to the NP surfaces. The extracted aminothiols was derivatized with o-phthalaldehyde (OPA) followed by CE-LIF. The use of this nanoprobe provided approximately 11-, 282-, and 21-fold sensitivity improvements for homocysteine (HCys), glutathione (GSH), and £^-glutamylcysteine (GluCys), respectively. Furthermore, the limits of detection (LODs) at a signal-to-noise ratio of 3 for HCys, GSH, and GluCys are 4013, 80, and 383 pM, respectively. A practical analysis of aminothiols in human urine sample has been accomplished by our proposed method. For another application to determining thiol-containing peptides, we use dithiothreitol to remove thiol-containing peptides from the NP surface through ligand exchange. The released peptides are selectively derivatized with OPA to form tricyclic isoindole derivatives. After injecting a large sample volume, the sensitivity of these peptides was improved by stacking them via using polyethylene oxide (PEO) as additive for on-line concentration and separation. As a result, LODs for GSH, GluCys, and phytochelatins (PC2 ~ PC4) were down to 0.1-6 pM. The proposed method has the lowest LODs for five peptides compared to other reported methods, and it also detect dissolve thiols in seawater in practice. Our proposed method is capable of ultrasensitive detection for thiols in biological and environmental samples.

Uma das regiões produtoras de petróleo offshore que representa um papel importante na vanguarda dos desafios de extração em altas profundidades é a província do Pré-Sal, situada na costa brasileira, composta por grandes acumulações de óleo leve de excelente qualidade. O óleo proveniente dos poços do Pré-Sal brasileiro contém CO2 dissolvido, e após as separações de óleo e gases liberar o CO2 na atmosfera não condiz com as tentativas da indústria mundial em reduzir a emissão de gases do efeito estufa. Uma alternativa econômica e ecologicamente viável é a injeção do dióxido de carbono nos reservatórios para aumentar o fator de recuperação de óleo e, ao mesmo tempo, garantir a captura e armazenamento geológico deste gás. Caso haja uma descompressão repentina devido a uma falha nas linhas de transporte do CO2, uma abrupta redução de temperatura é observada nas paredes do vaso próximas ao vazamento. Uma vez que diretrizes de projeto indicam a utilização de materiais com boa tenacidade em baixas temperaturas, a utilização de aços ligados ao níquel se faz uma boa alternativa no transporte de CO2. O presente estudo visa avaliar a influência do tratamento térmico de têmpera e revenido na tenacidade à fratura de aços ligados ao níquel, conhecidos como 5,5Ni e 9Ni, em temperatura ambiente e também a -100 °C, bem como avaliar a ação do hidrogênio nestes aços quando em baixa temperatura. Foram utilizados corpos de prova do tipo SE(B) da mecânica da fratura sem e com tratamento térmico. Foi possível observar que os tratamentos térmicos de têmpera e revenido foram muito eficientes para manter a tenacidade original do aço 5,5Ni na temperatura de -100 °C. De fato, na condição de bruto de laminação, os valores de CTOD para esse aço nessa temperatura foram muito inferiores daqueles encontrados na temperatura ambiente, indicando que esse material experimenta uma transição muito importante do comportamento em fratura em baixas temperaturas. Já o aço 9Ni sem tratamentos térmicos apresentou valores praticamente constantes de CTOD nas condições de ensaio, com um leve aumento nos valores médios após a têmpera e revenido, principalmente em baixa temperatura. Não foi verificada grande influência do carregamento de hidrogênio nos resultados da tenacidade à fratura dos aços 5,5Ni e 9Ni na temperatura de -100 °C, uma vez que os valores de CTOD nestas condições apresentaram uma leve redução em relação aos valores para os aços sem hidrogenação e ensaiados na temperatura de -100 °C. / One of the regions offshore where the oil production performs an important role in the forefront of the challenges in deep-water extractions is the Pre-salt region, located in Brazilian coast, containing big concentrations of light oil with an excellent quality. The oil from Brazilian Pre-salt oilfields contains dissolved CO2, and after the oil and gases separation, simply release the CO2 in the atmosphere does not match the efforts of the global industries to reduce the greenhouse gases emissions. A viable economic and ecological alternative is the carbon dioxide injection into the reservoirs to enhance the oil recovery factor, meanwhile ensuring geological capture and storage of that gas. In case of a suddenly depressurization in the CO2 pipelines, a temperature drop is observed in the walls near the leakage. Since project guidelines indicates the use of materials with good low temperature toughness, the use of nickel alloyed steels are a good alternative for the CO2 transportation. This work aims to evaluate the influence of the heat treatment on fracture toughness of nickel alloyed steels, nominated 5.5Ni and 9Ni, at room temperature and also at -100 °C, as well as evaluating the hydrogen effect on fracture toughness of these steels in low temperature. SE(B) fracture mechanic samples were evaluated with and without quench and temper heat treatments. It was possible to observe that the quench and temper heat treatments were so much efficient to maintain the original toughness of 5.5Ni steel at temperature of -100 °C. Indeed, in as rolled condition, CTOD values for this steel at that temperature were much lower than those found at room temperature, indicating that this material faces a very important transition in fracture behavior at low temperatures. 9Ni steel without heat treatments showed CTOD values practically constants for the tests conditions, barely increasing the medium CTOD values after the quench and temper, mainly at low temperature. A major influence of hydrogen charging on fracture toughness of 5.5Ni and 9Ni steel at -100 °C temperature was not observed, since the CTOD values on these conditions showed a slightly reduction when related to values calculated for steels with no hydrogen charging and tested in temperature of -100 °C.

Orientador: Vicente Afonso Ventrella / Resumo: We carried out a study of laser welding provided "bead on plate" in micro-alloyed steel ARBL API 5L Gr. X70 in the form of plates with 1,0 x 20 x 120 mm (H x W x D). 12 welds was performed in argonic gas flow of 15 l/min, beam diameter 0,2 mm, angle of 90°, repetition rate of 9, 8, 7, 6 and 5 Hz, welding speed of 1 mm/s, gas depths focus equal to 0,57 mm below the surface of the workpiece and the pulse energy (Ep) set at 10,0 J. The time width (Lt) set at 10 ms. The heat input was varied at 90, 80, 70, 60 and 50 J/mm. The results were analyzed based on the relationship between power, weld bead geometry, corrosion, Vickers hardness, chemical analysis and microstructure. For structure revelation of the weld metals used both Nital 5%. Measures of geometry (width and depth) of the weld beads were made using images taken by digital camera on an ordinary optical microscope. Microscopy tests were carried out using a scanning electron microscope in a backscattered detector (BSD), in order to verify with greater clarity the microstructures of the samples. For verification of mechanical strength was tensile test on samples and base metal without notch insertion. For verification of hardness were analyzed four parameters being three horizontal lines and a vertical line in the center of the weld bead. To verify the corrosion, a potentiostat test was conducted for potentiodynamic polarization test where the polarization curves were analyzed. The greatest values of depth width were found i... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre

Uma das regiões produtoras de petróleo offshore que representa um papel importante na vanguarda dos desafios de extração em altas profundidades é a província do Pré-Sal, situada na costa brasileira, composta por grandes acumulações de óleo leve de excelente qualidade. O óleo proveniente dos poços do Pré-Sal brasileiro contém CO2 dissolvido, e após as separações de óleo e gases liberar o CO2 na atmosfera não condiz com as tentativas da indústria mundial em reduzir a emissão de gases do efeito estufa. Uma alternativa econômica e ecologicamente viável é a injeção do dióxido de carbono nos reservatórios para aumentar o fator de recuperação de óleo e, ao mesmo tempo, garantir a captura e armazenamento geológico deste gás. Caso haja uma descompressão repentina devido a uma falha nas linhas de transporte do CO2, uma abrupta redução de temperatura é observada nas paredes do vaso próximas ao vazamento. Uma vez que diretrizes de projeto indicam a utilização de materiais com boa tenacidade em baixas temperaturas, a utilização de aços ligados ao níquel se faz uma boa alternativa no transporte de CO2. O presente estudo visa avaliar a influência do tratamento térmico de têmpera e revenido na tenacidade à fratura de aços ligados ao níquel, conhecidos como 5,5Ni e 9Ni, em temperatura ambiente e também a -100 °C, bem como avaliar a ação do hidrogênio nestes aços quando em baixa temperatura. Foram utilizados corpos de prova do tipo SE(B) da mecânica da fratura sem e com tratamento térmico. Foi possível observar que os tratamentos térmicos de têmpera e revenido foram muito eficientes para manter a tenacidade original do aço 5,5Ni na temperatura de -100 °C. De fato, na condição de bruto de laminação, os valores de CTOD para esse aço nessa temperatura foram muito inferiores daqueles encontrados na temperatura ambiente, indicando que esse material experimenta uma transição muito importante do comportamento em fratura em baixas temperaturas. Já o aço 9Ni sem tratamentos térmicos apresentou valores praticamente constantes de CTOD nas condições de ensaio, com um leve aumento nos valores médios após a têmpera e revenido, principalmente em baixa temperatura. Não foi verificada grande influência do carregamento de hidrogênio nos resultados da tenacidade à fratura dos aços 5,5Ni e 9Ni na temperatura de -100 °C, uma vez que os valores de CTOD nestas condições apresentaram uma leve redução em relação aos valores para os aços sem hidrogenação e ensaiados na temperatura de -100 °C. / One of the regions offshore where the oil production performs an important role in the forefront of the challenges in deep-water extractions is the Pre-salt region, located in Brazilian coast, containing big concentrations of light oil with an excellent quality. The oil from Brazilian Pre-salt oilfields contains dissolved CO2, and after the oil and gases separation, simply release the CO2 in the atmosphere does not match the efforts of the global industries to reduce the greenhouse gases emissions. A viable economic and ecological alternative is the carbon dioxide injection into the reservoirs to enhance the oil recovery factor, meanwhile ensuring geological capture and storage of that gas. In case of a suddenly depressurization in the CO2 pipelines, a temperature drop is observed in the walls near the leakage. Since project guidelines indicates the use of materials with good low temperature toughness, the use of nickel alloyed steels are a good alternative for the CO2 transportation. This work aims to evaluate the influence of the heat treatment on fracture toughness of nickel alloyed steels, nominated 5.5Ni and 9Ni, at room temperature and also at -100 °C, as well as evaluating the hydrogen effect on fracture toughness of these steels in low temperature. SE(B) fracture mechanic samples were evaluated with and without quench and temper heat treatments. It was possible to observe that the quench and temper heat treatments were so much efficient to maintain the original toughness of 5.5Ni steel at temperature of -100 °C. Indeed, in as rolled condition, CTOD values for this steel at that temperature were much lower than those found at room temperature, indicating that this material faces a very important transition in fracture behavior at low temperatures. 9Ni steel without heat treatments showed CTOD values practically constants for the tests conditions, barely increasing the medium CTOD values after the quench and temper, mainly at low temperature. A major influence of hydrogen charging on fracture toughness of 5.5Ni and 9Ni steel at -100 °C temperature was not observed, since the CTOD values on these conditions showed a slightly reduction when related to values calculated for steels with no hydrogen charging and tested in temperature of -100 °C.

Uma das regiões produtoras de petróleo offshore que representa um papel importante na vanguarda dos desafios de extração em altas profundidades é a província do Pré-Sal, situada na costa brasileira, composta por grandes acumulações de óleo leve de excelente qualidade. O óleo proveniente dos poços do Pré-Sal brasileiro contém CO2 dissolvido, e após as separações de óleo e gases liberar o CO2 na atmosfera não condiz com as tentativas da indústria mundial em reduzir a emissão de gases do efeito estufa. Uma alternativa econômica e ecologicamente viável é a injeção do dióxido de carbono nos reservatórios para aumentar o fator de recuperação de óleo e, ao mesmo tempo, garantir a captura e armazenamento geológico deste gás. Caso haja uma descompressão repentina devido a uma falha nas linhas de transporte do CO2, uma abrupta redução de temperatura é observada nas paredes do vaso próximas ao vazamento. Uma vez que diretrizes de projeto indicam a utilização de materiais com boa tenacidade em baixas temperaturas, a utilização de aços ligados ao níquel se faz uma boa alternativa no transporte de CO2. O presente estudo visa avaliar a influência do tratamento térmico de têmpera e revenido na tenacidade à fratura de aços ligados ao níquel, conhecidos como 5,5Ni e 9Ni, em temperatura ambiente e também a -100 °C, bem como avaliar a ação do hidrogênio nestes aços quando em baixa temperatura. Foram utilizados corpos de prova do tipo SE(B) da mecânica da fratura sem e com tratamento térmico. Foi possível observar que os tratamentos térmicos de têmpera e revenido foram muito eficientes para manter a tenacidade original do aço 5,5Ni na temperatura de -100 °C. De fato, na condição de bruto de laminação, os valores de CTOD para esse aço nessa temperatura foram muito inferiores daqueles encontrados na temperatura ambiente, indicando que esse material experimenta uma transição muito importante do comportamento em fratura em baixas temperaturas. Já o aço 9Ni sem tratamentos térmicos apresentou valores praticamente constantes de CTOD nas condições de ensaio, com um leve aumento nos valores médios após a têmpera e revenido, principalmente em baixa temperatura. Não foi verificada grande influência do carregamento de hidrogênio nos resultados da tenacidade à fratura dos aços 5,5Ni e 9Ni na temperatura de -100 °C, uma vez que os valores de CTOD nestas condições apresentaram uma leve redução em relação aos valores para os aços sem hidrogenação e ensaiados na temperatura de -100 °C. / One of the regions offshore where the oil production performs an important role in the forefront of the challenges in deep-water extractions is the Pre-salt region, located in Brazilian coast, containing big concentrations of light oil with an excellent quality. The oil from Brazilian Pre-salt oilfields contains dissolved CO2, and after the oil and gases separation, simply release the CO2 in the atmosphere does not match the efforts of the global industries to reduce the greenhouse gases emissions. A viable economic and ecological alternative is the carbon dioxide injection into the reservoirs to enhance the oil recovery factor, meanwhile ensuring geological capture and storage of that gas. In case of a suddenly depressurization in the CO2 pipelines, a temperature drop is observed in the walls near the leakage. Since project guidelines indicates the use of materials with good low temperature toughness, the use of nickel alloyed steels are a good alternative for the CO2 transportation. This work aims to evaluate the influence of the heat treatment on fracture toughness of nickel alloyed steels, nominated 5.5Ni and 9Ni, at room temperature and also at -100 °C, as well as evaluating the hydrogen effect on fracture toughness of these steels in low temperature. SE(B) fracture mechanic samples were evaluated with and without quench and temper heat treatments. It was possible to observe that the quench and temper heat treatments were so much efficient to maintain the original toughness of 5.5Ni steel at temperature of -100 °C. Indeed, in as rolled condition, CTOD values for this steel at that temperature were much lower than those found at room temperature, indicating that this material faces a very important transition in fracture behavior at low temperatures. 9Ni steel without heat treatments showed CTOD values practically constants for the tests conditions, barely increasing the medium CTOD values after the quench and temper, mainly at low temperature. A major influence of hydrogen charging on fracture toughness of 5.5Ni and 9Ni steel at -100 °C temperature was not observed, since the CTOD values on these conditions showed a slightly reduction when related to values calculated for steels with no hydrogen charging and tested in temperature of -100 °C.