A zircônia estabilizada por ítria (Y-TZP) apresenta excelentes propriedades mecânicas; entretanto, sua microestrutura cristalina inerte faz com que tratamentos aplicados em porcelanas e vitrocerâmicas, como condicionamento com ácido fluorídrico e aplicação de compostos silânicos, sejam ineficazes para obter união aos cimentos resinosos. Neste trabalho, propõe-se uma alternativa para aumentar a reatividade da Y-TZP a cimentos resinosos por meio de um processo de modificação da superfície através da deposição de um filme vítreo. O objetivo deste estudo é, portanto, caracterizar um filme vítreo, sinterizado com diferentes ciclos térmicos, após deposição sobre Y-TZP (YZ 20/19, VITA Blocks Zahnfabrik, Bad Saackingen, Germany) e avaliar a resistência de união imediata e após ciclagem térmica (10.000 ciclos 5 e 55°C) a dois cimentos resinosos (Relyx Arc, 3M/ESPE, St. Paul, MN, USA e Rely-X U200 3M/ESPE, Neuss, Germany). A caracterização do filme foi efetuada por meio de microscopia eletrônica de varredura, para avaliar a morfologia; EDS (Espectroscopia por dispersão de energia), para estabelecer uma análise qualitativa e semi-quantitativa dos elementos químicos presentes e mensuração do ângulo de contato. Foram propostas as seguintes condições experimentais na superfície da YTZP: deposição dos filmes sinterizados à 700°C, 900°C ou ciclo de sinterização para o auto glaze; aplicação do primer contendo MDP (Alloy Primer, Kuraray Medical Inc, Kurashiki, Okayama, Japan); e silicatização da superfície (sistema Rocatec Soft, 3M/ESPE, St. Paul, MN, USA). Após o ensaio mecânico, o padrão de fratura foi avaliado por meio de microscopia óptica. Para os dados obtidos, o traço de Pillai (p = 0,00) mostrou que o tipo de tratamento empregado tem um efeito significativo sobre a resistência de união. Para determinar a diferença entre os grupos estudados foi aplicado um teste de comparações múltiplas (Tukey). O filme 900 apresentou maior resistência de união imediata (42,2 MPa), sendo este valor estatisticamente superior a silicatização (35,5 MPa) e MDP (28,0 MPa). Os resultados obtidos após termociclagem, mostram que o filme 900 novamente apresentou maior resistência de união (36,8 MPa) e também foi estatisticamente superior ao MDP (16,1 MPa) e silicatização (27,3MPa). A análise em microscópio estereoscópico demonstrou um padrão de fratura predominantemente coesiva na resina para microtração imediata para os grupos com deposição do filme vítreo e silicatizados. Para o MDP, o padrão de fratura foi, na sua maioria, do tipo mista. O ângulo de contato medido imediatamente após os tratamentos de superfície apresentou-se menor para os grupos com filme e silicatização e manteve-se com baixos valores somente para os grupos com filme após limpeza com álcool absoluto. A análise por EDS das superfícies dos filmes indicou a presença de silício nos diversos pontos analisados. Concluiu-se, deste modo, que a deposição do filme vítreo mostrou-se como um meio eficiente para promover uma forte e durável união com da Y-TZP com os cimentos resinosos, independente da temperatura de sinterização utilizada. / The yttria stabilized zirconia (Y- TZP) has excellent mechanical properties, however its inert crystalline microstructure makes treatments applied in porcelain and glass ceramics, such as hydrofluoric acid etching and application of silane compounds, are ineffective for the union resin cements. In this work, we propose an alternative to increase the reactivity of the Y- TZP resin cement by a process of surface modification by depositing a glass film. The aim of this study is therefore to characterize a glass film, sintered with different thermal cycles, after deposition on Y- TZP (YZ - 20/19, VITA Blocks Zahnfabrik, Bad Saackingen, Germany) and to evaluate the bond strength immediately after thermocycling (10.000 cycles 5 and 55°C) to two resin cements (Relyx Arc, 3M/ESPE, St. Paul, MN, USA and Rely - X U200 3M/ESPE, Neuss, Germany). The characterization of the glass film was performed by means of scanning electron microscopy to assess the morphology, EDS (Energy Dispersive Spectroscopy), to establish a qualitative and semi-quantitative chemical elements and measuring the contact angle. Been proposed the following experimental conditions on the surface of YTZP: deposition of films sintering at 700°C, 900°C or sintering cycle for VM9 self glaze; primer containing MDP (Alloy Primer, Kuraray Medical Inc., Okayama, Okayama, Japan) and silica coating surface (Rocatec Soft, 3M/ESPE, St. Paul, MN, USA) . After mechanical testing, the fracture pattern was evaluated by light microscopy. For data, the trace of Pillai (p = 0.00) showed that the type of treatment used has a significant effect on the bond strength. To determine the difference between groups was applied multiple comparison test (Tukey). The 900 film showed higher bond strength immediately (42.2 MPa), and this value was statistically superior to silica coat (35.5 MPa) and MDP (28.0 MPa). The results obtained after thermocycling, show that 900 film again showed highest bond strength (36.8 MPa) and was also statistically superior to MDP (16.1 MPa) and silica coating (27.3 MPa). The analysis in stereoscopic microscopes showed a pattern of predominantly cohesive fracture in the resin for immediate microtensile for groups with film deposition and silica coat. In the MDP, the fracture pattern was mostly of the mixed type. The contact angle measured immediately after the surface treatments was lower for groups with film and silica coat and remained with low values only for groups with film after cleaning with absolute alcohol. Analysis by EDS surfaces of the films indicated the presence of silicon at the various points analyzed. It was concluded therefore that the glass film deposition proved to be an efficient way to promote a strong and durable bond with Y- TZP with resin cements, regardless of sintering temperature used.

The objectives of this research were 1) to investigate the effects of hydrodemolition treatment timing on chloride concentration profiles in concrete bridge decks for depths of concrete removal below the top mat of reinforcing steel and 2) to investigate factors that influence the occurrence of blow-throughs in concrete bridge decks when hydrodemolition is used. The research results are intended to provide engineers with guidance about the latest timing of hydrodemolition that can maintain a chloride concentration level below 2.0 lb of chloride per cubic yard of concrete at the levels of both the top and bottom mats of reinforcing steel, as well as about conditions that may indicate a higher probability of blow-through during hydrodemolition. The scope of this research included a questionnaire survey of hydrodemolition companies to summarize common practices in the field, numerical modeling of chloride concentration to investigate hydrodemolition treatment timing on typical Utah bridge decks, and structural analysis to investigate factors that influence the occurrence of blow-throughs during hydrodemolition. While some survey respondents indicated that certain parameters vary, the responses are valuable for understanding typical practices and were used to design the numerical experiments. The numerical modeling generated chloride concentration profiles through a 75-year service life given a specific original cover depth (OCD), treatment time, and surface treatment usage. The results indicate that, when a surface treatment is used, the concentration at either the top or bottom mat of reinforcing steel does not reach or exceed 2.0 lb of chloride per cubic yard of concrete after hydrodemolition during the 75 years of simulated bridge deck service life. The results also indicate that, when a surface treatment is not used, the chloride concentration at the top mat of reinforcement exceeds 2.0 lb of chloride per cubic yard of concrete within 10, 15, and 20 years for OCD values of 2.0, 2.5, and 3.0 in., respectively. The numerical experiments generated results in terms of the main effect of each input variable on the occurrence of blow-throughs and interactions among selected input variables. For each analysis, blow-through can be expected when the calculated factor of safety is less than 1.0. The factor of safety significantly increases with increasing values of transverse rebar spacing and concrete compressive strength and decreasing values of depth of removal below the bottom of the top reinforcing mat, orifice size, and water pressure within the ranges of these parameters investigated in this experimentation. The factor of safety is relatively insensitive to jet angle. For both case studies evaluated in this research, the blow-through analysis correctly predicted a high or low potential for blow-through on the given deck.

The papermaking industry uses a large amount of starch each year, both as a wet-end additive and as a rheological modifier in surface sizing and coating colors. It is important to be able to reduce the amount of chemicals used in the papermaking and surface treatment process, to reduce costs and to make the process even more efficient. Interest in new high-performance starches is great. By using these new types of starches, improved recycling of barrier products may be obtained as well as a reduction in the use of synthetic sizing agents. The objectives of this work were to understand the behavior of temperature-responsive hydrophobically modified starches, where the solubility in water simply can be adjusted by temperature or by polymer charge, to improve the barrier properties, like the water vapor permeability, mechanical properties and water resistance (Cobb and contact angle) of papers surface sized by starch-containing solutions, and to investigate the potential for industrial use of these temperature-responsive starches. It was demonstrated that the temperature-responsive starches phase separate upon cooling and, depending on the charge density of the starch, a particulate precipitation or a gel-like structure was obtained. The starch with zero net charge showed a larger increase in turbidity than the starch with a cationic net charge, indicating that particulate precipitation is favored by a zero net charge and that the formation of a gel network is favored by charged starch molecules. Further, the starches formed inclusion complexes with surfactants, giving stabilization to the starches in the presence of surfactants. The net charge density of the starch and the charge of the surfactant determined whether or not an inclusion complex would form between them. Important mechanisms for the stability of the starch seemed to be formation of mixed micellar-like structures between the hydrophobic chain of the starch and the surfactant along the starch backbone in addition to formation of inclusion complexes between the starch and the surfactant. The hydrophobically modified starches showed higher hydrophobic surface character when applied to the paper surface above the critical phase separation temperature than with application at room temperature. Free films of the temperature-responsive starches showed good barrier against oxygen, but no barrier against water vapor. The mechanical properties decreased with addition of glycerol to the films.

No description available.

Chip seals are a pavement surface treatment used for maintaining asphalt concrete pavements. National Cooperative Highway Research Program (NCHRP) Project 14-17 was performed to produce a national Chip Seal Manual which would consolidate the best chip seal engineering practices. A subcontract to NCHRP Project 14-17 performed at Texas A&M University was the basis for this thesis. It included the following tasks: investigation of a testing and grading system for grading asphalt binder residues from chip seal emulsions; and investigation of texture measurement methods for assessing existing pavement macrotexture before a chip seal is placed. The performance graded (PG) asphalt binder specification, which was developed to characterize asphalt binder properties related to the performance of hot mix asphalt concrete in pavements, cannot be directly applied to asphalt binders or emulsion residues for use in chip seals. Therefore, the surface performance graded (SPG) specification was developed using the same equipment as the PG system but with some procedural modifications and different limiting values for the test parameters. NCHRP Project 14-17 utilized the PG and SPG systems to grade base asphalt binders and recovered emulsion residues. Two emulsion residue recovery methods were compared: hot oven evaporation with nitrogen blanket and stirred can with nitrogen purge. The PG and SPG grades were found to be similar for the two emulsion residue recovery methods but slightly different from the base asphalt binder. A strawman specification for emulsion residues in chip seals was recommended for use with the stirred can recovery method. In chip seal construction, macrotexture of the existing pavement affects the rate at which chip seal emulsion must be applied. In this project, existing pavement macrotextures were measured at three chip seal projects immediately before construction using both the sand patch test and the circular track meter, CT Meter. The CT Meter was found to quickly and effectively measure pavement macrotexture. The CT Meter measurements correlated well with the sand patch test measurements. Finally, this project investigated the utility of measuring pavement macrotexture in the laboratory using the aggregate imaging system (AIMS) on pavement cores and on small samples cut from fabricated slabs. Statistical analyses showed good correlation between the mean profile depth, MPD, calculated from AIMS measurements on pavement cores and small samples, based on analysis using 50 mm (2 inch) segment lengths, and the MPD measured on the pavement or on the large fabricated slabs with the CTMeter. These results supported the use of AIMS to measure pavement macrotexture using small samples in the laboratory.

No description available.

The design and selection of surface treatment binders in service is currently based on specifications that only account for the penetration and ductility of emulsion residues or the penetration and viscosity of hot-applied asphalt cements. These specifications consider neither the entire range of temperatures that the binders may be subjected to during production and in service, nor long-term aging behavior. A surface performance-graded (SPG) specification for the selection of surface treatment binders was developed as part of previous Texas Department of Transportation (TxDOT) and National Cooperative Highway Research Program (NCHRP) projects. The work performed under the TxDOT Project 0-6616 was the basis for this thesis. In this project, the SPG specification, which is performance-based and takes into account the physical properties of the binder at the temperature ranges in which the material will be used, was further validated. This was accomplished by standardizing the emulsion residue recovery method through the evaluation of two warm oven methods, exploring the exclusive use of the dynamic shear rheometer (DSR) for determining performance-based properties, and further field validating the thresholds for these properties. The laboratory and field results were used to revise the SPG specification for surface treatment binders in service. Binder samples collected from chip seal projects constructed on selected highway sections in Texas in summer 2011 were tested and graded according to the existing SPG specification developed in previous research projects. Two warm oven emulsion residue recovery methods were used and compared. New DSR tests, including the multiple stress creep recovery (MSCR) test and the frequency sweep test were evaluated for developing additional criteria in the SPG specification. The SPG grades of the surface binder samples evaluated from laboratory tests were compared with the actual field performance of the highway sections one year after construction. The SPG specification was found to be functional in terms of enabling the selection of binders to ensure adequate surface treatment performance. Moreover, the results obtained from the MSCR and DSR frequency sweep tests were compared with field performance to develop additional criteria in the specification. Further validation is recommended to investigate the effects of construction and quality control processes, as this study is limited to producing a revised SPG specification for properties that address stiffness and aggregate retention in service.

Background Surface treatments and irregularities in the surfaces may affect the fracture of ceramics. The effects of various treatments on the surface texture of different types of ceramic cores/substructures was therefore qualitatively, quantitatively and numerically evaluated. Since fractures in ceramics are not fully understood, the fracture behavior in dental ceramic core/substructures was also studied using both established laboratory methods and newly developed numerical methods. Methods The surfaces of dental ceramic cores/substructures were studied qualitatively by means of a fluorescence penetrant method and scanning electron microscopy, quantitatively evaluated using a profilometer and also numerical simulation. In order to study fracture in zirconia-based fixed partial denture (FPD) frameworks, fractographic analysis in combination with fracture tests and newly developed two-dimensional (2D) and three-dimensional (3D) numerical modeling methods were used. In the numerical modeling methods, the heterogeneity within the materials was described by means of the Weibull distribution law. The Mohr–Coulomb failure criterion with tensile strength cut-off was used to judge whether the material was in an elastic or failed state. Results Manual grinding/polishing could smooth the surfaces on some of the types of dental ceramic cores/substructures studied. Using the fluorescence penetrant method, no cracks/flaws apart from milling grooves could be seen on the surfaces of machined zirconia-based frameworks. Numerical simulations demonstrated that surface grooves affect the fracture of the ceramic bars and the deeper the groove, the sooner the bar fractured. In the laboratory tests the fracture mechanism in the FPD frameworks was identified as tensile failure and irregularities on the ceramic surfaces could act as fracture initiation sites. The numerical modeling codes allowed a better understanding of the fracture mechanism than the laboratory tests; the stress distribution and the fracture process could be reproduced using the mathematical methods of mechanics. Furthermore, a strong correlation was found between the numerical and the laboratory results. Conclusion Based on the findings in the current thesis, smooth surfaces in areas of concentrated tensile stress would be preferable regarding the survival of ceramic restorations, however, the surfaces of only some of the ceramic cores/substructures could be significantly affected by manual polishing. The newly developed 3D method clearly showed the stress distribution and the fracture process in ceramic FPD frameworks, step by step, and seems to be an appropriate tool for use in the prediction of the fracture process in ceramic FPD frameworks.

Made available in DSpace on 2014-06-11T19:27:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-08-05Bitstream added on 2014-06-13T18:30:59Z : No. of bitstreams: 1 guimaraes_acm_me_guara.pdf: 1463910 bytes, checksum: 86d009497e85e3bccfe639908d568618 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Braquetes ortodônticos são feitos de diversos tipos de materiais, tais como, metais, cerâmicas e polímeros. Entre todos os materiais metálicos, o aço inoxidável é o mais empregado devido ao seu baixo custo associado a sua resistência à corrosão. No ambiente oral, eles estão sujeitos a fluídos agressivos e variações de pH, levando a liberação de íons nos tecidos e fluídos. Modificações na superfície destas ligas foram realizados utilizando tratamentos mecânicos, eletroquímicos, químicos e físicos. O carbono amorfo hidrogenado (a-C: H) preparado para técnicas de deposição apresentam muitas propriedades atraentes como alta dureza, serem químicamente inertes e biocompatíveis. Neste estudo in vitro, filmes de a-C:H foram depositados em braquetes ortodônticos pela técnica de deposição química por plasma de radiofreqüência (PECVD) e inibiu a liberação de íons níquel. Após o tratamento de superfície, os braquetes foram colados em incisivos bovinos com uma resina composta e as amostras foram imersas em soro fisiológico por 30 dias à 37 º C. Durante o tempo de imersão as amostras foram lavadas e imersas em flúor diariamente. Antes da imersão, o arranjo estrutural dos filmes foi analisado por espectroscopia de Raman e medidas do ângulo de contato foram realizadas, a fim de avaliar a molhabilidade da superfície. Espectrometria de absorção atômica foi usada para medir a liberação de elementos a partir de amostras e a análise superficial foi realizada em microscópio eletrônico de varredura (MEV). Os resultados mostraram que o revestimento previne a liberação de Ni dos braquetes nos testes estatísticos e o níquel foi liberado de outros grupos sem tratamento de superfície . A análise de variância não indicou diferença significativa entre os grupos depois do ensaio de cisalhamento. / Orthodontics brackets have been made from a variety of materials such as metals, ceramics and polymers. Among all the metallic materials, stainless steel are the most popular due low cost associated with reasonable corrosion resistance. In oral environment, they are subject aggressive fluids and pH variation can be leave nickel ions release to body tissues and fluids. Surface modifications of these alloys have been realized using mechanical, electrochemical, chemical and physical treatments. Hydrogenated amorphous carbon (a-C:H) prepared by deposition techniques have very attractive properties such as high hardness, chemical inertness and biocompatibility. In this in vitro study, a-C:H films were deposited on orthodontics brackets by r.f. plasmaenhanced chemical vapour deposition (PECVD) from inhibited nickel ions release. After treatment, brackets were bonded to bovine incisors with a composite resin and samples were immersed in physiological serum for 30 days at 37 ºC. During immersion time samples were brushed and/or immersed in mouthwashes daily. Prior immersion, the structural arrangement of films was probed by Raman spectroscopy and contact angle measurements were carried out in order to evaluate the wettability of surface. Atomic absorption spectrophotometry was used to measure the release of elements from the samples and SEM for surface analysis. Results showed that the coating prevents Ni release of brackets for statistic test and nickel was released for others groups. Analysis of variance no indicated significance different among groups after shear testing.

Made available in DSpace on 2014-06-11T19:28:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-03-26Bitstream added on 2014-06-13T20:18:31Z : No. of bitstreams: 1 almeidajunior_aa_me_arafo.pdf: 459545 bytes, checksum: df0008777c6ad28ca07cacdc0ed332ac (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Este estudo avaliou a resistência ao cisalhamento da união entre o titânio comercialmente puro fundido e o cimento resinoso não-adesivo (RelyX ARC – 3M ESPE) após diferentes tratamentos na superfície metálica. Noventa discos de titânio comercialmente puro foram divididos aleatoriamente em nove grupos, os quais receberam um dos seguintes tratamentos, antes da aplicação do RelyX ARC: (n=10): 01) Al2O3 (50 μm); 02) Al2O3 (50 μm) + adesivo; 03) Al2O3 (50 μm) + silano; 04) Cojet Sand (30 μm); 05) Cojet Sand + adesivo; 06) Cojet Sand + silano; 07) Al2O3 (50 μm) + Rocatec (110 μm); 08) Al2O3 (50 μm) + Rocatec + adesivo; 09) Al2O3 (50 μm) + Rocatec + silano. Os espécimes foram termociclados (5.000 ciclos - 5 – 55 oC - 30 segundos de imersão) e então submetidos ao ensaio de cisalhamento As médias de resistência ao cisalhamento da união dos grupos de 1 a 9 foram respectivamente: 4,10 ± 0,79CD; 6,14 ± 0,99B; 4,34 ± 0,71CD; 2,58 ± 0,37EF; 2,31 ± 0,23 F; 5,70 ± 0,93B; 3,65 ± 0,70DE; 5,25 ± 1,08BC e 8,36 ± 1,63A. O teste t de Student apontou igualdade estatística entre os grupos jateados com partículas de Al2O3 e com partículas revestidas por sílica (P=0,630). A análise de 22 variância (ANOVA) a dois critérios seguida pelo teste de Tukey indicaram que: 1) o Rocatec apresentou resistência significativamente maior que o Cojet Sand (P<0,05); 2) o jateamento com partículas de óxido de alumínio apresentou resistência significativamente maior quando associado ao adesivo (P<0,001) enquanto o silano foi o melhor tratamento pós jateamento para as partículas revestidas por sílica (P<0,001) e 3) O jateamento com Rocatec seguido da aplicação do silano proporcionou a maior resistência ao cisalhamento de união entre o titânio comercialmente puro e o RelyX ARC. Todos os grupos apresentaram falha 100% adesiva. / This study evaluated the shear bond strength of a conventional resin cement (RelyX ARC – 3M ESPE) to cast commercially pure titanium (cp Ti) after different treatments on metal surface. Ninety cp Ti disks were randomly divided into 9 groups which received one of the following treatments before the application of RelyX ARC: (n=10): 01) Al2O3 (50 μm); 02) Al2O3 (50 μm) + adhesive; 03) Al2O3 (50 μm) + silane; 04) Cojet Sand (30 μm); 05) Cojet Sand + adhesive; 06) Cojet Sand + silane; 07) Al2O3 (50 μm) + Rocatec (110 μm); 08) Al2O3 (50 μm) + Rocatec + adhesive; 09) Al2O3 (50 μm) + Rocatec + silane. All specimens were thermal cycled (5000 cycles, 5 - 55 oC – 30-second dwell time) before tested in shear mode. The mean bond strength values (Mpa) for all groups were, respectively: 4,10 ± 0,79CD; 6,14 ± 0,99B; 4,34 ± 0,71CD; 2,58 ± 0,37EF; 2,31 ± 0,23 F; 5,70 ± 0,93B; 3,65 ± 0,70DE; 5,25 ± 1,08BC e 8,36 ± 1,63A. The Student t test showed that there was no significant difference between Al2O3 particles and silica-modified Al2O3 particles (P=0.630). Two-way ANOVA and post hoc Tukey test (=.05) showed that: 1) Rocatec demonstrated significantly higher shear bond strength than Cojet Sand (P<0.05); 2) airborne-particle abrasion with Al2O3 particles exhibited the highest shear bond strength with adhesive (P<0.001) while silica-modified Al2O3 particles exhibited the best behavior when associated with silane (P<0.001); 3) Rocatec plus silane provided the highest shear bond strength between cp Ti and RelyX ARC. All groups showed 100% adhesive failure.