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Design and Processing of Ferrite Paste Feedstock for Additive Manufacturing of Power Magnetic ComponentsLiu, Lanbing 19 June 2020 (has links)
Reducing the size of bulky magnetic components (inductors and transformers) in power converters can be achieved by increasing switching frequency and applying innovative designs of magnetic components. Ferrite is the most suitable bulk magnetic material for working at high frequencies but it is difficult to fabricate novel designs of ferrite magnetic components because of the limitations of conventional fabrication methods. Additive manufacturing (AM) has the potential to make customize ferrite magnetic components. One big challenge in 3D printing ferrite magnetic components is the lack of compatible and functional ferrite materials as printers' feedstock. This work focuses on developing ferrite feedstock for 3D printing ferrite magnetic components and providing a guideline for formulating ferrite feedstock by studying the effects of materials and processing parameters on major properties of the ferrite feedstock.
The ferrite feedstock should not only be processable by a 3D printer but also make functional ferrite material that can work in power converters. To meet the requirements, the following four aspects of the feedstock are considered in this study: 1. the feedstock should be sinterable to achieve high enough magnetic permeability; 2. magnetic permeability of the feedstock can be easily tailored; 3. rheological properties of the feedstock should ensure reasonable printing resolution; 4. the feedstock can print high aspect ratio structures without slumping. Based on the four major considerations and the desired properties, materials were selected for formulating the ferrite feedstock. The effects of materials and processing variables on the major properties of the ferrite feedstock need to be studied to develop a formulation guidance of the feedstock.
The effects of materials fractions and the post-printing peak sintering temperature of the feedstock on maximizing magnetic permeability were studied. The peak sintering temperature had a significant impact on permeability and solid loading (SL) and solid loading excluding diluent (SLED) had smaller impacts. Densities and microstructures of the sintered ferrite cores were characterized to illustrate how the variables affect magnetic permeability.
Adding sintering additives to the feedstock was selected as an easy and effective way to tailor the permeability of the ferrite feedstock. The effect of the fractions of two types of additives, SiO2 and Co3O4, on permeability of ferrite were studied. Both SiO2 and Co3O4 can effectively reduce the permeability of the ferrite. A novel multi-permeability toroid core design was 3D-printed with ferrite feedstocks having different fractions of SiO2 to demonstrate the feasibility of fabricating special designs of ferrite magnetics using feedstocks with additives. Core-loss densities of ferrite cores fabricated with feedstocks having different fractions of the two additives were also characterized since it is another important property of ferrite cores in high-frequency converters. Adding SiO2 significantly increases the core-loss density of ferrite cores while adding proper fractions of Co3O4 decreased core-loss density at low magnetic flux densities. The mechanisms of how Co3O4 affect permeability and core-loss density were discussed.
The effect of the solid loading (SL) on print-line width resolution was studied by conducting line printing tests. The experiment results showed the best print-line width resolution was achieved using the feedstock with an intermediate SL. The is, which considered both viscosity of the feedstock and coagulation in the feedstock suspension, were discussed.
The effect of solid loading excluding diluent (SLED) and UV illumination time on the achievable aspect ratio of printed feedstock was studied. Yield shear strength (y) of feedstocks composition versus UV-curing time were characterized. We evaluated various phenomenological models reported in the literature for predicting the critical yield shear strength (y*) required to obtain a paste structure for a certain aspect ratio. Knowing y* would help to determine the shortest time needed for UV illumination. Applying the model that best fitted to our experimental results, we developed a processing guideline that from specified magnetic permeability and dimensions of a ferrite core, would prescribe the needed SLED and the minimal UV curing time for printing. The guideline was demonstrated by the successful fabrication of tall ferrite inductor cores commonly found in power converters.
The main contributions of this study are listed below:
1. Designed, formulated, and characterized ferrite feedstock that not only has functionality for power electronics applications but is also compatible with a direct extrusion type 3D printer. The feedstock can be made into ferrite cores with relative permeability ranging from 10 to 500 which are much higher than those of soft ferrite feedstocks currently reported elsewhere. The packing densities of 950℃ sintered ferrite cores made from the feedstock can be as high as 95%. With the Hyrel 30M 3D-printer, the smallest nozzle orifice diameter that the feedstock can be extruded from is 0.42 mm. We demonstrated printing of the feedstock into a cylinders with a height of 18 mm and an aspect ratio of 3 without slumping issue.
2. Identified the effects of materials and processing variales on 4 major considerations of the ferrite feedstock including maximizing sintered packing density, tailoring permeability, print-line resolution, and achievable dimensions of the printed feedstock without slumping. A deeper understanding of the mechanisms of how the variables affect main properties of the feedstock was provided.
3. Provided a preparation guideline of the ferrite feedstock that prescribe feedstock formulation and UV illumination time per print-layer from the target relative permeability and dimension of a ferrite core. / Doctor of Philosophy / To reduce the size of power electronic devices, applying novel designs of ferrite magnetic components (inductors and transformers) is a promising method. While conventional fabrication methods cannot fabricate novel designs of ferrite magnetic components that have odd or intricate geometries, additive manufacturing (AM) has the potential. One big challenge in 3D printing ferrite magnetic components is the lack of compatible and functional ferrite materials as printers' feedstock. This work focuses on developing ferrite feedstock for 3D printing ferrite magnetic components and providing a guideline for formulating ferrite feedstock by studying the effects of materials and processing parameters on major properties of the ferrite feedstock.
The ferrite feedstock should not only have the desired functionalities but also be suitable for printing. Major considerations and desired properties of the feedstock were discussed. Materials were selected to formulate the feedstock based on the desired properties. To develop a formulation guidance for the feedstock, the effects of materials and processing variables on the major properties of ferrite feedstock were studied. The studies included the following 4 aspects: 1. the effects of materials fractions in the feedstock and the post-printing sintering temperature of the feedstock on maximizing magnetic permeability; 2. the effect of additives in the feedstock on tailoring permeability; 3. the effect of feedstock rheology on print-line resolution; 4. the effect of materials fraction and ultraviolet light illumination time on achievable aspect ratio of printed feedstock.
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Effect of Superplasticizer on the Performance Properties of Cemented Paste Backfill at Different Curing TemperaturesHaruna, Sada 28 October 2022 (has links)
Cemented paste backfill (CPB) technology is widely used in the mining industry as an effective means of tailings disposal. CPB is a mixture of tailings, binder, water, and additional admixtures when required. It is prepared in a mixing plant on the ground surface and then transported into the mine cavities through pipelines either by gravity and/or using pumps. To ensure efficiency during transportation and avoid pipe clogging (which can cause unnecessary delays and loss of productivity), fresh CPB must have sufficient flowability. To achieve that, high-range water reducing admixtures, also known as superplasticizers, are usually added to the CPB during mixing. These admixtures are widely used in the construction industry due to their ability to improve flowability without undermining other important engineering properties. However, their influence on the rheology, mechanical strength and environmental performance (reactivity and permeability) of CPB is not fully understood. Thus, experimental studies were conducted to investigate the effects of superplasticizers on the performance properties of cemented paste backfill at different curing temperatures.
Yield stress and viscosity of fresh CPB cured for 0, 1, 2, and 4 hours were measured using a vane shear device and a Brookfield Viscometer respectively. Unconfined compressive strength (UCS) of samples cured for 1, 3, 7, and 28 days was determined in accordance with ASTM - C39. Superplasticizer contents were varied as 0%, 0.125%, and 0.25% of the total weight of the CPB. Preparations and curing of the specimens were performed at controlled conditions of 2, 20, and 35 °C to investigate the effect of ambient or curing temperatures. To have a better understanding of the environmental performance of CPB containing superplasticizer, reactivity, and hydraulic conductivity up to 90 days of curing were also investigated. The reactivity was measured using oxygen consumption test while hydraulic conductivity was measured using flexible wall permeability test. Microstructural analyses (thermogravimetric analyses, X-Ray diffraction, and mercury intrusion porosimetry) and monitoring tests (pH, zeta potential, electrical conductivity, and matric suction) were carried out to understand the principles behind the changes of the observed properties. The obtained results show that superplasticizer dosage and temperature variation have significant effects on the rheology, strength development, hydraulic conductivity and reactivity of the CPB. The polycarboxylic ether-based superplasticizer significantly reduces the yield stress and viscosity by creating strong electrostatic repulsion between the solid particles in the CPB and by steric hinderance. The CPB containing the superplasticizer remains fluid for longer period (as compared with the CPB without superplasticizer) due to the retardation of binder hydration. However, high curing temperature induces faster cement hydration, which thickens the fresh CPB. The unconfined compressive strength (UCS) of the CPB containing superplasticizer was observed to be lower in the early age (up to 7 days), which is also attributed to retardation of the binder hydration. At later ages, the superplasticizer improves the mechanical strength as the binder hydration accelerates and the solid particles self-consolidate. Coupled THMC processes in the CPB showed the role played by the changes in electrical conductivity, volumetric water content, matric suction, and temperature on the development of mechanical strength of the CPB containing superplasticizer. Similarly, addition of the superplasticizer in the CPB decreases both the hydraulic conductivity and reactivity of CPB, thus improving its environmental performance. The improvement is largely attributed to enhanced binder hydration and self-consolidation which decrease the porosity of the CPB. Increasing the curing temperature was found to magnify the improvement of the CPB properties by inducing faster binder hydration. The findings from this study will undoubtedly inform the design of CPB structure with better mechanical stability and environmental performance.
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Putting Pottery in Place: A Social Landscape Perspective on the Late Formative Upper Desaguadero Valley, BoliviaRivas-Tello, Daiana January 2017 (has links)
Recent archaeological investigations demonstrate that landscapes of the past are not just passive backdrops to people's practices, but rather play a key role in social, cultural, political, and economic processes. Archaeologists have typically studied landscapes by analysing settlement patterns and architecture, yet newer approaches include the study of production practices such as pottery or stone-tool production. One such approach focuses on the ‘taskscape’, which includes skilled agents, and daily tasks occurring on the landscape. Scholars using this framework consider the rhythms and the embodied experience of people in specific places, and explore both the social relationships and ecological affordances of landscapes. Archaeologists, in particular, have considered the embedded nature of daily tasks performed on the landscape, and the material remains of these tasks. In this project I focus on the taskscapes of the Late Formative Period (200 B.C.- A.D. 500), in the Upper Desaguadero Valley, just south of Lake Titicaca in Bolivia. Little is known of Late Formative landscapes, a period prior to the rise of the Tiwanaku state. I study Upper Desaguadero landscapes to contribute to scholarship exploring the social, political and economic changes of the Late Formative Period, prior to the emergence of the Tiwanaku state.
I study ceramics from two recently excavated sites, Khonkho Wankane and Iruhito. My research explores the difference between Khonkho Wankane and Iruhito taskscapes and whether this is evident through ceramics. Potters’ choices during production are based on their taskscapes, which can affect the materials selected for the paste (the mixture of clay and inclusions), to how the vessels were decorated. Pottery was not only made but also used during daily tasks and thus pottery usage can be used to examine taskscapes. I conduct attribute analysis, with particular attention to paste. For a more detailed analysis of paste I employ a Dino-Lite digital USB microscope. The digital USB microscope is portable, affordable and time efficient, allowing for analysis to be conducted in the field. This method is promising for ceramic analysis, as it encourages standardization and inter-site comparisons. Ultimately, this tool provides quick yet detailed insights into past social landscapes. / Thesis / Master of Arts (MA)
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Rapid Assessment of Sugars and Organic Acids in Tomato Paste Using a Portable Mid-Infrared Spectrometer and Multivariate AnalysisZhang, Congcong, Zhang 22 September 2016 (has links)
No description available.
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Current Technology and Techniques in Re-mineralization of White Spot Lesions: A Systematic ReviewPodray, Susan January 2012 (has links)
White Spot lesions are a common iatrogenic occurrence on patients who are treated with fixed orthodontic appliances. There is a dynamic chemical interaction between enamel and saliva at the tooth surface that allow a lesion to have phase changes involving demineralization of enamel and remineralization. This is due to calcium and phosphate dissolved in saliva that is deposited onto the tooth surface or removed depending on the surrounding pH. Caseinphosphopeptide-amorphous calcium phosphate (CPP-ACP) is gaining popularity in dentistry as a way to increase the available level of calcium and phosphate in plaque and saliva to improve the chemical gradient so that if favors remineralization. The aim of our investigation is to search the available current literature and formulate a recommendation for use of CPP-ACP in orthodontics. Publications from the following electronic databases were searched: PubMed, Web of Science, Cochrane Library and Science Direct. Searches from August 2010 to April 1st 2012 were performed under the terms "MI Paste OR Recaldent OR caseinphosphopeptide-amorphous calcium phosphate OR CPP-ACP or tooth mousse". The searches yielded 155 articles, These were reviewed for relevance based on inclusion and exclusion criteria. Articles with inappropriate study design or no outcome measures at both baseline and end point were also excluded. 13 articles were deemed of relevance with a high quality study design and were included in this study for evaluation. The current literature suggests a preventative treatment regimen in which MI Paste Plus is used. It should be delivered once daily prior to bed after oral hygiene for 3 minutes in a fluoride tray, throughout orthodontic treatment. It should be recommended for high risk patients determined by poor oral hygiene, as seen by the inability to remove plaque from teeth and appliances. This protocol may prevent or assist in the remineralization of enamel white spot lesions during and after orthodontic treatment. / Oral Biology
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Sintering of Micro-scale and Nanscale Silver Paste for Power Semiconductor Devices AttachmentZhang, Zhiye 23 September 2005 (has links)
Die attachment is one of the most important processes in the packaging of power semiconductor devices. The current die-attach materials/techniques, including conductive adhesives and reflowed solders, can not meet the advance of power conversation application. Silver paste sintering has been widely used in microelectronics and been demonstrated the superior properties. The high processing temperature, however, prevents its application of interconnecting power semiconductor devices. This research focuses processing and characterization of micron-scale and nanoscale silver paste for power semiconductor devices attachment.
Lowering the processing temperature is the essential to implement sintering silver paste for power semiconductor devices attachment. Two low-temperature sintering techniques - pressure-assisted sintering micro-scale silver paste and sintering nanoscale silver paste without external pressure - were developed. With the large external pressure, the sintering temperature of micro-scale silver paste can be significantly lowered. The experimental results show that by using external pressure (>40MPa), the commercial micro-scale silver paste can be sintered to have eighty percent relative density at 240oC, which is compatible with the temperature of solder reflowing. The measured properties including electrical conductivity, thermal conductivity, interfacial thermal resistance, and the shear strength of sintered silver joints, are significantly better than those of the reflowed solder layer. Given only twenty percent of small pores in the submicron range, the reliability of the silver joints is also better than that of the solder joints under the thermal cycled environment. The large external pressure, however, makes this technique difficult to automatically implement and also has a potential to damage the brittle power semiconductor devices.
Reducing silver particles in the paste from micro-size to nanoscale can increases the sintering driving force and thus lowers the sintering temperature. Several approaches were developed to address sintering challenges of nanoscale silver particles, such as particles aggregation and/or agglomeration, and non-densification diffusion at low temperature. These approaches are : nanoscale silver slurry, instead of dry silver powder, is used to keep silver particles stable and prevent their aggregation. Ultrasonic vibration, instead of conventional ball milling, is applied to disperse nanoscale silver particles in the paste from to avoid from agglomerating. Selected organics in the paste are applied to delay the onset of mass-diffusion and prevent non-densification diffusion at low temperature. The measured results show that with heat-treatment at 300oC within one hour, the sintered nanoscale silver has significantly improved electrical and thermal properties than reflowed solders. The shear strength of sintered silver interconnection is compatible with that of solder.
The low-temperature sinterable nanoscale silver paste was applied to attach the bare Silicon carbide (SiC) schottky barrier diode (SBD) for high temperature application. Limited burn-out path for organics in the silver layer challenges the sintering die-attach. This difficulty was lessened by reducing organics ratio in the silver paste. The effects of die-size and heating rate on sintering die-attach were also investigated. The single chip packaging of SiC SBD was fabricated by sintering die-attach and wire-bonding. The tested results demonstrate that the sintering nanoscale silver paste can be applied as a viable die-attach solution for high-temperature application. / Ph. D.
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Processing and Properties of Die-attachment on Copper Surface by Low-temperature Sintering of Nanosilver PasteZheng, Hanguang 30 May 2012 (has links)
As the first level interconnection in electronic packages, chip attachment plays a key role in the total packaging process. Sintered nanosilver paste may be used as a lead-free alternative to solder for die-attachment at sintering temperature below 300 °C without applying any pressure. Typically, the substrate, such as direct bond copper (DBC) substrates, has surface metallization such as silver or gold to protect the copper surface from oxidation during the sintering process. This study focused on developing techniques for die-attachment on pure copper surface by low-temperature sintering of nanosilver paste. One of the difficulties lies in the need for oxygen to burn off the organics in the paste during sintering. However, the copper surface would oxidize, preventing the formation of a strong bond between sintered silver and copper substrate.
Two approaches were investigated to develop a feasible technique for attachment. The first approach was to reduce air pressure as a means of varying the oxygen partial pressure and the second approach was to introduce inert gas to control the sintering atmosphere. For the first method, die-shear tests showed that increasing the oxygen partial pressure (PO₂ from 0.04 atm to 0.14 atm caused the bonding strength to increase but eventually decline at higher partial pressure. Scanning electron microscopy (SEM) imaging and energy dispersive spectroscopy (EDS) analysis showed that there was insufficient oxygen for complete organics burnout at low PO₂ condition, while the copper surface was heavily oxidized at high PO₂ levels, thus preventing strong bonding. A maximum bonding strength of about average 8 MPa was attained at about PO₂ = 0.08 atm. With the second method, the die-shear strength showed a significant increase to about 24 MPa by adjusting the oxygen exposure temperature and time during sintering.
The processing conditions necessary for bonding large-area chips (6 mm à 6 mm) directly on pure copper surface by sintering nanosilver paste was also investigated. A double-print process with an applied sintering pressure of less than 5 MPa was developed. Die-shear test of the attached chips showed an average bonding strength of over 40 MPa at applied pressure of 3 MPa and over 77 MPa under 12 MPa sintering pressure. SEM imaging of the failure surface showed a much denser microstructure of sintered silver layer when pressure was applied. X-ray imaging showed a bond layer almost free of voids. Because the samples were sintered in air, the DBC surface showed some oxidation. Wirebondability test of the oxidized surface was performed with 250 μm-diameter aluminum wires wedge-bonded at different locations on the oxidized surface. Pull test results of the bonded wires showed a minimum pull-strength of 400 gram-force, exceeding the minimum of 100-gf required by the IPC-TM-650 test standard. / Master of Science
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The effect of endodontic regeneration medicaments on mechanical properties of radicular dentinYassen, Ghaeth H. January 2013 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Endodontic regeneration treatment of necrotic immature teeth has gained popularity in recent years. The approach suggests a biological alternative to induce a continuous root development. In this project, three in vitro experiments were conducted to investigate the effect of three medicaments used in endodontic regeneration on mechanical properties and chemical structure of radicular dentin. In the first experiment, we investigated longitudinally the effect of medicaments on the indentation properties of the root canal surface of immature teeth using a novel BioDent reference point indenter. A significant difference in the majority of indentation parameters between all groups was found after one-week and one-month application of medicaments (p<0.0001): triple antibiotic paste (TAP) > double antibiotic paste (DAP) > control > calcium hydroxide [Ca(OH)2]. The four-week exposure of dentin to TAP and DAP caused 43% and 31% increase in total indentation distance outcome, respectively.
In the second experiment, we investigated longitudinally the effect of medicaments on the chemical structure of immature radicular dentin by measuring the phosphate/amide I ratios of dentin using Attenuated Total Reflection Fourier Transform Infrared Spectroscopy. Phosphate/amide I ratios were significantly different between the four groups after one week, two weeks and four week application of medicaments (p<0.0001): Ca(OH)2-treated dentin > untreated dentin > DAP-treated dentin > TAP-treated dentin.
In the third experiment, we investigated longitudinally the effect of medicaments on root fracture resistance and microhardness of radicular dentin. For the microhardness, the two-way interaction between group and time was significant (p<0.001). TAP and DAP caused a significant and continuous decrease in dentin microhardness after one and three month application, respectively. The three-month intracanal application of Ca(OH)2 significantly increased the microhardness of root dentin. The time factor had a significant effect on fracture resistance (p<0.001). All medicaments caused significant decrease in fracture resistance ranging between 19%-30% after three month application compared to one week application. The three medicaments used in endodontic regeneration caused significant change in the chemical integrity of the superficial radicular dentin and significantly affected the indentation properties of the root canal surface. Furthermore, the three month intracanal application of medicaments significantly reduced the fracture resistance of roots.
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Cemento atmainos ir cheminių įmaišų įtaka tešlos reologinėms savybėms / Influence of cement strains and additives on the rheological properties of cement pasteMacijauskas, Mindaugas 09 June 2014 (has links)
Baigiamojo magistro darbo tikslas – ištirti cheminių įmaišų poveikį reologinėms portlandcemenčio tešlos savybėms, panaudojant skirtingų tipų cementus. Darbe išnagrinėta lietuvių, užsienio mokslinė literatūra, aprašytos naudotos žaliavos, parinktos skirtingos cementinės tešlos sudėtys, kurios skiriasi cemento ir plastifikuojančios įmaišos tipu. Tyrimams naudotos šios medžiagos: AB „Akmenės cementas“ gamyklos portlandcementis CEM I 42,5 (N ir R ankstyvojo stiprumo), klinties portlandcementis CEM II/A-LL 42,5 N, plastiklis Centrament N3, naujausios kartos superplastiklis MC-PowerFlow 3140 ir vanduo. Ištirtas plastiklio ir superplastiklio poveikis portlandcemenčio tešlos vandens ir cemento (V/C) santykio pokyčiams ir sklidumui naudojant Sutardo viskozimetrą. Buvo tiriamos vienodo vandens ir cemento santykio portlandcemenčio tešlos su cheminėmis įmaišomis ir be jų. Tyrimai atlikti naudojant rotacinį viskozimetrą Rheotest NH 4.1 su bendraašiais cilindrais. Nustatytas cheminių įmaišų portlandcemenčio tešloje veiksmingumas, esant skirtingo tipo cementui. Pastebėta, kad portlandcemenčio tešlos dinaminis klampis gali būti reguliuojamas cheminėmis įmaišomis viso indukcinio hidratacijos periodo metu. Sukurta metodika portlandcemenčio tešlos reologinėms savybėms nustatyti bei parinktas reologinis modelis, kuris geriausiai apibūdina gautus tyrimų duomenis. Atlikus portlandcemenčio tešlos su cheminėmis įmaišomis ir be jų tyrimų rezultatų regresinę analizę, gautos klampio, tekėjimo lygtys... [toliau žr. visą tekstą] / The purpose of this thesis is to analyse the influence of chemical admixtures on the rheological properties of Portland cement paste, which differ depending on the type of cement used. In addition to the literature analysis, different cement paste compositions (differing in type of cement and plasticizers) were tested. Testing materials: Portland cement CEM I 42.5 (N and R early strength), limestone Portland cement CEM II/A-LL 42.5 N, plasticizer Centrament N3, the latest generation superplasticizer MC-PowerFlow 3140 and water. Research focused on effects of plasticizer and superplasticizer on water and cement (W/C) ratio and Portland cement paste slump-flow characteristics. Portland cement pastes with the same water-cement ratio with and without chemical admixtures were tested. Tests were carried out using a Suttard viscometer and rotation viscometer Rheotest NH 4.1 with coaxial cylinders. It was observed that viscosity of Portland cement paste can be controlled by chemical admixtures during the hydration induction period. The work provides analysis of the effectiveness of the chemical admixtures on the rheological properties of the Portland cement pastes, comparing it with a control composition of the Portland cement paste. Diagrams demonstrate changes in viscosity of the Portland cement pastes depending on the type and amount of the chemical admixtures. Obtained results were compared with the same consistence paste without admixtures. We created a new methodology of... [to full text]
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Influência do uso de filler calcário como material cimentício suplementar nas propriedades de fratura de pastas de cimento. / Influence of the use of limestone filler as a supplementary cementitious material on the fracture properties of cement pastes.Cecel, Rafael Testoni 21 May 2019 (has links)
Este estudo avaliou propriedades de fratura e seus parâmetros de superfície em composições de pasta de cimento de mesma porosidade capilar, variando o teor de filler calcário como substituinte ao cimento comercial. Ainda, para avaliação do efeito em composições de argamassa, foi avaliada a capacidade de redução de água que essa adição pode proporcionar e seu efeito na resistência mecânica. A avaliação dos parâmetros de fratura ocorreu por ensaio de flexão por carregamento em três pontos, com controle por taxa de deslocamento e as análises de superfície por ensaio de interferometria, em seções de fratura e entalhe. O aumento do teor de filler calcário proporcionou redução da demanda de água nas argamassas, para mesmo comportamento. A redução da demanda foi ainda maior para as composições dispersas com aditivo, em relação à referência com aditivo. As resistências à compressão das argamassas apresentaram boa correlação em relação ao ajuste com todas as composições, enquanto foi observado que argamassas de médio teor de filler podem apresentar mesma resistência à flexão que as argamassas de referência, mesmo que estas apresentem menor porosidade capilar. As pastas ensaiadas à flexão por carregamento três pontos não apresentaram comportamento quase-frágil, impedindo o cálculo da energia de fraturamento. Isto ocorreu devido ao método de ensaio adotado, com configuração inadequada, e que pode ser ajustada através da redução da taxa de deslocamento do ensaio, da geometria dos corpos de prova ou da geometria dos entalhes produzidos. Todas as composições apresentaram insensibilidade à profundidade de entalhe sob as condições de ensaio adotadas, possivelmente devido às falhas de configuração do método. As médias de resistência à flexão e do fator de intensidade de tensão crítico foram maiores para a composição de alto teor de filler, seguidos da referência e da composição de médio teor de filler, respectivamente. Em todas as análises e tipos de superfície estudadas, as composições de alto teor de filler apresentaram maior índice de rugosidade e amplitude entre picos e vales, enquanto não foi identificada diferença entre a referência e a composição de médio teor de filler. Estes dois parâmetros e a raiz quadrática da rugosidade indicaram que a rugosidade das superfícies fraturadas é maior que em superfícies cortadas com disco diamantado. / This study assesses fracture properties and their surface parameters in cement paste compositions of the same capillary porosity, varying the filler content of limestone as a substitute for commercial cement. Also, to evaluate the effect in mortar compositions, the water reduction capacity that this addition can provide and its effect on the mechanical resistance was evaluated. The evaluation of the fracture parameters was performed by three-point loading flexion test with displacement rate control and surface analysis by interferometry test in fracture and notch sections. The increase of limestone filler provided a reduction of the water demand in the mortars, in relation to the reference, for spreading of 265mm in table of consistency. The water demand reduction was even greater for compositions dispersed with admixture, relative to the reference with admixture. The compressive strength of the mortars presented a good correlation in the fit with all the compositions, while it was observed that mortars of medium filler content may have the same flexural strength as the reference mortars, even if they have lower capillary porosity. The pastes tested by three-point loading did not exhibit quasi-fragile behavior, preventing the calculation of fracturing energy. This was due to the inadequately configured test method adopted, which can be adjusted by reducing the test displacement rate, the geometry of the specimens or the geometry of the notches produced. All compositions presented insensitivity to the notch depth under the test conditions adopted, possibly due to method configuration failures. The averages of flexural strength and critical stress intensity factor were higher for the high filler composition, followed by the reference and medium filler composition, respectively. In all analyzes and surface types studied, high filler compositions presented higher roughness and amplitude index between peaks and valleys, while no difference between the reference and medium filler composition was identified. These two parameters and the quadratic root roughness indicated that the roughness of the fractured surfaces is greater than on surfaces cut with diamond disc.
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