Nanoporous (NP) metals are a unique class of materials that are characterized by extremely high surface-to-volume ratios and possess such desirable properties of metals as high electrical conductivity, catalytic activity, and mechanical strength. At the same time, understanding of their physical properties is often lacking, especially for hierarchical NP metals where individual struts and joints that make up open cell 3D network are nanocrystalline. The aim of this work is to employ a dedicated experimental campaign to understand the structure property relation of nanostructured nanoporous metals. Towards this goal, NP Pt and NP Cu have been synthesized for a range of strut sizes and their mechanical properties have been investigated via ex-situ and in-situ nanoindentation experiments. Both NP Pt and NP Cu exhibit relatively high hardness in the range of 0.2 to 1.3 GPa. The relative role of material effects arising from small dimensions of the struts/joints and the geometrical features of NP metals are discussed. Selected applications of the systems synthesized during this work in electrochemistry and catalysis are demonstrated. In the examined applications the NP metals exhibited catalytic activity comparable to or significantly exceeding the best available alternative systems, while offering superior stability.

No description available.

<p>Water hardness indicates the concentration of calcium and magnesium ions in water. Water with high concentrations of these ions is described as hard water and water with low concentrations is described as soft water. Water that is too hard or too soft can lead to technical and economical problems. In collaboration with Midvatten AB, groundwater hardness in the Badelunda esker between Leksand and Avesta has been mapped, and an attempt has been made to explain the variations. For this purpose, different GIS programs, such as ArcView, ArcInfo, IDIRISI, and one geochemical modelling program, PHREEQC, has been used. GIS programs were used for digitising geological and hydrological maps and then for combining them with other kinds of data. Simulations of chemical equilibria have been accomplished using PHREEQC.</p><p>The absolutely most important factor that affects groundwater hardness is dissolution of carbonate minerals. The dissolution is controlled by access to these minerals and pH value of groundwater. Soil samples taken along Badelunda esker indicated the presence of carbonate minerals, and showed significant variation in carbonate content. PHREEQC simulations have indicated that samples from most of wells were saturated with calcite, it means there is no lack of carbonates. The simulations indicated even the importance of carbon dioxide pressure for pH and hardness in groundwater. Because this pressure is much higher under the ground than in the atmosphere the pH value will change as soon the water comes in contact with atmospheric air. Measurements of pH in field are quite complicated and are not usually performed in the field. In this work, pH values were obtained from laboratory analyses, and no measurements were made in the field.</p><p>Also road salt effects hardness. From several wells located closely to way 70 were received data showing rising chloride contents and hardness during last 30-40 years. The direct effect of road salt on hardness (exchange of Ca2+ by Na+) was investigated using simulation in PHREEQC. Results of simulations showed that effect of road salt on groundwater hardness are of secondary significance.</p><p>In some cases, extreme values in groundwater hardness could be explained by infiltration of surface water or by the occurrence of relict seawater.</p> / <p>Hårdhetsgrad anger koncentration av kalcium- och magnesiumjoner i vatten. Vatten med höga koncentrationer av dessa joner betecknas som hårt och vice versa. Både för hårt och för mjukt vatten innebär tekniska och ekonomiska problem. På uppdrag av Midvatten AB har ett försök att kartlägga och förklara variationen i grundvattnets hårdhet i Badelundaåsen mellan Leksand och Avesta genomförts. I arbetet användes olika GIS-program, såsom ArcView, ArcInfo, IDRISI, och ett geokemiskt modelleringsprogram, PHREEQC. GIS-programmen användes för digitalisering av geologiska och hydrologiska kartor och sammanställning av dessa kartor med andra typer av data. I PHREEQC genomfördes simuleringar av kemiska jämvikter.</p><p>Den absolut viktigaste faktorn som påverkar grundvattnets hårdhet är upplösning av kalkrika mineral. Upplösningen styrs av tillgången på kalkrika mineral och vattnets pH-värde. Jordprover som upptogs längs Badelundaåsen visar på att det finns kalkrika mineral i marken och att karbonathalten i materialet varierar betydligt. Jämviktssimuleringar med PHREEQC visade dock att prover från de flesta brunnar var mättade med avseende på kalcit. Det innebär att tillgången på karbonat inte är den begränsande faktorn. Dessa simuleringar visade dessutom att koldioxidtrycket är en viktig faktor som påverkar pH-värde och hårdhet. Koldioxidtrycket i atmosfären är mycket lägre än det som råder under markytan och därför förändras den kemiska jämvikten i grundvattnet så fort det kommer i kontakt med atmosfärsluften. pH-mätningar i fält är tidskrävande och brukar inte utföras vid vanlig provtagning. I examensarbetet ingick inte några egna vattenprovtagningar. Analysresultat som användes i examensarbetet var framtagna på laboratorium, d.v.s. pH-mätningar utfördes inte i fält.</p><p>Salt som sprids ut på vägar under vintertid har också en hårdhetsökande effekt. Från flera vattentäkter som ligger i närheten av riksväg 70 (Rv70) erhölls tidsserier som visade på stigande trender i både kloridhalter och hårdhet. Den ökade trafikbelastningen på riksväg 70 har sannolikt en betydande påverkan på grundvattenkvalitet. Beräkningar och simuleringar utförda inom ramen för detta examensarbete visade att vägsaltets effekt på grundvattenhårdhet är av sekundär betydelse.</p><p>Inblandning av ytvatten respektive relikt vatten förklarade exceptionellt låga respektive höga hårdhetsvärden i vissa brunnar.</p>

This report presents results from a series of experiments in which YAG samples (undoped, as well as doped with Nd and Cr3+) were exposed to ionizing radiation (gamma rays and UV). These experiments were performed for the purpose of investigating the various phtodarkening processes taking place in these materials in response to the ionizing radiation. The purpose of this investigation was to establish whether and how co-doping YAG with Cr3+ improves the material's resistance to photodarkening due to the ionizing radiation. The experiments tracked time-resolved transmittance of the samples at 1064 nm in immediate response a pulsed exposure to the ionizing radiation, as well as steady-state spectrally-resolved changed in the samples' optical absorption after the irradiation. The investigation revealed a number of photodarkening processes occurring in the samples in response to the ionizing radiation, both transient and permanent. It was further revealed that inclusion of Cr3+ ions in YAG significantly reduces these photodarkening processes, improving the material's radiation resistance. It was observed that materials containing at least 0.5 at% Cr3+ are essentially radiation-hardened, resisting both transient and steady-state changes in transmittance observed in the materials not containing Cr3+.

CCI Valve Technology AB is a company located in Säffle, Sweden, that manufactures and installs bypass valves. Due to requirements outside normal standards on the valve's hardness values, some measurements have had difficulties meeting such requirements. During this thesis work, tests were carried out to determine how to overcome the difficulties. The experiments focused on five different areas that may affect the components hardness, welding method, soaking temperature during post weld heat treatment, measuring procedure, component thickness and number of heat treatment cycles. The Grade 91 steel specimens that were examined consisted of five solid cylinders and three various pipes that were welded together by using shielded metal arc welding (SMAW) or gas tungsten arc welding (GTAW). Each pipe was sawed apart into three equal parts. All specimens were hardness tested and eight of the specimens' microstructure was studied with an optical microscope. The hardness measurement instruments used, LECO V-100-C2 and GE-MIC 10, are Vickers hardness testers, one stationary and the other one portable. The measuring results contain a vast number of different hardness measurement data. From the analyzed data, the conclusions were drawn that the most suitable soaking temperature during post weld heat treatment were 750° C, that the SMAW method creates a more stable hardness profile than the GTAW method, and that one heat treatment cycle is more beneficial than two or more.

The goal of this PhD thesis was to develop dense aluminium compound-cubic boron nitride composites with a high cBN content. To achieve this goal, two different strategies were used: infiltration of cBN preforms and hot pressing of cBN-Al mixtures. The particle size of the cBN and the amount of aluminium were systematically varied and the influence of these parameters on densification and selected properties was evaluated. A basic understanding of the product that was formed over certain temperatures and times provides information that can be used in optimizing the infiltration and hot pressing of cBN with Al. For this reason, the reaction kinetics between Al and cBN was initially investigated. The reaction kinetics of the chemical interactions between Al and cBN was investigated in detail using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The reaction was studied using samples containing 50 volume percent of Al and 50 volume percent of cBN (12 μm) hot pressed at 800 oC. The prepared samples were allowed to react isothermally at temperatures between 1 000 oC and 1 400 oC under nitrogen (N2) and argon (Ar) atmospheres. It was found that the degree and rate of the reactions increased with increasing temperature in both N2 and Ar atmospheres. The degree of aluminium nitride (AlN) formation was considerably higher under N2 than under Ar. The difference in the formation of AlN between the two atmospheres was attributed to the reaction of N2 gas with the sample due to the open porosity. The infiltration of partially hexagonalized cBN matrix with molten Al was studied. The samples were found to have a density higher than 97% of the theoretical density. It was found that the amount of soft hBN phase present in the sample (due to hexagonalization) increases at temperatures higher than 1 300 oC, resulting in a hardness of the final material of Hv10 = 6.5 ± 4.8 GPa. Because of thie poor hardness this route was abandoned. Cubic boron nitride powder (12 μm) without hexagonal boron nitride (hBN) was also infiltrated with aluminium. The infiltrated samples were found to exhibit a density higher than 96% of the theoretical density. The Al reacted with cBN and no hBN was observed at temperatures below 1 400 oC. The resulting product showed a Vickers hardness of Hv10 = 14.4 ± 1.6 GPa compared with Hv10 = 6.5 ± 4.8 GPa obtained with the partially hexagonalized cBN matrix. Infiltration of 3 μm cubic boron nitride increased the Vickers hardness to 22.0 ± 0.6 GPa. However, this infiltration was not very reproducible. Al-cBN cermets were hot pressed at temperatures between 800 oC and 1 750 oC and at a pressure of 50 MPa in vacuum. The effect of the particle size of the starting powders, as well as the effect of the starting compositions and temperature, was investigated. The materials could only densify up to 80 – 92% of the theoretical density. After hot pressing at 800 oC, only Al and cBN could be observed by XRD, whereas higher hot-pressing temperatures resulted in the formation of AlN and AlB2 which retard the densification. The microstructure of the hot-pressed materials was studied using SEM. It was observed that there are oxide layers at the interface between the Al and cBN phases. The presence of these oxide layers prevented the Al from spreading, thereby preventing full densification.

Embora haja grande exigência por restaurações estéticas livres de metal, restaurações metalocerâmicas, cujas subestruturas feitas com ligas de metais básicos, são procedimentos de rotina nos planejamentos restauradores protéticos. No entanto, a alta resistência ao desgaste destas ligas, caracterizada pela grande dificuldade de acabamento e polimento, tem sido associada à dureza, geralmente elevada. A proposta deste estudo foi avaliar resistência à abrasão e dureza de seis ligas de metais básicos (4 ligas de Ni-Cr, 1 liga de Co-Cr e 1 Ti comercialmente puro – 99,5% Ti) disponíveis comercialmente para uso com cerâmica. A resistência à abrasão foi determinada pela perda de peso dos corpos-de-prova, ao longo de 4 séries de ciclos de abrasão. A dureza Rockwell 30N também foi avaliada nos mesmos intervalos. Os dados foram analisados com o nível de significância a = 0,05. O teste de regressão e correlação da resistência à abrasão e dureza mostrou que para 3 ligas de Ni-Cr (Vera Bond, Vera Bond II e Wiron 99) a linha de regressão foi descendente, indicando que um aumento na dureza correspondeu a uma redução nos valores de perda de peso, enquanto para 1 liga de Ni-Cr (Neochrom) a linha de regressão foi ascendente, indicando um aumento nos valores de perda de peso, apesar de um aumento na dureza. Por outro lado, para a ligas de Co-Cr (New Ceram) e de titânio (Rematitan), os valores de perda de peso se mantiveram constantes. As ligas avaliadas tiveram baixos coeficientes de correlação entre resistência à abrasão e dureza. A análise metalográfica revelou particularidades que podem ter sido determinantes para as taxas de desgaste de cada material. Com exceção da liga de titânio, não houve mudanças metalográficas das ligas avaliadas, durante as séries de ciclos de abrasão. / In spite of the demand for metal free restorations, metal ceramic restorations using base metal alloys are routine in prosthodontics. Nevertheless, the high abrasion resistance of base metal alloys, characterized by difficulty in finishing and polishing, has been related to excessive hardness. The purpose of this study was to evaluate abrasion resistance and hardness of six base metal alloys (4 Ni-Cr alloys, 1 Co-Cr alloy and 1 commercially pure Ti alloy – 99.5% Ti) available commercially for use with fused porcelain. Abrasion resistance was determined by specimen weight loss along 4 series of abrasion cycles. The Rockwell 30N hardness was also determined in the same periods. Data were analyzed statistically with the level of significance set at a = 0.05. Regression and correlation analysis of abrasion resistance and hardness showed that for three Ni-Cr alloys (Vera Bond, Vera Bond II and Wiron 99) the regression lines descended indicating that an increase in hardness corresponded to a reduction in weight loss, whereas for one Ni-Cr alloy (Neochrom) the regression line ascended indicating an increase in weight loss in spite of an increase in hardness. On the other hand, for the Co-Cr alloy (New Ceram) and Ti (Rematitan), the weight loss remained constant. The alloys tested had low correlation coefficients between abrasion resistance and hardness. Microscopic analysis showed details that may have been determining for the weight loss rate of each material. With the exception of the titanium alloy, there were no metallographic changes of the alloys tested during the abrasion tests.

Foi estudado o efeito da variação do teor de cromo, em 3%, 6% e 9% em massa, na microestrutura, dureza e oxidação de um ferro fundido branco multicomponente. O Thermo-Calc versão 5 foi a ferramenta utilizada para cálculos termodinâmicos que resultaram na previsão das fases formadas para cada liga. Experimentalmente, foram realizados os seguintes estudos: i) caracterização microestrutural das ligas fundidas com os diferentes teores de cromo na condição bruta de fundição; ii) ensaio de dureza na matriz duplamente revenida em cinco diferentes temperaturas entre 400 °C e 600 °C; e iii) ensaio de termogravimetria em atmosfera controlada de 71,2 % N2 + 17,8 % O2 + 11% H2O, com temperatura constante em 650 °C e por um tempo de 240 minutos. O resultado da caracterização microestrutural permitiu identificar que, com o aumento do teor de cromo, houve aumento da fração volumétrica de carbonetos eutéticos e redução do espaçamento dendrítico secundário. Com as medidas de dureza da matriz após tratamento térmico verificou-se que, independentemente do teor de cromo, o pico de máxima dureza ocorre na temperatura de duplo revenimento de 550°C e, nessa temperatura, a amostra com 9% de cromo exibiu o maior valor de dureza. O ganho de massa das amostras submetidas ao ensaio de termogravimetria foi inversamente proporcional ao aumento de teor de cromo e todas as ligas apresentaram cinética de oxidação parabólica. A caracterização da seção transversal das amostras oxidadas, realizada por meio de um FIB, permitiu identificar, na amostra com 9% de cromo, uma nano camada de óxido de cromo, estrutura decisiva para a menor taxa de oxidação. Os resultados desse estudo permitem concluir que a variação do teor de cromo afeta de maneira significativa a resistência à oxidação, a dureza da matriz e a fração volumétrica de carbonetos eutéticos. / The effect of chromium variation, 3%, 6% and 9% Cr in mass in the microstructure, hardness and oxidation of a Multicomponent White Cast Iron was studied. The Thermo-Calc software version 5 was the tool used for thermodynamic calculations to predict the phases formed for each alloy. Experimentally, the following studies were carried out: i) microstructure characterization of the as cast alloys with the different chromium contents, ii) hardness test in the double tempered matrix at five different temperature between 400°C and 600° and iii) themogravimetric test with steam atmosphere composed of 71,2 % N2 + 17,8 % O2 + 11% H2O at constant temperature of 650° for 240 minutes. The result of the microstructure characterization allowed to observe that with increasing chromium content, there was an increase in the volume fraction of eutectic carbides and a reduction of the secondary dendritic spacing. Independently of the chromium content, a maximum hardness was observed always for double tempered at 550°C and the alloy with 9% of chromium exhibited the highest hardness average value. The final weight gain was inversely proportional to the increase in chromium content and all alloys showed parabolic oxidation kinetics. The alloy with 9% Cr showed the lowest final mass gain and the surface characterization of the sample after oxidation was carried out and the cross section of the sample was performed by FIB and was observed the formation of a nano-oxide layer on the alloy surface with 9% Cr. The results of this study leads to the conclusion that the chromium content variation significantly affects the oxidation resistance, the final hardness of the matrix and the volume fraction of eutectic carbides.

Este trabalho apresenta uma metodologia experimental para investigar a relação entre taxas de desgaste abrasivo e dureza. Investigam-se os regimes moderado e severo de desgaste abrasivo em função da razão entre a dureza do abrasivo (HA) e a dureza do material desgastado (H). Foram realizados ensaios pino contra lixa, utilizando vidro como abrasivo em dois tamanhos, grana #80 e grana #240, e pinos com 3 mm de diâmetro sob força de 20 N. Os materiais ensaiados foram os aços AISI 1006 e AISI 52100, este último em diferentes condições metalúrgicas, e um ferro fundido branco de alto cromo, de composição eutética e matriz perlítica. Três tipos de resposta do sistema tribológico foram utilizadas para avaliar os regimes de desgaste: perda de massa, coeficiente de atrito e força de penetração do abrasivo. Determinaram-se as perdas de massa ao longo dos ensaios; o coeficiente de atrito medido por meio de célula de carga e a força de penetração com o uso de ensaios instrumentados de dureza estimando-se a profundidade máxima de penetração com base no parâmetro Rz. A partir das medidas de dureza, foi utilizado um parâmetro para incorporar os efeitos do comportamento elasto-plástico dos materiais, que considera a morfologia de impressão de dureza. Com este parâmetro, foi possível obter uma dureza denominada \"verdadeira\", que incorpora os efeitos de formação de bordas ou retração dos materiais. Verificou-se que os valores de resistência ao desgaste relativa não dependem do tamanho do abrasivo, mas que os valores de coeficiente de atrito dependem, sob regime severo de desgaste. Por sua vez, no regime moderado, os valores de coeficiente de atrito são independentes do tamanho do abrasivo. / This work presents an experimental methodology to investigate the relationship between abrasive wear rates and hardness. The mild and severe abrasive wear regimes are investigated in relation to the abrasive hardness-to-worn material hardness ratio (HA/H). Pin-against-paper tests were performed, using glass as abrasive material in two grain sizes, grit #80 and grit #240, and 3-mm diameter pins under 20 N of applied load. The tested materials were AISI 1006 e AISI 52100 steels, the last one in different metallurgical conditions, and a high-chromium white cast iron, with eutetic composition and pearlitic matrix. Three kinds of tribological system responses were used to evaluate the wear regimes: mass loss, friction coefficient and load of penetration of abrasive. Mass losses were determined along testing time; friction coefficient was determined by means of load cell and the load of penetration using instrumented hardness test, selecting the maximum depth penetration based on the Rz roughness parameter. From hardness measurements, a parameter was used to incorporate the elastic-plastic behavior of materials, which consider the indentation hardness morphology. Using this parameter, it was possible to obtain a kind of hardness called \"true\", which incorporate the pilling-up and sinking-in effects. It has been demonstrated that the relative abrasive resistance is not dependent of the abrasive particle size, but the friction coefficient values change, under severe wear regime. On the other hand, under mild regime, the friction coefficient values are independent of the abrasive particle size.

Este trabalho avalia as propriedades mecânicas, microestrutura resultante e força de estampagem da liga DIN 27MnCrB5 para o processo de estampagem a quente nas temperaturas de aquecimento de 750°C, 850°C e 950°C. Para isso foram realizados ensaios nas três temperaturas e medidos os valores da força necessária para a estampagem da chapa, que foi aplicada em uma área de 30mm x 1,50mm. A partir da peça estampada foram realizadas análises metalográficas da microestrutura resultante e medições de dureza para a correlação com as propriedades mecânicas. Para as temperaturas de aquecimento de 750°C e 850°C não foi verificada microestrutura martensítica nas peças estampadas. Para o ensaio realizado com uma temperatura de aquecimento de 950°C ocorreu transformação martensítica na peça na região que esteve em contato com o prensa chapa e a matriz. Esta transformação metalúrgica resultou em valores de dureza de 715±17HV0,2 em comparação com a condição inicial da chapa, cuja dureza era de 187±5HV0,2. As medições de força de estampagem para as três temperaturas de ensaio indicam uma redução da força com o aumento da temperatura de aquecimento da chapa. Para a temperatura de aquecimento da chapa de 750°C o valor médio da força de estampagem foi de 14kN, para a temperatura de 850°C o valor médio da força de estampagem foi de 9kN, enquanto para a temperatura de 950°C foi encontrado o valor médio de 5kN. / This work evaluates the mechanical properties, resulting microstructure and stamping force of the DIN 27MnCrB5 alloy for the hot stamping process at the heating temperatures of 750°C, 850°C and 950°C. For this, tests were carried out at the three temperatures and the values of the force required for the stamping of the sheet were measured, which was applied in an area of 30mm x 1,50mm. From the stamped part metallographic analyzes of the resulting microstructure and hardness measurements were performed for the correlation with the mechanical properties. For the heating temperatures of 750°C and 850°C, no martensitic microstructure was observed in the stamped parts. For the test performed with a heating temperature of 950°C martensitic transformation occurred in the part in the region that was in contact with the blank holder and the die. This metallurgical transformation resulted in hardness values of 715±17HV0,2 compared to the initial condition of the sheet, whose hardness was 187±5HV0,2. Stamping force measurements for the three test temperatures indicate a reduction in force with the increase of the sheet heating temperature. For the sheet heating temperature of 750°C the average value of the stamping force was 14kN, at the temperature of 850°C the average value of the stamping force was 9kN, while at the temperature of 950°C it was found The average value of 5kN.