The Experts below are selected from a list of 78 Experts worldwide ranked by ideXlab platform
I. Konyashin - One of the best experts on this subject based on the ideXlab platform.
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Cobalt Capping on WC–Co hard metals. Part II: A technology for fabrication of Co coated articles during sintering
International Journal of Refractory Metals and Hard Materials, 2014Co-Authors: I. Konyashin, S. Hlawatschek, B. Ries, F. Lachmann, Milos VukovicAbstract:Abstract The formation of cobalt layers on a surface of articles during sintering is designated in literature as “cobalt Capping”. Although the cobalt Capping Phenomenon is discussed in literature, its mechanism is not well understood and there is no information on its technological implementations. A new mechanism explaining the presence or absence of cobalt layers on hard metal articles during sintering was proposed in part 1 of this paper. The understanding of the Co Capping Phenomenon allowed us to develop a new technology for the fabrication of Co coated hard metal articles during sintering. The technology permits the formation of continuous, ductile and defect-free Co coatings on the surface of different hard metal grades. As a result, the transverse rupture strength of unground hard metal articles is significantly increased and that of ground articles is also improved due to “healing” surface defects by the Co coatings. The fracture toughness and wettability by braze alloys of the surface of WC–Co articles are also dramatically improved due to the presence of the Co coatings.
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Cobalt Capping on WC–Co hardmetals. Part I: A mechanism explaining the presence or absence of cobalt layers on hardmetal articles during sintering
International Journal of Refractory Metals and Hard Materials, 2014Co-Authors: I. Konyashin, S. Hlawatschek, B. Ries, F. Lachmann, Milos VukovicAbstract:Abstract A reason for the presence or absence of Co thin layers on a surface of WC–Co hardmetals during sintering has been a riddle for a long time. As a result of sintering, such thin shiny Co layers are sometimes present on the surface of WC–Co articles and their formation is referred to as “Co Capping” in the literature. Although the cobalt Capping Phenomenon is discussed in the literature, its mechanism is not well understood and there is no information on its technological implementations. Here we propose a new mechanism explaining the presence or absence of cobalt layers on hardmetal articles during sintering. The proposed mechanism is based on considering wetting phenomena of WC by liquid Co on the surface of hardmetal articles and capillarity phenomena acting on the liquid Co in narrow channels between WC grains in the hardmetal near-surface layer. The mechanism explains all the phenomena of the Co layer formation during sintering of various hardmetal grades followed by either fast or slow cooling.
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Engineered surfaces on cemented carbides obtained by tailored sintering techniques
Surface and Coatings Technology, 2014Co-Authors: I. Konyashin, B. Ries, S. HlawatschekAbstract:Abstract The paper consists of three parts. In the first part, functionally graded cemented carbides comprising hard surface layers with low Co contents are described. Such surface layers form as a result of a tailored sintering technique based on the selective carburization of the near-surface layer of carbide green bodies with original low carbon contents and consequent liquid-phase sintering, which leads to Co drifts from the surface towards the core during sintering. This novel sintering technique allows obtaining Co gradients between the surface layer and the core of carbide articles of up 7 wt.%. As a result of significantly different contraction rates between the near-surface layer and the core of such functionally gradient cemented carbides, high residual compression stresses are created in the carbide near-surface layer. This leads to a dramatically increased combination of both hardness and fracture toughness of the near-surface layer. The presence of the hard and tough surface layers on the novel functionally gradient carbides results in their significantly improved wear-resistance and prolonged tool lifetime in mining applications. In the second part of the paper, functionally graded cemented carbides comprising surface layers with high Co contents are described. They are fabricated by a tailored sintering technique based on the selective de-carburization of the near-surface layer of carbide green bodies with original high carbon contents resulting in Co drifts from the core towards the surface during the consequent stage of liquid-phase sintering. Such functionally graded cemented carbides are successfully employed as substrates for poly-crystalline diamond (PCD) layers. In the third part of the paper, a mechanism of formation of thin Co films on the surface of carbide articles during sintering, which is designated in literature as “Co Capping”, is briefly described. On the basis of understanding the mechanism of the Co Capping Phenomenon, an industrial technology for obtaining such thin Co films on the surface of carbide articles during sintering was developed. The wettability of non-ground carbide articles by braze alloys is dramatically improved by use of the thin Co films, resulting in better quality of various brazed wear parts and tools.
Nofrerias Roig Isaac - One of the best experts on this subject based on the ideXlab platform.
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Aplicació de la simulació de compressió a l’estudi del comportament i optimització de comprimits elaborats per compressió directa utilitzant el sistema expert SeDeM
'Edicions de la Universitat de Barcelona', 2019Co-Authors: Nofrerias Roig IsaacAbstract:[cat] El comprimit és la forma farmacèutica més freqüent al mercat. El procés tecnològic d’elaboració de comprimits d’elecció és la compressió directa perquè permet un estalvi en el nombre d’etapes. Tanmateix, aquest procés requereix que les pólvores presentin unes característiques adequades per la compressió per se. La necessitat de dissenyar ràpidament una fórmula farmacèutica que compleixi els estàndards de compressió i l’escalat a producció industrial, ha portat a la creació de sistemes experts i simuladors de compressió. En la present tesis, s’optimitza el sistema expert de diagrama SeDeM i es contrasta amb compressions industrials amb el simulador Styl’One. En primer lloc, es proposa una modificació en la metodologia per la determinació del paràmetre de l’Índex de cohesivitat del diagrama SeDeM, l’únic paràmetre que té en compte la compactabilitat de la mescla. Aquest paràmetre presentava desviacions per les mescles pulverulentes amb una densitat aparent molt elevada o molt baixa. També s’augmenta el nombre de paràmetres del SeDeM, afegint dos paràmetres mecànics en relació a la lubrificació. Aquests paràmetres són el punt de fusió (Mp) i la força d’ejecció (Fe). Els resultats del sistema expert de diagrama SeDeM són contrastats amb els resultats de compressió en condicions industrials. Cinc formulacions diferents es comprimeixen sota diferents perfils de compressió utilitzant un simulador de compressió industrial Styl’One. Els resultats indiquen que un ajust del pes del comprimit en funció de la densitat aparent de la pólvora permet la obtenció de comprimits de dimensions similars, evitant les desviacions esmentades. Fet demostrat en el desenvolupament d’una formulació la comparació de cel·luloses microcristal·lines de diferents fabricants i graus o tipus. També s’ha establert una metodologia ràpida i accessible per la determinació dels dos nous paràmetres mecànics i una conversió del valor experimental al valor radi. Fet que permet la seva integració en el sistema SeDeM. Els dos paràmetres integrats han demostrat tenir una rellevància en els resultats de la compressió i han permès augmentar el valor de l’índex de fiabilitat del SeDeM. Finalment, tres fórmules dissenyades per compressió directa i dues per granulació via humida es comprimeixen amb l’Styl’One simulant diferents perfils de compressió (Korsch XL 400, Fette 2909, Fette 3100, Kilian RX 47 i Kilian S 250) de màquines de comprimir rotatòries sota condicions de compressió diferents. Els resultats de la compressió demostren la precisió dels resultats previs obtinguts en els diagrames SeDeM i indiquen una relació entre valors deficients per l’Índex de Carr i l’Índex d’esponjositat i problemes d’exfoliació durant la compressió. L’addició d’una força de precompressió permet solucionar els problemes d’exfoliació en la majoria de les Referències. Els resultats indiquen que les referències desenvolupades per compressió directa presenten uns resultats equiparables o superiors a les referències per granulació via humida, amb un impacte econòmic menor (temps i costos) en el seu desenvolupament. En conclusió, s’ha optimitzat el sistema SeDeM, corregint desviacions i augmentant l’índex de fiabilitat. El simulador de compressió Styl’One ha posat de manifest la precisió i robustesa del sistema SeDeM en la selecció de la formulació més òptima i permet seleccionar les condicions de compressió més òptimes, maximitzar l’eficiència del procés i facilitar l’escalat.[eng] Tablets are the most common solid oral dosage forms. Direct Compression (DC) is a good methodology due to its low manufacturing times and a reduced number of steps. However, this methodology requires powders which display adequate properties in order to be compressible. The need of a swift design of pharmaceutical formulations which fulfill the compression standards and the scale-up led to create expert systems and press simulators. In this thesis, the expert system SeDeM is optimized: a new methodology to determine the Cohesion Index is stablished and two new mechanical parameters are introduced (Melting point and Ejection Force). Then, the results obtained from the SeDeM diagram are compared against the results obtained from the Styl’ONE press simulator in simulated industrial conditions. The results indicates that the new methodology is more accurate and it has been demonstrated in the development of a formula, and the comparison of different Microcrystalline Celluloses from different manufacturers. The inclusion of the two new mechanical parameters has increased the SeDeM’s reliability index. Then, three formulas developed by DC and two developed by wet granulation were compressed by means of Styl’One press simulator. Five different rotatory press’ compression profiles were simulated (Korsch XL 400, Fette 2090, Fette 3100, Kilian RX 47 I Kilian S 250) under different compression conditions. The results show the accuracy of SeDeM system and seems to indicate a correlation between Carr’s Index and Inter particle porosity Index, low radius values and Capping Phenomenon during the compression process. These issues where solved by applying a pre-compression force. Moreover, the DC formulas display results similar or higher than the wet granulation formulas. In conclusion, the SeDeM expert system has been optimized, correcting the Cohesion Index deviations and increasing the reliability index by adding two mechanical parameters. The Styl’One press simulator has enabled to highlight the SeDeM system’s accuracy and robustness on choosing the most optimal formulation as well as the most optimal compression conditions in order to maximize the process’ efficiency and the scale-up
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Aplicació de la simulació de compressió a l’estudi del comportament i optimització de comprimits elaborats per compressió directa utilitzant el sistema expert SeDeM
'Edicions de la Universitat de Barcelona', 2019Co-Authors: Nofrerias Roig IsaacAbstract:El comprimit és la forma farmacèutica més freqüent al mercat. El procés tecnològic d’elaboració de comprimits d’elecció és la compressió directa perquè permet un estalvi en el nombre d’etapes. Tanmateix, aquest procés requereix que les pólvores presentin unes característiques adequades per la compressió per se. La necessitat de dissenyar ràpidament una fórmula farmacèutica que compleixi els estàndards de compressió i l’escalat a producció industrial, ha portat a la creació de sistemes experts i simuladors de compressió. En la present tesis, s’optimitza el sistema expert de diagrama SeDeM i es contrasta amb compressions industrials amb el simulador Styl’One. En primer lloc, es proposa una modificació en la metodologia per la determinació del paràmetre de l’Índex de cohesivitat del diagrama SeDeM, l’únic paràmetre que té en compte la compactabilitat de la mescla. Aquest paràmetre presentava desviacions per les mescles pulverulentes amb una densitat aparent molt elevada o molt baixa. També s’augmenta el nombre de paràmetres del SeDeM, afegint dos paràmetres mecànics en relació a la lubrificació. Aquests paràmetres són el punt de fusió (Mp) i la força d’ejecció (Fe). Els resultats del sistema expert de diagrama SeDeM són contrastats amb els resultats de compressió en condicions industrials. Cinc formulacions diferents es comprimeixen sota diferents perfils de compressió utilitzant un simulador de compressió industrial Styl’One. Els resultats indiquen que un ajust del pes del comprimit en funció de la densitat aparent de la pólvora permet la obtenció de comprimits de dimensions similars, evitant les desviacions esmentades. Fet demostrat en el desenvolupament d’una formulació la comparació de cel·luloses microcristal·lines de diferents fabricants i graus o tipus. També s’ha establert una metodologia ràpida i accessible per la determinació dels dos nous paràmetres mecànics i una conversió del valor experimental al valor radi. Fet que permet la seva integració en el sistema SeDeM. Els dos paràmetres integrats han demostrat tenir una rellevància en els resultats de la compressió i han permès augmentar el valor de l’índex de fiabilitat del SeDeM. Finalment, tres fórmules dissenyades per compressió directa i dues per granulació via humida es comprimeixen amb l’Styl’One simulant diferents perfils de compressió (Korsch XL 400, Fette 2909, Fette 3100, Kilian RX 47 i Kilian S 250) de màquines de comprimir rotatòries sota condicions de compressió diferents. Els resultats de la compressió demostren la precisió dels resultats previs obtinguts en els diagrames SeDeM i indiquen una relació entre valors deficients per l’Índex de Carr i l’Índex d’esponjositat i problemes d’exfoliació durant la compressió. L’addició d’una força de precompressió permet solucionar els problemes d’exfoliació en la majoria de les Referències. Els resultats indiquen que les referències desenvolupades per compressió directa presenten uns resultats equiparables o superiors a les referències per granulació via humida, amb un impacte econòmic menor (temps i costos) en el seu desenvolupament. En conclusió, s’ha optimitzat el sistema SeDeM, corregint desviacions i augmentant l’índex de fiabilitat. El simulador de compressió Styl’One ha posat de manifest la precisió i robustesa del sistema SeDeM en la selecció de la formulació més òptima i permet seleccionar les condicions de compressió més òptimes, maximitzar l’eficiència del procés i facilitar l’escalat.Tablets are the most common solid oral dosage forms. Direct Compression (DC) is a good methodology due to its low manufacturing times and a reduced number of steps. However, this methodology requires powders which display adequate properties in order to be compressible. The need of a swift design of pharmaceutical formulations which fulfill the compression standards and the scale-up led to create expert systems and press simulators. In this thesis, the expert system SeDeM is optimized: a new methodology to determine the Cohesion Index is stablished and two new mechanical parameters are introduced (Melting point and Ejection Force). Then, the results obtained from the SeDeM diagram are compared against the results obtained from the Styl’ONE press simulator in simulated industrial conditions. The results indicates that the new methodology is more accurate and it has been demonstrated in the development of a formula, and the comparison of different Microcrystalline Celluloses from different manufacturers. The inclusion of the two new mechanical parameters has increased the SeDeM’s reliability index. Then, three formulas developed by DC and two developed by wet granulation were compressed by means of Styl’One press simulator. Five different rotatory press’ compression profiles were simulated (Korsch XL 400, Fette 2090, Fette 3100, Kilian RX 47 I Kilian S 250) under different compression conditions. The results show the accuracy of SeDeM system and seems to indicate a correlation between Carr’s Index and Inter particle porosity Index, low radius values and Capping Phenomenon during the compression process. These issues where solved by applying a pre-compression force. Moreover, the DC formulas display results similar or higher than the wet granulation formulas. In conclusion, the SeDeM expert system has been optimized, correcting the Cohesion Index deviations and increasing the reliability index by adding two mechanical parameters. The Styl’One press simulator has enabled to highlight the SeDeM system’s accuracy and robustness on choosing the most optimal formulation as well as the most optimal compression conditions in order to maximize the process’ efficiency and the scale-up
Milos Vukovic - One of the best experts on this subject based on the ideXlab platform.
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Cobalt Capping on WC–Co hard metals. Part II: A technology for fabrication of Co coated articles during sintering
International Journal of Refractory Metals and Hard Materials, 2014Co-Authors: I. Konyashin, S. Hlawatschek, B. Ries, F. Lachmann, Milos VukovicAbstract:Abstract The formation of cobalt layers on a surface of articles during sintering is designated in literature as “cobalt Capping”. Although the cobalt Capping Phenomenon is discussed in literature, its mechanism is not well understood and there is no information on its technological implementations. A new mechanism explaining the presence or absence of cobalt layers on hard metal articles during sintering was proposed in part 1 of this paper. The understanding of the Co Capping Phenomenon allowed us to develop a new technology for the fabrication of Co coated hard metal articles during sintering. The technology permits the formation of continuous, ductile and defect-free Co coatings on the surface of different hard metal grades. As a result, the transverse rupture strength of unground hard metal articles is significantly increased and that of ground articles is also improved due to “healing” surface defects by the Co coatings. The fracture toughness and wettability by braze alloys of the surface of WC–Co articles are also dramatically improved due to the presence of the Co coatings.
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Cobalt Capping on WC–Co hardmetals. Part I: A mechanism explaining the presence or absence of cobalt layers on hardmetal articles during sintering
International Journal of Refractory Metals and Hard Materials, 2014Co-Authors: I. Konyashin, S. Hlawatschek, B. Ries, F. Lachmann, Milos VukovicAbstract:Abstract A reason for the presence or absence of Co thin layers on a surface of WC–Co hardmetals during sintering has been a riddle for a long time. As a result of sintering, such thin shiny Co layers are sometimes present on the surface of WC–Co articles and their formation is referred to as “Co Capping” in the literature. Although the cobalt Capping Phenomenon is discussed in the literature, its mechanism is not well understood and there is no information on its technological implementations. Here we propose a new mechanism explaining the presence or absence of cobalt layers on hardmetal articles during sintering. The proposed mechanism is based on considering wetting phenomena of WC by liquid Co on the surface of hardmetal articles and capillarity phenomena acting on the liquid Co in narrow channels between WC grains in the hardmetal near-surface layer. The mechanism explains all the phenomena of the Co layer formation during sintering of various hardmetal grades followed by either fast or slow cooling.
S. Hlawatschek - One of the best experts on this subject based on the ideXlab platform.
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Cobalt Capping on WC–Co hard metals. Part II: A technology for fabrication of Co coated articles during sintering
International Journal of Refractory Metals and Hard Materials, 2014Co-Authors: I. Konyashin, S. Hlawatschek, B. Ries, F. Lachmann, Milos VukovicAbstract:Abstract The formation of cobalt layers on a surface of articles during sintering is designated in literature as “cobalt Capping”. Although the cobalt Capping Phenomenon is discussed in literature, its mechanism is not well understood and there is no information on its technological implementations. A new mechanism explaining the presence or absence of cobalt layers on hard metal articles during sintering was proposed in part 1 of this paper. The understanding of the Co Capping Phenomenon allowed us to develop a new technology for the fabrication of Co coated hard metal articles during sintering. The technology permits the formation of continuous, ductile and defect-free Co coatings on the surface of different hard metal grades. As a result, the transverse rupture strength of unground hard metal articles is significantly increased and that of ground articles is also improved due to “healing” surface defects by the Co coatings. The fracture toughness and wettability by braze alloys of the surface of WC–Co articles are also dramatically improved due to the presence of the Co coatings.
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Cobalt Capping on WC–Co hardmetals. Part I: A mechanism explaining the presence or absence of cobalt layers on hardmetal articles during sintering
International Journal of Refractory Metals and Hard Materials, 2014Co-Authors: I. Konyashin, S. Hlawatschek, B. Ries, F. Lachmann, Milos VukovicAbstract:Abstract A reason for the presence or absence of Co thin layers on a surface of WC–Co hardmetals during sintering has been a riddle for a long time. As a result of sintering, such thin shiny Co layers are sometimes present on the surface of WC–Co articles and their formation is referred to as “Co Capping” in the literature. Although the cobalt Capping Phenomenon is discussed in the literature, its mechanism is not well understood and there is no information on its technological implementations. Here we propose a new mechanism explaining the presence or absence of cobalt layers on hardmetal articles during sintering. The proposed mechanism is based on considering wetting phenomena of WC by liquid Co on the surface of hardmetal articles and capillarity phenomena acting on the liquid Co in narrow channels between WC grains in the hardmetal near-surface layer. The mechanism explains all the phenomena of the Co layer formation during sintering of various hardmetal grades followed by either fast or slow cooling.
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Engineered surfaces on cemented carbides obtained by tailored sintering techniques
Surface and Coatings Technology, 2014Co-Authors: I. Konyashin, B. Ries, S. HlawatschekAbstract:Abstract The paper consists of three parts. In the first part, functionally graded cemented carbides comprising hard surface layers with low Co contents are described. Such surface layers form as a result of a tailored sintering technique based on the selective carburization of the near-surface layer of carbide green bodies with original low carbon contents and consequent liquid-phase sintering, which leads to Co drifts from the surface towards the core during sintering. This novel sintering technique allows obtaining Co gradients between the surface layer and the core of carbide articles of up 7 wt.%. As a result of significantly different contraction rates between the near-surface layer and the core of such functionally gradient cemented carbides, high residual compression stresses are created in the carbide near-surface layer. This leads to a dramatically increased combination of both hardness and fracture toughness of the near-surface layer. The presence of the hard and tough surface layers on the novel functionally gradient carbides results in their significantly improved wear-resistance and prolonged tool lifetime in mining applications. In the second part of the paper, functionally graded cemented carbides comprising surface layers with high Co contents are described. They are fabricated by a tailored sintering technique based on the selective de-carburization of the near-surface layer of carbide green bodies with original high carbon contents resulting in Co drifts from the core towards the surface during the consequent stage of liquid-phase sintering. Such functionally graded cemented carbides are successfully employed as substrates for poly-crystalline diamond (PCD) layers. In the third part of the paper, a mechanism of formation of thin Co films on the surface of carbide articles during sintering, which is designated in literature as “Co Capping”, is briefly described. On the basis of understanding the mechanism of the Co Capping Phenomenon, an industrial technology for obtaining such thin Co films on the surface of carbide articles during sintering was developed. The wettability of non-ground carbide articles by braze alloys is dramatically improved by use of the thin Co films, resulting in better quality of various brazed wear parts and tools.
Berhane Dashew - One of the best experts on this subject based on the ideXlab platform.
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Studies on the arrangement of glucocorticoid receptors in the plasma membrane of S-49 lymphoma cells
Steroids, 1991Co-Authors: Bahiru Gametchu, Cheryl S. Watson, Charles C.-y. Shih, Berhane DashewAbstract:Abstract The presence of glucocorticoid receptors is required for glucocorticoid-mediated lymphocytolysis to take place. However, the explicit mechanism of involvement of this receptor continues to be debated. We have recently presented evidence that this response is mediated by a specialised form of the glucocorticoid receptor that resides in the plasma membrane (mGR). Using sequential cell separation techniques (“immunopanning,” fluorescent cell sorting, and soft agar cloning), a resultant population of membrane receptor-enriched cells have remained stable and provided material for further analysis. The mGR patching and Capping Phenomenon originally observed with fluoresceinated monoclonal antibody techniques was verified here with electron micrographic analysis using colloidal gold-conjugated antibody. Using 3H-labeled monoclonal antibody, a radioimmunoassay for membrane receptors was developed. Trypsin treatment removed the membrane receptor antigenic site from the surface of cells. Peptide mapping of receptor purified from plasma membranes reveals several trypsin and α-chymotrypsin cleavage sites. Larger fragments resulted from cleavage of the membrane receptor of cells enriched for mGR versus those found in cells depleted of the membrane form, although most of the resulting fragments are shared by the two forms. Confirmation of previous studies correlating membrane receptor with the mechanism of glucocorticoid sensitivity is now extended to include elimination of the lymphocytolysis effect in membrane receptor-stripped (trypsinized) S-49 cells. (Steroids 56:411–419, 1991)
