| 1. |
- Perez-Estébanez, Marta, et al.
(författare)
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SPS driven lithium differential diffusion in NASICON-like structures
- 2016
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Ingår i: Boletín de la Sociedad Espanola de Ceramica y Vidrio. - : Elsevier BV. - 0366-3175 .- 2173-0431. ; 55:1, s. 38-44
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Tidskriftsartikel (refereegranskat)abstract
- Samples of nominal composition Li1.3Fe0.3Ti1.7(PO4)(3) with a NASICON-type crystal structure, can be sintered up to 95% of the theoretical density at only 600 degrees C using spark plasma sintering, SPS. The final pellets however show different colouration in their upper and lower faces, being the upper face white and the lower one pink. The analysis of both surfaces by XPS shows a higher concentration of lithium on the white upper face, as a consequence of the polar diffusion of ions from the positive to the negative rams during SPS. On the other hand the study by XRD and SEM shows the formation of an extra phase in the upper face with nominal composition LiOPO4. A change in the cell parameters of the original NASICON structure is also observed, confirming the diffusion of lithium ions.
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| 2. |
- Sommarlund, Petra, et al.
(författare)
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En fungerande måltid – innovation mot undernäring : slutrapport - utmaningsdriven innovation steg 1, initiering, hösten 2016
- 2016
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Det övergripande syftet med projektet "En fungerande måltid - innovation mot undernäring" är att förebygga undernäring bland äldre genom ett holistiskt grepp av måltidssituationen. Fokus är att utveckla en mätmetod för att identifiera risker för fel- och undernäring på verksamhets- samt individnivå, samt att rekommendera åtgärder som minimerar riskerna. Visionen är ett samhälle där måltidssituationens alla beståndsdelar är så välfungerande att undernäring inte längre är ett problem inom omsorg och sjukvård. Runt detta har byggts tjänster och produkter som skapat tillväxt i Sverige. Det finns en stor potential för detta. I initieringsprojektet har fokus legat på måltidssituationen på äldreboenden (särskilt boende). Projektet har arbetat tillsammans med två demensboenden samt genomfört två tvärfunktionella workshops, för att skapa förståelse för måltidssituationen, vilka problem som finns, hur de skulle kunna mätas och åtgärdas samt vilka aktiviteter som sker på boendet i relation till måltidssituationen. Risken för undernäring är allra högst bland äldre som bor i ordinärt boende, dvs hemma i sin egen bostad med eller utan hemtjänst. Därmed ämnar projektet i steg 2 inkludera denna boendeform parallellt med särskilt boende och utveckla stöd både för den äldre själv, hens anhöriga samt hemtjänstpersonal och omsorgspersonal på boendet. Den rekommenderade lösningen är ett digitalt verktyg för äldre, anhöriga och personal att logga och följa verksamhetens kvalitet i måltidssituation samt individens näringsstatus och som också ger åtgärder för ökad kvalitet och förbättrad näringsstatus. Projektet har letts från SP Sveriges Tekniska Forskningsinstitut, enheten Mätteknik, och haft deltagare från Bestic AB, Högskolan Kristianstad, SP Food and BioScience, SP Service Labs samt två stycken boenden i privat drift; Soltorp från Förenade Care och Ribbingsbacke från Temabo. Både Soltorp och Ribbingsbacke har 32 demensplatser. Soltorp har utöver detta en korttidsavdelning med 9 platser och Ribbingsbacke har en somatisk avdelningmed 16 platser. För att driva projektet framåt planeras inkludering av hemtjänstverksamhet, kommunal omsorg, tillagningskök samt tillverkare av lösningar för hur måltidssituationen kan förbättras inklusive personalutbildning. Synergieffekter med nätverket Måltid Sverige som verkar för den offentliga måltiden förväntas i att spridas kunskap i samhället om måltidens viktiga roll i relation till vår hälsostatus.
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| 3. |
- Perez-Estebanez, M., et al.
(författare)
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Spark plasma versus conventional sintering in the electrical properties of Nasicon-type materials
- 2015
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 651, s. 636-642
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Tidskriftsartikel (refereegranskat)abstract
- Li1+xMxTi2-x(PO4)(3) powders with x = 0 and 0.3 and M = Al, Cr and Fe have been sintered by conventional sintering (CS) and Spark Plasma Sintering (SPS), and the electrical properties have been compared. The use of SPS allows preparing samples with higher density at lower temperature and shorter time than the CS, avoiding segregation of secondary phases and with reduced crystallite size. The introduction of aluminum, chromium and iron in the LiTi2(PO4)(3) (LTP) clearly enhances ionic conductivity even if the samples have similar densities. Despite the different level of density reached with CS and SPS, the activation energies of dc and grain boundary contributions are very similar and the differences in ionic conductivity are determined by pre-exponential factors. The samples produced by SPS showed a well-defined grain boundary meaning a more homogenous electrical contact.
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| 4. |
- Liu, Yi, et al.
(författare)
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Micro-hydrothermal reactions mediated grain growth during spark plasma sintering of a carbonate-containing hydroxyapatite nanopowder
- 2014
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 34:16, s. 4395-4401
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Tidskriftsartikel (refereegranskat)abstract
- A carbonate-containing hydroxyapatite nanopowder was consolidated by spark plasma sintering at the temperatures ranging from 650 to 1100 degrees C. It was found that the water released by dehydroxylation was trapped inside the nanopores in the densified HAp bodies over 900 degrees C. Based on the analysis by the X-ray diffraction, Fourier-transform infrared spectrometry and scanning electron microscope, the water-nanopore system was evaluated and its effect on the grain growth was also investigated. It was revealed that the water existed inside the closed nanopores most probably resulted in the formation of local micro-hydrothermal environments inside bulk HAp ceramics during SPS. Therefore, the grain growth was enhanced by the local micro-hydrothermal reactions activated above 900 degrees C. In addition, abnormal grain growth was also observed when a higher temperature or higher heating rate was employed, which may be attributed to the local highly active hydrothermal reactions.
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| 5. |
- Ortiz, Angel L., et al.
(författare)
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Improving the sliding wear resistance of SiC nanoceramics fabricated by spark plasma sintering via gentle post-sintering annealing
- 2014
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Ingår i: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 77, s. 9-12
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Tidskriftsartikel (refereegranskat)abstract
- Experimental evidence is presented for the improvement of the sliding wear resistance of an SiC nanoceramic processed by spark plasma sintering (SPS) with post-sintering annealing. It is inferred that gentle annealing without nanograin growth strengthens the grain boundaries induced by the ultrarapid nature of SPS, and the consequent improvement in grain cohesion delays the onset of the severe-wear regime without affecting the rates of mild and severe wear. Implications for the fabrication of highly wear-resistant nanoceramics are discussed.
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| 6. |
- Suarez, M., et al.
(författare)
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Analysis of the upconversion processes of Nd3+ ions in transparent YAG ceramics
- 2014
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 40:10, s. 15951-15956
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Tidskriftsartikel (refereegranskat)abstract
- Optical properties of Nd3+ ions in YAG transparent ceramics have been analysed. The samples were prepared by a high temperature (1650 and 1680 degrees C) sintering followed by hot isostatic pressing (HIP) at 1650 or 1700 degrees C in order to obtain a well-homogeneous diffusion of the ions and functional transparency. The emission and luminescence decay curves from the F-4(3/2) metastable laser level of these samples are very similar to the ones obtained on crystal samples grown with the Czochralski method. However, excitation upconversion spectra obtained detecting at 590 nm for the transparent ceramic samples present important differences compared to the bulk YAG crystal, which can be explained by a change in the upconversion mechanism involved and the different arrangements of the Nd3+ ions in the YAG matrix. The analysis of the upconversion excitation spectra is shown to be a good method to detect the differences between the positions occupied by the Nd3+ ions in different matrices.
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| 7. |
- Zamora, Victor, et al.
(författare)
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Effect of graphite addition on the spark-plasma sinterability of ZrB2 and ZrB2-SiC ultra-high-temperature ceramics
- 2014
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 40:7, s. 11457-11464
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Tidskriftsartikel (refereegranskat)abstract
- The effect of a 2 wt% addition of particulate graphite on the spark-plasma sintering (SPS) kinetics of both ZrB2 and ZrB2+30 vol% SiC was investigated using to that end two broad sets of powder mixtures prepared by high-energy co-ball-milling. It was observed that the particulate graphite addition enhances the SPS kinetics of both systems, and it was identified that, contrary to the case in conventional sintering, this improvement in sinterability is not due to the carbothermal reduction of oxides in situ during SPS but to the lubrication imposed by the graphite flakes inducing a greater green-body densification. Consequently, the graphite is not consumed during SPS but remains in the microstructure of the resulting ultra-high-temperature ceramics (UHTCs) as flaky particles dispersed homogeneously at grain boundaries. Implications of interest for the UHTC community are discussed.
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| 8. |
- Ciudad, Esther, et al.
(författare)
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Sliding-wear resistance of ultrafine-grained SiC densified by spark plasma sintering with 3Y(2)O(3)+5Al(2)O(3) or Y3Al5O12 additives
- 2013
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Ingår i: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 69:8, s. 598-601
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Tidskriftsartikel (refereegranskat)abstract
- The sliding-wear behavior of ultrafine-grained SiC densified by spark plasma sintering (SPS) with 3Y(2)O(3) + 5Al(2)O(3) or Y3Al5O12 additives was compared to elucidate the effect of the intergranular-phase source. Significantly greater sliding-wear resistance (i.e. lower mild- and severe-wear rates, and delayed mild-to-severe wear transition) is observed with the Y3Al5O12 additive, due to its carbothermal reduction during SPS resulting in a harder YAlO3 phase while reducing the intergranular phase content. Implications for the processing of superior SiC triboceramics are discussed.
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| 9. |
- Nunez-Gonzalez, Beatriz, et al.
(författare)
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Spark-plasma-sintering kinetics of ZrC-SiC powder mixtures subjected to high-energy co-ball-milling
- 2013
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 39:8, s. 9691-9697
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Tidskriftsartikel (refereegranskat)abstract
- The effect of SiC addition (5, 17.5, or 30 vol%) on the spark-plasma sinterability of ZrC ultra-high-temperature ceramics (UHTC) was investigated as a function of the intensity of high-energy co-ball-miffing. It was found that the spark-plasma-sintering (SPS) kinetics of the ZrC- SiC powder mixtures is enhanced progressively with increasing co-milling time, which is due to the progressive refinement of the crystallite sizes. It was also found that in practice the SiC addition is beneficial for the SPS kinetics of ZrC if the co-milling time is short enough so as to refine the SiC crystallite size only to the submicrometre range, although the improvement in sinterability does not correlate with the SiC content. On the contrary, the SiC addition is increasingly detrimental for those co-milling times that promote SiC refinement to the nanoscale. This unexpected trend is due to slower ZrC crystallite size refinement in the presence of SiC and, especially, to the complex role played during SPS by the passivating SiO2 films formed on the SiC particles, and is different from what has been observed in ZrB2-SiC. Finally, implications of interest for the UHTC community are discussed.
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| 10. |
- Silvestroni, Laura, et al.
(författare)
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Effect of the Sintering Additive on Microstructure and Mechanical Properties of Hi-Nicalon (TM) SiC Fibers in a HfB2 Matrix
- 2013
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Ingår i: Journal of The American Ceramic Society. - : Wiley. - 0002-7820 .- 1551-2916. ; 96:2, s. 643-650
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Tidskriftsartikel (refereegranskat)abstract
- This study is focused on the effect of the sintering additive on the microstructure and properties of HfB2 composites reinforced with SiC HiNicalon fibers. The materials were spark plasma sintered with addition of 510vol% of Si3N4 or ZrSi2. The fibers morphology was examined using scanning and transmission electron microscopy and remarkable differences were observed depending on the additive. Local hardness and Young's modulus were measured by nanoindentation to investigate the fiber mechanical behavior. The introduction of 20vol% SiC short fibers into the HfB2 matrix increased the fracture toughness up to 5.4MPam1/2 for the material sintered with ZrSi2. The room temperature flexural strength of the materials containing fibers slightly decreased when ZrSi2 was used, but with the addition of Si3N4 an improvement of more than the 40%, as compared to the unreinforced material was observed.
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