Profiles

Baltzar Stevensson

Baltzar Stevensson

Researcher

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Arbetar vid Institutionen för material- och miljökemi
E-post baltzar.stevensson@mmk.su.se
Besöksadress Svante Arrhenius väg 16 C
Rum C 532
Postadress Institutionen för material- och miljökemi 106 91 Stockholm

Om mig

  • Researcher in Physical Chemistry with Mattias Edén since 2005

  • Postdoctoral research fellow with Claudio Zannoni (Univ. di Bologna, Italy); 2004

  • Ph.D studies in Physical Chemistry (Stockholm University) with Arnold Maliniak; 1998-2003

Forskning

Solid-State NMR and Modeling in Materials Science

Collaborations

Synthesis and Processing of Active Calcium Phosphate Cements”, funded by the Swedish Foundation for Strategic Research (2016-2021). Håkan Engqvist (Uppsala Univ, PI); Molly Stevens (Karolinska Institute; Imperial College London); Peter Thompsen (Gothenburg Univ)

Publikationer

I urval från Stockholms universitets publikationsdatabas
  • 2020. Yang Yu, Baltzar Stevensson, Mattias Edén. Journal of The American Ceramic Society 103 (2), 762-767

    From a large ensemble of 34 silicate-based glasses from the borosilicate, phosphosilicate, and borophosphosilicate systems that comprise either Na as a sole glass-network modifier or when mixed with Ca, we established a good correlation between the Na-23 average isotropic chemical shift (delta over bar iso) and the average coordination number of Na and the mean Na-O distance. The latter parameters were obtained by atomistic molecular dynamics simulations. We also demonstrated that delta over bar iso is essentially independent on the precise network forming (Si, B, P) species but depends primarily on the net molar fraction of Na and Ca, thereby offering a straightforward Na-23 chemical shift prediction from the glass composition alone.

  • 2019. Yang Yu (et al.). Ceramics International 45 (16), 20642-20655

    From a suite of advanced magic-angle spinning (MAS) NMR spectroscopy and powder X-ray diffraction (PXRD) experiments, we present a comprehensive structural analysis of pyrophosphate-bearing calcium phosphate cements that are investigated for bone-inductive biomedical implants. The cements consist mainly of poorly ordered monetite (CaHPO4), along with minor Ca orthophosphate phases, and two distinct pyrophosphate constituents: crystalline beta-Ca2P2O7 and amorphous calcium pyrophosphate (ACPP), the latter involving one water bearing portion and another anhydrous component. Independent 2D MAS NMR experiments evidenced close contacts between the amorphous pyrophosphates and the monetite phase, where ACPP is proposed to form a thin layer coating the monetite particles. Heteronuclear H-1-P-31 and homonuclear P-31-P-31 correlation NMR experimentation enabled us to detect, identify, and quantify even minor cement constituents (less than or similar to 2 mol%) that could not be ascertained by the Rietveld method. Quantitative phase analyses of the cements, as determined independently by P-31 NMR and PXRD, are contrasted and discussed.

  • 2019. Yang Yu, Baltzar Stevensson, Mattias Edén. The Journal of Physical Chemistry C 123 (42), 25816-25832

    We present a comprehensive study of the Na environments in a large ensemble of 32 silicate-based glass compositions from the borosilicate, phosphosilicate, and borophosphosilicate systems, which comprise either Na as the sole glass-network modifier or mixed with Ca. We examined the spatial distribution of Na in the glasses using Na-23 NMR The relative propensities of Na to associate with the BO3 and BO4 structural moieties in B-bearing glasses were probed by heteronuclear dipolar-based B-11{Na-23} magic-angle-spinning NMR experimentation, which yielded both dipolar second moments M-2(B-[p]-Na) and M-2(Na-B-[p] for each B-[3] and B-[(4]) coordination in a single experiment. These data agreed well with results from atomistic molecular dynamics simulations. Both the spatial distribution of Na and the relative preferences for B-[3] -Na and B-[4]-Na contacts depend primarily on the amount of nonbridging oxygen (NBO) anions in the glass network, and thereby on the modifier (Na-2(+) and Ca2+) concentrations, where two regimes were identified: (I) For low modifier contents, the Na+ cations are relatively uniformly dispersed across the structure, while there is a strong preference for B-[4]-Na associations. (II) For moderately high modifier contents, Na+ distributes randomly and with nonpreferential associations with the BO3 or BO4 species. However, when the Na+ and Ca2+ contents are increased further, the growing NBO populations of the glass network coupled with the strong preferential NBO accommodation at the BO3 moieties (relative to BO4) progressively elevate the propensity for B-[3]-Na contacts. We discuss the partitioning of the Na reservoir among the BO3 and BO4 groups for each regime I and II. We also rationalize the increased disorder of the Na dispersion and the concomitant shift from a preference for B-[4]-Na contacts to one for B-[3]-Na. Both the nature of the spatial distribution of Na and the relative preferences for B-[4]-Na and B-[3]-Na contacts in the glass are essentially independent of its precise combination of (B, Si, P) network formers.

  • 2019. Yang Yu (et al.). International Journal of Molecular Sciences 20 (24)

    We present a solid-state nuclear magnetic resonance (NMR) spectroscopy study of the local P-31 and H-1 environments in monetite [CaHPO4; dicalcium phosphate anhydrous (DCPA)], as well as their relative spatial proximities. Each of the three H-1 NMR peaks was unambiguously assigned to its respective crystallographically unique H site of monetite, while their pairwise spatial proximities were probed by homonuclear H-1-H-1 double quantum-single quantum NMR experimentation under fast magic-angle spinning (MAS) of 66 kHz. We also examined the relative H-1-P-31 proximities among the inequivalent {P1, P2} and {H1, H2, H3} sites in monetite; the corresponding shortest internuclear H-1-P-31 distances accorded well with those of a previous neutron diffraction study. The NMR results from the monetite phase were also contrasted with those observed from the monetite component present in a pyrophosphate-bearing calcium phosphate cement, demonstrating that while the latter represents a disordered form of monetite, it shares all essential local features of the monetite structure.

Visa alla publikationer av Baltzar Stevensson vid Stockholms universitet

Senast uppdaterad: 8 maj 2020

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