| 1. |
- F. Abdel-Magied, Ahmed, et al.
(författare)
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Magnetic metal-organic frameworks for efficient removal of cadmium(II), and lead(II) from aqueous solution
- 2022
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier BV. - 2213-2929 .- 2213-3437. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- Efficient and convenient methods for the removal of toxic heavy metal ions especially Cd(II) and Pb(II) from aqueous solutions is of great importance due to their serious threat to public health and the ecological system. In this study, two magnetic metal-organic frameworks (namely: Fe3O4@ZIF-8, and Fe3O4@UiO-66–NH2) were synthesized, fully characterized, and applied for the adsorption of Cd(II) and Pb(II) from aqueous solutions. The adsorption efficiencies for the prepared nanocomposites are strongly dependent on the pH of the aqueous solution. The maximum adsorption capacities of Fe3O4@UiO-66–NH2, and Fe3O4@ZIF-8 at pH 6.0 were calculated to be 714.3 mg·g−, and 370 mg·g−1 for Cd(II), respectively, and 833.3 mg·g−1, and 666.7 mg·g−1 for Pb(II), respectively. The adsorption process follows a pseudo-second-order model and fit the Langmuir isotherm model. Moreover, the thermodynamic studies revealed that the adsorption process is endothermic, and spontaneous in nature. A plausible adsorption mechanism was discussed in detail. The magnetic adsorbents: Fe3O4@ZIF-8, and Fe3O4@UiO-66–NH2 showed excellent reusability, maintaining the same efficiency for at least four consecutive cycles. These results reveal the potential use of magnetic Fe3O4@ZIF-8, and Fe3O4@UiO-66–NH2 as efficient adsorbents in removing Cd(II) and Pb(II) from aqueous solutions.
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| 2. |
- Fu, Le, et al.
(författare)
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Doping of tantalum, niobium, and hafnium in a translucent ZrO2-SiO2 nanocrystalline glass-ceramic
- 2022
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Ingår i: Journal of the European Ceramic Society. - : Elsevier. - 0955-2219 .- 1873-619X. ; 42:4, s. 1731-1742
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Tidskriftsartikel (refereegranskat)abstract
- The addition of dopant(s) is an effective strategy to regulate the microstructure and properties of ZrO2-based ceramics. In this study, we investigated the effects of ternary element alloying, namely tantalum (Ta), niobium (Nb), and hafnium (Hf) elements, on the microstructure and transformability of ZrO2 nanocrystallites in a ZrO2SiO2 nanocrystalline glass-ceramic (NCGC) during sintering and thermal treatments. The ternary dopants enhanced the transformability of tetragonal ZrO2 (t-ZrO2) nanocrystallites during sintering, i.e., the dopants acted as t-ZrO2 destabilizer. The Ta, Nb and Hf elements dissolved in ZrO2 nanocrystallites, forming ZrO2 solid solution. Meanwhile, lamella nanotwins were formed within many ZrO2 nanocrystallites. No obvious segregation of dopants was detected at ZrO2 grain boundaries. t-ZrO2 and monoclinic (m) ZrO2 nanocrystallites were metastable in thermal treatments process, with "t" to "m" and the reverse "m" to "t" polymorphic transformation occurred simultaneously. Meanwhile, t-ZrO2 and m-ZrO2 nanocrystallites had a great tendency to grow larger during thermal treatments.
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| 3. |
- Fu, Le, et al.
(författare)
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New insights into the formation mechanism of zircon in a ZrO2-SiO2 nanocrystalline glass-ceramic : A TEM study
- 2022
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 48:18, s. 27097-27105
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Tidskriftsartikel (refereegranskat)abstract
- We have previously observed that doping of Ca ions was beneficial to the formation of zircon (ZrSiO4). It is well known that synthetic ZrSiO4 is typically formed via a solid-state reaction between ZrO2 and SiO2, in which the interfaces between the reactant and resultant play an important role. However, the interfaces are lacking detailed microstructural observation. This follow-up study aims at exploring the formation mechanism of ZrSiO4 by inspecting the interfaces at the nano and atomic scales with TEM techniques. Results demonstrated that ZrSiO4 was formed in the Ca-doped sample after sintering at 1200 ?, whereas, no ZrSiO4 was formed in the undoped sample even after sintering at 1230 ?. The Ca-doped sample consisted of a continuous ZrSiO4 matrix with dispersed ZrO2 nanocrystallites. Doping of Ca ions promoted the formation of ZrSiO4 by causing lattice distortion and oxygen vacancies in ZrO2 lattices. Thin amorphous grain boundary complexions were found between ZrO2 nanocrystallites and between ZrO2 and ZrSiO4 crystallites. These amorphous complexions acted as reaction sites and an intermediate metastable state for the solid-state reaction. A detailed formation mechanism of ZrSiO4 at the nanometer scale and atomic scale has been proposed.
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| 4. |
- Fu, Le, et al.
(författare)
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Understanding microstructure-mechanical properties relationship in ZrO2-SiO2 nanocrystalline glass-ceramics : The effect of ZrO2 content
- 2022
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Ingår i: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 840
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Tidskriftsartikel (refereegranskat)abstract
- The content of crystalline phase plays a significant role in manipulating the microstructure and mechanical properties of glass-ceramics. This study aims at exploring the optimum content of crystalline phase in ZrO2-SiO2 nanocrystalline glass-ceramics (NCGCs) in terms of obtaining the highest mechanical properties. To this end, the mechanical properties of ZrO2-SiO2 NCGCs with 70 mol%, 75 mol%, 80 mol% ZrO2 were tested and compared with those of the previously prepared NCGCs with ZrO2 content ranging from 35 mol% to 65 mol%. Results showed that 65 mol% was the optimum content of ZrO2 in terms of obtaining the highest flexural strength. The flexural strength of NCGCs with ZrO2 content over 65 mol% was lower than that of the NCGCs with 65 mol% ZrO2. This was because the NCGC with 65 mol% ZrO2 had a homogenous microstructure, with ZrO2 nano crystallites homogeneously distributed in an amorphous SiO2 matrix. Whereas, when ZrO2 content was increased to 75 mol%, ZrO2 nanocrystallites were not homogeneously distributed in the SiO2 matrix anymore. The formation of SiO2 "holes/canyon " due to ZrO2 grain coalescence resulted in the decrease of flexural strength. The fracture mechanism and wear properties of the NCGCs were also investigated.
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| 5. |
- Ghajeri, Farnaz
(författare)
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Nanostructured Ceramics - Synthesis and Understanding
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During the last years, nanostructured ceramics have been favored for use in the industry due to their beneficial properties. For example, calcium phosphate ceramics with their biocompatible and bioactive characteristics are beneficial in biomedicine. On the other hand, silica-based nanoporous materials with large specific surface areas are efficient in adsorption applications. In such materials, the structure is the basis for efficiency in the mentioned applications. This investigation was conducted to understand the structure and its relation to the synthesis process. Two types of materials were investigated: silica-based nanoporous materials under the family name of Quartzene® and calcium phosphate ceramics. We have used different analysis methods, e.g., electron microscopy, nitrogen adsorption, and x-ray diffraction, to characterize the materials and understand the structure. We observed that similar synthesis processes could lead to different structures that were efficient for different applications, e.g., adsorption. The relation between the structure of Quartzene® and its efficiency in the adsorption application is discussed. Various factors (e.g., cleaning method and the storage time/conditions) influenced the resulting structures. Calcium phosphates were produced in aqueous solutions, and the effect of residual ions combined with various reaction temperatures and time was studied. We observed that the combination of residual ions and varying reaction temperature and time could influence the formation of the intermediate phase, octacalcium phosphate (OCP), and dicalcium phosphate dihydrate (DCPD), and particle size when the starting ion concentrations were fixed. High reaction temperature (60 °C) induced OCP and higher precipitation efficiency. For future investigation, fine-tuning the synthesis process is recommended to enhance the structure of the materials suitable for industrial use.
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| 6. |
- Ghajeri, Farnaz, et al.
(författare)
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The Influence of Residuals Combining Temperature and Reaction Time on Calcium Phosphate Transformation in a Precipitation Process
- 2022
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Ingår i: Journal of Functional Biomaterials. - : MDPI. - 2079-4983. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Precipitation is one of the most common processes to synthesize hydroxyapatite, which is the human body’s mineral forming bone and teeth, and the golden bioceramic material for bone repair. Generally, the washing step is important in the precipitation method to remove the residuals in solution and to stabilize the phase transformation. However, the influence of residuals in combination with the reaction temperature and time, on calcium phosphate formation, is not well studied. This could help us with a better understanding of the typical synthesis process. We used a fixed starting ion concentration and pH in our study and did not adjust it during the reaction. XRD, FTIR, ICP-OES, and SEM have been used to analyze the samples. The results showed that combining residuals with both reaction temperature and time can significantly influence calcium phosphate formation and transformation. Dicalcium phosphate dihydrate formation and transformation are sensitive to temperature. Increasing temperature (60◦C) can inhibit the formation of acidic calcium phosphate or transform it to other phases, and further the particle size. It was also observed that high reaction temperature (60◦C) results in higher precipitation efficiency than room temperature. A low ion concentration combining reaction temperature and time could still significantly influence the calcium phosphate transformation during the drying. © 2022 by the authors.
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| 7. |
- Katsaros, Ioannis, et al.
(författare)
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Bioactive Silicon Nitride Implant Surfaces with Maintained Antibacterial Properties
- 2022
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Ingår i: Journal of Functional Biomaterials. - : MDPI. - 2079-4983. ; 13:3
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Tidskriftsartikel (refereegranskat)abstract
- Silicon nitride (Si3N4) is a promising biomaterial, currently used in spinal fusion implants. Such implants should result in high vertebral union rates without major complications. However, pseudarthrosis remains an important complication that could lead to a need for implant replacement. Making silicon nitride implants more bioactive could lead to higher fusion rates, and reduce the incidence of pseudarthrosis. In this study, it was hypothesized that creating a highly negatively charged Si3N4 surface would enhance its bioactivity without affecting the antibacterial nature of the material. To this end, samples were thermally, chemically, and thermochemically treated. Apatite formation was examined for a 21-day immersion period as an in-vitro estimate of bioactivity. Staphylococcus aureus bacteria were inoculated on the surface of the samples, and their viability was investigated. It was found that the thermochemically and chemically treated samples exhibited enhanced bioactivity, as demonstrated by the increased spontaneous formation of apatite on their surface. All modified samples showed a reduction in the bacterial population; however, no statistically significant differences were noticed between groups. This study successfully demonstrated a simple method to improve the in vitro bioactivity of Si3N4 implants while maintaining the bacteriostatic properties.
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| 8. |
- Li, Siyu, et al.
(författare)
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Effects of surface treatment and shade on the color, translucency, and surface roughness of high-translucency self-glazed zirconia materials
- 2022
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Ingår i: The Journal of prosthetic dentistry (Print). - : Elsevier. - 0022-3913 .- 1097-6841. ; 128:2
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Tidskriftsartikel (refereegranskat)abstract
- Statement of problemThe impact of different surface treatments and shades on the color, translucency, and surface roughness of high-translucency self-glazed zirconia materials is unclear.PurposeThe purpose of this in vitro study was to investigate the effects of different external surface treatments (self-glazed, milled, polished, and glazed), intaglio surface treatments (milled and airborne-particle abraded), and shades (A1 and A3 shades) on the color, translucency, and surface roughness of high-translucency self-glazed zirconia materials, as well as the correlations among optical parameters, translucency, and surface roughness.Material and methodsEighty shade A1 and 80 shade A3 disks were fabricated with a thickness of 0.80 +/- 0.02 mm and divided into 16 groups (n=10). Different external and intaglio surface treatments were applied to the specimens. CIELab values were measured with a spectrophotometer, and color differences (Delta E-00) and relative translucency parameter (RTP) were calculated. Total transmittance (Tt%) and reflectance (R%) were tested with a spectrophotometer equipped with an integrating sphere. Surface roughness (Ra and Rz) (mu m) was measured with a noncontact 3-dimensional laser scanning microscope. One specimen from each group was subjected to scanning electron microscope (SEM) examination. Data were analyzed with ANOVA and the Tukey post hoc test. The correlation among optical parameters, translucency, and surface roughness was investigated by using Pearson correlation analysis (alpha=.05).ResultsThe effects of external surface treatments, intaglio airborne-particle abrasion, and shades on Delta E-00, RTP, and Ra values of the disks were significantly different (P<.001). The smoothest external polishing surface had the greatest RTP and color difference (P<.001). Shade A3 disks had lower RTP and Tt% values than shade A1 disks (P<.001). Delta E-00 had a highly positive relationship with the RTP (A1: r=0.884, P<.001; A3: r=0.859, P<.001). SEM images demonstrated that surface treatments affected the surface texture of monolithic zirconia ceramics.ConclusionsDifferent surface treatments affected the surface roughness, translucency, and final color of zirconia materials. The smoothest external polishing surface had the greatest RTP and color difference. Different shades influenced the translucency, as the darker the disk shade, the lower the translucency. The RTP was appropriate as an auxiliary indicator for evaluating the color of a dental ceramic.
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| 9. |
- Liu, Yang, et al.
(författare)
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Combining good mechanical properties and high translucency in yttrium-doped ZrO2-SiO2 nanocrystalline glass-ceramics
- 2022
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Ingår i: Journal of the European Ceramic Society. - : Elsevier. - 0955-2219 .- 1873-619X. ; 42:1, s. 274-285
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Tidskriftsartikel (refereegranskat)abstract
- It is challenging to develop a material that combines good mechanical properties and high translucency since these properties are generally not coincident in one material. In this study, we prepared ZrO2-SiO2 nano crystalline glass-ceramics that combines the above two types of properties. Raw powder with 55 mol%, 65 mol%, and 75 mol% ZrO2 and each with 5 mol% yttrium as a dopant was prepared by sol-gel method, followed by spark plasma sintering to obtain dense glass-ceramics. XRD results demonstrated that the glass-ceramics with 65 mol% and 75 mol% ZrO2 were composed of tetragonal-ZrO2, whereas, that with 55 mol% ZrO2 was composed of cubicZrO(2). The as-sintered glass-ceramics showed black/brown discoloration, but they obtained high translucency after thermal treatment. X-ray energy-dispersive spectrometry (EDS) results in scanning electron transmission microscopy (STEM) mode demonstrated yttrium dopants were predominately distributed in ZrO2 nano crystallites. The glass-ceramics with 65 mol% ZrO2 had the highest flexural strength, achieving an average value of 673 MPa. The glass-ceramics with different compositions sintered at different temperatures showed fracture toughness values ranging from 5.25 MPa m(1/2) to 6.69 MPa m(1/2). The strong and translucent ZrO2-SiO2 nano crystalline glass-ceramics showing great protentional to be used in many fields.
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| 10. |
- Wang, Bohan, et al.
(författare)
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Effects of dopants with various valences on densification behavior and phase composition of a ZrO2-SiO2 nanocrystalline glass-ceramic
- 2022
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 48:7, s. 9495-9505
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Tidskriftsartikel (refereegranskat)abstract
- Effects of dopants with different valences on the densification behavior and phase composition of a ZrO2-SiO2 nanocrystalline glass-ceramic (NCGC) during pressureless sintering were investigated in this study. The raw powder of Ca2+, La3+, Ce4+ and Ta5+ ions doped ZrO2-SiO2 (referred to as Ca-ZS, La-ZS, Ce-ZS, Ta-ZS, respectively) and pure ZrO2-SiO2 (PZS) sample were synthesized by sol-gel method, followed by pressureless sintering. Compared with the PZS sample, doping of Ca2+ and La3+ ions significantly promoted the densification of the NCGCs. The "densification promotion " effect was attributed to the formation of oxygen vacancies and the decrease of SiO2 viscosity due to doping of aliovalent cations. The dopants with various valences showed significant effects on the phase compositions of the NCGCs during sintering. Doping of Ca2+ ion accelerated the reaction kinetics between ZrO2 nanocrystallites and amorphous SiO2 to yield ZrSiO4. The La3+ ion acted as destabilizer of t-ZrO2, which resulted in a rapid tetragonal (t) to monoclinic (m) ZrO2 phase transformation during sintering, while in the Ta5+ and Ce4+ ions doped sample, the phase transformation occurred gradually. All the doping ions increased the lattice parameters and the volume of t-ZrO2 unit cell, while the effects of the doping ions on the lattice parameters of m-ZrO2 unit cell were more complex.
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