scholarly journals Mg or Zn for Ca substitution improves the sintering of bioglass 45S5

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
R. Wetzel ◽  
M. Blochberger ◽  
F. Scheffler ◽  
L. Hupa ◽  
Delia S. Brauer
Keyword(s):  
Glass Structure ◽  
Configurational Entropy ◽  
Scanning Calorimetry ◽  
Height Reduction ◽  
Sample Height ◽  
Heating Microscopy ◽  
Ca Substitution ◽  
Alkaline Earths ◽  
Ca Ions ◽  
Sintering Behaviour

Abstract Bioglass 45S5 is well-known for its bioactivity, but it possesses poor sintering behaviour owing to viscous flow being inhibited by the crystallisation of sodium calcium silicate phases. Mg or Zn were partially (0, 25, 50, 75%) or fully (100%) substituted for Ca on a molar base, and thermal properties (differential scanning calorimetry, dilatometry) and sintering (heating microscopy, SEM and X-ray diffraction) were investigated. Here we show that sintering can be improved significantly by partial or complete substitution of Mg or Zn for Ca, owing to a pronounced decrease in crystallisation tendency. Glass transition temperature and dilatometric softening point went through minima for mixed compositions, with random mixing of Mg/Ca or Zn/Ca ions in the glass structure and the resulting effect on configurational entropy being a likely explanation. As the onset of crystallisation did not vary much with substitution, substituted glasses possessed a wider temperature range for sintering, resulting in up to 57% and 27% sample height reduction for Mg and Zn substituted glasses, respectively, compared to only 3% height reduction for Bioglass 45S5. Taken together, these results suggest that using a combination of modifiers, particularly alkaline earths or zinc, may be a promising approach for improving the sintering of Bioglass 45S5.

scholarly journals OPTICAL PROPERTIES ON Li2O-K2O-WO3-B2O3 GLASS SYSTEM

2013 ◽  
Vol 22 ◽  
pp. 278-283
Author(s):  
A. EDUKONDALU ◽  
M. A. SAMEE ◽  
SHAIKH KAREEM AHMMAD ◽  
SAIR MD. TAQIULLAH ◽  
SYED RAHMAN ◽  
...  
Keyword(s):  
Glass Structure ◽  
Glass System ◽  
Alkali Concentration ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Mixed Alkali ◽  
Absorption Studies ◽  
Mixed Alkali Effect ◽  
Oxide Ion ◽  
B2o3 Glass

Mixed alkali tungsten borate glasses xLi2O–(30–x) K2O–10WO3–60B2O3 (0 < x < 30) were prepared from the melts. These glasses were characterized using X-ray diffraction, differential scanning calorimetry and density measurements. Optical absorption studies were carried out as a function of alkali content to look for mixed alkali effect (MAE) on the spectral properties of these glasses. From the study of ultraviolet absorption edge, the optical band gap energies and Urbach energies were evaluated. The average electronic polarizability of the oxide ion, optical basicity and the interaction parameters were also evaluated for all the glasses. Many of these parameters vary non-linearly exhibiting a minima or maxima with increasing alkali concentration, indicating the mixed alkali effect. An attempt is made to interpret MAE in this glass system in terms of its glass structure.

Energetics of the oxygen vacancy order-disorder transition in Ba2In2O5

1993 ◽  
Vol 8 (7) ◽  
pp. 1484-1486 ◽  
Author(s):  
T.R.S. Prasanna ◽  
Alexandra Navrotsky
Keyword(s):  
High Temperature ◽  
Oxygen Vacancy ◽  
Configurational Entropy ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Scanning Calorimetry ◽  
Disorder Transition ◽  
First Order ◽  
Enthalpy And Entropy ◽  
Entropy Of Transition

The heat capacity and the enthalpy associated with the reported oxygen vacancy order-disorder transition in Ba2In2O5 were measured by high temperature step scanning calorimetry. The transition temperature is 1205 ± 2 K. The transition appears first order or nearly so. The enthalpy and entropy of transition are 1.3 kJ/mol and 1.1 J/mol K, respectively. The latter is only 4.8% of the configurational entropy, arising from mixing one vacancy and five oxygens per formula unit, 22.5 J/mol K. This suggests that the transition involves only a small fraction of the oxygen vacancies and implies extensive short-range order, SRO, in the high temperature phase.

scholarly journals Sintering Behaviour of Al-Cu-Mg-Si Blends

2007 ◽  
Vol 534-536 ◽  
pp. 597-600 ◽  
Author(s):  
C. Lucien Falticeanu ◽  
I.T.H. Chang ◽  
J.S. Kim ◽  
R. Cook
Keyword(s):  
Alloy Powder ◽  
Effect Of Temperature ◽  
Microstructural Development ◽  
Al Alloy ◽  
Sintering Process ◽  
Scanning Calorimetry ◽  
Increasing Demand ◽  
Sintering Behaviour ◽  
Evolution Of Microstructure ◽  
Initial Starting

The increasing demand for automotive industries to reduce the weight of the vehicles has led to a growing usage of Al alloy powder metallurgy (P/M) parts such as camshaft bearing caps, shock absorber pistons and brake calipers [1,2]. In order to control the sintered microstructure and mechanical properties of the aluminium alloy powder metallurgical (P/M) parts, it is essential to establish a fundamental understanding of the microstructural development during the sintering process. Current research at Birmingham University is focussed on the investigation of the sintering behaviour of Al-Cu-Mg-Si powder blends using a combination of Scanning Electron Microscopy, Energy Dispersive Microanaylsis (SEM) and Differential Scanning Calorimetry (DSC). This paper presents a detailed study of the effect of temperature and initial starting materials on the evolution of microstructure during the sintering of Al-Cu-Mg-Si blends for PM.

scholarly journals Crystallization Kinetics and Structural Properties of the 45S5 Bioactive Glass and Glass-Ceramic Fiber Doped with Eu3+

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1281 ◽  
Author(s):  
Agata Baranowska ◽  
Magdalena Leśniak ◽  
Marcin Kochanowicz ◽  
Jacek Żmojda ◽  
Piotr Miluski ◽  
...  
Keyword(s):  
Bioactive Glass ◽  
Crystallization Kinetics ◽  
Glass Ceramic ◽  
Structural Changes ◽  
Glass Fibers ◽  
Glass Structure ◽  
Glass Ceramics ◽  
Luminescent Properties ◽  
Ceramic Fiber ◽  
Scanning Calorimetry

An investigation of the crystallization kinetics of 45S5 Bioglass® using differential scanning calorimetry is presented in this paper. Thermal analysis was performed using the Friedman method. The activation energy and the Avrami index were calculated. The glass samples were subjected to additional controlled heat treatment at 620 °C in order to obtain bioactive glass-ceramics with enhanced mechanical properties. X-ray powder diffraction (XRD) measurements indicated the formation of the glass-ceramic structures of three cyclosilicates: Na4Ca4(Si6O18) or Na6Ca3(Si6O18) or Na16Ca4(Si12O36). Based on middle infrared region (MIR) results, it can be concluded that the crystalline phase present in the tested materials was Na6Ca3(Si6O18) (combeite). Material was doped with Eu3+ ions, which act as a spectroscopic probe for monitoring the structural changes in the glass matrix. The decreasing value of the fluorescence intensity radio parameter indicated symmetry around the europium ions and, thus, the arrangement of the glass structure. The bioactive properties of the examined glass-ceramics were also determined. The bioactive glass fibers doped with Eu3+ were manufactured using two different methods. Its structural and luminescent properties were examined.

Fluoride-Containing Bioactive Glasses

2008 ◽  
Vol 39-40 ◽  
pp. 299-304 ◽  
Author(s):  
Delia S. Brauer ◽  
Natalia Karpukhina ◽  
Daphne Seah ◽  
Robert V. Law ◽  
Robert G. Hill
Keyword(s):  
Sodium Fluoride ◽  
Chemical Shifts ◽  
Glass Structure ◽  
Glass Network ◽  
The Body ◽  
Scanning Calorimetry ◽  
Bioactive Glasses ◽  
Living Bone

Fluoride is an important mineral for hard tissues in the body and appropriate fluoride exposure and usage are beneficial to bone and tooth integrity. Fluoride increases both bone density and bone mass due to stimulation of bone formation and it is used as a treatment for osteoporosis. Bioactive glasses have the capacity to form an intimate bond with living bone tissue due to formation of a mixed hydroxycarbonate apatite layer (HCA) in vitro and in vivo. This makes fluoride-containing bioactive glasses attractive biomaterials. In order to design fluoride-containing bioactive glasses, we need to understand the role of fluorine within the glass structure. A series of bioactive glasses with increasing fluoride content was prepared by a melt-quench route. Characterisation included differential scanning calorimetry (DSC), density measurements, MASNMR spectroscopy and studies in simulated body fluid (SBF). DSC results showed a linear decrease in glass transition temperature (Tg) with increasing amounts of fluoride. Density of the glasses increased with increasing amounts of fluoride. This may indicate an expansion of the silicate glass network accompanying incorporation of CaF2. 19F MAS-NMR spectroscopy showed broad peaks at chemical shifts between -135 and -120 ppm. As sodium fluoride gives a chemical shift of -223 ppm and calcium fluoride of -108 ppm, this indicated possible formation of mixed calcium sodium fluoride species. HCA and calcium phosphate layers were found on the glasses after one week of immersion in SBF showing the bioactivity of the glass series.

scholarly journals Characterization of Li2O-Al2O3-SiO2 glass-ceramics produced from a Brazilian spodumene concentrate

Cerâmica ◽  
2019 ◽  
Vol 65 (375) ◽  
pp. 366-377 ◽  
Author(s):  
L. B. Rebouças ◽  
M. T. Souza ◽  
F. Raupp-Pereira ◽  
A. P. Novaes de Oliveira
Keyword(s):  
Structural Changes ◽  
Glass Ceramics ◽  
Nucleating Agent ◽  
Raw Material ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Heating Microscopy ◽  
Shock Resistance ◽  
High Thermal Shock Resistance

Abstract Glass-ceramics in the LAS (Li2O-Al2O3-SiO2) system with high thermal shock resistance were successfully obtained using Brazilian spodumene concentrate as the main raw material (80-70 wt%). Two compositions (Li2O.Al2O3.nSiO2) were produced with n= 2 and 4, near to the stoichiometric compositions of β-eucryptite and β-spodumene. The characteristic temperatures of parent glasses were determined by contact dilatometry, differential scanning calorimetry and heating microscopy. The crystallization mechanism and the effect of the nucleating agent (TiO2.2ZrO2) required to promote volume crystallization in the parent glasses were investigated. Microstructural and structural changes with temperature were also evaluated by optical microscopy and X-ray diffraction. The obtained glass-ceramics presented coefficients of thermal expansion between -0.370x10-6 and 4.501x10-6 °C-1 in the 22 to 700 °C range.

scholarly journals Non-isothermal crystallization of LiNaGe4O9 glass

2021 ◽  
Vol 29 (1) ◽  
pp. 73-76
Author(s):  
Ye. V. Skrypnik ◽  
M. P. Trubitsyn ◽  
A. O. Diachenko ◽  
M. D. Volnianskii
Keyword(s):  
Differential Scanning Calorimetry ◽  
Glass Transition ◽  
Glass Structure ◽  
Exothermic Peak ◽  
Gravimetric Analysis ◽  
Thermal Gravimetric ◽  
Glass Crystallization ◽  
Scanning Calorimetry ◽  
Noticeable Increase ◽  
Characteristic Temperatures

The glass of lithium-sodium tetragermanate LiNaGe4O9 is crystallized on heating under the control of differential scanning calorimetry and thermal gravimetric analysis. The measurements were prepared in the temperature range 300-870 K and showed the relatively weak endothermic DSC anomaly and 40-50 K above the single exothermic peak. The endothermic anomaly observed at Tg testified to softening the glass structure whereas the exothermic peak at TC manifested crystallization of the amorphous phase. Studying of TGA demonstrated smooth nearly linear dependences without any visible anomalies. Varying the heating rate from 1.2 up to 40 K/min resulted in noticeable increase of the characteristic temperatures Tg and TC. Lower limit of the glass transition temperature Tg0 was estimated with the help of the existing model. The mechanism of the LiNaGe4O9 glass crystallization is discussed.

PROPERTIES AND STRUCTURE OF Ag-DOPED As2Se3 GLASSES

2007 ◽  
Vol 16 (01) ◽  
pp. 49-57 ◽  
Author(s):  
CONGJI ZHA ◽  
ANITA SMITH ◽  
AMRITA PRASAD ◽  
RONGPING WANG ◽  
STEVE MADDEN ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Raman Band ◽  
Glass Structure ◽  
Low Frequency ◽  
Glass Network ◽  
Scanning Calorimetry ◽  
Covalent Bonds ◽  
Frequency Shifts

Ag -doped As 2 Se 3 glasses were prepared by the melt-quenching method and the influence of silver doping on the glass structure and optical properties was studied using Raman and UV-Vis-IR spectroscopy and differential scanning calorimetry. For Ag concentrations less than 15 at%, introduction of Ag into As 2 Se 3 glasses mainly leads to the formation of Ag-Se covalent bonds, resulting in destruction of the glass network. This manifests itself by a decrease in the glass transition temperature and low frequency shifts in the As-Se Raman band. When the Ag concentration was higher than 25 at%, some Ag atoms exist in the glass matrix as coordinative bonds, resulting in a slight increase in the glass transition temperature and high frequency shifts in the Raman peaks. The relationship between the glass structure and properties is discussed.

Thermal Analysis of Ca1+xCu3Ti4O12+x Precursor in Nitrogen and Oxygen Environment at 1000 °C

2020 ◽  
Vol 1010 ◽  
pp. 268-273
Author(s):  
Julie Juliewatty Mohamed ◽  
Noruzaman Daud ◽  
Mohamad Johari bin Abu ◽  
Mohd Fariz Ab Rahman ◽  
Siti Roshayu binti Hassan ◽  
...  
Keyword(s):  
Mass Loss ◽  
Room Temperature ◽  
Single Phase ◽  
Xrd Analysis ◽  
Phase Changes ◽  
Oxygen Absorption ◽  
Atmospheric Gases ◽  
Scanning Calorimetry ◽  
Nitrogen Gas ◽  
Ca Ions

The thermal kinetic analyses are prepared on Ca1+xCu3Ti4O12+x powders using simultaneous thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) measurement in a dual atmospheric gases environment. Initially, the nitrogen gas flowed from room temperature to 1000 °C, and then the environment was shifted and hold for 1 hour with oxygen. The result shows that the TGA patterns of the temperature and mass loss are disorderly with x values. The mass loss % patterns slightly decreased with increased additional Ca-based element. The decreased of oxygen absorption as the values of x increased also can be explained by the reduction of single-phase CCTO structure when excess Ca ions. The DSC pattern shows two prominent endothermic peaks and two exothermic peaks that relate to the melting point of the reactant and crystalline phase changes of samples, while the significant endothermic peak at 1000 °C is corresponding to the formation of CCTO compounds as identified by XRD analysis.

scholarly journals Configurational Entropy Relaxation of Silica Glass—Molecular Dynamics Simulations

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 885
Author(s):  
Ondrej Gedeon
Keyword(s):  
Molecular Dynamics ◽  
Glass Transition ◽  
Undirected Graph ◽  
Glass Structure ◽  
Configurational Entropy ◽  
Vitreous Silica ◽  
Relaxation Model ◽  
Structural Units ◽  
Debye Relaxation ◽  
Dynamics Simulations

Vitreous silica was modelled using molecular dynamics (MD). The glass structure was transferred into an undirected graph and decomposed into disjoint structural units that were ideally mixed to calculate the configurational entropy. The Debye relaxation model was suggested to simulate the evolution of entropy during the cooling of the system. It was found that the relaxation of the configurational entropy of MD corresponds to the effective cooling rate of 6.3 × 106 Ks−1 and its extrapolation to 0.33 Ks−1 mimics the glass transition with Tg; close to the experimental value. Debye relaxation correctly describes the observed MD evolution of configurational entropy and explains the existence of freezing-in temperature and the shape of the curve in the transition region.

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