Papers by Maziar Montazerian
A B S T R A C T Nucleation kinetics of glass-ceramics is frequently determined using Tammann's do... more A B S T R A C T Nucleation kinetics of glass-ceramics is frequently determined using Tammann's double-stage heat-treatment. This method requires a complex deconvolution of the experimentally observed induction time (t ind), i.e. the intercept of the linear part of the crystal number density curve with the nucleation time axis, into two components. In this paper, double-stage heat treatments were performed, with heating rates between the nucleation and development temperatures covering two orders of magnitude, in samples of a homogeneously nucleating glass-forming system, lithium disilicate. Our results show that t ind increases with increasing heating rates with cubic root dependence. In accordance with the theory, t ind was split into the intrinsic time required to establish a steady-state cluster size distribution, τ (time-lag) at the nucleation temperature and an incubation time (t i), which is a size, heating rate and development temperature (T d) dependent growth time. We demonstrate that the Collins-Kashchiev nucleation model performs poorly if t i is approximated by the time needed to experimentally detect the first crystal. In contrast, the Shneidman approach is consistent with theory. We found that at any given nucleation temperature, t i is a strong function of the heating rate, and is proportional to t ind , whereas τ is a constant, as expected.
Most restorative dental materials are inert and biocompatible and are used in the restoration and... more Most restorative dental materials are inert and biocompatible and are used in the restoration and reconstruction of teeth. Among them, glass-ceramics (GCs) are of great importance because they are easy to process and have outstanding esthetics, translucency, low thermal conductivity, high strength, chemical durability , biocompatibility, wear resistance, and hardness similar to that of natural teeth. However, research and development are still underway to further improve their mechanical properties and esthetics to enable them to compete with their current contenders (e.g., zirconia and hybrids) for posterior restorations. Throughout this chapter, we summarize the processing, properties, and applications of restorative dental glass-ceramics. Current commercial dental glass-ceramics are explained, and also selected papers that address promising types of dental glass-ceramics are reviewed. Finally, we include trends on relevant open issues and research possibilities.
We show a scientometric analysis for glass researchers and compare it with those for researchers ... more We show a scientometric analysis for glass researchers and compare it with those for researchers in two fashionable research topics, representing the science-push area " graphene " and the market-pull area " lithium ion battery (LIB) ". We also present similar statistics for two widely different macro fields, " materials science " (which contains the other three) and " mathematics ". While productivity (number of published articles) of a researcher and his/her H-index are found to be correlated , these correlations are very different for different research fields, depending on their size, fragmentation, interdisciplinarity, and on the community's publication and citation culture. We also explore the correlation between citation statistics and scientific quality and find it to be elusive. While certain bibliometric indexes indeed indicate how active, prolific, and visible a researcher (or a research group) is, we argue that quality—evaluated by the originality, strength, reproducibility and relevance of the findings of a researcher's publications (as judged by peer review)—is much more important than the number of published articles and citations, and this is where efforts must be concentrated by researchers and evaluating bodies.
Here we review and summarize the groundbreaking scientific researches of the late Professor Larry... more Here we review and summarize the groundbreaking scientific researches of the late Professor Larry L. Hench, including several of his key discoveries in materials science and engineering. First, we provide a statistical overview of his exceptional scientific performance using Scopus, Web of Science, and other Web sites to extract statistical data on his scientific publications and patents. Professor Hench achieved an exceptionally high h-index of 77 (Scopus) for the field of materials science and engineering, which resulted from his 340 research papers, 210 conference papers, 41 patents, 24 books, 4 editorial notes, and 3 biographies starting in 1967. Then, we summarize and highlight his seminal articles, books, and patents in several research areas, such as bioactive glasses, optical gel glasses, biocomposites/coatings, glass–ceramics, biophotonics, advanced ceramics, semiconducting and ionic conducting glasses, glass corrosion , and nuclear waste disposal. Prof. Hench not only discovered the first man-made material to form a chemical bond with bone and initiated a whole new field—bioactive glasses and glass–ceramics—but also made several other important scientific discoveries. It is quite clear that he was one of the most influential materials scientists/engineers of all time! We hope that this review is not only useful for all persons interested in materials science and engineering but also encourages students and younger investigators to make use of this accumulated knowledge to design novel materials and discover new applications for glasses and ceramics.
The global market for dental materials is predicted to exceed 10 billion dollars by 2020. The mai... more The global market for dental materials is predicted to exceed 10 billion dollars by 2020. The main drivers for this growth are easing the workflow of dentists and increasing the comfort of patients. Therefore, remarkable research projects have been conducted and are currently underway to develop improved or new dental materials with enhanced properties or that can be processed using advanced technologies , such as CAD/CAM or 3D printing. Among these materials , zirconia, glass or polymer-infiltrated ceramics, and glass-ceramics (GCs) are of great importance. Dental glass-ceramics are highly attractive because they are easy to process and have outstanding esthetics, translucency, low thermal conductivity, high strength, chemical durability, biocompatibility, wear resistance, and hardness similar to that of natural teeth, and, in certain cases, these materials are bioactive. In this review article, we divide dental GCs into the following two groups: restorative and bioactive. Most restorative dental glass-ceramics (RDGCs) are inert and bio-compatible and are used in the restoration and reconstruction of teeth. Bioactive dental glass-ceramics (BDGCs) display bone-bonding ability and stimulate positive biological reactions at the material/tissue interface. BDGCs are suggested for dentin hypersensitivity treatment, implant coating, bone regeneration and periodontal therapy. Throughout this paper, we elaborate on the history, processing, properties and applications of RDGCs and BDGCs. We also report on selected papers that address promising types of dental glass-ceramics. Finally, we include trends and guidance on relevant open issues and research possibilities. V C 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 619–639, 2017.
The interest around bioactive glass-ceramics (GCs) has grown significantly over the last two deca... more The interest around bioactive glass-ceramics (GCs) has grown significantly over the last two decades due to their appropriate biochemical and mechanical properties. The intense research effort in this field has led to some new commercial products for biomedical applications. This review article begins with the basic concepts of GC processing and development via controlled heat treatments of mon-olithic pieces or sinter-crystallization of powdered glasses. We then go on to describe the processing, properties, and applications of some commercial bioactive GCs and discuss selected valuable reported researches on several promising types of bioactive GCs. The article finishes with a section on open relevant research directions for bioactive GC development. V
We synthesized four glasses of the system 61.2SiO 2 –(24.3–x)CaO–4.5P 2 O 5 –10ZrO 2 –xK 2 O (x¼0... more We synthesized four glasses of the system 61.2SiO 2 –(24.3–x)CaO–4.5P 2 O 5 –10ZrO 2 –xK 2 O (x¼0, 2, 4, 6 mol%¼Ca replaced by K) using a sol–gel route and compared their properties with a 68SiO 2 –27CaO–5P 2 O 5 (mol%) Zr-free base glass. Their structure, sintering and crystallization behavior were investigated with the aim of converting the gel-glasses into dense glass–ceramics. Then, the in vitro bioactivity and mechanical properties of the optimized sintered samples were characterized. The structure of the gel-glasses was investigated by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and high-resolution transmission electron microscopy (HR-TEM). The sintering and crystallization kinetics of the glasses were studied by hot stage microscopy (HSM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The microstructures of the resulting glass–ceramics were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) coupled with energy dispersive spectroscopy (EDS). The apatite-forming ability of the sintered glass–ceramics in simulated body fluid (SBF) was investigated using FTIR spectroscopy and SEM. The three-point bending strength, Vickers microhardness and fracture toughness were also measured. Structural analysis by NMR and FTIR revealed that Zr acts as a glass former and K is a modifier, as expected. The K 2 O addition strongly improved the material's sinterability, e.g., 2 mol% K 2 O decreased the optimum sintering temperature from 1300 1C to 1050 1C. Uniformly dispersed ZrO 2 nano-crystals, with particle sizes of 25–55 nm, were precipitated in the glass–ceramics. In vitro bioactivity tests confirmed that the K 2 O-free glass–ceramics (partially sintered at 1000 1C) were bioactive and hydroxycarbonate apatite (HCA) grew on their surface after 24 h in SBF. However, the 490% dense glass–ceramics with various contents of K 2 O exhibited low solubility and a much smaller tendency toward HCA formation. Improvement of some mechanical properties was observed for the sample containing 2 mol% K 2 O, in which apatite and zirconia crystallized. The 3p-bending strength and fracture toughness of the 94% dense sample were approximately 140 MPa and 2 MPa m 1/2 , respectively. We propose that crack deflection by the ZrO 2 crystals and the presence of Zr ions in the residual glass network are prevalent for improving the materials' mechanical properties. Some potential applications, such as bioactive scaffolds, are suggested for these glass–ceramics.
In this study, 10 mol% ZrO 2 was added to a 27CaO–5P 2 O 5 –68SiO 2 (mol%) base composition synth... more In this study, 10 mol% ZrO 2 was added to a 27CaO–5P 2 O 5 –68SiO 2 (mol%) base composition synthesized via a simple sol–gel method. This composition is similar to that of a frequently investigated bioactive gel–glass. The effects of ZrO 2 on the in vitro bioactivity and MG-63 cell proliferation of the glass and its derivative polycrystalline (glass–ceramic) powder were investigated. The samples were characterized using thermo-gravimetric and differential thermal analysis (TG/DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) coupled to energy dispersive X-ray spectroscopy (EDS). Release of Si, Ca, P and Zr into simulated body fluid (SBF) was determined by inductively coupled plasma (ICP). Upon heat treatment at 1000 °C, the glass powder crystallized into an apatite–wollastonite–zirconia glass–ceramic powder. Hydroxycarbonate apatite (HCA) formation on the surface of the glass and glass–ceramic particles containing ZrO 2 was confirmed by FTIR and SEM. Addition of ZrO 2 to the base glass composition decreased the rate of HCA formation in vitro from one day to three days, and hence, ZrO 2 could be employed to control the rate of apatite formation. However, the rate of HCA formation on the glass–ceramic powder containing ZrO 2 crystal was equal to that in the base glassy powder. Tests with a cultured human osteoblast-like MG-63 cells revealed that the glass and glass–ceramic materials stimulated cell proliferation, indicating that they are biocompatible and are not cytotoxic in vitro. Moreover, zirconia clearly increased osteoblast proliferation over that of the Zr-free samples. This increase is likely associated with the lower solubility of these samples and, consequently, a smaller variation in the media pH. Despite the low solubility of these materials, bioactivity was maintained, indicating that these glassy and polycrystalline powders are potential candidates for bone graft substitutes and bone cements with the special feature of radiopacity.
In this research, aluminum alloy (A356.1) matrix composites reinforced with 1.5, 2.5 and 5 vol% n... more In this research, aluminum alloy (A356.1) matrix composites reinforced with 1.5, 2.5 and 5 vol% nano-particle MgO were fabricated via stir casting method. Fabrication was performed at various casting temperatures, viz. 800, 850 and 950 • C. Optimum amount of reinforcement and casting temperature were determined by evaluating the density, microstructure and mechanical properties of composites. The composites were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Hardness and compression tests were carried out in order to identify mechanical properties. The results reveal that the composites containing 1.5 vol% reinforcement particle fabricated at 850 • C have homogenous microstructure as well as improved mechanical properties.
Glass–ceramic composites in the SiO 2 –CaO–MgO–(Na 2 O) system, reinforced with 5, 10 and 20 wt.%... more Glass–ceramic composites in the SiO 2 –CaO–MgO–(Na 2 O) system, reinforced with 5, 10 and 20 wt.% aluminum titanate were synthesized by pressureless sintering. Optimum sintering temperatures with maximum relative density were determined for each composition. The composites were fired above the crystallization peak temperature of glass–ceramic. Mechanical properties of glass–ceramic and sintered composites, such as fracture toughness, flexural strength and Vickers microhardness, were investigated. The sintered composites were characterized by scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD). The results showed that the composite containing 10 wt.% aluminum titanate has desirable behavior in comparison to the base glass–ceramic and the other compositions. It seems that crack deflection by aluminum titanate particles is the prevalent mechanism for improving mechanical characteristics.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Abstract In this study, mica–apatite glass–ceramic was reinforced with 5, 10 and 15 wt.% partially stabilized zirconia (Y-PSZ). The composites were prepared via pressureless sintering, which was performed on the mixtures of zirconia particulates and two frits belonging to the fluoro-mica and apatite-based glasses. The sintered composites were characterized by scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD). Mechanical properties of the sintered samples such as bending strength, Vickers micro-hardness and fracture toughness were also investigated. The results showed that Y-PSZ dissolved in the residual glass and caused the formation of prismatic zircon crystals (ZrSiO 4) precipitated during the final stage of sintering. Spherical zirconia particles were also detected. Mechanical properties improved for composite containing 10 wt.% ZrO 2 .
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Abstract Mica glass–ceramic composites toughened by 5, 10 and 15 wt.% partially stabilized zirconia (Y-PSZ) were prepared via pressureless sintering. Sinterability of composites was investigated in the temperature range of 1060–1170 • C using soaking time of 240 min. The sintered specimens were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods. The results revealed that during sintering, the dissolution of Y-PSZ occurred in the residual glass which caused the formation of zircon and transformation of tetragonal to monoclinic zirconia. Mechanical properties of the sintered samples such as bending strength, Vickers micro-hardness and fracture toughness were also investigated. Measurements showed that addition of 15 wt.% ZrO 2 to the mica glass–ceramic matrix increased the bending strength from 50.91 ± 10.50 to 132.47 ± 13.80 MPa. Fracture toughness was also improved up to 1.37 ± 0.14 MPa m 1/2 .
In this study, mica glass-ceramic reinforced with 5, 10 and 15 wt.% partially stabilized zirconia... more In this study, mica glass-ceramic reinforced with 5, 10 and 15 wt.% partially stabilized zirconia (ZrO 2 stabilized with 3 mol% Y 2 O 3 ) was synthesized via pressureless sintering. Sinterability of composite was investigated in the temperature range of 1060-1170 °C using soaking time of 240 min. The sintered specimens were characterized by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). Mechanical properties of sintered specimens such as three-point bending strength and Vickers micro hardness were also investigated. Microstructural observations revealed that plate-like mica crystals were crystallized in the vicinity of submicron and fine zirconia particles. Strength measurements showed that increasing the amount of zirconia increased the strength from 50.91 ± 10.50 MPa for mica glass-ceramic to 132.47 ± 13.80 MPa for the composite with a content of 15 wt.% ZrO 2 . The micro hardness of the glass-ceramic was also improved up to 4.35 ± 0.64 GPa.
In this research, aluminum alloy (A356.1) matrix composites reinforced with 1.5, 2.5 and 5 vol% n... more In this research, aluminum alloy (A356.1) matrix composites reinforced with 1.5, 2.5 and 5 vol% nanoparticle MgO were fabricated via stir casting method. Fabrication was performed at various casting temperatures, viz. 800, 850 and 950 • C. Optimum amount of reinforcement and casting temperature were determined by evaluating the density, microstructure and mechanical properties of composites. The composites were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Hardness and compression tests were carried out in order to identify mechanical properties. The results reveal that the composites containing 1.5 vol% reinforcement particle fabricated at 850 • C have homogenous microstructure as well as improved mechanical properties.
Glass-ceramic composites in the SiO 2 -CaO-MgO-(Na 2 O) system, reinforced with 5, 10 and 20 wt.%... more Glass-ceramic composites in the SiO 2 -CaO-MgO-(Na 2 O) system, reinforced with 5, 10 and 20 wt.% aluminum titanate were synthesized by pressureless sintering. Optimum sintering temperatures with maximum relative density were determined for each composition. The composites were fired above the crystallization peak temperature of glass-ceramic. Mechanical properties of glass-ceramic and sintered composites, such as fracture toughness, flexural strength and Vickers microhardness, were investigated. The sintered composites were characterized by scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD). The results showed that the composite containing 10 wt.% aluminum titanate has desirable behavior in comparison to the base glass-ceramic and the other compositions. It seems that crack deflection by aluminum titanate particles is the prevalent mechanism for improving mechanical characteristics. #
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Papers by Maziar Montazerian