Verres et vitrocéramiques à base de chalco: halogénures dopés par des ions de terres rares pour la luminescence dans le visible

Pós-graduação em Química - IQ

Estudos estruturais em vidros e vitrocerâmicas contendo 'PBF IND.2'-'CDF IND.2

Pós-graduação em Química - IQ

Thermal and structural study of glasses in the binary system TeO2-Pb(PO3)(2)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Unusual broadening of the NIR luminescence of Er3+-doped Nb2O5 nanocrystals embedded in silica host: Preparation and their structural and spectroscopic study for photonics applications

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Vitrocerâmicas porosas via conformação e consolidação com amidos

The search for new methods of manufacture of glass-ceramics with controlled porosity and permeability is interesting of the industrial and commercial point of view, and a challenge of great complexity. Porous glass-ceramics produced by sintering and crystallization of glasses can find applications, for example, as filters, materials with bactericidal properties, bio-implants, as catalytic and enzymes supports, among others. An alternative and low cost method of ceramic manufacture reaching different levels of porosity, for diverse purposes, is the conformation assisted by addition of starch, known as consolidation with starch. The objective of this project is to study the process of conformation with starch for making porous glass-ceramics from a commercial glass in the system Na2O-CaO-SiO2, whose kinetics of sintering by viscous flow and surface crystallization are known. The method of conformation with starches is innovative for glass-ceramics and its development opens the way for obtaining a new class of materials. We found a possible route for the production of porous compacts of glass particles, from the powder preparation to the removal of starch. It was observed that a glass powder obtained by dry milling in a ball mill with alumina balls for 24 h, afterwards mixed with water in an eccentric ball mill for 2 h, without the addition of a deflocculant, and subsequently mixed with starch also in an eccentric ball mill for 5 min resulted in slurries stable against sedimentation

Vitrocerâmicas para blindagens balísticas

The use of ceramic materials in ballistic armor is considerable. Such materials can be very harder and lighter than metallic materials commonly used and it presents advantages to replace metallic materials when necessary toughness can be achieved. However, as SiC and Al2O3 ceramic, traditionally used for shielding, still have high manufacturing cost or low density do not have enough to shield applications such as aircraft. An alternative is the glass-ceramics, ceramics obtained by controlled crystallization of glasses, whose properties can be adjusted by choosing the chemical composition of glass, heat treatment of crystallization and special treatments such as ion exchange on the surface, resulting in increased mechanical strength . The objective of this project is to study the kinetics of crystallization of a glass composition based on cordierite (2MgO.2Al2O3.5SiO2), low density and high hardness, for the manufacture of glass-ceramics for ballistic tests. Shown in this report are results of heat treatment of crystallization and characterization by thermal analysis (DSC) glass obtained previously, indicating uneven distribution of crystals, and drying, weighing, mixing of raw materials and a new fusion of glass, the same composition

EStudo fundamental da interação de nanopartículas metálicas com íons terras raras em vidros e vitrocerâmicas para aplicações na região do infravermelho

Pós-graduação em Química - IQ

In vitro evaluation of Biosilicate® dissolution on dentin surface: a SEM analysis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estética em sistema metal free associado a núcleos metalocerâmicos personalisados

The evolution of ceramic systems currently allows the manufacture of prosthesis similar to the natural teeth, meeting the expectations of patients. However, when using vitreous ceramic the color of substrate is significant for the esthetic result, requiring planning aesthetic cores when involved reconstruction of endodontically treated teeth without coronal structure. Thus, the aim of this study to describe a case report of aesthetic rehabilitation in upper anterior teeths using vitreous ceramic system for the reconstruction of elements: 11, 12, 21 and 22 after endodontically treated. It was emphasized the removal of crowns and manufacture of custom cast post and core with ceramic in coronal portion, prioritizing the aesthetic result. Through the clinical results observed can be seen that the use of custom cast post and core with ceramic in association lithium disilicate glass ceramics provided a satisfactory aesthetic result.

Estudo clínico retrospectivo de restaurações cerâmicas do tipo laminado sobre dentes com ou sem preparo dentário: 1 a 5 anos de acompanhamento

Pós-graduação em Odontologia - FOA

Mechanical strength and subcritical crack growth under wet cyclic loading of glass-infiltrated dental ceramics

Objectives. Evaluate the flexural strength (sigma) and subcritical crack growth (SCG) under cyclic loading of glass-infiltrated alumina-based (IA, In-Ceram Alumina) and zirconia-reinforced (IZ, In-Ceram Zirconia) ceramics, testing the hypothesis that wet environment influences the SCG of both ceramics when submitted to cyclic loading.Methods. Bar-shaped specimens of IA (n = 45) and IZ ( n = 45) were fabricated and loaded in three-point bending (3P) in 37 degrees C artificial saliva (IA(3P) and IZ(3P)) and cyclic fatigued (F) in dry (D) and wet (W) conditions (IA(FD), IA(FW), IZ(FD), IZ(FW)). The initial sigma and the number of cycles to fracture were obtained from 3P and F tests, respectively. Data was examined using Weibull statistics. The SCG behavior was described in terms of crack velocity as a function of maximum stress intensity factor (K(Imax)).Results. The Weibull moduli (m = 8) were similar for both ceramics. The characteristic strength (sigma(0)) of IA and IZ was and 466 MPa 550 MPa, respectively. The wet environment significantly increased the SCG of IZ, whereas a less evident effect was observed for IA. In general, both ceramics were prone to SCG, with crack propagation occurring at K(I) as low as 43-48% of their critical K(I). The highest sigma of IZ should lead to longer lifetimes for similar loading conditions.Significance. Water combined with cyclic loading causes pronounced SCG in IZ and IA materials. The lifetime of dental restorations based on these ceramics is expected to increase by reducing their direct exposure to wet conditions and/or by using high content zirconia ceramics with higher strength. (C) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Durability of feldspathic veneering ceramic on glass-infiltrated alumina ceramics after long-term thermocycling.

This study compared the bond strength durability of a feldspathic veneering ceramic to glass-infiltrated reinforced ceramics in dry and aged conditions. Disc shaped (thickness: 4 mm, diameter: 4 mm) of glass-infiltrated alumina (In-Ceram Alumina) and glass-infiltrated alumina reinforced by zirconia (In-Ceram Zirconia) core ceramic specimens (N=48, N=12 per groups) were constructed according to the manufacturers' recommendations. Veneering ceramic (VITA VM7) was fired onto the core ceramics using a mold. The core-veneering ceramic assemblies were randomly divided into two conditions and tested either immediately after specimen preparation (Dry) or following 30000 thermocycling (5-55 oC±1; dwell time: 30 seconds). Shear bond strength test was performed in a universal testing machine (cross-head speed: 1 mm/min). Failure modes were analyzed using optical microscope (x20). The bond strength data (MPa) were analyzed using ANOVA (α=0.05). Thermocycling did not decrease the bond strength results for both In-Ceram Alumina (30.6±8.2 MPa; P=0.2053) and In-Ceram zirconia (32.6±9 MPa; P=0.3987) core ceramic-feldspathic veneering ceramic combinations when compared to non-aged conditions (28.1±6.4 MPa, 29.7±7.3 MPa, respectively). There were also no significant differences between adhesion of the veneering ceramic to either In-Ceram Alumina or In-Ceram Zirconia ceramics (P=0.3289). Failure types were predominantly a mixture of adhesive failure between the veneering and the core ceramic together with cohesive fracture of the veneering ceramic. Long-term thermocycling aging conditions did not impair the adhesion of the veneering ceramic to the glass-infiltrated alumina core ceramics tested.

Recycling of glass cullet as aggregate for clays used to produce roof tiles

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Phase transition and dielectric properties of La-doped Pb(Zr, Ti)O-3 antiferroelectric ceramics

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of Airborne-Particle Abrasion and Mechanico-Thermal Cycling on the Flexural Strength of Glass Ceramic Fused to Gold or Cobalt-Chromium Alloy

Purpose: To evaluate the effect of airborne-particle abrasion and mechanico-thermal cycling on the flexural strength of a ceramic fused to cobalt-chromium alloy or gold alloy.Materials and Methods: Metallic bars (n = 120) were made (25 mm x 3 mm x 0.5 mm): 60 with gold alloy and 60 with Co-Cr. At the central area of the bars (8 mm x 3 mm), a layer of opaque ceramic and then two layers of glass ceramic (Vita VM13, Vita Zahnfabrick) were fired onto it (thickness: 1 mm). Ten specimens from each alloy group were randomly allocated to a surface treatment [(tungsten bur or air-particle abrasion (APA) with Al(2)O(3) at 10 mm or 20 mm away)] and mechanico-thermal cycling (no cycling or mechanically loaded 20,000 cycles; 10 N distilled water at 37 degrees C and then thermocycled 3000 cycles; 5 degrees C to 55 degrees C, dwell time 30 seconds) combination. Those specimens that did not undergo mechanico-thermal cyclingwere stored inwater (37 degrees C) for 24 hours. Bond strength was measured using a three-point bend test, according to ISO 9693. After the flexural strength test, failure types were noted. The data were analyzed using three factor-ANOVA and Tukey's test (alpha = 0.05).Results: There were no significant differences between the flexural bond strength of gold and Co-Cr groups (42.64 +/- 8.25 and 43.39 +/- 10.89 MPa, respectively). APA 10 and 20 mm away surface treatment (45.86 +/- 9.31 and 46.38 +/- 8.89 MPa, respectively) had similar mean flexural strength values, and both had significantly higher bond strength than tungsten bur treatment (36.81 +/- 7.60 MPa). Mechanico-thermal cycling decreased the mean flexural strength values significantly for all six alloy-surface treatment combinations tested when compared to the control groups. The failure type was adhesive in the metal/ceramic interface for specimens surface treated only with the tungsten bur, and mixed for specimens surface treated with APA 10 and 20 mm.Conclusions: Considering the levels adopted in this study, the alloy did not affect the bond strength; APA with Al(2)O(3) at 10 and 20 mm improved the flexural bond strength between ceramics and alloys used, and the mechanico-thermal cycling of metal-ceramic specimens resulted in a decrease of bond strength.