Search results for "CERAMICS"

Non-destructive automatic determination of aspect ratio and cross-sectional properties of fibres

2015

A novel method for computerised estimation of the aspect ratio distribution and various cross-sectional geometrical properties of fibres in short-fibre reinforced composites is proposed. The method, based on X-ray micro-computed tomography, is non-destructive and does not require user intervention. Based on results on specially fabricated model material, the accuracy and precision of the method seems adequate. The method is applied in analysing a manufacturing process of wood fibre reinforced thermoplastic composite. The results indicate a significant decrease of the aspect ratio of fibres during the processing steps. Finally, the feasibility of the method is assessed by estimating paramete…

Thermal stability of transition alumina nanocrystals with different microstructures

2018

Abstract The preparation of well-crystallized boehmite nanoparticles with different morphologies, encompassing from aciculae or rods of 320, 150 and 70 nm of length to platelets of 50 nm in diameter, allowed a comparative study of their respective thermal evolutions as alumina precursors. Static thermal treatments of boehmite nanocrystals at 600, 1000 and 1200 °C and a dynamic, in situ synchrotron study between 100 and 1000 °C revealed that original boehmite microstructures, i.e. size and shape of the nanoparticles, were kept not only in γ-Al 2 O 3 but also in transitional aluminas up to 1000 °C. Specifically, at that temperature, acicular samples presented θ-Al 2 O 3 structure, while in pl…

Mechanism of crystallization of fast fired mullite-based glass–ceramic glazes for floor-tiles

2006

Abstract The mechanism of crystallization from a B 2 O 3 -containing glass, with composition based in the CaO–MgO–Al 2 O 3 –SiO 2 system, to a glass–ceramic glaze was studied by different techniques. Glass powder pellets were fast heated, simulating current industrial tile processing methods, at several temperatures from 700 to 1200 °C with a 5 min hold. Microstructural study by field emission scanning electron microscopy revealed that a phase separation phenomenon occurred in the glass, which promoted the onset of mullite crystallization at 900 °C. The amount of mullite in the glass heated between 1100 and 1200 °C was around 20 wt%, as determined by Rietveld refinement. The microstructure …

Effect of boron oxide on the microstructure of mullite-based glass-ceramic glazes for floor-tiles in the CaO–MgO–Al2O3–SiO2 system

2006

Abstract The effect of increasing replacement of Al2O3 by B2O3 in a parent glass on the sintering and further crystallization of mullite was investigated. The composition of the parent glass was chosen in the mullite primary phase field of the CaO–MgO–Al2O3–SiO2 quaternary system. Glass powder pellets were heated under standard (10 °C/min and 2 h of hold time) and fast heatings (25 °C/min and 5 min of hold time) at different temperatures from 700 to 1190 °C. Sintering of B2O3-containing glasses took place in the range between 850 and 1050 °C. X-ray diffraction results showed that mullite formed as unique crystalline phase for glasses containing amounts of B2O3 larger than 6 wt%. For lower a…

Green composites: A brief review

2011

The rising concern towards environmental issues and, on the other hand, the need for more versatile polymer-based materials has led to increasing interest about polymer composites filled with natural-organic fillers, i.e. fillers coming from renewable sources and biodegradable. The composites, usually referred to as "green", can find several industrial applications. On the other hand, some problems exist, such as worse processability and reduction of the ductility. The use of adhesion promoters, additives or chemical modification of the filler can help in overcoming many of these limitations. These composites can be further environment-friendly when the polymer matrix is biodegradable and c…

Occupational leukoderma due to phenolic compounds in the ceramics industry?

1991

Tracheal Ceramic Rings for Tracheomalacia: A Review After 17 Years

2007

Background: Despite different support techniques, the surgical management of tracheomalacia is still a challenging problem. Satisfactory results after internal stenting are above 80%, whereas, when performing external stenting using biocompatible ceramic rings, results are reported at over 90%. Objective: The purpose of this study was to examine the efficiency of surgical treatment in patients with segmentary tracheomalacia using external ceramic ring grafts. Methods: In this retrospective study, we collected data from 12 patients who underwent surgery during the last 17 years for symptomatic segmentary tracheomalacia by use of biocompatible aluminum-oxide ceramic rings. All except one pati…

Tracheomalacia Repair Using Ceramic Rings

1992

Tracheomalacia resulting from tracheostomy or compressive thyroid disease often represents a difficult problem in airway management. In an attempt to improve this condition, biocompatible ceramic rings were surgically implanted in 16 patients to restore normal patency of the airway by first expanding the tracheal lumen lateral, and then in an anterior dimension. Preoperatively, patients displayed moderate to severe obstruction with marked restrictions in lifestyle, as confirmed by history, physical examination, and airway resistance studies. Additionally, three of these patients were trach-dependent at the time of implantation. Postoperatively all 16 patients have normal airway resistance p…

Bone Marrow Concentrate and Bovine Bone Mineral for Sinus Floor Augmentation

2011

Purpose: The purpose of this work was to evaluate the potential of substituting autogenous bone (AB) by bone marrow aspirate concentrate (BMAC). Both AB and BMAC were tested in combination with a bovine bone mineral (BBM) for their ability of new bone formation (NBF) in a multicentric, randomized, controlled, clinical and histological noninferiority trial.Materials and Methods: Forty-five severely atrophied maxillary sinus from 26 patients were evaluated in a partial cross-over design. As test arm, 34 sinus of 25 patients were augmented with BBM and BMAC containing mesenchymal stem cells. Eleven control sinus from 11 patients were augmented with a mixture of 70% BBM and 30% AB. Biopsies wer…

Efficacy of a bioactive alloplast, in the treatment of human periodontal osseous defects-a clinical study.

2010

Presently, bone replacement grafts are one of the modalities of therapy for which there is histologic evidence of regeneration coronal to the base of the previous osseous defect. Bioactive glasses are used extensively in medicine and dentistry. This study evaluated the additional efficacy of a bioactive alloplast, PerioGlas, in comparison with open flap debridement only. 8 systemically healthy volunteers were chosen, each having 2 collateral sites with ?6 mm clinical probing depth and radiographic evidence of an intrabony defect. Randomly, one defect was treated with open flap debridement plus bioactive glass (test) and the other with open flap debridement alone (control). At baseline, 3, 6…