scholarly journals Advanced Open-Celled Structures from Low-Temperature Sintering of a Crystallization-Resistant Bioactive Glass

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3653 ◽  
Author(s):  
Hamada Elsayed ◽  
Acacio Rincon Romero ◽  
Devis Bellucci ◽  
Valeria Cannillo ◽  
Enrico Bernardo
Keyword(s):  
Bioactive Glass ◽  
Room Temperature ◽  
Low Temperature Sintering ◽  
Organic Base ◽  
Digital Light Processing ◽  
Direct Foaming ◽  
Excellent Control ◽  
Manufacturing Technologies ◽  
45S5 Bioglass ◽  
Highly Porous

Most materials for bone tissue engineering are in form of highly porous open-celled components (porosity >70%) developed by means of an adequate coupling of formulations and manufacturing technologies. This paper is dedicated to porous components from BGMS10 bioactive glass, originally designed to undergo viscous flow sintering without crystallization, which is generally known to degrade the bioactivity of 45S5 bioglass. The adopted manufacturing technologies were specifically conceived to avoid any contamination and give excellent control on the microstructures by simple operations. More precisely, ‘green’ components were obtained by digital light processing and direct foaming of glass powders suspended in a photosensitive organic binder or in an aqueous solution, activated with an organic base, respectively. Owing to characteristic quite large sintering window of BGMS10 glass, sintering at 750 °C caused the consolidation of the structures generated at room temperature, without any evidence of viscous collapse.

A Convenient, Room-Temperature — Organic Base Protocol for Preparing Chiral 3-(Enoyl)-1,3-oxazolidin-2-ones.

ChemInform ◽  
2003 ◽  
Vol 34 (15) ◽  
Author(s):  
Vadim A. Soloshonok ◽  
Hisanori Ueki ◽  
Changchun Jiang ◽  
Chaozhong Cai ◽  
Victor J. Hruby
Keyword(s):  
Room Temperature ◽  
Organic Base

Engineering stiffness in highly porous biomimetic gelatin/tertiary bioactive glass hybrid scaffolds using graphene nanosheets

2020 ◽  
Vol 154 ◽  
pp. 104668
Author(s):  
Ehsan Zeimaran ◽  
Sara Pourshahrestani ◽  
Hui Yin Nam ◽  
Nasrul Anuar bin Abd Razak ◽  
Katayoon Kalantari ◽  
...  
Keyword(s):  
Bioactive Glass ◽  
Graphene Nanosheets ◽  
Hybrid Scaffolds ◽  
Highly Porous

scholarly journals RSM-BBD Optimization of Fenton-Like Degradation of 4-Nitrophenol Using Magnetite Impregnated Kaolin

2020 ◽  
Vol 13 ◽  
pp. 117862212093212
Author(s):  
Neway Belachew ◽  
Redeat Fekadu ◽  
Amare Ayalew Abebe
Keyword(s):  
Room Temperature ◽  
Low Cost ◽  
Quadratic Model ◽  
Vibrating Sample Magnetometer ◽  
X Ray Diffraction ◽  
Box Behnken Design ◽  
X Ray ◽  
Sem Image ◽  
Pure Phases ◽  
Highly Porous

In this work, we have reported a low-cost and environmentally friendly Fe3O4-modified activated kaolin (AK-Fe3O4) composite for efficient Fenton-like degradation of 4-nitrophenol (4-NP) and optimization of the degradation variables. The AK-Fe3O4 composites were characterized by Fourier transform infrared spectroscopy, powder x-ray diffraction, scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). X-ray diffraction confirms the syntheses of pure phases of Fe3O4 and AK-Fe3O4. The SEM image of the AK-Fe3O4 composite reveals the formation of a highly porous surface. The room temperature VSM analysis describes the superparamagnetic nature of AK-Fe3O4 composites with 25 emu/g magnetization values. Response surface methodology coupled with Box-Behnken design was used to optimize the 4-NP degradation (%) variables such as contact time (10-90 minutes), 4-NP concentration (10-30 mg/L), and pH (3-8). The high regression value ( R² = 0.9964 and adjusted R² = 0.9917) and analysis of variance ( P < .0001) show that the quadratic model can sufficiently explain the 4-NP degradation (%). The optimum 4-NP degradation was found to be 96.01% ± 1.89% using 1 mg/mL of AK-Fe3O4, 20 mg/L of 4-NP, 97.9 mmol/L of H2O2, and pH of 3 at the end of 75 minutes of reaction time. Moreover, the catalyst shows good recyclability and stability after 5 successive degradations of 4-NP. In general, a low-cost and magnetically separable AK-Fe3O4 composite is an effective Fenton-like catalyst for the degradation of 4-NP.

scholarly journals A Comparison of Bioactive Glass Scaffolds Fabricated ‎by Robocasting from Powders Made by Sol–Gel and Melt-Quenching Methods

Processes ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 615
Author(s):  
Basam A. E. Ben-Arfa ◽  
Robert C. Pullar
Keyword(s):  
Mechanical Properties ◽  
Bioactive Glass ◽  
Bone Growth ◽  
Sol Gel ◽  
Glass Network ◽  
Silica Content ◽  
Bioactive Glasses ◽  
Phosphorous Content ◽  
High Silica ◽  
45S5 Bioglass

Bioactive glass scaffolds are used in bone and tissue biomedical implants, and there is great interest in their fabrication by additive manufacturing/3D printing techniques, such as robocasting. Scaffolds need to be macroporous with voids ≥100 m to allow cell growth and vascularization, biocompatible and bioactive, with mechanical properties matching the host tissue (cancellous bone for bone implants), and able to dissolve/resorb over time. Most bioactive glasses are based on silica to form the glass network, with calcium and phosphorous content for new bone growth, and a glass modifier such as sodium, the best known being 45S5 Bioglass®. 45S5 scaffolds were first robocast in 2013 from melt-quenched glass powder. Sol–gel-synthesized bioactive glasses have potential advantages over melt-produced glasses (e.g., greater porosity and bioactivity), but until recently were never robocast as scaffolds, due to inherent problems, until 2019 when high-silica-content sol–gel bioactive glasses (HSSGG) were robocast for the first time. In this review, we look at the sintering, porosity, bioactivity, biocompatibility, and mechanical properties of robocast sol–gel bioactive glass scaffolds and compare them to the reported results for robocast melt-quench-synthesized 45S5 Bioglass® scaffolds. The discussion includes formulation of the printing paste/ink and the effects of variations in scaffold morphology and inorganic additives/dopants.

scholarly journals Simple methods for identification of radiative properties of highly-porous ceria ceramics in the range of semi-transparency

2017 ◽  
Vol 27 (5) ◽  
pp. 1108-1117 ◽  
Author(s):  
Leonid A. Dombrovsky ◽  
Wojciech Lipinski
Keyword(s):  
Absorption Coefficient ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Radiative Properties ◽  
Spectral Absorption ◽  
Spectral Absorption Coefficient ◽  
Content Type ◽  
Hemispherical Reflectance ◽  
Steady Oscillations ◽  
Highly Porous

Purpose The aim of this paper is to present advanced experimental–numerical methods for identification of spectral absorption and scattering properties of highly porous ceria ceramics in the range of semi-transparency at room and elevated temperatures. Design/methodology/approach At room temperature, a period of quasi-steady oscillations of the sample surface temperature generated in response to recurrent laser heating at fixed values of the maximum and minimum temperature of the irradiated surface is measured along with the normal-hemispherical reflectance. Radiative properties are then identified using a combined heat transfer model. At elevated temperatures, an analytical solution proposed in an earlier study for zirconia ceramics is used to retrieve spectral absorption coefficient of ceria ceramics from the measured normal emittance. Findings and Originality/value This method can be used to obtain small absorption coefficient of ceria ceramics at room temperature. The required measurements of both the normal-hemispherical reflectance and the period of quasi-steady oscillations of the irradiated surface temperature of the ceramics sample between fixed values of the maximum and minimum temperatures can be readily conducted using thermal laboratory equipment. Another method has been suggested for identification of the spectral absorption coefficient of ceria ceramics at elevated temperatures. This method is based on a relation between the measured normal emittance of an isothermal sample and the absorption coefficient.

Thermal Debinding of Ceramic-Filled Photopolymers

2015 ◽  
Vol 825-826 ◽  
pp. 75-81 ◽  
Author(s):  
Markus Pfaffinger ◽  
Gerald Mitteramskogler ◽  
Robert Gmeiner ◽  
Jürgen Stampfl
Keyword(s):  
Ceramic Powder ◽  
Volume Ratio ◽  
Ceramic Composites ◽  
Mechanical Analysis ◽  
Temperature Cycle ◽  
Digital Light Processing ◽  
Organic Components ◽  
Dense Ceramic ◽  
Thermal Debinding ◽  
Manufacturing Technologies

Within the large variety of different additive manufacturing technologies stereolithography excels in high precision and surface quality. Using the Digital Light Processing (DLP) Technology a stereolithography-based system was developed, which is specifically designed for the processing of highly filled photopolymers.The powder-filled suspension enables the 3D-fabrication of a so called ceramic green part. In order to get a dense ceramic structure, subsequent thermal processing steps after the 3D-printing process are necessary. First, the polymer-ceramic composites heated up to 400°C. During this processing step, called debinding, the organic components are burned out. The resulting part, consisting of powder particles stabilized by physical interactions, is further heated to sinter the particles together, and the final, fully dense ceramic part is obtained.The debinding step is the most critical process. The used components have different evaporation or decomposition temperatures and behaviors. Thereby a reduction in weight and also in dimension occurs, which depends on the portion and composition of the organic components and especially on the temperature cycle. Furthermore, the physical characteristics of the ceramic powder, such as the particle size and the size distribution influence the debinding behavior. To measure the changes in weight and dimension a thermo-gravimetric (TGA) and a thermo-mechanical analysis (TMA) can be used. To avoid too high internal gas pressures inside the green parts a preferably constant gas evolution rate is seeked. Also the ‘surface-to-volume ratio’ affects the debinding characteristics. Therefore, optimized debinding cycles for specific geometries allow the crack-free debinding of parts with a wall thickness up to 20 mm.

Wetting of bioactive glass surfaces by poly(α-hydroxyacid) melts: interaction between Bioglass® and biodegradable polymers

e-Polymers ◽  
2005 ◽  
Vol 5 (1) ◽  
Author(s):  
Jonny J. Blaker ◽  
Véronique Maquet ◽  
Aldo R. Boccaccini ◽  
Robert Jérôme ◽  
Alexander Bismarck
Keyword(s):  
Bioactive Glass ◽  
Contact Angles ◽  
Scanning Electron Micrographs ◽  
Powder Bed ◽  
Solid Substrates ◽  
Gas Atmosphere ◽  
Adhesive Interactions ◽  
Glass Surfaces ◽  
45S5 Bioglass ◽  
Interfacial Characteristics

AbstractThe interfacial characteristics between bioactive glass (45S5 Bioglass®) surfaces and poly(α-hydroxyacid) melts have been assessed by direct wetting measurements. In particular, the wettability of Bioglass® powder by poly(D,Llactide) (PDLLA) and poly(D,L-lactide-co-glycolide) (PLGA) was assessed by imbibition measurements. Additionally, the equilibrium contact angles of PDLLA and PLGA melts on a sintered Bioglass® surface were measured. The surface energy of the bioactive glass and the polymers was determined from contact angles measured using various test liquids on PDLLA, PLGA and Bioglass® solid substrates. There are sufficient adhesive interactions between the polymers and Bioglass®. A simple heat treatment of the bioactive glass in an inert gas atmosphere leads to an improved wetting behaviour, indicating increased adhesive interactions. Scanning electron micrographs of the polymer + Bioglass® composites formed by polymer penetration into the powder bed show the formation of a ‘good quality’ interface.

scholarly journals Noise Properties of Graphene-Polymer Thick-Film Resistors

2017 ◽  
Vol 24 (4) ◽  
pp. 585-590 ◽  
Author(s):  
Krzysztof Mleczko ◽  
Piotr Ptak ◽  
Zbigniew Zawiślak ◽  
Marcin Słoma ◽  
Małgorzata Jakubowska ◽  
...  
Keyword(s):  
Thick Film ◽  
Room Temperature ◽  
Low Frequency ◽  
Frequency Noise ◽  
Potential Applications ◽  
Noise Measurements ◽  
Manufacturing Technologies ◽  
Main Component ◽  
Resistance Fluctuations ◽  
Parameter Values

AbstractGraphene is a very promising material for potential applications in many fields. Since manufacturing technologies of graphene are still at the developing stage, low-frequency noise measurements as a tool for evaluating their quality is proposed. In this work, noise properties of polymer thick-film resistors with graphene nano-platelets as a functional phase are reported. The measurements were carried out in room temperature. 1/f noise caused by resistance fluctuations has been found to be the main component in the specimens. The parameter values describing noise intensity of the polymer thick-film specimens have been calculated and compared with the values obtained for other thick-film resistors and layers used in microelectronics. The studied polymer thick-film specimens exhibit rather poor noise properties, especially for the layers with a low content of the functional phase.

Ceramic Component Processing Development for Advanced Gas Turbine Engines

1993 ◽  
Vol 115 (1) ◽  
pp. 1-8 ◽  
Author(s):  
B. J. McEntire ◽  
R. R. Hengst ◽  
W. T. Collins ◽  
A. P. Taglialavore ◽  
R. L. Yeckley
Keyword(s):  
Injection Molding ◽  
Room Temperature ◽  
Slip Casting ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Processing Conditions ◽  
Technology Applications ◽  
Ceramic Components ◽  
Manufacturing Technologies ◽  
Engine Components

Norton/TRW Ceramics (NTC) is developing ceramic components as part of the DOE-sponsored Advanced Turbine Technology Applications Project (ATTAP). NTC’s work is directed at developing manufacturing technologies for rotors, stators, vane-seat platforms, and scrolls. The first three components are being produced from a HIPed Si3N4, designated NT154. Scrolls were prepared from a series of siliconized silicon-carbide (Si-SiC) materials designated NT235 and NT230. Efforts during the first three years of this five-year program are reported. Developmental work has been conducted on all aspects of the fabrication process using Taguchi experimental design techniques. Appropriate materials and processing conditions were selected for power beneficiation, densification, and heat-treatment operations. Component forming has been conducted using thermal-plastic-based injection molding (IM), pressure slip-casting (PSC), and Quick-Set™ injection molding.1 An assessment of material properties for various components from each material and process were made. For NT154, characteristic room-temperature strengths and Weibull Moduli were found to range between ≈920 MPa to ≈1 GPa and ≈10 to ≈19, respectively. Process-induced inclusions proved to be the dominant strength-limiting defect regardless of the chosen forming method. Correction of the lower observed values is being addressed through equipment changes and upgrades. For the NT230 and NT235 Si-SiC, characteristic room-temperature strengths and Weibull Moduli ranged from ≈240 to ≈420 MPa, and 8 to 10, respectively. At 1370°C, strength values for both the HIPed Si3N4 and the Si-SiC materials ranged from ≈480 MPa to ≈690 MPa. The durability of these materials as engine components is currently being evaluated.

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