Morphological Control of Porous Structure in Al-Ti Intermetallics Foam Manufactured by Reactive Precursor Process

2014 ◽  
Vol 794-796 ◽  
pp. 790-795
Author(s):  
Makoto Kobashi ◽  
Naoyuki Kanetake
Keyword(s):  
Melting Point ◽  
Porous Structure ◽  
Cell Structure ◽  
Exothermic Reaction ◽  
Combustion Reaction ◽  
Maximum Temperature ◽  
Reaction Products ◽  
Open Cell ◽  
Morphological Control ◽  
Novel Processing

In this paper, a novel processing method (reactive precursor method) to manufacture high-melting point porous Al-Ti intermetallics is investigated. Especially, morphological control of porous structure is focused. In the reactive precursor process, precursors are made by blending aluminum and titanium powders. The precursor is heated to ignite an exothermic reaction (so called “combustion reaction”) between the elemental powders. Pore formation is a well-known intrinsic feature of the combustion reaction, and we tried to control the pore morphology. Fundamentally, the closed-cell structure can be obtained when the maximum temperature during the reaction exceeds the melting point of the reaction product. By blending the exothermic agent powder in the precursor, the maximum temperature is increased and the reaction products are melted. The porosity is controlled by the maximum temperature. In contrast, an open-cell porous structure can be obtained when the maximum temperature is below the melting point of the reaction product. Microwave heating turned out to be an effective method to create an open cell structure. A powdery substance that does not react with other elemental powders (heat-absorbing agent powder) decreases the temperature during the reaction. Closed, open and bimodal-sized open pores have been achieved by the reactive precursor process so far.

Fabrication of three dimensional open porous regular structure of PA-2200 for enhanced strength of scaffold using selective laser sintering

2016 ◽  
Vol 22 (4) ◽  
pp. 752-765 ◽  
Author(s):  
Jatender Pal Singh ◽  
Pulak M. Pandey ◽  
Anita Kamra Verma
Keyword(s):  
Porous Structure ◽  
Pore Size ◽  
Process Parameters ◽  
Cell Structure ◽  
Selective Laser Sintering ◽  
Three Dimensional ◽  
Laser Sintering ◽  
Open Cell ◽  
Content Type ◽  
Open Porous Structure

Purpose Scaffolds are essentially required to have open porous structure for facilitating bone to grow. They are generally placed on those bone defective/fractured sites which are more prone to compressive loading. Open porous structure lacks in strength in comparison to solid. Selective laser sintering (SLS) process is prominently used for fabrication of polymer/composite scaffolds. So, this paper aims to study for fabrication of three-dimensional open porous scaffolds with enhanced strength, process parameters of SLS of a biocompatible material are required to be optimized. Design/methodology/approach Regular open porous structures with suitable pore size as per computer-aided design models were fabricated using SLS. Polyamide (PA-2200) was used to fabricate the specimen/scaffold. To optimize the strength of the designed structure, response surface methodology was used to design the experiments. Specimens as per ASTM D695 were fabricated using SLS and compressive testing was carried out. Analysis of variance was done for estimating contribution of individual process parameters. Optimized process parameters were obtained using a trust region algorithm and correlated with experimental results. Accuracy of the fabricated specimen/scaffold was also assessed in terms of IT grades. In vitro cell culture on the fabricated structures confirmed the biocompatibility of polyamide (PA-2200). Findings Optimized process parameters for open cell process structures were obtained and confirmed experimentally. Laser power, hatch spacing and layer thickness have contributed more in the porous part’s strength than scan speed. The accuracy of the order of IT16 has been found for all functional dimensions. Cell growth and proliferation confirmed biocompatibility of polyamide (PA-2200) for scaffold applications. Originality/value This paper demonstrates the biocompatibility of PA-2200 for scaffold applications. The optimized process parameters of SLS process for open cell structure having pore size 1.2 × 1.2 mm2 with strut diameter of 1 mm have been obtained. The accuracy of the order of IT16 was obtained at the optimized process factors.

Novel Processing of Porous Titanium Composite for Producing Open Cell Structure

2007 ◽  
Vol 539-543 ◽  
pp. 1004-1009 ◽  
Author(s):  
Makoto Kobashi ◽  
Naoyuki Kanetake
Keyword(s):  
Latent Heat ◽  
Volume Fraction ◽  
Cell Structure ◽  
Processing Condition ◽  
Physical And Mechanical Properties ◽  
Titanium Boride ◽  
Porous Titanium ◽  
High Porosity ◽  
Reaction Products ◽  
Open Cell

Processing technique to produce open-cell porous titanium composite was developed. One of the outstanding benefits of porous titanium composite is both physical and mechanical properties can be controlled widely by changing the metal/ceramic fraction and cell structures. In this work, porous titanium composite was fabricated by a chemical reaction between titanium powder and boron carbide (B4C) powder. The reactions between titanium and B4C generates a large amount of latent heat and, therefore, it was a combustion and self-propagating mode. Precursors were made by compacting the starting powder blend (Ti and B4C), and heated in an induction furnace to induce the reaction. The reaction was strongly exothermic and, therefore, the precursor was sintered by its latent heat when the Ti/B4C blending ratio was appropriate. The reaction products were titanium boride (TiB and/or TiB2) and titanium carbide (TiC). By controlling the Ti/B4C blending ratio, it was possible to control the volume fraction of reaction products in titanium matrix. The combustion synthesized titanium composite was porous and its cell structure was strongly affected by the processing condition of the precursor (porosity and Ti/B4C blending ratio). High porosity with open pores was obtained with small Ti/B4C ratios and high porosity of the precursor, while the cell structure was closed and spherical with high Ti/B4C ratio. The cell-wall size was varied from several tens of microns to about 500 microns by changing the combustion temperature.

Organic Open-cell Porous Structure Modeling

2020 ◽  
Author(s):  
Lihao Tian ◽  
Lin Lu ◽  
Weikai Chen ◽  
Yang Xia ◽  
Charlie C. L. Wang ◽  
...  
Keyword(s):  
Porous Structure ◽  
Structure Modeling ◽  
Open Cell

Predictions of Current Attachment at Thermionic Cathode for TIG Arcs

2008 ◽  
Vol 580-582 ◽  
pp. 319-322 ◽  
Author(s):  
Manabu Tanaka ◽  
Kentaro Yamamoto ◽  
Tashiro Shinichi ◽  
John J. Lowke
Keyword(s):  
Melting Point ◽  
Work Function ◽  
Atmospheric Pressure ◽  
The Other ◽  
Numerical Calculations ◽  
Maximum Temperature ◽  
Arc Plasma ◽  
Melting Points ◽  
Thermionic Cathode ◽  
Uniform Current

Study of current attachment at thermionic cathode for TIG arc at atmospheric pressure is attempted from numerical calculations of arc-electrodes unified model. The calculations show that the maximum temperature of arc plasma close to the cathode tip for W-2% ThO2 reaches 19,000 K and it is the highest value in comparison with the other temperatures for W-2% La2O3 and W-2% CeO2, because the current attachment at the cathode tip is constricted by a centralized limitation of liquid area of ThO2 due to its higher melting point. The calculations also show that, in cases of W- 2% La2O3 and W-2% CeO2, the liquid areas of La2O3 and Ce2O3 are widely expanded at the cathode tip due to their lower melting points and then produce uniform current attachments at the cathode. It is concluded that the current attachment at thermionic cathode is strongly dependent on work function, melting point and Richardson constant of emitter materials.

Porous Bioceramics (Open Cell Foams) Expanded in Vacuum

2006 ◽  
Vol 309-311 ◽  
pp. 1023-1026
Author(s):  
E.T. Uzumaki ◽  
C.S. Lambert
Keyword(s):  
Zirconium Oxide ◽  
Cell Structure ◽  
The Body ◽  
Carbon Coatings ◽  
Open Cell ◽  
Glass Foam ◽  
Open Cell Foams ◽  
Titanium Foam ◽  
Porous Bioceramics ◽  
Scanning Electron

In this study, porous bioceramics (titanium foam with diamond-like carbon coatings, glass foam and zirconium oxide foam) were produced using expansion in vacuum. The porosity, the pore size and pore morphology can be adjusted in agreement with the application. The different 3D structures were obtained by varying the parameters of the process. The microstructure and morphology of the porous materials were observed by scanning electron microscopy (SEM) and optical microscopy. The foam exhibit an open-cell structure with interconnected macropores, which provide the potential for tissue ingrowths and the transport of the body fluids.

Too Hot to Handle? Full-Thickness Burn Injury in a Child Caused by Cyanoacrylate Glue and Cotton—A Case Report and Experimental Study

2020 ◽  
Author(s):  
Madeleine Jacques ◽  
Sonia Tran ◽  
Monique Bertinetti ◽  
Andrew J A Holland
Keyword(s):  
Case Report ◽  
Burn Injury ◽  
Exothermic Reaction ◽  
Skin Grafting ◽  
Radiant Heat ◽  
Maximum Temperature ◽  
Full Thickness ◽  
Cyanoacrylate Glue ◽  
Potential Harm ◽  
Education And Awareness

Abstract Domestic superglue (cyanoacrylate) in the hands of children can have devastating consequences, especially when cotton clothing is involved. When cotton comes into contact with cyanoacrylate, an intense exothermic reaction occurs, creating temperatures high enough to cause significant thermal injury. A literature review found 16 such cases of burns documented (2 adult and 14 pediatric). This article presents a case report of a 4-year-old child sustaining a full-thickness burn injury to her leg requiring skin grafting when superglue was spilt onto cotton pants. She was sitting near a fan heater at the time. An experiment was conducted to replicate the exothermic reaction between superglue and cotton and to determine if the addition of radiant heat would have any significant effect. The maximum temperature reached with one 3-g tube of superglue onto cotton pyjamas was 91°C (196°F) and occurred approximately 90 seconds postapplication. It took more than 3 minutes for the temperature to cool below 40°C (104°F). The addition of radiant heat from a fan heater placed 60 cm from the clothing found that the temperature peak was similarly reached and cooled, but the temperature did not reduce below 52°C (126°F) for over 20 minutes, proving that potential harm may be amplified if first aid is not appropriately sought. Product labeling and the knowledge of potential harm from such mechanism of injury remain inadequate. It is hoped that the reporting of this case contributes to an increase in public education and awareness of such dangers and may contribute to preventing avoidable future incidences.

scholarly journals Formation of Phases in Reactively Sintered TiAl3 Alloy

Molecules ◽  
2020 ◽  
Vol 25 (8) ◽  
pp. 1912
Author(s):  
Andrea Školáková ◽  
Pavel Salvetr ◽  
Jindřich Leitner ◽  
Tomáš Lovaši ◽  
Pavel Novák
Keyword(s):  
Melting Point ◽  
Exothermic Reaction ◽  
Intermetallic Phase ◽  
Optical Pyrometer ◽  
Heating Rates ◽  
Preferential Formation ◽  
High Temperature Synthesis ◽  
Chemical Equations ◽  
New Finding ◽  
Two Stages

This work highlights new results on the synthesis of the TiAl3 intermetallic phase using self-propagating high-temperature synthesis. This method is considered a promising sintering route for intermetallic compounds. It was found that the reactions proceed in two stages. Below the melting point of aluminum, the Ti2Al5 phase forms at 450 °C after long annealing times by a direct solid-state reaction between the aluminum and titanium, and is converted consequently to TiAl3. This is a completely new finding; until now, many authors have believed in the preferential formation of the TiAl3 phase. The second stage, the self-propagating strongly exothermic reaction, proceeds above the melting point of aluminum. It leads to the formation of the TiAl3 phase accompanied by Ti2Al5 and Ti3Al phases. The reaction mechanism was shown in the form of chemical equations, which were supported by calculating Gibbs energy. Reaction temperatures (Tonset, Tmaximum, and Toffset) were determined after induction heating thanks to recording by an optical pyrometer. This finding provides completely new opportunities for the determination of activation energy at heating rates, in which common calorimeters are not able to detect a response or even measure. Now, the whole procedure will become accessible.

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