Fabrication and characterization of aluminum nitride sponges using a mixture of two porous formation methods

MRS Advances ◽  
2019 ◽  
Vol 4 (54) ◽  
pp. 2977-2987
Author(s):  
Rodrigo Alan Martínez Molina ◽  
José Egberto Bedolla Becerril ◽  
Ena Athenea Aguilar Reyes ◽  
Raul Alejando Pulido Aguilar ◽  
Carlos Arreola Fernandez
Keyword(s):  
Aluminum Nitride ◽  
Ceramic Powder ◽  
Inert Atmosphere ◽  
Gel Casting ◽  
Hydrolysis Products ◽  
Porous Formation ◽  
Stirring Time ◽  
Mean Size ◽  
Gelcasting Process

ABSTRACTA method for the fabrication of interconnected ceramic sponges was used in the present work, designed by using a combination of two different, aqueous gel casting and sacrificial template, using aluminum nitride powder (99.97%) with a mean size of 2.4 micrometers. Two types of sponges were made by using two different monomers, acrylamide and methacrylamide, the resultants sponges have 60% of porosity after being sintered and pyrolyzed at temperature of 1673 K using an inert atmosphere of argon for 1 h. The hydrolysis evolution of this ceramic powder during the gelcasting process was studied by measuring the pH during the stirring time, the microstructure changes during the time of exposure were observed in a SEM. XRD were made to study the present phases after the gel was eliminated by thermal treatment at 873 K using an oxidizing atmosphere, observing a formation of up to 4 %wt. of cubic alumina phase which was made after the hydrolysis products. Infrared spectroscopy was used to study the changes in the ceramic powder.

Influence of Preparation Parameter on the Grain Size of LaB6 Powder Synthesized by SHS with Reduction Process

2010 ◽  
Vol 105-106 ◽  
pp. 351-354 ◽  
Author(s):  
Ni Jiang ◽  
Wei Min Wang ◽  
Zheng Yi Fu ◽  
Hao Wang ◽  
Yu Cheng Wang ◽  
...  
Keyword(s):  
Grain Size ◽  
Ceramic Powder ◽  
Reduction Process ◽  
Synthesis Temperature ◽  
Inert Atmosphere ◽  
High Temperature Synthesis ◽  
Compact Pressure ◽  
Mean Grain Size ◽  
Mean Size ◽  
The Mean

Self-propagating high-temperature synthesis with reduction process was used to fabricate LaB6 ceramic powder from La2O3-B2O3-Mg system. The combustion reaction carried out in inert atmosphere (Ar) and the combustion temperature was about 1600°C. The products were washed with dilute hydrochloric acid and distilled water, respectively, to remove LaBO3, Mg3B2O6, MgO and other impurities. The influence of compact pressure and addition of SHS diluent on the grain size was studied. The result indicates that as the compact pressure increased, the mean size of powder decreased gradually. The addition of diluents reduced the synthesis temperature, and as the amount of diluent increased, the grain size of LaB6 powder was found to reduce continuously. Microstructure analyses show that the mean grain size of LaB6 powder prepared by SHS with reduction process is less than 500 nm, which is finer compared with the grain size prepared by traditional process.

Construction of plastic contact deformation maps on ceramics: a case study on aluminum nitride

1996 ◽  
Vol 54 ◽  
pp. 636-637
Author(s):  
D. L. Callahan
Keyword(s):  
Plastic Deformation ◽  
Aluminum Nitride ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Bright Field Image ◽  
Perfectly Plastic ◽  
Contrast Analysis ◽  
Deformation Patterns

Modern polishing, precision machining and microindentation techniques allow the processing and mechanical characterization of ceramics at nanometric scales and within entirely plastic deformation regimes. The mechanical response of most ceramics to such highly constrained contact is not predictable from macroscopic properties and the microstructural deformation patterns have proven difficult to characterize by the application of any individual technique. In this study, TEM techniques of contrast analysis and CBED are combined with stereographic analysis to construct a three-dimensional microstructure deformation map of the surface of a perfectly plastic microindentation on macroscopically brittle aluminum nitride.The bright field image in Figure 1 shows a lg Vickers microindentation contained within a single AlN grain far from any boundaries. High densities of dislocations are evident, particularly near facet edges but are not individually resolvable. The prominent bend contours also indicate the severity of plastic deformation. Figure 2 is a selected area diffraction pattern covering the entire indentation area.

CBED analysis of impurity distributions in AlN

1990 ◽  
Vol 48 (4) ◽  
pp. 214-215
Author(s):  
Daniel Callahan ◽  
G. Thomas
Keyword(s):  
Aluminum Nitride ◽  
Bulk Material ◽  
Strong Dependence ◽  
Lattice Parameter ◽  
Promising Technique ◽  
Nitride Ceramics ◽  
Surface Phases ◽  
Convergent Beam ◽  
Oxygen Impurities

Oxygen impurities may significantly influence the properties of nitride ceramics with a strong dependence on the microstructural distribution of the impurity. For example, amorphous oxygen-rich grain boundary phases are well-known to cause high-temperature mechanical strength degradation in silicon nitride whereas solutionized oxygen is known to decrease the thermal conductivity of aluminum nitride. Microanalytical characterization of these impurities by spectral methods in the AEM is complicated by reactions which form oxygen-rich surface phases not representative of the bulk material. Furthermore, the impurity concentrations found in higher quality ceramics may be too low to measure by EDS or PEELS. Consequently an alternate method for the characterization of impurities in these ceramics has been investigated.Convergent beam electron diffraction (CBED) is a promising technique for the study of impurity distributions in aluminum nitride ceramics. Oxygen is known to enter into stoichiometric solutions with AIN with a consequent decrease in lattice parameter.

Fabrication, Optimization and Characterization of Paclitaxel and Spirulina Loaded Nanoparticles for Enhanced Oral Bioavailability

2020 ◽  
Vol 16 (5) ◽  
pp. 723-733
Author(s):  
Keerthi G.S. Nair ◽  
Yamuna Ravikumar ◽  
Sathesh Kumar Sukumaran ◽  
Ramaiyan Velmurugan
Keyword(s):  
Gastric Cancer ◽  
Oral Bioavailability ◽  
Surfactant Concentration ◽  
Polymer Concentration ◽  
Central Composite Rotatable Design ◽  
Normal Cells ◽  
Stirring Time ◽  
Nanoparticle Formulation ◽  
Central Composite

Background: Paclitaxel and spirulina when administered as nanoparticles, are potentially useful. Methods: Nanoformualtions of Paclitaxel and Spirulina for gastric cancer were formulated and optimized with Central composite rotatable design (CCRD) using Response surface methodology (RSM). Results: The significant findings were the optimal formulation of polymer concentration 48 mg, surfactant concentration 45% and stirring time of 60 min gave rise to the EE of (98.12 ± 1.3)%, DL of (15.61 ± 1.9)%, mean diameter of (198 ± 4.7) nm. The release of paclitaxel and spirulina from the nanoparticle matrix at pH 6.2 was almost 45% and 80% in 5 h and 120 h, respectively. The oral bioavailability for the paclitaxel spirulina nanoparticles developed is 24.0% at 10 mg/kg paclitaxel dose, which is 10 times of that for oral pure paclitaxel. The results suggest that RSM-CCRD could efficiently be applied for the modeling of nanoparticles. The paclitaxel and spirulina release rate in the tumor cells may be higher than in normal cells. Paclitaxel spirulina nanoparticle formulation may have higher bioavailability and longer sustainable therapeutic time as compared with pure paclitaxel. Conclusion: Paclitaxel-Spirulina co-loaded nanoparticles could be effectively useful in gastric cancer as chemotherapeutic formulation.

Application of Aluminum Nitride Thin Film for Micromachined Ultrasonic Transducers

2005 ◽  
Vol 892 ◽  
Author(s):  
Qianghua Wang ◽  
Jianzeng Xu ◽  
Changhe Huang ◽  
Gregory W Auner
Keyword(s):  
Thin Films ◽  
Aluminum Nitride ◽  
Ultrasonic Transducers ◽  
X Ray Diffraction ◽  
Effective Coupling ◽  
Resonant Frequencies ◽  
X Ray ◽  
Coupling Factors ◽  
Sandwiched Structure

AbstractThis paper reports the fabrication and characterization of micromachined ultrasonic transducers (MUT) based on piezoelectric aluminum nitride (AlN) thin films. The MUT device is composed of an Al/AlN/Al sandwiched structure overlaid on top of a silicon (Si) diaphragm. X-ray diffraction (XRD) scan shows that highly c-axis oriented AlN (002) thin films have been grown on Al/Si(100) substrates. Electrical impedance of the MUT devices is analyzed as a function of frequency. The fundamental resonant frequencies of the devices are found in the range of 65-70 kHz, which are in approximation to the theoretical calculation. The effective coupling factors of the devices are also derived as 0.18.

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