Cobalt/Silica Nanocomposites Overview

Questions and Answers

What is the total length when adding 3440 cm and 160 cm?

3602 cm

3600 cm (correct)

3500 cm

3300 cm

What is the relationship between 1635 cm and 800 cm?

800 cm is less than 1635 cm (correct)

1635 cm is less than 800 cm

1635 cm is a multiple of 800 cm

800 cm is greater than 1635 cm

If you subtract 160 cm from 3440 cm, what is the result?

3300 cm (correct)

3200.5 cm

3280 cm

3200 cm

When comparing 3440 cm, 160 cm, and 800 cm, which statement is true?

800 cm is the second largest Signup and view all the answers

If you average 3440 cm, 160 cm, and 800 cm, what is the result?

1380 cm Signup and view all the answers

Which statement best describes the relationship of 3440 cm to the other two measurements?

3440 cm is more than the sum of 160 cm and 800 cm Signup and view all the answers

Which method was used to analyze the thermal behavior of the precursor and calcined samples?

Thermal gravimetric analysis Signup and view all the answers

What was the maximum operating voltage for the mission electron microscopy used?

200 kV Signup and view all the answers

What was used as a capping agent in the experiment?

Ethylene glycol Signup and view all the answers

At what heating rate was the sample heated during the thermal analysis?

10 °C min−1 Signup and view all the answers

Which precursor was used for cobalt in the experiment?

Cobalt(II) nitrate hexahydrate Signup and view all the answers

What role did ammonium hydroxide solution play in the preparation process?

pH adjustment Signup and view all the answers

Which chemical was used as a silica precursor?

TEOS Signup and view all the answers

What was the weight range of the sample loaded in the ceramic sample holder for thermal analysis?

10–20 mg Signup and view all the answers

What was the primary method used to synthesize the Co/SiO2 nanocomposite powders?

Thermal calcination-reduction process Signup and view all the answers

Which phase formation was confirmed after the calcination and reduction stages?

Co3O4 and Co Signup and view all the answers

The Co-gelation method was found to be the best approach for which of the following?

Combining cobalt and silica sources in the same solution Signup and view all the answers

What was one of the key characteristics of the Co/SiO2 nanocomposite powders produced?

Thermal stability Signup and view all the answers

Which analytical techniques were used to confirm phase formation?

XRD and FTIR Signup and view all the answers

When were the Co/SiO2 nanocomposite powders received for review?

26 August 2010 Signup and view all the answers

Where was the research conducted?

Central Metallurgical Research and Development Institute Signup and view all the answers

Which of the following best describes the received revisions for the research article?

Received in revised form on 11 February 2011 Signup and view all the answers

What is the estimated average particle size of the cobalt oxide phase?

10 nm Signup and view all the answers

Which of the following particle sizes corresponds to the results of the pore volume measurements?

3.10 nm Signup and view all the answers

What shape do the cobalt particles take in the reduced sample?

Spherical Signup and view all the answers

What range of sizes do the particles in the sample fall into?

30–70 nm Signup and view all the answers

What method was used to obtain the particle size distribution for the cobalt oxide phase?

TEM imaging Signup and view all the answers

What structural formation is noted for the cobalt particles in relation to silica?

Core/shell structure Signup and view all the answers

At what temperature was the sample calcined before reduction?

400 °C Signup and view all the answers

What is the significance of the values obtained from XRD data in this study?

They support the particle size data. Signup and view all the answers

What is the effect of adding EG as a protective agent in the formation of cobalt nanoparticles?

It enhances the formation of regular pores. Signup and view all the answers

What is the maximum thermal stability achieved for cobalt nanoparticles in a silica matrix?

400 °C Signup and view all the answers

What type of nanoparticles are being discussed in the context of silica matrix?

Cobalt nanoparticles Signup and view all the answers

What does TGA measure in the provided context?

Thermal stability and decomposition Signup and view all the answers

What was the drying temperature for the SGP50 sample in the experiment?

80 °C Signup and view all the answers

What is indicated by the DTG curve in the experiment?

Rate of weight loss as a function of temperature Signup and view all the answers

What is the significance of well-dispersed cobalt nanoparticles as mentioned in the content?

They have high thermal stability. Signup and view all the answers

What temperature range does the TGA and DTG analysis cover?

100 to 600 °C Signup and view all the answers

Study Notes

Synthesis of Cobalt/Silica Nanocomposites

Cobalt/silica (Co/SiO2) nanocomposite powders achieved successful synthesis through a thermal calcination-reduction process applied to gel precursors.
The Co-gelation method effectively combines cobalt and silica sources in a single solution, optimizing the materials' preparation.

Characterization Techniques

X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) confirmed the formation of single Co3O4 and metallic cobalt (Co) phases after calcination and reduction.
Transmission Electron Microscopy (TEM) utilized a JEOL-1230 microscope operating at a maximum voltage of 200 kV for particle size analysis.

Materials Used

Cobalt(II) nitrate hexahydrate (Co(NO3)2·6H2O) served as the cobalt precursor, while TEOS (Tetraethoxysilane) was used for silica.
Ethylene glycol and dimethylformamide acted as capping and reducing agents, respectively, while ammonium hydroxide controlled the pH during synthesis.

Thermal Analysis

Thermal behavior of the samples analyzed through Thermal Gravimetric Analysis (TGA) and Differential Thermal Analysis (DTA) recorded data during heating up to 700°C at a rate of 10°C/min in an air stream.
Well-dispersed cobalt nanoparticles demonstrated high thermal stability up to 400°C.

Particle Characteristics

The cobalt oxide (Co3O4) exhibited a near-spherical shape with an average particle size of about 10 nm.
Reduced samples displayed spherical cobalt particles within a silica matrix, forming a core/shell structure, with sizes ranging from 30-70 nm.

Pore Structure and Stability

The addition of ethylene glycol improved pore formation during calcination and reduction, resulting in a well-dispersed arrangement within the silica matrix.
Pore volume measurements reported values ranging from 3.10 nm to 5.73 nm across different samples.

Conclusion

The proposed synthesis route successfully produced thermally stable Co/SiO2 nanocomposites, emphasizing the controlled synthesis and characterizations leading to favorable nanocomposite properties.

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Description

This quiz explores the synthesis and characterization of cobalt/silica (Co/SiO2) nanocomposite powders. It covers techniques such as thermal calcination-reduction and the Co-gelation method, highlighting their effectiveness in materials preparation. Additionally, X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) are discussed for confirming material properties.