Direct Inkjet Printing of Digitally Designed 2D TiN Patterns

Round 1

Reviewer 1 Report

The main purpose of this study is preparing TiN suspention for their implementation in Direct Inkjet Printing . This work is quite interesting, but further experimental works and rewriting must be required in order to meet the standard of Coatings journal.Below are some comments that authors should take into account

1. What is the comparison with other similar work?
2. What is the advantage of new suspentions over other types?
3. more description on why this type is selected?
4. more analysis of the results is needed.
5. Enhancement of the literature review is useful.

Author Response

We thank for the reviewer’s comments. Mistakes has been edited and corrected.

 

1. What is the comparison with other similar work?

There are not publications dealing with Inkjet printing with a TiN-based ink.

TiN coatings have been tackled using different techniques, where the thickness or sintered mass and temperature are key parameters to define the final properties of the surface, substrate or coating. Consequently, considering that we have design different grinds by inkjet printing, not a coating, a comparative study is difficult to handle. However, a couple of publication dealing with the TiN coatings of Ti and Ni foams has been added and commented. Lines: 29-34 were added.

 

2. What is the advantage of new suspensions over other types?

The low solid content inks we formulated has the advantage of being printable by inkjet printing. It was tune to fit the jet requirements for the used printer as well as to avoid evaporation defects. Novelty of the suspension is mainly focus on the particle. Up to our knowledge, TiN nanoparticles have been never printed by Inkjet.

The advantage of this suspension is that it can be printed by IJP, but probably other solvent composition and additives can be also formulated for the same purpose. Lines 68-69 were added to the text “The choice of the solvent and co-solvent is related with the printability of the ink…”

 

3. more description on why this type is selected?

Solvents and additives are chosen to fit printing conditions of a nonoxide nanoparticles inks Lines 142 -146 explain why the combination of this two solvents were necessary. “As it can be observed in the Figure 2a the printed patterns were poorly defined due to the spreading of the ink on the surface. Therefore, it was necessary to modify the characteristics of the suspension. by diluting with DEG in a 3:1 suspension:DEG ratio. In this case the suspension was suitable for printing obtaining solid line as shows in Figure 2b.”

 

4. more analysis of the results is needed.

We agreed with the referee that this is work shows very good results being the first time that TiN has been use in IJP. Authors plan to do more research on these coatings due to the novelty of the material that enhances the hardness of the substrate in the area which was coated by ink. Future works will study different printed patterns, more layers, etc.

 

5. Enhancement of the literature review is useful.

Some new articles have been added to the bibliography and commented in the text.

- Yakovlev, A., Milichko, V., Pidko, E. et al. Inkjet printing of TiO2/AlOOH heterostructures for the formation of interference color images with high optical visibility. Sci Rep 6, 37090 (2016). https://doi.org/10.1038/srep37090

- A. Sobolev, P. Stein, K. Borodianskiy, Synthesis and characterization of NiO colloidal ink solution for printing components of solid oxide fuel cells anodes, Ceramics International, Volume 46, Issue 16, Part A, 2020, Pages 25260-25265, https://doi.org/10.1016/j.ceramint.2020.06.318.

-Gonzalez, Z., Yus, J., Moratalla, R., & Ferrari, B. (2021). Electrophoretic deposition of binder-free TiN nanoparticles to design 3D microstructures. The role of sintering in the microstructural robustness of supercapacitor electrodes. Electrochimica Acta, 369. https://doi.org/10.1016/j.electacta.2020.137654

-Mendoza, C., González, Z., Castro, Y., Gordo, E., & Ferrari, B. (2016). Improvement of TiN nanoparticles EPD inducing steric stabilization in non-aqueous suspensions. Journal of the European Ceramic Society, 36(2), 307–317. https://doi.org/10.1016/j.jeurceramsoc.2015.06.023

-Mendoza, C., Gonzalez, Z., Gordo, E., Ferrari, B., & Castro, Y. (2018). Protective nature of nano-TiN coatings shaped by EPD on Ti substrates. Journal of the European Ceramic Society, 38(2), 495–500. https://doi.org/10.1016/j.jeurceramsoc.2017.09.046

 

 

 

Reviewer 2 Report

Major

• The authors showed that they reformed Ti surface by inkjet printing of a TiN nanoparticles ink with grid patterns, followed by thermal treatment. However, it is not clear how homogeneous are the coatings achieved by the 0.5 to 1 mm grid patterns: Figure 4 and the last sentence in the conclusion reveal that there are significant inhomogeneity, while Table 3 and Figure 5 imply that the average values are valid. It is strongly recommended that the authors should give the readers dimensionally distributed data along the surface to estimate the blurring or diffusion of the sintered pattern.

Minor

• A number of abbreviations (EPD, IJP, Re, We, SS, TT…) appear without explanation in the context.
• IJP is used (mixed) with its complete term, ‘inkjet printing,’ throughout the context.
• A scale bar should be given in Fig. 1(a).
• The common and varied experimental conditions for patterns (lines) in Fig. 1 and Fig. 2 should be given.
• Typos are found (in 30, 111, 160, …).

Author Response

Authors thank for the reviewer’s comment.

• A number of abbreviations (EPD, IJP, Re, We, SS, TT…) appear without explanation in the context.

 Mistakes has been edited and corrected.

• IJP is used (mixed) with its complete term, ‘inkjet printing,’ throughout the context.

IJP has been used as unique term after explaining the abbreviation.

• A scale bar should be given in Fig. 1(a).

Scale bar has been added.

• The common and varied experimental conditions for patterns (lines) in Fig. 1 and Fig. 2 should be given.

The electrical parameters have been added and rewritten.

• Typos are found (in 30, 111, 160, …).

Typos have been corrected, and the whole text was revised.

Reviewer 3 Report

Dear authors,

Please make the following changes to your article:

1. In the introduction, it is necessary to add not only alternative methods for obtaining coatings, but also the novelty and interest of inkjet printing technology using other types of inks (based on metal nanoparticles, oxide ceramics, etc.), for example:

- Yakovlev, A., Milichko, V., Pidko, E. et al. Inkjet printing of TiO2/AlOOH heterostructures for the formation of interference color images with high optical visibility. Sci Rep 6, 37090 (2016). https://doi.org/10.1038/srep37090

- A. Sobolev, P. Stein, K. Borodianskiy, Synthesis and characterization of NiO colloidal ink solution for printing components of solid oxide fuel cells anodes, Ceramics International, Volume 46, Issue 16, Part A, 2020, Pages 25260-25265, https://doi.org/10.1016/j.ceramint.2020.06.318.

2. The purpose of this study is not very clear, add to the introduction.
3. Paragraph 2.1 Describe how the suspension was dispersed and in what modes (Time, speed, etc.). Add the voltage used on the piezoelectric head and frequency, etc.
4. Paragraph 3.1 To the tabular data (Table 2) it is necessary to add graphs measuring the zeta potential and particle size.
5. Briefly describe the mechanism of suspension micellization upon the addition of TiN particles to polyethyleneimine.
6. What is the aggregative stability of this suspension?

Author Response

1.- In the introduction, it is necessary to add not only alternative methods for obtaining coatings, but also the novelty and interest of inkjet printing technology using other types of inks (based on metal nanoparticles, oxide ceramics, etc.), for example:

Authors acknowledge the reviwer’s comments. These two references have been added to the text. Authors have also included a new paragraph describing better the novelty of this technology with TiN. Lines 79-81 “The objective of the present work focuses on the validation of IJP technology for the fabrication of 2D TiN patterns with high design resolution.”

- Yakovlev, A., Milichko, V., Pidko, E. et al. Inkjet printing of TiO2/AlOOH heterostructures for the formation of interference color images with high optical visibility. Sci Rep 6, 37090 (2016). https://doi.org/10.1038/srep37090

- A. Sobolev, P. Stein, K. Borodianskiy, Synthesis and characterization of NiO colloidal ink solution for printing components of solid oxide fuel cells anodes, Ceramics International, Volume 46, Issue 16, Part A, 2020, Pages 25260-25265, https://doi.org/10.1016/j.ceramint.2020.06.318.

2- The purpose of this study is not very clear, add to the introduction.

We added the text “The objective of the present work focuses on the validation of IJP technology for the fabrication of 2D TiN patterns with high design resolution. These digitally designed TiN patterns will improve the resistance to aggressive environments and high temperatures of the coated substrates” in lines 77-81

 

3.- Paragraph 2.1 Describe how the suspension was dispersed and in what modes (Time, speed, etc.). Add the voltage used on the piezoelectric head and frequency, etc.

A deeper study of the PEI adsorption can be found in reference 34.

A short description of this process has been added to the text. Lines 116-122

“The drops were optimized to obtain a homogenous pattern (Figure 1b) by adjusting the voltage (230 V), frequency (1036 Hz), and the pulse of the piezoelectric (135 us). Negative air pressure (-20 mBar) at the nozzle were established to avoid dripping. Moreover, constant pass condition with a separation of 0.01 mm between drops, and 30 ˚C of nozzle temperature, were selected”

 

4.- Paragraph 3.1 To the tabular data (Table 2) it is necessary to add graphs measuring the zeta potential and particle size.

Measurements of zeta potential and particle size were done using a DLS Malvern nanosizer Z series. This results were published previously in the reference 38. That’s why we did not added them in this paper. Moreover, with the data shown in table 1 we believe that the characterization is sufficient.  This text has been added to the manuscript. Lines 94-95 “2 wt% using polyethyleneimine (PEI, Sigma Aldrich, Germany) as dispersant (1.5 wt.% of PEI) following the procedure described by Mendoza et al. [38], reaching a Zeta potential value of +70 mV.”

 

5.- Briefly describe the mechanism of suspension micellization upon the addition of TiN particles to polyethyleneimine.

Basically, the negatively charged surface of the TiN nanoparticles will adsorb the positively charged amine groups of the PEI, covering until covering the whole particle.

Authors have implemented this text in the manuscript. Lines 139-143

“…+70mV due to the PEI adsorption, thus the dispersion and stabilization of the particles against aggregation is manly done by electrical repulsion but also steric intercations, obtaining a stable and well dispersed suspension that will not flocculate even at the isoelectric point. Basically, the negatively charged surface of the TiN nanoparticles will adsorb the positively charged amine groups of the PEI, until fully covering the particle surface.”

 

6.- What is the aggregative stability of this suspension?

The incorporation of PEI helps here due to the electrostatic and steric interactions among the coated particles. Even if at certain conditions the surface charge is 0 and some particles could aggregate, they will never flocculate due to the steric interactions of the polymer which is covering the surface of the nanoparticle. Particle surfaces will never be in actual contact, making the redispersion super easy. Authors have included some lines in the text to describe this phenomenon. Lines 139-143

“…+70mV due to the PEI adsorption, thus the dispersion and stabilization of the particles against aggregation is manly done by electrical repulsion but also steric interactions, obtaining a stable and well dispersed suspension that will not flocculate even at the isoelectric point. Basically, the negatively charged surface of the TiN nanoparticles will adsorb the positively charged amine groups of the PEI, until fully covering the particle surface.”

 

 

 

Reviewer 4 Report

Direct Inkjet Printing of Digitally Designed 2D TiN Patterns- J. Yus et al.

General Comments: This is a very well-written paper on TiN ceramic, and is of interest to the community. Inkjet printing of TiN is explored via some optimized parameters that resulted in 2D printed patterns. The paper may be accepted in its present form. My specific comments are provided below.

 

Specific Comments:

• Was there any optimization performed for the sintering? Was there any influence on temperature/pressure on the part quality?
• The measured harness is influenced by the coated and uncoated areas. How was the dispersion obtained? Were these locations for measurements ascertained in a random manner?

Author Response

Authors acknowledge the reviwer’s comments.

• Was there any optimization performed for the sintering? Was there any influence on temperature/pressure on the part quality?

The optimization of the temperature were performed in previous works, the use of vacuum avoid the oxidation however similar results can be obtained under a reductor atmosphere. The common temperature for this material is around 1200 ºC to obtain a full consolidation of the microstructure. However, in our case due to the grid design of the coating 1100ºC was enough to sinter it.

 

• The measured hardness is influenced by the coated and uncoated areas. How was the dispersion obtained? Were these locations for measurements ascertained in a random manner?

Very interesting point. The reviewer is right, the hardness was measured with the nanoindentator at random locations for several tests.  The distribution of points in the figure 5 shows clear differences in the mechanical compression form areas uncoated (3.5GPa) to coted ones (5.5 GPa). In addition, the micrograph in Figure 4 shows areas where after sintering the coating disappears, this is because part of the TiN enters into solid solution with the Ti of the substrate, which also causes a hardness gradient and not two distinct areas in the scattering of points in the graphs of Figure 5.

Round 2

Reviewer 1 Report

Thanks to the authors for their response. Under the current conditions, accept the article in present form for published

Author Response

Thank you very much for your comments! 

Kind regards, 

Joaquin Yus

Reviewer 2 Report

The authors didn't response to the reviewers' major comments.

Even though the authors mentioned that the condition was suitable for printing obtaining solid line, more explanation is needed about the different aspects of printed lines in Fig1b as well as in Fig2b.

Author Response

Authors thank the reviewer for his/her inputs. We apologize if the previous comments weren't fully answered. We revised and corrected them. 

Previous comments (Review 1):

• The authors showed that they reformed Ti surface by inkjet printing of a TiN nanoparticles ink with grid patterns, followed by thermal treatment. However, it is not clear how homogeneous are the coatings achieved by the 0.5 to 1 mm grid patterns: Figure 4 and the last sentence in the conclusion reveal that there are significant inhomogeneity, while Table 3 and Figure 5 imply that the average values are valid. It is strongly recommended that the authors should give the readers dimensionally distributed data along the surface to estimate the blurring or diffusion of the sintered pattern.

Answer: Very interesting point. The reviewer is right, the hardness was measured with the nanoindentator at random locations for several tests.  However, authors wanted to show the reader an idea of the average hardness of the surface, first. Then an explanation of how this values doesn't follow a trend is explained from line 204. The distribution of points in the figure 5 shows clear differences in the mechanical compression from areas uncoated (3.5GPa) to coated ones (5.5 GPa). In addition, the micrograph in Figure 4 shows areas where after sintering the coating disappears, this is because part of the TiN enters into solid solution with the Ti of the substrate, which also causes a hardness gradient and not two distinct areas in the scattering of points in the graphs of Figure 5.

An improved in the description of figure 5b was added lines 217-224: "[...], both grids showed a similar distribution of hardness and Young’s modulus points for both coatings, being the 0.5 grid (figure 5b) slightly higher. In both graphs, the distribution of points shows clear differences in the mechanical compression from uncoated areas (3.0-3.5GPa) to coated ones (5.0-5.8 GPa). In addition, the micrograph in Figure 4 shows areas where after sintering the coating disappears, this is because part of the TiN enters into solid solution with the Ti of the substrate, which also causes a hard-ness gradient and not two distinct areas in the scattering of points in the graphs of Figure 5. [...] The larger the coated surface, the higher the hardness values obtained"

 

Specific comments (Review 2):

• -Even though the authors mentioned that the condition was suitable for printing obtaining solid line, more explanation is needed about the different aspects of printed lines in Fig1b as well as in Fig2b.

Answer: A new paragraph (highlighted in blue) was added to the Figure 1 description, making sure the defects were described:  "The drops were optimized to obtain a homogenous pattern (Figure 1b) by adjusting the voltage (230 V), frequency (1036 Hz), and the pulse of the piezoelectric (135 us). Negative air pressure (-20 mBar) at the nozzle was established to avoid dripping. Moreover, constant pass conditions with a separation of 0.01 mm between drops, and 30 ˚C of nozzle temperature, were selected. Figure 1a shows the spherical drops after optimizing the printing parameters. Low operating pressures provide uniform jetting without satellite drops. In figure 1b, different defects were obtained due to the fact that the oscillation frequency and pulse were not adjusted, producing ink smudges (first, third, and fourth lines) and discontinuities (second line) in the line thickness. Finally, a well-defined line – bottom line – was created by adjusting the frequency, the pulse voltage, and the speed movement of the printer head."

 

 

Reviewer 3 Report

Good job

Author Response

Thank you very much! We really appreciated your previous comments and suggestions.

Best regards, 

Joaquin Yus