Effect of Gold Tailing Addition on the Mechanical Properties and Microstructure of Foam Ceramics

Round 1

Reviewer 1 Report

This manuscript focuses on the characterisation of ceramic foams for insulation purposes that incorporate gold tailings in the replacement of pearlite. Here are my comments.

1-    There are several occurrences in the manuscript where the decimal separator is a comma instead of a baseline dot. This should be corrected.

2-    The weight percent sum up in Table 2 does not account to 100 in some cases. How to authors attributed the difference?

3-    In line 97 what does CS mean? This should be defined in the text.

4-    There is a process step missing in Figure 3, the breaking down of the blocks according to the description.

5-    In line 128 the authors state that the raw materials were mixed. Where the raw materials ground prior to mixing? If so, it should be mentioned.

6-    In line 137 what do authors mean by microcrystalline?

7-    I suggest the authors to modify the charts in Figure 6a, b. Is does not make much sense having a line linking two points in a xx-yy chart, especially when the xx axis does not represent a numerical variation. A bar chart comparing the wet and dry conditions seems more adequate.

8-    In line 170, how does the variation in volume density is defensible according to Figure 5?

9-    In line 180, how much do authors mean by ‘significantly’?

10- In line 182, what are the requirements for light materials? Perhaps it should be indicated.

11- Authors state that 0.9% of SiC is the best amount. My question is related to the meaning of this value in terms of reproducibility. How many experiments did authors do to confirm this amount?

12- I recommend a careful proofreading. There are several typos along the manuscript.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The article is interesting from practical and economical points of view. Each technology that helps to manage waste should be developed. Especially when it is connected with a reduction of production costs (energy and raw materials). However, in the present form, the manuscript requires several improvements:

There is no need to introduce a comma in four-digit numbers such as temperature. It causes mistakes eg.  in Fig 9 in a caption there is (1,000 / Tp ) and the numbers in X axis are in hundreds while in Table 5 we can find the column (1,000 / Tp ) with numbers after the comma.

The authors should write in the introduction what parameters of the foam ceramics are the most desirable and what parameters have commercially available materials.

The authors should explain in the introduction why they want to add glass granules - justification

to prove the economical value of the research the authors should compare the average price (per tone) of perlite and gold tailing

The author should explain (define) what they have in mind when they write about crystallisation temperature what exactly is happening in this temperature.

At around 1000°C perlite can expand. Does this process influence the foaming process of samples with perlite?

line 67 and line 355, the polycarboxylic acid is called water reducer and superplasticizer. In the colloidal processing of ceramics, polycarboxylic acid is used as dispersing agent. What is the real function of this compound?  Please, keep the uniform nomenclature.

Table 1, All values are in weight %. However, when you add up the numbers you get 101,2%. Please explain this in text

Line 110, “…..a foaming agent made of silicon carbide….”- the foaming agent was a SiC

Lines 115-120, the description is unclear eg. “the powdered billet was poured into….”( liquid can be poured) or “…cooled from 900°C to room temperature using a furnace.”

 Also, explain that during sintering the volume of samples increases due to the foaming process. Is it possible to connect the chemical composition with the increase of volume (in number)?

In the results the authors wrote about wet and dry grinding, however, in the preparation part there is nothing about dry grinding.

Line 188, typo

The authors should propose an explanation why they observed a drastic change of properties when the addition  of glass granules exceeded 30%

Figure 6 and others – the size of characters should be increased

Line 221,  “ .. the higher value and…” – the higher value of what?

Iine 222 – what does it mean that the crystallisation peak tends to become sharp?

Section 3.2 – the authors calculate the crystallization activation energy. What is a practical aspect of this research (in respect to technology)? How it can be use in practice?

Line 250, typo

Line 296, “F.ig. 12e shows the crystal growth and pore wall in the 2-3 samples. There is a small amount of needle-like crystals between the bulk crystals….”  - These needle-like crystals are invisible!!!! Please, give an image where they can be found.

Table 7, there is no units here

Line 339, “..The microcrystalline foam ceramic samples with superior crystallinity can be prepared….”- what does it mean a “superior crystallinity”?

Line 343-350,  the authors showed only one result of EDS analysis but here they draw a huge conclusion based on EDS analysis. The authors should support this conclusion  by delivering the proper experimental results

Line  376, “…and the number of crystals gradually decreases.” – how it was calculated?

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Generally, the authors modified the text properly but still, there are a few small (minor) things to correct.

 Ad .2 )

The authors introduce nice text but they should add some numbers eg. low volume density (<400kg/m³)

Foamed ceramic is a kind of building fire insulation material with high porosity ( …%) , low thermal conductivity (……), high compressive strength  (> ….) and small volume density (<400kg/m³). It can be made into ceiling and floor and other building panels.

 

Ad. 7)

Change from “…… water reducer (The water reducer was a polycarboxylic acid (PC) high-efficiency water reducer which was produced by Beijing Muhu admixture Co., Ltd. (Beijing, China)) were added to prepare foam ceramics (Table 1).”     to    “……. water reducer (polycarboxylic acid (PC) produced by Beijing Muhu admixture Co., Ltd. (Beijing, China)) were added to prepare foam ceramics (Table 1).”

 

Ad. 10)

The improved sentence “Then the raw materials are mixed into……..” should be rewritten because it is unclear (English language correction is required)

 

Ad. 11)

The main idea of this comments was that the authors should give in text how the perlite replacement by gold tailing influenced on the final volume: the same, decreased, increased. Quantify it in cm or %

 

Ad.12)

English language correction is required

 

Ad. 14)

This explanation should be placed in the text

 

Ad. 15)

The size of the letters on the figure should be increased.

In my opinion, the violet letters are a bad choice due to low visibility

The caption under the figure is unchanged !!!!!

The authors introduce the “delta” into the figure thus they should write in the text what it means.

 

Ad. 18)

This explanation (justification of this section) should be incorporated into the text. Otherwise, it is unclear why the authors write about it

 

Ad. 20)

Still, I can not see these needle-like structures in a microstructure. Please check this https://www.nonmet.mat.ethz.ch/education/courses/Materialwissenschaft_2/brevier.pdf  on page 17. Here the authors gave a good SEM and clearly marked the needle-like crystals.

Author Response

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Author Response File: Author Response.docx