A Comparative Study on the Crystalline and Surface Properties of Carbonized Mesoporous Coconut Shell Chars

: In the present work, the facile thermal decomposition of raw coconut shells was carried out for the exploitation of the role of inert gas in the carbonization process and its role in determining the morphology, crystallographic parameters, and surface area of biochar before activation. The comparative investigation of mesoporous carbonized products synthesized with the mufﬂe and tube furnace was carried out at a similar temperature and an assessment was made with a commercial carbon. The focus of the work was aimed at the interpretation of surface morphology, elemental identiﬁcation, phase composition, interplanar spacing, full-width half maximum, crystallite size, lateral size, number of layers, dislocation density


Introduction
Carbon black is emerging as one of the most economical, as well as recurrently, used materials in various industries in modern applications.Owing to its porous structure, it can be effectively modified and, in the activated form, can be utilized for wastewater treatment and other adsorption purposes [1,2].Effective practical utilization of carbon black has encouraged an increasing demand for the production of low-budget carbon black.Bio-carbon obtained from agricultural waste is a potent material to synthesize carbon black because of its cost-effective advantages and low levels of inorganic compounds.Carbon black is known as one of the copiously formed materials of carbon, and it is estimated that roughly seventy percent of it is utilized as a pigment, as filler/reinforcement in rubber, and as elastomeric materials.The utilization of rubber in different applications relying on the addition of carbon black has been investigated for more than a hundred years [3].
Renewable energy sources and carbon capture applications are the current scientific verdict statements on other usages of carbon black that are of considerable attention [4].
Other key areas for the consumption of black carbon are now applicable to modern worldwide challenges, highlighting especially cleaner production, energy, various sensors [5,6], dielectric and electromagnetic interference materials [7], high-performance batteries [8], and polymer modifications [9].Current exploration has also extended the chemistry of carbon black to utilize it as a starting material for quantum dots of graphene and hollow spheres of carbon for extending its employment in the renewable energy sector in storage devices for electrochemical energy and remedy of the environment [10].Subsequently, the carbon black nanostructural product in the current methodologies is utilized for the grafting of polymers because functional groups are translated to carbon black with ease [11].Different carbon-containing natural materials (such as plant wood, agricultural waste, hardened shells of nuts, peat, lignite, char, coal) and amorphous porous materials (such as biochar, carbon gels, etc.) are utilized as common sources of raw material to produce activated carbon [12][13][14][15][16][17].The crop's routine need of the creatures on earth and their production led to excessive by-products and residual waste on the planet.These agricultural wastes are inexpensive and their fruitful consumption can be made by transforming these into useful products [18].As a result, the high surface area containing carbon products can be synthesized easily using agricultural by-products [19].Most of the biowastes are now utilized for the production of commercial carbon products.The abundance in availability of inexpensive agricultural raw materials and by-products supports their utilization [20].
Carbon black prepared from agricultural waste is used as an electrode material and supercapacitors in electronic devices [21][22][23][24][25]. Due to the inherently high surface area, inbuilt porosity, and easy tailoring ability, the synthesized material can meet the requirement of devices used for energy storage [26,27].Carbon black can be used to increase electrical conductance.Composites of insulated polymers can be fabricated using conductive fillers, including carbon black [28].It can be easily dispersed in an insulating matrix to get a composite with increased conductivity [29].Polymer composites prepared using carbon-based materials are useful candidates for shielding applications [30].The characteristics of the carbon black can also be varied depending on carbonization conditions, so optimization of carbonization conditions can be achieved by the appropriate selection of the heating rate and the activation temperature [31].It has been reported that the physical and chemical characteristics of carbon depend upon the source of origin or raw material used [32].One of the characteristics that distinguish a product from one another is the material composition (i.e., hemicellulose, cellulose, or lignin) [33].Carbon black showed microstructural variations depending on heat treatment.This knowledge is helpful to understand the role of heat-treatment practices such as carbonization, physical activation, chemical activation, graphitization, and stabilizing the product.
It is a known fact that carbon-based materials (such as carbon black, chars, or activated carbon) have demonstrated fine pore-size development than wood-based carbon products.The majority of the pores have shown a radius in nanometers, in the case of coconut shells, while carbon material originating from other woods has a significant number of macropores and mesopores [34,35].Black nanocarbon, specifically obtained from coconut shells as a bio-carbon source, has the potential for substituting the conventional thermoset filler in wear applications due to their high strength, low density, hardness, abrasion resistance, and modulus properties [36,37].It is reported that to produce mesoporous or macroporous material, lignocellulosic material is useful [38].Herein coconut shell also contains lignin as the major ingredient (i.e., 29.35%) so most of the pores are macro or mesoporous [39].The mesoporous-carbon coconut shell is a suitable raw material because it carries superb natural structure and possesses relatively a smaller ash as a by-product [40].By exposing the coconut shell to different experimental conditions, the structure and porosity of the activated carbon can be assessed.
The main focus of the current study is to provide a possibly inexpensive and lowcost carbonized product from agricultural wastes as a substitute for the synthesis of the current commercial carbon black [41,42].Carbon black is manufactured globally in tons each year because of its reasonably low associated cost compared to other conductive substances.Commercially, carbon is used in several industrial progressions and operations, such as the gasification of coal, ethanol synthesis, manufacture of fertilizer, natural gas production, refinery processing, and composites synthesis [43][44][45].Various activation techniques are available, however, the methods following non-activation techniques are useful for reducing the cost of manufactured materials [21].
Carbon materials, specifically mesoporous carbon, is an encouraging material having several applications.One of the crucial uses presented in the literature is through oral drug delivery systems [46][47][48], water purification [49][50][51], adsorbing media for the substrates [52,53], and catalytic support [54,55].There has been literature available us-ing thermal, XRD (X-ray Powder Diffraction), and BET (Brunauer, Emmet, and Teller) analysis of biochar of plant waste [56,57].Comparative studies are available for different carbonization and activation methods [58][59][60], but no information is available about the char's characteristics before activation.Gas flow can affect the surface properties of the material, so samples prepared in a tube furnace can have altered properties when compared with a muffle furnace.Activation of material through physical means is known as one of the easiest ways to increase the adsorption capacity of a surface [61,62].There is an observed lack of literature in a comparative investigation of the role of inert gas in determining the surface area of carbonized products.The basic difference between a tube and a muffle furnace is the circulation of inert gas.The inert gas is missing in a muffle furnace, so considering it the easiest way for a comparative study of the role of the inert gas current research was conducted using the carbonization method.The focus is given to investigating the properties of the mesoporous carbonized product synthesized using two extremely facile fundamental thermal decomposition processes.The purpose of the study is to explore the surface morphology, estimation of elemental composition, XRD parameters, and surface characteristics of carbonized products developed by facile thermal decomposition strategy.The comparison of properties is also made with product available activated commercial carbon black (CP).

Raw Materials
Coconut shells were used as raw materials to produce mesoporous carbon.The coconut shells were cleaned with distilled water.The drying of the cleaned coconut shell was carried out in an oven at 80 • C. The granulation of coconut was carried out in a granulator (SHINI, China Model No. SG-21P) to get smaller-sized naked particles.Carbon nanopowder (CP) with stock no US1078 size (<100 nm) was purchased from the US Research Nanomaterials, Inc. (Houston, TX, USA) for a comparative study.

Thermal Decomposition of Coconut Shells
The granules of coconut shells were thermally degraded in the following way.a.
Muffle Furnace sample (MFCB) The ceramic boat was loaded with granules of coconut shells and mounted in a muffle furnace (PROTHERM, France Model: PLF 120/15) with dimensions D × W × H = 30 × 22 × 23 cm at 400 • C for 2 h.After giving the annealing time of 6 h, the product was removed and ground in a laboratory blender (WARING, USA Model No. HGBTWTG4) to get powder.The powder product was sieved further to get the mesoporous product.The powder was further sieved using 3 U.S. mesh to get the product (Figure 1).

b.
Tube Furnace sample (TFCB) The ceramic boat was filled with granules of coconut shells and heated inside a tube furnace (PROTHERM, France model: PTF 12/75/800, dimensions: D × W × H = 635 × 850 × 400, tube type: C610) at a temperature of 400 • C at a heating rate of 5 • C/min for 2 h under an inert atmosphere of N 2 .After carbonization, the product was cooled to room temperature and after annealing for 6 h, it was ground in a laboratory blender to get powder.The carbonized product was obtained by sieving the product.The carbonized product given in Figure 1 was obtained by sieving the product with 3 U.S. mesh.

Characterization
Three characterization techniques were utilized to study morphology, elemental identification, phase composition, crystallinity, particle size, dimension, and specific surface area of the carbonized product.The field-emission scanning electron microscope (FESEM) imaging, along with the elemental distribution spectra (EDS), was obtained using Carl Zeiss, Germany (Supra 55vp) instrument.
The surface area and particle size (SAP) analysis was performed on Micromeritics, USA (ASAP 2020) instrument to measure the specific surface area of the material.Brunauer-Emmett-Teller's theory aims to explain the physical adsorption of gas molecules on a solid surface and serves as the basis for an important analysis technique for the measurement of the specific surface area of materials.

Characterization
Three characterization techniques were utilized to study morphology, elemental identification, phase composition, crystallinity, particle size, dimension, and specific surface area of the carbonized product.The field-emission scanning electron microscope (FESEM) imaging, along with the elemental distribution spectra (EDS), was obtained using Carl Zeiss, Germany (Supra 55vp) instrument.
An X-ray Powder Diffraction (XRD) analysis was carried out on (Bruker, Germany AXS, D8 advance) instrument with Cu Kα (λ 1 = 1.54056The surface area and particle size (SAP) analysis was performed on Micromeritics, USA (ASAP 2020) instrument to measure the specific surface area of the material.Brunauer-Emmett-Teller's theory aims to explain the physical adsorption of gas molecules on a solid surface and serves as the basis for an important analysis technique for the measurement of the specific surface area of materials.

Results and Discussion
The carbonized products in the TFCB and the MFCB were prepared at the same carbonization temperature of 400 • C. The TFCB was supplied with a constant flow of nitrogen gas at 5 • C/min.Both products were characterized and compared with the commercial product using the following techniques.

Surface Morphology and Composition
The MFCB and the TFCB mesoporous products were prepared using the thermal decomposition method.FESEM imaging, with the EDS, is a useful microscopic analytical technique.The surface characterization of the carbonized material, in terms of morphology and composition, was achieved using this technique.The images presented in Figure 2 were captured at an acceleration potential of 5 to 15 kV using different magnifications.The mesopores are pores classified in the nanoscale range (from 2 to 50 nm), thus, these pores are not visible in the presented scale range.The visible pores present in the FESEM images of the TFCB and the MFCB are macropores (pores larger than 50 nm) [63].Such pores are not manifested in the CP at a given magnification.As a result, the CP shows different morphological behavior at observed analytical conditions.

Results and Discussion
The carbonized products in the TFCB and the MFCB were prepared at the same carbonization temperature of 400 °C.The TFCB was supplied with a constant flow of nitrogen gas at 5 °C/min.Both products were characterized and compared with the commercial product using the following techniques.

Surface Morphology and Composition
The MFCB and the TFCB mesoporous products were prepared using the thermal decomposition method.FESEM imaging, with the EDS, is a useful microscopic analytical technique.The surface characterization of the carbonized material, in terms of morphology and composition, was achieved using this technique.The images presented in Figure 2 were captured at an acceleration potential of 5 to 15 kV using different magnifications.The mesopores are pores classified in the nanoscale range (from 2 to 50 nm), thus, these pores are not visible in the presented scale range.The visible pores present in the FESEM images of the TFCB and the MFCB are macropores (pores larger than 50 nm) [63].Such pores are not manifested in the CP at a given magnification.As a result, the CP shows different morphological behavior at observed analytical conditions.Backscattered electron (BSE) and the elemental distribution spectra (EDS) are presented in Figures 3 and 4, respectively.This explains the complementary evidence of the chemistry of the subsurface and the morphology of the product.The EDS depicts that 2µ m 500 nm Backscattered electron (BSE) and the elemental distribution spectra (EDS) are presented in Figures 3 and 4, respectively.This explains the complementary evidence of the chemistry of the subsurface and the morphology of the product.The EDS depicts that obtaining the mesoporous product from a tube furnace, having a flow of nitrogen inert gas, has resulted in 78.3% carbon in the end product with some residual amounts of sodium, potassium, and chlorine from the coconut shell ingredients.However, the product obtained from the muffle furnace possesses a smaller content of mesoporous carbon (i.e., 75.2% only).According to the results, both products showed some common residual contents in the form of potassium, chlorine, and sodium.The product MFCB is owing some additional inorganic ingredients in the form of magnesium, phosphorous, and sulfur.
The carbonization technique breaks down the intricate carbonaceous material using air for the burning purpose and the complex ingredients of the source are degraded into carbon and other elemental precursors [64].It is assumed from the finding that the spontaneous degradation or breakdown of the same source material during different carbonization atmospheres gives different residual elements in the end product.A muffle furnace is using atmospheric conditions for the oxidation of coconut shells, while a tube furnace is using inert atmosphere.The oxygen percentage of the product observed in the muffle furnace is more compared with the tube furnace showing a greater possibility of the formation of oxidized products.In a tube furnace, due to controlled inert conditions, the pyrolysis is maximum, and the breakdown of the product happens with a greater loss of ingredients and less yield of oxidized products in the char.obtaining the mesoporous product from a tube furnace, having a flow of nitrogen inert gas, has resulted in 78.3% carbon in the end product with some residual amounts of sodium, potassium, and chlorine from the coconut shell ingredients.However, the product obtained from the muffle furnace possesses a smaller content of mesoporous carbon (i.e., 75.2% only).According to the results, both products showed some common residual contents in the form of potassium, chlorine, and sodium.The product MFCB is owing some additional inorganic ingredients in the form of magnesium, phosphorous, and sulfur.The morphology of the MFCB and the TFCB products is also compared with the available commercial product, CP.Macropores are not observed in the CP at the given magnification.However, the EDS spectra of the CP are found to have 90.2% carbon content, which indicated fewer residual constituents are present in the starting material.Most of the inorganic constituents are found to be missing in the CP.Less carbon content in the TFCB and the MFCB is assumed to be present due to residual contents of coconut shells which are absent in the purchased commercial product.The source of the commercial product was not known.It is assumed that the variation in the percentage of carbon and inorganic content in the EDS spectra of the CP is due to the difference in the composition of raw materials and the synthesis procedure utilized.

X-ray Diffraction Analysis
The XDR pattern obtained for the mesoporous MFCB, TFCB, and CP is presented in Figure 5. Carbon black is a combination of heterogeneous particles whose thickness varies from mono graphitic layer to a multilayer arrangement.It shows a pattern consisting of two to three diffused rings.The position of spectral peaks in powder diffraction analysis is approximately at the same location as in the spectra of graphite.Sometimes it is assumed that carbon black is a fine-grained form of graphite with crystalline nature.However, studies have also demonstrated loose packing of grains with very little size, just like amorphous solids [65].Therefore, it's not probable to predict the ratio of graphitic crystals and mesomorphic forms of carbon.Usually, the sloppy packing of particularly small particles gives rise to intense scattering at a small-scale angle.The analysis usually shows two clear Braggs peaks related to reflections from ( 002) and ( 10) planes.
zation atmospheres gives different residual elements in the end product.A muffle furnace is using atmospheric conditions for the oxidation of coconut shells, while a tube furnace is using inert atmosphere.The oxygen percentage of the product observed in the muffle furnace is more compared with the tube furnace showing a greater possibility of the formation of oxidized products.In a tube furnace, due to controlled inert conditions, the pyrolysis is maximum, and the breakdown of the product happens with a greater loss of ingredients and less yield of oxidized products in the char.
The morphology of the MFCB and the TFCB products is also compared with the available commercial product, CP.Macropores are not observed in the CP at the given magnification.However, the EDS spectra of the CP are found to have 90.2% carbon content, which indicated fewer residual constituents are present in the starting material.Most of the inorganic constituents are found to be missing in the CP.Less carbon content in the TFCB and the MFCB is assumed to be present due to residual contents of coconut shells which are absent in the purchased commercial product.The source of the commercial product was not known.It is assumed that the variation in the percentage of carbon and inorganic content in the EDS spectra of the CP is due to the difference in the composition of raw materials and the synthesis procedure utilized.

X-ray Diffraction Analysis
The XDR pattern obtained for the mesoporous MFCB, TFCB, and CP is presented in Figure 5. Carbon black is a combination of heterogeneous particles whose thickness varies from mono graphitic layer to a multilayer arrangement.It shows a pattern consisting of two to three diffused rings.The position of spectral peaks in powder diffraction analysis is approximately at the same location as in the spectra of graphite.Sometimes it is assumed that carbon black is a fine-grained form of graphite with crystalline nature.However, studies have also demonstrated loose packing of grains with very little size, just like amorphous solids [65].Therefore, it's not probable to predict the ratio of graphitic crystals and mesomorphic forms of carbon.Usually, the sloppy packing of particularly small particles gives rise to intense scattering at a small-scale angle.The analysis usually shows two clear Braggs peaks related to reflections from (002) and ( 10) planes.The MFCB peak, due to the reflection from the (002) plane, is found to be major and intense at 28.3 • on the 2θ scale.The second peak of two-dimensional reflection from the (10) plane is due to a graphite-like structure and is present at 40.5 • on a 2θ scale.The TFCB also shows a similar pattern with the main reflection at 28.2 • on the 2θ scale and due to two-dimensional reflection from the (10) plane at 40.4 • on the 2θ scale.However, in the CP, only one peak is observed due to the graphitic structure at 40.3 • and the peak due to (002) plane is not clear.Therefore, the commercial product has a pronounced peak at a larger angle with the indication of more amorphous characters.Further structural information, in terms of interplanar pacing (d hkl ), full-width half maximum (FWHM), the crystallite size (L c ), lateral size (L a ), the number of layers (N), dislocation density (δ), microstrain (ε), packing density (ρ), and crystallinity index (I), were determined using the formula from the literature [36] and presented in Table 1 for the MFCB and the TFCB.There exist controversies among the results of the microstructural calculations as the results are unpredictable.The reason behind such variations is unknown.One of the major factors is found to be the oxidation method or heat-treatment procedure [66].Small changes in the operating conditions can give the product different characteristics [67].The microstructural parameters show that the interplanar spacing of all three samples is almost the same.The crystalline size and lateral size of the TFCB are better than the MFCB.The number of layers in each stack and packing density is found to be greater for the TFCB than for the MFCB.There is an observed difference of 0.02 g/cm 3 in packing density between the MFCB and the TFCB, which highlighted the fact that the TFCB sample is more compact and ordered compared with the MFCB.
The smaller the crystalline size, the lower the degree of graphitization will be [36].The CP is observed to have the greatest interplanar spacing with the greatest FWHM, as the peak is broader with small intensity.It is also observed that most of the calculated microstructural parameters of the CP are not comparable to the MFCB and the TFCB.The reason behind the observed variation is assumed to be the greater graphitic character.The dislocation density is found to be the highest for the CP, which also supports the greater amorphous properties in the commercial product.Similarly, N is calculated to be 12.03 and 12.79 for the MFCB and the TFCB respectively while it is negligible for the CP.As predicted, all the microscopic parameters calculated from the XRD data suggest that the size of the primary atoms in the TFCB is the smallest in the analyzed samples, which emphasizes the carbonization conditions to be favorable in the tube furnace.The X-ray Diffraction analysis was also used to predict the degree of crystallinity using the diffraction intensity ratio of the crystalline peak with the amorphous peak as it related to the respective mass ratios [68].
In the present work, the relative proportions of the amorphous and the crystalline were determined based on the maximum reflection peak from the (002) planes.The crystallinity index is calculated using Equation (1).
Crystallinity Index (%) = (I crystalline /I total ) × 100 (1) The MFCB showed a crystallinity index of 25.8 %, compared to 23.4 % in the case of the TFCB.There is found to be a calculated difference of 2.4 %, which is attributed to the difference in processing conditions.Thus, nitrogen has displayed a critical role in the production of coconut shell chars with better properties.As per the prediction of determined microstructural parameters, the crystallinity calculation also presented a similar trend.The CP contains the least crystalline nature with 13% crystalline properties and a more graphitic character.

SAP Analysis
A solid adsorbent surface has been identified by the International Union of Pure and Applied Chemistry (IUPAC) to give five traditional types of isotherms [69].The surface area available for adsorption is associated with the size, volume, and diameter of the pores that are presented on a surface.This information was utilized to study the surface properties of the coconut shell chars.Following the classification given by the IUPAC, pores on adsorbent surfaces are categorized into three divisions:
Properties related to the surface of a material can be predicted by studying the physical adsorption phenomena.Brunauer-Emmett-Teller's theory aims to explain the physical adsorption of gas molecules on a solid surface and serves as the basis for an important analysis technique for the measurement of the specific surface area of materials.The driving force behind the physical adsorption of a substance is believed to be London dispersion forces.In some cases, electrostatic forces also play an important role in trapping adsorbate on the surface under observation.
The obtained isotherm linear plot at the STP for the MFCB and the TFCB samples is presented in Figure 6.The SAP analysis showed smooth type III isotherm, predicting stronger adsorbent adsorbate interactions according to the IUPAC classification.In the isotherm, the adsorption and desorption curves are abbreviated as Ad and De respectively.The initial region of the linear isotherm plot of the isotherm for all samples represents the saturation of the micropore with the nitrogen gas filling indicated by a rise in the adsorbed quantity of absorbate.This is followed by a regular decrease in adsorbed gas with a rise in temperature in the form of desorption.
It was revealed that the size, diameter, and volume of pores that are present on a material have an important role in porosity developed specific surface area obtainable for effective adsorption, which, ultimately, determines the number and size of particles that can be easily diffused into the adsorbent.All of these are directly related to processing conditions which are the same for the synthesized samples except for the nitrogen gas, thus, it has a leading role in the determination of properties.As a suitable structure with the required pore parameters is of major concern for adsorption applications [70], processing conditions must be regulated because the activation process plays a major role in pore growth and improvement [71,72].
The surface was investigated for the change in relative pressure of nitrogen gas from 0.1 to 1, at P/P o = 1.029.All the active sites are exposed to adsorbate gas molecules having the same kinetics energy, so the adsorbate interactions are independent of the neighboring active sites.The absorption of the adsorbate is related to the number of active sites available.The nature of the synthesized carbon shell char in all samples is mesoporous as the pore diameter lies above 2 nm in all samples.The results are listed in Table 2.The specific surface is found to be highest for samples synthesized under the flow of nitrogen gas as compared to the MFCB.
Therefore, the flow of nitrogen gas seems to have a prominent role in the physical modification of char, which, in turn, has resulted in a smaller pore diameter.While comparing the results of synthesized samples with those of commercial products, it can be noticed that it contains a higher surface area than the synthesized materials.As the commercial product was available in activated form, the additional activation step involved in a commercial sample raised the surface area of the product.The TFCB and the MFCB can be explored further following the activation step.It was revealed in the literature that the amorphous character can lead to a rise in the surface area of the product [72].Although the commercial product has less crystalline character shown by the XRD, as it was in an activated form.Therefore, it has been more active toward absorption as shown by the SAP results.It was concluded that the surface properties of a material are independent of its crystalline or amorphous nature.

Figure 1 .
Figure 1.Samples of coconut shell (a) Before treatment, (b) After treatment in a muffle furnace (c) After treatment in the tube furnace.

Figure 1 .
Figure 1.Samples of coconut shell (a) Before treatment, (b) After treatment in a muffle furnace (c) After treatment in the tube furnace.
5) radiation source (45 kV & 40 mA) in continuous scanning mode.The samples were analyzed at a scanning speed of 1 • min −1 from 10 • to 100 • on a 2θ scale.

Figure 3 .
Figure 3. BSE images of carbonized products (a) BSE image of MFCB, (b) BSE image of TFCB, and (c) BSE image of CP.Figure 3. BSE images of carbonized products (a) BSE image of MFCB, (b) BSE image of TFCB, and (c) BSE image of CP.

Figure 3 .
Figure 3. BSE images of carbonized products (a) BSE image of MFCB, (b) BSE image of TFCB, and (c) BSE image of CP.Figure 3. BSE images of carbonized products (a) BSE image of MFCB, (b) BSE image of TFCB, and (c) BSE image of CP.

Figure 4 .
Figure 4. EDS spectra of the carbonized products (a) EDS spectra of MFCB, (b) EDS spectra of TFCB, and (c) EDS spectra of CP.Figure 4. EDS spectra of the carbonized products (a) EDS spectra of MFCB, (b) EDS spectra of TFCB, and (c) EDS spectra of CP.

Figure 4 .
Figure 4. EDS spectra of the carbonized products (a) EDS spectra of MFCB, (b) EDS spectra of TFCB, and (c) EDS spectra of CP.Figure 4. EDS spectra of the carbonized products (a) EDS spectra of MFCB, (b) EDS spectra of TFCB, and (c) EDS spectra of CP.

Table 1 .
Structural information of samples determined from XRD patterns.

Table 2 .
SAP parameters of samples.