Optimised graphite/carbon black loading of recycled PLA for the ...

The 17 sustainable development goals developed by the United Nations are an urgent call for action in a global partnership between developed and developing countries [1]. They form the core of the Agenda for Sustainable Development, which was adopted by all UN member states in , and cover a vast range of challenges that are crucial to overcome for the prosperity of ourselves and our planet. Specifically, sensing devices play a vital role to ensuring that many of these goals are met and then subsequently monitored with accuracy and reliability. In particular, Goals 3 and 6, Good Health and Wellbeing and Clean Water and Sanitation, respectively, require the constant monitoring of water supplies to guarantee that standards are met in all areas. Water pollution is a huge issue worldwide, with freshwater accounting for a tiny proportion of the world’s total water supply. Both natural and anthropogenic activities can cause changes in the water quality, with the latter being mainly caused by agricultural processes, inefficient irrigation practices, deforestation, domestic sewage, mining, and industrial effluents [2]. One compound seen increasingly within water sources is β-estradiol (or 17-β-estradiol), a steroidal hormone important within female reproductive processes, regulating bone growth, and brain maintenance [3]. This hormone is excreted by humans in urine and released by pharmaceutical industries, whereby it bioaccumulates in water sources and can lead to significant complications for fauna in the local ecosystem [4,5,6]. It is such the importance of the known environmental risk caused by the presence of estrogens in water ecosystems [7] that, from January , the European Commission has included β-estradiol in the first watch list of substances of concern for water intended for human consumption [8, 9].

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Monitoring of these environmental contaminants, such as β-estradiol, is commonly carried out in a laboratory utilising standard benchtop techniques such as high performance liquid chromatography coupled with tandem quadrupole mass spectrometry (HPLC-MS/MS) [10, 11] or liquid chromatography-mass spectrometry (LC-MS) [12, 13]. These testing regimes are expensive, slow, require skilled operators to perform meticulous preparation, and involve the transportation of samples from the environment to the lab. All these factors contribute to increase the ineffectiveness of environmental monitoring, with costs either being too high or results being unreliable due to timescales. However, the use of modern electrochemical devices for the analysis of environmental contaminants has the potential to remove these roadblocks, allowing rapid quantification of trace-level pollutants directly in the field and minimising the risk associated with the sampling, storage, and transportation of environmental specimens. Nowadays, portable and miniaturised potentiostats are readily available for less than £, do not require highly skilled end-users, and allow for the collection of large amounts of real-time data in decentralised settings. For some time, screen-printed electrodes have been the only alternative electrochemical technology for transitioning analysis from the laboratory into the field [14, 15]. These electrodes utilise the deposition of conductive ink onto a flat ceramic or plastic substrate to produce typically single-use electrodes which can easily be used in situ with no additional preparation. Although these electrodes have excellent scales of economy and are simple to use, their disposable nature and the materials typically used in their fabrication make them a questionable option environmentally.

One area of interest for portable sensor development is additive manufacturing, which utilises the deposition of material in a layer-by-layer fashion to produce a 3D object from a computer-aided design file. This technology allows for on-demand manufacturing, low (potentially zero) waste, short lead times, low costs for short production runs, a high degree of customisability, ease of global collaboration, and the ability to produce complex parts [16]. Within the field of electrochemistry, fused filament fabrication (FFF) has become extremely popular due to its inexpensive entry level, availability of commercial electrically conductive filament, and reproducible results. As such, it has been utilised throughout electrochemical research labs for the production of accessories, specialist equipment, electrochemical cells, and, of course, electrodes [17, 18]. Through the use of commercially available conductive filament, many electroanalytical sensors have been reported for the determination of environmental contaminants such as pesticides [19], pharmaceuticals [20, 21], and heavy metals [22, 23]. Due to the flexibility of FFF and the available printers, full electrochemical platforms have been produced in a single print, with any number of electrodes embedded within the cell [19, 24]. Although these sensing platforms offer unique advantages, their electroanalytical performance remains substandard compared to traditional electrodes, primarily due to the limited conductivity of the filament.

To overcome this issue, researchers have begun to produce their own bespoke filaments with improved conductivities. This is typically achieved through mixing nanocarbons with the base polymer through either solvent or thermal mixing, with thermal being the preferred choice in terms of production timescales, removal of solvent requirements, and the possibility to power machinery through green energy sources [25]. Various bespoke filaments have now been reported for use within electroanalysis, such as for the determination of bisphenol A in water samples [26]. To further improve bespoke conductive filaments, researchers have experimented with novel combinations of multi-walled carbon nanotubes with carbon black to produce high-performance conductive filament [27] or mixing graphite with carbon black to reduce the cost and improve the sustainability of the filament [28]. This work looks to build upon this work through understanding the optimal carbon black and graphite composition whilst also maximising the loading to achieve the best possible electrode at the lowest cost. Reducing the cost of electrode production is a significant step toward the commercial application of this technology, but the improvements in sustainability are vital to keep this field in line with the UN’s sustainable development goals, such as Goal 12: Sustainable Consumption and Production.

In addition to the incorporation of graphite, mentioned above, researchers have taken significant steps toward improving the overall sustainability of additive manufacturing electrochemistry [29]. Sigley and co-workers described the first use of recycled poly(lactic acid) (PLA) from coffee pods to produce both conductive and non-conductive filaments for the development of an electroanalytical sensor applied for caffeine detection [30]. Crapnell and co-workers then took this approach further through the replacement of the poly(ethylene succinate) plasticiser with the bio-based reagent castor oil [26], whilst also showing the effectiveness of recycling the used electroanalytical sensing platforms into a new filament that can once again print the same electroanalytical platforms whilst maintaining the performance of the original material [31].

As such, in this work, we look to optimise the production of electrically conductive additive manufacturing filament for excellent electrochemical performance, low production cost, and improved sustainability. We aim to achieve this through optimising the graphite-to-carbon black ratio in the filament whilst also using recycled PLA and the bio-based plasticiser castor oil. Once the nanocarbon ratio is optimised, we look to incorporate the highest loading possible to produce the best-performing conductive filament and then utilise this for the detection of β-estradiol within different water sources.

Optimisation of graphite and carbon black loading

To optimise the ratio of CB to graphite within the recycled PLA (rPLA), different compositions were made at a total nanocarbon loading of 15 wt%. The overall loading was reduced compared to previous work [28] to allow for easier differentiation between the measured resistances; as with high loadings, all filaments tend to perform well. Filaments were made with CB to graphite ratios of 100:0, 80:20, 60:40, 40:60, and 20:80, but not 0:100 because of the high degradation of the rPLA upon mixing with 100% graphite due to its abrasive nature. We note that high levels of only graphite loading have been reported using solvent mixing methods [36, 37]; however, thermal is the preferred method used here for reasons outlined in the introduction. All the filaments that were produced had excellent low-temperature flexibility, as shown in Figure S1. Following this, the resistance across 10 cm of filament was measured, and this allowed for comparisons between the filaments but also to the commercially available conductive PLA, as this is a quoted value of 2–3 kΩ for a 1.75 mm filament. The resistance values obtained for each filament are summarised in Table 1. Both the 80:20 and 60:40 mixes show the lowest resistance; whereafter, increasing the amount of graphite within the filament causes a sharp increase. This is attributed to the morphologies of the nanocarbons themselves, whereby the carbon black is present as small spherical particles and the graphite is present as large flakes, as seen in the SEM images of the powders in Figure S2. It is thought that the combination of small amounts of graphite flakes in combination with a larger number of small particles improves the electrically conductive network through the polymer, enhancing the conductivity. Once the concentration of large flakes becomes too high, there is inadequate linking between the dispersed graphite to form a good conductive network.

Next, the electrochemical performance of additive manufactured electrodes printed from these filaments was analysed using scan rate studies against the near-ideal outer sphere redox probe [Ru(NH3)6]3+ (1 mM in 0.1 M KCl). This probe is chosen as it allows for the best determination of the heterogeneous electron (charge) transfer rate constant (k0) and the real electrochemical surface area (Ae) of the additive manufactured electrodes [38]. A summary of the findings can also be found in Table 1. It can be seen that again, the filaments comprised of 80:20 and 60:40 CB to graphite ratio produced the best results, with a faster k0 and larger Ae, showing good agreement with the data obtained for the filament resistances. To maximise both the environmental and cost benefits of the filament, the larger the proportion of graphite within the filament, the better. This is due to the fact that carbon black is produced using the partial oxidation of petrochemical precursors, whereas graphite can be obtained from naturally occurring sources. As such, the ratio of 60 wt% CB and 40 wt% graphite was chosen to progress with.

Physicochemical characterisation of optimised filament

Utilising the optimal ratio of nanocarbons calculated above, the maximum loading of this mixture was then explored within the rPLA, once again maintaining a constant 10 wt% castor oil as the plasticiser [26]. Then, subsequent filaments prepared with 15, 20, 25, 30, 35, and 40 wt% of total carbon loading were thoroughly tested. It was found that a total of 35 wt% nanocarbon loading in this ratio was possible before the filament produced became significantly more brittle, leading to a reduction in printability. The filament obtained using 35 wt% total loading, comprising 21 wt% CB and 14 wt% graphite, is pictured in Fig. 1A, which demonstrates the excellent low-temperature flexibility of this filament. Across 10 cm of this filament, an extremely low average resistance of 277 ± 9 Ω was measured, which matches the published bespoke filament range from ~ 250 to Ω [26,27,28, 39] and represents a significant improvement on the commercially available conductive PLA which has a quoted resistance of 2–3 kΩ [40, 41]. Importantly, this filament achieves such a level of conductivity at a low material cost of under £0.06 per gram, compared to £0.72 per gram previously reported [27] and a current purchasing cost of commercial filament of ~£1.20 per gram.

It is interesting to see the inset of Fig. 1A corresponds to an image of three additive manufactured electrodes printed from this filament, highlighting the excellent printing quality, surface finish, and reproducibility.

Once printed, it is important to characterise the surface of the additive manufactured electrodes to gain insight into their performance. Within the field of additive manufactured electrochemistry, especially when utilising PLA-based materials, activation of the electrode surface is commonplace. This term effectively refers to the removal of an outer layer of polymer that coats the electrode surface, allowing access to increased amounts of conductive filler below. There have been numerous ways of activating additive manufactured electrodes reported within the literature [42, 43], with electrochemical activation in a sodium hydroxide solution (0.5 M) being one of the most popular [35], and therefore, it will be used throughout this work. Then, additive manufactured electrodes were analysed through X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and scanning electron microscopy (SEM) before and after electrochemical activation.

Figure 1B, C shows the XPS C 1s spectra for the as-printed and electrochemically activated additive manufactured electrodes, respectively. The as-printed spectra show excellent agreement with previously published C 1s spectra for additive manufactured electrodes that utilise rPLA as the base polymer and castor oil as the plasticiser [26]. To adequately fit the as-printed electrode, three symmetric peaks were fitted, with the C-C peak at 285.0 eV being significantly larger in magnitude. This indicates the presence of castor oil on the surface of the print, as PLA exhibits three symmetric peaks of similar intensities [30]. When activated (Fig. 1C), an additional peak is required for adequate fitting of the C 1s spectra. The addition of an asymmetric peak at 284.5 eV is consistent with the X-ray photoelectron emission of graphitic carbon [44, 45]. This provides evidence that the electrochemical activation has exposed significant amounts of nanocarbons, with the atomic concentration increasing from 0 in the as-printed sample to 7.85% in the activated sample. The removal of the non-conductive PLA and castor oil from the surface means that the nanocarbons are now within the range of the XPS (a few nanometers) and expose the edge plane/site defects at the triple phase boundary, which should lead to enhanced electrochemical performance toward inner-sphere redox molecules.

To further confirm the presence of the nanocarbons on the surface of the additive manufactured electrodes, Raman analysis was performed (Fig. 1D). There are clearly defined peaks present at , , and  cm−1, which are attributed to the characteristic F-, G-, and 2D-bands found within the Raman spectra for graphitic-like structures. The ID/IG ratio for these peaks was calculated to be 0.12, showing a low number of defects and a very ordered structure, which indicates the presence of graphite on the surface of the electrode. These findings are further supported by the SEM images for the as-printed and activated additive manufactured electrodes seen in Fig. 1E, F, respectively. For the as-printed electrode (Fig. 1E), the morphologies of the nanocarbons can be observed, but there is a clear covering of smooth material attributed to both the plastic polymer and castor oil. On the other hand, for the activated electrode (Fig. 1F), there is a clear removal of this layer, and the well-defined morphologies of the carbon black and graphite become apparent. This characterisation clearly provides evidence that the electrochemical activation removes PLA and castor oil from the surface of the additive manufactured electrode, exposing increased amounts of conductive nanocarbons below. This is expected to lead to an improved electrochemical performance of the electrodes.

Electrochemical characterisation of the additive manufacture electrodes

Once physicochemically characterised, the additive manufactured electrodes were tested for their electrochemical performance. This was first done through scan rate studies against the near-ideal outer sphere redox probe [Ru(NH3)6]3+ (1 mM in 0.1 M KCl), as this allowed for the best determination of the heterogeneous electron (charge) transfer rate constant (k0) and the real electrochemical surface (Ae) [38]. An example of the scan rate study (5–500 mV s−1) obtained for the bespoke filament and the commercial PLA used as a benchmark are presented in Fig. 2A, with only the scans obtained at 25 mV s−1 are presented in Fig. 2B. It can be observed that there is a large improvement in terms of both the measured peak currents and the peak-to-peak separations (ΔEp) when using the CB-G/PLA. At 25 mV s−1, the ΔEp measured for the bespoke filament is 82 ± 4 mV compared to 212 ± 7 mV for the commercial conductive filament. This translates into a huge improvement in the k0, with the CB-G/PLA filament producing a value of (2.6 ± 0.1) × 10−3 cm s−1 compared to (0.46 ± 0.03) × 10−3 cm s−1 for the commercial PLA.

To further evaluate the electrochemical performance of the CB-G/PLA filament after being activated, it was tested against the inner-sphere redox probe [Fe(CN)6]4−/3− (1 mM in 0.1 M KCl). Figure 2C presents the cyclic voltammograms (25 mV s−1) obtained using additive manufactured electrodes printed from the bespoke filament and commercial conductive PLA after activation. It can be seen that once again, there is a significant improvement in the ΔEp, with the CB-G/PLA filament producing a value of 135 ± 8 mV compared to 500 ± 34 mV for the commercial conductive PLA, indicating a massive improvement in electrochemical performance. Finally, the additive manufactured electrodes were tested through electrochemical impedance spectroscopy recorded between frequency values from 0.1 to 100,000 Hz against [Fe(CN)6]4−/3− (1 mM in 0.1 M KCl). EIS allows for the accurate determination of the resistance introduced into the system by the additive manufactured electrode through the calculation of the solution resistance (Rs) and the resistance to the electrochemical processes happening at the electrode/solution interface through the charge-transfer resistance (RCT) [46, 47]. The Nyquist plots obtained for additive manufactured electrodes printed from both bespoke and commercial PLA can be seen in Fig. 2D. There is clearly a significant disparity in both the Rs and RCT values obtained for each electrode. The CB-G/PLA electrode produced an Rs and RCT of 117 Ω and Ω, respectively, compared to Ω and 10,065 Ω for the commercial electrode. Since the RCT parameter is inversely proportional to the heterogeneous electron (charge) transfer rate constant (k0) [48], the results obtained from EIS analysis corroborate that our bespoke graphite filament, displaying a significantly lower RCT and higher k0 values, is a better candidate for enhanced electrochemical performance in further potential applications of this material.

Electroanalytical determination of β-estradiol

Once electrochemically characterised, the additive manufactured electrodes printed from the CB-G/PLA filament were applied for the electroanalytical determination of β-estradiol. First, the response of β-estradiol (100 µM) was tested through square wave voltammetry within Britton-Robinson buffer at different pH values (2–10) (Fig. 3A). Through plotting the obtained peak potentials against the pH, we obtain a gradient of 56 mV per pH, which indicates that there is an equal number of electrons and protons involved in the redox reaction of β-estradiol. Next, cyclic voltammetry recorded at different scan rates (ν) was performed alongside the Laviron approach to estimate the number of electrons transferred in this reaction. It is stated by Laviron’s theory that the slope value obtained from plotting peak potential versus Log ν (Figure S3) corresponds to −2.3RT/αnF, where R is the gas constant (8.314 JK−1mol−1), T is the thermodynamic temperature (298.15 K), α is the transfer coefficient (α = 0.5 for irreversible processes), F is the Faraday constant (96,485 Cmol−1), and n is the number of electrons transferred. Considering the slope value of 0. obtained from Figure S3, the value of n calculated was 2.3. This work shows good agreement with the mechanism described previously in the literature for the irreversible oxidation of β-estradiol involving two electrons and two protons [49].

It is interesting to note the two voltametric peaks observed for β-estradiol at different pH. Therefore, in agreement with the literature [49], the second anodic peak has been selected as representative of the voltametric behaviour of β-estradiol in further analyses. Figure 3B shows the peak current values measured for β-estradiol within the different pH Britton-Robinson buffer solutions, clearly showing a maximum peak current obtained at pH 2. Following this, the response within different electrolyte systems was explored through the detection of β-estradiol (100 µM) in pH 2 solutions (0.1 M) of H2SO4, HCl, and H3PO4 alongside the Britton-Robinson buffer. The square wave voltammograms obtained are presented in Figure S4A, which clearly shows an increased peak current obtained whilst using H2SO4. Interestingly, the inset in Figure S4A shows the need of facilitating the solubility of β-estradiol in H2SO4. This was achieved by adding 20% methanol to the solution, which avoids β-estradiol precipitating in the electrochemical cell. Therefore, we established that for the exploration of the electroanalytical response toward β-estradiol, a 0.1 M solution of H2SO4 with 20% methanol is used.

The cyclic voltammetric response of an additive manufactured electrode printed from the CB-G/PLA electrode and the commercial PLA within this matrix and in the presence of β-estradiol is presented in Fig. 4A. For the commercial PLA electrode, there is no peak observed for the oxidation of β-estradiol, whereas for the bespoke electrode, a clear irreversible peak is obtained at ~ 1.0 V vs. Ag|AgCl/KCl (3 M). For the electroanalytical detection of β-estradiol, more sensitive techniques than CV were tested, observing a better performance of SWASV compared to DPV, as shown in Figure S4B.

The square wave voltammetric responses of β-estradiol (1 µM) are shown in Fig. 4B for additive manufactured electrodes printed from the CB-G/PLA filament and the commercial PLA. It can clearly be seen that the CB-G/PLA electrode produces a significant improvement in the peak current values obtained, which were then further tested through the production of an electroanalytical curve. The square wave voltammograms for the detection of β-estradiol (0.04–1.5 µM) are presented in Fig. 4C, with the corresponding calibration plot in Fig. 4D. A linear response was found for the peak current over this concentration range, with the sensitivity calculated to be 400 nA µM−1, a limit of quantification (LOQ) of 70 nM, and a limit of detection (LOD) of 21 nM, highlighting the excellent performance of this electrode. Next, the electroanalytical performance of the additive manufactured electrodes printed from the bespoke carbon black and graphite filament was tested within real water samples to establish their real-world applicability.

The square wave voltammograms obtained for the determination of β-estradiol within four different real-world water samples are presented in Fig. 5. These included tap water obtained from the laboratory, bottled drinking water obtained from a local convenience store, and river and lake water obtained from local sources in accordance with EPA guidelines [50]. Note that tap and bottled water did not require any pretreatment, whilst river and lake water were filtered using a PTFE 0.45 μm syringe filter before the analysis to remove suspended natural particles. Quantification of β-estradiol in water samples was performed using the standard addition method, where successive additions of a standard solution of ꞵ-estradiol at concentrations of 100, 150, 200, 250, 300, 350, and 400 µM were added to the electrochemical cell. It is demonstrated that β-estradiol was successfully detected in all water samples. Interestingly, there is clearly an unknown contaminant within both the river and lake water samples, showing a large peak at ~ 1.2 V. Even so, the detection of β-estradiol was achieved, highlighting the excellent performance of these additive manufactured electrodes in real conditions.

The electroanalytical parameters obtained from the detection of β-estradiol within these water samples are summarised in Table 2, where they all show excellent results. The results obtained within the lake water sample show a reduction in sensitivity, LOQ, and LOD in comparison to the other samples which is attributed to the large contamination peak detected, which is clearly hindering the β-estradiol peak. Even so, excellent recovery values were obtained in all cases between 95 and 109%, showing evidence that this low-cost additive manufacturing filament provides excellent results toward quantifying β-estradiol in environmental samples and could be a great potential alternative for on-site analysis, considering both the simplicity of the methodology and the low cost of the electrode’s production (< £0.01).

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In comparison of the performance of the additive manufactured electrodes to other reports of β-estradiol within the literature (Table 3), it can be recognised that these electrodes perform exceptionally well. The obtained linear range and LOD compare to the literature, especially when considering the electrode materials and modifications required for some of the reports, with glassy carbon electrodes costing significantly more than the £0.01 per electrode from this filament. When compared to the only other additive manufactured electrode reported in the literature, it can be seen that the bespoke carbon black and graphite filament shows significant improvements in both the linear range and the LOD, improving this from 310 with the commercial PLA to 21 nM in this work.

Finally, the reproducibility of the β-estradiol voltammetric signals and the interference study in the presence of other compounds of interest using the bespoke additive manufactured electrodes were studied. Figure 6A shows the square wave voltammograms obtained for the detection of three different concentrations of β-estradiol with five different electrodes. The average peak currents obtained are summarised in Fig. 6B, showing the excellent inter-electrode reproducibility of these additive manufactured electrodes. This can be attributed to the excellent low-temperature flexibility and printability obtained with this CB-G/PLA formulation.

The effect of eleven different possible interferents was then tested, and no interference was seen when the β-estradiol was present in a 10:1 excess (Fig. 6C). Moreover, when the molecules were present with a 10:1 excess of the interferent, there was no significant interference detected for caffeine, acetaminophen, copper sulphate, urea, ascorbic acid, sodium carbonate, calcium chloride, or iron sulphate. However, there were noticeable interferences at these concentration levels by carbaryl, which reduced the peak current by 78%, and by bisphenol A, which increased the peak current by 836% (Fig. 6D). This shows that for the accurate determination of β-estradiol in environmental samples potentially contaminated with those molecules, some matrix modification methods must be developed or utilised to ensure the reliability of the results obtained. Likewise, complementing the electroanalytical approach with validation using standard benchtop instrumentation, such as chromatographic methods, in those analyses where interferents could compromise the electrochemical determination of β-estradiol to give a high reading has to be considered to verify on-site results. Even so, the bespoke electrochemical platform developed in this work presents an extremely low cost, and it can be used as a portable method for the sensitive electroanalytical detection of low concentrations of β-estradiol within water samples. Through the creation of bespoke, low-cost additive manufacturing feedstock, there is the potential to revolutionise the ability to perform quick and simple field analysis.

What is a Carbon Raiser?

Carbon raiser is an efficient carbon additive material widely used in steel and casting, improving their hardness, strength, and wear resistance. Carbon raisers appear as black granules with sizes of 0.2–2mm, 1–3mm, and 5–8mm. Their chemical composition mainly consists of fixed carbon (F.C), sulfur (S), and nitrogen (N). The primary raw materials for producing carbon raisers include petroleum coke, anthracite, and graphite powder, which are extensively used to manufacture different types of carbon raisers to meet various application needs. XLS Metals has developed high-efficiency carbon raiser products based on user requirements, featuring high F.C content, high absorption rates, and high purity.

Applications of Carbon Raiser

Steel making: By using carbon raisers during steelmaking, the carbon content in steel can be effectively adjusted, improving the steel’s hardness, toughness, and wear resistance.

Casting: Carbon raisers used in casting have the advantages of low sulfur and low nitrogen. They effectively promote the formation of graphite nuclei, improving the graphite distribution and significantly enhancing the quality and yield of castings.

Metallurgy: Carbon raisers adjust the carbon content in alloys, improving various performance aspects, thereby serving the role of carbon enhancement and replenishment.

Specifications of Carbon Raisers

Classification Chemical Composition (%) CPC (Calcined Petroleum Coke) Carbon Raiser Grades F.C(Fixed Carbon) Ash V.M(Volatile Matter) S(Sulphur) Moisture CPC-1 98.5% min 0.5% max 0.5% max 0.3% max 0.5% max CPC-2 98.5% min 0.5% max 0.5% max 0.5% max 0.5% max CPC-3 98.5% min 0.7% max 0.8% max 0.8% max 0.5% max CPC-4 98.5% min 0.7% max 0.8% max 1.2% max 0.5% max Size: 0~1mm, 1~3mm, 3~8mm, 1~10m or at customers' option CAC (Calcined Anthracite Ccoal) Carbon Raiser CAC-1 95% min 4.0% max 1.0% max 0.3% max 1.0% max CAC-2 93% min 5.5% max 1.5% max 0.3% max 1.0% max CAC-3 90% min 8.0% max 2.0% max 0.5% max 1.0% max Size: 0~1mm, 1~4mm, 1~5mm, 1~10m, 4~10mm or at customers' option GPC (Graphitized Petroleum Coke) Carbon Raiser GPC-1 98% min 1.0% max 1.0% max 0.05% max 0.5% max GPC-2 98.5% min 0.7% max 0.8% max 0.05% max 0.5% max GPC-3 99% min 0.5% max 0.5% max 0.03% max 0.5% max Size: 1~3mm, 1~5mm, 0.5~6mm, 1~10m, or at customers' option

Advantages of Carbon Raiser

• High fixed carbon content

• Low impurities and high purity

• Efficient carbon raising

• High absorption rate

• Good thermal insulation properties

• Low sulfur and low nitrogen characteristics for casting carbon raiser

• Easy to use

• Convenient storage

Classifications of Carbon Raiser

Based on different raw materials, carbon raisers can be categorized into calcined coal carbon raisers, graphite carbon raisers, and petroleum coke carbon raisers. Depending on production processes, they can also be divided into graphite carbon raisers and calcined coal carbon raisers. Combining production processes and raw materials, the main types include graphitized petroleum coke carbon raisers (GPC), calcined anthracite carbon raisers (CAC), and calcined petroleum coke carbon raisers (CPC).

Carbon Raisers for Different Fields

Carbon Raiser for Steel: To reduce steel production costs, carbon raisers for steel usually focus on calcined coal carbon raisers. By calcining anthracite at °C, impurities are effectively reduced, resulting in high carbon content, low costs, and good carbon raising effects. Calcined coal carbon raisers are widely used in various steel production processes, enhancing strength, improving plasticity, and increasing weldability.

Carbon Raiser for Casting: Since sulfur (S), phosphorus §, and nitrogen (N) severely affect casting quality, carbon raisers for casting are often required to have low sulfur, low nitrogen, and low phosphorus characteristics. Graphitized petroleum coke carbon raisers and graphitized carbon raisers are the primary types used in casting, featuring high thermal insulation, high purity, and low harmful elements, widely applied in the production of ductile iron and gray cast iron. They effectively reduce the tendency for white iron defects and enhance the fluidity of molten iron during the casting process, preventing nozzle blockage and improving the plasticity and wear resistance of castings.

Sustainability

As market demands for steel performance diversify, carbon raisers are widely used in the smelting processes of different steel grades and cast iron, effectively improving the mechanical properties of steel and cast iron. With the increasing environmental protection requirements in various countries, carbon raisers have prompted companies to seek greener production methods, becoming a promising eco-friendly furnace material. XLS Metals has been dedicated to the research and production of carbon raisers for over a decade, holding multiple patented technologies, opening new raw material procurement channels, and establishing an independent R&D laboratory. This has created more possibilities for the production and application of carbon raisers, enhancing their performance and range of applications.

Wholesale Bulk Carbon Raisers at Best Prices

As an essential furnace material for steelmaking and casting, carbon raisers have a high market demand. Users prefer to purchase bulk carbon raisers in wholesale quantities at discounted prices. Buying bulk carbon raisers directly from manufacturers not only provides more discounts but also offers more professional guidance and reliable after-sales service. By wholesale directly from manufacturers, the procurement process is significantly streamlined, reducing labor and time costs, thus allowing users to genuinely purchase carbon raisers at best prices. Due to its natural raw material advantages, China is currently the largest producer of carbon raisers globally, with numerous manufacturers and suppliers available domestically. Users can expand their wholesale options for carbon raisers from China, comparing several manufacturers or suppliers to find more best prices for procurement. XLS Metals, located in Anyang, Henan, China, is a highly reputable manufacturer of carbon raisers, serving customers across multiple countries worldwide, primarily supplying high-quality carbon raiser products to steel mills and foundries. XLS Metals has significantly streamlined the purchasing process for users of carbon raisers and optimized related raw material procurement channels, enabling users to buy high quality carbon raiser products at even more competitive prices. Over the years, XLS Metals has earned widespread acclaim among its customer base for its reliable quality and more professional service.

XLS Metals Carbon Raisers

XLS Metals is a high-tech manufacturer engaged in the research and production of carbon raisers, equipped with advanced production facilities and laboratories, and holding multiple patents related to carbon raisers. Over the years, XLS Metals has carefully listened to user needs and continually improved carbon raisers to achieve higher purity and optimal carbon raising effects. To assist users, XLS Metals has established a 24/7 online service and assembled a professional and youthful technical team ready to address any issues users may encounter, providing more specialized purchasing plans and usage guidance. XLS Metals has received praise from users as the best "carbon raiser supplier and manufacturer" due to its reliable product quality and excellent service.

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