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Thermal Conductivity of Calcium Carbonate

Calcium carbonate is an abundant mineral found in the earth’s crust. It is the main chemical found in chalk, eggshells, and seashells. It is a common substance found in limestone and aragonite. This odourless white powder finds its main uses as filler in building materials, ceramic tiles, and blackboard chalk. However, it is also an excellent additive for paints, adhesives, and sealants.

It has several medical uses, including heartburn treatment and a dietary calcium supplement. Calcium carbonate powder’s thermal conductivity (W/m·K) will be measured using the Transient Plane Source (TPS) method in this application sheet. Measurements will be made with the Measurement Platform Versatile (MP-V).

Equipment and Materials

A sample of calcium carbonate powder was measured for thermal conductivity (W/m·K), thermal diffusivity (mm²/s), and volumetric specific heat (MJ/m³K) using the Modified Transient Plane Source (MTPS) sensor, with Thermtests’ MP-V device. There is a selection of testing modules under the TPS method that are grouped based on their testing theory. In this application, the standard bulk module will be used asymmetrically.

Calcium Carbonate

Calcium Carbonate

Figure 1. Sample of Calcium Carbonate.

Calcium carbonate (CaCO3) is one of the planet’s most common minerals, making up 4% of the Earth’s crust. This mineral dates back to 40,000 BC when it was used as chalk in cave paintings. As time passed, the Romans began using this mineral to construct road systems and to reduce soil acidity to promote crop growth.

By the 18th century, calcium carbonate was extended into paints, household cleaning products, and plastic manufacturing. Today, calcium carbonate has many uses in a wide variety of industries. CaCO3 is found commonly in chalk, limestone, and marble. It is insoluble in water and chemically stable at normal temperatures. In the industrial world, this mineral can be used as a building material, a cement ingredient, or a fluid additive in the oil drilling field.

Aside from industrial uses, CaCO3 is also widely used in other industries. In agriculture, calcium carbonate is used as soil fertilizer to reduce acidity and improve purity. The basic nature of the chemical allows it to be used as a pH corrector and disinfectant in drinking water and swimming pools. Medicinally, CaCO3 is used as an inexpensive dietary calcium supplement and may be used as a treatment for conditions caused by low calcium levels, such as osteoporosis. It is also commonly used as an antacid for reducing heartburn, upset stomach or indigestion.

Calcium carbonate is vital in emerging energy technologies, environmental fields, biological systems, and industrial processes. Understanding the thermal conductivity of calcium carbonate is critical in these industries for optimum, cost-effective product design.

MP-V

Thermtest MP-V

Figure 2. Measurement Platform | Versatile (MP-V)

The MP-V tests the absolute thermal conductivity, thermal diffusivity, specific heat, and thermal effusivity of solids, liquids, pastes, and powders. The MP-V features a powerful combination of the transient plane source (TPS, ISO 22007-2) and transient hot wire (THW, ASTM D7896-19) methods with a variety of compatible sensors.

The MP-V features the proprietary intelligent Transient Plane Source (iTPS) function designed for testing and analysis automation. iTPS requires only the sample name as user input, and the appropriate sensor and test parameters for each individual sample are determined. The MP-V can measure a thermal conductivity range of 0.01 to 500 W/m·K and undergo temperatures of -75 to 300°C.

Transient methods share similar theories with differences specific to their primary design. The sensors electrically connect to a power supply and sensing circuit. A current passes through the sensor, creating an increase in temperature, which is recorded over time. The heat generated is then diffused into the sample at a rate dependent on the thermal transport characteristics of the material.

The Modified Transient Plane Source (MTPS) sensor comprises of a TPS sensor configured with known backing insulation, permanently housed in a rugged single-sided configuration. This unique design combines the intelligent design of the sensor and measurement capabilities to generate bulk and directional properties for all materials. This sensor can test isotropic, anisotropic, slab and one-dimensional samples in either a standard configuration with the sample placed on top of the sensor or, for larger sample sizes, an alternate configuration with the sensor placed on top of the sample.

Modified Transient Plane Source Sensor (MTPS, Absolute)

Figure 3. Modified Transient Plane Source (MTPS) sensor.

Results

Approximately 12.0 g of white blackboard chalk was ground to a fine powder and measured asymmetrically using the absolute MTPS sensor. Chalk is typically 98% CaCO3, with its other 2% being other minerals such as quartz and clay. Optimal measurement parameters were determined with the help of the proprietary iTransient Plane Source (iTPS) application. A test time of 20s was used with a power of 18mW. The extended sensor correction removes the contact resistance between the sensor and sample, guaranteeing the calculations use the best analysis possible.

MP-V with MTPS  
Temperature (°C) Thermal Conductivity (W/m·K)
22.0 0.302
0.304
0.299
0.297
0.300
Mean 0.300
St.Dev. 0.003
%RSD 0.9

Conclusion

In this application, the thermal properties of calcium carbonate powder were measured via the Transient Plane Source (TPS) method using Thermtests’ Measurement Platform Versatile (MP-V). The TPS method is an accurate and reliable method of testing powders, which is displayed in the results.

References

Measurement Platform Capabilities. Thermtest Inc. (n.d.). https://thermtest.com/wp-content/uploads/MP-model-comparison.pdf

Momenzadeh, L., Moghtaderi, B., Buzzi, O., Liu, X., Sloan, S. W., & Murch, G. E. (2018). The thermal conductivity decomposition of calcite calculated by molecular dynamics simulation. Computational Materials Science, 141, 170–179. https://doi.org/10.1016/j.commatsci.2017.09.033

MP-2 Thermal Conductivity Measurement Platform. Thermtest. (2023, June 20). https://thermtest.com/mp-2

MP-V – Transient Plane Source – Modified Transient Plane Source. Thermtest. (n.d.). https://thermtest.com/mp-v

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