Introduction of Silicon Nitride Thermocouples

Silicon Nitride thermocouples are temperature measuring devices made from the ceramic material silicon nitride (Si₃N₄) and are primarily used for temperature monitoring in extremely high temperature and corrosive environments. Silicon nitride is a high-performance engineering ceramic with excellent resistance to high temperatures, abrasion, and chemical stability, making it an ideal material for high-temperature thermocouple protection tubes. Widely used in metallurgy, chemical, aerospace, and energy applications, silicon nitride thermocouples are capable of providing accurate and reliable temperature measurements under harsh conditions.

Features of Silicon Nitride Thermocouples

High-temperature resistance: able to work stably for a long time in high-temperature environments above 1200°C, with a maximum operating temperature of up to 1400°C.

Excellent thermal shock resistance: able to withstand rapid temperature changes, suitable for frequent heating and cooling conditions.

Chemical stability: excellent corrosion resistance to acids, alkalis and most molten metals, suitable for harsh chemical environments.

High mechanical strength: high flexural strength and fracture toughness, able to withstand greater mechanical stress.

Low thermal conductivity: good thermal insulation, reducing heat loss and improving measurement accuracy.

Abrasion resistance: high hardness, able to resist high-speed fluid or particle scouring to extend the service life.

Electrical insulation: Maintains good electrical insulation performance at high temperatures and is suitable for high-temperature electrical measurements.

Parameters of Silicon Nitride Thermocouples

Property	Specification
Material Composition	Si₃N₄ (Silicon Nitride)
Density	~3.20 g/cm³
Hardness (Vickers)	~1500-1800 HV
Fracture Toughness	~6-7 MPa·m½
Young’s Modulus (Elastic Modulus)	~280-320 GPa
Compressive Strength	~3000-4000 MPa
Flexural Strength (Bending Strength)	~800-1000 MPa
Coefficient of Thermal Expansion	~3.2 × 10⁻⁶ /°C (at room temperature to 1000°C)
Thermal Conductivity	~25-35 W/m·K
Max Service Temperature in Air	Up to 1200°C (continuous), up to 1400°C (intermittent)
Chemical Resistance	Excellent resistance to acids, alkalis, and molten metals
Electrical Resistivity	High (>10¹² Ω·cm at room temperature)
Wear Resistance	Excellent, suitable for high-wear applications
Thermal Shock Resistance	Outstanding, capable of withstanding rapid temperature changes
Corrosion Resistance	Superior, especially in aggressive environments
Self-Lubricating Properties	Reduces friction in moving parts
Biocompatibility	Suitable for medical applications
Temperature Measurement Range	Up to 1200°C continuously, up to 1400°C intermittently
Accuracy and Precision	High precision with minimal drift over time
Response Time	Fast response to temperature changes
Nozzle/Probe Dimensions	Inner diameter, outer diameter, length, and shape can be customized based on application requirements
Surface Finish	Can be polished or left as-sintered depending on the application needs
Environmental Impact	Environmentally friendly, no harmful substances

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Applications of Silicon Nitride Thermocouples

Metallurgical industry: used for temperature monitoring of high-temperature melting furnaces, electric arc furnaces, and continuous casting equipment; used as a high-temperature measuring device in the melting and purification process of rare and precious metals.

Chemical industry: for temperature monitoring of high-temperature reactors and corrosive media handling equipment, such as corrosion-resistant thermocouple protection tubes in catalytic reactions and exhaust gas treatment.

Aerospace: for high-temperature measurement of aviation engines and rocket propulsion systems, as temperature monitoring devices in thermal protection systems and high-temperature experimental equipment.

Energy: for high-temperature measurements in solid oxide fuel cells (SOFC) and gas turbines; as high-temperature resistant temperature monitoring devices in solar and nuclear energy equipment.

Glass and ceramics industry: used for temperature monitoring in glass melting kilns and ceramic firing furnaces, as well as high temperature measurement devices in the preparation of optical glass and special glass.

Laboratories and research institutes: for high-temperature experiments and temperature monitoring in material science research; as a precise temperature measurement tool in the preparation of nanomaterials and high-performance ceramics.

Company Profile

RBOSCHCO is a trusted global chemical material supplier & manufacturer with over 12 years experience in providing super high-quality chemicals and Nanomaterials.

The company has a professional technical department and Quality Supervision Department, a well-equipped laboratory, and equipped with advanced testing equipment and after-sales customer service center.

If you are looking for high-quality Silicon Nitride Thermocouples please feel free to contact us or click on the needed products to send an inquiry. 

Payment Term

T/T, Western Union, Paypal, Credit Card etc.

Packing and Storage

The product is in powder form and should be stored in a cool, ventilated place. Avoid inhalation when using it and keep away from open flames, heat sources, etc.

Shipment Term

By air, by sea, by express, as customers request.

FAQs of Silicon Nitride Thermocouples

Question 1: What is the primary role of silicon nitride in thermocouples?

Answer: The primary role of silicon nitride in thermocouples is to act as a protective sleeve or support structure to provide physical protection for the thermocouple, especially in high temperature, corrosive or abrasive environments. It can withstand extremely high temperatures and has excellent resistance to many chemicals.

Question 2: Why was silicon nitride chosen as the material for thermocouple protection tubing?

Answer: Silicon nitride was chosen for thermocouple protection tubing because of its high hardness, low density, good thermal shock resistance, and excellent creep resistance. These properties make silicon nitride ideal for thermocouple protection where prolonged exposure to extreme conditions is required.

QUESTION 3: What is the maximum operating temperature that silicon nitride protection tubing can withstand?

Answer: Silicon Nitride tubing can withstand operating temperatures as high as 1400°C or higher, depending on the manufacturing process and the environment in which it is used. This makes them particularly suitable for high-temperature measurements where conventional metal materials are not capable of doing the job.

QUESTION 4: Does silicon nitride protection tubing have any effect on thermocouple signal transmission?

Answer: Silicon Nitride is an excellent electrical insulator and, therefore, will not interfere with the small voltage signals generated by thermocouples. It also has a certain degree of thermal conductivity that ensures that heat is quickly transferred to the thermocouple element without affecting the accuracy of the temperature reading.

QUESTION 5: Are silicon nitride protection tubes available for all types of thermocouples?

Answer: While silicon nitride protection tubing provides excellent protection, it is not suitable for all types of thermocouples. For example, in a reducing atmosphere, silicon nitride may react and lose its excellent properties. In addition, given the cost factor, other more economical options may be preferred for application scenarios that do not require such a high level of protection. When making a selection, it is important to consider the specific conditions of use and requirements.