High-Temperature Differential Thermal Analyzer

What is the High-Temperature Differential Thermal Analyzer?

A high-temperature differential thermal analyzer reaches 1500 to 1600 degrees Celsius with platinum-rhodium or tungsten-rhenium thermocouples, making it suitable for cements, refractories, ceramics, glasses, slags and minerals whose reactions occur far above 700 degrees Celsius.

Overview

Platinum-rhodium or tungsten-rhenium thermocouples and an alumina or platinum holder allow operation to 1500 or 1600 degrees Celsius in air, argon or nitrogen. The furnace uses silicon carbide or molybdenum disilicide elements, and above 1600 degrees Celsius a graphite furnace with a protective atmosphere is required. Peak positions are usually reported in air or inert gas because some reactions depend strongly on oxygen availability. Typical specifications include a temperature accuracy of about plus or minus 3 degrees Celsius, heating rates from 1 to 30 degrees Celsius per minute, and sample masses of 50 to 200 milligrams for weakly reacting inorganic materials. Applications include quartz inversion, carbonate decomposition, cement clinker formation, glass transition and crystallization, and the study of sintering additives and ceramic binders. Holding the sample in a shallow crucible and controlling packing are essential for reproducible peak shapes.

How does it work?

The sample and a thermally inert reference, usually calcined alumina, sit in the same furnace and are heated on the same program. A differential thermocouple or two matched thermocouples measure the temperature difference between them, recorded as microvolts against temperature or time, alongside the sample temperature. When the sample undergoes a transition that absorbs heat, its temperature lags the reference and produces an endothermic peak; exothermic reactions such as crystallization or oxidation give a peak in the opposite direction. The peak position identifies the transition temperature and the peak area is roughly proportional to the enthalpy change, although DTA is less quantitative than DSC because the heat path is not calibrated in absolute terms. Sensitivity depends on sample mass, packing density, thermocouple position and atmosphere. Typical samples are 10 to 100 milligrams, and inert, oxidising, reducing or vacuum atmospheres are selectable.

What are the key features?

• Furnace operation to 1500–1600 °C with silicon carbide or MoSi₂ elements
• Platinum-rhodium or tungsten-rhenium thermocouples matched to the range
• Alumina, platinum or graphite sample holders
• Atmosphere control with air, argon, nitrogen or vacuum options
• Sample masses of 50–200 mg for weak inorganic transitions
• Peak evaluation software with onset and area reporting

What are the technical specifications?

A typical high-temperature differential thermal analyzer configuration offers temperature range of Ambient–1600 °C, heating rate of 1–30 °C/min, thermocouple type of Type S, Type B or tungsten-rhenium, temperature accuracy of ±3 °C, signal resolution of 0.5 °C and sample mass of 50–200 mg. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The High-Temperature Differential Thermal Analyzer is used in cement clinker and gypsum studies, refractory and ceramic development, glass transition and crystallization, slag and fly ash characterisation and catalyst support phase transitions. Across the wider DTA class, laboratories also deploy it for clay and mineral phase identification, cement and gypsum dehydration studies and ceramic and refractory development.

Which standards and certifications apply?

Relevant standards and methods include ASTM E967, ASTM E794, ASTM D3418, ISO 11357-1, IEC 61010-1 and GB/T 13464. Certification candidates for this model are CE, IEC 61010-1 safety and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Package the sample uniformly and keep mass and packing the same as the reference to avoid baseline distortion, and dilute reactive samples with alumina when necessary. Select crucible and thermocouple materials that do not react with the sample at the working temperature, and use a platinum or alumina holder for oxidising conditions. Purge the furnace with the intended gas at a stable flow, and verify the thermocouple pair against melting point standards such as indium, tin, aluminium, silver or gold depending on range. Record the crucible type, sample mass, gas, flow rate and heating rate with every curve. Thermal analysis of minerals often shows overlapping peaks that require a consistent, documented heating rate and reference material to be compared between laboratories, so method details should be exchanged with results.

How do I select the right High-Temperature Differential Thermal Analyzer?

Choose the high-temperature configuration for inorganic materials whose reactions lie between 700 and 1600 degrees Celsius, typically cements and ceramics. If reactions occur above 1600 degrees Celsius, a graphite-furnace version is required. In an RFQ, state maximum temperature, thermocouple type, holder material and atmosphere.

How does it compare with other DTA variants?

The decisive parameter is the temperature range, because DTA is chosen mainly when transitions lie above the working range of a DSC: minerals, clays, cements, refractories and glasses often require 1500 to 1600 degrees Celsius, and some slags and alloys need graphite furnaces above 2000 degrees Celsius. Below 700 degrees Celsius a DSC is usually a better choice because it also gives enthalpies. After range, consider the thermocouple type and hence the maximum temperature, the crucible and thermocouple materials compatible with the sample, atmosphere and vacuum control, sensitivity to small transitions, and whether automation is required. Peak resolution depends on the heat path, so sample packing and mass must be matched between runs. For routine quality control, an automated instrument with a sample changer reduces operator time, and calibration with melting point and phase transition references should be part of the method.