The choice of adsorbed gas for surface area analysis depends on the specific purpose of the test. While some gases may be ideal for characterizing surface properties, they might not be the best option when studying adsorption phenomena. Helium and nitrogen are two commonly used gases, but their suitability varies depending on the material being tested. For instance, materials like organic compounds or metal powders with low surface areas (less than 1 m²/g) typically adsorb only small amounts of gas. In such cases, it is advantageous to maximize the difference between the amount of gas introduced and the residual amount after equilibrium.
At liquid nitrogen temperature, the saturation pressure of helium is about 1/300 that of nitrogen (helium: 2.5 torr; nitrogen: 760 torr). This means there are significantly fewer helium molecules in free space compared to nitrogen at the same relative pressure. However, when a monolayer is formed, the number of helium and nitrogen molecules becomes similar, leading to a much greater proportional increase in the gas uptake when using helium. This makes helium particularly useful for analyzing low-surface-area materials.
When it comes to microporous analysis, the choice between nitrogen and argon becomes important. Argon is an inert, spherical monoatomic gas, while nitrogen is a non-spherical diatomic molecule. The quadrupole moment of nitrogen can lead to localized adsorption, especially on polar surfaces. Argon, on the other hand, has a molecular size and heat of adsorption very close to that of nitrogen, but its boiling point is higher (87.29 K vs. 77.35 K for nitrogen). As a result, argon adsorption at liquid argon temperatures is often more effective for microporous analysis, as it reduces equilibrium time and improves measurement accuracy.
In addition, argon's higher filling pressure compared to nitrogen allows for more precise measurements. Its inert nature also minimizes unwanted interactions with the sample surface, making it an excellent choice for accurate microporous studies.
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**High Precision Three-Station Side-by-Side Automatic Mesoporous Micropore Analyzer**
The JW-BK300 series is a state-of-the-art, fully automatic mesoporous and microporous analyzer designed for high-accuracy pore structure analysis. Built on the foundation of the JW series, this instrument features advanced hardware, including a turbomolecular pump and multi-range pressure sensors (1000Torr, 10Torr, 1Torr). With full modular design and precise application of microporous analysis models, it delivers exceptional accuracy, reaching a minimum pore size of 0.35nm. It is ideal for research and applications involving activated carbon, activated alumina, molecular sieves, zeolites, MOF materials, and nano-powder materials.
**Performance Parameters:**
- **Model:** JW-BK300 Three-Station Automatic Mesoporous Micropore Analyzer
- **Method:** Static capacity method, low-temperature nitrogen adsorption
- **Test Functions:** Isothermal adsorption/desorption curves, single/multi-point BET specific surface area, Langmuir surface area, external surface area, total pore volume, average pore size, BJH mesoporous analysis, plot method, as-plot method, DR method, MP method, HK method, SF method, NLDFT pore size distribution, true density, gas adsorption, adsorption heat, mass input method
- **Test Gases:** Nitrogen, oxygen, hydrogen, argon, helium, COâ‚‚, methane, etc.
- **Test Range:** Surface area from 0.0005 m²/g upwards, pore size from 3.5 Å to 5000 Å
- **Repeatability:** Specific surface area ≤ ±1.0%, pore size ≤ 0.2 Å
- **Testing Efficiency:** Average surface area per 10 minutes, mesoporous/macroporous analysis 1–1.5 hours, microporous analysis 10–16 hours per sample
- **Analysis Stations:** 3 independent stations for simultaneous testing
- **Pâ‚€ Stations:** 3 real-time monitoring Pâ‚€ positions
- **Lifting System:** 2 sets of independent lifting systems for each station
- **Vacuum System:** Multi-channel parallel vacuum system with adjustable pumping speed (2–200 ml/s)
- **Vacuum Pump:** External two-stage rotary vane pump + built-in turbomolecular pump, ultimate vacuum up to 10â»â¶ Pa
- **Degassing System:** 3 in-situ degassing stations with programmable temperature control (up to 10 steps), maximum degassing temperature 400°C
- **Pressure Sensors:** 1000 Torr, 10 Torr, 1 Torr (upgradeable to 0.1 Torr), accuracy ≤ ±0.15%
- **Data Acquisition:** Ethernet-based, compatible with Windows 7/XP 32/64-bit systems
**Key Features:**
- 3 independent stations for simultaneous analysis and degassing
- External 4-station vacuum degassing system with high-temperature capability
- Auto-multi-point BET surface area test within 30 minutes
- Integrated liquid nitrogen control system ensures stable temperature during testing
- Advanced thermostat clamp technology with 3L vacuum dewar for long-lasting experiments
- Multi-channel vacuum system with anti-splash design for ultra-fine powder handling
- Turbo molecular pump and mechanical pump combination for ultra-low pressure
- Real-time Pâ‚€ measurement and atmospheric pressure input method
- User-friendly control panel with valve status display
- NLDFT model standard configuration for international-level analysis
- HK and SF models certified by China Metrology Institute
- Intelligent pressure control for high-precision isothermal curves
- Ethernet software for remote operation and multi-instrument control
- Expandable to 3 independent micropore analysis stations
**Applications:**
- Catalysts: Activated alumina, molecular sieve, zeolite
- Environmental: Activated carbon, adsorbents
- Nanomaterials: Nano ceramic powders, metal powders, carbon nanotubes
- Coal Industry: Coal, shale gas, coalbed methane
- Other: Porous fabrics, composites, microfibers
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