In UHV systems such as electron microscopes, mass spectrometers, particle accelerators, and high-vacuum coaters, the performance of the diffusion pump working fluid directly determines the system's ultimate vacuum, pumping speed, and long-term stability. Mineral oil diffusion pump fluids have high vapor pressure and poor thermal stability, unable to break through the 10⁻⁴ Pa level; ordinary silicone oils degrade over long residence above 200℃ due to preferential evaporation of light fractions, leading to increased backstreaming and decaying ultimate vacuum. With escalating demands for "untrapped ultimate vacuum 1×10⁻⁹~10⁻¹⁰ torr, 25℃ vapor pressure ≤3×10⁻¹⁰ torr, long-term thermal stability at 300℃", sourcing a UHV diffusion pump silicone oil with "single-component, pentaphenyl-dense, MW 546, flash ≥243℃" has become the core gap for domestic cutting-edge research and high-end manufacturing localization. Addressing this, Anhui IOTA Silicone Oil Co., Ltd. officially launches IOTA 705 Ultra-High Vacuum Diffusion Pump Oil (Chemical Name: 1,3,5-trimethyl-1,1,3,5,5-pentaphenyltrisiloxane; Pentaphenyl Trimethyl Trisiloxane; CAS 3390-61-2). Characterized by "colorless transparent oily liquid; viscosity 170-175mm²/s (25℃); RI 1.5765-1.5785; sp.gr. 1.090-1.10; COC flash ≥243℃; congealing point ≤-14~-18℃; 25℃ extrapolated vapor pressure 3×10⁻¹⁰ torr; untrapped ultimate vacuum 1×10⁻⁹~10⁻¹⁰ torr; 25kg PE drum or 200kg iron drum; non-toxic non-hazardous transport; 3-year shelf life", backed by "pentaphenyl conjugate dense-graft + single-component zero light fraction + 3×10⁻¹⁰ torr ultra-low vapor pressure", it serves as the "ultimate vacuum engine" for UHV systems, featuring identical chemical structure to Dow Corning 705 (same CAS), enabling import substitution. Molecular Architecture: Pentaphenyl Dense-Graft + Single-Component Uniformity + Si-O Bond Energy Lift

• Pentaphenyl Conjugate Vapor Suppression: Five benzene rings densely distributed on the siloxane backbone; π-π conjugation combined with large molecular volume synergistically suppress 25℃ extrapolated vapor pressure to 3×10⁻¹⁰ torr. Phenyl steric hindrance also suppresses the depolymerization that limits PDMS high-temp performance, enabling 705 to reside long-term without decomposition at typical diffusion pump operating temperatures of 200-250℃.
• Single-Component Zero Light Fraction: Unlike market-common multi-fraction blended silicone oils, 705 is a single-component pure fluid — every molecule in the charge is identical. This means no light fractions can preferentially evaporate; while ordinary blended silicone oils gradually drift in composition as light components escape during long-term use, leading to decaying ultimate vacuum, 705 maintains compositional constancy from the first drop to the last, delivering long-term vacuum stability and predictability far exceeding blended oils.
• 170-175cSt Engineering Viscosity: Viscosity 170-175mm²/s at 25℃ (61-64mm²/s at 40℃), ensuring stable high-speed jet at the nozzle while maintaining manageable fluidity at operating temperature; sp.gr. 1.090-1.10 high density maintains stable jet morphology in pump nozzle assemblies.

Performance Leap: From "10⁻⁷ torr Ceiling" to "10⁻¹⁰ torr UHV"

• Ultimate Vacuum: Untrapped ultimate vacuum reaches 1×10⁻⁹~10⁻¹⁰ torr, meeting the stringent demands of electron microscopes, mass spectrometers, and molecular beam epitaxy.
• Minimal Backstreaming: 25℃ vapor pressure only 3×10⁻¹⁰ torr; ultra-low vapor pressure leads to minimal backstreaming — in properly designed systems, 10⁻¹⁰ torr vacuum can be achieved without cold traps, eliminating the need for baffles and thus improving pumping speed.
• Thermal-Oxidative Dual Stability: Flash point ≥243℃ provides ample safety margin; superior oxidation resistance prevents decomposition during long-term high-temp operation, effectively delaying aging upon trace air exposure and reducing sludge formation.
• Wide-Temp No-Freeze: Congealing point ≤-14~-18℃, ensuring start-up reliability in cooler environments, suitable for laboratories and production facilities with ambient temperature fluctuations.
• Rad-Hard & Weathering: High phenyl content grants excellent radiation resistance, suitable for nuclear industry and other high-energy environments.

Application Penetration: From Electron Microscope to Particle Accelerator

• Electron Microscopes & Mass Spectrometers (Main Battlefield): EM, MS, molecular devices — 705's ultra-low vapor pressure and single-component stability serve as the "vacuum heart" ensuring long-term stable operation of such analytical instruments.
• Atomic Accelerators: Particle accelerators, atomic energy research facilities — maintaining beam stability in UHV environments; radiation resistance adapts to high-energy physics experiments.
• High-Vacuum Metallurgy & Coating: Melting, degassing, and sintering of refractory metals in high-vacuum furnaces; thick-film deposition; anti-reflective coatings, optical filters, mirror surface improvement in optical industry.
• Electron Tube & Display Industry: TV tubes, fluorescent tubes, cathode ray tubes, ordinary bulbs, capacitors, rectifier metallized film vacuum systems.
• High-Temp Carrier & Transmission Fluid: Can function as transmission fluid in high-temperature carriers and various instruments.

IOTA Technical Guide: Moisture-Proof & Light-Proof, 3-Year Long Efficiency

• Application: As diffusion pump working fluid, fill per pump specification; typical boiler temperature 250-270℃, 0.5 torr boiling point 245℃; 705's viscosity is higher than 704 (175cSt vs 38cSt), with slower start-up and greater heating power consumption — only choose 705 when the process genuinely requires vacuum beyond 10⁻⁹ torr, otherwise 704 is more economical.
• ⚠️ Taboo: Store diffusion pump oil sealed, no mixing with other oils, water, or impurities; immiscible with mineral/ester oils, no blending; avoid contact with oxidants.
• Storage: Store in moisture-proof, damp-proof, sunlight-protected warehouse at indoor temperature -40~50℃; 25kg PE drum or 200kg iron drum; non-toxic non-hazardous transport and storage; 3-year shelf life.
• Handling: Single-component nature ensures compositional constancy during long-term high-temp operation, but regularly check oil level and color; if significant discoloration is found, promptly investigate system contamination.

Industry Insight: The three core metrics of diffusion pump oil — vapor pressure, thermal stability, and molecular weight — determine the performance ceiling of UHV systems. IOTA 705, with "pentaphenyl trimethyl trisiloxane + 3×10⁻¹⁰ torr vapor pressure + 1×10⁻⁹~10⁻¹⁰ torr ultimate vacuum + ≥243℃ flash + single-component pure + 3-year shelf life", fills the key supply chain link for domestic UHV diffusion pump oil in electron microscopy, mass spectrometry, accelerators, and high-vacuum coating fields, providing import-substitution for downstream cutting-edge research and high-end manufacturing enterprises (identical chemical structure to Dow DC 705, same CAS 3390-61-2, priced at approximately 50-60% of Dow's, domestic spot delivery in 3-5 days). This confirms domestic specialty silicone oils are leaping toward "single-component pentaphenyl UHV silicone oil", with growing technical say in UHV media.