I. Mechanism of Cerium Oxide’s Action in Material Polishing
The key ingredient in high-performance polishes, cerium oxide (CeO₂), gets its inherent superiority from its built-in chemical-mechanical synergy of polishing. Despite not being hard, about 6 (well short of the diamond (10) or alumina (9)) on Mohs scale, but in comparison to silicon-base material polishing, relative efficacy is dramatically improved. Mechanism of action can be differentiated into two phases:
1. Chemical softening: The Ce4+ has a strong oxidating property that buffs the surface material such as silicon wafers or glass in order to form a soft silicate thin coating in the nanoscale.
2. Mechanical elimination: The softened layer is removed mechanically in a selective way by physical friction to prevent deep – layer damage. The process is favored by the oxygen vacancies in the crystal lattice and valence – change mechanism between Ce3+/Ce4+ in enhancing surface reaction activity. In this manner, for example, hydroxylation of the quartz surface would be catalyzed by Ce3+, hydrolysis of the Si – O – Si bonds could be promoted, and the chemical elimination rate could be increased.
II. Morphological Influence and Optimal Performance Optimization
The size and the morphology of the cerium oxide particles could directly influence the polishing action. The following will reveal some of the cases:
1. Octahedral particles: High surface Ce3+ and oxygen vacancies, high chemical activity. The MRR is up to 870 nm/h (17% higher than that of quasi – spherical particles), but the surface roughness is slightly higher (Ra≈0.327 nm).
2. Quasi-sphere particles: These are of isotropic contact pressure and have the ability to attain ultra-low levels of roughness (Ra < 0.1 nm), and are suitable for ultra-precision applications like optical uses like lenses.
3. Particle size control: Sub-4 nm particles can be polished on the atomic scale (RMS < 0.1 nm), and 30-50 nm particles can compete in cost and efficiency.
Stability in dispersion and high purity (>99.9%) are also essential. Low scratches due to impurities are achieved through high purity, and surfactants (e.g., CTAB, PEG) control the Zeta potential, preventing agglomeration and enhancing the service life of the polishing solution.
III. Areas of Application and Technological Advantages
1. Optical element processing:
Sub- 4nm cerium oxide polished quartz substrates reach ultra-smooth finishing with RMS < 0.1 nm, within the stringent requirement of high- energy lasers and space communication lenses.
2. Processing of hard and brittle material
For SiC wafers, the octahedral CeO₂ increases the MRR due to high local stress (5.233 nm deformation of wafer), while quasi-spherical particles ensure maximum surface integrity.
IV. Other Civilian Fields of Cerium Oxide
1. Cerium Oxide for Environmental catalysis sector
The cerium oxide in automobile three-way catalysis is utilized as an “oxygen storage material” that controls the amount of oxygen by reversible oxidation/reduction of the oxidations states of Ce3+/Ce4+, in favor of the efficient convetion of the species CO, HC, and NOx to innocuous products CO₂, N₂ on the support of noble metals like Pt, Pd. The use of the noble metal would be decreased by over 30% and the low-temperature activity could be enhanced.
Besides, it is also able to degrade VOCs in the treatment of industrial waste gas. Volatile organic compounds like benzene and formaldehyde would be oxidized catalytically at the temperature of 200 – 350°C or so, the percentage of catalytic conversion being higher than 95%, in the support of the transition metals (Mn, Co) in the nanoscale cerium oxide catalyst. Catalyst employed in the flue gas denitration for the power plant, CeO₂ – WO₃/TiO₂, is superior to the traditionally employed vanadium – based catalysts in resistance to sulfur – poisoning. It is called the effective and environmentally-friendly “catalytic magician”.
2. Cerium Oxide for Biomedical field
The biocomposite of cerium oxide nanoparticles, extracted through chitosan and chlorella, initiates the release of reactive oxygen species (ROS) via oxygen vacancies to abolish the membrane organization of bacteria, inhibit biofilm synthesis, and enhance biocompatibility. PEG/chitosan-functionalized CeO₂ NPs reduces the time of skin remodelling in animal models by 30% via the amplified synthesis of collagen and angiogenesis. It could thus be inferred that cerium oxide plays a pivotal role in antibacterial and wound repair and healing.
In addition, IC50= 37.89 μg/mL polymer-coated cerium oxide nanoparticles could potentially cause the loss of the mitochondrial membrane potential of liver cancer cells, the objective of target therapy.
3. Cerium Oxide for Energy field
Gd-doped CeO₂-based electrolytes like GDC have high ionic conductivity of oxygen in the temperature range of 500-700°C, and the battery quality is enhanced.
- Special ceramic and composite materials
The bending strength of the composition of the ceram of the cerium oxide-stabilized zirconia is 892 MPa, and the fracture toughness is 14.3 MPa·m¹/². High-temperature (≥650°C) wear-resistant parts are made from them in the production of high-strength ceramics that are wear-resistant. In addition to that, the composition’s coatings with the addition of the nanoscale cerium oxide are self-cleaning, and also protective against ultraviolet rays.
- Cerium Oxide for glass industry additives
Cerium oxide (Ce4+) is broken down to release oxygen, oxidize the low-valency sulfur and carbon atoms of the glass, and release bubble to make the glass clearer. Simultaneously, oxidize Fe2+ to Fe3+, reduce yellow color, and substitute poisonous arsenic oxide. 0.5 – 1.5% cerium oxide is added to make/automobile glass absorb 400 – 700 nm ultraviolet rays and reduce the vehicle’s interior temperature. In addition, cerium oxide is mixed with TiO to make yellow glass, or mixed with neodymium oxide to make color deeper.
V. Conclusion and Perspectives
With its strong synergistic chemical-mechanial action and morphological regulation, cerium oxide has become an indispensable polishing agent in high-precision processing and has innumerable indispensable uses. It also has to pierce ultra-fine manipulations (e.g., batch processing of particles smaller than 3 nm) and establish intelligent adaptation tactics in the future. Along the way, it also has to catalyze the high-value addition of the sources of rare-earth raw materials as well as recycling of waste methods. Constant R & D is sure to consolidate its core status in markets such as optics and new-energy devices.
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