Super-smooth Surface Research Articles

Recent Patents for Optical Component Polishing Technology

Background: Fluid jet polishing, Airbag polishing, Magnetorheological polishing, and Ion beam polishing are all emerging polishing technologies commonly used for processing optical components, which can be used to manufacture various high-precision and high-quality optical components. Their processing mechanisms are to remove materials by high-speed jet impacting the surface of the workpiece; using a spherical flexible airbag as a polishing tool to obtain a super-smooth surface by adding polishing fluid containing fine abrasives; controlling the magnetic field to form a flexible polishing belt of Magnetorheological fluid, which undergoes relative motion to achieve material removal; using a neutral ion beam to bombard the surface of the workpiece to remove workpiece surface atoms and obtain a super-smooth surface through energy and momentum transfer between ions and workpiece atoms. The characteristics and removal mechanisms of various polishing methods are briefly described, and the advantages and key issues that need to be addressed for each polishing technology are pointed out, and suggestions and prospects for future research, application, and development are also given. Objective: In order to meet the growing demand for high-precision optical components and mass-manufactured optical components, this paper aims to study the various polishing technologies that are continuously improved and suggestions are made for future research and development directions. Method: This paper reviews the current patents related to various polishing technologies, such as Fluid jet polishing, Airbag polishing, Magnetorheological polishing and Ion beam polishing and other representative polishing technologies. Results: Various types of polishing technologies have been studied, and the main problem at the current stage is the lack of accuracy. The problem of the polishing device, such as fluid jet polishing, only considers the change of fluid velocity and pressure to construct the removal function model for analysis and summary, and suggestions for the latest research progress of various polishing technologies are given. Conclusion: The improvement and optimization of polishing technology are beneficial to improving the polishing accuracy and quality of optical components and have great help for the future development of related patents.

Experimental study of key factors on super smooth surface fabrication upon single crystal silicon based on mechanochemical synergy

Due to rapid advancements in fields of modern optics and opto-electronics, the need for the production of super-smooth surfaces on single crystal silicon has become increasingly pressing. Although previous research has elucidated the mechanism of material removal and defect evolution in chemical mechanical polishing, brittle characteristic of the vulnerable silicon material makes it rather challenging to catch up with the extreme requirements of high performance and highly efficient manufacture. Nevertheless the critical polishing pressure for scratch free super-smooth surface in pragmatic machining remains undiscovered, which greatly hinders improvement in related fields. Consequently, this paper presents a series of analyses and experiments focused on the material removal process at the micro scale. A micron-sized SiO2 ball tip is utilized to simulate the scratching on surface of a single crystal silicon substrate. Experimental results reveal that appropriate pH conditions and a maximal contact pressure of 0.97 GPa (at a scratching speed of 2 µm/s) between the particle and substrate are crucial for achieving a super-smooth surface. Based on these findings, a defect-free chemical mechanical polishing method is proposed, which involves controlling contact pressure for practical fabrication. Further verification using the KDOSP 650γ machining system and ion beam figuring has demonstrated that a defect-free surface with a roughness of 0.209 nm RMS (Root Mean Square) can be achieved at an average removal rate of 316 nm/min. These insights provide new understandings in the fabrication of super-smooth surfaces on single crystal silicon, offering significant benefits for enhancing the performance of brittle single crystal silicon-based devices and the corresponding machining capabilities.

Experimental investigation on the problems in the achievement of super-smooth surface of cemented carbide WC-Co through diamond turning

The processing of cemented carbide (WC-Co) with mechanical methods has become problematic in the production of functional parts and molds due to the great brittleness and hardness. The application of ductile-regime machining to process the WC-Co has been attempted, but the outcomes are not satisfactory. To better understand the processing of WC-Co, the Vickers indentation, nanoindentation, single point diamond turning, and taper cutting experiments are carried out by referring to the empirical parameters, instrument options, and published works. Firstly, the effectiveness of the reported models in predicting the critical uncut chip thickness of brittle-ductile transition of WC-Co are verified and discussed in terms of the experimental observations. Then the impact of diamond turning on the morphologies and mechanical properties of the machined surface are examined. After that, the defects that affect the surface quality of WC-Co are analyzed. The results indicate that the deterioration of surface quality is dominantly decided by the breakage of WC grain. The grain breakage induced defects and further observations of taper cutting on the WC-Co reveal that the critical uncut chip thickness (40–50 nm) required to produce a super-smooth surface is much smaller than the depths predicted by the reported models of brittle-ductile transition (0.674–1.008 μm). Such difference may be derived from the improper use of fracture toughness and application of models that treat the workpiece material as a continuous and evenly distributed medium. Finally, a modified diamond turning process is conducted to verify the effectiveness of the analysis.

Thin film nanocomposite polyamide membrane doped with amino-functionalized graphene quantum dots for organic solvent nanofiltration

Thin film nanocomposite (TFN) organic solvent nanofiltration (OSN) membrane with improved separation performance was fabricated via interfacial polymerization reaction between amine-functionalized graphene quantum dots (af-GQDs) doped aqueous monomer solution of m-phenylenediamine (MPD) and n-hexane solution containing trimesoyl chloride (TMC) monomer. We emphasize the employment of extra-low content for both af-GQDs and MPD, so that we could maximize the function of these nanomaterials and eliminate their aggregation at the same time. The af-GQDs nanomaterials could regulate the interfacial polymerization process and could be strongly anchored in the polyamide film via covalent bonding, hence could prevent their loss while providing more channels for faster solvent penetration. As a result, the optimized OSN membrane, TFN-50, shows a super-smooth surface, with a surface roughness as low as 4.3 ± 0.2 nm, and excellent pure solvent permeances which reach 135.8, 112.7, and 69.8 L m−2 h−1 MPa−1 for methanol, DMF and ethanol, respectively, as well as a very high Rhodamine B (RDB, 479 Da) rejection of up to 99.2%, and an ethanol permeance of 61.4 L m−2 h−1 MPa−1. Furthermore, the TFN-50 OSN membrane still shows excellent filtration performance after being submerged in DMF for 336 h or continuous crossflow filtration with Rose bengal (RB, 1017 Da)/DMF solution for 136 h, demonstrating its excellent solvent resistance.

Biomimetic corneas of individual profile-followed coating for encapsulated droplet array

The ability to acquire a varifocal optical system with excellent reversibility and repeatability is crucial for many applications. However, current strategies for improving varifocal ability primarily focus on enlarging tunable focal length. The demonstration of an individually encapsulated microlens array is one of the key technological challenges in the varifocal microoptic industry. Inspired by corneas of natural eyes, we develop a self-assembly flow molding approach to fabricate a profile-followed coating onto the droplet surface for long-term encapsulation. Meanwhile, the coating has a supersmooth surface with roughness less than 1 nm within an area of 10 [Formula: see text] 10 μm2, which unprecedentedly facilitates the high transparency and photosensitivity of a micro-optical system. Significantly, the elastic modulus of profile-followed coating is as low as 0.25 MPa, which satisfies the large varifocal capacity ranging from 773 to 1600 μm at a low voltage of 5 V. This work opens a new window for exploring the encapsulated fluid components with profile-followed coating in tunable optical systems.

Polyethylene Glycol Diacrylate (PEGMA) and Polyvinylpyrrolidone (PVP) Delivering Solifenacine as Super Smooth Coating of Ureteral Stent to Relieve Stent Syndrome: In Vitro and In Vivo Study

Urinary calculus is a very common disease in urology. Ureteral stent is popularly used in patients after surgeries to protect the ureter. Indwelling ureteral stent inevitably causes stent syndrome for the reason of foreign body stimulation and rough stent surface. Clinicaly, oral administration of solifenacine is a solution to relieve the symptoms, however it is with several complications. In our study, ureteral stent was coated with bioactive solifenacine in polyethylene glycol diacrylate (PEGMA) and polyvinylpyrrolidone (PVP) to realize super smooth surface and controlled release of solifenacine. Scanning electron microscopy (SEM) and friction test of solifenacin-loaded super-smooth stent (SSSS) revealed its smooth surface. Fourier transform infrared spectroscopy and controlled release test showed its solifenacin delivering and controlled releasing. The polymerase chain reaction (PCR) showed inhibited α-smooth mucle actin expression in SSSS treated smooth muscle cells. The SSSS was applied in male New Zealand rabbits and revealed the effect of inhibiting the abnormal contraction of bladders. The Histology of SSSS treated bladder revealed a diastolic muscle layer of bladder. The SSSS after implantation showed smoother surface and less calcium deposition. In conclusion, it’s demonstrated that the SSSS has the efficacy of relieving stent syndrome and potential for clinical translation and application.

Molecular dynamics simulations of Carbyne/Carbon nanotube gigahertz oscillators

Quasi one-dimensional carbon nanotubes (CNTs) and one-dimensional carbyne are two kinds of promising carbon-based nanomaterials and attract much attentions due to their excellent mechanical, thermal and electrical properties. By combing these two typical nanostructures, a novel carbyne/CNT oscillator (CMO) is proposed and oscillation properties at constant energy and constant temperature are systematically investigated via molecular dynamics simulations. The results show that CMO possess extremely high frequency which is up to 360 GHz, higher than most traditional nano-oscillators. Besides, due to the super-smooth surface between carbyne chain and CNT, the energy dissipation of CMO is also extremely low. And at constant energy, amplitude of CMO could keep nearly constant over 2000 ps. However, at constant temperature, energy dissipation of CMO is pretty high when temperature is 1 K. And when temperature slightly increases to 30 K, oscillation behavior of CMO could be stable and CMO could keep oscillating over 2000 ps. Therefore, it can be concluded that CMO possess excellent oscillation properties and possess promising potential applications in nano-oscillators. This work systematically investigates the influence of structural parameters on the oscillation frequency and amplitude of CMO and provides important references for their further design and application.

Fused silica with sub‐angstrom roughness and minimal surface defects polished by ultrafine nano‐CeO2

AbstractSurface quality of fused silica, particularly surface defect and surface roughness, is a key factor affecting the performance of high‐power laser and short‐wave optical instrument, and so on. Herein, the super smooth surface of fused silica with roughness of sub‐angstrom level and exceedingly few submicron defects was achieved by using ultrafine nano‐CeO2 with primary particle size less than 4 nm, low secondary particle agglomeration strength, and high Ce3+ concentration. Furthermore, CeO2 involve in polishing process in the form of primary particle was certified by experiment. Moreover, the cause for the generation of submicron defects on fused silica surface was investigated for the first time from the perspective of secondary particle agglomeration strength of CeO2. The concentration of Ce3+ in CeO2 was characterized by the redshift of the band‐gap energy, and the analysis of material removal rate (MRR) and contact angle of polished fused silica shows that Ce3+ enhances MRR through increasing the silanol group on fused silica.

Achieving a super-smooth surface of stainless bearing steel with chemical mechanical polishing via controlling corrosive wear of Fe and Cr

Achieving a super-smooth surface of stainless bearing steel with chemical mechanical polishing via controlling corrosive wear of Fe and Cr

Low‐Cost Volumetric 3D Printing of High‐Precision Miniature Lenses in Seconds (Advanced Optical Materials 17/2022)

Targeting the fast prototyping and massive production of complicated lenses, Zhiwei Zhu and co-workers report a low-cost volumetric 3D printing method for the ultra-fast and high-precision fabrication of miniature lenses with sub-nanometric roughness (see article number 2200488). The complex-shaped lenses are generated by the volumetric projection stereolithography and corrected by introducing an iterative learning scheme. Super-smooth surfaces are guaranteed by the meniscus equilibrium effect.

Ultra-smooth surface with 0.4 Å roughness on fused silica

Ultra-smooth surface with sub-nanometer roughness is of great significance in various fields, including Ring Laser Gyro (RLG), high-power laser apparatus, ultraviolet optical systems, and the semiconductor industry. However, the mechanism of the ultra-smooth polishing process remains to be studied, which is of great value for understanding and optimizing optical-fabrication methods. This paper establishes a relationship between surface densification characteristics and surface roughness in conventional polishing. Moreover, we conclude that the densification process created by the longitudinal pressure, which avoids non-uniformity, is beneficial to forming super-smooth surfaces in the conventional polishing methods. Under this guidance, we can stably fabricate ultra-smooth surfaces on fused silica with 0.4 Å roughness. This result overturns the mainstream view that the longitudinal pressure in polishing should be minimized. This conclusion is meaningful for the understanding of the ultra-smooth surface formation not only in conventional polishing but also in other optical-fabrication technologies.

Characteristics of cutting force and surface finish in diamond turning of polycrystalline copper achieved by friction stir processing (FSP)

Cutting force and surface finish are two critical characteristic parameters for diamond turned polycrystalline copper components. In this work, polycrystalline copper with different grain sizes achieved by friction stir processing (FSP) was machined by single point diamond turning. To accurately predict cutting force in diamond turning, a theoretical prediction model considering grain size of copper, Hall-Petch effect, and stress distribution on a diamond tool was developed. Three-direction cutting forces, i.e., principal cutting force, thrust force, and feed force, in the diamond turning process were calculated, respectively. To analyse the material microstructure and mechanical property, Electron Back Scattered Diffraction (EBSD), X-Ray Diffraction (XRD) and nano-indentation analysis were successively performed on the work material. Combing theoretical model and experimental results, the relationship between principal cutting force and thrust force on various processing parameters was successfully revealed. Furthermore, surface roughness of the copper work material processed by FSP is smaller than that without treatment. According to material analysis results, the combination of misorientation angle and Hall-Petch effect reduces the step height on diamond turned surface, which further contributes to a flatter diamond turned surface. Therefore, the combination of friction stir processing and single point diamond turning has the application potential to achieve a super-smooth surface finish in industry.

Evolution of material removal in the magnetorheological polishing of Ti6Al4V by laser power bed fusion

This study aimed to obtain super smooth surface medical implant laser power bed fusion Ti6Al4V samples. A self-modified magnetorheological polishing device and polishing fluid were used to polish the laser power bed fusion additive shaped Ti6Al4V samples to study the effect of the main factors such as abrasive grain size, polishing pressure, and polishing time on the surface roughness and material-removal efficiency of the samples. With continuously decreased Al2O3 abrasive-particle size, the surface roughness initially increased and then decreased, and the material-removal rate decreased. The polishing result of 5 µm Al2O3 was better, no new scratch damage was found after 3 µm Al2O3 polishing; With increased polishing pressure from 5 N to 25 N, the deeper the abrasive particles were pressed, the greater the cutting effect and the more obvious the scratches. Surface roughness initially decreased and then increased, and the material-removal rate increased from 1.19 nm/min to 8.68 nm/min. With continuously extended polishing time, the grinding and polishing effect continued to accumulate, and the surface quality significantly improved, decreasing from 366.33 nm to 19.77 nm. These results showed that magnetorheological polishing technology was very effective in removing LPBF forming defects; the surface roughness was reduced by 96.27% and the additive defects can be completely removed.

Effects of nanoscale abrasive agglomeration on material removal in magnetorheological finishing

AbstractMagnetorheological finishing (MRF) is a main technology to achieve super smooth surfaces of ultra‐precision optics. Although the nanoscale abrasives in MRF fluid are agglomerated to various extents, such effects on material removal in MRF are seldom discussed. Herein, the agglomeration of the nanodiamond (ND) abrasive on material removal rate (MRR) of MRF is studied by both experimental and molecular dynamic simulation (MDS) pathways. The agglomeration degrees of ND abrasives are being characterized by the hydrodynamic scattering method. The number of removed atoms by a single agglomerated ND abrasive is calculated by the MDS. Then by using a novel active abrasive contact sites model, the simulated MRR of fused silica (FS) can be obtained. Theoretical calculated MRRs compare well with the experimental MRF results. This work provides an insight into controlled nanoscale material removal and atomic adhesion friction mechanism in MRF.

Single point diamond turning of silicon for flat X-rays mirrors

Silicon Mirrors are essential components for guiding the X-Ray beam and focusing it to a particular location. Due to lower X-ray wavelength, these mirrors require super smooth surface finish to avoid the strong scattering from surface. Single Point Diamond Turning is used to examine the fabrication possibility of X-Ray mirror. A number of machining cuts are performed with parameters like tool feed rate, Spindle Speed and depth of cut. The surface is characterized by mechanical profiler, optical profiler, Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). The optimized surface roughness achieved is 0.873 nm. Copyright © 2017 VBRI Press.

Correlation Among Particle Size Distribution, Subsurface Damages Distribution and Surface Roughness in Optical Polishing Process

Restricting polishing induced subsurface damage and obtaining super smooth surfaces are important in high quality laser systems. Here, experiments and theoretical simulations are combined to investigate correlations among particle size distribution, subsurface damage distribution, and surface roughness evolution in the optical polishing process. This reveals that the fraction of observable subsurface damage increases rapidly with increased particle size, which results in greater and deeper subsurface damage. In addition, control of the tail end particle size distribution is also critical for controlling polishing-induced subsurface damage. In the high surface roughness period, the surface roughness increases linearly with increased subsurface damage. In the low surface roughness period, without any polishing induced subsurface damage, optimizing pad properties to reduce microscale surface undulation could further improve surface roughness. Making sure that no observable subsurface damage is generated is the precondition for obtaining a super smooth surface. Using nanosized particles could greatly reduce the particles’ bear load and finally obtain a super smooth surface without any subsurface damages.

Fabrication and Application of Gel Forming Ultrafine Diamond Abrasive Tools

To solve the problem of phase agglomeration and microstructure inconsistency in the conventional powder pressing method of ultrafine diamond abrasive tool, a fabrication method of ultrafine diamond abrasive tool based on gel forming was proposed. The gel experiments of polyvinyl alcohol (PVA) and phenolic resin (PF) were carried out, and the basic physicochemical properties of the gel were tested by SEM, IR and TGA. The mechanical properties of gel forming and hot pressing forming abrasive tools were Compared. The polishing experiments of the gel abrasive tool and the hot-pressing abrasive tool were carried out. The results showed that when the PF/PVA ratio was between 5:1 and 10:1, the porous network gel structure was formed. The IR and TGA analysis indicated that the molecular crosslinking of PF and PVA occurred after gel. Compared with hot pressing abrasive samples, the abrasive distributions of gel abrasive samples were more uniform. The supersmooth surface of the SiC flat mirror with surface roughness Ra below 3 nm was obtained by the gel abrasive tool, which was better than by hot pressing abrasive tool. The surface flatness value PV 0.213 μm could be obtained by using the gel abrasive tool with low PVA content.

Improvement the InAs, InSb, GaAs and GaSb surface state by nanoscale wet etching

Various experimental approaches of the wet nanoscale treatment have been proposed to account for features of the InAs, InSb and GaAs, GaSb semiconductor dissolution process in the (NH4)2Cr2O7–HBr–EG etching solution. Etching kinetics data showed that a crystal dissolution has diffusion-determined nature. The lowering of the solvent concentration from 80 to 0 vol.% in the solution was accompanied by a significant increase in the semiconductor etching speed. Depending on the solution composition, we have studied two types of crystal surface morphology, polished and passivated by the film, which was formed after chemical-dynamic (CDP) and/or chemical-mechanic polishing (CMP) in the solution, saturated by solvent and by oxidant, accordingly. It was found that in the polished etchants both CDP and CMP procedures lead to the formation of the mirror-like and super-smooth surface with nanoscale roughness less than 1 nm. The obtained results of surface state indicate that the (NH4)2Cr2O7–HBr–EG etchants could be used successfully for controllable CDP and CMP treatment of III–V semiconductors and formation of super-smooth surface.

Fundamental study on CNC polishing method with inner channel liquid supply

The various optical components have wide applications in aerospace industries. In the manufacturing process of optical components that are made of optical glass materials, the main challenges still are how to ensure the high requirements in dimensional accuracy and surface quality. In this paper, the CNC polishing method with inner channel liquid supply (ICLS) is proposed to polish glass materials based on the chemical mechanical polishing mechanism. The comparative experiment with both inner and external liquid supply was designed, and it is found that the successive and steady material removal rate (MRR) can be achieved by using the proposed polishing method. Then, the effect of polishing pressure, tool rotation speed, and polishing time on polishing quality was analyzed with single-factor experiments. Finally, the optimal polishing parameters were obtained with the orthogonal experiment. The results show that the average surface roughness is reduced from 238.16 to 1.34 nm, and the nanoscale super-smooth surface is achieved, which proves the feasibility of the CNC polishing method with ICLS.

Structural and thermodynamic aspects of the evolution of supersmooth surface of oxide crystals

Evolution of the α-Al2O3, La3Ga5SiO14, and LaMgAl11O19 single crystals supersmooth surfaces at annealing in air was investigated using thermodynamic calculations. In particular the characteristic temperatures and annealing ranges were calculated when the surface melting phenomena took place or atomically smooth steps were formed and moved due to the surface diffusion processes. Later conclusion was confirmed in the surface probe microscopy experiments with regard to the crystal structure data of α-Al2O3, La3Ga5SiO14, and LaMgAl11O19, specifically the surface diffusion processes dominated at comparably low annealing temperatures (less than surface melting temperature Tsm). In this temperature range the crystal structure near the surface was rather stable, that is why one could assume the electrically neutral clusters of Al2O3, LaMgAl11O19 и La3Ga5SiO14 involved in the surface diffusion processes instead of single atoms. A further increase in annealing temperature to Tsm resulted in the La3Ga5SiO14 crystal surface thermodestruction due to probably incongruent melting of La3Ga5SiO14 compound and related friability of its structure if to compare it with Al2O3 and LaMgAl11O19 structures with the layers of close-packed oxygen atoms.