Polishing Technology Research Articles

Polycrystalline Diamond Film Growth on Gallium Nitride with Low Boundary Thermal Resistance

As the demand for high-frequency and high-power electronic devices has increased, gallium nitride (GaN), particularly in the context of high-electron mobility transistors (HEMTs), has attracted considerable attention. However, the ‘self-heating effect’ of GaN HEMTs represents a significant limitation regarding both performance and reliability. Diamond, renowned for its exceptional thermal conductivity, represents an optimal material for thermal management in HEMTs. This paper proposes a novel method for directly depositing diamond films onto N-polar GaN (NP-GaN) epitaxial layers. This eliminates the complexities of the traditional diamond growth process and the need for temporary substrate steps. Given the relative lag in the development of N-polar material growth technologies, which are marked by surface roughness issues, and the recognition that the thermal boundary resistance (TBRGaN/diamond) represents a critical factor constraining efficient heat transfer, our study has introduced a series of optimizations to enhance the quality of the diamond nucleation layer while ensuring that the integrity of the GaN buffer layer remains intact. Moreover, chemical mechanical polishing (CMP) technology was employed to effectively reduce the surface roughness of the NP-GaN base, thereby providing a more favorable foundation for diamond growth. The optimization trends observed in the thermal performance test results are encouraging. Integrating diamond films onto highly smooth NP-GaN epitaxial layers demonstrates a reduction in TBRGaN/diamond compared to that of diamond layers deposited onto NP-GaN with higher surface roughness that had undergone no prior process treatment.

Prediction of the material removal rate in bonnet polishing using a Bayesian optimization deep neural network

The material removal mechanism in robotic bonnet polishing is complex and influenced by multiple factors, necessitating an appropriate method to establish a material removal model. This study employs a Bayesian optimized deep neural network (BO-DNN) to model the intricate relationship between polishing parameters and material removal rate (MRR) using removal function spot experimental data. The tree-structured Parzen estimator (TPE) improves model convergence speed and accuracy, while particle swarm optimization (PSO) assists in inverse verification. Results show that the BO-DNN model achieves a root mean square error (RMSE) of 0.0293 and a Pearson correlation coefficient (PCC) of 99.42% for the total sample, representing approximately a 50% improvement in predictive accuracy over the unoptimized DNN model. The inverse verification results closely match the experimental data, confirming the model’s reliability. This study offers theoretical insights and practical references for advancing robotic bonnet polishing technology.

Spiral feed polishing uniform removal and compensation strategy of sapphire components

A single crystal sapphire component has been widely used in various high-tech fields because of its significant advantages such as high hardness, high stability, and excellent optical and mechanical properties, and has put forward high requirements for surface accuracy and quality. The existing sapphire polishing technology has problems such as low polishing efficiency, difficult control of polishing accuracy, and difficulty in removing surface defects and subsurface damage introduced by the front grinding process. Therefore, for the polishing and damage removal stage of sapphire optical components, the surface shape accuracy should be strictly controlled, especially for the surface shape accuracy after ultra-precision grinding. It is of great significance to study the uniform removal technology of grinding damage based on not destroying the surface shape. This study focuses on the mechanical polishing of sapphire. Firstly, the characteristics of the sapphire removal function of the elastic polishing tool are analyzed and the stability of the polishing tool is verified. Secondly, by establishing the relationship between the amount of workpiece material removal and the radius of rotation, the feed rate is planned to achieve the effect of uniform spiral removal. By optimizing the center feed speed of the tilting axis small-size polishing tool, the center feature of the polishing surface is controlled to be sharp. Finally, based on the sub-aperture polishing figuring theory, the influence of the center feature on the surface profile is reduced by using the spiral grating processing method. This study provides an efficient and stable strategy for the uniform removal and polishing of rotationally symmetric optical elements (such as aspheric surfaces) of high-hardness material sapphire and is expected to play a role in scenes that are particularly difficult to process, difficult to detect full aperture, difficult to calculate removal function and dwell time, such as higher steep aspheric surfaces and Gaussian aspheric surfaces.

Application and development of bonnet polishing technology

Application and development of bonnet polishing technology

Surface finishing of 3D-printed Ti–6Al–4 V alloy by electrolyte plasma polishing: Process optimization and microstructure

The electrolyte plasma polishing (EPP) technology is proposed to remove the unmelted powder particles and oxide film for high-quality surface finishing of 3D-printed Ti–6Al–4 V alloy. An orthogonal experiment is conducted to investigate multiple factors that contribute to the surface quality of the alloy during the polishing process. The optimal parameters determined for the EPP process are a voltage of 300 V, a polishing time of 12 min, a polishing depth of 12 cm, and a temperature of 75 °C. Based on the extent of the effect, the factors influencing surface roughness were ranked: voltage > time > depth > temperature. The surface crest and trough area of the alloy is substantially reduced after polishing, while the average roughness experienced a reduction of 76 %. The improvement in surface quality is attributed to the corrosion of the oxide layer by F ions in the electrolytic solution, and the melting of surface protrusions due to the impact of high-energy electrons under high-temperature and high-pressure conditions during plasma discharge. Additionally, the surface hardness of the material decreases slightly, but its corrosion resistance and hydrophobicity are enhanced, and the calibration rate of the EBSD sample can reach 92.51 %, demonstrating that it is an excellent surface finishing technique. Hence, EPP is a promising approach for smoothening 3D-printed metals, especially for alloy parts with complex geometry and porous structure.

Review on chemical mechanical polishing for atomic surfaces using advanced rare earth abrasives

Abstract During the past decades, high-performance devices and setups have been widely used in the fields of precision optics, semiconductors, microelectronics, biomedicine, optoelectronics and aerospace. It is a challenge to achieve ultralow surface roughness free of damages. Due to the unique physicochemical properties of rare earths, ceria has garnered great progresses for atomic surfaces induced by chemical mechanical polishing. Compared with conventional mechanical removal by alumina and silica, rare earth abrasives achieve selective material removal on surface via their special chemical activity, without introducing microscopic scratches and defects. Nevertheless, polishing performance of rare earth abrasives depends on series of factors, e.g. size of abrasive particles, microscale topological structure, configuration of chemical slurry, auxiliary energy fields etc. As a result, it is significant to conduct a comprehensive review to understand state-of-the-art polishing technologies. This review summarizes the effect of polishing slurries composed of different rare earth abrasives on polishing performance under different conditions. Additionally, various energy-assisted polishing strategies are discussed using diverse kinds of rare earth abrasives for distinct polishing forms. Finally, future directions of polishing on rare earth abrasives are addressed.

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.

Effect of the gas layer evolution on electrolytic plasma polishing of stainless steel

In recent years, electrolytic plasma polishing technology has attracted wide attention due to its advantages of shape adaptability, high efficiency, better precision, environmental friendliness, and non-contact polishing. However, the lack of research on the evolution mechanism of the gas layer at the anode interface restricts the improvement of the material removal mechanism and the regulation of the polishing effect. Firstly, the thermodynamic conditions of gas layer formation were analyzed based on the Clapeyron-Clausius equation, and the key parameters affecting the gas layer were identified. Secondly, the laws of voltage and electrolyte temperature on the dynamic evolution of the gas layer and its polishing effect were revealed. Additionally, the influence of the gas layer on the voltage-current characteristics was also investigated by analyzing the experimental phenomena. The results indicate that the optimal polishing effect is achieved at a voltage level of 300 V resulting in a decrease in Ra from 0.451 μm to 0.076 μm. Similarly, superior polishing results are obtained when the electrolyte temperature is 80 °C, with a decrease in Ra from 0.451 μm to 0.075 μm. This study provides theoretical guidance for the further development and application of electrolytic plasma polishing technology.

Micro-mechanism of glycine action in tribochemical mechanical polishing of single-crystal sapphire substrate: Experimental and first-principles analysis

With the rapid development of novel optoelectronic devices, an environmentally friendly and highly efficient polishing technology for SC-sapphire substrates is imminent. In this work, the micro-mechanism of Gly action in TCMP of SC-sapphire substrate is systematically studied by TCMP experiments and first-principles calculations. The results of TCMP experiments confirm that the maximum MRR of 5.37 μm/h with Ra of 0.42 nm can be attained at optimal concentration of Gly, without any acid or alkali corrosive solution. The first-principles calculations of the Gly/SC-sapphire heterostructure further reveal the reaction behavior of the -COOH functional group with and without lattice distortion. The results of both TCMP experiments and VASP simulations demonstrate that the incorporation of Gly can facilitate the friction-induced Gly/SC-sapphire reaction, which significantly enhances the processing surface quality and the processing efficiency of SC-sapphire substrates. Finally, based on the above research, a microscopic material removal model for the Gly-based SC-sapphire substrate TCMP is constructed. The above findings are of great significance in promoting the development of green ultra-precision polishing technology for semiconductor substrates.

Nano-CeO2 for the Photocatalytic Degradation of the Complexing Agent Citric Acid in Cu Chemical Mechanical Polishing

Cu interconnect chemical mechanical polishing (CMP) technology has been continuously evolving, leading to increasingly stringent post-CMP cleaning requirements. To address the environmental pollution caused by traditional post-CMP cleaning solutions, we have explored the use of photocatalytic processes to remove citric acid, which is a commonly used complexing agent for CMP. In this study, CeO2 abrasives, characterized by a hardness of 5.5, are extensively employed in CMP. Importantly, CeO2 also exhibits a suitable band structure with a band gap of 2.27 eV, enabling it to photocatalytically remove citric acid, a commonly used complexing agent in Cu CMP. Additionally, the integration of H2O2, an essential oxidant in Cu CMP, enhances the photocatalytic degradation efficiency. The research indicates that the removal rate of single-phase CeO2 was 1.78 mmol/g/h and the degradation efficiency increased by 40% with the addition of H2O2, attributed to the hydroxyl radicals generated from a Fenton-like reaction between H2O2 and CeO2. These findings highlight the potential of photocatalytic processes to improve organic contaminant removal in post-CMP cleaning, offering a more sustainable alternative to conventional practices.

Comprehensive Overview of Patents on Microstructure Surface Polishing Technology

Comprehensive Overview of Patents on Microstructure Surface Polishing Technology

Innovation governance in Poland. Technological trends with an outlook to 2030

The research problem of the article concerns adapting current innovation governance theories to assess national innovation systems. The operationalization of this task in the Polish context translated into identifying the most promising trends and technological areas for the Polish economy in the 2030 perspective. The study included a horizon scanning and trend radar variant, identifying seven trends: nanomaterials and nanotechnologies, smart grids and energy storage, Food Tech, smart/precision farming, drone technologies, telemedicine, application of hydrogen in steel, and the technological areas included in them. Results were further assessed based on CAWI surveys conducted on a sample of experts representing the Łukasiewicz Research Network. Smart/precision farming, telemedicine, smart grids and Food Tech proved the most promising for the Polish economy. The small difference in results leads us to believe that nanomaterials and nanotechnologies, drone technologies and hydrogen applications in steel production should also be in the spotlight, but special attention should be paid to the accompanying challenges, such as development costs or insufficient R&D infrastructure. The size and scope of the research make it unique and, at the same time, support the significance of the results for Polish technology, economy and science.

Investigation on the Dry-Type Electrochemical Polishing of 304 Stainless Steel with Ion-Exchange Resin Particles

Dry-type electrochemical polishing (DECP) technology integrates the mechanical action of resin particles with the electrochemical action of working solutions to enhance the results of existing treatments. Homogeneous polishing across the entire surface of the piece is the main advantage compared with mechanical polishing. This article utilizes this method to polish the surface of 304 stainless steel, leading to an improved surface roughness from the original 1.23 μm to the final 98 nm. This innovation expands the potential applications of 304 stainless steel in the medical and food industries. Energy dispersive X-ray spectroscopy (EDS) analysis subtle detect residual electrolyte components. It implies that resin particles containing liquid electrolytes can effectively prevent the remained harmful substance from the metal surface. Electrochemical analysis of polished sample shows that the E corr was −0.109 V for DECP specific sample compared with −0.0385 V for initial sample. The polishing process can be seen as the generation and removal of corrosion products.

Optimization of electrolytic plasma polishing process and surface performance analysis for 6061 aluminum alloy

Electrolytic Plasma Polishing (EPP), an innovative technology for polishing, has been utilized to improve the surface performance of 6061 aluminum alloys. An orthogonal experimental approach was carried out to investigate the multiple factors influencing the surface quality of aluminum alloys during the polishing process. The results indicated that peaks and scratches on the surface were successfully removed after polishing, with the average roughness reduced to 0.138 μm, approximately 1/8 of the original roughness. Additionally, the EPP process enhanced the substrate's corrosion resistance and hydrophobicity. Finally, it is proposed that the mechanism of surface smoothing effect of EPP is attributed to the combined action of plasma chemical dissolution and cavitation forces peeling. This research indicates EPP as a promising finishing technique with considerable potential for enhancing the surface performance of aluminum alloys in electronic component applications.

Study on electrochemical polishing mechanism of TC4 titanium alloy

To achieve a high-quality and precise surface on TC4 titanium alloy for demanding engineering applications, electrochemical polishing (ECP) technology was employed to investigate the polishing process of TC4 titanium alloy in an ethylene glycol-sodium chloride green electrolyte. The macro and micro morphology, surface roughness, material removal rate, surface elements, surface corrosion resistance, and surface hardness of TC4 titanium alloy were measured before and after polishing. Single-factor experiments were conducted to explore the effects of processing gap, electrolyte temperature, polishing voltage, and polishing time on TC4 titanium alloy surface quality. Optimal polishing parameters were determined to be an electrode gap of 12 mm, a voltage of 20 V, a temperature of 40 °C, and a polishing time of 10 min. The experimental results indicated that after electrochemical polishing, the workpiece surface roughness Ra decreased from 256 nm to 25 nm, achieving a roughness reduction rate of 90.23%, the material removal rate was 3.348 μm min−1. The self-corrosion potential of the polished surface increased from −0.416 V to −0.375 V and the self-corrosion current density decreased from 4.447 × 10−7 A·cm−2 to 1.873 × 10−7 A·cm−2, the surface indentation hardness of the workpiece decreased from 5.8669 GPa to 4.6726 GPa. Based on the characterization of polished surface, the mechanism of electrochemical polishing of TC4 titanium alloy was proposed. The results demonstrate that electrochemical polishing of TC4 titanium alloy is highly efficient, involves no mechanical action, and causes no subsurface damage, making it a promising technology to meet medical requirements.

Mapping model of ribbon contour and tool influence function based on distributed parallel neural networks in magneto-rheological finishing.

Magnetorheological finishing (MRF) stands out as a notable polishing technology, characterized by high precision and minimal damage. However, establishing an accurate and practical model for the tool influence function (TIF) of MRF poses a significant challenge. In this paper, a TIF modeling method of MRF based on distributed parallel neural networks is proposed for the first time. Assessment of the viability of this approach through multiple sets of robot-assisted MRF experiments is detailed. The experimental results conclusively demonstrate the successful intelligent prediction of TIF, with key indicators such as volume removal rate and peak removal rate achieving an average prediction accuracy exceeding 95%. This method can remarkably advance the intelligence of the TIF model in MRF and serve as a valuable reference for other optical fabrication methods.

Overview of Patents on Diamond Polishing Apparatus

Diamond, with its unparalleled combination of physical and chemical attributes, occupies a critical role in future technological domains; yet, the caliber of its surface quality is decisively linked to its performance within advanced applications. Thus, engaging in super-precision processing to elevate the surface integrity of diamond constitutes a central tenet for broadening its application potential. This paper systematically dissects patents pertaining to diamond polishing apparatus, not only revealing the distinctive strengths and pragmatic features inherent in contemporary diamond polishing technology but also identifying limitations and avenues for refinement within current polishing methodologies. With the continuous expansion and deepening of modern industrial sectors, there is a growing demand for diversified and specialized material performance. Diamond, as a pivotal raw material, exhibits immense potential in its composite applications with a variety of other materials, forming an entire industrial chain that has permeated numerous industries. Throughout the comprehensive preparation process of diamond, from rough stone to finished product, polishing techniques play a critical role, representing an indispensable step in enhancing the surface quality and functional attributes of diamond products. This study provides a comprehensive review of representative patents in the field of diamond polishing apparatus, analyzing the distinctive functional attributes and performance characteristics of various diamond polishing devices. The study classifies polishing devices according to their design characteristics and application domains into five distinct categories: polishing apparatuses specifically designed for single-crystal diamonds, systems tailored for the polishing of complex curved surface diamonds, laser-assisted diamond polishing setups, structurally-enhanced diamond polishing equipment, and functionally-specialized diamond polishing tools. The analysis underscores the unique innovative aspects and advantages demonstrated by each patent in addressing the inherent limitations of traditional polishing devices. Moreover, it elucidates the technological constraints and developmental gaps that exist within each respective area. Presently, the essence of polishing technology research revolves around the precision and efficacy in polishing single-crystal diamonds and intricate curved diamond surfaces, alongside the structural innovation and functional refinement of polishing apparatuses. Predominant among these devices are those that largely depend on mechanical polishing methods integrated with laser-assisted and chemical mechanical polishing methodologies, where patent advancements are mainly geared towards boosting efficiency, guaranteeing surface integrity, fortifying adaptability across different operating scenarios, and incorporating multiple functionalities. Concurrently, considerable attention is given to enhancing the ecological performance of these systems. There remains a significant underdevelopment and limited widespread application of diamond polishing apparatus in advanced technologies such as thermal chemical polishing and ion beam polishing. This gap presents an enormous potential for innovation breakthroughs and diversified advancements in polishing techniques. There is an urgent need for increased investment to propel the development and integration of automated control systems, intelligent monitoring, and deeper exploration of new materials within polishing technology. The aim is to realize higher-level automated and intelligent diamond polishing solutions that can achieve more efficient, precise, and environmentally friendly polishing objectives.

Role of fictive temperature distribution involved in CO2 laser polishing of fused silica and its optimization for achieving even heat-affected zones

CO2 laser polishing process is a highly effective way for enhancing the surface quality and laser-induced damage threshold of fused silica optics. Nevertheless, due to the thermal history and spatial gradient of the thermodynamic temperature, the heat-affected zones can be formed unevenly on the surface with an increased fictive temperature, which causes the material densification and residual stress. In this work, a 3D model of structural relaxation coupled with temperature and flow fields was innovatively established to explore the role of fictive temperature distribution involved in CO2 laser polishing of fused silica. The Raman spectrum was applied to verify this model. Subsequently, the impacts of laser beam power, scanning speed, track overlapping, substrate temperature on the fictive temperature were discussed. The results indicate that decreasing the scanning speed and increasing the substrate temperature can decrease the fictive temperature. Additionally, a higher track overlapping can reduce the height of the fictive temperature “tool mark”. Moreover, an optimization strategy based on laser beam scanning speed was proposed based on the uniform distribution of fictive temperature. The depth difference of the heat-affected zones was reduced from 164.26 μm to 31.74 μm. This work could be used to quantitatively predict the 3D fictive temperature distribution and proposed an optimization strategy based on scanning speed to suppress the non-uniformity of fictive temperature distribution, which can provide significant theoretical guidance for CO2 laser polishing technology of fused silica optics.

Vector magnetic field sensor based on coreless D-shaped fiber and magnetic fluid.

A vector magnetic field sensor based on a ferrofluid-encapsulated coreless D-shaped fiber is proposed and demonstrated. The core of the singlemode fiber (SMF) is completely removed by fiber polishing technology, and the remaining part transformed into a multimode interference (MMI) waveguide. The exposed side-polishing plane enable the evanescent field to interact with surrounding magnetic fluid (MF). Relying on the non-circularly symmetric geometry of the coreless D-shaped fiber and the MF refractive index modulation by the orientation and intensity of the applied magnetic field, vector magnetic field sensing is achieved. The magnetic field response characteristics of the coreless D-shaped fibers with different residual thicknesses (RTs) are investigated. The experimental results show that a reduced RT yields enhanced sensitivity, and the magnetic field intensity sensitivity reaches -0.231 nm/mT and -0.483 dB/mT at a RT of 42.7 µm. The developed coreless D-shaped fiber sensor exclusively utilizes SMF, thereby offering a cost-effective scheme for the fabrication of vector magnetic field sensors.

Photocatalytic assisted chemical mechanical polishing for silicon carbide using developed ceria coated diamond core-shell abrasives

The practical application of current photocatalytic-assisted chemical mechanical polishing (PCMP) technology still faces some challenges and difficulties, such as complex preparation process of abrasives, chemical failure, and the use of toxic chemicals. Herein, novel CeO2-coated diamond core/shell structure abrasives were successfully synthesized using a chemical precipitation method and applied in SiC-PCMP. After coating CeO2 on the surface of the diamond, the materials removal rate (MRR) was 56 % higher than that of the diamond abrasives. With ultraviolet (UV) irradiation, the MRR of CeO2/diamond abrasives (11.5 nm/min) increased by about 195 % compared with CeO2/diamond composite abrasives without UV. High surface quality (Ra: 0.4 nm) of the SiC substrate was obtained under UV light irradiation. The materials removal mechanism of SiC-PCMP was proposed.