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Perovskite materials have performed so excellently in semiconductor field due to their fascinating photoelectric properties. As solar cell absorber materials, they have attracted more and more interests. Quantitative characterization on the optical parameters and geometric features of the perovskite film is crucial to optimize its design of material and structure, and then to improve the photoelectric performance of perovskite solar cells (PSCs). The spectroscopic ellipsometry (SE) has been used to characterize the optical properties and thickness of nano-scale thin films in photovoltaic system, LED, organic panel, etc. It starts from the measurement of amplitude ratio spectrum (Psi-wavelength) and phase shift spectrum (Delta-wavelength) of polarized lights upon reflection or transmission on a sample. The literatures related to measurement and analysis of perovskite thin film for solar cells using SE were reviewed as: the analysis of related factors of perovskite properties; the selection of SE measurement parameters; the establishment of optical model for theoretical generated data; the selection of fitting method for experimental data; the extraction of optical constants and geometric parameters; and the characterization of photoelectric properties of the perovskites, etc. The review systematically and comprehensively summarized the usage of SE as a powerful tool for characterizing the optoelectronic properties of perovskite films and PSCs.

In this paper, a characterisation of diamond abrasive grains of grinding tools using industrial X-ray computed tomography (XCT) is carried out. One of the most challenge tasks in the characterisation is extracting the diamond abrasive grains from the XCT volume data. Methods that are able to extract the grains are then developed and introduced in this paper. The first step is to create a triangular mesh surface from the reconstructed volume file using a gradient anisotropic diffusion filter. The second step is to convert the measured greyscale volume into a signed distance field using a global threshold value and then a localised method for grain segmentation. To validate the proposed method, three different types of grinding tool specimens are measured and analysed. Each abrasive grain is segmented and the distributions of grains (with both random and designed patterns) are then calculated, plotted and analysed. The quantitative analysis clearly shows the deviations between the measured distribution and the designed pattern of the grinding tool, which indicates that the proposed method can provide an accurate and comprehensive characterisation of the grinding tools.

An investigation was conducted to explore the mechanisms of the scratching of monocrystalline silicon carbide with a single diamond grit. The scratching was repeated on a silicon carbide workpiece to generate different wear shapes of the diamond grit. The forces were recorded during each scratching and the wear of the diamond grit together with the silicon carbide morphologies was monitored at a fixed interval. Based on the different diamond wear shapes determined through scratching experiments, a smoothed particle hydrodynamics method was used to simulate the scratching process. In addition to the items monitored in the experiments, the simulation was also used to analyze the change of subsurface damages on silicon carbide and to predict the mechanisms of diamond damage. It is shown that double-edged abrasive grits might lead to a better silicon carbide surface quality in scratching. The simulation results indicate that the maximum equivalent stress distribution might be used to predict the damage of the diamond grits during scratching. The findings of this article will be of benefit to the optimal selection of machining parameters and the optimal design of diamond tools for abrasive machining of monocrystalline silicon carbide.

The newly developed sol–gel (SG) polishing pad based on the sodium alginate (AGS) binary compound system can be used for dry polishing hard and brittle materials to obtain high-quality surfaces. Based on the flexible SG polishing technology, a suitable biopolymer material is selected, and a binary compounding technology is used to prepare an AGS binary compound gel system, thereby optimizing the water-holding and mechanical properties of the gel. Through dry polishing experiments of a hard and brittle SiC material, the advantages of the SG polishing pad based on the sodium alginate-xanthan gum (AX) binary compound system under dry polishing conditions are obvious. The durability of the SG polishing pad is significantly improved compared with that of the AGS single system, which effectively solves the problem of pollution caused by the polishing waste liquid produced during the wet polishing process. At the same time, a high material removal rate will effectively shorten the processing time of hard and brittle materials, improve production efficiency. These results will lay the foundation for the industrialization of dry polishing with SG polishing pads.

An optical functional film with triangular pyramidal texture is proposed to reduce the reflection loss of crystalline silicon cells in order to solve the problem where directly fabricating the light-trapping texture on the surface of crystalline silicon can increase of surface photogenerated carrier recombination in crystalline silicon cells. The models of the reflection and refraction loss of light on the surface of an optical functional film with triangular pyramidal texture are developed. Afterwards, the triangular pyramidal textured film is bonded to the smooth surface of crystalline silicon cells and the angle between the base and side of the triangular pyramid is optimized. According to the large-area fabricating process of the optical functional film with triangular pyramidal texture, the proper structural parameters of the textured film are obtained. The optical functional film with triangular pyramidal texture was fabricated by means of ultra-precision cutting, electroforming, and embossing processes. Moreover, the effect of the fabricating precision on the optical performance of the triangular pyramid textured film is analyzed. The experimental and analytical results indicate that, by using the triangular pyramid textured film, the reflection loss of the smooth surface crystalline silicon cells decreases from 22.3% to 7.2% and the photovoltaic conversion efficiency increases from 18.30% to 20.47%. Compared with conventional textured crystalline silicon cells, the photovoltaic conversion efficiency of smooth surface crystalline silicon cells with the proposed optical functional film increases by 0.99%. An optical functional film with a triangular pyramidal texture can effectively improve the absorbance and photovoltaic conversion efficiency of smooth surface crystalline silicon cells.

Sapphire substrates with different crystal orientations are widely used in photoelectric applications. Double-sided planetary grinding is a new process for the rapid thinning and flattening of sapphire, and experiments with it were carried out on sapphire substrates with four commonly used crystal orientations (C-plane (0001), A-plane (11 2 ‾ 0), M-plane (10 1 ‾ 0), and R-plane ( 1 ‾ 012)). By comparing the material removal rates (MRRs), surface topographies, damages, and wear debris among substrates with the four crystal orientations, the removal mechanism for each orientation was revealed. The results showed that the MRR and surface quality of the substrates varied greatly with the four orientations. The R-plane was removed in the form of large pieces of spalled material and had the highest MRR and the largest surface roughness (Sa) of approximately 780 nm among the orientations studied. The C-plane was mainly removed in the form of unique large step-like pieces of spalled material, had the lowest MRR among the orientations observed, and exhibited an Sa of approximately 430 nm. The machinability of the A-plane and M-plane orientations were similar. Both were removed as small pieces of spalled material, and their surface quality was good, with Sa values of 340–390 nm. The experimental results revealed that crystal orientations with lower Young's modulus and fracture toughness values were easier to remove material from, and vice versa. Therefore, to obtain a reasonable material removal rate and a good surface quality of sapphire substrates, different processing techniques are needed for different crystal orientations.

This article aimed to study the nanomechanical properties of silicon carbide under nanoindentation and nanoscratching by the molecular dynamics (MD). First, the MD models were established and experimentally verified. Then, the MD results were used to analyze the subsurface morphology and crystal defects occurring during the processes, which are comparatively difficult to study through experiments. For comparison, the C face and the Si face of 4H-SiC and 6H-SiC were selected for research. The results indicate that 4H-SiC shows greater normal resistance than 6H-SiC for both faces, and the C face may be easier to machine than the Si face for both 4H- and 6H-SiC. In addition, the hexagon amorphous patterns were found in the horizontal cross-sections views after the indentation, which were deemed to make up of two mutually central symmetric triangles. The results show that these amorphous patterns may be caused by the slip systems of 4H-SiC and 6H-SiC, which are mainly take place on the (0001) basal plane and along the directions, depending on their special lattice structures. Through MD simulations, the formation mechanism of sub-surface damage of SiC substrates is much clearer.

SnO2 is widely used as the electron transport layer (ETL) in perovskite solar cells (PSCs) due to its excellent electron mobility, low processing temperature, and low cost. And the most common way of preparing the SnO2 ETL is spin-coating using the corresponding colloid solution. However, the spin-coated SnO2 layer is sometimes not so compact and contains pinholes, weakening the hole blocking capability. Here, a SnO2 thin film prepared through magnetron-sputtering was inserted between ITO and the spin-coated SnO2 acted as an interlayer. This strategy can combine the advantages of efficient electron extraction and hole blocking due to the high compactness of the sputtered film and the excellent electronic property of the spin-coated SnO2. Therefore, the recombination of photo-generated carriers at the interface is significantly reduced. As a result, the semitransparent perovskite solar cells (with a bandgap of 1.73 eV) based on this double-layered SnO2 demonstrate a maximum efficiency of 17.7% (stabilized at 17.04%) with negligible hysteresis. Moreover, the shelf stability of the device is also significantly improved, maintaining 95% of the initial efficiency after 800-hours of aging.

The freeform surfaces including both the aspherical and prismatic concave/convex have been widely utilized in optical, electronical, and biomedical areas. Most recently, it is reported that grinding with structured wheels provides new possibility to generate patterns on hard and brittle materials. This paper reports the latest research progress on micro-grooving glass ceramic using laser structured bronze bond diamond grinding wheels. A nanosecond pulse laser is firstly integrated into an ultra-precision machine tool and used for the in-line conditioning of super abrasive grinding wheels, i.e. truing, dressing, and profiling/texturing. Meanwhile, an offset compensation method, considering the shifting depth of focus (DoF) at different laser irradiation position, is proposed to accurately generate various profiles on the periphery of the grinding wheels. Three types of patterns (riblets, grooves, and pillars) are successfully fabricated on the ceramic substrate using the laser textured grinding wheels. The results indicate that the integrated laser system offers high flexibility and accuracy in shaping super abrasive grinding wheels, and the grinding using textured grinding wheels provide a promising solution to generate functional structures on hard and brittle materials.

The microstructures on a diamond surface have attracted extensive attention in microelectronics, ultra-precision machining tools, and optical elements, etc. In this work, microgrooves were fabricated on a single-crystal diamond surface using ultraviolet nanosecond or infrared picosecond laser pulses. The surface and internal morphologies of the microgrooves were characterized. The chemical composition and phase transition of the diamond after laser irradiation were analyzed. Furthermore, the ablation threshold, ablation rate, and material removal rate of the diamond processed by nanosecond or picosecond lasers were also calculated. In addition, the temperature distributions of the diamond ablated by nanosecond or picosecond lasers were simulated. Finally, the material removal mechanisms of a single-crystal diamond processed by nanosecond or picosecond lasers were revealed. This work is expected helpful to provide a guidance for the laser fabrication of microstructures on diamond.

A new parameter, the uniformity coefficient (UC), was proposed to overcome the difficulty in quantitatively characterizing the uniformity of the pyramidal textured surface of silicon wafers widely used for monocrystalline silicon cells (MSCs). The UC was defined based on the areal material ratio Smr(c) from the standard ISO 25178-2. First, the values of Smr(c) for MSC wafer surfaces with a uniform texture and an arbitrary texture were calculated. For the ideal uniform texture, Smr(c) was calculated using one pyramid assuming equal pyramids distributed over the wafer surface. For any arbitrary texture, based on the pyramidal geometrical structure, Smr(c) was calculated from the heights of pyramids extracted from their 2D projections. Second, the areas bounded by the Smr(c) curves with two coordinate axes were calculated accordingly. Then, the ratio of the two areas was defined as the UC. Fifteen kinds of monocrystalline silicon wafers were prepared by chemical texturing for 5 min, 15 min, 25 min, 35 min and 45 min with three groups of solutions, and the corresponding MSCs were fabricated. The UCs of the fifteen silicon wafers and the photovoltaic conversion efficiencies (PCEs) of the MSCs were tested. The relationships between the UC, texturing process (solution and time) and PCE were analyzed. The PCE increased monotonically with an increase in the UCs The silicon wafer obtained by texturing with 2% TMAH solution for 25 min had a textured surface with a maximum UC of 0.89, and the MSC exhibited a maximum PCE of 20.3%. The experimental results indicated that the UC is an effective parameter for the quantitative characterization of the pyramidal texture of silicon wafer surfaces and has a definite relationship with the PCE of the MSC. The UC is a useful and convenient measure for texturing process optimization.

A novel diamond@carbon core/shell structure, constituting diamond as a hard core and carbon as a soft shell, was synthesized from resole resin and nanodiamond as the starting materials via in-situ polymerization and subsequently high-temperature carbonization. The diamond@carbon nanocomposite was characterized using field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectra, and Fourier transform infrared spectroscopy (FT-IR). The results indicated that the shell material are comprised of amorphous carbon. The thickness of carbon shell was controlled from 502.5 nm to 27 nm by adjusting the concentration of the nanodiamond. As confirmed by TEM, FT-IR and XPS, the diamond@carbon nanocomposite revealed a stable structure, due to the formation of the chemical bonding between diamond and carbon shell after calcination process. Overall, the diamond@carbon nanocomposite abrasives could lead to a reducted surface roughness and damage of SiC wafer comparing with the nanodiamond abrasives, due to the spring-like effect coming from the elastic component of the amorphous carbon shell. Moreover, the as-prepared nanoparticles exhibited better dispersion stability than the pure diamond in the pH range from 8 to 11.

The grain geometrical features of grinding wheels are critically important to evaluate their quality and grinding performance. Therefore, grain geometrical features should be comprehensively and systematically characterized. Such characterization parameters were defined from the geometric features of individual grains (for each grain) to the distribution features of grains (for a group of grains on a given wheel surface) on the basis of grain cross-sections. For each grain, characterization parameters included cross-section area, equivalent diameter, volume, and sharpness ratio of the grain. For a group of grains, the characterization parameters were distribution density, cross-section area, cross-section area-supporting rate, and volume proportion of the grains on a sectioning depth. The cross-sections of grains were extracted from the section-scanning images captured by an optical measurement system. A system based on optical vertical scanning using a narrow depth of field microscope was adopted to obtain the optical sectioning images, and the grain cross-section boundaries on each image were extracted through an image-processing program. The defined characterization parameters, vertical sectioning step, and sectioning numbers were calculated efficiently. A monolayer brazed grinding wheel with a grain size of 425–500 μm was selected for an experiment. The individual and group parameters, such as sharpness or strength, active volume, or area-supporting ratio, of grains were used for performance analysis. Experimental results indicated that the proposed parameters based on grain cross-sections are not only efficient to calculate but also effective to characterize the geometric features of grains for monolayer brazed grinding wheels.

In recent years, the application prospect of single crystal diamond (SCD) in the field of electronics is remarkable, and material processing technologies are the basis for the application of semiconductor materials. In this paper, a novel polishing method for SCD substrates was developed utilizing a sol-gel (SG) polishing pad, which is a semi-fixed abrasive polishing tool fabricated by SG technique. The surface morphology of SCD substrates was observed with a 3-D optical profiler and scanning electron microscopy (SEM). The results showed that the surface roughness was 1.32 nm Ra and the material removal rate of SCD (111) was about 120 nm/h. The polished diamond surfaces and wear debris were investigated using Raman spectroscopy and transmission electron microscopy (TEM), respectively. The results showed the removal mechanism of SCD using an SG polishing pad was mainly dominated by the mechanical removal and phase transformation, including the mechanical cleavage, amorphization, and graphitization.

Titanium alloys are widely employed in aerospace and biomedical applications. During the cutting process of Ti 6Al 4V alloy, the material characteristics of high specific strength and poor thermal conductivity lead to a stress concentration occurred at the tool/chip interface, which may cause severe failure of the coated tools. Besides, the titanium alloy gives rise to serrated chips, whose thickness varies regularly in the cycle mode, which lead to the variation of cutting force and tool stress. So a cyclic impact with high frequency is applied on the coated tool surface, and this induces the fatigue fracture of coating. In this study, repetitive contact between the coating and Vickers diamond indenter through the high frequency cyclic impact tester was developed by employing the ultrasonic actuator device. High frequency cyclic impact testing has been used to study the impact resistance of the TiSiN/TiAlN bilayer coating and TiSiN/TiAlN nanolayered coating. Besides, stress concentration resulting in the failure of coatings can be generated by using the sharp Vickers indenter. The crack propagation in coatings was investigated by the scanning electron microscope (SEM), and the fracture processes of coatings were studied from the force measurement data acquisition system. In addition, the cutting performance of cemented carbide tools coated with these two coatings was evaluated in turning Ti 6Al 4V titanium alloy. The correlation between the fatigue impact resistance of coatings at high frequency and the wear behavior of coated tools under different cutting conditions was studied. It can be concluded that the TiSiN/TiAlN nanolayered coating showed better properties to resist fatigue impact at the lower impact load, but worse properties to resist fatigue impact at the higher impact load.

A series of single-grain scratching experiments are conducted to understand the grinding mechanism of 2D carbon fibre reinforced carbon silicon carbide composite (2D Cf/C–SiC). On the basis of the woven and laminated structure of the fibre bundles, three typical surfaces (SA, SB, SC) are selected and scratched under various combinations of scratching speed and depth. Three cut-in modes which are defined according to the direction of grain motion in relation to the axis of the fibres, namely longitudinal (∥), transverse (⊥) and normal (⊙). The scratching forces (SFs) of all tested surfaces fluctuate periodically. The peak SFs under the different cut-in modes follow the order of ⊙ > ⊥ > ∥. The averaged SFs on the three surfaces are generally ranked as SB > SA > SC. Under all tested scratching conditions, the composite is removed by the brittle mode, but the chipping affected width depends on the cut-in mode. Fibre bundles scratched under ⊥ and ∥ tend to be removed as a block by either peel-off or push-off, especially on the lamination plane. All these findings explain the grinding results obtained in previous related researchs. Besides the fibre orientation and woven structure, the lamination factor must also be considered. For a given cut-in mode, the SF on the lamination plane is the lowest, which agrees with the previous result that the grinding force on the lamination plane is lower than that on any other surface. The results presented herein help in improving the collective understanding of the grinding mechanism of C/SiC composites.

Sol–gel (SG) pads are used to polish different types of marble tiles and obtain high-gloss, low roughness, and scratch-free surfaces. The main features of such tools are semiconsolidated abrasives and flexible substrates. Through experiments with three types of polishing methods and two different types of tools used to polish marble tiles, the polishing mechanism of SG pads was confirmed. An abrasive yield phenomenon was observed for the semiconsolidated abrasive polishing tool with a flexible matrix, which resulted in a mirrored marble surface with high gloss, and the polishing steps were simplified. For SG polishing pads, a larger abrasive can be used to obtain high-gloss marble surfaces compared to the fine abrasives used in traditional resin polishing tools. Therefore, the agglomeration problem associated with fine particle size abrasives is avoided. In addition, after SG pad polishing, the surface of the marble tiles exhibited hydrophobic properties, and the oleophobic properties were simultaneously improved.

Material characteristics of pure copper, pure cobalt and Cu–Co metal-powder composite were comparative studied through biomachining by Acidithiobacillus ferrooxidans (A. ferrooxidans) in three groups of culture solutions. Material removal mechanisms of Cu–Co metal-powder composite involved in biomachining were explored. It was first observed that the pure cobalt and Cu–Co metal-powder composite were machined by the A. ferrooxidans. The material removal of three workpieces presented linear increase along the machining process due to the metabolic activity of the A. ferrooxidans. Different with the pure metal, the material removal mechanism of Cu–Co metal-powder is explained by the dual effect of micro-galvanic corrosion and participation of Cu2+ and Fe3+ for oxidization of cobalt.

Due to its superior mechanical, optical and chemical properties, sapphire (α-Al2O3) is widely used in engineering, optics, medicine, and other scientific research fields. The atomic structure of sapphire gives rise to anisotropy in its mechanical properties, which affects the machinability of sapphire materials on different crystal planes. Different cutting directions will affect the wafer economy and surface quality achieved during wire sawing due to this anisotropy. In this study, the machinability of A-plane sapphire was investigated for diamond wire sawing in three different directions, following the C-plane, R-plane and M-plane. The results show that the direction following the M-plane could be the best direction for diamond wire sawing because this direction results in the minimal sawing forces, the lowest specific energy and the smallest volume of material that will need to be removed during subsequent processing. These characteristics correspond to the direction with the highest fracture strength since the material is removed by brittle machining. The force ratio for sawing in the direction of the R-plane is the smallest because this direction is associated with the minimum hardness and the lowest critical load for the transition from plastic to brittle removal of the workpiece material. The 3D height parameters show no obvious pattern among the three sawing directions. The mechanism of material removal is mainly brittle removal, with some plastic removal, and is obviously affected by the crystal orientation.