Diamond Wire Sawing Research Articles

Mediation analysis of fuel cost on maintenance cost and production- bench drilling phase of diamond wire sawing technique of Stone Extraction

Mediation analysis of fuel cost on maintenance cost and production- bench drilling phase of diamond wire sawing technique of Stone Extraction

An additive-free non-metallic energy efficient industrial texturization process for diamond wire sawn multicrystalline silicon wafers

Texturing of diamond wire sawn (DWS) monocrystalline silicon (c-Si) wafers by alkaline process is well established. However, texturing of multicrystalline silicon wafers (mc-Si) is discerned to be a concern. All the DWS mc-Si texturing schemes reported so far either use additives or require additional processing steps which entail additional monetary investment. An additive-free, cost-effective, non-metallic, energy efficient acid based texturing scheme is demonstrated here for the DWS mc-Si wafers. The proposed novel texturing technique recommends hydrofluoric (HF) acid rich acidic solution for obtaining uniform porous silicon (Por-Si) layer, followed by a dilute alkaline dip to obtain a porous inverted rounded structures on the DWS mc-Si wafer surface. The percentage of HF volume in acid texturing solution was varied from 40% to 60% in achieving the best minority carrier lifetime of ∼90 μs in our optimized recipe, therefore suitable for industrial texturing process. The weighted average reflectance (WAR) of our textured mc-Si wafers are ∼29.0% and ∼6.5% after texturing and after final anti-reflective coating, respectively. The cells fabricated using the new acid texturing scheme exhibited an excellent batch average efficiency of 18.46% in industry environment. In the present study, DWS textured wafers are characterized for optoelectronic properties like total reflectance and Photoluminescence (PL) imaging on full wafer area and benchmarked in detail against standard acid textured multi-wire slurry sawn (MWSS) mc-Si wafers, and promising results are reported. A detailed methodology to understand the chemical process of texturing mc-Si wafers using HF-rich acid chemistry is discussed. The reported HF-rich acid texturing process can be easily implemented in any industrial acid texturing tool without any additional investment.

Study on Wear Mechanism of Diamond Particles in the Cutting of Pipeline Steel

The wear of diamond particles is an important factor that limits the working efficiency of diamond wire saws. In this paper, the physical model of diamond particle is established and the mechanical analysis is carried out. ANSYS finite element analysis software was applied to establishing unworn model and worn model for diamond particles. The cone angle of diamond particle, the protrusion height of diamond particle and the depth of the diamond particles press into the cutting face were analysed to study theirs effect on the shear stress extreme value of diamond particles in the process of cutting underwater pipeline. The results shown that the depth of the diamond particles press into the cutting surface and the cone angle of diamond particle have a great influence on the wear of the diamond particles, and the protrusion height of diamond particle is relatively small for the wear of the diamond particles.

An 18.9% efficient black silicon solar cell achieved through control of pretreatment of Ag/Cu MACE

With diamond wire sawn (DWS) technique becoming mainstream of multicrystalline silicon (mc-Si) solar cells, the corresponding texturing technology for light harvesting is more prominent. In order to further reduce production costs of mature Ag-based metal assisted chemical etching (MACE), an Ag/Cu MACE method was proposed. In this paper, the influence of different pretreatment method which has few studies reported before was investigated. The experimental results indicated that appropriate pretreatment could contribute to achieve uniform nanostructure, low reflectivity and recombination velocities of the silicon wafers. The light trapping mechanism of different texturing method was analyzed. The impact of nanostructure on surface passivation was also studied. Industrial large area solar cells have been fabricated by applying different texturing method. The results showed that the pretreatment using hot alkaline solution with texturing additive was more beneficial to achieve high conversion efficiency. Finally, an efficiency of 18.91% was obtained on DWS mc-Si wafer, which is 0.4% absolutely higher than the cells with traditional acid texturing.

Cost Estimation for Bench Drilling Phase of Diamond Wire Sawing Technique for Granite Mining

Cost Estimation for Bench Drilling Phase of Diamond Wire Sawing Technique for Granite Mining

High-Efficient Solar Cells Textured by Cu/Ag-Cocatalyzed Chemical Etching on Diamond Wire Sawing Multicrystalline Silicon.

We reported a novel texture method through one-step Cu/Ag-cocatalyzed chemical etching which can be widely used in the photovoltaic industry because of its simple and low-cost process. The etching mechanism of an inverted rectangular pyramid is the cooperation of Ag-catalyzed vertical etching and Cu-catalyzed lateral etching. In our texture method, neither saw damage removal nor post-treatment is needed. During the etching process, the digging holes by Ag-catalyzed etching and enlarging holes by Cu-catalyzed etching completed at the same step. Benefiting from the excellent light-trapping and passivation effect of the inverted rectangular pyramid, diamond wire sawing multicrystalline silicon (mc-Si) Al-BSF solar cells with a super high efficiency of 19.49% had been obtained.

Research on the machinability of A-plane sapphire under diamond wire sawing in different sawing directions

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.

Nucleation location and propagation direction of radial and median cracks for brittle material in scratching

At present, diamond wire sawing technology is a mainstream method for wafering brittle materials such as silicon crystal, SiC crystal, sapphire, ceramics, optical glass and so on. Microcracks will occur on the wafers surface inevitably during sawing owing to the high brittleness and hardness of brittle material. The existence of microcracks and their size, orientation and distribution not only affect the surface quality and fracture strength of wafers, but also have an important impact on the subsequent processing effect of wafers after sawing. Therefore, the further investigation on the formation and propagation direction of microcracks is needed during diamond wire sawing. In this paper, an analytical model of the elastic stress field for brittle material is established during single abrasive scratching. The stress fields in front of and behind the indenter are analyzed respectively. Two different material removal modes, ductile removal and brittle removal, are considered. To evaluate the two different material removal modes, influence factor μ is proposed. The nucleation location and propagation direction of radial crack and median crack of several materials are predicted by analytical model. The result show that the radial crack nucleates behind the indenter. The deflection angle between propagation direction and scratching direction is about 35–60°, and its size depend on the material removal modes. The nucleation location of median crack is no longer at the bottom of the plastic zone, but will deflect toward the scratching direction during scratching. The size of deflection angle depends on the tip half angle of indenter. When the tip half angle is 55–80°, the deflection angle decreases with the increase of the indenter half angle. All predicted results are in good agreement with the experimental data of relevant scholars. At the end, the half-penny crack (radial/median crack system) presented in indentation process is extended to scratching process.

Safe technologies for cutting reinforced concrete structures by means of diamond tools

The advantages and the need to improve the safety of work when using modern diamond technologies for cutting concrete and reinforced concrete structures which are common during the dismantling and reconstruction of civil objects are shown. Improved organizational, structural and technological schemes of cutting these structures with diamond disc and wire saws with remote control are reasonably proposed. Preliminary fastening of cut elements on independent spatial scaffolding with screw jacks is a distinctive feature of the proposed schemes. In case of reconstruction by means of a device or an increase of the size of openings in load-bearing reinforced concrete and stone walls, a preliminary installation and commissioning of reinforcement steel frames provided for by the project are proposed, on them – guides of diamond disc, chain or wire saws and only then – cutting of reinforced concrete with its forced canting outside the working area for recycling.

Analysis on Vibration Characteristics of the Stringed Bead Wire of an Underwater Diamond Wire Saw

Vibration is one of the most important factors when the diamond stringed bead wire cuts pipeline, which not only affects the quality and efficiency of cutting operations but also affects the life of the stringed bead wire. The finite element model of the stringed bead wire is established by ANSYS Workbench in the paper. The all kinds of vibration of the stringed bead wire is analyzed by the dynamic simulation of diamond bead vibration, and The natural frequency and vibration amplitude of each order are obtained. The results show that the third - order model of stringed bead wire has large amplitude. The influence of the central distance of the drive wheel and the guide wheel and the diameter of the stringed bead wire on the vibration of the bead rope is studied, which obtain the third-order vibration amplitude of the stringed bead wire with the change of the two parameters and determine the best value of the amplitude of the bead rope in the saw cutting. The experimental results show that the effective cutting time of the stringed bead wire is the longer when the vibration amplitude is the optimum value,which means that service life of stringed bead wire is the longer.

Improved technology for the safe constructing of large-size openings in stone walls with diamond wire saws

Improved technology for the safe constructing of large-size openings in stone walls with diamond wire saws

Application of Diamond Wire Saw Cutting in Demolition of Large Reinforced Concrete Members

With the rapid development of construction engineering and densely populated of urban buildings, it is impossible to adopt traditional methods for demolition construction due to the constraints of the surrounding environment. This paper combines the demolition engineering practice of the foundation pit support system of Jinyuan International Plaza, expounds the superiority of the application of diamond wire saw cutting in the demolition of large reinforced concrete members, and puts forward the effective construction operation points, which can provide beneficial for similar projects reference.

An Experimental Verification on the Development of an Innovative Diamond Wire Saw Cutting Technology

An Experimental Verification on the Development of an Innovative Diamond Wire Saw Cutting Technology

The effect of cut depth and distribution for abrasives on wafer surface morphology in diamond wire sawing of PV polycrystalline silicon

Due to the existence of an acid etch resistant thin amorphous silicon layer over the smooth grooves of the diamond wire sawing polycrystalline silicon wafer surface, the anti-reflection effect is usually not ideal using the mature acidic texturization. The amorphous silicon layer will be produced on the machined surface by material ductile removal. Therefore, during the process of cutting photovoltaic polycrystalline silicon wafers, the material removed in the brittle way is expected and the surface topography of the wafers formed with the brittle fracture is better for the texture fabricating. In this paper, a mathematical model considering the influences of process parameters and wire saw parameters was developed based on indentation fracture mechanics. The variations of cutting groove profile formed by different material removal modes were also included. The effect of abrasives distributed on the wire saw on material removal and surface formation of polysilicon was analyzed. The results showed that most of abrasives removed material with ductile removal mode, however, the volume of the material removed by abrasive in ductile mode is less than 10% of the total removal volume. Brittle fracture removal mode was still the major way of material removal in diamond wire sawing. With the same ratio of the feed rate and wire speed, the faster feed rate and wire speed will not only improve the cutting efficiency, but also is easier to obtain a brittle fracture surface. There is a critical angle θc for the distribution of abrasives on the wire saw surface. Only when the position angle of the abrasive removing material in brittle mode is less than θc, the brittle fracture can be formed on the wafers surface.

Recycling and reuse of kerf-loss silicon from diamond wire sawing for photovoltaic industry

With the rapid growth of the global photovoltaic (PV) industry, the waste from PV industry cannot be ignored, especially the solid wastes from silicon kerf loss and the used quartz crucibles from silicon casting. The silicon kerf loss during wafer sawing was nearly 160,000 tonnes and the used crucible waste was nearly 70,000 tonnes in 2017. With the transition of wafering technology from the slurry-based wire to diamond wire sawing, recycling and reuse of kerf-loss silicon have become more feasible due to the lower impurity contents. In this paper, we aimed to find a simple approach to recycle the kerf loss and identify the purity for reuse. We first analyzed the contents of the as-received kerf-loss silicon from the industry. Then, suitable acids and refining procedure were proposed. The metals, especially nickel, could be easily reduced to several ppmw, boron and phosphorous to sub-ppmw, and carbon to several hundred ppmw, while oxygen was less than 5 wt%. Although the purity of the recycled silicon was not sufficient for casting feedstock, it had a comparable purity of about 5 N with the commercial silicon nitride releasing agent and crucibles used in silicon casting for solar cells. Because the nitride crucibles could be reused a few times for casting, the used crucible waste could be significantly reduced as well.

Research of the Cutting Possibility of Magnesium Alloys with Abrasive Diamond Wire Saw

Abstract Wire saw technology is a method that works great in industrial applications – it is a dominant method in the production of silicon wafers. But almost all kinds of brittle materials (ceramics, rocks, meteorite and minerals or wood) can be cut using wire saw. Question, this article will try to answer is whether this is also applicable to magnesion alloys? Article presents selected problems from an area of abrasive treatment of magnesium alloys. This includes effects of research, concerning possibilities of application of abrasive diamond wire in the process of cutting magnesium alloys AM60 and AZ91 as well as results concerning surface quality obtained after cutting with the abrasive diamond wire German Company HK Präzisionstechnik.

Thermal pretreatment of diamond wire sawn multi-crystalline silicon wafers for wet acid texturization of solar cells

Diamond wire sawn (DWS) multi-crystalline (mc) silicon wafers for solar cells are known to be difficult to texturize with the conventional wet acidic etching technology. Thermal annealing as pretreatment for wet acid texturization of the DWS mc-Si wafers has been studied. Improvement in morphology and reduction of the light reflectivity of the texture has been obtained with the pretreatment. Solar cells fabricated with the pre-treated DWS mc-Si wafers have been found to yield an ∼0.15% absolute efficiency gain in average, as compared with the solar cells fabricated in the same line with the same batch of wafers without the pretreatment. The thermal pretreatment was found to crystallize the amorphous surface layers on DWS mc-Si wafers. This is believed to be the reason for the above improvement. The present thermal pretreatment provides a promising low cost technology for texturization of DWS mc-Si wafers in photovoltaic industry.

MACE nano-texture process applicable for both single- and multi-crystalline diamond-wire sawn Si solar cells

The photovoltaic (PV) industry requires efficient cutting of large single and multi-crystalline (sc- and mc-) silicon (Si) wafers. Historically multi-wire slurry sawing (MWSS) dominated, but the higher productivity of diamond-wire-sawing (DWS) holds promise for decreasing PV costs in the future. While surface texturing of DWS wafers is more complicated than of MWSS wafers, especially in mc-Si wafers, nanotexturing has been shown to overcome this challenge. While the benefit of nanotexturing is thus clearer in mc-Si, a universal nano-texture process that also works on sc-Si would simplify and reduce the investments costs of PV production-lines. In this paper, such a nano-texture process is developed using a metal-assisted chemical etch (MACE) technique. Step-by-step characterization of surface structure and reflectance of the MACE process is used after: 1) wafering, 2) standard acidic texturing etch, 3) silver nanoparticles deposition, and 4) MACE nanotexturing for both sc and mc-Si. The results show that the same MACE process works effectively for both sc-Si and mc-Si wafers. Finally, the nano-textured wafers are processed into PV cells in an industrial process line with conversion efficiencies of 19.4% and 18.7%, for sc-Si and mc-Si solar cells, respectively.

The impact of damage etching on fracture strength of diamond wire sawn monocrystalline silicon wafers for photovoltaics use

To reduce silicon kerf loss, we have cut silicon bricks into wafers using a thin diamond wire (the diameter of core wire: 80 µm, the average size of abrasives: 10 µm). Damages caused by diamond wire sawing are responsible to have an asymmetry in fracture strength, a lower strength in parallel bending and a higher strength in perpendicular bending to the saw marks. To elucidate the asymmetry to the depth of subsurface damage, front and backside surfaces of wafers are etched in 3, 5, and 10 µm depth by 24% KOH aqueous solution. By etching 3 and 5 µm, the strength are enhanced by a factor of 1.96 and 2.9 times in parallel bending and by 1.03 and 1.31 times in perpendicular bending compared to bare wafers. Etching more than 5 µm removes the asymmetry, showing the equal strength in the bending in both directions. We cystallographically consider several fracture mechanisms of bare and etched wafers through the observation of each fracture surface.

Field stitching approach for the wave optical modeling of black silicon structures.

The interest in black silicon structures as an anti-reflective interface at the front side of silicon solar cells increased strongly with the rise of diamond wire sawing. The application of optical modeling in order to predict optimal structure parameters could be highly valuable. However, due to the random nature of the structure as well as dimensions in the range of the wavelengths of interest, optical modeling is still a challenge. Within this work, the stitching method of rigorously calculated fields is extended and applied to a black silicon structure. A Fourier transform is used to determine the angular intensity distribution in the far field. In combination with the OPTOS formalism, this allows modeling of silicon substrates with black silicon front side and shows a reasonably good agreement with optical measurement results. Implementing the investigated structure into a solar cell configuration reveals not only a low reflectance but also a very good light trapping performance close to that of a Lambertian scatterer.