Wet Grinding Research Articles

Investigation on the effect of grinding wheel for grinding of AISI D3 tool steel under different conditions

The surface finish of ground samples is highly influenced by the grinding parameters, grinding conditions and the type of grinding wheel. This paper emphasizes on the effect of various grinding factors such as the grinding conditions, the type of grinding wheel and operating process parameters like depth of cut and table speed on the surface roughness of the ground samples. Two types of grinding wheels alumina (Al2O3) and cubic boron nitride (CBN) were used for grinding AISI D3 tool steel under dry and wet conditions. The material removal rate and surface roughness were evaluated for all the ground samples. The results showed that wet grinding outperformed dry grinding and provided a better surface finish while using both grinding wheels. Machine Learning was implemented to optimize the grinding parameters. Multi-objective optimization using genetic algorithm was done and a Pareto frontier chart was made to help determine what values for the input parameters would achieve the required outputs such as material removal rate and surface roughness. Two different approaches Genetic Algorithm and Principle Component Analysis were then compared for multi-objective optimization. The type of grinding wheel used had a dominant effect on the surface roughness of ground samples while the depth of cut had a lesser effect.

Surface reinforcement of recycled aggregates by multi-diameter recycled powder blended cement paste

Surface coating is a simple and effective method to reinforce recycled aggregate (RA), and its efficacy is closely related to the basic property of surface-coated material (SM), such as mechanical strength, water absorption, compactness and permeability. In present work, recycled powder was treated by wet grinding to obtain micron-recycled powder (MRP) and submicron-recycled powder (SRP) for preparing the high-preforming SM. MRP was utilized to partly substitute cement to improve the compressive strength, water absorption, permeability and compactness; on this basis, MRP was slightly replaced with SRP to further enhance these properties. The relationship between coat-paste weight or thickness and SM fluidity was obtained. Microstructure, hardness and elastic modulus around interfacial transition zone were studied by SEM-EDS and nanoindentation, and the crushing value, water absorption of surface-reinforced recycled aggregates (SRA) were also tested, as well as the compressive strength and workability of recycled concrete. Results indicated that the comprehensive property of SM was enhanced significantly by the substitute of cement with MRP and SRP. Surface coating evidently decreased the crushing value from 14.6% to 10.2%, however, the water absorption was hardly changed. Besides, recycled concrete prepared with SRA performed much better than that of RA, regardless of workability or compressive strength. This work would provide guidance for the design of coating material and the prediction of coated paste thickness.

Strategies to improve joint strength of friction lap welded AA7475/PPS hybrid joint with surface pre-treatment on AA7475

Friction lap welding (FLW) technology has recently emerged as a promising joining technology to join aluminium alloys and polymers. The strength of the metal-polymer hybrid joint can be enhanced by surface pre-treating of the metal. In this study, FLW experiments were performed on the surface pre-treated aluminium alloy 7475-T761 (AA7475-T761) with Polyphenylene sulfide (PPS) polymer. Three different kinds of laser texturing patterns were made, includes grooves, circles, and square grid patterns. In addition, the alloy surface is also roughened with the wet grinding process. Surface roughness, surface topography characteristics, and contact angle (CA) were measured for treated surfaces. Furthermore, the tensile lap shear strength (TLS) of surface pre-treated FLWed joints was compared to that of untreated weldments. Results showed that the wet grinding process had minimal effect on joint strength. TLS was enhanced by 120% on a laser-textured square grid-patterned substrate in comparison with the untreated specimen weldment. The X-ray photoelectron spectroscopy (XPS) examination confirmed that the AlOC chemical bond represents the secondary bonding mechanism along the micro-mechanical interlocking.

Reduction of submicron particle agglomeration via melt foaming in solid crystalline suspension

Particle size reduction of poorly water-soluble drug crystals down to the submicron region (0.1–1 µm) is a focus strategy to increase bioavailability. In this context, solid crystalline suspensions (SCS) manufactured in an adapted wet milling process have been introduced as a promising formulation technique. However, for such particle size, agglomeration due to the prevailing attractive interactions poses a major limitation to product quality. As a countermeasure, steric and electrostatic stabilizers have been extensively used in conventional wet grinding applications to introduce kinetic stability to primary particles. In this study the formulation of SCS, containing Xylitol and Griseofulvin, is optimized using the surfactant sodium dodecyl sulfate (SDS). The stabilizer did not impact suspension stability during grinding, as a constant apparent grinding limit (d50=0.35-0.40 µm) was observed over a wide range of concentrations. Nevertheless, redispersion of primary particles from the solidified SCS in water was enhanced at concentrations of 1 wt.% and above. This behavior of the optimized formulation positively impacted the dissolution kinetics of the Griseofulvin particles compared to the binary system. Different imaging techniques revealed the morphology of the solidified Xylitol matrix and the particle location inside it. At 1 wt.% SDS a porous matrix was obtained, which is caused by a foaming process during grinding. Further investigations indicated the importance of this foam regarding the improved particle redispersion, rather than an electrostatic stabilization. A mechanism, which is inspired by particle stabilized foams and emulsions, is proposed.

Optical photothermal infrared spectroscopy with simultaneously acquired Raman spectroscopy for two-dimensional microplastic identification

In recent years, vibrational spectroscopic techniques based on Fourier transform infrared (FTIR) or Raman microspectroscopy have been suggested to fulfill the unmet need for microplastic particle detection and identification. Inter-system comparison of spectra from reference polymers enables assessing the reproducibility between instruments and advantages of emerging quantum cascade laser-based optical photothermal infrared (O-PTIR) spectroscopy. In our work, IR and Raman spectra of nine plastics, namely polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, silicone, polylactide acid and polymethylmethacrylate were simultaneously acquired using an O-PTIR microscope in non-contact, reflection mode. Comprehensive band assignments were presented. We determined the agreement of O-PTIR with standalone attenuated total reflection FTIR and Raman spectrometers based on the hit quality index (HQI) and introduced a two-dimensional identification (2D-HQI) approach using both Raman- and IR-HQIs. Finally, microplastic particles were prepared as test samples from known materials by wet grinding, O-PTIR data were collected and subjected to the 2D-HQI identification approach. We concluded that this framework offers improved material identification of microplastic particles in environmental, nutritious and biological matrices.

Influence of wet grinded slag on the hydration of phosphogypsum-slag based cement and its application in backfill tailings

Phosphogypsum-slag based cement (PSBC) has a great potential in tailings backfill because of low cost and CO2 emission in comparison with Portland cement. However, slow early hydration was often observed, and this problem was generally solved by adding cement clinker, which could provide alkalinity to hasten the hydration of ground granulated blast furnace slag (GGBS). In this study, GGBS by wet grinding (i.e., WGGBS) was used to partially replace raw GGBS in PSBC, with intent to promote the early hydration and cementitious performance in backfill tailings. Results showed that 60 % replacement ratio of GGBS by WGGBS enhanced the 3 d compressive strength by 507 %, and that for a 28 d was 45 MPa, which meet the strength requirement of 42.5 grade cement; besides, its carbon emission was only 5 % of that of cement. Due to the high reactivity of WGGBS at the early age, pH of PSBC system was promoted, and this hastened dissolution of GGBS and formation of hydrates. This was the reason for the significant increase in early compressive strength. Moreover, with the continuous hydration of PSBC, the hydrates were produced, and the microstructure was densified over time, leading to the increase in later compressive strength. It seemed that the PSBC with WGGBS showed an excellent cementitious performance in iron tailings filling. Under the condition of 1:10 wt ratio of cementitious material to iron tailings, 28 d compressive strength of PSBC with WGGBS was up to 3.1 MPa, while that for cement was only 0.8 MPa.

Improvement of suspension-assisted total reflection X-ray fluorescence analysis of ores using wet grinding and empirical calibrations

In this study, the suspension-assisted total-reflection X-ray fluorescence analysis of ores was improved using the wet grinding procedure to produce ultra-fine suspended powder mixed with internal standard solution in aqueous media. The advantages of the proposed technique were demonstrated by the example of the determination of S, Fe, Ni, and Cu in sulfide copper‑nickel ores containing various ratios of sulfide and silicate minerals. We showed that the powerful mixing of 100 mg of ore powder and 4 mL of ultra-pure water as a dispersing medium with 20 g of grinding balls of 1 mm in diameter leads to the preparation of homogeneous suspension with monomodal particle size distribution having 90% of the particle size <6 μm. The suspension after wet grinding was diluted up to 50 mL with ultra-pure water to obtain a final concentration of the suspended powder of 2 mg/mL. Relative precision of the described sample preparation technique calculated from duplicate pairs of suspensions was 16% for S, 9% for Fe, 15% for Ni and 10% for Cu. Three spectral data processing techniques were further compared with respect to the quantification accuracy of target elements: internal standard, univariate and multivariate regressions. It was shown that the two latter methods can be used to improve the trueness of the internal standard method, especially for Cu and Fe.

The effects of dry grinding and chemical conditioning during grinding on the flotation response of a Cu-Zn sulphide ore and a spodumene pegmatite silicate ore

Dry processing of metal containing ores is often easily discarded as a viable option because of the higher energy consumption of dry grinding and several other challenges introduced from the handling of the dry ore. However, possible positive aspects include improved surface properties, reduced wear of the grinding media, and improved efficiency of water usage, which will become increasingly important in the future due to the water scarcity and global warming.Laboratory scale flotation tests with various grinding and conditioning methods were conducted with the Pyhäsalmi massive sulphide ore (Cu-Zn) and the Syväjärvi spodumene pegmatite silicate ore (Li) to determine the effects of dry processing on the flotation performance of these ores. Products were characterized utilizing XRF and MP-AES, and metallurgical efficiency was assessed. EDTA-leaching of the grinding products, and electrochemical measurements were conducted to further assess the chemical conditions after various processing atmospheres.Dry grinding the Pyhäsalmi sulphide ore resulted in higher flotation mass recoveries compared to wet grinding, but at the cost of selectivity. Beneficial effects emerging from the chemical conditioning during grinding were observed regarding kinetics, selectivity, and overall performance. Conditioning the Syväjärvi spodumene ore with a fatty acid collector during dry grinding had a tremendous activating effect on the ore, and detrimental effect on the selectivity. Overall, the spodumene ore responded poorly to the dry processing conditions, but some potential applications were identified.These initial results showed clear differences in the separation performance between the various grinding and conditioning conditions, and future efforts will be focused on determining the effects of these different processing conditions on the mineralś surface properties in a more precise manner.

力積型個別要素法による湿式ビーズミルの粉砕性能評価

力積型個別要素法による湿式ビーズミルの粉砕性能評価

Improving intestinal absorption and antibacterial effect of florfenicol via nanocrystallisation technology

To study the effects of nanocrystallisation technology on the intestinal absorption properties and antibacterial activity of florfenicol (FF). The florfenicol nanocrystals (FF-NC) were prepared by wet grinding and spray drying. Additionally, changes in particle size, charge, morphology, and dissolution of FF-NC in the long-term stability were monitored by laser particle sizer, TEM, SEM, paddle method, and the structure of FF-NC powder was characterised by nuclear magnetic resonance (NMR) test. The antibacterial activity, intestinal absorption and intestinal histocompatibility of FF-NC were investigated by the stiletto, mini broth dilution susceptibility test, in situ single-pass intestinal perfusion (SPIP) and haematoxylin–eosin (H–E) staining. After 12 months of storage, the particle size and zeta potential of FF-NC were 280.43 ± 8.21 nm and −19.64 ± 3.45 mV, and the electron microscopy results showed that FF-NC were nearly circular with no adhesion between particles. In addition, the drug loading, encapsulation efficiency, and dissolution of FF-NC did not change significantly during storage. The inhibition zone of FF-NC against Escherichia coli and Staphylococcus aureus was 21.37 ± 1.70 mm and 25.17 ± 2.47 mm, respectively. Compared with the FF, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of FF-NC are reduced, and the absorption rate constant (K a) and efficient permeability coefficient (P eff) of FF-NC in the three intestinal segments were increased by 1.28, 0.25, and 9.10 times and 0.59, 0.17, and 6.0 times, respectively. The results of tissue sections showed that FF-NC had little damage to the small intestinal. Nanocrystallisation technology is an effective method to increase the intestinal absorption and antibacterial activity of FF.

Analytical Evaluation of Wet and Dry Mechanochemical Syntheses of Calcium-Deficient Hydroxyapatite Containing Zinc Using X-ray Diffractometry and Near-Infrared Spectroscopy.

Calcium-deficient zinc-containing calcium phosphate (ZnAP), which has sustained zinc release properties that are effective for treating osteoporosis, can be efficiently synthesized as a biomaterial through wet grinding. To elucidate the physicochemical mechanism of these mechanochemical syntheses, ground products were obtained from the starting material powder (S-CP), consisting of calcium hydrogen phosphate dihydrate (CHPD), calcium oxide (CaO), and zinc oxide (ZnO), by wet and dry grinding for 0–3 h in a centrifugal ball mill. The ground S-CP products were analyzed using powder X-ray diffraction (XRD) and near-infrared spectroscopy (NIRS); the crystal transformations and molecular interactions of the ground products were kinetically analyzed. The XRD and second-derivative NIRS results indicate that the S-CP is primarily transformed into ZnAP via amorphous solid formation in wet grinding, and the reaction follows a consecutive reaction model. In contrast, in dry grinding, the ground product of CHPD and CaO is transformed into an amorphous solid following an equilibrium reaction model; however, ZnO is predominantly not transformed and remains crystalline.

Wet mechanical grinding regulates the micro-nano interfaces and structure of MXene/PVA composite for enhanced mechanical properties and thermal conductivity

The applications of MXene/polymer-based functional materials have been widely reported, while the understanding of the structural evolution of MXene/polymer composites during combination is still limited. Herein, mechanical grinding is applied for the delamination and dispersion of multilayer MXene particles in PVA aqueous solution, during which they are gradually delaminated into nanosheets. Low-field nuclear magnetic resonance spectroscopy and rheological properties analysis demonstrate that the specific surface area and exposed functional groups of MXene sheets are drastically increased, which greatly contributes to the construction of MXene-PVA interfacial interactions and the enhancement of gel networks. Furthermore, the exfoliated MXene nanosheets are uniformly distributed in the resultant MXene/PVA composite films, which greatly facilitates the stress transfer and the transportation of electrons/phonons, leading to significantly improved mechanical properties and electrical/thermal conductivities. This work provides fruitful insights into the optimized fabrication of MXene/polymer composites.

Utilization of submicron autoclaved aerated concrete waste to prepare eco-friendly ultra-high performance concrete by replacing silica fume

Silica fume (SF), as the main submicron filler material in ultra-high performance concrete (UHPC), determines the bulk density and final mechanical properties of UHPC. With the rapid increase in the demand for UHPC in the construction industry, SF is gradually becoming a luxury material. In the present work, wet grinding technology was used to prepare an alternative submicron material to replace SF. Wet-grinded submicron autoclaved aerated concrete waste (WSA) was prepared, and UHPC was prepared with the replacement of SF by WSA under different replacement levels (up to 100%). The results showed that at the level of 100% WSA replacement, UHPC's hydration process was promoted, the 28-day compressive strength was the same, and the pore structure was refined. But the cost of WSA is only 41% of SF, indicating that it is possible to completely replace SF in UHPC using WSA. The results propose a new technical approach for the replacement of high-cost SF in UHPC, which is expected to achieve high value-added benefits for construction waste.

Aqueous carbonation of peridotites for carbon utilisation: a critical review.

Peridotite and serpentinites can be used to sequester CO2 emissions through mineral carbonation. Olivine dissolution rate is directly proportional with temperature, presence of CO2, surface area of mineral particles and presence of ligands and is inversely proportional to pH. Olivine dissolution is better under air flow and increases seven times when rock-inhibiting fungus (Knufia petricola) is used. Olivine dissolution retards as silica layers form during reaction. Sonication, acoustic and concurrent grinding using various grinding medias have been used to artificially break these silica layers and achieve high magnesium extraction. Wet grinding using 50 wt.% ethanol enhanced CO2 uptake of dunite 6.9 times and CO2 uptake of harzburgite by 4.5 times. The best economical process is single-stage concurrent grinding at 130 bar, 185 °C, 15 wt.% solids and 50 wt.% grinding media (zirconia) using 0.64 M NaHCO3. Ratio of grinding media to feed should not be less than 3:1. Yield increases with temperature, pressure, time of reaction, pH and rpm and using additives and grinding media and reducing particle size. This review aims to investigate the progress from 1970s to 2021 on aqueous mineral carbonation of olivine and its naturally available rocks (harzburgite and dunite). This paper comprehensively reviews all aspects of olivine carbonation including olivine dissolution kinetics, effects of grinding and concurrent grinding, thermal activation of olivine feedstock (dunites and harzburgites) as well as chemistry of olivine mineral carbonation. The effects of different reaction parameters on the carbonation yield, role of mineral carbonation accelerators and costs of mineral carbonation process are discussed.

Preparation and performance characterization of steel slag-based thermal storage composites for waste recycling and thermal energy storage

ABSTRACT At present, the steel industry produces a large amount of steel slag during the smelting process, which causes serious pollution to the environment and land. Therefore, new technologies must be used to deal with steel slag. In this study, the steel slag powder refined by the wet grinding technology is used as the matrix material, MgO as material additive, and the clay is used as the binder to prepare a new type of composite heat storage material. The results indicate that the mass ratio of wet grinding steel slag powder, MgO powder and clay is 6:3:1, the composite heat storage material can have a strong compressive strength of 70.9 MPa. The thermal conductivity of the heat storage material is 0.98 W/m⋅K and can reach 1.27 J/g⋅K at 720 ℃, which has good thermal conductivity and long service life. When the heat storage material rises to 900 ℃, the heat storage density can reach 905 J/g, with good heat storage performance and thermal cycle stability. The objective is to develop sustainable and low-cost thermal energy storage material for industry waste heat recovery and in renewable energy applications. At the same time, this valuable market for slag in the energy field provide a new way to directly utilize steel slag with extraordinary economic and environmental benefits.

Synergistic effects of steel slag and wet grinding on ambient cured ground granulated blast furnace slag activated by sodium sulfate

Weak base Alkali-activated materials (AAM) is a potential approach to further reduce energy consumption and eco-friendly. Long setting time and low early strength limit the application in engineering. In this study, steel slag (SS) was used as a partial-substitution precursor of ground granulated blast furnace slag (GGBFS), and wet-grinded SS-GGBFS (WSS-GS) binary binders activated by sodium sulfate were designed. The results showed that the alkalinity of WSS-GS slurry was improved by the addition of SS, and the early hydration reaction and strength were promoted greatly. However, excessive SS was harmful to strength development at later age for quantity reduction of hydration products and microstructure deterioration. 15%SS-85%GGBFS activated by 3% Na2O-E sodium sulfate was verified with a desired performance, initial setting time was shortened by 60% and 1 d compressive strength was increased by 91% compared to GGBFS. These results provide guidance on designing of weak base-activated slag system and utilization of mass SS.

Distribution and Speciation of Rare Earth Elements in Coal Fly Ash from the Qianxi Power Plant, Guizhou Province, Southwest China

Coal fly ash (CFA), hazardous to the environment and human health, has been considered to be a potential alternative source for rare earth elements (REEs) in recent years. However, information on how REEs distribute and occur in coal fly ash is still incomplete. In this work, particle size analysis, inductively coupled plasma–mass spectrometry, scanning electron microscopy, and electron probe microanalysis were applied to study the occurrence and distribution of REEs in a fly ash sample from the Qianxi coal-fired power plant in Guizhou province. The results show that the REEs content in the CFA was 630.51 ppm. Wet grinding-enhanced leaching experiments revealed that a part of the rare earth particles was encapsulated within the glass body. These rare earth particles could be liberated and released to a certain extent by wet grinding, which would increase the acid-leaching recovery of REEs from 23.49% to 41.68%. This study classifies the speciation of REEs in coal fly ash as (1) amorphous glassy particles with REE minerals or compounds encapsulated inside; (2) amorphous glassy particles with REEs distributed throughout; and (3) discrete REE minerals or compounds. The results of this study are a basis for developing an economically viable and environmentally sustainable technology for recovering REEs from CFA.

Fast HCl-free Synthesis of Lead-free Rb2ZrCl6:xSb3+ Perovskites.

Due to the toxicity and instability issues of lead halide perovskites, lead-free perovskites have recently emerged as a viable alternative. However, significant optical band gaps of lead-free perovskites exert influence on their luminescent properties. Fortunately, the addition of dopants becomes an efficacious solution. The current widely utilized methods for synthesizing perovskites almost require high temperatures, a long period, and atmosphere protection, which cost more energy and resources. In this paper, we report that Rb2ZrCl6:xSb3+ perovskite phosphors can be easily prepared by a wet grinding approach at room temperature, which is a more efficient and facile process. Due to the self-trapped excitons of the host structure and Sb3+ ions, the produced samples display blue-white and orange fluorescence under UV lamp irradiation at 254 and 365 nm, respectively. In the photoluminescence spectrum, the doped perovskite exhibits an emission peak at 630 nm under excitation at 365 nm. Importantly, the prepared phosphors have tunable emissions related to the excitation wavelength. In addition, our produced powders show remarkable stability at room temperature, laying the foundations for this approach to be widely used in perovskite production.

Preparation of fly ash supporting nano-TiO2 composite photocatalyst by a wet mechanical grinding method

In this study, nano-TiO2 and FACs were used to prepare a composite photocatalyst (FACs-TiO2) by a wet mechanical grinding method. FACs-TiO2 was fabricated by using nano-TiO2 that was uniformly loaded on the surface of FACs, and the TiO2 particles were 20–30 nm in size. The degradation effect of FACs-TiO2 was comparable to that of commercial nano-TiO2 (P25). The reduction in TiO2 dosage in FACs-TiO2 could markedly reduce TiO2 application costs; thus, it shows promise for practical application.

Effects of wet grinding combined with chemical activation on the activity of iron tailings powder

Utilizing iron tailings powder (ITP) as supplementary cementitious materials (SCMs) has significant economic and environmental benefits, while the low pozzolanic activity of ITP limits its incorporation to some extent. This paper aims to study the effect of compound activation (wet grinding with a chemical activator) on the activity of ITP. Two kinds of sulfate (CaSO4·2H2O and Na2SO4) were used as chemical activators, and the optimal dosages of CaSO4·2H2O and Na2SO4 were determined by the mechanical strength tests of cement-ITP pastes. Results demonstrate that adding 3 % CaSO4·2H2O (wet grinding with ITP) caused a slight increase in the early and later strength of cement pastes containing 30 % ITP, while adding 3 % Na2SO4 (wet grinding with ITP) resulted in a significant improvement in the early strength and a slight increase in the later strength. Compared to a single wet grinding activation, compound activation could produce more amorphous substances in ITP and cause a more prominent decrease in the surface binding energy of internal chemical bonds of ITP, thereby further improving the activity of ITP. Moreover, the hydration products of cement pastes containing 30 % compound activated ITP were compared with those of cement pastes containing 30 % wet ground ITP, and the activation mechanism of two sulfates on ITP was studied.