Grinding Treatment Research Articles

Bending compensated surface mechanical grinding treatment overcoming the strength-ductility trade-off in thin copper sheet

Gradient nano-grained (GNG) structure has been developed to solve the notable dilemma of the strength-ductility. However, the surface plastic strain-induced grain refinement often results in cracking or peeling of materials when overloaded. This study proposed a bending compensated surface mechanical grinding treatment (BC-SMGT) for thin metallic sheets, where the elastic bending dynamically compensates the perpendicular indentation-induced penetration. This unique deformation feature results in gradient nanostructured layers, with a grain size ranging from ∼80 nm to a few microns in a pure Cu sheet processed at both room temperature (RT) and cryogenic temperature (CT). A relatively thicker deformation layer and smaller top surface grain size in the CT Cu sample yields better strength-ductility synergy than that in the RT Cu sample, which benefits from the preserved nanograins. Our results advance the fundamental understanding of this newly developed deformation technique and enlighten the future application of GNG structures in metallic sheets at industrial scale.

Contribution to Improvement of Fatigue Properties of Zr-4 Alloy: Gradient Nanostructured Surface Layer versus Compressive Residual Stress.

The gradient nanostructured (GNS) layer forms beneath the surface of Zr-4 samples by the surface mechanical grinding treatment (SMGT) process, which increases the fatigue strength apparently due to the synergistic effect of the gradient nanostructured layer and compressive residual stress. The SMGTed Zr-4 samples are subjected to annealing to remove residual stress (A-SMGT) and the individual effect of the GNS layer and compressive residual stress can be clarified. The results show that the gradient nanostructure in the surface is stable after annealing at 400 °C for 2 h but residual stress is apparently removed. Both SMGTed and A-SMGTed Zr-4 samples exhibit higher fatigue strength than that of coarse-grained (CG) Zr-4 alloy. The fatigue fracture of Zr-4 alloy indicates that the hard GNS surface layer hinders fatigue cracks from approaching the surface and leads to a lower fatigue striation space than that of CG Zr-4 samples. The offset fatigue strength of 106 cycles is taken for SMRT-ed, A-SMRT-ed, and CG Zr-4 samples and the results indicate clearly that the GNS surface layer is a key factor for the improvement of fatigue strength of the Zr-4 alloy with surface mechanical grinding treatment.

Ultra‐strong phosphorescence with 48% quantum yield from grinding treated thermal annealed carbon dots and boric acid composite

AbstractMetal‐free room‐temperature phosphorescence (RTP) materials are of great significance for many applications; however, they usually exhibit low efficiency and weak intensity. This article reports a new strategy for the preparation of a high‐efficiency and strong RTP materials from crystalline thermal‐annealed carbon dots (CDs) and boric acid (BA) composite (g‐t‐CD@BA) through grinding‐induced amorphous to crystallization transition. Amorphous thermal‐annealed CDs and BA composite (t‐CD@BA) is prepared following a thermal melting and super‐cooling route, where the CDs are fully dispersed in molten BA liquid and uniformly frozen in an amorphous thermal annealed BA matrix after super‐cooling to room temperature. Upon grinding treatment, the fracture and fragmentation caused by grinding promote the transformation of the high‐energy amorphous state to the lower energy crystalline counterparts. As a result, the CDs are uniformly in situ embedded in the BA crystal matrix. This method affords maximum uniform embedding of the CDs in the BA crystals, decreases nonradiative decay, and promotes intersystem crossing by restraining the free vibration of the CDs, thus producing strong RTP materials with the highest reported phosphorescence quantum yield (48%). Remarkably, RTP from g‐t‐CD@BA powder is strong enough to illuminate items with a delay time exceeding 9 s.

Extraction of Nanocellulose from Yerba Mate Residues Using Steam Explosion, TEMPO-mediated Oxidation and Ultra-fine Friction Grinding

ABSTRACT In this work, we evaluated the extraction of nanocellulose from agro-industrial residue of yerba mate (YM, Ilex paraguariensis, St.Hil) sticks through chemical (bleaching and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation), physical (steam explosion) and mechanical (ultra-fine friction grinding) treatments, divided into three distinct sequences for method comparison. The results showed that steam explosion as the initial treatment step makes an increase of up to 23% in the crystallinity index of cellulose nanofiber (CNF) in relation to the raw sample. The TEMPO-mediated oxidation resulted in more dispersed CNF, verified by transmission electron microscopy (TEM). Samples treated by steam-explosion and ultrafine grinding showed a higher yield in relation to steam-explosion and oxidative treatment (24.3% versus 16.2% respectively). CNFs with a diameter of 6 nm and a length range of 2200 to 2600 nm were obtained.

Mechanical grinding alters physicochemical, structural, and functional properties of tobacco (Nicotiana tabacum L.) leaf powders

Utilizing tobacco industrial waste can increase added value without increasing the environmental burden. The physicochemical, structural, and functional properties of tobacco leaf powders produced by coarse and superfine grinding treatments with different particle size were investigated. The particle size was significantly reduced by superfine grinding to micron scale (10.3 μm), and the specific surface area sharply increased. With decreasing particle size, the bulk density, tap density, angles of repose and slide increased, but water and oil holding capacities decreased, indicating the worse flowability and hydration property. The increasing lightness and yellowness but decreasing redness were observed after superfine grinding. Differential scanning calorimetry curves showed that superfine grinding insignificantly affected the conformation stability and denaturation degree of proteins. Fourier transform infrared spectroscopy proved unchanged main structure and decreased chain length of polysaccharide polymer. Morphology revealed that the shape of superfine ground sample was changed from an irregular polygon to spherical-like, and surface roughness was reduced. All cell walls were disrupted after superfine grinding, but the dissolution yields of nicotine and total phenolic, and antioxidant activities were not enhanced. The median particle size of 93.9 μm was the most effective for the ingredient dissolution and antioxidant capacity. This study was expected to supply new insights in guiding the development of discarded tobacco in practice.

Integration of fine grinding and H2SO4 leach for the liberation, dissolution and redistribution of long-life radionuclides in copper flotation concentrate

The economically significant deposits – iron oxide-copper-gold (IOCG) usually contains elevated amount of naturally occurring radioactive material (NORM), which hinders the utilization of IOCG deposits and leads to the waste of resources on site due to the presence of these radionuclides. Herein, a new fine grinding – H2SO4 leach method was used to efficiently dissolve and liberate long-life radionuclides (238U, 230Th, 226Ra, 210Pb, 210Po) from uranium-bearing NORM that are finely disseminated in the major economical minerals. The fine grinding treatment reduced the average particle sizes, interrupted the mineral textures and partially dissolved uranium minerals, thereby liberating them onto the newly formed secondary copper phases. The following H2SO4 leach changed the chemical and phase compositions by dissolving non-copper elements where the locked 238U and 230Th were largely removed close to the safe activity (1 Bq/g) and 226Ra, 210Pb, 210Po were mobilized onto the copper mineral surfaces. For the first time, the quantitative correlations between radionuclide species and major mineral phases were built by QXRD and radionuclide analysis. Such quantification methodology of radionuclide deportment can be applied in the processing a broad range of NORM-bearing resources, providing a crucial guidance in radionuclide management for environmental and process engineers.

The effect of mechanical grinding and thermal treatment on the recovery of rare earth elements (REEs) from kaolinite

REE recovery from a kaolinite sample was conducted in the present study. The results of mineralogical analyses, salt leaching, and acid leaching tests confirmed that REEs predominantly existed as florencite (REEAl3(PO4)2(OH)6) in the material, and the proportion of ion-exchangeable and ion-substituted REEs was negligible. Mechanical grinding for 4 h completely destroyed the crystal structure of the material, but the recovery of total REEs was less than 20%, indicating that insufficient liberation of the REE-bearing particles is not the only factor leading to the low recovery. Thermal treatment of the raw material at 600 °C for 2 h largely enhanced the total REE recovery to as high as 92%. The improved recovery was ascribed to the thermal decomposition of crystallized florencite into an amorphous phase, which was proved through transmission electron microscopy - energy dispersive X-ray analysis. Findings from the study will contribute to REE recovery and comprehensive utilization of kaolinite.

Effect of mechano-chemical pretreatment on valorizing plant waste for 5-hydroxymethylfurfural under microwave hydrothermal treatment

Plant waste (PW) is a common and abundant renewable biomass resource whose total amount is constantly increasing and accounts for up to 50% of municipal solid waste. This study aims to develop a valorization method for PW. A two-stage treatment method combining mechanical ball milling (BM) and microwave hydrothermal treatment (MHT) was investigated. BM can effectively destroy the crystallization of cellulose and reduce the particle size to increase the specific surface area and improve the MHT efficiency. The BM-MHT process could improve the 5-hydroxymethylfurfural (HMF), which is significantly higher than physical methods like grinding, ultrasonic and liquid nitrogen treatment. The BM conditions were further optimized by using a Box-Behnken Design with response surface methodology. The model showed that the highest HMF yield could reach 1.8% at 150 °C in MHT process after BM. An economic analysis indicated that BM-MHT offers a green treatment method with great economic benefits. It provides a novel valorization strategy for organic waste like PW.

English

BACKGROUND A smooth zirconia surface is necessary to protect the opposing natural dentition, to prevent plaque accumulation and to increase the survival rate of restoration by reducing the chances of failure by crack propagation. Surface roughness can be incorporated by routine dental procedures done in labs and clinics to adjust the restoration. It is unclear which surface treatment is most appropriate to achieve clinically acceptable zirconia surface. The purpose of this study was to evaluate the effect of grinding and subsequent various surface treatments on the surface roughness of full contour monolithic zirconia. METHODS In this invitro study 10 zirconia bars of final dimensions 20 x 4 x 2 mm & 40 zirconia bars of final dimensions 20 x 4 x 2.2 mm were milled and sintered. The zirconia bars with final dimensions 20 x 4 x 2mm were glazed and selected as samples for control group (Group C) (n = 10). Forty zirconia bars with dimensions of 20 x 4 x 2.2 mm were grounded using a standard straight cylindrical diamond point (105 – 125 µm) by placing them in a customized grinding apparatus till the dimensions became similar to that of control group i.e. 20 x 4 x 2 mm. After grinding and confirming the dimensions of each full contour monolithic zirconia bar using digital vernier caliper, zirconia bars were randomly allocated into 4 groups with 10 samples in each group (n = 10), namely (Group G: Grinding only, Group G+R: Grinding & Reheating, Group G+G: Grinding & Glazing, Group G+P: Grinding & Polishing) respectively. Surface roughness values were measured using a profilometer. Differences between groups were examined using one-way analysis of variance (ANOVA) (P ≤ 0.05) and Post hoc Tukey HSD test was done for multiple comparisons of surface roughness in between the groups using Statistical Package for Social Sciences (SPSS) software. RESULTS Group C showed the least surface roughness values. The maximum surface roughness values were seen in Group G. Surface roughness of Group G, Group G + H and Group G + G were statistically significant from Group C and Group G + P. There was no statistically significant difference in surface roughness values between Group C and Group G + P. CONCLUSIONS It can be concluded that polishing after grinding significantly reduced the surface roughness and re-established the surface smoothness of full-contour monolithic zirconia bars. KEY WORDS Surface Roughness, Zirconia, Monolithic, Full Contour, Profilometer

Phase Transitions Among of Valsartan Polymorphs due to Grinding and Humidity Variations

Phase transition between drugs with polymorphisms needs attention due to unconscious changes in quality. Valsartan (VAL) is a drug model with polymorphic events to be studied here. Two polymorphic forms were obtained from recrystallization with various organic solvents such as acetonitrile and n-butyl acetate. With untreated materials (from the market) were used as a comparison in this study. The phase transition of each polymorph was studied through grinding and humidity variations (RH 75% and 98%) treatment. The polymorph characterization was observed by microscope light polarization (PLM), Fourier Transform Infrared (FTIR), and Powdered X-ray Diffractometer (PXRD). The transition among polymorphic VAL was monitored by PXRD. There were significant differences in morphology, IR spectra, and diffractograms pattern. Found that the untreated VAL was amorphous, whereas the others were in high crystallinity. The polymorph form from n-butyl acetate was a metastable one that transformed easier into stable crystalline (from acetonitrile) than another polymorph.Keywords : Valsartan, Phase transition, Polymorphism, Recrystallization

On the microstructural evolution pattern of 300 M steel subjected to surface cryogenic grinding treatment

In the present work, an ultrahigh strength 300 M steel was treated by the surface plastic deformation with surface cryogenic grinding treatment (SCGT) technique. The SCGT was carried out by rotational grinding wheel embedded with numerous zirconium corundum abrasive grits, which contributes to a decreasing distribution of strain, strain rate and strain gradient from the treated surface to the matrix. The depth-dependent microstructural evolution was systematically evaluated from micrometer to nanoscale and in particular, the deformation mechanisms and texture alternation were addressed. It was identified that the microstructural evolution starts from the formation of dislocation structures, that is subsequently followed by the distorted microstructures featured as the origination and evolution of ultrafine laminates and ultrafine grains in the form of dislocation activities. Nanocrystalline was generated in the topmost surface region and nanoparticle precipitates induced by the SCGT process occur within a few microns of the treated surface. In SCGT, a very high strain rate of over 10 6 s −1 and a strain gradient of over 0.2 μm −1 were induced on the topmost surface of 300 M steel sample, which impels the martensite-matrix lamella extended into the elongated structure and finally transformed into the nanosized grains during processing. A dislocation slip-dominated process that was supplemented by the mechanical twinning governs the microstructural evolution pattern during the SCGT process, the nucleus of dynamic recrystallization initiated from the pre-existing dislocation cells were observed, and the transformation from martensite to austenite was effectively suppressed. The increase of grain size from nanoscale to submicron and finally microscale contributes to a decrease of microhardness by 25.6% (from 7.8 GPa at the treated surface to 5.8 GPa at a depth of over 100 μm from the processed surface). • Gradient microstructures are observed after being subjected to the SCGT process • Nanoparticle precipitates induced by the SCGT process appear within a few microns of the treated surface • A dislocation slip-dominated process governs the microstructural evolution pattern • The relationship between the microstructural evolution and microhardness is analyzed

Effects of different physical technology on compositions and characteristics of bean dregs

The effects of ultrafine grinding (U), high pressure (HP), microwaves (M), high-temperature cooking (HTC) and combination technologies (U-HP, U-M, U-HTC) on the nutritional compositions and characteristics of bean dregs were investigated. The results showed that both single treatments and combination treatments significantly increased the soluble dietary fiber (SDF) content and water solubility of bean dregs; however, the protein content, fat absorption capacity and swelling capacity of bean dregs were decreased compared with those of the control. The combination technologies significantly increased the contents of K, Ca, Na and Fe in bean dregs. HTC and U-HTC had prominent effects on inhibiting trypsin inhibitor activity, which were decreased from 7365 TIU/g to 1210 and 96 TIU/g, respectively. The bean dregs by ultrafine grinding and combined treatments showed honeycomb structure and small particle distribution, and their processing performances improved. In conclusion, combination technologies were effective methods for improving the quality of bean dregs and expanding their development.Industrial relevance: A combined method may have greater effects than any single approach in improving the quality of bean dregs. Ultrafine grinding technology combined with other physical techniques used in bean dregs can solve quality problems; for example, bean dregs are characterized by poor taste, perishability, low soluble fiber content, and high trypsin inhibitor activity, all of which are related to human health and safety. However, to the best of our knowledge, ultrafine grinding combined with other physical techniques has not been used with bean dregs. The present paper highlights the effects of ultrafine grinding technology (U) combined with high pressure (HP), microwave (M), and high temperature cooking (HTC) technologies on the nutritional and functional compositions of bean dregs. The obtained results contribute to enhance SDF content, reduce anti-nutrition factors, and expand development and utilization of bean dregs, which constitute the basis for its application in baked food, flour products and the food industry.

Ultra-fine-grained and gradient FeCrAl alloys with outstanding work hardening capability

FeCrAl alloy is a promising accident tolerant fuel cladding material for next generation nuclear reactors. Grain refinement may lead to FeCrAl alloys with improved mechanical properties. However, the addition of Al retains the ferrite phase and makes the grain refinement difficult through conventional thermomechanical treatments. In this study, a model FeCrAl alloy, C35M, was processed by surface mechanical grinding treatment. Microscopy studies show the formation of gradient microstructures, consisting of surface nanolaminate layer and ultra-fine-grained sublayer. In situ micropillar compression tests reveal the gradient FeCrAl alloy has a high flow stress, exceeding 1.4 GPa, and excellent work hardening capability. A modified Kocks-Mecking model was utilized to explain the grain size-dependent work hardening behavior. This study sheds lights on the design of gradient ferritic steels with high-strength and good work hardening ability for various industrial applications.

Impact of surface gradient structures on mechanical properties of a dual-phase AlCrFe2(Ni0.85Co0.15)2 multi-component eutectic alloy

The multicomponent eutectic alloys (MCEAs) have demonstrated great potential applications in industrial fields owing to their excellent castability during solidification. The cast MCEAs can achieve a good strength-ductility synergy. However, they usually suffer from mechanical failure at surface due to high surface residual stress resulting from direct solidification. Here we introduce a surface treatment technique through electromagnetic induction heating (EMIH), by which the stress level at surface (−24 MPa) was significantly reduced compared to that of the base MCEA (+573 MPa) with a chemical composition of AlCrFe2(Ni0.85Co0.15)2. This EMIH treatment not only mitigates surface residual stress but also enhances tensile ductility by 30 % without sacrificing its yield strength. In contrast, surface gradient structure synthesized by surface mechanical grinding treatment (SMGT) exhibited a dual-phase nanostructure, together with a compressive residual stress that is an order of magnitude higher than that of the EMIH-processed MCEA. The SMGT-processed MCEA showed marginal improvement in its tensile ductility because of limited work hardening ability resulting from limited dislocation sources at surface. Our study envisages an approach to process MCEAs by surface treatment with relatively a low cost.

Aggregation-induced emission and remarkable piezochromism based on tetraphenylethene modified cyanostilbene derivative

The D-π-A-π-D type tetraphenylethene-based cyanostilbene derivative TPEAN had been designed and synthesized. Solvatochromic experiment and theoretical calculation illustrated that TPEAN occurred unique intramolecular charge transfer (ICT) process. Luminogen TPEAN also exhibited AIE activity. The nanoparticles gradually formed and emitted intense fluorescence at high water content in a mixture of THF/water. Interestingly, TPEAN displayed remarkable piezochromism. A emission color change from bright green to dark yellow occurred for the pristine solid of TPEAN after grinding treatment. This emitting color change could recover to its original state after fuming. The current work could be help us to effectively design molecular structure to achieve an obvious fluorescence response to external force.

Study of Metal, Silicon Carbide Crystals and Ceramic Bond Transfer to the Surface of Titanium Alloy during Grinding

The high adhesive activity of titanium alloys in interaction with abrasive materials is the main cause of poor grinding treatment. The most common abrasive material for grinding titanium alloys is silicon carbide. Silicon carbide wheels operate primarily in self-sharpening mode. Wear of the abrasive tool in the self-sharpening mode occurs as a result of brittle destruction of the fret. The purpose of the study was to determine experimentally the crystalline wear products of an abrasive tool, made of silicon carbide, on the treated surface during grinding of a titanium alloy. Samples of VT9 titanium alloy were processed by flat mortise grinding by a wheel of silicon carbide with the use of VOLTES coolant and the characteristic of the abrasive tool - 64CF80L7V. The treated surface was examined on the electron microscope Versa 3D Dual Beam. The condition of the treated surface testifies to the intensive adhesive interaction of the titanium alloy with the abrasive tool. The thickness of the metal deposits reaches 3 microns. As a result of morphological analysis, objects are identified on the treated surface, the appearance of which allows us to attribute them to crystals. The chemical composition of the selected objects was determined by a microprobe analysis in a microscope camera. On the basis of the conducted researches, a presence on the grinded surface of silicon carbide crystals of various sizes and a ceramic ligament is established.

Improving the grindability of Inconel 718 by hydrogen embrittlement in ultrasonic-assisted grinding

Inconel 718 has been widely investigated due to its machining properties. The purpose of this work was to investigate a novel proposed grinding technique for Inconel 718 with a combination of ultrasonic-assisted grinding and hydrogen embrittlement (HE) treatment. The technique was hence named hydrogen embrittlement-enhanced ultrasonic-assisted grinding (HEUAG). Before grinding, a thin stress layer was formed on the surface of the workpiece. To reveal its fundamental performance in the grinding of Inconel 718, experiments were conducted to investigate the effect of ultrasonic vibration on the grinding forces and the surface roughness in the presence of hydrogen embrittlement. To investigate the material removal process for HEUAG, single-grit grinding tests were also conducted with hydrogenated samples. Furthermore, the subsurfaces for HEUAG samples were obtained with the transmission electron microscope (TEM) micrographs. The HE treatment reduced the generation of burrs around the scratches and improved the surface quality after grinding.

Comparing medium pressure dielectric barrier discharge (DBD) plasmas and classic methods of surface cleaning/activation of pure Mg for biomedical applications

Abstract Pure magnesium (Mg), being a lightweight biodegradable material, is increasingly attracting attention for its use in biomedical applications. However, surface contaminations arising from material machining can result in a deleterious degradation behavior thus a poor implant biocompatibility performance. Therefore, this paper represents a comparative study tackling the surface chemistry, cytocompatibility and degradation of Mg discs subjected to classical grinding and chemical treatments and to unconventional medium pressure (5 kPa) plasmas operated in Ar and NH3/He. Results reveal that both plasmas remove more than 40% of the carbonaceous contaminations while introducing surface oxygen (and nitrogen) containing functionalities. However, grinding only removes 34% of the initial surface carbon. Despite being the most efficient in eliminating the organic layer, the chemical treatment leads to an excessive surface oxidation. In vitro tests involving mesenchymal stem cells reveal that plasma-treated samples outperform their ground and chemically cleaned counterparts in terms of cell-surface affinity as more spread out cells with significantly bigger areas are detected, suggesting higher cell attachment. Moreover, plasma does not alter the degradation rate of Mg discs, thus providing a striking insight for their application in tissue engineering. Overall, one can conclude that the eco-friendly and economical sub-atmospheric plasma is an effective alternative synergistically cleaning and improving the cytocompatibility of Mg surfaces.

Thermal Stability of Nanocrystalline Gradient Inconel 718 Alloy

Gradient structures containing nanograins in the surface layer have been introduced into Inconel 718 (IN718) nickel-based alloy using the surface mechanical grinding treatment technique. The thermal stability of the gradient IN718 alloy was investigated. Annealing studies reveal that nanograins with a grain size smaller than 40 nm exhibited significantly better thermal stability than those with larger grain size. Transmission electron microscopy analyses reveal that the enhanced thermal stability was attributed to the formation of grain boundaries with low energy configurations. This study provides new insight on strategies to improve the thermal stability of nanocrystalline metals.

Effects of grinding treatment on surface properties and deformation microstructure in alloy 304L

Different types of sandpapers were used to grind surface of 304L alloy, and the effects of grinding treatment on surface properties and deformation microstructure were studied. Three dimensional profilometer, Vickers hardness tester, X-ray diffraction (XRD), scanning electron microscopy (SEM), focused ion beam (FIB), and transmission electron microscopy (TEM) were used to characterize the microstructure and mechanical properties. The results showed that with the increase of grinding particle size the surface roughness and hardness increased, while the absolute value of residual compressive stress decreased, however the grinding particle size had no effect on the average tension strength because the groove did not lead to the effect of notch stress concentration. After grinded by coarse sandpaper (No. 60), the surface metal deformed in the way of martensite shear from γ-austenite to α′-martensite, which conformed to K-S model, and surface nano-crystal layers with a thickness of about 2.3 μm, 1.5 μm and 0.6 μm were found at the groove peak, slope and valley, respectively. By comparison, after grinded by fine sandpaper (No. 2000), the nano-crystallization did not occur, and a high-density dislocation layer with a thickness of more than 1 μm was observed at the groove peak, slope and valley. • Hardness increase and compressive stress decrease with the increase of roughness. • Roughness had no effect on tension strength and notch stress concentration. • Surface metal deforms in the way of γto nano-α′ after grinded by No. 60 sandpaper. • Thickness of nano-α′ layer at groove peak, slope and valley decreases gradually. • Surface metal deforms as dislocation slip after grinded by No. 2000 sandpaper.