Reverse Indentation Size Effect Research Articles

Evolution of fundamental mechanical properties with aliovalent Co/Cu partial substitution and preparation method for Y-123 system

This study investigates the effect of aliovalent Co/Cu replacement and preparation method on fundamental mechanical performance features of YBa2Cu3−xCoxO7−δ (Y-123) ceramic system depending on the crack propagation mechanism by Vickers hardness measurements (Hv) and mechanical investigation models for the first time. All the findings are verified by the scanning electron microscopy (SEM) examinations. Besides, the electron-dispersive X-ray (EDX) technique verifies the successful substitution mechanism. Besides, the Vickers hardness parameters improve systematically with the increment in the Co/Cu partial substitution (serving as a barrier) level due to formation of operable slip systems, ionic bond formations, and decrement of stress-amplified strain fields. Moreover, the Y-123 ceramic produced by solid-state reaction method and molecular weight of 0.20% presents the densest and smoothest surface morphology with the largest particle distributions and well-linked cobblestone-like grains. On the other hand, the Y-123 ceramic compounds produced by the sol–gel method are more sensitive and responsive to the indentation test loads. All the findings are wholly supported by the mechanical performance properties, including the shear modulus, resilience, and degree of granularity. Furthermore, the mechanical models indicate that every compound prepared exhibits the untypical reverse indentation size effect (RISE). Additionally, the modeling studies display that the induced cracking (IIC) approach is found to be the most appropriate method to examine true Vickers hardness parameters in the plateau limit regions. All in all, this comprehensive study reports efficiently exploiting the process–structure–property relationships in Y-123 ceramic material design for physical science and mechanical application fields using the aliovalent partial substitution and preparation condition.

Load-Independent Hardness and Indentation Size Effect in Iron Aluminides.

In this paper, an iron-aluminide intermetallic compound with cerium addition was subjected to Vickers microhardness testing. A full range of Vickers microhardness loadings was applied: 10, 25, 50, 100, 200, 300, 500, and 1000 g. Tests were conducted in two areas: 0.5 mm under the surface of the rolled specimen and in the center. The aim was to find the optimal loading range that gives the true material microhardness, also deemed load-independent hardness, HLIH. The results suggest that in the surface area, the reverse indentation size effect (RISE) occurred, similar to ceramics and brittle materials, while in the center, indentation size effect (ISE) behavior was obtained, more similar to metals. This clearly indicated an optimal microhardness of over 500 g in the surface region and over 100 g in the central region of the specimen. Load dependencies were quantitatively described by Meyer's law, proportional specimen resistance (PSR), and the modified PSR model. The modified PSR model proved to be the most adequate.

Mechanical properties of Ag-added DyBa2Cu3Oy superconducting melt-textured bulks prepared by the single-direction melt growth method

Ag-added DyBa2Cu3Oy superconducting melt-textured bulks were prepared using the newly developed single-direction melt growth (SDMG) method with different pre-heat-treatment conditions. Clearly distinct microstructures were observed depending on the pre-heat-treatment conditions and thickness of the bulks. Their mechanical properties were evaluated by use of Vickers microhardness measurements at varying applied forces. Vickers microhardness increases with an increase in the applied force for each sample, up to an importantly high value of ∼9 GPa at the saturated region, indicating all the prepared bulks demonstrate the untypical reverse indentation size effect (RISE) performance. In addition, the experimental results found from the saturation regions are examined by the mechanical methods such as Meyer's law, proportional sample resistance model, elastic/plastic deformation, Hays-Kendall (HK) approximation, and indentation-induced cracking (IIC) model. According to the mechanical modelling findings, the HK and IIC models are found as appropriate mechanical models describing the hardness values for all the studied bulks exhibiting RISE feature and the true values are suggested to lie between the estimated values of HK and IIC models.

Synthesis, In silico mapping for anti-cancer proviso, hardness studies of d-gluconic acid monohydrate crystals for usage in electronic, mechanical and biological sectors

d-Gluconic acid monohydrate - DGAMH crystals are grown in a period of 61 days by using the customary slow evaporation method with a, b and c as 8.4309, 5.409 and 10.4071 in Å units; β as 96.87°; monoclinic system, space group as P21. The material is an anticancer stipulation to inhibit them with the docked score of the DGAMH as −6.0 and −7.1 for both cases. Considering the mechanic behaviour of the DGAMH; the n as 7.57 of the DGAMH – work hardening coefficient value as Reverse ISE (indentation size effect) response for DGAMH. The computational structural info of DGAMH provides the supercell proviso, VanderWaal's impact with the nano-tubular proviso of DGAMH for cell impacting, weak type of interactions and devices with nano-tube impact. The electronic fluxing is in microns for macro-DGAMH; micro-DGAMH; thin-film DGAMH and nano-DGAMH for filtering property confirmations. The frequency by IC741 is twice over the input values with DGAMH crystal.

Growth, studies of milled and irradiated crystalline samples of DBNT for macro-photonic and electro-mechano functionalities

Single crystals of organic type of NLO crystalline material of DBNT - 8, 9-Dimethoxybenzo[b]naphtho [2,3-d] thiophene are proceeded to be grown by slow evaporation procedure and milled to micro scale and irradiated of Co-60 source of 100 Gy, 500 Gy and 5000 Gy for better scope of classification of system of the monoclinic type of DBNT-pure, micro and irradiated ones. The hardness study specifies the reverse indentation size effect (RISE) with work hardening coefficient above two of all DBNT specimen leads to the micro-tribological workings for springs with proper elastic parameters; the transmittance of DBNT of 5 specimens are 321 nm, 323 nm, 341 nm, 351 nm, and 352 nm for macro, micro, 100 Gy, 500 Gy, 5000 Gy. The photonic utility of identity for 3.86 eV and is 3.8629 eV by the transmittance data. The Non Linear Optical - NLO component this of 1.9, 1.94, 1.95, 1.96, 1.99 times that of KDP from which phase matching provision is enabled the influx property for the DBNT specimens is in the order of microns the (110) and (111) indexing represent for display device configuration. The dielectric behaviour of DBNT shows that polarization properly enabled for all categories by electrical performance, the abnormal variation is due to the vacancies created in the molecule by irradiation.

Crystal design of novel Piperazinum Isophthalate (PIP): Growth, Structural, Thermal, Spectral, Mechanical and Optical properties for NLO application

Novel organic single crystal Piperazinum Isophthalate (PIP) has been synthesized and grown by the slow evaporation solution growth technique. The structural analysis of the single crystal was assessed by the single crystal X-ray diffraction and from a thorough literature survey, it is confirmed that the structure is claims to be the reported for the first time. The FT-IR analysis is used to confirm the different vibrational modes present in the crystal. Utilizing Vicker's Microhardness tester, the mechanical behavior of the crystal was examined and its related constants were computed. Mechanical analysis reveals that the grown crystal exhibits Reverse Indentation Size Effect (RISE) and also found that it belongs to the soft material category with n = 8. The TG/DTA technique is used to analyze the thermal property of the grown crystal and found that PIP is thermally stable up to 271°C. The optical property of the PIP crystal is analyzed using the UV–Vis NIR Spectroscopy, it is observed that PIP has good transparency in the entire visible region with a cutoff wavelength of 281 nm. The Laser Damage Threshold (LDT) of the PIP single crystal was studied by the Q-switched Nd-YAG laser of the wavelength 532 nm and the computed LDT value is 7.3047 GW/cm2. The third order non-linear optical properties of the grown crystal were analyzed by Z - scan technique and the obtained results confirm high nonlinear susceptibility(X(3) = 1.2728× 10−7esu) with self-defousing nature. From the above discussion, we may infer that the grown PIP crystal will be a promising material for optoelectronic device fabrication.

Improvement in deformation degree of Zr surface-layered Bi-2223 ceramics by diffusion annealing temperature

This study investigated the effects of different annealing temperatures (650 °C ≤ T ≤ 840 °C) on the surface morphological and mechanical performance properties of Zr surface-layered Bi-2223 materials with scanning electron microscopy (SEM) images, Vickers microhardness (Hv) measurements, and semi-empirical mechanical approaches. It was observed that the ceramic compound exposed to 650 °C annealing temperature exhibited the superior performance features due to the enhancement in the deformation degree. This is because the Zr ions behaved as the nucleation centers to prevent the propagations of cracks and dislocations throughout the main matrix depending on the decrease in the degree of granularity and distributions of crystal structure problems over a wider area. Similarly, the SEM pictures indicated that the diffusion mechanism increased the random distributions of the thinner plate-like granular structures (serving as nucleation centers), leading the decrease in the coupling problems between the grains. Among the materials, the highest surface densification was observed for the compound exposed to 650 °C. Namely, surface morphological analysis showed a strong correlation between microstructure and mechanical performances. Further, the zirconium ions were found to decrease in the non-recoverable stress concentration sites, crack-initiating defects, and dislocations in the ceramic system. Accordingly, the sensitivity to the applied test load was noted to decrease dramatically. Shortly, crack growth size and velocity were observed to be more easily under control. Correspondingly, the Zr ions delayed considerably the beginning points of saturation limit (load-independent) regions for the bulk Bi-2223 superconducting materials. Additionally, the Zr ions led to the change in the mechanical characteristic behavior from typical indentation size effect to reverse indentation size effect. Lastly, the microindentation hardness measurements were semi-empirically analyzed by the different models. According to the comparison, Hays-Kendall mechanical model was noted to provide the closest parameters to the load-independent microhardness results.

Effect of Strain Rate on Nano-Scale Mechanical Behavior of A-Plane (112¯0) ZnO Single Crystal by Nanoindentation

In this study, nanoindentation tests at three different strain rates within 100 nm indentation depth were conducted on an a-plane (112¯0) ZnO single crystal to investigate the effect of strain rate on its nano-scale mechanical behavior. The load-indentation-depth curves, pop-in events, hardness and Young's moduli of an a-plane (112¯0) ZnO single crystal at different strain rates were investigated at the nano-scale level. The results indicated that, with the indentation depth increasing, the load increased gradually at each maximum indentation depth, hma, during the loading process. A distinct pop-in event occurred on each loading curve except that corresponding to the hmax of 10 nm. The applied load at the same indentation depth increased with the increasing strain rate during the nanoindentation of the a-plane (112¯0) ZnO single crystal. The higher strain rate deferred the pop-in event to a higher load and deeper indentation depth, and made the pop-in extension width larger. The hardness showed reverse indentation size effect (ISE) before the pop-in, and exhibited normal ISE after the pop-in. Both the hardness and the Young's modulus of the a-plane (112¯0) ZnO single crystal increased with the increasing strain rate, exhibiting the positive strain-rate sensitivity.

Investigations on the Growth and Characterization of L-Leucine Doped Rubidium Sulfate Nonlinear Optical Single Crystal

Objectives: To grow crystal of inorganic material Rubidium sulfate by doping with an organic material L-leucine. Methods: Crystal has been grown by solution method. Crystallographic studies were done. Mechanical studies were carried out to find the mechanical strength and other parameters. Dielectric studies of L-leucine doped rubidium sulfate crystals were carried out to evaluate dielectric constant, dielectric loss and activation energy. UV-visible- NIR spectral studies were done in the wavelength range 200-1100 nm. Second order Non Linear Optical (NLO) studies of the grown crystal of LLRS were carried out by Kurtz-Perry technique. Findings: The grown LLRS crystal is observed to be crystallizing in orthorhombic structure by single crystal XRD studies. The optical band gap of LLRS crystal was found to be slightly more than that of undoped rubidium sulphate crystal. The SHG efficiency of LLRS crystal is observed to be 0.61 times that of the reference KDP sample. Dielectric parameters are found to decrease with increase in frequency. Dielectric constant and dielectric loss factor increase when the temperature of the samples increases. AC conductivity increases with increase of temperature. Activation energy is increasing when the frequency increases. The band gap value is found to be 4.43 eV for undoped rubidium sulfate crystal. For L-leucine doped rubidium sulfate (LLRS) crystal, the optical band gap is 4.48 eV. From the Microhardness teat, it is observed that the hardness increases with increase of the applied load for both the samples and this is due to reverse indentation size effect. Novelty: In this study, as a novel work, a very first attempt has been made to combine an organic material L-leucine with an inorganic crystal viz. rubidium sulfate to alter its physical and chemical properties. Keywords: Inorganic Single Crystal; Crystal Structure; Mechanical Properties; Dielectric properties; Optical Properties; Spectral Properties

Effects of Pr concentration on the structural, mechanical and optical properties of KCl0.5Br0.5:Pr3+ crystals

KCl0.5Br0.5:XPr3+ [X = 0.0 (pure KCl0.5Br0.5), 0.002, 0.004, 0.006, 0.008, 0.01, 0.02 and 0.04] crystals were successfully grown by Czockralski (Cz) pulling method and the structural, mechanical and optical properties of crystals were thoroughly investigated. X-ray diffraction (XRD) and X-ray photoelectron spectroscopic (XPS) studies indicated that the Pr ions have been incorporated into the KCl0.5Br0.5 host lattice and existed mainly as trivalent Pr. UV–Vis absorption spectra showed that the presence of peaks at 211, 227, 293, 457, 479, 494 and 601 nm. Hardness was found to increase with increasing of in Pr3+ concentration and indentation load, the hardness of the Pr doped crystals were larger than the un-doped crystal and the reverse indentation size effect was observed. The intensity of photoluminescence (PL) peaks was strongly depended on the Pr3+concentration. thermo-luminescence (TL) glow curves exhibited one peaks at 63–76 °C, indicating that one kind of trap existed in the crystals. The optimal luminous (both PL and TL) properties the KCl0.5Br0.5:XPr3+ crystals were obtained at X = 0.006. These results indicated that the KCl0.5Br0.5:Pr3+ crystals could be considered as a promising candidate for their use in optical and dosimetry applications.

Investigating mechanical properties of sintered ZnGa2O4 ceramics using nanoindentation

The role of sintering on the microstructure and mechanical properties of ZnGa2O4 pellets has been systematically investigated in this work. The hardness (H) and elastic modulus (E) of the sintered pellets are obtained via quasi-static and dynamic nanoindentation. The force versus displacement curves revealed the elastic-plastic behaviour of the ZnGa2O4 ceramics. The H and E values of the sintered pellets vary within 5.29–3.94 GPa and 149.25–111.04 GPa, respectively. A decreasing trend is observed in both H and E of the sintered pellets with increased sintering duration which could be ascribed to the grain size of the sintered products. In addition, the viscoelastic properties of the sintered ZnGa2O4 ceramics were examined via dynamic nanoindentation. The results from the dynamic nanoindentation testing revealed that ZnGa2O4 ceramics show the reverse indentation size effect (RISE). Further, a high storage modulus of 121 GPa was obtained with a corresponding low damping factor. Thus, the above investigations not only provide a new insight into the microstructural and mechanical properties of ZnGa2O4 spinel but also open avenues for its wider commercial applications.

The Indentation Size Effect (ISE) of Metals

The literature regarding the Reverse Indentation Size Effect (RISE) is scarce, the occurrence of which is assumed for plastic materials, including metals. The content of this article is to study the relationship between applied load and measured values of the Vickers micro-hardness of 19 metals with different types of lattices, measured with a Hanemann tester. The values of the load ranged between 0.09807 N (10 g) and 0.9807 N (100 g). The size and character of the Indentation Size Effect (ISE) were evaluated by Meyer’s power law (index n), Proportional Specimen Resistance (PSR), and Hays—Kendall methods. Meyer’s index n ranged between 1.65 for Mo and 2.44 for Ni. A correlation was found between the micro-hardness and Meyer’s index for metals with FCC and HCP lattices. The measured value of Vickers micro-hardness is influenced by the size and nature of the ISE. If this is not taken into account, it may be misleading. For this reason, we recommend using the “true hardness”, determined by the presented method.

Indentation Size Effect of Composite A356 + 6%FA Subjected to ECAP

In this study, metal matrix-based composite (MMC) was subjected to Equal Chanel Angular Pressing (ECAP) in several passes to determine the influence of deformation on the hardness of the samples. Composite based on A356 aluminum alloy and reinforced with Fly Ash (FA) particles was obtained by the compo casting method. The microstructural analyses and microhardness measurements were performed on the cast and pressed samples. Vickers hardness measurement of composite samples was performed with different indentation load sizes: HV0.02, HV0.05, HV0.1 and HV0.2. Results showed that hardness increases after each ECAP pass. The lowest hardness value of 42 (HV0.02) as well as the lowest arithmetical mean value of 46 (HV0.2) was measured at the cast composite. The greatest composite hardness of 107 (HV0.1) and the highest arithmetical mean value of 94 (HV0.1) was measured at the three-time pressed sample. The mathematical model named Meyer’s law was used for data analysis. In the cast sample, a decrease in hardness was detected with increasing indentation load, termed Indentation Size Effect (ISE), was confirmed with Meyers index n = 1.9112 < 2. Pressed samples showed opposite behavior—an increase in hardness with increasing indentation load—where Meyers index n > 2 indicated Reverse Indentation Size Effect (RISE). For all samples, a high coefficient of determination R2 > 0.99 confirmed that Meyer’s law described this phenomenon well.

Imidazole added sulphamic acid single crystals with optimal properties for optoelectric devices

Single crystals of imidazole incorporated sulphamic acid (IMSA) of 12 × 7 × 7 mm3 dimension were successfully grown by slow evaporation technique. XRD study reveals that the grown crystal has the tetragonal structure. Various chemical groups formed in the sample have been found by FTIR spectral study. The linear optical parameters such as transmittance, reflectance, absorption coefficient, extinction coefficient, refractive index, optical conductivity and electrical conductivity of IMSA crystal have been analyzed Using UV–visible spectroscopy. Hardness studies reveal that the crystal shows reverse indentation size effect. An antibacterial activity developed by IMSA crystals against different pathogenic bacteria were examined using the Agar disk diffusion process. The antibacterial inhibitory activity of IMSA crystal revealed that it can be used to treat a variety of bacterial infections.

A comprehensive study on the mechanical properties of Yb2SiO5 as a potential environmental barrier coating

Yb2SiO5 is a promising damage tolerant material to be used as an environmental barrier coating (EBC) for silicon-based ceramic substrates. However limited research is available on its mechanical properties, thus hindering the detailed evaluation of its performance as a possible EBC candidate. In this work, dense Yb2SiO5 is synthesized from Yb2O3 and SiO2 and sintered at 1580 °C. The mechanical properties of the material, including Young's modulus, Vickers hardness and fracture toughness are comprehensively studied to better understand the reliability of Yb2SiO5 as an EBC. Yb2SiO5 has a low Young's modulus of 119 GPa leading to low thermal stresses when deposited on a SiC/SiC substrate. It also has a low hardness value of 6.4 GPa, but a comparatively high fracture toughness value of 1.97 GPa. The effect of different loads on hardness was also investigated and it was noted that Yb2SiO5 exhibits reverse indentation size effect (ISE). This suggests that Yb2SiO5 undergoes relaxation when loaded. These promising results show that Yb2SiO5 could be used as a potential candidate for EBC applications.

Investigation of structural, mechanical, optical, thermal and in vitro antimicrobial study of l-phenylalaninium formate single crystals

In this investigation, an organic single crystal of l-phenylalaninium formate (LPAF) has been successfully synthesized and grown by slow evaporation technique at ambient temperature using double distilled water as a solvent and their physiochemical and antimicrobial activities were tested. Single crystal X-ray diffraction studies indicate that LPAF belongs to orthorhombic configuration. The interaction of characteristic functional groups was confirmed by FTIR spectra. Mechanical behavior has been assessed by employing Vickers microhardness test. The results explored that the synthesized crystal exhibited reverse indentation size effect and belonged to the category of soft materials. UV–visible spectral analysis of the title compound shows 85% of transmittance with lower cut-off wavelength at 220 nm and the linear refractive index of the material was found to be 1.59. The photoluminescence spectrum of LPAF reveals that the emission of light occurs at 490 nm and it can be used as a material for blue lightening. The thermal tolerance and decomposition mechanism of the synthesized compound was examined by simultaneous TG-DTG-DSC analysis, which showed that material is thermally stable up to 205 °C and the melting point was observed to be 226.17 °C. The morphology of the synthesized crystal was analyzed by HR-TEM with SAED analysis and the result shows that the grown LPAF crystal is of good crystallinity. The antimicrobial activity of the grown crystal was evaluated against Gram-negative and Gram-positive bacteria as well as fungal pathogens by Agar disk diffusion method. The results established that the newly synthesized compound has a dual antibacterial and antifungal activity. Besides that LPAF showed powerful antibacterial activity against Gram-negative bacterium Pseudomonas aeruginosa and antifungal activity against a Gram-positive fungal Aspergillus flavus with zone of inhibition of 21 mm and 14 mm, respectively. These results signify that LPAF is a potential candidate for biomedical, photonic, and optical applications.

Structural, spectroscopic, thermal, electrical and mechanical properties of lanthanum chloride coordinated with salicylic acid and lanthanum chloride coordinated with glycine and salicylic acid complexes

Lanthanum chloride coordinated with salicylic acid (LaS) and lanthanum chloride coordinated with glycine and salicylic acid (LaGS) have been grown by slow evaporation technique at room temperature. The coordination and modes of vibration of different molecular group in the complexes are confirmed by Fourier transform infrared spectroscopy. Scanning electron microscopy (SEM) revealed the impact of glycine on the morphology of LaS complex. Absorbance spectrums are recorded, and the absence of absorbance peaks in the visible region suggests the potential of both the complexes to be used in second-harmonic generations. Optical parameters like band gap and extinction coefficient are determined. With the incorporation of glycine in LaS, the value of extinction coefficient decreases with an increase in energy. Photoluminescence spectroscopy shows a broad emission band with Gaussian-like curve shape for both the complexes. The highest peaks for LaS and LaGS lie in violet emission in the visible region; hence, such complexes find their applications for violet LED devices. The thermal stability and thermal decomposition of the complexes have been analyzed by thermogravimetric/differential thermo-analytical (TG/DTA). Kinetic and thermodynamic parameters such as activation energy, frequency factor, entropy and order of reaction were calculated using three equations, viz. Horowitz–Metzger, Coats–Redfern and Piloyan–Novikova. Dielectric constant decreases with the increase in temperature as well as frequency. Vickers hardness test revealed that hardness increases with the increase in load for both crystals, thereby representing reverse ISE effect. Meyer’s index (n) is found to be greater than ‘2’ and hence both the grown complexes belong to soft material category.

Analysis of indentation size effect (ISE) in nanoindentation hardness in polycrystalline PMN-PT piezoceramics with different domain configurations

Piezoelectric materials contain microstructural features (e.g., domain walls, interdomain spacing, and grain size) that span across several length scales, i.e., few nm in the case of interdomain wall spacing to several μm in case grain sizes. Recent experimental findings indicated that the domain configurations have more influence on the hardness of these materials than the grain size. In this study, nanoindentation experiments are conducted on polycrystalline PMN-PT (a relaxor ferroelectric material) with a focus to investigate the influence of domain configurations on the indentation size effect (ISE) in hardness, H. Different domain configurations are achieved by selectively annealing the as poled samples above and below the Curie temperature. Nanoindentation hardness is obtained in the load range of 1–5 mN with the maximum penetration depth well below the grain size of the samples. The experimental results reveal that all the samples, albeit to a different order, exhibit strong Reverse Indentation Size Effect (RISE) and normal ISE in H. The observed ISE is then analyzed using classical Meyer's law, the proportional specimen resistance (PSR) model and modified PSR (mPSR) model. The critical analysis of nanoindentation data reveals that the PSR model provides a satisfactory understanding of the genesis of RISE and ISE considering the elastic resistance of test material and frictional resistance at indenter facet/test material.

Load effect on the mechanical behaviour of zirconia-reinforced lithium silicate glass ceramics

The mechanical behaviour of pre-crystallized and crystallized zirconia-reinforced lithium silicate glass ceramics (ZLS) using micro-indentation techniques is reported. Vickers micro-indentations were conducted on these materials at the load of 0.245 N–9.8 N and 4.9 N–9.8 N to determine the load effect on the hardness and fracture toughness, respectively. The hardness increased with the load by 78.2% (ANOVA, p < 0.05) and 163% (ANOVA, p < 0.05) on pre-crystallized and crystallized ZLS, respectively, indicating the occurrence of the reverse indentation size effect (RISE) on both materials. The fracture toughness increased with the load by 20% and 12.3% on pre-crystallized and crystallized ZLS, respectively. Hardness data of both materials were analyzed using the Meyer's, indentation-induced cracking (IIC), proportional specimen resistance (PSR), modified PSR, Hays–Kendall and elastic plastic deformation (EPD) models. The Meyer's and IIC models described the RISE behaviour of both materials satisfactorily. The PSR, Hays–Kendall and EPD models provided consistent load-independent hardnesses while the modified PSR model gave erratic load-independent hardnesses for both materials. The continuum model provided intrinsic compressive yield strengths of both materials which were consistent with those obtained from the EPD model and the Tabor relation, implying the EPD model as the most successful. The brittleness index predicted better machinability for crystallized ZLS than pre-crystallized ZLS. Finally, the variations of hardness and fracture toughness with load might account for the different micro-material removal mechanisms in the sharp abrasive machining of these materials.

Thermo-mechanical properties of high density polyethylene with zinc oxide as a filler

This study investigates the microstructural, thermal, and mechanical behavior of high density polyethylene (HDPE)-based composites prepared using compression molding technique. HDPE was mixed with either micro-size zinc oxide (bulk ZnO) or zinc oxide nanoparticles (nano-ZnO) as fillers’ contents at 0, 10, 20, 30, and 40 wt%. The structural, morphological, and thermal properties of the composites were identified using X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectrophotometer (FTIR), and thermal gravimetric analysis (TGA). The results showed good dispersion and interaction mechanisms between HDPE and the fillers at low weight percentage. The thermal stability of HDPE was enhanced by adding both bulk and nano-ZnO, especially for higher filler loading. Tensile tests at different speeds and Vickers microhardness tests conducted at different indentation loads (0.25–5 N) at t = 60 s were performed to realize how the mechanical properties of the composites were influenced. The values of stiffness, ultimate tensile strength, and yield stress increased by increasing the filler loading to 20 wt% of either bulk ZnO or nano-ZnO. The values of ultimate tensile strain and ductility were deteriorated by increasing the filler loading. Nano-ZnO, at 20 wt% content in composite, showed higher mechanical properties than bulk composite, so it has been recommended for a better tensile performance at higher strain rates. Vickers microhardness measurements showed that the tested samples exhibited reverse indentation size effect (RISE) behavior. The obtained results were analyzed using Meyer’s law which was a preferred approach for analysis of HDPE/ZnO composite.