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A new ternary compound, Mg11-xZnxSr in the Mg-Zn-Sr system was observed and studied using Scanning Electron Microscopy (SEM), Energy-Dispersive Spectroscope (EDS), X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The XRD patterns were refined by the Rietveld refinement method and the results revealed that the crystallized Mg11-xZnxSr phase belonged to tetragonal I41/amd space group and had the Cd11Ba prototype. The Mg atoms were successfully doped into Zn11Sr crystal lattice by occupying Zn atomic sites. Moreover, the Rietveld refinement and computational results demonstrated a gradual decrease in the a-axis and c-axis lattice parameters with decreasing concentration levels of Mg coordination substitution in the lattice of Mg11-xZnxSr compound. The elastic constants and modulus of the Mg11-xZnxSr compounds calculated by first-principles calculations (FPC) indicated they were increased with the increasing of Zn content. The variation of hardness, d-band widths and the total density of states for Mg11-xZnxSr compounds with Zn content was discussed.

This study investigated the mechanical and tribological properties of branched polyethyleneimine/polyacrylic acid (bPEI/PAA) coatings. (bPEI/PAA) coatings were prepared on Ti6Al4V substrate using layer-by-layer assembly technique. The coatings have good tribological behaviors with the rotating mode under the deionized water. In particular, (bPEI/PAA)40 has the lowest friction coefficient with the reciprocating mode, about 0.14. The cross-linked network structures were formed with the electrostatic attraction. The amorphous phase of coatings provides a crucial buffer during the loads applying on the surface. The (bPEI/PAA)n coatings have the swelling ability, and there are large decreases of storage modulus and loss modulus in deionized water compared with removing from the deionized water. The excellent tribological properties are ascribed to the cross-linked network structure, amorphous phase, and swelling ability. [ABSTRACT FROM AUTHOR]

Coatings with tunable refractive index and high mechanical resilience are useful in optical systems. In this work, thin films of HfO2 doped with Al2O3 were deposited on silicon at 300 °C by using plasma-enhanced atomic layer deposition (PE-ALD). The mainly amorphous 60–80 nm thick films consisted Al in the range of 2 to 26 at.%. The refractive indexes varied from 1.69 to 2.08 at the wavelength of 632 nm, and they consistently depended on the composition. The differences were higher in the UV spectral region. At the same time, the hardness of the films was from 12–15 GPa; the modulus was in the range of 160–180 GPa; and the mechanical properties did not have a good correlation with the deposited compositions. The deposition conditions, element contents, and refractive indexes at respective wavelengths were correlated. The results indicated that it is possible to tune optical properties and retain mechanical properties of atomic layer-deposited thin films of HfO2 with Al2O3 as doping oxide. Such films could be used as mechanically resilient and optically tunable coatings in, for instance, micro- or nano-electromechanical systems or transparent displays. [ABSTRACT FROM AUTHOR]

Structural coloring of dental resin-based composites (RBC) is used to create universal chromatic materials designed to meet any aesthetic need, replacing the mixing and matching of multiple shades. The microstructural adjustments to create this desideratum involve nanoscale organic–inorganic core–shell structures with a particular arrangement. The generally higher polymer content associated with these structures compared to universal chromatic RBCs colored by pigments, which in their microstructure come close to regularly shaded RBCs, can influence the way the material ages. Accelerated and slow aging up to 1.2 years of immersion in artificial saliva at 37 °C were therefore compared in relation to their effects on the materials described above and in relation to the immersion conditions prescribed by standards. Quasi-static and viscoelastic parameters were assessed to quantify these effects by a depth-sensing indentation test equipped with a DMA module. The microstructure of the materials was characterized by scanning electron microscopy. The results convincingly show a differentiated influence of the aging protocol on the measured properties, which was more sensitively reflected in the viscoelastic behavior. Accelerated aging, previously associated with the clinical behavior of RBCs, shows a 2- to 10-fold greater effect compared to slow aging in artificial saliva of up to 1.2 years, highly dependent on the microstructure of the material. [ABSTRACT FROM AUTHOR]

A new ternary compound, Mg 11-x Zn x Sr in the Mg-Zn-Sr system was observed and studied using Scanning Electron Microscopy (SEM), Energy-Dispersive Spectroscope (EDS), X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The XRD patterns were refined by the Rietveld refinement method and the results revealed that the crystallized Mg 11-x Zn x Sr phase belonged to tetragonal I41/amd space group and had the Cd 11 Ba prototype. The Mg atoms were successfully doped into Zn 11 Sr crystal lattice by occupying Zn atomic sites. Moreover, the Rietveld refinement and computational results demonstrated a gradual decrease in the a- axis and c -axis lattice parameters with decreasing concentration levels of Mg coordination substitution in the lattice of Mg 11-x Zn x Sr compound. The elastic constants and modulus of the Mg 11-x Zn x Sr compounds calculated by first-principles calculations (FPC) indicated they were increased with the increasing of Zn content. The variation of hardness, d -band widths and the total density of states for Mg 11-x Zn x Sr compounds with Zn content was discussed. [ABSTRACT FROM AUTHOR]

A variety of rechargeable Na batteries are under development for use in energy storage systems. For these batteries, a Na-ion conducting solid electrolyte is desired. One such electrolyte under consideration is NaSICON (Na Super Ionic Conductor). One important aspect of the NaSICON electrolytes that has been overlooked is their mechanical properties. Such information is required if NaSICON has to be used as a solid electrolyte in rechargeable Na batteries that exhibit long life cycle and high power. This paper reviews the elastic, plastic, and fracture properties of NaSICON electrolytes. Young's modulus values for NaSICON range from ~ 56 to 97 GPa with Poisson's ratio ~ 0.26. Hardness values determined by micro-indentation for NaSiCON are 4.4–4.9 GPa. The value of the Gilman-Chin parameter suggests the bonding in NaSICON is covalent. As a result of its covalent bonding, NaSICON exhibits a high Peierls which leads to low fracture toughness, with KIC values ~ 1–1.5 MPa m0.5. The fracture strength of NaSICON is between 50 and 110 MPa and is controlled by the amount and size of the second-phase ZrO2 particles. [ABSTRACT FROM AUTHOR]

In this work, Gd2O3 bulks were sintered at temperatures ranging from 1400 °C to 1600 °C for times from 6 h to 24 h, and their microstructure and properties were studied for a wider application of materials in thermal barrier coatings. The densification of the Gd2O3 bulk reached 96.16% when it was sintered at 1600 °C for 24 h. The elastic modulus, hardness, fracture toughness and thermal conductivity of the bulks all increased with the rise in sintering temperature and extension of sintering time, while the coefficient of thermal expansion decreased. When the Gd2O3 bulk was sintered at 1600 °C for 24 h, it had the greatest elastic modulus, hardness, fracture toughness and thermal conductivity of 201.15 GPa, 9.13 GPa, 15.03 MPa·m0.5 and 2.75 W/(m·k) (at 1100 °C), respectively, as well as the smallest thermal expansion coefficients of 6.69 × 10−6/°C (at 1100 °C). [ABSTRACT FROM AUTHOR]

Coatings with tunable refractive index and high mechanical resilience are useful in optical systems. In this work, thin films of HfO2 doped with Al2O3 were deposited on silicon at 300 °C by using plasma-enhanced atomic layer deposition (PE-ALD). The mainly amorphous 60–80 nm thick films consisted Al in the range of 2 to 26 at.%. The refractive indexes varied from 1.69 to 2.08 at the wavelength of 632 nm, and they consistently depended on the composition. The differences were higher in the UV spectral region. At the same time, the hardness of the films was from 12–15 GPa; the modulus was in the range of 160–180 GPa; and the mechanical properties did not have a good correlation with the deposited compositions. The deposition conditions, element contents, and refractive indexes at respective wavelengths were correlated. The results indicated that it is possible to tune optical properties and retain mechanical properties of atomic layer-deposited thin films of HfO2 with Al2O3 as doping oxide. Such films could be used as mechanically resilient and optically tunable coatings in, for instance, micro- or nano-electromechanical systems or transparent displays.

Structural coloring of dental resin-based composites (RBC) is used to create universal chromatic materials designed to meet any aesthetic need, replacing the mixing and matching of multiple shades. The microstructural adjustments to create this desideratum involve nanoscale organic–inorganic core–shell structures with a particular arrangement. The generally higher polymer content associated with these structures compared to universal chromatic RBCs colored by pigments, which in their microstructure come close to regularly shaded RBCs, can influence the way the material ages. Accelerated and slow aging up to 1.2 years of immersion in artificial saliva at 37 °C were therefore compared in relation to their effects on the materials described above and in relation to the immersion conditions prescribed by standards. Quasi-static and viscoelastic parameters were assessed to quantify these effects by a depth-sensing indentation test equipped with a DMA module. The microstructure of the materials was characterized by scanning electron microscopy. The results convincingly show a differentiated influence of the aging protocol on the measured properties, which was more sensitively reflected in the viscoelastic behavior. Accelerated aging, previously associated with the clinical behavior of RBCs, shows a 2- to 10-fold greater effect compared to slow aging in artificial saliva of up to 1.2 years, highly dependent on the microstructure of the material.

Elaborating an instrumented nanoindentation is to exercise non-destructive tests to be applied to volumes of polymethylmetacrylate (PMMA) materials in miniature. This work focuses on factors that explain the trends variation of mechanical properties like Young's modulus (E), contact hardness (H) and indentation force (P). The evolution of E and H with depth (h) and P shows a 2.77 nm inflection point at low penetrations, separating two zones: the first increasing and the second decreasing. This is respectively explained by the surface hardening induced by preparing the material surface, and the existence of a surface hardness gradient denoted by an indentation size effect (ISE) observed at very low depths. Moreover, In addition, a critical penetration depth of 9.71 nm below which the surface effect dominates the variation of the penetrating load is detected. E and H results differences between dynamic and static modes are 8.46% and 6.44% inducing an overestimation of 35 MPa in E value, and an underestimation of 1.23 MPa in H value. This tends to affect the expected nanoscale precision of the indentation to determine the nanomechanical properties of PMMA.

In this work, Gd2O3 bulks were sintered at temperatures ranging from 1400 °C to 1600 °C for times from 6 h to 24 h, and their microstructure and properties were studied for a wider application of materials in thermal barrier coatings. The densification of the Gd2O3 bulk reached 96.16% when it was sintered at 1600 °C for 24 h. The elastic modulus, hardness, fracture toughness and thermal conductivity of the bulks all increased with the rise in sintering temperature and extension of sintering time, while the coefficient of thermal expansion decreased. When the Gd2O3 bulk was sintered at 1600 °C for 24 h, it had the greatest elastic modulus, hardness, fracture toughness and thermal conductivity of 201.15 GPa, 9.13 GPa, 15.03 MPa·m0.5 and 2.75 W/(m·k) (at 1100 °C), respectively, as well as the smallest thermal expansion coefficients of 6.69 × 10−6/°C (at 1100 °C).

Elaborating an instrumented nanoindentation is to exercise nondestructive tests to be applied to volumes of polymethylmetacrylate (PMMA) materials in miniature. This work focuses on factors that explain the trends variation of mechanical properties like Young's modulus (E), contact hardness (H) and indentation force (P). The evolution of E and H with depth (h) and P shows a 2.77 nm inflection point at low penetrations, separating two zones: the first increasing and the second decreasing. This is respectively explained by the surface hardening induced by preparing the material surface, and the existence of a surface hardness gradient denoted by an indentation size effect (ISE) observed at very low depths. Moreover, In addition, a critical penetration depth of 9.71 nm below which the surface effect dominates the variation of the penetrating load is detected. E and H results differences between dynamic and static modes are 8.46% and 6.44% inducing an overestimation of 35 MPa in E value, and an underestimation of 1.23 MPa in H value. This tends to affect the expected nanoscale precision of the indentation to determine the nanomechanical properties of PMMA. [ABSTRACT FROM AUTHOR]

Nanoindentation is widely used to investigate the surface-mechanical properties of biocomposites. In this study, polypropylene random copolymer (PPRC) and biowaste rice husk (BRH) were used as the main raw materials, and glass-fiber-reinforced polypropylene and talc were also used with BRH to enhance the mechanical characterization of the biocomposites. The interfacial bonding between the polymer and the rice husk was increased by treating them with maleic anhydride and NaOH, respectively. The results obtained from the nanoindentation indicated that the plastic behavior of the biocomposites was prominent when untreated BRH was used and vice versa. The modulus and hardness of the biocomposite improved by 44.8% and 54.8% due to the neat PPRC, respectively. The tribological properties were studied based on the hardness-to-modulus ratio and it was found that BRH- and talc-based biocomposites were better than other samples in terms of low friction and wear rate. The creep measurements showed that untreated rice husk biocomposite exhibited high resistance to load deformation.

Previous studies have dealt with Cr and its alloy films that exhibit promising characteristics as surface modification layers for antiwear, anticorrosive, and decorative applications. However, the effect of Ti alloying on the structure and mechanical properties of Cr films has not been studied. This work aimed to the structure and mechanical properties of Cr-Ti alloy films in the Cr-rich side. To this end, pure Cr, Cr-6 at.% Ti, Cr-11 at.% Ti, Cr-16 at.% Ti, and Cr-21 at.% Ti alloy films were prepared by magnetron sputtering, and the structure and mechanical properties of the films were evaluated. The results indicated that all the films exhibited a Cr-based growth with body-centered cubic structure, and increasing the Ti content decreased the (110) orientation growth of Cr basis. Ti alloying increased the hardness of the films, while leaded to a monotonic decrease in the modulus of the films. The first-principles method was employed to demonstrate that the reduced modulus was determined by the Ti alloying degree, rather than the orientation evolution of the films. The analysis of H/E value suggested that the wear resistance of the films was improved by Ti alloying. The mechanical properties of present Cr-Ti alloy films, and other Cr-based alloy films or metallic glasses in publications were compared and discussed. We proposed that Ti alloying is a considerable way to explore advanced mechanical properties of Cr-based alloy films.

Gd and Yb elements have high chemical stability, which can stabilize the solid solution in ZrO2. Gd2O3 and Yb2O3 have high melting points, and good oxidation resistance in extreme environments, stable chemical properties. Therefore, Gd2O3 and Yb2O3 were added to ZrO2 to stabilize oxides, improve the high temperature stability, and effectively decrease the thermal conductivity at high temperature. In this work, 5 wt% Yb2O3 and 5 wt%, 10 wt%, 15 wt% Gd2O3 were doped into 8 wt% Y2O3 stabilized ZrO2 (8YSZ) powders as thermal barrier coating materials, and sintered at 1650 °C for 6 h, 12 h, 24 h. The effects of Gd2O3 addition on the microstructure, density, thermal conductivity, hardness, and fracture toughness of Gd2O3-Yb2O3-Y2O3-ZrO2 (GYYZO) bulk composite ceramics were investigated. It was found that the densification of the 8YSZ bulk and GYYZO bulk with 15 wt% Gd2O3 reached 96.89% and 96.22% sintered at 1650 °C for 24 h. With the increase of Gd2O3 addition, the hardness, elastic modulus and fracture toughness of the GYYZO bulk increased and the thermal conductivity and thermal expansion coefficient of the GYYZO bulk decreased. GYYZO bulk with 15 wt% Gd2O3 sintered at 1650 °C for 24h had the highest hardness, elastic modulus and fracture toughness of 15.61 GPa, 306.88 GPa, 7.822 MPa·m0.5, and the lowest thermal conductivity and thermal expansion coefficient of 1.04 W/(m·k) and 7.89 × 10−6/°C at 1100 °C, respectively. The addition of Gd2O3 into YSZ could not only effectively reduce the thermal conductivity but also improve the mechanical properties, which would improve the thermal barrier coatings’ performances further.

In materials science and engineering, a significant amount of research has been carried out using indentation techniques in order to characterize the mechanical properties and microstructure of a broad range of natural and engineered materials. However, there are many unresearched or partly researched areas, such as, for example, the investigation of the shape of the indentation load–displacement curve, the associated mechanism in porous materials with clastic texture, and the influence of the texture on the constitutive behavior of the materials. In the present study, nanoindentation is employed in the analysis of the mechanical behavior of a benchmark material composed of plaster of Paris, which represents a brand of highly porous-clastic materials with a complex structure; such materials may find many applications in medicine, production industry, and energy sectors. The focus of the study is directed at the examination of the influence of the porous structure on the load–displacement response in loading and unloading phases based on nanoindentation experiments, as well as the variation with repeating the indentation in already indented locations. Events such as pop-in in the loading phase and bowing out and elbowing in the unloading phase of a given nanoindentation test are studied. Modulus, hardness, and the elastic stiffness values were additionally examined. The repeated indentation tests provided validations of various mechanisms in the loading and unloading phases of the indentation tests. The results from this study provide some fundamental insights into the interpretation of the nanoindentation behavior and the viscoelastic nature of porous-clastic materials. Some insights on the influence of indentation spacing to depth ratio were also obtained, providing scope for further studies.

Tantalum thin films may be deposited in two phases. The stable bulk alpha phase is well known, but the metastable tetragonal beta phase is relatively poorly understood. We reported previously on a series of 100% β -Ta films deposited under varying sputter pressures in a low-oxygen environment, and discussed texture, stresses, and phase selection. Here, we discuss microstructure, morphology, and properties of these same β -Ta films. Grain size increases with sputter pressure, which can be explained by the energies of incident species at the growing film. Mechanical properties were measured by nanoindentation. Hardness decreases with grain size in accordance with the Hall-Petch relation while comparison of indentation modulus with biaxial modulus measurements indicates that the β phase is elastically anisotropic, and much stiffer in the [001] direction than in others. Finally, a canonical resistivity value for virtually oxygen-free, 100% β -Ta films of 169 ± 5 µΩcm is reported for the first time. Image, graphical abstract [ABSTRACT FROM AUTHOR]

In this work, the effects of chemical pretreatment and different fiber loadings on mechanical properties of the composites at the sub-micron scale were studied through nanoindentation. The composites were prepared by incorporating choline chloride (ChCl) pretreated rice husk waste (RHW) in low-density polyethylene (LDPE) using melt processing, followed by a thermal press technique. Nanoindentation experiments with quasi continuous stiffness mode (QCSM) were performed on the surface of produced composites with varying content of pretreated RHW (i.e., 10, 15, and 20 wt.%). Elastic modulus, hardness, and creep properties of fabricated composites were measured as a function of contact depth. The results confirmed the appreciable changes in hardness, elastic modulus, and creep rate of the composites. Compliance curves indicated that the composite having 20 wt.% of pretreated RHW loading was harder compared to that of the pure LDPE and other composite samples. The values of elastic modulus and hardness of the composite containing 20 wt.% pretreated RHW were increased by 4.1% and 24% as compared to that of the pure LDPE, respectively. The creep rate of 42.65 nm/s and change in depth of 650.42 nm were also noted for the composite with RHW loading of 20 wt.%, which showed the substantial effect of holding time at an applied peak load of 100 mN. We believe that the developed composite could be a promising biodegradable packaging material due to its good tribo-mechanical performance.

Present work describes the mechanical behaviour of three virtual alloy systems comprising of matrix phase and W grains with fcc-bcc interface. The properties are evaluated for a composite tungsten heavy alloy. The compositions of the matrix phase have been considered similar to different tungsten heavy alloys (WHAs). The energy of the alloy systems decreases with increase in W contents. The lattice parameters of the matrix phase of WHAs are good agreement with those of the matrix phase of the virtual systems. The values of lattice constant, strength parameters (0.2 and 9% strain) and modulus increase with increase in W content. The nature of theoretical stress – strain curves of systems are similar to typical experimental ones. The addition of W increases the strength values and also shifts flow behaviour with higher strengths as function of strain. The yielding starts in typical WHAs in matrix phase only. [ABSTRACT FROM AUTHOR]

In this study, the influence of alloying elements on the mechanical properties of iron borides FeB and Fe2B formed in Fe-B-X (X = C, Cr, Mn, V, W, Mn + V) alloys were evaluated using instrumented indentation measurement. The microstructural characterization of the alloys was performed by means of X-ray diffraction and scanning electron microscope equipped with an energy dispersive X-ray analyzer. The fraction of the phases present in the alloys was determined either by the lever rule or by image analysis. The hardest and stiffest FeB formed in Fe-B-X (X = C, Cr, Mn) alloys was observed in the Fe-B-Cr alloys, where indentation hardness of HIT = 26.9 ± 1.4 GPa and indentation modulus of EIT = 486 ± 22 GPa were determined. The highest hardness of Fe2B was determined in the presence of tungsten as an alloying element, HIT = 20.8 ± 0.9 GPa. The lowest indentation hardness is measured in manganese alloyed FeB and Fe2B. In both FeB and Fe2B, an indentation size effect was observed, showing a decrease of hardness with increasing indentation depth.

Nano-indentation, a depth sensing technique, is a useful and exciting tool to investigate the surface mechanical properties of a wide range of materials, particularly polymers. Knowledge of the influence of experimental conditions employed during nano-indentation on the resultant nano-mechanical response is very important for the successful design of engineering components with appropriate surface properties. In this work, nano-indentation experiments were carried out by selecting various values of frequency, amplitude, contact depth, strain rate, holding time, and peak load. The results showed a significant effect of amplitude, frequency, and strain rate on the hardness and modulus of the considered polymer, ultrahigh molecular weight polyethylene (UHMWPE). Load-displacement curves showed a shift towards the lower indentation depths along with an increase in peak load by increasing the indentation amplitude or strain rate. The results also revealed the strong dependence of hardness and modulus on the holding time. The experimental data of creep depth as a function of holding time was successfully fitted with a logarithmic creep model (R2 ≥ 0.98). In order to remove the creeping effect and the nose problem, recommended holding times were proposed for the investigated polymer as a function of different applied loads.

In this paper, theoretical models of the critical indentation depth and critical force on brittle materials using cleavage strength and contact theory are proposed. A Berkovich indenter is adopted for nanoindentation tests on a 4H-SiC single crystal sample to evaluate its mechanical behaviors. The stages of brittle material deformation (elastic, plastic, and brittle) can be characterized by the load versus indentation depth curves through the nanoindentation test. The curve of the elastic deformation stage follows the Hertz contact theory, and plastic deformation occurs at an indentation depth of up to 10 nm. The mechanism of 4H-SiC single crystal cracking is discussed, and the critical indentation depth and critical force for the plastic−brittle transition are obtained through the occurrence of the pop-in point. This shows that the theoretical results have good coherence with the test results. Both the values of the elastic modulus and hardness decrease as the crack length increases. In order to obtain more accurate mechanical property values in the nanoindentation test for brittle materials such as SiC, GaN, and sapphire, an appropriate load that avoids surface cracks should be adopted.

The effect of aging on the nanohardness, modulus and creep properties of non-quenched and tempered steel wire strengthened by cold forming to an area reduction of 37% was investigated by nanoindentation. It was found that aging at 300 °C can improve the nanohardness, modulus, wear resistance and creep resistance of the cold-drawn non-quenched and tempered steel. An aging time longer than 2 h is not necessary since the degree of improvement decreases. The creep procedure of all tested samples includes two distinct stages, the transient creep and steady-state creep. Aging treatment slows down the creep rate at the steady-state stage. [ABSTRACT FROM AUTHOR]

Abstract: Mechanical anisotropy in an austenitic ferromagnetic shape memory alloy (SMA), Ni50Mn26.25Ga23.75, is investigated along (010), (120), (121), (231) and (232) using nanoindentation. While (010) exhibits the highest reduced modulus, Er, and hardness, H, (232) shows the lowest amongst the grain orientations examined in this study. The significant elastic anisotropy measured is attributed to differences in planar packing density and number of in-plane Ni–Mn and Ni–Ga bonds, whereas the plastic anisotropy is due to the differences in the onset of slip, which is rationalized by recourse to Schmid factor calculations. This would help determine the grain orientations in austenitic NiMnGa which exhibit better mechanical properties for SMA applications such as improving vibration damping characteristics of the alloy.

Mechanical properties of cylindrical bi-phasic high-entropy alloy CuZrTiAlNi (3 mm in diameter) were characterized by nanoindentation test in each phase. The results show that the constituent FCC phase is of low nanohardness (2.35 GPa) and modulus (60.9 GPa), while another constituent phase in the alloy, the HCP phase, shows much higher nanohardness (6.5 GPa) and modulus (115.3 GPa). Creep occurs in both phases during the indentation. [ABSTRACT FROM AUTHOR]

Nanoindentation is widely used to investigate the surface-mechanical properties of biocomposites. In this study, polypropylene random copolymer (PPRC) and biowaste rice husk (BRH) were used as the main raw materials, and glass-fiber-reinforced polypropylene and talc were also used with BRH to enhance the mechanical characterization of the biocomposites. The interfacial bonding between the polymer and the rice husk was increased by treating them with maleic anhydride and NaOH, respectively. The results obtained from the nanoindentation indicated that the plastic behavior of the biocomposites was prominent when untreated BRH was used and vice versa. The modulus and hardness of the biocomposite improved by 44.8% and 54.8% due to the neat PPRC, respectively. The tribological properties were studied based on the hardness-to-modulus ratio and it was found that BRH- and talc-based biocomposites were better than other samples in terms of low friction and wear rate. The creep measurements showed that untreated rice husk biocomposite exhibited high resistance to load deformation. [ABSTRACT FROM AUTHOR]

The experimental study on the modulus and hardness (in-press rigidity) of ettringite is carried out in this work. Firstly, the ettringite is obtained by chemical synthesis method. Secondly, samples are formed by filling the ettringite into resin matrix. Thirdly, the indentation modulus and hardness of ettringite are measured with different indentation depths by virtue of the instrument of MTS Nanoindenter XP. Finally, analysis on the modulus and hardness of the ettringite is performed according to the sample unloading curves. The results given by this work indicate that the magnitude of the modulus is 20.07 GPa and the hardness is 0.613 GPa. [ABSTRACT FROM AUTHOR]

Highlights: [•] Hardness of cured UF resins was evaluated by nanoindentation technique. [•] Both HB and HM value was consistently changed as a function of F/U mole ratio. [•] However, both Er and Es of cured UF resins displayed inconsistent trend. [•] Both HM and Er showed much greater in the COV at lower F/U mole ratios 1.0 and 1.2. [•] Crystalline structures in the low F/U mole UF resins contributed to this variability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Inclined nanohair arrays show excellent directional microdrop self-jumping. • The structure fabricated by nanoimprinting followed by oriented template removal. • Modulus and hardness influence the directional microdrop self-jumping. • Directional jumping is ascribed to the unbalanced lateral force. Anisotropic surfaces comprised of organized asymmetric nanostructures have provided the basis for diverse functions due to their direction-dependent properties, such as directional liquid self-transportation by condensed microdroplet self-jumping (CMDSJ). However, it is still a challenge to facile fabricate the organized asymmetric nanostructures to realize the directional CMDSJ. On the other hand, mechanical properties of the nanosurface is a key factor influencing the CMDSJ, which is always ignored. Here, inspired by the inclined tapered setae on the leg of water striders, inclined nanohair arrays which form a ratchet structure is facilely fabricated at low cost and large area by nanoimprinting followed by directional template removing. Microdroplets with diameter larger than 10 µm show directional CMDSJ on this surface whose mechanical properties (hardness and modulus) are strengthened by depositing silica nanoparticles. This is because the moving droplet suffers less lateral force which prevents the movement of the droplet as moving along the inclined direction of the nanohair than that moving along the opposite direction. The simulation result is corresponding to the experiment well. This work shows a facile way to obtain anisotropic structure with directional CMDSJ property and has a deep insight into how mechanical properties of the nanostructure influence the CMDSJ. [ABSTRACT FROM AUTHOR]

Gd and Yb elements have high chemical stability, which can stabilize the solid solution in ZrO2. Gd2O3 and Yb2O3 have high melting points, and good oxidation resistance in extreme environments, stable chemical properties. Therefore, Gd2O3 and Yb2O3 were added to ZrO2 to stabilize oxides, improve the high temperature stability, and effectively decrease the thermal conductivity at high temperature. In this work, 5 wt% Yb2O3 and 5 wt%, 10 wt%, 15 wt% Gd2O3 were doped into 8 wt% Y2O3 stabilized ZrO2 (8YSZ) powders as thermal barrier coating materials, and sintered at 1650 °C for 6 h, 12 h, 24 h. The effects of Gd2O3 addition on the microstructure, density, thermal conductivity, hardness, and fracture toughness of Gd2O3-Yb2O3-Y2O3-ZrO2 (GYYZO) bulk composite ceramics were investigated. It was found that the densification of the 8YSZ bulk and GYYZO bulk with 15 wt% Gd2O3 reached 96.89% and 96.22% sintered at 1650 °C for 24 h. With the increase of Gd2O3 addition, the hardness, elastic modulus and fracture toughness of the GYYZO bulk increased and the thermal conductivity and thermal expansion coefficient of the GYYZO bulk decreased. GYYZO bulk with 15 wt% Gd2O3 sintered at 1650 °C for 24h had the highest hardness, elastic modulus and fracture toughness of 15.61 GPa, 306.88 GPa, 7.822 MPa·m0.5, and the lowest thermal conductivity and thermal expansion coefficient of 1.04 W/(m·k) and 7.89 × 10−6/°C at 1100 °C, respectively. The addition of Gd2O3 into YSZ could not only effectively reduce the thermal conductivity but also improve the mechanical properties, which would improve the thermal barrier coatings' performances further. [ABSTRACT FROM AUTHOR]

Abstract: This paper scrutinizes the reliability of indentation-based damage quantification, frequently used by many industrial and academic researchers. In this methodology, damage evolution parameters for continuum damage models are experimentally measured by probing the deformation-induced degradation of either hardness or indentation modulus. In this critical assessment the damage evolution in different sheet metals was investigated using this indentation approach, whereby the obtained results were verified by other experimental techniques (scanning electron microscopy, X-ray microtomography and highly sensitive density measurements), and by finite element simulations. This extensive experimental–numerical assessment reveals that the damage-induced degradation of both hardness and modulus is at least partially, but most likely completely, masked by other deformation-induced microstructural mechanisms (e.g. grain shape change, strain hardening, texture development, residual stresses and indentation pile-up). It is therefore concluded that hardness-based or modulus-based damage quantification methods are intrinsically flawed and should not be used for the determination of a damage parameter. [Copyright &y& Elsevier]

In materials science and engineering, a significant amount of research has been carried out using indentation techniques in order to characterize the mechanical properties and microstructure of a broad range of natural and engineered materials. However, there are many unresearched or partly researched areas, such as, for example, the investigation of the shape of the indentation load–displacement curve, the associated mechanism in porous materials with clastic texture, and the influence of the texture on the constitutive behavior of the materials. In the present study, nanoindentation is employed in the analysis of the mechanical behavior of a benchmark material composed of plaster of Paris, which represents a brand of highly porous-clastic materials with a complex structure; such materials may find many applications in medicine, production industry, and energy sectors. The focus of the study is directed at the examination of the influence of the porous structure on the load–displacement response in loading and unloading phases based on nanoindentation experiments, as well as the variation with repeating the indentation in already indented locations. Events such as pop-in in the loading phase and bowing out and elbowing in the unloading phase of a given nanoindentation test are studied. Modulus, hardness, and the elastic stiffness values were additionally examined. The repeated indentation tests provided validations of various mechanisms in the loading and unloading phases of the indentation tests. The results from this study provide some fundamental insights into the interpretation of the nanoindentation behavior and the viscoelastic nature of porous-clastic materials. Some insights on the influence of indentation spacing to depth ratio were also obtained, providing scope for further studies. [ABSTRACT FROM AUTHOR]

The micro- and nano-indentation techniques and compression tests were employed to determine the mechanical properties of PZT based composites dispersed with Al2O3 nano-particles for comparison. Compared with the reduced modulus, the nano-hardness, which exhibited indentation size effect (ISE), seemed to be more sensitive to the indentation depth. The true hardness values were deduced, based on the modified proportional specimen resistance (PSR) model, from the depth sensing machine and micro-indenter. Both the micro- and nano-hardness of the nano-composites confirmed that the hardness was best improved by addition of 0.5wt% of Al2O3. [ABSTRACT FROM AUTHOR]

The objective of this study was to compare the hardness and modulus of the continuum of direct tooth-colored restorative materials using a depth-sensing microindentation approach. The effects of thermal fatigue on mechanical properties were also evaluated. Six restorative materials representing the continuum were selected. They included an ormocer (Admira [AM], Voco), a giomer (Beautifil [BF], Shofu), a compomer (Dyract Extra [DE], Dentsply), a minifill composite (Esthet-X [EX], Dentsply), resin-modified (Fuji II LC [FL], GC) and highly viscous (Fuji IX [FN], GC) glass ionomer cements (GICs). Fourteen specimens (3 mm wide×3 mm long×2 mm deep) were made for each material. The specimens were randomly divided into two groups and treated as follows: Group A—stored in distilled water at 37°C for 30 days; Group B—thermal cycled for 5000 cycles (35°C [28 s], 15°C [2 s], 35°C [28 s], 45°C [2 s]) and stored for 26.5 days. Hardness and modulus of the materials were determined using depth-sensing microindentation testing with the Instron MicroTester. Hardness was computed by dividing the peak load over the maximum projected contact area while modulus was calculated by analysis of the loading/unloading load–displacement (P–h) curves and the analytical model according to Oliver and Pharr (J. Mater. Res. 7 (1992) 1564). Results were analyzed using ANOVA/Scheffe''s post hoc test and independent samples T-test (p<0.05). Hardness ranged 46.44–72.65 and 49.11–78.97 HV, while modulus ranged 7.86–12.78 and 8.12–13.13 GPa for Groups A and B, respectively. Although the ranking of mechanical properties were generally similar for both groups, disparities in statistical differences between materials were observed between Groups A and B for both hardness and modulus. For both groups, BF was significantly harder than DE, AM, FL and EX was significantly harder than FL. The modulus of FN was significantly greater than EX, DE, AM and FL was significantly stiffer than AM. With the exception of BF, no significant change in hardness and modulus was observed for all materials with thermocycling. The hardness and modulus of some glass ionomer-based/containing materials may be comparable or even superior to minifill and ormocer composites. Thermal fatigue should be considered when comparing mechanical properties between materials. [Copyright &y& Elsevier]

Low-K dielectric films have reduced hardness and modulus relative to traditional dielectric materials. There are many potential challenges associated with these materials to integrate with integrated circuit (IC) technologies. It is important to evaluate the mechanical properties of low-K materials along with their electrical characterization to implement them in sub—0.25μm devices. In this investigation, we have discussed the mechanical properties of low-K dielectric materials and evaluated the mechanical behavior of SiLK and Xerogel samples using nano-indentation studies. Surface behavior after indentation is also investigated with high resolution scanning electron microscopy. Nano-indentation using the continuous stiffness measurement technique is shown to be reliable for evaluating the mechanical properties of thin and low modulus films. [ABSTRACT FROM AUTHOR]