Indentation Modulus Research Articles

Impact of Paraben on Uterine Collagen: An Integrated and Targeted Correlative Approach Using Second Harmonic Generation Microscopy, Nanoindentation, and Atomic Force Microscopy.

This study investigates the structural and mechanical changes in uterine collagen following exposure to propylparaben (PP), using a combined methodology of Second Harmonic Generation (SHG) microscopy, Nanoindentation (NI), and Atomic Force Microscopy (AFM). SHG analysis identified significant disorganization in collagen fibril orientation in the circumferential layer and heterogeneous distribution of regions with elevated forward to backward ratios (F/B) across all uterine layers due to PP exposure. High F/B can indicate multiple potential fibril-level changes like thickened fibrils, higher crosslinking, fibril disorganization - changes not fully decipherable by SHG alone. Recognizing this limitation, the study employs NI and AFM to provide complementary mechanical and nanoscale insights. NI revealed increased indentation modulus in the exposed uteri, suggesting increased stiffness. Co-registration of the indentation response with SHG parameters uncovered that elevated F/B regions show enhanced mechanical stiffness, suggesting a fibrotic transformation following PP exposure. AFM was specifically performed on regions identified by SHG as having low or high F/B, providing the necessary nanoscale resolution to elucidate the structural changes in fibrils that are likely responsible for the observed alterations. This approach confirmed the presence of disordered and entangled collagen fibrils in the circumferential layer in all regions and an increase in fibril diameter in the high F/B regions in the exposed uteri. Together, these findings demonstrate significant alterations in collagen architecture due to PP exposure, revealing disruptions at both the fiber and fibril levels and highlighting the potential for broader applications of the multi-scale, multi-modal approach in collagenous tissue studies.

Comparison of indentation test results and well-logging data for estimation of uniaxial compressive strength and Young’s modulus

Indentation test results and well-logging data are indirect methods of estimating Young’s modulus (E) and uniaxial compressive strength (UCS). The current study compared the results of indirect methods for a well in an oil field in southern Iran. The indentation tests were conducted by an indenter with a diameter of 260 µn on over 500 drill cuttings. The axial load versus displacement curve was used to determine the indentation modulus (IM) and critical transfer force (CTF) for each drill cutting. Indentation tests were performed perpendicularly and parallel to the weakness surface and were determined CTFV, IMV, CTFP, and IMV. The shear and compressive wave velocity (VS and VP ) for the well-logging data were determined and the UCS and static Young’s modulus (Esta.) were determined. Empirical equations for UCS-CTFV, UCS-CTFP, UCS-IMV, UCS-IMP, Esta-CTFV, Esta-CTFP, Esta-IMV, and Esta–IMP were proposed. It was determined that the relationships between UCS-CTFV and Esta-CTFV were more valid and meaningful than the other relationships. Therefore, it is suggested that the indentation test be performed perpendicular to drill cuttings with a weakness surface. The results showed that the values obtained for CTFV and IMV were 20% higher than for CTFP and IMP.

Quantitative characterization and mapping relationship between microstructure, composition, orientation, and mechanical properties of nickel-based superalloy Inconel 718

Abstract This study explores the relationship between the microstructure, composition, orientation, and mechanical properties of the nickel-based superalloy Inconel 718. Employing scanning electron microscopy (SEM), electron microprobe (EMP), nano-indentation, and other techniques, the study observes the structure, confirms the composition, determines orientation, and tests mechanical properties in specific micro-zones. Findings reveal a uniform grain distribution in Inconel 718, with a minor δ-phase presence at grain boundaries. There is a notable enrichment of Nb at the grain boundaries, whereas Fe and Cr levels are lower at these boundaries compared to the grain interiors. The indentation hardness and modulus at the grain boundaries are markedly higher than those within the grains. Moreover, grains with different orientations exhibit diverse microscale mechanical properties, such as hardness and elastic modulus. This research establishes a quantitative mapping relationship between the microstructure, composition, orientation, and mechanical properties of Inconel 718, providing a foundation for future multiscale (micro to macro) mechanical property investigations.

The impact of relative humidity on the nanoindentation relaxation in calcium silicate hydrates

Despite extensive research efforts, understanding the time-dependent behavior of concrete remains an enigma due to the complex nature of cement microstructure. In this study, the statistical nanoindentation was employed to investigate the influence of relative humidity (RH) on the relaxation behavior of calcium silicate hydrates (C-S-H) in a cement paste. Our experiments, performed at RH levels of 33 % and 86 %, revealed significant enhancements in both the indentation modulus and hardness of the C-S-H as RH increased. Remarkably, the internal water exerted a significant influence on the asymptotic relaxation behavior, displaying a clear power-law fashion. Further analysis identified the presence of short- and long-term viscoelastic behaviors within the C-S-H, distinguished by a transition observed within the initial seconds. These findings advance the understanding of nanoscale mechanisms driving concrete creep under different humidity conditions.

Estimates of natural frequencies for nuclear vibration, and an assessment of the feasibility of selective ultrasound ablation of cancer cells

Selective ablation of cancer cells by ultrasound would be transformative for cancer therapy, but has not yet been possible. A key challenge is that cancerous and non-cancerous cells typically have similar acoustic impedance and are thus indistinguishable as materials in their responses to ultrasound. However, in certain cancers, cytoskeletal and nuclear lamin structures differ between healthy and malignant cells, opening the possibility of exploiting structural differences that manifest as different vibrational responses. To assess the possibility that the nuclei of certain cancerous cells might vibrate at different frequencies, we measured sizes and effective indentation moduli of a range of cancerous and non-cancerous cells from several cell lines and regions of the brain, and estimated the natural frequencies for nuclear vibration. Results suggest a potential difference in natural frequency for nuclear vibration between certain cancerous and non-cancerous cells, on the order of tens of kHz. This gap is potentially sufficient for selective ablation and motivates future experimentation on these specific cell types.

Improved mechanical and tribological properties of (TiZrHfNbTa)C with the addition of silicon carbide whiskers

Dense (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C with up to 10 wt % SiC whisker were prepared by spark plasma sintering. The influence of SiCw on the microstructure development, mechanical and tribological properties has been investigated. Nanohardness of HEC and SiCw phases varied between 38 GPa and 40 GPa, and indentation modulus of elasticity was ∼605 GPa. The hardness of the composites increased from 22 GPa to 27 GPa and indentation fracture resistance from 3.55 MPa m1/2 to 4.59 MPa m1/2 with increasing SiCw content. The main toughening mechanisms were crack deflection, crack branching, and crack bridging. The system HEC +5 wt% of SiCw was found to possess the highest bending strength of 623 ± 25 MPa. The composites exhibited similar coefficients of frictions with around 0.3 and wear rates approximately 1.50 × 10−6 mm3/N⋅m at 5 N and 2.66 × 10−6 mm3/N⋅m at 25 N with positive influence of SiC phase on the wear mechanisms.

Time-varying moisture characteristics and C-S-H gel properties of concrete in dry and hot environments

The construction of deeply buried tunnels has intensified concerns regarding shrinkage cracking and the long-term performance deterioration of lining concrete in dry-hot environments. These issues are related to the dynamic interconversion of internal moisture states, the changing moisture behavior over time, and the evolution of calcium silicate hydrate (C-S-H) properties. However, the mechanisms underlying these phenomena are not fully understood. This study investigates the dynamics of moisture content across different states, the source and composition of evaporated water, as well as the mechanism of change in the microscopic properties of C-S-H in concrete subjected to dry-hot conditions (40℃ and 60℃) and standard curing environments through tests on water loss rates, chemically bound water, and low-field nuclear magnetic resonance. The findings reveal that at 40℃ and 60℃, hydration products were generated rapidly before mold removal, leading to significant increases in chemically bound water, interlayer water, and gel water, while capillary water was notably consumed. After mold removal, the rate of chemically bound water increase slowed, while interlayer water, gel water, and capillary water evaporated significantly, with gel water comprising 87.27 % and 83.51 % of the evaporated water at 40℃ and 60℃, respectively. From day 1 to day 28, interlayer water, gel water, and capillary water contents decreased significantly, with reductions of up to 85.98 % at 60℃. In dry-hot environments, moisture primarily exists as chemically bound water and gel water, contrasting with standard curing conditions where capillary water is also present. The study concludes that drying of C-S-H gels leads to both positive effects, such as interlayer space compression and increased indentation modulus, and negative effects, including increased microporosity and reduced matric densification, ultimately contributing to the deterioration of long-term mechanical properties.

Atomic force microscopy-based nanoindentation technique for characterizing the transverse and shear moduli of flax fibers

Experimentally evaluating the elastic properties of flax fibers is challenging due to their complex hierarchical structure, and a standard test procedure for measuring their transverse and shear moduli is currently not reported in the literature. Hence, this study presents an atomic force microscopy (AFM) based nanoindentation technique to evaluate the transverse and shear moduli of flax fiber. A high-precision focused ion beam (FIB)-milling process was used to fabricate a flat surface for indentation along the longitudinal fiber cross-section of the fiber and transverse fiber cross-section by polishing the unidirectional (UD) lamina in order to evaluate the indentation modulus. Further, Swanson's numerical contour approach was adopted to evaluate the elastic properties of the fiber from the measured indentation modulus. The accuracy of the experimentally obtained fiber properties is verified by using it in a micromechanics model for predicting the elastic properties of the UD lamina and comparing it with experimental results reported in the literature.

Influence of silver coated zeolite fillers on the chemical and mechanical properties of 3D-printed polyphenylene sulfone restorations

ObjectivesTo investigate the chemical and mechanical properties of polyphenylene sulfone (PPSU) depending on its composition and manufacturing. MethodsUnfilled–PPSU1 and with antimicrobial silver coated zeolites filled–PPSU2 specimens were made of granulate–GR, filament–FI, or printed–3D. Scanning microscopy and X-ray spectroscopy were performed. Martens hardness–HM, elastic indentation modulus–EIT and flexural strength–FS were determined initially and after aging. Shear bond strength–SBS to veneering and luting composite after conditioning with 7 adhesive systems were examined after aging. Silver leaching was tested after 1-, 3-, 7-, 14-, 21-, 28- and 42 days. Analyses of variance, Kolmogorov–Smirnov, Kruskal–Wallis, Mann–Whitney U, unpaired t-tests and Weibull modulus were computed (p < 0.05). ResultsZeolites were homogeneously distributed. PPSU1-GR and PPSU1-FI showed the highest HM/EIT, followed by PPSU2-GR, PPSU1-3D and PPSU2-3D. PPSU2-FI presented the lowest HM/EIT, displaying micro pits. Aging showed reduced HM/EIT in PPSU1 and no impact on PPSU2, while FS increased (PPSU1) or decreased (PPSU2). PPSU2-3D presented lower FS than PPSU1-3D. High SBS to the luting (7.0–16.2 MPa) and veneering composite (11.8–22.2 MPa), except for adhesive system PR, were observed. PPSU2-3D showed the highest silver release (9.6%), with all compositions dispensing silver over 42 days. ConclusionsFor the examined period of 6 weeks, antimicrobial silver ions were released from filled PPSU. The high SBS between PPSU and veneering/luting composite confirmed the feasibility of esthetically veneering and luting filled PPSU. To achieve mechanical properties like unfilled PPSU, the processing parameters of filled PPSU require refinement. Clinical significanceThis investigation provides proof of principle that PPSU can be successfully doped with silver-coated zeolites. The combination of 3D-printing with an antimicrobial thermoplastic constitutes a great opportunity in the field of prosthetic dentistry. Potential applications include clasps for removable dental prostheses, provisional or permanent fixed dental prostheses and implant abutments.

A comprehensive study on the microstructure evolution and mechanical property characterization of selective laser melted 18Ni300 stainless steel during heat treatment processes

The influence of different heat treatment processes on the microstructure and mechanical properties of 18Ni300 stainless steel manufactured by selective laser melting has been investigated in the present study. The microstructures, nanoprecipitates, and mechanical properties of the differently heat-treated samples were analyzed using various precision instruments. Compared with a non-treated 18Ni300 stainless steel sample, the results showed that the microstructure was mainly composed of fine lath-like martensite, with a large number of nano-precipitates dispersed both within the martensite and in the boundaries. In addition, there was a preserved amount of austenite between the lath-like martensite and the spherical nanoprecipitate in the SAT sample. The interactions between the martensite matrix and the nanoprecipitates and dislocations were assumed to be the main reason for the high strength of 18Ni300 stainless steel. These precipitates included rod-shaped or needle-shaped, Ni3Ti, Ni3Mo, and Ni3(Ti, Mo) nano-precipitates, as well as spherical Ti–Al nano-oxidized precipitates and massive Ni-rich precipitates. The shear and by-pass mechanisms between the strengthened nano-precipitate and the dislocations were found to depend on the size of the nanoprecipitate. The influence of the nanoprecipitation on the indentation hardness became more evident after heat treatment, but the effect on the indentation modulus was not that obvious. The AT- and SAT-treatments significantly improve the strength, hardness, and modulus of samples but were found to reduce the toughness and plasticity. After the AT- and SAT-treatments, the protrusions became smaller, and the small isometric protrusion of a shear lip became significantly smaller than for the as-built material.

Structural, mechanical, corrosion, and early biological assessment of tantalum nitride coatings deposited by reactive HiTUS

This study examined microstructure, mechanical, corrosion properties and initial biological evaluation of the tantalum nitride (Ta-xN, where x – nitrogen flow rate during deposition) coatings prepared by reactive High Utilization Sputtering (HiTUS) at various nitrogen flow rates (x = 0, 2, 4, 6, and 8 sccm). Coatings were deposited on a novel Mg alloy (Mgbal.-Zn0.9-Y2.05-Al0.25 at. %) containing long-period stacking ordered (LPSO) phases. The coatings' structure was analyzed using a combination of SEM/FIB/TEM techniques, while XRD determined the phase composition. The mechanical parameters investigated included hardness, indentation modulus, and scratch behavior. The corrosion resistance of the coatings with respect to the bare substrate was evaluated in chloride-containing solutions. The wettability and early biological assessment of the coatings were also examined. The phase evolution strongly influenced the hardness and indentation modulus. The Ta-xN coatings made at x = 2 sccm nitrogen corresponding to HCP-Ta2N exhibited the highest hardness and indentation modulus. An increase in nitrogen flow rates resulted in the formation of FCC structure with slightly reduced hardness and indentation modulus. In addition, Ta-xN coatings (x ≥ 4sccm) showed superior corrosion resistance compared to BCC structured α-Ta, enhancing the corrosion performance of the Mg-LPSO bulk substrate. Finally, at the early incubation stage (24 h), L929 fibroblasts exhibited better cell attachment to the Ta-6N coating than to the bare Mg-LPSO substrate.

A mechanical TiAl/TiAlN multinanolayer coating model based on microstructural analysis and nanoindentation

A finite element model reproducing the mechanical behaviour during nanoindentation tests on Ti0.67Al0.33/Ti0.54Al0.46N multilayer coatings was developed. Coatings with two different nanoperiods (10 and 50 nm) were deposited by radio-frequency magnetron sputtering from a single sintered titanium/aluminium target using the reactive gas pulsing process. X-ray diffraction and transmission electron microscopy confirmed the multilayer stacking of the coatings. The finite element models of coatings with these two stacking periods were built considering successive hypotheses: equal thicknesses for metal and nitride nanolayers stacked without transition layer, equal thicknesses stacking with a transition layer between each metal and nitride nanolayer and finally imbalanced thicknesses stacking with a transition layer. The elastic and plastic properties of the stacked nanolayers were determined on thick monolithic coatings of metal and nitride using indentation testing and the finite element model updating method respectively. The elastic-plastic properties of the interface were introduced in the multilayer model as a rule of mixtures of the metal and nitride properties using two hypotheses: parallel or serial. For 50 nm-period film, the interface has a negligible effect on the overall indentation response. On the other hand, for the 10 nm period, the imbalanced stacking model with precise knowledge of the transition layer thickness obtained by N K-edge electron energy loss spectroscopy is required to reproduce the experimental indentation curve. Compared to classical analytical models accounting for hardness, not only the hardnesses but also the indentation moduli appear to be well predicted and evaluated in this work.

Underwater carbonation of alkali-activated slag pastes

Carbonation of alkali-activated slag (AAS) materials has been primarily concerned in atmospheres with gaseous CO2. This study, by contrast, highlights that AAS pastes would also be carbonated under tap water immersion. Calcite is the main CO2-bear phase in both sodium hydroxide- and sodium silicate-activated AAS pastes, and the paste pre-cured for a longer curing period shows more severe carbonation. Additionally, calcium carbonate can densify the deteriorated microstructure of sodium hydroxide-activated paste caused by long-term leaching. The indentation modulus of pastes subjected to tap water immersion is higher than those under deionized water immersion. The uptake of CO32- by hydrotalcite (Ht) and gels is also detected, resulting in the formation of Ht-CO3 and decalcification of gels. Due to the synergistic effect of leaching and carbonation, a characteristic layered distribution of pastes close to the exposure front is observed, comprising the carbonated layer, transitional (carbonated + leached) layer, and leached layer, progressing from the outermost to the inner regions. Eventually, the kinetics of underwater carbonation, as well as the discrepancy between dry and underwater carbonation, is revealed.

Cold-sintered laterite-based geopolymers: Densification, microstructure and micromechanics

The consolidation of natural iron-rich aluminosilicates is enhanced using geopolymerisation, external pressure, and temperature in a ultra-low energy sintering context. Optimized formulations of laterite and Rice Husk Ash (RHA) are used to investigate the effects of the external pressure and temperature on the porosity, phases composition development, micromechanics and microstructure. FT-IR spectroscopy, scanning electron microscopy (SEM 0, Mercury Intrusion Porosimetry (MIP), Transmission Electronic Microscopy (TEM), and the Archimedes Porosimetry method were used to characterize the cold sintered products of geopolymerization of the iron-rich aluminosilicate binders and composites. Results showed that ultra-low energy sintering process allows the reduction of ∼ 99 % of capillary porosity thank to the physico-chemical bonding and the formation of enhanced nanosized ferrisilicates. The indentation modulus > 50 GPa, the hardness modulus of 3,18 GPa and the fracture toughness > 1 MPa m0.5 are in agreement with the compact microstructure, high bulk density (> 2.00 g.cm−3), and low water Absorption. The interlocking of globular units of H-N-(A, Fe)-S with nanosized ferrisilicates leads to high performance ceramics that cannot be achieved with conventional sintering process. Therefore, the cold sintering process demonstrated here is promising for the manufacturing of sustainable matrices using natural iron-rich aluminosilicates.

Processing-Microstructure-Mechanical Property Paradigm in Hot Rolled Ti-6Al-4V Alloy

Abstract The effects of hot rolling temperature and subsequent cooling at different cooling rates on the microstructure, texture, and mechanical properties of α + β titanium alloy Ti-6Al-4V were studied using a battery of structural and mechanical characterization tools. To this end, Ti-6Al-4V samples were subjected to a rolling reduction of 50 % below the β-transus (750°C and 850°C) and near the β-transus (950°C) temperature followed by water quenching and air cooling. Detailed electron back scatter diffraction provided information on the fraction, morphology, and orientation of the alpha and β-phases for different processing conditions and bulk texture analysis provided information on the orientation relationship at the macroscale. Mechanical properties, like hardness and modulus, were determined at different length scales using the Vickers microhardness experiment, instrumented microindentation, and nanoindentation. Hot rolling at sub β-transus temperatures (750°C and 850°C) leads to the equiaxed morphology of the α-phase and the absence of a Burgers orientation relationship (BOR) with the β-phase, whereas near the β-transus, hot rolling leads to the multi-variant lamellar morphology of the α-phase and a strong BOR with the β-phase for both the cooling conditions. Hot rolling at 850°C followed by water quenching showed an optimum combination of indentation hardness and modulus. This has been primarily attributed to the relatively low kernel average misorientation of the basal-prism-oriented grains compared with the prism-pyramidal oriented grains after indentation. The basal oriented grains are both elastically and plastically harder compared with the prism-oriented grains that are elastically soft but plastically hard. The orientation specific indentation hardness property is reflected in the microhardness property for sub β-transus deformed samples. A clear processing-microstructure-texture-mechanical property paradigm in the context of variant selection and distinct cooling rates for hot rolling of Ti-6Al-4V is established.

Synthesis and property enhancement of Ti-Si/SiC composites by reactive infiltration for semiconductor applications

Poor machinability and limited electrical conductivity present significant challenges for silicon carbide (SiC) composites used in the semiconductor industry. In this study, Ti-Si/SiC composites were synthesized by liquid infiltration of a Ti-Si eutectic alloy, using SiC and Carbon black as raw materials. The reactive sintering mechanism and properties of Ti-Si/SiC composites were investigated using the reactive infiltration sintering process. The relative density of Ti-Si/SiC composites reached 98.43 % at 1600 °C. The results indicate that continuous infiltration of the Ti-Si eutectic alloy and dissolution-reprecipitation are critical for synthesizing Ti-Si/SiC composites. The coefficient of thermal expansion for the composites is 5.16 × 10−6 °C−1. Remarkably, the exponential increase in electrical conductivity with rising temperature strongly supports the enhanced conductive properties of this composite semiconductor. The Ti-Si/SiC composites exhibit maximum flexural strength, indentation modulus, and hardness values of 310.4 MPa, 434.1 GPa, and 29.4 GPa, respectively. This research aims to advance the application of high-performance Ti-Si/SiC materials in semiconductor technology.

Physico-Mechanical Properties and Bonding Performance of Graphene-Added Orthodontic Adhesives.

This study aimed to assess the key physico-mechanical properties and bonding performance of orthodontic adhesives with graphene addition for bonding a fixed retainer. Transbond LR (3M) and Transbond LV (3M) with no graphene were set as the control groups. Graphene was added into LR and LV at concentrations of 0.01 wt%, 0.05 wt% and 0.1 wt%. The stickiness of the uncured samples (n = 5) and real-time degree of conversion (DC) of the samples (n = 3) were measured over a 24-h period using Fourier-transform infrared spectroscopy. The hardness and other mechanical parameters, including the Martens hardness (HM), indentation modulus (EIT), elastic index (ηIT) and creep (CIT), were measured (n = 5). To measure the shear bond strength (SBS), adhesive composites were applied using a mold to bond the retainer wire to the lingual surfaces of bovine incisors (n = 10). Fracture modes subsequent to the SBS test were examined under light microscopy. Statistical analysis was conducted using ANOVA and Tukey tests (α = 0.05). In the LR groups, the LR + 0.01 showed the highest SBS (12.6 ± 2.0 MPa) and HM (539.4 ± 17.9 N/mm2), while the LV + 0.05 (7.7 ± 1.1 MPa) had the highest SBS and the LV + 0.1 had the highest HM (312.4 ± 17.8 N/mm2) among the LV groups. The most frequent failure mode observed was adhesive fracture followed by mixed fracture. No statistical difference was found between the graphene-added groups and the control groups in terms of the EIT, ηIT and CIT, except that the CIT was significantly lower in the LR + 0.01 than in the control group. Graphene addition had no significant adverse effect on the stickiness and DC of both LR and LV.

Sheet Forming via Limiting Dome Height (LDH) Test: Influence of the Application of Lubricants, Location and Sheet Thickness on the Micro-Mechanical Properties of X8CrMnNi19-6-3

This work is concerned with forming, specifically deep drawing, and its influence on the micro-mechanical properties of sheet metal. In practice, there are several applications in which fractions can occur due to weak spots in the deep-drawn sheet metal, especially after long-term use. The deep drawing process was carried out on BUP–600 machines using the LHD (Limiting Dome Height) method, which uses a forming tool with a diameter of 100 mm and bead groove. Sheet metals X8CrMnNi19-6-3 (1.4376) with thicknesses of 1, 1.5, and 3 mm were selected for this process. To study the effect of a lubricant on the formability of the sheet metal, deep drawing without and with a lubricant was compared. An FEM analysis was conducted to identify critical points in the deep drawing process, and the results were later compared with real results. The analysis was conducted using the AutoForm program. The micro-mechanical properties of these points were subsequently examined. The specified points on the formed part showed significant differences in their micro-mechanical properties, suggesting a higher strength but also less resistance to fractures. The difference in micro-mechanical properties (indentation and Vickers hardness) in points that were not deep-drawn and points located in critical areas was up to 86%. Significant changes in behavior were found in the indentation modulus and plastic/elastic deformation work as well. This study demonstrates the significant effect of the use of a lubricant in achieving the deep drawing of the sheet metal. The application of a lubricant resulted in a 33% increase in drawing range compared to drawing without lubrication. This study has a significant influence on the deep drawing of sheet metals in practice, showing the fundamental influence of the lubricant on the drawing process and also showing the problem of critical points that need to be eliminated.

Combining fast scanning chip calorimetry and nanoindentation: Young's modulus and hardness of poly (l-lactic acid) containing α′- and α-crystals

Fast scanning chip calorimetry (FSC) allows subjecting polymer melts to well-defined vitrification, crystal nucleation, and crystal growth pathways and, therefore, precise control of morphologies, from fully amorphous glassy states to semicrystalline structures containing perfect crystals. Due to the required use of nanogram-sized samples, needed to achieve high cooling rates, their mechanical properties, in order to establish structure-property relations, are difficult to assess. In this work, indentation modulus and indentation hardness of FSC samples are successfully determined on example of semicrystalline poly (ʟ-lactic acid) (PLLA) containing spherulitically grown disorder α′- or rather perfect α-crystals, with the correctness of the applied preparation and analyses routes confirmed by nanoindentation measurements on milligram-sized samples prepared through hotstage microscopy, and by applying both static single-step and quasi-continuous stiffness measurements. Modulus and hardness data are consistent with prior analyses of bulk samples, confirming that semicrystalline PLLA containing α-crystals exhibits around 10–20 % higher values of these properties compared to PLLA containing α′-crystals, related to the different molecular-chain packing in the crystal lattice. This work demonstrates that combination of FSC and nanoindentation techniques is an effective tool for determining mechanical properties of samples solidified at specific thermal pathways which otherwise cannot be realized.

Instrumented indentation of PMMA/ZnO nanocomposites films

Piezoelectric nanocomposite films comprise zinc oxide (ZnO) nanoparticles as reinforcement and poly-methyl methacrylate (PMMA) as the matrix. These films can potentially be used as structural and functional components of microdevices that can harvest energy from ambient mechanical vibrations. The design of such energy-scavenging micro/nano-systems will require knowledge of the process-microstructure-property relationships of nanocomposite films. This study synthesized PMMA/ZnO nanocomposite films using ultrasonic probe sonication and solution-casting. The nanomechanical characterization of the nanocomposite films was conducted using a nanoindenter via quasi-static mode. Quasi-static nanoindentation revealed that the indentation modulus ranged from 3.49 ± 0.03 GPa for PMMA to 4.71 ± 0.07 GPa for PMMA/ZnO 5 wt% nanocomposite film. However, the indentation modulus of 10 wt% ZnO nanocomposites decreases, i.e. 4.22 ± 0.60 GPa. The indentation hardness varied from 311.97 ± 6 MPa for PMMA thermoplastic polymer to 432.94 ± 83.81 MPa for PMMA/ZnO 10 wt% nanocomposites film. In addition, the properties of the nanocomposite film vary, as supported by scanning electron micrographs.