Coefficient Of Thermal Expansion Values Research Articles

A novel SiC composite material infiltrated by basalt glass-ceramic with a high hardness

New high-performance materials for environments with high abrasive and erosive loads resistant are in a great demand for the modern industry. For the first time, a composite material obtained by infiltration of SiC porous oxide bonded preform with a basalt rock melt at a temperature of 1400 °C in air was proposed. The produced composite material significantly reduces porosity from 31.0 to 1.2%. Interestingly, an aluminosilicate phases crystallizes on the surface of SiC grains meanwhile the migration of Ca and Fe to the melt basalt volume due to atomic radii mismatch with the forming phases. The crystallinity of the basalt glass matrix obtained by petrurgical method is 66.9%. All together allows to improve hardness of the obtained composite material SiC/basalt glass-ceramics from 2.6 (preform) and 6.8 (basalt glass ceramics) to >9.6 GPa. The composite material fracture toughness (K1c ∼ 0.85 MPa·m1/2) also increases in comparison to a highly fragile basalt glass ceramics matrix. Thermal expansion coefficient value of the produced composite material is close to the dense polycrystalline SiC one and no sample destruction was observed caused by materials TEC mismatch.

Experimental study on pre-hydrogenation of catalytic slurry oil and co-carbonization of middle distillate and high boiling point distillate

A catalytic slurry oil (SO) was treated by moderate pre-hydrotreating, and the structural compositions, the thermal stability, the distillate oil yield, and the coking behavior of SO before and after hydrotreating were analyzed. The carbonization performance as well as the co-carbonization performance of the middle distillate (350–500 °C) and the high boiling point distillate (500–550 °C) derived from the hydrogenated SO (HSO) were investigated. The results show that the content of naphthenes and hydrogenated aromatics of HSO increases, while the olefin content decreases, and the olefinic hydrogen content of HSO decreases from 2.71% to 0.97%. Thus, the thermal stability of HSO is fundamentally improved. Additionally, compared with SO, the yields of the middle distillate and the high boiling point distillate of HSO increased by 25.8% and 23.1%, respectively. More importantly, there is no significant coke formation during distillation of HSO. The carbonization experimental results show that the anisotropic textural structure of the coke obtained from the middle distillate derived from HSO is the large flow domain structure, and the coke has the lowest coefficient of thermal expansion (CTE) value of 2.25×10−6 °C−1. The carbonization performance of the high boiling point distillate derived from HSO is poor, while the co-carbonization with the middle distillate significantly improves the carbonization performance of the high boiling point distillate. The anisotropic textural structure of the coke derived from carbonization of combined fraction is the large flow domain structure and the CTE value is less than 2.30×10−6 °C−1, when the mass ratio of aromatic fraction to middle fraction is not higher than 2:1.

Dependence of the formation of the five-layer Aurivillius phase on the chemical prehistory of the Initial composition

Materials with a layered perovskite-like structure of the Aurivillius phase type are important for such fields of technology as magnetoelectronics and photocatalysis. The paper describes the features of phase formation during the synthesis of nano- and macrocrystalline materials based on the Bi6Fe2Ti3O18/ 8 compound with the five-layer Aurivillius phase structure. Samples were characterized by powder XRD, DSC/TG, dilatometry, SEM/EDX. The temperatures of the beginning of formation, the Curie point, the beginning of decomposition and activation of sintering of the obtained materials, as well as the value of the linear thermal expansion coefficient were determined. The technological possibility of controlling the dispersion of the obtained materials by changing the synthesis conditions is shown. Ill. 5. Ref. 20. Tab. 1.

Comparison of five empirical potential models for aluminosilicate systems: Albite and anorthite as test cases

In this work we have carried out a systematic investigation of the performance of different force fields in correctly reproducing the structure, densities as a function of temperature and the properties (Young's and Bulk moduli and the coefficient of thermal expansion) of both albite and anorthite crystals and glasses. After this first step of comparison, we selected the potential which gave the better overall performances (the Bertani-Menziani-Pedone potential) and investigated the effect of the cooling rate on structure and properties of albite and anorthite glasses and verified the predicting power of MD simulations for the simulation of the coefficient of thermal expansion (CTE) for a series of several aluminosilicate glasses whose compositions go from the albite-like one to the anorthite-like one.The tested interatomic potentials provide reliable short-range order around the constituting cations, but some differences are detected in the medium-range order described by the T-O-T angles (T= network formers cations, Si and Al), the Al/Si distributions and Qn distributions. In general, all the potentials overestimate the CTE because of the high quenching rate used but we have shown that extrapolated properties at room temperature provide a more reliable comparison with experiments. The CTE trend of the albite-anorthite plagioclase glass series is well reproduced and associated with the substitution of Na with Ca ions rather than the Al/Si one. The error associated with the computed CTE values decreases with box dimension and we found that simulation boxes containing 50k atoms are necessary to reliably estimate this property.

Low-temperature thermal expansion behavior of the entropy-stabilized oxide (MgCoNiCuZn)O

The coefficient of thermal expansion (CTE) of entropy-stabilized oxide (MgCoNiCuZn)O has been firstly experimentally measured and studied at low temperatures below room temperature. The temperature-dependent lattice parameters of (MgCoNiCuZn)O were determined by synchrotron X-ray diffractometry. A CTE value of α = 2.2780x10-5 K−1 at 113 K for (MgCoNiCuZn)O was calculated using a second-degree polynomial fitting. The quenched homogeneous NaCl-type (MgCoNiCuZn)O structure has the highest CTE value below 133 K among all its constituent oxides. An unquenched (MgCoNiCuZn)O was also investigated, and the homogeneity was found to affect CTE values. Finally, the anisotropic behavior of the constituent oxides and (MgCoNiCuZn)O were also compared.

Effect of eggshell powder on the microstructural and thermal behavior of Al7075/waste eggshell surface composites produced by solid-state friction stir processing developed for potential thermal applications

Lightweight composite materials for potential thermal applications are the contemporary demand for manufacturing and aircraft industries where the possibility to improve and tailor the desired properties is based on the application. Carbonized eggshell powder is a solid lubricant with absorbent capability and has proven as a reinforcement for metallic base composites. In the present work, an attempt is made to investigate the effect of carbonized chicken eggshell powder (3 to 9% by weight) on the microstructural and thermal properties of Al7075 alloy processed by solid-state friction stir processing. An infrared thermography and three K-type thermocouples equipped with the base plate at three equal distances are used to measure the temperature with respect to time. The comparative study of microstructure and grain structure analysis has been done by light microscopy, scanning electron microscopy, and electron backscattered diffraction methods. The findings explored the dynamic recrystallization and grain recovery with a reduced grain size of 6.2 to 10.3 µm at a varying percentage of eggshell powder (3 to 9%) in the stir zone. The thermal conductivity and coefficient of thermal expansion (CTE) were measured for the temperature range of 50 to 400 °C. In addition to it, differential thermal analysis (DTA), thermo-gravimetric analysis (TGA), and derivative thermo-gravimetric analysis (DTG) are conducted for the temperature range of 25 to 900 °C to discuss the endothermic, exothermic nature, and degradation characteristics. The result revealed the decreasing trend of thermal conductivity, and CTE values were found in the range of 97 to 53 W/mK and 26.6 to 24 × 10−6 K−1 (heating cycle), 27.2 to 23.8 × 10−6 K−1(cooling cycle), respectively. Furthermore, the higher and lower thermal conductivity of 108 W/mK and 62 W/mK is observed at higher and lower terminal voltages, 250 V and 100 V, respectively. The DTA, TGA, and DTG curves explored the maximum weight loss, which varies up to 5.25% with exothermic peaks and decomposition steps for each surface composite.

Effects of electrode materials on the performance of Zr0.75Hf0.25O2-based ferroelectric thin films via post deposition annealing

In this work, the effects of top electrode (TE) and bottom electrode (BE) on the ferroelectric properties of zirconia-based Zr0.75Hf0.25O2 (ZHO) thin films annealed by post-deposition annealing (PDA) are investigated in detail. Among W/ZHO/BE capacitors (BE = W, Cr or TiN), W/ZHO/W delivered the highest ferroelectric remanent polarization and the best endurance performance, revealing that the BE with a smaller coefficient of thermal expansion (CTE) plays a vital role in enhancing the ferroelectricity of fluorite-structure ZHO. For TE/ZHO/W structures (TE = W, Pt, Ni, TaN or TiN), the stability of TE metals seems to have a larger impact on the performance over their CTE values. This work provides a guideline to modulate and optimize the ferroelectric performance of PDA-treated ZHO-based thin films.

Temperature-dependent elastic constants of thorium dioxide probed using time-domain Brillouin scattering

We report the adiabatic elastic constants of single-crystal thorium dioxide over a temperature range of 77–350 K. Time-domain Brillouin scattering, an all-optical, non-contact picosecond ultrasonic technique, is used to generate and detect coherent acoustic phonons that propagate in the bulk perpendicular to the surface of the crystal. These coherent acoustic lattice vibrations have been monitored in two hydrothermally grown single-crystal thorium dioxide samples along the (100) and (311) crystallographic directions. The three independent elastic constants of the cubic crystal (C11, C12, and C44) are determined from the measured bulk acoustic velocities. The longitudinal wave along the (100) orientation provided a direct measurement of C11. Measurement of C44 and C12 was achieved by enhancing the intensity of quasi-shear mode in a (311) oriented crystal by adjusting the polarization angle relative to the crystal axes. We find the magnitude of softening of the three elastic constants to be ∼2.5% over the measured temperature range. Good agreement is found between the measured elastic constants with previously reported values at room temperature, and between the measured temperature-dependent bulk modulus with calculated values. We find that semi-empirical models capturing lattice anharmonicity adequately reproduce the observed trend. We also determine the acoustic Grüneisen anharmonicity parameter from the experimentally derived temperature-dependent bulk modulus and previously reported temperature-dependent values of volumetric thermal expansion coefficient and heat capacity. This work presents measurements of the temperature-dependent elasticity in single-crystal thorium dioxide at cryogenic temperature and provides a basis for testing ab initio theoretical models and evaluating the impact of anharmonicity on thermophysical properties.

Determination of the coefficient of thermal expansion of ultra-low-expansion glass using anultrasonic immersion testing method.

The coefficient of thermal expansion (CTE) of ultra-low-expansion (ULE) glass is critical to the development of precision optical systems. Herein, an ultrasonic immersion pulse-reflection method is proposed to characterize the CTE of ULE glass. The ultrasonic longitudinal wave velocity of ULE-glass samples with significantly different CTE values was measured using a correlation algorithm combined with moving-average filtering, which can achieve 0.2m/s precision with a contribution to the ultrasonic CTE measurement uncertainty of 0.47ppb/°C. Furthermore, the established ultrasonic CTE measurement model predicted the 5°C-35°C mean CTE with a root-mean-square error of 0.9ppb/°C. Notably, a complete uncertainty analysis methodology was established in this paper, which can provide directional guidance for the subsequent development of higher-performance measurement devices and the improvement of relevant signal processing procedures.

Phase stability and thermophysical properties of CeO2-Re2O3 (Re[dbnd]Eu, Gd, Dy, Y, Er, Yb) co-stabilised zirconia

A series of 16 mol% CeO2-2 mol% Re2O3 co-stabilised zirconia (ZrO2) (16Ce4ReSZ, ReEu, Gd, Dy, Y, Er, Yb) ceramic materials were synthesised using a chemical coprecipitation– high-temperature roasting method. Their phase structure, high-temperature phase stability, mechanical properties, thermal conductivity and coefficient of thermal expansion (CTE) were investigated. The results show that the ZrO2 tetragonal phase co-stabilised by CeO2 and Re3+ with a smaller radius has better stability. The 16Ce4ReSZ (ReDy, Y, Er, Yb) materials have high fracture toughnesses, low thermal conductivities, and high CTE values. As the radius of the Re3+ ions decreases, the lattice energy increased, while the lattice distortion decreases, the CTE decreases slightly and the thermal conductivity of the material increases slightly. Owing to the high phase stability of 16Ce4YbSZ, its mechanical properties are best after 100 h of sintering at 1400 °C.

Preparation and electrochemical stability of Co-doped La1.5Sr0.5Ni1−xCoxO4+δ cathode materials

A series of Co-doped La1.5Sr0.5Ni1−xCoxO4+δ cathode materials (x =0, 0.2, 0.4 and 0.6) were synthesized by sol-gel method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), coefficient of thermal expansion (CTE) measurement and scanning electron microscope (SEM). The results suggest that all La1.5Sr0.5Ni1−xCoxO4+δ samples have a single pure phase with the perovskite-like structure and the doping with the Co element can increase the CTE value. Using La1.5Sr0.5Ni1−xCoxO4+δ as the cathode materials in the solid oxide fuel cell (SOFC), their electrical conductivity and electrochemical impedance spectroscopy were measured. The results indicate that the conductivity increases with the increase of Co doping amount and the La1.5Sr0.5Ni0.6Co0.4O4+δ sample with x = 0.4 displays the highest conductivity of 51.21 S/cm at 800 °C; however, a higher content of Co (x > 0.4) leads to a decrease of the conductivity. In addition, La1.5Sr0.5N0.6Co0.4O4+δ exhibits the lowest polarization resistance of 4.180 Ω·cm2 in electrochemical impedance spectrum at 700 °C, displaying its excellent electrochemical properties as the cathode materials.

Use of pumice aggregate in cementitious rheoplastic lightweight concrete

Rheoplastic lightweight concrete (RLC) is generally designed for pumping applications as fluid concrete free from segregation. Concrete is produced using polymeric admixtures to enhance concrete workability, strength, drying shrinkage, and durability. This research investigated the suitability of natural porous pumice aggregates in Turkey to obtain rheoplastic lightweight concrete with cement content in normal ranges. To produce and experience rheoplastic concrete mix design data, rheoplastic lightweight concrete mixes were tested with fine pumice aggregate (FPA) and coarse pumice aggregate (CPA) supplied from the Nevşehir region of Turkey. For rheoplastic lightweight concrete with cement contents in the 250 to 400 kg/m3 range, the percentage of fine pumice aggregates required was in the 73.6-81.0% range with complimentary water/cement ratios of between 0.53 and 0.68. The upper compressive strength limit was circa 30 N/mm2 . The research findings determined that the rheoplastic concrete samples with pumice aggregate met the design requirement of a slump value of 200 mm for fresh concrete predicted for fluid concrete forms. While technical properties of hardened concrete such as oven-dry density (1198-1362 kg/m3 ), strength values, static elasticity modulus (9236- 10756 MPa), thermal expansion coefficient (5.354 x10-6/°C - 6.929x10-6/°C) and thermal conductivity value (0.405-0.619 W/mK) decrease with increasing aggregate/cement ratios, they increase with increasing cement dosage. In addition, the high amount of fine pumice in concrete composition results in lower drying shrinkage and wetting expansion with decreasing cement dosage. The technical findings showed that RLC might be produced by using a superplasticizer and air-entraining admixtures and mixtures of different sizes of pumice aggregates.

Assessment of the Y-doped Ca3Co4O9+δ as cathode material for proton-conducting fuel cells

This work presents the investigation of functional properties of the yttrium-doped Ca3Co4O9+δ complex oxides as the prospective cathode materials for the proton-conducting fuel cells. The phase equilibria in the ½Y2O3–CaO–⅓Co3O4 system at 900 °C in air is experimentally observed, and the phase diagram is constructed. The misfit-layered structure of the Ca3-kYkCo4O9+δ solid solutions, and their chemical compatibility in air with proton-conducting electrolytes BaCe0.7 Ba3Ca1.18Nb1.82O8.73 are established. Functional properties of the obtained Ca3-kYkCo4O9+δ materials have been studied. The oxygen non-stoichiometry values of δ at room temperature are equal to 0.48 and 0.62 for Ca2.5Y0.5Co4O9+δ and Ca2YCo4O9+δ, respectively. The electrical conductivity in air reaches maximum value of 32 S cm−1 at 800 °C for Ca2.5Y0.5Co4O9+δ. The values of linear thermal expansion coefficient for Ca2.5Y0.5Co4O9+δ and Ca2YCo4O9+δ are equal to 13.5 × 10−6 and 14 × 10−6 K−1 in the temperature range of 25–800 °C in air. Minimum value of the polarization resistance Rp of 0.86 Ω cm2 at 600 °C is observed for the Ca2YCo4O9+δ electrode on the BaCe0.7Zr0.1Y0.1Yb0.1O3-δ substrate. Results of the work demonstrate that Y-doping of Ca3Co4O9+δ can be recommended as the successful strategy for the enhancement of the electrochemical performance of the cathodes, based on Ca3Co4O9+δ, in the solid oxide fuel cells with the proton-conducting electrolytes.

Achieving both low thermal expansion and low birefringence for polyimides by regulating chain structures

The synthesis of polyimides (PIs) with both low coefficient of thermal expansion (CTE) and low birefringence still faces a big challenge. In this study, we prepared a new kind of PI (PI-c-P), derived from a diamine monomer (cis-diamine-DBCOD) that contains dibenzocyclooctadiene (DBCOD) units, which exhibits near-zero thermal expansion with a CTE value of 1.5 ppm/K in the temperature range of 0–150 °C due to the unique conformation transition of DBCOD unit. The increase in chain rigidity and cis-diamine-DBCOD content could effectively reduce the CTE values by promoting conformation transition. Cross-linking could restrict chain conformation transition and impair thermal contraction, leading to higher CTE values. Unlike the conventional low CTE PIs with high orientation or crystallization, the birefringence of DBCOD-containing PI films was in the range of 0.0021 ∼ 0.0094, showing both low birefringence and low thermal expansion, this property is extremely important for its application in optical and electronic devices.

Effects of post-treatment on metal-ceramic bond properties of selective laser melted Co-Cr dental alloy. Part 1: Annealing temperature

Statement of problemDental cobalt-chromium (Co-Cr) alloy manufactured by selective laser melting (SLM) is not recommended for clinical applications before annealing because of excessive residual stress. However, limited information is available regarding the relationship between annealing temperature and the metal-ceramic bond properties of SLM Co-Cr alloys. PurposeThe purpose of this in vitro study was to investigate the effects of annealing temperature on the metal-ceramic bond properties of SLM Co-Cr alloys. Material and methodsFour groups with different annealing temperatures (850 °C; 950 °C; 1050 °C; 1150 °C) were prepared by using SLM techniques. Bond strengths were measured by using a 3-point bend test; subsequently, debonded surface morphologies and elements were assessed by using a scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS). The area fraction of adherence porcelain (AFAP) value was introduced to analyze fracture characteristics. Microstructural and interfacial characteristics were characterized by SEM/EDS and X-ray diffraction analysis. The coefficient of thermal expansion (CTE) test was used to analyze thermal matching. A 1-way ANOVA and the Tukey honestly significant difference tests were used to analyze bond strengths and AFAP values statistically (α=.05). ResultsThe mean ±standard deviation values of the metal-ceramic bond strengths were 40.68 ±4.34 MPa for the 850 °C group, 37.54 ±5.34 MPa for the 950 °C group, 45.97 ±2.18 MPa for the 1050 °C group, and 50.79 ±1.79 MPa for the 1150 °C group. Significant differences (P<.05) were observed among all groups. Debonded surfaces and AFAP analysis displayed a mixed fracture mode of adhesive and cohesive fracture, and 1150 °C-annealing specimens exhibited better fracture characteristics close to cohesive fractures. As the temperature increased, native oxide film thicknesses remained unchanged; the 850 °C group had the thinnest diffusion layer, while the other 3 groups had similar thicknesses. Although the 1050 °C and 1150 °C groups displayed higher CTE values, their microstructures were more conducive to atomic diffusion and improved chemical bonding. Microstructure analysis found that ε phase and second-phase precipitates jointly affected metal-ceramic bond strength. ConclusionsAnnealing temperatures affected the metal-ceramic bond strengths of SLM Co-Cr porcelain specimens. 1150 °C annealing SLM Co-Cr specimens displayed higher bond strengths and improved fracture and interface characteristics among the 4 groups.

Linear Thermal Expansion and Specific Heat Capacity of Cu-Fe System Laser-Deposited Materials

The coefficient of linear thermal expansion and the specific heat capacity of laser-deposited Cu-Fe alloys fabricated from tin, aluminum, chromium bronze (89–99 wt.% Cu), and SS 316L were studied. The investigated alloys had a 1:1 and a 3:1 bronze–steel ratio. The Al–bronze-based alloy showed the lowest value of linear thermal expansion coefficient: (1.212 ± 0.095)∙10−5 K−1. Contrarily, this value was the highest {[(1.878–1.959) ± 0.095]∙10−5 K−1} in the case of functionally graded parts created from alternating layers of bronze and steel. Differential scanning calorimetry provided experimental results about the specific heat capacity of the materials. In the case of Al–bronze-based specimens, it demonstrated a decrease in the specific heat capacity until ~260 °C and its further increase during a heating cycle. Exothermic peaks related to polymorphic transformations were observed in the Al–bronze-based specimens. Cooling cycles showed monotonous behavior for specific heat capacities. It had exothermic peaks in the case of Cr–bronze-based alloys. A Lennard-Jones potential equation was used for testing the relation between heat capacity and thermal expansion. A three-way interaction regression model validated the results and provided the relative thermal expansion of commercially pure DED-fabricated SS 316L. Its specific heat capacity was also studied experimentally and was 15–20% higher in comparison to the traditional method of production.

Fabrication and characterization of polylactic acid/natural fiber extruded composites

AbstractIn this work, the fabricated polylactic acid (PLA) and hybrid natural fiber (NF) biocomposites via a melt extrusion method were investigated. NFs from locally grown plants were utilized as fillers. Polyethene glycol (PEG) was used as the plasticizer to improve the processability of the PLA. The effect of PLA/NF biocomposite processing was assessed by mechanical characterization (tensile, modulus, strain at break, and impact tests), and thermal properties (thermogravimetric analysis and differential scanning calorimetry [DSC] analysis). The dynamic mechanical analysis (DMA), and thermo‐mechanical analysis (TMA) of the samples were also analyzed. The mechanical properties of PLA/NF biocomposites improved as compared with that of PLA. The DMA findings show that the storage modulus and loss modulus exhibited a slight reduction for PLA/NF biocomposites compared with the PLA sample. In opposite, the glass transition temperature (Tg) from DSC thermogram results showed no obvious changes in values compared with the PLA sample. Furthermore, the findings of TMA showed a significant decrease in coefficient of thermal expansion values of PLA/NF biocomposites compared with those of PLA samples. The overall findings from this work indicated that PLA/NF biocomposites have the potential to make novel biocomposites and suitable for further application especially in biomedical applications due to its good stiffness, tensile strength, and dimensional stability.

Negative Thermal Expansion of Sulphur-Doped Graphene Oxide

The sulfur content present in graphene oxide prepared by Hummers' method has only been addressed by few papers so far. By modified Hammers method we synthesized thermally stable in ambient environment multilayer sulphur-doped graphene oxide. The samples were heat treated in an electrical furnace setup at different ambient temperatures and their crystallite size and linear coefficient of thermal expansion were extracted from Raman band intensity peak ratio as a function of temperature. We found unusually large (in comparison with graphene oxide) contraction on heating of multilayer two weight percent sulphur-doped graphene oxide with carbon to oxygen ratio of 2.3 in a narrow temperature range (308-318 K) with the lowest value of the linear thermal expansion coefficient of -18 ppm 1/K. Based upon an examination of the synthesized sulphur-doped graphene diffractograms, it is suggested that negative thermal expansion stems from the phonon backscattering by the sulphur impurity sites and the edges of the layers. The obtained experimental results have potential practical applications for fabrication of solar cells, sensors, lubricators, thermal actuators and also wavelike (second sound) thermal transport structures.

Direct Measurement of the Thermomechanical Properties of Poly(3-hexylthiophene) Thin Films on Ionic Liquid Surfaces

Thermomechanical properties of conjugated polymers (CPs) have emerged as critical factors for the long-term stability of CP-based electronics. However, very little is known about the thermomechanical properties of CP thin films (thickness ≤100 nm) without constraints from a supporting substrate. Herein, we investigate the intrinsic thermomechanical properties of CP thin films by direct measurement of thermal strains of thin films floating on an ionic liquid (IL). The IL surface provides almost frictionless gliding and thermal expansion of the pseudo-free-standing CP thin films for a wide range of temperatures up to 250 °C. We apply the method to examine the thermomechanical properties of poly(3-hexylthiophene)s (P3HTs) with different regioregularities (RRs). With increasing IL temperature, the P3HT thin film exhibits a linear in-plane thermal expansion, followed by a rapid increase in thermal strain above the melting temperature (Tm). When RR decreases from 95 to 60%, we observe a higher coefficient of thermal expansion (CTE) (from 164 to 395 ppm K–1) and a lower Tm (from 189 to 57 °C) due to the reduced crystallinity and crystal size. At the same RR, both CTE and Tm values decrease as the film becomes thinner. When the thickness of 82% RR P3HT film decreases from 550 to 45 nm, CTE and Tm values reduce from 294 to 201 ppm K–1 and from 160 to 128 °C, respectively. The in-plane hardening of the amorphous phase decreases the CTE, while the smaller crystal size from the thickness limitation reduces Tm. Our methods enable the direct measurements of thermomechanical properties of the CP thin films over a wide temperature range.

Dynamic and thermo-mechanical properties of polypropylene reinforced with date palm nano filler

Lignocellulosic based nano-sized filler are effective substituent for switching from manmade nanofillers (i.e. carbon, glass etc.) to reinforce polymer composites owing to their lightweight, plentifulness, and fully compostable characteristics. The present study adapted a dry mechanical ball mill assisted downsizing process to produce nanoscale filler from waste date palm agro residue. Then, the melt mixing technique was used to fabricate biocomposites of polypropylene (PP) with 1–5 wt% loading of this nanofillers. To investigate the variations in dimensional stability of the composites, thermo-mechanical analysis (TMA) was used. The thermomechanical analysis indicated that these composites exhibits low coefficient of thermal expansion (CTE). The CTE values for the highest nanofiller loaded sample (i.e.5 wt%) was found to be 95 and 138 at 40 °C and 80 °C, respectively, when compared to neat PP (which is 80.4 and 125) at the same temperatures. Moreover, the viscoelastic parameters of the biocomposites, such as storage modulus (E’), loss modulus (E′′), and damping factor (tan δ) were examined by using dynamic mechanical analysis (DMA) in both solid and molten state. It is observed that the both E′ and E′′ decreases with temperature in all composites compared to the neat PP in the solid state. The storage modulus (E’) difference between the biocomposites and PP at −50 °C was found to be only 9 %. On the other hand, E′ and E′′ were found to increase with the entire angular frequency range in the molten state. The E’ at 0.1 rad/s of the neat PP is 732 Pa, while the sample with 1 wt% of nanofiller loading shows storage modulus 850 Pa. Overall, these composites demonstrated good dimensional stability in a given temperature range and frequency in the solid state, as well as typical viscoelastic behavior of entangled polymeric liquid in the molten state. Consequently, these analyses provided useful information for the development of natural fiber-based composites for long-term stability in outdoor applications.