The results of physical studies of the hybrid CER-silica composites with 0.01–10 wt.% silica prepared via a sol–gel technology are presented. HAADF-STEM, EDXS, DMA, DSC, and TGA were used for their characterization. It was found that the greatest positive effect of introducing covalently embedded silica units into the matrix is observed at their ultra-low content of 0.02–0.1 wt.%. The possibility of creating subnanometer-sized silica nodes in the matrix network in the absence of clustering was revealed in this case, and the term “subnanocomposites” was introduced into the literature. The effect of the quasi-regular distribution of silica subnanounits or molecularly dispersed nanoparticles in nanovolumes of amorphous matrix was detected. The superiority of the properties of polymer subnanocomposites over those of the corresponding composites with SiO2 nanoclusters was shown. Certain correlations between the nanostructure, matrix dynamics, and the properties of the investigated composites were traced. Additional calculations based on the obtained structural data were performed, which made it possible to establish the nature of the above effects. It turned out that the dynamics of the matrix as a whole transformed into the state of constrained interfacial dynamics in this case.

The structure and properties of three types of cured PhN/metal oxide nanocomposites with Al2O3, TiO2, or ZnO nanoparticles of an average diameter of 60 nm, which were treated with aminopropyltrimethoxysilane GX-540 as coupling agent, are described. In all cases, a satisfactory dispersion of nanoparticles was achieved. A significant improvement in the thermomechanical properties of nanocomposites with respect to the properties of the neat matrix was shown. The experimental data obtained for the elastic modulus of the studied Al2O3-containing nanocomposites were compared with the Series, Halpin–Tsai, and Kerner theoretical models; the best match was shown for the Halpin–Tsai model. The barrier properties of the TiO2-containing nanocomposites as anticorrosive protective coatings were shown. The UV–visible transmittance spectra of the ZnO-containing nanocomposites showed that adding ZnO nanoparticles improved the UV-shielding properties of the neat matrix.

This book presents a comprehensive overview of the structure and physical properties of polymer nanocomposites for use in high-temperature applications

The results of physical studies of the structure, dynamics, mechanical, and thermal properties of CER/epoxy-POSS nanocomposites based on CE monomers (DCBE, DCBA, 6F-DCBA) or oligomer (PT-30) published during the last decade are presented. The nanoparticle content in the nanocomposites varied from 0.01 wt.% to 10 wt.%, and their analysis was performed by TEM, EDXS, mid-IR, far-IR, XRD, SAXS, DSC, DMA, CRS, and TGA methods. The effective molecular dispersity of nanoparticles in the amorphous matrix and the most uniform POSS distribution in the composite nanovolumes were achieved only at their contents < 1 wt.%. This and the covalent “embedding” of POSS units into the matrix led to significant suppression of matrix (cycles) dynamics and to a significant improvement in the thermal and mechanical properties of the nanocomposites. The extremal dependencies of Tg on POSS content, with its increase from 240–250° to 280–300 ℃ at low POSS contents and the appearance of additional interfacial dynamics transition at 375 ℃, and the dynamic heterogeneity around Tg were found. The superiority of oligomer-based nanocomposites with Tg ~ 400 ℃, total thermal stability up to this temperature, regardless of the nature of the environment, and the increase of the modulus from ~ 2 GPa to ~ 4 GPa at 20 ℃ and from 0.1 GPa to 2 GPa at 300 ℃ are shown.

A new interpretation of factors controlling the kinetics of reverse transformation of martensites stabilized by prestrain is suggested. We investigate the effect of amount of prestrain in the β1´martensite and in the β-phase on temperature and kinetics of the reverse martensitic transformation in Cu-Al-Ni shape memory alloy single crystals. Calorimetry and video recording of the jumping samples, provoked by the burst strain recovery during temperature-induced reverse transformation, are used in experiments. For crystals deformed both in the β´1 martensite and in the β-phase, we report the existence of a sharp transition (crossover) from the mechanical stabilization of martensite to the burst reverse martensitic transformation which proceeds as a single avalanche. The crossover occurs for prestrain values close to the maximum transformation strain. The specific energy of the jump during burst strain recovery depends on the maximum stress applied during prestraining the sample. The crossover from a broad transformation range to an infinite or spanning avalanche is predicted by 3D random field Ising model for disordered systems undergoing the first order phase transition. Based on this model, we explain the crossover in deformed Cu-Al-Ni crystals by a rapid decrease of structural disorder towards the critical one at the final stage of the formation of detwinned γ´1martensite. A simple solution is obtained for the critical transformation rate which produces jumping of the sample during burst reverse transformation after prestrain.

The structure and properties of six types of cured PhN nanocomposites containing functionalized silicon nitride, boron nitride, MAX phase, tungsten nanoparticles, MXene nanosheets, and graphite nanoplatelets are described. In all cases, the introduction of nanoparticles led to a significant improvement in the thermomechanical properties of the matrix. The most striking examples of their positive influence are as follows. For PhN/BN nanocomposites, the storage modulus increased from 1.94 GPa up to 7.2 GPa at 50 °C and from ~ 0 to 4 GPa at 300 °C. The flexural modulus and strength at 20 °C increased from 1.8 GPa and 75 MPa to 8.5 GPa and 190 MPa, respectively, and a 26-fold increase in thermal conductivity was registered. The nano-MXene phase (3 wt.%) resulted in increasing mass loss temperature T10% from 493 °C to 649 °C for the nanocomposite. For nanotungsten-containing composites, the effectiveness in shielding against gamma radiation was shown. Adding graphite nanoplatelets decreased the electric resistivity of the matrix from ~1014 Ω cm down to 107 Ω cm. The data of X-ray photoelectron spectroscopy, IR spectroscopy, and other information allowed us to conclude that the main reasons for the ultra-high thermal properties of phthalonitrile nanocomposites are the leading role of uniquely heat-stable phthalocyanine heterocycles in their structure and constraining matrix dynamics by the covalently embedded nanoparticles.

Nanoporous silicon and ceramics based on lead zirconate titanate (PZT-ceramics) have unique properties. It is shown that their mechanochemical interaction makes it possible to create compositions with a metallic type of conductivity. The formation of conductive paths occurs when silicon particles are wedged into microcracks creating unique highly sensitive layers of piezoceramic compounds including intercalates. The embedded silicon atoms deform the elementary cells of crystals and redistribute charges in them. The connection with the lattice is formed due to the transition of electrons to the boundary layers or the space between them. In the transition layers at T < 260 K, chains with electrical conductivity of the metallic type, shunting the piezodielectric, appear.

This introductory chapter gives a brief overview of the four classes of the most heat-resistant polymer matrices of nanocomposites capable of long-term service at temperatures of 250–300 °C and short-term service at 400 °C. Their approximate characteristics are given, including the attainable limit values of Tg, thermal stability, elastic modulus, dielectric constant, thermal conductivity, and other properties of nanocomposites based on them.

The results of physical studies of molecular structure, nanostructure, relaxation, elastic and thermal properties of a group of hybrid phthalonitrile nanocomposites with different contents, from 0.03 to 5 wt.%, of functionalized MMT nanolayers, using TEM, EDXS, DMA, DSC, TGA, and mid-IR/far-IR spectroscopy are shown. Far-IR spectra confirmed the main contribution of phthalocyanine heterocycles to the molecular structure of nanocomposites and the effect of constraining matrix dynamics after “embedding” MMT. The degree of exfoliation of MMT blocks in nanocomposites increased with decreasing their content: at 0.03–0.1 wt.% MMT single nanolayers were formed. For cured materials, neat matrix and nanocomposites, Tg = 380–390 °C but after post-curing Tg of the matrix increased to 446 °C, whereas the nanocomposites exhibited dynamic heterogeneity in the glass transition and their Tg's reached 540° and 570 °C. After treatment at high temperatures in an inert medium, the complete suppression of the glass transition and constant modulus E’ = 3 GPa in the range from 20° to ~ 600 °C were observed for the nanocomposites. The nanocomposites were stable when heated up to 400 °C, regardless of the nature of the environment. The incorporation of MMT nanolayers led to a substantial improvement in the resistance to thermo-oxidative degradation in the air environment. The char residue at ~ 700 °C increased from 7% for the neat matrix to 45% for the nanocomposite with 2% MMT.

The results of the physical study of a series of phthalonitrile nanocomposites with 0.5 wt.% of functionalized POSS nanoparticles are of four types. Their nanostructure, dynamics, relaxation, elastic and thermal properties were examined by TEM, mid-IR, far-IR, EDXS, DMA, DSC, and TGA techniques. Polymerization at temperatures not exceeding 300 °C resulted in the completion of the process by ~70–80% only, and post-curing at higher temperatures increased the degree of polymerization to 90–95%. Far-IR spectra confirmed the main contribution of phthalocyanine cycles to the matrix structure. TEM images and histograms of Si content in the nanovolumes of the composites (EDXS data) indicated a quasi-regular, at the first approximation, distribution of POSS nanoparticles in the amorphous matrix. The introduction of POSS nanoparticles and post-curing led to some suppression of the matrix dynamics and increasing Tg from 380–410 °C to 446 °C for neat matrix and to 520–560 °C for the nanocomposites, with the manifestation of dynamic heterogeneity in the glass transition. A complete suppression of the glass transition as well as the constancy of the dynamic modulus E′ ≈ 3.2 GPa over the range from 20° to 560 °C was observed after heating nanocomposites in an inert atmosphere. The total thermal stability of the nanocomposite up to ~ 400 °C and the “switching on” of thermo-oxidation processes in an air medium from 550 °C were registered by TGA.

The results of physical studies of nanostructure, dynamics, mechanical and thermal properties of DCBE-based CER/amino-MMT nanocomposites are presented. The 2D MMT nanolayers content in these composites varied from 0.01 wt.% to 5 wt.%, and their analysis was performed by TEM, EDXS, mid-IR, far-IR, XRD, DSC, DMA, CRS, and TGA methods. The process of MMT exfoliation increased with decreasing MMT content in the composite, down to the formation of individual nanolayers at 0.1 wt.%. The ambivalent influence of MMT nanolayers on matrix dynamics, Tg, and thermal stability is shown, with the most positive effect at small and ultra-low MMT contents (0.025–0.5 wt.%). Anomalous composition and mechanical properties of the subsurface micron layers in the CER-based nanocomposites were detected.

This chapter considers the structure and properties of CER-based nanocomposites containing mesoporous silica particles, graphene oxide (GO), carbon nanotubes (CNTs), or “unzipped” carbon nanotubes (uCNTs). It is shown that by introducing glycidyl silane functionalized mesoporous silica FMCM-41, the thermal stability increases, whereas the dielectric constant and the dielectric loss tangent of the material decrease from 3.2 to 1.98 and from 0.023 to 0.009, respectively. GO produced a strong catalytic effect on the matrix curing process, and the addition of 1% GO significantly improved its mechanical properties. Of particular interest are the results of studying nanocomposites with functionalized uCNTs. In addition to significantly improving the mechanical and thermal properties of the matrix, uCNTs significantly enhanced its luminescence properties and absorption in the UV region.

We studied the ability of Cu 82.5 wt %–Al 13.5 wt %–Ni 4.0 wt % martensitic single crystals to perform work by moving a load with an impact during the shape-memory-strain recovery of reverse martensitic transformation. The dependence of this work on preload is studied. The transition to the impact mode occurs after the precompression of the crystal until the complete deformation of the shape memory (~9%) when the load exceeds the martensite detwinning stress by more than a factor of 2. Differential scanning calorimetry showed that, after such compression of the crystal to 200–250 MPa and more, the temperature range of the reverse martensitic transformation sharply narrows.

Structure formation during solidification of a Pd-Ni-Cu-P melt is studied. It is demonstrated that changes in the heat transfer conditions lead to a nonlinear change in the characteristics of the structure. The article presents the regimes of cooling the samples and the results of their structure and composition studies. It is found that a decrease in the cooling rate of the alloy leads to an increase in the size, proportion and composition of nanoinclusions in an amorphous matrix. X-ray diffraction method, electron probe microanalysis, transmission microscopy and scanning calorimetry are used for samples characterization. This article is part of the theme issue 'Transport phenomena in complex systems (part 2)'.

Our study clarifies the nature of the exceptional impact of the ultra-low content of silica (SiO2) units on the properties of the heterocyclic cyanate ester resin (CER) network matrix in the subnano- or nanocomposites. To this effect, we have performed a series of calculations of average distances between SiO2 units and the interfacial area values in the composites as functions of the content and size of SiO2 units. The estimates were made for the CER composites with SiO2 and POSS additives, based on these calculations and the composites' previously measured structural characteristics. It was found that the aforementioned unusual effect was controlled by the constrained interfacial matrix dynamics in the composites. Thus, when (a) the SiO2 content was 0.03-0.1 wt%, (b) SiO2 units and the matrix network had covalent bonding, and (c) SiO2 units had quasi-regular distribution in the amorphous matrix (as found for the subnanocomposites), we found that distances between SiO2 units equaled 6 and 10 nm, that is, these distances were commensurable with the lengths of Kuhn segments in heterocyclic macromolecules.

The study of nanostructure, thermal and relaxation properties (by HAADF-STEM, EDXS, DMA and DSC), combined with the calculations of interparticle distances and interfacial areas, has been performed for a series of the hybrid Cyanate Ester Resin (CER)/Si0 2 polymer composites with 0.01 to 10 wt.% Si0 2 units introduced via a sol-gel process. The absence of clusterization, arising only subnanometric Si0 2 nodes and their quasi-regular distribution within the amorphous matrix, with the shortest distances between nodes, provided their exceptional positive impact on the matrix properties at ultra-low Si0 2 contents of 0.03-0.1 wt.%. The superiority of these subnanocomposites over the nanocomposites was determined by the role of constrained interfacial dynamics over the whole matrix.

A series of the hybrid Bisphenol A based Phthalonitrile (BAPhN)/amino-Montmorillonite (amino-MMT) polymer nanocomposites with the complex heterocyclic matrix network and 0.03–5.0 wt.% amino-MMT were synthesized and studied. Their molecular structure, nanostructure, molecular dynamics, thermal, relaxation and elastic properties were characterized using TEM, EDXS, DMA, TGA, FTIR and Far-IR spectroscopies including also the experiments in flowing nitrogen medium. Depending on nanofiller content, different extents of MMT stacks exfoliation, from a single nanolayer to stacks with tens nanolayers-thickness, were registered in these nanocomposites. The exceptional combining of high temperature properties was revealed for these nanocomposites.

Here we report on compressive stress-strain behavior, ordinary and burst-like shape memory (SM) strain recovery, and associated caloric effects in Cu - 14.02% wt. Al - 4.0% wt. Ni single crystals which have multiphase martensitic structure at room temperature. The effect of repetitive thermo-mechanical cycling on the recovery of the shape memory deformation is investigated. The stress-strain curves of the specimens are smooth in all tests. Immediately after quenching, crystals exhibited burst-like strain recovery accompanied by the jumping of the whole specimen in each deformation-recovery. After several days from quenching, crystals showed weaker jumping which was also reducing with each thermo-mechanical cycle. The average values of the integral thermal effect remained the same from cycle to cycle. Although the starting temperature of burst-like reverse martensitic transformation stochastically varied from cycle to cycle, it showed a general tendency to decrease with an increasing number of cycles until the burst-like effect disappears completely. The heating rate does not significantly affect the position of the DSC peak. Low temperature aging of the specimens resulted in the gradual weakening and disappearance of the burst-like strain recovery. Thus, thermal treatment and loading regimes should be optimized for high-cycle applications of Cu-Al-Ni alloys.

In the present work we report results of the model experiments that allow us to study effect of different cooling rates of samples on relationship for amorphous/crystalline phase in freezed Pd-based samples. For the model experiments Pd 40 Cu 30 Ni 10 P 20 alloy samples were used which are typical bulk metal glasses with a relatively small temperature interval of liquid to glass transition. The main focus of the study was on the effect of cooling rate and glass transition temperature on the microstructure of samples, cooled from the liquid to (semi)amorphous states of the alloy. Ground based experiments were conducted using the multi-zone vacuum furnace MEP-01 situated in the institute of launch complexes (NIISK, Moscow). Composition, structure and thermodynamic properties of the samples were determined by electron probe microanalysis, X-ray diffraction, transmission electron microscopy and differential scanning calorimetry.

Shape recovery in conventional shape memory alloys is typically a relatively slow process showing low heating rate sensitivity. In contrast to that, some shape memory alloys such as Ni–Fe–Ga–Co, Cu–Al–Ni, Cu–Al–Fe–Mn can exhibit the effect of burst-like shape recovery when the original shape is restored almost instantaneously in a very narrow temperature range. Here we report on an abnormal stress-strain behavior of Ni49Fe18Ga27Co6 single crystals upon uniaxial compression along the [110] axis and caloric effects during burst-like recovery of shape memory strain in the samples. Differential scanning calorimetry (DSC) study revealed that DSC peak shifts to lower temperatures with increasing heating rate.