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We studied a gradient anti-oxidation coating of C/C composite materials for aircraft brake discs with a simple process and low costs. The gradient coating consists of two layers, of which the inner layer is prepared with tetraethyl orthosilicate (Si (OC2H5)4), C2H5OH, H3PO4 and B4C, and the outer layer is prepared with Na2B4O7.10H2O, B2O3, and SiO2 powder. The experimental results show that after being oxidized at 700 °C for 15 h, the oxidation weight loss of the sample with the coating was only −0.17%. At the same time, after 50 thermal cycles in air at 900 °C, the sample's oxidation weight loss was only −0.06%. We conducted the 1:1 dynamic simulation test for aircraft brake discs, and the brake disc did not oxidize, thus meeting the requirements for aircraft use. In addition, the anti-oxidation mechanism of the coating was analyzed via scanning electron microscopy (SEM), X-ray diffraction (XRD), differential thermal analysis (DSC-TGA), and high-temperature in situ SEM. [ABSTRACT FROM AUTHOR]

The mechanical properties and ageing resistance of 0.5–10 mol% HfO 2 doped 3Y-TZP have been investigated. All samples were sintered at 1500 ◦C-2 h and characterized by density testing. Samples with polished surfaces were submitted to X-Ray diffraction (XRD) and microstructure testing and then cut into standards for 3-point bending testing. Group 2 was characterized by Vickers hardness and fracture toughness. Group 3 was accelerated ageing procession in autoclave condition containing at 134 °C and 0.2 MPa 10 h up to 40 h, and then detected by transmission electron microscopy (TEM) analysis. All sintered specimens presented nearly full densification. The grain size of 3Y0.5Hf-TZP was smaller than that of undoped 3Y-TZP after sintering. 3Y0.5Hf-TZP enhanced the bending strength by 34.6% compared to 3Y-TZP. The ageing kinetic parameter (n ∼ (0.66–1.64)) was related to the grain size and the ageing time from the onset of the transition until the transition reaches saturation. [ABSTRACT FROM AUTHOR]

The first‐principles calculation is performed to explore the mechanical properties and electronic structures of transition elements X (X = V, Mn, Fe, Ni) doped WCoB (tungsten cobalt boron), which has shown high oxidation resistance and melting point under high pressure. The energy analysis indicates that the high pressure leads to the lower lattice constants and less stable structures. The deviation of cohesive energy and formation enthalpy between doped and undoped structures indicates that W4Co3FeB4 and W4Co3NiB4 have similar stability. The high pressure contributes to the increasing of elastic, shear, and bulk moduli, which indicates the increase of covalence. The increase of Poisson's ratio, B/G ratio, and anisotropy index AU indicates the higher ductility and higher anisotropy under high pressure. Based on bulk modulus and shear modulus, the hardness of W4Co4B4, W4Co3FeB4, and W4Co3NiB4 increases under high pressure, which consists of the variation of electronic structures. The density of states (DOS) and partial DOS analysis indicate that the high pressure leads to lower density around Fermi level and higher hybridization. W4Co4B4, W4Co3FeB4, and W4Co3NiB4 show similar variation of mechanical properties, which is determined by the similar atom properties of Co, Fe, and Ni. Similarly, W4Co3VB4 and W4Co3MnB4 also imply similar variation of mechanical properties and electronic structures. [ABSTRACT FROM AUTHOR]

A machine learning (ML) process on composition optimization was performed to design Ni-based turbine disc superalloys with improved yield strength. Based on published data of polycrystalline Ni-based superalloys, the design process is finished through regression algorithm, feature rank method, and genetic algorithm, which is simple and high-efficient to optimize composition. The two designed alloys are assessed using the Calculation of Phase Diagram (CALPHAD), finding the microstructure of both alloys according with superalloys. Comparing with commercial Ni-based turbine disc superalloys, the designed alloys have trade-offs on mechanical and physical properties. The ML architecture and the assessment results are then discussed, indicating that the design ability of ML to automatically optimize is promising. This work is of much practical significance in reducing trial-and-error test to improve design efficiency for material design, providing an effective way to development novel Ni-based turbine disc superalloys. [ABSTRACT FROM AUTHOR]

Sb 2 Te thin film exhibits remarkable crystallization speed, which allows rapid data conversion in phase change memory (PCM). Thermal stability is a key challenge to enable reliable data retention. Meanwhile, it is necessary to study the transition energy in the process of crystallization when the thermal stability of the amorphous state is improved. Herein, we demonstrated an alloying strategy to optimize thermal stability and transition energy. Zn was screened to be a promising alloying element. Nano-composite Zn 0.75 Sb 2 Te thin film was designed, which exhibited excellent thermal stability and optimized transition energy. The data retention temperature for 10 years (T 10-yr) increased by ∼ 218 %, and the transition energy consumption decreased by ∼ 27 % compared with Sb 2 Te thin film. The enhancement of these properties originated from Zn-modified local chemical bonding. Zn induced the formation of tetrahedron with strong bonds (Zn–Te and Zn–Sb bonds) and dragged the atomic diffusion in amorphous phase to improve thermal stability. The structural disorder and complexity of the first and second nearest neighbors of atoms were stimulated by Zn alloying, which inhibited the carrier transports, increased the amorphous resistance, and reduced the transition energy in the process of crystallization. [Display omitted] • An alloying strategy is proposed to improve the thermal stability. • Transition energy could also be reduced by the alloying strategy. • Zn induces the formation of tetrahedrons in amorphous Sb 2 Te film. • Nano-composite Zn–Sb 2 Te film is prepared. • Microstructure and phase change mechanism of Sb 2 Te film depend on the Zn content. [ABSTRACT FROM AUTHOR]

MoCoB–Co cermets with varying Mo/B atomic ratios (AR Mo/B) and Co contents were fabricated, and their microstructure, mechanical properties, and corrosion behavior were investigated. The MoCoB hard phase exhibited the maximum grain size and anisotropy when the AR Mo/B was 0.84, which degraded the mechanical properties. For AR Mo/B ≥ 1.08, a third phase, Co 7 Mo 6 , and dense three-dimensional networks composed of stacking faults and ε-martensite plates were observed. These three-dimensional networks limited the dislocation slip in face-centered cubic γ-Co and ε-martensite, improving the hardness of the cermet and decreasing the transverse fracture strength (TRS). The corrosion resistance of the cermets was influenced by the MoCoB particle size, the Mo content of the binder phase, and the ε-martensite content. With an increase in the AR Mo/B , the corrosion resistance of cermets initially decreased and then increased. Additionally, as the Co content increased, the hardness gradually increased, whereas the TRS and fracture toughness steadily decreased. For AR Mo/B = 0.92 and a Co content of 45 at.%, the cermet displayed the best overall performance, with hardness, TRS, and fracture toughness values of HRA 89, 1720 MPa, and 13.2 MPa m1/2, respectively. [ABSTRACT FROM AUTHOR]

WCoB based cermet is a potential hard alloy to replace WC-Co cermets with high hardness and corrosion resistance. WCoB based cermets with different Cr doping contents were fabricated by spark plasma sintering in liquid phase sintering stage. The densification behavior, phase composition, microstructure and mechanical properties of Cr doped WCoB cermets were investigated by XRD, EDS and SEM. Due to the lower density of Cr, the density of WCoB cermets decreased with the increasing of Cr doping content. The phase composition consisted of Cr doped WCoB, unreacted W, Co–Cr binary binder phase. When the doping content exceeded 11.736 wt%, the Cr enrichment zones appeared, which was harmful to the TRS. The increasing of Cr doping content contributed to the increase of unreacted W phases content and the formation of pores. The maximum value of Vickers hardness was 1751 Hv0.5 at 9.356 wt% Cr doping content. The variation trend was explained by first principle calculation, which is consistent with Hv-Zhou hardness model. • The Cr doped WCoB cermets were studied by SPS in liquid sintering stages. High Cr doping content leaded to the increment of hardness and the formation of Cr enrichment zones. • The first-principle calculation was performed to study the hardness of Cr doped WCoB structures by four hardness models. • EDS analysis indicated similar variation trend of theoretical hardness and experimental hardness, which proved the correctness of first principle calculation. [ABSTRACT FROM AUTHOR]

To develop tungsten-free cermets, a novel MoCoB–Co cermet composed of MoCoB as a hard phase and Co as a binder phase was synthesized by the reaction sintering of Mo, Co, and B powders. The microstructure evolution, phase transformation, and mechanical properties of the cermet were investigated. We demonstrated that the mixed powders experienced three solid-phase reactions, Co + B → Co 2 B, 11Mo + 15Co 2 B → Mo 2 Co 21 B 6 + 9MoCoB, and 4Mo + Mo 2 Co 21 B 6 → 6MoCoB +15Co, and underwent two liquid-phase reactions. Nanosized, tremella-like Co structures were formed on the surface of the particles between 1100 and 1200 °C. The formation of these structures may be due to the Kirkendall effect. Further, the first liquid, L 1 , was formed at 1242 °C by a eutectic reaction between the tremella-like Co structures and MoCoB. This led to an increase in the relative density of the sample from 43% to 71.7%. At 1268 °C, the second liquid, L 2 , was formed as a result of a eutectic reaction between Co and MoCoB that further increased the relative density of the sample to 95%. At 1300 °C, the cermet exhibited the highest hardness and transverse rupture strength of 83.9 HRA and 1700 MPa, respectively. [ABSTRACT FROM AUTHOR]

WCoB based cermets were prepared by spark plasma sintering at sintering temperature among 600°C-1200 °C. The phase evolution was investigated by detecting density behavior, phase composition, microstructure and mechanical properties during sintering process. The sintering process can be divided into three stages: powder densification, solid phase reaction and liquid phase sintering. WCoB hard phase forms at 1000 °C during solid phase sintering, showing better mechanical properties than Co 2 B, especially on Vicker's hardness. WCoB hard phase forms on the basis of Co 2 B binary boride and its content increases in liquid phase sintering stage with high density. The Vicker's hardness and transverse rupture strength (TRS) reach the maximum value of 1262 Hv and 1212 MPa at 1200 °C and 1170 °C, respectively. The fracture toughness reaches the maximum value of 21.8 MPa m1/2 at 1050 °C, and the inter-granular fracture is the main fracture mechanism. [ABSTRACT FROM AUTHOR]

The sintering behavior of Cu-9Al alloys prepared from die pressing of elemental powders was investigated. The experimental results and kinetic analysis showed the formation of three consecutive layers of Al 2 Cu, Al 4 Cu 9 , and AlCu phases, with Al 2 Cu appearing first in the initial solid phase sintering stage. A liquid phase formed in the intermediate stage, resulting from the eutectic reaction between Al and Al 2 Cu phases at 500 °C, which is 47 °C lower than the equilibrium reaction temperature. Swelling occurred when the liquid phase infiltrated the gaps between the copper particles, leaving pores at the original sites of Al particles and Al 2 Cu. In the final stage of sintering, the Al-rich phases (Al 2 Cu and AlCu) transformed to Al-poor phases (Al 4 Cu 9 and α-Cu) in the temperature range of 500–565 °C. Al 4 Cu 9 and α-Cu then transformed to AlCu 3 (β) above the eutectoid reaction temperature (565 °C), whereas AlCu 3 transformed to α-Cu and eutectoid phases (α-Cu + Al 4 Cu 9) during cooling. The pure copper transformed to AlCu 3 , and the pore volume decreased at 1000 °C. The microstructure study helps manipulate precisely the sintering process of Cu-Al alloys and optimize the microstructure with a high dimensional accuracy. Image 1 • The microstructure evolution of Cu-Al alloys during sintering were studied. • The swelling mechanism of Cu-Al alloys during sintering were studied. • Three consecutive layers form in the temperature range of 480–500 °C. • Eutectic liquid forms between the Al and Al 2 Cu phases at 500 °C. [ABSTRACT FROM AUTHOR]

To find high-performance ternary borides as the hard phase of the cermets, first-principles calculation was applied to systematically investigate the structure, mechanical, electronic and thermal properties of 26 ternary borides MⅠ x MⅡB x (x = 1 or 2). The phase stability and mechanical properties were evaluated by formation enthalpy and elastic constants. Debye temperatures were calculated to study the thermal conductivity, and the hardnesses of the candidates were predicted via the overlap populations calculation and hardness model. The results show that all the candidates possess thermodynamic and mechanical stability. Most of the MⅠ x MⅡB x (x = 1 or 2) exhibit a better ductility than WC, except Ta 2 FeB 2 , Mo 2 MnB 2 , Nb 2 CrB 2 , Nb 2 FeB 2 and Ti 2 ReB 2. Moreover, sorted from high to low, Nb 2 CrB 2 , Mo 2 CoB 2 , W 2 MnB 2 , Mo 2 FeB 2 , Ti 2 ReB 2 , NbFeB, MoCoB, Mo 2 NiB 2 , Nb 2 FeB 2 , and Mo 2 NbB 2 have a larger Debye temperature than WC. All the candidate ternary borides exhibit a lower hardness than WC, with the maximum hardness of 26.3 GPa for MoCoB. The analysis of electronic properties indicates that all the MⅠ x MⅡB x (x = 1 or 2) exhibit metallic, ionic and covalent hybrid properties. The calculated results are expected to provide guideline for developing ternary boride-based cermets or coating materials that may replace WC-Co cermet. • Ternary boride-based cermets may replace WC-Co. • The mechanical and thermal properties of 26 MⅠ x MⅡB x (x = 1,2) were investigated. • A novel high hardness and thermal conductivity MoCoB-Co cermet was proposed. • A scientific foundation for accelerated design of tungsten substitutable cermets. [ABSTRACT FROM AUTHOR]

The study investigated the effect of nickel content on the microstructure and mechanical properties of Cu–12Al-xNi alloys prepared using powder metallurgy. The results indicated that the alloys investigated consisted of α-Cu and γ 2 (Al 4 Cu 9), containing less than 4 wt% Ni content. The α-Cu phase gradually increased, while the γ 2 (Al 4 Cu 9) phase gradually decreased as the sintering temperature increased. Both the strength and hardness of the alloy thus reduced. When the Ni content increased above 4 wt%, the NiAl phase precipitated at the grain boundaries, which resulted in an increase in the strength of the alloy. Additionally, the tensile strength reached a maximum of 390 MPa when the Ni content reached 6 wt%. The decrease in the tensile strength for higher Ni content was attributed to the formation of a NiAl phase network. And the addition of nickel did not significantly alter the sintering density of the alloy. The mechanisms of microstructure evolution and strengthening mechanisms were investigated and discussed. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract The mechanical properties of powder metallurgy (PM) materials are closely related to their density. In this case we demonstrate an approach of utilizing machine-learning algorithms trained on experimental data to predict the sintered density of PM materials. Descriptors were selected from the features including processing parameters, chemical composition, property of raw materials and so on. And the training data are collected by the experimental setup in our lab and the literatures on five kinds of P/M alloys. The multilayer perceptron model (MLP) outperformed other four regression and neutral network models with high coefficient of correlation and low error. The sintered density predicted by MLP model agreed well with the experimental data with a tolerable error less than 0.028, which confirms its capability over P/M materials design procedures. Then the obtained MLP model is used for Cu-9Al P/M alloy to guide selecting the processing parameters to reach the expected sintered density of 0.88. The Cu-9Al powders were fabricated with the predicted parameters including the specific shape factor, particle size, pressing pressure and sintering temperature, and the obtained relative sintered density is 0.885. [ABSTRACT FROM AUTHOR]

The Mo–W–N and C–Mo–W ternary systems have been critically evaluated by means of the CALPHAD approach, wherein the C–Mo–W system was reassessed to ensure the model consistency. The Gibbs energies of individual phases in the ternary systems are described with corresponding models, such as substitutional solution model and sublattice model. A set of self-consistent thermodynamic parameters is obtained. Comprehensive comparisons between the calculated and reported phase diagram data show that the reliable information is satisfactorily accounted for by the present modeling. Based on the present work together with the previously reported assessments of C–Mo–N and C–W–N ternary sub-systems, a thermodynamic description of the C–Mo–W–N quaternary system is obtained and used to calculate the phase equilibria and thermodynamic stability of the hexagonal structured (Mo,W)(C,N) carbonitride phase. [ABSTRACT FROM AUTHOR]

The lattice parameters, structural stability, mechanical properties, hardness and electronic structure of WCoB with Cr alloying were investigated by using first-principles calculations. The Cr atom was selected to replace 0, 1, 2, 3, 4 Co atoms in WCoB crystal and 0, 1, 2 Co atoms in W2CoB2 crystal. The calculated cohesive energy and formation enthalpy showed that all structures can retain good structural stability with different Cr doping content. The calculated mechanical properties showed Cr doping will decrease the shear modulus, Young’s modulus, bulk modulus and hardness, but increase the ductility. The larger number of valence electrons of Cr led to the increasing of bond covalence and population. According to the electronic structures analysis, the nonmetal–metal hybridization and metal–metal interactions contributed to relatively high toughness. [ABSTRACT FROM AUTHOR]

The Ta–Mo–C system was assessed by means of the CALPHAD approach. All of the phase diagram and thermodynamic information available from the literature were critically reviewed. The liquid was modeled as substitutional solution phase, while the carbides including fcc-(Mo,Ta)C 1- x , bcc-(Mo,Ta), hcp-(Mo,Ta) 2 C and η-MoC were described by using corresponding sublattice models. The ζ-Ta 4 C 3- x was considered as a linear compound with carbon content fixed, while shp-MoC was treated to be a binary stoichiometric phase. There was no ternary compound reported in this system. The modeling of Ta–Mo–C ternary system covers the entire composition and temperature ranges, and a set of self-consistent thermodynamic parameters for the Ta–Mo–C system was systematically optimized. Comprehensive comparisons between the calculated and reported phase diagram and thermodynamic data show that the reliable information is satisfactorily accounted for by the present modeling. The liquidus projection and reaction scheme of the Ta–Mo–C system were also generated by using the present thermodynamic parameters. [ABSTRACT FROM AUTHOR]

The influence of N 2 atmosphere on the microstructure of gradient zone in Ti(C,N)-Mo 2 C-Ni cermet was systematically investigated by the coupling analysis of experimental characterization and thermodynamic calculation. Under the guidance of calculated carbon window, the composition of Ti(C,N)-Mo 2 C-Ni cermet was designed, and the cermet was produced via liquid-phase sintering at 1450 °C for 2 h under N 2 pressure of 20, 200, 400 and 600 mbar. The microstructure and element distribution of cermet were analyzed by using Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-ray spectroscopy (EDX). A homogeneous microstructure was obtained for cermet sintered in 20-mbar nitrogen atmosphere, whereas the thickness of gradient layer increased with nitrogen pressure. EDX mapping demonstrate that Mo and Ti are enriched in gradient zone, while Ni is lacking and partially segregated near the surface. The diffusion of elements in cermet is caused by the different nitrogen activity between surface and interior. The carbonitride grains show typical black core and gray rim structure in the bulk of cermets, while it present light-gray core and gray rim in the surface gradient layer. In addition, the Vickers microhardness measurement was performed for the gradient zone of cermets, and the hardness increased for cermets sintered in higher nitrogen pressures, which exhibit slower grain growth phenomena. [ABSTRACT FROM AUTHOR]

[Display omitted] • A computational materials design to develop novel single crystal superalloys. • Achieving design balance of multi-objective properties. • Comprehensive design through DFT, empirical models, CALPHAD, and machine learning. • 12 alloys selected from 779,625 alloys in trade-offs between different factors. The computational materials design is performed to develop novel single crystal superalloys with balance of multi-objective properties. The entire design process is carried out by materials computation from systems selection to composition determination. The design rules are proposed to optimize compositions of Ni-based single crystal superalloys for materials characteristics, using first-principles calculations, CALPHAD calculations, theoretical models, and machine learning. By first-principles calculations, the effect of alloying elements on structural, elastic, electronic properties of Ni 3 Al are investigated and the Ni-Al-V-Cr-Nb-Mo-Ta-W-Re systems are determ5ined. Application of theoretical models and CALPHAD calculations allows the large materials exploring space to become narrow, based on materials design criterion: microstructure, density, castability, and processability. The creep resistance of remained alloys is estimated by using machine learning and creep merit index. There are 12 alloys selected from 779,625 composition combinations, reaching the balance of multiple design properties. With comparing to commercial superalloys, the selected alloy has excellent performance in trade-offs between different factors, specifically prominent in the aspect of Cr-Al space of oxidation resistance. This design procedure is expected to reduce excessive consumption of cost and time in the process of trial-and-error testing, providing a guide on developing potential Ni-based superalloys systems. [ABSTRACT FROM AUTHOR]

A first-principles study on Ni-based superalloys is performed to estimate the properties of D0 22 structure Ni 3 X (Ni 3 Nb, Ni 3 Ta, Ni 3 V) phases and L1 2 structure Ni 3 Al phase with loading stress and high temperature. By stress-strain curve, the strength is higher in D0 22 structure Ni 3 X than in L1 2 structure Ni 3 Al. Loading stress causes systems unstable to increase decomposition tendency through calculating enthalpy and E above hull. The elastic properties reflect stress decreases system modulus and increases anisotropy. The lattice misfit is affected by stress and temperature. Loading stress increases lattice misfits of D0 22 structure Ni 3 X. Raising temperature decreases lattice misfit of each system. The effect on lattice misfit is larger in stress than in temperature. Ni 3 V can form negative lattice misfit with high temperature and low stress. Through overall comparison, the D0 22 Ni 3 V has advantages on high mechanical resistance, high thermodynamic stability, excellent elastic properties, negative lattice misfit in condition of high temperature and loading stress, which can be used to develop a new precipitation strengthening Ni-based superalloy. • First-principles to evolute stabilities of D0 22 Ni 3 X with stress and temperature. • Mechanical resistance is stronger in D0 22 Ni 3 X than in L1 2 Ni 3 Al. • D0 22 Ni 3 V has advantages on thermodynamic stability and lattice misfit. [ABSTRACT FROM AUTHOR]

Highlights: [•] Using high velocity compaction we compact Cu–0.9Al2O3 composite powder. [•] At impact velocity 9.4m/s the relative green density was obtained 96.8%. [•] Axial and radial shrinkage increased with increase in sintering temperature. [•] The mechanical properties were improved with an increase sintering temperature. [Copyright &y& Elsevier]

Highlights: [•] Cholesterol (CL) was incorporated into pH-sensitive polymersomes. [•] The CL incorporation enhanced colloidal stability of the polymersomes. [•] The CL incorporation did not damage on pH sensitivity of the polymersomes. [•] CL-incorporating polymersomes played a role as an intracellular drug carrier. [Copyright &y& Elsevier]

Highlights: [•] Ti–10Mo alloy powder has been compressed by high velocity compaction technique. [•] Density of compacts depends on impact force per unit area of powder filled in die. [•] Maximum relative green density of the compacts was obtained 90.86% at 1615Nmm−2. [•] Spring back of compacts decreases with the increment of impact force. [•] Impact force per unit area affects the mechanical properties of the compacts. [Copyright &y& Elsevier]

Highlights: [•] Studying the W and Mo effect on the mechanical properties of Ti(C,N) cermets. [•] Studying the W and Mo effect on the electronic properties of Ti(C,N) cermets. [•] Distinguish the different property of hard phase and rim phase in Ti(C,N) cermets. [•] Explaining from theory the different property of Ti(C,N) and (Ti,Mo,W)(C,N) cermets. [ABSTRACT FROM AUTHOR]

A novel flame retardant (PSiN), containing silicon and nitrogen, was synthesized using N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH-602) and diphenylsilanediol through solution polycondesation and it was used together with potassium-4-(phenylsulfonyl)benzenesulfonate (KSS) to prepare a flame-retardant system for polycarbonate (PC). The structure and thermal property of PSiN were characterized by Fourier transform infrared spectroscopy (FTIR), HNMR and thermogravimetric analysis (TG) tests. Flammability and thermal behaviors of PC/KSS/PSiN systems were estimated by limited oxygen index (LOI), cone calorimeter, vertical burning test (UL-94), and TG tests. The results showed that the flame retardancy and char residues of PC/KSS system were improved with the addition of PSiN. When 1 mass% PSiN and 0.5 mass% KSS were incorporated, the LOI value of PC was found to be 46, and class V-0 of the UL-94 test. Moreover, both the heat release rate and the total heat release of PC/KSS/1 mass% PSiN decreased compared with those of PC and PC/KSS systems. The microstructures observed by scanning electron microscopy and FTIR indicated that the surface of the char for PC/KSS/PSiN system hold a more cohesive and denser char structure when compared with the pure PC and PC/KSS system. [ABSTRACT FROM AUTHOR]

Highlights: [•] We compacted Ti–6Al–4V powder by HVC technique. [•] As impact force rises up, the green density of the compacts increases gradually. [•] At impact force 1.857kN relative sintered density of the compacts reaches 99.88%. [•] Spring back of the green compact’s decreases gradually with increasing impact force. [•] Mechanical properties of the samples increases with increasing impact force. [ABSTRACT FROM AUTHOR]

A novel flame retardant (PSiN), containing silicon and nitrogen, was synthesized using N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and diphenylsilanediol through solution polycondensation and it was added to polycarbonate (PC). The structure and thermal properties of PSiN were characterized by fourier transform infrared spectroscopy and thermogravimetric analysis (TG) tests. The effect of PSiN on the flame retardancy and thermal behaviors of PC was investigated by limited oxygen index (LOI), vertical burning test (UL-94), and TG tests. The results showed that the flame retardancy and the thermal stability of PC are improved with the addition of PSiN. When 1 mass% PSiN and 0.5 mass% diphenylsulfone sulfonate (KSS) are incorporated, the LOI value of PC is found to be 46, and class V-0 of UL-94 test is passed. The char structure observed by scanning electron microscopy indicated that the surface of the char for PC/KSS/PSiN system holds a firmer and denser char structure when compared with neat PC and PC/KSS system. [ABSTRACT FROM AUTHOR]

In this article, the laboratory-made poly ( p-ethylene terephthalamide) (PETA) was used as a novel charring agent and it combined with ammonium polyphosphate (APP) to prepare the intumescent flame retardant (IFR). For improving the flame-retardant efficiency of IFRs on polypropylene (PP), several general synergistic agents, such as common zinc oxide (Com-ZnO), nanometer structural zinc oxide (Nano-ZnO), zeolite 4A, and aluminum hypophosphite(Al(HPO)), were added in composites of PP/IFR, and the synergistic effect was investigated by the limited oxygen index (LOI), the UL-94 (vertical flame) test, thermogravimetric analysis (TG), thermogravimetry-fourier transform infraredspectroscopy (TG-IR) test, and scanning electron microscopy (SEM). It indicated that the flame retardancy was significantly enhanced in terms of prompting the char formation of PETA and interaction between APP and synergistic agents. Overall, Al(HPO) was the most effective synergistic agent among them. TG-IR analysis showed that the addition of Al(HPO) could delay the release of NH, and make the release of NH more smooth, which was useful to form a dense char. SEM presented that compact, continuous and good intumescent charring layers were observed in all PP/IFR systems with synergistic agent. [ABSTRACT FROM AUTHOR]

Abstract: Nonnegative matrix factorization (NMF) is a recently developed technique for finding parts-based, linear representations of nonnegative data based on minimizing least square error (L 2 norm). However it has been observed that the proper norm for images is the bounded total variation (TV) norm other than the L 2 norm. The space of functions of bounded TV allows discontinuous solution and plays an important role in image processing. In this paper, we propose a new NMF model with bounded TV regularization for identifying discriminate representation of image patterns. We provide a simple update rule for computing the factorization and give supporting theoretical analysis. Finally, we perform a series of numerical experiments to show evidence of the good behavior of the numerical scheme. [ABSTRACT FROM AUTHOR]

A new Bregman iterative regularization method is introduced for wavelet-based image deblurring. By using a suitable sequence of penalty parameters, we solve the issue of solvability of minimization problems arising in each step of the iterative procedure. Moreover, we give a projection-based algorithm to compute the solution. The convergence of the algorithm is also stated. The procedure is very fast and easy to implement. We also show numerical results of image deblurring using the algorithm. [ABSTRACT FROM AUTHOR]

Abstract: Viscoelastic solutions formed in a catanionic surfactant system of dodecyltriethylammonium bromide (DTEAB)/sodium dodecylsulfate (SDS) at the molar ratio of 27/73 were systematically studied using a combination of rheology and dynamic light scattering (DLS). Wormlike micelles began to form above the total surfactant concentration (C total) of 120mM by the growth of small cylindrical micelles. Subsequently the system was found to exhibit linear viscoelasticity with characteristic of a Maxwell fluid in the intermediate concentration range of 170–210mM, which arose from a 3D entangled network of wormlike micelles. At higher surfactant concentrations, a transition from linear micelles to branched structures probably took place. Finally and significantly, the effect of the surfactant headgroup on the rheological property of catanionic surfactant mixtures was discussed. [Copyright &y& Elsevier]

Abstract: Micro powder injection molding (µPIM) differs from conventional powder injection molding (PIM) with respect to the effects of the mold dimensions. In this study, the rheological properties of the feedstock (mixture of carbonyl iron powders and binder) in molds with different diameters were analyzed by numerical simulation based on the powder-binder two fluid model. Viscosity, temperature, shear strain rate, velocity and the flow distance of the feedstock varied for different molds, but did not just reduce by proportion when the mold was smaller which would lead to many defects in green parts. The inner wall of the mold that was the key factor influencing the filling step in µPIM needed more studies. [Copyright &y& Elsevier]

Abstract: In this study, doxorubicin (DOX) was physically incorporated into pH-sensitive micelles made from a mixture of poly(l -histidine)-b-poly(ethylene glycol)/poly(l -lactide)-b-poly(ethylene glycol) (75/25, wt.%). The DOX-loaded mixed micelles were formulated using dialysis methods and optimal DOX incorporation was achieved at a drug/polymer feed ratio of 0.2 (wt./wt.) when a proper amount of aqueous phase (0.2, v./v.) was added into the common solvent (DMSO) solution, followed by dialysis at 4°C. Based on the results obtained from dynamic light scattering, UV–Vis absorption, and fluorescence experiments, it was demonstrated that the encapsulated drugs were mainly located inside the hydrophobic micelle cores, well protected and inaccessible to the exterior molecules. Under in vitro conditions, although the microstructure of the micelles was altered below pH 8.0 by the encapsulated drugs, the drug-loaded micelles still exhibited a desirable ability to control the drug release in response to tumor extracellular pH. [Copyright &y& Elsevier]

Transition metal boride enable applications in fields of cutting tools as the hard phase, but their fabrication suffers from shortcomings in high temperature for binary and hard/soft phase balance. Here, we leveraged a WCoB-Co cermets prepared by using elemental powders of W, Co and B powders via in situ synthesis method and investigated the microstructure evolution of a composite structure of WCoB/Co. The phase evolution, microstructure evolution and mechanical properties were investigated using X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The complete sintering process consist of three solid-phase reaction stages and one liquid-phase sintering stage. The solid-phase reaction stage includes the following three reactions: B + 2Co → Co 2 B, 11 W +15 Co 2 B → 9WCoB + W 2 Co 21 B 6 , and 14 W + 2W 2 Co 21 B 6 → 12WCoB + 23Co + Co 7 W 6. The eutectic liquid phase, essential for the densification, forms at 1323 °C. The Rockwell hardness and density value reach 87.5HRA and 12.11 g/cm3, respectively. At 1380 °C, the traverse rupture strength (TRS) reaches the peak value of 1495 MPa. Moreover, the results show that transgranular fracture is the main fracture mode. The densification stage was completed at ~1400 °C. In particular, Co 7 W 6 phase was discovered during the study of the evolution of WCoB-Co cermets. An increase of the B content was found to be beneficial to eliminate the Co 7 W 6 phase that proved to be detrimental to mechanical properties. • WCoB-Co cermets were prepared using elemental powders. • The paper focuses on phase evolution and microstructure evolution. • Increasing the content of B element can improve the mechanical properties and eliminate Co 7 W 6 phase. [ABSTRACT FROM AUTHOR]

Abstract: A novel pH-sensitive polymeric micellar system composed of poly(l-Histidine)-b-poly(ethylene glycol) and poly(l-Lactide)-b-poly(ethylene glycol) block copolymers was studied by dynamic/static light scattering, spectrofluorimetry and differential scanning calorimetry. The mixed micelles displayed ultra pH sensitivity which could be tuned by varying the mixing ratio of the two polymers. In particular, mixed micelles composed of 25 wt.% poly(l-Lactide)-b-poly(ethylene glycol) exhibited desirable pH dependency which could be used as a drug delivery system that selectively targeted the extracellular pH of acidic solid tumors. Micelles were quite stable from pH 7.4 to 7.0 but underwent a two-stage destabilization as pH decreased further. A significant increase in size and aggregation number was observed when pH dropped to 6.8. Further disruption of the micelle core eventually caused phase separation in the micelle core and dissociation of ionized poly(l-Histidine)-b-poly(ethylene glycol) molecules from the micelles as pH decreased to 6.0. Increased electrostatic repulsions which arise from the progressive protonation of imidazole rings overwhelming the hydrophobic interactions among uncharged neutral blocks is considered to be the mechanism for destabilization of the micelle core. [Copyright &y& Elsevier]

Abstract: In this study, the hot deformation behavior of molybdenum was investigated by means of thermal simulation on a Gleeble-1500 machine. The experiments were carried out under different temperatures, ranging from 1100 to 1400°C, and with a strain rate of 1S−1 to 50S−1. The flow stress under the above mentioned hot deformation conditions was predicted using a back propagation (BP) artificial neural network. The architecture of the network included three input parameters: strain rate, temperature and true strain, and just one output parameter: the flow stress. One hidden layer was adopted, which include nine neurons. Compared with the prediction method of flow stress using the Zerilli–Armstrong model, the prediction method using the BP artificial neural network had higher accuracy. [Copyright &y& Elsevier]

Owing to its excellent wear resistance and good mechanical properties, the sintered Cu–Al–Ni alloy is an ideal material for preparing sliding bearings and self-lubricating sleeves. Adding trace elements into the Cu–Al–Ni alloy is expected to further enhance these properties. Hence, in this work, the microstructure and properties of sintered Cu-12 Al-6 Ni alloys with varying contents of added Ti are studied. Results indicated that the NiAl, γ 2 , and α phases were distinctly refined when the Ti addition was 0.2 wt%, and a small amount of the granular X phase ((Cu, Ni) 2 AlTi) appeared in the alloy. The X phase increased and coarsened with increasing Ti addition. When the Ti addition was 0.7 wt%, pores appeared in the center of the large granular X phase. With increasing Ti addition, the sintered density of the alloys gradually decreased, while the hardness and tensile strength increased first and then decreased. When the Ti addition was 0.7 wt%, the hardness reached the maximum (160 HB), while when the Ti addition was 0.2 wt%, the tensile strength reached the maximum (412.2 MPa). Moreover, the friction coefficient and wear loss of the alloy were the lowest when the Ti addition was 0.2 wt%. These findings can provide some theoretical guidance for fabricating high-performance Cu–Al–Ni powder alloys. [ABSTRACT FROM AUTHOR]

The Hong Kong–Zhuhai–Macao Bridge has a total length of 55 km. One of the greatest technical challenges is an immersed tunnel section stretching over 5.664 km and consisting of 33 prefabricated units (tunnel elements). The tunnel is buried 22 m below the seabed, and is therefore subjected to a significant overburden pressure (at a level of ∼100 kPa) during its whole service life. Conventional tunnel elements are either monolithic or segmented. Monolithic elements act like rigid beams, whereas segmented elements behave like a flexible chain. Under this high level of overburden pressure, the tunnel is liable to problems such as concrete cracking, joint opening and leaking. A novel solution for the semi-rigid (structural) system was proposed and adopted. The central idea is to use compressive force and frictional force at the vertical faces of the segment joints to improve the integrity of the longitudinal structure of the tunnel elements. This paper reviews the concept, design and in situ post-construction observations of this semi-rigid system. [ABSTRACT FROM AUTHOR]

The C-Co-Mo-W and C-Mo-Ni-W quaternary systems have been critically evaluated by means of the CALPHAD approach, in which the Co-Mo-W system was readjusted to ensure the model consistency. The thermodynamic models of Gibbs energies for individual phases in the ternary and quaternary systems are described, including substitutional solution model, sublattice model and linear compound model. The modeling covers the whole temperature and composition ranges, and a set of self-consistent thermodynamic parameters for the C-Co-Mo-W and C-Mo-Ni-W quaternary systems is obtained. According to the comprehensive comparisons between the reported and calculated phase diagram data, the reliable equilibria information is satisfactorily accounted for by the modeling. Based on the present work together with the previously reported assessments of binary, ternary and quaternary sub-systems, a thermodynamic database for the C-Co-Mo-Ni-W quinary system is constructed and applied to calculate the sintering region phase equilibria of the (W,Mo)C-(Co,Ni) cemented carbides. • Thermodynamic evaluations of C-Mo-W-Co/Ni quaternary systems are performed. • Reliable experimental data are well accounted for by the present modeling. • Calculated sintering region of (W,Mo)C-(Co,Ni) cemented carbides are presented. • The assessment is important to the design of (W,Mo)C-based cemented carbides. [ABSTRACT FROM AUTHOR]

MoCoB‐based cermets have been regarded as the potential substitution of WC cermets with high hardness, high melting point and high oxidation resistance. Ternary borides‐based cermets are widely used in extreme environment, such as high‐pressure environment. Therefore, it is significant to explore the mechanical properties and electronic structures of transition elements X (X = V, Mn, Fe, Ni) atoms doped MoCoB under high pressure, which are performed by first‐principles calculations to provide guidance for industry applications. The analysis of cohesive energy and formation enthalpy indicates high pressure leads to unstable states with lower lattice constants and crystal volumes. The deviation of cohesive energy and formation enthalpy indicate Mo4Co3FeB4 and Mo4Co3NiB4 have similar stability. The shear modulus, Young's modulus and bulk modulus increase under high pressure, which consists with the increasing of covalence. The variation of ductility and anisotropy indicate similar upward trend, which is verified by Poisson's ratio, B/G ratio and anisotropy index AU. The analysis of overlap population indicates high pressure leads to the increasing of covalence of B‐Co covalent bonds and the decreasing of the covalence of B‐Mo covalent bonds. The analysis of electronic structures indicates the high pressure leads to higher hybridization and lower density of states of metallic bonds. The analysis of charge density difference consists with the variation of mechanical properties, implying shorter bond length and higher bonds strength under high pressure. [ABSTRACT FROM AUTHOR]

For the purpose of exploring new hard materials and doping methods, the structural, mechanical and electronic properties of WCoB and W2CoB2 ternary boride were investigated with 0, 8.33, 16.67, 25 and 33.33 at.% V doping content and W2CoB2 with 0, 5, 10, 15 and 20 at.% V doping content by first-principle calculations. The cohesive energy, impurity formation energy and formation energy indicate the structural stability of V doped WCoB and W2CoB2. The elastic constants and mechanical properties imply that V doping leads to the decrement of shear modulus and the increment of ductility. Two different kinds of hardness models verify that V doping contributes to the decrement of hardness, which is closely related to shear modulus. The electronic structure is analyzed by DOS (density of states), PDOS (partial density of states) and charge density difference, which indicate the formation of weaker B–V covalent bonds, W–V and W–W metallic bonds lead to the decrement of mechanical properties. Compared with previous studies of Cr, Mn doped WCoB and W2CoB2, V doping leads to worse mechanical properties and hardness, indicating V may not be a suitable choice of doping transition elements. [ABSTRACT FROM AUTHOR]

The heat dissipation requirements of the new generation of semiconductors are placing higher demands on the overall performance of aluminum nitride (AlN) ceramics. This has led to an increasing emphasis on AlN ceramics that combine thermal conductivity and strength. AlN ceramics are often strengthened by hot-press sintering, but their thermal conductivity is typically modest. In this study, pre-sintering and annealing processes are introduced to optimize the thermal conductivity of hot-pressed AlN ceramics to avoid the detrimental effects of oxygen impurities in the AlN lattice. The effect of the oxide layer on the surface of commercial AlN particles is investigated, including density, phase composition, microstructure, and fracture behavior. The effect of annealing on the improvement of thermal conductivity and flexural strength is also verified. Electron paramagnetic resonance (EPR) analysis is performed to examine the concentration of intercrystalline defects under various conditions. Finally, AlN ceramics with a thermal conductivity of 204 W m−1 K−1 and a flexural strength of 376 MPa are obtained. [ABSTRACT FROM AUTHOR]

Highlights • The memory bearing can limit shear transfer in intermediate (immersion) joint of immersed tunnel. • The memory bearing was invented by trial-and-error tests of tearing metal rods. • The memory bearing enables the structure to fully utilize its capacity. Abstract The immersed tunnel in the Hong Kong–Zhuhai–Macao Bridge (HZMB) project has a deep alignment and poor geological conditions; the soft soil layer is up to 30-m thick. To protect the structure of the element joints of the immersed tunnel from differential settlement, we developed a special type of bearing that can be placed between the vertical shear keys of the element joints. These bearings 'remember' the maximum capacity that the tunnel structure can undertake so that they can guide the force flow from overloads via the tunnel structure to the foundation in the most appropriate manner to protect the shear-transferring structure while fully utilising it. As of now, all the element joints of the thirty-three elements in the HZMB tunnel are being protected with the bearings installed. This paper elaborates on our concept and experiments, based on which our design and applications were carried out. [ABSTRACT FROM AUTHOR]

The C-Mo-Zr system was assessed by means of the CALPHAD approach. All of the phase equilibria available from the literature were critically reviewed. The liquid was modeled as substitutional solution phase, while the carbides including fcc-(Mo,Zr)C1−x, bcc-(Mo), bcc-(Zr), hcp-Mo2C, hcp-(Zr) and η-MoC were described by using corresponding sublattice models. The laves-Mo2Zr and shp-MoC phases were considered as binary compounds with no solubility for the third component. The existence of ternary phase was not reported in this system. The modeling of C-Mo-Zr ternary system covers the entire composition and temperature ranges, and a set of self-consistent thermodynamic parameters for the C-Mo-Zr system was systematically optimized. Comprehensive comparisons between the calculated and reported phase diagram data show that the reliable information is satisfactorily accounted for by the present modeling. The liquidus projection and reaction scheme of the C-Mo-Zr system were also generated based on the present thermodynamic assessment. [ABSTRACT FROM AUTHOR]

MoCoB–Co cermets with different Mn contents were synthesized using an in-situ sintering reaction, and the effect of Mn addition on the microstructure, interfaces, and mechanical properties was investigated. The addition of Mn inhibited the transition of the binder phase from fcc to hcp. Adding an appropriate Mn can increase the density of the material and refine the hard phase grain. With increasing Mn content, the hardness decreased marginally and then gradually increased, and the transverse rupture strength (TRS) and fracture toughness (K IC) gradually decreased. The cermet with 6 wt% Mn addition had the smallest grain size and lower porosity. The hardness of the cermet increased from HRA 89.0 to HRA 91.7. The interface bonding strength of MoCoB/hcp-Co is higher than that of MoCoB/fcc-Co. After isothermal aging treatment, the content of hcp-Co in the binder phase increased markedly; thus, the K IC and TRS increased from 11.3 MPa m1/2 and 1200 MPa–13.3 MPa m1/2 and 1750 MPa, respectively. [ABSTRACT FROM AUTHOR]

A first-principles study was performed to assess the potential of MAB 2 (M = Nb, Ta; A = Co, Ni) ternary borides as friction-resistance cermet. The formation energy, decomposition energy, phonon dispersion curves and elastic constants were calculated to evaluate stabilities. The bulk modulus, shear modulus, Pugh's ratio, Poisson's ratio and elastic anisotropy were adopted to analyze elastic properties. The Debye temperature was used to reflect thermal conductivity. The density of states, charge density and Mulliken population were performed to reveal physical mechanisms. Through calculational results, MAB 2 possesses structure and mechanical stabilities, and then MAB 2 has excellent elastic properties. Both NbNiB 2 and TaCoB 2 are ductile materials; in addition, the thermal conductivity of NbNiB 2 and NbCoB 2 are satisfying. The calculations imply MAB 2 is a mixture of covalent, ionic and metallic bonds, indicating covalent bonds are vital. Especially, the theory hardness of NbCoB 2 , NbNiB 2 , TaCoB 2 and TaNiB 2 are 25.30, 27.71, 30.78 and 31.91 respectively, indicating MAB 2 has high-hardness potential. The comprehensive properties are more outstanding in MAB 2 than in MAB. The method from atomic scale to macroscale can accelerate optimization of novel friction-resistance cermet. • Studying the potential of MAB 2 -type borides as friction-resistance cermet. • Ratio of B in MAB 2 borides playing a vital role. • MAB 2 borides belonging to a mixture of covalent, ionic and metallic bonds. • Covalency mainly affecting properties of MAB 2 Borides. • Optimization way from atomic scale to macroscale. [ABSTRACT FROM AUTHOR]

Benefiting from ordered atomic structures and strong d‐orbital interactions, intermetallic compounds (IMCs) are promising electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, the body‐centered cubic IrGa IMCs with atomic donor–acceptor architectures are synthesized and anchored on the nitrogen‐doped reduced graphene oxide (i.e., IrGa/N‐rGO). Structural characterizations and theoretical calculations reveal that the electron‐rich Ir sites are atomically dispersed in IrGa/N‐rGO, facilitating the electron transfer between Ir atoms and adsorbed species, which can efficiently decrease the energy barriers of the potential determining step for both HER and OER. Impressively, the IrGa/N‐rGO||IrGa/N‐rGO exhibits excellent performance for overall water splitting in alkaline medium, requiring a low cell voltage of 1.51 V to achieve 10 mA cm−2, meanwhile, exhibiting no significant degradation for 100 h. This work demonstrates that the rational design of noble metal electrocatalysts with donor–acceptor architectures is beneficial for catalytic reactions in energy conversion applications. [ABSTRACT FROM AUTHOR]

We developed a 3D rotational viscometer model based on the finite volume method and analyzed the effects of the shear rate, glass bead solid fraction, and particle size on the viscosity of water and maltose syrup. We developed a novel Gidaspow model and introduced particle sphericity as a parameter. The effects of sphericity, solid fraction, and particle size on the viscosity of different fluids were simulated and calculated. Compared with the experimental findings, the maximum relative error was 10.7% before the solid fraction was 30%, and the calculated data suitably agree with the experimental results. The results also show that when the solid fraction is above 10%, the particle fluid viscosity increases with increasing shear rate and solid fraction and decreases with increasing sphericity and particle size. The novel Gidaspow equation can suitably predict the initial apparent viscosity of different solid–liquid mixtures before reaching a solid fraction of 50%. The new model has a wide range of applications and can be applied to arbitrary particle shapes (spherical range of 0–1) in various materials and fields. The proposed model can provide a reference for further theoretical and experimental studies on solid–liquid two-phase flow. [ABSTRACT FROM AUTHOR]

Refractory high-entropy alloys (RHEAs) composed of Ti, Zr, Hf, and Nb have emerged as promising materials for high-temperature aerospace applications due to their exceptional balance of strength and toughness, coupled with a reduced density and softening resistance. This study delves into the influence of alloy composition on the mechanical properties, a pivotal aspect in the design of RHEAs. We investigate a series of Ti 48-x Zr x Hf 26 Nb 26 (x = 14, 18, 22, 26, 30, 34) alloys, prepared through suction casting and homogenization treatments. The phases, microstructure, and fracture morphology of these alloys are analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron backscattered diffraction (EBSD), subsequent tensile tests provide insights into the strength and elongation characteristics of alloys. The homogenized alloys consistently exhibit one BCC phase with equiaxed grains, whereas the fracture mode shifts from intergranular to transgranular, and return to intergranular as the Zr content increases. Experimental results reveal an asymmetry mechanical behavior, alloys with higher Ti content display superior toughness (elongation 17.83 % for Ti = 34 at%) compared to those with higher Zr content (elongation 16.05 % for Zr = 34 at%). Among them, the Ti 22 Zr 26 Hf 26 Nb 26 alloy achieves the peak tensile strength of 695.25 MPa, indicating an inverse relationship between strength and toughness. Solid-solution strengthening and chemical short-range orderings emerge as the predominant contributors to the overall strength of the TiZrHfNb alloys. To gain a deeper understanding of the mechanical behavior at the atomic scale, we performed first-principles calculations to investigate the elastic properties and charge density of Ti 48-x Zr x Hf 26 Nb 26 alloys in the BCC structure. These calculations shed light on the underlying mechanisms governing the strength and toughness behavior. The present work offers valuable insights into the design of mechanical properties of TiZrHfNb RHEAs, serving as a paradigm for future materials development in this field. • Microstructure and mechanical behaviors of TiZrHfNb RHEAs are investigated. • The asymmetrical tensile strength and elongation exhibited, alloys with a lower content of Zr have superior toughness. • DFT calculations of the elastic modulus and charge density are performed to elucidate the experimental findings. • CSROs and solid-solution strengthening significantly contribute to tensile strength, the peak value reaching 695.25 MPa. [ABSTRACT FROM AUTHOR]