Shift Of Transition Temperature Research Articles

Studies on the physical properties of BaTi1-xSnxO3 (x = 0, 0.04, 0.08, 0.12, 0.16, 0.20) synthesized using solid state ceramic route

The pristine and Sn-doped BaTiO3 was successfully synthesized using a conventional ceramic route by calcination at 1200 °C. All the samples synthesized in the present investigation belong to the tetragonal phase crystallized under P4mm space group. The lattice parameters, c/a ratio, and X-ray density of samples increase with dopant due to larger ionic radii and heavier mass of dopant Sn than host Ti. Raman spectrum analysis of samples reconfirms the structure and solubility of Sn at the Ti site of BaTiO3. The microstructure analysis of all samples reflects spherical grains that increase the grain size with doping of Sn from 0.38 to 1.92 μm. The optical properties of samples suggest the presence of direct and indirect bandgap whose values range from (3.04–3.29) eV and (2.47–3.02) eV, respectively. The variation in dielectric constant and dissipation factor with frequency suggests the presence of interfacial and orientation polarization. A transition peak was observed in pristine sample around 120 °C, and it shifted towards room temperature with doping of Sn. The shift in transition temperature can be explained in terms of structure transition from tetragonal to cubic. The present materials are suitable candidates for radiation filters, piezoelectric devices, and ferroelectric applications.

Mechanical characteristics of epoxy nanocomposites derived through reinforcing carbonaceous fillers

Epoxy nanocomposites (ENCs) were fabricated through reinforcing various carbonaceous fillers (CFs, 3.0 wt%) into epoxy resin followed by curing with polyamine hardener. For this purpose, nanographite (NG), pine needle cone derived biochar (BC), and related graphene oxide (GO) were used as fillers for epoxy modification. Test specimens were fabricated and investigated for their tensile (ASTM D 638-02a), compressive (ASTM D 695-02a) and dynamic mechanical (ASTM E1820-01) behavior with reference to cure epoxy. Effect of chemical identity of CFs on morphology and average roughness of ENCs was investigated through atomic force microscopy. Study reveals that ENCs derived from GO exhibited maximum tensile strength (84.75 MPa) as compare to the other NG and BC derived analogues. ENCs derived through reinforcing NG has exhibited maximum elastic modulus (1307.72 MPa) in compare to their GO and BC derived analogues. ENCs derived through reinforcing BC have exhibited maximum compressive strength (46.93 MPa) and modulus (102.98 MPa) in comparision to their NG and GO analogues. Dynamic mechanical analysis reveals moderate shift in glass transition temperature (Tg, °C) of ENCs derived from GO (77.73) and NG (81.75) ranging to over cured epoxy (66.67).However, reinforcing BC into epoxy has raised the Tg of ENCs to 95.46 °C.

Structural Assessment of the European DEMO Water-Cooled Lithium Lead Breeding Blanket Central Outboard Segment Under Remote Maintenance Loading Conditions

Within the framework of the European research activities devoted to design the DEMO breeding blanket (BB), the Water-Cooled Lithium-Lead (WCLL) BB concept is one of the candidates currently assessed in EU. One of the main issues connected to its design is represented by the remote maintenance (RM) operations. In particular, previous thermo-mechanical analysis highlighted a Ductile to Brittle Transition Temperature (DBTT) shift above the room temperature within the WCLL central outboard (COB) segment during normal operation. This may pose problems during the RM operations foreseen in the BB replacement phase. Indeed, within those WCLL COB segment’s regions where the DBTT shifted above the room temperature, the stress level arising during RM operations may be able to promote crack growth and migration resulting in a fragile fracture event. Then, in this work, the structural assessment of the DEMO WCLL COB segment under RM scenarios is performed, in order to provide the fracture mechanics analysis with the necessary input in terms of stress spatial distribution and to understand if the deformation occurring during RM can be accommodated by the available space reservation. Several potential RM scenarios have been considered, taking into account also the potential occurrence of a seismic event or the necessity to remove the WCLL COB segment with the liquid breeder not drained. The study has been performed adopting a numerical approach based on the Finite Element Method and adopting the quoted Abaqus code. The obtained results are quite encouraging and will allow, in the follow up, the refinement of the RM plan foreseen for the WCLL BB.

Synthesis, crystal structure and phase transition in a perovskite type (CH3NH3)2M(X)2(Y)2(M=Sn; X=SCN; Y=Cl)

The exploration of ferroelectric hybrid materials is highly appealing due to their great technological significance. In line with this, we herein report the development of a new ferroelectric relaxor: (CH3NH3)2Sn(SCN)2Cl2 was synthesized and studied by single-crystal X-ray diffraction, powder XRD, Differential scanning calorimetry (DSC), IR spectroscopy and dielectric measurements. The phase purity was confirmed by Rietveld refinement of the X-ray powder diffraction pattern. It crystallizes, at room temperature, in the orthorhombic system with the Pnm21 space group. The crystal structure is formed of discrete ionic entities (CH3NH3)+ and (Sn(SCN)2Cl2)2-. The methylammonium cations are bonded to these chains by hydrogen-bonding contacts. DSC measurement shows that this compound exhibits a diffuse ferro–paraelectric phase transition around 355 K. Dielectric study exhibits a relaxor behavior characterized by the transition temperature shifts toward higher temperature with the rise of frequency. This behavior was validated by the modified Curie–Weiss law. The diffuseness parameter was the γ is approach to 1.96 at 2000 KHz.

Radiation embrittlement of clad-HAZ of RPV of a decommissioned BWR plant

Radiation hardening/embrittlement was investigated for clad-heat affected zone (clad-HAZ)) of reactor pressure vessel (RPV) of Hamaoka unit-1 boiling water reactor (BWR) under decommissioning process. The neutron irradiation fluence in the HAZ of the RPV steel was 1.5 × 1022 n/m2 (E > 1MeV). The shift in ductile-brittle transition temperature, ΔDBTT, was measured to be +26 °C using 1/3-sized Charpy specimens, while the increase in Vickers hardness, ΔHv, was 19 HV in the clad-HAZ of 1.6 mm depth from the clad boundary. Atom probe tomography (APT) was conducted at the locations 0.1, 0.8, 1.6. 4 and 10 mm away from the clad boundary, and revealed that solute clusters were formed in both clad-HAZ and base metal (10 mm depth), and the clusters were rich in Mn, Ni, Si, Cu with the averaged diameter of about 2.5 nm and the number density of 2 × 1022/m3, being almost independent of depth location. As for the chemical compositions of the clusters, Mn content increased with decreasing Cu content. This suggests that there might be site completion between Mn and Cu for clustering. Radiation hardening of clad-HAZ induced by the formation of solute clusters was estimated on the bases of the dispersed barrier hardening (DBH) model in terms of N·d, and well interpreted with α = 0.06–0.08. The ΔDBTT-Vf plot, of which the data was measured with 1/3 size specimens sampled from the clad-HAZ at 1.6 mm depth, agreed with the previous surveillance test results measured in surveillance tests with standard size specimens of base metal.

Phase-field modelling of paramagnetic austenite–ferromagnetic martensite transformation coupled with mechanics and micromagnetics

A three-dimensional phase-field model is proposed for simulating the magnetic martensitic phase transformation. The model considers a paramagnetic cubic austenite to ferromagnetic tetragonal martensite transition, as it occurs in magnetic Heusler alloys like Ni2MnGa, and is based on a Landau 2-3-4 polynomial with temperature dependent coefficients. The paramagnetic–ferromagnetic transition is recaptured by interpolating the micromagnetic energy as a function of the order parameter for the ferroelastic domains. The model is numerically implemented in real space by finite element (FE) method. FE simulations in the martensitic state show that the model is capable to correctly recapture the ferroelastic and -magnetic microstructures, as well as the influence of external stimuli. Simulation results indicate that the paramagnetic austenite to ferromagnetic martensite transition shifts towards higher temperatures when a magnetic field or compressive stress is applied. The dependence of the phase transition temperature shift on the strength of the external stimulus is uncovered as well. Simulation of the phase transition in magnetocaloric materials is of high interest for the development of energy-efficient magnetocaloric cooling devices.

Colloidal bag of marbles: The structure and properties of lipid-coated silica nanoclusters

Silica particles find applications in drug delivery and bio-sensing, where their large specific surface area can accumulate or release biologically active substances. Such applications would benefit from the ability to control diffusion access to the surfaces of a larger number of silica particles simultaneously. In the present work, we show that a phospholipid bilayer can contain clusters of silica nanoparticles ranging in number from a few to several tens, forming structures resembling a colloidal version of a bag of marbles. The lipidic membrane serves as a diffusion gate that prevents premature leakage of encapsulated substances from the nanoparticles to the bulk during storage, but allows diffusion when the phase transition temperature is exceeded. Using 30 nm SiO2 nanoparticles with or without surface amino groups, combined with lipid membranes containing DPPC, DPPG and cholesterol at molar ratios ranging from 25:60:15–85:0:15, we show that the electrostatic interactions between the nanoparticle surface and the lipid bilayer are crucial for the existence and stability of lipid-coated nanoclusters. We demonstrate the gating mechanism by measuring temperature-dependent diffusion of a model substance 5-(6)-carboxyfluorescein from the clusters. A shift in the phase transition temperature of approx. 20 K has been observed in the lipid-coated silica nanoclusters compared to plain liposomes of identical lipid bilayer composition.

Dynamic mechanical analysis of nylon 6 fiber-reinforced acrylonitrile butadiene rubber composites

Dynamic mechanical properties of polymeric materials are of direct relevance to a range of unique polymer applications. The aim of the study is to investigate the dynamic mechanical properties of composites of short nylon 6 fiber with acrylonitrile butadiene rubber (NBR). The storage modulus (G′), loss modulus (G″), and the damping factor (tan δ) have been analyzed with reference to the effects of fiber loading, curing systems, and bonding agents over a range of temperature and at varying frequencies. The storage modulus increases with increment in fiber loading, whereas loss modulus and damping factor decrease. The glass transition temperature shifts to higher temperature upon increment in fiber loading. Dicumyl peroxide (DCP)–cured composites show higher storage modulus and lower damping than the corresponding sulfur-cured one. The addition of hexa-resorcinol and phthalic anhydride as bonding agents enhances the dynamic mechanical properties of the composites. The experimental results have been evaluated by comparing with Einstein, Guth, and Nielsen models.

Barocaloric and magnetocaloric effects in isostructurally alloyed (MnCoGe)-(CuCoSn) systems

In the present work, the structural, magnetic properties and barocaloric effects of the (MnCoGe)0.96-(CuCoSn)0.04 alloy were investigated. At an ultra-low pressure of 0.3 kbar, the isothermal entropy change of 20 J∙kg−1K−1 and adiabatic temperature change of 3.4 K can be obtained, performing a low-pressure-driven large barocaloric effect. The transition temperature shifts with pressure are as high as −8.8 K∙kbar−1 and −11.8 K∙kbar−1 for forward and reverse transformations, respectively. Such a promising barocaloric performance is mainly attributed to the large entropy change of structural transformation and large volume expansion as high as 3.9%.

Interfacial Contributions in Nanodiamond-Reinforced Polymeric Fibers.

We study the interfacial energy parameters that explain the reinforcement of polymers with nanodiamond (ND) and the development of mechanical strength of electrospun ND-reinforced composites. Thermodynamic parameters such as the wettability ratio, work of spreading and dispersion/aggregation transition are used to derive a criterion to predict the dispersibility of carboxylated ND (cND) in polymeric matrices. Such a criterion for dispersion (Dc) is applied to electrospun cND-containing poly(vinyl alcohol) (PVA), polyacrylonitrile (PAN), and polystyrene (PS) fiber composites. The shifts in glass transition temperature (ΔTg), used as a measure of polymer/cND interfacial interactions and hence the reinforcement capability of cNDs, reveal a direct correlation with the thermodynamic parameter Dc in the order of PAN < PS < PVA. Contrary to expectation, however, the tensile strength of the electrospun fibers correlates with the Dc and ΔTg only for semicrystalline polymers (PAN < PVA) while the amorphous PS displays a maximum reinforcement with cND. Such conflicting results reveal a synergy that is not captured by thermodynamic considerations alone but also factor in the contributions of polymer/cND interface stress transfer efficiency. Our findings open the possibility for tailoring the interfacial interactions in polymer-ND fiber composites to achieve maximum mechanical reinforcement.

Deuteration triggered downward shift of dielectric phase transition temperature in a hydrogen-bonded molecular crystal

Deuteration of hydrogen-bonded phase transition crystals can increase the transition temperatures due to the isotope effect. But rare examples show the opposite trend that originates from the structural changes of the hydrogen bond, known as the geometric H/D isotope effect. Herein, we report an organic crystal, diethylammonium hydrogen 1,4-terephthalate, exhibits a reversible structural phase transition and dielectric switching. Structural study shows the cations reside in channels formed by one-dimensional hydrogen-bonded anionic chains and undergo an order-disorder transition at around 206 K. The deuterated counterpart shows an elongation of the O···O hydrogen bond by about 0.005 Å. This geometric isotope effect releases the internal pressure of the anionic host on the cation guests and results in a downward shift of the phase transition temperature by 10 K.

The influence of non-stationarity and interphase curvature on the growth dynamics of spherical crystals in a metastable liquid

This manuscript is concerned with the theory of nucleation and evolution of a polydisperse ensemble of crystals in metastable liquids during the intermediate stage of a phase transformation process. A generalized growth rate of individual crystals is obtained with allowance for the effects of their non-stationary evolution in unsteady temperature (solute concentration) field and the phase transition temperature shift appearing due to the particle curvature (the Gibbs-Thomson effect) and atomic kinetics. A complete system of balance and kinetic equations determining the transient behaviour of the metastability degree and the particle-radius distribution function is analytically solved in a parametric form. The coefficient of mutual Brownian diffusion in the Fokker-Planck equation is considered in a generalized form defined by an Einstein relation. It is shown that the effects under consideration substantially change the desupercooling/desupersaturation dynamics and the transient behaviour of the particle-size distribution function. The asymptotic state of the distribution function (its 'tail'), which determines the relaxation dynamics of the concluding (Ostwald ripening) stage of a phase transformation process, is derived. This article is part of the theme issue 'Transport phenomena in complex systems (part 1)'.

Machine learning modeling of irradiation embrittlement in low alloy steel of nuclear power plants

In this study, machine learning (ML) techniques were used to model surveillance test data of nuclear power plants from an international database of the ASTM E10.02 committee. Regression modeling was conducted using various techniques, including Cubist, XGBoost, and a support vector machine. The root mean square deviation of each ML model for the baseline dataset was less than that of the ASTM E900-15 nonlinear regression model. With respect to the interpolation, the ML methods provided excellent predictions with relatively few computations when applied to the given data range. The effect of the explanatory variables on the transition temperature shift (TTS) for the ML methods was analyzed, and the trends were slightly different from those for the ASTM E900-15 model. ML methods showed some weakness in the extrapolation of the fluence in comparison to the ASTM E900-15, while the Cubist method achieved an extrapolation to a certain extent. To achieve a more reliable prediction of the TTS, it was confirmed that advanced techniques should be considered for extrapolation when applying ML modeling.

SILICON-CONTAINING OLIGOMERIC AZOINITIATORS IN THE SYNTHESIS OF BLOCK COPOLYMERS

The aim of the work was to develop methods for the synthesis and study of the properties of silicon-containing oligomeric azo- and polyazoinitiators based on bis-γ-hydroxypropylpolysiloxane (HPS) and bis-γ-aminopropylpolysiloxane (APS). Silicon-containing oligomeric azoinitiators using HPS were synthesized on the basis of cyclohexanone azo-bis-isobutyrohydrazone (AGN-CH) and bis-γ-hydroxypropylpolysiloxane bifunctional macrodiisocyanate (MDIHPS). MDIHPS was obtained by the interaction of GPS with 2,4 toluene diisocyanate (2,4-TDI). Oligomeric azoinitiators have been obtained, which have the structure RXR and (RX)nR, where R is a propylpolysiloxane block, X is a azo initiator block. For the synthesis of an oligomeric azo initiator based on bis-γ-aminopropyl polysiloxane (APS), a method was first developed for the synthesis of a monomeric azo initiator with terminal oxadiazolinylcarbamanate isocyanate groups (AGN-NCO) by the interaction of AGN-CH and 2,4-TDI at a molar ratio of 1: 2. On the basis of the obtained AGN-NCO and APS at a molar ratio of AGN-NCO: APS = 1: 1, an oligomeric azo initiator (OAI APS-P) was synthesized, which has the structure (RX)nR, where R is a propylpolysiloxane block, X is an azo initiator block. The structures of monomeric and oligomeric azo initiators have been studied by UV and IR spectroscopy, and the kinetic regularities of their synthesis have been calculated. On the basis of oligomeric azo initiators and styrene, block copolymers of the (AB)nA type were obtained by the method of thermal and photoinitiated radical polymerization, where A is a propylpolysiloxane block, B is an oligosyrene block with a constant value of the organosilicon block and a different size of the oligostyrene block. The structure of block copolymers was investigated by IR spectroscopy. It was shown that during photopolymerization, oligostyrene blocks of shorter length are formed than during thermopolymerization, and possible oxidation processes. The study of relaxation transitions by DSC in oligostyrene and propylpolysiloxane blocks of the BCP showed that the common heat capacity curves are the presence of two jumps in the heat capacity at the glass transition temperatures of the polysiloxane and oligostyrene microphase. A slight shift in the glass transition temperature of polysiloxane microphases in BCP towards higher temperatures compared to the homopolymer may be associated with the effect of oligostyrene microphase. With a decrease in the length of the oligosyrene block, a low-temperature shift in the glass transition temperature of oligostyrene blocks relative to the homopolymer and a depression of ∆Cp,2 are observed, which is associated with the suppression of mobility in oligodienic microphases by less mobile propylpolysiloxane blocks.

Ultrasound-induced structural modification and thermal properties of oat protein

The objective of this study was to characterize the solubility, structural, thermal, and aggregation properties of oat protein under high-intensity ultrasound (HIU) treatment. Suspensions of oat protein isolate (OPI) at pH 2.0–8.0 were subjected to HIU for 5 min at 70% amplitude; solubility, particle size, surface attributes, UV–Vis absorption, intrinsic fluorescence, polypeptide profiles, calorimetric properties, and thermal aggregation were determined. The HIU treatment significantly reduced particle size (up to 37%) and increased surface charge of OPI leading to solubility increases (up to 48%, P < 0.05) at pH 2.0–3.0 and pH 5.5–8.0. However, HIU did not alter the protein profile nor disrupt disulfide linkages between α and β subunits. Reduced enthalpy of denaturation with no shift in thermal transition temperature were observed in HIU samples unless disulfide bonds were pre-cleaved. While control OPI displayed variable changes in particle size upon heating from 20 to 95 °C, the HIU sample maintained a relatively uniform and smaller particle size. The findings indicate that protein particle disruption and weakening of intermolecular forces by HIU improved physicochemical and thermal properties of OPI, which are of value to processing oat protein-based beverages and other food products.

Core-Shell Structure and Dielectric Properties of Ba0.6Sr0.4TiO3@ Fe2O3 Ceramics Prepared by Co-Precipitation Method

Ba0.6Sr0.4TiO3 (BST) ceramic materials have been widely used in the field of multilayer ceramic capacitors. Surface modification through the surface coating to form a heterogeneous layer could effectively improve the dielectric properties. In this work, BST powders were prepared by a co-precipitation method. The effects of reaction conditions on the microstructure of the BST powder were investigated. The reaction temperatures significantly affected the morphology of BST powder, and the rhombic-type particles were obtained with the reaction temperature around 80 °C. Meanwhile, the BST@Fe2O3 was prepared by the chemical precipitation method using BST powders with rhombic-type microstructure as “core”, and the so-called “core-shell” microstructure was confirmed in the BST@Fe2O3 powder. Then, BST@x wt%Fe2O3 (x = 2.5, 5, 7.5, and 10, denoting the different content of Fe2O3) ceramics were further prepared, and the influence of “core-shell” structure on the phase structure, microstructure, and dielectric properties was investigated. With the increasing of Fe2O3 content, the ferroelectric–paraelectric phase transition temperature shifts toward lower temperatures, and dielectric peaks gradually become broad and frequency-dependent, which may be due to inconsistent chemical composition from core to shell.

Understanding release kinetics and collapse proof suture retention response of curcumin loaded electrospun mats based on aliphatic polyesters and their blends

The paper aims at designing and fabrication of PLA/PCL blended suture resistant electrospun mats (EMs) encapsulating non-toxic curcumin and optimization of its release behavior, to facilitate its sustained release at the targeted areas, without complexation with any chemical and/or synthetic drug. The release of curcumin from PLA/PCL blended EMs followed a diffusion-controlled mechanism, as evident from the agreement of the experimental release data with Peppas- Korsmeyer, Higuchi, and Kopcha model. The curcumin embedded EMs have effectively rendered a release confirming to a new generalized logarithmic model. PLA/PCL blended EMs have proved to be an excellent carrier system, exhibiting enhanced cumulative curcumin release with an increase in curcumin loading. The evaluation of structural and viscoelastic properties of the fabricated EMs showed an increase in modulus and strength, along with a subsequent decrease in elongation, with an increase in curcumin content. Suture-induced cooperative collapse dynamics the EMs have been found to be a three-stage process involving stable, stable-unstable, and fast-unstable structural failure corresponding to network realignment, lateral pullout/fracture of fibers, and divergent tearing along the crack path. The viscoelastic responses showed a prominent shift in glass transition temperature (Tg) of the PCL phase indicating the development of curcumin-induced microstructural changes attributed to the H-bonding interaction with polymer segments of PLA/PCL-based EMs. Our study demonstrates, functionally efficient designing of PLA/PCL-based curcumin-loaded biodegradable EMs with sustained retention of tunable mechanical properties and hydrophobicity, irrespective of the extent of (in-vitro) curcumin release.

Influence of Ni-Mn contents on the embrittlement of PWR RPV model steels irradiated to high fluences relevant for LTO beyond 60 years

Understanding the irradiation induced degradation of the reactor pressure vessel (RPV) steels at high fluences becomes more important in view of safe long term operation (LTO) of existing nuclear power plants. Specifically, the role of Ni, Mn and Si and associated synergetic effects on embrittlement behaviour need to be further investigated to understand accelerated embrittlement at high neutron fluences (ca. 1 × 10 20 n.cm −2 , E>1 MeV) observed in certain types of RPV steels. In addition, it is required to verify the validity of existing embrittlement trend curves (ETCs) at high fluence values. To address these issues, NRG and JRC performed a unique irradiation experiment called LYRA-10 in the High-Flux Reactor (HFR) Petten. In LYRA-10 a variety of specimens (e.g. tensile, Charpy, mini-Charpy and microscopy) of RPV steels (base metal and welds) with systematic variations in Ni, Mn and Si contents, while keeping the base composition representative of VVER-1000 and PWR RPV steels, have been irradiated for 16 HFR cycles to achieve the nominal fast neutron fluence of 1.11 × 10 20 n.cm −2 at a nominal temperature of 286 °C. A large post-irradiation examination campaign on LYRA-10 specimens has been initiated within the STRUMAT-LTO, which is an international collaboration project co-funded by EURATOM. The research reported in this paper includes results from tensile and mini-Charpy impact testing of four PWR RPV model steel specimens irradiated in LYRA-10, which is performed as part of STRUMAT-LTO in-kind pilot project before the start of the EURATOM co-funded project. The combined influence of Ni and Mn on embrittlement behaviour, characterized by irradiation hardening and shifts in transition temperature (T k ) properties, has been evaluated. The measured shifts in T k values for all four model steels have been compared with predicted values from two selected ETCs in order to check their validity for these steels at the above high neutron fluence values.

INFLUENCE OF KRAFT LIGNIN ON THE PROPERTIES OF RUBBER COMPOSITES

The influence of lignin content on reclaimed rubber (RR)/natural rubber (NR) blend composite properties has successfully been studied. Scanning electron microscopy (SEM) were used to understand morphology. Fourier-transform infrared spectroscopy (FTIR) for the possible chemical interaction, whereas thermogravimetric analysis (TGA) and tensile tester were used to predict strength and elongation for possible practical applications. The results indicated that the presence of lignin forms cavities which seemed to arise from complex interactions of the blend with the lignin. Those cavities dominated tensile fractured surface and the increase in lignin indicated inconsistencies of interfacial interactions. Lignin RR/NR blend composites revealed a drop in tensile strength and shift in glass transition temperature, except for the highest lignin containing blend composite. More active interactive constituent of the blend appeared to be NR. The interaction has not favored the thermal stability and crosslinking density.

Development of new embrittlement trend curve based on Japanese surveillance and atom probe tomography data

• A new embrittlement trend curve based on Japanese surveillance data was developed. • A simple analytical solution of the embrittlement trend curve (ETC) can be obtained from the original differential equation. • The new ETC can predict microscopic and macroscopic changes caused by neutron irradiation. We have developed a new embrittlement trend curve (ETC) for neutron-irradiated reactor pressure vessel(RPV) steels based on Japanese surveillance and material test reactor data. Our model is based on experimental data obtained by atom probe tomography (APT) and Charpy V-notch impact tests. The square root of the volume fraction ( V f ) of the solute atom cluster (SC) formed by neutron irradiation, which is determined by APT, is correlated to the Charpy transition temperature shift ( ΔT 41J ). In addition to the ΔT 41J and V f data, other APT data (the average volume of solute clusters (SC), the number density of SC, and the matrix Cu content in RPV steels) were also used to calibrate the coefficients in the new ETC model. The new ETC model has a simple functional form and, unlike the current version of JEAC4201, does not require numerical time integration. The new ETC model has similar ΔT 41J prediction performance to the current JEAC4201 model. Furthermore, the APT data are also predicted well, which suggests a good physical basis for the new ETC.