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Pentavalent uranium compounds are key components of uranium‘s redox chemistry and play important roles in environmental transport. Despite this, well‐characterized U(V) compounds are scarce primarily because of their instability with respect to disproportionation to U(IV) and U(VI). In this work, we provide an alternate route to incorporation of U(V) into a crystalline lattice where different oxidation states of uranium can be stabilized through the incorporation of secondary cations with different sizes and charges. We show that iriginite‐based crystalline layers allow for systematically replacing U(VI) with U(V) through aliovalent substitution of 2+ alkaline‐earth or 3+ rare‐earth cations as dopant ions under high‐temperature conditions, specifically Ca(UVIO2)W4O14 and Ln(UVO2)W4O14 (Ln=Nd, Sm, Eu, Gd, Yb). Evidence for the existence of U(V) and U(VI) is supported by single‐crystal X‐ray diffraction, high energy resolution X‐ray absorption near edge structure, X‐ray photoelectron spectroscopy, and optical absorption spectroscopy. In contrast with other reported U(V) materials, the U(V) single crystals obtained using this route are relatively large (several centimeters) and easily reproducible, and thus provide a substantial improvement in the facile synthesis and stabilization of U(V). [ABSTRACT FROM AUTHOR]

90Sr, as a typical artificial radionuclide, poses a serious threat to human health and the ecological environment. The selective removal of this radionuclide from industrial nuclear waste is crucial for our environment. Here we report a novel potassium fluoroaluminate, K2[(AlF5)H2O], which was synthesized by a simple low‐temperature one‐step method. It adopts a 1D AlF6‐chain structure, which consists of exchangeable potassium ions in between the infinite chains of octahedral Al centers. As a remarkable inorganic ionic exchanger, K2[(AlF5)H2O] has a high chemical stability (resistance of pH=~3‐12) and thermal stability (≥~300 °C). It possesses an excellent adsorption selectivity (Kd=~6.1×104 mL ⋅ g−1) and a maximum adsorption capacity of qm=~120.32 mg ⋅ g−1 for Sr2+. Importantly, it still keep a very good selectivity for Sr2+ ions even in the presence of competing Na+, Mg2+ and Ca2+ aqueous solutions. K2[(AlF5)H2O] is the first example of fluoroaluminate ionic exchange materials that can capture Sr2+. This result opens up a new way to design and synthesize inorganic ionic exchangers for the selective removal of Sr2+ ions from radioactive waste water. [ABSTRACT FROM AUTHOR]

Four new phosphites/phosphates, namely Al[P2O3(OH)3](H2O), Al[(HPO3)(OH)(H2O)], Ca[HPO3] and Al3P6O19.5, were designed and synthesized by low temperature flux methods. They crystallized in P63mc, P1¯, P43212, and P63/m space groups, respectively. The basic units of Al[P2O3(OH)3](H2O), Al[(HPO3)(OH)(H2O)] and Ca[HPO3] are composed of [PO3]3− or/and [AlO6]9− groups, whereas the structure of Al3P6O19.5 is built from [PO4]3− tetrahedra and [AlO6]9− octahedra. The structure of Al[P2O3(OH)3](H2O) features a two-dimensional (2D) layered motif of Al[P2O3(OH)3]. Meanwhile, Al[(HPO3)(OH)(H2O)] has high porosity and relatively large channels, and has an excellent molecular sieve structure. Both Al[P2O3(OH)3](H2O) and Al[(HPO3)(OH)(H2O)] display deep ultraviolet (UV) cut-off edges of ∼195 nm and ∼193 nm. The three-dimensional (3D) structure of Al3P6O19.5 is formed by [Al2O9] dimers connected with six PO4 tetrahedra, and one PO4 tetrahedron linked three [Al2O9] dimers alternately. Importantly, Ca[HPO3] shows a moderate second harmonic generation (SHG) effect with a short UV cut-off edge of ∼192 nm in the deep-UV region. The syntheses and topological structures of Al[P2O3(OH)3](H2O), Al[(HPO3)(OH)(H2O)], Ca[HPO3] and Al3P6O19.5, together with some related properties, such as nonlinear optical (NLO) properties, elemental analysis, thermal stability, infrared spectroscopy, Raman spectroscopy and UV-vis diffuse reflectance spectroscopy, are also discussed. [ABSTRACT FROM AUTHOR]

A novel polymorph of ThB2O5, denoted as β-ThB2O5, was synthesised under high-temperature high-pressure (HT/HP) conditions. Via single crystal X-ray diffraction measurements, β-ThB2O5 was found to form a three-dimensional (3D) framework structure where thorium atoms are ten-fold oxygen coordinated forming tetra-capped trigonal prisms. The only other known polymorph of ThB2O5, denoted α, synthesised herein using a known borax, B2O3–Na2B4O7, high temperature solid method, was found to transform to the β polymorph when exposed to conditions of 4 GPa and ∼900 °C. Compared to the α polymorph, β-ThB2O5 has smaller molar volume by approximately 12%. Exposing a mixture of the α and β polymorphs to HT/HP conditions ex situ further demonstrated the preferred higher-pressure phase being β, with no α phase material being observed via Rietveld refinements against laboratory X-ray powder diffraction (PXRD) measurements. In situ heating PXRD measurements on α-ThB2O5 from RT to 1030 °C indicated that α-ThB2O5 transforms to the β variant at approximately 900 °C via a 1st order mechanism. β-ThB2O5 was found to exist only over a narrow temperature range, decomposing above 1050 °C. Ab initio calculations using density functional theory (DFT) with the Hubbard U parameter indicated, consistent with experimental observations, that β is both the preferred phase at higher temperatures and high pressures. Interestingly, it was found by switching from B2O3–Na2B4O7 to H3BO3–Li2CO3 flux using consistent high temperature solid state conditions for the synthesis of the α variant, β-ThB2O5 could be generated. Comparison of their single crystal measurements showed this was identical to that obtained from HT/HP conditions. [ABSTRACT FROM AUTHOR]

• A robustness index considering cascading failures caused by failed units is proposed. • Robustness improvement by structure adjustment is studied for fixed characteristics. • TS with directed and undirected edge swap operators is designed to solve the problem. • A case study of structure adjustment for improving robustness in the HST is performed. • Robustness of the optimized HST is greatly enhanced and hardly affected by failures. To enhance the ability of a high-speed train (HST) to provide services under various adverse conditions, this paper studies robustness improvement of the HST by adjusting its structure. We model the HST as an interdependent machine-electricity-communication network (IMECN) composed of a machine network (MN), an electricity network (EN) and a communication network (CN), and propose a robustness metric of the IMECN subject to node failures considering failure propagation. Then, a robustness optimization model is constructed for structure adjustment. A Tabu search algorithm with directed and undirected edge exchange operators is designed to solve this problem. A case study on a practical HST is used to verify the feasibility and effectiveness of the proposed method. The results show that robustness of the IMECN is significantly improved by structure adjustment. Furthermore, most nodes have little effect on robustness, and impact of failures on any node is minimized after optimization. In addition, in terms of topology, nodes with low and high degrees in the MN and CN reconnect with those with a similar degree, their clustering coefficients become larger, and closeness of all nodes in the subnetworks increases. Finally, adjusting the structures leads to a slight difference of loads in the EN and CN. [ABSTRACT FROM AUTHOR]

The interdependent network is particularly vulnerable to attacks on high degree nodes; therefore, the improvement of its robustness under intentional attacks has become an important topic. In this paper, we put forward a new metric to quantify the robustness of interdependent networks against intentional attacks and develop an improved simulated annealing algorithm (ISAA) to maximize this metric by optimizing the allocation of intra-links in subnetworks. Based on the comparison between the ISAA and existing algorithms, it is found that the algorithm presented in this paper is more effective to enhance the robustness of an interdependent scale-free network (ISFN). By applying the ISAA to ISFNs with different coupling preferences, there is a key finding that the robustness of the optimized ISFN is significantly stronger than that of the original ISFN. In particular, for cases of disassortative and random couplings, no sudden collapse occurs in optimized ISFNs. According to the analysis of the degree and the clustering coefficient, we find that the subnetwork of the optimized ISFN exhibits an onion-like structure. In addition, the ISFN whose robustness is enhanced to resist the attacks on high degree nodes is still robust to the intentional attacks concerning the betweenness and PageRank. [ABSTRACT FROM AUTHOR]

Many studies on cascading failures adopt the degree or the betweenness of a node to define its load. From a novel perspective, we propose an approach to obtain initial loads considering the harmonic closeness and the impact of neighboring nodes. Based on simulation results for different adjustable parameter θ, local parameter δ and proportion of attacked nodes f, it is found that in scale-free networks (SF networks), small-world networks (SW networks) and Erdos-Renyi networks (ER networks), there exists a negative correlation between optimal θ and δ. By the removal of the low load node, cascading failures are more likely to occur in some cases. In addition, we find a valuable result that our method yields better performance compared with other methods in SF networks with an arbitrary f, SW and ER networks with large f. Moreover, the method concerning the harmonic closeness makes these three model networks more robust for different average degrees. Finally, we perform the simulations on twenty real networks, whose results verify that our method is also effective to distribute the initial load in different real networks. [ABSTRACT FROM AUTHOR]

Three new sodium thorium arsenates, Na5Th4(AsO4)7 (1), Na5Th(AsO4)3 (2), and Na4Th(As2O7)2 (3) were synthesized via a high temperature route and their structures and optical properties were studied. Compound 1 adopts a three‐dimensional structure that consists of tetrameric fundamental building blocks (FBBs) [Th4(AsO4)7]5–, which are constructed by ThO8 and ThO9 polyhedra. The structures of 2 and 3 are based on open frameworks with channels running along the a or c axes, respectively, which are occupied by Na cations. Structural relations between the structures of 2 and 3 have been discussed regarding their composition. In contrast to the other two compounds, the arsenate anions in the structure of 2 play role of bridging ligands and do not connect more than two Th atoms. Owing to this, the underlying net of this compound contains only Th nodes has a lon topology. The Raman spectra of 1 and 2 contain similar peaks due to As–O vibrations of AsO4 groups, while the Raman spectrum of 3 differs significantly owing to the presence of As–O–As bridging group in As2O74– anions. [ABSTRACT FROM AUTHOR]

Crystals of three novel highly porous aluminophosphates, namely, α-NaAlPO4(OH) (1), β-NaAlPO4(OH) (2) and Al3.5P5.5O19 (3), were synthesized through mild hydrothermal methods. Interestingly, among these three porous aluminophosphates, 1 is polar, whereas the other compounds are nonpolar and centrosymmetric. The 3D framework structure of 1 is built from AlO6 octahedra and isolated PO4 tetrahedra. 1D Al-chains are linked by PO4 tetrahedra via sharing corners, forming the 3D framework, and 1D 8-membered ring (MR) tunnels were observed along the c-axis. Importantly, the material of 1 exhibits a moderate second harmonic generation (SHG) effect. 2 features a unique 3D anionic framework composed of corner-sharing [Al2O11] dimers and isolated PO4 tetrahedra. Three intersecting tunnels along the axes can be observed; the small tunnels along the c-axis are based on 4-MRs, whereas the two 6-MRs are along the a- and b-axes. The structure of 3 displays a unique 3D framework based upon face-sharing [Al2O9] dimers and isolated PO4 tetrahedra. The small tunnels along the a- and b-axes are based upon 4-MRs, whereas the 1D larger tunnels are based on 12-MRs along the c-axis. Here, the syntheses and topological structures of α-NaAlPO4(OH) (1), β-NaAlPO4(OH) (2) and Al3.5P5.5O19 (3) as well as their elemental analysis, thermal stability, infrared spectroscopy, UV-vis diffuse reflectance and nonlinear optical (NLO) properties are also reported. [ABSTRACT FROM AUTHOR]

A systematic investigation of uranyl borates under different synthetic conditions resulted in five new 2D compounds, namely, (H3O)[(UO2)(BO3)], Li[(UO2)(BO3)]·(H2O), α‐K4[(UO2)5(BO3)2O4], β‐K4[(UO2)5(BO3)2O4] and K2.5[(UO2)5(BO3)2O2.5(OH)1.5]·(H2O)2.5. (H3O)[(UO2)(BO3)] and Li[(UO2)(BO3)]·(H2O) were obtained from hydrothermal reactions at 220 °C using the same mineralizer. Both materials possess the uranophane sheet topology with different symmetry of the unit cells. In the structure of (H3O)[(UO2)(BO3)] and Li[(UO2)(BO3)]·(H2O), UO7 pentagonal bipyramids share edges and vertexes with four BO3 planar triangles. α‐K4[(UO2)5(BO3)2O4] and β‐K4[(UO2)5(BO3)2O4] are polytypes. α‐K4[(UO2)5(BO3)2O4] was synthesized from a high‐temperature solid‐state reaction under ambient pressure; whereas β‐K4[(UO2)5(BO3)2O4] was obtained from a high‐temperature/high‐pressure (HT/HP) reaction. Both structures have an identical anion topology, but β‐K4[(UO2)5(BO3)2O4] crystallizes in space group with higher symmetry. In K2.5[(UO2)5(BO3)2O2.5(OH)1.5]·(H2O)2.5, which was obtained from a hydrothermal reaction, UO7 polyhedra share vertexes and edges with two independent BO3 triangles, forming the most complex uranyl borate layers among all five compounds. The different synthetic routes, novel topologies, thermal behavior and Raman spectra are discussed. [ABSTRACT FROM AUTHOR]

• A high-speed train is modeled as an interdependent network. • A robustness metric is proposed based on network theory and practical factors. • Assessment and optimization models of resilience are constructed. • The tabu search algorithm is developed to solve the optimization problem. • The optimal repair strategy of failed units in the high-speed train is analyzed. High-speed trains (HSTs) are used to transport passengers to destinations efficiently and safely. However, when HST units fail, strategies for repairing them are not available. Hence, to optimize repair strategies, an interdependent network is used to model an HST, and a metric of resilience based on network theory is introduced. Based on practical factors, an interdependent machine–electricity–communication network (IMECN) and related cascading failure models are developed. Comprehensive robustness metrics for the IMECN and nodes are proposed considering the topology of networks and functional features of nodes. Accordingly, a resilience optimization model of the IMECN subject to disturbances is formulated and solved using a tabu search (TS) algorithm. Finally, a real-world HST is considered to analyze the optimal repair strategy for different numbers of failed nodes. Analysis results show that the recovery process under the optimal repair strategy has at most three stages. When a few nodes and less than half of the nodes fail, the highest and lowest resilience levels of the IMECN are achieved, respectively. Moreover, the characteristics of the preferentially repaired node in terms of importance, vulnerability, network type, and interdependency are analyzed. Results indicate that the optimal repair strategy is not necessarily determined by topological metrics. [ABSTRACT FROM AUTHOR]

• A high-speed train is modeled based on network theory. • A multi-objective optimization model for identifying critical elements is proposed. • A novel importance metric of critical elements is designed. • The proposed model is verified by a practical high-speed train. • Critical nodes, intra-links and inter-links for a high-speed train are identified. This paper proposes a multi-objective optimization-based approach to identify critical elements, including units and interactions within and between systems, in a high-speed train (HST). In the framework, network theory is used to model the HST as an interdependent machine-electricity-communication network (IMECN) composed of a machine network (MN), an electricity network (EN) and a communication network (CN). Cascading failure models for the subnetworks and IMECN, and topological and functional metrics for robustness are developed. We then formulate a multi-objective optimization model for maximizing the impact of the failure of critical elements on the topological and functional robustness of the IMECN and minimizing their number. We use NSGA-II to solve the optimization problem. Considering a practical HST as a case study, we apply the multi-objective optimization framework to search the groups of critical nodes, intra-links and inter-links. The results show that critical nodes, intra-links and inter-links of the IMECN are within the MN and CN. In particular, end nodes of the critical intra-links and inter-links may also be critical, and the critical elements of subnetworks tend to also be critical for the IMECN. In addition, we find that the critical nodes, intra-links and inter-links are not related to their topological importance. [ABSTRACT FROM AUTHOR]

In order to overcome the limitation of existing weighting methods and mitigate the effect of cascading failures, the harmonic closeness is adopted to define the node weight whose strength is controlled by a weight parameter θ , so that the initial load can be obtained by the node weight. We find that regardless of the average degree < k > in Barabási–Albert (BA networks), Newman–Watts (NW networks), and Erdos–Renyi networks (ER networks), the critical threshold T c achieves the minimum value under optimal θ. In these artificial networks except for NW and ER networks with big tolerance parameter T , the bigger the value of θ , the smaller the value of the normalized avalanche size C F N . Through the comparison of different methods, a key finding is that the value of T c obtained by the method proposed in this paper is significantly smaller than the ones by methods concerning the degree and the betweenness in artificial and real networks. In the range of big T , our method results in the smallest value of C F N in the networks mentioned above compared with previous methods. These results may be helpful for optimizing the distribution of the initial loads in real-life systems, and extending the research on cascading failures in the light of the harmonic closeness. • The harmonic closeness is first adopted to define the node weight. • The critical threshold is minimized under the optimal weight parameter. • The critical threshold with our method is smaller than those with existing methods. • The impact of failed nodes is mitigated by our method under high capacities. [ABSTRACT FROM AUTHOR]

Investigation of the Pt-B-O system reveals the first magnesium platinum borate Mg 3 Pt(BO 3) 2 O 2 obtained from the high temperature flux method. The compound crystallizes in the centrosymmetric monoclinic space group C 2/ m (no. 12) with the lattice parameters of a = 16.8073(8) Å, b = 3.10610(1) Å, c = 5.2107(2) Å, and β = 90.546(4)° (Z = 2). The crystal structure of Mg 3 Pt(BO 3) 2 O 2 is based upon isolated BO 3 triangles and PtO 6 and MgO 6 octahedra. The PtO 6 octahedra are connected with each other in an edge-sharing manner forming one dimensional (1D) chains. Each of the PtO 6 octahedra links with two BO 3 units to form anionic [Pt(BO 3) 2 O 2 6- chains along the b -axis. MgO 6 octahedra are arranged in the form of two dimensional (2D) layers. The 2D MgO 6 layers are further connected by the anionic [Pt(BO 3) 2 O 2 6- chains into the 3D framework structure of Mg 3 Pt(BO 3) 2 O 2. The material was experimentally and theoretically characterized in regards to its optical and spectroscopic properties. The first HT platinum borate was experimentally and theoretically characterized in regards to its optical and spectroscopic properties. Image 1 • The first HT platinum borate Mg 3 Pt(BO 3) 2 O 2 was synthesized by high temperature flux method. • The structure was determined by single-crystal X-ray diffraction. • The novel structural chemistry and comparison with related phases were discussed in detail. • Optical properties of the new phase was experimentally and theoretically studied detailly. [ABSTRACT FROM AUTHOR]

• A complex electromechanical system is abstracted as a multi-layer and multi-state network. • A UGF-based method is presented to calculate the reliability of the complex electromechanical system. • A cascading failure model is proposed for quantifying the values of different performance states of the system. • The proposed model is illustrated by a practical high-speed train system. • The validity of the proposed method is verified through three cases. The large-scale adoption of complex electromechanical systems (CMESs) renders it challenging to perform reliability assessments for such systems. In terms of the reliability evaluation of CMESs, previous studies generally assume that only binary states exist within the systems. However, owing to the stochastic failures and various operating characteristics of the system components, not only the good/bad states but also the performance levels within the system should be taken into account when analyzing the reliability of CMESs. Hence, we abstract the CMES as a multi-layer and multi-state network in which minimum maintenance units (MMUs) and three types of connections constitute nodes and edges in different layers. Furthermore, multi-state models for different MMUs in the CMES are developed based on universal generating functions (UGFs). Aggregation operators are then utilized to aggregate these UGFs to obtain the multi-state models. Subsequently, a cascading failure model is introduced to incorporate MMUs into the system reliability assessment. Thus, the effects of the operating mechanism and topological attributes can be considered in the reliability evaluation of the CEMS. Finally, the CRHX high-speed train system is used as an example to demonstrate the applicability and effectiveness of the proposed method in the reliability assessment of the CMES. [ABSTRACT FROM AUTHOR]

With the development of mechatronic systems, different kinds of subsystems within them are highly correlated to each other due to the demand for the special function. To assess the robustness in the mechatronic system under various disturbances, we build an interdependent mechatronic system as an interdependent machine-electricity-communication network (IMECN) and adopt the improved cascading failure model where the occurrence of the failure propagation is decided by a proportion threshold δ. In order to fully explore the robustness under different disturbances, we develop attack strategies concerning nodes, edges, and interdependent links by considering measures for a node. Then, we also define the robustness metric to quantify the performance of IMECN during the entire attack process. The mass transit vehicle is taken as an example to investigate the impact of attack strategies on the robustness at different δ in a real-world mechatronic system. It is found that each subnetwork in this IMECN has a scale-free property. Based on simulation results, we obtain the most efficient attack strategies to remove nodes, edges, and interdependent links for different possibilities of triggering the failure propagation. In addition, we find that the attacks on nodes and interdependent links make IMECN more vulnerable compared with the ones on edges. This work provides theoretical insights into the comprehensive analysis of the robustness in interdependent mechatronic systems. [ABSTRACT FROM AUTHOR]

Since the complex electromechanical system (CMES) is a complex integration of multiple minimum maintenance units (MMUs), a single faulty MMU can trigger multi-step failures and eventually damage a substantial portion of the CMES. To investigate the failure propagation process and analyze the impact of the CMES under MMU attacks, we first abstract the system as a directed network composed of MMUs, machine-electricity-information connections, and functional properties. Subsequently, a fault propagation model is constructed based on the fault occurrence probability and matrix transformation, which considers the topological and functional attributes of the system. Then, we build the attack graphs to evaluate the faulty edges on the system's vulnerability and propose some vulnerable indices based on the node attack strategies to quantify the attack impact of the malfunctioning nodes on the CMES network. Finally, a bogie system of the high-speed train is selected as a case study to verify the validity of the proposed method. Based on the findings, we can clarify the failure propagation behavior and quantify the impact of the faulty nodes and edges on the CMES network. Furthermore, the critical connections and nodes that significantly impact system vulnerability can be identified. Hence, our work can provide guiding significance for developing maintenance strategies to reduce losses and optimize the management scheme. • The complex electromechanical system is abstracted as a directed network to analyze the interactions among compositions. • The reachable matrix and the matrix transformation are used to model the fault propagation. • The attack graphs are proposed to analyze the impact of malfunctioning edges on the system vulnerability. • Seven node attack strategies combined with two vulnerable metrics are adopted to make a system vulnerability analysis. • The feasibility and rationality of the methods are verified through a bogie system of the high-speed train. [ABSTRACT FROM AUTHOR]

Two novel alkali metal aluminophosphates, namely, Li3[Al(PO4)2(H2O)1.5] and Na[AlP2O7], were synthesized through low-temperature flux methods. They crystallized in the P4 and C2/c space groups, respectively. Both structures of Li3[Al(PO4)2(H2O)1.5] and Na[AlP2O7] were built up by AlO6 octahedra and PO4 tetrahedra. The structure of Li3[Al(PO4)2(H2O)1.5] was composed of novel two-dimensional (2D) aluminophosphate layers, which contained two types of eight-membered rings (8-MRs) along the c-axis. The structure of Na[AlP2O7] featured a unique 3D anionic framework composed of corner-sharing isolated AlO6 octahedra and PO4 tetrahedra. Three intersecting tunnels along the [001], [110], and [101] directions could be observed. Importantly, the material Li3[Al(PO4)2(H2O)1.5] crystallized in the polar space group P4, showing a moderate second-harmonic generation (SHG) effect. Moreover, Na[AlP2O7] exhibited a wide transparency range with a short ultraviolet (UV) cut-off edge (∼190 nm), which indicated its potential application in the deep-UV region. Herein, the syntheses and topological structures of Li3[Al(PO4)2(H2O)1.5] and Na[AlP2O7], as well as elemental analysis, thermal stability, infrared spectroscopy, UV-vis diffuse reflectance, structural properties, and nonlinear optical (NLO) properties are also discussed. [ABSTRACT FROM AUTHOR]

The interconnectivity of components in complex electromechanical system (CMES) plays a critical role in ensuring system reliability. To examine the effect of component failures on system reliability, this work proposes a new reliability assessment method for CEMS based on improved network connectivity entropy. This method takes into account the mechanical, electrical, and information characteristics of components, and employs a comprehensive component importance calculation approach based on PageRank, which considers the functional impact of components. The reliability assessment model, considering both functional and topological attributes of the system, is established through the theory of network connectivity entropy. The proposed method is then demonstrated through an application to a bogie system of the CRH2008A high-speed railway. The proposed approach, rooted in topological networks, integrates component degradation into the physical structure of CEMS, providing a comprehensive way to deduce the impact of component failures on system reliability. Validity is demonstrated through case studies. • Construction of topological network model for complex electromechanical systems. • Component comprehensive importance integrates structure and function of systems. • Improved network connectivity entropy model assesses system reliability. • Method validated by two railway subsystems. [ABSTRACT FROM AUTHOR]

The effect of rare earth elements (Y, La, Nd, Sm, and Gd) on the structures, thermal expansion, chemical stability and crystallization behavior of phosphate-based glasses were characterized by using powder X-ray diffraction (PXRD), Scanning Electron Microscope (SEM), X-Ray Fluorescence (XRF), Diffuse reflectance UV–Visible spectra, thermal expansion coefficient, inductively coupled plasma mass spectrometry (ICP-MS) and Differential scanning calorimetry (DSC). UV–Vis spectra not only exhibit the absorption peaks of rare earth cations but also reveal the reduction of band gap (E g) with increasing the cationic field strength (CFS) of rare earth elements, further establishing the change of non-bridging oxygen (NBOs) density in the glass structures. It is found that there is a decrease in thermal expansion coefficient (α) with increasing the CFS of rare earth, and the study shows a strong correlation between α values and NBOs in the rare earth phosphate glass systems. The chemical durability tests of glass blocks demonstrate that the normalized leach rates (NR RE) increase with decreasing the radius of rare earth elements, and La-doped phosphate glass with high thermal expansion coefficient has good chemical durability. By a two-stage thermal treatment, a preliminary study of the crystallization mechanism for the rare earth phosphate glasses is carried out, and the major crystalline phases are identified. • NBOs studied by UV–Vis spectra reduce with increasing the CFS of rare earth. • There is a reduction in thermal expansion coefficient owing to the increase of NBOs. • The leach rates of RE cations increase with the decreasing of their radius. • The crystallization mechanism for the phosphate glasses is surface crystallization. • The crystalline phases were identified as monazite/xenotime-type REPO 4 and FePO 4. [ABSTRACT FROM AUTHOR]