The thermomechanical method for evaluation of the crosslinking parameters in irradiated polyethylene

The measurement of penetration deformation above the melting point was used for determination of viscoelastic parameters, compliance and retardation time, in γ-irradiated polyethylene systems. The time-dependent penetration deformation was followed over two creep and recovery cycles. The five-element mechanical model equation was used for calculation of amplitudes, time factors and remained deformations. The modulus of elasticity, derived from the equilibrium compliance was used to obtain M_c, the value of the average molecular weight between crosslinks.     

A new strategy for the synthesis of pillared clays with super galleries: Direct intercalation of metal oxide sols (DIMOS)

The direct intercalation of metal oxide sols (DIMOS) is a promising new route to pillared clays with highly expanded super galleries, as judged from the properties of products obtained from the reaction of silica sols with Na⁺-montmorillonite. Silica-clay compositions in the range 1:1 to 10:1 (wt./wt.) were prepared by allowing mixtures of positively charged sol (pH=3.0) and clay to evaporate in air at room temperature. A stabilized commercial sol (Nalco 1115, ∼40 Å) and a sol freshly prepared by tetraethylorthosilicate hydrolysis gave products with similar XRD, thermogravimetric, and N₂ BET surface area properties. Although regular intercalation was not observed for any of the products, complete segregation of the clay and silica into separate phases was precluded by surface area values (250–460 m²/g) that were substantially larger than those from the pure silica (176–259 m²/g) and clay (50 m²/g) components. Thus, specific sol-clay interactions stabilize the sol particles against further particle growth during reaction. Such interactions are essential for the successful implementation of DIMOS routes to pillared clays with very large gallery heights. Additional pre-requisites for efficient DIMOS pathways to new generations of super gallery clays are identified and discussed.     

Temperature hysteresis of the elastic modulus and low-temperature local phase transformations of the order-disorder type in the superconductor YBa2Cu3Ox

The temperature hysteresis of the Young modulus is observed in YBa₂Cu₃O_x compounds with 6.24⩽x⩽6.9. The effect is interpreted in terms of local order-disorder phase transitions of the first kind in the temperature range 4.2–300 K.     

The reliability of a test procedure for identifying defective components

Fast and simple tests for detecting defects in components (or units) may be less reliable but they have obvious advantages over those that are exact but more costly and/or time-consuming. In this study, a model is proposed for predicting the reliability of a test procedure where simple and exact tests are combined so as to minimize the number of costly and time-consuming tests. The maximum likelihood method is used to estimate the necessary parameters, such as the actual number of abnormal units in a multi-unit system under test, and the probabilities of correctly and incorrectly identifying a unit as abnormal.     

The Impact of Foaming Effect on the Physical and Mechanical Properties of Foam Glasses with Molecular-Level Insights

Foaming effect strongly impacts the physical and mechanical properties of foam glass materials, but an understanding of its mechanism especially at the molecular level is still limited. In this study, the foaming effects of dextrin, a mixture of dextrin and carbon, and different carbon allotropes are investigated with respect to surface morphology as well as physical and mechanical properties, in which 1 wt.% carbon black is identified as an optimal choice for a well-balanced material property. More importantly, the different foaming effects are elucidated by all-atomistic molecular dynamics simulations with molecular-level insights into the structure–property relationships. The results show that smaller pores and more uniform pore structure benefit the mechanical properties of the foam glass samples. The foam glass samples show excellent chemical and thermal stability with 1 wt.% carbon as the foaming agent. Furthermore, the foaming effects of CaSO₄ and Na₂HPO₄ are investigated, which both create more uniform pore structures. This work may inspire more systematic approaches to control foaming effect for customized engineering needs by establishing molecular-level structure–property–process relationships, thereby, leading to efficient production of foam glass materials with desired foaming effects.     

接触爆炸荷载对钢筋混凝土梁的局部毁伤效应

为得到接触爆炸下钢筋混凝土（reinforced concrete,RC）梁的局部破坏模式和毁伤效应,对同一尺寸的RC梁进行了不同装药量的接触爆炸试验研究。试验中采用框架结构中典型工程尺度RC原型梁为研究对象,通过4次爆炸试验,观测了RC梁在不同装药量下的局部破坏模式和破坏特征,分析了装药量对局部毁伤效应的影响。研究结果表明:接触爆炸荷载作用下,RC梁将发生正面成坑、侧面崩落、背面震塌和截面冲切等局部破坏模式,爆坑深度、震塌厚度、表面毁伤面积以及受压区纵筋变形均与装药量立方根近似呈线性增加关系。在试验数据基础上,将RC梁局部毁伤程度划分为轻度毁伤、中度毁伤、重度毁伤和严重毁伤4个等级,采用比例装药量判据进行评估。研究成果可为抗爆结构设计和结构毁伤评估提供理论依据。     

Interconversion of acetyl- and terminal-carbonyl groups on labeled (η5-indenyl)(CO)2Fe13C(O)CH3

The ¹³C-labeled (95–99%) acetyl complex (η⁵-In)(CO)₃Fe¹³C(O)CH₃ (8) (In = indenyl) has been prepared by acylating In(CO)₂Fe⁻ Na⁺ (1) with CH₃ ¹³C(O)Cl. All of the starting 1 must be consumed in this reaction (at −78°C), or 45% of the product results as In(CO)(¹³CO)FeC(O)CH₃ (9). Once isolated, neither 8 nor mixtures of 8 and 9 further redistribute or lose this label after pressurizing under 800 atm CO, or after heating in heptane, THF, or acetonitrile solution. Treating 8 with even trace amounts of 1 or of Cp(CO)₂Fe⁻ Na⁺ (5) rapidly interconverts the acetyl and terminal carbonyls, thus transforming 8 into mixtures of 8 and 9. A mechanism is proposed that involves a labile metalla-β-diketonate In(CO)Fe(Fp-CO)(CH₃¹³CO)⁻ Na⁺.     

Low temperature XPS and AES studies of O2 adsorption on Al(100)

Adsorption of O₂ on Al(100) at 80 K was studied by means of Auger and XP spectroscopies. At low surface coverages Al_xO_y oxides were formed with x : y ratios from 3 : 1 to 1 : 1, depending on surface coverage. At higher coverages or heating to room temperature the oxide layer transformed to the familiar Al₂O₃.