‘Age-hardened alloy’ based on bulk polycrystalline oxide ceramic

We report here for the first time the development of ‘age-hardened/toughened’ ceramic alloy based on MgO in the bulk polycrystalline form. This route allows for the facile development of a ‘near-ideal’ microstructure characterized by the presence of nanosized and uniformly dispersed second-phase particles (MgFe₂O₄) within the matrix grains, as well as along the matrix grain boundaries, in a controlled manner. Furthermore, the intragranular second-phase particles are rendered coherent with the matrix (MgO). Development of such microstructural features for two-phase bulk polycrystalline ceramics is extremely challenging following the powder metallurgical route usually adopted for the development of bulk ceramic nanocomposites. Furthermore, unlike for the case of ceramic nanocomposites, the route adopted here does not necessitate the usage of nano-powder, pressure/electric field-assisted sintering techniques and inert/reducing atmosphere. The as-developed bulk polycrystalline MgO–MgFe₂O₄ alloys possess considerably improved hardness (by ~52%) and indentation toughness (by ~35%), as compared to phase pure MgO.     

简式元认知问卷中文版的心理计量学特性

以大学生为被试,考察简式元认知问卷(BQM)在中国文化背景下的心理计量学特性。采用探索性和验证性因素分析方法对BQM的结构效度进行交叉检验,结果支持了元记忆和元注意的双因子结构;问卷及其因子的内部一致性和重测信度良好;项目分析的结果显示,问卷的条目具有良好的分数分布、区分度和内部一致性;BQM分数与负性情绪、执行功能和睡眠质量的关联性也为效标关联效度提供了支持性证据。上述结果表明BQM中文版具有良好的心理计量学特性,可作为青年群体元认知水平的测量工具。     

Psychometric properties of the Norwegian version of the Childhood Trauma Questionnaire in high‐risk groups

The Childhood Trauma Questionnaire ‐ Short Form (CTQ‐SF) is widely used to measure childhood abuse of all types. In the present study, we examined the psychometric properties of the Norwegian version of the instrument. The participants constituted four subsamples (n = 517): substance abusers (n = 126), psychiatric patients (n = 210), prisoners (n = 109) and adolescents in out‐of‐home placements (n = 72). Confirmatory factor analysis revealed a reasonable fit of the data to the original five‐factor structure of the CTQ‐SF. Measurement invariance was found across gender and the four subsamples. It was concluded that the Norwegian version of the CTQ‐SF has acceptable psychometric properties, with good reliability and satisfactory accuracy, to assess different dimensions of childhood trauma.     

Structure images of unaged martensite containing a high carbon content

Abstract

A highly tetragonal (large c/a ratio) martensite in a Fe-4 wt% Al-1·6 wt% Mn-2 wt% Calloy, which is not aged and considered to be as ‘fresh’ as possible, has been observed by high-resolution electron microscope. From the arrangement of atom rows in the [010] structure image and the corresponding electron diffraction pattern, it is concluded that carbon atoms are clustered on the (305) plane. The unit structure of these carbon-clustered regions is similar to that of the modulated structure observed in Fe-C alloys, although a periodic layer distribution of carbon atoms is not observed.     

Distortion analysis of magnetic excitation – a novel method for non-destructive evaluation of depth of surface-hardening in ferritic steels

The influence of ferritic steel samples with different case-depths on the distortion behaviour of magnetic excitation voltage has been investigated. The systematic changes in the height and position of the peak and the trough on the ((dV_E/dt) vs. V_T) profile (distortion analysis of the magnetic excitation, DAME profile) reflect the difference in the magnetization process and hence the effect of distortion of V_E in samples with different case-depths. This study shows the potential of this simple DAME method for evaluation of ferromagnetic steel components.     

Electropulsing-induced strengthening of steel at high temperature

Electropulsing usually promotes a metastable phase to evolve towards its equilibrium state. This work reports an alternative case, where electropulsing promotes the decomposition of the stable δ-phase in duplex stainless steel at high temperature. This decomposition enables both the γ-phase and the σ-phase in the steel to survive and hence to strengthen it at high temperature. The hardness of the quenched sample with electropulsing treatment is 49.4% higher than that without electropulsing treatment. A fundamental understanding of the observation is developed.     

Room temperature ferromagnetism and photoluminescence of nanocrystalline Zn1 − xCoxO thin films prepared by sol–gel MOD

Zn_1???xCo_xO (ZC) [x?=?0, 1, 3, 5, 7 and 9?mol%] thin films were prepared by sol–gel combined metallo-organic decomposition method. The films were deposited on the Si substrate with spin-coating technique and annealed at 600?°C for 3?h. X-ray diffraction pattern shows the formation hexagonal wurtzite phase and distortion (c/a) decreases with increasing Co concentration in ZnO. The average grain size is measured using Scherer relation. Atomic force microscopy is used to confirm the formation of nanograins resulted by the use of polyethylene glycol as surfactant. The photoluminescence was recorded by using He-Cd laser of excitation wavelength 325?nm in wavelength region of 350–650?nm which exhibits some influence of Co doping on the multiplication of defects such as O vacancies, Zn interstitials and grain boundary defects. All thin films show room temperature ferromagnetism except pure ZnO which is diamagnetic and 9?mol% of Co shows paramagnetism. This behaviour is interpreted as due to fluctuations in the magnetic ordering, depending on grain size and site location in grain boundaries or oxygen vacancies.     

Characterization of PLZT ceramics modified by isovalent (Ba,Sr), donor (Nb) and acceptor (Zn) dopants for piezoelectric applications

This article describes the influence of microstructure on the dielectric and piezoelectric properties of isovalent- donor- and acceptor-modified lead lanthanum zirconium titanate (PLZT) ceramics. The ceramic compositions, with formula: [Pb_0.954La_0.016Ba_0.01Sr_0.02][Zr_0.525Ti_0.475]_{0.981?( m /2)}Nb_0.012Zn _m O₃ where m =?0, 0.2, 0.4, 0.6, 0.8 and 1.0 mol% Zn, were synthesized via a solid-state reaction method. X-ray diffraction studies are supported by tolerance factor and electronegativity difference measurements. Scanning electron microscopy studies reveal grain growth enhancement with increase of Zn concentration. As the Zn concentration increased from 0 to 0.8 mol%, the room-temperature dielectric constant increased while the Curie temperature decreased continuously. An increase in the Zn content had the most significant effect on the piezoelectric properties. The optimum piezoelectric properties were observed for 1 mol% Zn composition.     

Electromechanical behavior of single-walled carbon nanotube thin films

Carbon nanotubes have been intensively studied owing to their great potential in nanoelectronics and nanomechanical devices. Recently, experimental results have shown that single-walled carbon nanotubes (SWCNTs) change their electronic properties when subjected to strain. In this study, the electromechanical characteristics of SWCNT networks were investigated for the application of printable strain sensors on flexible substrates. SWCNT films were formed on plastic substrates of poly(ethylene terephthalate) using a spray process. In this manner, we were able to control the transparency and obtain uniform electrical properties of the films. The films are isotropic on account of the random orientation of bundles of SWCNTs. Experimental results showed a nearly linear change in the resistance across a film when it was subjected to tensile strain, even in the inelastic range of the flexible substrate. The results demonstrate the potential use of SWCNT films for highly sensitive printable strain sensors on a macroscale.     

Development and Initial Validation of a General Psychological Well-being Scale (GPWS) in an African Context

This study aimed to develop and validate the General Psychological Well-being Scale (GPWS) in an African sample, based on the empirical overlap between hedonic and eudaimonic facets of well-being as found in previous research. The quantitative cross-sectional study was conducted in three phases: secondary data analysis (n = 2005), pilot study (n = 296) and main study (n = 459). The pilot and main study included the GPWS as well as other psychological well-being measures for criterion-related validity. The pilot study yielded satisfactory psychometric properties. The main study yielded a high, reliable Cronbach alpha of.89 and evidence of construct validity. The GPWS appears to be a unidimensional scale suitable for research use with Setswana-speaking people.