Fine limestone additions to regulate setting in high volume fly ash mixtures

High volume fly ash (HVFA) concrete mixtures are being considered more frequently due to their cost and sustainability advantages. While the long term performance of these HVFA concretes typically meets or exceeds that of conventional concretes, their early age performance is often characterized by excessive retardation of the hydration reactions, delayed setting times, and low strengths. Extending an HVFA mixture to a ternary blend that incorporates a fine limestone powder may provide a viable solution to these deficiencies, particularly the hydration retardation and setting issues. In this paper, a nano-limestone powder and two other limestone fillers of increasing median particle size (4.4 μm and 16.4 μm) are investigated for their propensity to accelerate early age reactions and reduce setting times in a Class C fly ash/cement blend. The fineness of the limestone has measurable effects on its efficacy in accelerating hydration and decreasing setting times. Companion specimens prepared with a fine silica powder suggest that the fine limestone may act favorably through both a physical and a chemical mechanism. Isothermal calorimetry and Vicat needle penetration measurements on pastes are accompanied by strength measurements on mortars, to verify that the limestone powder substitutions are not negatively impacting strength development. A linear relationship with a reasonable correlation is found to exist between 1 d and 7 d compressive strengths of mortars and their accompanying cumulative heat release values as determined using isothermal calorimetry.     

Thermoelectric performance of polycrystalline Sn1-xCuxSe (x = 0–0.03) prepared by high pressure method

P-type Sn_1-xCu_xSe (x = 0–0.03) polycrystal was prepared through melting synthesis and high pressure (6.0 GPa) sintering (HPS) method. The composition and microstructure of the samples was analyzed, and the thermoelectric transport properties were investigated in the temperature range of 303 K–823 K. The results indicate that the electrical conductivity increases as Cu content increases. An observable improvement is found for the Seebeck coefficient when x is 0.01. In addition, the total thermal conductivities (κ_tot) of all samples decrease with rising temperature, and reach its minimum values at 773 K. As a result, the maximum power factor (PF) and ZT_max value are 378 μW m⁻¹ K⁻² and 0.79 for Sn_0.97Cu_0.03Se at 823 K, respectively.     

Metal forming and forging – finding a new place within high value manufacturing through advanced,industrial scale research

Abstract

Since the banking crisis governments have placed renewed emphasis on the importance of manufacturing in providing the basis for a balanced economy. The term High Value Manufacturing (HVM) has been used in the UK to describe manufacturing based industries with a high R&D content and therefore which in turn will support knowledge based job creation into the future. The UK Government has supported the development of a network of manufacturing research centres aimed at providing a step change in research and development activity and impact termed the HVM Catapult. The Advanced Forming Research Centre (AFRC) within the University of Strathclyde is a founder member of the HVM Catapult, with a focus on metal forming and forging technologies.

To outsiders however, forming and forging are established technologies employed within traditional, and in many cases declining, manufacturing environments whose roots can be traced back to the industrial revolution and beyond. It is not surprising, therefore, that the position of metal deformation technologies within the HVM taxonomy is sometimes questioned. This paper aims to address the common arguments which are used to question the position of metal forming and forging within HVM at a general level, and through examples of ongoing work themes with the AFRC.     

Highly permeable macroporous cordierite ceramics with controlled microstructure produced by particle-stabilized emulsions with a reactive thermal treatment

Macroporous cordierite ceramics, comprising hierarchical microstructures, are produced by a method of particle-stabilized emulsions, combined with a followed reactive thermal treatment. The microstructure is tailored by altering sintering temperature and solid content in the emulsion templates. Pore throats generate in-situ by introducing magnesite in templates, in contrast to conventional methods, which use either surfactants or depending on thin film contact. Moreover, microstructural evolution of samples is studied by DTA/TG, XRD, and SEM analyses. The results of analyses show that the formation of much more pore throats is closely related to the release of gas from the raw materials and volume shrinkage. The optimal process conditions are a temperature of 1300 °C and a solid content of 30 vol.%. The as-prepared sample displays a nitrogen permeability of ∼1.8 × 10⁻¹¹ m². The method shows great promise for producing many other highly permeable ceramics using pore former agents in the emulsion templates.     

几种典型目标体外形的高频回声特性研究

本文研究常见、典型的水中目标体外形的回声特性是目标回声特性研究的基础内容。采用基于Kirchhoff近似的平面元方法和几何建模软件相结合的数值方法计算研究了三种典型外形的收发合置的目标强度。通过对计算结果的对比分析,归纳得到了一些高频回声规律。     

Non-targeted analysis of tea by hydrophilic interaction liquid chromatography and high resolution mass spectrometry

Tea is the second most consumed beverage in the world and its consumption has been associated with numerous potential health benefits. Factors such as fermentation methods, geographical origin and season can affect the primary and secondary metabolite composition of tea. In this study, a hydrophilic interaction liquid chromatography (HILIC) method coupled to high resolution mass spectrometry in both positive and negative ionisation modes was developed and optimised. The method when combined with principal component analysis to analyse three different types of tea, successfully distinguished samples into different categories, and provided evidence of the metabolites which differed between them. The accurate mass and high resolution attributes of the mass spectrometric data were utilised and relative quantification data were extracted post-data acquisition on 18 amino acids, showing significant differences in amino acid concentrations between tea types and countries. This study highlights the potential of HILIC chromatography combined with non-targeted mass spectrometric methods to provide a comprehensive understanding of polar metabolites in plant extracts.     

Synthesis and photophysical properties of host materials with high triplet energy based on dibenzofuran and triphenylamine functionalities

A host material with high triplet energy based on dibenzofuran and triphenylamine interconnected through diphenylmethylene linkage was synthesized and photophysical properties of the host material were investigated. A high triplet energy of 2.90 eV was obtained due to complete separation of an electron donating triphenylamine and accepting dibenzofuran by diphenylmethylene linkage. It was found out that intermolecular charge transfer dominated the light emission of the host material.     

A TEM study of morphological and structural degradation phenomena in LiFePO4‐CB cathodes

LiFePO₄‐based cathodes suffer from various degradation mechanisms, which influences the battery performance. In this paper, morphological and structural degradation phenomena in laboratory cathodes made of LiFePO₄ mixed with carbon black (CB) in a 1 mol/L LiPF₆ in EC : DMC (1:1 by weight) electrolyte are investigated by transmission electron microscopy at various preparation, assembling, storage, and cycling stages. High‐resolution transmission electron microscopy imaging shows that continuous SEI layers are formed on the LiFePO₄ particles and that both storage and cycling affect the formation. Additionally, loss of CB crystallinity, CB aggregation, and agglomeration is observed. Charge–discharge curves and impedance spectra measured during cycling confirm that these degradation mechanisms reduce the cathode conductivity and capacity. Copyright © 2016 John Wiley & Sons, Ltd.     

Three-level designs: Evaluation and comparison for screening purposes

Since their introduction by Box and Hunter, resolution criteria have been widely used when comparing regular fractional factorials designs. In this article, we investigate how a generalized resolution criterion can be used to assess some recently developed three-level screening designs, such as definitive screening designs (DSDs) and screening designs from weighing matrices. The aim of this paper is to capture the projection properties of those three-level screening designs, complementing the work of Deng and Tang, who used generalized resolution and minimum aberration criteria for ranking different two-level designs, particularly Plackett-Burman and other nonregular factorial designs. An advantage of generalized resolution, extended here to work on three-level designs, is that it offers a useful criterion for ranking three-level screening designs, whereas the Deng and Tang resolution is used mainly for the assessment of two-level designs. In addition, we applied a projection estimation capacity (PEC) criterion to select three-level screening designs with desirable properties. Practical examples and the best projections of the designs are presented in tables.     

Influence of Mo doping on the tribological behavior of Ti3AlC2 ceramic at different temperatures

(Ti_0·8Mo_0.2)₃AlC₂ solid solutions were successfully synthesized from Ti, Al, TiC, and Mo powders using the in situ hot-pressing sintering method. The tribological properties of (Ti_0·8Mo_0.2)₃AlC₂ and the reference Ti₃AlC₂ in the temperature range 25–800 °C were evaluated in ambient air with the counterpart of Al₂O₃ balls. The results show that (Ti_0·8Mo_0.2)₃AlC₂ has improved lubricating properties and wear resistance above 400 °C compared with Ti₃AlC₂. This can be contributed to the formation of tribo-oxidation films containing MoO₃ and MoO_3-x. Structural characterization of the tribo-oxidation films was conducted using SEM, EDS, Raman spectroscopy, and XPS to evaluate the effect of Mo doping on the wear mechanisms of Ti₃AlC₂ in detail.