Critical methods of geopolymer feedstocks activation for suitable industrial applications.

As health and safety issues emanating from human activities on terrestrial environment is becoming ever challenging, the production of Ordinary Portland Cement is identified as a key contributor. This technology threatens environmental quality by emitting significant quantity of carbon dioxide (CO2) that threatens Net Zero delivery. Consequently, the development of cement alternatives with substantial CO2 reduction/sequestration during production has become imperative. Geopolymers obtained from industrial residues are poised as promising alternatives in managing environmental systems but selection of appropriate method of activation has limited their wider industrial applications. This article discusses four key activation methods and their combinations used in four main feedstocks to advise on their energy requirements, product compressive strength and environmental/industrial applications. Reviewing and characterising 302 published literatures with focus on most relevant and recent advances in the field, this review found that hybrid techniques combining mechanical activation method produces geopolymers with the highest compressive strength and thus the best method. Geopolymer made by mechano-chemical activation method of slag achieved the highest compressive strength while geopolymer produced by microwave assisted activation of clay and ultrasonic activation of fly ash cum slag are most economical in curing energy demand. Hybrid activation is the current development in the field and integration of this method with mechanical activation is poised as the future geopolymer activation technology as it demonstrates greatest efficiency potential.

A review of technology, materials and R&D challenges of upper limb prosthesis for improved user suitability.

INTRODUCTION: Hand amputation significantly challenges one's independence in carrying out daily activities. With the UK and Italy recoding circa 5200 and 3500 upper limb (UL) amputations (ULAs) yearly, respectively, and about 541,000 Americans losing ULs in 2005, incidence victims constitute a considerable proportion of our population and should be adequately supported. The use of upper limb prosthesis (ULP) offers amputees a new opportunity of living a quality life - but poses challenges on the physically and psychologically traumatised. With reports that up to 20% of adult UL amputees choose not to use a prosthesis, roughly 26% of adults and 45% of children and adolescents are dissatisfied with their devices and abandon them with reasons of poor solution to basic needs, a review of ULP for suitability has become crucial. OBJECTIVES: These include, to review UL prosthetic technology (PT), the materials used in the manufacturing of ULP, challenges in research and development of ULP, and to advise on the suitability of different devices to the needs of amputees. METHODS: They involve an extensive review of relevant literature and application of statistics to analyse data obtained from literature. RESULTS: ULAs are characterised to show affected bones in seven types of amputations. The characterisation depicts key causes of incidences that lead to amputations while advising on device suitability. PT is classified in terms of cost, nature, functions/operations of each type of device while providing the design challenges. Users' opinions on PT materials are analysed and used to suggest new materials for the next generation of the devices. R&D challenges hindering future developments of PT is reviewed and results used to identify characteristics for the next generation of the technology. CONCLUSIONS: To increase user satisfaction and reduce device abandonment, amputees need useful information on the trend in PT and engineers need information about device field performance for improvements. The use of better performing ULP will improve users' everyday lives.

Effect of Relative Density on Compressive Load Response of Crumpled Aluminium Foil Mesh.

In recent years, a large number of metal foams and porous metals have been developed. Due to the high cost of these materials alternative manufacturing methods for cellular metallic materials are being explored. Crumpled metallic foil meshes, manufactured via die compression techniques, are evolving as a potential alternative method. However, the non-availability of sufficient data on their load response is limiting their uptake. Uniaxial compressive load response of crumpled aluminium foil meshes (CAFMs) of varying densities, forged by open and closed die compression, are studied. A 0.05 mm thick aluminium sheet mesh, manufactured by the expanded metal process is used. X-ray computed micro-tomography is employed to image the CAFM's internal cellular structure. The stress-strain relation demonstrates that the CAFMs produce identical load response profile irrespective of their relative density. Power law functions E R = 17110 ρ r 3.6547 and σ Y , E = 53.092 ρ r 2.2249 define the relationships between real Young's Modulus E R and effective yield strength, σ Y , E . The study provides new knowledge on the effect of relative density on the compressive properties of CAFMs which have applications across lightweight structural design.