Molten hydroxide synthesis as an alternative to molten salt sythesis for producing K0.5Na0.5NbO3 lead free ceramics

Lead-free piezoelectric materials have grown in importance through increased environmental concern and subsequent EU and worldwide legislation, with the aspiration to reduce the use of Pb-based materials in all sectors. Integration of the next generation of lead-free piezoelectric materials with substrates to form functional micro devices has received less attention. Low temperature synthesis methods for K0.5Na0.5NbO3 powder were developed to overcome the issue of poor purity of the final product during high temperature sintering. Molten hydroxide synthesis (MHS), derived from molten salt synthesis (MSS), has been developed to overcome a Na ion preference in the molten salt synthesis reaction that leads to NaNbO3 production instead of K0.5Na0.5NbO3 when stoichiometric amounts of precursors are used. MHS makes use of a KOH molten reaction aid in place of the NaCl/KCl molten salt mix of the MSS. In a two stage reaction K rich intermediate niobates are produced and subsequent reactions with Na species produce KNN

Investigation of Electromechanical Properties on 3-D Printed Piezoelectric Composite Scaffold Structures

Piezoelectric composites with 3-3 connectivity gathered attraction due to their potential application as an acoustic transducer in medical imaging, non-destructive testing, etc. In this contribution, piezoelectric composites were fabricated with a material extrusion-based additive manufacturing process (MEX), also well-known under the names fused deposition modeling (FDM), fused filament fabrication (FFF) or fused deposition ceramics (FDC). Thermoplastic filaments were used to achieve open and offset printed piezoelectric scaffold structures. Both scaffold structures were printed, debinded and sintered successfully using commercial PZT and BaTiO3 powder. For the first time, it could be demonstrated, that using the MEX processing method, closed pore ferroelectric structure can be achieved without pore-former additive. After ceramic processing, the PZT scaffold structures were impregnated with epoxy resin to convert them into composites with 3-3 connectivity. A series of composites with varying ceramic content were achieved by changing the infill parameter during the 3D printing process systematically, and their electromechanical properties were investigated using the electromechanical aix PES device. Also, the Figure of merit (FOM) of these composites was calculated to assess the potential of this material as a candidate for transducer applications. A maximum for the FOM at 25 vol.% of PZT could be observed in this stud

Integrated Hybrid Life Cycle Assessment and Supply Chain Environmental Profile Evaluations of Lead-based (Lead Zirconate Titanate) versus Lead-free (Potassium Sodium Niobate) Piezoelectric Ceramics

The increasing awareness of the environmental and health threats of lead as well as environmental legislation, both in the EU and around the world targeted at decreasing the use of hazardous substances in electrical appliances and products has reinvigorated the race to develop lead-free alternatives to lead zirconate titanate (PZT), which presently dominates the market for piezoelectric materials. Emphasis has been placed on one of the most likely piezoelectric materials, potassium sodium niobate (KNN), as a lead-free replacement for PZT. KNN has been speculated to have better environmental credentials and is considered as a “greener” replacement to PZT. However, a comparative environmental impact assessment of the life cycle phases of KNN versus PZT piezoelectric materials has not been carried out. Such a life cycle assessment is crucial before any valid claims of “greenness” or environmental viability of one material over the other can be made and is the focus of this paper. Against this backdrop, a methodologically robust life cycle supply chain assessment based on integrated hybrid life cycle framework is undertaken within the context of the two piezoelectric materials. Results show that the presence of niobium in KNN constitutes far greater impact across all the 16 categories considered in comparison with PZT. The increased environmental impact of KNN occurs in the early stages of the LCA due to raw material extraction and processing. As a result, the environmental damage has already occurred before its use in piezoelectric applications during which it doesn’t constitute any threat. As such, the use of the term “environmentally friendly” for the description of KNN should be avoided. Cost-benefit analysis of substituting PZT with KNN also indicates that the initial cost of conversion to KNN is greater, especially for energy usage during production. This environmental assessment has allowed us to define and address environmental health and safety as well as sustainability issues that are essential for future development of these materials. Overall, this work demonstrates insightful findings that can be garnered through the application of life cycle assessment and supply chain management to a strategic engineering question which allows industries and policy makers to make informed decisions regarding the environmental consequences of substitute materials, designs, fabrication processes and usage

Synthesis and processing of KNN powders and thick films for MEMS devices

Pb-free piezoelectric materials have grown in importance through increased environmental concern related to the presence of Pb and the subsequent legislation that has arisen including directives such as Waste Electrical and Electronic Equipment (WEEE) and the Restriction of Hazardous Substances Directive (RoHS). While much progress has been made on producing Pb-free bulk materials, the need to integrate these next generation Pb-free piezoelectric materials with substrates to form functional micro devices has received less attention and raises a number of challenges. With respect to the high temperature mixed oxide synthesis method, a simple, cost effective and robust low temperature molten hydroxide synthesis (MHS) method derived from the molten salt synthesis (MSS) method, has been developed to produce K0.5Na0.5NbO3 (KNN) small grain powders and is a method that lends itself easily to industrial scale up. A powder/sol gel composite ink film forming technique has been used to produce KNN thick films on silicon substrates. Characterisation of the produced films has shown the films to exhibit piezoelectric coefficients for un-doped material in the region of 30pC/N. The work will report on the Na ion favouring mechanism of the MSS and the related mechanism of the MHS. The work will also report on the dielectric and piezoelectric characteristics of initial KNN thick films produced and an investigation into use of dopants and process modification to improve the KNN thick film’s characteristics

Ferroelectric KNNT Fibers by Thermoplastic Extrusion Process: Microstructure and Electromechanical Characterization

B-site substitution in KNN with tantalum results in a higher d33 and dielectric constant. This higher value makes KNNT interesting for lead-free actuator applications. KNNT fibers with diameters of 300 and 500 μm have been extruded and sintered at 1200 °C in a KNNT-enriched atmosphere. Subsequently, the influence of fiber diameter on the microstructure (porosity and grain size) was investigated. The measurements revealed that with decreasing fiber diameter, the porosity increases, whereas the grain size decreases. The influence of these microstructural differences on the piezoelectric properties was evaluated using a novel characterization procedure for single fibers. The larger diameter fibers show an increase in the electromechanical properties measured, i.e., d33, tanδ, Pr, Ec and the free longitudinal fiber displacement, when compared to smaller diameter fibers. The lower alkali losses result in a larger grain size, a higher density during sintering and lead to higher electromechanical properties

Structural and Legal Frameworks Guiding Multi-Agency Operations and Countering Terrorism in Kenya

Kenya has in the last decade been faced by a constant terror threat from al-Shabaab, ISIS and al Qaeda. This study sets out to assess the effects of structural and legal frameworks guiding multi-agency operations on countering terrorism in Kenya. The study questions were as follows: Are there existing or lack thereof of multi-agency strategic policies on coordination in response to international terrorism in Kenya? The study adopted mixed methods and exploratory research designs. The target population was all the members of the Kenya Defense Forces Special Operations Forces (KDF SoFs), the National Police Service (NPS) Recce squad, and ATPU Officers as well as policy level Military, Intelligence and Police Officers. The target population is estimated at 3400 personnel from which a sample of 97 was obtained. The used primary data collected from the respondents using mainly questionnaires and interviews as well as secondary data that was obtained from library-based research via books, e-books, journals, government publications, and published thesis, among other reputable academic publications. The data collected from questionnaires were analyzed using the Statistical Package for the Social Sciences (SPSS) version 24. The findings were presented in descriptive statistics, tables, graphs, charts and inferential statistics. On its part, data from interviews were analyzed thematically based on the objectives so as to establish the key themes and trends from which findings, conclusions, and recommendations were drawn. The study findings make it manifest that the existence of structural and legal frameworks guiding multi-agency operations on countering terrorism in Kenya had led to effective response through standardizations of operation guidelines, better sharing of information, joint training and exchange of best practices among the various responders. This was evidenced in the Dusit D2 Attack in which synchronization of operations showed better response to the attack by the various operational and tactical teams as compared to the Westgate Attack. The study recommends that there is need for multinational frameworks for undertaking financing and creation of joint information infrastructure for security agencies so as to reign in on international terrorism in the East African Region

Effect of Polymer-Ceramic Fibre Interphase Design on Coupling Factor in Low Fibre Volume Content Piezoelectric Composites

In this work, we investigated different short molecule polymer coatings in piezoelectric ceramic-polymer composites with low fibre volume contents. Modifying the interphase between the piezoelectric PZT (lead zirconate titanate) fibre and the epoxy matrix thus enhances the electromechanical coupling factor for 1–3 ultrasound transducers with low fibre contents. It is known that the electromechanical coupling factor can be increased by precoating a ceramic fibre with a soft interlayer polymer [1-1-3]. In this paper, we investigate the so-called 1-1-1-3 composites composed of a ferroelectric ceramic fibre (core), a soft polymer layer (e.g., fatty acids, amides, waxes, or oils), an epoxy resin shell, and an epoxy resin matrix. Some soft polymer layers allowed the free movement of the ferroelectric fibres reducing blocking or clamping by the inactive polymeric matrix, resulting in higher electromechanical coupling factors (kt) for composites with low fibre volume contents. Using an oil-based interlayer, the dielectric constant can be significantly increased. The lowest fibre push-out stress could be achieved with the paraffin interlayer; however, no correlation with the coupling factor could be observed

Understanding the financial burden of incomplete abortion: An analysis of the out-of-pocket expenditure on postabortion care in eight public-sector health care facilities in Dakar, Senegal

Timely access to treatment is essential for women when they experience abortion complications. Out-of-pocket (OOP) expenditure is a known barrier to health care access. In 2018, we assessed the financial burden of accessing postabortion care (PAC) borne by women in Dakar, Senegal, where studies estimate that half of poor women with complications obtain PAC. We interviewed 729 women following discharge from PAC. Women reported expenditures on transportation, admission, treatment, family planning, hospitalisation, complementary tests, prescriptions, other medicines and materials. We compare women’s OOP on PAC by expenditure category, type of treatment and facility type, and use multiple generalised linear regression analysis to explain variation in overall OOP and forecast it under alternate scenarios. The average OOP was USD $93.84. At health centres it was$65.47 and at hospitals it was $120.47. The average cost of PAC using dilation and curettage was$112.37, manual vacuum aspiration was $99.84, and misoprostol$61.80. Overall OOP on PAC amounts, on average, to 15% of the average monthly salary for women living in Dakar. Strategies that emphasise timely access to misoprostol for treating complications in primary care settings will address the contribution of OOP costs to Senegal’s appreciable unmet need for PAC among the poor