Solution combustion synthesis of (Ni,Fe)Cr2O4 pigments: Effect of post-synthesis thermal treatments

Mixed spinel pigments Ni1− ΨFeΨCr2O4 (0 ≤ Ψ ≤ 1) were synthesized by means of a method known as Solution Combustion Synthesis, using urea as fuel. Effects on mineralogy, microstructure and colouring power of composition and parameters of post-synthesis thermal treatments (temperature and kiln atmosphere) were studied. The as-synthesized powders were calcined at two different temperatures (800 and 1000 °C) and atmospheres (oxidizing and inert). Powders were characterized by X-ray diffraction (XRD), thermogravimetry (TG), scanning electron microscopy (FEG-SEM) and colour development in glaze. Mineralogy was highly affected by post-synthesis parameters. A progressive evolution from a Fd-3m face-centred spinel to a rhombohedral (Fe,Cr)2O3 structure was identified as the calcination temperature increased and composition enriched in iron. Inert atmosphere slowed down spinel→(Fe,Cr)2O3 transformation. Moreover, crystallite size of both phases showed characteristic critical points with composition and calcination conditions. On the other hand, microstructure analysis showed an important grain growth as the calcination temperature increased using the oxidizing atmosphere, but it was considerably altered with inert atmosphere. Regardless of post-synthesis thermal treatment parameters, all pigments showed high colouring power in a glaze. As Ψ increased, generated colours evolved from yellow-greenish to brown. Only luminosity coordinate L* of glazes subtly decreased as calcination temperature of the pigment increased, while a* and b* were nearly constant. This behaviour is related to the evolution of the pigment during the heating interval of the firing cycle of the glazed samples

Effects of composition and furnace temperature on (Ni, Co) (Cr, Al)2O4 pigments synthesized by solution combustion route

The effects of composition and furnace temperature on Ni1-ΨCoΨCr2−2ΨAl2ΨO4 (0≤Ψ≤1) pigments prepared by Solution Combustion Synthesis were studied. As-synthesized samples showed spinel-like spongy structure, very easy to grind. However, important differences on crystallinity, crystal size, and microstructure were observed depending on composition and furnace temperature. All pigments developed intense tones, covering a wide color palette because of composition influence, although little effect was observed with furnace temperature. Stable crystalline structures, suitable grain size, and high resistance against synthesizing variables and ceramic glazes make SCS pigments perfect candidates to be used in the ceramic ink-jet decoration

Solution combustion synthesis of (Co,Ni)Cr2O4 pigments: Influence of initial solution concentration

Initial solution concentration effect was studied on the synthesis of mixed spinels Co1-ΨNiΨCr2O4 (0≤Ψ≤1) obtained by Solution Combustion Synthesis. Fd-3m spinel structure was developed in all range of compositions analysed, regardless of the concentration. However, structural characteristics such as ion rearrangement and crystal size showed a noticeable dependence on the initial concentration, being the spinel network more ordered and with higher crystallite size as the concentration increased. Cell parameter, however, presented dependence on composition but not on initial solution concentration. All as-synthesized pigments showed a significant colouring power in ceramic glazes without any significant influence of initial solution concentration. Therefore, a second thermal treatment was not needed. The coloured glazes covered a broad range of tones in the green section of colour space, which evolved as a function of composition

Obtainment of bactericidal inkjet inks based on Ag-nanocomposites

In this study, ceramic inks were formulated that are able to develop bactericidal properties and are appropriate for application by inkjet printing. These inks contain silver nanocomposites and are applied on to unfired glazed ceramic bodies, yielding single-fired tiles. Silver nanocomposites were obtained from different precursors, which were made to react in order to obtain more stable structures that, in addition to incorporating bactericidal components, were able to reduce their reactivity and dissolution in the glassy matrix during the ceramic tile firing stage, avoiding the ensuing loss of properties. The study also examined how the nature of the base glaze affected the reactivity of the resulting nanocomposites. The base glaze that enabled the bactericidal compounds to remain at the ceramic tile surface was selected as the optimum base glaze for the study

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Solution combustion synthesis of (Ni,Fe)Cr2O4 pigments: Effect of post-synthesis thermal treatments

Mixed spinel pigments Ni1− ΨFeΨCr2O4 (0 ≤ Ψ ≤ 1) were synthesized by means of a method known as Solution Combustion Synthesis, using urea as fuel. Effects on mineralogy, microstructure and colouring power of composition and parameters of post-synthesis thermal treatments (temperature and kiln atmosphere) were studied. The as-synthesized powders were calcined at two different temperatures (800 and 1000 °C) and atmospheres (oxidizing and inert). Powders were characterized by X-ray diffraction (XRD), thermogravimetry (TG), scanning electron microscopy (FEG-SEM) and colour development in glaze. Mineralogy was highly affected by post-synthesis parameters. A progressive evolution from a Fd-3m face-centred spinel to a rhombohedral (Fe,Cr)2O3 structure was identified as the calcination temperature increased and composition enriched in iron. Inert atmosphere slowed down spinel→(Fe,Cr)2O3 transformation. Moreover, crystallite size of both phases showed characteristic critical points with composition and calcination conditions. On the other hand, microstructure analysis showed an important grain growth as the calcination temperature increased using the oxidizing atmosphere, but it was considerably altered with inert atmosphere. Regardless of post-synthesis thermal treatment parameters, all pigments showed high colouring power in a glaze. As Ψ increased, generated colours evolved from yellow-greenish to brown. Only luminosity coordinate L* of glazes subtly decreased as calcination temperature of the pigment increased, while a* and b* were nearly constant. This behaviour is related to the evolution of the pigment during the heating interval of the firing cycle of the glazed samples

Solution combustion synthesis of (Co,Ni)Cr2O4 pigments: Influence of initial solution concentration

Initial solution concentration effect was studied on the synthesis of mixed spinels Co1-ΨNiΨCr2O4 (0≤Ψ≤1) obtained by Solution Combustion Synthesis. Fd-3m spinel structure was developed in all range of compositions analysed, regardless of the concentration. However, structural characteristics such as ion rearrangement and crystal size showed a noticeable dependence on the initial concentration, being the spinel network more ordered and with higher crystallite size as the concentration increased. Cell parameter, however, presented dependence on composition but not on initial solution concentration. All as-synthesized pigments showed a significant colouring power in ceramic glazes without any significant influence of initial solution concentration. Therefore, a second thermal treatment was not needed. The coloured glazes covered a broad range of tones in the green section of colour space, which evolved as a function of composition

Ink-jet technology applied to engineer low-cost ceramic membranes

This contribution analyses the suitability of the ceramic ink-jet technology to apply layers over a porous ceramic support, as the basis for a development of a standardized method to synthesize multilayer ceramic membranes

Effects of pre-operative isolation on postoperative pulmonary complications after elective surgery: an international prospective cohort study an international prospective cohort study

We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care. We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care

Delaying surgery for patients with a previous SARS-CoV-2 infection

Not availabl