What are students’ opinions of ‘Flipped learning’ in secondary science?

Flipped learning has emerged in recent years as an alternative method of teaching. The premise of Flipped learning is that students learn new material at home, and then use lesson time to tackle problems and interact with the subject matter. The rationale behind this is that students get more time with a teacher when they are solving problems or applying knowledge in the classroom, so teachers can help build higher levels of understanding. It also allows the lesson to be more interactive, as less time is spent teaching new material. Whilst many recent studies have concentrated on how Flipped learning is used at university level teaching, I was eager to undertake my enquiry on Flipped learning at secondary school. Having spoken at length to teachers about their opinions on Flipped learning, I was keen to discover what students’ opinions were. This enquiry made use of a questionnaire, and interview with sixth form biology students at an all-girls grammar school who are taught via Flipped learning. Student opinions were largely positive, with students expressing being able to learn at their own pace, more interactive lessons and being better prepared for lesson time among the benefits of Flipped learning

Control of steam input to the pyrolysis-gasification of waste plastics for improved production of hydrogen or carbon nanotubes

Carbon nanotubes (CNTs) have been proven to be possible as high-value by-products of hydrogen production from gasification of waste plastics. In this work, steam content in the gasification process was investigated to increase the quality of CNTs in terms of purity. Three different plastics-low density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS) were studied in a two stage pyrolysis-gasification reactor. Plastics samples were pyrolysed in nitrogen at 600°C, before the evolved gases were passed to a second stage where steam was injected and the gases were reformed at 800°C in the presence of a nickel-alumina catalyst. To investigate the effect that steam plays on CNT production, steam injection rates of 0, 0.25, 1.90 and 4.74gh-1 were employed. The CNTs produced from all three plastics were multiwalled CNTs with diameters between 10 and 20nm and several microns in length. For all the plastic samples, raising the steam injection rate led to increased hydrogen production as steam reforming and gasification of deposited carbon increased. High quality CNTs, as observed from TEM, TPO and Raman spectroscopy, were produced by controlling the steam injection rate. The largest yield for LDPE was obtained at 0gh-1 steam injection rate, whilst PP and PS gave their largest yields at 0.25gh-1. Overall the largest CNT yield was obtained for PS at 0.25gh-1, with a conversion rate of plastic to CNTs of 32wt%

Thermal processing of plastics from waste electrical and electronic equipment for hydrogen production

Plastic waste from waste electrical and electronic equipment (WEEE) produced from a real-world commercial WEEE recycling centre has been processed using pyrolysis–gasification using a two-stage reaction system to produce hydrogen. In the first stage, the plastic fraction was pyrolysed at 600 °C and the evolved pyrolysis gases were passed directly to a second reactor at 800 °C and reacted with steam in the presence of a Ni/Al2O3 catalyst. In addition, high impact polystyrene (HIPS) and acrylonitrile–butadiene–styrene (ABS) which were the main components of the WEEE plastic were reacted to compare with the WEEE plastic. The results showed that the introduction of steam and the catalyst increased the yield of hydrogen. Increasing the nickel content in the catalyst also resulted in higher hydrogen yield. The comparison of the results of WEEE with those of HIPS and ABS showed that WEEE plastic was mainly composed of ABS. The catalyst, after reaction, showed significant deposition of coke composed of filamentous and layered type carbon. Overall the novel processing of waste plastic from electrical and electronic equipment using a two stage pyrolysis–gasification reactor shows great promise for the production of hydrogen

Effect of growth temperature and feedstock:catalyst ratio on the production of carbon nanotubes and hydrogen from the pyrolysis of waste plastics

Abstract Carbon nanotubes have been produced from a low density polyethylene (LDPE) feedstock via a two stage pyrolysis process. The temperature of the second stage, where carbon deposition on an iron alumina catalyst occurs (growth temperature), was varied using catalyst temperatures of 700, 800 and 900 °C. An increase in catalyst temperature led to a higher yield of both carbon nanotubes and hydrogen, as the rate of carbon deposition increased. Changing the amount of feedstock relative to the catalyst also had an effect on the production of both carbon nanotubes and hydrogen. As more feedstock is used a larger source of carbon gives rise to a larger amount of carbon nanotubes per gram of catalyst. However, in terms of the percentage of feedstock converted into carbon nanotubes and hydrogen gas, a reduction was observed. Conversion of plastic into carbon nanotubes was 29.1 wt.% when 0.5 g LDPE was used, but reduced to 13.1 wt.% with 1.25 g LDPE. This is because the catalyst activity reduces as it becomes overloaded, and much of the hydrocarbon gases are left unreacted. This gives an economic playoff between large conversion of plastics into carbon nanotubes and hydrogen gas, and large yields of carbon nanotubes per gram of catalyst used

The use of different metal catalysts for the simultaneous production of carbon nanotubes and hydrogen from pyrolysis of plastic feedstocks

Nickel, iron, cobalt and copper catalysts were prepared by impregnation and used to produce carbon nanotubes and hydrogen gas from a LDPE feedstock. A two stage catalytic pyrolysis process was used to enable large yields of both products. Plastics samples were pyrolysed in nitrogen at 600. °C, before the evolved gases were passed to a second stage and allowed to deposit carbon onto the catalyst at a temperature of 800. °C. Carbon nanotubes were successfully generated on nickel, iron and cobalt but were barely observed on the copper catalyst. Iron and nickel catalysts gave the largest yield of both hydrogen and carbon nanotubes as a result of metal-support interactions which were neither too strong, like cobalts, nor too weak like copper. These metal support interactions proved a key factor in CNT production. A nickel catalyst with a weaker interaction was prepared using a lower calcination temperature. Yields of both carbon nanotubes and hydrogen gas were lower on the Ni-catalyst prepared at the lower calcination temperature, as a result of sintering of the nickel particles. In addition, the catalyst prepared at a lower calcination temperature produced metal particles which were too large for CNT growth, producing amorphous carbons which deactivate the catalyst instead. Overall the iron catalyst gave the largest yield of CNTs, which is attributed to both its good metal-support interactions and irons large carbon solubility