Effect of Milling on Size Reduction and Microstructural Changes to Gamma-Alumina

This thesis sets out to evaluate the effects of milling on the microstructural changes to gamma-Alumina, a well-used catalyst support. It reviews the literature as it relates to the characterisation that has been done so far on this material, different milling methods and effects of milling. The review section considers the strengths and weaknesses of previous work in the areas of structural characterisation of gamma-Alumina as well as reports on the effects of milling of the material with particular interest in size reduction and phase transformation. Working from the base of current knowledge, experiments that can fill in the gap identified from the review are designed. The material under investigation is characterised as received for particle size and morphology and this gives a base for further experimental investigations. Various experiments are designed centred around exposure of gamma-Alumina to different milling conditions. These include the use of different mills, variation of milling conditions and isolation of stress modes. Furthermore, results from Discrete Element Method simulations of one selected mill, provided by Professor Junya Kano of Tohoku University in Japan are analysed for energy quantification. Data processing of the results of the operation of a second mill, simulated by Discrete Element Method at the University of Leeds by Dr Colin Hare and Dr Ali Hassanpour is also used to quantify energies associated with the milling process. It is concluded that microstructural changes to gamma-Alumina are very much energy driven processes. The jet mill has proven a worthy candidate for size reduction in small scale processes. The size reduction analysis shows that gamma-Alumina requires the presence of a dispersive agent such as water or compressed air for efficient size reduction. The characterisation work combined with the simulation results show that the amount of energy dissipated into the microstructure of gamma-Alumina during a collision governs the extent of microstructural effects. Results also show that with the supply of different energies to milling processes, mechanical energy can achieve a phase transformation from gamma-Alumina to alpha-Alumina similar to that achieved by calcination where delta-alumna and theta-Alumina are observed as intermediate phases. Simulation also provides a tool for prediction and selection of milling processes appropriate for the required end product

Mechanically Induced Amorphization of Diaqua-bis(Omeprazolate)-Magnesium Dihydrate

The influence of milling diaqua-bis(omeprazolate)-magnesium dihydrate (DABOMD), an active pharmaceutical ingredient (API), was investigated. DABOMD was processed in a planetary ball mill at different milling times, from 1 to 300 min. The milling process resulted in a prominent comminution (size reduction) and amorphization of the API. DABOMD amorphization was identified with various characterization techniques including thermogravimetric analysis, differential scanning calorimetry, powder X-ray diffraction, and attenuated total reflection-Fourier transform infrared spectroscopy. The solid–solid crystalline to amorphous phase transformation is driven by compression, shear stresses, and heat generated in the planetary ball mill. This leads to distortion and breakage of hydrogen bonds, release of water molecules from the crystalline lattice of DABOMD and the accumulation of defects, and eventually a collapse of the crystalline order. Model fitting of the kinetics of comminution and the amorphization of DABOMD revealed a series of events: a rapid comminution at the start of milling driven by crystal cleavage of DABOMD, followed by partial amorphization, which is driven by rapid water diffusion, and subsequently, a slow steady comminution and amorphization

Effect of mill type on the size reduction and phase transformation of gamma alumina

The influence of stress modes and comminution conditions on the effectiveness of particle size reduction of a common catalyst support; γ-Alumina is examined through a comparative assessment of three different mill types. Air jet milling is found to be the most effective in reducing particle size from a d90 of 37 µm to 2.9 µm compared to planetary ball milling (30.2 µm) and single ball milling (10.5 µm). XRD and TEM studies confirm that the planetary ball mill causes phase transformation to the less desired α-Alumina resulting in a notable decrease in surface area from 136.6 m2/g to 82.5 m2/g as measured by the BET method. This is consistent with the large shear stresses under high shear rates prevailing in the planetary ball mill when compared to the other mill types. These observations are consistent with a shear-induced phase transformation mechanism brought about by slip on alternate close packed oxygen layers from a cubic close packed to a hexagonal close packed structure

Effect of jar shape on high-energy planetary ball milling efficiency: Simulations and experiments

The present work was partly supported by Fondazione Caritro, under project No 2013-0247 “Mechanical activation to improve bioavailability and reduce adverse effects of drugs in the therapy of chronic diseases”. The authors are especially grateful to Dr. D. Catelani (MSC Software) for precious collaboration and support to the research work. NMP is supported by the European Research Council (ERC StG Ideas 2011 BIHSNAM n. 279985, ERC PoC 2015 SILKENE nr. 693670) and by the European Commission under the Graphene Flagship (WP14 Polymer Composites, no. 696656)

Production of food nanomaterials by specialized equipment

In the past decade, there has been a great interest in using nanotechnology by different industries, including food, pharmaceutical, and beauty. Nanotechnology provides many advantages to produce functional compounds which tend to be delivered for desired properties, such as protection from the environment or food matrix, controlled release, and increased bioavailability and bioaccessibility (Muhammad et al., 2019, Sedaghat Doost et al., 2019b, Sedaghat Doost et al., 2018c). There is a variety of methods to prepare food nanomaterials. Specialized equipment is frequently employed for the production of efficient nano-delivery systems, which is the focus of this chapter; the basic principle of conventional and recent techniques, as well as their advantages and disadvantages are described

A livelihoods approach to assessing the role of sand river aquifers for irrigation purposes : A case of Tshelanyemba community along Shashani River in Zimbabwe

Effects and impacts of climate change have been experienced by Sub-Saharan African (SSA) countries, and Zimbabwe is not an exception, with drought, and prolonged dry spells being the most critical climate-related dangers. Although irrigation development had since been a worthwhile investment, much attention has been given to the establishment and rehabilitation of communal irrigation schemes by both the Government of Zimbabwe, as well as external development agencies. However, due to collective action issues, these irrigation schemes have proved to be financially unsustainable. Due to the existence of Shashani sand river, which has proved to be a reliable nature-based water storage during droughts and dry seasons, different farmers are engaging in irrigated crop production as one of their livelihood strategies. These farmers include brushwood garden farmers, owning small gardens, community garden farmers, where Dabane Water Works (DWW) established such gardens since the 1990s, as well as individual farmers, with gardens at their homesteads whilst pumping water from the sand river. Additionally, an action research (AR) project in the form of two Arid African Alluvial Aquifers Laboratories (A4Labs) project gardens was established along Shashani river to find out the reason behind the underutilisation of Shashani sand river. This study aimed to qualitatively assess the contribution that access and use of water from Shashani sand river for irrigated crop production had on the livelihoods of different people, both irrigating and non-irrigating farmers. To assess the contribution towards the livelihood of irrigated crop production livelihood strategy through accessing Shashani sand river aquifers, the study looked first at how different farmers’ livelihoods were before irrigation, including the livelihood strategies that farmers used to pursue. Through farmers’ experiences and perceptions, the contribution that access to Shashani sand river through irrigated crop production was captured through changes in the state of livelihoods and livelihood strategies. In-depth semi-structured interviews were conducted with 54 informants from various farming groups including brushwood garden farmers, community and A4Labs garden farmers, individual farmers, rainfed farmers, Tshelanyemba hospital, as well as key informants, where 81% of the interviewees were women. The study concludes that despite small gardens being given less attention, access and use of water from Shashani sand river for irrigated crop production through gardening have contributed significantly towards influencing different farmers’ livelihoods. This was mainly due to the production of vegetables for household consumption, as well as generation of income from excess. However, due to mainly poverty, there is a lack of developmental trajectories by farmers in the absence of external assistance. The study also concludes that despite the abundance of water from the sand river, due to distances travelled by farmers from homesteads to the gardens, some farmers’ plans disregard the use of the river for irrigation in the future. Additionally, not all farmers residing relatively close to the river are accessing the sand river for irrigated crop production due to reasons ranging from lack of branches to having other means of surviving. The study recommends intervention through development agencies in the form of assisting brushwood garden farmers in upscaling their own small gardens, awareness, and trainings of community garden farmers towards increasing their sense of ownership as well as on operation and maintenance funds. Further research may be required on evaluating the gendered nature of farmer-led irrigators, and the potential opportunities for women and youth emerging farmers

Endogenous irrigation in arid Zimbabwe: farmer perceptions of livelihood benefits and barriers to scaling

In Zimbabwe, farmer-led irrigation is far more widespread than planners and policy makers realise. Along the Shashani sand river, in the arid to semi-arid lands of south-western Zimbabwe, diverse farmer-initiated irrigation ventures exist. This qualitative case study focuses on bucket irrigation, in which very small vegetable fields of up to 450 m2 are fenced by tree branches, and irrigated with water from scoop holes in sandy river beds. Farmers initiate and operate their fields with no external assistance. This study presents the benefits of bucket irrigation as an often-overlooked form of farmer-led irrigation development. Through this qualitative and strongly observational study, 26 bucket irrigation farmers and 4 non-irrigators were interviewed using semi-structured interviews where farmers’ perceptions and experiences were captured. We investigate what drives and sustains bucket irrigation, its significance to rural livelihoods under harsh economic and climatic conditions, and the barriers towards scaling this type of farmer-led irrigation development. The results show that drivers for bucket irrigation stem from economic hardship and are gendered. Women are motivated to irrigate mainly by the need to produce vegetables for household consumption, whereas men pursue irrigation due to a lack of employment. Bucket irrigators experience enhanced food security, and have more secure income, contributing to improved wellbeing. Furthermore, despite the desire to scale, the farm size is mainly constrained by fencing and energy for transporting water, which is a result of a persistent lack of financial capital to invest in irrigation technologies. We conclude that bucket irrigation acts as an important livelihood strategy, and that it significantly enhances farmers’ resilience to economic and climatic shocks.  Bucket irrigation should not be overlooked in policies that advocate scaling of irrigation. Bucket irrigators have the potential to expand and benefit significantly if supported with innovative financial mechanisms that enable investments in the required technology and knowledge