FEA on Grey Cast Iron Assets: A Case Study on Penstocks in the Waste Water System

Penstocks have been used in the water industry for flow control since the Victorian expansion and consolidation of clean and waste water networks. However, the Victorians were the first to use grey cast iron (GCI) castings to manufacture large scale penstocks. Most of these ageing assets are still in operation, however engineering assessments are necessary to determine a structure’s fitness-for-service. Even today, penstocks in the sewer system tend to be made from GCI, due to ease of manufacturing, resistance to corrosion and cost. One characteristic property of grey cast iron is the graphite flake structure in the material, contributing to its low toughness, inconsistency in material strength and brittle behaviour, despite exhibiting slight hardening properties. Finite element analysis (FEA), is a numerical method which allows the analysis of complex structures by splitting it into finite parts and solving them with a computer processor. Despite the versatility of FEA, appropriate considerations and assumptions are necessary due to the difficulty to obtain data from inspection and unique material behaviour of GCI. The article shows concerns for an analysis of GCI penstocks using FEA, which extends into the application of fracture mechanics approaches for defect assessments.

An Analysis of Relationship between the Microfracture Features and Mineral Morphology of Granite

Using the techniques of X-ray diffraction, polarizing microscopy, uniaxial compression, and scanning electron microscopy (SEM), the relationships between the microfracture features and mineral morphology of granite were studied. The results showed that feldspar, quartz, and biotite are the main components of the granite samples in this study. Biotite has a self-shaped flake structure with perfect cleavage. K-feldspar has a lattice double crystal structure with two groups of cleavage. Plagioclase has a semi-self-shaped plate structure with two groups of cleavage. Quartz is prismatic or granular and exhibits noncleavage. The microfracture features of biotite are flaky with exfoliation, and flake cleavage fracture is mainly determined by its peculiar flaky cleavage. Feldspar (K-feldspar and plagioclase) is plate, layered, or two groups of cleavage and is also mainly determined by its peculiar two groups of cleavage. The microfracture features of quartz are highly irregular, with many randomly distributed intergranular and transgranular cracks, small particles or granule bulges, similar to quartz crystal, and this is due to the noncleavage feature of quartz itself. It is demonstrated that microfractures are preferentially ruptured along cleavage planes for these granite minerals under the action of external forces.

Research on Purification Technology of Ultra-Large Flake Graphite Based on Alkali-Acid Method

Graphite is a strategically scarce resource, and the preparation of high-purity graphite is the prerequisite and basis for the application of graphite. In order to determine the optimal purification technology parameters of an ultra-large flake graphite mine pneumatic separation ore with a fixed carbon content of 77.69%, a particle size of mainly 10 to 40 mesh, and main impurities of calcium carbonate, iron oxide and silica , two additional experiments of acid method and alkali method were added on the basis of alkali-acid method, to investigate the purification effect of different technological processes and acid leaching times on graphite raw materials, as well as to analyze the retention extent of different methods and alkali fusion temperature on graphite ultra-large flake structure. The results show that all three methods can increase the fixed carbon content of graphite to above 99%. However, compared with the acid method and the alkali method, the alkali-acid method can obtain high-purity graphite while also better protecting the graphite's ultra-large flake structure. The optimal fusion temperature is 400 °C, the optimal acid leaching time is 30% sulfuric acid thrice and 5% hydrofluoric acid once. After purification, the fixed carbon content of the product exceeds 99.97%.

Enhancement of performance for graphite felt modified with carbon nanotubes activated by KOH as Cathode in electro-fenton systems

The electro-Fenton (EF) process is one of the advanced oxidation processes (AOPs). Graphite felt is widely used as an cathode material for the EF process, and its performance can be improved by surface modification. Active carbon nanotubes (ACNTs) have more oxygen-containing functional groups and better electrochemical properties compared to Multi-wall carbon nanotubes (MWCNTs). In this study, graphite felt was used as the substrate, and composite cathodes were prepared by surface treatment using MWCNT, graphene, and ACNTs. Rhodamine B (RhB) dye decolorization tests were then conducted to investigate the degradation performance of the EF system with different cathodes. The results showed that based on the micromorphology of ACNT, the tubular form of MWCNT was activated into a GR-like flake structure, it was also found that the strength of the oxygen-containing functional groups of ACNT improved significantly. The activated MWCNT/C cathode exhibited a 60-min decolorization rate of 77.28% compared to the unactivated MWCNT/C cathode, whereas the decolorization rate of the ACNT/C cathode increased to 85.01% after activation, which was close to that of the GR/C cathode at 88.55%. In summary, the ACNT/C cathode exhibited degradation efficiency comparable to that of the GR/C cathode.

Synthesis and Characterization of BaAl2O4 Catalyst and its Photocatalytic Activity Towards Degradation of Methylene Blue Dye

Hexagonal BaAl2O4 catalyst has been prepared using a gamma-ray irradiation assisted polyacrylamide gel method. The catalysts synthesized at different calcining temperatures were analyzed to insight into their effects on the structural, crystalline, surface morphology, color, optical, fluorescence and photocatalytic properties of the hexagonal BaAl2O4 catalyst. Increasing the calcining temperature has obvious influences on the crystallinity, color, optical properties and the formation of the hexagonal BaAl2O4 catalyst. The optical energy gap (Eg) value of the hexagonal BaAl2O4 catalyst increases with the increasing of calcining temperature. TEM image of the pure hexagonal BaAl2O4 catalyst shows a morphology of flake structure and aggregation. Raman spectroscopy of the pure hexagonal BaAl2O4 catalyst exhibits four luminescent background peaks at 400, 415, 428 and 445 nm mainly due to the oxygen vacancies (VO), Ba vacancies (VBa) and some color centers exists in the BaAl2O4 sample. A comparison of photocatalytic activity among samples for degradation of methylene blue (MB) dye indicates that the pure hexagonal BaAl2O4 catalyst exhibits highest photocatalytic activity under the irradiation of both visible and ultraviolet light. Based on the fluorescence experiment, electrochemical and active species tests, the high photocatalytic activity of the pure hexagonal BaAl2O4 catalyst to be related to hole (h+) and hydroxyl radical (⋅OH) and also to the defects in the sample.

SYNTHESIS AND CHARACTERIZATION OF GRAPHENE FROM COCONUT FIBER (COCOS NUCIFERA) AS ANODE MATERIALS FOR LI-ION BATTERY

Synthesis of graphene from coconut fiber conducted in two stages. The first stage is heating the powder of coconut fiber that passes 325 meshes by hydrothermal method at 200o C for 4 hours. Furthermore, the pyrolysis then treated at temperature of 1000° C for 2 hours. The grain size and surface morphology from graphene observed using SEM in the 1000X magnification. From the SEM image of graphene, it shows the pattern of several thick layers build mutual three-dimensional, forming a flake structure. Observations also show stacks of graphene structure with more big flakes forming a thick pallet. Another characterization was performed by using X-ray diffractometer (XRD), Raman Spectrometer and LCR meter. From XRD observation there is an amorphous pattern at the first stage of synthesis, after pyrolysis at 1000o C for 2 hour a peak near 2θ = 24o, 42oand 52o which corresponds to crystal indexes (002), (400) and (511) became visible. The peak at around 1350 cm-1 in the Raman is the D band. The D band is represented defects, like disruption in the sp2 bonding because of heptagon and pentagon rings, vacancies, edge effect, and etc. DC conductivity or bulk electrical conductivity of about 4.6 x 10-3 Scm-1.

Potential Peat Clay for Minerals Source Utilized as Adsorbent and Catalyst

The existence of peat clay is scattered in many parts of the world with the huge amount. The high compound of minerals in the peat clay can be potentially used as adsorbent and catalyst. This research aims to study the composition of peat clay and functional group of the compound in the peat clay. The characterization of x-ray fluorescence (XRF), fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and scanning electron microscope-energy dispersive x-ray (SEM- EDX) were assigned to compare the sample before and after calcination process at 700 oC 120 min. FTIR analysis showed the presence of quartz, kaolinite, hematite, illite in peat clay. The results of XRF analysis showed that chemical composition of peat clay was dominantly in the form of silica oxide (18%), aluminum oxide (7%), and iron oxide (15%). The amount of compounds was observed to increase to be 32%, 18% and 11%, respectively after calcinations. XRD analysis confirmed the presence of this mineral in the peat clay. SEM analysis showed flake structure of peat clay with EDX which indicated composition of the dominant element namely the presence of Al, Si, and Fe before and after calcination. This high amount of minerals in peat clay led to potential source to be utilized as adsorbent for removing the pollutant or as and catalyst for chemical process.