bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical Properties and Microstructure of the Fly Ash Based-Geopolymer/Granule Composites
Authors: Won Ji Hwan , Kang Seung Gu
Published: October 2014

In this research, the fly ash (F/A) discharged from a thermal power plant was recycled to manufacture geopolymer containing granules instead of sand. Several types of granules using fly ash were assessed. The properties of the geopolymer/granule composites were analyzed as a function of the crystalline phase and size of the granules, as well as the molding pressure. The compressive strength and density of the geopolymer composites containing the hydrated granules fabricated by hand-tapping were 5.7 MPa and 1.47 g/cm3, respectively, while composites created by pressure molding were 15.6 MPa and 1.73 g/cm3. These results are comparative or superior to those of commercial cement bricks (8 MPa according to KS F 4004). Therefore, the geopolymer/granule composites fabricated in this study can be applied to cement bricks and can be a base for the enhancement of the recycling rate of fly ash.
Hydropower Development and Prospects Analysis
Authors: Xu Shu Qin
Published: October 2014

As a renewable green energy, hydropower resources in the sustainable development of power industry occupies very important position. Water resources are abundant in China, analyze the present situation of hydropower development prospects of the development of hydropower resources, hydropower development for building a harmonious society, to promote economic development and environmental protection has important significance.
Effects of Bi3+ Doping Amounts on the Magnetic Properties of FeSmO3 Nanopowders
Authors: Liu Xuan Wen , Liu He , Zhang Yu , Qi Xi Wei
Published: October 2014

The samples of FeSmO3 nanopowders were synthesized from the main raw materials of FeCl3 and SmCl3 by coprecipitation process. The samples were prepared by different precipitating agents including Na2CO3,NaOH and triethylamine (C6H15N). When the precipitating agent was NaOH, almost all of the Sm3+ and Fe3+ were precipitated. In this series of experiments, the molar ratios of Sm3+ to Fe3+ were 0.95:1, 1:1, 1.05:1, 1.1:1, 1.15:1 and 1.2:1. And when the molar ratio was 1.2:1, there was the least impurities in the obtained samples. The samples were sintered in the oven at different temperatures including 600°C,700°C, 800°C and 900°C. And only at 900°C, were the FeSmO3 nanopowders made without impurities. The Sm3+ in FeSmO3 was substituted by the Bi3+ in different doping amounts, which urged the preparation of BixFeSm(1-x)O3 nanopowders. And these nanopowders were characterized by XRD, VSM, SEM and fluorescent property technologies. The results showed that the obtained nanopowders were in high purity when x was 5% and it had the highest remanent polarization when x was 15%.
Effect of La-Zn Doping on Magnetic Properties of SrFe12O19
Authors: Liu Xuan Wen , Chen Xiao , He Wang De , Qi Xi Wei
Published: October 2014

La-Zn doped strontium ferrite, Sr1-xZnxFe12(1-x) La12xO19, was prepared by chemical co-precipitation method. The samples were characterized by XRD, SEM and VSM and the results reveal that La-Zn ions are dispersed completely into the strontium ferrite lattice at 900°C. The VSM analysis shows that Hcj increases to 240.1 KA/m, almost double the value of the original sample. And the specific saturation magnetization increases from 48.78 A • m2/Kg to 63.11A• m2/Kg.
Experimental Investigation on Compression and Chemical Properties of Aluminium Nano Composite
Authors: Vijaya Ramnath B. , Parswajinan Chakravarthi , Elanchezhian C. , Pragadeesh S. Venkatesan , Kavin C. , Ramkishore P.R. , Sabarish V.
Published: October 2014

Aluminium metal matrix composites are being widely investigated with Carbon Nanotubes (CNTs) as one of their reinforcing agents. This is done in order to improve the mechanical strength of the composite. Various studies on this concept have already been recorded. In this study, Aluminium has been reinforced with CNTs using powder metallurgy technique. The powders of aluminium and CNT are ball milled, compacted in a die made up of die steel, and then sintered. The specimens thus obtained were subjected to hardness, compression and chemical tests and the values were compared with pure aluminium specimen fabricated by same technique. The study indicated that there was no improvement in hardness of the composite on addition of CNT. The compressive strength of the composite was increased by 143.58 MPa. The microstructure of pure aluminium and Al-CNT composite had fine grains of pure aluminium particles and Al-Si eutectic particles throughout the matrix phase.
A Brief Review and Framework towards Synthesising Silicone-Hydrogel Materials that Mimic Skin Deformation Behaviour
Authors: Azmi Nurul Nadiah , Shahrul Azhar Ilya Izyan , Mahmud Jamaluddin
Published: October 2014

Skin is an important organ which provides multiple functions. Thus, if skin fails i.e. due to burns or diseases, body will lose the protection provided by skin against infections and the harmful outer environment. Due to that, synthetic skin is seen as a very important alternative in the future. A number of studies have been carried out to understand skin’s basic functions and behaviour as its mechanical properties and behaviour are important in various fields. Nevertheless, to date no breakthrough has been reported. Therefore, this paper aims to briefly review and outline a framework which ultimately will lead to the synthesising silicone-hydrogel materials that potentially becoming a skin substitute. The newly synthesised composite materials will be tested mechanically to characterise its behaviour based on Ogden hyperelastic model. It could be emphasised that the present study is significant and will contribute to the body of knowledge in the area of skin mechanics.
Contact Angle Analysis on Glass Based Surface
Authors: Aziz Muhammad Hafiz Ab , Sauli Zaliman , Retnasamy Vithyacharan , Wan Norhaimi Wan Mokhdzani , Taniselass Steven , Kamarudin Hussin
Published: October 2014

This paper reports on the contact angle measurement analysis on a glass based surface for anodic bonding process cleaned by three distinct cleaning processes. The three types of glass based surface used were silica, pyrex, and soda lime glass. The three cleaning solutions tested in this experiment were RCA, piranha and acetone. Water Droplet Test (WDT) was done to analyze the contact angle of micro droplet on sample surface. It can be done by dropping a droplet of water in constant volume at the fixed height and angle. Only RCA process constantly decreases the contact angle value after cleaning. The compilations of data strongly proved that all samples become hydrophilic after RCA cleaning process. The solid surface is considered hydrophilic when water contact angle is smaller than 90°, and hydrophobic profile if the water contact angle is larger than 90°. Samples which undergo piranha and acetone cleaning did not prove any characteristic of hydrophilic or hydrophobic surface after cleaning.
Experimental Study on the Single-Sided Double-Point Resistance Welding of Bus Roof Skin
Authors: Huang Hai Bin , Liu Jian Chun , Ke Xiao Long , Lin Xiao Hui
Published: October 2014

In order to weld the skin and skeleton of bus roof, it analysis the welding process of bus Outer Roof-panels , and specify the weld area and solder joint distance of outer roof-panel firstly , then built a single-sided double-point resistance welding experiment platform for bus outer roof-panels, the platform consists of guide、gantry、gantry moving mechanism、 pneumatic torch、electrode support mechanism、transformers、torch lateral movement organizations and torch longitudinal movement phenomenon . it set the unevenness of the skin and the skeleton as 1mm, single-sided double-point resistance welding experiment was conducted on the welding experiment platform. The experimental results of welding area visual examination and tear experiments indicate that welding heat will penetrate the skeleton when the welding current is greater than 11.0KA;the welding Reliability of galvanized steel is better than low carbon steel.
Application of Fuzzy Control Technology in the System of Electric Boiler Temperature Control
Authors: Tian Jia
Published: October 2014

As a new product of integration of mechanics and electrics, electric boiler is acomparatively environment-friendly and energy-saving heating equipment at the present time. For the electric boiler, the performance of intelligent temperature control will directly affect the effect of energy saving, satisfaction of consumers andthe competitive ability of products in the market. Temperature control with large timelag and disturbances is widely used in the production of industry and daily necessities.It is affected by many factors such as the control plant and production condition, so itis very difficult to build the accurate mathematical model. Thus, the conventionalcontrol method such as PID control can’t meet requirements. Fuzzy control instead of establishing a precise mathematical model by simulation comparison of electric boiler control objects have very good results
Research and Simulation of STATCOM Based on PSCAD/EMTDC
Authors: Deng Yuan , Gao Yang
Published: October 2014

In this paper, it uses PSCAD/EMTDC to build simulation system of STATCOM (Static Synchronous Compensator). According to the principle of coordinate transformation and the theory of instantaneous reactive power, it creates self-defined components in PSCAD/EMTDC. The working principle of the system is explained fistly.Then the theory of instantaneous reactive power and the diagram of simulation system is presented. Each functional module is also discussed in detail. Through the simulation test, it emphatically analyzes real-time tracking ability of the system when the capacitive and inductive loads are added. In this way, correctness and validity of the system has been proved.
Review of Condition Assessment for Power Transformer
Authors: Kong Jin Jiao , Wang Feng , Li Yong Liang , Wu Xu Tao , Bi Jian Gang
Published: October 2014

Transformer is one of the most important equipment in power system, and accurate condition assessment for transformer is the key for condition based maintenance (CBM). So the study of condition assessment is particularly important. In this paper, the function, role and steps of condition assessment, research status, existing problems and future directions are analyzed and summarized. And this paper can be a reference for transformer’s condition assessment.
Study of Effect of Diesel Fuel Properties on Pressure Wave Profile
Authors: Qaisar Hayat , Fan Li Yun , Song En Zhe , Ma Xiu Zhen , Tian Bing Qi , Farouk Naeim
Published: October 2014

High pressure (HP) fuel pipeline is one of the vital components of Combination Electronic Unit Pump (CEUP) fuel injection system besides pump and injector. Effect of four key fuel properties including density, viscosity, acoustic wave speed and bulk modulus on pressure wave profile has been investigated using a 1D viscous damped mathematical model. Wave equation (WE) based mathematical model has been developed in MATLAB using finite difference method. Dynamic variations of these fuel properties during fuel injection cycles have also been incorporated in mathematical model by utilizing empirical formulas. The results show that these four key fuel properties not only vary with the pressure during fuel injection process but also define the trend of pressure wave propagation inside HP fuel pipeline.
Finite Element Analysis on Acoustic Wind Tunnel Structure of Special-Shaped Thin-Walled Concrete
Authors: Li Bo Ping , Bing Guang Li , Wang Zi Jian
Published: October 2014

The main structure of wind tunnel is special-shaped thin-walled structure. During the design and construction phase, its static strength, static stiffness and dynamic characteristics have to be taken into account. The author explains the meshing method of the main structure of wind tunnel in which finite element computing model is established through ABAQUS according to model simplification principle and analysis of stress, deformation and modality is done on this wind tunnel model. Analysis results show that the main structure of this wind tunnel caters for requirements of static strength and static stiffness in which overall stiffness distributes reasonably, modal frequency presents good distribution and condition permits to do further optimization on part of components. Straight section wall of wind tunnel affords the most pressures while dip angle section amplifies or reduces according to cross section of downwind section. Amplification section is suction-based and wall of amplification section is pressure-based. This analysis result would provide references for tension analysis of roof surface.
Simulation Research for the Excavation Stability of IV Brittle Rock Based on Vault Settlement Effect
Authors: Liu Ke Ling , Guo Long
Published: October 2014

Due to the brittle rock deformation is not obvious, and the destruction process has the features of sudden and concealment, it is often neglected in the field during construction. In this paper, Brittle rock was selected as the research object. Using the vault subsidence as monitoring parameters, the excavation process was simulated in single line tunnel by the finite element analysis tool of ANSYS, we obtain the maximum displacement of brittle rock and stress variation with time. Then the subsidence effect of different buried condition were analyzed, to determine the stability period of IV Brittle surrounding rock. The research results can be used to guide the development of the monitoring standard, in underground engineering construction of the brittle rock.
A High Efficiency Coffee Roaster Development Based on Gas Baking Technology for Home Use
Authors: Hsu Hsiu Chen , Lo Rong Chin
Published: October 2014

Home coffee roasting becomes increasingly popular in recent years. Besides freshness, coffee lover can achieve personal favorite flavors and make it with fun. In this paper, a new coffee roaster development based on gas baking method is introduced. Premixed fuel and direct-fired baking technologies are adapted for increasing energy efficiency, in which premixed flame contacts the beans inside the vertical-rotated drum. Meanwhile, a touch screen controller with fancy human machine interface is also designed for presetting roasting modes, controlling the procedures of roasting, and/or storing recent roast profile for use at other time. Experimental results show that the proposed structure is eco friendly, enriches the energy efficiency, reduces the gaseous emission, and achieves a consistent roast.
Application of TVAC-PSO for Optimal Taiwan Power Dispatch with Carbon Emission Control
Authors: Lin Whei Min , Tu Chia Sheng , Tsai Ming Tang , Cheng Fu Sheng
Published: October 2014

This paper integrated the Particle Swarm Optimization and time-varying inertia weight model to propose a Time-Varying Acceleration Coefficients in Particle Swarm Optimization (TVAC-PSO) for dealing with the emission-constrained dynamic economic dispatch (ED) problems. The objective function of Taiwan power dispatch with emission considerations includes the sub-objective functions of operating cost and emissions. The objective function of emissions is estimated by IPCC. TVAC-PSO is used to find the objective function under the operational and system’s constraints. The effectiveness and efficiency of the TVAC-PSO are demonstrated by using a simplified Taiwan power system. It can also provide an interactive mechanism to adjust the emission permit.
The Study of Product Configuration Information Model and Repository
Authors: Xie Hua Long , Shen Ming Bin
Published: October 2014

Product configuration design model is established on the basis of the base type product of standardization, seriation. According to the needs of customers, This paper arranges the physical and functional structure of the product, and sets up configuration model of the whole model. Through the analysis and configuration design, provides the final product to meet customer requirements. In this article, introduces the mix of configuration design knowledge representation methods, so as to adapt to the requirements of different types of product design.
Analysis and Simulation of Parallel Lifting Mechanism for Schnable Car Based on Complex Vector
Authors: Zhao Yan Zhi , Wang Xiang Nan , Bai Xue Gang , Ren Yu Bo
Published: October 2014

The working conditional model of schnable car has been established and the principle of lifting mechanism has been analyzed. By complex vector method, we analyze the kinematics of the lifting mechanism and get the position, speed and acceleration curves of relevant objects under the lifting progress. We have a static analysis on lifting mechanism, and get the relationship curve of the cylinder’s force and generator’s mass by mathematical Calculation. Kinematics simulation test is proceeded by ADAMS.
A Structural Damage Classification Algorithm Based on AiNet Immune Aggregation
Authors: Zhou Yue , Yue Lin Bei , Zhang Li Xin
Published: October 2014

This paper presents an unsupervised structure damage classification method based on the AiNet immune network clustering for the large-scale structure. The AiNet clustering is employed to update memory cell sets and get the clustering center. The memory cell sets are used to classify measured data. The algorithm is tested using a Benchmark structure. The test results show the feasibility of using this algorithm for the unsupervised structure damage classification.
Influence of Interstitial Impurities on Deformational Behavior and Fracture Mechanism of Submicrocrystalline Titanium at Room and Elevated Temperatures
Authors: Dudarev Evgenii , Bakach Galina , Potekaev Aleksandr I. , Kolobov Yurii R. , Kashin Oleg , Zhorovkov Mickle
Published: October 2014

General trends and other aspects of the deformational behavior, localization of plastic deformation on the macroscale level, and fracture of submicrocrystalline and coarse-grained titanium with different interstitial impurity levels are established. It is shown that for the submicrocrystalline structure as well as for the coarse-grained structure, strengthening by interstitial impurities decreases with increase of the deformation temperature. Experimental data are presented which indicate that in the development of grain-boundary sliding in submicrocrystalline titanium with simultaneous onset of recrystallization, a high degree of plastic deformation is reached before fracture occurs, where the deformational behavior and localization of plastic deformation on the macroscale level are analogous to the same processes under superplastic flow.
Structure and Properties of Wear-Resistant Weld Deposit Formed on Martensitic Steel Using the Electric-Arc Method
Authors: Popova Natal'ya , Nikonenko Elena L. , Ivanov Yurii F. , Gromov Victor , Budovskikh Evgeni , Raikov Sergei , Kapralov Evgenii , Vashuk Evgenii
Published: October 2014

Studies on the structure and the phase composition of the deposited material were carried out using methods of X-ray structure analysis and electron diffraction microscopy of extract coal replicas and thin foils on steel Hardox 400. Formation of a multiphase state, represented by grains of α-iron and inclusions of carbide phases based on iron, chromium, and niobium, is revealed.
Structural Phase Transformations and Morphological Changes of Icosahedral Small Copper Particles in Temperature Fields and Reactive Media
Authors: Vikarchuk Anatolii A. , Gryznova Natal'ya , Dovzhenko Olga , Dorogov Maksim V. , Romanov Aleksei E.
Published: October 2014

The influence of temperature fields and different reactive media on the structure and morphology of small icosahedral particles (ISPs) are investigated. It is shown experimentally that ISPs of micron size can be transformed into advanced functional materials with a developed surface. The leading role of disclination defects for the transformations occurring in ISPs is established. Potential fields of application of the new functional materials based on transformed ISPs are discussed.
Models of Dislocation Formation and Mechanical Twinning by Local Reversible Martensitic Transformations in FCC Nanocrystals
Authors: Tyumentsev Alexander , Litovchenko Igor
Published: October 2014

An atomic model is proposed which describes the formation of dislocations and deformation twins through a direct plus reverse martensitic transformation localized in two or several slip planes. The reasons and mechanisms for the formation of partial dislocations and mechanical twinning in nanocrystals under plastic deformation are discussed.
Two-Level Model of Inelastic Deformation of FCC Polycrystals and Structure Evolution Description
Authors: Volegov Pavel S. , Trusov Peter V.
Published: October 2014

The general structure of the multilevel models of inelastic deformation of materials including the internal structure evolution description was considered in the present paper. It also provides variants to address the key issues of similar type models, which are important for further development of such models. A new approach for constitutive relations coupling between constitutive relations of different scale levels was described. The suggested approach establishes connection of similar characteristics in different scale levels. The proposed coupling method also provides an unambiguous determination of material frame indifferent derivative of the Cauchy stress tensor at the macro scale, which is necessary for the formulation of constitutive relations for large deformations. In order to make it clearer an example of a two-level model of polycrystalline metals is considered; based on the physical sense analysis the hardening laws and lattices rotations of crystallites are suggested.
Mathematical Modelling of the Flow Structure and Heat Transfer in a Channel with a Porous Insert
Authors: Matvienko Oleg V. , Bubenchikov Aleksei , Baigulova Anastasiya
Published: October 2014

The paper deals with the results of studying the flow structure and heat transfer in a cylindrical channel with a porous insert. While formulating the problem the space-averaged model of interpenetrating continuums was used. The modelled system is described by the equations of continuity, motion and thermal conductivity of a gas phase, as well as the equations of thermal conductivity for a porous backfill. The results of the research show that, due to the displacement of the gas flow from the wall region to the central part of the channel, in the initial flow section a low-temperature area is formed at the inner boundary of the porous layer. The temperature of the structural frame in the initial flow section also decreases because of its cooling by the flow displaced from the wall. In the downward flow direction heating-up of the structural frame occurs due to heat transfer from the gas flow moving in the axial zone. In addition, the structural frame performs the role of a thermal reservoir and, in turn, heats the gas flow in the porous layer.
Mathematical Modeling of Elementary Crystallographic Slip, Limited by an Expanding Piecewise-Continuous Closed Dislocation Loop
Authors: Kolupaeva Svetlana , Petelin Aleksander , Petelina Yulia , Polosukhin Konstantin A.
Published: October 2014

A mathematical model of elementary crystallographic slip, limited by a closed piecewise-continuous dislocation loop is proposed. A study of the evolution of the first dislocation loop emitted by a dislocation source in copper is carried out. It has been shown that on the dislocation loop on screw orientation and orientations close to it, about half a free path length before the stopping point there arises a concavity, which grows in size up to the stopping of the dislocation loop. In the final configuration the radius of the dislocation loop on screw orientation is practically by an order of magnitude less than the radius on edge orientation.
Study of Strain-Induced Change in Structural Characteristics and Long-Range Order in Ni3Al Alloy
Authors: Starenchenko Svetlana , Starenchenko Vladimir
Published: October 2014

In this paper the study of structural characteristics of the coarse-crystalline Ni3Al alloy deformed by cold-rolling at a room temperature is presented. The research was carried out by the X-ray methods. It is established that plastic deformation leads to an increase in lattice strain, causes disturbance of a grain structure and order-disorder phase transition. Lowering the long-range order degree of the alloy is accompanied by inhomogeneous decrease in the antiphase domains sizes. Heterogeneity of the order - disorder transformation is connected with strain localization.
Microtwins of Transformation and their Effect on Excess Dislocation Density of FCC Deformed Material
Authors: Kiseleva Svetlana , Popova Natal'ya , Koneva Nina , Kozlov Eduard
Published: October 2014

The excess density of dislocations and internal stresses in local places of all polycrystal grain are determined. In work the methods of bending extinction contours observed by TEM is used to determine internal stresses of the deformed material. Thus depending on the deformation nature in each case components of elastic and plastic deformations or only plastic deformation was considered. The paper discusses the results of distribution of excess dislocation density and internal stresses within the grains of the austenitic steel deformed by tension (ε = 25%).
Competitiveness of South African Foundries – A Review and Comparison of Sand, Permanent Mould and Investment Foundries
Authors: Reinhardt Carl J.
Published: October 2014

South African Foundries have promptly been met with challenges from international competition due in part to trade “liberalisation” of South African foreign trade. To objectively evaluate the challenge, data from selected local foundries were analysed together with and compared to international data from selected countries from industry and specific foundry macro level. The review seeks to evaluate the impact of resource use efficiency and resource specific cost on the local foundry and compare the challenges and opportunities available specifically to the local foundry industry. A simplified financial model was used to output an income statement type result containing the major cost elements, to arrive at levels of profitability, which was used to evaluate and compare the competitiveness of the local to international foundry industry. From these results, some macro suggestions for the local foundry industry to achieve sustainable cost competiveness improvements become apparent. Index Terms: South African Foundries, Sand, Investment, Die, Gravity, High Pressure, Benchmarking, Resource efficiency, Resource usage, Resource costs, International comparison.
Microstructure and Compression Creep Strength of the Newly Developed Magnesium Alloy DieMag422
Authors: Dieringa Hajo , Hort Norbert , Kainer Karl Ulrich
Published: October 2014

Magnesium alloys have been finding increasingly more types of application in the automotive and aerospace industries for over twenty years. Despite the fact conventional magnesium alloys have limited high-temperature strength and creep resistance, especially when they contain aluminium as an alloying element. Aluminium is necessary to improve the castability when high-pressure die casting is the favoured process. Applications with higher operating temperatures require additional alloy elements, which form precipitates with the aluminium during solidification and therefore prevent the formation of Mg17Al12, which is responsible for the low creep resistance of magnesium alloys that contain aluminium. The precipitates formed may also strengthen grain boundaries and so improve the creep strength. Barium and calcium were investigated as elements in a magnesium alloy containing aluminium (DieMag422: 4 wt.-% Al, 2 wt.-% Ba, 2 wt.-% Ca). The compression creep strength was compared at 240°C for stresses between 60 and 120 MPa with two commercial creep-resistant magnesium alloys, AE42 and MRI230D. The stress exponents were calculated from the stress dependence of the minimum creep rate. The concept of a threshold stress was applied and true stress exponents ntclose to 5 were found. The new alloy DieMag422 exhibits improved creep strength compared to both commercial alloys and also has proven it is die castable.
Challenges Experienced in Scaling-Up the CSIR-Ti Process
Authors: Oosthuizen Salomon Johannes , Swanepoel Jaco Johannes , van Vuuren Dawid Steyn
Published: October 2014

The CSIR-Ti process produces titanium metal powder through continuous stepwise metallothermic reduction of titanium tetrachloride (TiCl4) in molten salt medium, and represents a cost-effective alternative to the standard Kroll process to produce titanium metal. Subsequent to proving the CSIR-Ti process at bench scale producing batches of ±2 kg titanium powder, the design, build and test of a continuous 2 kg/h Ti pilot plant was authorised. The scale-up process highlighted limited expertise in South Africa with regards to handling molten salt and molten reducing metals. Such gaps in knowledge are addressed in this study, which discusses a number of the engineering challenges faced and solutions developed around agitation of molten salt reactors, process pipe heating and insulation, molten salt flow measurement and also feeding of a highly reactive molten reducing metal. Scaling up the CSIR-Ti process, with requirements of continuous operation, compact size, effective agitation, pumping and maintaining salt in the molten state brought an unusual set of challenges requiring development of unique and prototype equipment. Further challenges were encountered in the handling and continuous feeding of molten reducing metal at the relatively small scale of the pilot plant. Solutions developed and discussed in this study include custom-modified agitators, custom-developed flow meters for measuring molten salt and molten metal flows, and a custom-designed molten metal feed system. Specialised materials such as, ultra-high temperature heating tape and ultra-low thermal conductivity insulation had to be imported as well as a special high-temperature pump that can pump a slurry consisting of molten salt containing a high weight percentage of suspended metal powder. The experience illustrates the technological difficulty of bridging the chasm between science and technology in that many unforeseen problems are encountered when developing and scaling up a new technology.
Wall Heat Transfer Coefficient in a Molten Salt Bubble Column: Testing the Experimental Setup
Authors: Skosana P.J. , van Vuuren D.S. , Heydenrych M.D.
Published: October 2014

One of the advantages of bubble columns is high heat transfer rates. High heat transfer is important in reactors when high thermal duties are required. An appropriate measurement of heat transfer coefficient is of primary importance for designing reactors that are highly exothermic or endothermic. This paper presents the design and operation of experimental setup used for measurement of the heat transfer coefficient in molten salt media. The experimental setup was operated with tap water, heat transfer oil 32, LiCl–KCl eutectic and argon gas. Tap water was operated at the temperature of 40oC and heat transfer oil was operated at the temperature of 75oC, 103oC and 170oC. There were some challenges when operating the bubble column with molten salt due to leakages on the welds and aggressive corrosion on the column. All the experiments were run at superficial gas velocities of 0.01–0.05 m/s. Three heating tapes, each connected to a corresponding variable AC voltage controller, were used to heat the column media. Heat transfer coefficients were measured by inducing a known heat flux through the column wall and measurement of the temperature difference between the wall and the contents. In order to balance the system, heat was removed by the cooling water flowing through a copper tube on the inside of the column. Temperature differences between the column wall and the liquid were measured at five axial locations. It was found that the heat transfer coefficient increases with superficial gas velocity. The values of heat transfer coefficient for argon–water system were higher than those of argon–heat transfer oil system. Heat transfer coefficient was also found to increase with an increase in temperature.
Thermo-Gravimetric Analysis and Debinding Study of Powder Injection Moulded Titanium Alloy
Authors: Crombie C.T.C. , Blaine Deborah C.
Published: October 2014

An investigation into the solvent and thermal debinding behaviour of a typical paraffin wax-polymer binder system for titanium alloy Ti-6Al-4V powder injection moulding (PIM) feedstock was conducted. Details of the mixing parameters, powder loading, temperature and mixing speed were evaluated for optimal compounding of the feedstock. The feedstock was injection moulded into 22 mm diameter by 3 mm thick disks. Debinding is conducted in two stages, an initial solvent debinding step to remove the waxes, followed by a thermal debinding step to remove the polymers. Solvent debinding was conducted by immersing the injection moulded specimens in n-heptane heated to 50 °C for a period of 5 hours. The mass loss rate was logged during solvent debinding in order to determine the efficiency of the solvent debinding step. From these measurements, it was determined that 94 wt% of the wax (paraffin wax and stearic acid) components of the binder were removed during solvent debinding. A thermo-gravimetric analysis (TGA) was conducted in air on the Ti-6Al-4V powder, as well as the green and solvent debound feedstock. These results show the effect of debinding the feedstock in air and were used to design a thermal debinding cycle for the system.
Fatigue and Fracture Toughness of Ti-6Al-4V Titanium Alloy Manufactured by Selective Laser Melting
Authors: Dhansay Nur Mohamed , Tait Robert , Becker Thorsten
Published: October 2014

The research focuses on the fatigue and fracture toughness of Ti-6Al-4V manufactured by Selective Laser Melting (slm) of fine powder. This manufacturing approach offers remarkable design flexibility as layers can be built up at approximately 50-100 micron layer increments. Consequently very complex shapes can be achieved and minimal machining is required. For very complex parts selective laser melting may be a viable alternative to conventional casting, forging and machining. The process does, however, result in significant residual stresses as well as significant surface roughness and some minor porosity, all of which can impair mechanical properties. The fatigue and fracture toughness behaviour of suchslmTi-6Al-4V alloys fabricated by laser melting can depend substantially on the interlayer bonding, as this method could lead to lines of weakness between melted layers or even very poorly melted and bonded layers. This project then endeavours to measure the fatigue behaviour in the form of a fracture mechanics based “Paris equation” and fracture toughness of selective laser melted material in two orientations, namely the fatigue crack grown (i) perpendicular and (ii) parallel to build direction. Such fatigue data would be invaluable in the assessment of fatigue lives of components made of such material.
Microstructure and Dry Sliding Wear Property of Laser Clad Ti-6Al-4V under Different Counterface Materials
Authors: Obadele Babatunde Abiodun , Olubambi Peter Apata , Pityana Sisa
Published: October 2014

The titanium alloy (Ti-6Al-4V) coated with commercially pure (CP) Ti particles was fabricated by the laser cladding process. Coating quality was investigated by scanning electron microscopy and X-ray diffraction, while wear resistance of the alloys was evaluated on a ball-on-flat dry sliding wear tester at room temperature under a load of 25 N, frequency of 5 Hz and stroke length of 2 mm using three counterface materials (302 SS, Brass and WC). Mass loss of the laser cladded samples as well as the wear rate of each counterface material was calculated. SEM images revealed growth of acicular widmanstätten α, also known as α′ martensite, embedded in a prior β matrix at the coating-substrate interface. Smearing of Ti from the cladded samples was observed on the worn surfaces of the counterface materials except for brass which showed high material removal.
Hot Deformation Behavior of Ti-6Al-4V Alloy with a Transitional Microstructure in the Isothermal Hot Compression
Authors: Xu Yong , Yang Xiang Jie , Jiang Xiong Xin , He Yi , Du Dan Ni
Published: October 2014

The hot deformation behavior of Ti-6Al-4V alloy with transitional microstructure over temperature 800°C~950°C and strain rate ranges of 0.001~10s-1 has been studied by Gleeble-3500 hot working simulation testing machine. The flow softening of stress-strain curves is resulted from the spheroidization of transitional microstructure, dynamic recrystallization and superplasticity. Both temperature and strain rate are important factors affecting the deformation behavior. Flow instability induced by adiabatic shear bands occurs at 800-880°Cand 0.32-10 s-1. With the increasing of strain rate and decreasing of temperature, the degree of strain localization increases. The optimum working region of Ti-6Al-4V alloy with a transitional microstructure is at 820-910°C and 0.001-0.1 s-1.
Interaction between Yttria Fully Stabilized Zirconia or Yttria-Zirconia Blended Face-Coat with Ti6Al4V during Investment Casting
Authors: Mutombo Kalenda , Kgomo Christina , Rossouw P.
Published: October 2014

The interaction between the Ti6Al4V alloy and the mould materials was investigated. The alpha-case was characterized by Vickers hardness tester, optical and scanning electron microscopy equipped with electron dispersive X-ray spectrometry (EDX). X-ray diffraction (XRD) analysis was performed on as cast and on YFSZ or YZ-Blended face-coats. From the experimental results, a distinct alpha-case formation was revealed. The YFSZ led to a thicker and harder alpha-case than the YZ-Blended face-coat. The EDX revealed the presence of Zr and Si elements in both alpha-cases. Therefore, from experimental results and thermodynamic calculations, pure ZrO2and SiO2may react with Ti.
Alpha Case Characterization of Hot Rolled Titanium
Authors: Conradie Francois , Treurnicht Nico , Sacks Natasha
Published: October 2014

Titanium alloys offer excellent corrosion resistance, good strength to weight ratio, is nonmagnetic and biocompatible. This allows them to be used in demanding applications and specialised industries ranging from aviation to medicine. However, at high temperatures the metal is chemically reactive which requires several manufacturing processes such as melting and welding to be performed either in vacuum or inert gas atmosphere. Some processes such as rolling are impractical to be performed in inert gas atmosphere. Titanium alloys, notably Ti-6Al-4V, develops a hard oxide layer on the outer surface during hot processing, such as rolling, in atmospheric conditions. This oxide layer, commonly referred to as the alpha case, is both hard and brittle. The increased Young's modulus of the alpha case creating an outer layer with increased stiffness where maximum stresses occur, results in localized micro failure. The micro failures in this layer serve as a fatigue crack initiation zone, compromising the integrity of the component and causing it to fail. Traditionally alpha case is removed by means of chemical milling in hot acid baths using aggressive acids such as Hydrofluoric acid. The facilities needed for chemical milling require high capital costs as well as stringent and costly safety requirements. Lastly, the disposal of used acids is proving to become increasingly difficult due to the strict South African environmental laws. Removal of this layer by means of light pass machining has therefore become more desirable, however at present it remains economically infeasible. This study presents an overview of the materials background, alpha case formation and related machining considerations. Experiments that investigate alpha case properties are included.
Influence of Cooling Path on the Dynamic Transformation of Austenite-to-Ferrite in Low Carbon Manganese Steels
Authors: Oguh Jerry Chika , Siyasiya Charles , Stumpf Waldo E.
Published: October 2014

For an effective thermomechanical process control, knowledge of the start and finish temperatures of the austenite transformation is critical. Continuous Cooling uniaxial-Tension (CCT*) is a useful way to measure these values. Therefore, the dynamic transformation of austenite to ferrite (γ → α) was investigated in C-Mn steels to understand the hot ductility behaviour of these steels after varying the cooling paths i.e. simulating “hard” and “soft” cooling rates of the strand during continuous casting. Results show that hard cooling into the dual phase (γ + α) region significantly increases the dynamic transformation temperatures due to a higher driving force owing to double transformation and precipitation of AlN during the process. A comparison of dynamic versus static transformation (Ar3 and Ar1) temperatures and equilibrium transformation temperatures gives a better understanding of the contribution of strain to transformation during casting or hot deformation.
Pt/Au Alloys as Reduction Promoters for Co/TiO2 Fischer-Tropsch Catalysts
Authors: Kunene Avela , Claeys Michael , van Steen Eric
Published: October 2014

Noble metals, such as platinum or gold, may promote the reduction of cobalt in supported cobalt catalysts either by direct contact or indirectly via hydrogen spill-over. The synthesis go gold nano-particles using THPC in the presence of a calcined Co/TiO2-catalyst precursor results in a broadening of the gold particle size distribution possibly due to the association of gold with Co3O4. This was not observed for platinum and platinum-gold alloys synthesized in the same manner. Platinum-gold alloys are less effective than platinum as a reduction promoter, possibly due to the presence of gold on the surface of the alloy particles.
Thermal Properties of Amorphous TiPt Alloy Produced by Mechanical Alloying
Authors: Mahlatji M.L. , Chikosha Silethelwe , Chikwanda Hilda Kundai , Stumpf W.E. , Siyasiya C.W.
Published: October 2014

The thermal properties of amorphous Ti-50at.%Pt alloy produced by mechanical alloying were studied by differential scanning calorimetry (DSC). The powders, sampled at various time periods during the milling process, displayed non-reversible exothermic reactions in the temperature range of 641-668 °C, and in the higher temperature range of 839-970 °C. The reaction peak temperatures and heat effects vary with milling time. The reactions at the lower temperature range were determined by X-ray diffraction analysis of the powder, heated beyond the onset temperature of the exothermic peaks, to be crystallisation into B19 TiPt. The reactions at higher temperatures are suspected twinning transformation of the B19 grains to form martensite. This requires confirmation by analysis with a transmission electron microscope, planned as part of future work.
Development of an Affordable GD-OES Support Matrix for Analysis of Non-Conducting Zirconium Powders
Authors: Lötter Steven James , Purcell Walter , Nel Johann T.
Published: October 2014

Glow Discharge Optical Emission Spectroscopy (GD-OES) is an analytical technique mainly used in the analysis of solid metallic samples. The technique requires a conductive sample as the analyte serves as the cathode when generating the glow discharge plasma. GD-OES is useful for both bulk quantification and depth profiling of thin layers of conducting materials. The objective of this study was to develop a new sample support matrix for the preparation of conductive pressed pellets suitable for the analysis of non-conducting materials with GD-OES. In previous work non-conducting powders, such as uranium oxide, have been mixed with fine metal powders such as copper, silver or tantalum. Another solution has been to use a quick setting, conductive thermoplastic, such as diallyl phthalate impregnated with copper, as support. Both of these methods are, however, expensive and fairly time consuming. Graphite, a cheap, readily available conductive powder, proved not to form a strong enough pellet to withstand the conditions required during the GD analysis. This limitation was overcome by the addition of a binding agent, bakelite, to produce a relatively cheap, conductive matrix for the analysis of non-conducting powders. Spectroscopically pure zirconium oxide was used as a reference material and mixed with various quantities of graphite and bakelite powder. Two distinct regions of linearity were obtained. Samples with less than six percent zirconium yielded a gradient of 0.0011 with an R2 value of 0.9949. Samples with higher zirconium content yielded a gradient of 0.0042 with an R2 value of 0.9991. These results indicate the suitability of this sample matrix for analysis of zirconium materials by GD-OES.
Sublimation Kinetics of Zirconium Tetrafluoride
Authors: Pretorius C.J. , Pienaar A.D. , Crouse P.L. , Niemand H.F.
Published: October 2014

An important step of a new process being developed for the beneficiation of the mineral zircon (Zr (Hf)SiO4) to produce nuclear grade zirconium (Zr) metal, is the separation of the Zr from the hafnium (Hf). Zr ores typically contain between 1 and 3% Hf , whereas the use of Zr metal in the nuclear industry requires a Hf content <100 ppm, owing to its high neutron-capture cross section. The separation step is therefore key in the preparation of nuclear grade Zr, which is considered to be very difficult due to the various similarities in their chemical properties. The preparation of hafnium free zirconium relies on the traditional wet separation systems, for example solvent extraction systems. In contrast to the traditional aqueous chloride systems, Necsa focusses on dry fluoride-based processes. Dry processes have the advantage of producing much less hazardous chemical waste. In the work reported her, separation is achieved by sublimation/de-sublimation in the tetrafluoride form. The tetrafluoride is prepared by fluorination of plasma dissociated zircon (PDZ or Zr (Hf)O2•SiO2) with ammonium bifluoride (ABF). The separation involves the selective sublimation of the two tetrafluorides in an inert atmosphere under controlled conditions, and subsequent similarly selective desublimation. An accurate estimation of the sublimation rates the zirconium tetrafluoride (ZrF4) and hafnium tetrafluoride (HfF4) as a function of temperature is required since this forms the basis of the development of a sublimation model to determine whether the concept under consideration is theoretically possible. The sublimation kinetics of ZrF4is reported in this paper.
The Time Dependent Solvent Extraction of Ta and Nb
Authors: de Beer Leon , Ungerer Marietjie J. , van der Westhuizen Derik J. , Krieg Henning M.
Published: October 2014

The suitability of Liquid-liquid extraction (LLE) for the selective extraction of chemically similar tantalum (Ta) and niobium (Nb) mixtures was investigated by determining the influence of the acid concentration, extractant to metal mole ratio (E:M) as well as the ageing of the feed on extraction using the extractants, bis (2-ethylhexyl) phosphate (D2EHPA) and di-iso-octylphosphinic acid (PA). The system consisted of a solvent in varying E:M ratio’s, diluted in cyclohexane with 3% (v\v) 1-octanol added as modifier and a feed solution containing sulphuric acid and 100 ppm of the NH4TaF6and NH4NbF6complexes. Depending on the acid concentration, extraction percentages (%E) of up to 100% for Ta and 10-20% for Nb were attained. An initial lack of repeatability in experimental results was shown to be caused by variations in the age of the feed solution. The change in extraction trends expressed as a normalized %E for the aged feed solutions were nearly identical for both extractants when using 3, 6, 9 and 14mol/dm3H2SO4. For the 3 and 6mol/dm3solutions, the %E decreased significantly within the first 4-5 hours of ageing. At 9mol/dm3the %E remained stable for feed ages up to 3.5 hours before declining, while the %E remained near constant at 14mol/dm3even after ageing for 24 hours.