24,989 research outputs found
Analysis of rheological behaviour of titanium feedstocks formulated with a water-soluble binder system for powder injection moulding
No full textBinder selection and formulation are critical in powder injection moulding. Binders play a key role in controlling the rheological properties of a feedstock and influence whether the resulting feedstock can be successfully injection moulded, debound and sintered without defects. A four-step process was used to mix hydride-dehydride titanium alloy (processed) powder (Ti-6Al-4 V) with a polyethylene glycol (PEG) based water soluble binder system. The rheological properties, including flow behaviour index, flow activation energy, fluidity and melt flow index of the homogeneous feedstock, were determined with a capillary rheometer. All feedstock formulations exhibited shear thinning flow behaviour. The optimum feedstock consisting of 60 vol.% powder content, 32 vol.% PEG, 6 vol.% polyvinyl butyryl and 2 vol.% stearic acid was suitable for titanium injection moulding
Wet granulation in laboratory scale high shear mixers: Effect of binder properties
No full textThe effect of binder properties on torque curves, granule growth kinetics, wet mass consistency and dry granule strength has been investigated in this study. Granulation runs have been performed on a fine cohesive microcrystalline cellulose powder (Avicel 105, d50 = 20 μm) in two types of laboratory high shear mixers: a Mi-Pro high shear mixer using a 1.9 L bowl and a 6 L Diosna high shear mixer. Binders used included ultra-pure water and solutions of varying concentrations of PVP and HPMC allowing us to cover different values for parameters like viscosity and work of adhesion. Torque curves recorded during granulation are found to allow good control of the process. Optimum liquid requirement for granulation has been found to vary with binder type and decrease with increasing viscosity while granule growth kinetics has been found to be to be related to the work of adhesion for low viscosity binders. Granule strength has been evaluated for wet granules by the means of wet mass consistency measurements on a mixer torque rheometer and for dried granules by means of uniaxial compression tests on a Texture Analyser mechanical testing machine. For low viscosity binders both wet mass consistency and dry granule strength have been found to depend on the work of adhesion. For high viscosity bindershigherwet mass consistencies but lower dry granule strengths have been observed. Granulating on the larger 6 L scale has shown that constant impeller tip speed offers good agreement in terms of mean granule size however granule size distribution seems to be scale dependan
Desenvolvimento de aços autolubrificantes via compactação de pós granulados
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Ciência e Engenharia de Materiais, Florianópolis, 2012O objetivo deste trabalho foi o desenvolvimento de aços com baixo coeficiente de atrito via metalurgia do pó através de uma rota de processamento que unisse as características metalúrgicas próximas aos aços produzidos por metalurgia do pó via injeção (MPI) com a facilidade e o custo do processo de fabricação via compactação de pós. Assim neste trabalho estudou-se uma rota de granulação de pós, utilizando a matéria prima empregada na MPI e um aglomerante orgânico para formar os grânulos. Os ligantes orgânicos estudados foram a parafina (PW) e o Etileno-Acetato de Vinila (EVA), e devido as características dos polímeros e dos pós empregados, o ligante que apresentou melhores resultados foi o EVA, que manteve os grânulos formados durante o manuseio dos pós granulados. A composição da liga estudada foi Fe+0,6C+3SiC, devido aos melhores resultados encontrados em trabalhos anteriores realizados no Laboratório de Materiais da UFSC. No presente trabalho, foi avaliada a influência do tamanho médio das partículas de ferro e de carboneto de silício (SiC), e as diferenças estruturais do material ao adicionar o polímero como agente formador de grânulos. Os pós inicialmente misturados em um misturador do tipo "Y" foram granulados via granulação a tambor, devido a escala laboratorial em que foi feito o trabalho. Assim que os processos de preparação dos pós foi concluído, partiu-se para a etapa de compactação e sinterização em ciclo único de extração de aglomerante e sinterização dos componentes. As peças foram submetidas a análises materiolográficas, mecânicas e tribológicos onde pode ser verificado que o objetivo do trabalho foi alcançado, as peças produzidas via compactação de pós granulados alcançaram resultados próximos aos resultados da liga de mesma composição produzida via MPI, com um tempo de processamento e custo próximo ao da metalurgia do pó via compactação.Abstract : The aim of this work was the development of powder metallurgy steels with low friction coefficient made by a new route. It is join metallurgical characteristics of steels produced by powder injection molding (MPI) with facilities and cost of the manufacturing process for compaction powders. In this work, it was studied the granulation of powders using the raw material used in the MPI and organic binder to form the granules. The organic binders studied were Paraffin Wax (PW) and Ethylene-Vinyl Acetate (EVA), and due to the characteristics of the polymers and the powder employed, the binder which presented better results was EVA, which retained the granules formed during the handling until the forming. The alloy composition studied was Fe +0.6 C +3 SiC, due to better results found in previous studies conducted in the Laboratory of Materials of UFSC. In the present study, we evaluated the influence of the average particle size of iron and silicon carbide (SiC), structural differences and with polymer as granulate agent. The powders were initially mixed in a Y-type mixer and they were granulated by tumbling granulation. Once the process has completed, it started the preparation of the compaction powders and sintering in a single cycle of binder removal and sintering of the components. The pieces were metallurgical, mechanical and tribologically analyzed and the aim of the work was achieved. The parts produced via granulated powders compaction achieved similar results to the results of the same alloy composition produced via MPI, with a processing time and cost close to the powder metallurgy via compaction
Messe in C
No full textop. 33 / Binder. - [Autograph] - [s.l.], [1884]. - [39 Sti.] ; 33 x 26 cm - (Nachlass Adolf Binder)
12-zeiliges Notenpapier, schwarze Tinte. Vl 1 (6), Vl 2 (5), Va (2), Vc (2), Fl (1), Klar 1 in C (1), Klar 2 in C (1), Hr in F (1), Sopran (10). Alt (8), Ten (1), Bass (1), und weitere Fragmente der Singstimmen.op. 33 / Binder. - [Autograph] - [s.l.], [1884]. - [39 Sti.] ; 33 x 26 cm - (Nachlass Adolf Binder)
12-zeiliges Notenpapier, schwarze Tinte. Vl 1 (6), Vl 2 (5), Va (2), Vc (2), Fl (1), Klar 1 in C (1), Klar 2 in C (1), Hr in F (1), Sopran (10). Alt (8), Ten (1), Bass (1), und weitere Fragmente der Singstimmen
Development and design of binder systems for titanium metal injection molding: An overview
No full textTitanium metal injection molding (Ti-MIM) has been practiced since the late 1980s. Logically, the Ti-MIM practice follows the similar processes developed for the antecedent materials such as stainless steel and ceramics. Although Ti-MIM is a favorite research topic today, the issue of convincing the designers to use Ti injection-molded parts still exists. This is mainly because of the concern about contamination which seems unavoidable during the Ti-MIM process. Much information about the binder formulation, powder requirements, debinding, and sintering is available in the literature. There are several powder vendors and feedstock suppliers. However, most of the binders in the feedstock are proprietarily protected. The disclosed information on the binders used for formulating powder feedstock is very limited, which in turn discourages their adoption by engineering designers. This overview intends to discuss some of major binder systems for Ti-MIM available in the literature. It serves to provide a guideline for the Ti-MIM practitioners to choose a suitable powder feedstock
The Formulation of Titanium - based Metal Feedstocks and the Fabrication of Parts using the Powder Injection Moulding Process
No full textDevelopment of a profitable titanium industry for New Zealand will not come about without innovative technologies. Plastic injection moulding has long held a place in NZ manufacturing to produce large quantities of complex parts and holds the key to such innovation.
Titanium metal parts were fabricated by injection moulding titanium based metal powder feedstock followed by a debinding process and subsequent sintering. The fabrication process in its entirety was investigated in four distinct steps. Feedstock formulation involved combining the metal powders with various carrier components. Injection moulding enabled the shaping of the feedstock into geometries approximating the final part. Debinding being the process whereby the carrier/binder system is removed from the part to create a powder compact retaining the required geometry. Sintering being the final step where the metal powders are consolidated into a fully dense metal part of net shape.
The feedstock binder consisted of water soluble polyethylene glycol that reduced feedstock viscosity, improved particle wetting, aided greenpart shape retention and eliminated toxic solvents in debinding. Carnauba wax and bees wax aided dispersion, lubricated particles, were safe to handle and better for the environment (than petroleum waxes). Their low melt temperatures aided removal during thermal debinding and supported residue elimination.
By optimising the ratio of water soluble, wax and polyolefin binder components (3: 2: 1 respectively) for melt flow and pellet formation, greenparts defect free with uniform particle distribution were made. The optimal binder system proved suitable for titanium alloy and irregular shape pure titanium powders (hydride-de-hydride). Increasing powder loading (wP = (0.60 to 0.65)) had no appreciable effect on viscosity while enabling feedstock with good uniformity and pellet formation. Dimensional change was not affected by uniformity of the feedstock however molecular weight, volume and dispersion of binder components affected interparticular distances. Low processing temperatures reduced disruption to part geometry, benefitted particle bonding and helped retain handling strength.
The use of low temperatures for thermal debinding (t = 250 °C) enabled removal of the binder below the temperatures that facilitate interstitial diffusion and oxide/carbide formation, although part thickness, mass and overall volume effected the processing time. A strong correlation was seen between handling strength of the greenparts and defects, such as non-uniform density distribution and cracking after sintering.
Sintering was essential to produce the final part and showed that a binder free brownpart was not the only criteria for eliminating impurities. The furnace atmosphere must remain free from contamination to eliminate transfer back to the parts. This was addressed using an argon sweep gas, however, the design and efficacy of the system was considered inadequate. Decomposition products need to be removed quickly from the furnace as they evolve before impurities from the sweep gas diffuse back into the parts during the extended duration at sinter temperatures (t = 1300 °C).
The combination of an optimised titanium feedstock and the use of a low temperature thermal debinding technique produced a consolidated MIM part of relatively large dimensions. The parts were seen to have uniform microstructure throughout the cross-section with density comparable to that of MIM standards. In difference to the literature, a high powder loading (φp = 0.65) of HDH powders was used and shown to be readily mouldable. The higher powder loading also eliminate separation defects and shape distortions evident using lower amounts of powder
Synthesis of Dopamine-Modified Sodium Alginate as a Binder for Nanosilicon Anode in Lithium Ion Battery
No full textThe potential of silicon as the anode material of future high-capacity lithium-ion batteries is still difficult to realize due to the low mobility of electrons and the material's vulnerability to damage from considerable volume expansion. The development of binders is one way to overcome this problem because a good binder can reduce the rate of electrode damage. In this research, dopamine-modified sodium alginate binders have been synthesized by sticking dopamine molecules to the sodium alginate polymer backbone through amide bonds. The modified material, NA-DA, was confirmed by Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR) Spectroscopy, and UV-Vis Spectroscopy. The modified NA has new absorption at wavenumbers 1705 cm-1, 1311 cm-1, and 1026 cm-1 which are signals from the ‒CONH‒, C‒O catechol, and C‒N functional groups. The H-NMR spectrum of NA-DA shows a peak in chemical shifts of 6.7-6.9 ppm indicating the detection of aromatic protons from dopamine molecules. The signal at a wavelength of 276 cm from the UV-Vis spectrum also proved successful grafting of dopamine molecules to the sodium alginate polymer. Electrochemical tests that have been carried out on anodes using NA-DA binders show that a good anode material mass ratio for fabricating silicon electrodes with NA-DA binders is Si:AB:NA-DA = 50:30:20. It is proven that dopamine modification of sodium alginate binders results in batteries with better performance than sodium alginate without modification. However, the value of charge transfer resistance of the resulting electrode is still fairly large because the dopamine molecules attached to the backbone of sodium alginate polymer are in small quantity. This can be seen by the low intensity of aromatic proton signals in the H-NMR spectrum. CV data showed oxidation peak at 1,39 volt and reduction peak at 0,55 volt which indicates the reversibility of redox reaction inside the battery.77 PagesSkripsi Sarjan
Preparation and Characterisation of Binder-Free All-Cellulose Composites
No full textThe copyright of this thesis rests with the author and no quotation from it or information derived from it may be published without the prior written consent of the authorA recent emerging concept of all-cellulose composites within the field of
environmentally friendly materials has received increasing attention. The main
advantage of these materials is the lack of using additional bonding agents such as
polymer resins as in the case of e.g. phenolic resin based panel products or natural
fibre reinforced plastics that increase their environmental impact. Two different
routes for the production of all-cellulose composites have been followed. The
obtained materials were characterised by scanning electron microscopy, X-ray
diffraction, flexure and tensile mechanical tests, thermogravimetric analysis,
pycnometry and water absorption tests.
The first strategy makes use of the selective dissolution method where the
cellulose fibre skins are partially dissolved to form a matrix phase that bonds the
fibres together, while the strong core fibres are maintained and impart a reinforcing
effect to the composites. The influence of the dissolution time, activation time and
the fibre source were assessed. It was found that a dissolution time of 18 h led to
materials with the best overall mechanical performance (5.5 GPa and 145 MPa for
Young’s modulus and tensile strength, respectively), as this time allowed for the
dissolution of a sufficient amount of fibre surface to obtain good interfacial bonding
between fibres, while keeping a considerable amount of remaining fibre cores that
provide a strong reinforcement to the composite, leading to materials that outperform
natural fibres reinforced polypropylene composites.
Still, the previous methodology has the drawback of using chemical
substances of high environmental impact (solvents). In order to overcome this, a new
concept in the production of all-cellulose composites is proposed in this work, which
makes use of the intrinsic bonding capability between cellulose fibres to enhance the
hydrogen bond network in order to produce materials of good mechanical
performance. A new experimental procedure was developed, based on the refinement
Abstract
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of cellulose fibres in order to increase their specific surface area, thus increasing the
interfibre bonding capability, and achieving materials with excellent mechanical
properties, up to 17 GPa and 119 MPa for flexural modulus and strength,
respectively, and low water absorption. These new high-performing environmentally
friendly materials are based on renewable resources and are 100% recyclable and
biodegradable.Financial support from the Engineering and Physical Sciences Research
Council through a Technology Strategy Board project REFLECT no. MATH1E2R,
under the Design & Manufacture of Sustainable Products Call, is gratefully
acknowledged
A Method to Measure the Swelling of Water-Soluble PVDF Binder System and Its Electrochemical Performance for Lithium Ion Batteries
No full textWater-soluble CMC/PVDF binder systems were used to prepare graphite anodes and compared mechanically and electrochemically with CMC/SBR binder systems. The effect of crystallinity of PVDF binder on the mechanical and electrochemical performance of the anodes is studied. A contact free method easy to operate and equipped with high accuracy was developed by using capacitance measurement. The swelling of graphite electrodes was controlled and showed different results for different binder crystallinities (no swelling of binder with high crystallinity vs 12% for medium crystallinity and 17% for low crystallinity binder). The discharge capacity depends on the crystallinity of the binders and half-cells delivered a capacity in the range of 230-360 mAh g(-1). The binder with medium crystallinity in particular exhibited the best mechanical and electrochemical performance and showed an excellent C-rate stability with specific capacities up to 10 C. Full cell tests showed good cycling stability over 180 cycles. The water-based PVDF binders seem to be a promising alternative to solvent-based binders. (C) 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited
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