Injection Moulding and Heat Treatment of Ni-Cr-Si-B Alloy Powder

Injection moulding, debinding, sintering and heat treatment of Ni-Cr-Si-B alloy powder of high hardness value have been studied. A binder system comprised of two polymers, a major component of water soluble polyethylene glycols (PEGs) and a minor component of very finely dispersed polymethyl methacrylate (PMMA) derived from an emulsion was employed. Mixing of a number of different feedstocks was carried out manually. Following the identification of the optimum binder composition (20 wt. % PMMA, 80 wt. % PEGs) and solid loading (65 Vol. %), several test specimens were injection moulded for further processing. The PEGs were removed by leaching with water. The PMMA was removed by pyrolysis, prior to the sintering stage. Samples were sintered to ~ 99 % of theoretical density. With careful control of the various processing parameters, including sintering temperature and time, cooling rate and heat treatment conditions, good mechanical properties including high hardness of HRC ~57 were attained. In an attempt to reduce the process cycle time, the sintering ramp was modified to include solutionising and oil-quenching in a single sintering cycle. The hardened samples were tempered at temperatures from 250 to 350 °C for 2 hours. Scanning electron microscopy was used to reveal the micro-structural changes during various sintering and heat-treatment stages

A Study on Injection Moulding of Two Different Pottery Bodies

Injection moulding of a conventional high clay pottery body and an unconventional low clay pottery body has been described. The Sheffield Binder System comprising of a major component of PEG and a minor component of PMMA was used. The behavior of these pottery bodies during various stages of injection moulding has been analyzed. Optical and scanning electron microscopy was used to examine the structure of green and sintered specimens

Evaluating the Biocompatibility of materials: Routes and strategies of exploring the host response

A Biomaterial is a synthetic material which is used in living body as replacement of any part and its evaluation and performance is measured by its activity, stability and compatibility with living system. Usually in the field of biomaterial characterization its performance is based upon Biocompatibility. The aim of the present research is to describe the parameters and standards for evaluation of biocompatibility of biomaterials. In this study various techniques of biocompatibility testing have been described such as  Cytotoxicity Testing, Genotoxicology / Mutagenicity Testing, Hemocompatibility Testing, Implantation Testing, Irritation/Intracutaneous Reactivity Testing, Pyrogenicity Testing (In Vivo), Sensitization Testing, Subacute/Subchronic Toxicity Testing, Systemic (Acute) Toxicity Testing, Chronic Toxicity and Carcinogenicity Testing, Immunogenicity testing, Pharmacokinetics and Pharmacodynamics testing, Cell Culture Test, Mucosal damage and Mucosa usage tests, Periapical tissue damage and endodontic usage test, Intraosseous Implant test, Diagnostic tests on patients, Patch test, Prick Test, Radio allegro sorbent test (RAST) and Corrosion testing. The description of the basics of these techniques along with evaluation standards is also the fundamental objective of this work

Production of Tin Powder Using Gas Atomization Process

Gas atomization process is widely used for the production of various metal and pre-alloyed powders. The process involves the disintegration of a liquid stream of molten metal into liquid metal droplets by the impingement of high pressure gas jets. The liquid metal droplets subsequently cool and solidify into metal powder particles, which can typically range from 1 to 150 µm. After a detailed study of various atomizing processes, the cross jet gas atomizing scheme was selected for the present research work. Experiments were carried out using air and argon gas as atomizing media. Particle shape was observed using Scanning Electron Microscope. The particle size distribution was measured using the Laser Particle Size Analyzer. XRD analysis of different powder samples was carried out to measure the oxygen contents. Spherical shape particles ranging from 1 µm to 60 µm sizes were produced

Viscosity of lead bismuth gallate glasses containing minor addition of silica and germania

Heavy metal oxide glasses with and without minor additions of Silica and Germania in the system PbO-Bi203-Ga203 have been prepared which have potential applications for infrared fibers. Viscosity measurements using penetration viscometry were first carried out on sample of glass No. 711 provided by National Bureau of Standards (NBS) over a range of 107 to 1010 Pa.s and showed good agreement with NBS data with a mean error of 1.35% using modified-Nemilov equation. The viscosity of glasses studied fell sharply about three orders of magnitude in a temperature interval of less than 45 degrees (on Celsius scale). The results have been discussed in relation to activation energy for viscous flow and the fragility of the melts has been compared

Hyperbranched polyethyleneimine induced polycationic membranes for improved fouling resistance and high RO performance

The study shows a new method for hyperbranched polyethyleneimine (HPEI) induced polycation membranes with an objective of achieving better fouling resistance and high reverse osmosis (RO) performance. Chemically crosslinked composite membrane (CCCM) was prepared with polyvinyl alcohol (PVA), maleic acid (MA) and Pluronic F127 via chemical crosslinking methodology. Polycation induced membranes were fabricated by surface coating of HPEI onto the CCCM (PVA/MA/PluronicF127) RO membranes. Functional group analysis, morphology and surface roughness of CCCM and HPEI-RO membranes were analyzed by Fourier transform infrared spectroscopy, scanning electron microscopy and atomic force microscopy respectively. The hydrophilicity and water permeability of CCCM and HPEI-RO were examined with water contact angle measurement and RO performance test. Optimum RO performance was obtained for HPEI-RO3 membrane with NaCl and MgSO4, as for RNaCl = 96.1%, JNaCl = 58.2 L m�2 h�1 and RMgSO4 = 99.6%, JMgSO4 = 15.8 L m�2 h�1 (testing with 3.28 wt.% aqueous NaCl and MgSO4 solution at 25 �C and 55 bar). Moreover, cetyl trimethylammonium bromide (CTAB) as standard foulants presented a smaller fouling tendency for the modified HPEI-RO3 membrane. HPEI-RO3 compared to the unmodified membrane, was able to decrease the stickiness of charged bacteria, Gram negative Escherichia coli and Gram positive Staphylococcus epidermidis. Therefore, the permeation flux, salt rejection and fouling resistant property of membrane (HPEI-RO3) were significantly improved with polycation induction into the membranes

The Beneficiation of Thal Silica Sand and the Production of High grade Silicon

Silica sand from Bita site of Thal desert, situated in Punjab province of Pakistan was processed to produce nanoparticles using a ball mill. The produced nanoparticles of silica sand were verified using Zetasizer nanoparticles analyzer. It was observed that the ball milling process not only reduced the particle size but also librated the silica particles from the impurities resulting in increased purity of silica in Thal silica sand from 86.60 wt. % to 95.52 wt. % as major impurities consisting of  Al2O3 and CaO, were liberated during grinding and separated during sieve analysis process. The leaching of silica sand nanoparticles with a mixture of HCl and CH3COOH further improved the wt.% purity of silica in Thal silica sand up to 96.60 wt.%.   The beneficiated Thal silica sand nanoparticles were then reduced with Magnesium to produce silicon particles at 900oC with and without the presence of argon atmosphere. The production of silicon particles during reduction was verified with XRD analysis and FESEM with EDX analysis. It was observed that the presence of argon atmosphere during reduction of silica sand nanoparticles increased the wt. % of reduced silicon in processed sample. The leaching of reduced samples with a mixture of HF and CH3COOH futher improved its purity

Novel polymer matrix composite membrane doped with fumed silica particles for reverse osmosis desalination

Novel polymer matrix composite membranes of cellulose acetate (CA)/polyethylene glycol (PEG) doped with 10–30 wt.% fumed silica particles (FSP) were synthesized. The dissolution casting methodology was used to construct reverse osmosis (RO) membrane which accounts the explicit application for desalination process. The interactions between polymer chains and doped FSP were confirmed by Fourier transform infrared spectroscopy (FTIR). Differential scanning calorimetry thermograms support the physical nature of polymer matrix composite membranes (PMCMs) and an improved glass transition temperature (Tg) from 78.3 to 92.4 °C was observed. The thermal stability of the composite membranes significantly enhanced with the addition of FSP. The typical morphology of PMCM was observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The 30 wt.% of FSP filled PMCM showed substantial improvement in tensile strength (8.2 MPa) and Young's modulus (854.0 MPa) as compared to the PMCM without FSP. The percentage water content (WC) of the membrane doped with 30 wt.% FSP absorbed more water as compared to the other membranes. It was also noticed that the FSP doped PMCM enhanced the desalination process which was monitored in terms of permeation flux (L/m2·h) and salt rejection (%). The optimum performance of desalination process was shown by 30 wt.% FSP doped PMCM; the permeation flux was 0.66 L/m2·h and salt rejection was 98.4% for the initial feed of 0.35 wt.% NaCl aqueous solution at 25 °C and operating pressure of 4.0 bar (osmotic pressure 2.9 bar)