Preparation of Novolac composites with improved properties for disk brake systems

The effect of composition and the dry and wet operating conditions on the adhesive wear resistance of polymeric composite materials were studied in this work. The composite are designed to be used as pads for disc brake system of heavy vehicles. The composites were prepared with weight ratios, Ψ, in the range: 60-90% using the dry method. The composites were reinforced with a number of fillers and friction improvement agents like:  silicon carbide, carbon fibers, alumina, etc at various ratios to establish diverse properties in comparison with Novolac resin. The used ceramic disc brake materials were also utilized in this preparation at certain weight ratios as one of the components of the composites. The wear resistance measurements indicated that a ratio higher than 70% will reduce the hardness of the disc material. Thus, composites with 60% Novolac weight ratio, which indicated the best performance, were prepared with 14-22% of the hardener, the HMTA. The study revealed that the abrasion rate decrease with the reinforcement of the Novolac, i.e., increase in abrasion resistance, especially when the carbon fibers ratio were increased from 1.5 to 3.0%. Meanwhile, the increase of the hardener resulted in increase in the in wear resistance. Further, it appears that the rate of abrasion changes from moderate to in accordance with operating conditions like the applied load, operating time and sliding distance. To mimic the real application conditions, the specimens were subjected to rain water by spraying for 2 min during operation. The wetting caused a lowering of the wear resistance. However, in comparison with the available disc brake materials, our specimens proved either comparable or better performance. Keywords: Novolac composites, wear resistance, brake pads, rain water

Preparation and Characterization of Barium Titanate Nano Particles Using Solution Combustion

Ferroelectric materials are gaining increased importance as a result of their high dielectric constants making them useful for electrical capacitors, high piezoelectric constants to make sensors, actuators, RF Filters, ferroelectric hysteresis suit making non-volatile memories, high pyroelectric properties for infra-red detectors, thermistors, and strong electro-optic effects to be used in optical switches, data storage, etc. Barium titanate undergoes change in shape from perovskite into cubic structure Curie temperature which causes polarization, or spontaneous, polarization. Many techniques were described for the synthesis of Barium titanate including solid-state reaction, sol-gel method, hydrothermal and solution combustion. Solution combustion. The last method offers good control of the properties to meet specific requirements of the products and allows the preparation of nanomaterials  to suit energy saving and protection of environment made it attractive for many purposes. In the present work barium titanate is synthesized as submicro to nano sized particles using the solution combustion technique utilizing urea and glycerin as fuel / oxidant mixture. The experimental parameters were varied to suit the optimization of the process

Evaluation of quality of drinking water from Baghdad, Iraq

This is a joint work between the Italian Red Cross and the Environmental Laboratories, Baghdad. The drinking water (DW) samples from 16 residential districts in Baghdad were chemically evaluated with reference to the raw water samples and water directly taken from the purification plants. In addition to the routinely measured parameters, 17 metals and 11 trihalomathane (THM) were measured. Generally, the samples of water analysed can be considered of good quality. The relatively high sulphate and aluminium contents results from the use of aluminium sulphate as flocculent. The ammonia and Nitrite concentrations were lower than the detectable limit, because ammonia is converted into chloramines and nitrite is converted into Nitrate during chlorination. This indicates no sewage contamination of the drinking water. The high chloride contents can be referred to the use of partially degraded hypo for the disinfection. The presence of THM's in the samples analysed is indicative of good disinfection process. The presence of these compounds is preferred better than bacterial contamination. The relatively high levels of zinc and iron have no impact on the quality of DW. Iron, however, was efficiently removed during the treatment, together with Manganese. Reference was done to the EU specification of drinking water regarding total hardness, chloride contents, sulphate, iron and THM's. As for the iron content, the original pH of the river water (7.5 and 8.0) ensures that Iron should not be present in soluble form at a detectable level. Corrosion of the pipes could be one of the reasons for the presence of iron. Key Words: Drinking water quality, heavy metals, sulphate, Aluminium, Trihalomethans, hardness

Oxytetracycline Sorption Onto Iraqi Montmorillonite

This paper assesses the use of certified Iraqi montmorillonite clay as a potential sorbent for the removal of oxytetracycline (OTC) from aqueous solutions. The clay is characterized by a cation exchange capacity of 0.756 meq g-1 and a zero point charge at pH 8.7. Aqueous solutions of OTC were equilibrated with montmorillonite under various experimental conditions, such as OTC concentration, pH and clay content, for 24 h at fixed ionic strength. Two forms of montmorillonite were evaluated: regular and iron-modified form. The effect of pH was minor on OTC adsorption. Kinetic study revealed that the sorption follows a pseudo-second-order model. Sorption isotherm showed a good fit with the Freundlich model. OTC sorption onto Fe-saturated montmorillonite was analyzed statistically using a response surface design to study the effects of experimental conditions. The introduction of iron improved the adsorption characteristics of the clay due to the ability of ferric ions to make stable complexes with OTC. The most favorable operating conditions for the treatment were deemed as follows: clay content, 6.85 g L-1, oxytetracycline concentration, 1.0 mmol L-1 and pH, 5.5 for the iron-modified form

Electrothermal Atomic Absorption Spectrophotometric Determination of Vanadium, Nickel And Lead In Hydrocarbon Polluted Soils

The present work is a part of a project on the environmental site assessment ofa local petroleum refinery to evaluate the extent of pollution of the site with focuson selected places of potential pollution. Soil samples were collected at variousdepths from almost all locations including: production units, storage tanks, thelandfill lagoons at the outside boarder of the refinery and the residence location.The analyses of vanadium, nickel and lead were carried out on extracts of the soilsamples made by five different dilute solutions of acetic acid, nitric acid, calciumchloride, EDTA. The nature of the solvent is a determining factor in the efficiencyof transport of heavy metals from the soil into the solution. All of themeasurements were conducted by graphite furnace atomic absorptionspectrophotometry.It was concluded that heavy metals are available even for the weakest extractingsolvent. This was an indication on the nature of the V, Ni and Pb, where they arein inorganic forms due to the degradation by the microorganisms of the soil andaided by dozens of raining seasons and severe hot summers of Iraq. However thesoil keeps some of the heavy metals in the original organo-metallic nature whichresulted in only partial extraction of these metals with the solutions employed.Thus, the danger from these metals is limited due to their insolubility in water.The range of vanadium detected in the various extracts is ; for nickel, the rangewas and for lead the concentration range was . The V contents were in the range of0.01 – 0.37 mg/Kg. The Ni content ranged between 0.06 and 4.5 mg/Kg. Therange of Pb contents obtained was in the range of 0.025 – 22.5 mg/Kg. The V andNi concentrations at the deep soil samples were less than that of the surfacesamples in most locations. Meanwhile, the penetration of lead contaminationseems easier than V and Ni