Background

In aerospace and military applications, equipment is expected to work in a wide range of climatic conditions. Consequently, these applications provide a harsh testing ground for all components and particularly the adhesives that hold them together.

The benefits of adhesive bonding are well known and the specific advantage of weight saving is very important to the aerospace industry. However there are many problems associated with adhesive bonding and two typical areas under development are the durability of joints and their high temperature resistance. In the main, durability can be improved by making the interphase more stable and by increasing the moisture resistance of the adhesives. Most commercial adhesives have poor high temperature resistance for many high-speed applications so it has been necessary to develop adhesives to play this role.
Moisture Resistance

Water acts aggressively on bonded joints. For example, if a typical bond, in which two metals are epoxy joined, is immersed in water at 600°C for 1500 hours, it loses over 75% of its initial strength. The locus of failure moves from being cohesive in the adhesive to being purely interfacial. This test regime may seem severe when compared to other regimes which use a variety of time spans, temperatures and degrees of humidity. But this method can produce a well defined and successful adhesive. Experience has shown that unless an adhesive passes such a critical test it will cause problems during its lifetime.
Silanes

A primer system based upon an organosilane is often recommended to enhance the bonding of epoxy resins to steel substrates. Most commercially available organosilane coupling agents are based on the following generalised structure

R-Si-(X)3

where X is a hydrolysable group and R is an organofunctional group capable of some form of interaction with a given polymer matrix. It is generally believed that organosilanes impart a covalent bridge structure across the interfacial zone. This results in a structure that is more resistant to the effects of water than those solely reliant on secondary force interactions.

It is important, however, to apply the silane in the correct way. The silane must have time to react with the steel surface before the epoxy is applied. If such time is not allowed, perhaps by accelerated drying of the silane-coated surface, then little if any durability improvement will be seen. Three parameters affect the silane priming process: the age of the silane solution, the solvent used for the silane and the drying time/temperature. Only by optimising these conditions can the best durability be obtained.

The age of the silane solution when it is applied to the substrate critically influences the eventual durability. The durability of joints improves with age so that it reaches a maximum about one hour after the silane is mixed with water. When the majority of the water is replaced by ethanol there is little change in silane efficiency with time and the eventual durability is significantly lower than with the water based system. An equally important parameter is the drying temperature used on the substrates after priming. Higher temperatures reduce the effectiveness of the silane, probably by not allowing the silane complex to react with the substrate.

Although bismaleimide-based adhesives offer substantial improvement in high temperature capability in comparison to their epoxy counterparts, they do suffer a number of disadvantages. Firstly, although their processability can be considered a significant improvement over more traditional high temperature polymers they still do not compare directly with epoxy type processing. An approach which the Design Research Agency (DRA) is taking is to combine the high temperature properties of bismaleimides with epoxy resins. A series of compositions were manufactured, based on combinations of diglycidylether of bisphenol A, diphenylsulphone and bismaleimide. In the majority of cases the introduction of the epoxy to the bismaleimide increases the fracture toughness and the fracture energy with modest reductions in both the modulus and the glass transition temperature. A modest improvement in lap shear properties is possible, but the most important benefits will accrue at higher temperatures. It is hoped that the toughness of these systems can be improved by the incorporation of a second phase rubber.

By developing such adhesive systems it is possible to create tough high temperature adhesives which will withstand the sorts of service temperature and loads experienced by modern aerospace equipment.

A problem with all air-carried weapons is the very high temperatures reached during high speed aircraft manoeuvres. This is caused by the aerodynamic heating of the structure as it moves through the air: of approximately 50°C at Mach 1, 200°C at Mach 2, 450°C at Mach 3 rising to over 800°C at Mach 3.5. The use of basic epoxy resins as adhesives becomes very difficult above Mach numbers of the order of 2. High temperature resistant adhesives are obviously required; a class of materials with such a high temperature resistance are the bismaleimides.

These materials are much easier to process than other high temperature resins such as polyimide. Condensation polyimides require great pressure to be applied when they are used as adhesives to prevent the water evolved during the cure forming voids. An inherent problem with all high temperature resins systems is the lack of toughness because of the high degree of cross-linking present in the materials. The Defence Research Agency (UK) has done much work to improve the mechanical properties of bismaleimide resins. Incorporating a second phase such a carboxyl terminated butadiene acrylonitrile rubber can toughen these materials. This rubber phase acts both to absorb energy itself and to promote other energy-absorbing mechanisms in the matrix resin. This improvement in properties can be attained without loss of other desirable qualities such as modulus and glass transition temperature. When used as adhesives the lap shear strength increases with the addition of rubber. Although the adhesive properties are not an improvement over toughened epoxies at room temperature they do maintain their properties over a larger temperature range as shown in figure 1. As would be expected, the materials containing the largest amount of rubber show the greatest change in strength with temperature.

Background

Abresist Corporation, based in Urbana, Indiana, manufactures ABRESIST® fused cast basalt and various ceramic linings that provide excellent wear protection. The linings are custom designed for use wherever abrasion and impact wear are a problem. The wear resistant linings reduce downtime and maintenance in processing equipment handling bulk materials such as silica, ore, glass, slag, fly ash, limestone, coal, coke, feed, grain, cement clinker, fertilizer, salt, and other highly abrasive materials.
Company History

The original Abresist material was developed in the 1920s by Kalenborn Kalprotect, the German parent of Abresist Corporation. To form the ABRESIST linings, basalt volcanic rock is melted at temperatures of 1300° C / 2400° F, cast into tiles or cylinders and annealed to give the cast basalt a uniform, crystalline structure that is abrasion-resistant with a Mohs hardness of 8. Engineered tiles and cylinders provide a long service life even in the harshest conditions.
Markets Served

Abresist Corporation, founded in 1977, markets these linings throughout the United States, Canada, and Mexico. Industries working with abrasive raw materials and by-products are ideal candidates for using Abresist linings, especially where equipment is susceptible to friction-induced abrasion. Customers in material handling and processing operations include the steel, coal, power, mine, and food industries. Effective applications include piping systems, separators, cyclones, silos, bunkers, troughs, chutes, impellers, agitators, fan blades and fan casings, conveyor screws, chain conveyors, and mixers.
Support Services

Abresist Corporation individually designs its materials to meet the customer's specific abrasion, impact and corrosion problems. Sales representatives and engineers visit customers on-site to assess problems and gather accurate data to provide an optimal solution, using the Abresist material or combination of materials that would provide the best, most economical solution to the wear problems. Then the specified materials are pre-engineered and labeled for precise identification during installation.

Customers may install the linings or have Abresist Corporation technicians install the materials. Technicians are also available to supervise the installation by the customer or his contractor to ensure the products will perform as intended.
Benefits

The use of Abresist protective linings on wear prone components adds up to significant savings with their longer service life. The cost of replacement parts, the downtime of operations, plant clean-up, and the cost of maintenance work are all dramatically reduced. The savings incurred will pay for the linings and installation in a short time.

Background

The stability of metals and metal oxides at elevated temperatures is a crucial problem in many industries such as aerospace, power generation, metallurgical processing, chemical engineering, automotive, petrochemicals, and catalysis. Will a catalyst remain stable at elevated temperature or revert to an inac­tive form? Might formation of a non-protecting oxide film cause loss of strength in a supersonic aircraft?
Ellingham Diagrams

To address these questions, scientists at Accelrys employed a combination of tools (classical thermodynamics & ab initio quantum mechanics) to compute Ellingham diagrams, plots of the standard free energy of reaction (∆G°) vs. temperature. The stability of materials at high temperatures has been tradi­tionally investigated in metallurgy and materials engineering using such plots. Ellingham diagrams provide a simple and rapid means to determine the threshold temperature and oxygen pressure required for oxide formation. Formation of oxides is the most common reaction in high temperature corro­sive environments, and therefore has a direct relevance to the industries men­tioned above.
Oxidation Of Corundum Type Oxides

The study focussed on the oxidation of corundum-type oxides (M2O3) into rutile-type structures (MO2), where M=Rh and Ru. These metals were considered because of their relevance in industrial catalytic processes. Both, Rh and Ru oxides occur naturally in the rutile structure. However, whereas rutile-type RuO2 has proved to be the preferred phase over a wide range of temperatures and pressures, its rhodium isomorph (RhO2) transforms into the corundum form (alpha-Rh2O3) at 750 °C under ambient oxygen pressure. This is a known component in the poisoning of three-way emission catalysts. The corundum form of ruthenium oxide (Ru2O3), in contrast, has never been observed. Why the difference?
Phase Predictions

The present results combining CASTEP density functional calculations with classical thermodynamics techniques predict that a Ru2O3 phase cannot be observed due to the high stability of RuO2 with respect to reactions due to both Ru and ambient oxygen. In contrast, the ambient oxygen pressure at which alpha-Rh2O3 decomposes into RhO2 was found to increase with temperature consistently with experimental findings.

Cost Effective Predictions

Techniques like the ones employed here provide rapid and cost-effective ways of predicting the behaviour of metal oxides in high temperature environments. By employing modelling methods, a broad range of elements, crystal struc­tures, and environmental conditions can be screened rapidly in silico, and the results provided in a commonly-used representation.

Abstract

Our interest in Environmental Chemistry has prompted us to design new materials containing polyfunctional units able to bind certain metallic ions. These materials can be used as modifying agents to produce chemically modified electrodes. We expect to facilitate the detection of organic pollutants in water by binding these materials to an electrode surface. We report a Ni(II) and Co(II) complexes prepared from the Schiff base macroligand N,N´-bis(2-nitrobenzyl)ethylendiimine (L1) with Ni(II) salt and L1 with Co(II) salt. The nature of the complex was established by common spectroscopic techniques. A thermal gravimetric analysis of the complex showed that it is thermodynamically stable. Its formation constant was obtained by conductimetric analysis (Kf = 1.25x106). The affinity of L towards Ni(II) and Co(II) was determined by atomic absorption. The electrochemical study of the complex [Ni(II)-L1]SO4 was also performed by the cyclic voltammetry technique. The results showed that, under certain conditions, this complex is capable of polymerizing on the electrode surfaces made of vitreous carbon and indium tin oxide. The chemical modification on the surface was probed by exploring the cyclic voltammograms, which showed oxidation and reduction peaks that are characteristic of the Ni(II)/Ni(III) pair. The sensing capability towards 2,4-dichlorophenol of these modified electrodes is currently under study.

Keywords

Schiff base Ni(II) complex, electrodes, modifiers

Introduction There has been a considerable effort in recent years towards the preparation of new materials containing polyfunctional units (ligands) able to bind metallic ions. The Schiff base macroligands [1-6] are synthesized from the reaction of dialdehydes and amino compounds. Given that these materials form stable complexes, they provide the opportunity to design new systems selective to specific metallic ions. These materials could be applied in different areas such as electrochemistry, bioinorganic, catalysis, metallic deactivators, separation processes and environmental chemistry among others [7-9]. New Schiff base [2, 4, 10-11] macroligands have been synthesized to study their selectivity towards complexation of different metallic ions. These newly synthesized compounds are also used as precursors for the formation of other acyclic and cyclic ligands. Complexes of Schiff base ligands with structural similarities to phtalocyanines (N4-macrocycles) [7, 12-14], and other related compounds [15-20], are currently used as modifiers of the active surface of electrodes to improve their catalytic activity in the selective detection of organic pollutants [15, 21-24] and the entrainment of metals. Along the same line, our interest is to evaluate the capability of N,N’-bis(2-nitrobenzyl)ethylendiimine L1 (Figure 1), to bind diverse metallic ions such as Ni(II) and Co(II), and carry out selectivity studies. These complexes are later studied to test their potential in the development of chemically modified electrodes for use in pollutant detection. Figure 1. Structural Formula of the ligand N,N’-bis(2-nitrobenzyl)ethylendiimine (L1). The selectivity studies showed that the complex [NiL1]SO4 is very stable at Standard temperature and pressure. It is currently being tested as a possible modifier of the active surface of an electrode. Under certain specific conditions this compound has been electrochemically polymerized over a vitreous carbon (VC) surface and over a glass surface covered with indium tin oxide (ITO) respectively. These chemically modified electrodes are being tested for the detection and degradation of organochlorinated pollutants. Experimental All the reactants used to obtain the ligands and their corresponding complexes were analytic grade from Sigma-Aldrich Chemical Company Inc, USA. Synthesis of N,N´-Bis(2-nitrobenzyl)ethylendiimine (L1) L1 was obtained by a condensation of a Schiff base according to a procedure previously reported, [3]. The nature of this compound was probed by infrared (IR) spectroscopy, and Nuclear Magnetic Resonance (NMR) and by melting point. Complexation reaction The ligand L1 was mixed directly in a refluxing solution with Co(II) and Ni(II) sulfates in equimolar amounts in acetonitrile. The corresponding complexes were characterized by IR spectroscopy and thermogravimetric analysis. The IR spectrum of the ligand shows a band at 1637 cm-1 corresponding to the imine group. The spectra of the complexes Ni(II)-L1 and Co(II)-L1 are consistent with the presence of the imine group showing the same band. It was also observed a shift of the bands corresponding to nitro groups along with a decrease in their intensity. This displacement suggests the presence of a heteroatom-M bond. The spectra also show an intense band around 1080 cm-1 corresponding to the sulfate ion. A solution of Ba(II) and Pb(II) was added to both complexes and an instantaneous precipitation occurred, suggesting that the sulfate ion is outside of the coordination sphere. Measurement of the Equilibrium Constants The formation constants for the complexes of Ni(II) and Co(II) with L1 were determined by conductimetry. Conductivities were measured for a series of solutions of each complex using an Orion conductimeter model 162. The formation constants are expressed in molar concentration at 25oC. Modification of Electrodes The electrochemical studies of the complex [Ni(II)- L1]SO4 were performed with a conventional three-electrodic potentiostatic system (CV-50W/ LG-50) (BAS)). The working electrodes were either a vitreous carbon electrode (VC) (BAS) of 3 mm diameter polished prior to all experiments, or an indium tin oxide (ITO) electrode. The potentials were measured with reference to the Ag/AgCl(s), KCl (BAS) electrode, placed in a compartment containing the supporting electrolyte. All the experiments were performed at room temperature. Table 1. Infrared data for N,N’-bis(2-nitrobenzyl)ethylendiimine (L1), [NiL1]SO4 and [CoL1]SO4. Compound –NO2 Group u cm-1 >C=N u cm-1 –C=O and –NH2 Groups u cm-1 Sulfate ion u cm-1 L1 1335 , 1516 (s) 1637 Absent Absent Ni-L1 1350 , 1530 (w) 1630 Absent 1080 Co-L1 1347-1527 (w) 1637 Absent 1130 Results and Discussion The ligand L1 was obtained as yellow crystals with 83% yield. This yield was higher than the results reported in the literature [3]. The nature of the ligand was established using IR and NMR spectroscopy as well as analysis of monocrystal X- ray diffraction. The results of the IR analysis verify that the condensation reaction of the Schiff base was successful. The previous assumption was based on the presence of bands corresponding to the imine group at 1637 and the nitro group at 1335 and 1516 cm-1 as well as absence of the characteristic signals of the carbonyl and amine L1 groups, as can be seen in Table 1. The spectrum 1H NMR of the diimine ligand (L1) presents signals in the interval of 8.75-8.85 ppm corresponding to CH=N. This signal proves the integrity of the product. (Figure 2). The resonance data of the ligand are consistent with the proposed structure. Figure 2. 1H NMR spectrum for N,N’-bis(2-nitrobenzyl)ethylendiimine (L1). A single crystal of L1 for XRD studies was obtained. The Figure 3 shows the molecular structure of L1, it belongs to the monoclinic system. The Crystallographic data for L1 is reported in Table 2. Figure 3. Monoclinic structure of L1 determined by monocrystal X-Ray diffraction. The interaction of Ni(II) and Co(II) with the ligand L1 was investigated. The complexes were obtained from direct reaction between the metallic ions and the ligand using acetonitrile as solvent. The compounds showed different colors and were obtained with a 45 - 48% yield. Table 2. Crystal data for N,N’-bis(2-nitrobenzyl)ethylendiimine (L1). Empirical formula C8H7N2O2 Color and shape Yellow, prismatic Crystal size 0.36 x 0.20 x 0.12 mm Crystal system Monoclínico Space group P21/c Unit cell dimensions a =7.4290(10) Å b= 15.503(2) Å c= 7.083(10) Å a= 90.00o b= 108.65o g= 90.00o Volumen (U/ Å3) 772.93(18) Formula weight 652.622 Density (calculated) 1.402 mg/m3 With respect to the IR data for the complexes, they were consistent with the presence of the imine group. Each complex exhibited a band between 1630 and 1637 cm-1. A shift and an intensity decrease of the bands of the nitro groups could also be observed. This suggests the presence of a heteroatom-M bond. The spectra also showed a band between 1080 and 1130 cm-1 which corresponds to the sulfate ion. The instantaneous precipitation of the sulfate ions upon addition a solution of Ba(II) and Pb(II) suggests that the sulfate is outside of the coordination sphere. The selectivity studies were carried out by atomic absorption. Table 3 shows the results which illustrates the preferences of the ligand to Ni(II) and Co(II) ions. Table 3. Selectivity Studies of the ligand L1 toward the Co(II) and Ni(II) ions determined by Atomic Absorption. Complex Color Molar % non complexed metal Complex [NiL1]SO4 Blue. 2.44 [NiL1]SO4 [CoL1]SO4 Light pink 3.88 [CoL1]SO4 The conductimetric analysis for the complexes (shown in Tables 4 and 5) provide Kf = 1.25 x 106 for [NiL1]SO4 and 5.6 x 105 for [CoL1]SO4, these values show that the Ni(II) complex is slightly more stable than Co(II) complex. The results are in agreement with the stability reported in the literature for a series of complexes of Ni(II) and Co(II) based on their ionic radius [25]. A change of color at 87oC was observed while measuring the melting point of Ni(II)-L1 complex. This temperature is lower than 100oC, therefore one could think that such change in color is the result of the loss of non-essential water (hygroscopic or hydration type). The compound remained stable until 300oC where it begins to decompose. Table 4. Determination of the Formation Constant of [NiL1]SO4 by Conductimetry. Concentration M [NiL1]SO4 Conductivity mS/m Equivalent Conductivity Ùeq CÙ 1/Ù 5x10-4 1180 2360 1.18 4.24x10-4 2x10-4 930 4650 0.93 2.15x10-4 8x10-5 650 8125 0.65 1.23x10-4 3x10-5 420 14000 0.42 7.14x10-5 2x10-6 350 175000 0.35 5.71x10-6 Kf = 1.25x106 Table 5. Determination of the Formation Constant of [CoL1]SO4 by Conductimetry. Concentration M [CoL1]SO4 Conductivity mS/m Equivalent Conductivity Ùeq CÙ 1/Ù 2x10-4 2300 4600 2.3 2.174*10-5 4x10-5 1180 2360 1.18 2.119*10-5 8x10-6 930 4650 0.93 1.344*10-5 2x10-6 650 8125 0.65 9.615*10-6 Kf = 5.60 x105 The thermograms from thermal studies performed on the complex [Ni(II)-L]SO4 are shown in Figure 4. These results show a loss of weight at approximately 90oC and also an endothermal peak at the same temperature. It can be thought that the complex loses hygroscopic and/or crystallization water at around 90oC (i.e. not directly bonded to the central metal ion). Latter can be demonstrated with the color changes of the compound, that it was due to the loss of water molecules. Figure 4. Thermograms of the complex [Ni(II)-L1]SO4. The alternatives previously mentioned for the case of the complex [Ni(II)-L1]SO4 could be possible because the Ni can form stable complexes acting with a coordination number of 4 or 6. Nevertheless, the chances of the water being coordinated at that temperature where the loss of weight occurs, are very small. Electrochemical studies were carried out on the complex [NiL1]SO4 and it was possible to polymerize this compound on the surface of vitreous carbon (VC), and indium tin oxide (ITO) electrodes. The studies were made using cyclic voltammetry in sweeps of 30 cycles. The chemical modification on the surface of the electrodes was proved by the presence of oxidation and reduction peaks which are characteristic of the Ni2+/Ni3+ redox pair. Different conditions were tested regarding sweep velocity and pH with the main aim of chemical modification for both electrodes. According to the obtained voltammograms, the best conditions were found at pH 10 and a sweep velocity of 250 mV/s as shown in Figures 5 and 6. Figure 5. Modification of VC, pH 10, sweep velocity 250 mV/s, 30 cycles, solution 1 mM [Ni(II)-L1]SO4, 0.1 M Na2SO4, sweep of potential from 0 to1000 mV. Figure 6. Modification of ITOP, pH 10, sweep velocity 250 mV/s, 30 cycles, solution 1 mM [Ni(II)-L]SO4, 0.1 M Na2SO4, sweep of potential from 0 to1000mV.

Softball bats were at one time made chiefly of wood, but advances in technology have introduced materials such as aluminum, graphite, and composites. Each material has its positive and unique features.

Wood: Wood softball bats are very rare but are slowly regaining favor with softball enthusiasts who would rather hear a whack and not a ping when the bat meets ball. A wood softball bat is bottle-shaped and can weigh between 32-35 ounces (around 8 ounces heavier than an aluminum bat). Traditionally, wood bats have been made from ash. However, ash is light and soft and bats made from ash tend to splinter and dent fast. Wood from maple, oak, and bamboo is also used for these bats. Maple is harder and its grain is denser as compared to ash, making it less susceptible to splintering and chafing. Bats made from Chinese bamboo are the closest wood bat equivalent of an aluminum bat. Bamboo is extremely light-weight and ha a tensile strength higher than that of steel.

Aluminum: The increased research and engineering in the science of bat making has resulted in high-tech aluminum softball bats that can cost upward of $300. Aluminum bats are lighter thereby enabling batters to generate greater bat speed and control. They are stronger and more durable than wood bats and they do not break; however, they may dent or crack over a period of time. Aluminum bats are available in different alloy and weight combinations. Light aluminum alloys that are thinner are more resilient and provide a larger hitting zone or “sweet spot”. Aluminum bats are made in single-layer and double-layer combinations; double-layer bats are used by the power-hitters.

Graphite/Titanium lined: Aluminum bats are lined with graphite or titanium. These light, durable, and strong materials are added to aluminum bats with thin walls in order to make the bats lighter. Lighter bats help batters to generate more power in their swing. Bats lined with graphite or titanium have a greater hitting zone or “sweet spot”. These materials are shock-absorbent as well and aid in reducing the shock felt when a stroke is mistimed.

Composite materials: Bats made from composite materials such as carbon, glass, or Kevlar are light weight, rigid, and sturdy. Composite materials enable bat manufacturers to incorporate varying strengths and stiffness in different parts of a bat. The result is a bat with stiff bat handles for greater control, low stiffness hitting areas for better performance and reduced shock, and differentiated swing weights. Bats made from composite materials have a large hitting surface with a more pronounced “sweet spot”. However, the extreme velocities at which the ball rebounds off the bat can pose a safety hazard to the pitcher who has to react in a very limited time.

Sheet metal stamping is the system wherein metal sheets are used for producing final products. When a metal sheet is inserted into the die or the press, it is molded into the required shape and size. Metal sheets of only a certain thickness can be inserted into metal stamping machines. The maximum limit for most metal stamping machines is ¼ inch. However, machines can be designed to accommodate sheets of greater thickness also. Even the kind of metal sheets that can be processed in metal stamping are also specific. Only certain metals or alloys can be used like aluminum, brass, steel (hot rolled or cold rolled), galvanized steel, stainless steel, copper, zinc and titanium.

Before the metal sheet is inserted into the machine, the customer provides the prototype or at least a diagram of the final product. In case the customer doesn’t have a clear idea of what the final product should look like, most metal stamping producers also offer engineering services for designing the products as well. Even some secondary services such as deburring and plating are provided by the metal stamping companies after the metal sheet is stamped.

There are three main components in sheet metal stamping -- the die, the punch and the binder/blank holder. The sheet is kept between the blank holder and the die and the punch is driven into the die wherein the sheet spreads over the die because of the drawing and stretching. The blank holder provides the restraining force that is required to control the sheet flow into the die. This force prevents wrinkling and tearing of the sheet as the quantity of material going into the machine can be controlled. For some processes where the blank holder force is too high for the material, draw beads are used to create the restraining force.

Sheet metal stampings are also known as thin stampings. Sheet metal stamping is used most primarily in the case-building process. It is also the most important part as each of the panels has to be stamped one by one. First the motherboard tray is stamped, then one-side panels on the right and left from bottom to top and back.

Most cutting tools have replaceable attachments. These are called cutting tool inserts. They can be of various shapes and sizes – round, triangular, square, rectangular, rhombic, five-sided or even eight-sided. Cutting tool inserts are used in varied applications – from cutting and drilling to boring, grooving, sawing, threading, mining and milling. Some of them are so adjustable that when the edges become worn out, other unused edge portions come into use!

Besides their shape, inserts also come with different angles for their tips. A ball nose mill is used for grooves or semicircles. A radius tip mill is used on milling cutters. A chamfer tip mill is ideal for an angled cut or a chamfered edge. A dogbone tip is two-edged and is used for grooving.

What are inserts made of? They are usually made of carbide, high-speed steel, silicon nitride, ceramic, cobalt, diamond particles, etc. They are then coated with substances like titanium aluminum nitride, zinc nitride or chromium nitride to make them even stronger. Some of these composite alloys go up to a hardness of 60 RC. These new age super alloys are becoming very popular in industry today. They withstand a high amount of shock and heat and resist wear and tear. So economizing on inserts may not be such a good idea for a manufacturing unit because they pay for themselves in a very short time. However, investing in costly inserts without warranting it would not be advisable because working them with wrong speeds and feeds would be detrimental to the life of these tools.

Advice and training from an acknowledged cutting tool inserts manufacturer would go a long way in ensuring you get the best possible output from your investment. Today, there are cutting tool inserts that last up to 40% longer than they used to. High cutting force, feed without vibration and the same insert used for various applications are some of the advantages of today’s inserts.

Steel and aluminum are the favored materials for metal shed building. Both of them are strong and light enough to make sheds. Metal sheds are very easy to construct since they do not require foundations. They can be constructed and placed in their suitable locations much as one would buy and keep a cupboard inside the house.

Metal shed designs are quite monotonous and they have flat or slightly V-shaped roofs. In metal sheds, the emphasis is on storage space and there are several shelves already attached to their inner walls. In metal sheds, utility wins over elegance. Homeowners buy metal sheds more for their durability rather than their looks.

Yet, to their advantage, metal sheds are marginally cheaper than wood sheds. If one needs a shed just for stowing certain tools in an obscure corner of their lawn, then it is wise to have a metal shed. Houses with small gardens may go for metal sheds. Also, metal sheds are easy to construct. They can be raised by the homeowners themselves from do-it-yourself kits with a little knowledge of carpentry. Metal sheds not only cut costs on the material, but also on the labor that is needed to construct them.

Steel and aluminum are both corroding metals. Metallurgical companies treat these metals for rust and corrosion at the extraction stage itself. Despite that, a prolonged exposure to humid environments may cause them to get rusty and corroded. A rusty shed is a terrible eyesore in the lawn of any house. Alloys of aluminum like duralumin and magnalium, the same alloys that heavy vehicles and aircraft are made, are also used for manufacturing metal sheds and are known to be non-rusting, but are more expensive than typical metal.

Metal sheds are hazardous if there are children in the house. Their edges are usually rough and can be incredibly sharp. While constructing a metal shed, it is extremely important to check that there are no sharp edges or loose screws left.

Metal sheds are utilitarian and are usually not objects to be flaunted. People generally keep their metal sheds in hidden corners of their gardens or lawns and they are primarily used for storage.

As an exceptionally versatile metal, nickel enjoys a special place in the industrial world. With its lustrous, silvery-white appearance, low thermal and electrical conductivities, high resistance to corrosion and oxidation, excellent strength and toughness at higher temperatures, ability to be magnetized, and a melting point of 1453° C, nickel is not only attractive and durable in its own pure form; it also readily alloys with many other metals.

Nickel is readily recognized in coins, where it is used by many countries in both pure and alloy forms, and as bright and durable electrolytically-applied “nickel plating” coatings on steel. Its primary use, however, is as an alloying component with chromium and other metals in the production of stainless and heat-resistant steel used not only in industry and construction, but also for household products such as pots and pans, kitchen sinks, and other everyday items. Stainless steel is produced in a wide range of compositions to meet industry requirements for corrosion and heat resistance, and also to facilitate a clean and hygienic surface for food and other processing.

About 65% of nickel is used to manufacture stainless steel. Around 20% is used in other steel and non-ferrous alloys, often for specialized industrial, aerospace and military applications. About 9% is used in plating, while 6% in used in other applications, including coins and a variety of nickel chemicals. As the emerging middle class in countries such as China and other Asian nations demand more stainless steel products from sinks to door handles, nickel consumption is on the rise. Stainless steel currently accounts for about two-thirds of nickel consumption up from one-third in the past three decades. While nickel demand in Europe and the Americas decreased in the period from 1997-2002, this demand increased in Asia and the former East Bloc countries.

Chinese nickel consumption increased by 15.4% in 2005, slightly less than the 19.1% growth reported in 2004. Chinese consumption during this decade has actually been the single largest factor impacting the nickel market, with supply struggling to keep pace with this rising demand due to a physical shortage of the metal. In fact, China recently announced a cut-back in stainless steel production because they are unable to source enough nickel.

This rising demand and limited supply is pushing up prices. As of July 2006, nickel was trading at over $12.00US per pound in contrast to historical prices of less than $5.00US over the previous 15 years. Experts predict that this continued high demand – based not only on China 's continuing economic boom but also on the West's demand for hygiene, will continue for the foreseeable future.

Only about 1.3 million tons of new or primary nickel are produced and consumed annually, compared with over 15 million tons of copper and nearly 800 million tons of steel. The growing world economy through the mid-nineties triggered an expansionary drive in nickel capacity by existing manufacturers resulting in a production increase of 30% in the five year period from 1993-1998. European expansion in both Finland and the United Kingdom accounted for most of the 48% (60,000 ton) increase in production, while expanded production in Australia and New Caledonia accounted for all of the 39% (35,000 ton) increase in Oceania . Japan accounted for most of the 22% increase in production in Asia during that same period.

The most common types of bearings are wheel bearings. Motorcycle wheels have them, so do skateboards. The bearings help give you a smooth ride.

Proper maintenance of the ball bearings is the key to ensuring they don’t give you any problems. Bad bearings usually are the causes of the clunking noises you hear as you turn the wheel, or the gritty feel on the wheel. If you’re wondering what these wheel bearings look like, you might have actually seen them in your broken bicycle or if you have tried to repair your wheels. Most types conceal the balls in these bearings. These balls are made of special alloys of stainless steel.

It was no less than Renaissance man himself, Leonardo Da Vinci who described a type of wheel bearing in his studies in the beginning of the 16th century. The invention of the wheel bearing, alongside the other inventions of the rebirth, is one of the most significant heirlooms of the era that have changed little over time. Leonardo da Vinci is said to have described a type of wheel bearing around the year 1500.

One issues with ball bearings is that they can rub against each other, causing additional friction, but this can be prevented by placing the balls in a cage and heavily lubricate them.

To find a good lubricant, take a look at the back of the can and make sure that they are made of proper oils that will not destroy the metal of your wheel bearing. The bearings tend to wear over time, and you can’t really do anything about it but to replace them. It is advised that you find the same quality, as some lesser quality wheel bearings may not keep up with your original ball bearings, and you may end up ruining your skateboard or motorcycle wheels.

One key decision to make when you build your own engagement rings is the metal. Yellow, white gold and platinum are most common. Titanium bands and silver are less so. Rose gold engagement rings or copper are pretty rare.

Titanium bands are the new black in the wedding industry. Titanium has a long history in industries such the military, aerospace, medicine, etc. but has only been widely seen on the fingers of brides and grooms for the last 20 years. While titanium is not rare, it is one of the strongest materials around, compared to other materials of similar weight. For example, titanium weighs 75% less than gold, but is 50% stronger than steel of the same weight. Titanium is a tough cookie and will outlast other metals such as gold and platinum.

Wait, there are even more advantages to titanium bands. Since titanium is one of the 9th most abundant metals around, it is relatively inexpensive, thus, it will usually cost less than platinum and sometimes less than gold. The cost in titanium jewelry is not for the raw metal but the artistry and labor involved in designing the ring. Titanium is also hypoallergenic and will not make your skin turn green or other unsightly shades. It is a low maintenance metal and doesn't tarnish

Titanium can be combined with other metals such as silver, gold, and platinum and embellished with any kind of gemstone. It can also be colored to have sheens of any shade of the rainbow.

Titanium bands also have a few downsides. Titanium is often marketed as being scratch-resistant, but that's not exactly true. Titanium bands will show small scrapes and scratches just like gold and platinum wedding bands. However, any local jeweler should be able to polish a titanium ring look new again. you need to take care when picking out your ring size because re-sizing titanium rings is nearly impossible. You may be able to slightly increase a titanium ring size, but you really can't make it any smaller. Thus, don't plan on losing any weight after you purchase your ring.

There is an urban legend surrounding titanium, since it is such a strong metal, that if you get a titanium ring stuck on your finger, you will not be able to get it off and your finger will have to be amputated. What a horrible thought! This is not true--- as with other metals such as gold or platinum, if need be, titanium can be cut off one's fingers with a professional-grade ring cutting tool.

I don't think I've ever seen any women wearing rose gold engagement rings. Nonetheless, they exist and while not typically sold in most mainstream jewelry stores, can be found in antique stores. Victorian antique engagement rings (1835-1900) were often set in rose gold. You can also find rose gold engagement rings that are produced today. There are some online jewelry stores that actually specialize in producing them.

Most people have preferred the color of gold to remain close to that of pure yellow gold itself. Gold only naturally occurrs in the yellow shade. All others shades are produced by mixing 24K gold with other metals. Pure gold is too soft to wear as jewelry and so alloys are almost always added to it, regardless of the color desired. The term alloys refers to a combination of two or more metals. Gold alloys are a combination of gold, copper and silver. Nickel, zinc, and palladium are common components of white gold alloys. To create rose gold alloys, the silver content of gold is reduced while the content of copper is increased slightly. The more copper that is added to it, the deeper the rose hue.

One thing to note when shopping for a rose gold, is that the color of rose gold may subtly intensify with age due to a tarnishing of the the copper.