fuel cell car

   

Fuel Cell Stacks

This is the heart of the hydrogen fuel cell car—the fuel cell stacks. Their maximum output is 86 kilowatts, or about 107 HP. Because hydrogen fuel cell stacks produce power without combustion, they can be up to twice as efficient as internal combustion engines. They also produce zero carbon dioxide and other pollutants. For more information on the stacks.

Fuel Cell Cooling System

This has several parts. Perched at an angle at the front of the vehicle is a large radiator for the fuel cell system, while two radiators for the motor and transmission lie ahead of the front wheels below the headlights. The car also has a cooling pump located near the fuel cell stacks to stabilize temperature within the stacks.

Ultra capacitor

This unit serves as a supplementary power source to the fuel cell stack. Like a large battery, the ultra capacitor recovers and stores energy generated during deceleration and braking. It uses this energy to provide a "power assist" during startup and acceleration.

Hydrogen Tanks

Space in a car is limited, yet hydrogen is the most dispersive element in the universe and normally requires lots of room. A challenge for manufacturers is how to compress the gas into tanks small enough to fit in a compact car and yet still provide enough fuel for hundreds of miles of driving between refueling. The two high-pressure hydrogen tanks in this vehicle can hold up to 3.75 kilograms of hydrogen compressed to roughly 5,000 PSI—enough to enable an EPA-rated 190 miles of driving before refueling, the manufacturer says.

Electric Motor

(General area only—motor not visible) The electric motor offers a maximum output of 80 kilowatts, enabling a top speed of about 93 miles per hour. The manufacturer says this vehicle can also start in subfreezing temperatures (down to about -4°F), a perennial problem in fuel cell prototypes. Being electric, the engine and the car as a whole are quiet, with none of the vibration or exhaust noise of a gas-powered automobile.

Air Pump

(General area only—air pump not visible) Run by a high-voltage electric motor, this pump supplies air at the appropriate pressure and flow rate to the fuel cell stacks. The air, in turn, mixes with the stored hydrogen to create electricity.

Humidifier

The humidifier monitors and maintains the level of humidity that the fuel cell stack needs to achieve peak operating efficiency. It does this by recovering some of the water from the electrochemical reaction that occurs within the fuel cell stack and recycling it for use in humidification.

Power Control Unit

(General area only—power control unit not visible) This controls the vehicle’s electrical systems, including the air and cooling pumps as well as output from the fuel cell stacks, electric motor, and ultra capacitor.

Cabin

With the fuel cell stacks hidden beneath the floor and the hydrogen tanks and the ultra capacitor beneath and behind the rear seats, respectively, the four-passenger cabin is isolated from all hydrogen and high-voltage lines. Hydrogen gas is colorless and odorless, and it burns almost invisibly. In case of a leak, therefore, the manufacturer has placed hydrogen sensors throughout the vehicle to provide warning and automatic gas shut-off. Also, in the event of a collision, the electrical source power line shuts down.

Hydrogen Filler Mouth

(Not visible—located on other side of vehicle) Drivers would fill the car with hydrogen just as they do with gasoline, through an opening on the side of the vehicle. The main difference is that a fuel cell car must be grounded before fueling to rid the car of hazardous static electricity. For this reason, this model has two side-by-side openings, with the latch to open the hydrogen filler mouth located inside the opening for the grounding wire. The manufacturer says filling up this model’s two tanks at a hydrogen filling station would take about three minutes.

Note

The limited-production vehicle seen in this feature is a Honda 2005 FCX, which is typical of the kinds of hydrogen fuel cell automobiles that some major automakers are now researching and developing. With such vehicles at present costing about $1 million apiece, none is currently for sale, though hundreds of fuel cell cars are now undergoing tests on the world’s roads.

fuel cells

Think of them as big batteries, but ones that only operate when fuel—in this case, pure hydrogen—is supplied to them. When it is, an electrochemical reaction takes place between the hydrogen and oxygen that directly converts chemical energy into electrical energy. Various types of fuel cells exist, but the one automakers are primarily focusing on for fuel cell cars is one that relies on a proton-exchange membrane, or PEM. In the generic PEM fuel cell pictured here, the membrane lies sandwiched between a positively charged electrode (the cathode) and a negatively charged electrode (the anode). In the simple reaction that occurs here rests the hope of engineers, policymakers, and ordinary citizens that someday we’ll drive entirely pollution-free cars.

Here’s what happens in the fuel cell: When hydrogen gas pumped from the fuel tanks arrives at the anode, which is made of platinum, the platinum catalyzes a reaction that ionizes the gas. Ionization breaks the hydrogen atom down into its positive ions (hydrogen protons) and negative ions (electrons). Both types of ions are naturally drawn to the cathode situated on the other side of the membrane, but only the protons can pass through the membrane (hence the name "proton-exchange"). The electrons are forced to go around the PEM, and along the way they are shunted through a circuit, generating the electricity that runs the car’s systems.

Using the two different routes, the hydrogen protons and the electrons quickly reach the cathode. While hydrogen is fed to the anode, oxygen is fed to the cathode, where a catalyst creates oxygen ions. The arriving hydrogen protons and electrons bond with these oxygen ions, creating the two "waste products" of the reaction—water vapor and heat. Some of the water vapor gets recycled for use in humidification, and the rest drips out of the tailpipe as "exhaust." This cycle proceeds continuously as long as the car is powered up and in motion; when it’s idling, output from the fuel cell is shut off to conserve fuel, and the ultra capacitor takes over to power air conditioning and other components.

A single hydrogen fuel cell delivers a low voltage, so manufacturers "stack" fuel cells together in a series, as in a dry-cell battery. The more layers, the higher the voltage. Electrical current, meanwhile, has to do with surface area. The greater the surface area of the electrodes, the greater the current. One of the great challenges automakers face is how to increase electrical output (voltage times current) to the point where consumers get the power and distance they’re accustomed to while also economizing space in the tight confines of an automobile.

Kinetic Energy Recovery System

The introduction of Kinetic Energy Recovery Systems (KERS) is one of the most significant technical introductions for the Formula One Race. Formula One have always lived with an environmentally unfriendly image and have lost its relevance to road vehicle technology. This eventually led to the introduction of KERS.

KERS is an energy saving device fitted to the engines to convert some of the waste energy produced during braking into more useful form of energy. The system stores the energy produced under braking in a reservoir and then releases the stored energy under acceleration. The key purpose of the introduction was to significantly improve lap time and help overtaking. KERS is not introduced to improve fuel efficiency or reduce weight of the engine. It is mainly introduced to improve racing performance.

KERS is the brainchild of FIA president Max Mosley. It is a concrete initiative taken by F1 to display eco-friendliness and road relevance of the modern F1 cars. It is a hybrid device that is set to revolutionize the Formula One with environmentally friendly, road relevant, cutting edge technology.

Components of KERS

The three main components of the KERS are as follows:

• An electric motor positioned between the fuel tank and the engine is connected directly to the engine crankshaft to produce additional power.
• High voltage lithium-ion batteries used to store and deliver quick energy.
• A KERS control box monitors the working of the electric motor when charging and releasing energy.

A – Electric motor

B – Electronic Control Unit

C – Battery Pack

Working Principle of KERS

Kinetic Energy Recovery Systems or KERS works on the basic principle of physics that states, “Energy cannot be created or destroyed, but it can be endlessly converted.”

When a car is being driven it has kinetic energy and the same energy is converted into heat energy on braking. It is the rotational force of the car that comes to stop in case of braking and at that time some portion of the energy is also wasted. With the introduction of KERS system the same unused energy is stored in the car and when the driver presses the accelerator the stored energy again gets converted to kinetic energy. According to the F1 regulations, the KERS system gives an extra 85 bhp to the F1 cars in less than seven seconds.

This systems take waste energy from the car’s braking process, store it and then reuse it to temporarily boost engine power. This and the following diagram show the typical placement of the main components at the base of the fuel tank, and illustrate the system’s basic functionality – a charging phase and a boost phase. In the charging phase,

kinetic energy from the rear brakes (1)

is captured by an electric alternator/motor (2),

controlled by a central processing unit (CPU) (3),

which then charges the batteries (4).

 

In the boost phase, the electric alternator/motor gives the stored energy back to the engine in a continuous stream when the driver presses a boost button on the steering wheel. This energy equates to around 80 horsepower and may be used for up to 6.6 seconds per lap. The location of the main KERS components at the base of the fuel tank reduces fuel capacity (typically 90-100kg in 2008 ) by around 15kg, enough to influence race strategy, particularly at circuits where it was previously possible to run just one stop. The system also requires additional radiators to cool the batteries. Mechanical KERS, as opposed to the electrical KERS illustrated here, work on the same principle, but use a flywheel to store and re-use the waste energy.

Types of KERS

There are basically two types of KERS system:

Electronic KERS

Electronic KERS supplied by Italian firm Magneti Marelli is a common system used in F1 by Red Bull, Toro Rosso, Ferrari, Renault, and Toyota.

The key challenge faced by this type of KERS system is that the lithium ion battery gets hot and therefore an additional ducting is required in the car. BMW has used super-capacitors instead of batteries to keep the system cool.
With this system when brake is applied to the car a small portion of the rotational force or the kinetic energy is captured by the electric motor mounted at one end of the engine crankshaft. The key function of the electric motor is to charge the batteries under barking and releasing the same energy on acceleration. This electric motor then converts the kinetic energy into electrical energy that is further stored in the high voltage batteries. When the driver presses the accelerator electric energy stored in the batteries is used to drive the car.

Electro-Mechanical KERS

The Electro-Mechanical KERS is invented by Ian Foley. The system is completely based on a carbon flywheel in a vacuum that is linked through a CVT transmission to the differential. With this a huge storage reservoir is able to store the mechanical energy and the system holds the advantage of being independent of the gearbox. The braking energy is used to turn the flywheel and when more energy is required the wheels of the car are coupled up to the spinning flywheel. This gives a boost in power and improves racing performance.

Limitations of KERS

Though KERS is one of the most significant introductions for Formula One it has some limitations when it comes to performance and efficiency. Following are some of the primary limitations of the KERS:

• Only one KERS can be equipped to the existing engine of a car.
• 60 kw is the maximum input and output power of the KERS system.
• The maximum energy released from the KERS in one lap should not exceed 400 kg.
• The energy recovery system is functional only when the car is moving.
• Energy released from the KERS must remain under complete control of the driver.
• The recovery system must be controlled by the same electronic control unit that is used for controlling the engine, transmission, clutch, and differential.
• Continuously variable transmission systems are not permitted for use with the KERS.
• The energy recovery system must connect at one point in the rear wheel drive train.
• If in case the KERS is connected between the differential and the wheel the torque applied to each wheel must be same.
• KERS can only work in cars that are equipped with only one braking system.

Nano Composite Material

If someone does a lot of arm curls at the gym, the typical result is that the bones and muscles in their arms will get stronger. Recently, researchers at Houston’s Rice University inadvertently created a nano composite that behaves in the same way. Although the material doesn’t respond to static stress, repeated mechanical stress will cause it to become stiffer.

The discovery was made in the lab of Pulickel Ajayan, Rice University professor of mechanical engineering and materials science, and of chemistry. Graduate student Brent Carey had created a composite material by infiltrating a batch of vertically aligned, multi-walled nanotubes with Polydimethylsiloxane, which is an inert, rubbery polymer. He was testing the high-cycle fatigue properties of the composite, and was surprised to discover that instead of weakening when subjected to repeated loads, it actually got stronger.
Over the course of a week, the material was subjected to 3.5 million compressions. This caused its stiffness to increase by 12 percent, with indications that there was potential for further stiffening. The reason for this type of reaction is still something of a mystery.
"We were able to rule out further cross-linking in the polymer as an explanation," said Carey. "The data shows that there’s very little chemical interaction, if any, between the polymer and the nanotubes, and it seems that this fluid interface is evolving during stressing."
What is known is that the use of nanomaterials greatly increases the surface area available to that fluid interface, so whatever reaction is taking place is much more pronounced than would be the case with a conventional composite.
Carey is already envisioning potential uses for materials utilizing the process. "We can envision this response being attractive for developing artificial cartilage that can respond to the forces being applied to it but remains pliable in areas that are not being stressed," he stated.

New Battery Technology

Of all the criticisms of electric vehicles, probably the most commonly-heard is that their batteries take too long to recharge – after all, limited range wouldn’t be such a big deal if the cars could be juiced up while out and about, in just a few minutes. Well, while no one is promising anything, new batteries developed at the University of Illinois, Urbana-Champaign do indeed look like they might be a step very much in the right direction. They are said to offer all the advantages of capacitors and batteries, in one unit.

 

"This system that we have gives you capacitor-like power with battery-like energy," said    U Illinois’ Paul Braun, a professor of materials science and engineering. "Most capacitors store very little energy. They can release it very fast, but they can’t hold much. Most batteries store a reasonably large amount of energy, but they can’t provide or receive energy rapidly. This does both."

The speed at which conventional batteries are able to charge or discharge can be dramatically increased by changing the form of their active material into a thin film, but such films have typically lacked the volume to be able to store a significant amount of energy. In the case of Braun’s batteries, however, that thin film has been formed into a three-dimensional structure, thus increasing its storage capacity.

Batteries equipped with the 3D film have been demonstrated to work normally in electrical devices, while being able to charge and discharge 10 to 100 times faster than their conventional counterparts.

To make the three-dimensional thin film, the researchers coated a surface with nano scale spheres, which self-assembled into a lattice-like arrangement. The spaces between and around the spheres were then coated with metal, after which the spheres were melted or dissolved away, leaving the metal as a framework of empty pores. Electro polishing was then used to enlarge the pores and open up the framework, after which it was coated with a layer of the active material – both lithium-ion and nickel metal hydride batteries were created.

The system utilizes processes already used on a large scale, so it would reportedly be easy to scale up. It could also be used with any type of battery, not just Li-ion and NiMH.

The implications for electric vehicles are particularly exciting. "If you had the ability to charge rapidly, instead of taking hours to charge the vehicle you could potentially have vehicles that would charge in similar times as needed to refuel a car with gasoline," Braun said. "If you had five-minute charge capability, you would think of this the same way you do an internal combustion engine. You would just pull up to a charging station and fill up."

Braun and his team believe that the technology could be used not only for making electric cars more viable, but also for allowing phones or laptops to be able to recharge in seconds or minutes. It could also result in high-power lasers or defibrillators that don’t need to warm up before or between pulses.

Floating Solar Power Plants

There’s a lot of surface area on this planet for solar panels. The ocean’s are a vast area to utilize this solar technology.  But,  the weather can make the installation and use of floating solar arrays difficult.  That’s not the case with LSAs (Liquid Solar Arrays) by Sunengy Pty LTD.

The floating solar power units, called Liquid Solar Arrays (LSA), use concentrated photovoltaic technology where a lenses direct the light onto solar cells and move throughout the day to follow the sun.

The company says the advantage to floating a solar power plant is that it erases the need for expensive structures to protect it from inclement weather and high winds — when rough weather comes along, the lenses just submerge.  Floating on water, whether it be the ocean, a lake or a tiny pond, also keeps the solar cells cool, which increases their efficiency and lifespan.

“The LSA system is based on floating solar collectors made mostly of plastic. Each has a very small area of silicon photovoltaic cells at the water surface with a large, thin plastic focusing lens rotating slowly above to track the sun. The water cools the silicon cells and in bad weather the lens is protected by rotating it fully under the water to avoid damage in high winds. ”

What is liquid solar array technology: In this technology, lens and photo voltaic cells are made to float on the water.  These absorb solar energy during the day.  There is no need to undertake any construction in water as these are made to float with the new technology.  This can withstand all adverse weather conditions.  This new technology will convert the dam into a big battery.  Solar energy can be stored without any cost.  Liquid Solar Array technology provides an opportunity to maintain water resources more effectively.

Special features of LSA: LSA technology is cheap and it can even withstand cyclones.  Land is not needed for establishing this plant and so there will not be any problems for procuring the land.  In India, there is 30 thousand square kilometers of water area and even if 1% of it is utilized for this technology, electricity that is equal to the electricity produced by 15 big thermal electricity plants can be produced.

mechanical technical interveiw questions

What happens if gasoline is used in a Diesel engine?Diesel engine will work ?

No, It will not work,as the Compression ratio of Petrol engine is 6 to 10 & that of Diesel engine is 15 to 22. Thus on such high compression, gasoline gets highly compressed & it may blast.

• Which Mechanism is used in Automobile gearing system

Differential mechanism

• Why different types of sound are produced in different bikes though they say run on SI engine

Engine specifications are different in different manufactures like as Bore Diameter(CC), Ignition timing.Also the exhaust passage take more responsible for sound.

• Why entropy decreases with the increase in temperature?

ds=dQ/TEntropy is inversely proportional to the temperature so.as temp. increases,entropy decreases.

• 1 hp how much watt?

746.2Watt

• How to calculate bearing number to diameter of the inner and outer

• Divide the shaft diameter size by 5, it will give last two digitof the bearing no. and according to type of load we have tochose the type of bearing and that will give prior no. ofthe bearing.

  • Explain Bicycle rear wheel Sprocket working?

  Rear wheel sprocket works under the principle of ratchet and pawl.

  • Definition of Octane number & Cetane number

  Octane No.- Octane number is defined as the percentage, by volume, of iso octane in the mixture of iso octane and h-heptane. It is the measure of rating of SI engine.

  Cetane No.- Cetane number is defined as the percentage, by volume, of n-cetane in the mixture of n-cetane and alpha methyl naphthalene. It is the measure of rating of CI engine.

  • Poisons ratio is higher in (rubber/steel/wood)

  When a material is compressed in one direction, it usuallytends to expand in the other two directions perpendicular tothe direction of compression. This phenomenon is called thePoisson effect. Poisson’s ratio is a measure of the Poisson effect.

  For rubber = 0.5

  For steel = 0.288

  For wood < 0.2

  Thus Poisson’s ratio is higher in RUBBER.

  • The Fatigue life of a part can be improved by ?

  Improving the surface finish by Polishing & providing residual stress by Shot peening.

  • When crude oil heated Which Hydro carbon comes first?

  Natural gas(Gasoline)… at 20 Celsius

• Which type of shaft is preferred for power transmission,solid or hollow one?

Hollow shaft utilize material strength more efficiently, so hollow shaft used if you concerned about weight.
But, when weight is not a concern, solid shaft is better (stronger, of course), easy to fabricate.

• What is structurally stronger, solid steel or hollow steel?

If a solid and hollow shape have the same outside dimensions, the solid one is clearly stronger.
The reason you see so many hollow sections is that they have an incredibly higher strength/weight ratio and can resist the same load with much less material used.

• What will be the difference in torsional strength of hollow shaft & solid shaft of same outer diameter at equal load.

Compare the polar moment of inertia of the solid cross section to the hollow cross section. You’ll find that the difference between the two is equal to the polar moment of inertia of the portion removed from the hollow section.

The deflection of the shaft under a torsional load would be the product of the torsional load and the length of the shaft divided by the product of Polar Moment of inertia and modulus of rigidity of the shaft: theta=TL/JG.

• What are the units for Poisson’s ratio?

It is a unit less quantity. Because it is one quantity divided by another quantity of the same units.
In fact, even the parent quantities that define Poisson’s ratio are unit less. Strain has no units.

• What is the difference between Stress and Pressure?

Stress=Resistive force/Area
Stress is pull force and Pressure is push force.

• 1.Heat Treatment Process HRC Stands for

• 2.Material OHNS Stands for

HRC Stands for –Rockwell Hardness C scale
OHNS Stands for — Oil Hardenable Non Shrinkage steel

• Function of Fly wheel

Flywheel stores the Kinetic Energy during the idle portion of the work cycle,and delivers this Kinetic Energy during peak-load.

• Bullet Proof Glass is made up of which material?

Bulletproof glass is usually constructed using a strong but transparent material such as polycarbonate thermoplastic or by using layers of laminated glass. The desired result is a material with an appearance and light-transmitting behavior of standard glass but offers varying degrees of protection from small arms fire. The polycarbonate layer, usually consisting of products  such as Cyrolon, Lexan and Tuffak, is often sandwiched between layers of regular glass. The use of plastic in the laminate provides impact-resistance, such as physical assault with a hammer, an axe, etc. The plastic provides little in the way of bullet-resistance. The glass, which is much harder than plastic, flattens the bullet and thereby prevents penetration. This type of bullet-resistant glass is usually 70-75 mm thick.

• Difference between Performance and Efficiency?

Performance is the measure of quality of the work done by any machine. better  the quality better will be the performance of that machine. while efficiency is the ratio of desired output to the required input for any machine.

Performance is about the quality that a machine or plant is producing suppose there are two machines, first produces the job of accuracy .002mm and the second one produce product of the accuracy .001mm. then the second one will have higher performance.  while efficiency is the ratio of the o/p to the i/p. if same machines are producing 200 and 100 product per day respectively for the same i/p,then the eff. of the first machine will be high.

• What are the causes of main engine black smoke?

There is many cause of black smoke.

1. It’s improper mixture of fuel supply by carburetor like very rich mixture so the fuel improper burn.

2. It’s when piston or piston ring is fail so back side cooling oil release in combustion chamber it cause black smoke.

3. Improper ignition system like not sufficient time of pressure rise delay period .

mechanical interview questions

What is the purpose of scrapper ring

Scrap the excess lube oil from the cylinder walls. There by preventing oil from entering combustion zone.

• How catalyst converter works?

In Fuel Cell, a catalyst is a substance that causes or accelerates a chemical reaction without itself being affected. Catalysts participate in the reactions, but are neither reactants nor products of the reaction they catalyze.

• WHAT WILL HAPPEN IF RELIEF VALVE IN HYDRAULIC SYSTEM FAILS?

The main function of pressure relief valve is to maintain the pressure inhydraulic system. It is one mounting which is used for safety. When pressure increases then safety valve comes into action & if the valve get fail the system get damage due toexcessive pressure.

• What does CC Stand for?

CC is the abbreviated form of cubic centimeter. It is the unit by which the capacity of an engine is designated. It is the volume between TDC and BDC. It represents the quantity of fuel-air mix or exhaust gas that is pumped out in a single piston stroke. Alternatively it can represent the volume of the cylinder itself.

• We have read that when the piston goes up and down then the engine works i.e. the suction,compression etc etc. then what happens in the case of big vehicles, which start at stable condition, i.e. how does their piston moves when they are at rest. how suction,compression etc

Smaller vehicles like bikes, cars are started with the help of motors. initially, motors turn the crank shaft tillsufficient suction pressure is reached. when sufficient suction pressure is reached, the engine starts to suck the fuel in and then the cycle begins when the fuel is taken in and ignited. similarly, for huge engines, instead of motors, we use starting air. air at a pressure of 10-30 bar is fed to the engine which is at rest. this air rotates the engine till it attains sufficient suction pressure. once the pressure is reached, the cycle starts and it starts firing.

• What is the difference between S.S to EN8

SS- Stainless steel
En- Medium carbon steel
SS is Non Magnetic material & EN8 is Magnetic material
SS is Corrosion resistant & EN8 is Magnetic material

• The Compression ratio of Petrol engine is always less than Compression Ratio of Diesel engine why?

Petrol is not self igniting , it needs spark to flame up in chamber. Where as diesel is self igniting in dieselengine , to attain that state it requires high temp &pressure. This temperature & pressure is more than what’s required in Petrol Engines by property of that fluid .

• What is the temperature of space ?

The short answer is that the temperature in space is approximately 2.725 Kelvin. That means the universe is generally just shy of three degrees above absolute zero – the temperature at which molecules themselves stop moving. That’s almost -270 degrees Celsius, or -455 Fahrenheit.

• How to calculate the speed of conveyer in Meter Per Minute

Measure the diameter of the rollers around which the conveyor belt is wrapped. Multiply the diameter of the roller by pi (3.14159). This calculation will yield the circumference of the rollers. Every time the roller spins one revolution, the conveyor will be moved a linear distance equivalent to the circumference of the roller. Pi is a dimensionless factor, meaning it does not matter whether inches, centimeters or any other units of measurement are used. Measure the revolutions per minute (RPM) of the rollers. Count how many full revolutions (rotations) are made by the roller in one minute. Multiply the RPM by the circumference of the roller. This calculation will give the linear distance traversed by a point on the conveyor belt in one minute.

New Nano Composite Processing Technique

A new technique for creating films of barium titanate (BaTiO3) nano particles in a polymer matrix could allow fabrication of improved capacitors able to store twice as much energy as conventional devices. The improved capacitors could be used in consumer devices such as cellular telephones – and in defense applications requiring both high energy storage and rapid current discharge.

This capacitor array device made with a barium titanate nanocomposite.

Because of its high dielectric properties, barium titanate has long been of interest for use in capacitors, but until recently materials scientists had been unable to produce good dispersion of the material within a polymer matrix. By using tailored organic phosphonic acids to encapsulate and modify the surface of the nano particles, researchers at the Georgia Institute of Technology’s Center for Organic Photonics and Electronics were able to overcome the particle dispersion problem to create uniform nano composites.

For capacitors and related applications, the amount of energy you can store in a material is related to these two factors.

1. High Dielectric Constant

2. High Dielectric breakdown Strength

The new nanocomposite materials have been tested at frequencies of up to one megahertz, and the research says operation at even higher frequencies may be possible. Though the new materials could have commercial application without further improvement, their most important contribution may be in demonstrating the new encapsulation technique – which could have broad applications in other nanocomposite materials.

This work opens a door to effectively exploit this type of particle in nano composites using the coating technology.

Because of their ability to store and rapidly discharge electrical energy, capacitors are used in a variety of consumer products such as computers and cellular telephones. And because of the increasing demands for electrical energy to power vehicles and new equipment, they also have important military applications.

Key to developing thin-film capacitor materials with higher energy storage capacity is the ability to uniformly disperse nano particles in as high a density as possible throughout the polymer matrix. However, nano particles such as barium titanate tend to form aggregates that reduce the ability of the nanocomposite to resist electrical breakdown. Other research groups have tried to address the dispersal issue with a variety of surface coatings, but those coatings tended to come off during processing – or to create materials compatibility issues.

The robust Designed coating for the particles, which range in size from 30 to 120 nanometers in diameter.

“Phosphonic acids bind very well to barium titanate and to other related metal oxides”. “The choice of that material and ligands were very effective in allowing us to take the tailored phosphonic acids, put them onto the barium titanate, and then with the correct solution processing, to incorporate them into polymer systems. This allowed us to provide good compatibility with the polymer hosts – and thus very good dispersion as evidenced by a three- to four-fold decrease in the average aggregate size.”

Though large crystals of barium titanate could also provide a high dielectric constant, they generally do not provide adequate resistance to breakdown – and their formation and growth can be complex and require high temperatures. Composites provide the necessary electrical properties, along with the advantages of solution-based processing techniques.

“One of the big benefits of using a polymer nanocomposite approach is that you combine particles of a material that provide desired properties in a matrix that has the benefits of easy processing,”.

Scanning electron micrographs of barium titanate (BaTiO3) nano composites with polycarbonate (left, top and bottom) and Viton (right, top and bottom) polymer matrices. The images show the dramatic improvement in film uniformity through the use of phosphonic acid coated BaTiO3 nano particles (bottom images) as compared to uncoated nano particles (top images). The higher uniformity results in greatly improved dielectric properties.

Though the new materials may already offer enough of an advantage to justify commercializing. The research team also wants to scale up production to make larger samples – now produced in two-inch by three-inch films – available to other researchers who may wish to develop additional applications.

“Beyond capacitors, there are many areas where high dielectric materials are important, such as field-effect transistors, displays and other electronic devices,” Perry added. “With our material, we can provide a high dielectric layer that can be incorporated into those types of applications.”

RTV Molding | Urethane Casting | Room Temperature Vulcanized

What Is a Composite Part?

A part that combines a resin and reinforcing strands can properly be referred to as a composite.  This includes what is commonly referred to as fiberglass (technically, it should be called fiberglass reinforced plastic), but there are many other materials that are used in composite parts.  To achieve desired properties in composites, the chemistry of the resin used, the type of reinforcing strands, and the ratio of resin to reinforcing strands can be varied.  In general, the more strands in the mix, the stronger the final part becomes.

Why Mold?

 

There are many desirable features of molded composite parts.  Molded parts are almost always more durable, repairable, heat-resistant, and lighter than comparable strength carved wood parts, and they don’t soak up oil or moisture.  In the case of a molded composite cowl, its thin wall property (about 0.05"…and you can’t carve a wood cowl to match!) gives much better air flow around the motor as a big side benefit.   Molded composite wheel pants can handle bigger wheels and mount more conveniently.  Other possibilities are wing tips, gear legs, dummy exhausts, spinners, etc., and all are made in a similar way.

Once a proper mold is made, composite parts can be replicated quickly and easily, each one almost identical to its predecessors.  So, you can make as many parts   as  you and your   friends  need,  you  can  sell   them,  or ,   in  the event  of   a   crash,  make   a  new one   exactly  like   the original   in  just   a   fraction of   the   time   it  would  take   to carve   and hollow  another .

Molds and Plugs

Actually, anything you can lay resin in or on and pull away a part with the opposite shape can be considered a mold.  Male molds can be used, but a part made from a male mold has a smooth interior and a rough exterior, which requires quite a bit of work to make ready for a finish. A female mold, on the other hand, produces parts with smooth exteriors, so every part molded in one will come out with a smooth exterior that is exactly the shape desired.  To create a female mold with a smooth, perfectly-shaped interior cavity, a male plug is carved and finished, and the female mold is cast around the male plug.  This requires just a bit of extra work, but keep in mind that there is no need to hollow the plug, so making one goes quite quickly.

Plaster and even composite materials can be used to make a female mold, but in my experience, the absolute best overall material to use is RTV (room temperature vulcanized)
molding rubber.  It’s easy to handle, and a female mold made from it is flexible enough to allow a flex and peel technique to free the molded part without doing any damage to the mold, so it can be used over and over again.

 

Polyester or Epoxy?

 

 

Polyester is cheaper and weaker than epoxy, but it’s certainly adequate for first attempts. Polyester gets drops of hardener, more will accelerate the cure.  A down side is that finished parts often have pin holes. Polyester has a strong odor, and you need to wear eye protection because the catalyst can be highly dangerous if it gets in your eyes.

Reinforcing Fiber

 

 

The material used for reinforcing fiber has great influence on the overall strength and ultimate weight of the finished part.  Molding is best done with woven cloth, typically two to four ounces per square yard, in as many layers as needed to get the desired strength. Materials most used in composites for model applications are E-glass (fiberglass, white color), Kevlar (yellow), or carbon fiber (black).  E-glass is the least expensive and is fully adequate for most molding.  Kevlar is much more expensive, difficult to bend and cut, and would be best to avoid if you’re just starting out.  Carbon fiber is the strongest, but by far the most costly, hard to buy economically in small quantities, and is best left for after you’re a seasoned molder.  Carbon veil is easy to handle, but it’s not well-suited to molding composite parts typically found in models.

In full-scale aircraft composite parts, the weight ratio of the fibers and the resin is carefully engineered and calculated for each part.

Fillers

 

All epoxy suppliers sell fillers, such as a Cab-O-Sill, milled fibers, and Q-Cells.  These are useful on some shapes to make a paste to get good edges and corners.  Painted in corners, they help define small details, too.  A paste made with filler is useful to fix flaws that may appear in the final part, also.

Portable Solar Power Plant, Water Purifier And Fuel Cell In One |

In many areas of the world, and also during times of natural disasters, clean drinking water and access to power are scarce.  The company The Essential Element has designed the Hydra water purifier and fuel cell to take care of both of those problems at once.

The Hydra is equipped with a 2.88 kW solar panel array that runs a pump that pushes water through a self-cleaning filtration device (capable of purifying 87,000 liters a day), juices up lead-acid gel batteries and runs an electrolyzer that splits some of that water to fill a .37 cubic-meter tank with pressurized hydrogen.

The fuel cell can be used to power communication devices or a camp stove.  The whole device can easily be set up and collapsed for easy transport and includes PV mats that can be plugged into the device for extra power.

Interior Farming

This Modern Decorative blends in beautifully with any interior and does a magnificent job of recycling wasted organic matter. A part of the waste is used for cultivating and maintaining a green patch and the rest is used to produce methane.

Home / Restaurants dispose huge amount of organic waste. One part of the waste is recycled to grow food and the other part produces Methane turned into energy thanks to a co-generator. The energy obtained produces light to stimulate the growth of the plants.

The water is naturally filtered as it enters the container. This system self contained biosphere home farm system that not only allows to cultivate vegetables but also produces fresh air and light.

 

 

 

Reliability Analysis

It is defined as the probability that a given system will perform it’s function adequately for it’s specified period of lifetime under specified operating conditions.

Common measures are :

1. Failure rate.
2. Mean time between failures(MTBF)
3. Survival percentage.

Failure Rate:

Rate which components of population fail.

R(t)=N_s(t)/N_f(t)

 

Where,
            N_s(t)- No. of components that survived during time ’t’
            N_f(t) – No. of failures that occurred during the same time.


Mean time between Failures(MTBF):

The reciprocal of the failure rate(1/λ).
Where
           λ —-Failure rate.

Failure rate = (No.of failure )/(Time period during all components were exposed to failure)

Reliability Analysis:
Failure Mode and Effect Analysis(FMEA)

Purpose :
1. To recommend design changes.
2. To identify design weakness.
3. To help in choosing alternatives.

Four Stages:
I^st Stage – System boundaries and the scope of the analysis is decided.
II^nd Stage – Data Collection
                      Ex: Specification,Operating Procedure,Working Conditions.
III^rd Stage- Preparing the component or parts list.

IV^th Stage – Failure frequency and the functions of the part identified,causes of       failures,Failure detection.

CRITICALITY

CRITICALITY is a measure of the frequency of occurrence of an effect.
                       – May be based on qualitative judgement or
                       – May be based on failure rate data (most common)

Qualitative analysis:
        –Used when specific part or item failure rates are not available.
Quantitative analysis:
        –Used when sufficient failure rate data is available to calculate criticality numbers.

Qualitative Approach:

• Because failure rate data is not available, failure mode ratios and failure mode probability are not used.
• The probability of occurrence of each failure is grouped into discrete levels that establish the qualitative failure probability level for each entry based on the judgment of the analyst.
• The failure mode probability levels of occurrence are:

–Level A – Frequent
–Level B – Reasonably Probable

          –Level C – Occasional
          –Level D – Remote
          –Level E – Extremely Unlikely
Quantitative Approach
Failure Mode Criticality (CM) is the portion of the criticality number for an item, due to one of its failure modes, which results in a particular severity classification (e.g. results in an end effect with severity I, II, etc…).

• Category I – Catastrophic: A failure which may cause death or weapon system loss (i.e., aircraft, tank, missile, ship, etc…)
• Category II – Critical: A failure which may cause severe injury, major property damage, or major system damage which will result in mission loss.
• Category III – Marginal: A failure which may cause minor injury, minor property damage, or minor system damage which will result in delay or loss of availability or mission degradation.
• Category IV – Minor: A failure not serious enough to cause injury, property damage or system damage, but which will result in unscheduled maintenance or repair.

The quantitative approach uses the following formula for Failure Mode Criticality:

Cm = βαλpt

Where
            Cm = Failure Mode Criticality
               β = Conditional probability of occurrence of next higher failure effect
              α = Failure mode ratio
            λp = Part failure rate
              T = Duration of applicable mission phase