Plastic materials and its all types, the functions of semiconductors and use of fertilizes.ppt
- 2. Plastics
- 3. Definition “Plastic materials are any of a wide range of synthetic or semi-synthetic organic solids that are moldable. They consists of a long chain of carbon molecules”
- 4. Types of Plastics Thermoplastics Thermosetting plastics
- 5. Thermoplastics: Thermoplastics are the plastics that do not undergo chemical change in their composition when heated and can be molded again and again. Thermosetting plastics: Thermosets can melt and take shape once; after they have solidified they stay solid .In the thermosetting process , a chemical reaction occur that is irreversible.
- 7. Thermoplastics Thermosetting Plastics Thermoplastics can be repeatedly softened by heating and hardened by cooling Thermosetting plastics hardened permanently after being heated once. Thermoplastics molecules are not or less branched. Thermosetting plastics have branches and complex stucture. They are not brittle They are brittle They can be reshaped and reused They can not be reshaped They are reclaimed for waste They cannot be reclaimed E. G ….polyvinyl, polyethylene E.G ……bakelite and epoxy resin
- 8. Plastics and Environment • Plastic is durable means it degrades slowly. Plastics are very long-lived products that could have service over decade. • Chemicals added to plastics are absorbed by human bodies and affect human health. • Burning plastics can result in toxic fumes. • Pollutes air, land and water and exposes workers to toxic chemicals, including carcinogens.
- 9. Ceramics
- 10. Definition “A ceramic is an inorganic non- metallic,metalic or semi metallic solid made up of clay that have been shaped and then hardened by heating to high temperatures”
- 11. Properties • Ceramics are hard , extremely strong and stiff. • Ceramics are corrosion resistant and durable. • Ceramics are refractory material with high melting point. • Ceramics are inert to chemical action and generally don’t react with acids and alkalis • Ceramics are brittle and having less elasticity.
- 12. Applications • Consumer usage: Ceramics have greater usage in our homes like glassware, pottery etc • Building and construction: Manufactures use ceramics to make bricks, tiles, piping and other construction materials. • Coating: Because ceramics material are more corrosion resistance most metals are coated with ceramics. • Automotive Industry: Ceramics are widely used in automotive industry e.g catalytic converter, thermostats . • Electronics: Computer parts like capacitors superconductors are made up of ceramics
- 13. SEMICONDUCTORS • Electronic materials generate and control the flow of an electrical current. • Conductors: Allow Electric current to flow through them • Insulators: Do not Allow Electric current to flow through them • Semiconductors: Materials whose conductivity lies in between of Conductors and
- 14. Semiconductor • Semiconductors are materials that essentially can be conditioned to act as good conductors, or good insulators, or any thing in between. • Common elements such as carbon, silicon, and germanium are semiconductors. • Silicon is the best and most widely used semiconductor.
- 15. Band Model of conduction Conductors Metals are conductors. There is no band gap between their valence and conduction bands, since they overlap. There is a continuous availability of electrons in these closely spaced orbitals. Insulators In insulators, the band gap between the valence band the the conduction band is so large that electrons cannot make the energy jump from the valence band to the conduction band. Semiconductors Semiconductors have a small energy gap between the valence band and the conduction band. Electrons can make the jump up to the conduction band, but not with the same ease as they do in conductors.
- 16. Conduction band Band gap Electron Insulator Semiconductor Condcutor Valence band Valence band E n e rg y E n e rg y E n e rg y Conduction band Conduction band Valence band Band gap
- 17. Types of Semiconductors Semiconductors are mainly two types 1. Intrinsic (Pure) Semiconductors Semiconductors that are free of doping impurities are called intrinsic semiconductors. 2. Extrinsic (Impure) Semiconductors Semiconductors formed after adding impurities are called extrinsic semiconductors. Note: Doping is a process of adding a certain amount of specific impurities called dopants to a pure semiconductor to increase its electricity conductivity
- 18. Classification of Semiconductor Materials • The silicon doped with extra electrons is called an “N type” semiconductor. “N” is for negative, which is the charge of an electron. • Silicon doped with material missing electrons that produce locations called holes is called “P type” semiconductor. “P” is for positive, which is the charge of a hole.
- 19. Semiconductor Uses • Since semiconductor itself is not sold in stores as electrical appliances it is used in many electric appliances. • Temperature sensors used in air conditioners are made with semiconductors. • CPUs that operate personal computers are also made with semiconductors. • Many digital consumer products such as mobile phones, digital cameras, televisions etc also use semiconductors.
- 20. FERTILIZERS “Fertilizers are substances which are added to the soil to make up the deficiency of essential elements like N, P and K which are required for proper growth of plants.” Plant nutrients are of two types: (i) Micronutrients (ii) Macronutrients
- 21. i)Micronutrients “Those nutrients which are required in very small amounts for growth of plants are called micronutrients.” Examples • Boron, copper, iron, manganese, zinc, molybdenum and chlorine. (ii) Macronutrients “Those nutrients which are required in larger amount for the growth of plants are called Macronutrients.” Example • Nitrogen, potassium, phosphorous, calcium, magnesium, sulphur, carbon, hydrogen and oxygen.
- 22. Properties of a Good Fertilizer • The nutrient elements present in it must be readily available to the plants. • It must be fairly soluble in water so that it thoroughly mixes with soil. • It should not be injurious to plants. • It should be cheap. • It should not alter pH of soil. • It should remain available for longer time to growing plants.
- 24. Classification on the Basis of Nature/Types of Elements (i) Nitrogenous Fertilizers Nitrogenous fertilizers provide nitrogen to the plants. Nitrogen is important for plants because it: (a) accelerates early growth (b) imparts green colour to leaves (c) enhances yield and quality of plants Examples • Ammonia, urea, ammonium nitrate, ammonium phosphate, ammonium sulphate, ammonium chloride.
- 25. (ii) Phosphatic Fertilizers Phosphatic fertilizers provide phosphorous to the plants. Phosphorous is essential for plants because it: (a) accelerates growth; (b) accelerates seed and fruit formation during later stages (c) increases resistance against diseases. Examples • Calcium super phosphate Ca (H2PO4)2, Triple phosphate (NH4)2PO4H.
- 26. (iii) Potassium Fertilizers Potassium fertilizers provide potassium to the plants. Potassium is necessary for: (a) formation of starch sugar and fibrous material. (b) increasing resistance (c) root development (d) ripening of seed, fruits and cereals. Examples: Potassium Nitrate, Potassium Nitrite.
- 27. Fertilizers and Water Pollution • Nitrates and phosphates present in fertilizers when leached into water bodies like rivers, ponds, lakes, and water get polluted. • Nitrates accelerate growth of plants like weeds, algae, etc. and formation of green sludge takes place (Green Sludge Pollution). • These algae when undergo decomposition produce disagreeable smell. • These plants also decrease dissolved oxygen (DO) value and it is threatening to aquatic life. • Due to accumulation of sludge, lakes and moving water bodies are converted into swamps and marshy areas. • Water contaminated with nitrates and phosphates is unfit for drinking and is poisonous.
- 28. PESTICIDES A pesticide is a substance or mixture of substances used to kill a pest. A pesticide may be a chemical substance, biological agent (such as a virus or bacteria), antimicrobial, disinfectant or device used against any pest. What is Pest? Pests include insects, plant pathogens, weeds, mollusks, birds, mammals, fish, nematodes (roundworms) and microbes that compete with humans for food, destroy property, spread or are a vector for disease or cause a nuisance. Although there are benefits to the use of pesticides, there are also drawbacks, such as potential toxicity to humans and other animals.
- 29. Types of Pesticides There are multiple ways of classifying pesticides. Algicides or Algaecides for the control of algae. Avicidesfor the control of birds. Bactericides for the control of bacteria. Fungicides for the control of fungi and oomycetes. Herbicides (e.g. glycol phosphate) for the control of weeds.
- 30. Insecticides (e.g. organochlorines, organophosphates, carbonates, and pyrethroids) for the control of insects - these can be ovicides (substances that kill eggs), larvicides (substances that kill larvae) or adulticides (substances that kill adults). Miticides or Acaricides for the control of mites. Molluscicides for the control of slugs and snails. Nematicides for the control of nematodes. Rodenticides for the control of rodents. Virucides for the control of viruses (e.g. H5N1).
- 31. • Pesticides can also be classed as synthetic pesticides or biological pesticides (bio- pesticides), although the distinction can sometimes blur. • Broad-spectrum pesticides are those that kill an array of species, while narrow-spectrum, or selective pesticides only kill a small group of species.
- 32. Health Effects • The World Health Organization and the UN Environment Programme estimate that each year, 3 million workers in agriculture in the developing world experience severe poisoning from pesticides, about 18,000 of whom die. • Organophosphate pesticides have increased in use, because they are less damaging to the environment and they are less persistent than organo-chloride pesticides. • These are associated with acute health problems for workers that handle the chemicals, such as abdominal pain, dizziness, headaches, nausea, vomiting, as well as skin and eye problems. • Additionally, many studies have indicated that pesticide exposure is associated with long-term health problems such as respiratory problems, memory disorders, dermatologic conditions, cancer, depression, neurological deficits, miscarriages, and birth defects. • According to researchers, pesticide applicators who used chlorinated pesticides on more than 100 days in their lifetime were at greater risk of diabetes.