Tasks on Particles Process - Assignment Example

Assignment tasks on particles process University Affiliation Student’s Name Date Q1. Type 1 isotherms In this type, adsorption is restricted to the completion of a single monolayer of the adsorbate at the adsorbate surface. Isotherms of this type also are observed for the adsorption gases which are on microporous solids and whose size of pores, are not that much larger than molecular diameter of the adsorbate. In this case, completion of a monolayer is achieved when these narrow pores are filled. Fig: type 1 isotherms Type 2 isotherms Unlike type 1, these isotherms do not exhibit a saturation limit. It is characterized by indefinite formation of of multilayer after its completion of monolayer and is usually found in adsorbents having a wide pore size distribution. Fig: type 2 isotherms Type 3 Isotherms in this section is attained when the quantity of adsorbed gas increases without a limit as its saturation approach unity. Usually obtained when bromine is adsorbed on silica gel at about 20 deg. Celsius Fig: type 3 isotherms Type 4 It shows a finite multilayer formation which correspond to complete filling of the capillaries and is a variation of type 11. The adsorption is seen to terminate near to a relative pressure of unity. This isotherm type is usually achieved by the absorption of H2O vapour on activated carbon. Fig: showing type 4 isotherms Type 5 This type is a similar variation of type 3 and is usually obtained when water vapour gets adsorbed in activated carbon at 100 deg. Celcious Fig: type 5 isotherms . Q2 (a) For range 25 to 30, f(x)=40/sum where, sum=40+25+20+15=100 Therefore f(x)=40/100=0.4 Average values of size= 27.5,35,50, and 80 respectively. Total=192.5 fv(x)=27.5/192.5=0.143 For range 30 to 40; f(x)=25/100=0.25 fv(x)=35/192.5=0.182 Range 40 to 60; f(x)=20/100=0.2 fv(x)=50/192.5=0.260 Range 60-100 f(x)=15/100=0.15 fv(x)=80/192.5=0.416 Mean sizes x1,0, x4,3.= 27.5,35,50, and 80 respectively (b) The figure below represents the cooling of a substance from the liquid to solid through a eutectic point. Point A represents the clear solution and at this point the nucleation rate will be lower since the solid is not stable. Point B represents the dust contaminated solution and here solid and liquid are both stable so there is no driving force for solid. Part D, in this case, represents the crystal-seeded solution and here, liquid phase is unstable therefore nucleation rate will be faster of all the solutions c) Q3. Proton exchange membrane It is a membrane (semi-permeable) that comprises of ionomers and is designed to conduct protons at the same time being impermeable to gases such a hydrogen or oxygen. They are usually incorporated to proton membrane electrolyser, membrane electrode assembly (MEA) of a PEMFC or used transport of protons, as well as separation of reactants. These PEMs can be manufactured from either pure or composite membranes. Electrical double-layer capacitors They are special types of electrochemical capacitors. Unlike most capacitors, they do not have the usual dielectric. Of all the capacitors, the double-layer capacitors have the highest capacitance values per unit volume and also the greatest energy density. The high capacitance values of these capacitors ( up to 10000 times the value of electrolytic capacitor) act as a form of a battery. However, the capacity of a battery is still high. Due to their properties, these types of capacitors are applied in, memory backups and power electronics. Lithium-ion battery It is a rechargeable type battery its working involves movement of lithium ions from the negative to the positive electrode. Lithium-ions are divided into categories and are described below; Lithium Cobalt Oxide (LiCoO2) It is a common type battery has a high specific energy offering a longer lasting time and is usually used in mobile phones, digital cameras and laptops. The cathode consists of a layered structure and at the instance of discharge, lithium ions move from anode to the cathode. This process is reversed during charging. These batteries can only be charged and discharged at the rated capacity. Lithium manganese oxide This cell consist lithium manganese oxide which is the cathode material. Its architecture assumes a three dimensional spinnel structure which aids at improving ion flow in the electrode resulting in a lower internal resistance. This reduced internal resistance improves current handling. Lithium ion phosphate This cell type has phosphate as the cathode material. lithium phosphate usually offers good electrochemical performance having a low resistance. This is achieved due the nano-scale phosphate cathode. These batteries offer some advantages which include; excellent thermal stability, enhanced safety, high current rating and a longer cycle (Crabtree, R. H, 2010). Dye sensitised solar cell This is a low-cost solar cell and belongs to the group thin film solar cells. Unlike other glass based solar cells, these type of cell is semi-flexible and also semi-transparent. These unique features makes it easily produced in the normal roll printing techniques. A modern DSSC is made up of a porous layer, usually of titanium dioxide nanoparticles and are covered with a molecular type dye that absorbs sunlight in a similar way as in a plant’s chlorophyll. The titanium dioxide which is immersed in an electrolyte also has a platinum-based catalyst. Like in conventional alkaline batteries, the cathode (platinum) and the anode (the titanium dioxide) are fitted on either side of the electrolyte. When sunlight passes through the transparent electrode, and into the dye layer electrons are excited and flow into the titanium dioxide. Once these electrons are fed into an external load, they are re-introduced back to the cell by means of a metal electrode usually located at the back and flows back to the electrolyte. The electrolyte then transports them to the dye molecules (Kalyanasundaram,2010). Q4 . Due to the large surface areas and good electrical and thermal conductivity with good mechanical and chemical stability, nanoporous carbons(NPCs) are used for storage devices. Their performance are usually determined to electrical double layer characteristics of the porous carbon electrodes. Electrical charge is usually stored in the double layer, and the storage is usually by means of electrostatic interactions. Optimization of the pore characteristics and carbon material allows achieving the best association of power density and energy. Basically, the capacitance of these capacitor type is dependent mainly on the surface area of carbon material used. LI-ION A lithium-ion battery has a series of cells which produce electricity. Each of these cells has a cathode, anode and electrolyte. When there is a connection between the anode and cathode is introduced, electrons will flow from the anode to cathode via the wire. An electric current is thus created, and the electrolyte will be conducting positive current in the form of positive ions. The storage of power is possible since the cathode and anode materials such a=that the anode donate electrons while the cathode accepts. The difference between potentials of the anode and cathode is what determines the voltage of the cell. Q5. Fig: graph of p/a against p at 85deg.celcious From the graph; Slope=192.3077-67.79661/250-80=0.73 y-intercept is 6.04 to find am we use the relation S=1/ am Where, S is the slope. Therefore, am =1/S=1/0.73=1.37 The surface occupied by molecule m is given as 55A^2 Therefore, the specific surface area S= am x N x m =1.37 x 55A^2 x 6.023 x10^23 S=4.54 X10^25 A^2 Fig: graph of p/a against p for 150 oc From the graph, slope=0.9158 Y-intercept=32.036 But the specific surface area S=4.54 X10^25 A^2= am x N x m But am =1/s=1/0.9158=1.0919 Therefore, 4.54 X10^25 A^2= 1.0919x 6.023 x10^23 x m m =69.0335 A^2 Q.6 Fig. BET plot Slope=0.004398-0.001471/0.45-0.15=0.00976 Y-intercept I=0 But Vm =1/S+I=1/0.00976+0=102.459 Specific surface area is usually given by; SBET =Vm*N* Am x10^-20/2214=102.459x 16.2 A^2 x10^-20/2214 Therefore References Brain, Marshall. 'How Lithium-Ion Batteries Work - Howstuffworks'. HowStuffWorks. N.p., 2015. Web. 7 Apr. 2015. Chemistrylearning.com,. 'Adsorption Isotherm And Its Types | Chemistry Learning'. N.p., 2015. Web. 7 Apr. 2015. Crabtree, R. H. (2010). Energy production and storage: Inorganic chemical strategies for a warming world. Chichester, West Sussex, U.K: Wiley. Kalyanasundaram, K. (2010). Dye-sensitized solar cells. Boca Raton, Fla: CRC Press Protonex.com,. 'Protonex | Technology | Fuel Cell | Protonex'. N.p., 2015. Web. 7 Apr. 2015. Read More