TRAVISTRA

 SCANNING ELECTRON MICROSCOPE It is used for the surface characterization of materials. It produces images of a sample by scanning the surface with a focused beam of electrons. It provides information about topography(surface features), morphology (shape and size), composition, and crystallographic information. PRINCIPLE The electrons interact with the atoms in the sample, producing various signals that contain information about the surface topography and composition of the sample.  The accelerated electrons in an SEM carry significant amounts of kinetic energy, and this energy is dissipated as a variety of signals produced by electron sample interactions. Backscatter electrons are incidental electrons reflected backward which provide composition data related to element and compound detection. Diffracted backscatter electrons determine crystalline structures as well as the orientation of minerals and micro-fabric, X-rays emitted from beneath the sample surface, can provide ele...

 GAS CHROMATOGRAPHY It is used for the separation as well as analysis of gaseous mixture and volatile organic compounds. Principle The components of a mixture are separated depending upon the extent of adsorption or partition of the stationary phase and at the rate at which the component is carried out by the mobile phase.  The mobile phase is a gas like Argon, Nitrogen, Helium, or hydrogen. The stationary phase may be solid or liquid. If the stationary phase consists of a solid material like silica, alumina, then chromatography is termed as Gas Solid Chromatography (GSC), and if the stationary phase is a liquid held as a thin layer on a solid support, then the technique is known as Gas-Liquid Chromatography (GLC)GSC- adsorption. GLC- partition INSTRUMENTATION  Carrier gas: It is allowed to flow through the system, carrying the sample in the vapor state through the column. It should be chemically inert, suitable for the detector employed, it should give the best column pe...

 HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY It is a method used for the separation, purification, and identification of various nonvolatile high molecular weight organic compounds and natural products like cholesterol, terpenoids. ADVANTAGES High-speed separation Excellent column separation Solvent consumption is minimum Sensitive and accurate Separation can be done at an ambient temperature. PRINCIPLE The components of the mixture are separated depending upon the extent of adsorption and partition on the stationary phase and the rate at which the component is carried by the mobile phase. The mobile phase is liquid and the stationary phase can be solid or liquid. INSTRUMENTATION Solvent reservoirs are used to collect the different solvents. Pressure pump to apply pressure  Sample injector to give the mixture which is to be separated in the analytical column Regulator to adjust the flow rate Guard column to remove the particulate matter and contaminants from the solvent. The analyt...

 THIN LAYER CHROMATOGRAPHY It is a chromatographic separation method used to separate mixtures, to check the purity of a mixture, and to monitor the progress of the reaction. Procedure A glass plate coated with a material of the adsorbent will constitute the stationary phase. The material is made into a slurry or a paste and the glass plate is coated with it by a thin layer applicator and dried. This glass plate with a thin layer of stationary phase is called chromatoplate. The mixture to be separated is applied to one end of the plate and it is placed in the solvent. When the solvent reaches near the top, it is removed and dried. If the components are colored the spots can be readily located. If the components are colorless the dried plate is sprayed with a suitable reagent to make the spot colored. In this way, the position of the components is located and their Rf values are determined. Rf value is the ratio of the distance traveled by a component to the distance traveled by the...

 COLUMN CHROMATOGRAPHY It is a technique in which the stationary phase is solid or a liquid supported by a solid. When a column is used as the adsorbent it is called adsorption column chromatography. When the solid column is acting only as a support to the liquid adsorbent then it is called partition column chromatography. SEPARATION The selection of solvent is based on the nature of the components in the mixture. Adsorption depends upon the nature of the solvent and the adsorbent.  The rate at which the components of a mixture are separated depends upon the activity of the adsorbent and the polarity of the solvent. If the activity of the adsorbent is very high and polarity is low, then separation is low but gives good separation. If the activity of the adsorbent is low and the polarity of the solvent is high, then the separation is rapid but gives poor separation PROCEDURE A proper adsorbent is selected and made a slurry with a suitable liquid and placed in a suitable tube wh...

CHROMATOGRAPHY  It is a method used for the separation, purification, and identification of a mixture of substances. It is useful when components of a mixture have similar physical and chemical properties and hence cannot be separated by other methods. Principle: It is based on the distribution of the components in a mixture between a stationary and a mobile phase. The stationary phase may be a column of adsorbent, a paper, a thin layer of adsorbent through which the mobile phase moves on. The mobile phase may be a liquid or gas. The principle of chromatographic separation is always adsorption (absorption of a constituent on the surface of the solid stationary phase) or partition (distribution of a constituent in between two liquid stationary phases). THEORY OF CHROMATOGRAPHY The separation takes place due to the differential migration of components which depends on the relative affinity towards the stationary and mobile phases.  The component which is less strongly held by th...

COVID19- DENMARK Denmark lifts all their COVID19 restriction Denmark opens their border for TRAVELERS All the covid vaccinated travelers who have EU visas can enter DENMARK Denmarks opens their borders for visitors from the world they can travel anywhere in Denmark without any restriction of covid 19. From February 19 Denmark is open for every who has got vaccinated. Denmark withdrawals all there need for social distancing, mask-wearing, and quarantine for those who tested positive for covid 19. Denmark is the first country to lift all the covid 19 restrictions. The Government of Denmark took off its digital COVID pass and the mask is only required in hospitals The Danish authorities last month the list of vaccines entering was expanded with four additional vaccines Covisheild  Covaxin Sinovac Sinopharm " Two years into the pandemic, populations in most countries have reached a high level of immunity from vaccines or natural illness " Danish epidemiologist Lone Simonsen of Un...

 DIFFERENTIAL THERMAL ANALYTICS  It is a thermal analytic technique that can be used as a fingerprint for the identification of different materials like clays, minerals, cement, etc. DTA allows the detection of every chemical and physical change whether or not it is accompanied y a change in weight. In DTA, the temperature of the samples and a thermally inert reference material are measured as a function of temperature. The differential temperature (∆T) vs the programmed temperature (T) gives the temperature at which the transition occurs and whether the transition is exothermic or endothermic.

 THERMOGRAVIMETRIC ANALYSIS It is a thermal analytic technique in which the mass of a substance is measured as a function of increasing temperature. As the temperature increases, the sample undergoes physical and chemically changed will be accompanied by mass loss.  It is used to determine a material’s thermal stability and its fraction of volatile components by measuring the weight change.  It is carried out in air or inert atmosphere such as nitrogen, helium, or Argon.  The graph obtained is known as a thermogram. It is a plot of mass vs temperature. It can provide information about physical phenomena such as vaporization, sublimation. Absorption, adsorption, and desorption. And chemical phenomena like chemisorption, dehydration, decomposition, oxidation, and reduction.  WORKING OF TGA The sample is placed in a crucible or shallow dish that is attached to an automatic recording balance and is continuously heated by the power source. The weight change of the sa...

 NMR SPECTROSCOPY  NMR depends on the absorption of energy when the nucleus of an atom is excited from its lowest energy nuclear spin state to the next higher one.  The nuclear energy levels are produced by keeping nuclei in a magnetic field. The NMR spectrum is produced by EM radiation in the radio wave frequency region (60-500MHz).  NMR spectroscopy deals with nuclei having I=1/2. The spin quantum number (I) is related to the atomic number and mass number of the nucleus. Elements with either odd mass numbers or add atomic numbers have the property of nuclear spin. Radio waves are the lowest energy form of EM radiation. This energy is too small to vibrate, rotate or excite an atom or molecule. It is sufficient to influence the nuclear spin of the atoms of a molecule.  Principle of NMR The nucleus of an atom is positively charged, when it spins it develops a magnetic field and acts like a tiny bar magnet with a magnetic moment (µ) µ= I(I+1)1/2 h/2 π  The sp...

 ELECTRONIC TRANSITION  1. σ-------> σ* transitions       An electron is excited from the bonding σ orbital to the corresponding σ* orbital. The transition energy required is very high. This type of transition occurs below 150nm. Therefore the absorption occurs in the vacuum UV region. This type of transition occurs in saturated hydrocarbons. Thus saturated hydrocarbons do not show any absorption in the UV, visible region. Therefore they are colorless and known as UV transparent compounds. 2. π------->   π* transitions     The unsaturated hydrocarbons containing double or triple bond shows this type of transition. The π ---->π* bands appear at 180-190nm in the case of aliphatic compounds and at 200-210nm in the case of simple aromatic compounds.  Eg: Ethene-190nm, 1,3-butadiene – 217nm, 1,3,5-hexatriene – 247nm, Benzene- 255nm 3. n------->    π* transitions These transitions are observed in aldehydes and ketones whi...

 U-V VISIBLE SPECTROSCOPY  UV-Vis spectrum results from the interaction of EM radiation in the UV-Vis region with atoms and molecules. The UV radiation region extends from 200nm to 400nm and the visible region extends from 500nm to 800nm. Organic compounds, inorganic compounds, and coordination compounds fall in the UV-Vis spectrum. THEORY The absorption of radiation in the UV-Vis region of the spectrum is dependent on the electronic structure of the absorbing species.  When a photon of a given wavelength interacts with a molecule it may cause a transition among the electronic energy levels if its energy matches with the difference in the energies of these levels. A given electronic energy level has a number of vibrational energy levels in it and each of the vibrational energy levels has a number of rotational energy levels in it. So along with the electronic transition, vibrational and rotational transitions also occur simultaneously. So electronic spectrum appears broad...

BEER LAMBERTS LAW   When a beam of monochromatic EM radiation is passed through an Absorbing solution of concentration (c), the rate of decrease in intensity(-dI) of radiation with a thickness of the solution (dx) is proportional to the intensity of the radiation (I) and concentration (c) of the solution. -dI/dx ∝ Ic  -dI/dx = kIc  -dI/I =kcdx Beer Lambert's law gives the linear relationship between the absorbance of EM radiation and the concentration of an absorber. A = εcL A is the absorbance c is the concentration L is the path length Ε is the molar extinction coefficient

 CATHODIC PROTECTION  It is a method of preventing a metallic object from corrosion. It is an electrochemical process in which the metal which is to be protected is forced to act as a cathode. Corrosion occurs only in the anodic area. Therefore the entire surface of the metal can be turned into a cathode, then corrosion can be prevented. In this case, corrosion is not actually eliminated but moved to a known location by adding an anode, which undergoes slow and controlled corrosion. There are two main methods of applying  cathodic protection: Sacrificial anode protection and Impressed current cathodic protection SACRIFICIAL ANODE PROTECTION In this method, the metallic structure which is to be protected is connected to a more anodic metal through a wire, so the entire corrosion is concentrated on the anodic metal, and the metallic structure is protected sacrificially. Anode metals commonly used for this are Mg, Zn, Al, and its alloys.   They are based on the position...

 CORROSION Corrosion is the destruction of metals and alloys by the chemical or electrochemical reaction with the environment.  During corrosion, metals are converted to metallic compounds at the surface and these compounds wear away as corrosion products. The corrosion of iron is known as rusting. Examples of corrosion are: Rusting of iron in the moist atmosphere form Fe2O3.2H2O Formation of basic CuCO3 (green film) on the surface of copper. The reaction of chlorine gas with Mg or Sn. Rate of corrosion It is expressed in Milligrams per year (mpy). mpy= 534W/DAT  Where W=weight loss in mg, D= the density of the material in g/cm2, A= the area of the material in sq. inch, T= exposure time in an hour. Mechanism of Corrosion They are of two types Direct chemical corrosion or dry corrosion (oxidation, corrosion due to other gases, liquid metal corrosion) and Electrochemical corrosion or wet corrosion.0 Electrochemical or WET corrosion This type of corrosion takes place when...

 LITHIUM-ION BATTERY Lithium-ion batteries are secondary rechargeable batteries.  It has an emf that varies from 3.5-4V depending on electrode potential. Construction The 3 primary components of a lithium-ion battery are: The anode is lithiated graphite (graphite in which lithium ions are inserted in between the layer of carbon atoms. The cathode is a mixed metal oxide like LiCoO2,  LiMnO2 or LiFeO2  The electrolyte is a lithium salt (LiPF6, LiBF4, or LiClO4 ) in an organic solvent. This is rechargeable. This is done by applying a higher voltage than the voltage of the battery, across the electrodes. The lithium-ion moves from anode to cathode during discharging and from cathode to anode while charging. Cell reaction Anode : LixC6  --->   6C + x Li+  + x e- Cathode : Li1-x CoO2 + x Li+  + xe ----->   LiCoO2 Overall cell reaction : LixC6 + Li1-x CoO2  ------->   LiCoO2  +6C Characteristics Depending on ...

 FUEL CELL They are electrochemical cells. It is an energy conversion device or electricity generator. ADVANTAGES Fuel cells are efficient and convert about 75%-83% of available chemical energy to electrical energy. The electrode materials are supplied in the gaseous form. Examples H2 , CO, hydrocarbons, coal gas, producer gas etc. It is light, compact, simple and easy to maintain    Whatever may be the electrode material, CO2 and H2O should be the end products. The concentration of the electrolyte remains invariant. Less green house and noise pollution. They can be stacked and connected in series to generate higher voltage without making any noise. Reduces the thermal pollution from power generation. HYDROGEN-OXYGEN FUEL CELL It is based on the reaction, combustion of H2 in O2 to form water. 2H2 +O2   ------->          2H2O       The cell consist of two electrodes made of porous graphite, impregnated with plat...

 GLASS ELECTRODE It is a secondary reference electrode that produces a constant and reproducible electrode potential. It is an ion-selective electrode used with other reference electrodes to generate a potential difference. Construction It is made up of a special glass of relatively low melting point and high electrical conductivity, in the form of a sealed glass tube filled with 0.1M HCl, a platinum wire is inserted into it, to make electrical contact. The glass electrode is represented as Pt| 0.1M HCl | Glass | H+    The H+ ion concentration inside the electrode is constant. When the electrode is immersed into a solution of unknown H+, it becomes sensitive to the outside concentration in the solution. Such a sensitivity arises because of the difference between the H+ ion concentration inside and outside.       The electrode potential of the glass rod is : EG = EG0 + 0.0591 log [ H+ ]     EG = EG0 - 0.0591 pH  The glass electrode i...

CALOMEL ELECTRODE  It is a secondary reference electrode. It consists of a glass tube at the bottom of which is kept, Hg2Cl2, and a solution of KCl. A Pt wire is dipped into the Hg layer used for making electrical contact.  The side tube is used for making electrical contact with the salt bridge. The electrode is represented as Hg| Hg2Cl2| KCl. Electrode reaction is represented as :    2Hg + 2 Cl    ---->       Hg2Cl2 + 2 e- The potential of the electrode depends upon the concentration of KCl solution.  Electrode potential if saturated calomel electrode (SCE) is 0.2422V. Determination of electrode potential (E⁰) using calomel electrode  The electrode whose potential is to be found out is connected with a saturated calomel electrode through a salt bridge internally and the emf of the cell is determined using a potentiometer. 

STANDARD HYDROGEN ELECTRODE  The standard hydrogen is an example of a glass electrode, used as a primary reference electrode whose electrode potential is fixed as zero.  CONSTRUCTION OF SHE Hydrogen gas at 1atm pressure is bubbled through a one molar H+ ions as HCl solution at a temperature of 298⁰K. Under these conditions both hydrogen as well as hydrogen ions will be in their standard state and hence the name standard hydrogen electrode.  The platinum wire makes electrical contact and it is surrounded by an outer glass tube that has an inlet for hydrogen gas at the top and a number of holes at the base for the escape of hydrogen gas. It can act as a cathode as well as an anode depending on the potential of the electrode to which it is coupled.  If the potential of the coupled electrode is less than zero (Zn, Mg, Li) reduction takes place in SHE and it acts as the cathode. If the potential of the coupled electrode is greater than zero (Cu, Ag) oxidation takes place ...