Zone melting is a technique for purifying materials by melting and re-solidifying sections called zones. It was developed in the 1950s to purify germanium for transistors. Zone melting involves moving a heated zone down a rod to selectively melt and re-solidify sections, leaving impurities behind in the liquid. Multiple zone passes are needed to achieve high purity. Factors like zone size, heating rate, and stirring affect the purification process and properties of the purified material.
Zone refining, melting and leveling in crystal growthSum K
Zone refining, melting and leveling in crystal growth is an important process in extractive metallurgy for manufacturing of ultra pure materials with wide ranging applications in semiconductor material synthesis, single crystal growth etc.
Synthesis and characterization of nano tio2 via different methodshena78
Titanium Dioxide nanoparticles are the ultra fine particles Particles of titanium dioxide (TiO2) have the diameters less than 100 nm. It is believed to be one of the three most produced nanomaterials , along with silicon dioxide nanoparticles and zinc oxide nanoparticles.
A key vacuum deposition technique for making highly homogenous and high-performance solid-state thin films and materials is Chemical vapor deposition. The types of CVD systems and their key applications would also be discussed in this presentation. It is a key bottom-up processing technique, widely used in graphene fabrication, also the fabrication of various oxides, nitrides is possible, with this technique.
Zone melting is a key technique for single crystal growth fabrication. Zone melting is a group of techniques used to purify an element or compound and control its composition. This presentation will discuss the basics of the zone melting technique and with help of 2-3 research papers, the examples of zone melting would be explained. Single crystal growth is a quite useful technique used in various applications in the field of metallurgy as well as nanomaterials synthesis. The technique is used for the removal of unwanted impurities from the material, control the discontinuities in impurity distribution, and also maintaining uniform doping of the impurity in the material.
Zone refining, melting and leveling in crystal growthSum K
Zone refining, melting and leveling in crystal growth is an important process in extractive metallurgy for manufacturing of ultra pure materials with wide ranging applications in semiconductor material synthesis, single crystal growth etc.
Synthesis and characterization of nano tio2 via different methodshena78
Titanium Dioxide nanoparticles are the ultra fine particles Particles of titanium dioxide (TiO2) have the diameters less than 100 nm. It is believed to be one of the three most produced nanomaterials , along with silicon dioxide nanoparticles and zinc oxide nanoparticles.
A key vacuum deposition technique for making highly homogenous and high-performance solid-state thin films and materials is Chemical vapor deposition. The types of CVD systems and their key applications would also be discussed in this presentation. It is a key bottom-up processing technique, widely used in graphene fabrication, also the fabrication of various oxides, nitrides is possible, with this technique.
Zone melting is a key technique for single crystal growth fabrication. Zone melting is a group of techniques used to purify an element or compound and control its composition. This presentation will discuss the basics of the zone melting technique and with help of 2-3 research papers, the examples of zone melting would be explained. Single crystal growth is a quite useful technique used in various applications in the field of metallurgy as well as nanomaterials synthesis. The technique is used for the removal of unwanted impurities from the material, control the discontinuities in impurity distribution, and also maintaining uniform doping of the impurity in the material.
Rosa alejandra lukaszew a review of the thin film techniques potentially ap...thinfilmsworkshop
SRF is a surface phenomenon where only ~10 penetration depths are needed (l=40 nm for niobium), thus it has been recognized for some time now that it would be economically convenient to use thin film coated cavities. But problems arise with defects within 1 or 2 l of the surface or on the surface, and insufficient attention has been paid to this topic, including trapping of impurities like oxygen in defects as well as surface roughness enabling magnetic field pinning sites. Earlier attempts at CERN applied standard sputter PVD methods, but the grain size for the CERN Nb/Cu films was 100 nm, which is 10,000 times smaller than for conventional SRF cavities with the ensuing problems that appear at grain boundaries. Thus, these prior attempts showed higher surface resistance and worst Q-slope than bulk. I will review more modern approaches using higher energetic PVD methods for thin film deposition which offer promise to achieve thin films with improved superconducting performance.
Furnaces in Refinery and Petrochemicals
Process furnaces
Crude distillation unit
Reaction Heaters
Reformer Heater
Heater Performance objectives
Reasons to save Energy
Heater Types
Radiant section
Convection section
Crossover section
Burners
Centrifugal Pump
Type of pumps
Centrifugal Pump working
Centrifugal Pump calculation
How to choose pump
Characteristics curves
Pump head compensation
Cavitation and NPSH
Priming
Multi stage centrifugal Pump
Pump safety
Effluent Treatment Plant
What is ETP
Need fo ETP
Design of ETP
Design of ETP
Sludge treatment process
Flowchart of ETP
Case study of ETP
ETP plant operation
Textile plant ETP
Equalization
Sedimentation
Settlers
Sludge treatment process
Flowchart of ETP
Case study of ETP
ETP plant operation
Textile plant ETP
Equalization
Sedimentation
Settlers
PH adjustment
Rotating equipment maintenance.
PUMPS
COMPRESSORS
AGITATORS
FANS / BLOWERS
TURBINES
VACUUM PUMPS
VALVES
Type of Seals
Stuffing
SINGLE MECHANICAL SEAL Pusher Type
Bellows Mechanical Seal
Double Mechanical Seal
STEAM TRAPS
Steam trap is a type of automatic valve that filters out
condensate (i.e. condensed steam) and non-condensable gases
such as air without letting steam escape.
Steam ejector working principle
An ejector is a device used to suck the gas or vapour from the desired vessel or system. An ejector is similar to an of vacuum pump or compressor. The major difference between the ejector and the vacuum pump or compressor is it had no moving parts. Hence it is relatively low-cost and easy to operate and maintenance free equipment.
Piping and Instrument Diagram
Piping and Instrument Diagram Standard Symbols Detailed Documentation provides a standard set of shapes & symbols for documenting P&ID and PFD,
including standard shapes of instrument, valves, pump, heating exchanges, mixers, crushers, vessels, compressors, filters, motors and connecting shapes.
Permit To Work
Types of Permit To Work
Hot Work Permit
Confined Space Entry Permit
Electrical Permit
Excavation Permit
Radiography Permit
Crane Critical Lifts Permit
Man Basket Operation
Permit Issuer Responsibilities
Permit Receiver Responsibilities
HSE Permit Coordinator
Responsibilities
Revalidation of the Permit
Work Permit Flow Chart
Heat exchangers
TUBE AND SHELL
PLATE HEAT EXCHANGER
FLOW OF ARRANGEMENT
REGENERATIVE HEAT EXCHANGER
log mean temperature difference (LMTD)
Number of Transfer Units (NTU) Method
EFFECTIVENESS OF HEAT EXCHANGER
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
Forklift Classes Overview by Intella PartsIntella Parts
Discover the different forklift classes and their specific applications. Learn how to choose the right forklift for your needs to ensure safety, efficiency, and compliance in your operations.
For more technical information, visit our website https://intellaparts.com
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
6th International Conference on Machine Learning & Applications (CMLA 2024)ClaraZara1
6th International Conference on Machine Learning & Applications (CMLA 2024) will provide an excellent international forum for sharing knowledge and results in theory, methodology and applications of on Machine Learning & Applications.
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
2. Introduction
• Zone melting is a technique for
purification by melt
crystallization.
• developed in the early 1950s at
Bell Telephone Laboratories in
response to the need for extremely
pure germanium by William
Pfann. It was an essential step for
the development of the transistor
and thus for the entire electronics
revolution.
• Before that time, purification was
carried out by normal freezing,
also called progressive freezing.
3. • Zone melting also known as Zone refining can be applied to the
purification of almost every type of substance that can be melted and
solidified, eg, elements, organic compounds, and inorganic compounds.
Because the solid–liquid phase equilibria are not favorable for all
impurities, zone refining often is combined with other techniques to
achieve ultrahigh purity.
• The high cost of zone refining has thus far limited its application to
laboratory reagents and valuable chemicals such as electronic materials.
The cost arises primarily from the low processing rates, handling, and high
energy consumption owing to the large temperature gradients needed.
4. Zone melting
• Zone of mass mz moves a short distance in such a manner that the mass dm of solid is frozen
out and an identical mass melts into the zone. For the first zone pass, it is assumed that the rod
is initially at uniform composition wo to obtain the following:
• For constant k = ws/wl , this may be integrated to yield:
• m/mz is approximately the number of zone lengths down the rod.
5. • With subsequent zone passes, back-mixing becomes increasingly significant.
• The number of zone passes required to approach the ultimate distribution is about
twice the number of zone masses in the rod for small effective distribution
coefficients. Thus, longer zones permit the attainment of the ultimate distribution
sooner. On the other hand, the attainable separation increases as the zone size
becomes smaller (permitting less back-mixing).
• The equations in the previous slide is based on the assumption that there is no
varying distribution coefficient k, eutectic-forming phase behavior, varying mass
mz of zone, and solid-state diffusion.
• Now for nonideal separations a steady-state fictitious stagnant-film treatment may
be employed to arrive at an effective distribution coefficient,
6. where k is the equilibrium distribution coefficient,
δ is the film thickness,
V the linear freezing rate,
ρs the density of the solid,
D the binary diffusion coefficient in the melt, and
ρl the density of the liquid.
The film thickness δ is related to the mass-transfer coefficient kc and the
Sherwood number Sh by
7. • As the zone-travel rate is increased, a
breakdown of the freezing interface
from smooth to dendritic is eventually
observed. Dendrites are treelike
structures that trap melt and
dramatically reduce separation. The
onset of interface breakdown is
predicted by the elementary theory of
constitutional supercooling.
• k< 1 causes impurity to accumulate in
the melt at the freezing interface,
thereby lowering the freezing point.
Thus, the actual temperature may be
below the melting point for some
distance into the melt, even though the
two are identical at the freezing
interface. This is known as
constitutional supercooling because it is
brought about by a change in
constitution or composition
Constitutional supercooling. (a) impurity concentration profile during
solidification; (b) actual temperature T and
equilibrium freezing temperature Te during solidification.
8. • At the onset of constitutional supercooling, the melting-point gradient
exceeds the temperature gradient. Equating these gradients leads to the
criterion for constitutional supercooling:
• where G is the imposed interfacial-temperature gradient and ∂Te/∂wi is the
slope of the liquidus on the phase diagram
• the tendency toward constitutional supercooling increases as the freezing
rate V increases, the temperate gradient G decreases, the impurity content w
increases, the separation (ws − wi) between liquidus and solidus in the
phase diagram increases, and the stirring decreases (δ increases).
9. Float zone melting
• Zone refining with electrical heating coils
did not work for substance like silicon
which melts at high temperature (1415°C).
• Beginning in 1952, Bell Labs chemist
Henry Theurer developed a variation on
this technique called float-zone refining in
which a rod of silicon clamped at both ends
passes vertically through a heating coil. The
small molten segment remains fixed in
place between the solid portions of the rod
due to surface tension. Using steam refining
to remove the most stubborn impurities,
such as boron, he produced silicon with
impurity levels below one part per billion in
early 1955. The process was developed
independently at two other laboratories; by
P. H. Keck and M. J. E. Golay, at the U. S.
Army Signal Corps, Fort Monmouth, NJ
and by R. Emeis working under the
direction of Eberhard Spenke at Siemens in
Pretzfeld, West Germany.
10. Stirring
• For maximum purification, the zone should move as slowly as possible, the sample
should be many zone lengths long, the melt should be stirred, and more zone passes
should be made than several times the number.
• Stirring is essential to maximize the rate of purification, and the travel rate V should
be adjusted in such a way that δV/D ≈ 1
• Stirring increases optimal zone travel rate by lowering film thickness and aids
significantly in removal of foreign particles.
• Stirring can be done by rotating the tube along its axis. Vigorous stirring can be
provided when the crucible is spun rapidly, suddenly stopped, spun rapidly, etc
• Induction heating also causes vigorous convection because of the spatially varying
average force field imposed along the melt surface.
• transverse rotating magnetic field or passage of electric current axially with a
transverse magnetic field, oscillators, ultrasonic vibrators etc can also be used for
stirring
11. Containers
• Ideal containers for zone melting should not contaminate the melt nor be damaged
by the melt.
• Containers for different substances:-
For organic materials: borosilicate glasses, metals, fluorocarbon, and other
polymers.
For metals and semiconductors: fused silica is ideal.
sometimes the substance sticks to glass and causes break. This is prevented by
coating the inside of vessel with film of carbon, deposited by passing acetone vapor
through glass tube at 700 C. but at high temperature such coating may result in
contamination with carbon or silicon.
For metals like Al with high free energy oxidation: it reacts with silica glass, so use
oxide container of higher free energy of formation like alumina, zirconia and boron
nitride.
high melting inorganic salts: treated in noble metal containers like platinum,
rhodium, and irridium. Also refractory containers like graphite, molybdenum,
tungsten have been used.
Low melting salts: fused silica.
Container shape: tube, horizontal boat, horizontal boat with a tilt.
horizontal boat with tilt reduces back mixing in subsequent passes and is not
feasible if substance is volatile.
12. Heating and Cooling
• Heat must be applied to form the molten zones, and this heat much be removed
from the adjacent solid material. In principle, any heat source can be used,
including direct flames.
• However, the most common method is to place electrical resistance heaters around
the container. In air, nichrome wire is useful to heat up to 1000◦C and platinum-
rhodium alloys to 1700◦C. In an inert atmosphere or vacuum, molybdenum,
tungsten, and graphite can be used to well over 2000◦C.
• Conductors can be heated to very high temperatures by induction heating wherein
the sample is surrounded by a water-cooled coil carrying high current at high
frequencies. A frequency of 450 kHz is typical for good conductors with a diameter
>1 − 2 cm. Floating-zone melting requires frequencies of several MHz.
• Molten zones are also formed by radiant heating. The light source may be focused
carbon arcs, xenon lamps, sunlight, or lasers. Very high temperatures have been
achieved with all of these. For example, sapphire has been float-zoned in this
manner, at over 2000◦C.
13. • An electron beam can be used for floating-zone melting of a conducting rod.
• Electric heaters have also been directly immersed in the molten zone.
• It is important to control temperature and power input of the heaters. A fluctuating
heat input leads to a fluctuating freezing rate, thereby reducing separation. It can
also cause breakage of the container because ρl ≠ ρs .
• Heat is often removed by simply allowing it to escape by convection, radiation, and
conduction. However, such uncontrolled escape can lead to very large temperature
fluctuations. It is better to surround the entire container, heaters and all, with a
controlled-temperature cooled chamber. Even then, buoyancy-driven free
convection from the ampul can lead to small temperature fluctuations. Jets of air or
cooling water applied directly onto the ampul adjacent to the heater have been
employed.