Enhancing Physics Knowledge for Teaching – Atoms and Light
In this session we shall look at how light interacts with atoms. This will enable us to determine the internal structure of atoms and also the quantum behaviour of light.
TALAT Lecture 2710: Static Design Example
Example of structure design of the industrial building developed with the Mathcad software.
FOAMCARP closed cell aluminium foam
Additions such as SiC are made to molten aluminium or aluminium alloy to modify the melt viscosity and make it suitable for foaming. Calcium carbonate is then added to the melt which is solidified to form a precursor which can be foamed in a controlled manner by a subsequent heat treatment. The resulting foam has a fine and relatively uniform cell structure.
Cu 55, Zn 45 (wt%) brass, as cast, dendritic
A cast alloy of high zinc brass, consisting of β dendrites. The α precipitates out of solution at the crystal boundaries, forming a structure of β dendrites surrounded by α. This is known as a Widmanstätten structure because a geometrical pattern of α forms on certain crystallographic orientations of the β lattice.
High magnification SEM image of open cell polyurethane foam
If a gas is injected into a liquid it forms a cellular foam structure. When a thermoset prepolymer of low viscosity is foamed, the polymer can drain from the cell walls (driven by surface tension) before it sets at the cell edges, leaving an open-celled foam. The cell edges have three concave sides, and some remnants of collapsed cell walls can be seen at the cell edges.
Fe, Ni 30, C 0.3 (wt%), quenched - martensite plates
This sample was quenched to -80 °C to give a metastable martensitic microstructure. The martensite plates show a lenticular morphology as the material attempts to shear as it transforms but is unable to open up voids at the grain boundaries. The plates form in a similar way to mechanical twins but the shear processes lead to changes in crystal structure as well as crystallographic orientation.
This sample shows the typical structure of silal, irons with high Si content (5.5-7.9 wt%). It is a grey cast iron alloyed with 4-6wt% Si to provide good oxidation resistance. The high Si content forms a dense, adherent iron silicate surface film, which is resistant to oxygen penetration. The flake graphite iron Silal was one of the first heat resisting cast irons developed. Spheroidal graphite Si irons have higher strength and improved ductility. The structure shows cored dendrites of ferrite w
Thin section of ZnO varistor
The micrograph shows structure of ZnO, containing small amounts of oxides such as Sb2O3 and Bi2O3. Thin section was produced using liquid phase sintering: gives rise to a structure consisting of conductive ZnO grains with the additional oxides being preferentially located at grain boundaries. A varistor is used to short-circuit transient high voltage spikes in electronic devices. Incorporated into circuits, in parallel with the device to be protected. Acts as an insulator below a certain breakdo
FORMGRIP closed cell aluminium foam
Additions such as SiC are made to molten aluminium or aluminium alloy to modify the melt viscosity and make it suitable for foaming. 1 to 3 wt% of pre-oxidised titanium hydride is then added to the melt which is solidified to form a precursor which can be foamed in a controlled manner by a subsequent heat treatment. The resulting foam has a relatively fine and uniform cell structure.
Cu 70, Ni 30 (wt%), cored dendrites
This alloy is typical of many copper based alloy systems. The dendrite structure shows coring (variation in solute concentration). The light areas are rich in nickel and the darker areas are low in nickel. Chill casting extracts heat quickly enough to prevent significant solid state diffusion, resulting in cored dendrites. The centres of the dendrites that cool near the liquidus temperature, are nickel rich compared to the outer layers that solidify at progressively lower temperatures. Because t
Deeply etched dendrites (cobalt samarium copper)
Using this alloy composition, a relatively low volume fraction of pro-eutectic dendrites are formed. The eutectic material between these dendrites can be etched away to reveal the three-dimensional structure of dendrites. The dendrite tips are a volume of revolution, and anisotropy develops behind them with the secondary dendrite arms.See R. Glardon, W. Kurz, "Solidification path and phase diagram of directionally solidified Co-Sm-Cu alloys", J. Cryst. Growth, 51 (1981) 283-291.
Zn, cold rolled - mechanical twins
This sample was cold rolled. Zinc has a hexagonal structure so it contains only two independent slip systems. However, for slip to occur, five slip systems are required so zinc does not undergo general plasticity. Instead it forms mechanical twins as an alternative to dislocation motion to accommodate the deformation.
Anisotropic quartz rotated between crossed polarisers
Anisotropic quartz rotated through 180° between crossed polarisers. The intensity of light transmitted through the analyser varies as a function of the angle of rotation of the quartz sample in the plane of the filters. At certain orientations, no light is transmitted. These "extinction positions" are found at 90° intervals. From TLP: Atomic Scale Structure of Materials, http://www.msm.cam.ac.uk/doitpoms/tlplib/atomic-scale-structure/index.php
ChemTube3D contains interactive 3D animations and structures, with supporting information for some of the most important topics covered during an undergraduate chemistry degree including organic structure and bonding, organic reaction mechanisms, solid state inorganic materials and polymers.
Largest reservoir in U.S. drops to historic lows
Lake Mead, the largest reservoir in the U.S., provides stark visual evidence of the western United States' ongoing drought, as the waterline drops to a historic low. Nathan Frandino reports. Subscribe: http://smarturl.it/reuterssubscribe More updates and breaking news: http://smarturl.it/BreakingNews Reuters tells the world's stories like no one else. As the largest international multimedia news provider, Reuters provides coverage around the globe and across topics including business, financia
Roll-bonded aluminium alloy diffusion couple in the as-rolled condition.
This micrograph shows the grain structure of a roll-bonded aluminium alloy diffusion couple in the as-rolled condition. The upper half of the couple is Al-0.5Fe-1.0Mn (wt.%), the lower half is Al-1.0Si (wt.%). Rolling heavily deforms the microstructure, producing thin, elongated grains parallel to the roll-bonded interface.The Barker's etch produces a thick oxide layer on the grains of aluminium (anodising). When viewed in cross-polarised light, interference in the oxide layer produces colours w
Roll-bonded aluminium alloy diffusion couple annealed for 60 minutes at 600°C.
This micrograph shows the grain structure of a roll-bonded aluminium alloy diffusion couple annealed for 60 minutes at 600°C. The upper half of the couple is Al-0.5Fe-1.0Mn (wt.%), the lower half is Al-1.0Si (wt.%). Annealing has recrystallised the microstructure. The Al-Fe-Mn alloy has many intermetallic particles (the dark phase). These help create recrystallisation nuclei, hence this alloy has a high density of small grains relative to the Al-Si alloy.The Barker's etch produces a thick oxide
As-cast wrought-grade aluminium alloy
The micrograph shows Al-Mg-Fe-Si containing < 1wt.% of each solute. Addition of TiB2 particles facilitates the formation of a fine, equiaxed grain structure (grain refinement). This micrograph illustrates one of the possible growth morphologies that a solidifying metal can adopt (c.f. micrograph 711). The grains in this structure exhibit no dendritic branching, i.e. the solid-liquid interfaces of the growing grains are smooth. When a solid grain is growing from the liquid phase, it will initiall
Theories and concepts
This is a module framework. It can be viewed online or dowloaded as a zip file As taught in Autumn Semester 2009/10 The War on Iraq and the US and British invasion of the country in 2003 has led to huge tensions in geopolitics. At the same time, the supposed ‘threat’ of international terrorism and continuing financial turmoil in the world economy have both brought to the fore the global politics of co-operation and confrontation. Whilst it might be possible to agree on the significance of th
IN718 nickel-based superalloy held for 6 hours at 850°C
IN718 is a nickel-based superalloy composed of approximately 53 wt% Ni, 19 wt% Fe, 18 wt% Cr, 5 wt% Nb, and small amounts of Ti, Mo, Co, and Al. The alloy has a number of distinct phases present in its microstructure. These are namely the matrix, γ, and the precipitates, γ', γ'', and δ. The primary strengthening phase is γ'' , the composition of which is Ni3Nb. It has a body-centred tetragonal structure, and forms semi-coherently as disc-shaped platelets within the γ matrix, having thre