AS/A Level Chemistry (A) specimen question papers and mark
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THE RISE OF GRAPHENE A.K. Geim and K.S. Novoselov
... thinnest flakes are found. A similar approach was tried by other groups (earlier35 and independently22,36) but only
graphite flakes 20 to 100 layers thick were found. The problem is that graphene crystallites left on a substrate are
extremely rare and hidden in a “haystack” of thousands thick (graph ...
The Chemistry and Applications of Metal
... which revealed 61% porosity and a BrunauerEmmett-Teller (BET) surface area of 2320 m2/g
(2900 m2/g Langmuir). These values are substantially higher than those commonly found for zeolites and activated carbon (14).
To prepare MOFs with even higher surface
area (ultrahigh porosity) requires an increas ...
purdue university - IUPUI ScholarWorks
... Three parts consist of my thesis work centered on the synthesis of inorganic
phosphates and then metal organic frame work (MOF). The first part is the synthesis of
mesoporous chromium phosphates using the room temperature solid state reaction (SSR)
approach. One of the major aims of this work is to ...
New Visible-Light Active Semiconductors
... photocatalysts, among others. In particular, oxides with perovskite structure formed
by TaO6 or NbO6 octahedra layers have shown the capability to develop an
important catalytic activity have reported photocatalytic activity in tantalates and
niobates of the type NaMO3 (M ¼ Ta and Nb) for the stoich ...
... A LEVEL CHEMISTRY Specimen Assessment Materials 3
Thermal Decomposition of Polymers - Marcelo Hirschler
... chemical changes when heat is applied; this will usually
result in undesirable changes to the properties of the
material. A clear distinction needs to be made between
thermal decomposition and thermal degradation. The
American Society for Testing and Materials’ (ASTM) definitions should provide help ...
... temperatures 4530 - 5430°F (2500 - 3000°C). Under these conditions amorphous carbon
transforms to crystalline graphite. Primary synthetic graphite has a high purity: more than 99.5%
Secondary synthetic graphite. Secondary synthetic graphite is recovered from machining
operations of grap ...
Structure and Properties of Polymers
... macromolecule, it can become a trifunctional branch point because three chains can
emanate from it. Similarly, a monomer molecule containing two double bonds or four
functional groups capable of condensation can give rise to a tetrafunctional branch point
in a forming macromolecule because four chai ...
Multiwalled Boron Nitride Nanotubes: Growth, Properties, and
... deformation in BNNTs was predicted through first-principles pseudopotential
density-functional calculations. In zigzag BN nanotubes, radial deformations due to
transverse pressures of about 10 GPa decrease the direct band gap of BNNTs from
5 to 2 eV, allowing for optical applications in the visible ...
A Review of using Spray Pyrolysis through Sol-gel
... would be NH4·H2PO4.34,35 Two synthesis routes following the
sol-gel process were discussed to show that the pure olivine
structure could be formed regardless of the different starting
materials. The first method involved dissolving stoichiometric
amounts of Li (OH)·H2O, FeC2O4·2H2O and NH4·H2PO4 rea ...
Synthesis and Characterization of Amorphous and Hybrid Materials
... which a charged catalytic species, for example an OH- nucleophile or H3O+ electrophile, is
attracted to or repelled from potential reaction sites, depending on their charge. The
availability of labile protons determines whether anions or cations are solvated more
strongly through hydrogen bonding. B ...
Prohibited and Restricted Materials
... This publication provides an overview of Cummins’ position and standards on Prohibited and Restricted Materials in our processes
and products. In this context the term “materials” refers generically to elements, compounds and chemicals. There are many
existing and emerging local and regional regulat ...
Non-native transition metal monoxide nanostructures
... crystal formation energy, which stabilizes an unstable phase of the
nano-structured materials and dominates all of their physicochemical
properties.11–14 Importantly, thermodynamically unstable phases can
be stabilized by coupling the excess surface energy of nanomaterials
with careful control of ki ...
... renewed, this eliminates the poisoning effect.
Mercury forms amalgams (solid solution) with many metals.
The diffusion current assumed a steady value immediately
after each change of applied potential and is reproducible.
The large hydrogen over-potential of mercury renders
possible deposition of ...
Electrical Effects and Devices/Dielectrics and Insulators
... The characterization of dielectric materials must be carried out in order to determine their properties for
various applications over different parts of the electromagnetic frequency spectrum. There are many techniques
and methods available for this purpose that are too numerous and detailed to atte ...
comparison of candidate materials for seasonal storage of solar heat
... (Thermo Chemical Material) storage system. Of
these subsystem models, the TCM storage system is
the most complicated one. It consists of two chemical
reactors with heat exchangers for the reaction
C + heat ⇔ A + B and a separate material buffer for
each of the three reactants.
By using the configura ...
Physical Properties of Food Materials
... and is expressed in units of mass per unit volume. Materials consisting of particles or
grains with interstitial air spaces have different values of particle density and bulk
density. Materials without internal air spaces, such as fluids and solids, have equal
particle and bulk density. Particle den ...
Rapid Microwave Synthesis, Characterization and Reactivity
... Powder X-ray diffraction (PXD) was conducted using a Bruker D8 diffractometer (Bruker
Corporation, Billerica, MA, USA, Cu Kα source) or a PANalytical X’Pert Pro MPD powder
diffractometer (Cu Kα1 source) in capillary mode. The air-sensitive samples were ground into fine
powders and placed in 0.5 mm d ...
Transition metals and coordination chemistry
... The Concept of Coordination Numbers
The concept of coordination numbers was an important result of Werner's
research. It clearly established the two most important aspects that are
required to discuss chemical structure and change:
oxidation state and coordination number.
The concept of oxidation s ...
Design of Thermal Interface Material With High Thermal Conductivity
... Th and Tl, respectively. Therefore, thermal resistance R and thermal impedance of a specimen will be calculated by Eqs. 共2兲 and
2.2 Thermal Interface Material. A TIM usually consists of
thermally conductive fillers and a matrix. Fillers transfer heat rapidly, while the matrix f ...
chm 434f/1206f solid state materials chemistry
... • Single crystal (SC) that has been defect modified
with dopants - intrinsic vs extrinsic, nonstoichiometry - is the way to control the chemical
and physical properties, function and utility
• SC preferred for structure and properties
Thermoelectric materials show the thermoelectric effect in a strong or convenient form.The thermoelectric effect refers to phenomena by which either a temperature difference creates an electric potential or an electric potential creates a temperature difference. These phenomena are known more specifically as the Seebeck effect (converting temperature to current), Peltier effect (converting current to temperature), and Thomson effect (conductor heating/cooling). While all materials have a nonzero thermoelectric effect, in most materials it is too small to be useful. However, low-cost materials that have a sufficiently strong thermoelectric effect (and other required properties) could be used in applications including power generation and refrigeration. A commonly used thermoelectric material in such applications is bismuth telluride (Bi2Te3).Thermoelectric materials are used in thermoelectric systems for cooling or heating in niche applications, and are being studied as a way to regenerate electricity from waste heat at electric power plants.