Quiz in ECE 322 Nano-Ceramics Sean Clarvin Andor 3ECE-D Department of Electronics Engineering Faculty of Engineering

Quiz in ECE 322
Nano-Ceramics

Sean Clarvin Andor
3ECE-D

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Department of Electronics Engineering
Faculty of Engineering, University of Santo Tomas
España, Manila, Philippines
[email protected]

Abstract— In this research paper, the researcher presented the
concepts and applications of ceramic nanoparticles or Nano-
ceramics including its environmental impact and health hazard.
The organization of the discussion provides an extensive
explanation on how, why, when, and what questions about the
topic. From the developmental history to its composition and
material properties and its application in biomedical field is
discussed in the paper. At the last section of the paper, the
biological hazard of using and production of nanomaterials, in
general, provides explanation on different ways on how the
exposure of nanomaterials can affect an individual.

Index Terms –Ceramics, Nanotechnology, Nano-ceramics

I. INTRODUCTION

A ceramic is an inorganic non-metallic solid made up
of either metal or non-metal compounds that have been shaped
and then hardened by heating to high temperatures. The
properties of such materials are hard, corrosion-resistant and
brittle. A senior research scientist with Industrial Research
Limited, Dr. Ian Brown, explains that the term ‘ceramics’ has a
more extensive meaning today. The origin of the word
'Ceramic' comes from the Greek word meaning ‘pottery’. The
clay-primarily based domestic wares, artwork items and
building merchandise are acquainted to us all, but pottery is
simply one a part of the ceramic world. In recent times the term
‘ceramic’ has more meaning and consists of materials like
glass, advanced ceramics and a few cement systems as well.

Traditional ceramics are clay–base. The composition
of the clays used, kind of additives and firing temperatures
decide the character of the end product. Advanced ceramic
substances these days are properly established in lots of regions
of regular use, from refrigerator magnets to a growing variety
of industries, inclusive of metals production and processing,
aerospace, electronics, automotive and employee’s safety.
Manufacturing processes firstly contain thoroughly mixing the
very fine constituent material powders. The high temperature
permits the tiny grains of the individual ceramic additives to
fuse collectively, forming a tough, hard, durable and corrosion-
resistant product. 1

It has been well established that the majority behavior
of materials can be dramatically altered when made out of
nanoscale building blocks. Mechanical, magnetic, optical, and
different characteristics of substances have been discovered to
be favorably affected. Hardness and strength, for instance, can
be significantly more advantageous through consolidating
ceramic materials from nanoscale particles. Ductility and
superplastic-forming abilities of nanophase ceramics have now
end up viable, leading to new processing routes as a way to be
more price-effective than traditional techniques. exceptional
development in synthetic chemistry has caused significant
advances in material science, making viable the synthesis of
numerous substances and materials. The manufacture of
ceramics includes heat treatment of tightly squeezed powders.
The scale of the building block of those powders has been
discovered to have an effect on the properties of the final
product. The technique of preparation is very often a
determining element in shaping the material and its properties.
2

Ceramic nanoparticles are generally made from
oxides, carbides, phosphates and carbonates of metals and
metalloids which includes calcium, titanium, silicon, and many
others. They have a huge variety of applications due to a lot of
favorable properties, including high heat resistance and
chemical inertness. Out of all of the regions of ceramic
nanoparticles applications, biomedical field is the most
explored one. within the biomedical field, ceramic
nanoparticles are taken into consideration to be outstanding
carriers for pills, genes, proteins, imaging agents and so on.
Deciding on a suitable approach to put together nanoparticles,
together with loading of considerable quantity of drug(s) results
in development of effective drug delivery systems which are
being explored to an exceptional extent. Ceramic nanoparticles

were efficiently used as drug delivery systems against some of
diseases, including bacterial infections, glaucoma, and many
others., and most extensively, against cancer. 3

II. DEVELOPMENTAL HISTORY

Ceramics is one of the most historical industries on the
earth. as soon as people determined that clay may be dug up and
shaped into objects through first mixing with water after which
firing, the industry was born. As early as 24,000 BC, animal and
human figurines had been crafted from clay and different
substances, then fired in kilns partly dug into the ground. Nearly
10,000 years later, as settled groups were set up, tiles had been
manufactured in Mesopotamia and India. the primary use of
practical pottery vessels for storing water and food is idea to be
around 9000 or 10,000 BC. Clay bricks had been also made
around the same time.

Fig. 1. Jomon Ware Deep Bowl (Middle Period)
Glass was believed to be found in Egypt around 8000
BC, when overheating of kilns produced a colored glaze on the
pottery. Experts estimate that it was not until 1500 BC that glass
was produced independently of ceramics and customary into
separate objects. Fast forward to the middle ages, when the
metal industry was in its infancy. Furnaces at that time for
melting the metal had been built of natural materials. When
artificial substances with higher resistance to high temperatures
(known as refractories) had been developed within the 16th
century, the industrial revolution was born. Those refractories
created the essential conditions for melting metals and glass on
a commercial scale, in addition to the manufacturing of coke,
cement, chemical compounds, and ceramics.
Another major improvement happened within the
second half of the 19th century, when ceramic materials for
electrical insulation had been developed. As different inventions
came on the scene-which includes automobiles, radios,
televisions, computers-ceramic and glass materials have been
needed to assist these emerge as a fact, as proven in the following
timeline. 4

Year Development
24,000 B.C. Ceramic figurines used for ceremonial purposes
14,000 B.C. First tiles made in Mesopotamia and India
9000-10,000 B.C. Pottery making begins
5000-8000 B.C. Glazes discovered in Egypt
1500 B.C. Glass objects first made
1550 A.D. Synthetic refractories (temperature resistant) for
furnaces used to make steel, glass, ceramics,
cement
Mid 1800’s Porcelain electrical insulation
Incandescent light bulb
1920’s High-strength quartz-enriched porcelain for
insulators
Alumina spark plugs
Glass windows for automobiles
1940’s Capacitors and magnetic ferrites
1960’s Alumina insulators for voltages over 220 kV
Application of carbides and nitrides
1970’s Introduction of high-performance cellular
ceramic substrates for catalytic converters and
particulate filters for diesel engines
1980’s High temperature superconductors
Table 1 History of Ceramics

In the 19th century, with the invention of the electric
light with the aid of Thomas Alva Edison and the telephone
through Alexander Graham Bell, a brand-new generation which
could be called the “generation of electricity” started. Ceramics,

previously used only as vessels, began to play completely new
roles suitable to this new generation.
In general, ceramics do not conduct electricity. in
comparison to other insulators, which includes paper and wood,
ceramics are much less stricken by environmental elements
which includes temperature and humidity, giving ceramic
components better reliability. through the history of ceramics
going back greater than 10,000 years, we’ve found out
modeling technology to provide ceramic merchandise in a
myriad of shapes. Ceramics have therefore come into massive
use as insulators or as insulating materials in regions starting
from power lines to family products and have grown to be
essential materials that permit people to apply electricity
without difficulty.
The 20th century brought the arrival of electronics,
with the start of radio and tv broadcasts and the discovery of
the transistor. this period was facilitated through ceramics from
the start, whilst big vacuum tubes of the early 20th century
depended on ceramic materials. within wireless device, only
ceramics possessed the properties important to provide high
signal output even over high frequency levels. Ceramics
couldn’t be replaced with other materials. Ceramics have helped
to lessen the dimensions of capacitors and inductors in
electronics.
Fig. 2 Transistors
Since the middle of the 20th century, ceramics have
gone through a persistent evolution, and now own exceptional
dielectric and magnetic properties. As an end result, electronic
components have been miniaturized and made exceptionally
functional. Ceramics therefore made a widespread contribution
to the downsizing of electronic equipment. If capacitors had no
longer been made from ceramics, the portable electronic
gadgets we rely on each day, including pocket-sized cellular
phones and laptop computers, would in no way have appeared.
5
Today, fine ceramics (also known as ‘Advanced
Ceramics’) can be made to possess a huge type of unique
characteristics through variations in raw materials, synthesizing
techniques and manufacturing strategies. therefore, they have
turn out to be the standard for new materials in countless fields
of advanced technology. Because of their light weight, rigidity,
physical stability and chemical resistance, huge ceramic
components numerous meters in size at the moment are utilized
in system for production semiconductors and liquid crystal
displays. further, their high reliability and successful
integration with metals permits them for use in a developing
variety of automobile additives. 6
Fig. 3 Advanced ceramics materials

Segment Products
Automotive Diesel engine cam rollers, fuel pump rollers,
brakes, clutches, spark plugs, sensors, filters,
windows, thermal insulation, emissions control,
heaters, igniters, glass fiber composites for door
chassis and other components
Aerospace Thermal insulation, space shuttle tiles, wear
components, combustor liners, turbine
blades/rotors, fire detection feedthroughs,
thermocouple housings, aircraft instrumentation
and control systems, satellite positioning
equipment, ignition systems, instrument displays
and engine monitoring equipment, nose caps,
nozzle jet vanes, engine flaps
Chemical/
petrochemical
Thermocouple protection tubes, tube sheet boiler
ferrules, catalysts, catalyst supports, pumping
components, rotary seals

Coatings Engine components, cutting tools, industrial wear
parts, biomedical implants, anti-reflection,
optical, self-cleaning coatings for building
materials
Electrical/
electronic
Capacitors, insulators, substrates, integrated
circuit packages, piezoelectric, transistor
dielectrics, magnets, cathodes, superconductors,
high voltage bushings, antennas, sensors,
accelerator tubes for electronic microscopes,
substrates for hard disk drives
Environmental Solid oxide fuel cells, gas turbine components,
measuring wheels/balls for check valves
(oilfields), nuclear fuel storage, hot gas filters
(coal plants), solar cells, heat exchangers, isolator
flanges for nuclear fusion energy research, solar-
hydrogen technology, glass fiber reinforcements
for wind turbine blades
Homeland
security/military
Particulate/gas filters, water purification
membranes, catalysts, catalyst supports, sulfur
removal/recovery, molecular sieves
Table 2 Applications of Advanced Ceramics
The development of products and methods containing
ceramic nanoparticles has generated novel and captivating
applications of these materials within the past decades. similarly,
to these thrilling findings, ceramic nanoparticles tend to be
exceptionally stable. Their routes of synthesis are widely
recognized and comparatively cheap. The mixture of technical
benefits and profuse funding in research and improvement
expanded the wide variety of patents and publications on this
area. Even more currently (since 2002), research applications
primarily based on toxicology, eco-toxicology, ethics and public
notion of nanotechnologies have talked about capable dangers
and influences associated with nanotechnologies. due to their
extensive employment, the ceramic nanoparticles considerably
have been studied through approach of these new techniques and
numerous surprising unsafe consequences which includes high
toxicity and environmental persistency were discovered. The
future of nanoceramics is most anticipated especially in the field
of biomedical area to treat diseases especially cancer while
providing a cost-effective method.
III. COMPOSITION/MATERIAL CHEMISTRY

Remarkable progress in synthetic chemistry has led to
significant advances in material science, making possible the
synthesis of various substances and materials. The manufacture
of ceramics involves heat treatment of tightly squeezed
powders. The size of the building block of these powders has
been found to affect the properties of the final product.

Fig. 4 Nanoceramic Material

A. Preparations

The method of preparation is very often a determining
factor in shaping the material and its properties. For example,
burning Mg in O2 (MgO smoke) yields 40-80-nm cubes and
hexagonal plates, whereas thermal decomposition of
commercial Mg(OH)2, MgCO3, and especially Mg(NO3)2
yields irregular shapes often exhibiting hexagonal platelets.
Surface areas can range from 10 m2/g (MgO smoke) to 150
m2/g for Mg(OH)2 thermal decomposition. On the other hand,
aerogel-prepared Mg(OH)2 can lead to MgO with surface areas
as high as 500 m2/g. 2

1) Physical Methods

a) Vapor condensation methods
Gas-condensation techniques to produce
nanoparticles directly from a supersaturated vapor of
metals are among the earliest methods for producing
nanoparticles. They generally involve two steps: First, a
metallic nanophase powder is condensed under inert
convection gas after a supersaturated vapor of the metal is
obtained inside a chamber. Second, the powder is oxidized
by allowing oxygen into the chamber (to produce metal
oxide powder). A subsequent annealing process at high
temperatures is often required to complete the oxidation.
The system consists of a vapor source inside a vacuum
chamber containing a mixture of an inert gas, usually argon
or helium, mixed with another gas, which is selected based
on the material to be prepared. Oxygen is mixed with the
inert gas to produce metal oxides. NH3 is usually used to
prepare metal nitrides and an appropriate alkane or alkene,
as a source of carbon, is usually used to prepare metal
carbides. Nanoparticles are formed when supersaturation

is achieved above the vapor source. A collection surface,
usually cooled by liquid nitrogen, is placed above the
source. The particles are transported to the surface by a
convection current or by a combination of a forced gas
flow and a convection current, which is set up by the
difference in the temperature between the source and the
cold surface. Some improved systems involve a way to
scrap the nanoparticles from the cold collection surface so
that the particles would fall into a die and a unit where they
can be consolidated into pellets. Supersaturated vapor can
be achieved by many different vaporization methods. The
most common techniques include thermal evaporation,
sputtering, and laser methods. A variety of nanoscale metal
oxides and metal carbides have been prepared using laser-
vaporization techniques.
The advantages of vapor condensation methods
include versatility, ease in performance and analysis, and
high-purity products. On the other hand, they can be
employed to produce films and coatings. Furthermore,
laser-vaporization techniques allow for the production of
high-density, directional, and high-speed vapor of any
metal within an extremely short time. Despite the success
of these methods, they have the disadvantage that the
production cost is still high because of low yields. Heating
techniques have other disadvantages that include the
possibility of reactions between the metal vapors and the
heating source materials.

b) Spray pyrolysis

Fig. 5 Spray pyrolysis process
This technique is known by several other names
including solution aerosol thermolysis, evaporative
decomposition of solutions, plasma vaporization of
solutions, and aerosol decomposition. The starting
materials in this process are chemical precursors, usually
appropriate salts, in solution, sol, or suspension. The
process involves the generation of aerosol droplets by
nebulizing or” atomization” of the starting solution, sol, or
suspension. The generated droplets undergo evaporation
and solute condensation within the droplet, drying,
thermolysis of the precipitate particle at higher temperature
to form a microporous particle, and, finally, sintering to
form a dense particle.
Different techniques for atomization are
employed including pressure, two-fluid, electrostatic, and
ultrasonic atomizers. These atomizers differ in droplet size
(2-15 mm), rate of atomization, and droplet velocity (1-20
m/sec). These factors affect the heating rate and residence
time of the droplet during spray pyrolysis which, in turn,
affect some of the particle characteristics including particle
size. For a specific atomizer, particle characteristics,
including particle size distribution, homogeneity, and
phase composition depend on the type of precursor,
solution concentration, pH, viscosity, and the surface
tension.
Aqueous solutions are usually used because of their
low cost, safety, and the availability of a wide range of water-
soluble salts. Metal chloride and nitrate salts are commonly
used as precursors because of their high solubility. Precursors
that have low solubility or those that may induce impurities,
such as acetates that lead to carbon in the products, are not
preferred.
The advantages of this method include the production
of high-purity nanosized particles, homogeneity of the particles
as a result of the homogeneity of the original solution, and the
fact that each droplet/particle goes through the same reaction
conditions. The disadvantages of spray pyrolysis include the
need for large amounts of solvents and the difficulty to scale-
up the production. The use of large amounts of nonaqueous
solvents increases the production expenses because of the high
cost of pure solvents and the need for proper disposal.

2) Chemical Methods
a) Sol-gel technique

Fig. 6 Sol-gel process

The sol-gel process is typically used to prepare
nanometer-sized particles of metal oxides. This process is
based on the hydrolysis of metal reactive precursors,
usually alkoxides in an alcoholic solution, resulting in the
corresponding hydroxide. Condensation of the hydroxide
by giving off water leads to the formation of a network-
like structure. When all hydroxide species are linked,
gelation is achieved and a dense porous gel is obtained.
The gel is a polymer of a three-dimensional skeleton
surrounding interconnected pores. Removal of the solvents
and appropriate drying of the gel result in an ultrafine
powder of the metal hydroxide. Further heat treatment of
the hydroxide leads to the corresponding powder of the
metal oxide. As the process starts with a nanosized unit and
undergoes reactions on the nanometer scale, it results in
nanometer-sized powders. For alkoxides that have low
rates of hydrolysis, acid or base catalysts can be used to
enhance the process.
When drying is achieved by evaporation under
normal conditions, the gel network shrinks as a result of
capillary pressure that occurs and the hydroxide product
obtained is referred to as xerogel. However, if supercritical
drying is applied using a high-pressure autoclave reactor at
temperatures higher than the critical temperatures of
solvents, less shrinkage of the gel network occurs as there
is no capillary pressure and no liquid-vapor interface,
which better protects the porous structure. The hydroxide
product obtained is referred to as an aerogel. Aerogel
powders usually demonstrate higher porosities and larger
specific surface areas than analogous xerogel powders.
Sol-gel processes have several advantages over
other techniques to synthesize nanopowders of metal oxide
ceramics. These include the production of ultrafine porous
powders and the homogeneity of the product as a result of
homogeneous mixing of the starting materials on the
molecular level.

b) Precipitation from solutions
Precipitation is one of the conventional methods
to prepare nanoparticles of metal oxide ceramics. This
process involves dissolving a salt precursor, usually
chloride, oxy-chloride or nitrate, such as AlCl3 to make
Al2O3, Y(NO3)3 to make Y2O3, and ZrCl4 to make
ZrO2, in water. The corresponding metal hydroxides are
usually obtained as precipitates in water by adding a base
solution such as sodium hydroxide or ammonium
hydroxide solution. The remaining counter-ions are then
washed away and the hydroxide is calcined after filtration
and washing to obtain the final oxide powder. This method
is useful in preparing ceramic composites of different
oxides by co-precipitation of the corresponding hydroxides
in the same solution. Solution chemistry is also used to
prepare non-oxide ceramics or pre-ceramic precursors that
can be converted to ceramics upon pyrolysis.
One of the disadvantages of this method is the
difficulty in controlling the particle size and size
distribution. Very often, fast and uncontrolled precipitation
takes place resulting in large particles.

IV. MATERIAL PROPERTIES
Ceramics possess their own chemical, physical,
mechanical, and magnetic properties that are different from
those of other materials such as metals and plastics. The
properties of ceramics depend mainly on the type and the
amounts of materials in their composition. However, the size of
the building blocks of a ceramic material has been found to play
an important role in its properties.
When materials are prepared from nanometer-sized
particles, a significant portion of the atoms become exposed on
the surface. As a result, such materials exhibit unique properties
that are remarkably different from those of the corresponding
bulk. The physical and chemical properties of nanoparticles
show the gradual transition from atomic or molecular to
condensed matter systems. 2
1) Chemical Properties
Ceramic materials are relatively inert, especially
crystalline materials that tend to have perfect structures with
minimum number of defects. Most of the reactivity of these
materials involves the surfaces where coordinatively
unsaturated as well as defect sites exist. The behavior of the
surface toward other species and the nature of interaction
depend on the composition and the morphology, which
determine the nature and the degree of surface interactions
with other substances. Most of the time, interactions are
limited to adsorption on the surface, which does not affect
the bulk making these materials good corrosion-resistant.
The possibility of preparing ceramic powders in
high surface areas with high porosity makes them well
desired in some advanced applications. One example is the
use of ceramic materials as supports for heterogeneous
catalysts. Another example is the use of such materials in
biomedical applications, where the surface of nanophase
ceramics exhibits a remarkably improved biomedical

compatibility compared to conventional ceramics, as
discussed below.
2) Mechanical Properties

Ceramics are very strong materials showing
considerable resistance against compression and bending.
Some ceramic materials are similar to steel in strength. Most
ceramics retain their strength at high temperatures. Silicon
carbides and silicon nitrides, as an example, retain their
strength at temperatures as high as 1400°C. As a result, such
materials are used in high-temperature applications. Many of
the physical and mechanical properties are particle-size
dependent. As a result, several systems of nanophase
ceramics have exhibited quite interesting and favorably
enhanced mechanical properties.

3) Electrical Properties
Ceramics include electrical conducting, insulating,
and semiconducting materials. Chromium oxide is an
electrical conductor, aluminum oxide is an insulator, while
silicon carbide behaves as a semiconductor. As a result,
ceramic materials have been used in a variety of electronic
applications based on their electrical behavior.
Several electrical properties are particle-size and
composition dependent. Electrical resistance and dielectric
constant, as an example, for some systems increased as a
result of small particle size. Conductivity of some mixed
oxide ceramics, such as lithium aluminosilicate, is higher
than that of their constituent oxides.
4) Magnetic Properties
Some ceramic materials possess magnetic
properties. These include iron oxide-based ceramics and
oxides of chromium, nickel, manganese, and barium.
Ceramic magnets are known to exhibit high resistance to
demagnetization. As a result, several ceramic powders have
been employed in a wide range of electronic and magnetic
applications as discussed below.
The fabrication of such materials from ultrafine
particles can significantly enhance their magnetic behavior.
The fact that in nanometer-sized particles a large portion of
the atoms are on the surface, where the coordination numbers
are less than that for bulk atoms, affects several parameters
including unique surface/interface behavior and different
band structure, which both lead to magnetism enhancement.
It is now well established that one of the requirements to
achieve appropriate coercivity and high magnetization
saturation is to fabricate such materials in highly divided
particles, preferably in the nanometer-sized range, with
homogeneity and narrow size distribution.

5) Reduced brittleness and enhanced ductility and
superplasticity

Superplasticity and ductility refer to the capability of
some polycrystalline materials to undergo extensive tensile
deformation without necking or fracture. Ceramic brittleness
is the biggest technical barrier in practical applications,
especially in load-bearing applications. Theoretical and
experimental results provide evidence for the possibility that
traditional brittle materials can be ductilized by reducing their
grain sizes. 1 When made from nanoparticles, brittle
ceramics can be superplastically deformed at modest
temperatures and then heat treated at higher temperatures for
high-temperature strengthening.

The capability to synthesize superplastic ceramic
materials is now established. Nanocrystalline ceramics
deform at faster rates, lower stresses, and lower temperatures.
One important use of superplasticity in ceramics is diffusion
bonding, where two ceramic parts are pressed together at
moderate temperatures and pressures to form a seamless bond
through diffusion and grain growth across the interface.
Diffusion bonds form more easily in nanocrystalline ceramics
than in larger grained ceramics as a result of both the
enhanced plastic flow of nanocrystalline ceramics and the
larger number of grain boundaries they provide for diffusional
flux across the interface.
V. APPLICATIONS

Ceramic Nanoparticles: Fabrication Methods and
Applications in Drug Delivery 7

Ceramic nanoparticles are inorganic systems with porous
characteristics. Since these particles can be easily engineered with the
desired size and porosity, keen interest has recently been shown in
utilizing ceramic nanoparticles as drug vehicles. Considerable
research has been done exploring typical biocompatible ceramic
nanoparticles such as silica, Titania, alumina etc. The newly emerging
area of utilizing inorganic (ceramic) particles with entrapped
biomolecules has potential applications in many frontiers of modern
materials science including drug delivery systems.

Fig. 7 Types of Nanoceramic drugs
The advantages of ceramic nanoparticles include easy
preparation with desired size, shape and porosity, and no effect on
swelling or porosity with change in pH. In recent times, the
development of new ceramic materials for biomedical applications has
hastened. Nanoscale ceramics such as hydroxyapatite (HA), calcium
carbonate (CaCO3), zirconia (ZrO2), silica (SiO2), titanium oxide
(TiO2), and alumina (Al2O3) were made from new synthetic methods
to improve their physical-chemical properties seeking to reduce their
cytotoxicity in biological systems. The controlled release of drugs is
one of the most exploited areas in terms of ceramic nanoparticle
application in biomedicine where, the dose and size are important.
Also, some features that make these nanoparticles a potential tool in
controlling drug delivery are high stability, high loading capacity, easy
incorporation of hydrophobic and hydrophilic systems, and different
routes of administration (oral, inhalation, etc.). In addition, a variety
of organic groups which may be functionalized on their surfaces allow
for a directed effect.

Calcium phosphates are suitable to be used as a carrier for
drugs, non-viral gene delivery, antigens, enzymes, and proteins.
Calcium phosphate nanoparticles provide the following advantages:

• Deliver drugs in minimally invasive manner just as
polymeric nanoparticles

• Easy to fabricate and inexpensive

• Longer biodegradation time

• Do not swell or change porosity

• Stable upon variation in temperature and pH

• Possess same chemistry, crystalline structure and size as
the constituents of targeted tissues

• Fabrication methods enhance their bioavailability and
biocompatibility even before releasing drugs

Sol-Gel Process

In the soft chemistry route, the metal alkoxides convert to
amorphous gels of metal oxides through hydrolysis and condensation
reactions. Liu et al. successfully synthesized hydroxyapatite using the
sol-gel process at lower temperatures. A two-step procedure was
employed. Triethyl phosphite was initially hydrolysed with water,
followed by the addition of an aqueous calcium nitrate solution.
Subsequently, the amorphous gel transformed into a well crystallized
apatite at relatively low temperatures (300-400°C). The calcinated gels
showed a nanoscale microstructure, with grains of 20-50 nm
diameters. Appropriate heat treatment between 300 and 400 °C
resulted in preparation of apatite exhibiting a nanoscale size, low
crystallinity, carbonated apatitic structure, resembling that of human
bone apatite.

The final product and the optimum synthesis conditions
such as calcination temperature largely depend on chemical nature of
the precursors. The sol–gel materials are transformed to ceramics by
heating at relatively low temperatures and have better chemical and
structural homogeneity than those obtained by conventional methods.
The sol-gel method offers a molecular-level mixing of the calcium and
phosphorus precursors, which is capable of improving the chemical
homogeneity of the resulting hydroxyapatite to a significant extent. A
number of calcium and phosphate precursor combinations have been
employed for sol-gel synthesis. The major limitation of the sol-gel
technique is linked to the possible hydrolysis of phosphates.

Fig. 8 Drug Delivery using nanoceramic carriers

Application of Calcium Phosphate in Drug Delivery,
especially hydroxyapatite has been widely used in treatment of bone
diseases such as osteoporosis. These are also being explored as drug
carriers for the treatment of cancer and other diseases. The formulated
delivery systems were able to prolong drug release due to very low
rate of degradation of hydroxyapatite (at neutral or alkaline pH) and
possessed excellent biocompatibility.

The paper concludes that the methods of synthesis and
applications of inorganic nanoparticles (Ceramic nanoparticles) in the
field of drug delivery makes it evident that these nanoparticles hold a

great potential as drug carriers to deliver and target the active
pharmaceutical ingredient to the desired site in a controlled manner,
resulting in achievement of a therapeutic concentration of drug at
target site. Ceramic nanoparticles offer a number of technical
advantages in terms of drug delivery. Most researched area for the
application of ceramic nanoparticles is cancer, where promising
results have been obtained. A number of facile methods for preparation
of these nanoparticles are available and have been continuously
undergoing modifications to achieve better desired characteristics of
synthesized nanoparticles. All these favorable facts have resulted in
several patents and publications in this area during recent years. Thus,
ceramic nanoparticles hold the promise of better, safer and cost-
effective drug delivery agents in future of biomedical science.

VI. ENVIRONMENTAL IMPACT

Size, shape, and surface chemistry are among key
properties central to the utility of nanomaterials. These
properties also fundamentally influence the way these materials
interact within the human body. Understanding how the various
characteristics of nanomaterials affect their biocompatibility
and toxicity will support development of safer nanomaterials
and nanotechnology products. Development of well-integrated
multidisciplinary research teams is critical to enable these
studies.

One example of the roles nanomaterial properties play
is how changes to surface chemistry can affect the
biocompatibility and toxicity of particular nanomaterials.
Positively charged nanoscale lipid vesicles (nanovesicles)
induce cerebral edema, but neutral and low concentrations of
negatively charged nanovesicles do not (Lockman et al., 2004).
Studies have shown that modifying the surface of
nanomaterials with surfactants or biocompatible polymers
(e.g., polyethylene glycol) reduces the toxicity in vitro (Derfus
et al. 2004) and alters the half-life and tissue deposition in vivo
(Ballou et aL, 2004). Such findings are relevant to drug
delivery, for understanding the potential distribution of
nanomaterials in the body, and for evaluating biocompatibility
and toxicity. However, these findings are material-specific and
are difficult, at present, to extend to broad categories/classes of
materials.

Nanoscale materials similarly may vary in their ability
to be introduced into and circulated though the body. For
example, one study discovered ultrafine carbon transport from
the olfactory mucosa in nasal passages, via the olfactory nerve,
to the olfactory bulb inside the blood-brain barrier (Oberdorster
et al., 2004). Other studies have demonstrated that
semiconducting quantum dots translocate to local lymph nodes
in animals following intradermal or footpad injections (Kim et
al., 2003; Roberts et aL, 2005) or following topical application
to dermabraded skin (Gopee et al., 2006).

Seemingly more so than at larger scales, the shapes of
nanomaterials have interesting implications for
biocompatibility. Current manufacturing technologies with
atom-by-atom assembly of nanomaterials under highly
controlled conditions allow synthesis of materials having the
same chemical composition but different shapes. Studies of
zinc oxide (ZnO) nanomaterials suggest that changes in shape
alone (e.g., particles, cages, and “belts’) influence
physicochemical properties (Wang et al., 2004), which in turn
can influence biological activity. 8

Exposure Routes

Assessing exposure to nanomaterials requires
understanding relevant routes of exposure. For a material
(nanoscale or otherwise) to induce a measurable biological
response, it must enter the body, usually through the respiratory
tract, skin, eyes. or digestive tract, or through intravenous
exposure of patients and healthy donors, and reach an
appropriate site in the body at sufficient concentration and for
a necessary length of time. The relationship of exposure to
uptake differs for each route of exposure and is a function of
the physicochemical characteristics of the material and the
structure and function of the organ or system that acts as the
entry point. 8

A. Respiratory Tract

The upper airways of the lung have a relatively robust
protective cellular layer (epithelium), but the alveoli (the
regions of the lungs where gas exchange occurs) are deeper and
more vulnerable. Research has shown that nanomaterials
smaller than 100 am (that is, those not in large agglomerates)
deposit at higher concentrations in the alveoli, whereas
agglomerated nanomaterials with diameters larger than 100 am
deposit at higher concentrations in the upper Sway. Research
has also demonstrated that nanoscale particles can be taken up
by sensory nerve endings within the airway epithelia. followed
by axonal translocation to ganglionic and central nervous
system structures. For example. as noted earlier. animal studies
have shown that inhaled or intranasally instilled nanoscale
particles can be transported via the olfactory nerve to the
olfactory bulb (Oberdorster et aL, 2004; International
Commission of Radiologic Protection, 2003).

B. Skin

The skin has a strong external bather, the stratum
come= which protects sensitive internal organs from
environmental exposures. Although healthy skin is generally
considered impervious to particle exposures. some studies

suggest that nanoscale materials penetrate hair follicles and
sebaceous glands or move through the lipid pathway located
between the cells of the stratum corium (Banat Muller-
Goymana, 2000). The relationship of the dose of nanomaterial
to which the skin is exposed and the dose absorbed into the skin
is not well understood. Furthermore, there is conflicting
evidence regarding the ability of particulates to penetrate
through the stratum comeum. Several unpublished studies
suggest that nanoscale titanium dioxide does not penetrate the
skin (RS/RAEng, 2004). whereas other recent reports
demonstrate that nanoscale particles can enter the epidermis
and dermis though intact stratum comeum (Ryman-Rasmussen
et al., 2006) and through compromised stratum corium,
resulting in translocation of materials to the lymph nodes and
liver (Gopee et al. 20067).

C. Digestive Tract

Particle uptake in the digestive tract has been well
studied mostly for drug delivery. This complex system absorbs
macromolecules at numerous points along its length. Several
studies demonstrate uptake of nanomaterials, including organ-
spPrifir targeted uptake that tailinis surface modification as the
targeting methodology. Nanomaterials also can be ingested
when they are transferred from hand to mouth, and ingestion
accompanies inhalation exposure when particles are cleared
from the respiratory tract via the mucosocilialy escalator
(International Commission of Radiologic Protection, 2003).

D. Injection or Implantation

Particles may be injected into a patient via the
subcutaneous. intramuscular. or intravenous routes. or may be
injected directly into a tissue. organ. or tumor. These may be
intended to target specific organs. tumors, and diseases or may
serve as imaging and diagnostic agents. The disposition and
biocompatibility of the particles will depend on ADNIETOX
profiles—which are blown to be tightly linked to particle size
and surface chemistry. Particles may also be released from
implanted devices. whether as a result of designed resorption.
or as a result of matrix material wear and degradation. These
may accumulate in local tissues or be transported to filter
organs. or maybe excreted.

VII. REFERENCES

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