Palladium (Pd) - Properties, Applications

Topics Covered

Introduction
Chemical Properties
Physical Properties
Mechanical Properties
Thermal Properties
Applications

Introduction

Palladium is the least dense and has the lowest melting point of the platinum group metals. It can be found alloyed with gold and other platinum-group metals in Ethiopia, Australia, Ural Mountains as well as South and North America.

At room temperatures, the metal has an unusual property of absorbing nearly 900 times its own volume of hydrogen. It dissolves slowly in concentrated nitric acid, sulfuric acid and hydrochloric acid when finely divided.

Chemical Properties

The chemical properties of palladium are provided in the table below.

Chemical Data
CAS number 5/3/7440
Thermal neutron cross section 8 barns/atom
Electrode potential -0.570 V
Ionic radius (Crystal ionic radius for valence +4) 0.650 Å
Electronegativity 2.2
X-ray absorption edge 0.509 Å

Physical Properties

The following table discusses the physical properties of palladium.

Properties Metric Imperial
Density 12.02 g/cm3 0.4343 lb/in3
Melting point 1552°C 2826°F
Boiling point 2963°C 5365°F

Mechanical Properties

The mechanical properties of palladium are tabulated below.

Properties Metric Imperial
Tensile strength (annealed) 180 MPa 26100 psi
Poisson’s ratio 0.39 0.39
Modulus of elasticity 117 GPa 17000 ksi
Bulk modulus 180 GPa 26106 ksi
Shear modulus 44 GPa 6382 ksi
Elongation at break 2% 2%
Hardness, Vickers 37 37

Thermal Properties

The thermal properties of palladium are tabulated below.

Properties Metric Imperial
Thermal expansion co-efficient (@20-100°C/68-212°F) 11.1 µm/m°C 6.17 µin/in°F
Thermal conductivity 71.2 W/mK 494 BTU in/hr.ft².°F

Applications

One of the major applications of palladium is catalytic converters. It acts as a critical catalyst in the manufacture of polyester. It is useful in eliminating harmful emissions produced by internal combustion engines. It is used in the refining of nitric acid and developing raw materials for synthetic rubber and nylon.

Palladium-based alloys are being extensively used in fuel cell technology applications. The metal is also employed in historic photographic printing process.

Some of the other applications of palladium include the following:

  • Jewelry
  • Dentistry
  • Watch making
  • Aircraft spark plugs
  • Electrical contacts
  • Surgical instruments
  • Blood sugar test strips

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