Question

A new Titanium-Aluminum-Niobium alloy is needed for a pediatric orthopedic application. It is hypothesized that because growing bones require a softer interaction with orthopedic implants the current Ti6Al7Nb is unacceptable (ρ = 4.4 g/cm³). Without changing the elements involved, design an alloy that has a density of 4.2 g/cm³ and show all supporting calculations that validate your answer. (There may be several designs that satisfy this requirement)  

Answer 1

density = mass/ volume

Ti6Al7Nb has a density of 4.4 g/cm3

Ti - 47.867

Al - 26.9815

Nb - 92.9064

Now to get the mass of this lets calculate the molecular weight :

#	Atom	Molar Mass (MM)	Subtotal Mass	Subtotal Mass
		(g/mol)	(%)	(g/mol)
6	Ti	47.87	50.48	287.20
7	Al	26.98	33.19	188.87
1	Nb	92.91	16.33	92.91
		Total Molecular Weight:		568.98

Hence the volume is : mass/density

= 568.98/4.4 = 129.31 cm3

Now we need to reduce the density to 4.2 g/cm3, hence lets calculate the new molecular mass for this.

mass = density * volume = > 129.31 * 4.2 => 543.1 gms

Hence the new formula should have the molecular mass = 543.1 gms

Ti6Al6Nb can be new molecule which has a molecular weight of 542.00 gms.