Remove duplicates form a Powershell object

Question

I'm trying to remove duplicate entries of a object.

$results = @()
$array = @("Windows","Linux","Linux")

foreach ($test in $array)
    {
        $test
        $result = New-Object -type psobject
        $result | Add-Member -type NoteProperty -Name "Name" -Value $test
        $result | Add-Member -Type NoteProperty -Name "Value" -Value "test"
        $result | Add-Member -Type NoteProperty -Name "This" -Value "123"
        $result | Add-Member -Type NoteProperty -Name "That" -Value "567"
        $results += $result
    }

$duplicates = $results | Sort-Object -Unique
$duplicates

This is the result without "sort-object -uniqe":

Name    Value This That
----    ----- ---- ----
Windows test  123  567
Linux   test  123  567
Linux   test  123  567

And this is with "sort-object -unique":

Name    Value This That
----    ----- ---- ----
Windows test  123  567

I have expect two entries. Can someone help?

$duplicates = $results | Sort-Object -Unique