Solid State Reaction & Densification of Transparent Luminescent Ceramics by Current Activated Pressure Assisted Densification

Elias H. Penilla, Ph.D. Student
University of California, Riverside

The study of transparent ceramics has significantly rebounded in the past decade as higher quality materials have been achieved  with  traditional  sintering  techniques.  The  densities  and  transparencies  of  sintered  bodies  often  rival  their single-crystal  counterparts.  As  such  polycrystalline  ceramics  are  replacing  single  crystals  as  optical-structural, photoluminescent (PL), laser host, and energy efficient solid-state lighting materials. Typically, ceramic host materials are  synthesized  and  doped  with  transition  metals  and  rare-earths  (RE)  using  equilibrium  processing  techniques (Czochralski,  sintering  etc.).  While  largely  developed,  these  techniques  have  limitations.  For  example  producing transparent, non-cubic ceramics with grain sizes that mitigate birefringence has largely been elusive with traditional techniques.  Additionally,  RE-doping  of  alumina  to  levels  requisite  for  PL  purposes  is  impossible  with  equilibrium techniques because the equilibrium RE-solubility is too low (~10-4%). Conversely, little attention has been given to producing RE-doped bulk transparent ceramics  with non-equilibrium processing techniques.   Here  we  report on the application  of  the Current Activated Pressure Assisted Densification  (CAPAD)  technique  for  producing  functional transparent oxide ceramics such as ruby, and RE-doped alumina, with grain sizes that mitigate birefringence and with dopant  concentrations  as  high  as  0.5  at%,  orders  of  magnitude  higher  than  previously  reported.  The  application  of CAPAD  for  the  production  of  cubic  symmetry  ceramics  such  as  yttria  stabilized  zirconia  (YSZ),  and  yttrium aluminum  garnet  (YAG),  will  also  be  discussed.  We  have  investigated  the  effects  of  temperature,  heating  rate,  and holding time, etc., during CAPAD processing on the sample densification and material properties.

Mr. Elias H. Penilla received his Bachelor of Arts Degree in Physics from Pomona College in 2006, where he studied synthesis  and  characterization  of  metal  and  carbon  1D  and  2D  systems.  He  joined  UCR  in  2007  and  received  his Master’s  Degree  in  Mechanical  Engineering  in  2009,  continuing  to  research  2D  systems,  now  focusing  on  the synthesis  of  non-equilibrium  nitride  ceramics,  under  the  guidance  of  Dr.  Junlan  Wang.  Currently,  Mr.  Penilla  is  a Doctoral Candidate at the University of California, Riverside, Department of Mechanical Engineering working under
the guidance of Dr. Javier E. Garay in the Advanced Materials Synthesis and Processing Laboratory (AMPS Lab). His current research interests focus on the synthesis of 3D-bulk nanostructured transparent ceramics, with focus on light emitting and controlling applications.

Reducing Mobile Air Conditioner Power Consumption Using Active Cabin Air Recirculation in Hybrid Electric Vehicles

Eli Brewer, Ph.D. Student
University of California, Riverside

The power consumed by an air conditioner accounts for a significant fraction of the total power used by hybrid and electric vehicles especially during summer. This study examined the effect of recirculation of cabin air on power consumption of mobile air conditioners. Real time power consumption and vehicle mileage were recorded by an On Board Diagnostic monitor and carbon balance method. Vehicle mileage improved with increased cabin air
recirculation. The recirculation of cabin air also significantly reduced in-cabin particle concentrations. Recirculation of cabin air is an excellent and immediate solution to increase vehicle mileage and improve cabin air quality.

Eli is currently a Master’s student in Prof. Jung’s lab at CE-CERT, UC Riverside. His research is on automotive fuel economy and cabin air quality, and on the ultrafine particle emissions of natural gas turbines. In 2013 he completed a B.S. in Mechanical Engineering from UC Riverside. He is a certified E.I.T. and Rescue SCUBA Diver. In his spare time he enjoys cycling, cooking, hiking and home brewing.