18 research outputs found
Free-sustaining three-dimensional S235 steel-based porous electrocatalyst for highly efficient and durable oxygen evolution
A novel oxygen evolution reaction (OER) catalyst (3D S235-P steel) based on steel S235 substrate has been successfully prepared via a facile one-step surface modification. The standard Carbon Manganese steel was phosphorizated superficially leading to the formation of a unique 3D interconnected nanoporous surface with high specific area which facilitates the electrocatalytically initiated oxygen evolution reaction. The prepared 3D S235-P steel exhibits enhanced electrocatalytic OER activities in alkaline regime confirmed by a low overpotential (η=326 mV at j=10 mA cm-2) and a small Tafel slope of 68.7 mV dec-1. Moreover, the catalyst was found to be stable under long-term usage conditions functioning as oxygen evolving electrode at pH 13 as evidenced by the sufficient charge to oxygen conversion rate (Faradaic efficiency: 82.11% and 88.34% at 10 mA cm-2 and 5 mA cm-2, respectively). In addition, it turned out that the chosen surface modification renders steel S235 into an OER electrocatalyst sufficiently and stable to work in neutral pH condition. Our investigation revealed that the high catalytic activities are likely to stem from the generated Fe/(Mn) hydroxide/oxo-hydroxides generated during the OER process. The phosphorization treatment is therefore not only an efficient way to optimize the electrocatalytic performance of standard Carbon-Manganese steel, but also enables for the development of low cost and abundant steels in the field of energy conversion
ScannerâBased Capillary Stamping
Classical microcontact printing and polymer pen lithography (PPL) involve ink transfer to substrates using solid elastomeric stamps. Ink depletion thus limits the number of successive stamping steps without reinking. Porous stamps developed to overcome this limitation are used only for manual proofâofâprinciple experiments. Here, porous composite stamps for scannerâbased capillary stamping (SCS) that can be mounted on automated printing devices designed for PPL are developed. Porous SCS composite stamps consist of a rigid controlled porous silica glass (CPG) layer and a porous polymeric stamping layer. The latter can be topographically structured with contact elements by replication molding. The mechanical stabilization by the CPG layer ensures that the contact elements are coplanar. SCS allows automated, continuous, highâthroughput patterning enabled by ink supply through the porous SCS composite stamps. Even after more than 800 consecutive stampâsubstrate contacts without reinking (the porous SCS composite stamps themselves are used as ink reservoirs), ink microdroplets are deposited without deterioration of the pattern quality. However, SCS also allows supply of additional ink during ongoing stamping operations through the pore systems of the porous SCS composite stamps. SCS can easily be adapted for multiâink patterning and may pave the way for further upscaling of contact lithography
1.28 and 5.12 Gbps multi-channel twinax cable receiver ASICs for the ATLAS Inner Tracker Pixel Detector Upgrade
We present two prototypes of a gigabit transceiver ASIC, GBCR1 and GBCR2,
both designed in a 65-nm CMOS technology for the ATLAS Inner Tracker Pixel
Detector readout upgrade.
The first prototype, GBCR1, has four upstream receiver channels and one
downstream transmitter channel with pre-emphasis. Each upstream channel
receives the data at 5.12 Gbps through a 5 meter AWG34 Twinax cable from an
ASIC driver located on the pixel module and restores the signal from the high
frequency loss due to the low mass cable. The signal is retimed by a recovered
clock before it is sent to the optical transmitter VTRx+. The downstream driver
is designed to transmit the 2.56 Gbps signal from lpGBT to the electronics on
the pixel module over the same cable. The peak-peak jitter (throughout the
paper jitter is always peak-peak unless specified) of the restored signal is
35.4 ps at the output of GBCR1, and 138 ps for the downstream channel at the
cable ends. GBCR1 consumes 318 mW and is tested.
The second prototype, GBCR2, has seven upstream channels and two downstream
channels. Each upstream channel works at 1.28 Gbps to recover the data directly
from the RD53B ASIC through a 1 meter custom FLEX cable followed by a 6 meter
AWG34 Twinax cable. The equalized signal of each upstream channel is retimed by
an input 1.28 GHz phase programmable clock. Compared with the signal at the
FLEX input, the additional jitter of the equalized signal is about 80 ps when
the retiming logic is o . When the retiming logic is on, the jitter is 50 ps at
GBCR2 output, assuming the 1.28 GHz retiming clock is from lpGBT. The
downstream is designed to transmit the 160 Mbps signal from lpGBT through the
same cable connection to RD53B and the jitter is about 157 ps at the cable
ends. GBCR2 consumes about 150 mW when the retiming logic is on. This design
was submitted in November 2019.Comment: 7 pages, 15 figure
Nanoporous block copolymer stamps: design and applications
This thesis focuses on the surface patterning by using nanoporous block copolymer (BCP) stamps. Polystyreneâblockâpoly(2âvinylpyridine) (PSâbâP2VP) was used as model BCP. Nanoporous BCP stamps were fabricated by replication of lithographically patterned silicon molds. Nanopores inside of BCP stamps were generated by swellingâinduced pore formation. A method for scanner-based capillary stamping (SCS) with spongy nanoporous BCP stamps was developed. First, in the course of stamps design using replication molding of PS-b-P2VP against surface-modified macroporous silicon molds, PS-b-P2VP fiber rings remaining on the macroporous silicon molds were obtained that allow immobilization of water drops on the hydrophobically modified surfaces of the macroporous silicon molds. Water drops immobilized by these rings can be prevented from dewetting within the PSâbâP2VP fiber rings. Second, after spongy nanoporous PS-b-P2VP stamps had been obtained, preliminary experiments with non-inked PS-b-P2VP stamps revealed that parts of the stampsâ contact elements can be lithographically transferred onto counterpart surfaces. As a result, arrays of nanostructured submicron PSâbâP2VP dots with heights of âŒ100 nm onto silicon wafers and glass slides were produced. Lastly, the SCS technique was developed, which overcomes the limitation of time-consuming re-inking procedures associated with classical soft lithography including microcontact printing (”CP) and polymer pen lithography (PPL) with solid stamps, as well as the limitations regarding throughput of scanning probeâbased serial writing approaches such as nanoscale dispensing (NADIS) and other micropipetting techniques. In addition, sizes of stamped droplets can be controlled by adjusting surface wettability and dwell time
Spiral and Mesoporous Block Polymer Nanofibers Generated in Confined Nanochannels
Spiral-like or various porous polymer
nanofibers have great applications in biosensor, bioengineering, and
template-fabrication of functional inorganic materials. However, the
fabrication of polymer nanostructures with controllable porous or
spiral morphology in one process is a big challenge. Here we first
demonstrated a general and easy method to generate spiral or porous
block copolymer (BCP) nanofibers by using geometric confinement of
nanochannels to disturb the self-assembly of BCP while nonsolvent
is induced into BCP solution. Continuous spiral polymer nanofibers
and polymer nanofibers with hierarchical porous nanostructures can
be easily generated within channels of anodic aluminum oxide (AAO)
membranes by tuning the composition and concentration of BCP. This
study first reports the influence of cylinder confinement to the arrangement
of BCP micelles. These spiral and porous BCP nanostructures are not
only good templates to generate functional inorganic nanostructures,
but also promising candidates to create biosensors or to load catalyst
because their enlarged surface area enables high guest concentrations
Nanostructured Submicron Block Copolymer Dots by Sacrificial Stamping: A Potential Preconcentration Platform for Locally Resolved Sensing, Chemistry, and Cellular Interactions
Classical
contact lithography involves patterning of surfaces by
embossing or by transfer of ink. We report direct lithographic transfer
of parts of sacrificial stamps onto counterpart surfaces. Using sacrificial
stamps consisting of the block copolymer polystyrene-<i>block</i>-polyÂ(2-pyridine) (PS-<i>b</i>-P2VP), we deposited arrays
of nanostructured submicron PS-<i>b</i>-P2VP dots with heights
of âŒ100 nm onto silicon wafers and glass slides. The sacrificial
PS-<i>b</i>-P2VP stamps were topographically patterned with
truncated-pyramidal contact elements and penetrated by spongy-continuous
nanopore systems. The spongy nature of the sacrificial PS-<i>b</i>-P2VP stamps supported formation of adhesive contact to
the counterpart surfaces and the rupture of the contact elements during
stamp retraction. The submicron PS-<i>b</i>-P2VP dots generated
by sacrificial stamping can be further functionalized; examples include
loading submicron PS-<i>b</i>-P2VP dots with dyes and attachment
of gold nanoparticles to their outer surfaces. The arrays of submicron
PS-<i>b</i>-P2VP dots can be integrated into setups for
advanced optical microscopy, total internal reflection fluorescence
microscopy, or Raman microscopy. Arrays of nanostructured submicron
block copolymer dots may represent a preconcentration platform for
locally resolved sensing and locally resolved monitoring of cellular
interactions or might be used as microreactor arrays in lab-on-chip
configurations