8 research outputs found
Achieving a Collapsible, Strong, and Highly Thermally Conductive Film Based on Oriented Functionalized Boron Nitride Nanosheets and Cellulose Nanofiber
Boron
nitride nanosheet (BNNS) films receive wide attention in both academia
and industry because of their high thermal conductivity (TC) and good
electrical insulation capability. However, the brittleness and low
strength of the BNNS film largely limit its application. Herein, functionalized
BNNSs (f-BNNSs) with a well-maintained in-plane crystalline structure
were first prepared utilizing urea in the aqueous solution via ball-milling
for the purpose of improving their stability in water and enhancing
the interaction with the polymer matrix. Then, a biodegradable and
highly thermally conductive film with an orderly oriented structure
based on cellulose nanofibers (CNFs) and f-BNNSs was prepared just
by simple vacuum-assisted filtration. The modification of the BNNS
and the introduction of the CNF result in a better orientation of
the f-BNNS, sufficient connection between f-BNNS themselves, and strong
interaction between f-BNNS and CNF, which not only make the prepared
composite film strong and tough but also possess higher in-plane TC.
An increase of 70% in-plane TC, 63.2% tensile strength, and 77.8%
elongation could be achieved for CNF/f-BNNS films, compared with that
for CNF/BNNS films at the filler content of 70%. Although at such
a high f-BNNS content, this composite film can be bended and folded.
It is even more interesting to find that the in-plane TC could be
greatly enhanced with the decrease of the thickness of the film, and
a value of 30.25 W/m K can be achieved at the thickness of ∼30
μm for the film containing 70 wt % f-BNNS. We believe that this
highly thermally conductive film with good strength and toughness
could have potential applications in next-generation highly powerful
and collapsible electronic devices
Completely Green Approach for the Preparation of Strong and Highly Conductive Graphene Composite Film by Using Nanocellulose as Dispersing Agent and Mechanical Compression
Graphene
films receive tremendous attention due to their ultrahigh
electrical and thermal conductivities, which show great application
prospects in modern electronic devices. However, the brittleness and
low strength of graphene films largely limit their use in advanced
applications. And the preparation processes of graphene films reported
so far are also not completely green. In this work, a novel strong
and green graphene composite film with outstanding electromagnetic
interference shielding effectiveness (EMI SE), electrical and thermal
conductivities was successfully fabricated by using nanofibrillated
cellulose (NFC) as dispersing agent and mechanical compression. In
this way, graphene nanosheets (GNs) were not only efficiently dispersed
in the aqueous solution but also linked together by NFC to enhance
mechanical strength of the prepared films. Simultaneously, mechanical
compression could powerfully induce strong alignment and increase
the contact area of the GNs. As a result, the optimum electrical and
thermal conductivities of the obtained films reached up to 988.2 S
cm<sup>–1</sup> and 240.5 W m<sup>–1</sup> K<sup>–1</sup>, respectively, along with a high tensile strength of 61 MPa and
a superior EMI SE of 43 dB with only ≈13 μm in thickness.
Even more, the resultant films revealed excellent flame resistance.
And the NFC can be removed by burning the films, resulting in complete
graphene films with much higher electrical and thermal conductivities.
The manufacturing route in our study is facile, cost-effective and
completely green for the preparation of strong and highly conductive
graphene-based thin films
Design and Preparation of a Unique Segregated Double Network with Excellent Thermal Conductive Property
It is still a challenge to fabricate
polymer-based composites with
excellent thermal conductive property because of the well-known difficulties
such as insufficient conductive pathways and inefficient filler–filler
contact. To address this issue, a synergistic segregated double network
by using two fillers with different dimensions has been designed and
prepared by taking graphene nanoplates (GNPs) and multiwalled carbon
nanotubes (MWCNT) in polystyrene for example. In this structure, GNPs
form the segregated network to largely increase the filler–filler
contact areas while MWCNT are embedded within the network to improve
the network-density. The segregated network and the randomly dispersed
hybrid network by using GNPs and MWCNT together were also prepared
for comparison. It was found that the thermal conductivity of segregated
double network can achieve almost 1.8-fold as high as that of the
randomly dispersed hybrid network, and 2.2-fold as that of the segregated
network. Meanwhile, much higher synergistic efficiency (<i>f</i>) of 2 can be obtained, even greater than that of other synergistic
systems reported previously. The excellent thermal conductive property
and higher <i>f</i> are ascribed to the unique effect of
segregated double network: (1) extensive GNPs–GNPs contact
areas via overlapped interconnections within segregated GNPs network;
(2) efficient synergistic effect between MWCNT network and GNPs network
based on bridge effect as well as increasing the network-density
Noninvasive Fetal Trisomy (NIFTY) test: an advanced noninvasive prenatal diagnosis methodology for fetal autosomal and sex chromosomal aneuploidies
<p>Abstract</p> <p>Background</p> <p>Conventional prenatal screening tests, such as maternal serum tests and ultrasound scan, have limited resolution and accuracy.</p> <p>Methods</p> <p>We developed an advanced noninvasive prenatal diagnosis method based on massively parallel sequencing. The Noninvasive Fetal Trisomy (NIFTY) test, combines an optimized Student’s t-test with a locally weighted polynomial regression and binary hypotheses. We applied the NIFTY test to 903 pregnancies and compared the diagnostic results with those of full karyotyping.</p> <p>Results</p> <p>16 of 16 trisomy 21, 12 of 12 trisomy 18, two of two trisomy 13, three of four 45, X, one of one XYY and two of two XXY abnormalities were correctly identified. But one false positive case of trisomy 18 and one false negative case of 45, X were observed. The test performed with 100% sensitivity and 99.9% specificity for autosomal aneuploidies and 85.7% sensitivity and 99.9% specificity for sex chromosomal aneuploidies. Compared with three previously reported z-score approaches with/without GC-bias removal and with internal control, the NIFTY test was more accurate and robust for the detection of both autosomal and sex chromosomal aneuploidies in fetuses.</p> <p>Conclusion</p> <p>Our study demonstrates a powerful and reliable methodology for noninvasive prenatal diagnosis.</p