Chao Yuan

Non‐Porous Low‐k Dielectric Films Based on a New Structural Amorphous Fluoropolymer

A non-porous and amorphous fluoropolymer PFN with low dielectric constant of 2.33 and dielectric loss less than 1.2 × 10(-3) is reported here. PFN also exhibits good mechanical properties and high thermostability. This study is a new example of a fully dense material showing a low k value and having good thermo/mechanical properties.

Multi-carbazole derivatives: new dyes for highly efficient dye-sensitized solar cells

Three new multi-carbazole derivatives (2C–4C) with a twisted and zigzag-shape structure were designed, synthesized and used as sensitizers for dye-sensitized solar cells (DSSCs). The results showed that this non-planar structure of 2C–4C, combined with multi alkyl chains, can efficiently inhibit dye aggregation and charge recombination, which gave DSSCs with a high open circuit voltage (Voc) and an overall solar-to-electric conversion efficiency (η) of up to 6.33%.

A novel one-pot synthesized organosiloxane: synthesis and conversion to directly thermo-crosslinked polysiloxanes with low dielectric constants and excellent thermostability

A novel organosiloxane containing a thermally cross-linkable benzocyclobutene group was successfully synthesized through a one-pot Grignard reaction procedure. The organosiloxane can be easily polymerized or copolymerized to form the oligomers which can be directly converted to cross-linked network structures with excellent thermostability and low dielectric constants, implying that the organosiloxane has potential application in the electrical and microelectronics industry.

Benzocyclobutene resin with fluorene backbone: a novel thermosetting material with high thermostability and low dielectric constant

A fluorene-based monomer (FB) with thermally cross-linkable benzocyclobutene groups is reported here. This monomer showed good solubility in the common organic solvents and had a low melting point (128 °C). When being treated at high temperature (>200 °C), the monomer was converted to a cross-linked network structure (PFB). TGA data exhibited that PFB had high thermostability with a 5% weight loss temperature of 437 °C and 372 °C in N2 and air, respectively. Moreover, PFB showed a char yield of 47.6% at 1000 °C in N2. With regard to the electrical properties, PFB indicated an average of dielectric constants of about 2.7 ranging from 0.15 MHz to 30 MHz. All these results suggest that FB could be used as the varnish for insulating enameled wire in the electrical industry, and as encapsulation resins in the microelectronics industry.

A new low dielectric material with high thermostability based on a thermosetting trifluoromethyl substituted aromatic molecule

A thermally cross-linkable molecule composed of bis(trifluoromethyl)benzene and benzocyclobutene units (F1) was successfully prepared. Heating F1 (>200 °C) gave a cured resin, which showed a dielectric constant (k) of 2.47 at 30 MHz and an average k value of less than 2.51 in a range of frequencies from 0.15 MHz to 30 MHz. Such low k values are comparable to other polymeric low-k materials. For comparison, a perfluorobenzene with benzocyclobutene groups (F2) was also synthesized. The cured F2 exhibited an average k value of 2.98, indicating that the introduction of a trifluoromethyl group into the backbone of the molecules can efficiently decrease the dielectric constant of the molecules. The cured F1 also exhibited high thermostability (T5 = 429 °C, weight residual = 47.7% at 1000 °C under N2). These results suggest that F1 is suitable for the utilization in ultra large scale integration circuits.

New organic dyes containing E- or Z-trifluoromethyl acrylic acid as the electron acceptors for dye-sensitized solar cell applications: an investigation of the effect of molecular configuration on the power conversion efficiency of the cells

Two new organic dyes containing E- or Z-trifluoromethyl acrylic acid as the electron acceptors were synthesized and used as sensitizers for dye-sensitized solar cells (DSSCs). The Z-isomer achieved a power conversion efficiency (η) of 4.05%, which was much higher than that of the E-isomer (η = 1.35%). Such results give a new insight into in design of new dyes for DSSCs.

Aerodynamic Force and Moment Measurement Under Duplicated Hypersonic Flight Conditions in the JF12 Shock Tunnel

Traditional hypersonic wind tunnels usually produce test flows with low total temperatures and at low sound speeds, and therefore, the thermochemical reaction, one of the key mechanisms in hypersonic flows, is ignored in its experiments. As a result, the real gas effect on the aerodynamic force and moment measurement becomes a very difficult problem to solve in the hypersonic ground tests, and once it was identified as an unknown “unknown” [1]. During the high Mach number and high-altitude segment of the first entry flight of the Space Shuttle orbiter, the vehicle exhibited a nose-up pitching moment increment relative to preflight prediction. Woods et al. [2] noted that preflight predictions based on the aerodynamics in the aerodynamic design data book indicated that a 7.5° deflection of the body flap would be required to trim the Space Shuttle orbiter for the center of gravity and vehicle configuration. In reality, the body flap had to deflect too much large values (δ ≈ 16°) to maintain trim at the proper angle of attack (α = 40°). The deflection of 16° was close to the possible deflection limitation, and the more deflection would lead to a serious flight test accident. Comparison of equilibrium-air computations with perfect gas mode indicates that at least the main part of the so-called hypersonic anomaly was due to real gas effects at very high Mach numbers [3].