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Using a modified Landau-Devonshire type thermodynamic potential, we show that dielectric tunability η of a tetragonal ferroelectric film can be analytically solved. At a given electric field E, η is a function of the remnant polarization ($$P_0^f$$ P 0 f ) and the small-field relative dielectric permittivity ($$\chi _0^f$$ χ 0 f ), which are commonly measured material properties. After a survey of materials, a large η~80% is predicted to be achievable in a (001)-oriented tetragonal (K0.5,Na0.5)NbO3 film. This strain-stabilized tetragonal phase is verified by density functional theory (DFT) calculations. (K0.5,Na0.5)NbO3 films based on this design were successfully prepared via a sputtering deposition process on SrRuO3-buffered (100)SrTiO3 substrates. The resulted epitaxial films showed a sizable $$P_0^f$$ P 0 f (~0.21C m−2) and a large $$\chi _0^f$$ χ 0 f (~830–860), as well as a large η close to the theoretical value. The measured dielectric tunabilities as functions of E are well described by the theoretical η(E) curves, validating our integrated approach rooted in a theoretical understanding.

In order to accomplish efficient CO2 capture, poly(ethyleneimine) (PEI) and tetraethylenepentamine (TEPA), with commonly used and inexpensive, was codispersed into the as-prepared SBA-15 (SBA-15(p)) to prepared blended amine functionalized adsorbent. The influence of the mass ratio of PEI to TEPA on the adsorption property was investigated. The promoting effects of TEPA on CO2 capture property were investigated. The adsorbents were characterized using N2 adsorption/desorption, Fourier transform infrared spectroscopy (FTIR), Transmission electron microscope (TEM) and in situ diffuse reflectance infrared fourier transform spectroscopy (in situ DRIFTS). Among the prepared adsorbents, the SBA-15(p) with 30 wt% PEI and 40 wt% TEPA has the CO2 capture capacity of 4.64 mmol/g and the optimal amine efficiency (0.359 molCO2/molN) at 75 °C with 20 vol% CO2 in N2. The addition of TEPA species could improve the CO2 adsorption amount with high amine utilization. The P123 with wheel-like distribution in SBA-15(p) promotes the CO2 capture by optimizing the accessibility of amine to the CO2. After 15 adsorption cycles, the SBA-15(p) with 40 wt% PEI and 30 wt% TEPA has better reusability and cyclic performance, the adsorption capacity can keep around 4.13 mmol/g. The result indicated that more PEI in the adsorbent would improve the adsorbent cyclic stability. Meanwhile, the in-situ DRIFTS results suggested that the reaction of CO2 molecule with the amine active sites in the adsorbent, agrees with anionic and cationic mechanisms.

With the highest Curie temperature in all known ferroelectrics and a lead-free composition, CaBi 2 Nb 2 O 9 (CBNO) has a good potential in electromechanical applications demanding a good temperature stability and environmental friendliness. However, due to its highly anisotropic crystalline lattice (a = 5.435 A, b = 5.466 A, c = 24.970 A, P a = P b , P c ≈ 0), a/b -axis oriented CaBi 2 Nb 2 O 9 films with excellent ferroelectric and piezoelectric properties are difficult to grow on Si substrates (a ≈5.431 A) at 500 °C or lower, temperatures compatible with the existing CMOS-Si technology. It is also difficult to grow them a / b -axis oriented on those commonly used semiconductor substrates (such as SrTiO 3 and MgO), whose lattice parameters well match with the diagonal length of the CBNO (00 l )-plane (a ≈4 A ≈ a CBNO /√2). In this work, CaBi 2 Nb 2 O 9 thin films with a SrRuO 3 (a ≈3.96 A) buffer layer, which promoted the growth of grains tilting away from the weakly polarized c -axis, were successfully prepared on platinum-coated (100)Si substrates at 500 °C via a radio-frequency magnetron sputtering process. These films exhibited a (117) texture with enhanced electrical properties, including a high dielectric constant ( ɛ r ∼ 480 @ 1 kHz), large electric polarizations ( P r ∼ 12 μC/cm 2 , P s ∼ 63 μC/cm 2 @ E max = 1800 kV/cm), and a good transverse piezoelectric coefficient e 31 ,f (∼1.25 C/m 2 ). As a consequence of its high Curie temperature (>600 °C), the dielectric constant of the CBNO film showed a slow declination with temperature (∼0.1%/ o C before 300 °C, and less than 0.03%/ o C from 300 °C to 600 °C). Its dielectric loss is less than 5% at temperatures lower than 200 °C under a low working frequency (5 kHz/10 kHz), and it stays lower than 5% up to 500 °C when a high working frequency (500 kHz/1 MHz) is used. These enhanced electrical properties will greatly promote applications of CBNO thin films in lead-free ferroelectric devices, especially in those demanding a good high temperature stability.

In order to relieve the amine agglomeration phenomenon in solid amine adsorbent and realize the efficient CO2 capture, a novel double-functionalized adsorbent was synthesized by grafting 3-aminopropyltriethoxysilane and impregnating tetraethylenepentamine, using original mesoporous silica molecular sieves as support. The effects of organic amine loading, gas flow rate and adsorption temperature on CO2 adsorption properties of adsorbent were studied. The results show that SBA-15(p)-AP-70T modified with 70% TEPA has the maximum N content (15.81 mmol/g) and the maximum saturated adsorption capacity (5.69 mmol/g) at 75 °C。Moreover, the CO2 adsorption capacity of this adsorbent can still remain about 5.2 mmol/g after 15 adsorption/desorption cycles. It is mainly because that the grafted APTES and residual P123 in the support pore provide space and hydrogen bonding functional groups for TEPA dispersion and fixation, while reduce the loss of TEPA during the cycle process. Therefore, compared with adsorbent modified by only TEPA, the adsorption capacity and stability of this adsorbent can be effectively improved. In addition, kinetic studies indicate that CO2 adsorption on SBA-15(p)-AP-70T is mainly chemisorption. According to the in situ DRIFTS results, CO2 adsorption mechanism on SBA-15(p)-AP-70T adsorbent is consistent with the zwitterion mechanism.

SBA-15(P) mesoporous material with 2D hexagonal was synthesized as the precursor, then a series of Amine-functionalization SBA-15(p)-xTEPA CO2 adsorbents were prepared by impregnating with TEPA. The adsorbents were characterized using BET, XRD, FTIR, TEM, TGA and In situ IR DRIFTs. Characterization results show that additional impregnated TEPA has a negative effect on the textural properties of adsorbents and additional impregnated TEPA has not change the channel structure of the adsorbent. It also is found that the synergistic effect of TEPA and P123 enhance the initial decomposition temperature and enhance the stability of adsorbent. Compared with SBA-15-60TEPA, SBA-15(p)-60TEPA (SP60T) has better reusability and cyclic performance. After 9 times cycle, the SP60T sorbent still adsorbs around 5.0 mmol/g of CO2 from 20% CO2 in N2 at 75 °C and 1 atm, CO2 adsorption capacity only reduces 7.8%. It is mainly because that the template in carrier makes TEPA evenly dispersed, effectively prevent the TEPA reunion and loss, and improve the utilization ratio of amine. According to adsorption dynamics and inactivation model, CO2 adsorption of SP60T is mainly chemical adsorption. The in situ infrared spectroscopy reveals that CO2 adsorption of SP60T follows anionic and cationic mechanisms.