Pyrolysis of single large biomass particle: Simulation and experiments

Pyrolysis and heat transfer characteristics of single large biomass particle were investigated using threedimensional unsteady heat transfer model coupled with chemical reactions.The consumption of biomass and the production of products were simulated.Some experiments were designed to provide model parameters for simulation calculations.The simulation was verified by pyrolysis experiments of large biomass particle in a vertical tube furnace.The simulation results show the internal heat and mass transfer law during the pyrolysis of large biomass particle.When the biomass particle diameter is between 10 and 30 mm,for every 5 mm increase in particle diameter,the time required for complete pyrolysis will increase on average by about 50 s.When the pyrolysis temperature is between 673 K and 873 K,a slight decrease in the pyrolysis temperature will cause the time required for the biomass to fully pyrolyze to rise significantly.And the phenomenon is more obvious in the low temperature range.The results indicate that the numerical simulation agrees well with the experimental results.

Efficient photoelectrochemical conversion of CO_(2)to syngas by photocathode engineering

The synthesis of renewable chemical fuels from CO_(2) and H_(2)O via photoelectrochemical(PEC)route reprensents a promising room-temperature approach for transforming greenhouse gas into value-added chemicals(e.g.,syngas),but to date it has been hampered by the lack of efficient photocathode for CO_(2) reduction.Herein,we report efficient PEC CO_(2) reduction into syngas by photocathode engineering.The photocathode is consisting of a planar p-n Si junction for strong light harvesting,GaN nanowires for efficient electron extraction and transfer,and Au/TiO_(2)for rapid electrocatalytic syngas production.The photocathode yields a record-high solar energy conversion efficiency of 2.3%.Furthermore,desirable syngas compositions with CO/H_(2)ratios such as 1:2 and 1:1 can be produced by simply varying the size of Au nanoparticle.Theoretical calculations reveal that the active sites for CO and H_(2)generation are the facet and undercoordinated sites of Au particles,respectively.

Synthesis of thiol-functionalized TiO_2 nanocomposite and photocatalytic degradation for PAH under visible light irradiation

In this paper, a thiol-functionalized nanophotocatalyst MPTES/TiO2 was first synthesized by one-pot method using P123 as a template. X-ray diffraction confirms the complete anatase crystalline of thiol-functionalized TiO2, N2 adsorption-desorption isotherm demonstrated that these materials possess high surface area and mesoporous structure. The results of XPS show that MPTES has been successfully polymerized in mesoporous structured TiO2. The photodegradation of phenanthrene （PHE） was investigated under visible light irradiation （λ 〉 420 nm） to evaluate the photocatalytic activity of these materials. Based the experiment results of GC-Mass analysis, a possible mechanism was proposed.

Enhanced photoelectrochemical water splitting with a donor-acceptor polyimide

Polyimide(PI)has emerged as a promising organic photocatalyst owing to its distinct advantages of high visible-light response,facile synthesis,molecularly tunable donor-acceptor structure,and excellent physicochemical stability.However,the synthesis of high-quality PI photoelectrode remains a challenge,and photoelectrochemical(PEC)water splitting for PI has been less studied.Herein,the synthesis of uniform PI photoelectrode films via a simple spin-coating method was reported,and their PEC properties were investigated using melamine as donor and various anhydrides as acceptors.The influence of the conjugate size of aromatic unit(phenyl,biphenyl,naphthalene,perylene)of electron acceptor on PEC performance were studied,where naphthalene-based PI photoelectrode exhibited the highest photocurrent response.This is resulted from the unification of widerange light absorption,efficient charge separation and transport,and strong photooxidation capacity.This paper expands the material library of polymer films for PEC applications and contributes to the rational design of efficient polymer photoelectrodes.

Multiscale nanowire-microfluidic hybrid strain sensors with high sensitivity and stretchability

Nanomaterials with low-dimensional morphology have been explored for enhancing the performance of strain sensors,but it remains difficult to achieve high stretchability and sensitivity simultaneously.In this work,a composite structure strain sensor based on nanomaterials and conductive liquid is designed,demonstrated,and engineered.The nanowire-microfluidic hybrid(NMH)strain sensor responds to multiscale strains from 4%to over 400%,with a high sensitivity and durability under small strain.Metal nanowires and carbon nanotubes are used to fabricate the NMH strain sensors,which simultaneously exhibit record-high average gauge factors and stretchability,far better than the conventional nanowire devices.Quantitative modeling of the electrical characteristics reveals that the effective conductivity percolation through the hybrid structures is the key to achieving high gauge factors for multiscale sensing.The sensors can operate at low voltages and are capable of responding to various mechanical deformations.When fixed on human skin,the sensors can monitor large-scale deformations(skeleton motion)and small-scale deformations(facial expressions and pulses).The sensors are also employed in multichannel,interactive electronic system for wireless control of robotics.Such demonstrations indicate the potential of the sensors as wearable detectors for human motion or as bionic ligaments in soft robotics.

Topology-optimized thermal metamaterials traversing full-parameter anisotropic space

It is widely adopted in thermal metamaterials that mixing different materials could conveniently result in effective thermal conductivities(ETCs)beyond naturally-occurring materials.When multiple materials are isotropically mixed,the ETC is a direct average governed by their filling fractions and given bulk conductivities.That could lead to an inhomogeneous and anisotropic value within the maximal and minimal thermal conductivities of constituent materials.Usually thermal metadevices rely on anisotropic thermal conductivity tensor,whose tensorial elements are frequently inter-dependent and confined within a limited parametric space.It is thus nontrivial to establish a design recipe for advanced thermal metamaterials whose ETCs could cover full-parameter anisotropic space.We demonstrate topological functional cells(TFCs)with copper and polydimethylsiloxane,and show that the anisotropic ETCs traverse their full-parameter space.Such robust scheme based on topology-optimized TFCs unlocks unexplored opportunities for functional thermal metadevices whose parameters may not be reached in previous mixing approaches.This study also sheds light on the developments in emerging acoustic,mechanical and electromagnetic composite materials.

[0001]-Oriented InN Nanoleaves and Nanowires: Synthesis,Growth Mechanism and Optical Properties

Novel indium nitride （INN） leaf-like nanosheets and nanowires have been grown on Si substrate by chemical vapor deposition method. The characterization results indicate that the samples are single-crystalline, and the growth direction of the nanowires and nanoleaves is [0001]. The growth mechanism of the InN nanoleaves is following the pattern of vapor-liquid-solid process with a three-step growth process. In addition, the room temperature photoluminescence spectra of two nanostructures show band-to-band emissions around 0.706 eV, where the emission from single nanoleaf is stronger than nanowire, showing potential for applications in optoelectronic devices.

Enhanced thermal performance from liquid metal in copper/graphite filled elastomer

With the increasing integration level of modern electronics,thermal management becomes an urgent issue for guaranteeing the work efficiency and lifespan of electronics.On the basis of intrinsic high thermal conductivity nature,highly ordered graphite and copper stripes are densely aligned in the silicone gel pads in vertical(VCuGr)and oblique(@15°CuGr)directions to couple the high thermal conductivity and mechanical softness.The wetting nature of liquid metal(LM)on the chemically treated Cu surface is utilized to form a LM layer on the two surfaces of thermal pads.The obtained LM-pad TIMs possessed ultrahigh through-plane thermal conductivity(VCuGr:71.4 W/(m K),@15°CuGr:62.5 W/(m K))under the normal packaging pressure.The thermal resistance decreased from 0.69 cm^(2) K/W to 0.25 cm^(2) K/W with the surface modification with LM.Theoretical simulation and practical thermal dissipation test results further demonstrate the excellent thermal management capability of these composites in high-power electronics.