Exploring the effect of cooling rate on non-isothermal crystallization of copolymer polypropylene by fast scanning calorimetry

Polypropylene is commonly used as a binder for ceramic injection molding,and rapid cooling is often encountered during processing.However,the crystallization behavior of polypropylene shows a strong dependence on cooling rate due to its semi-crystalline characteristics.Therefore,the influence of cooling rate on the quality of final product cannot be ignored.In this study,the fast differential scanning calorimetry(FSC)test was performed to study the influence of cooling rate on the non-isothermal crystallization behavior and non-isothermal crystallization kinetics of a copolymer polypropylene(PP BC03B).The results show that the crystallization temperatures and crystallinity decrease as the cooling rate increases.In addition,two exothermic peaks occur when cooling rate ranges from 30 to 300 K·s^(-1),indicating the formation of another crystal phase.Avrami,Ozawa and Mo equations were used to explore the non-isothermal crystallization kinetics,and it can be concluded that the Mo method is suitable for this study.

Role of Crystal Seed in Aluminum Hydroxide Crystallization from Ammonia System with Added NH_(4)Al(SO_(4))_(2)·12H_(2)O

A method to promote aluminum hydroxide crystal growth through pickling Al(OH)_(3)as seed in the ammonia system was proposed to overcome these defects.The experimental results show that,under the conditions of pickling time of 15 min,the acid concentration of 10%,the addition of 70 g/L pickling-Al(OH)_(3)seed,and the coarse granular Al(OH)_(3)products(d0.5=85.667)can be obtained.The characterization results show that the phase of the product is gibbsite,consistent with the seed.Moreover,the steps and ledges can be formed on pickling Al(OH)_(3)seed surface under the ammonia system,effectively promoting crystal growth.During crystal growth,the roughness of the crystal surface was first increased and then decreased,and the lamellar structure was deposited on the crystal seed surface.The final particles are approximately round,the surface is compact and dense.The growth of the product is surface reaction controlled.In addition,the content of the AlO_(6)unit is increased and contributed to Al(OH)_(3)crystal growth.

Polycrystalline ZSM-5 Aggregates Induced by Seed and Catalytic Performance in Methanol to Hydrocarbon

Synthesis of ZSM-5 zeolite typically utilizes small molecule polyamines or quaternary ammonium salts as organic structure guiding agent(OSDA).By contrast,the OSDA-free hydrothermal synthesis system eliminates the use of organic templates and the subsequent calcination procedure.This not only reduces the cost of synthesis,but also prevents environmental pollution from the combustion of organic templates,representing an eco-friendly approach.Despite this,literature suggests that even so-called template-free synthesis systems often involve trace amount of organic substances like alcohol.In the present work,a calcined commercial ZSM-5 zeolite was served as seed,with sodium aluminate as aluminum source and silica sol as silicon source,ensuring an entirely template-free synthesis system.Polycrystalline ZSM-5 aggregates consisted of rod-like nanocrystals were successfully prepared in the completely OSDA-free system.Effects of the Si/Al ratio in ZSM-5 seed,dosage and crystallization conditions such as crystallization temperature and crystallization time on ZSM-5 synthesis were investigated.The results show that a highly crystallinity ZSM-5 aggregate consisting of primary nano-sized crystals less than 100 nm is produced from a gel precursor with 5.6%(in mass)seed after hydrothermal treatment for 48 h.Furthermore,the Si/Al ratio in ZSM-5 seed has little effect on the topological structure and pore structure of the synthesized samples.However,the seeds with a low Si/Al ratio facilitate faster crystallization of zeolite and enhance the acidity,especially the strong acid centers,of the catalyst.The catalytic performance of the synthesized polycrystalline ZSM-5 was evaluated during dehydration of methanol and compared with a commercial reference ZSM-5r.The results exhibit that as compared with the reference catalyst,the fabricated sample has a longer catalytic lifetime(16 h vs 8 h)attributed to its hierarchical pores derived from the loosely packed primary nanoparticles.Additionally,the prepared polycrystalline catalyst also exhibits a higher aromatics selectivity(28.1%-29.8%vs 26.5%).

Tunable dispersion relations manipulated by strain in skyrmion-based magnonic crystals

We theoretically investigate the propagation characteristics of spin waves in skyrmion-based magnonic crystals. It is found that the dispersion relation can be manipulated by strains through magneto-elastic coupling. Especially, the allowed bands and forbidden bands in dispersion relations shift to higher frequency with strain changing from compressive to tensile,while shifting to lower frequency with strain changing from tensile to compressive. We also confirm that the spin wave with specific frequency can pass the magnonic crystal or be blocked by tuning the strains. The result provides an advanced platform for studying the tunable skyrmion-based spin wave devices.

CDBS:基于CRYSTALS-Dilithium算法的盲签名方案

为了应对传统盲签名方案在用户端、签名方和验证者交互过程中无法抵御量子计算攻击的这一难题,以NIST选定的后量子数字签名算法CRYSTALS-Dilithium为基础框架,设计了一种新型抗量子计算攻击的盲签名方案CDBS。整体方案采用Fiat-Shamir签名结构,包括密钥生成、盲化、签名、去盲和验证5个阶段,方案内部结合拒绝采样技术防止密钥泄露,使用NTT算法优化多项式计算以提高签名和验证效率。分析表明,所提方案安全性依赖于模误差学习(MLWE)问题和小整数解(SIS)问题,同时满足正确性、盲性和不可伪造性。与其他基于格的盲签名方案相比,所提方案具有较高的安全性,且签名生成过程更高效,占用开销更小。在相同样本参数设置下,所提方案整体开销仅为MBS方案的67.1%。经软件测试验证,实现一次完整的盲签名和验证过程平均仅需657.65μs。所提方案为CRYSTALS-Dilithium数字签名算法的拓展应用提供了参考。

Liquid crystal-integrated metasurfaces for an active photonic platform

Metasurfaces have opened the door to next-generation optical devices due to their ability to dramatically modulate electromagnetic waves at will using periodically arranged nanostructures.However,metasurfaces typically have static optical responses with fixed geometries of nanostructures,which poses challenges for implementing transition to technology by replacing conventional optical components.To solve this problem,liquid crystals(LCs)have been actively employed for designing tunable metasurfaces using their adjustable birefringent in real time.Here,we review recent studies on LCpowered tunable metasurfaces,which are categorized as wavefront tuning and spectral tuning.Compared to numerous reviews on tunable metasurfaces,this review intensively explores recent development of LC-integrated metasurfaces.At the end of this review,we briefly introduce the latest research trends on LC-powered metasurfaces and suggest further directions for improving LCs.We hope that this review will accelerate the development of new and innovative LC-powered devices.

Multi-dimensional multiplexing optical secret sharing framework with cascaded liquid crystal holograms

Secret sharing is a promising technology for information encryption by splitting the secret information into different shares.However,the traditional scheme suffers from information leakage in decryption process since the amount of available information channels is limited.Herein,we propose and demonstrate an optical secret sharing framework based on the multi-dimensional multiplexing liquid crystal(LC)holograms.The LC holograms are used as spatially separated shares to carry secret images.The polarization of the incident light and the distance between different shares are served as secret keys,which can significantly improve the information security and capacity.Besides,the decryption condition is also restricted by the applied external voltage due to the variant diffraction efficiency,which further increases the information security.In implementation,an artificial neural network(ANN)model is developed to carefully design the phase distribution of each LC hologram.With the advantage of high security,high capacity and simple configuration,our optical secret sharing framework has great potentials in optical encryption and dynamic holographic display.

Crystal structure,phase transitions,and thermodynamic properties of magnesium metavanadate(MgV_(2)O_(6))

As a promising anode material for magnesium ion rechargeable batteries,magnesium metavanadate(MgV_(2)O_(6))has attracted considerable research interest in recent years.A MgV_(2)O_(6)sample was synthesized via a facile solid-state reaction by multistep-firing stoichiometric mixtures of MgO and V2O5 powder under an air atmosphere.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)occurred at 841 K and the enthalpy change was 4.37±0.04 kJ/mol.The endothermic effect at 1014 K and the enthalpy change was 26.54±0.26 kJ/mol,which is related to the incongruent melting ofβ-MgV_(2)O_(6).In situ XRD was performed to investigate phase transition of the as-prepared MgV_(2)O_(6)at high temperatures.The cell parameters obtained by Rietveld refinement indicated that it crystallizes in a monoclinic system with the C2/m space group,and the lattice parameters of a=9.280 A°,b=3.501 A°,c=6.731 A°,β=111.76°.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)was further studied by thermal kinetics,indicating that this process is controlled first by a fibril-like mechanism and then by a spherulitic-type mechanism with an increasing heating rate.Additionally,the enthalpy change of MgV_(2)O_(6)at high temperatures was measured utilizing the drop calorimetry,heat capacity was calculated and given as:Cp=208.3+0.03583T-4809000T^(−2)(298-923 K)(J mol^(−1)K^(−1)),the high-temperature heat capacity can be used to calculate Gibbs free energy of MgV_(2)O_(6)at high temperatures.

Crystal-Kyber算法的FPGA高效并行优化

多项式乘法运算制约着基于格的后量子密码在现实中的应用.为提高后量子密码Crystal_Kyber算法的性能效率,减少运行时间,降低多项式乘法的影响,本文设计了一种新的蝶形运算单元对素模q=3329的Kyber方案进行优化.首先,采用16路并行调度新型蝶形运算单元的方式执行算法,缩短了计算周期;其次,使用流水线技术以及改进的K2RED算法,设计实现新型蝶形运算单元,用于降低资源消耗;最后,利用多RAM的方式存储数据,并且多通道优化RAM,允许数据交替存储在RAM中,提高资源复用率.实验结果表明,本文优化后的数论变换(Number Theoretic Transform,NTT)、逆数论变换(Inverse NTT,INTT)、点对位相乘(Point-Wise Multiplication,PWM)的效率达到200 MHz,合并执行Kyber效率达到175 MHz,优于其他方案,具有良好的性能.

Accelerated Sequential Deposition Reaction via Crystal Orientation Engineering for Low-Temperature,High-Efficiency Carbon-Electrode CsPbBr_(3) Solar Cells

Low-temperature,ambient processing of high-quality CsPbBr_(3)films is demanded for scalable production of efficient,low-cost carbon-electrode perovskite solar cells(PSCs).Herein,we demonstrate a crystal orientation engineering strategy of PbBr_(2)precursor film to accelerate its reaction with CsBr precursor during two-step sequential deposition of CsPbBr_(3)films.Such a novel strategy is proceeded by adding CsBr species into PbBr_(2)precursor,which can tailor the preferred crystal orientation of PbBr_(2)film from[020]into[031],with CsBr additive staying in the film as CsPb_(2)Br_(5)phase.Theoretical calculations show that the reaction energy barrier of(031)planes of PbBr_(2)with CsBr is lower about 2.28 eV than that of(O2O)planes.Therefore,CsPbBr_(3)films with full coverage,high purity,high crystallinity,micro-sized grains can be obtained at a low temperature of 150℃.Carbon-electrode PSCs with these desired CsPbBr_(3)films yield the record-high efficiency of 10.27%coupled with excellent operation stability.Meanwhile,the 1 cm^(2)area one with the superior efficiency of 8.00%as well as the flexible one with the champion efficiency of 8.27%and excellent mechanical bending characteristics are also achieved.

Single crystal growth and characterization of 166-type magnetic kagome metals

Kagome magnets were predicted to be a good platform to investigate correlated topology band structure,Chern quantum phase,and geometrical frustration due to their unique lattice geometry.Here we reported single crystal growth of 166-type kagome magnetic materials,including HfMn_(6)Sn_(6),ZrMn_(6)Sn_(6),GdMn_(6)Sn_(6)and GdV_(6)Sn_(6),by using the flux method with Sn as the flux.Among them,HfMn_(6)Sn_(6)and ZrMn_(6)Sn_(6)single crystals were grown for the first time.X-ray diffraction measurements reveal that all four samples crystallize in HfFe6Ge6-type hexagonal structure with space group P6/mmm.All samples show metallic behavior from temperature dependence of resistivity measurements,and the dominant carrier is hole,except for GdV6Sn6 which is electron dominated.All samples have magnetic order with different transition temperatures,HfMn_(6)Sn_(6),ZrMn_(6)Sn_(6)and GdV_(6)Sn_(6)are antiferromagnetic with TN of 541 K,466 K and 4 K respectively,while GdMn_(6)Sn_(6)is ferrimagnetic with the critical temperature of about 470 K.This study will enrich the research platform of magnetic kagome materials and help explore the novel quantum phenomena in these interesting materials.The dataset of specific crystal structure parameters for HfMn_(6)Sn_(6)are available in Science Data Bank,with the link.

CRYSTALS-Kyber算法的IP核设计与验证方案研究

随着量子计算机的不断发展,现有的公钥密码算法随时面临着失效的危机。而抗量子密码(PQC)算法的出现,使得这一危机得到化解。与此同时,CRYSTALS-Kyber算法由于其安全性高、速度快等优点在美国国家标准与技术研究院(NIST)标准化算法中脱颖而出。为提高硬件实现的效率及安全性,提出了一种基于CRYSTALS-Kyber算法的知识产权(IP)核设计与验证的方案。介绍了该系统的硬件实现方法及其中包含的3个模块,密钥生成模块、加密模块和解密模块,研究了实现IP核的关键单元数论变换(NTT)、高级可扩展接口(AXI)以及仿真验证的具体方案,并对总体方案进行了可行性分析。

Preparation, Crystallization and Mechanical Properties of Potassium Aluminosilicate Glass-ceramics

In this study,transparent K_(2)O-Al_(2)O_(3)-SiO_(2)(KAS)glass-ceramics with leucite as the main crystalline phase were prepared by melting-quench method and two-step heat treatment.The effects of SiO_(2)/Al_(2)O_(3) ratio and heat treatment on crystallization and mechanical properties were studied.The crystallization kinetics and X-Ray Diffraction(XRD)results showed that SiO_(2)/Al_(2)O_(3) ratio and heat treatment system had a direct impact on the crystallization behavior of potassium aluminosilicate glass-ceramics.When heat-treated at 680℃/2 h and 780℃/1 h,cracks generated on the surface of the sample with the addition of SiO_(2)/Al_(2)O_(3)=4.8(in mol)due to the huge difference in the coefficient of thermal expansion between glass matrix and surface.When the addition of SiO_(2)/Al_(2)O_(3)(in mol)was 4,the sample with leucite as the main crystalline phase showed an excellent fracture toughness(1.46 MPa·m^(0.5))after the heat treatment of 680℃/2 h and 780℃/5 h.And there was a phase transformation from kaliophilite to leucite.The crystalline phases of the sample heat-treated at 680℃/8 h and 780℃/1 h were leucite and kaliophilite,which resulted in the visible light transmittance of 63%and the fracture toughness of 0.91 MPa·m^(0.5).Furthermore,after the heat treatment of 680℃/2 h and 780℃/5 h,the main crystalline phase of the sample with SiO_(2)/Al_(2)O_(3)=3.2(in mol)was still kaliophilite.Because leucite only grows on the surface of the sample and is hard to grow inward,it is hard to achieve the bulk crystallization of leucite in the sample with SiO_(2)/Al_(2)O_(3)=3.2(in mol).

Dielectric anisotropy in liquid crystal mixtures with nematic and smectic phases

The modulation of dielectric anisotropy(△ε)is pivotal for elucidating molecular interactions and directing the alignment of liquid crystals.In this study,we combine liquid crystals with opposing dielectric anisotropies to explore the impact of varying concentrations on their properties.We report the sign-reversal of△εin both the nematic and smectic A phases of these mixed liquid crystals,alongside a dual-frequency behaviour across a broad temperature spectrum.Our research further quantifies the influence of mixture ratios under various temperatures and electric field frequencies.This exploration may pave the way for the discovery of new physical phenomena.

Effect of Fluoride on the Ion-association of Calcium Phosphate and Crystallization of Hydroxyapatite

Using a titration setup to accurately control the reaction conditions and in situ monitor the reaction,we showed that fluoride exhibited negligible effects on the ion association process of calcium and phosphate and the formation of ACP nanospheres in a buffer solution with constant ionic strength.However,the stability of ACP increased with increasing fluoride concentration,which was ascribed to the inhibitory effect of fluoride on the aggregation of ACP nanospheres and the nucleation of nanocrystals on the surface of ACP nanospheres.Furthermore,fluoride could inhibit the lateral growth of HAP nanosheets and promote the formation of rod-like crystals.These results further improve our understanding of the crystallization pathway of HAP crystals and the regulatory effects of fluoride.

Boosting kinetic separation of ethylene and ethane on microporous materials via crystal size control

The adsorptive separation of C_(2)H_(4)and C_(2)H_(6),as an alternative to distillation units consuming high energy,is a promising yet challenging research.The great similarity in the molecular size of C_(2)H_(4)and C_(2)H_(6)brings challenges to the regulation of adsorbents to realize efficient dynamic separation.Herein,we reported the enhancement of the kinetic separation of C_(2)H_(4)/C_(2)H_(6)by controlling the crystal size of ZnAtzPO_(4)(Atz=3-amino-1,2,4-triazole)to amplify the diffusion difference of C_(2)H_(4)and C_(2)H_(6).Through adjusting the synthesis temperature,reactant concentration,and ligands/metal ions molar ratio,ZnAtzPO4 crystals with different sizes were obtained.Both single-component kinetic adsorption tests and binary-component dynamic breakthrough experiments confirmed the enhancement of the dynamic separation of C_(2)H_(4)/C_(2)H_(6)with the increase in the crystal size of ZnAtzPO_(4).The separation selectivity of C_(2)H_(4)/C_(2)H_(6)increased from 1.3 to 98.5 with the increase in the crystal size of ZnAtzPO_(4).This work demonstrated the role of morphology and size control of adsorbent crystals in the improvement of the C_(2)H_(4)/C_(2)H_(6)kinetic separation performance.

Ultrasonic scalpel based on fusiform phononic crystal structure

In response to the ultrasonic scalpels with the vibrational modal coupling which leads to a decrease in efficiency,an ultrasonic scalpel based on fusiform phononic crystals(PnCs)is proposed.An accurate theoretical model is constructed,which is mainly composed of electromechanical equivalent circuit models to analyze the frequency response function and the frequency response curves of the admittance.Bragg band gaps exist in the fusiform PnCs owing to the periodic constraint,which can suppress the corresponding vibrational modes.The vibration characteristics(vibration mode,frequency,and displacement distribution)of the ultrasonic scalpel are analyzed,and the validity of the electromechanical equivalent circuit method is verified.The results indicate that other vibration modes near the working frequency can be isolated.In addition,blades based on fusiform PnCs have a function akin to that of the horn,which enables displacement amplification.

Petrology,geochemistry,and crystal size distribution of the basaltic andesite-dacite association at Mt.Sumbing,Central Java,Indonesia:Insights to magma reservoir dynamics and petrogenesis

Ten rock samples consisting of one pyroclastic density current(PDC1)deposit,seven lava flows(LF1–7),and two summit lava domes(LD1,2)were studied to understand the petrogenesis and magma dynamics at Mt.Sumbing.The stratigraphy is arranged as LF1,PDC1,LF2,LF3,LF4,LF5,LF6,LF7,LD1,and LD2;furthermore,these rocks were divided into two types.TypeⅠ,observed in the oldest(LF1)sample,has poor MgO and high Ba/Nb,Th/Yb and Sr.The remaining samples(PDC1–LD2)represent typeⅡ,characterized by high MgO and low Ba/Nb,Th/Yb and Sr values.We suggest that type I is derived from AOC(altered oceanic crust)-rich melts that underwent significant crustal assimilation,while typeⅡoriginates from mantle-rich melts with less significant crustal assimilation.The early stage of typeⅡmagma(PDC1–LF3)was considered a closed system,evolving basaltic andesite into andesite(55.0–60.2 wt%SiO_(2))with a progressively increasing phenocryst(0.30–0.48φ_(PC))and decreasing crystal size distribution(CSD)slope(from-3.9 to-2.9).The evidence of fluctuating silica and phenocryst contents(between 55.9–59.7 wt%and 0.25–0.41φ_(PC),respectively),coupled with the kinked and steep(from-5.0 to-3.3)CSD curves imply the interchanging condition between open(i.e.,magma mixing)and closed magmatic systems during the middle stage(LF4–LF6).Finally,it underwent to closed system again during the final stage(LF7–LD2)because the magma reached dacitic composition(at most 68.9 wt%SiO_(2))with abundant phenocryst(0.38–0.45φ_(PC))and gentle CSD slope(from-4.1 to-1.2).

Manipulating Crystal Growth and Secondary Phase PbI_(2)to Enable Efficient and Stable Perovskite Solar Cells with Natural Additives

In perovskite solar cells(PSCs),the inherent defects of perovskite film and the random distribution of excess lead iodide(PbI_(2))prevent the improvement of efficiency and stability.Herein,natural cellulose is used as the raw material to design a series of cellulose derivatives for perovskite crystallization engineering.The cationic cellulose derivative C-Im-CN with cyano-imidazolium(Im-CN)cation and chloride anion prominently promotes the crystallization process,grain growth,and directional orientation of perovskite.Meanwhile,excess PbI_(2)is transferred to the surface of perovskite grains or formed plate-like crystallites in local domains.These effects result in suppressing defect formation,decreasing grain boundaries,enhancing carrier extraction,inhibiting non-radiative recombination,and dramatically prolonging carrier lifetimes.Thus,the PSCs exhibit a high power conversion efficiency of 24.71%.Moreover,C-Im-CN has multiple interaction sites and polymer skeleton,so the unencapsulated PSCs maintain above 91.3%of their initial efficiencies after 3000 h of continuous operation in a conventional air atmosphere and have good stability under high humidity conditions.The utilization of biopolymers with excellent structure-designability to manage the perovskite opens a state-of-the-art avenue for manufacturing and improving PSCs.

Simultaneous guidance of electromagnetic and elastic waves via glide symmetry phoxonic crystal waveguides

A phoxonic crystal waveguide with the glide symmetry is designed,in which both electromagnetic and elastic waves can propagate along the glide plane at the same time.Due to the glide symmetry,the bands of the phoxonic crystal super-cell degenerate in pairs at the boundary of the Brillouin zone.This is the so-called band-sticking effect and it causes the appearance of gapless guided-modes.By adjusting the magnitude of the glide dislocation the edge bandgaps,the bandgap of the guided-modes at the boundary of the Brillouin zone,can be further adjusted.The photonic and phononic guided-modes can then possess only one mode for a certain frequency with relatively low group velocities,achieving single-mode guided-bands with relatively flat dispersion relationship.In addition,there exists acousto-optic interaction in the cavity constructed by the glide plane.The proposed waveguide has potential applications in the design of novel optomechanical devices.