Rapid Microwave-assisted Hydrothermal Synthesis of Bi0.76Sb1.24S3 and Its Application in the Photocatalytic Degradation of Pollutants by Visible Light Irradiation

Bi（0.76）Sb（1.24）S3 nanocrystals were synthesized by a rapid microwave-assisted hydrothermal method using bismuth nitrate, antimony pentoxide and thioacetamide as starting materials and characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and UV-vis diffuse reflectance spectroscopy（DRS）. The effects of the synthetic condition on the product composition were investigated. The photocatalytic activities of Bi（0.76）Sb（1.24）S3 nanocrystals for the degradation of methyl orange and p-hydroxyazobenzene under visible light irradiation were evaluated. Bi（0.76）Sb（1.24）S3 exhibited good and stable visible light photocatalytic activity.

Degradation of PCDD/Fs in MSWI fly ash using a microwave-assisted hydrothermal process

In this work,microwave treatment was introduced to a hydrothermal treatment process to degrade PCDD/Fs(Polychlorinated dibenzo-p-dioxins and dibenzofurans)in municipal solid waste incineration(MSWI)fly ash.Three process additives(NaOH,Na2 HPO4,H2 O),temperatures(150℃,185℃,220℃)and reaction times(1 h,2 h,3 h)were investigated to identify their effect on the disposal of fly ash samples through orthogonal experiments.High-resolution gas chromatography–mass spectrometry(HRGC/MS)was applied to determine the PCDD/F concentrations in MSWI fly ash.The experimental results revealed that 83.7%of total PCDD/Fs was degraded.Reaction temperature was the most important factor for the degradation of the total PCDD/Fs.Both direct destruction and chlorination reactions(the chlorination degree of PCDFs increased)took part in the degradation of PCDD/Fs in fly ash,which was a new discovery.Several PCDD/F indexes determined by the concentration of indicative congeners were found to quantitatively characterize the dioxin toxicity of the fly ash.Furthermore,heavy metals in the fly ash sample were solidified using microwave-assisted hydrothermal treatment,which provided an experimental basis for the simultaneous disposal of dioxins and heavy metals.Thus,the microwave-assisted hydrothermal process should be considered for the future disposal of MSWI fly ash.

Microwave-assisted Hydrothermal Synthesis of Carbon Materials with Tunable Microstructure

A facile microwave-assisted hydrothermal route has been developed for a synthesis of versatile carbon materials. The monosaccharide fructose aqueous solution was adopted as the starting material, and the p H of the solution was adjusted to be in acidic（pH 4）, neutral（pH 7） and basic（pH 10.5） conditions. The p H buffered fructose solutions were treated at different temperatures by a microwave-assisted hydrothermal technique. As-prepared carbon materials displayed p H and temperature dependent multi-morphologies（porous, spherical or core-shell）, which were determined by transmission and scanning electron microscopic analyses（TEM and SEM）. And the hypothesis of dehydration mechanism of hydrothermal synthesis was analyzed by ultraviolet extinction and Fourier transform infrared spectroscopy. It was found that as compared with normal hydrothermal synthesis, microwave assistance could efficiently increase the production yield and improve the spherical geometry of the carbon particles in neutral condition. By changing the p H of the system, acidic p H induces aggregation of the spheres, while basic p H produces more trends toward core-shell or sponge-like porous structure. The study opens a novel route to the production of polytropic carbon materials and suggests a potential niche market established from the green synthesis.

Structure and Photocatalytic Performance of Zr4+Doped Bi2WO6 Synthesized by Fast Microwave-assisted Hydrothermal Method

Zr4＋ doped Bi2WO6 was prepared by a fast microwave-assisted hydrothermal method and used for photocatalytic degradation of organic dyes. The as-prepared samples were characterized by X-ray diffraction（XRD）, transmission electron microscopy（TEM） and UV-Vis spectroscopy. The results indicate that cell volume of Bi2WO6 has a slight increase dependent on the substitution of W6＋ by Zr4＋ with increasing the Zr doping amount. The photocatalytic performance of Zr4＋ doped Bi2WO6 was evaluated by the photodegradation of MO under visible light irradiation. Compared with samples obtained with traditional hydrothermal method as well as pure Bi2WO6, an obviously improved photocatalytic efficiency of Zr4＋ doped Bi2WO6 is achieved by this microwave-assisted hydrothermal way. The 3% Zr doped Bi2WO6 sample exhibited the best photocatalytic activity, which is probably because of the appropriate proportion of components and optimum amount of oxygen vacancies of the sample.

Microstructure and thermoelectric properties of nanoparticled copper selenide alloys synthesized using a microwave-assisted hydrothermal method

With the fabrication of high-performance thermoelectric(TE)materials,developments are being made in enhanc-ing the figure of merit,zT,of TE materials.Liquid-like binary copper selenide(Cu_(2) Se)chalcogenides recently gained significant recognition because of their anomalous but fascinating electrical and thermal transport perfor-mances.In this study,a facile synthesis technique was adopted in fabricating Cu_(2) Se nanoparticles using a rapid microwave-assisted hydrothermal route at different reaction times.The results were compared with those of the Cu_(2) Se solid-state(SS)sample synthesized using the traditional melting and annealing technique.X-ray diffrac-tion patterns revealed successful synthesis of nanoparticles and a phase transition from orthorhombic𝛼-phase and cubic𝛽-phase to a single orthorhombic structure after hot-pressing.Scanning electron microscopic images revealed that although the grain sizes of the nanoparticle(NP)bulk samples increased with the reaction time of the microwave hydrothermal process,the grain sizes were significantly smaller than that of the SS sample.Additionally,NP bulk samples exhibited plenty of nano-grains and pores that are absent in the SS sample.The size and distribution of the grains and pores were measured to study their effects on the transport of carriers and phonons.The NP30 sample exhibited the highest power factor of 983.3μW K−2 m at 673 K among the NP samples,exhibiting intermediate values of resistivity and Seebeck coefficient that are close to those of the SS sample.Moreover,the NP samples exhibited appreciably lower thermal conductivity than the SS sample that is attributed to strengthened phonon scattering.The minimum thermal conductivity of the NP05 sample,0.78 WK−1 m−1 at 348 K,is 1.7 times lower than that of the SS sample.Finally,a maximum zT of 0.56 at 673 K,being approximately 1.3 times higher than that of the SS sample owing to the optimized thermal conductivity,was achieved for the NP30 sample.This value is comparable to or higher than that reported for Cu_(2) Se synthesized using the traditional SS method.Investigations revealed that the proposed microwave hydrothermal synthesis technique is a facile,rapid,and reliable method that results in Cu_(2) Se alloys with excellent TE performance.

Microwave-assisted hydrothermal synthesis and gas sensitivity of nanostructured SnO_2

Precursors for nanostructured SnO2 were synthesized via a microwave-assisted hydrothermal method under different conditions, using SnCI2.2H2 O, urea and citric acid as reactants. After calcination of the pre-cursors at 700 ℃ for 2 h, nanostructured SnO2 with different morphologies were obtained, and were then characterized using X-ray powder diffraction （XRD）, and field-emission scanning electron microscopy （FESEM）. The results show that synthesis temperature and time play an important role in the formation of the 3D hierarchical morphology of the nanostructured SnO2. Gas sensing experiments demonstrate that the synthesized SnO2 materials, especially those with a 3D network structure, exhibit superb sensitivity to alcohol vaoors at 240 ℃.

Rapid Microwave-assisted Hydrothermal Synthesis of SrWO4：Eu^3＋ Nanowires and Their Luminescence Properties

SrWO4：Eu^3＋ nanowires were synthesized at 160 ℃ within 10 min via a microwave-assisted hydrothermal method. In examining the influences of synthesis temperature and reaction time on the morphology of nanowires, it was found that any temperatures and reaction time except 160 ℃ and 10 min gave rise to poorer morphologies under otherwise equal conditions. The synthesized nanowires were characterized by means of X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, high-resolution transmission electron microscopy（HRTEM）, energy dispersive X-ray（EDX） and Raman spectrometry, respectively. The results suggest that the samples are homogenous and dispersive single phase nanowires. The photoluminescence properties of the nanowires were determined with a spectrofluorometer. Two obviously sharp peaks at 395 and 464 nm and a broad peak centered at 290 nm were found in their excitation spectrum. Under excitation at 395 and 464 nm, the ^5D0→^7F2 transition is the dominant process which means Eu^3＋ ion is located at a low symmetry site, while the ^5D0→^7F2 transition dominates under the excitation at 290 nm, showing a highly symmetric field around the Eu^3＋ ion, which indicates the presence of the two local Eu^3＋ environments.

Discovery and characterization of a new hydrothermal field at 2°N on the slow-spreading Carlsberg Ridge

A new hydrothermal field(Tianshi)was discovered on the rift valley wall through plume anomaly surveys and geological work conducted in 2012 and 2018 between 2°35′N and 2°43′N of the slow-spreading Carlsberg Ridge(CR).Here,the results of two expeditions conducted to detect and characterize the new hydrothermal field are reported.Mineralogical and geochemical data,as well as 14 C ages of a sediment core collected near the field are presented to reveal the hydrothermal history.Results show that the Tianshi field is a basalt-hosted hydrothermal system.Geochemical data of the sediments collected near the field indicate a strong hydrothermal contribution,and hydrothermal Fe and Cu fluxes range from 30 to 155 mg/(cm^(2)·ka)and 0.59 to 11.49 mg/(cm^(2)·ka),respectively.Temporal variations in the fluxes of hydrothermal Fe indicate that there have been at least three amplified hydrothermal venting events(H 1,H 2,and H 3)in the Tianshi field over the last 35.2 ka,in 28.6-35.2 ka BP,22.0-27.6 ka BP,and 1.2-11.4 ka BP,respectively.Hydrothermal event H 2 was driven by an increased magmatic production associated with sea level fall during the Last Glacial Maximum,while event H 3 was promoted by tectonic activity associated with a rapid sea level rise.This study further verified the role of sea level change in modulating hydrothermal activity on mid-ocean ridges.

Episodic hydrothermal alteration on Middle Permian carbonate reservoirs and its geological significance in southwestern Sichuan Basin,SW China

To analyze the episodic alteration of Middle Permian carbonate reservoirs by complex hydrothermal fluid in southwestern Sichuan Basin,petrology,geochemistry,fluid inclusion and U-Pb dating researches are conducted.The fractures and vugs of Middle Permian Qixia–Maokou formations are filled with multi-stage medium-coarse saddle dolomites and associated hydrothermal minerals,which indicates that the early limestone/dolomite episodic alteration was caused by the large-scale,high-temperature,deep magnesium-rich brine along flowing channels such as basement faults or associated fractures under the tectonic compression and napping during the Indosinian.The time of magnesium-rich hydrothermal activity was from the Middle Triassic to the Late Triassic.The siliceous and calcite fillings were triggered by hydrothermal alteration in the Middle and Late Yanshanian Movement and Himalayan Movement.Hydrothermal dolomitization is controlled by fault,hydrothermal property,flowing channel and surrounding rock lithology,which occur as equilibrium effect of porosity and permeability.The thick massive grainstone/dolomites were mainly altered by modification such as hydrothermal dolomitization/recrystallization,brecciation and fracture-vugs filling.Early thin-medium packstones were mainly altered by dissolution and infilling of fracturing,bedding dolomitization,dissolution and associated mineral fillings.The dissolved vugs and fractures are the main reservoir space under hydrothermal conditions,and the connection of dissolved vugs and network fractures is favorable for forming high-quality dolomite reservoir.Hydrothermal dolomite reservoirs are developed within a range of 1 km near faults,with a thickness of 30–60 m.Hydrothermal dolomite reservoirs with local connected pore/vugs and fractures have exploration potential.

Hydrothermal hydrogenation/deoxygenation of palmitic acid to alkanes over Ni/activated carbon catalyst

To produce paraffin from hydrogenation/deoxygenation of palmitic acid,model compound of bio-oil obtained by hydrothermal liquefaction(HTL)of microalgae has been an attractive focus in recent years.In order to avoid energy-intensive separation process of water and bio-oil,it is of importance that deoxygenation upgrading of fatty acids under hydrothermal conditions similar to HTL process.Herein,it is the first time to explore the application of activated carbon(AC)-supported non-noble-metal catalysts,such as Ni,Co,and Mo,and so on,in the hydrothermal hydrogenation/deoxygenation of long-chain fatty acids,and the obtained Ni/AC-H(the Ni/AC was further H_(2)pre-reduced)is one of the best catalysts.In addition,it is found that the catalytic activity can be further improved by H_(2)pre-reduction of catalyst.Characterization results that are more low valences of nickel and oxygen vacancy can be obtained after H_(2)pre-reduction,thus significant promoting the deoxygenation especially the decarbonylation pathway of fatty acids.The total alkanes yield can reaches 95.9%at optimal conditions(280℃,360 min).This work confirmed that the low-priced AC-supported non-noble-metal catalysts have great potential compared with the noble-metal catalyst,in hydrothermal upgrading of bio-oil.

Hydrothermal treatment of pearl millet grains:Effects on nutritional composition,antinutrients and flour properties

Pearl millet(Pennisetum glaucum)is one of the major millets with high nutritional properties.This crop exhibits exceptional resilience to drought and high temperatures.However,the processing of pearl millet poses a significant challenge due to its high lipid content,enzyme activity,and presence of antinutrients.Consequently,it becomes imperative to enhance the quality and prolong the shelf life of pearl millet flour by employing suitable technologies.Hydrothermal treatment in the food industry has long been seen as promising due to its potential to reduce microbial load,inactivate enzymes,and improve nutrient retention.This study aims to investigate the effects of hydrothermal treatment on the quality characteristics of pearl millet.The independent variables of the study were soaking temperature(35,45,55℃),soaking time(2,3,4 h),and steaming time(5,10,15 min).Treatment conditions had a statistically significant effect on nutrient retention.Major antinutrients like tannins and phytates were reduced by 0.99% to 5.94% and 0.36% to 6.00%,respectively,after the treatment.Lipase activity decreased significantly up to 10% with the treatment conditions.The findings of this study could potentially encourage the use of pearl millet flour in the production of various food items and promote the application of hydrothermal treatment in the field of food processing.

Cross-upgrading of biomass hydrothermal carbonization and pyrolysis for high quality blast furnace injection fuel production:Physicochemical characteristics and gasification kinetics analysis

The paper proposes a biomass cross-upgrading process that combines hydrothermal carbonization and pyrolysis to produce high-quality blast furnace injection fuel.The results showed that after upgrading,the volatile content of biochar ranged from 16.19%to 45.35%,and the alkali metal content,ash content,and specific surface area were significantly reduced.The optimal route for biochar pro-duction is hydrothermal carbonization-pyrolysis(P-HC),resulting in biochar with a higher calorific value,C=C structure,and increased graphitization degree.The apparent activation energy(E)of the sample ranges from 199.1 to 324.8 kJ/mol,with P-HC having an E of 277.8 kJ/mol,lower than that of raw biomass,primary biochar,and anthracite.This makes P-HC more suitable for blast furnace injection fuel.Additionally,the paper proposes a path for P-HC injection in blast furnaces and calculates potential environmental benefits.P-HC of-fers the highest potential for carbon emission reduction,capable of reducing emissions by 96.04 kg/t when replacing 40wt%coal injec-tion.

Characterization of Hydroxyapatite Extracted from Crab Shell Using the Hydrothermal Method with Varying Holding Times

Hydroxyapatite(HA)is a bio ceramic commonly utilized in bone tissue engineering due to its bioactive and osteoconductive properties.Crab shells are usually disregarded as waste material despite their significant CaCO_(3) content,and have not been widely utilized in the synthesis of HA.This study aims to synthesize and analyze HA derived from crab shells using the hydrothermal method with different durations of holding time.This study utilized precipitated calcium carbonate(PCC)derived from crab shells.With a hydrothermal reactor set at 160°C and varying holding times of 14(HA_14),16(HA_16),and 18(HA_18)h,a PCC and(NH4)2HPO4 mixture was used to synthesize HA.The synthesis results were analyzed using scanning electron microscopy(SEM),fourier transform infrared spectroscopy(FTIR),and X-ray diffraction(XRD)tests.This study has accomplished the synthesis of HA from crab shells.Nonetheless,the final product of synthesis still contained CaCO_(3) as an impurity.The prolonged hydrothermal holding time of 14 to 18 h resulted in a reduction of impurities while increasing the percentage of crystal weight and crystallite size of HA.Specimen CH_18 is the best-quality product generated in this study.This specimen produced HA with the highest percentage of crystal weight and crystallite size compared to the other specimens.Furthermore,specimen CH_18 exhibited the lowest concentration of impurities.The Ca/P ratio in this specimen was also the closest to 1.67.The Ca/P ratio,crystallite size,and crystal weight percentage of this specimen are 1.54,19.06 nm,and 99.1%,respectively.

Mass-Based Environmental Factor and Energy Assessment of Microwave-Assisted Synthesized Transition Metal Nanostructures

This paper describes mass-based energy phase-space projection of microwave-assisted synthesis of transition metals (zinc oxide, palladium, silver, platinum, and gold) nanostructures. The projection uses process energy budget (measured in kJ) on the horizontal axes and process density (measured in kJg−1) on the vertical axes. These two axes allow both mass usage efficiency (Environmental-Factor) and energy efficiency to be evaluated for a range of microwave applicator and metal synthesis. The metrics are allied to the: second, sixth and eleventh principle of the twelve principle of Green Chemistry. This analytical approach to microwave synthesis (widely considered as a useful Green Chemistry energy source) allows a quantified dynamic environmental quotient to be given to renewable plant-based biomass associated with the reduction of the metal precursors. Thus allowing a degree of quantification of claimed “eco-friendly” and “sustainable” synthesis with regard to waste production and energy usage.

Conditions for the enrichment of karst hydrothermal resources in Bohai Bay Basin

Drilling for karst hydrothermal resources in eastern China has posed challenges,including disparities between the temperature and yield of geothermal water.It is evident that relying solely on geothermal anomalies or indications of karst reservoirs is inadequate for the exploration of karst hydrothermal resources.This study seeks to elucidate the cause of geothermal sweet spots by analyzing the interplay between geothermal anomalies and karst reservoirs and the underlying geological conditions for karst hydrothermal enrichment.Key findings include:(1)the Bohai Bay Basin has been geologically favorable for the development of karst hydrothermal resources since the Mesozoic era;(2)the karst hydrothermal enrichment varies significantly between the basin’s margin and its interior.On the basin margin,the enrichment is largely driven by groundwater activity and faults,particularly where faults facilitate the upwelling of geothermal water.In contrast,within the basin’s interior,karst hydrothermal resources are predominantly influenced by buried hills and are especially enriched in areas facilitating the discharge of deep geothermal waters.

Microwave-assisted Synthesis of Al_(4)SiC_(4) and Its Effect on Properties of MgO-C Refractories

Al_(4)SiC_(4) was synthesized from Al powder, silicon carbide, and graphite by microwave sintering, and characterized by XRD and SEM. Then the synthesized material was added to the magnesia carbon refractory brick to study its effect on the oxidation resistance, apparent porosity, bulk density, elastic modulus, and modulus of rupture. It is found that Al_(4)SiC_(4) can be synthesized by microwave sintering at 1 300 ℃ and the addition of Al_(4)SiC_(4)-containing material as an antioxidant can enhance the oxidation resistance of the magnesia carbon refractory brick.

Towards a new avenue for rapid synthesis of electrocatalytic electrodes via laser-induced hydrothermal reaction for water splitting

Electrochemical production of hydrogen from water requires the development ofelectrocatalysts that are active,stable,and low-cost for water splitting.To address these challenges,researchers are increasingly exploring binder-free electrocatalytic integratedelectrodes (IEs) as an alternative to conventional powder-based electrode preparation methods,for the former is highly desirable to improve the catalytic activity and long-term stability for large-scale applications of electrocatalysts.Herein,we demonstrate a laser-inducedhydrothermal reaction (LIHR) technique to grow NiMoO4nanosheets on nickel foam,which is then calcined under H2/Ar mixed gases to prepare the IE IE-NiMo-LR.This electrode exhibits superior hydrogen evolution reaction performance,requiring overpotentials of 59,116 and143 mV to achieve current densities of 100,500 and 1000 mA·cm-2.During the 350 h chronopotentiometry test at current densities of 100 and 500 m A·cm-2,the overpotentialremains essentially unchanged.In addition,NiFe-layered double hydroxide grown on Ni foam is also fabricated with the same LIHR method and coupled with IE-NiMo-IR to achieve water splitting.This combination exhibits excellent durability under industrial current density.The energy consumption and production efficiency of the LIHR method are systematicallycompared with the conventional hydrothermal method.The LIHR method significantly improves the production rate by over 19 times,while consuming only 27.78%of the total energy required by conventional hydrothermal methods to achieve the same production.

A Comparison of Hydrothermal Aging, SO2 and Propene Poisoning Effects on NH3-SCR over Cu-ZSM-5 and Cu-SAPO-34 Catalysts

This study was aimed to investigate the effects of hydrothermal aging, propene and SO2 poisoning on the ammonia-selective catalytic reduction (NH3-SCR) performance of both Cu-SAPO-34 and Cu-ZSM-5. The catalytic activities of fresh, aged and poisoned samples were tested in ammonia-selective catalytic reduction (NH3-SCR) of NOx conditions. The XRD, TG and N2-desorption results showed that the structures of the Cu-SAPO-34 and Cu-ZSM-5 remained intact after 750˚C hydrothermally aged, SO2 and propene poisoned. After hydrothermal aging at 750˚C for 12 h, the NO reduction performance of Cu-ZSM-5 was significantly reduced at lower temperatures, while that of Cu-SAPO-34 was less affected. Moreover, Cu-SAPO-34 catalyst showed high NO conversion with SO2 or propene compared to Cu-ZSM-5. However, Cu-ZSM-5 showed a larger drop in catalytic activity with SO2 or propene compared to Cu-SAPO-34 catalyst. The H2-TPR results showed that Cu2 ions could be reduced to Cu and Cu0 for Cu-ZSM-5, while no significant transformation of copper species was observed for Cu-SAPO-34. Meanwhile, the UV-vis DRS results showed that CuO species were formed in Cu-ZSM-5, while little changes were observed for the Cu-SAPO-34. Cu-SAPO-34 showed high sulfur and hydrocarbon poison resistance compared to Cu-ZSM-5. In summary, Cu-SAPO-34 with small-pore zeolite showed higher hydrothermal stability and better hydrocarbon and sulfur poison resistant than Cu-ZSM-5 with medium-pore.

Microwave-assisted hydrothermal synthesis of copper oxide-based gas-sensitive nanostructures

Hydrothermal methods are widely used in chemical synthesis of target products with specific morphology and nanostructure.Those methods are very efficient for the preparation of well-controlled structures but the reaction time is usually long.The assistance of microwave makes the reaction system heat up faster,more uniformly and reactions are accelerated,it also can be utilized to change the morphology or structure of materials,which improves the physic-chemical properties of synthesized products and influences its gas-sensing performance.Copper oxide(CuO)is widely applied in semiconductor gas sensors because of its good reactivity and stability.This review article briefly introduces the principle,mechanism and recent development of CuO nanostructures obtained by microwave-as sis ted hydrothermal synthesis(MWHS)process.It also discussed the relation between endopathic factors of material and its gas-sensitive performance.The technical challenges and prospective solutions for highperformance CuO-based gas-sensitive materials with unique nanostructure are proposed.It is pointed out that the hierarchical CuO-based nanostructures and their composite materials prepared by MWHS process are efficacious methods to improve the gas-sensitive performance of the materials.On the basis of the morphology,the materials are divided into nanorods,nanoflowers,nanosheets,nanospheres and other nanostructures.The influence of microwave parameters on the properties of synthetic products is analyzed.The influence followed by metal element loading on the structure and properties of CuO-based materials by MWHS process is further discussed.Then this review summarizes the research progress of graphene-CuO and metal oxide-CuO composites prepared by MWHS process in recent years.

Microwave-assisted hydrothermal synthesis of cube-like Ag-Ag_2MoO_4 with visible-light photocatalytic activity

Cube-like Ag-Ag2MoO4 composite has been successfully prepared in the presence of PVP （potyvinylpyrrolidone） via a facile microwave-assisted hydrothermal process. Studies of its photocatalytic performance in the decomposition of RhB indicate that the cube-like Ag-Ag2MoO4 composite exhibits good catalytic activities under visible-light irradiation. The face that Ag pro- motes the absorption of visible light may be attributed to the surface plasmon resonance. Further XRD characterization after recycle photocatalytic tests confirms that partial Ag~ ions in Ag2MoO4 have been reduced to metallic Ag. Reaction temperature, reaction time and the amount of PVP have also been studied and found to play crucial roles in the formation of the cube-like microstructures.