27Al MAS Research Articles

Validity of Android-Based Attitude Assessment Application in Islamic Religious Education (PAI) Courses

The 2013 curriculum mandates that psychomotor, emotional, and cognitive domains be included in educational evaluation. Teachers, including those who teach PAI subjects, still struggle with affective or attitude evaluation. In order to determine the validity of the development product in the form of an attitude assessment application, the authors are interested in creating an android-based attitude assessment application for PAI subjects. The ADDIE research and development model method is being used in this project. A total of 50 instructors teaching Islamic religious education courses from 5 distinct madrasahs—MAN 1 Mojokerto, MAN 2 Mojokerto, MA Nurul Islam, MA Al Mas'udy, and MA Al Islamy in Mojokerto Regency—participated in this study. The study took place between January and June 2022. The methods used to acquire the data were observation, interviews, and questionnaires. Both qualitative and quantitative data analysis is used. Data from interviews and observations were analyzed qualitatively, while information from questionnaires was analyzed quantitatively. Based on the evaluation of information technology experts, who gave the development of an android-based attitude assessment application an average score of 4.25, and evaluation experts, who gave it an average score of 4.37, the results demonstrated that it was a very valid application.

Nanocrystalline HZSM‐5prepared by supercritical hydrothermal synthesis and its catalytic esterification performances

AbstractThe nanocrystalline HZSM‐5 was synthesized by supercritical hydrothermal synthesis for the first time and investigated in catalytic esterification of pyromellitic dianhydride(PMD)and n‐butanol to tetrabutyl pyromellitate(TBPM). The HZSM‐5 prepared by conventional hydrothermal synthesis was also examined for comparison. The catalysts were studied using XRD, N2 adsorption, NH3‐TPD, Pyridine‐adsorption FT‐IR, SEM,[27] Al MAS NMRandCHNS analysis. According to the results of characterization, the supercritical hydrothermal condition was helpful to reduce the size of crystal particles and improve the crystallinity of HZSM‐5, and shorten the crystallization time. The surface area, especially external surface area, and pore volume were increased, and the total acidity was increased. The strong acid sites were transformed into the weak acid sites, and the strength of weak and strong acid was weakened. The amount of framework tetrahedral Al species and Brönsted acid sites were increased. Therefore, the formation of coke was retarded, and thePMD conversion, the TBPM selectivity and the catalytic stability were obviously improved.

NH4F modified β zeolite for aniline condensation to diphenylamine and its catalytic mechanism

The main factors affecting the performance of solid acid catalyzed liquid-phase condensation of aniline to diphenylamine are acidity and pore structure. Fluorine has strong electron affinity due to its special electronic structure, which can adjust the acidity and pore structure of zeolite. β zeolite was modified with different concentrations of NH4F solution. The aluminum in the framework of aluminosilicate zeolite was removed to a certain extent, and the acidity and pore size of β zeolite were controlled. Combined with XRD, Py-IR, Al MAS NMR and DRIFTS the active center and reaction mechanism of the catalytic reaction were discussed.

Mesoporosity and Acidity Manipulation in ZSM‐23 and theirn‐Hexadecane Hydroisomerization Performance

AbstractThe enhanced mesoporosity in the networks is expected to offer a potential route to surmount mass‐transport constraints within one‐dimensional microporous structural zeolites. Highly crystalized ZSM‐23 zeolite was synthesized and subsequently post‐treated with alkali‐etching and acid‐etching, the effects of post‐treatments on the physical and chemical properties of the parent zeolite were investigated via XRD, N2physical adsorption, FE‐SEM, TEM,27Al MAS NMR, Py‐IR and NH3‐TPD. The catalytic activity of various Pt supported bifunctional catalysts was investigated vian‐hexadecane hydroisomerization. The post‐treated process not only increased the pore volume as well as the specific surface area, which efficiently improved the diffusion efficiency, but also changed the acidity and acid distribution of zeolite: alkali treatment could increase the content of total Brönsted acid while acid treatment exhibited an opposite trend. Acid treatment effectively promoted the density of weak Brönsted acid sites and suppressed the med‐strong Brönsted acid sites. With the manipulation of acidity and development of mesoporosity in zeolite, the formation of isomers and the suppression of cracked products in then‐hexadecane hydroisomerization were accomplished. The catalytic performance of catalysts showed that acid treatment could effectually promote the formation of isomeric products and inhibit cracking reactions. Especially, Pt/Z(1.0 HN) catalyst with suitable distribution of acid sites and textural properties, exhibited an outstandingn‐C16hydroisomerization performance with the highesti‐C16yield of 64 wt.% at 340 °C.

Innovation Of Amaly Interpretation Learning At Primaganda Senior High School Jombang

This study aims to describe the learning innovation of Tafsir Amaly at SMA Primaganda Jombang. Tafsir Amaly is a local content subject that is included in the Primaganda High School curriculum. Tafsir Amaly is a Sufism-based interpretation developed by Thoriqoh Syadziliyah Al Mas'udiyah Jombang. This type of research uses a qualitative approach. Data collection methods: observation, interviews, and documentation. Technical analysis includes data reduction, data presentation, and concluding. To check the validity of the data, research extension, observation persistence, and triangulation were used. The results showed that the innovation of the implementation of Amaly's Tafsir includes the application of a combination of student-centered and conventional methods in the form of jigsaw cooperative methods, drills, discussions, questions and answers, peer tutorials, exemplary affective methods, and so on supported by the book Tafsir Amaly juz 1 and Quran song as a compliment. Then the teaching aids use qurany 1-5 if needed according to the learning theme of Amaly's Tafsir, Then the learning media can be supported by other means, for example, audio speakers, and so on.

The promotional role of Nd on the catalytic activity and hydrothermal stability of Cu-SAPO-18 catalyst for NH3-SCR reaction

The Cu-SAPO-18 was prepared by the one-pot method and modified through hydrothermal post-treatment, metal-doped Nd(x)/Cu-SAPO-18 (x = 0.4, 0.8, 1.2, 1.6) catalysts were obtained. The catalytic performance of fresh and aged Nd(x)/Cu-SAPO-18 was evaluated by ammonia selective catalytic reduction (NH3-SCR) reaction. The NOx conversion rate of Nd (1.2)/Cu-SAPO-18 was highest. More than 94.5% NOx conversion was maintained over the aged Nd(x)/Cu-SAPO-18 during 250–450°C, which was almost 10% higher than the conversion of aged Cu-SAPO-18. Various techniques including XRD, XRF, BET, SEM, 27Al MAS NMR, XPS, UV-vis, NH3-TPD, H2-TPR, were applied to explore the effect of Nd content on the physiochemistry property of Cu-SAPO-18. The addition of Nd effectively maintained the relatively large specific surface area and uniform pore size distribution. Moreover, the dealumination progress of Cu-SAPO-18 was mitigated and the aggregation of copper species during hydrothermal aging process was restrained. Thus, Nd(x)/Cu-SAPO-18 owed less CuOx and more amount of isolated Cu2+ ions, which stabilized catalyst structure by entering the double 6-membered ring (D6R). Meanwhile, the incorporation of Nd enhanced the redox property and stabilised surface acid sites of Cu-SAPO-18, which were responsible for facilitating the adsorption and activation of reactants.

Alteration in molecular structure of alkali activated slag with various water to binder ratios under accelerated carbonation

Carbonation of alkali activated materials is one of the main deteriorations affecting their durability. However, current understanding of the structural alteration of these materials exposed to an environment inducing carbonation at the nano/micro scale remains limited. This study examined the evolution of phase assemblages of alkali activated slag mortars subjected to accelerated carbonation (1% CO2, 60% relative humidity, up to 28 day carbonation) using XRD, FTIR and 29Si, 27Al, and 23Na MAS NMR. Samples with three water to binder (w/b) ratios (0.35, 0.45, and 0.55) were investigated. The results show that the phase assemblages mainly consisted of C-A-S-H, a disordered remnant aluminosilicate binder, and a minor hydrotalcite as a secondary product. Upon carbonation, calcium carbonate is mainly formed as the vaterite polymorph, while no sodium carbonate is found after carbonation as commonly reported. Sodium acts primarily as a charge balancing ion without producing sodium carbonate as a final carbonation product in the 28-day carbonated materials. The C-A-S-H structure becomes more cross-linked due to the decalcification of this phase as evidenced by the appearance of Q4 groups, which replace the Q1 and Q2 groups as observed in the 29Si MAS NMR spectra, and the dominance of Al(IV) in 27Al MAS NMR. Especially, unlike cementitious materials, the influence of w/b ratio on the crystalline phase formation and structure of C-A-S-H in the alkali activated mortars before and after carbonation is limited.

Characterization of Monochromate and Hemichromate AFm Phases and Chromate-Containing Ettringite by 1H, 27Al, and 53Cr MAS NMR Spectroscopy

The calcium aluminate hydrate AFm and AFt phases formed upon hydration of Portland cement have an important role in the stabilization and solidification of hazardous chromate ions in hardened cement. AFm monochromate (Ca4[Al(OH)6]2(CrO4)·12H2O), AFm hemichromate (Ca4[Al(OH)6]2(CrO4)0.5(OH)·12H2O) and the chromate-containing AFt phase, Ca6[Al(OH)6]2-(CrO4)3·24H2O, were synthesized and investigated by 1H, 27Al, and 53Cr MAS NMR spectroscopy. 27Al quadrupolar coupling parameters (CQ, ηQ) and isotropic chemical shifts (δiso) were determined for the three phases, including two distinct Al sites in chromate-AFt, as observed by 27Al MAS and MQMAS NMR. Two dominant peaks are apparent in the 1H MAS NMR spectra of each of the phases. For the AFm phases, these resonances are assigned to framework hydroxyl groups (1.7–2.0 ppm) and water molecules/hydroxyls (5.0–5.5 ppm) in the interlayer. For chromate-AFt, the peaks are ascribed to framework hydroxyl groups in the [Ca6Al2(OH)12]6+ columns (~1.4 ppm) and water molecules (~4.8 ppm) associated with the Ca ions. 53Cr MAS NMR spectra acquired at 22.3 T for the samples show a narrow resonance for both chromate AFm phases, whereas indications of three distinct Cr resonances are apparent for the chromate AFt. The absence of any second-order quadrupolar effects in the 53Cr NMR spectra strongly suggests that the chromate ions are highly mobile in the anionic sites of the AFm and AFt structures. The NMR data reported in this work are in agreement with the reported crystal structures for the chromate AFm and AFt phases and may be useful for identification and characterization of chromate fixation in cementitious systems, complementing information gained from conventional powder X-ray diffraction studies.

Hierarchically porous Beta/SBA-16 with different silica-alumina ratios and the hydrodesulfurization performances of DBT and 4,6-DMDBT

Hierarchically porous Beta/SBA-16 (BS) composite materials, combining the characteristics of the acidity from the Beta zeolite and the three-dimensional structure from SBA-16, were synthesized successfully through a two-step in-situ assembly hydrothermal crystallization method. A series of NiMo catalysts supported on BS with different silica-alumina ratios were prepared. The supports and the corresponding catalysts were characterized by XRD, N 2 physisorption, 27 Al MAS NMR, TEM, pyridine-FTIR, Raman, XPS and HRTEM. The activities of series catalysts were evaluated by the hydrodesulfurization (HDS) performances of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). It was found that the Beta crystallites were embedded into SBA-16 through silanols accompanied by dealumination on the T3–T9 sites of Beta crystallites. NiMo/BS-3 with a silica-alumina ratio of 100 exhibited the highest DBT and 4,6-DMDBT HDS activities at the WHSV value of 10 h −1 , with the conversions of 95.9% and 86.9% respectively, due to the synergistic effects of the suitable specific surface areas, the relatively large pore size, appropriate acidity, the relatively high sulfidation degree, moderate dispersity and good stacking degree of MoS 2 active phases.

Facile synthesis of hierarchical macro/microporous ZSM-5 zeolite with high catalytic stability in methanol to olefins

Hierarchical macro/microporous ZSM-5 zeolite (defined as ZSM-5(MM)) was successfully synthesized by using silica spheres as silica source. The effects of template, sodium ions, hydroxyl ions, aluminum and water contents as well as crystallization temperature on the morphology and pore structure of ZSM-5 were investigated in detail. The formation mechanism was studied by XRD, SEM, N 2 sorption, ICP-AES, XPS, 27 Al MAS NMR and 29 Si MAS NMR, confirming that the silica spheres during synthesis process were served as not only silica nutrients to accelerate the generation of crystal nucleus, but also morphology guiding agents that induce the formation of macro/microporous structure followed by quasi solid hydrogel transformation mechanism. The prepared ZSM-5(MM) zeolite exhibited much longer catalytic lifetime and higher light olefins selectivity in the methanol to olefins (MTO) than those of the conventional microporous sample. This is because the hierarchical macro/microporous structure can effectively improve the diffusion of feedstocks and products, suppressing the rapid coke deposition. Meanwhile, the contribution of alkene cycle in MTO is enhanced and it produces more propene and butene. ● A facile strategy has been developed to synthesize hierarchical macro/microporous ZSM-5 zeolite ● The silica spheres not only serve as silica source, but also play a morphology-oriented role ● The formation of hierarchical structure is related to the dissolution rate of silica spheres. ● Macro/microporous ZSM-5 exhibited longer catalytic lifetime and higher olefin selectivity in MTO

Hydrochloric Acid Modification and Lead Removal Studies on Naturally Occurring Zeolites from Nevada, New Mexico, and Arizona

Four naturally occurring zeolites were examined to verify their assignments as chabazites AZLB-Ca and AZLB-Na (Bowie, Arizona) and clinoptilolites NM-Ca (Winston, New Mexico) and NV-Na (Ash Meadows, Nevada). Based on powder X-ray diffraction, NM-Ca was discovered to be mostly quartz with some clinoptilolite residues. Treatment with concentrated HCl (12.1 M) acid resulted in AZLB-Ca and AZLB-Na, the chabazite-like species, becoming amorphous, as confirmed by powder X-ray diffraction. In contrast, NM-Ca and NV-Na, which are clinoptilolite-like species, withstood boiling in concentrated HCl acid. This treatment removes calcium, magnesium, sodium, potassium, aluminum, and iron atoms or ions from the framework while leaving the silicon framework intact as confirmed via X-ray fluorescence and diffraction. SEM images on calcined and HCl treated NV-Na were obtained. BET surface area analysis confirmed an increase in surface area for the two zeolites after treatment, NM-Ca 20.0(1) to 111(4) m2/g and NV-Na 19.0(4) to 158(7) m2/g. 29Si and 27Al MAS NMR were performed on the natural and treated NV-Na zeolite, and the data for the natural NV-Na zeolite suggested a Si:Al ratio of 4.33 similar to that determined by X-ray fluorescence of 4.55. Removal of lead ions from solution decreased from the native NM-Ca, 0.27(14), NV-Na, 1.50(17) meq/g compared to the modified zeolites, 30 min HCl treated NM-Ca 0.06(9) and NV-Na, 0.41(23) meq/g, and also decreased upon K+ ion pretreatment in the HCl modified zeolites.

Synthesis, Structure and Properties of an Extra‐Large‐Pore Aluminosilicate Zeolite NUD‐6

Pure silica zeolites possessing uniform micropores, large surface area and high thermal and chemical stability have been widely studied and used in the fields of fine chemicals and oil industry. The incorporation of aluminium into the framework of silica zeolites changes their properties, making them more industrially useful as adsorbents and catalysts. Herein, we report the synthesis and characterization of an extra-large-pore aluminosilicate zeolite NUD-6 with a 16-membered-ring pore channel. Aluminium was directly incorporated into the zeolite NUD-6 framework, as confirmed by 27 Al MAS NMR studies and ammonia temperature-programmed desorption probes. Al-NUD-6 was not stable when heated at 550 °C to remove the organic templates. However, the organic templates in Al-NUD-6 could be removed by oxidation in nitric acid at room temperature. The obtained Al-NUD-6H retained the crystalline structure and possessed both micropores and mesopores despite the occurrence of severe structural distortions due to the presence of the corner-sharing Q3 Si2 O7 units. The incorporation of aluminium resulted in both medium and strong acid sites in Al-NUD-6H, and could facilitate its use in adsorption and catalysis.

The role of thermal analysis in the development of high-iron-content kaolinite-based photocatalysts

Dynamic and controlled-rate thermogravimetric analyses have been carried out on acid-treated (11 and 5.8 M HCl), high-iron-content kaolinites as potential photocatalysts. The mineral contaminants were determined by XRD, while the defect sites of reduced coordination number obtained by surface treatments were identified with 27Al MAS NMR spectroscopy. Upon heating, water is evolved from the surface-treated samples in three main stages: (1) removal of adsorbed water up to ~ 200 °C, (2) goethite dehydroxylation between 200 and 350 °C and (3) dehydroxylation of the clay in the 300–700 °C temperature range. Identification of water released from the above mass loss steps is difficult due to the significant overlap of steps 2 and 3, as well as to the presence of coordinated water at broken edges and defect sites (–OH2+ groups). As a result, the thermal behavior of surface-treated kaolinites should be taken into account both in the preparation of hybrids/composites and in the acid–base characterization of the catalytic surface.

Synthesis and Characterization of a New Aluminogermanate Thiocyanate Aluminogermanate Sodalite Na8[AlGeO4]6(SCN)2

Thiocyanate enclathrated sodalite with aluminogermanate host framework was obtained by high temperature hydrothermal synthesis at 423 K. X-ray power diffraction, IR, ESR, TGA, SEM, and NMR spectroscopy on 27Al and 23Na nuclei were used to characterize this new sodalite. The crystal structure of aluminogermanate, Na8[AlGeO4]6(SCN)2 sodalite was refined from X-ray powder diffraction data in the space group P$$\bar {4}$$3n: a = 9.239 A, V = 788.630 A3, Rwp = 0.8515, Rp = 1.3241, and Al–O–Ge angle is 136.820°. The 27Al MAS NMR study confirms alternating Ge and Al ordering in sodalite framework. The recorded infrared spectrum show absorption band typical for the sodalite structure and frequency at 2200 cm–1 also clearly indicate the incorporation of thiocyanate anions in the sodalite cage. Thermogravimetric analysis has provided information on the extent of thiocyanate entrapment, stability within the sodalite cage and decomposition properties. SEM study shows the retention of cubical morphology of the thiocyanate enclathrated sodalite.

Kreiranje mezopora u zeolitu ZSM-5 alkalnim tretmanom - uticaj koncentracije NaOH, temperature i trajanja tretmana

The work presented in this paper was dedicated to the investigation of the influence of the alkaline treatment parameters on the formation of mesopores in zeolite ZSM-5, SiO2/Al2O3=50. Concentration of NaOH, temperature and tretment duration were varied. The obtained samples were characterized using low temperature nitrogen adsorption, X ray diffraction and solid state 27Al MAS NMR spectroscopy. Formation of mesopores was found to be a process sensitive to changes of treatment parameters, which can lead to creation of hierarchical zeolites with different mesopore surfaces and distributions of pore size diameters. Also, treatment duration was found to have a lesser influence on the process, compared to other two investigated parameters. Mesopore introduction resulted in partial crystallinity reduction, in all modified samples. No significant buildup of extraframework Al was detected.

Effect of silicon content on active catalytic phase for hydrocracking of heavy crude oils

The silicon composition effect on acidic properties of Ni[sbond]Mo catalysts was investigated for hydrocracking reaction, where an optimal Si and Al ratio is required for the formation of Brønsted acid sites and as well as of Al3+ (IV) tetrahedral coordinated sites. The support composition affects the Si[sbond]OH[sbond]Al network, where cations (Al3+ or Si4+) have a coordination number of IV generating higher Brønsted acidity and macro-pores. The supports and fresh catalysts were characterized by atomic absorption, nitrogen physisorption, FT-IR of CO and pyridine adsorption and 27Al MAS NMR.

Structural investigation of hydrous phosphate glasses

Dissolved water has major impact on the physical and chemical properties of phosphate glasses. In the present study we have investigated the structural response to water incorporation for glasses in the system Li2O–MgO–Al2O3–P2O5. Glasses containing 0–8 wt% H2O were synthesised at 500 MPa confining pressure in internally heated gas pressure vessels at 1323 K (LMP, Al-poor glass) and 1423 K (LMAP, Al-enriched glass). Water contents of glasses were determined by pyrolysis and subsequent Karl-Fischer titration (KFT) and/or by infrared spectroscopy. Density varies nonlinearly with water content implying large structural changes when adding up to 2 wt% H2O to the dry glass. Glass Transition temperatures measured by differential thermal analysis (DTA) continuously decrease with water content. The trend can be explained by depolymerisation of the phosphate network. Near-infrared spectroscopy shows that even in Al poor glasses only a minority of dissolved water is present as H2O molecules, but the largest amount is present as OH Groups formed by hydrolysis of P–O–P bonds. The network is stabilised by aluminium which is predominantly six-coordinated in these glasses as shown by 27Al MAS NMR spectroscopy. With increase of Al in the glasses, breaking up of the Phosphate network through hydrolysis is depressed, i.e. much lower OH Contents are formed at same total water content. Network depolymerisation upon addition of H2O is evident also from 31P MAS NMR spectroscopy. While Phosphate tetraheda are crosslinked by two to three bridging oxygen in dry glasses, diphosphate Groups are dominant in glasses containing 8 wt% H2O.

Synthesis of aluminophosphate xerogels by non-hydrolytic sol–gel condensation of EtAlCl2 with trialkylphosphates

We have investigated the preparation of high-surface-area mesoporous aluminophosphates by non-hydrolytic sol–gel method based on reactions of EtAlCl2 with trialkylesters of phosphoric acid (OP(OR)3, R = Me, Et, iPr, nBu, in dry organic solvents. The condensations proceed by alkylchloride elimination. Various reaction and calcination conditions were examined. Porosity is obtained after calcination by removal of organic residual groups. This thermal processing at 300 °C of as-synthesized precursor gels leads to amorphous aluminophosphate xerogels with surface areas of 400–500 m2 g–1 provided by small mesopores (2–8 nm). Changes in the coordination environment of aluminium from six- to four-coordinate are evidenced by shift of 27Al MAS NMR resonances.

Modification of mordenite by carbon black template and utilization as supports for iron catalyst in phenol hydroxylation

Abstract The aim of this work was to prepare mordenite zeolite in sodium form by using silica-alumina source and carbon as the second template (C-NaMOR) then transformed to proton form (C-HMOR). Both C-NaMOR and C-HMOR were characterized by XRD and N2 adsorption-desorption to confirm their structure, morphology and textural properties including surface area, micro- and mesopores volume, respectively. Results from 27Al MAS NMR provided the information of structural defect corresponding to Bronsted and Lewis acid sites. NH3-TPD suggested the amount of acid increasing with structural defects. Both C-NaMOR and C-HMOR were impregnated with Fe(NO3)3⋅9H2O. The form of Fe in 5Fe/C-NaMOR and 5Fe/C-HMOR catalysts which analyzed by XANES was mainly Fe2O3 and the oxidation state was +3. Catalytic testing of Fe supported on C-xMOR zeolites showed improvement the conversions (68%) and selectivities (catechol/hydroquinone ratio = 1).

Additional Lewis acid sites of protonated fibrous silica@BEA zeolite (HSi@BEA) improving the generation of protonic acid sites in the isomerization of C6 alkane and cycloalkanes

This paper describes a study of the nature of metal-free protonated fibrous silica BEA (HSi@BEA) and its ability to generate protonic acid sites originating from molecular hydrogen and from C6 alkanes and cycloalkanes. HSi@BEA was successfully synthesized by a microemulsion system and subsequently applied in n-hexane, cyclohexane and methylcyclopentane isomerization. The HSi@BEA consisted of microspheres with a bicontinuous concentric lamellar structure morphology. Its core was mainly composed of an aluminosilicate framework of BEA, while the lamellar structure consisted of silica. The particle size of HSi@BEA was in the range of 400 nm to 700 nm with pore diameters between 3.6 nm to 5.6 nm and 15 nm to 25 nm. 27 Al MAS NMR results showed that the additional silica lamellar structure of the HSi@BEA increased the extra-framework aluminum (AlOH) which acts as Lewis acidic sites in the catalyst. FTIR results revealed that these additional Lewis acid sites in the metal-free catalyst generated a high amount of protonic acid sites by playing a role as electron acceptors after the dissociation of H2 and C6 alkane and cycloalkanes. Significantly, the participation of more protonic acid sites enhanced the catalytic performance of the C6 alkanes and cycloalkanes, n-hexane, cyclohexane and methylcyclopentane, at a low reaction temperature of 423 K. The presence of a silica lamellar structure resulted in a two to threefold higher isomer yield of n-hexane, cyclohexane and methylcyclopentane compared to bare HBEA catalyst which mainly produces cracking products. In addition, a kinetics study showed that the activation energy could be lowered by two to three times at elevated temperatures in the range of 423 K to 623 K.