This work reports on the determination of the heat conductivity of high temperature stable carbon materials in the temperature range well above 2000 °C where classic material characterization methods fail. Dense graphite (DG) materials as well as rigid and soft felt isolation (RFI/SFI) components have been investigated which are used during crystal growth of SiC by the physical vapor transport method (PVT) in the temperature regime of 2000 and 2400 °C. The applied materials characterization methods include low temperature physical heat conductivity measurements using laser flash analysis (LFA) in the temperature range 25–1200 °C, data extrapolation to elevated temperatures up to 2400 °C, and a correlation of heating processes and computer simulation of the temperature field of different hot zone designs. Using this approach, the calculated temperatures and experimentally determined values with an error of less than ± 2% at 2400 °C can be merged.
{"title":"Determination of Thermal Properties of Carbon Materials above 2000 °C for Application in High Temperature Crystal Growth","authors":"Jonas Ihle, Peter J. Wellmann","doi":"10.1002/crat.202400080","DOIUrl":"https://doi.org/10.1002/crat.202400080","url":null,"abstract":"This work reports on the determination of the heat conductivity of high temperature stable carbon materials in the temperature range well above 2000 °C where classic material characterization methods fail. Dense graphite (DG) materials as well as rigid and soft felt isolation (RFI/SFI) components have been investigated which are used during crystal growth of SiC by the physical vapor transport method (PVT) in the temperature regime of 2000 and 2400 °C. The applied materials characterization methods include low temperature physical heat conductivity measurements using laser flash analysis (LFA) in the temperature range 25–1200 °C, data extrapolation to elevated temperatures up to 2400 °C, and a correlation of heating processes and computer simulation of the temperature field of different hot zone designs. Using this approach, the calculated temperatures and experimentally determined values with an error of less than ± 2% at 2400 °C can be merged.","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"30 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141947253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Dropka, M. Holeňa, Cornelia Thieme, Ta-Shun Chou
Development of the Vertical Growth Freeze crystal growth process is a typical example of solving the ill‐posed inverse problem, which violates one or more of Hadamard's well‐posedness criteria of solution existence, uniqueness, and stability. In this study, different data‐driven approaches are used to solve inverse problems: Reduced Order Modelling method of Proper Orthogonal Decomposition with Inverse Distance weighting (ROM POD InvD), an approximation method of Kriging and Artificial Neural Networks (ANN) employing images, combination of images and numerical data and solely numerical data, respectively. The ≈200 training data are generated by Computational Fluid Dynamics (CFD) simulations of the forward problem. Numerical input data are related to the temperatures and coordinates in 10 characteristic monitoring points in the melt and crystal, while the image input data are related to the interface shape and position. Using the random mean squared error as a criterion, the Kriging method based on images and numerical data and the ANN method based on numerical data are able to capture the system behavior more accurately, in contrast to the ROM POD InvD method, which is based solely on images.
冻结晶体垂直生长过程的发展是解决病态逆问题的一个典型例子，它违反了Hadamard解的存在性、唯一性和稳定性的一个或多个适定准则。在本研究中，采用了不同的数据驱动方法来解决反问题:基于逆距离加权的适当正交分解的降阶建模方法(ROM POD InvD)， Kriging和人工神经网络(ANN)的近似方法，分别采用图像，图像和数值数据的组合以及单独的数值数据。约200个训练数据由计算流体动力学(CFD)模拟正演问题生成。数值输入数据与熔体和晶体中10个特征监测点的温度和坐标有关，图像输入数据与界面形状和位置有关。与仅基于图像的ROM POD InvD方法相比，以随机均方误差为标准，基于图像和数值数据的Kriging方法和基于数值数据的ANN方法能够更准确地捕捉系统行为。
{"title":"Development of the VGF Crystal Growth Recipe: Intelligent Solutions of Ill‐Posed Inverse Problems using Images and Numerical Data","authors":"N. Dropka, M. Holeňa, Cornelia Thieme, Ta-Shun Chou","doi":"10.1002/crat.202300125","DOIUrl":"https://doi.org/10.1002/crat.202300125","url":null,"abstract":"Development of the Vertical Growth Freeze crystal growth process is a typical example of solving the ill‐posed inverse problem, which violates one or more of Hadamard's well‐posedness criteria of solution existence, uniqueness, and stability. In this study, different data‐driven approaches are used to solve inverse problems: Reduced Order Modelling method of Proper Orthogonal Decomposition with Inverse Distance weighting (ROM POD InvD), an approximation method of Kriging and Artificial Neural Networks (ANN) employing images, combination of images and numerical data and solely numerical data, respectively. The ≈200 training data are generated by Computational Fluid Dynamics (CFD) simulations of the forward problem. Numerical input data are related to the temperatures and coordinates in 10 characteristic monitoring points in the melt and crystal, while the image input data are related to the interface shape and position. Using the random mean squared error as a criterion, the Kriging method based on images and numerical data and the ANN method based on numerical data are able to capture the system behavior more accurately, in contrast to the ROM POD InvD method, which is based solely on images.","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"116 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84068718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Masthead: Crystal Research and Technology 12'2021","authors":"","doi":"10.1002/crat.202170033","DOIUrl":"https://doi.org/10.1002/crat.202170033","url":null,"abstract":"","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"92 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73006646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"(Crystal Research and Technology 12/2021)","authors":"","doi":"10.1002/crat.202170032","DOIUrl":"https://doi.org/10.1002/crat.202170032","url":null,"abstract":"","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"10 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84977378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Masthead: Crystal Research and Technology 11'2021","authors":"","doi":"10.1002/crat.202170031","DOIUrl":"https://doi.org/10.1002/crat.202170031","url":null,"abstract":"","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"49 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77043996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"(Crystal Research and Technology 11/2021)","authors":"","doi":"10.1002/crat.202170030","DOIUrl":"https://doi.org/10.1002/crat.202170030","url":null,"abstract":"","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"136 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88919440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Vilela, M. C. Rodrigues, B. Fronza, R. B. Trinca, F. M. Vichi, R. Braga
Calcium orthophosphates (CaP) synthesis involves several chemical equilibria that define the phases present in the final product. From the biomaterials standpoint, it is important to gain knowledge on how synthesis parameters affect phase formation and particle size. This study evaluates the interaction between temperature (24 or 45 °C) and pH conditions (4.5, 6.5, or drifting) on CaP precipitation in terms of yield, phase formation, density, morphology, and size distribution. Calcium and phosphate solutions (Ca/P = 1.0) are mixed and kept under stirring for 3 h. The precipitate is freeze‐dried and characterized. Under drifting pH and pH 4.5, dicalcium phosphate dihydrate (DCPD, CaHPO4 × 2H2O) is the predominant phase at both temperatures; however, some samples also present peaks ascribed to dicalcium phosphate anhydrous (DCPA, CaHPO4). At pH 6.5, diffractograms reveal a mixture of low‐crystallinity DCPD and DCPA (24 °C) or low crystallinity hydroxyapatite [HAP, Ca10(OH)2(PO4)6] (45 °C). In spite of the different morphologies (plates or aggregates), particle size remains within a relatively narrow range (D50 = 12–28 µm). DCPD precipitation is favored under more acidic or drifting pH, while HAP is formed under nearly neutral pH 6.5.
{"title":"Effect of Temperature and pH on Calcium Phosphate Precipitation","authors":"H. Vilela, M. C. Rodrigues, B. Fronza, R. B. Trinca, F. M. Vichi, R. Braga","doi":"10.1002/crat.202100094","DOIUrl":"https://doi.org/10.1002/crat.202100094","url":null,"abstract":"Calcium orthophosphates (CaP) synthesis involves several chemical equilibria that define the phases present in the final product. From the biomaterials standpoint, it is important to gain knowledge on how synthesis parameters affect phase formation and particle size. This study evaluates the interaction between temperature (24 or 45 °C) and pH conditions (4.5, 6.5, or drifting) on CaP precipitation in terms of yield, phase formation, density, morphology, and size distribution. Calcium and phosphate solutions (Ca/P = 1.0) are mixed and kept under stirring for 3 h. The precipitate is freeze‐dried and characterized. Under drifting pH and pH 4.5, dicalcium phosphate dihydrate (DCPD, CaHPO4 × 2H2O) is the predominant phase at both temperatures; however, some samples also present peaks ascribed to dicalcium phosphate anhydrous (DCPA, CaHPO4). At pH 6.5, diffractograms reveal a mixture of low‐crystallinity DCPD and DCPA (24 °C) or low crystallinity hydroxyapatite [HAP, Ca10(OH)2(PO4)6] (45 °C). In spite of the different morphologies (plates or aggregates), particle size remains within a relatively narrow range (D50 = 12–28 µm). DCPD precipitation is favored under more acidic or drifting pH, while HAP is formed under nearly neutral pH 6.5.","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"48 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87928394","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Molybdenum dioxide (MoO2) with amorphous and porous nanostructure is synthesized via a facile hydrothermal methodology in a short reaction time and used as a supercapacitors electrode material. X‐ray diffraction, transmission electron microscopy and cyclic voltammetry, galvanostatic charge–discharge measurements, and cycle stability tests of the amorphous and porous MoO2 are investigated. The novel‐innovative structure conduces to the high specific capacity of 444.7 F g−1 at 1 A g−1 in 0.5 m H2SO4 solution. After 1000 cycles, 92% capacity is retained, indicating that the as‐prepared electrodes possess excellent stabilities. Furthermore, at a high current density of 8 A g−1, the capacity can reach 210.67 F g−1, exhibiting outstanding rate characteristics. The amorphous and porous MoO2 achieves preeminent electrochemical performance, which can be attributed to the short ion diffusion routes and can provide reversible and fast faradic reactions and the porous structure will increase the utilization of the electrode materials. Besides that, the amorphous and porous MoO2 will let each MoO2 nanoparticles to participate in electrochemical reactions due to the full contact between electrolyte and MoO2. Therefore, MoO2 will be a promising anode material for aqueous supercapacitors.
采用水热法在短时间内合成了具有非晶多孔纳米结构的二氧化钼(MoO2)，并将其用作超级电容器电极材料。研究了非晶和多孔MoO2的X射线衍射、透射电子显微镜和循环伏安法、恒流充放电测量和循环稳定性测试。这种新颖的创新结构有助于在0.5 m H2SO4溶液中，在1 A g−1时达到444.7 F g−1的高比容量。经过1000次循环后，92%的容量保留，表明制备的电极具有优异的稳定性。此外，在8 a g−1的高电流密度下，容量可达到210.67 F g−1，具有出色的速率特性。无定形多孔MoO2具有优异的电化学性能，这主要归功于离子扩散路径短，可以提供可逆和快速的faradic反应，多孔结构将提高电极材料的利用率。此外，由于电解质与MoO2的充分接触，无定形和多孔的MoO2将使每个MoO2纳米颗粒参与电化学反应。因此，MoO2将是一种很有前途的水性超级电容器负极材料。
{"title":"Amorphous Porous Molybdenum Dioxide as an Efficient Supercapacitor Electrode Material","authors":"Shuhua Liu, Li Tian, Xiang Qi","doi":"10.1002/crat.202100083","DOIUrl":"https://doi.org/10.1002/crat.202100083","url":null,"abstract":"Molybdenum dioxide (MoO2) with amorphous and porous nanostructure is synthesized via a facile hydrothermal methodology in a short reaction time and used as a supercapacitors electrode material. X‐ray diffraction, transmission electron microscopy and cyclic voltammetry, galvanostatic charge–discharge measurements, and cycle stability tests of the amorphous and porous MoO2 are investigated. The novel‐innovative structure conduces to the high specific capacity of 444.7 F g−1 at 1 A g−1 in 0.5 m H2SO4 solution. After 1000 cycles, 92% capacity is retained, indicating that the as‐prepared electrodes possess excellent stabilities. Furthermore, at a high current density of 8 A g−1, the capacity can reach 210.67 F g−1, exhibiting outstanding rate characteristics. The amorphous and porous MoO2 achieves preeminent electrochemical performance, which can be attributed to the short ion diffusion routes and can provide reversible and fast faradic reactions and the porous structure will increase the utilization of the electrode materials. Besides that, the amorphous and porous MoO2 will let each MoO2 nanoparticles to participate in electrochemical reactions due to the full contact between electrolyte and MoO2. Therefore, MoO2 will be a promising anode material for aqueous supercapacitors.","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"13 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77082015","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
One of the best‐known benzophenone derivatives for nonlinear optical applications, 4‐aminobenzophenone (ABP), is grown as single crystals from saturated solutions employing fast and slow evaporation methodologies with different solvent environments by means of varied dipole moment, viscosity, and evaporation rates such as toluene, ethanol, methanol, ethyl acetate, acetone, dimethyl formamide, dimethylsulfoxide (DMSO), and a mixture of ethanol‐DMSO (1:1) at 32 °C. Variation in the solubility determined by gravimetric analysis, end‐crystal morphology perceived through in‐situ optical microscopy, and origination of growth defects observed along different crystallographic directions are investigated based on the solute‐solvent interactions permissible according to the polarity and aforementioned physical properties of the solvents. Bravais‐Friedel‐Donnay‐Harker morphology, crystalline purity, thermal stability, optical transmittance, and infrared vibrational modes are analyzed through the single crystal and powder X‐ray diffraction, differential scanning calorimetry, UV‐visible‐near IR, and Fourier‐transform infrared spectral analyses. The second‐harmonic generation (SHG) ability of the ABP crystals grown with different solvents and solvent mixture is studied through Kurtz and Perry powder technique in comparison with that of the inorganic and organic standards. The results reveal that the ABP crystals grown from mixed solvent environment ethanol:DMSO (1:1) to become eventually with improved quality, size, and SHG ability among the other crystals grown in the present study.
{"title":"Effect of Solvent Properties on the Growth, Morphology, and Second Harmonic Generation Ability of 4‐Aminobenzophenone (ABP) Single Crystals","authors":"Mythili Aruchamy, Srinivasan Karuppannan","doi":"10.1002/crat.202000246","DOIUrl":"https://doi.org/10.1002/crat.202000246","url":null,"abstract":"One of the best‐known benzophenone derivatives for nonlinear optical applications, 4‐aminobenzophenone (ABP), is grown as single crystals from saturated solutions employing fast and slow evaporation methodologies with different solvent environments by means of varied dipole moment, viscosity, and evaporation rates such as toluene, ethanol, methanol, ethyl acetate, acetone, dimethyl formamide, dimethylsulfoxide (DMSO), and a mixture of ethanol‐DMSO (1:1) at 32 °C. Variation in the solubility determined by gravimetric analysis, end‐crystal morphology perceived through in‐situ optical microscopy, and origination of growth defects observed along different crystallographic directions are investigated based on the solute‐solvent interactions permissible according to the polarity and aforementioned physical properties of the solvents. Bravais‐Friedel‐Donnay‐Harker morphology, crystalline purity, thermal stability, optical transmittance, and infrared vibrational modes are analyzed through the single crystal and powder X‐ray diffraction, differential scanning calorimetry, UV‐visible‐near IR, and Fourier‐transform infrared spectral analyses. The second‐harmonic generation (SHG) ability of the ABP crystals grown with different solvents and solvent mixture is studied through Kurtz and Perry powder technique in comparison with that of the inorganic and organic standards. The results reveal that the ABP crystals grown from mixed solvent environment ethanol:DMSO (1:1) to become eventually with improved quality, size, and SHG ability among the other crystals grown in the present study.","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"14 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91150306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zirconium nitride films are deposited onto stainless steel AISI 316L and silicon (100) by radio frequency magnetron sputtering at different nitrogen flow ratios [N2/(Ar+N2)] varied between 0 and 0.25). Scanning electron microscope, atomic force microscopy, X‐ray diffraction (XRD), and Raman are used to investigate the surface morphology and microstructure of the thin films. The mechanical and electrochemical properties of all coatings are evaluated and compared with the uncoated AISI 316L to explore the efficiency of surface modification. The XRD and Raman analysis show that all the films are crystalline. This shows that the increased nitrogen content leads to a transformation from hexagonal α‐Zr phase to cubic c‐Zr and then to mixed α‐Zr and face centered cubic c‐ZrN phases. The films deposited with nitrogen flow ratio of 0.2 show the highest hardness of 32.2 GPa. Using the potentiodynamic polarization method, the corrosion behavior of the films is studied in Hank's solution. The comparison between uncoated and coated substrates shows a decrease in corrosion current density for all coated samples.
{"title":"Effects of Nitrogen Content on the Structural, Mechanical, and Corrosion Properties of ZrN Thin Films Grown on AISI 316L by Radiofrequency Magnetron Sputtering","authors":"M. Azibi, N. Saoula, N. Madaoui, H. Aknouche","doi":"10.1002/crat.202100096","DOIUrl":"https://doi.org/10.1002/crat.202100096","url":null,"abstract":"Zirconium nitride films are deposited onto stainless steel AISI 316L and silicon (100) by radio frequency magnetron sputtering at different nitrogen flow ratios [N2/(Ar+N2)] varied between 0 and 0.25). Scanning electron microscope, atomic force microscopy, X‐ray diffraction (XRD), and Raman are used to investigate the surface morphology and microstructure of the thin films. The mechanical and electrochemical properties of all coatings are evaluated and compared with the uncoated AISI 316L to explore the efficiency of surface modification. The XRD and Raman analysis show that all the films are crystalline. This shows that the increased nitrogen content leads to a transformation from hexagonal α‐Zr phase to cubic c‐Zr and then to mixed α‐Zr and face centered cubic c‐ZrN phases. The films deposited with nitrogen flow ratio of 0.2 show the highest hardness of 32.2 GPa. Using the potentiodynamic polarization method, the corrosion behavior of the films is studied in Hank's solution. The comparison between uncoated and coated substrates shows a decrease in corrosion current density for all coated samples.","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"24 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78521975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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